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Biomedical subjects

C R Thomas

Publications and source records attributed to C R Thomas.

At least 127 records · Page 7Linked to original sources
PubMed1983

A novel method for the isolation of calsequestrin from porcine skeletal muscle sarcoplasmic reticulum.

Calsequestrin was selectively solubilized from porcine skeletal muscle sarcoplasmic reticulum by incubation with HgCl2 and deoxycholate. While deoxycholate alone caused non-specific solubilization of calsequestrin and other extrinsic proteins, HgCl2 alone failed to extract significant amounts of extrinsic proteins. The simultaneous presence of HgCl2 and deoxycholate was necessary for the selective and quantitative solubilization of calsequestrin. Following DEAE-Sephadex ion-exchange chromatography of the HgCl2/ deoxycholate-solubilized material, calsequestrin was obtained in nearly homogeneous form. Porcine calsequestrin was similar to rabbit calsequestrin with respect to its amino acid composition and apparent molecular weight as determined by SDS-polyacrylamide gel electrophoresis. The calcium-binding capacity of porcine calsequestrin was 400 nmol of Ca2+ bound/mg protein, lower than the values reported for the rabbit protein.

Amino Acids↗
PubMed1983

Occurrence of wax esters in the tissues of the orange roughly (Hoplostethus atlanticus).

The skin, skeleton and a fat-filled swim bladder of the orange roughly (Hoplostethus atlanticus) each contained greater than 20% lipid by wet weight which was almost entirely wax esters. These had carbon numbers of 34-40 consistent with the major fatty acid being 18:1 and the major fatty alcohols being 16:0, 18:1, 20:1 and 22:1. In contrast, the liver and the roe contained appreciable quantities of glycerolipids with 18:1 and 22:6 as the major fatty acids.

Alcohols↗
PubMed1983

Conversion of thyroxine to 3,3',5'-triiodothyronine in the guinea pig placenta: in vivo studies.

Studies of placental inner-ring deiodination of T4 were carried out in pregnant guinea pigs, by in situ placental perfusion. When [131I]T4 and [125I]rT3 were administered to the mother, the ratio of fetal side to maternal side [131I]rT3 was more than 10 times greater than the corresponding ratio for [125I]rT3. When radiolabeled T4 was supplied to the fetal side of the placenta in perfusion fluid, and the perfusate recycled through the placental circuit, there was a progressive increase in labeled rT3 concentration in the perfusate. These results indicate that the guinea pig placenta actively deiodinates both maternal and fetal T4 in the inner ring in vivo. We found evidence of very little outer ring deiodination of either T4 or rT3. The quantitative contribution of placental deiodination of maternal T4 to circulating rT3 in the fetus appears to be small; however, placental deiodination of fetal T4 (about 0.5 nmol/kg fetal BW X day) could contribute significantly to fetal rT3 levels. Our observations are consistent with the hypothesis that placental inner-ring deiodination of T4 plays a part in the regulation of fetal iodothyronine metabolism.

Animals↗
PubMed1983

Arginine8 vasopressin potentiates the beta-endorphin-releasing activity of ovine corticotropin-releasing factor (oCRF) in vitro.

The ability of arginine8 vasopressin (AVP) to potentiate the beta-endorphin-releasing activity of synthetic ovine corticotropin releasing factor (oCRF) was examined using an anterior-pituitary quarter assay. Both AVP and oCRF stimulated the release of beta-endorphin immunoreactivity (beta-END-I) in a dose-dependent manner, with AVP being approximately 10 times less effective than oCRF. Marked potentiation of beta-END-I release was observed when pituitary quarters were incubated in the presence of a combination of 0.5 nM oCRF and 1.0 nM AVP. Further potentiation was not observed when the higher doses of 1.0 nM oCRF and 2.0 nM AVP were tested in combination; however, maximal beta-END-I release may have been attained by the addition of 1.0 nM oCRF alone. These results suggest that AVP may play a role in the mediation of beta-endorphin release from the adenohypophysis.

Animals↗
PubMed1983

Placental transfer of free fatty acids: factors affecting transfer across the guinea-pig placenta.

