Insulin accelerates recovery from QRS complex widening in a frog heart model of hyperkalemia

Hyperkalemia is one of the most common electrolyte disorders. By injecting various concentrations of potassium chloride (KCl) solutions intravenously into bullfrogs, we demonstrated characteristic electrocardiogram (ECG) abnormalities of hyperkalemia in frog hearts. The widened QRS complexes induced by 100 mM KCl injection were accompanied by an increase in the resting membrane potential in cardiomyocytes and a decreased slope of phase 0 in the action potential. Recording both ECG waveforms and the cardiac action potential enabled us to reveal the mechanisms of hyperkalemia-induced ECG abnormalities. Additionally, pre-treatment with insulin, a powerful stimulator of Na⁺/K⁺-ATPase activity, significantly accelerated the recovery from the widened QRS complexes in the ECG, demonstrating a pronounced shift of extracellular potassium ions into the intracellular space.     

Inhibitory effects of SKF96365 on the activities of K+ channels in mouse small intestinal smooth muscle cells

In order to investigate the effects of {"type":"entrez-protein","attrs":{"text":"SKF96365","term_id":"1156357400","term_text":"SKF96365"}}SKF96365 (SKF), which is a non-selective cationic channel blocker, on K⁺ channel currents, we recorded currents through ATP sensitive K⁺ (I_KATP), voltage-gated K⁺ (I_Kv) and Ca²⁺ activated K⁺ channels (I_BK) in the absence and presence of SKF in single small intestinal myocytes of mice with patch-clamp techniques. SKF (10 µM) reversibly abolished I_KATP that was induced by cromakalim (10 µM), which is a selective ATP sensitive K⁺ channel opener. These inhibitory effects were induced in a concentration-dependent and voltage-independent manner. The 50% inhibitory concentration (IC₅₀) was 0.85 µM, which was obviously lower than that reported for the muscarinic cationic current. In addition, SKF (1 µM ≈ the IC₅₀ value in I_KATP suppression) reversibly inhibited the I_Kv that was induced by repetitive depolarizing pulses from −80 to 20 mV. However, the extent of the inhibitory effects was only ~30%. In contrast, SKF (1 µM) had no significant effects on spontaneous transient I_BK and caffeine-induced I_BK. These results indicated that SKF inhibited ATP sensitive K⁺ channels and voltage-gated K⁺ channels, with the ATP sensitive K⁺ channels being more sensitive than the voltage-gated K⁺ channels. These inhibitory effects on K⁺ channels should be considered when SKF is used as a cationic channel blocker.     

High-magnesium exposure to bullfrog heart causes ST segment elevation

Hypermagnesemia occurs in elderly people or patients with renal insufficiency after excessive ingestion of magnesium-containing laxatives. In addition to typical electrocardiogram (ECG) findings caused by conduction defects, changes in the ST segments and T waves are also observed in patients with severe hypermagnesemia. This suggested the involvement of similar pathophysiology to acute myocardial infarction, as we previously demonstrated using burn-induced subepicardial injury model in frog hearts. In the present study, by exposing the bullfrog heart to high-magnesium solution, we reproduced prominent ST segment changes in ECG as actually observed in patients with severe hypermagnesemia. In addition to the great increase in the T waves, the ECG showed a marked elevation of the ST segments and the cardiac action potential demonstrated a marked shift of the resting membrane potential to the depolarized side. High-magnesium exposure did not affect the abundance of Na⁺/K⁺-ATPase proteins. However, the pharmacological stimulation of Na⁺/K⁺-ATPase activity by insulin quickly retrieved the elevated ST segments in ECG. From these results, the functional blockade of Na⁺/K⁺-ATPase activity by magnesium ions was thought to be responsible for generating the potassium concentration gradient and the subsequent ST segment changes.     

