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Biomedical subjects

M Cox

Publications and source records attributed to M Cox.

At least 163 records · Page 9Linked to original sources
PubMed1984

Affinity labelling of 5-aminolevulinic acid dehydratase with 2-bromo-3-(5-imidazolyl)propionic acid.

2-Bromo-3-(5-imidazolyl)propionic acid, a zinc-directed thiol reagent, inactivates the enzyme 5-aminolevulinic acid dehydratase from bovine liver (5-aminolevulinate hydro-lyase (adding 5-aminolevulinate and cyclizing, EC 4.2.1.24). The substrate, 5-aminolevulinic acid, completely protects against inactivation. The reagent inhibits the zinc-containing enzyme to a greater extent than the zinc-deprived enzyme; and it competes with the zinc chelator 1,10-phenanthroline. The reagent alkylates essential sulfhydryl groups of the enzyme, since the extent of the inactivation depends on the reduction of the enzyme protein by thiol compounds. It is concluded that the zinc site, the substrate site and the essential sulfhydryl groups are in close proximity in the active site.

Affinity Labels↗
PubMed1984

The mitogenic principle of Escherichia coli lipoprotein: B-lymphocyte mitogenicity of the synthetic analogue palmitoyl-tetrapeptide (Pam-Ser-Ser-Asn-Ala).

N-Palmitoyl-(S)-seryl-(S)-seryl-(S)-asparaginyl-(S)-alanine (Palmitoyl-tetrapeptide) is an analogue of the N-terminal part of the lipoprotein from the outer membrane of Escherichia coli. It was prepared by chemical synthesis and tested for biological activity in in vitro lymphocyte culture systems. In spleen cells of the inbred mouse strains C3H/HeJ, C3H/He/Bom/ nunu , and Balb/c, the compound exhibited stimulatory activity towards B-lymphocytes comparable to the effect of native lipoprotein, as measured by the incorporation of 3H-thymidine and 3H-uridine, and by a hemolytic plaque assay. The B-lymphocyte tumor cell line BCL1 was also activated by the compound. The results demonstrate, that the N-terminal tetrapeptide moiety of lipoprotein, linked to a lipophilic molecule, constitutes by itself a novel B-lymphocyte mitogen.

Animals↗
PubMed1984

Steroid-induced protein synthesis in giant-toad (Bufo marinus) urinary bladders. Correlation with natriferic activity.

We have identified a group of proteins (Mr approximately 70 000-80 000; pI approximately 5.5-6.0) in giant-toad (Bufo marinus) urinary bladders whose synthesis appears to be related to aldosterone-stimulated Na+ transport. Spironolactone, a specific mineralocorticoid antagonist in renal epithelia, inhibits the synthesis of these proteins as well as the natriferic effect of the hormone. Since a variety of other steroids (some of which are traditionally considered to be glucocorticoids) also stimulate Na+ transport in toad urinary bladders, we examined whether their natriferic activity was expressed in a fashion similar to that of aldosterone. Short-circuit current was used to measure Na+ transport, and epithelial-cell protein synthesis was detected with high-resolution two-dimensional polyacrylamide-gel electrophoresis and autoradiography. At a concentration of approximately 100 nM, dexamethasone, corticosterone and aldosterone were equinatriferic. Dexamethasone and aldosterone had identical dose-response curves, maximal and half-maximal activity being evident at concentrations of approximately 100 nM and 10 nM respectively. In contrast, at a concentration of approximately 10 nM, corticosterone had no effect on Na+ transport. The natriferic activities of these three steroids correlate with their known affinities for the putative mineralocorticoid receptor in toad urinary bladders. Natriferic concentrations of dexamethasone and corticosterone (140 nM) induced the synthesis of proteins with characteristics identical with those induced by aldosterone. Spironolactone, at an antagonist/agonist ratio of 2000:1, inhibited steroid-induced Na+ transport and the synthesis of these proteins. Thus it appears that all natriferic steroids share a common mechanism of action in toad urinary bladders. Natriferic activity can be correlated not only with relative steroid-receptor affinity but also with the induction of a specific group of epithelial-cell proteins.

