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Biomedical subjects

R Hall

Publications and source records attributed to R Hall.

At least 289 records · Page 16Linked to original sources
PubMed1986

Mitral valve closure and left ventricular filling time in patients with VDD pacemakers. Assessment of the onset of left ventricular systole and the end of diastole.

The effect of mitral valve closure on left ventricular filling time and its relation to the onset of systole were assessed from mitral valve echocardiograms and simultaneous apex cardiograms in 21 normal subjects, 11 patients with left bundle branch block, and 19 patients with VDD pacemakers programmed for atrioventricular intervals of 50, 150, and 250 ms. The interval between the electrocardiograph Q wave and the apex cardiogram upstroke was similar in normal subjects and patients with left bundle branch block, but was significantly longer in patients with VDD pacemakers at all atrioventricular intervals. Similarly there was little difference in the time interval between the Q wave and mitral valve closure in normal individuals and patients with left bundle branch block but this was considerably delayed in VDD pacemaker patients with the atrioventricular interval set at 50 ms. With increasing atrioventricular intervals the mitral valve closed significantly earlier, whereas the onset of left ventricular systole and the timing of mitral valve opening remained unchanged. Thus as a result of earlier mitral valve closure left ventricular filling time decreased progressively as the atrioventricular interval was increased. Since the onset of left ventricular systole, with respect to left ventricular stimulation, is considerably delayed in VDD pacemaker patients a short atrioventricular interval is required in these patients to maintain the normal time relations between atrial and ventricular contraction and hence maximise left ventricular filling.

Adult↗
PubMed1986

Differential production of SRIF 14 and 28 by fetal rat hypothalamic cells enriched by velocity sedimentation.

Dispersed day-17 fetal rat hypothalamic cells have been enriched according to size by velocity sedimentation prior to culture, and the SRIF production by these enriched populations was compared with that of other enriched cell fractions and with mixed-cell cultures. Cultures of mixed cells produced 100-400 pg SRIF/10(6) cells/4 h over a period of 28 days. Total SRIF production by mixed cells was inversely proportional to seeding density over the range 0.25-1 X 10(6) cells/ml/well and SRIF 14 and 28 were secreted in a ratio of approximately 6:1. Although secretory rates by low cell densities remained higher than those by high cell densities, SRIF production decreased with time at all seeding densities (up to 21 days). Dispersed fetal hypothalamic cells were enriched according to size by allowing them to sediment over 4 h through a shallow gradient of BSA in culture medium and subsequent cell fractions developed widely differing morphologies in monolayer cultures. In contrast to mixed-cell cultures, SRIF production at 8 days by both large and small cells were directly proportional to initial seeding density. Furthermore, the smaller cells secreted very much less SRIF than the larger cells (100 pg/10(6) cells/4 h vs. 1,300 pg/10(6) cells/4 h), whereas there was little difference in overall SRIF content (350 pg/10(6) cells vs. 400 pg/10(6) cells). Characterisation by HPLC of the SRIF content and secretion of smaller cells revealed SRIF 14 to 28 ratios of 7:1 and 3:1, respectively. In contrast in the large cells, the ratio was 1:1 for both content and secretion. Therefore, these cell groups contain and secrete different proportions of these 2 molecular forms of SRIF.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Thyrotropin regulates thyrotroph responsiveness to dopamine in vitro.

The effect of conditioned vs. fresh culture medium on the dopaminergic inhibition of TSH and PRL secretion by primary cultures of male rat anterior pituitary cells has been studied. In the presence of conditioned medium (that had been in contact with the cells over the 3-day culture period) 10(-6) M dopamine (DA) inhibited PRL secretion by 50% and TSH secretion by 30%. After 4 h of incubation with fresh medium 10(-6) M DA still inhibited PRL secretion by 50% but increased TSH release by 20%. TSH release was rapid and could be prevented by 10(-6) M prazosin, an alpha 1 adrenoreceptor antagonist. Fresh medium did not alter TRH induced TSH release. In parallel cultures and under identical conditions fresh medium reduced [3H]dihydroergocryptine (DHE) binding to DA receptors from 2.5 +/- 0.4 fmol/10(5) cells to 0.95 +/- 0.3 fmol/10(5) cells (means +/- SEM, n = 5, P less than 0.001). The effect of fresh medium was dose dependent against the dopaminergic inhibition of TSH secretion and against DA receptor binding. If 1 mU TSH was included, in fresh medium, the dopaminergic inhibition of TSH secretion remained unchanged and [3H]DHE binding to DA receptors did not fall. The rank order of potency of thyroid stimulators was bovine TSH (21 U/mg) greater than semipurified bovine TSH (Thytropar, 1.4 U/mg) greater than endogenous rat TSH (0.03 U/mg expressed as NIADDK-rat TSH-RP2) greater than Graves' immunoglobulin G (0.01 U/mg) when either DA or bromocriptine was used as the dopaminergic agonist. When anterior pituitary cells from hypothyroid rats were examined, the effects of culture medium on the dopaminergic inhibition of TSH and on DA receptor binding were approximately twice those observed in normal cells, but the inclusion of 1 mU TSH in the fresh medium completely prevented the loss of DA function and binding. PRL, human CG, ACTH, insulin, glucagon, and heat-inactivated TSH were unable to prevent the effect of medium replacement on dopaminergic inhibition of TSH and DA receptor binding. The data suggest a mechanism whereby TSH may control its own secretion via DA.

