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Biomedical subjects

A Barber

Publications and source records attributed to A Barber.

90 records · Page 5Linked to original sources
PubMed1986

Influence of aerobic energy deficit, ouabain and harmaline on the phenylalanine and galactose active transport by snail intestine.

The effect of anaerobiosis (N2 bubbling of the medium) or 10(-4) M dinitrophenol on the penetration of 0.5 mM Phe in snail and rat everted intestine, in 2 min and 30 min incubation periods, has been studied. The aerobic energy deficit inhibits the amino acid net entry in both species, but whereas the active transport is annulled in rat, snail intestine is capable of continuing to accumulate Phe against a gradient. The prolonged action (30 min of preincubation) of 1 mM ouabain inhibits 0.1 mM Phe and 0.1 mM galactose entry in snail intestine. Amino acid uptake is far higher than the one obtained in the absence of Na+, in which condition Phe keeps accumulating against a gradient in the tissue water. Galactose active transport, instead, becomes null in the presence of the glucoside or in the absence of Na+. One mM harmaline is able to inhibit the initial entry of galactose into the tissue, while higher than 5 mM concentrations are required to inhibit that of Phe. Results confirm that snail intestine is capable of easily carrying out active transport processes with energy from anaerobic origin. On the other hand Phe transport is less sensitive to the absence of Na+, presence of ouabain or harmaline than that of galactose, so that contrary to what has been observed for the sugar, the active transport of the amino acid is not annulled in any of the three conditions.

Anaerobiosis↗
PubMed1985

The bleeding time as a preoperative screening test.

To examine the benefit of determination of the bleeding time as a preoperative screening test, the medical records of all patients who had a prolonged bleeding time during a six-month period were reviewed. At Northwestern Memorial Hospital, where the bleeding time test is part of the presurgical panel, 1,941 bleeding time determinations were performed during six months. Prolonged bleeding times were recorded in 110 preoperative patients, of whom 83 (75 percent) had bleeding risk factors, including drug ingestion, thrombocytopenia, and azotemia. In these patients, the bleeding time ranged unpredictably from 10 to more than 20 minutes. However, of the 27 patients without apparent risk factors, only two had bleeding times of more than 20 minutes. This small number probably does not justify the routine use of the test in all preoperative patients. Rather, the test should be used selectively for those subjects who, on the basis of history or laboratory evidence, are suspected of being at risk of hemorrhage. Moreover, even in these patients, prolongation of the bleeding time may not always be associated with excessive surgical blood loss.

Aspirin↗
PubMed1985

Actions of acetylcholine on the salivary gland cells of the pond snail, Planorbis corneus.

Intracellular recordings have been made from salivary gland cells of the pond snail Planorbis corneus. Gland cells produced a dose-dependent biphasic response to the bath application of acetylcholine (ACh), an initial depolarization being followed by a hyperpolarization. Nicotine and the nicotinic agonist tetramethylammonium had an excitatory action on the gland cells. The muscarinic agonists acetyl-beta-methyl choline and arecoline were also stimulants, but muscarine, bethanechol and pilocarpine produced no response from gland cells at 10(-3) M. A number of cholinergic antagonists, including atropine, hexamethonium and curare, effectively blocked the response to ACh. The depolarizing phase of the ACh response resulted from an increased membrane permeability to Na+ ions, though the participation of other ionic species cannot be ruled out. The hyperpolarizing phase of the ACh response was produced by the activity of an electrogenic Na+/K+ pump.

Acetylcholine↗
PubMed1985

D-galactose uptake by snail intestine: competitive inhibition by phlorizin and sodium dependence.

The net entry of galactose into the tissue of snail everted intestinal rings with 2 or 15 minute long incubation periods has been measured. With 10(-4) M phlorizin, the mediated transport is completely blocked while only the passive entry of sugar is produced. Lower concentrations of the glycoside partially inhibit transport according to competitive inhibition kinetics (K1 = 10(-7) M). The transport of galactose is Na+ dependent. In the absence of Na+, transport ceases and the sugar entry can be explained through simple diffusion. With 15 mM Na+ (control 71,4 mM) transport diminishes and a marked increase in the apparent Km with no changes in the Vmax is observed. One mM harmaline completely blocks galactose (0.5 mM) transport. One mM ouabain also makes transport null, but only after tissue preincubation with the inhibitor on the serosal side.