Aldosterone↗
PubMed1984

Impaired nitrazepam metabolism in hypothyroidism.

Delayed metabolism of a number of drugs has been described in hypothyroid patients. We report an elderly hypothyroid female who had prolonged delay in the metabolism of a commonly-used sedative, nitrazepam, and discuss the importance of delayed drug metabolism in hypothyroidism.

Aged↗
PubMed1983

Mineralocorticoid-specificity of aldosterone-induced protein synthesis in giant-toad (Bufo marinus) urinary bladders.

We have identified a group of proteins (Mr approximately 70000-80000; pI approximately 5.8-6.4) in giant-toad (Bufo marinus) urinary-bladder epithelial cells whose synthesis appears to be related to aldosterone-stimulated Na+ transport. To define this relationship further, we examined whether submaximal natriferic concentrations of aldosterone induced these proteins and whether spironolactone (a specific mineralocorticoid antagonist in renal epithelia) inhibited their synthesis. Short-circuit current was used to measure Na+ transport and epithelial-cell protein synthesis was detected with high-resolution two-dimensional polyacrylamide-gel electrophoresis and autoradiography. Submaximal natriferic concentrations of aldosterone (1.4 X 10(-8) M) induced the same proteins as maximal concentrations of the hormone (1.4 X 10(-7) M). In contrast, in previous experiments, similar proteins were not induced by subnatriferic concentrations (5.0 X 10(-8) M) of cortisol, a glucocorticoid. A spironolactone/aldosterone molar ratio of 2000:1 was required to inhibit aldosterone-stimulated Na+ transport completely; ratios of 200:1 and 500:1 produced partial inhibition. Concentrations of spironolactone that abolished aldosterone-stimulated Na+ transport also inhibited aldosterone-induced protein synthesis. We conclude that the synthesis of the proteins we have identified is specifically related to activation of the mineralocorticoid pathway.

Aldosterone↗
PubMed1983

Discriminating somatic evoked potentials using a pairwise procedure.

Generally, investigators use only the magnitude spectra of a signal for processing or for discriminant analysis, with the phase information discarded. However, it is not difficult to generate two different time domain signals having identical magnitude spectra in the frequency domain. Thus the phase information should not be neglected. This paper presents the results of a simulation study of a discriminant analysis procedure for paired variables, e.g. magnitude and phase pairs. The procedure is then applied to discriminating somatic evoked potentials from normal and damaged spinal cords with excellent results.

Animals↗
PubMed1983

Prospective evaluation of the risk of bacteremia and the role of antibiotics in ERCP.

To determine the frequency of bacteremia associated with endoscopic retrograde cholangiopancreatography (ERCP), we obtained blood cultures before, during, and after ERCP in 51 consecutive patients. Patients with radiographically demonstrated abnormalities in pancreatic and/or biliary ducts were routinely given antibiotic therapy after ERCP. Bacteremia after successful cannulation of the papilla of Vater was observed in only one patient with multiple strictures of the main pancreatic duct. No episodes of acute febrile illness was observed in any patient during the 48-hour follow-up period after ERCP. Our observations suggest that the risk of bacteremia from ERCP is minimal, and that any possibility of sepsis after ERCP in patients with abnormal pancreatic or biliary ducts may be prevented by administering appropriate antibiotics after the procedure.

Adolescent↗
PubMed1982

Aldosterone-induced proteins in renal epithelia.

Similar aldosterone-induced proteins have been demonstrated in two renal epithelia, the urinary bladder of the toad, Bufo marinus, and epithelia formed by cells of the A6 line derived from the kidney of the toad, Xenopus laevis. The proteins are induced along with the stimulation of Na+ transport but their synthesis is not dependent on Na+ transport per se. In view of the similar characteristics of the aldosterone-induced proteins in these two different epithelia, we suggest that they may have an important role in aldosterone-induced Na+ transport.