Adrenocorticotropic Hormone↗
PubMed1986

Hypothalamic D2 receptors mediate the preferential release of somatostatin-28 in response to dopaminergic stimulation.

We have studied the effect of dopamine (DA) together with agonist and antagonist drugs of varying specificity on the release of immunoreactive forms of somatostatin (SS) from the perfused, adult rat hypothalamus in vitro. Levels of SS increased from 14.7 +/- 3.7 pg (mean +/- SE) under basal conditions to 137 +/- 23.0 pg after exposure to 10(-6) M DA. This dopaminergic effect was mimicked by the specific D2 agonists bromocriptine (10(-7) M) and LY 171555 (10(-6) M) but not by the D1 agonist SKF 38393A (10(-6) M). The stimulatory action of DA (10(-6) M) was blocked by the active (d) but not the inactive (l) isomer of butaclamol (10(-7) M). Similar blockade was achieved with the specific D2 antagonists metoclopramide (10(-8) M) and domperidone (10(-8) M), whereas the D1 antagonist SCH 23390 partially blocked the stimulation of DA but only when used at X100 greater concentration (10(-6) M). SCH 23390 (10(-8) M) did not affect the dopaminergic stimulation of SS release. HPLC characterization of the immunoreactive forms of SS yielded two peaks which corresponded to SS-28 and SS-14. The ratio of these forms varied significantly under different conditions. In the basal state the ratio of SS-28 to SS-14 was 1:4.4; in response to stimulation with DA, the ratio was 1:1.7 and in response to depolarization with 60 mM K+ the ratio was 1:3.1. In conclusion, the stimulatory action of DA on SS release is mediated via hypothalamic D2 receptors. Furthermore dopaminergic stimulation increases the molar ratio of SS-28 to SS-14 in the total immunoreactive SS which is released.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1986

Growth hormone responses to growth hormone-releasing factor (1-29) in euthyroid, hypothyroid and hyperthyroid rats.

In order to investigate whether the impaired GH secretion associated with hypothyroidism and hyperthyroidism is due to a hypothalamic or a pituitary disorder, we have studied plasma GH responses to GH-releasing factor (1-29) (GRF) in euthyroid, hypothyroid and hyperthyroid rats. Hypothyroid rats showed a significant (P less than 0.001) reduction in GH responses to GRF (5 micrograms/kg) at 5 min (350 +/- 35 vs 1950 +/- 260 micrograms/l), 10 min (366 +/- 66 vs 2320 +/- 270 micrograms/l) and 15 min after GRF injection (395 +/- 72 vs 1420 +/- 183 micrograms/l; mean +/- S.E.M.) compared with euthyroid rats. Hyperthyroid rats showed a significant (P less than 0.05) decrease in GH responses to 5 micrograms GRF/kg after 30 min (200 +/- 14 vs 325 +/- 35 micrograms/l) but not at other time-points, or after the administration of 1 microgram GRF/kg. These data indicate that in hypothyroidism and perhaps hyperthyroidism there is an alteration in the responsiveness of the somatotroph to GRF administration.

Animals↗
PubMed1986

Effects of thyroid status on brain catecholamine biosynthesis in adult rats: assessment by a steady-state method.

Effects of thyroid status on brain catecholamine turnover in adult rats were investigated using a steady-state method. Rats were treated for 3 weeks with s.c. injections of L-thyroxine (0.4 mg/kg), aminotriazole in drinking water (0.1%, w/v) or vehicle. After 2 weeks of treatment rats were implanted chronically with lateral intracerebroventricular (i.c.v.) cannulae. They were injected i.c.v. with [3H]tyrosine 1 week later. Catecholamine and tyrosine content and specific activity were measured in mediobasal hypothalamus, anterior hypothalamus and striatum, using high-performance liquid chromatography with electrochemical detection. Thyroxine treatment resulted in a significant increase in noradrenaline and dopamine synthesis localized to the mediobasal hypothalamus. Conversely, aminotriazole treatment resulted in a significant decrease in noradrenaline synthesis localized to the mediobasal hypothalamus. The localization of these changes in catecholamine turnover to the mediobasal hypothalamus suggests that they may be specific functional effects which are of importance in the overall integrated control of thyroid function.

Amitrole↗
PubMed1986

Prediction of outcome in Graves' disease after carbimazole treatment.

