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Biomedical subjects

J Everett

Publications and source records attributed to J Everett.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Selective attention in major depression: clinical retardation and cognitive inhibition].

Relationships between clinical retardation (measured by the Hamilton Depression Inventory) and selective attention (measured with a computerized version of the Stroop word colour test) were studied in a population of 21 depressed patients. Stroop interference was higher in depressed patients than in normals. Desynchronized presentations of the distractor and the target and intervals between responses and succeeding stimuli permitted depressed subjects to respectively apply and lift inhibition of the distractor so that their interference was reduced to control levels. Finally, successive inhibition scores were correlated with the retardation score in depressed subjects. The results are consistent with the hypothesis of a retardation in the application and the lifting of cognitive inhibition in depression.

Adult↗
PubMed1991

Cognitive effects of psychostimulant medication in hyperactive children.

Hyperactive and normal children were given a test of selective attention (Stroop test) and a neurocognitive test sensitive to a functional deficit of prefrontal cortex (Wisconsin Card Sorting Test). Hyperactive children showed significant deficits on both measures. After a year of psychostimulant medication, the hyperactive children all showed clinical and neurocognitive improvement, but continued to show a selective attention deficit compared with normal children. The results indicate a dissociation between the cognitive processes measured by the Wisconsin test and selective attention as measured by the Stroop, and that the selective attention deficit is more resistant to psychostimulant intervention.

Attention↗
PubMed1989

The selective attention deficit in schizophrenia. Limited resources or cognitive fatigue?

The Stroop Word-Color Test was used to study selective attention deficits in schizophrenic and nonschizophrenic psychiatric patients, compared with nonpsychiatric control subjects. Parts of the Weschler Memory Test and a shortened version of the Stroop Test were administered to test the hypotheses that the attentional deficit could be explained by problems of memory or cognitive fatigue. All patients showed deficits on all of the Stroop scales, but closer analysis of the results permitted discrimination of schizophrenic from nonschizophrenic patients. Schizophrenic patients showed as much difficulty as nonschizophrenic subjects on a limited-duration selective-attention task, but deteriorated significantly more when selective attention had to be maintained. The results could not be attributed to memory problems in the schizophrenic group. The results support the existence of two separable selective attention deficits in schizophrenic patients: a difficulty in selectively attending to the salient aspect of a complex stimulus, a difficulty shared with nonschizophrenic subjects, and a difficulty in maintaining selective attention over time that seems to be more marked in schizophrenic subjects.

Adult↗
PubMed1988

Effects of chronic iron deficiency anaemia on myoglobin content, enzyme activity, and capillary density in the human skeletal muscle.

The influence of chronic iron deficiency anaemia on myoglobin content, maximal enzyme activities and capillarization in the human skeletal muscle was investigated. Muscle samples from musculus vastus lateralis were screened in an Indonesian population. The causes of iron deficiency were chronic intestinal bleeding or repeated pregnancy combined with low iron intake. The maximal activities of iron-dependent and non-iron-dependent glycolytic and oxidative enzymes as well as myoglobin showed similar values in the iron-deficient group and the matched control group. The activities of the oxidative enzymes in both the iron-deficient group and the controls were lower, however, compared even to untrained Swedish subjects. The capillary density was essentially within a normal range in both groups. It is concluded that chronic iron deficiency anaemia of a moderate or severe degree, with Hb concentrations of about 80-100 g.1(-1), does not cause an impaired biochemical function of the human skeletal muscle.

Adult↗
PubMed1987

Spin-echo proton NMR spectroscopy of urine samples. Water suppression via a urea-dependent T2 relaxation process.

