Pathogenesis of placentitis in the goat inoculated with Brucella abortus. II. Ultrastructural studies

Pregnant goats were inoculated intravenously or in uterine arteries with Brucella abortus, and tissues from the uterus and placenta were examined by electron microscopy. Identification of B. abortus in placentae was with antibody-coated colloidal gold. B. abortus was first seen in phagosomes of erythrophagocytic trophoblasts and in the rough endoplasmic reticulum of chorioallantoic trophoblasts. Subsequently, trophoblast necrosis and ulceration of chorioallantoic membranes were present. Coincidently, B. abortus was present in the lumen of placental capillaries. In late stages of infection, placental vasculitis was present, and placentomal trophoblasts were separated from maternal syncytial epithelium. In lesions with vasculitis, large numbers of B. abortus were in connective tissue of chorionic villi. Within the placentome, trophoblasts that lined chorionic villi contained no intracellular bacteria and were separated from B. abortus by intact basement membranes. These results suggest that bacteremic B. abortus is endocytosed by erythrophagocytic trophoblasts and that B. abortus replicates in the rough endoplasmic reticulum of chorioallantoic trophoblasts. Replication of brucellae in trophoblastic rough endoplasmic reticulum is unique; we believe that B. abortus may utilize endoplasmic reticulum for synthesis and glycosylation of bacterial membrane proteins or that B. abortus catabolizes trophoblast secretory proteins.     

Effect of sodium bicarbonate and sodium bentonite on digestion, solid and liquid flow, and ruminal fermentation characteristics of forage sorghum silage-based diets fed to steers

Six ruminally cannulated steers, five Holsteins and one Hereford (250 to 295 kg), were fed 84% forage sorghum silage plus 16% supplement or 50% forage sorghum silage plus concentrate and supplement diets containing either no addition (controls), 1% sodium bicarbonate (NaHCO3) or 2% sodium bentonite in a 2 X 3 factorial arrangement of treatments in a 6 X 6 Latin-square experiment with 3-wk periods. Sodium bicarbonate increased dry matter (DM) intake when concentrate was included, but neither compound affected intake of the 84% silage diet. Bentonite lowered DM, neutral detergent fiber (NDF), and acid detergent fiber (ADF) digestibilities, but NDF disappearance from nylon bags was unchanged. Ruminal pH, osmolality and L(+) and D(-) lactate were not affected by treatment. Both NaHCO3 and bentonite tended to lower ruminal NH3-N concentrations. Bentonite lowered the molar proportion of isobutyrate in ruminal fluid relative to controls, but proportions of other volatile fatty acids (VFA) and total VFA concentrations were unchanged. Neither NaHCO3 nor bentonite affected ruminal liquid or solid volumes, dilution rate constants or ruminal outflow rates. Markers overestimated volumes, but correction with measured volumes did not change interpretation of treatment effects. It was concluded that control diets had sufficiently high baseline values of pH, dilution rate and acetate proportion to preclude changes induced by either compound, especially at 1 or 2% of DM intake. An effect on palatibility through neutralization of silage acids may have been responsible for the intake response to NaHCO3.     

Tidal breathing flow-volume loop analysis for clinical assessment of airway obstruction in conscious dogs

Using a mask, pneumotachograph, and X-Y recorder, tidal breathing flow-volume loops (TBFVL) were evaluated in 33 healthy dogs and in 18 dogs with acquired obstructive respiratory tract disease. The loops were evaluated for qualitative shape, tidal volume (VT), respiratory rate, peak and midtidal inspiratory flow (PIF and IF50, respectively), peak and midtidal expiratory flow (PEF and EF50, respectively), inspiratory and expiratory flow at end expiratory volume plus 25% VT (IF25 and EF25, respectively), inspiratory time, and expiratory time. Indices of loop shape were developed by division of flow measurements (eg, PEF/PIF and IF50/IF25). Twenty healthy dogs had the same TBFVL (type 1). Typically, PEF occurred at the beginning of expiration, and PIF occurred toward the end of inspiration. Three other TBFVL types were identified in the remaining dogs. Mean coefficients of variation for TBFVL indices ranged from 7% to 18%. Dogs with a fixed-type upper airway obstruction (pharyngeal or laryngeal mass, n = 7) had TBFVL abnormalities, indicating inspiratory and expiratory phase flattening. Concavity or late expiratory phase flattening was detected in TBFVL from dogs with chronic bronchitis/tracheal collapse (n = 11). The TBFVL were easily evaluated in conscious dogs and were useful in the functional assessment of airway obstruction.     

Influence of calf removal on the serum luteinizing hormone response to naloxone in the postpartum beef cow

Twelve anestrous, postpartum beef cows were used to determine the effect of calf removal on the effect of naloxone on serum luteinizing hormone (LH) concentrations. On d 1, six cows were injected iv with saline and six with 200 mg naloxone dissolved in saline. Blood samples were taken at 15-min intervals for 2 h before and 2 h after naloxone or saline administration. At the beginning of blood sampling, calves were removed from three cows in each treatment. At 48 h after calf removal (d 3), all cows were injected iv with 200 mg naloxone and blood samples were collected as on d 1. On d 1, naloxone treatment increased (P less than .01) serum LH concentrations from 1.2 +/- .3 ng/ml at time 0 to 4.3 +/- .6 ng/ml and 4.7 +/- .8 ng/ml at 15 and 30 min, respectively. Injection of saline had no effect on serum LH concentrations. Forty-eight-hour calf removal increased (P less than .01) serum LH concentrations in five of six cows (1.7 +/- .8 vs 4.4 +/- 1.2 ng/ml). Naloxone treatment failed to increase serum LH concentrations in these cows. Injection of naloxone increased (P less than .01) serum LH concentrations in the one cow that did not exhibit an LH increase after calf removal and in six cows whose calves were not removed (1.4 +/- .2 vs 4.4 +/- .5 ng/ml). The present study provides additional evidence that endogenous opioids regulate LH in the postpartum beef cow. We hypothesize that suckling stimulates an opioid inhibition of LH secretion and removal of the suckling stimulus removes the opioid inhibitory tone.     

