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Biomedical subjects

J John

Publications and source records attributed to J John.

At least 127 records · Page 7Linked to original sources
PubMed1987

Characterisation of the metal-ion-GDP complex at the active sites of transforming and nontransforming p21 proteins by observation of the 17O-Mn superhyperfine coupling and by kinetic methods.

Kinetic studies on the interaction of three Ha-ras-encoded p21 proteins with GDP and MgGDP have yielded values for the association (10(6)-10(7) M-1 s-1) and dissociation (10(-3)-10(-5) s-1) rate constants at 0 degrees C. Dramatic differences in the rate constants were not observed for the three proteins. Under non-physiological conditions (absence of Mg2+), the rate constant for GDP release was an order of magnitude faster for the viral protein p21v than for the cellular form p21c or the T24 mutant p21t, but this was reduced to a factor of about 3 in the presence of Mg2+. In all cases, there was an increase of about one order of magnitude in the rate of GDP release on removing magnesium. The binding affinities ranged from 5.7 X 10(10) M-1 for p21c to 1.3 X 10(11) M-1 for p21v. Electron paramagnetic resonance (EPR) measurements on Mn2+ bound together with stereospecifically 17O-labelled GDP showed direct coordination of a beta-phosphate oxygen to the metal ion with a superhyperfine coupling constant of 0.16-0.22 mT, but no interaction with the alpha-phosphate oxygens at the active site of all three proteins. The association constant of Mn(II) to p21 proteins in the absence of nucleotides was estimated to be greater than 10(5) M-1. In agreement with the EPR results, experiments on the metal ion dependence of the binding of thiophosphate analogs of GDP provided further evidence for the absence of direct coordination of the metal ion to the alpha-phosphate group. These results have been used to construct a model for the interactions of Mg X GDP with the active site of p21 proteins.

Binding Sites↗
PubMed1987

Influence of aquatic humus and pH on the uptake and depuration of cadmium by the Atlantic salmon (Salmo salar L.).

Uptake and release of cadmium by Atlantic salmon at the concentrations near the background values for fresh water have been studied using cadmium labelled with Cd-109. Cumulation constant and biological half-time of release were established for different concentrations of humus and values of pH. The uptake is strongly dependent on the concentration of humus, showing a pronounced maximum at a DOC concentration of 2.7 mg/l. Release of cadmium is relatively slow, the biological half-time exceeds one year in the water without humic substances. Calculated bioconcentration factors range from 130 to several thousands, which may explain the wide differences of bioconcentration factor reported for natural systems. A general equation enabling calculation of bioconcentration factors for various conditions has been derived. An attempt is done to discuss the results from the point of view of physico-chemical forms of cadmium in respective waters. The amount of cadmium adsorbed on the surface of the fish was proved to be insignificant when compared with total concentration of cadmium bioaccumulated in the fish.

Adsorption↗
PubMed1987

Cost containment in a statutory health insurance scheme by substitution of outpatient for inpatient care? The case of the Bavarian Contract.

Among manifold attempts at containing the rapid growth of health care expenditure, one which attracted considerable attention was the 1979 agreement between Bavarian sick-funds and the office-based physicians of Bavaria that, in some ways, reshaped the remuneration scheme for ambulatory medical treatment. This so-called 'Bavarian Contract' tried to approach cost containment by initiating transsectoral substitution processes in favour of outpatient medical care and to the disfavour of, above all, the hospital sector of the health care system. This paper deals with the question whether in Bavaria (between 1979 and 1983/84) the structure of services and prescriptions was modified in a way that indicates the occurrence of substitution processes as intended by the 'Bavarian Contract'; also, whether there is any evidence of cost containment effects brought about the intensifying the ambulatory services of office-based physicians. The study results provide some weak hints at substitution processes in favour of ambulatory services; but there is no evidence that expanding ambulatory medical services may help to contain the growth of health care expenditure.