Animals↗
PubMed1984

The effect of oral contraceptives in malaria infections in rhesus monkey.

Rhesus monkeys, Macaca mulatta, were treated with the oral contraceptives Brevicon (norethisterone with ethinylestradiol) and Ovral (norgestrel with ethinylestradiol), and subsequently inoculated with the simian malaria parasites Plasmodium cynomologi bastianellii or P. coatneyi. Parasitological, serological, and serum biochemical studies indicated that although there were some significant differences, in general the patterns of response to infection in both treated and control animals were similar. During the primary infection, however, Brevicon resulted in increased levels of parasitaemia, whereas Ovral resulted in decreased parasitaemias, as compared with the untreated control animals. There were no differences in the responses following secondary parasite infection.

Animals↗
PubMed1983

A monoamine-detecting histofluorescence technique for use on wholemounts of molluscan tissues.

A histochemical procedure is described which has been used to visualize monoamine-containing neurons, fibers and varicosities within wholemounts of a number of tissues of the marine gastropod mollusc, Philine aperta. The method is rapid and simple and the morphology of the specimen is preserved without distortion. This technique may facilitate studies of the distribution of monoamines in the tissues of other marine molluscs.

Animals↗
PubMed1983

Properties of the serotonergic cerebral ganglion neurons of the gastropod mollusc, Philine aperta.

The characteristics of a pair of identified neurons found in the cerebral ganglia of the gastropod mollusc Philine aperta have been examined. Because they appear to contain serotonin, and since they probably also use serotonin as a neurotransmitter, these neurons were named the serotonergic cerebral neurons (SCNs). Each SCN sent an axon out of the ipsilateral cerebro-buccal connective to the buccal ganglia. The SCNs also had extensive projections to all the ipsilateral, and most of the contralateral, buccal nerve trunks. Stimulating the SCNs produced the hyperpolarization of a pair of identified buccal ganglion mechano-sensory neurons (the S-cells), and had an excitatory action on the electrical activity of acinar cells of the salivary glands. A comparison of the properties of the Philine SCNs with those of similar serotonin-containing cerebral ganglion neurons in other gastropod molluscs provides evidence of homology with these neurons.

Action Potentials↗
PubMed1982

Plasmodium falciparum gametocytes from culture in vitro develop to sporozoites that are infectious to primates.

Gametocytes of two strains of the human malaria parasite Plasmodium falciparum have been produced in high density by means of a continuous-flow cultivation system. The gametocytes of these two strains infected a mean of 36 percent and 71 percent, respectively, of Anopheles freeborni mosquitoes that fed on a suspension of red blood cells containing the culture gametocytes. Sporozoites harvested from the infected mosquito salivary glands were infective to the chimpanzee (Pan troglodytes) and the owl monkey (Aotus trivirgatus).

Animals↗
PubMed1982

A micromethod for the analysis of zinc in plasma or serum by atomic absorption spectrophotometry using graphite furnace.

A micromethod is described for the analysis of zinc in plasma or serum by electrothermal atomisation and graphite furnace utilising less than 20 microliters sample volume. The sample matrix introduced an error when aqueous standards were used. Therefore standards were made up in serum which had been treated with Chelex 100 to remove as much zinc as possible. The residual zinc (less than 0.125 mg/l) was determined by flame analysis using the method of additions and each standard assigned a value equal to the sum of the residual zinc and the amount added. Furnace analyses using standards made up in Chelex-treated serum compared favourably with flame analyses over the whole range, and recovery experiments gave 98 +/- 2% of the expected value with 95 +/- 6% recovery of the added zinc. The within-batch coefficient of variation was 2.5%, day-to-day variation 5.6%. The mean concentration of zinc in paired samples of plasma and serum from 50 adults analysed by flame with viscosity-matched aqueous standards were: plasma (mean +/- SD) 0.821 +/- 0.085 mg/l; serum 0.821 +/- 0.07 mg/l. The same samples were analysed in the graphite furnace using serum standards, and the results were: plasma 0.812 +/- 0.082 mg/l; serum 0.815 +/- 0.08 mg/l. In contrast to earlier reports we were unable to demonstrate a significant difference between plasma and serum zinc concentration in the paired samples.

