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Biomedical subjects

R G Jones

Publications and source records attributed to R G Jones.

At least 91 records · Page 5Linked to original sources
PubMed1987

Electron microscopic cytochemical localization of adenylate cyclase in amphibian urinary bladder epithelium: effects of antidiuretic hormone.

A cytochemical technique for electron microscopic localization of adenylate cyclase was used to identify this enzyme in quiescent and hormone-stimulated toad urinary bladder epithelium. In the absence of vasopressin (antidiuretic hormone), adenylate cyclase was detected along the outer surface of the basolateral plasma membranes of granular cells, mitochondria-rich cells, and basal cells, the major cell types comprising the hormone-sensitive urinary epithelium. In the presence of antidiuretic hormone, the basolateral precipitates were markedly increased. The latter was true for both tissues incubated in the presence of an osmotic gradient and those stimulated in the absence of such a gradient. A significant mucosal reaction was never seen. Such data indicate that the hormone receptors for vasopressin are located along the basolateral membranes of all epithelial cells comprising the mucosal hormone-sensitive epithelium. All cells of the epithelium also demonstrate a vasopressin-sensitive adenylate cyclase. We discuss possible mechanisms that attempt to integrate the cytochemical data into an overall scheme for the physiological action of this hormone on amphibian urinary bladder.

Adenylyl Cyclases↗
PubMed1986

Phenytoin-induced connective tissue growth in the rat.

Rats were treated daily for 9 days with 100, 50, or 25 mg/kg phenytoin i.p. This treatment resulted in a significant increase in the thickness of the connective tissue capsules of the liver, spleen, and pancreas, and of the subepithelial connective tissue of the mesentery but not the epicardium or visceral pleura of the lung where exposure to the drug was via the vascular route. Many areas of connective tissue growth exhibited obvious proliferation of fibroblasts and in some areas contained seemingly large numbers of macrophages and an increase in vascularity. It was demonstrated by electron microscopy that the macrophages occasionally were seen in intimate contact with the fibroblasts. Our observations clearly showed that intraperitoneal exposure of visceral connective tissues of the rat to phenytoin rapidly resulted in a dose-related proliferation of that tissue. The presence of numerous macrophages leads to the suggestion that macrophage-derived growth factor could be responsible for the increased growth.

Animals↗
PubMed1986

Cytochemical localization of malate synthase in amphibian fat body adipocytes: possible glyoxylate cycle in a vertebrate.

The adipocytes of amphibian abdominal fat bodies contain typical microperoxisomes, as indicated by their fine structure. Electron microscopic cytochemistry showed that these organelles contain the enzymes catalase, typical for peroxisomes, and malate synthase. The latter is an enzymatic component characteristic of the glyoxylate cycle, a biochemical pathway known to exist in plant glyoxysomes (peroxisomes). This metabolic pathway makes possible the net conversion of lipid to carbohydrate. Toad adipocytes may represent yet another example of vertebrate peroxisomes which contain one of the marker enzymes (malate synthase) characteristic of the glyoxylate shunt.

Adipose Tissue↗
PubMed1985

Evidence that the stimulation of lipogenesis in the mammary glands of starved lactating rats re-fed with a chow diet is dependent on continued hepatic gluconeogenesis during the absorptive period. Effects of a gluconeogenic inhibitory, mercaptopicolinic acid, in vivo.

The rapid stimulation of lipogenesis in mammary gland that occurs on re-feeding starved lactating rats with a chow diet was decreased (60%) by injection of mercaptopicolinic acid, an inhibitor of hepatic gluconeogenesis at the phosphoenolpyruvate carboxykinase step. Mercaptopicolinate had no effect on lipogenesis in mammary glands of fed lactating rats. The inhibition of lipogenesis persisted in vitro when acini from mammary glands of re-fed rats treated with mercaptopicolinate were incubated with [1-14C]glucose. Mercaptopicolinate added in vitro had no significant effect on lipogenesis in acini from starved-re-fed lactating rats. Mercaptopicolinate prevented the deposition of glycogen and increased the rate of lipogenesis in livers of starved-re-fed lactating rats, whereas it had no significant effect on livers of fed lactating rats. Administration of intraperitoneal glucose restored the rate of mammary-gland lipogenesis in re-fed rats treated with mercaptopicolinate to the values for re-fed rats. Hepatic glycogen deposition was also restored, and the rate of hepatic lipogenesis was stimulated 5-fold. It is concluded that stimulation of mammary-gland lipogenesis on re-feeding with a chow diet after a period of starvation is in part dependent on continued hepatic gluconeogenesis during the absorptive period. Possible sources of the glucose precursors are discussed.