Spin-echo methods have been used to effect solvent suppression during the collection of 400 and 500 MHz 1H NMR spectra of urine samples containing urea in the concentration range 0.7-1.2 M. There was a marked trough of water Tobs2 values in the pH range 2.6 to 4.1, due to acid-catalyzed proton exchange between urea and the solvent water. Minimum values of Tobs2 (9 ms at 500 MHz) of water were obtained at about pH 3.2 in urine samples containing 1.2 M urea. However, good solvent suppression factors were obtained with endogenous urea concentrations of only 0.7 M. There was a strong field dependence on the water, T2, over the pH range 2 to 4. Attenuation of the water signal was estimated to be at least an order of magnitude greater at 500 MHz rather than at 400 MHz. Using the Carr-Purcell-Meiboom-Gill spin-echo pulse sequence, water signals broader than 13 Hz were attenuated by factors of greater than 10(3), and factors of greater than 10(4) were possible with water linewidths greater than 20 Hz, thus allowing the signals from metabolites in the sample to be efficiently digitized. This approach allowed metabolite signals at or near the water resonance to be observed without serious distortion of their intensities. The utility of this approach to solvent suppression in real systems is illustrated by observation of paracetamol and benzyl penicillin metabolites in human urine samples.

Humans↗
PubMed1986

Fluorescence quenching of cytochrome b5 in vesicles with an asymmetric transbilayer distribution of brominated phosphatidylcholine.

Several fluorescence techniques have been used to estimate the depth, in the membrane, of the endogenous tryptophans of membrane-bound proteins. We reported recently the use of phosphatidylcholines specifically brominated at different positions of the sn-2 acyl chain for this purpose (Markello, T., Zlotnick, A., Everett, J., Tennyson, J., and Holloway, P. W. (1985) Biochemistry 24, 2895-2901). The membranes made from these brominated lipids will have the brominated lipid in both monolayers, and so the estimated depth of the fluorophore will be relative to either the inner or outer surface of the membrane, but will not distinguish between these two extremes. To differentiate between these two models vesicles have now been made with an asymmetric distribution of brominated lipid, by use of phosphatidylcholine exchange protein. The asymmetric vesicles were isolated by virtue of their density, and their asymmetry was established by addition of an amphipathic fluorescent carbazole compound. With these vesicles it was shown that the tryptophan in the membrane-binding domain of cytochrome b5 which is quenched by bromolipid is located 0.7 nm below the outer surface of the membrane vesicles, rather than 0.7 nm from the inner surface.

Animals↗
PubMed1985

Determination of the topography of cytochrome b5 in lipid vesicles by fluorescence quenching.

Cytochrome b5, a protein isolated from the endoplasmic reticulum by detergent extraction, interacts spontaneously with small unilamellar phosphatidylcholine vesicles. When the vesicles are made from 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), the tryptophan fluorescence of the cytochrome is enhanced, and when they are made from 1-palmitoyl-2-(dibromostearoyl) phosphatidylcholine (BRPC), the fluorescence is quenched. A series of BRPC were synthesized with bromine atoms at the 6,7, 9,10, 11,12 or 15,16 positions. The vesicles synthesized from each of these lipids were similar in size to those made from POPC. The relative fluorescence intensities of the cytochrome b5 in POPC and 6,7-, 9,10-, 11,12- and 15,16- BRPC were 100, 19.4, 29.4, 37.1, and 54.0, respectively. These data suggest that the exposed tryptophan(s) is (are) at a depth of 0.7 nm below the surface of the vesicle. Bromine is a collisional quencher; hence, these data may indicate the relative position of the lipid annulus around the protein rather than the depth of the protein below the average vesicle surface. Cytochrome b5 contains three potentially fluorescent tryptophans, and determinations of fluorescent quantum yield indicate all three potentially fluorescent tryptophans, and determinations of fluorescent quantum yield indicate all three are fluorescent with an average quantum yield, when in POPC vesicles, of 0.21. Fluorescence lifetime measurements by the demodulation technique indicated heterogeneity of fluorescence lifetimes in all vesicles. The lifetimes in the BRPC vesicles ranged from 2.0 to 2.4 ns compared to a value of 3.3 ns in POPC.(ABSTRACT TRUNCATED AT 250 WORDS)

Calorimetry, Differential Scanning↗
PubMed1984

Obstetric care.