Using an in situ perfusion of the fetal side of the guinea-pig placenta the quantitative effects of changes in the perfusate flow rate and albumin concentration, and of changes in the transplacental free fatty acid (FFA) concentration gradient on FFA transfer across the placenta were investigated. Unidirectional transfer from mother to perfusate was assessed by the transfer of [14C]palmitic acid given as a constant infusion to the mother. The results of bidirectional FFA flux were assessed by measuring total unlabelled FFA accumulated by the perfusate during a single passage through the placenta. In 4 animals a factorial experiment was performed using perfusate in which the albumin concentration was changed from 1 to 3g/dl, whilst the flow was maintained at either 1 or 3 ml/min. A change from 1 to 3g/dl albumin averaged over both flow rates caused a significant increase in labelled palmitate, and unlabelled net FFA transfer, both for each ml of perfusuate (P less than 0.05, P less than 0.001) and for each minute of perfusion (P less than 0.005, P less than 0.001, respectively). A change from 1 to 3 ml/min flow rate averaged over both albumin concentrations caused a significant (P less than 0.001) decrease in labelled palmitate but no change in unlabelled FFA transfer per ml, but caused significant increases in labelled and unlabelled (P less than 0.05, P less than 0.001) FFA transfer per minute. From the results of these experiments and 32 more non-factorial experiments it was found that, whilst maternal and perfusate FFA concentrations were in the normal range, maternal plasma FFA levels significantly correlated (P less than 0.01) with net FFA transfer to the perfusate. When maternal plasma FFA levels became elevated then this relationship broke down. Inflowing perfusate FFA levels significantly (P less than 0.001) negatively correlated with net transfer, which changed direction and resulted in FFA transfer from perfusate to maternal blood when inflowing perfusate levels exceeded 1.7 microM/ml. It was concluded that the increases reported in fetal plasma albumin and flow rate as gestation advances enable the fetus to obtain increasing amounts of circulating maternal lipid. If this lipid is not extracted by the fetus then the reduction in the transplacental gradient will reduce net fat transfer to the fetus.

Animals↗
PubMed1982

The clearance and placental transfer of free fatty acids and triglycerides in the pregnant guinea-pig.

Bolus injections of [14C]palmitic acid and endogenously prepared very low density lipoprotein (VLDL) were given to 12 guinea-pigs in late gestation in whom the fetal side of the placenta was perfused in situ. Disappearance of [14C] palmitate in the mother was rapid, with a half life of 2.4 min. The [14C] palmitic acid which crossed the placenta into the perfusate disappeared in parallel with the maternal label but with a delay time of 1.6 min. Following injection of [14C] labelled very low density lipoprotein maternal plasma [14C] triglyceride declined rapidly (half life of 0.7 to 9.8 min) and gave rise to [14C] free fatty acids in the plasma. These fatty acids disappeared at a slower rate (half life of 13.5 min) than found following [14C]palmitate bolus. No [14C] triglyceride appeared to cross the placenta, but triglyceride derived free fatty acids did with a delay time of 9.4 min. In experiments performed after 55 days gestation quantities of [14C] free fatty acids were higher in the perfusate than in maternal plasma implying hydrolysis of triglyceride within the placenta. It is concluded that maternal triglyceride may make a considerable contribution to fetal lipids which increases with gestational age.

Animals↗
PubMed1981

Immunohistochemical demonstration of a testicular substance related to luteinizing hormone-releasing hormone.

A substance related to luteinizing hormone-releasing hormone was demonstrated, by immunohistochemical procedures, in the cytoplasm of interstitial cells within the rat testes. In many seminiferous tubules, nuclei of spermatogonial cells were also immunopositive. Both cytoplasmic and nuclear fractions of testicular homogenates contain immunoreactive compounds, and this report identifies which cell types contain this substance. The localization of a peptide hormone within the nucleus of a target cell population may indicate its mode of action.

Animals↗
PubMed1981

In vivo and in vitro release of ACTH by synthetic CRF.