Animals↗
PubMed1985

Activation of actin-containing microfilaments by vasopressin in the amphibian urinary bladder epithelium: a fluorescent study using NBD-phallacidin.

The effect of an antidiuretic hormone (ADH, vasopressin) on the microfilament system of the toad urinary bladder lumenal epithelium was investigated using NBD-phallacidin (NBD-ph). The latter material is a specific fluorescent label for F actin. In the presence of an osmotic gradient, both ADH and cyclic adenosine monophosphate (cAMP) appear to induce the polymerization of monomeric actin into F actin-containing microfilaments. The latter may then be involved in the morphological changes, including the formation of lateral intercellular lakes, associated with the typical hydroosmotic response.

Actins↗
PubMed1985

Muscle cell membranes from early degeneration muscle cell fibers in Solenopsis are leaky to lanthanum: electron microscopy and X-ray analysis.

Lanthanum infusion techniques, transmission electron microscopy, and X-ray microanalysis were utilized to compare the permeability of muscle cell membranes from normal and degenerating muscle fibers of Solenopsis spp. In normal fibers, the electron-dense tracer was limited to components of the sarcotubular system. However, the insemination-induced degeneration of muscle fibers was characterized by the presence of an electron-dense precipitate within the myofibrils and mitochondria as well as in the extramyofibrillar spaces. The electron-dense material was subsequently identified by elemental analysis to be lanthanum. Such data indicate that one of the earliest stages of muscle degeneration involves an alteration in cell membrane permeability.

Animals↗
PubMed1985

Leupeptin, a protease inhibitor, blocks insemination-induced flight muscle histolysis in the fire ant Solenopsis.

The effect of the protease inhibitor leupeptin on flight muscle histolysis in queen fire ants was studied by electron microscopy. In untreated animals artificially inseminated, muscle involution was apparent at 6 hr post-insemination and complete by 24 hr post-insemination. However, in animals pre-treated with leupeptin and subsequently artificially inseminated, no morphologic evidence of flight muscle breakdown was seen at any interval between 6 and 24 hr post-insemination. Such information appears to indicate that one or more proteases are involved in the process of insemination-induced muscle atrophy in fire ants. The most likely candidate is a soluble, calcium-activated myofilament-associated protease.

Animals↗
PubMed1984

Regulation of lactating-rat mammary-gland lipogenesis by insulin and glucagon in vivo. The role and site of action of insulin in the transition to the starved state.

Starvation for 6h and 24h caused an 80% and 95% decrease in the rate of mammary-gland lipogenesis respectively in conscious lactating rats. 2. Plasma insulin concentrations decreased and circulating ketone-body concentrations increased with the length of starvation. 3. The inhibition of lipogenesis after 24h starvation was accompanied by increased concentrations of glucose, glucose 6-phosphate and citrate in the mammary gland. Qualitatively similar changes were observed after 6h starvation. 4. Infusion of insulin at physiological concentrations caused a 100% increase in the rate of lipogenesis in fed animals and partially reversed the inhibition of lipogenesis caused by starvation. 5. Infusion of insulin tended to reverse the changes seen in intracellular metabolite concentrations. 4. Infusion of glucagon into fed rats caused no change in the rates of lipogenesis in mammary gland, liver or white adipose tissue. 7. It is concluded that (a) insulin acts physiologically to regulate lipogenesis in the mammary gland, (b) hexokinase and phosphofructokinase are important regulatory enzymes in the short-term control of lipogenesis in the mammary gland, which are under the influence of insulin, and (c) the unresponsiveness of mammary-gland lipogenesis in vivo to infusions of glucagon is consistent with an adaptive mechanism which diverts substrate towards the lactating mammary gland and away from other tissues.

Animals↗
PubMed1984

Physiological significance of altered insulin metabolism in the conscious rat during lactation.

