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S Barnes

Publications and source records attributed to S Barnes.

At least 163 records · Page 9Linked to original sources
PubMed1991

Effect of cholecystokinin octapeptide on endogenous amino acid release from the rat ventromedial nucleus of the hypothalamus and striatum.

The sulphated octapeptide of cholecystokinin (CCK-8S) was found to cause a dose-dependent increase in the basal release of aspartate, glycine, and gamma-aminobutyric acid from the striatum and the ventromedial nucleus of the hypothalamus (VMH). No effect on amino acid release was observed after electrical (VMH) or potassium (striatum) stimulation. Experiments performed using the CCKB-selective antagonist L-365,260 and the CCKA-selective antagonist L-364,718 suggested that this action of CCK-8S was mediated via the CCKB receptor. The ability of CCK-8S to evoke amino acid release was not dependent on the presence of extracellular calcium, though the effect was abolished by tetrodotoxin. Inhibition of protein kinase activity by staurosporine prevented the excitatory effects of CCK-8S on amino acid release.

Alkaloids↗
PubMed1991

Validation of the five minute speech sample in measuring expressed emotion.

The relationship of the Five Minute Speech Sample (FMSS) to the Camberwell Family Interview and its coding system were evaluated. The Camberwell Family Interview and the FMSS were administered to twenty-three relatives of patients diagnosed with schizophrenia. Overall, the results supported the utility of the FMSS and its coding system as a brief screening device for measuring expressed emotion.

Adult↗
PubMed1991

Modulation of calcium-activated chloride current via pH-induced changes of calcium channel properties in cone photoreceptors.

The activity of calcium-activated chloride channels is controlled through the complex interaction of cellular mechanisms affecting calcium entry, buffering, and extrusion, and an unknown stoichiometric relation between intracellular Ca concentration and Cl channel activation. Here, we show that calcium-activated chloride current [ICl(Ca)] in cone photoreceptors is also highly sensitive to external pH, being strongly reduced by acidification and enhanced by alkylinization of the bathing medium. We propose that this modulation is accounted for by the pH sensitivity of Ca channel activation and permeation, already well characterized in other cells, which we now extend to cone photoreceptor Ca channels. Acidification of the external medium from a control pH of 7.4 shifts the Ca channel activation range positively by about 10 mV at pH 6.8, reducing the magnitude of calcium current with a consequent reduction of chloride current. Alkylinization shifts the Ca channel activation range negatively by about 8 mV at pH 8 and produces larger calcium currents during step depolarizations that in turn elicit larger chloride tail currents. Modulation of ICl(Ca) by pH suggests other consequences of the pH-induced shift in Ca channel gating, for one, modification of Ca-dependent transmitter release, which could be especially significant in photoreceptors where the cell's operating voltage range overlaps only the lower end of the Ca channel activation range.

Ambystoma↗
PubMed1990

2-Fluoro-beta-alanine, a previously unrecognized substrate for bile acid coenzyme A:amino acid:N-acyltransferase from human liver.

Our laboratory has demonstrated recently that conjugates of 2-fluoro-beta-alanine (FBAL) and bile acids are the major biliary metabolites of 5-fluorouracil (FUra) in cancer patients. Bile acids are normally conjugated with glycine or taurine, and therefore the identification of the FBAL-bile acid conjugates suggested that FBAL may also be a substrate for the bile acid conjugating enzyme, bile acid CoA:amino acid:N-acyltransferase. Enzyme activity detected using glycine and taurine as substrates was purified 8-fold from human liver cytosol using a DEAE-cellulose column. This preparation when tested for its activity towards beta-alanine and FBAL using cholyl CoA as the bile acid substrate only catalyzed the formation of FBAL-cholate. beta-Alanine was not a substrate. Confirmation of FBAL-cholate as the enzymatic product was demonstrated by (1) coelution of the product of this reaction on HPLC with authentic FBAL-cholate, (2) specific hydrolysis of this product by cholylglycine hydrolase, and (3) molecular weight of the product (497) being identical to that of the authentic FBAL-cholate. Kinetic experiments demonstrated that the enzyme had an affinity for FBAL (Km 1.45 mM) comparable to taurine (Km 1.32 mM), but greater than glycine (Km 6.45 mM). Formation of FBAL-cholate was inhibited competitively by taurine (Ki 1.27 mM) and glycine (Ki 4.47 mM), suggesting that a single enzyme is responsible for conjugation of glycine, taurine and FBAL with bile acids. These data indicate that the formation of the FBAL-bile acid conjugates in patients receiving FUra results from high affinity of the bile acid conjugating enzyme for FBAL.