Aldosterone↗
PubMed1982

Proprioception in schizophrenia.

B. Ritzler (J. Abnorm. Psychol., 86: 501-504, 1977) failed to replicate previous weight-lifting studies showing a proprioceptive deficit in schizophrenics. However, Ritzler did not use the same standard weights that the previous studies employed. Could this difference in procedure have caused his failure to replicate? Two experiments were completed to provide additional information about this question and related issues. In Experiment I, chronic hospitalized schizophrenics and normals were tested with light and heavy weights. Rosenbaum's original modified method of limits and the method of constant stimuli were utilized. Both methods provided comparable results, which, like Ritzler's data, failed to show a differential impairment in the discrimination of the light weights for paranoid schizophrenics. In Experiment II, outpatient paranoid schizophrenics, outpatient nonparanoid schizophrenics, outpatient psychiatric patients, and aged normals were evaluated utilizing the same psychophysical procedure and standard weights employed in the original studies. No differential impairment was found for the light weights for any group. These results provide strong support for Ritzler's position that a proprioceptive deficit is not unique to schizophrenia.

Adult↗
PubMed1982

'I took a life because I needed one': psychotherapeutic possibilities with the schizophrenic offender-patient.

This paper's fulcrum is a schizophrenic's explanation as to why he had taken a life: 'I took a life because I needed one.' It attempts to describe the exploration of therapeutic possibilities with the schizophrenic offender-patient. Particular attention is paid to the Associative Mode. This is a way of safely engaging with the patient in the depth of his experience without shattering his precarious defences. The discussion illustrates the close inter-dependence between the dynamic content of individual and group psychotherapy, the life of the hospital as a whole and the significance of therapeutic space being contained within a secure perimeter.

Commitment of Persons with Psychiatric Disorders↗
PubMed1982

Lithium and the kidney: a review.

The effects of lithium on renal water and electrolyte transport have generally been considered to be reversible following the cessation of lithium treatment. However, several recent reports have suggested that lithium-induced nephrogenic diabetes insipidus may persist for months or even years after lithium is discontinued. In addition, a number of reports have described the development of renal insufficiency (in association with interstitial nephritis) in some patients who have been chronically treated with lithium. The authors briefly review the effects of lithium on renal tubular transport and critically examine the reports of lithium-induced renal disease.

Acid-Base Equilibrium↗
PubMed1982

Step test predictions of maximum oxygen uptake before and after an employee fitness programme.

The Canadian Home Fitness Test has been administered to two large office populations on three occasions over a 9 month period. At the control company (87M, 89F), there was some improvement of test scores from the initial to the final visit (decrease of heart rate in 6th minute of exercise 5.7 beats X min-1 in men, 9.5 beats X min-1 in women); this may reflect habituation to the test procedure. At the experimental company (180M, 258F), employees were given the opportunity of participation in an Employee Fitness Programme. High adherents to this programme (61M, 97F) showed a substantial decrease of 6 min exercise heart rate (12.8, 16.0 beats X min-1) with an increase of CHFT duration (2.59, 2.33 min) and VO2max (Jetté prediction, 3.8, 2.9 ml X kg-1 min-1). These changes were much larger than in either the control group, or in "non-participants" (54M, 46F) and "drop-outs" (19M, 48F) in the experimental company. Low adherents to the fitness programme (46M, 67F) occupied an intermediate position. Given accurate pulse counting, about a sixth of the high adherents would have detected no change of CHFT score if a single test was carried out after completing 6 months in the fitness programme; however, in some of these subjects there may indeed have been no training response. Because it gives a low weighting to exercise heart rate, the Jetté equation indicates a smaller effect of training than the Astrand nomogram.

Adult↗