Uptake of radioactively labelled insulin by the mammary gland of the rat increased 12-fold in lactation compared with non-lactating controls. This uptake was decreased by the presence of unlabelled insulin, indicating that it occurred via insulin receptors. The plasma half-life of insulin is decreased in lactation from 9.4 min to 4.8 min, and the metabolic clearance rate for insulin increased from 7.26 to 13.03 ml/kg body wt. per min. The basal insulin and glucose concentrations in the plasma were decreased in lactation. Infusion of insulin at a dose which led to a small physiological rise in plasma insulin concentration increased lipogenic rates in the mammary gland by 100% without causing marked hypoglycaemia. It is concluded that the lactating mammary gland is a highly insulin-sensitive tissue and that the lower plasma insulin during lactation occurs primarily as a result of this sensitivity increasing extraction of glucose by the gland and thus producing a decrease in the plasma glucose concentration. It is suggested that a secondary result of the fall in plasma insulin concentration is the preferential direction of substrates (glucose and non-esterified fatty acids) towards the lactating mammary gland and away from adipose tissue and the liver.

Animals↗
PubMed1984

Alterations in mammary-gland blood flow and glucose metabolism in the lactating rat induced by short-term starvation and refeeding.

Six-hour starvation of lactating rats caused a 75% decrease in mammary-gland lipogenesis. The inhibition of lipogenesis was accompanied by a 45% decrease of blood flow to the mammary gland and a 60% decrease in glucose uptake. Within 2 h of refeeding, lipogenesis and glucose uptake by the gland increased to fed values though blood flow to the gland remained at only 63% of that in the fed state. It is concluded that blood flow, and hence substrate supply, is not a rate-limiting factor for lipogenesis by the lactating mammary gland in the rat.

Animals↗
PubMed1984

Peroxisomes in the absorptive cells of normal, rachitic, and vitamin-D replete chick intestine: ultrastructure and histochemistry.

Using routine transmission electron microscopy and light and electron microscopic techniques for the histologic demonstration (localization) of catalase (a peroxisomal enzyme), peroxisomes in chick duodenal epithelial cells were identified and studied. In these cells, peroxisomes were seen to be small, ovoid structures, delimited by a single unit membrane. They were concentrated in the supranuclear cytoplasm in initimate association with the smooth endoplasmic reticulum. As demonstrated histochemically, the heterogeneous matrix of these organelles was catalase positive. In addition, most of the larger peroxisomes revealed central nucleoids; however, the smaller peroxisomes were generally anucleoid. It thus appears that two classes of peroxisomes exist in chick intestinal absorptive cells: (1) small, anucleoid microperoxisomes, and (2) larger, nucleoid-containing peroxisomes. In addition to the above morphological characteristics, both peroxisome types were numerous in normal and vitamin-D-replete tissues, but were conspicuously decreased or absent from the apical cytoplasm of rachitic epithelial cells. From these observations it is hypothesized that these organelles may be involved in the overall vitamin-D response of the small intestine.

3,3'-Diaminobenzidine↗
PubMed1984

Biochemical basis of dietary influences on the synthesis of the macronutrients of rat milk.

In this contribution the regulation of the synthesis of the macronutrients (lactose, lipid, protein) of rat milk are briefly reviewed. Lactose synthesis and lipid synthesis in mammary gland have glucose as the common precursor, and the rates of both processes show diurnal changes that correlate with the variations in food intake. Short-term (6-h) removal of food results in large decreases in the rates of synthesis of lactose and lipid, despite any change in plasma glucose or insulin. Similarly, an intragastric load of fat rapidly decreases de novo lipogenesis in the mammary gland. The existence of a factor in the circulation that signals the dietary intake of carbohydrate is postulated. This putative factor may originate from the intestine. Synthesis of protein appears less sensitive to dietary intake and is regulated mainly by prolactin.

Amino Acids↗
PubMed1983

Analysis of the common polysaccharide antigens from the cell envelope of Clostridium perfringens type A.

