Normal lambs born following transfer of embryos by laparoscopy.
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Animals↗
Biomedical subjects
J J Robinson
Publications and source records attributed to J J Robinson.
Collection of embryos from ewes by laparoscopy.
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Animals↗
Correction of entropion in newborn lambs.
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Animals↗
Cystic hyperplasia of the gall bladder in breeding ewes.
Reproduction in Finnish Landrace X Polled Dorset Horn ewes was accompanied by thickening of the wall of the gall bladder. The thickening was caused by hypertrophy of the epithelium, the presence of cysts, proliferation of blood vessels, glands and fibrous tissue in the lamina propria and hypertrophy of smooth muscle. The changes appeared to be initiated during pregnancy but to persist in a modified and chronic form in post-parturient animals.
Animals↗
Structure of fumarate reductase on the cytoplasmic membrane of Escherichia coli.
The terminal electron transfer enzyme fumarate reductase has been shown to be composed of a membrane-extrinsic catalytic dimer of 69- and 27-kilodalton (kd) subunits and a membrane-intrinsic anchor portion of 15- and 13-kd subunits. We prepared inverted membrane vesicles from a strain carrying the frd operon on a multicopy plasmid. When grown anaerobically on fumarate-containing medium, the membranes of this strain are highly enriched in fumarate reductase. When negatively stained preparations of these vesicles were examined with an electron microscope, they appeared to be covered with knob-like structures about 4 nm in diameter attached to the membrane by short stalks. Treatment of the membranes with chymotrypsin destroyed the 69-kd subunit, leaving the 27-, 15-, and 13-kd subunits bound to the membrane; these membranes appeared to retain remnants of the structure. Treatment of the membranes with 6 M urea removed the 69- and 27-kd subunits, leaving the anchor polypeptides intact. These vesicles appeared smooth and structureless. A functional four-subunit enzyme and the knob-like structure could be reconstituted by the addition of soluble catalytic subunits to the urea-stripped membranes. In addition to the vesicular structures, we observed unusual tubular structures which were covered with a helical array of fumarate reductase knobs.
Cell Membrane↗
Ovulation rate in induced oestrous cycles of anoestrous ewes given bromocriptine.
The suppression of prolactin in anoestrous ewes by daily injections of bromocriptine reduced the average number of corpora lutea on Day 8 after induced oestrus from 2.8 to 1.6 (P less than 0.02). There was a significant correlation (r = 0.87, P less than 0.05) between the preovulatory peak values for prolactin and ovulation rate in treated but not in control ewes. Bromocriptine failed to prevent the ewes from returning to anoestrus after the induced oestrus.
Anestrus↗
Location and nucleotide sequence of frdB, the gene coding for the iron-sulphur protein subunit of the fumarate reductase of Escherichia coli.
The frdB gene, encoding the iron-sulphur protein subunit of fumarate reductase, has been located and its complete nucleotide sequence determined. The identity of the gene was confirmed by protein chemical studies and determination of the NH2-terminal sequence of the FrdB protein. The frdB gene is situated distal to and partially overlapped by frdA which codes for the flavoprotein subunit of the reductase. Its reading frame contains 244 codons and predicts a protein of Mr 27092. In composition, the FrdB protein is strikingly similar to the corresponding subunit of the related flavoenzyme, succinate dehydrogenase. Analysis of the protein's primary structure revealed several features characteristic of iron-sulphur proteins.
Base Sequence↗
Identification of membrane anchor polypeptides of Escherichia coli fumarate reductase.
Fumarate reductase of Escherichia coli has been shown to be a membrane-bound enzyme composed of a 69,000-dalton catalytic-flavin-containing subunit and a 27,000-dalton nonheme-iron-containing subunit. Using gene cloning and amplification techniques, we have observed two additional polypeptides encoded by the frd operon, with apparent molecular weights of 15,000 and 14,000, which are expressed when E. coli is grown anaerobically on glycerol plus fumarate. Expression of these two small polypeptides is necessary for the two large subunits to associate with the membrane. The four subunits remain associated in Triton X-100 extracts of the membrane, and a holoenzyme form of fumarate reductase containing one copy of each of the four polypeptides has been isolated. Unlike the well-characterized two-subunit form, the holoenzyme is not dependent on anions for activity and is not labile at alkaline pH. In these respects, it more closely resembles the membrane-bound activity.
Cell Membrane↗
Molecular properties of fumarate reductase isolated from the cytoplasmic membrane of Escherichia coli.