Acyltransferases↗
PubMed1990

Phosphorylation by protein kinase C inactivates an inositol 1,4,5-trisphosphate 3-kinase purified from human platelets.

An inositol 1,4,5-trisphosphate 3-kinase purified from human platelets contains two major components, 53 and 36 kDa polypeptides. Each polypeptide expresses Ca2+/calmodulin-dependent enzymatic activity and is phosphorylated by an unidentified protein kinase in the enzyme preparation. The 36-kDa polypeptide may be further phosphorylated on serine residues by protein kinase C to a stoichiometry of 0.8 mole phosphate per mole of protein. Phosphorylation of the 36-kDa component is correlated with inhibition of the kinase activity; the inhibitory effect is dependent upon Ca2+ and phosphatidylserine/diolein and may be blocked by a selective peptide inhibitor of protein kinase C. Phosphorylation by protein kinase C decreases the Vmax of the enzyme from 160 to 28 nmol/mg/min; the Km (0.76 microM) is not altered. These data suggest that protein kinase C may negatively regulate inositol 1,4,5-trisphosphate 3-kinase activity in the human platelet.

Amino Acid Sequence↗
PubMed1990

Biological properties of the 2-fluoro-beta-alanine conjugates of cholic acid and chenodeoxycholic acid in the isolated perfused rat liver.

The isolated perfused rat liver was used to examine the hepatic extraction, biliary secretion and effect on bile flow of the 2-fluoro-beta-alanine conjugates of cholic acid and chenodeoxycholic acid. The naturally occurring taurine and glycine conjugates of these bile acids were used for comparisons. The 2-fluoro-beta-alanine conjugates were extracted by the liver to a similar extent as the taurine and glycine conjugates. The biliary secretion rate and increase in bile flow were similar for all the cholic acid conjugates. On the other hand, the maximal biliary secretion rate of the 2-fluoro-beta-alanine conjugate of chenodeoxycholate was similar to that of the glycochenodeoxycholate, but 47% lower than that of taurochenodeoxycholate. In addition, the 2-fluoro-beta-alanine conjugate of chenodeoxycholate produced a decrease in bile flow that was comparable to that observed with the glycochenodeoxycholate (54% vs. 74%), but which was greater than that produced by the taurochenodeoxycholate (12%). In summary, these data demonstrate that the biological properties of the 2-fluoro-beta-alanine conjugates of cholic acid and chenodeoxycholic acid are not markedly different from those of the naturally occurring taurine and glycine conjugates. These data also suggest that the amino acid moiety can influence the biliary secretion and cholestatic properties of chenodeoxycholic acid conjugates.

Alanine↗
PubMed1990

Prevalence of antibodies to human immunodeficiency virus and to human T cell leukemia virus type I in transfused sickle cell disease patients.

The prevalence of the human immunodeficiency virus (HIV) antibody and the human T cell leukemia virus type I (HTLV-I) antibody was examined in 116 adults with sickle cell disease. Eighty-eight of them had received a mean of 18.6 transfusions of red blood cells between 1978 and 1985, and none was positive for the HIV antibody. Of 116 patients, 9 (7.8%) tested positive for HTLV-I antibodies. HTLV-I-positive patients were similar to those without HTLV-I antibody with respect to age, number of transfusions, and proportion of patients with greater than 40 transfusions. However, 3 of the 9 HTLV-I-positive patients came from West Africa or from the Caribbean, whereas this proportion was much lower (7/107) in the HTLV-I-negative group (x2, 7.564; P less than .01). Our analysis suggests that the risk of HIV infection in transfused sickle cell disease patients is low. Although HTLV-I antibodies in these patients may not be related to blood transfusions, it seems prudent to screen blood donors for HTLV-I infection.