Preliminary Studies on the Concentration of Na+,K+-ATPase in Skeletal Muscle of Draught Cattle in Mozambique: Effect of Sex,Age and Training

The effect of training on the potential for work in draught cattle was assessed by measuring the Na⁺,K⁺-ATPase in the muscle cell membrane and the elevation in the concentration of K⁺ in plasma during exercise. Biopsies of the semitendinosus muscle and venous blood samples were taken from the cattle used for draught work in Mozambique. No differences were found in the plasma ion or Na⁺,K⁺-ATPase concentrations in samples taken from Nguni, Africander and Angoni breeds. There were no significant differences in plasma ions (Na⁺, K⁺ and Cl^–) or muscle Na⁺,K⁺-ATPase concentrations between the Angoni males and females, although the males showed an increase in Na⁺,K⁺-ATPase with age, while the females showed a decrease. The increase in males might be attributed to their higher level of activity in the herds than that of females. After a training period of 15 days, a significant increase in Na⁺,K⁺-ATPase concentration in semitendinosus muscle was found in Angoni cattle. In females, this was significant after 8 days of training (about 30%); in males after 15 days of training (about 16%). On day 15, there was a reduction in the elevation of plasma K⁺ during the 2 h of draught work, indicating an increased capacity of the Na⁺,K⁺ pumps to maintain the extracellular K⁺ concentration in working muscles and a possible delay in the moment of fatigue.     

Effect of Cadmium in Feed on Organs and Meat Colour of Growing Pigs

One hundred and ninety-two barrows (Duroc × Landrace × Yorkshire, initial weight 27.7 kg) were used to investigate the effects of cadmium in feed on the function of selected organs and meat colour of growing pigs. The pigs were randomly allocatted into four different treatments. Each treatment included three replications with 16 pigs per replicate. The animals were fed corn–soybean basal diet and supplemented with 0, 0.5, 5.0, 10.0 mg/kg cadmium (as CdCl₂), respectively. The feeding trial ended when the average body weight of the pigs reach 90 kg. The results showed that, compared with controls, addition of 10 mg/kg cadmium to the diet resulted in significant elevations of relative weight of liver and spleen by 18.3% (p < 0.05) and 19.7% (p < 0.05) respectively, and of serum glutamic-pyruvic transaminase (GPT) and glutamic-oxaloacetic transaminase (GOT) activities by 17.8% (p < 0.05) and 27.4% (p < 0.05) respectively; and significant decreases of Na⁺/K⁺-ATPase activity in the liver by 24.6% (p < 0.05), the redness of longissimus dorsi by 26.6% (p < 0.05) and 24.9% (p < 0.05) at 0.75 h and 16 h post mortem, respectively, and of the myoglobin content of longissimus dorsi by 19.4% (p < 0.05). No changes were found in these indices above when the pigs were fed the diet supplied with 0.5 or 5 mg/kg cadmium (p > 0.05), nor in renal functions among cadmium-treatment treatments (p > 0.05) as indicated is the activities of urinary N-acetyl-β-d-glucosaminidase (NAG) and alkaline phosphatase (ALP) and the content of urinary protein. The study indicated the adverse effects of 10 mg/kg cadmium in feed on liver functions and meat colour of growing pigs.     

Factors affecting disease manifestation of toxocarosis in humans: Genetics and environment

Toxocara canis is regarded as the main cause of human toxocarosis but the relative contribution of T. cati is probably underestimated; serological and other diagnostic methods used in most studies of this zoonotic disease do not distinguish between the two parasites. The definitive hosts for T. canis are caniidae. Pups generally have higher infection rates than adult animals and are a major source of eggs in the environment. Humans usually acquire T. canis infection by accidental ingestion of embryonated eggs or encapsulated larvae from the environment or contaminated food, such infections may lead to visceral larva migrans (VLM), ocular larva migrans (OLM) or covert toxocarosis (CT). Although a mixed Th1- and Th2-mediated immunological response, particularly with high levels of IgE and eosinophilia is observed, the underlying mechanisms of molecular and immunopathogenesis for the development of the symptomatic syndromes of VLM, OLM, or of asymptomatic CT are largely unclear. Studies have indicated that immunological defences against various infectious diseases may be highly influenced by complex interactions of environmental and host genetic factors e.g. MHC class I and II, also known as human leucocyte antigen (HLA). Toxocara spp. infections are associated with a polarized CD4⁺ Th2 response with high IgE levels and eosinophilia, mediated mainly by HLA class II molecules. Associations have been made between HLA class II and pathological severity and host genetic effects on exposure to infection. Recent research suggests Foxp3⁺ CD4⁺CD25⁺-expressing T regulatory (Treg) cells play a role in regulation of the immunopathology of granulomas in experimental toxocaral granulomatous hepatitis and in enhanced expression of TGF-β1, which is an important factor for the local survival and function of Treg observed during T. canis invasion in the mouse small intestine, liver, muscle, and brain. Since the potential susceptibility loci HLA class II molecules, are considered involved in the regulation of a Th2-dominant immunity which is highly controlled by Foxp3⁺ CD4⁺CD25⁺ Treg cells by stimulation through TGF-β1, which thus provides a beneficial environment to T. canis larvae but severe injuries to local organs. However, TGF-β1 variant Leu10Pro known to be involved in disease severity warrants further elucidation as this too may have a role in the severity of human toxocarosis. Exploration of TGF-β1 polymorphism, Foxp3⁺ CD4⁺CD25⁺ Treg cells, and MHC polymorphisms may allow insight into the contribution made by environmental and genetic factors in influencing disease syndrome type and severity in humans with toxocarosis.     

