Search PubMed⌕ Search

Biomedical subjects

C Shaw

Publications and source records attributed to C Shaw.

At least 361 records · Page 20Linked to original sources
PubMed1984

Characteristics and distribution of muscimol binding sites in cat visual cortex.

In vitro receptor binding techniques were used to study the characteristics and distribution of [3H]muscimol binding sites in cat visual cortex. [3H]muscimol, a specific GABA agonist, labeled a single population of binding sites with a Kd of 18 nM. Specific binding was saturable, reversible, and was blocked by the addition of GABA or (+)-bicuculline. Autoradiograms revealed that the highest density of [3H]muscimol binding sites occurred in cortical layer IV. Little variation between the various visual cortical areas was noted in contrast to marked regional heterogeneity within subcortical structures.

Animals↗
PubMed1984

Biotransformation of norgestimate in women.

The metabolism of norgestimate (ORF-10131; 14C-d-13-ethyl-17-acetoxy-18,19-dinor-17 alpha-pregn-4-en-20- yn -3-oxime) was studied in humans. Compound labeled with carbon-14 in the 17 alpha-ethynyl group was administered to four female subjects. An average of 46.8 percent of the administered radioactivity was excreted in the urine and 36.8 percent in the feces over a two-week collection period. About 12 percent of the urinary radioactivity represented freely extractable metabolites and another 57 percent consisted of extractable material released by enzyme hydrolysis. The ethynylated metabolites of norgestimate were separated from endogenous compounds and non- ethynylated metabolites by silver- sulfoethyl cellulose column chromatography. Metabolites were subsequently isolated by high performance liquid chromatography and thin layer chromatography. The identification of five urinary metabolites was accomplished by combined gas-liquid chromatography/mass spectrometry. These metabolites include norgestrel, 16 beta- hydroxynorgestrel , 2 alpha- hydroxynorgestrel , 3 alpha, 5 beta- tetrahydronorgestrel , and a fifth trihydroxylated metabolite of undetermined stereochemical configuration; 3,16-dihydroxy-5- tetrahydronorgestrel .

Biotransformation↗
PubMed1984

Ontogenesis of muscarinic acetylcholine binding sites in cat visual cortex: reversal of specific laminar distribution during the critical period.

Acetylcholine appears to act as a modulator of neuronal activity in cat visual cortex and, like noradrenaline, may be involved with cortical plasticity mechanisms during the critical period. To explore possible ACh involvement in these mechanisms we have examined acetylcholine binding sites in cat visual cortex during development using [3H]QNB, a muscarinic antagonist. At 3 days postnatal [3H]QNB preferentially labelled binding sites in layer IV. During development the pattern of binding reversed, so that by 95 days postnatal layer IV was the least densely labelled. The number of binding sites increased during development peaking at 1 month postnatal. The Kd of [3H]QNB binding sites increased to 95 days postnatal, with a peak value of 0.76 nM. The results show that during development, and especially within the critical period, changes in [3H]QNB binding site distribution, number and affinity occur.

Animals↗
PubMed1984

Alterations in receptor number, affinity and laminar distribution in cat visual cortex during the critical period.

The number, affinity, and laminar distributions of various receptors in cat visual cortex were examined during postnatal development using homogenate and in vitro autoradiographic techniques. For all receptor populations examined, the total number of receptors (Bmax) increased from relatively low early values to peak values during the first three months of postnatal life followed by a drop or plateau in the number of receptors. This peak in Bmax occurred during the physiologically-defined period for cortical plasticity. For most receptors examined, the affinity (KD) was also altered during postnatal development. Many of the receptor populations examined exhibited changes in their initial laminar distributions during the first three months of postnatal development, although other did not. The results show a more complex picture of receptor ontogenesis than previously reported, and suggest that the observed receptor modifications affect the synaptic efficacy and the basic chemical circuitry of the visual cortex during the critical period.

Animals↗
PubMed1984

Ontogenesis of muscimol binding sites in cat visual cortex.

