Seasonal cycles in the blood plasma concentration of FSH, inhibin and testosterone, and testicular size in rams of wild, feral and domesticated breeds of sheep

Seasonal cycles in testicular activity in rams were monitored in groups of wild (mouflon), feral (Soay) and domesticated breeds of sheep (Shetland, Blackface, Herdwick, Norfolk, Wiltshire, Portland and Merino) living outdoors near Edinburgh (56 degrees N). The changes in the blood plasma concentrations of FSH, inhibin and testosterone, and the diameter of the testis were measured every half calendar month from 1 to 3 years of age. There were significant differences between breeds in the magnitude and timing of the seasonal reproductive cycle. In the mouflon rams, the seasonal changes were very pronounced with a 6-15-fold increase in the plasma concentrations of FSH, inhibin and testosterone from summer to autumn, and a late peak in testicular diameter in October. In the Soay rams and most of the domesticated breeds, the seasonal increase in the reproductive hormones occurred 1-2 months earlier with the peak in testicular size in September or October. In the two southern breeds (Portland and Merino), the early onset of testicular activity was more extreme with the seasonal maximum in August. In cross-bred rams, produced by mating Soay ewes (highly seasonal breed) with Portland or Merino rams (less seasonal breeds), there was a seasonal reproductive cycle that was intermediate compared to that of the parents. A comparison between all 11 breeds showed a significant correlation between the timing of the seasonal cycle in plasma FSH concentration and testicular diameter (time of peak FSH vs testis, r = 0.95). The overall results in the rams are consistent with a primary role of FSH in dictating the seasonal cycle in testicular size and the secretion of inhibin. The earlier seasonal onset in the testicular cycle in the southern breeds of domesticated sheep, and the differences from the wild type, are taken to represent the effects of genetic selection for a longer mating season.     

Improving multispecies rocky reef fish censuses by counting different groups of species using different procedures

Synopsis A number of factors can influence the accuracy and precision of underwater visual transect techniques. Among these are observer swimming speed and, during multispecies surveys, the effect of counting all fishes on estimates of particular species. This paper examines the effect of these factors on population estimates of inconspicuous fishes (defined as Type 1) in a temperate reef fish assemblage near Sydney, Australia. Counting Type 1 fishes with all others yielded significantly lower estimates of species richness and abundance than when counted alone. This suggests that multispecies surveys should be split into 2 or more counts, using a census procedure that is appropriate to the group of species cencused. Further, the effect of counting all other fishes on estimates of Type 1 fishes varied according to the relative abundance of the former: their effect was lowest when abundance of other fishes was lowest. There was a negative relationship between observer speed and estimated abundance for Type 1 fishes. Survey precision of Type 1 fishes was generally improved by surveying at slower observer speeds.     

Increased sensitivity of the rapid hydrophobic grid membrane filter enzyme-labeled antibody procedure for Escherichia coli O157 detection in foods and bovine feces

Several strains of Escherichia coli O157:H7 artificially inoculated into vegetables and dairy products were recovered on hydrophobic grid membrane filters and enumerated by an enzyme-labeled antibody assay. The mean of the recoveries from 12 fresh vegetables was 108.8%, whereas that from 10 dairy products was 93.2%. Modified tryptic soy broth at 43 degrees C with shaking at 100 rpm provided optimum recovery of the organism from meat, with a sensitivity of less than or equal to 1 CFU/g, which is 10 times more sensitive than direct plating. The method performed equally well with vegetable and dairy products. Tryptic soy broth, however, under the same conditions gave the best results for fecal samples. Of 22 asymptomatic dairy cattle, reported as having positive Brucella titers when assayed with polyclonal antibodies, eight were found to contain E. coli O157 in their feces as demonstrated by the enzyme-labeled antibody assay by using monoclonal antibodies. This finding may explain some of the false-positive Brucella tests.     

Long-term reproductive cycles in rams after pinealectomy or superior cervical ganglionectomy

Long-term cycles in diameter of the testes, colouration of the sexual skin and plasma concentrations of testosterone, FSH and prolactin were monitored in groups of pinealectomized (PINX), superior cervical ganglionectomized (SCGX), and control Soay rams living near Edinburgh (56 degrees N). In Exp. 1, PINX, SCGX and control rams were kept outside for 4 years, and well defined seasonal cycles in each of the reproductive parameters were evident in all 3 groups (e.g. testosterone cycle length assessed by sine-wave analysis: 12.08 +/- 0.17, 12.39 +/- 0.14 and 12.15 +/- 0.10 months for PINX, SCGX and control rams respectively). Qualitative differences, however, were apparent between the groups in the timing and amplitude of the reproductive cycle. The seasonal peak in reproductive function occurred from July to September in the PINX and SCGX rams, some 2 months earlier in the year than in controls, while the amplitude of the cycle was less marked in the PINX and SCGX rams. There were no significant differences between the experimental groups in the seasonal cycle in the plasma concentrations of prolactin. In Exp. 2, SCGX and control rams were kept indoors under an artificial environment with a 32-week light cycle and constant nutrition for 4 years. Compared to the controls, in which the reproductive changes were synchronized to the driving light cycle, the SCGX rams showed poorly defined reproductive cycles of lower amplitude and longer period (e.g. testosterone cycle length: 57.8 +/- 6.1 and 32.1 +/- 0.2 weeks for SCGX and control rams, respectively). There was evidence of a cycle in some of the reproductive parameters in the SCGX rams with a period close to 32 weeks during the second half of the study (e.g. testosterone cycle 32.4 +/- 0.8 weeks), which was taken to indicate social induction from the neighbouring control rams. In two further short-term experiments, SCGX rams showed a decline in testicular activity in response to receiving a restricted diet (60% of controls) and an increase in testosterone secretion in response to exposure to oestrous ewes. The overall results illustrate that PINX and SCGX rams can generate long-term synchronized cycles in pituitary and testicular activity. The animals are apparently unable to respond to changes in daylength due to the loss of the functional pineal gland but they remain competent to respond to other environmental cues such as changes in nutrition, temperature and social factors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hydration of oleic acid by a Selenomonas strain from the ovine rumen