The 41-residue corticotropin releasing factor (CRF) was synthesized by the solid phase method. The synthetic CRF and arginine vasopressin (AVP) were examined for ACTH releasing activity and effects on the release of 5 other pituitary hormones in vivo and in vitro. Injection of the CRF into pharmacologically blocked rats increased plasma corticosterone levels in a dose-related manner. The minimum effective dose was 1.6 x 10(-12) mol/100 g body weight. CRF also significantly stimulated release of ACTH-like immunoreactivity in a dose-related manner from rat pituitary quarters beginning at a concentration of 10(-9) M. AVP, a peptide known to have CRF activity, exhibited slightly lower corticotropin releasing activity than the CRF at equimolar dose levels. Secretion of other pituitary hormones was not appreciably altered by either the CRF or AVP.

Adrenocorticotropic Hormone↗
PubMed1980

Placental lactogen in the goat in relation to stage of gestation, number of fetuses, metabolites, progesterone and time of day.

Placental lactogen has been measured in goats throughout pregnancy by radioreceptor assay of prolactin-like activity. Lactogenic activity, which is not prolactin, increased from less than 5 nmol/l in week 8 to 27 nmol/l by week 16. There was no further change until term. Plateau concentrations (week 16 to term) were highest in animals carrying triplets, 49.5 nmol/l. There were marked functuations in placental lactogen over a 24 h period. These short-term fluctuations were not related to changes in glucose, non-esterified fatty acids or, in two animals, progesterone. However, there was a negative correlation between mean concentrations of placental lactogen and glucose in plasma of 20 goats sampled over a 24 h period between weeks 15 and 20 of gestation. There was no difference in placental lactogen concentration from week 16 to term between goats in their first and second pregnancies although the normal period of increase in placental lactogen was delayed by some 3 weeks in goats in their second pregnancy. In hemimastectomized goats, hypophysectomy on day 60 did not affect placental lactogen but daily treatment with bromocriptine (5 mg/day) from day 60 to day 120 blocked the normal rise in concentration.

Animals↗
PubMed1979

Action of shear on enzymes: studies with alcohol dehydrogenase.

Yeast alcohol dehydrogenase (ADH) solutions (approximately 1 mg/ml, pH 7) were sheared in a coaxial cylindrical viscometer. This was fitted with a lid sealing the contents from the atmosphere and preventing evaporation. At 30 degrees C after a total of 5 hr intermittent shearing at 683 sec-1 no losses of activity were observed. No losses were found after 5 hr continuous shearing and in a no-shear control. At 40 degrees C and 683 sec-1 there were only small activity losses in 5 hr. Shearing at 3440 sec-1 no measurable losses of activity were found with a 1.03 mg/ml solution in 5 hr at 30 degrees C, a 1.03 mg/ml solution in 8 hr at 5 degrees C, and with a 3.89 mg/ml solution in 3 hr at 5 degrees C. In all these cases, however, a white precipitate formed that was not observed in zero shear control experiments. The sheared 3.89 mg/ml solution was clarified by centrifugation. It was shown that there were no ADH aggregates in the supernatant and that the precipitate was less than 2% of the original protein. At 30 degrees C under adverse pH conditions (pH 8.8) there was no significant difference in activity losses of an approximately 1 mg/ml solution sheared at 65 and 744 sec-1. An approximately 0.5 mg/ml ADH solution, pH 7, was agitated in a small reactor with no free air-liquid interface. Peak shear rates near the impeller were estimated to be about 9000 sec-1. Only a small decrease in specific activity was observed until over 15 hr total running at 5 degrees C.

Alcohol Oxidoreductases↗
PubMed1979

Effect of number of young born (litter size) on milk yield of goats: role for placental lactogen.

Relationships of number of fetuses, placental mass, and lactogenic activity of plasma to development of mammary gland during pregnancy and of litter size to milk yield were examined in British Saanen goats. In late pregnancy lactogenic activity, measured in plasma by radioreceptor assay, increased with number of fetuses. Total weight of placentomes increased with total fetal weight and, hence, fetal number. The weight of the lobulo-alveolar component of the udders was correlated positively with placental mass and fetal number. In hand -milked goats which bore triplets or twins, mean milk yield was 47% and 27%, respectively, higher than in mothers of single kids after correction for lactation number. Milk yield was correlated with the weekly mean of placental lactogen titers between wk 11 and term. This supports the view that placental lactogen has a significant role in the control of normal mammary development and function in goats.