Adult↗
PubMed1990

Characterization of cholecystokinin octapeptide-stimulated endogenous dopamine release from rat nucleus accumbens in vitro.

1. The effect of cholecystokinin sulphated octapeptide (CCK8S) on endogenous dopamine release was examined in rat striatal and nucleus accumbens slices, by high performance liquid chromatography (h.p.l.c.) with electrochemical detection. 2. CCK8S was shown to increase dopamine release from slices of nucleus accumbens but not striatum in a dose-dependent manner between 0.1 and 10 microM. 3. Pentagastrin was without effect on dopamine release at doses up to 10 microM. 4. The dopamine release produced in the presence of CCK8S was abolished by preincubation of the slice with 1.0 or 10.0 nM L-364,718 (the CCKA-selective antagonist) while 1 microM L-365,260 (the CCKB-selective antagonist) had no action. 5. These results suggest that the CCK8S-evoked release of dopamine from the nucleus accumbens is mediated by a CCKA-receptor.

Animals↗
PubMed1990

Preliminary characterization of the repeated DNA sequence from Vicia sativa.

We have identified a family of interspersed repeated sequences present in about 40,000 copies in the genomes of Vicia sativa and its near relative Vicia faba. The element vif is at least 6 kb in length, and members of the repeat family display a degree of heterogeneity in restriction pattern. Homologous elements in V. faba are much more heterogeneous than their V. sativa counterparts; however, analysis of five different V. faba lines revealed substantially the same patterns, suggesting that this family was reamplified prior to the divergence of the lines studied.

Cloning, Molecular↗
PubMed1990

A modified cancer education program. Effect on cancer knowledge and beliefs of the elderly.

This pilot study examines the effect of a cancer education program on the knowledge and beliefs of elderly adults. The program, developed for this age group, was based on principles of adult education and on an understanding of changes related to aging. It focused on cancer risks and early diagnosis of cancer for older adults. The sample included 21 elderly adults from three retirement centers. The questionnaire used to determine knowledge and beliefs about cancer included seven scales based on the Health Beliefs Model: knowledge, severity, susceptibility, utility, barriers, behavioral intentions, and cues to action. A week following administration of the questionnaire, a program was presented: the modified cancer education program, a conventional cancer education program, or a program not related to cancer. The questionnaire was then readministered as a posttest. Findings were insignificant except that the group receiving the modified cancer program had increased scores on the knowledge scale from pretest to posttest; and the level of education accounted for 25% of the variability of posttest utility scores. The pilot study was useful for identifying problems with the questionnaire, the testing procedure, and the educational program that need to be corrected before a larger study can be undertaken.

Aged↗
PubMed1989

Radioassay of bile acid coenzyme A:glycine/taurine: N-acyltransferase using an n-butanol solvent extraction procedure.

A rapid, specific, and sensitive radioassay for measuring bile acid CoA:glycine/taurine: N-acyltransferase (EC 2.3.1) has been developed. In this assay, 3H-labeled amino acids (glycine or taurine) are conjugated with unlabeled bile acid CoA derivatives to form 3H-labeled bile acid amidates. Following incubation, the 3H-labeled bile acid amidate is separated from the unreacted amino acid by an n-butanol extraction method. The extraction procedure was developed by evaluating the effects of buffer concentration and pH on the recovery of radiolabeled bile acid amidate standards in the presence of human hepatic cytosol. Highest recovery (greater than 90%) of bile acid amidate standards occurred under acidic conditions (pH 2) in the presence of 1% (w/v) SDS. When the radioassay and accompanying n-butanol extraction procedure were utilized to study the amidation of glycine or taurine with cholic acid in human hepatic cytosol, a single peak of radioactivity corresponding with either authentic glycocholate or taurocholate was detected in the n-butanol phase by high-performance liquid chromatography. This assay for bile acid CoA:glycine/taurine: N-acyltransferase activity was linear with incubation time and protein concentration. This assay should be useful in the biochemical studies of this enzyme, as well as in the examination of bile acid amidation in clinical liver specimens.