Algorithms↗
PubMed1986

Expression of p21 proteins in Escherichia coli and stereochemistry of the nucleotide-binding site.

v-Ha-ras encoded p21 protein (p21V), the cellular c-Ha-ras encoded protein (p21C) and its T24 mutant form p21T were produced in Escherichia coli under the control of the tac promoter. Large amounts of the authentic proteins in a soluble form can be extracted and purified without the use of denaturants or detergents. All three proteins are highly active in GDP binding, GTPase and, for p21V, autokinase activity. Inhibition of [3H]GDP binding to p21C by regio- and stereospecific phosphorothioate analogs of GDP and GTP was investigated to obtain a measure of the relative affinities of the three diphosphate and five triphosphate analogs of guanosine. p21 has a preference for the Sp isomers of GDP alpha S and GTP alpha S. It has low specificity for the Sp isomer of GTP beta S. Together with the data for GDP beta S and GTP gamma S these results are compared with those obtained for elongation factor (EF)Tu and transducin. This has enabled us to probe the structural relatedness of these proteins. We conclude that p21 seems to be more closely related to EF-Tu than to transducin.

Cell Line↗
PubMed1986

Failure of electrical myofeedback to augment the effects of physiotherapy in stroke.

Electromyographic biofeedback has been used with some success to treat patients with disturbances of muscle tone resulting from neurological disease. The aim of this study was to incorporate electrical myofeedback as an integral part of a physiotherapeutic regime designed to improve quality of movement and function in limbs weakened or paralysed by stroke. A portable, inexpensive E. M. G. biofeedback machine was used. Stainless steel skin electrodes were applied which needed minimal skin preparation. Twelve adults, (five male, seven female, mean age 44.2 years and 51.3 years respectively) who were referred for treatment due to weakness of limb muscles due to disease of the brain or spinal cord, were treated. The mean time from onset of incidence to treatment was 75.5 days. Each patient received six weeks of treatment. This was divided into two phases. Phase 1, (weeks 1, 2, 3) and phase 2 (weeks 4, 5, 6). Physiotherapy, and physiotherapy with biofeedback was randomly allocated to either phase. Each patient acted as his/her own control. A validated assessment was carried out by an independent therapist at the start of treatment, after three weeks and after six weeks of treatment. General function, knee function, range of movement of the affected side and timed tests were measured. Results show an overall improvement in general function. The second phase of treatment was slightly more favourable to improvement, but there was no indication that biofeedback significantly improved the outcome. In three tests it was equally significant to the physiotherapy applied; in one test it improved the effectiveness of physiotherapy and in one test it reduced the effectiveness of physiotherapy. This suggests that a six week course of physiotherapy improved muscular function and range of movements in patients with weakness due to upper motor neurone disease, but that these effects are not enhanced by myofeedback.

Adolescent↗
PubMed1984

Grading of muscle power: comparison of MRC and analogue scales by physiotherapists. Medical Research Council.

The M.R.C. scale for grading muscle power in stages from 0 to 5 has been compared with an analogue scale in which power is expressed as a percentage of the maximum expected for that muscle. Twenty therapists examined many patients in a series of comparative tests. The M.R.C. grade is more reliable and accurate for this type of clinical assessment in weak muscles, that is grades 0-3 on the M.R.C. scale or 0-62% on the analogue scale. The analogue scale is more reliable and accurate for the assessment of stronger muscles, that is grades 4 and 5 of the M.R.C. scale or 62-100% on the analogue scale. Therefore, analogue scales could be usefully adopted when testing bulky muscles operating at 50% or more of their normal power.

Evaluation Studies as Topic↗
PubMed1978

Abnormal forms of Trichomonas vaginalis.

Abnormal forms of Trichomonas vaginalis have been demonstrated by both conventional and scanning electron microscopy after inoculation of media with clinical material from cases of trichomonal vaginitis. Twenty-six cases of vaginitis have been studied; 10 of them showed the abnormal forms of trichomonads after growth in a modification of the medium described by Bushby and Copp (1955), while 16 showed only normal forms.

Atypical Bacterial Forms↗
PubMed1978

Asymptomatic urethral gonorrhoea in men.

Over a period of nine months 203 cases of urethral gonorrhoea were seen in 188 men. In 36 (17%) of the cases there were no symptoms, and in 14 (7%) the symptoms were considered so mild that the patients thought medical care was unnecessary. The symptomless patients and those with mild symptoms were found only as a result of efficient contact tracing. This high incidence illustrates the importance of good contact tracing and careful investigation.

Gonorrhea↗