Adult↗
PubMed1982

Monoamine-containing varicosities in the neural sheath of a gastropod mollusc demonstrated by glyoxylic acid histofluorescence.

The glyoxylic acid monoamine-detecting technique of Bolstad et al. (1979) was applied to wholemounts of intact ganglia of the gastropod mollusc Philine aperta. A dense network of fluorescent varicosities was found in the sheath of the suboesophageal, visceral and genital ganglia, and most of their nerves. Drug treatment experiments suggest that these projections to the neural sheath contain serotonin. The significance of these terminals in the sheath is discussed and proposals for further work are given.

Animals↗
PubMed1982

Active transport of L-phenylalanine by snail intestine, Helix (Cryptomphalus) aspersa.

Snail intestine was found to actively accumulate L-phenylalanine. The uptake of L-phenylalanine was a saturable function of the amino acid concentration and sodium-dependent. The KT for L-phenylalanine uptake increased as the Na+ concentration was reduced, being 2.2 mM at 71.4 mM Na+, 5.9 mM at 10 mM Na+ and 9.9 mM at 0 mM Na+. Variations in Na+ concentration were without effect on the Vmax. At low concentrations of L-phenylalanine (0.5 and 1 mM) the tissue was able to concentrate the amino acid even in the absence of Na+. L-phenylalanine uptake was competitively inhibited by L-methionine (KI = 0.58 mM). This finding suggests that both amino acids might share a common transport system, being the affinity for L-methionine higher than for L-phenylalanine.

Animals↗
PubMed1981

Nitrogen metabolism in preterm infants fed human donor breast milk: the possible essentiality of glycine.

Nitrogen metabolism was studied in three preterm infants (mean gestation 32 wk) by the method of consecutive metabolic balance. The absorption and retention of nitrogen from breast milk was measured, and protein turnover, synthesis, and breakdown were calculated from isotopic plateau of urinary urea and ammonia using an intermittent oral administration of 15N-glycine. Weight gain and nitrogen retention were compared with the weight gain and nitrogen accumulated for a foetus of equivalent gestational age in utero. The average composition of the milk was 289 +/- 19 KJ dl-1 and 1.44 +/- 24 g protein dl-1. The intake of energy was 572 +/- 61 KJ kg-1 day -1 and of nitrogen 447 +/- 99 mg kg-1 day-1. Stool output of nitrogen was 100 +/- 32 mg kg-1 day-1 giving an absorption of 348 +/- 78 mg kg-1 day-1, as urinary excretion was 91 +/- 17 mg kg-1 day-1 retained nitrogen was 256 +/- 71 mg kg-1 day-1, or 56% of intake. The specific weight gain was 15.6 +/- 2.6 g kg-1 day-1 and 53% of this comprised lean tissue (range 34 to 89%). In all but one study the postnatal retention of nitrogen fell far short of calculated in utero accumulation. The results of protein turnover were surprising. In six of the eight studies urinary urea failed to become enriched at all. Protein turnover calculated from the ammonia plateau was 1.94 +/- 0.54 g nitrogen kg-1 day-1, synthesis 10.9 +/- 3.4 g protein kg-1 day-1 and breakdown 9.3 +/- 3.4 g protein kg-1 day-1. It is concluded that the amino acid composition of breast milk may be inappropriate for supporting rates of lean tissue deposition equivalent to in utero accumulation.

Body Weight↗
PubMed1979

Competitive kinetics of sugar active transport in snail intestine.

