No abstract

SUMMARYAn experiment was conducted at Toorak Research Station, Julia Creek, in semi-arid northern Australia (141° E, 21° S) during 1990 to determine the relationship between placental and fetal weight in sheep after placental growth had been restricted by chronic heat stress during mid-pregnancy. Placental and fetal weight were measured in single bearing ewes housed either in a thermoneutral environment throughout pregnancy, or in a heated room between the 30th and 80th days of pregnancy followed by a thermoneutral environment until the 140th day of pregnancy. The placental weight of the heat-treated ewes was lower than that of the control ewes at the 80th (P< 0·05) and 140th (P< 0·01) days of pregnancy. Fetal weight and dimensions did not differ significantly between control and heat-treated ewes at the 80th day of pregnancy, although fetal weight (P< 0·01) and fetal dimensions (P< 0·05) for the previously heat-treated ewes were lower than those for the control ewes at the 140th day of pregnancy. Placental and fetal weight at the 140th day of pregnancy were correlated (P< 0·05) with the rectal temperature of ewes measured at 08.00 and 16.30 h during the period of heat-treatment, but not with the change in rectal temperature between 08.00 and 16.30 h. It was concluded that restricted placental growth in heat-treated ewes retarded fetal growth during late pregnancy even in the absence of heat treatment, and it is suggested that selection of ewes which can maintain normal rectal temperatures during periods of heat stress would produce lambs of normal birthweight in a hot climate.

Seasonal changes in fleece parameters were studied in mature feral doe goats, known to produce commercial quantities of cashmere and housed in natural light (NL) or continuous light (CL).Circannual changes in volume growth rate (VGR) of cashmere in NL were asynchronous with those of hair, resulting in maxima in April and November respectively, indicating that follicle-specific mechanisms are controlling the rate of follicle activities.Cycles of cumulative length of cashmere and hair in NL were synchronous. Cashmere maxima of 64.0 and 62.3 mm occurred in June and July respectively for two consecutive years. Distinct circannual cycles of linear growth (period, 365 days) were evident. While exposure to CL initially reduced the cycle period, after 2 years an extended cycle period emerged; this may have been due to photodesensitization.In NL, cashmere fibre diameter minima occurred at June-July and February each year. Hair fibres underwent only one cycle of diameter change each year. The period of the cycles was reduced by CL.An annual cycle of cashmere brush end fibre formation was apparent in NL. This cycle was associated with the cessation of growth in June-July, and a subsidiary event occurred between December and March. Continuous light accelerated brush end formation.Cyclic fibre shedding produced a circannual rhythm in fleece composition with maximum cashmere: hair ratio (CHR) in April-May in non-breeding goats. The maximum CHR of 5.9: 1 in NL did not reach its potential, as illustrated by the follicle S:P ratio of 6.9:1 in the skin. This suggests an irreversible loss of cashmere fibres from the fleece following the cycle of brush end formation in February.The maximum mean length of cashmere and time of occurrence were similar in grazing and penned does, although grazing does were only sampled in 4 months of one year.

Nitric oxide (NO) or NO-generating compounds like sodium nitroprusside (SNP) increase cellular levels of cGMP and produce S-nitrosylation of glyceraldehyde-3-phosphate dehydrogenase [GAPDH; D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase (phosphorylating), EC 1.2.1.12]. In search of a reagent that could discriminate between these two effects, we used the sesquiterpene antibiotic koningic acid, which binds to GAPDH at the Cys-149 of the active site. Koningic acid inhibited basal and sodium nitroprusside-stimulated NAD-dependent covalent modification of purified rabbit muscle GAPDH in a dose-dependent manner. Furthermore, we tested the effect of koningic acid on human platelets. Approximately 90% of GAPDH is present in the cytosol of human platelets, and the exposure of platelet cytosol to koningic acid inhibited GAPDH activity, while the soluble guanylyl cyclase (basal and sodium nitroprusside-stimulated) activity remained unaltered. Pretreatment of intact platelets with koningic acid slowed the rate of aggregation induced by a sub ximal concentration of thrombin. In addition, the antibiotic also inhibited the cGMP increases triggered by SNP, S-nitroso-N-acetylpenicillamine (SNAP), and 3-morpholinosydnomidine (SIN-1) but failed to prevent an increase in cGMP caused by nitrosylated albumin. Under the same conditions, koningic acid also inhibited basal and SNP-SNAP-, and SIN-i-stimulated NAD-dependent modification ofGAPDH and its enzymatic activity. These results suggest that the mechanism of delivery of NO from SNP, SNAP, and SIN-1 to platelets may require the active form of GAPDH. When NO is delivered by nitrosylated albumin, active GAPDH was not necessary.

The normal distribution of red blood cell viability for ACD and CPD units stored for 21 days was studied. For ACD and CPD units, respectively (n=41,37), the means and standard deviations were as follows: 24‐hour survival, 75.7 + 6.2 and 79.4 + 6.4; early recovery, 91.6 + 3.6 and 94.1 + 3.5; t/2, 29.4 + 3.0 and 27.9 + 4.3. Early recovery and survival were significantly higher for CPD, but more important than the difference in mean survival is that by current standards of acceptability, the incidence of donors who will be deemed undesirable is approximately 6 per cent for CPD, as opposed to 20 per cent for ACD. Neither early recovery, 24‐hour survival, nor t/2 could be shown to correlate with pH, plasma potassium, plasma sodium, per cent hemolysis, and osmotic fragility. The mean and standard deviation of survival for 18 units of 28‐day‐old CPD blood was 70.7 + 11. Since the standard error was large, the frequency distribution could not be determined, and the number of units with survivals that would fall below the minimum standard could not be ascertained. Nevertheless, comparison with 21‐day old ACD did not show a significant difference in the mean survival, although the range observed was much wider. The results also point out the need for greater number of observations with increasing duration of storage for adequate appraisal of blood preservative solutions.