Studies with Radioactive Endotoxin II. Clearance of 3H-Labelled Endotoxin from the Blood of Calves

The clearance of ³H-labelled Pseudomonas endotoxin from the blood was studied in a nontolerant and in an endotoxin tolerant state. Calves were rendered tolerant to the toxic effects of the endotoxin by four daily intravenous injections of endotoxin at the dose rate of 5 µg/kg body weight.

Clearance of ³H-endotoxin from the blood of nontolerant calves occurred more slowly than did clearance of ⁵¹Cr-endotoxin and was not significantly (P<0.05) affected by the development of tolerance. The lungs and liver were the major organs involved in the clearance of ³H-endotoxin from the blood of calves. Leukocytes and erythrocytes, but not platelets, were shown to participate in endotoxin clearance in calves. ³H₂O, the control substance used in calves, was not concentrated within any particular organ but rapidly equilibrated with total body water and was slowly excreted.

     

Changes in urinary and plasma oestrone sulphate concentrations after induction of foetal death in mares at 45 days of gestation

Foetal death was induced in 10 Standardbred mares at day 45 of gestation by injecting 20 to 45 ml of hypertonic (24% W/V) saline into the conceptus at surgery. Ten mares underwent sham treatment and acted as controls. Blood and urine samples were collected every other day between days 30 and 45 post ovulation and at 0, 3 and 6 h relative to the infusion of saline in the treated mares, or sham treatment in control mares. Blood and urine samples were then collected daily between days 46 and 55 post ovulation. Urine oestrone sulphate (E1S) concentrations, measured by radioimmunoassay, increased between day 34 and day 36 of gestation in treated and control groups. In mares in which foetal death was induced, urine E1S concentrations declined post-operatively and were significantly (p less than .05) lower than controls by day 50. In plasma, E1S concentrations showed a major increase between days 36 and 40 in both groups. This was followed by a rapid decline after treatment in saline-injected mares, so that by day 48 plasma E1S concentrations in treated mares were significantly (P less than .05) lower than the controls. The results show that urinary and plasma E1S concentrations rise rapidly during early pregnancy, and are associated with a viable foetus after day 45 of pregnancy.     

Reproductive performance of Thoroughbred mares on six commercial stud farms

The records of 1630 mare years from 6 Thoroughbred stud farms in south eastern Australia were analysed for the years 1981 to 1986. Overall pregnancy and foaling rates were 83.9% and 69.3%, respectively. When calculated per served oestrous cycle, pregnancy and foaling rates were 54.7% and 43.1%, respectively. Pregnancy and foaling rates were higher (P < 0.001) for mares 3 to 10 years of age than for older mares. There was no difference in the pregnancy rates of maiden, barren and foaling mares. The foaling rate was significantly higher (P < 0.001) in mares that became pregnant during the first served oestrous cycle (77.8%) than in mares that needed two served oestrous cycles to become pregnant (65.4%). Of all diagnosed pregnancies, 19.5% were not completed. Pregnancy loss was lower (P < 0.05) in maiden (12.4%) than in barren (19.7%) or foaling (20.9%) mares. Twins were diagnosed in 7.8% of all pregnancies. If one conceptus was lost without external interference, 84.1% of pregnancies went to term. If one conceptus was manually crushed, 55.9% of pregnancies were maintained. If prostaglandin was used to terminate twin pregnancies, 60% of mares so treated produced foals the following year.     

Compensatory increase in calcium extrusion activity of untreated lymphocytes from swine susceptible to malignant hyperthermia

We tested the hypothesis that lymphocytes from swine with susceptibility to malignant hyperthermia (MH) had calcium extrusion activity higher than unaffected swine. Cytoplasmic concentration of ionized calicum was determined by use of dual emission spectrofluorometry and measurement of the ratio of free to calcium-bound form of the fluorescent calcium dye indo-1. Net calcium accumulation and unidirectional calcium extrusion rate were dependent on intracellular calcium concentration. Calcium extrusion from calcium-loaded lymphocytes was monitored while calcium influx was inhibited by suspending the cells in calcium-free medium with a calcium chelator. Net calcium accumulation of untreated lymphocytes was monitored in calcium-replete medium. A novel method of calculation of ionized calcium was used. This method confirmed our previous findings of lower ionized calcium concentration (86 +/- 40 and 370 +/- 216 nmol/L; P less than 0.01) and slower rates of calcium accumulation 39 +/- 16 and 127 +/- 52 nmol/L/min) in untreated lymphocytes from MH-susceptible swine compared with controls. These changes were attributable to calcium extrusion activity two- to three-fold higher in lymphocytes of MH-susceptible swine (154 +/- 36 and 408 +/- 47 nmol/L/min at 175 nmol/L; 972 +/- 111 and 1,690 +/- 505 nmol/L/min at 425 nmol/L). These data were compatible with our model of higher calcium extrusion activity being a compensatory adaptation of MH-susceptible swine lymphocytes to their hypersensitivity to stimuli that increase cytoplasmic calcium concentration.     