In vitro receptor binding techniques were used to study the characteristics, distribution, and ontogenesis of muscimol binding sites in cat visual cortex. [3H] Muscimol, a GABA agonist, labelled a single population of binding sites with a KD of 18 nM in adult cats. Specific binding was saturable, reversible and was blocked by the addition of GABA or (+) bicuculline. Autoradiograms revealed that the highest density of [3H] muscimol binding occurred in cortical layer IV. Similar patterns of [3H] muscimol binding were observed at all ages examined, although the binding densities differed. The peak [3H] muscimol binding density, corrected for amount of protein, occurred at 3 months postnatally. In 3 day old and adult cats binding density was 41% and 69%, respectively, of the peak value.

Animals↗
PubMed1983

Intact neurotensin (NT) in human plasma: response to oral feeding.

Neurotensin-like immunoreactivity (NTLI) increases in human plasma postprandially. Intact neurotensin (NT) however, has been found to be a minor component of NTLI, the major components being the N-terminal fragments 1-11 and 1-8. Intact NT is the only known biologically-active form. A radioimmunoassay (RIA) has been developed which employs an antiserum unreactive to 1-11 or smaller N-terminal NT fragments. Using this RIA, intact NT response to a mixed meal has been assessed in 10 healthy humans. Intact NT levels were significantly elevated over basal 15 min after ingestion of the meal and remained so for the duration of the experiment (120 min). The suggestion that intact NT is a circulating hormone has been substantiated. Due to the rapidity of the rise in plasma NT after feeding it is proposed that the initial NT response is mediated by neural or hormonal means, rather than by direct luminal stimulation of the N cell-rich jejunoileum.

Eating↗
PubMed1982

The neural circuitry of the neocortex examined in the in vitro brain slice preparation.

The in vitro brain slice technique has been applied to the study of the neocortex. Cortical blocks were removed from adult rats deeply anesthesized with halothane, sectioned coronally at 400-700 micrometer, and placed in a brain slice chamber. Cortical slices typically showed spontaneous and evoked potential activity and normal histology for 8 h or longer. Single units and evoked potential recordings were made from different layers of the cortex using micropipettes. The evoked potentials to electrical stimulation of differing intensity, frequency, and from different cortical layers were analyzed. Evoked potential from all but the most superficial layers of the cortex showed a characteristic 6-component response to stimulation of nearby white matter. This evoked potential closely resembled cortical responses recorded in vivo by other investigators following afferent stimulation. The response amplitude of all components increased as stimulus intensity was raised. Radial movement of the recording electrode showed that components 1-3 had their largest amplitudes in the deepest cortical layers, component 4 reached its greatest amplitude and shortest latency in layer IV, and components 5 and 6 reached their greatest amplitudes in layers IV to II. The frequency following for various components was measured showing greater decline in amplitude for components 4-6 than 1-3. This, together with the results of previous investigators, suggests that the first 3 components represent afferent fiber input, while component 4 represents the first cortical response (layer IV). Components 5 and 6 represent later, additional cortical responses. Further support for the intracortical origin of component 4 was provided by lateral intracortical stimulation within layer IV, giving an evoked potential composed mostly of component 4. With lateral movement of the recording electrode in layer IV the evoked potential disappeared in under 1 mm, suggesting a fairly restricted afferent input to the cortex. The present results encourage the use of the cortical brain slice preparation as an appropriate model system in which to study cortical neural circuitry.

Action Potentials↗
PubMed1981

Integration specificity of an artificial kanamycin transposon constructed by the in vitro insertion of an internal Tn5 fragment into IS2.

IS2 has been marked genetically by the in vitro insertion into its HindIII site of a 3.3 Kb HindIII fragment of Tn5 conferring resistance to kanamycin. The transposition of the IS2::Km, thus obtained, to lambda has been found and insertion sites were characterised. Each of ten independent IS2::Km insertions were found at the same site at 61.2% of the lambda map, always in the same orientation (orientation II relative to the xis gene). The integration sites of IS2::Km in five of the kanamycin-transducing phages were determined by DNA sequence analysis, and were found to be identical at the nucleotide level. Further transposition of IS2::Km from lambda to the bacterial chromosome was demonstrated.

Bacteriophage lambda↗
PubMed1981

Computerized intravenous arteriography: a technique for visualizing the peripheral vascular system.

