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Biomedical subjects

R W Shaw

Publications and source records attributed to R W Shaw.

At least 19 recordsLinked to original sources
PubMed1979

The oxygen reactions of reduced cytochrome c oxidase. Position of a form with an unusual EPR signal in the sequence of early intermediates.

The order of appearance of intermediates in the reoxidation of reduced cytochrome c oxidase by oxygen has been examined. Particular emphasis was placed on determining where the intermediate with the EPR signal at g = 5, 1.78, 1.69 (Shaw, R.W., Hansen, R.E. and Beinert, H. (1978) J. Biol. Chem. 253, 6637--6640) appears in the sequence of events during reoxidation. Flash photolysis of reduced, CO-complexed samples of cytochrome c oxidase in the presence of oxygen in a buffer containing 30% (v/v) ethylene glycol at 77 K and 195 K has been used to generate states of partial reoxidation. The intermediate with the EPR signal at g = 5, 1.78, and 1.69 can be detected as a product of the photolysis and subsequent oxidation but does not appear until the photolyzed sample is incubated at temperatures well above 196 K. In the course of the reoxidation, the intermediate characterized by the g = 5, 1.78, 1.69 signal occurs in the reaction sequence after the states referred to as 'Compound A' and 'Compound B' (Chance, B., Saronio, C., and Leigh, J.S. (1975) J. Biol. Chem. 250, 9226--9237). Its appearance is within the time range reported for the formation of 'oxygenated' cytochrome c oxidase (Orii, Y. (1979) in Cytochrome Oxidase (King, T.E., Orii, Y., Chance, B. and Okunuki, K., eds.), pp. 331--340, Elsevier/North-Holland Biomedical Press, Amsterdam).

Animals↗
PubMed1979

Hyperfine structure resolved by 2 to 4 GHz EPR of cytochrome c oxidase.

Using low frequency 2 to 4 GHz EPR at 10 K, we have resolved previously unseen hyperfine structure associated with the EPR-detectable copper signal of cytochrome c oxidase. The observed hyperfine structure appears consistent with hyperfine coupling to copper; although to account for all of the observed structure, an additional magnetic interaction is required as well. This work points out the utility of the 2 to 4 GHz EPR technique for resolving electronic hyperfine structural information from copper and possibly other paramagnetic sites in biomolecules when random variation in electronic g values is a cause of EPR line-broadening.

Copper↗
PubMed1979

Ovary.

Explore the source record for details and available documents.

Adrenal Gland Diseases↗
PubMed1979

Oestrogen-gonadotrophin feedback abnormalities in hyperprolactinaemic amenorrhoea demonstrated by the response to clomiphene administration.

Clomiphene was administered to 16 patients with elevated serum prolactin levels in doses of 100, 200 and 300 mg/day for five days in succeeding months and total urinary oestrogens estimated on days 0, 5, 8, 12 and 15 following commencement of treatment. The responses were compared with six patients who were amenorrhoeic but had normal serum prolactin levels and absent positive feedback to oestrogen. The increased outputs of oestrogens were similar in the two groups. In the hyperprolactinaemic group 5 out of 16 subjects showed evidence of ovulation whilst the remainder showed a secondary failure of response. Six subjects who failed to ovulate were treated with clomiphene and human chorionic gonadotrophin (HCG) and ovulations were induced in 31 out of 34 treatment cycles but no pregnancies were achieved. The responses to clomiphene therapy in the hyperprolactinaemic subjects were compared to the assessment of positive feedback mechanisms by means of oestrogen provocation and oestrogen amplification tests and good correlation was obtained. Only those with evidence of positive feedback to these tests were likely to ovulate on clomiphene.

Amenorrhea↗
PubMed1978

Responses of the a3 component of cytochrome c oxidase to substrate and ligand addition.