Chronic pneumonia in calves after experimental infection with Mycoplasma bovis strain 1067: Characterization of lung pathology,persistence of variable surface protein antigens and local immune response

Background

Mycoplasma bovis is associated with pneumonia in calves characterized by the development of chronic caseonecrotic lesions with the agent persisting within the lesion. The purposes of this study were to characterize the morphology of lung lesions, examine the presence of M. bovis variable surface protein (Vsp) antigens and study the local immune responses in calves after infection with M. bovis strain 1067.

Methods

Lung tissue samples from eight calves euthanased three weeks after experimental infection with M. bovis were examined by bacteriology and pathology. Lung lesions were evaluated by immunohistochemical (IHC) staining for wide spectrum cytokeratin and for M. bovis Vsp antigens and pMB67 antigen. IHC identification and quantitative evaluation of CD4⁺ and CD8⁺ T lymphocytes and immunoglobulin (IgG1, IgG2, IgM, IgA)-containing plasma cells was performed. Additionally, expression of major histocompatibility complex class II (MHC class II) was studied by IHC.

Results

Suppurative pneumonic lesions were found in all calves. In two calves with caseonecrotic pneumonia, necrotic foci were surrounded by epithelial cells resembling bronchial or bronchiolar epithelium. In all calves, M. bovis Vsp antigens were constantly present in the cytoplasm of macrophages and were also present extracellularly at the periphery of necrotic foci. There was a considerable increase in numbers of IgG1- and IgG2-positive plasma cells among which IgG1-containing plasma cells clearly predominated. Statistical evaluation of the numbers of CD4⁺ and CD8⁺ T cells, however, did not reveal statistically significant differences between inoculated and control calves. In M. bovis infected calves, hyperplasia of bronchus-associated lymphoid tissue (BALT) was characterized by strong MHC class II expression of lymphoid cells, but only few of the macrophages demarcating the caseonecrotic foci were positive for MHC class II.

Conclusions

The results from this study show that infection of calves with M. bovis results in various lung lesions including caseonecrotic pneumonia originating from bronchioli and bronchi. There is long-term persistence of M. bovis as demonstrated by bacteriology and immunohistochemistry for M. bovis antigens, i.e. Vsp antigens and pMB67. The persistence of the pathogen and its ability to evade the specific immune response may in part result from local downregulation of antigen presenting mechanisms and an ineffective humoral immune response with prevalence of IgG1 antibodies that, compared to IgG2 antibodies, are poor opsonins.     

Predicting the effect of fresh gas flow on tidal volume in volume-controlled mechanically ventilated dogs

ObjectivesTo determine if the tidal volume (V_T) delivered (V_TDEL) to canine patients being mechanically ventilated by a volume-controlled ventilator differed from the volume set on the ventilator (V_TSET) at three fresh gas flow (FGF) rates. To determine if V_TDEL could be accurately predicted by an FGF-based mathematical model.Study designProspective proof-of-concept study.AnimalsA total of 23 adult client-owned dogs undergoing elective orthopedic surgery.MethodsDogs were anesthetized and ventilated with a volume-controlled mechanical ventilator with constant respiratory rate (f_R) of 10 breaths minute^–1, inspiratory-to-expiratory ratio of 1:2 [fraction of inspiratory time (T_I) in one respiratory cycle (T_tot) 1:3], and V_TSET as body weight (kg) × 15 (mL kg^–1). V_TDEL was measured in 20 dogs at three FGF (500, 1000 and 4000 mL minute^–1). A mathematical model was used to calculate predicted volume (V_TPRED) for each animal at each FGF: V_TSET + {FGF × [(T_I/T_tot)/f_R]}. Linear repeated measures models were fit comparing V_TDEL to V_TSET and to V_TPRED by FGF.ResultsV_TDEL was significantly higher than V_TSET at every FGF (p < 0.05), and differences were larger at higher FGF (p < 0.001). There were no statistically significant differences between V_TDEL and V_TPRED at FGF rates of 500 and 4000 mL minute^–1 and, although the mean V_TDEL was statistically significantly higher than V_TPRED at FGF 1000 mL minute^–1 (p = 0.017), the mean difference of 9 mL was not clinically significant.Conclusions and clinical relevanceDogs on volume-controlled ventilators may be ventilated at a higher V_TDEL than intended depending on the FGF settings. Ventilation of small animals at high FGF could inadvertently induce pulmonary damage. A mathematical equation can be used to achieve a desired V_TDEL by adjusting V_TSET values based on FGF, f_R and T_I/T_tot.     