Congenital cardiac defects in calves

In a 14-year study of calves with cardiac defects, 36 had 78 congenital cardiac defects: ectopia cordia cervicalis (n = 10 defects), common aortic trunk (n = 3 defects), dextraposed aorta (n = 8 defects), duplicated major trunks (n = 1 defect), hypoplastic aorta (n = 2 defects), interventricular septal defect (n = 11), interatrial septal defect (n = 2), left ventricular hypoplasia (n = 10), patent ductus arteriosus (n = 5), patent foramen ovale (n = 5), right ventricular hypoplasia (n = 10), cor triloculare biatriatum (n = 1), endocardial fibroelastosis with calcification (n = 3), and valvular hematomas (n = 7). All septal defects were high in location and ranged from 5 to 35 mm in diameter. One calf with a septal defect also had bilateral microphthalmia.     

Effects of low and high calcium intake prepartum on calcium mobilization rate around parturition in dairy cows

Forty-one dairy cows were fed a low (LCa-13 g/d) and a high (HCa-83.5 g/d) calcium ration in the 8 weeks prior to parturition and the effect on the Ca mobilization rate around parturition was studied. Plasma Ca values were stable in the LCa group around parturition. In the older cows of the HCa group a very slight decrease in the mean plasma Ca was observed: 2.58 mmol/l at 12-36 h ante partum decreased to 2.38 mmol/l at parturition. Hypocalcaemia, which commonly occurs around parturition, did not occur in 40 of the cows. A subclinical hypocalcaemia (1.8 mmol/l) occurred in one cow (parity 10) from the HCa group. To assess the efficiency of Ca mobilization, a severe hypocalcaemia (1.0 mmol/l) with clinical signs was induced by means of Na2EDTA infusion (0.90 mmol/min), starting at 10 h post-partum. The older cows in the LCa group required more Na2EDTA than those in the HCa group. Higher urinary hydroxyproline excretion in the week before parturition in the LCa than in the HCa group suggested a higher bone turnover. Plasma PTH levels around parturition were not significantly different between the groups. The amount of colostrum milked out in the first 10 h post-partum did not influence Ca homeostasis around parturition. The results contradict those of many other experiments in which hypocalcaemia was observed in cows ingesting high levels of Ca. It is concluded that the restricted feed intake prepartum possibly had a favourable effect on Ca homeostasis.     

Crystalluria. Observations, interpretations, and misinterpretations

Crystalluria results from oversaturation of urine with crystallogenic substance. However, oversaturation may occur as a result of in vitro as well as in vivo events. The microscopic appearance of crystals only represents a tentative identification of their composition because variable conditions associated with their formation, growth, and dissolution may alter their appearance. Definitive identification is dependent on physical methods such as optical crystallography, x-ray diffraction, and electron microscopic analysis.     

Infectivity of Cryptosporidium sp isolated from wild mice for calves and mice

A study was conducted to determine the incidence of cryptosporidiosis in wild mice (Mus musculus) and the infectivity of oocysts from their feces for susceptible calves. The presence of oocysts and the duration of shedding of oocysts in the feces were evaluated in 115 wild mice. Approximately 30% of the mice shed Cryptosporidium sp oocysts, without evidence of clinical infection; recurrence of oocyst shedding was found in about 50% of the mice. Oocysts from the feces of naturally infected mice were infective for calves and mice. Calves began shedding oocysts at 7 days and shed oocysts for about 10 days. Nonfatal, clinical cryptosporidiosis developed in 7 infected calves. The mice began shedding oocysts at 6 days and shed oocysts for 12 days. Fatalities or clinical infection did not develop in 5 infected mice. The results indicated that Cryptosporidium-infected wild mice may be a source of cryptosporidiosis in susceptible calves.     

Evaluation by scoring and computerized morphometry of lesions of early Mycoplasma pulmonis infection and ammonia exposure in F344/N rats

To evaluate lesions of ammonia exposure and Mycoplasma pulmonis infection in gnotobiotic F344/N rats, groups of rats were inoculated with M. pulmonis, exposed to 76 micrograms/liter (100 parts per million) ammonia, or both, or served as controls. Six rats from each group were killed 3, 5, 7, and 9 days after inoculation and their respiratory organs prepared for histologic examination. Lesions were assessed by subjective scoring and computerized morphometry, and results obtained by the two methods were compared to assess agreement of results. Lesions were limited to the nasal passages. Ammonia exposure resulted in hyperplastic and degenerative changes in the anterior nasal epithelium. Lesions of mycoplasmosis were more severe in ammonia-exposed than unexposed rats, but qualitative differences in lesions were not apparent. Results of the two methods agreed in assessment of submucosal inflammatory cell accumulation. Epithelial lesions were difficult to evaluate by both methods in infected, ammonia-exposed rats. In evaluation of lesions of ammonia exposure alone, agreement was adequate. Both methods indicated that exudates were significantly greater in ammonia-exposed infected rats than in non-exposed infected rats. Thus, scoring and morphometry provided similar assessments of differences in lesion severity among the treatment groups.