J.A. HUDSON, C.A.M. MACKENZIE AND K.N. JOBLIN. 1996. A Selenomonas sp., isolated from the ovine rumen, was characterized with regard to its ability to hydrate oleic acid to 10-hydroxystearic acid. Hydration occurred only in stationary phase in a medium containing 0.1%, 0.5% (w/v) galactose or 0.5% (w/v) glucose, but not in a medium containing 1% galactose. Growth under a hydrogen headspace did not result in the production of stearic acid, the biohydrogenated product of oleic acid. Linoleic and linolenic acids (0.1% v/v) were not hydrated. It is concluded that the growing bacterium is unlikely to contribute to oleic acid hydration in the rumen.     

Pathogenesis of SIVmac251 after atraumatic inoculation of the rectal mucosa in rhesus monkeys

Intrarectal inoculation of rhesus monkeys with low doses of SIV_mac led to a prolonged clinical and virological latency that was not observed for high intrarectal doses or for intravenous inoculation. Animals infected intrarectally with low virus doses remained negative for serum antibody responses to SIV for at least one year even though they readily transferred SIV to naive recipients via transfusion of whole blood.     

Cardiovascular and metabolic responses to noradrenaline in men acclimatized to cold baths

The purpose of this study was to see whether artificial acclimatization to cold would reduce the pressor response to noradrenaline (NA) as natural acclimatization has been shown to do, and whether it would induce nonshivering thermogenesis. Three white men were infused with NA at four dosage levels between 0.038 and 0.300 g·kg^–1·min^–1 (2–23 g·min^–1), before and after artificial acclimatization to cold and again 4 months later when acclimatization had decayed. Acclimatization was induced by ten daily cold (15°Q baths of 30–60 min followed by rapid rewarming in hot (38–42°C) water, and was confirmed by tests of the subjects responses to whole-body cooling in air. Three control subjects also underwent the first and third tests. Acclimatization substantially reduced the pressor response to NA at 0.150 and 0.300 g·kg^–1·min^–1, confirming earlier findings by the same technique in naturally acclimatized men, and its decay increased this response to beyond its initial levels (P<0.05 for both changes). Acclimatization did not change the response to NA of heart rate, subjective impressions, skin temperature of finger and toe, pulmonary ventilation, or plasma free fatty acids and ketone bodies. At no time did NA increase oxygen consumption, or increase skin temperature or heat flow over reported sites of brown fat. These findings would seem to show that acclimatization to cold reduces sensitivity to the pressor effect of NA but does not induce nonshivering thermogenesis, and that the reduced sensitivity is replaced by a hypersensitivity to NA when acclimatization decays.     

Diagnostic dilatation and curettage: is it used appropriately?

OBJECTIVE--To determine patterns of use of dilatation and curettage in Britain as compared with those in the United States; to examine variations in utilisation rates within one regional health authority. DESIGN--Analysis of routinely collected hospital inpatient statistics. SETTING--Statistics for England, Scotland, and the United States; local statistics for Oxford region. SUBJECTS--All inpatient episodes in which dilatation and curettage was performed but excluding those related to pregnancy. RESULTS--Dilatation and curettage rates remained stable in Britain between 1977 and 1990, whereas in the United States they declined dramatically. In 1989-90 the rate was 71.1 per 10,000 women in England as compared with only 10.8 per 10,000 in America. In 1989, 6936 women underwent diagnostic dilatation and curettage in the Oxford region, making it the most common elective operation. A total of 2726 (39%) of these women were under 40. There was a more than twofold variation in usage of the procedure among district health authorities within the region and even greater variation in rates in women under 40. The proportion of patients treated as day cases in the district general hospitals ranged from 22% to 82%. CONCLUSIONS--Dilatation and curettage may frequently be used inappropriately. The considerable variations in usage of dilatation and curettage internationally and nationally indicate differences in clinical perception of its appropriateness. This makes it suitable for audit. In developing guidelines it will be important to agree on the most appropriate patients and the relative merits of alternative methods of endometrial sampling. Probably this could result in considerable cost savings at no risk and possibly some benefit to patients.     

ISOLATION AND PROPERTIES OF A CELL FROM LIVER CHARACTERIZED BY LIPID-RICH PARTICLES

A cell has been isolated from explanted rabbit liver which contains, during all phases of its growth in culture, hundreds of lipid-rich particles with a distinct limiting membrane. The cell grows logarithmically with a generation time of 19 to 20 hours and during mitosis the particles are distributed between the daughter cells. Associated with the particles is the high total lipid content of the rabbit liver cell as compared with a rat liver cell, which contains few, if any, lipid-rich particles. This difference in lipid content between the two cells is due primarily to an increase in the triglyceride fraction, in contradistinction to small differences in the polar lipid and sterol ester fractions. The lipid-rich particles have been isolated and found to contain 90 per cent triglyceride on a dry weight basis. The "genetic" factors responsible for the high concentration of lipid-rich particles and triglycerides in the rabbit liver cell require for their full expression one or more factors which are present in much higher effective concentrations in rabbit serum than in horse serum. The hypothesis is advanced that the lipid-rich particles represent a normal state of the non-structural cell lipid. A procedure is described for the quantitative isolation of the lipid of cultured cells.