Different stressors elicit different responses in the salivary biomarkers cortisol,haptoglobin, and chromogranin A in pigs

Most commonly, salivary cortisol is used in pig stress assessment, alternative salivary biomarkers are scarcely studied. Here, salivary cortisol and two alternative salivary biomarkers, haptoglobin and chromogranin A were measured in a pig stress study. Treatment pigs (n = 24) were exposed to mixing and feed deprivation, in two trials, and compared to untreated controls (n = 24). Haptoglobin differed for feed deprivation vs control. Other differences were only found within treatment. Treatment pigs had higher salivary cortisol concentrations on the mixing day (P < 0.05). Chromogranin A concentrations were increased on the day of refeeding (P < 0.05). Haptoglobin showed a similar pattern to chromogranin A. Overall correlations between the salivary biomarkers were positive. Cortisol and chromogranin A were moderately correlated (r = 0.49, P < 0.0001), correlations between other markers were weaker. The present results indicate that different types of stressors elicited different physiological stress responses in the pigs, and therefore including various salivary biomarkers in stress evaluation seems useful.     

Salivary testosterone measurements in growing pigs: validation of an automated chemiluminescent immunoassay and its possible use as an acute stress marker

This study aimed to validate the use of an automated chemiluminescent immunoassay analyser for salivary testosterone measurements in growing pigs and study how circadian pattern during daytime and stress can influence its values. The test method had intra- and inter-assay coefficient of variation lower than 10%. The method showed good linearity and recovery, and detection limits were low enough to detect salivary testosterone levels. No significant differences were observed in testosterone concentrations at different sampling time, and age and gender did not influence circadian pattern. In addition, this assay was used to quantify testosterone in two models of acute stress and, in both cases, significant increases (P < 0.01) in salivary testosterone were detected. Therefore, the automated assay system tested for porcine testosterone determinations would be suitable for its use in saliva samples and, furthermore, salivary testosterone levels could be used as a possible marker of acute stress in pigs.     

Analysis of mortality pattern among indigenous and upgraded pigs under subtropical hill agro climatic conditions in eastern Himalayas

Mortality records of indigenous and upgraded pigs, reared under subtropical hill agro climatic conditions, were collected for the period of 11 years (1993–2003), analyzed and the mortality pattern was correlated with genetic group, age of pigs, climatic factors and causes of death. Results revealed that there was significant (p < 0.05) difference in mortality between the indigenous (6.05%) and upgraded (5.64%) pigs. The mortality percentage was significantly (p < 0.05) higher in both genetic groups between 0 and 4 months of age compared to seven months and above age groups. Among different seasons, significantly (p < 0.05) higher mortality was observed during post-monsoon and winter compared to other seasons. The overall mortality percentage was 4.74, 5.25, 7.51 and 6.56 during pre-monsoon, monsoon, post-monsoon and winter seasons, respectively. Indigenous pigs recorded significantly (p < 0.05) higher pre-weaning mortality (14.26%) than the upgraded (9.58%) pigs. Among different causes, digestive disorders accounted to significantly (p < 0.05) higher mortality followed by miscellaneous and respiratory disorders. The study developed a linear regression model, which could fairly predict the mortality pattern based on the rainfall, relative humidity and temperature (R² = 58.3%).     

Effect of different time intervals after feeding on plasma metabolites in growing pigs: an UPLC‐MS‐based metabolomics study

A diet consumed by pigs provides the nutrients for the production of a large number of metabolites that, after first‐pass metabolism in the liver, circulate systemically where they may exert diverse physiologic influences on pigs. So far, little is known of how feeding elicits changes in metabolic profiles for growing pigs. This study investigated differences in plasma metabolites in growing pigs at several intervals after feeding using the technique of metabolomics. Ten barrows (22.5 ± 0.5 kg BW) were fed a corn‐soybean meal basal diet and were kept in metabolism crates for a period of 11 days. An indwelling catheter was inserted into the jugular vein of each pig before the experimental period. Plasmas before and 1, 4, and 8 hr after feeding were collected at day 11 and differential metabolites were determined using a metabolomics approach. Direct comparison at several intervals after feeding revealed differences in 14 compounds. Identified signatures were enriched in metabolic pathways related to linoleic acid metabolism, arginine and proline metabolism, lysine degradation, glycine, serine and threonine metabolism, and lysine biosynthesis. These results suggest that plasma metabolites of growing pigs after feeding were modulated through changes in linoleic acid metabolism and amino acid metabolism.     