We have previously described a transient high spin ferric heme species in cytochrome c oxidase (EC 1.9.3.1) which represent a3+(3) (Beinert, H. and Shaw, R.W.(1977) Biochim. Biophys. Acta 462, 12u--130), and can be detected and quantitatively determined by EPR. We have now used out ability to generate this species to study reactions of a3+(3) with substrates and ligands and also responses to pH changes. This was accomplished by multiple rapid mixing and freezing techniques in conjunction with low temperature EPR and optical reflectance spectroscopies. The substrates used were O2 and ferrocytochrome c and the ligands cyanide, sulfide, azide and carbon monoxide. Contrary to the oxidized, resting form of the enzyme, the transient high spin species of a3+(3) reacts within less than 10 ms stoichiometrically with cyanide and sulfide and at a slower rate with azide. The transient a3+(3) species responds to O2 and CO by changes in signal size or shape, although no oxidoreduction is involved, indicating that a3+(3) registers the presence of these gases. The high spin signal of the transient species is readily abolished by ferrocytochrome c or on raising the pH. Decreasing the pH induces a shift from the rhombic towards the axial component of the signal. Since the responses to CO and pH are analogous for the rhombic transient species to those observed with the rhombic high spin ferric heme species produced on partial reduction, it is suggested that the rhombic signals represent a3+(3) in either case. In all these experiments, in which EPR detectable a3+(3) was observed in large yield, no extra signals for copper or correspondingly increased intensity in the copper signal at g = 2 were seen. The relationship is discussed of the obviously reactive transient species of a3+(3) to other 'activated' species that have been reported and to the oxidized resting form of the enzyme, which is known to react only slowly with ligands and to respond sluggishly to substrate.

Azides↗
PubMed1978

A novel electron paramagnetic resonance signal of "oxygenated" cytochrome c oxidase.

It had been observed previously that a pair of transient EPR resonances (g = 1.78 and 1.69) appears within less than 5 ms on reoxidation of reduced cytochrome c oxidase by O2. Since the location of other lines that are part of the same signal was not known, the quantity of the paramagnetic species involved, and thus the significance of the observed resonances, remained questionable. We have now found a broad resonance at g = 5 which is obviously associated with those at g = 1.78 and 1.69. The width of the signal (approximately 250 mT) at the observed intensity suggests that it represents a significant fraction of one of the components of the enzyme. The signal disappears within less than 5 ms on addition of cyanide or sulfide but only within several hundred milliseconds after addition of ferrocytochrome c. This behavior suggests that it originates from the a3 component of the enzyme. It is suggested that the species represented in the signal is either identical with or part of what has been named collectively the "oxygenated" form and recently described "activated" forms of the enzyme. On reoxidation of reduced oxidase with oxygen enriched 90% in 17O, no change of signal shape was seen.

Cyanides↗
PubMed1978

Sex hormone levels and gonadotrophin release in premature ovarian failure.

Premature ovarian failure was studied in ten women under the age of 30; eight had an ovarian biopsy and five of these showed primordial follicles. Plasma levels of oestradiol and progesterone were similar to the follicular phase of a normal menstrual cycle, but in eight patients cervical smears showed a cornification index of less than one per cent. Levels of both androgens and of sex hormone binding globulin capacity were generally normal. Administration of LH-RH caused a release of FSH which was similar to post menopausal women and higher than both. Two patients were treated with exogenous gonadotrophins without effect.

Adolescent↗
PubMed1978

Randomized controlled trial of Syn-Ergel and an active placebo in the treatment of heartburn of pregnancy.

A randomized controlled trial was performed to study the efficacy of Syn-Ergel with an active placebo in the treatment of heartburn of pregnancy in ninety-two patients completing 7 days of therapy. Syn-Ergel was significantly better (p less than 0.001) in all groups of pre-treatment pain severity in relieving the symptoms, and had a longer duration of action, than the active placebo. Complete relief of pain was achieved in 79.5% of Syn-Ergel treatments with a further 10% of treatments resulting in marked easing of discomfort at 1 hour following administration. The corresponding figures for the 'active placebo' were 56% and 20%. The combination of an antacid and a protective mucosal coating agent would appear to be a useful approach in the treatment of heartburn of pregnacy.

Agar↗
PubMed1976

Hydrogen ion titration of horse heart ferricytochrome c.

Continuous hydrogen ion titration curves of deionized solutions of horse heart ferricytochrome c have been obtained at 25 degrees C. at a constant ionic strength of 0.10 from pH 3.0 to 11.0. Titration of the oxidized protein in KCl required 28.4 equiv over that pH range, and a small hysteresis between the forward and reverse limbs was displayed. The Linderstrom-Lang approximation, which takes into account electrostatic interactions between charged groups on the protein surface, was used in a computer simulation program to analyze the forward and reverse limbs of the titration curve separately. The results indicated 1 alpha-, 12 beta- and gamma-, and 1 heme propionic carboxylic, 1 imidazole, 1 phenolic, and 18 epsilon-amino residues appear to titrate normally. Variations in the electrostatic interaction factor omega suggest conformational changes in the protein at the extremes of pH, although the relationship of the variations in omega to the magnitude of the conformational changes does not appear to be strictly quantitative for cytochrome c. These results show the acid-base behavior of cytochrome c to be complex in nature, and suggest that the Lindenstrom-Lang model may not be adequate for cytochrome c.