Fumarate reductase, purified from the cytoplasmic membrane of Escherichia coli, has been cross-linked with the bifunctional reagent dimethylsuberimidate and shown to exist as an alpha beta dimer of polypeptides of molecular weights 69,000 and 25,000 in a 1:1 molar ratio. The protein has an s20,w of 7.67S and a D20,w of 6.5 X 10(-7) cm2/s. The purified enzyme contained 4-5 mol of nonheme iron and 4-5 mol of acid labile sulfur while the visible absorption spectrum showed a broad peak between 400 and 470 nm owing to the presence of an Fe-S centre and 8 alpha[N-3]histidyl FAD. Fumarate reductase activity was readily inhibited by the sulfhydryl reagents 5,5'-dithiobis-(2-nitrobenzoic acid), p-chloromercuribenzoate, and iodoacetamide. Using 5,5'-dithiobis-(2-nitrobenzoic acid) sulfhydryl group modification was followed as a function of enzyme activity. A single cysteine residue was shown to be required for activity and this essential sulfhydryl group was located in the 69,000 dalton subunit. The amino acid composition of E. coli fumarate reductase was similar to the succinate dehydrogenases from beef heart mitochondrion and Rhodospirillum rubrum.
Amino Acids↗
The effects of anions on fumarate reductase isolated from the cytoplasmic membrane of Escherichia coli.
A broad range of anions was shown to stimulate the maximal velocity of purified fumarate reductase isolated from the cytoplasmic membrane of Escherichia coli, while leaving the Km for fumarate unaffected. Reducing agents potentiate the effects of anions on the activity, but have no effect by themselves. Thermal stability, conformation as monitored by circular dichroism and susceptibility to the thiol reagent 5,5'-dithiobis-(2-nitrobenzoic acid) are also altered by anions. The apparent Km for succinate in the reverse reaction (succinate dehydrogenase activity) varies as a function of anion concentration, but the maximal velocity is not affected. The membrane-bound activity is not stimulated by anions and its properties closely resemble those of the purified enzyme in the presence of anions. Thus it appears that anions alter the physical and chemical properties of fumarate reductase, so that it more closely resembles the membrane-bound form.
Anions↗
Radioactivity measurements of former military personnel exposed to weapon debris.
Sixteen former military personnel who were present at the "Smoky" atmospheric nuclear weapon test have been investigated for internal deposits of radioactivity. Whole-body and thorax gamma-ray measurements, thorax and skeletal actinide measurements, and urinalyses for plutonium-239 and strontium-90 indicated no evidence of radioactivity in excess of that found in the general population.
Adult↗
Energy requirements of ewes during late pregnancy and early lactation.
Recent estimates of the energy requirements of the pregnant ewe, based on either the amounts of food required to maintain 3-hydroxy-butyrate concentrations in plasma below 0.7 mmol per litre or to prevent the loss of energy from the ewe's body suggest that current recommended feeding standards would result in a fairly severe degree of undernutrition. There is now evidence to suggest that the efficiency of utilisation of metabolisable (ME) energy for fetal growth is positively related to the ME concentration of the diet. During early lactation ewes seldom achieve the high energy intakes (25 to 30 MJ of ME) necessary for the production of the milk (3.5 kg per day) required to achieve desirable total lamb growth rates of 600 to 700 g per day for twins. In this situation the provision of dietary protein supplements which in part escape degradation in the rumen enables the ewe to augment the energy deficit in its diet by utilising body fat.
Animal Feed↗
The effect of amphipaths on the flavin-linked aerobic glycerol-3-phosphate dehydrogenase from Escherichia coli.
When assayed by the phenazine methosulphate coupled 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) reduction assay, the flavin-linked aerobic glycerol-3-phosphate dehydrogenase from Escherichia coli strain 7 showed a marked loss of activity if depleted of detergent, and this activity could be reconstituted with amphipaths. However, enzyme activity, as measured by the ferricyanide reduction assay, showed no loss of activity upon detergent depletion. Cross-linking studies indicated that amphipath was not inducing any significant quaternary structural change in the enzyme. Flavin fluorescence titration experiments indicated a single type of binding site for glycerol 3-phosphate whose affinity was unaffected by the presence of amphipath; apparent Kd values of 19.5 and 17.1 mM were measured in the presence and absence of amphipath, respectively. The Michaelis-Menten constants for DL-glycerol 3-phosphate, as measured by the phenazine methosulphate coupled MTT and ferricyanide reduction assays in the presence of amphipath, were found to be 1.9 and 10.2 mM, respectively. Cupric ions were found to specifically inhibit the phenazine methosulphate coupled MTT reducing activity while zinc ions inhibited the ferricyanide reducing activity. Circular dichroic studies provided initial evidence for a conformation change in the presence of the nonionic detergent Brij 58 and this was substantiated by quenching of tryptophan fluorescence at concentrations of Brij 58 equivalent to those needed to stimulate activity. We conclude from these studies that amphipaths may specificity induce a phenazine methosulphate binding site thus permitting reduction of this electron acceptor.