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Developing Countries↗
PubMed1983

The transcortical reflex triggered by cutaneous or muscle stimulation in the cat with a penicillin epileptic focus: relative importance of regions 3a and 4.

After establishment of a cortical penicillin epileptic focus in the cat, stimulation of an anterior paw muscle can evoke a late myographic response (LMR) in the same muscle via a transcortical reflex. It is shown here that (1) an LMR can also be obtained with cutaneous stimulation in the region of the muscle; (2) an LMR cannot be elicited when the focus in on area 3a; (3) after inactivation of area 3a by TTX, the motor cortex evoked potential and spike thresholds are increased for proprioceptive but not for cutaneous stimulation, and the LMR persists. It is concluded that area 4 is the critically important structure for the triggering of an LMR. The results concerning area 3a are discussed in terms of this region's efferent connections to the motor cortex and to the spinal cord.

Afferent Pathways↗
PubMed1980

Monoamine roles in retention and reversal of delayed response in cats.

Two experiments were performed to study the effects of manipulation of central monoamines upon behavior in a delayed response (DR) situation. In the first study, serotonin (5-HT) levels were increased by administration of 5-hydroxy-L-tryptophan (5-HTP) and RO4-4602, a decarboxylase inhibitor, to cats that had overlearned the DR. This intervention had no significant effect upon performance in the 0 sec delay condition, but significantly increase error and non-response scores during delay trials; the effect is specific to an "information holding" demand upon the animal and according to the neurochemical analysis appears to be due to a central effect of 5-HT. In a second experiment, dopamine levels were raised by L-DOPA administration during a reversal of the original DR situation, and the effect of L-DOPA on the evolution of response strategies was observed. All animals developed a position habit that proved impossible to correct but L-DOPA animals developed a significant position habit more quickly than controls, thus suggesting a possible relationship between the neostriatal dopamine accumulation and behavioral plasticity.

5-Hydroxytryptophan↗
PubMed1976

The climbing fibers of the cerebellar cortex, their origin and pathways in cat.

The sources and pathways of the climbing fibers to the cerebellar posterior vermis were studied with comibined electrophysiological and anatomical methods in cats. Recording from identified cerebellar Purkinje cells, monosynaptic climbing fiber (CF) responses have been obtained both for stimulation of the inferior olive (IO) and various parts of the brain stem (BS). CF responses were found to of three types, IO only, BS only or both IO and BS. However the responses to BS stimulation were very few in number in comparison with IO or IO and BS types of responses. The latencies of the responses were shorter for the BS cases consistent with their distance from the cerebellum. A comparison of latencies and the relative responsiveness of the different area of the brain stem which were studied, indicate that part of the CF ascend through the pontine region and enter the cerebellum by way of the medium and superior penduncles. This finding is confirmed by the results of anatomical studies in which degenerating fibers were found in the molecular layer (using the Nauta technique) after lesion of the brachium pontis but not after lesions of the medial portion of the pons. Similarly, injection of radioactive leucine into the pontine nuclei failed to show any labeled fibers in the molecular layer. Horseradish peroxidase (HRP) was injected into localized regions of the posterior vermis after total bilateral destruction of the inferior peduncles. Large numbers of positive, marked cells were still found in the inferior olive. It is concluded that nearly all, if not all, the climbing fibers originate in the inferior olive and that they ascend to the cerebellum by way of all the peduncles.

Afferent Pathways↗
PubMed1976

Biohazard potential: recovery of infectious virus from the liquid nitrogen of a virus repository.

Flame-sealed glass ampules containing vesicular stomatitis (VSV) were submerged in a liquid nitrogen (LN2) refrigerator for storage. Onseveral occasions cracked or shattered ampules were discovered upon removal from the refrigerator. Subsequently, VSV was recovered from the LN2 of the virus repository indicating a source of potential danger to those employing glass ampules submerged in LN2 for preservation of pathogenic organisms.

Laboratories↗