Comparative study on the chemical composition of different bones/parts of bones in growing pigs differently supplied with inorganic phosphorus and phytase

From the veterinarian point of view, the precise assessment of the phosphorus (P) supply of pigs is of great interest, especially in cases of clinical disorders like ‘leg weakness’ or lameness when bone mineralisation may be disturbed. Thus, the question arises which bone is most suitable for diagnostic purposes and is reflecting changes in dietary P supply most clearly. Thirty-six growing pigs (BHZP db.Viktoria x Piétrain, about eleven weeks old, mean bw: 28.3 ± 3.44 kg) were allotted to three groups differently supplied with P by receiving a diet either supplemented with inorganic P (iP) and phytase (500 FTU/kg; controls/group C), without iP but phytase added (500 FTU/kg; group 1) or containing only endogenous phytase (group 2). The inclusion of iP resulted in total P contents in diets for group C of 4.76 and 4.23 g/kg as fed from 28 to 57 and >57 kg body weight (bw), respectively. In diets for group 1 and 2, the corresponding P contents were 3.08/2.72 g/kg as fed (group 1) and 3.08/2.88 g/kg as fed (group 2). On days 26, 47 and 82 of the dietary treatment, four pigs of each group were euthanised. Furthermore, four additional pigs were euthanised one day before starting the experiment. Standardised samples of the femur (distal part), tibia/fibula (proximal part) and os metatarsale III (MT III, in toto) were taken during dissection and submitted to chemical analysis. At all time points, pigs of group C had significantly higher ash contents in all types of bone samples compared to pigs from group 1 and 2. Relative differences between means of groups (C = 100%) were less for the ash content in MT III (reduction by up to −9.1%) compared to the distal femur and the proximal tibia/fibula (reduction by up to −23.2 resp. −22.7%). Variation coefficient (irrespective of group and time point) was lower for ash content in MT III (4.29%) compared to the distal femur and the proximal tibia/fibula (both: 11.8%). Under the conditions of this study, ash contents of the distal femur and the proximal tibia/fibula reflected the different P supply more pronounced indicating higher sensitivity compared to MT III.     

Identifying and measuring stakeholder preferences for disease prioritisation: A case study of the pig industry in Australia

We describe stakeholder preference modelling using a combination of new and recently developed techniques to elicit criterion weights to incorporate into a multi-criteria decision analysis framework to prioritise exotic diseases for the pig industry in Australia.     

Relationship between haptoglobin, serum amyloid A, and clinical status in a survey of dairy herds during a 6-month period

BACKGROUND: Haptoglobin and serum amyloid A are major acute phase proteins in cattle. Dairy cattle often develop pathologic conditions in the peripartum period; acute phase proteins may be useful in their diagnosis. OBJECTIVES: The purpose of this study was to compare the accuracy of serum haptoglobin (Hp) and serum amyloid A (SAA) concentrations with clinical health status for diagnosing disease during the peripartum period in dairy cattle. METHODS: Dairy cows from 4 herds were evaluated every 15 days over a 6-month period. Health status was determined by thorough clinical examination. Haptoglobin and SAA concentrations were measured in serum using validated methods and the results were classified as positive or negative based on defined cutoff points. Disease prevalence, sensitivity, and specificity were compared using clinical examination as the gold standard. RESULTS: A total of 1896 samples from 158 cows were analyzed. Significant increases in mean Hp and SAA concentrations were observed in the week following parturition in both primiparous and multiparous cows, although high interindividual variability was observed. Both Hp and SAA had low sensitivity but higher specificity in determining disease status compared with clinical examination. Increased concentrations of Hp and SAA were found in <10% of samples from clinically healthy cows, except in the week after parturition. CONCLUSIONS: Haptoglobin and serum amyloid A should be used with caution as markers of inflammation in the week after calving. Poor sensitivity in other postpartum periods could be related to the higher incidence of chronic (vs acute) inflammation. Haptoglobin may be appropriate for routine screening, but further work needs to be done to assess its value as an indicator of herd health.     