Aerobiosis↗
Effects of season, lactation and plane of nutrition on the reproductive performance and associated plasma LH and progesterone profiles in hormonally treated ewes.
Two experiments were designed to determine the effects of duration of lactation and plane of nutrition on the reproductive performance of Finn x Dorset Horn ewes mated at a hormonally induced oestrus 9 weeks after lambing. In Exp. 1, ewes were mated on 4 December or 19 March and lactation was terminated at 35 or 15 days before mating or 7 or 35 days after mating. The fertility of ewes lactating at the time of mating was reduced, particularly in ewes mated in March. This was not attributable to differences between lactating and non-lactating ewes for the incidence of oestrus, ovulation rate, litter size or the pattern of LH production. Indirect evidence based on progesterone profiles and returns to service suggest that reproductive failure was due to failure of fertilization and to embryonic death. In Exp. 2 ewes were mated on 1 July or 15 October. Lactation was terminated 15 days before or 7 days after mating and the ewes in each group were subjected to a high or low plane nutrition. Lactation depressed fertility in ewes mated in July but not in those mated in October. While the fertility of non-lactating ewes was independent of nutritional treatment, lactating ewes on a low plane and mated in July had a higher lambing rate than those on a high plane of nutrition. Nutritional effects on fertility appeared to be mediated through changes in milk production and reproductive failures were attributed to failure of fertilization and embryonic death. Seasonal and treatment effects on the incidence of oestrus and on ovulation rates, litter sizes and LH production were small and of little importance.
Animal Nutritional Physiological Phenomena↗
Ovulation and embryo survival rates and plasma progesterone concentrations of prolific ewes treated with PMSG.
Finnish Landrace x Dorset Horn ewes of two flocks comprising 47 and 51 animals were mated to Suffolk rams at a synchronized oestrus on 9 December (Flock D) and 8 April (Flock A) after treatment with 500 i.u. PMSG. The ewes were slaughtered between 50 and 145 days of pregnancy. The mean +/- s.e.m. ovulation rates were 4.5 +/- 0.24 (Flock D) and 5.0 +/- 0.32 (Flock A) for ewes which conceived to the induced oestrus and the corresponding litter sizes were 2.8 +/- 0.15 and 2.8 +/- 0.18. Mean concentrations of progesterone in the peripheral plasma during pregnancy were higher for Flock D than for Flock A ewes both in early (P less than 0.001) and late (P less than 0.05) pregnancy. An increase in ovulation rate, up to 4 or 5, was associated with an increase in mean litter size. There was evidence that higher ovulation rates were counterproductive.
Animals↗
Effects of season, lactation and plane of nutrition on prolactin concentrations in ovine plasma and the role of prolactin in the control of ewe fertility.
Plasma prolactin concentrations during the first 2 months after lambing, at oestrus, and during early pregnancy were investigated in 2 experiments in which Finn x Dorset Horn ewes were mated at an induced oestrus approximately 9 weeks after lambing. Mean prolactin concentrations between lambing and mating were dependent on seasons, being greater than 260 ng/ml plasma in lactating ewes mated in July and less than 150 ng/ml in those mated in October. Within 8 days of weaning of the lambs at 50 days post partum values declined to 122 and 30 ng/ml respectively. Plane of nutrition had little effect on prolactin levels. Higher prolactin values were recorded during oestrus in ewes mated in March or July, the normal period of anoestrus, than in December, the normal breeding season, mean values being approximately 200 ng/ml and 35 ng/ml respectively. The mean increases in the concentrations of prolactin during oestrus were smaller in lactating than non-lactating ewes. It is suggested that these differences in prolactin levels may be responsible for the effects of season and lactation on ewe fertility.
Animal Nutritional Physiological Phenomena↗