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Biomedical subjects

N Baker

Publications and source records attributed to N Baker.

134 records · Page 8Linked to original sources
PubMed1966

Water-soluble inhibitor(s) of tumor respiration formed from ultraviolet-induced oxidation of linoleic and linolenic acids.

Inhibition of Ehrlich ascites carcinoma respiration by aqueous extracts of oxidized linoleic or linolenic acid (aqueous emulsions UV-irradiated, 90 min) was associated entirely with relatively involatile compounds which were both thiobarbituric acid (TBA)-reactive and peroxidase-reactive. Inhibitory compounds were heat stable and migrated in thin-layer chromatography with aldehydes, "hydroperoxides," and TBA-reactive compounds. Peroxidase-catalyzed reduction of the "hydroperoxide" diminished the inhibition. At 4.7 x 10(-5) M "hydroperoxide" concentration, the residues from both linoleic and linolenic acid inhibited tumor oxygen consumption to a similar degree. However, at this concentration of "hydroperoxide" only the dried extract from linolenic acid was able to produce inhibition (100%) of aerobic glucose utilization by tumor cells. No glycolytic inhibition by the dried residue of oxidized linoleic acid was observed. At least 12 compounds (approximate chain length, 7C-13C) containing alpha,Beta-unsaturated carbonyl groups were isolated by gas-liquid chromatography (GLC) of dried extracts of oxidized linolenic acid. No single fraction inhibited tumor respiration, but the recombined mixture of all compounds caused complete respiratory inhibition of ascites tumor cells. Less material was required to inhibit oxygen consumption before than after GLC presumably because the more highly inhibitory components of the extract (along with "hydroperoxides" and TBA-reactive compounds) were lost during GLC. Extracts from oxidized linolenic acid were found to produce in all tumor cells cytoplasmic evaginations which were readily detected by phase microscopy.

Animals↗
PubMedDate not supplied

Use of tannic acid to study cytoplasmic vesicles and membrane invaginations in epididymal fat pads of ageing mice.

A staining technique based upon the known ability of tannic acid to selectively stain the outer layer of the triple-layered plasma membrane was used, along with electron microscopic examination of stained, serial sections, to differentiate between surface invaginations, clusters of invaginations, free vesicles and tubular channels in epididymal fat pads from young, fed and fasted mice and from old, fed mice. A preliminary semiquantitative evaluation of the average number of each type of structure per cell was attempted. There were no significant numbers of free cytoplasmic vesicles of approximately 50 nm diameter (the dimension of most surface invaginations) under any conditions studied. Most apparent vesicles were stained by tannic acid and were, therefore, actually invaginations of the plasma membrane. There were no tubular channels of this size seen in any of the electron micrographs examined in serial sections. We estimated that there are about 50 single invaginations per micron2 of plasma membrane surface in both young and old fed mice. In addition there were about 20 invaginations/micron2 grouped as clusters of 2-15 per group (mean, 4 per group) in the fed mice. There was a tendency for the number of invaginations in clusters to increase during fasting; about 40% of the surface invaginations were grouped in clusters in adipocytes of fasted mice. Although there was no effect of ageing on the concentrations of surface invaginations or in their groupings as clusters, the total number of invaginations per cell must have increased almost 3-fold as the cells enlarged. The function of these surface invaginations and deeply penetrating groups of invaginations remains to be elucidated.

Adipose Tissue↗
PubMedDate not supplied

Lack of relationship of auditory gating defects to negative symptoms in schizophrenia.