Comparison of respiratory function during TIVA and isoflurane anaesthesia in ponies Part II: breathing patterns and transdiaphragmatic pressure

ObjectiveTo compare breathing patterns and transdiaphragmatic pressure during total intravenous (TIVA) and isoflurane anaesthesia in ponies.Study designExperimental, cross–over study.AnimalsSix healthy ponies weighing 286 (233–388) ± 61 kg, age 13 (9–16) ± 3 years.MethodsFollowing premedication with romifidine [80 μg kg^?1 intravenously (IV)], general anaesthesia was induced with midazolam (0.06 mg kg^?1 IV) and ketamine (2.5 mg kg^?1 IV) and maintained with either isoflurane (Fe’Iso = 1.1%) (T-ISO) or an IV combination of romifidine (120 μg kg^?1 per hour), midazolam (0.09 mg kg^?1 hour^?1) and ketamine (3.3 mg kg^?1 hour^?1) (T-TIVA), while breathing 60% oxygen (FIO₂). The circumference changes of the rib cage (RC) and abdominal compartment (ABD) were recorded using respiratory ultrasonic plethysmography (RUP). Balloon tipped catheters were placed in the distal oesophagus and the stomach and maximal transdiaphragmatic pressure (P_{di max)} was calculated during Mueller's manoeuvre.ResultsThe breathing pattern T-ISO was more regular and respiratory rate significantly lower compared with T-TIVA. Ponies in T-TIVA showed regularly appearing sighs, which were never observed in T-ISO. Different contribution of the RC and ABD compartments to the breathing pattern was observed with a smaller participation of the RC to the total volume change during T-ISO. Transdiaphragmatic pressures (mean 13.7 ± SD 8.61 versus 23.4 ± 7.27 cmH₂O, p < 0.0001) were higher in T-TIVA compared to T-ISO. The sum of the RC and ABD circumferential changes was lower during T-TIVA compared to T-ISO (6.32 ± 4.42 versus 11.72 ± 4.38 units, p < 0.0001).Conclusion and clinical relevanceMarked differences in breathing pattern and transdiaphragmatic pressure exist during inhalation- and TIVA and these should be taken into account for clinical estimation of anaesthetic depth.     

Steroid Responsive Meningitis-Arteritis: A Prospective Study of Potential Disease Markers, Prednisolone Treatment, and Long-Term Outcome in 20 Dogs (2006–2008)

Background: Previous multidrug studies have identified the value of prednisolone in treating steroid responsive meningitis-arteritis (SRMA) and the potential value of acute phase proteins (APPs) and immunoglobulin A (IgA) in diagnosis and monitoring.
Hypothesis: (1) Prednisolone monotherapy is a successful immunosuppressive modality in the treatment of SRMA; (2) protein markers are useful in identifying the potential for relapse.
Animals: Twenty client-owned dogs with SRMA presented to the University of Glasgow Small Animal Hospital between May 2006 and May 2008.
Methods: A prospective, observational study: CBC, biochemistry, and cerebrospinal fluid (CSF) analyses were performed. C-reactive protein (CRP), serum amyloid-A, α-1-acid glycoprotein, and haptoglobin (Hp) were assessed in the serum. IgA concentrations were determined in the serum and CSF.
Results: Clinical resolution of SRMA was achieved in all 20 dogs. Serum CRP concentration remained increased at remission in 16/20 dogs whereas CSF cytology was within normal limits in 20/20 dogs. Serum APPs decreased significantly on treatment ( P < .05) except Hp, which remained unaltered. Serum and CSF IgA concentrations remained increased for the duration of treatment.
Conclusions and Clinical Importance: The prednisolone regimen presented was successful in treating SRMA without the need for additional drugs. Serum APPs are of use in the diagnosis and management of SRMA, particularly in relation to identifying relapse. Serum and CSF IgA concentrations remain increased throughout disease, aiding in diagnosis but not contributing to the management of SRMA.     