Cyclical changes of vaginal cytology in the cat

Vaginal smears from seven cats were examined at two-day intervals for 32 days in order to describe the cyclical pattern of epithelial cells exfoliated throughout the stages of the estrus cycle. Vaginal epithelial cells were classified as parabasal, intermediate and superficial (nucleate and anucleate) cells, and their dimensions were measured for the purpose of definition. The percentages of the epithelial cell populations (i.e. Maturation Index) from Wright's stained smears, were determined at all stages of the estrus cycle. The Eosinophilic Index was estimated on Papanicolaou stained smears.Smears of cats in estrus were populated almost entirely with nucleate and anucleate superficial epithelial cells. Proestrus was characterized by intermediate epithelial cells with increasing eosinophilia, and rare neutrophils. Metestrus was associated with desquamation of intermediate and parabasal epithelial cells, neutrophils and debris. In the anestrus period, groups of intermediate cells and some parabasal epithelial cells were exfoliated.Two cats in the study did not cycle and exhibited anestrus. Of the five cats cycling, eight estrus periods were observed of two to five days duration. The cycles were of 15 to 17 days interval in three normal cats. Two cats did not show a second estrus within 30 days, and were subsequently found to have bacterial growth on the culture of vaginal swabs, however the presence of an initial ovular estrus cannot be ruled out. The rare presence of erythrocytes was associated with vaginal bacterial infections and discharge in two cats.     

In vitro bactericidal efficacy of equine polymorphonuclear leukocytes against Corynebacterium equi

Polymorphonuclear leukocytes from adult horses were separated from whole blood, using a 2-step Percoll gradient, and were tested for bactericidal function against Corynebacterium equi. Staphylococcus aureus, an organism against which equine neutrophils have proved efficacy, was a positive control. The percentage of uptake after a 15-minute preincubation of the neutrophils and bacteria in the presence of normal horse serum was also calculated. The results indicated that equine neutrophils effectively phagocytosed and killed C equi and S aureus. The percentage of uptake for S aureus (95% +/- 3%) was greater than that for C equi (85% +/- 6%) (P less than 0.001), but the bactericidal efficacy was equivalent. More than 90% of the ingested or attached bacteria were destroyed during the 3-hour incubation period (mean percentage of C equi killed = 96 +/- 2%; mean percentage of S aureus killed = 91 +/- 8%). These results indicated that a failure of bacterial killing by neutrophils is unlikely to be important in the pathogenesis of C equi pneumonia in the horse.     

In planta transient expression as a system for genetic and biochemical analyses of chlorophyll biosynthesis

Background  

Mg chelatase is a multi-subunit enzyme that catalyses the first committed step of chlorophyll biosynthesis. Studies in higher plants and algae indicate that the Mg chelatase reaction product, Mg-protoporphyrin IX plays an essential role in nuclear-plastid interactions. A number of Mg chelatase mutants have been isolated from higher plants, including semi-dominant alleles of ChlI, the gene encoding the I subunit of the enzyme. To investigate the function of higher plant CHLI, bacterial orthologues have been engineered to carry analogous amino acid substitutions to the higher plant mutations and the phenotypes examined through in vitro characterization of heterologously produced proteins. Here, we demonstrate the utility of a transient expression system in Nicotiana benthamiana for rapidly assaying mutant variants of the maize CHLI protein in vivo.     

Optimizing Electrical Activation of Porcine Oocytes by Adjusting Pre‐ and Post‐Activation Mannitol Exposure Times

Modifying electrical activation conditions have been used to improve in vitro embryo production and development in pigs. However, there is insufficient information about correlations of porcine embryo development with oocyte pre‐ and post‐activation conditions. The purpose of this study was to compare the developmental rates of porcine oocytes subjected to different mannitol exposure times, either pre‐ or post‐electrical activation, and to elucidate the reason for the optimal mannitol exposure time. Mannitol exposure times around activation were adjusted as 0, 1, 2 or 3 min. Blastocyst development were checked on day 7. Exposure of oocytes to mannitol for 1 or 2 min before electrical activation produced significantly higher blastocyst rates than exposure for 0 or 3 min. There was no significant difference in blastocyst rates when activated oocytes were exposed to mannitol for 0, 1, 2 or 3 min after electrical activation. While exposure of oocytes to mannitol for 1 min pre‐ and 3 min post‐activation showed significantly higher blastocyst development than 0 min pre‐ and 0 min post‐activation. It also showed higher maintenance of normal oocyte morphology than exposure for 0 min pre‐ and 0 min post‐activation. In conclusion, exposure of oocytes to mannitol for 1 min pre‐ and 3 min post‐activation seems to be optimal for producing higher in vitro blastocyst development of porcine parthenogenetic embryos. The higher blastocyst development is correlated with higher maintenance of normal morphology in oocytes exposed to mannitol for 1 min pre‐ and 3 min post‐activation.