The differences between schizophrenic patients with positive and negative symptoms have been the subject of extensive investigations. Psychophysiologists have proposed that there are elementary auditory sensory processing deficits in schizophrenia, but their prevalence in particular positive or negative subtypes has not been described. Our previous studies have shown that schizophrenics have impaired auditory sensory gating relative to normal controls, as demonstrated by the P50 auditory evoked potential conditioning-testing paradigm. In this paradigm, schizophrenics fail to show the normally expected diminished response to the second or 'test' stimulus. In the present study we assessed the possible relationship of this defect to negative symptoms in 20 schizophrenic patients treated with neuroleptics. Nine patients met the Andreasen criteria for predominantly 'negative schizophrenia'. 12 normal controls with no family history of schizophrenia were also studied electrophysiologically. Negative schizophrenics showed greater impairment than patients without such symptoms on the Trails B test of organic impairment, but there were no differences between groups on electrophysiological measurements of auditory sensory gating. Both schizophrenic groups showed impaired P50 auditory gating compared to normal controls. Both groups of schizophrenics also had a significantly diminished amplitude of the N100 waveform in the conditioning response, compared to normal controls. Auditory sensory processing defects in schizophrenia appear to be independent of negative symptoms.

Adult↗
PubMedDate not supplied

MR imaging of dedifferentiated chondrosarcoma.

MR imaging of a dedifferentiated chondrosarcoma of the humerus is presented and correlated with gross and microscopic histology from the surgical specimen. The classification of chondrosarcoma and specific MR signal characteristics that suggest dedifferentiation are discussed.

Bone Neoplasms↗
PubMedDate not supplied

Further modification to soft drinks to minimise erosion. A study in situ.

Soft drinks have been successfully modified to reduce enamel erosion. The aim of this study was to further modify an original low erosive blackcurrant drink product by the addition of a gum, to manipulate more favourably other drink parameters. The study was a single-blind, randomised four treatment crossover design involving 12 healthy volunteers. During 10 working-day study periods, subjects wore enamel samples in the mid palatal region of a removable appliance. Specimens were taped to expose a 2-mm enamel window. The drinks under test were: (1) Orange juice, (2) Original blackcurrant drink, (3) Water, and (4) Experimental blackcurrant drink. Drinks were imbibed at 250-ml volumes 4 times a day during appliance wearing from 09.00 to 17.00. Appliances were removed at lunchtime. Measurements of specimens were made at baseline, 2, 5 and 10 days using a profilometer. One 5-day and one 10-day specimen from each subject during each treatment were ultrasonicated. Significant differences, in erosion between drinks, were seen at days 5 and 10. Comparisons of preselected pairs of drinks of interest showed significantly reduced erosion by the two blackcurrant drinks compared to orange juice with no significant differences from water. The original blackcurrant drink produced significantly less erosion than the experimental drink. Ultrasonication removed enamel from the Orange juice specimens but very little from those exposed to water and the two blackcurrant drinks. Extrapolating the effects of both blackcurrant drinks suggested that alone they should not cause significant clinical erosion in a lifetime's intake of 1 litre per day.

Adult↗
PubMedDate not supplied

Electrophysiological effects of low dose alcohol on human subjects at high altitude.

Low dose alcohol significantly altered auditory evoked potentials in normal human subjects. Effects of alcohol were studied on the P50 evoked potential wave following click stimulation, which was presented in a conditioning-testing paradigm. The conditioning-testing paradigm uses paired stimuli to demonstrate inhibitory sensory gating, measured as suppression of the amplitude of the second or "test" response following the first or "conditioning" response. Alcohol at blood levels under 0.1 g per dl caused significant decrement in the size of the P50 wave in the initial conditioning response and also decreased the suppression normally seen in the conditioning-testing paradigm. These data suggest that low doses of alcohol affect both the excitatory mechanisms responsible for the formation of the P50 wave in the conditioning response and the inhibitory mechanisms responsible for its suppression in the test response. Nine of the 17 subjects studied using this paradigm were recorded both at Denver, Colorado (5,280 feet above sea level) and on Mt. Evans (14,264 feet above sea level). Despite the commonly held belief that alcohol causes more intoxication at high altitudes there was no significant difference in the effects of alcohol on evoked potentials in these subjects at these two attitudes.

Adult↗