Risk for interspecies transmission of zoonotic pathogens during poultry processing and pork production in Peru: A qualitative study

Interspecies transmission of pathogens is an unfrequent but naturally occurring event and human activities may favour opportunities not previously reported. Reassortment of zoonotic pathogens like influenza A virus can result from these activities. Recently, swine and birds have played a central role as “mixing vessels” for epidemic and pandemic events related to strains like H1N1 and H5N1. Unsafe practices in poultry markets and swine farms can lead to interspecies transmission, favouring the emergence of novel strains. Thus, understanding practices that lead to interspecies interactions is crucial. This qualitative study aimed to evaluate poultry processing practices in formal and informal markets and the use of leftovers by swine farmers in three Peruvian cities: Lima (capital), Tumbes (coastal) and Tarapoto (jungle). We conducted 80 direct observations at formal and informal markets and interviewed 15 swine farmers. Processors slaughter and pluck chickens and vendors and/or processors eviscerate chickens. Food safety and hygiene practices were suboptimal or absent, although some heterogeneity was observed between cities and chicken vendors versus processors. Both vendors (76%) and processors (100%) sold the chicken viscera leftovers to swine farmers, representing the main source of chicken viscera for swine farms (53%). Swine farmers fed the chicken viscera to their swine. Chicken viscera cooking times varied widely and were insufficient in some cases. Non‐abattoired poultry leads to the sale of poultry leftovers to small‐scale swine farms, resulting in indirect but frequent interspecies contacts that can lead to interspecies transmission of bacterial pathogens or the reassortment of influenza A viruses. These interactions are exacerbated by suboptimal safety and hygiene conditions. People involved in these activities constitute an at‐risk population who could play a central role in preventing the transmission of pathogens between species. Educational interventions on hygiene and food safety practices will be important for reducing the risk of interspecies influenza transmission.     

Differential gene expression of Eph‐ephrin A1 and LEPR‐LEP with high or low number of embryos in pigs during implantation

The objective of this study was to ascertain whether mRNA and protein expressions of implantation‐related genes (erythropoietin‐producing hepatocellular receptor–ligand A1, Eph‐ephrin A1 and leptin receptor–leptin, LEPR‐LEP) differed between pigs with high and low number of embryos, and whether these differences in gene expression might affect embryo implantation. Experimental pig groups (n = 24) for high and low number of embryos were prepared by altering the number of eggs ovulated in pre‐pubertal gilts treated with 1.5 × (High) or 1.0 × (Low) PG600 ([400 IU PMSG + 200 IU hCG]/dose, AKZO‐NOBEL). Gilts expressing oestrus were artificially inseminated twice and maintained in breeding and gestation until the reproductive tract was collected on day 22 of pregnancy. At slaughter, the reproductive tracts from each pregnant gilt from each treatment were immediately processed to collect samples for RNA and protein analysis. Within each gilt, three conceptus points were sampled, one from each horn and then a random conceptus within the tract. At each conceptus point, endometrial attachment site, chorion–allantois and embryo were collected and immediately frozen in liquid nitrogen. Number of corpus luteum (CL) (35.4 vs. 12.6) and total embryo number (18.8 vs. 10.2) were greater in the high‐embryo compared to the low‐embryo group, respectively (p < .05). Real‐time qPCR results showed that Eph‐ephrin A1 mRNA expression was less in the high‐embryo (p < .05) compared to the low‐embryo group. In addition, Western blotting analysis indicated that Eph‐ephrin A1 and LEP protein expression at endometrial attachment site in high‐embryo was less (p < .05) compared to low‐embryo group. It was also noted that mRNA expression of Eph‐ephrin A1 and LEPR‐LEP was greater in pregnant than non‐pregnant gilts (p < .05). Moreover, mRNA expression of Eph‐ephrin A1 (p < .05) and LEPR‐LEP was greatest at endometrial attachment site among all three tissues. There was a positive correlation between expressions of Eph‐ephrin A1, LEPR‐LEP and embryo length with the correlation coefficient 0.31–0.59. For Eph‐ephrin A1, the highest correlation coefficient appeared between Eph A1 expression and normal embryo number, between ephrin A1 expression and embryo length. For LEPR‐LEP, the highest correlation coefficient appeared between LEPR‐LEP expression and ovary weight (0.79 for both, p < .05), followed by embryo length and weight. The results of this study suggest that low expression of Eph‐ephrin A1 and LEPR‐LEP is somehow related to increased embryo number during implantation and that endometrial attachment site might be the main target tissue of these gene products. Yet, the increased expression of Eph‐ephrin A1 and LEPR‐LEP appeared associated with increased embryo growth (length and weight) and ovary weight, Eph‐ephrin A1 and LEPR‐LEP might play roles in the regulation of embryo implantation in pigs.     