The major, common antigen of Clostridium perfringens type A, isolated and purified independently from three selected strains (Hobbs 5, Hobbs 9, and Hobbs 10), is composed of equimolar amounts of 2-acetamido-2-deoxy-D-mannose (Man-NAc) and 2-acetamido-2-deoxy-D-glucose (GlcNAc). The purified antigen gave a strong immunoprecipitin line by double immunodiffusion in gel. Smith degradation of the major, common antigen caused decomposition of all of the GlcNAc, without concomitant loss in ManNAc, or a perceptible change in serological activity. Therefore, the serological activity of the major, common antigen depended solely on the presence of ManNAc. Data obtained by the 13C-n.m.r.-spectral analysis of the Smith-degradation product revealed that it was a linear-backbone polysaccharide analogous to a Rhodotorula glutinis mannan, but composed of pairs of 2-acetamido-2-deoxymannopyranosyl residues alternately linked beta-(1 leads to 3) and beta-(1 leads to 4). The one-bond, carbon-hydrogen coupling-constant of 162 Hz for both anomeric centers was consistent with the proposed beta-linkages. A similar, 13C-n.m.r.-spectral analysis of the native, common antigen indicated that the GlcNAc residues were randomly connected to three of the four hydroxyl groups not already involved in linking the ManNAc backbone, the 4-hydroxyl group being the exception. A second, serologically inactive, polysaccharide composed of rhamnose, GalNAc, and galactose was identified, but not obtained in homogeneous state. The rhamnosyl residues were probably situated as nonreducing antennae, as they were quantitatively removed by Smith degradation without concomitant decomposition of the polymeric structure of the remaining residues.

Amino Acids↗
PubMed1983

Short-term dietary regulation of lipogenesis in the lactating mammary gland of the rat.

Short-term (6 hr) withdrawal of chow diet from lactating rats decreases the rate of lipogenesis in mammary gland by 87%. This inhibition is in part explained by a 60% decrease in the extraction of glucose (the major lipogenic precursor) by the mammary tissue. These changes are not accompanied by any significant alteration in the arterial concentrations of glucose, lactate or insulin; the concentration of acetoacetate did increase by about 30%. Removal of food for 6 hr did not alter the activation state of acetyl-CoA carboxylase or the total activity of the enzyme. Glucose utilization by mammary gland acini from short-term starved rats was not depressed although a higher proportion of the glucose appeared as lactate in the medium and consequently less glucose was converted to lipid. Insulin was able to reverse these changes. Glucagon, adrenaline or cAMP did not inhibit glucose utilization or lipogenesis in isolated acini. It is concluded that the inhibition of lipogenesis in mammary gland after short-term withdrawal of food is mainly due to decreased extraction of glucose. The signal for this change does not appear to be an alteration in plasma insulin and it is postulated that there may be an intestinal factor(s) which acts synergistically with insulin.

Acetyl-CoA Carboxylase↗
PubMed1983

Exploratory study to evaluate staff attitudes towards geriatric psychiatry.

This work is part of a larger study carried out at the Murray Royal and Murthly Hospitals within the Tayside Health District. The survey was concerned with staff attitudes towards geriatric psychiatry patients and shows that the nurses in these peripheral hospitals hold a positive attitude towards this area of nursing. These findings appear to contradict the popular opinion held throughout the nursing service, that the geriatric psychiatry nursing area is very unpopular with trained, untrained and learner nurses. In the study by Hooper [Nursing Times (1981) 77 37-40/43-44], anxiety levels among learners towards the geriatric nursing areas were found to be very high. This appears to correlate with Kogan [Journal of Abnormal and Social Psychology (1961) 62, 616-622], which summarized is as follows: Young subjects were imputed to have a more consistently negative view of old people.' By using a series of two precoded questionnaires that the subjects completed, an overview of staff attitudes towards the geriatric psychiatry areas was obtained. The hypothesis on which the study was based was as follows: that a negative view towards geriatric psychiatry would be found among the staff of the Murray Royal and Murthly Hospitals.' However, the findings of this study did not support the hypothesis on any counts and gave a highly positive attitude scale.

Adolescent↗
PubMed1983

Pulsatile insulin has greater hypoglycemic effect than continuous delivery.

The relative hypoglycemic effects of pulsatile versus steadily infused insulin have been examined in six normal subjects in whom pancreatic insulin output was suppressed by somatostatin-14. Soluble insulin was infused continuously overnight on one occasion and on another occasion the same quantity was given in pulses of 2-min duration with a gap of 11 min. The mean plasma glucose concentrations were lower when pulsed insulin was given [mean for the last hour: 4.66 +/- 0.08 mmol/L (+/- SEM) versus 5.53 +/- 0.06 mmol/L (+/- SEM) for steady infusion], diverging significantly (P less than 0.05 paired t test) 7 h after the start of the study. The specific binding of 125I(A14)mono-iodo-insulin to monocytes was greater after pulsed insulin (2.9% with pulsed versus 2.4% with steadily infused insulin at tracer-only point; P less than 0.02 paired t test). Thus, intravenous insulin has greater hypoglycemic effect when pulsed, possibly mediated by greater insulin receptor binding.

Adult↗