Animals↗
PubMed1978

Extracellular hydrolytic enzymes of rabbit dermal tuberculous lesions and tuberculin reactions collected in skin chambers.

To evaluate extracellular hydrolytic enzymes in an in vivo system, plastic chambers were glued over rabbit dermal BCG lesions in various stages of development, after the central epithelium was removed with a scalpel. They were filled with tissue culture medium and left in place 2 days. The following enzymes in the fluid were assayed: collagenase (an enzyme secreted but not stored in macrophages); lysozyme (both secreted and stored); DNase and RNase (released on cell death and possibly regurgitated but not secreted); and, as a control, lactic dehydrogenase (released only on cell death). Tissue sections were prepared and studied histologically for the type of cell infiltrate, for beta-galactosidase (our marker enzyme for macrophage activation), and for necrosis. At 11 and 18 days of age the BCG lesions were largest and the number of activated macrophages in the chamber beds was highest. At this time the levels of the five enzymes assayed in the chamber fluids reached their peaks, tuberculin hypersensitivity was well developed, and the bacilli components would still be plentiful. In general, the chamber fluids from 11- and 18-day BCG lesions contained higher enzyme levels than chamber fluids from tuberculin reactions. Active collagenase was only detected in fluids from such BCG lesions. Evidently, the serum in the chamber fluids was sufficient to inhibit the lower amounts of collagenase probably released from smaller BCG lesions and tuberculin reactions (and from the 2-week polystyrene lesions that were also evaluated). These studies demonstrate that in chronic inflammatory reactions, both acid-acting and neutral-acting hydrolytic enzymes are released extracellularly. Tissue components would be hydrolyzed locally wherever the acid-acting hydrolytic enzymes encounter a drop in pH and wherever the concentration of neutral-acting hydrolytic enzymes exceeds the concentration of their inhibitors.

Animals↗
PubMed1977

Phenobarbital prophylaxis of neonatal hyperbilirubinemia. Evaluation of a nightly dose.

In an attempt to improve the success of a previous study of the prevention of neonatal hyperbilirubinemia employing phenobarbital in a single 30-mg nightly dose from 32 weeks' gestation until delivery, 246 patients were tested against 270 control subjects. A 39% reduction in significant hyperbilirubinemia was realized but this fell far short of previous findings with a larger dose. Premature infants received no apparent protection against jaundice. Mature infants had no severe jaundice (more than 16 mg/100 ml) and the resolution of hyperbilirubinemia was more rapid. No apparent difference in drowsiness or daytime sedation from previous experience was found. Female newborns responded much better (3:1) to prophylaxis. These disappointing results favor a return to the 1-g daily divided dose.

Birth Weight↗
PubMed1976

Routine phenobarbital for prevention of neonatal hyperbilirubinemia.

In a parallel study conducted over a 1-year period, involivng 460 private prenatal patients, the effect of routine prenatal phenobarbital for the prevention of neonatal jaundice was evaluated. The incidence of significant jaundice (bilirubin levels greater than or equal to 10 mg/100 ml) occurred in 4.1% of the 221 test patients compared to 16.3% of the 239 control patients. No significant complications resulted from the drug therapy, and the newborn infants demonstrated no adverse effects attributable to the phenobarbital. Mothers who were given prophylactic phenobarbital took their infants home earlier, less often brought infants back to the hospital for photo-therapy, and spent fewer dollars for their total medical care than their control conterparts. Routine phenobarbital prophylaxis was found to be a safe, effective, and economic method of preventing hyperbilirubinemia in the newborn.

Costs and Cost Analysis↗
PubMed1975

Studies on mild composition and lactogenic hormones in the mare.

Small samples of mammary secretion were collected from eight Thoroughbred mares during the last week of pregnancy, at foaling and after 1 week of lactation. Specific assays showed the presence of both lactose and triglyceride in all samples before birth and progressive increases in their concentrations in colostrum and in milk. Levels of 6-0 g lactose/100 ml and 1-8 g triglyceride/100 ml were present in milk at 7 to 9 days post partum. The secretory capacity of the udder is thus normally established well before parturition in the mare. Attempts to demonstrate the occurrence of a placental lactogen and to measure lactogenic hormones in plasma have been unsuccessful.

Animals↗