A recombinant chimera composed of repeat region RR1 of Mycoplasma hyopneumoniae adhesin with Pseudomonas exotoxin: in vivo evaluation of specific IgG response in mice and pigs

Using the binding and translocation domain of Pseudomonas exotoxin A [domain III deleted PE termed PE(ΔIII)] as a vehicle, this study characterized and evaluated a novel application of PE toxin in Mycoplasma hyopneumoniae adhesin used as an immunogen. PCR and sequence analysis revealed that 16 copies of AAKPV(E) in tandem repeat region 1 (RR1) of M. hyopneumoniae 97 kDa adhesion were successfully fused to the downstream of PE(ΔIII) to create a subunit vaccine, i.e. PE(ΔIII)-RR1. This chimeric protein, over-expressed in inclusion bodies of E. coli BL21(DE3)pLysS, was characterized by a monoclonal antibody (MAb) F2G5 prepared against RR1 of the 97 kDa adhesin and was readily purified. The data indicated that the epitope recognized by MAb F2G5 was located in the structure of PE(ΔIII)-RR1. Using ELISA and Western blot analyses, the specific IgG immune response against RR1 and whole adhesin in mice immunized with PE(ΔIII)-RR1 was found more marked than that in mice immunized with the M. hyopneumoniae whole cells. Similarly, PE(ΔIII)-RR1 also stimulated a remarkable IgG response against RR1 in pigs compared to that in pigs immunized with the conventional M. hyopneumoniae vaccine. The PE(ΔIII)-RR1 would be potentially useful for the future development of a M. hyopneumoniae adhesin vaccine.     

Detection and genetic characterization of porcine group A rotaviruses in asymptomatic pigs in smallholder farms in East Africa: Predominance of P[8] genotype resembling human strains

Viral enteritis is a serious problem accounting for deaths in neonatal animals and humans worldwide. The absence of surveillance programs and diagnostic laboratory facilities have resulted in a lack of data on rotavirus associated diarrheas in pigs in East Africa. Here we describe the incidence of group A rotavirus (RVA) infections in asymptomatic young pigs in East Africa. Of the 446 samples examined, 26.2% (117/446) were positive for RVA. More nursing piglets (78.7%) shed RVA than weaned (32.9%) and grower (5.8%) pigs. RVA incidence was higher in pigs that were either housed_free-range (77.8%) or tethered_free-range (29.0%) than those that were free-range or housed or housed-tethered pigs. The farms with larger herd size (>10 pigs) had higher RVA prevalence (56.5%) than farms with smaller herd size (24.1–29.7%). This study revealed that age, management system and pig density significantly (p < 0.01) influenced the incidence of RVA infections, with housed_free-range management system and larger herd size showing higher risks for RVA infection. Partial (811–1604 nt region) sequence of the VP4 gene of selected positive samples revealed that different genotypes (P[6], P[8] and P[13]) are circulating in the study area with P[8] being predominant. The P[6] strain shared nucleotide (nt) and amino acid (aa) sequence identity of 84.4–91.3% and 95.1–96.9%, respectively, with known porcine and human P[6] strains. The P[8] strains shared high nt and aa sequence identity with known human P[8] strains ranging from 95.6–100% to 92–100%, respectively. The P[13] strains shared nt and aa sequence identity of 83.6–91.7% and 89.3–96.4%, respectively, only with known porcine P[13] strains. No P[8] strains yielded RNA of sufficient quality/quantity for full genome sequencing. However analysis of the full genome constellation of the P[6], two P[13] and one untypeable strains revealed that the P[6] strain (Ke-003-5) genome constellation was G26-P[6]-I5-R1-C1-M1-A8-N1-T1-E1-H1, P[13] strains (Ug-049 and Ug-453) had G5-P[13]-I5-R1-C1-M1-A8-N1-T7-E1-H1 while the untypeable strain (Ug-218) had G5-P[?]-I5-R1-C1-M1-A8-N1-T1-E1-H? In conclusion, P[6] and P[8] genotypes detected were genetically closely related to human strains suggesting the possibility of interspecies transmission. Further studies are required to determine the role of RVA in swine enteric disease burden and to determine the genetic/antigenic heterogeneity of the circulating strains for development of accurate diagnostic tools and to implement appropriate prophylaxis programs.     