The γδ cells as marker of non-seroconverted cattle naturally infected with Mycobacterium avium subspecies paratuberculosis

Early diagnosis of MAP infection is a pressing need to enable efficient intervention with the spread of MAP infection in herds. Hence, study of lymphocyte subsets and their expressed adhesion molecules could contribute in defining a distinct diagnostic marker (or markers) at the subclinical period of the infection that could in turn facilitate the development of effective diagnostic approach. In accordance with this objective, milk and blood samples were collected from two groups of cattle naturally infected with MAP and their corresponding negative controls. Group (C) comprised 3-4 year-old ELISA negative/PCR positive-cattle that were considered as subclinical seronegative low shedder group (early stage). Group (A) included 6-8 year-old ELISA positive-cattle, which were considered as a clinical seropositive group (late stage). Flow cytometry of B cells, CD8⁺, CD4⁺ and γδ cells and the adhesion molecules CD44⁺, CD62L, LFA-1 and LPAM-1 indicated increase in CD4⁺ and B cells levels, with higher levels in blood than milk of group A, and significant expression of CD44⁺ in blood and milk and LPAM-1 in blood only. The CD8⁺ cells count in milk was higher than blood in the late stage. The peculiar feature of the early stage (group C) was the high level of γδ cells in the blood and milk, with tendency to express high level of CD62L. Compelling evidence could support the assumption that the dominant γδ cells at early stage of MAP infection could be of CD8CD2⁻WC+1⁺ phenotype. γδ cells appear as promising markers in defining early changes of MAP infection due to their important role in priming innate and cell mediated immunity. Possible utilization of these peculiar changes in the γδ cells level in the early diagnosis of MAP infection should be the subject of further research.     

Endostatin inhibits T-type Ca2+ channel current in guinea pig ventricular myocyte

Endostatin, a fragment of collagen XVIII, is known as an endogenous angiogenesis inhibitor, and its serum concentration increases in various cardiovascular diseases. T-type Ca²⁺ channel, low voltage-activated Ca²⁺ channel, is not expressed in adult ventricular myocytes. Re-expression of T-type Ca²⁺ channels in cardiac myocytes is thought to be involved in the development of cardiac hypertrophy. We examined the effects of endostatin on T-type Ca²⁺ channel current by whole-cell patch clamp technique in freshly isolated adult guinea pig ventricular myocytes, which exceptionally express T-type Ca²⁺ channels. Although endostatin 300 ng/ml had no effect on L-type Ca²⁺ current, it significantly inhibited T-type Ca²⁺ current. These data indicate that endostatin can be an endogenous inhibitor of T-type Ca²⁺ channels in the cardiac myocytes.     

荷斯坦牛红细胞Na+ -K+ -ATP酶的研究进展

作者对荷斯坦牛红细胞Na⁺ -K⁺ -ATP酶的分子结构和基本特征、分布、作用机制、调控机制、生理功能、影响因素及其与热应激的关系进行了综述。     

Involvement of the Ca2+ signaling pathway in osteoprotegerin inhibition of osteoclast differentiation and maturation

The purpose of this study was to determine whether the Ca²⁺ signaling pathway is involved in the ability of osteoprotegerin (OPG) to inhibit osteoclast differentiation and maturation. RAW264.7 cells were incubated with macrophage colony-stimulating factor (M-CSF) + receptor activator of nuclear factor-κB ligand (RANKL) to stimulate osteoclastogenesis and then treated with different concentrations of OPG, an inhibitor of osteoclast differentiation. The intracellular Ca²⁺ concentration [Ca²⁺]_i and phosphorylation of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) in the different treatment groups were measured by flow cytometry and Western blotting, respectively. The results confirmed that M-CSF + RANKL significantly increased [Ca²⁺]_i and CaMKII phosphorylation in osteoclasts (p < 0.01), and that these effects were subsequently decreased by OPG treatment. Exposure to specific inhibitors of the Ca²⁺ signaling pathway revealed that these changes varied between the different OPG treatment groups. Findings from the present study indicated that the Ca²⁺ signaling pathway is involved in both the regulation of osteoclastogenesis as well as inhibition of osteoclast differentiation and activation by OPG.     