Animals↗
PubMed1976

Modification by sex steroids of LHRH response in the polycystic ovary syndrome.

Exogenously administered oestradiol or progesterone was found to induce augmentation of LH and FSH release in response to LHRH administration in patients with the polycystic ovary (PCO) syndrome. The effect of oestradiol upon LH release in the patients was significantly less than the augmented release induced in normal women (P less than 0-02). In contrast, progesterone induced a significantly greater LH release in PCO patients than normal women studied during the early follicular phase (P less than 0-001) but less than that in normal women studied during the mid-follicular phase of the cycle (P less than 0-01). The effects on FSH release in the PCO patients were less marked but similar to those in normal women with comparable basal steroid levels. The results suggest that both oestradiol and progesterone can modify the hypothalamic-pituitary axis in the PCO syndrome in a manner similar to that observed in normal women and a failure of these 'positive feedback' mechanisms does not appear to be the cause of the ovulatory deficiency in this syndrome.

Clinical Trials as Topic↗
PubMed1976

The control of gonadotrophin release in women with hyperprolactinaemic amenorrhoea: effect of oestrogen and progesterone on the LH and FSH response to LHRH.

The effect of the administration of oestradiol benzoate and of progesterone on the subsequent response to LHRH has been investigated in women with hyperprolactinaemia. There was an amplification in the release of LH in four out of ten patients and of FSH in one out of ten patients at 44 h after the administration of 2-5 mg oestradiol benzoate. The average amount of LH released before and after oestrogen did not change, but there was a significant decrease in the amount of FSH released. There was no correlation between the LH released and the oestradiol concentration in serum at the time of the LHRH tests but there was a negative correlation between the FSH released and the oestradiol concentration (r = 0-507;P less than 0-05). These results contrast with those obtained in normal subjects in the follicular phase of the cycle when there is a positive correlation of oestrogen concentrations and the amount of LH and FSH released. As in normal subjects, however, a significant suppression of basal FSH concentrations, persisting until 44 h, was produced by the oestrogen (P less than 0-01). Seven out of eleven patients showed an amplification of LH response and six out of eleven an FSH response 20 h after the administration of 25 mg progesterone. The mean amplifications are not significantly different from those of normal subjects tested in the early follicular phase of the cycle, but are significantly less than those tested in the mid follicular phase of the cycle (LH P less than 0-001; FSH P less than 0-01). This may be related to the serum concentrations of oestradiol which in patients with hyperprolactinaemia are significantly less than those found in the mid follicular phase of the cycle (P less than 0-05). These results indicate that in women with hyperprolactinaemia oestrogen negative feedback, necessary for cycle initiation, is normal: failure of ovulation may be related to failure of positive feedback to oestroen. Oestrogen-negative feedback is unopposed and this may explain the follicullar development and lack of oestrogen in the mid-follicular phase.

Amenorrhea↗
PubMed1976

Tests of the hypothalamic-pituitary-ovarian axis.

The availability of RIA to measure the pituitary gonadotropins and ovarian sex steroids has greatly helped in the development of tests of hypothalamic-pituitary-ovarian function. The use of estimates of basal gonadotrophin and sex steroid hormones together with dynamic tests such as the LH-RH test, oestrogen provocation test, clomiphene tests and exogenous gonadotrophins can now test the integrity and functional capacity of each of the components of the HPO axis. Figure 4 demonstrates how these tests can be used in a logical sequence to investigate patients with a disorder of the HPO axis after having first excluded any other endocrine abnormality. Screening of serum for elevated levels of gonadotrophins, prolactin and progesterone is an important initial step. Interpretation of the oestrogen provocation and clomiphene tests requires a normally functioning pituitary gland and hence the response to an LH-RH test also plays a ket role. The flow chart also demonstrates the points at which specific ovulation induction treatment can be instituted and should be useful in saving patient and doctor investigative time. Using these types of tests it should be possible to reclassify disorders of the HPO axis on the basis of their underlying pathology.

Androgens↗