干旱胁迫下结缕草叶片抗坏血酸与相关生理指标变化的品种差异研究

通过盆栽试验,以日本结缕草与细叶结缕草为材料,研究了干旱胁迫下结缕草叶片AsA含量与相关生理指标的品种差异。结果表明,干旱胁迫下日本结缕草和细叶结缕草叶片中AsA含量与相关生理指标的动态变化规律基本相似,但品种间差异显著。干旱胁迫下2个品种的AsA含量和AsA/DHA均呈现先上升后下降的变化趋势,但日本结缕草下降的时间更早。干旱胁迫下叶片相对含水量、POD活性在2个品种中均呈下降趋势,但日本结缕草的下降趋势更明显,尤其在干旱胁迫后期。胁迫后日本结缕草叶绿素a与叶绿素b含量下降明显,而细叶结缕草变化不大。胁迫后两者的相对电导率和MDA含量均呈上升趋势,但日本结缕草增加的幅度更为显著。干旱胁迫后日本结缕草和细叶结缕草叶片Rubisco的含量均在第3天开始下降,胁迫后期日本结缕草Rubisco含量恢复到对照水平,而细叶结缕草Rubisco含量在胁迫后期显著高于对照。本研究结果表明,干旱胁迫下结缕草可以通过增加和维持叶片中AsA含量与POD活性来减缓Rubisco及叶绿素的降解,降低干旱胁迫对植株造成的氧化胁迫伤害程度,进而改善其抗旱能力。本研究结果进一步证实结缕草抗旱能力有品种差异,其中日本结缕草抗旱能力弱于细叶结缕草。     

Sarcoptic mange and production performance of swine: A review of the literature and studies of associations between mite infestation, growth rate and measures of mange severity in growing pigs

Cost-effective control of sarcoptic mange requires knowledge of the effects of the disease on production. This paper presents a critical review of the literature on the association between sarcoptic mange and reduced production performance of swine. One of the difficulties in interpreting inconsistent findings among studies is lack of information about the severity of disease, which is likely to vary considerably. Lack of standard methods and failure to quantify disease severity preclude meaningful interpretation of experimental results in commercial production. Three experiments with growing pigs were conducted to evaluate associations between sarcoptic mite infestation and growth rate, and to assess pruritic behaviour and mite-induced lesions at slaughter as indices of mange severity. Sarcoptic mange was associated with increased pruritic behaviour and the presence of papular dermatitis at slaughter. Pruritic behaviour decreased over time despite reinfestation and may be subject to numerous behavioural influences. Growth rate tended to be slower in mange infested pigs, but a significant effect of mange infestation on average daily gain was found in only one trial, in which the severity of skin lesions at slaughter was greatest. These observations suggest that the production effects of mange infestation of growing pigs are variable. Evaluating dermatitis lesions at slaughter may be an objective means for assessing the severity of mange infestation and for relating experimental results to commercial swine production.     

Variation in water disappearance,daily dose,and synovial fluid concentrations of tylvalosin and 3‐O‐acetyltylosin in commerical pigs during five day water medication with tylvalosin under field conditions