Further characterization of diabetes mellitus and body weight loss in males of the congenic mouse strain DDD.Cg-Ay

The A^y allele at the agouti locus causes obesity and promotes linear growth in mice. However, body weight gain stops between 16 and 17 weeks after birth, and then, body weight decreases gradually in DDD.Cg-A^y male mice. Body weight loss is a consequence of diabetes mellitus, which is genetically controlled mainly by a quantitative trait locus (QTL) on chromosome 4. This study aimed to further characterize diabetes mellitus and body weight loss in DDD.Cg-A^y males. The number of β-cells was markedly reduced, and plasma insulin levels were very low in the DDD.Cg-A^y males. Using a backcross progeny of DDD × (B6 × DDD.Cg-A^y) F₁-A^y, we identified one significant QTL for plasma insulin levels on distal chromosome 4, which was coincidental with QTL for hyperglycemia and lower body weight. The DDD allele was associated with decreased plasma insulin levels. When the DDD.Cg-A^y males were housed under three different housing conditions [group housing (4 or 5 DDD.Cg-A^y and DDD males), individual housing (single DDD.Cg-A^y male) and single male housing with females (single DDD.Cg-A^y male with DDD.Cg-A^y or DDD females)], diabetes mellitus and body weight loss were most severely expressed in individually housed mice. Thus, the severity of diabetes and body weight loss in the DDD.Cg-A^y males was strongly influenced by the housing conditions. These results demonstrate that both genetic and nongenetic environmental factors are involved in the development of diabetes mellitus and body weight loss in the DDD.Cg-A^y males.     

Studies of Enteric Pathogens and γ-Globulin Levels of Neonatal Calves in Sweden

Viring, S., S.-O. Olsson, S. Alenius, U. Emanuelsson, S.-O. Jacobsson, B. Larsson, N. Linde and A. Uggla: Studies of enteric pathogens and γ-globulin levels of neonatal calves in Sweden. Acta vet. scand. 1993, 34, 271-279.– Faecal and blood samples were taken from 10-30% of calves, 36 hours to 14 days old, in 47 dairy herds in different regions of Sweden from September 1987 to October 1988 (Olsson et al 1993). Faecal samples from 279 calves were analysed for the presence of Escherichia coli (K99⁺), rotavirus and Cryptosporidium sp. Twenty (7.2%) of these samples were from diarrhoeic calves. An ELISA was developed and used for the rotavirus analysis. E. coli K99⁺ was detected in 11.5%, Cryptosporidium sp. in 6.1% and rotavirus in 5.4% of the faecal samples. The presence of rotavirus alone and the combination rotavirus and E. coli (K99⁺) was found to be associated with diarrhoea (p<0.001 and p<0.01 respectively).Blood samples from 327 calves were analysed for the level of total protein and γ-globulin. In 43 of these samples (13%) γ-globulin did not separate from the ß₂-region by electrophoresis. The mean total protein concentration was 53.6 g/1 in calves free from diarrhoea. The mean γ-globulin concentration, adjusted to 7 days age was 5.9 g/1. The 20 diarrhoeic calves had lower levels of both total protein and γ-globulin, compared with calves without diarrhoea, but the difference was not significant. One litre more of colostrum at the first feed increased the level of total protein of the calves’ sera by 1.4 g/1 (p = 0.05). Calves born between May and September had a 2.0 g/1 higher (p<0.001) serum concentration of γ-globulin than calves born between October and April.     