Everted intestinal rings of the snail Cryptomphalus hortensis accumulate labelled sugars against a concentration gradient. The active transport of D-galactose (KT = 3.6 mM) is competitively inhibited by D-glucose (Ki = 8.2 mM) and by 3-0-methylglucose (Ki = 24 mM), but it is not affected by L-arabinose, D-fructose, L-arabinose and D-mannitol penetrate into the tissue at the same rate, they do not develop accumulation gradient, and all of them follow the kinetics of a diffusion process. D-glucose, on the contrary, like galactose, penetrates much more quickly and accumulates against a gradient.

Animals↗
PubMed1976

[Effect of the ionic environment and of various neurotransmitters on spontaneous motility in snail intestine (author's transl)].

A spontaneous rhythmic motility of the isolated intestine in snail, Chryptomphalus hortensis, has been registered at 30 degrees C with the aid of an electronic transductor and an appropriate amplification. These slow regular movements are affected by ionic composition changes in the suspension medium. Na+, K+ and Ca++ ions prove to be important in this motility, and the addition of Ba++ markedly stimulates it. ACh produces hypermotility from 1.8 X 10(-11) g/ml. Its effect decreases in the presence of atropine and increases in that of pyridostigmine. The intestine is sensitive to 5-HT from 10(-10) g/ml, which stimulates its activity. The effect of histamine is weak. Low concentrations of adrenaline tend to increase the amplitude, whereas concentrations from 10(-5) g/ml onward produce a cease of motility in relaxation.

Animals↗
PubMed1975

Active transport of sugars by the intestine of snail (Cryptomphalus hortensis Müller).

Sugar transport by sacs of everted intestine of snail have been measured in vitro at 30 degrees C. D-galactose, D-glucose and 3-O-methylglucose were actively transported against a concentration gradient from the mucosal to the serosal compartment. The transport of these sugars was inhibited by 5 times 10(-8) to 10(-6) M phlorizin. L-arabinose was also accumulated in the serosal compartment against a concentration gradient; in this case, transport was not affected by phlorizin. The snail intestine did not show any ability for D-fructose active transport but there was a clear uptake of this sugar by the tissue. The O2 uptake of the snail intestine was not significantly affected by the presence of either sugars or phlorizin.

Animals↗
PubMed1975

Effect of anaerobiosis, dinitrophenol and fluoride on the active intestinal transport of galactose in snail.

The active transport of galactose across the intestinal wall (everted sacs) of the snail Cryptomphalus hortensis Müller has been studied in vitro, under several metabolic conditions. Anaerobiosis does not change the serosal/mucosal galactose gradients which are developed in oxygen atmosphere. Dinitrophenol (10(-4) M) greatly increased the O2 uptake by the tissue and clearly inhibits the sugar transport. At 5 times 10(-4) M concentration, DNP totally prevents the uphill transport while the O2 uptake is normal. The inhibition produced by DNP does not increase by anaerobiosis. Fluoride inhibits the galactose transport and also the O2 uptake. It is deduced that in snail intestine the energy for the active transport of galactose can be supplied by aerobic as much as by anaerobic metabolism. The inhibition by dinitrophenol seems to be independent of its uncoupling action on the oxidative phosphorylation. The inhibitory effect of NaF may be due both to glycolisis inhibition and to alteration of the digestive epithelium.

Anaerobiosis↗
PubMed1975

Sodium dependence of intestinal active transport of sugars in snail (Cryptomphalus hortensis Müller).

Active transport of sugars (D-galactose, D-glucose, 3-0-methylglucose and L-arabinose) by sacs of everted intestine of snail (Cryptomphalus hortensis) was strongly inhibited, but not abolished, when all Na from the bathing solutions was substituted by K, Tris, Mg or Ca. Absence of Na produced also a marked inhibition of O2 consumption by the tissue. Omission of other cations (K, Ca, Mg), substituted by Tris, did not affect sugar transport or O2 uptake. Sodium seems to play a specific and important but not indispensable rôle in sugar active transport by snail intestine. Since anaerobiosis did not affect sugar transport, this Na role is independent of its effect on O2 uptake.

Animals↗