A unique method of computerized fluoroscopic enhancement allows direct visualization of the entire vascular system by intravenous injection of standard contrast agents, thereby avoiding the need for arterial puncture or hospitalization. This technique has been used to satisfactorily visualize the intra- and extracranial carotid and vertebral arteries, the aortic arch and upper extremity vessels, the abdominal aorta and its branches, as well as lower extremity vasculature. Although the technique is still under development, occlusions, stenoses, ulcerated plaques, and aneurysms have been visualized. Qualitative evaluation of these studies indicates a promising correlation with standard arteriography. This technique has great promise as a method of diagnostic screening in the management of peripheral vascular disease.

Aneurysm↗
PubMed1981

Site-specific mutagenesis of Agrobacterium Ti plasmids and transfer of genes to plant cells.

A general method is described for the use of tumor-inducing (Ti) plasmids as experimental gene-vectors for plant cells. Intermediate vectors, containing specific Ti plasmid sequences and capable of replication in both E. coli and Agrobacterium strains, were constructed and used for the in vitro introduction of isolated DNA fragments into predetermined sites of the T-region derived fragments. Site-specific inserts and/or deletions-substitutions in Ti plasmids were produced by exchange of the modified T-region sequences for the wild-type sequence by in vivo recombination between intermediate vectors and resident Ti plasmids. This method was applied for the isolation of mutant Ti plasmids affecting either morphogenetic properties or opine synthesis in crown gall tumors. Foreign DNA, inserted at different sites in the T-region of both octopine and nopaline Ti plasmids, was shown to be cotransferred with the T-DNA and to be stably maintained in the transformed plant cells.

Arginine↗
PubMed1979

A new assay for the measurement of mediator release from rat peritoneal mast cells.

In this report, we describe a new in vitro experimental system for monitoring the release, and inhibition of release, of [3H]-serotonin from rat peritoneal mast cells, which can be used as a novel screen for evaluation of compounds effective in immediate hypersensitivity reactions. This assay is an improvement on existing assays since the cells are not required to be exposed to hormones at any time during the procedure. In this assay, 1 microgram/ml of compound 48/80 consistently produced a 6- to 8-fold-increase in release of serotonin with a low background release of 4-5%. Disodium chromoglycate (DSCG), a standard inhibitor of histamine release, effectively inhibited compound-48/80-stimulated serotonin release with an average I50 of 2.1 X 10(-4) M. Several other potential antiasthmatic agents were far more potent than DSCG.

5-Hydroxytryptophan↗
PubMed1977

A potassium contribution to the response of the barnacle photoreceptor.

1. Intracellular recording from photoreceptors in the lateral eye of the barnacle show a brief negative-going 'dip' shortly after the onset of the late receptor potential. This phase can sometimes result in a hyperpolarization relative to the resting membrane potential. 2. The dip is prominent in light-adapted cells and is reduced by dark-adaptation. Low extracellular Ca2+ also reduces it. 3. The amplitude of the dip changes inversely with the K+ concentration in the saline. 4. The amplitude of the dip depends on the membrane potential, with a reversal potential near - 80 mV. 5. K+ blocking agents such as quinine and quinidine reduce or abolish the dip. 6. These observations indicate that the dip is due to a brief increase in K+ conductance which may be dependent on an influx of Ca ions. The fast decay of this phase may be brought about by a rapid uptake of Ca2+ by an intracellular mechanism.

Adaptation, Ocular↗
PubMed1977

Cellular immunity in adult marasmus.

Twelve patients with recent weight loss to less than 85% of standard weight-height ratio and a serum albumin level of at least 3 gm/100 ml were considered to have the adult equivalent to marasmus. Cellular immune function was assessed by delayed hypersensitivity skin testing to Monilia and streptokinase-streptodornase, peripheral lymphocyte count, proportion of T and B cells, whole blood and isolated lymphocyte transformation to phytohemagglutinin, pokeweed mitogen, concanavalin A, Monilia, and streptokinase-streptodornase. Significant impairment of skin test reactivity while in vitro responsiveness remained intact was noted in the marasmic patients. No impairment was found in 12 individuals with recent weight loss who remained at a weight greater than the 85% weight-height ratio. In four marasmic individuals in whom weight loss was arrested by nutritional repletion, skin reactivity returned without substantial change in weight. In this type of marasmus, both depleted nutritional status and weight loss must be present for impairement of skin test responsiveness. These findings confirm relative sparing of more vital functions dependent on protein metabolism in adult marasmus compared to the kwashiorkor-like syndromes of hypoalbuminemic malnutrition seen in adults.

Adult↗