Dendrotoxin-�� suppresses tumor growth induced by human lung adenocarcinoma A549 cells in nude mice

Voltage-gated K⁺ (Kv) channels have been considered to be a regulator of membrane potential and neuronal excitability. Recently, accumulated evidence has indicated that several Kv channel subtypes contribute to the control of cell proliferation in various types of cells and are worth noting as potential emerging molecular targets of cancer therapy. In the present study, we investigated the effects of the Kv1.1-specific blocker, dendrotoxin-κ (DTX-κ), on tumor formation induced by the human lung adenocarcinoma cell line A549 in a xenograft model. Kv1.1 mRNA and protein was expressed in A549 cells and the blockade of Kv1.1 by DTX-κ, reduced tumor formation in nude mice. Furthermore, treatment with DTX-κ significantly increased protein expression of p21^Waf1/Cip1, p27^Kip1, and p15^INK4B and significantly decreased protein expression of cyclin D3 in tumor tissues compared to the control. These results suggest that DTX-κ has anti-tumor effects in A549 cells through the pathway governing G1-S transition.     

Effect of end-inspiratory pause on airway and physiological dead space in anesthetized horses

ObjectiveTo evaluate the impact of a 30% end-inspiratory pause (EIP) on alveolar tidal volume (V_Talv), airway (V_Daw) and physiological (V_Dphys) dead spaces in mechanically ventilated horses using volumetric capnography, and to evaluate the effect of EIP on carbon dioxide (CO₂) elimination per breath (Vco₂br^–1), PaCO_2, and the ratio of PaO₂-to-fractional inspired oxygen (PaO₂:FiO₂).Study designProspective research study.AnimalsA group of eight healthy research horses undergoing laparotomy.MethodsAnesthetized horses were mechanically ventilated as follows: 6 breaths minute^–1, tidal volume (V_T) 13 mL kg^–1, inspiratory-to-expiratory time ratio 1:2, positive end-expiratory pressure 5 cmH₂O and EIP 0%. Vco₂br^–1 and expired tidal volume (V_TE) of 10 consecutive breaths were recorded 30 minutes after induction, after adding 30% EIP and upon EIP removal to construct volumetric capnograms. A stabilization period of 15 minutes was allowed between phases. Data were analyzed using a mixed-effect linear model. Significance was set at p < 0.05.ResultsThe EIP decreased V_Daw from 6.6 (6.1–6.7) to 5.5 (5.3–6.1) mL kg^–1 (p < 0.001) and increased V_Talv from 7.7 ± 0.7 to 8.6 ± 0.6 mL kg^–1 (p = 0.002) without changing the V_TE. The V_Dphys to V_TE ratio decreased from 51.0% to 45.5% (p < 0.001) with EIP. The EIP also increased PaO₂:FiO₂ from 393.3 ± 160.7 to 450.5 ± 182.5 mmHg (52.5 ± 21.4 to 60.0 ± 24.3 kPa; p < 0.001) and Vco₂br^–1 from 0.49 (0.45–0.50) to 0.59 (0.45–0.61) mL kg^–1 (p = 0.008) without reducing PaCO₂.Conclusions and clinical relevanceThe EIP improved oxygenation and reduced V_Daw and V_Dphys, without reductions in PaCO₂. Future studies should evaluate the impact of different EIP in healthy and pathological equine populations under anesthesia.     

Physicochemical determinants of pH in pectoralis major of three strains of laying hens housed in conventional and furnished cages

1. Post-mortem decline in muscle pH has traditionally been attributed to glycogenolysis-induced lactate accumulation. However, muscle pH ([H⁺]) is controlled by complex physicochemical relationships encapsulated in the Stewart model of acid–base chemistry and is determined by three system-independent variables – strong ion difference ([SID]), total concentration of weak acids ([A_tot]) and partial pressure of CO₂ (PCO₂).

2. This study investigated these system-independent variables in post-mortem pectoralis major muscles of Shaver White, Lohmann Lite and Lohmann Brown laying hens housed in conventional cages (CC) or furnished cages (FC) and evaluated the model by comparing calculated [H⁺] with previously measured [H⁺] values.

3. The model accounted for 99.7% of the variation in muscle [H⁺]. Differences in [SID] accounted for most or all of the variations in [H⁺] between strains. Greater PCO₂ in FC was counteracted by greater sequestration of strong base cations. The results demonstrate the accuracy and utility of the Stewart model for investigating determinants of meat [H⁺].

4. The housing differences identified in this study suggested that hens housed in FC have improved muscle function and overall health due to the increased opportunity for movement. These findings support past studies showing improved animal welfare for hens housed in FC compared to CC. Therefore, the Stewart model has been identified as an accurate method to assess changes in the muscle at a cellular level that affect meat quality that also detect differences in the welfare status of the research subjects.     

