Desulfovibrio of the sheep rumen.

A sulfate-reducing bacterium has been isolated in pure culture from sheep rumen contents. Its properties agree in all respects tested with those ascribed to Desulfovibrio desulfuricans. The populations observed (about 10(8)/ml) are sufficient to account for published rates of ruminal sulfide production.     

Fermentation of methanol in the sheep rumen.

Sheep fed a hay-concentrate diet were adapted to pectin administration and ruminal infusion of methanol. Both treatments resulted in a strong increase in the rate of methanogenesis from methanol. Quantitative data show that methanol was exclusively converted into methane. Treatments did not influence ruminal volatile fatty acid percentages.     

Ontogeny of neurotensin in the fetal sheep.

Neurotensin (NT) is a regulatory peptide involved in the control of gastrointestinal function. We have used the chronically cannulated ovine fetus to examine the ontogeny of circulating NT-like immunoreactivity (NTLI) in the fetus and neonatal lamb. In addition the placental transfer and clearance of NT has been determined. NTLI in the ovine fetus circulates at adult concentrations during the third trimester of pregnancy and is of fetal origin. NTLI is present in the fetal ileum, the richest source of NT, at adult concentrations and in the same molecular profile as in the adult. There is a transient increase in circulating NTLI at birth, and a small NT response to feeding in the lamb. While fetal concentrations of plasma NTLI are generally the same as in the adult and originate from the fetus, the fetus clears infused NT(1-13) twice as rapidly as the nonpregnant adult indicating a higher fetal production of NT. Thus it appears that the mechanisms involved in the production and processing of NT are mature some weeks before birth.     

Ontogeny of steroidogenesis in the fetal sheep gonad.

The aim of this study was to determine 1) the time of onset and cellular localization of gene expression for steroidogenic factor-1 (SF-1), steroidogenic acute regulatory protein, 3beta-hydroxysteroid dehydrogenase/Delta(5),Delta(4) isomerase (3beta-HSD), and the cytochrome P450 enzymes for cholesterol side-chain cleavage (P450(scc)), 17alpha-hydroxylase (P450(17alphaOH)), and aromatase (P450(arom)) during gonadal development; and 2) the amount of progesterone, androstenedione, testosterone, and 17beta-estradiol present in the fetal sheep gonad. Fetuses were collected on Days 24, 26, 28, 30, 32, 35, 40, 55, and 75 of gestation, and gene expression was determined by in situ hybridization. The steroid content of gonads collected on Days 30, 35, 55, and 75 of gestation was determined by RIA. Developing gonads collected from both male and female fetuses were steroidogenically active around the time of morphological sexual differentiation. In the female, the steroidogenic cells were initially located at the boundary of the cortex and medulla but become increasingly restricted to the mesonephric-derived cell streams. In the male, once tubules were identifiable, steroidogenesis was restricted to the interstitial regions. Interestingly, expression of both SF-1 and 3beta-HSD was observed prior to morphological sexual differentiation. In addition, expression of both of these genes was more widespread than the other genes in both males and females.     

Deep freezing of sheep embryos.

Sheep embryos, collected 1-8 days after oestrus, were placed in Dulbecco's phosphate-buffered saline medium (PBS). After treatment, the viability of the embryos was tested by temporary transfer to ligated rabbit oviducts. In Exp. 1, Days 5-8 embryos survived for at least 15 min at 0 degrees C in the presence of 1-5 M-DMSO. In Exp. 2, 12/14 Days 5-8 embryos survived after being frozen in 1-5 M-DMSO at 0-3 degrees C/min to temperatures ranging between-15 degrees and -60 degrees C and then thawed at 12 degrees C/min. In Exp. 3, Days 5-8 embryos were frozen in 1-5 M-DMSO at 0-3 degrees C/min to below-65 degrees C before being transferred to liquid nitrogen (-196 degrees C), and stored for 12 hr to 1 month. The embryos were thawed at 3 degrees C/min, 12 degrees C/MIN or 360 degrees C/min and, after transfer to rabbit oviducts, 0/4, 10/36 and 1/4, respectively, developed normally. The 11 embryos which were considered normal when recovered from the rabbit oviducts plus 1 slightly retarded embryo were transferred to 7 recipient ewes. Four ewes subsequently lambed, producing 5 lambs. In addition, 8 embryos were transferred to 4 ewes directly after thawing. Three of these ewes subsequently lambed, producing 3 lambs.