Biomedical subjects
Publications and source records attributed to G W Mitchell.
A 19-year-old phenotypic female with primary amenorrhea and 45X,0/46X,Y chromosomal mosaicism was found to have asymmetrical gonadal dysgenesis. Her lack of virilization precludes her precise categorization in the current nomenclature of gonadal dysgenesis and she is considered a unique variant of the syndrome of mixed gonadal dysgenesis.
A simple and rapid test that correlates with L/S ratios has been developed. By centrifuging fresh, unfrozen amniotic fluids at 200g for 10 minutes and measuring the optical density at at 650 nm, correlation with L/S ratios is obtained. Optical density readings of 0.15 or greater correlate 100% with L/S ratios of 2.0 or greater. Optical readings below 0.15 correlate 94% with L/S ratios below 2.0.
The stationary fluorescence polarization and the differential phase delay of the polarized components of the fluorescence of 1-phenylnaphthylamine in Escherichia coli suspensions were measured before and after addition of colicin E1. Both sets of measurements register an increase in the rotational relaxation time of the fluorescent probe when colicin is present. These increases are absent in an E. coli mutant tolerant to colicin E1. The physical interpretation of the changes demands separate estimation of the fraction f2 of the emitting fluorophores that change their properties upon colicin addition and of the rotational relaxation time p2 of this fraction, following the colicin-induced changes. By themselves, the steady state polarizaiton observations permit only the conclusion that f2 must be in the range of 1-0.06 and the change in p2/pi between 1.5 and a value larger than 10. Combination of the data of stationary polarization with those of differential phase fluorometry results in an important reduction in the uncertainty:f2 must be in the range 1-0.33 and the change in p2/pi in the range 1.5-2.5.
1. MPO, H2O2 and C1- form a complex that undergoes intramolecular rearrangement yielding the chlorinium ion. 2. The chlorinium ion can interact with MPO, bacteria and amino acids. 3. The reaction can occur at a wide range of pH, H2O2 concentration and C1- concentration. 4. The chlorinium ion can attack different protein molecules to cause structural changes. 5. Preincubation of MPO with bacteria results in greater bactericidal activity. 6. Diffusible bactericidal agents are also produced by the MPO-H2O2-C1- system.
The prostaglandin synthetase inhibitors indomethacin and acetyl salicylic acid did not affect the post-stimulus rebound excitation of guinea-pig duodenal and jejunal circular muscle with transmural electrical stimulation at 1 min intervals. In the absence of any drug, sequential time-dependent changes in amplitude of the rebound contractions were: (1) progressive increase during first 10 min, (2) a plateau at 30 min, (3) progressive decline to almost no response over 3 h. The results indicate that, in the circular muscle layer, prostaglandin synthesis is not required for production of the rebound response following electrical stimulation of inhibitory neurons.
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A retrospective analysis of the clinical data from 40 patients with amenorrhea has enabled us to reach useful generalizations applicable to the management of this problem. Chromosome studies when puberty is delayed and a thorough pelvic examination when menarche fails to appear at the proper time relative to the sequence of other pubertal events will lead to an early definitive diagnosis in most cases of primary amenorrhea. A schema for the functional categorization of patients with secondary amenorrhea is presented to obviate the necessity of obtaining a needlessly expensive battery of laboratory tests which often yield misleading or uninterpretable data.
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The steroid response of testes to exogenous gonadotropin administration was studied before castration in a patient with the complete form of the testicular feminization syndrome. Urinary steroid determination were made along with measurements of plasma testosterone during adrenal suppression with dexamethasone and after stimulation with human menopausal gonadotropin (HMG) and HMG plus human chorionic gonadotropin (HCG). Our data provide evidence that the gonads in the testicular feminization syndrome synthesize steroids normally. Estrogens and testosterone are secreted by the testes, and the Leydig cells of the testes are capable of responding to exogenous HMG and HCG stimulation. These findins are consistent with the hypothesis that there is no abnormal testicular steroidogenesis in these genotypic males. Additional evidence is provided that these gonads secrete testosterone in amounts comparable to those of normally functioning testes. Failure of virilization in the presence of androgen secretion as indicated by previous authors is probably the result of a deficiency of androgenic action at the end organs. The presence of sparse pubic and axillary hair in the mother and the finding of the same type of karyotype (46,XY) in a sibling suggest that hereditary factors play a role in this disorder.
A test that circumvents the complex methodology needed for the determination of L/S ratios has been developed. It has been observed that the optical density, measured at 400 nm, of supernatants collected from fresh amniotic fluids centrifuged at 2000 g for 10 minutes correlates with L/S ratios.
Congenital release thrombocytopathy must be included in the differential diagnosis of bleeding diatheses in women. A review of the coagulation profiles of 7 patients with congenital release thrombocytopathy suggests that more sophisticated platelet aggregation studies must be performed when routine screening procedures fail to determine the cause of a clinically suspected bleeding disorder. Establishing the diagnosis helps to avoid the use of medications which cause an acquired platelet dysfunction, and contributes to adequate prophylaxis against surgical and obstetric hemorrhage.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.