Effect of the Y chromosome on testis weight in mice

We investigated the effect of the Y chromosome on testis weight in (B6.Cg-A^y × Y-consomic mouse strain) F₁ male mice. We obtained the following results: (1) Mice with the Mus musculus domesticus-type Y chromosome had significantly heavier testis than those with the M. m. musculus-type Y chromosome. (2) Variations in Usp9y and the number of CAG repeats in Sry were significantly associated with testes weight. The A^y allele was correlated with a reduced testis weight, and the extent of this reduction was significantly associated with a CAG repeat number polymorphism in Sry. These results suggest that Y chromosome genes not only influence testis weight but also modify the effect of the A^y allele in mediating this phenomenon.     

Amino acid substitutions in gyrA and parC associated with quinolone resistance in nalidixic acid-resistant Salmonella isolates

This study was undertaken to identify and characterize amino acid substitutions in gyrA and parC related with quinolone resistance of 27 nalidixic acid-resistant (Na^R) Salmonella isolates collected in poultry slaughterhouses in Korea. A total of 51 Salmonella isolates were detected from 44.8% (47/105) of the total samples from 15 poultry slaughterhouses examined, among which 27 (52.9%) Na^R isolates were detected while ciprofloxacin (Cip) resistance was not present in the isolates. These 27 Na^R isolates of DNA sequencing revealed that it contained three types of gyrA mutations in only D87 codon. Mutations in the D87 codon resulted in substitutions to G in most of the isolates, but D87Y and D87N exchanges were also detected. Although Cip resistance was absent, reduced susceptibility characterized by mutations in gyrA was apparent among Salmonella isolates from poultry slaughterhouses in Korea.     

The effect of dietary vitamin D supplementation on sodium-dependent phosphate uptake and expression of NaPi-IIb in the small intestine of weanling pigs

Two experiments were conducted to investigate the effects of 1,25(OH)₂D₃ to stimulate Na⁺-dependent phosphate uptake in Caco-2 cells, and the effects of dietary vitamin D supplementation to vitamin D-deficient nursery pigs on Na⁺-dependent nutrient uptake and mRNA expression of NaPi-IIb cotransporter and calbindin D9k in the jejunum. In Exp. 1, 250,000 Caco-2 cells were seeded on Costar 12 mm Snapwell inserts with a 0.40 µm polycarbonate filter and a seeding density of 0.25 × 10⁶ and studied at 15 d postconfluence. Cells were treated with 10 nM of either 1,25(OH)₂D₃ or vehicle for 48 h and then mounted in modified Ussing chambers for transepithelial measurements. In Exp. 2, pigs (n = 32) were removed from sows at 3 d of age, placed on a vitamin D-deficient milk replacer diet and housed in a room devoid of sunlight and UV light in the range of 280 to 300 nm. On day 28, serum 25(OH)D₃ concentrations were measured to verify low vitamin D status. Pigs (BW 10.10 ± 0.38 kg) were then individually housed day 28 postweaning and allotted to 1 of 2 dietary treatments. Dietary treatments consisted of corn-soybean-based diets with vitamin D supplementations of 0 or 1,500 IU/kg diet for 12 d. Blood samples were taken from the brachiocephalic vein on the initial (day 0) and final day (day 10, 11, or 12) of the study for analysis of serum 25(OH)D₃, P, and Ca. Pigs were euthanized and jejunal segments were harvested and used in modified Ussing chambers and for RNA isolation and subsequent quantitative RT-PCR analysis. In Exp. 1, treating Caco-2 cells with 10 nM 1,25(OH)₂D₃ resulted in a 52% increase (P < 0.005) in Na⁺-dependent phosphate uptake compared with cells treated with a vehicle. In Exp. 2, Na⁺-dependent phosphate and glucose transport did not differ (P > 0.10) among treatment groups. Additionally, NaPi-IIb and calbindin D9k mRNA expression were not different (P > 0.10) between treatment groups. No differences (P > 0.10) were detected in final serum P or 25(OH)D₃ concentrations between treatments. However, serum Ca linearly increased (P < 0.05) as the concentration of supplemental vitamin D increased in the diet. Overall, while 1,25(OH)₂D₃ stimulated Na⁺-dependent phosphate uptake in Caco-2 cells, supplementing diets with 1,500 IU/kg vitamin D₃ from cholecalciferol did not increase jejunal Na⁺-dependent phosphate uptake or NaPi-IIb mRNA expression over that of pigs fed diets with no supplemental cholecalciferol.