1-Butanol↗
PubMed1989

Effects of potassium channel blockade on endogenous glutamate release from cerebellar slices.

The effects of potassium channel blockade on the spontaneous release of endogenous glutamate from rat cerebellar slices was studied. Tetrapentylammonium (TPeA), 4-aminopyridine and quinine all increased the spontaneous release of glutamate. The effect of TPeA and 4-AP was potentiated in the absence of Ca2+ from the perfusing fluid. In normal artificial cerebrospinal fluid (ACSF) the Ca2+ channel antagonist, verapamil, mimicked the effects of TPeA seen in Ca2+-free ACSF. The increased release of glutamate produced by TPeA under Ca2+-free conditions was inhibited by the sodium channel blocker, tetrodotoxin, and by Ruthenium red, which inhibits mobilization of mitochondrial Ca2+. The results suggest that external Ca2+ is not required in the TPeA-induced release of glutamate. It is proposed that the prolongation of depolarization seen with potassium channel blocking drugs enables sufficient sodium to enter the neurone and release Ca2+ from intraneuronal stores in order to facilitate transmitter release.

4-Aminopyridine↗
PubMed1989

Characterization of a voltage-gated K+ channel that accelerates the rod response to dim light.

In this study a K+ current, IKx, in isolated salamander rod photoreceptors was characterized and its role in shaping small photovoltages was examined. IKx is a standing outward current of about 40 pA at -30 mV that deactivates slowly when the cell is hyperpolarized (tau max = 0.25 s). The voltage and time dependence of IKx are similar to that of M-current, but IKx can be distinguished from M-current because it is not suppressed by acetylcholine and is "blocked" by external Ba2+ in a surprising manner: the activation range of IKx is shifted strongly in the positive direction. Using current-clamp recordings and a computer simulation of the photo-response, we show that IKx figures prominently in setting the dark resting potential and accelerates the voltage response to small photocurrents.

Animals↗
PubMed1989

Ionic channels of the inner segment of tiger salamander cone photoreceptors.

Cone photoreceptors were isolated enzymatically and their ionic currents studied by the whole-cell, gigaseal voltage-clamp technique. Five nonsynaptic currents were identified. A prominent, poorly selective cation current, Ih, activated after a delay during hyperpolarizations and then deactivated with a delay on return to potentials greater than -50 mV. An empirical model for Ih gating kinetics is developed with three open and two closed states. Depolarization elicits a small, voltage-gated calcium current (ICa). Block by nitrendipine, nickel, cadmium, and cobalt, increase of current with barium, lack of rapid inactivation, and relatively high threshold suggest an L-type Ca channel. No evidence was found for low-threshold Ca channels. An anion current ICl(Ca) was present after pulses that led to a significant inward ICa (but not IBa) and was not elicited when cobalt was present. Tails of ICl(Ca) were short (100 ms) after short depolarizations and were longer after longer depolarizations. Two TEA-sensitive K currents were also elicited by depolarizations. One, IK(Ca), was calcium sensitive. We looked for modulation of Ih, ICa, and ICl(Ca) by a number of neurotransmitters. No changes of Ih were seen, but ICa and ICl(Ca) were depressed in a few cones when GABA or adenosine were applied. We discuss how this modulation might contribute to the feedback effects of horizontal cells on cones when surrounding cones are illuminated.

Ambystoma↗
PubMed1989

Chemotherapy plus RA233 in the treatment of oat cell lung cancer.

One hundred and one patients with oat (small) cell lung cancer have been treated with CAVE [Cytoxan, Adriamycin, Vincristine, and etoposide (VP-16)] chemotherapy +/- RA233 (a platelet-inhibiting agent). There was no difference in disease-free interval, pattern of relapse, or survival between groups.

Actuarial Analysis↗