Tylvalosin (TVN) is a water soluble macrolide used in swine production to treat enteric, respiratory, and arthritic pathogens. There is limited data on its distribution to synovial fluid beyond gavage studies, which do not represent field conditions. This study measured water disappearance, TVN concentration in the medicated water, daily dose, and concentrations of TVN and 3‐O‐acetyltylosin (3AT) in the synovial fluid and plasma of treated pigs over the administration period. The study emphasized understanding variation in tissue TVN concentrations within the context of a field setting. Sixty finisher pigs were housed individually with individual waterers. Six pigs were randomly allocated to the following time points for sample collection: 0, 48, 60, 72, 84, 96, 102, 108, 114, and 120 hr on medication. TVN was administered daily in the water for 5 days. Water disappearance and medicated water concentration were measured daily. At each time point, six pigs were euthanized and plasma and synovial fluid were collected for analysis. Median TVN synovial fluid concentrations ranged between <1 ng/ml (hour 0) to 3.6 ng/ml (hour 84). There was substantial variation between individual pigs for water disappearance (mean 4.36L and range 0–7.84). Median TVN water concentration was 59 ppm (range 38–75 ppm).     

东祁连山不同退化阶段高寒草甸群落结构与植物多样性特征研究

采用样方法对东祁连山地区不同退化程度高寒草甸植物群落进行了调查,对群落结构、物种组成和群落生产力进行了分析,并运用α多样性、β多样性等指标研究了其物种多样性变化.结果表明,1)研究样地内共有植物种13科27属40多种,从未退化-轻度退化-中度退化-重度退化-极度退化,不同退化演替阶段的优势种分别为线叶嵩草 禾草、线叶嵩草 珠芽蓼、珠芽蓼 线叶嵩草、珠芽蓼 杂类草、平车前 杂类草.2)随退化程度的加剧,草地总盖度降低,优良牧草生物量减少,而毒杂草的比例逐渐上升,草地质量下降;地上、地下生物量均明显降低,地上生物量远低于地下生物量,分布在各层的植物根量越来越少,地下根系具有浅层化特点.3)高寒草甸植物群落α多样性指数基本上与均匀度、丰富度指数呈正相关,与生态优势度指数呈负相关;群落的物种丰富度在中度退化阶段最高,但多样性指数和均匀度指数在重度退化阶段最高,群落多样性更多地受均匀度的影响.4)随退化程度的加剧,样方内微生境或资源异质性减小,样方间异质性增大,从而导致β多样性增加;各草地植物群落物种替代速率由大到小的顺序为重度退化-极度退化>未退化-轻度退化>中度退化-重度退化>轻度退化-中度退化.     

Effects of orexigenic peptides and leptin on melatonin secretion during different photoperiods in seasonal breeding ewes: an in vitro study

The pineal gland (PG) acts as a neuroendocrine transducer of daily and seasonal time through the nocturnal release of melatonin. Here, we examined the interaction of season, orexin, ghrelin, and leptin on melatonin secretion by pineal explants in short-term culture. Glands were collected after sunset from 12 ewes during long days (LD; April and May) and from an additional 12 ewes during short days (SD; October and November). Glands were transected sagittally into strips, with each equilibrated in 2.5 mL of Dulbecco's modified Eagle's medium for 60 min, followed by a 2-h incubation in control medium or medium containing orexin B (10 and 100 ng/mL), ghrelin (10 and 100 ng/mL), or 50 ng/mL of leptin. After a 3-h incubation, some PG explants treated previously with lower doses of orexin or ghrelin were challenged with 50 ng/mL of leptin and those treated with both doses of orexin were challenged with 300 nM of the β-agonist isoproterenol. One milliliter of medium was harvested and replaced from each well every 30 min. Treatment with the low dose of orexin during LD increased melatonin secretion about 110% (P<0.01); treatment with a high dose increased melatonin secretion about 47% (P<0.001). During the SD period, leptin stimulated (P < 0.05) melatonin secretion slightly compared with mean melatonin concentration in controls. However, together, orexin and leptin depressed (P<0.01) melatonin secretion. Both doses of ghrelin reduced (P < 0.01) melatonin concentration during the SD season compared with control culture. Addition of ghrelin and leptin to culture medium increased (P<0.01) melatonin concentration compared with ghrelin-treated culture and decreased melatonin concentration (P<0.01) compared with leptin-treated culture during SD. Isoproterenol stimulated (P<0.01) melatonin secretion compared with values observed during the pretreatment period. We conclude that orexigenic peptides (orexin B and ghrelin) and an anorectic peptide (leptin) affect PG directly. The responses of PG to those hormones depend on day length. Moreover, secretion of melatonin from the ovine PG is under an adrenergic regulation.