In a prospective study to determine which factors would predict remission or relapse, 65 patients with hyperthyroid Graves' disease were treated for six months with a blocking replacement regimen of carbimazole, 40 mg daily, and triiodothyronine (T3). They were followed for one year after stopping treatment, by which time 32 (49 per cent) had relapsed. Although the treatment protocol, relapse rate and frequency of the HLA-DR3 antigen in this population were similar to those of a regionally separate Graves' population investigated previously, the predictive value of HLA-DR3 status together with thyroid stimulating antibody (TSAB) levels was strikingly different. In the present study there was no significantly abnormal distribution of any HLA antigen in the relapse group compared with those patients who achieved remission. Thyroid stimulating antibodies were detected in 62 patients (95 per cent) and fell significantly (p less than 0.05) after carbimazole treatment, irrespective of DR3 status or outcome; TSAB levels only became undetectable in nine patients (28 per cent) who subsequently relapsed and in nine patients (30 per cent) who maintained remission. T3-suppressed 20 min 123I uptake fell equally after treatment in the relapse and remission groups but continued to fall thereafter in the group which maintained remission. In these patients, 123I uptake was significantly lower at the end of the study period than at the end of treatment (p less than 0.05). Serum free T4 levels were higher before treatment in the patients who later relapsed than in those whose disease remitted (p less than 0.02). This proved the only significant marker associated with outcome but was of little predictive value in any patient. This study highlights the problem in predicting the outcome of antithyroid drug treatment, since even within the same country under similar conditions, divergent results have been obtained. It appears that the loci controlling the immune response in Graves' disease are likely to include genes lying outside the HLA-DR region. The results also suggest that the immunological effects of antithyroid drugs are maintained after stopping treatment in those patients whose disease remits.

Adult↗
PubMed1986

High-dose melphalan with autologous bone marrow transplantation for multiple myeloma.

A large dose of melphalan was given to 23 patients with advanced multiple myeloma that was refractory to multiple prior treatments. Sixteen patients received a dose of 80 to 100 mg/m2, and seven were given 140 mg/m2 followed by autologous bone marrow infusion. Tumor mass was reduced by more than 75% in 14 patients, including four who died of bone marrow aplasia. Serious infections were prevented in six of seven patients who received autologous bone marrow. The marked cytoreduction in patients with previously refractory disease indicated the apparent drug resistance could be overcome by dose escalation. However, short remission times in most responding patients were consistent with rapid regrowth of primordial tumor cells with high proliferative activity. Although high-dose melphalan was of limited benefit to patients with refractory myeloma, further studies are necessary to clarify its role during earlier phases of disease.

Adult↗
PubMed1986

Parent and social-skills training for mentally retarded mothers identified as child maltreaters.

The effectiveness and generality of a parent- and social-skills training program for three mildly retarded mothers identified as child maltreaters were investigated. The program was conducted by one trainer in a community-based facility and included the following components: individualized performance standards, response-specific feedback, self-monitoring, and group rewards. A multiple-baseline design across parenting- and social-skill areas was used to evaluate the training. The findings revealed that the game contingencies effectively increased the mothers' ability to identify the most effective action to take in common problematic parenting and social situations. Generalization and recidivism data supported the efficacy of treatment gains.

Adult↗
PubMed1985

Management of selected patients with hyperprolactinaemia by partial hypophysectomy.

Results are reported in 35 patients with prolactinomas who underwent pituitary surgery within the past five years. After surgery prolactin concentrations became normal in 26 patients and symptoms were alleviated, and nine normal pregnancies were achieved in seven women, including all those who had complained of infertility. Normal prolactin concentrations were restored in 16 of 17 patients with tumours 5-19 mm in diameter but in only six of 11 with tumours less than or equal to 4 mm and four of seven with tumours greater than or equal to 20 mm. Normal prolactin concentrations were restored in all those with preoperative concentrations below 1000 mU/l but in none of those with concentrations above 10 000 mU/l. Although not all of the patients were followed up for five years, hyperprolactinaemia did not recur in any patient whose prolactin concentration had returned to normal six weeks after surgery. This included 16 patients with macroprolactinomas (greater than 10 mm in diameter), who were followed up for from two to five years. These data contrast strikingly with those reported by others at similar stages of follow up and show clearly that partial hypophysectomy offers an acceptable alternative treatment for selected patients with prolactinomas.

Adenoma↗
PubMed1985

Diagnostic value of thyrotrophin releasing hormone tests in elderly patients with atrial fibrillation.

A prospective study was carried out to compare clinical and biochemical thyroid states with responses of thyroid stimulating hormone (TSH) to thyrotrophin releasing hormone (TRH) in elderly patients with either atrial fibrillation (n = 75; mean age (SD) 79.3 (6.0) years) or sinus rhythm (n = 73; mean age 78.4 (5.6) years) admitted consecutively to the department of geriatric medicine. No patient in either group had symptoms or signs of hyperthyroidism. Overall, the TSH responses to TRH did not differ significantly between the two groups. Ten (13%) of the patients with atrial fibrillation (of whom four had raised thyroid hormone concentrations) and five (7%) of the patients with sinus rhythm showed no TSH response to TRH while 26% of each group (20 and 19 patients, respectively) showed a much reduced response. Only one of 13 patients with apparently isolated atrial fibrillation showed no TSH response to TRH, and none of these 13 patients was hyperthyroid. In particular, three patients (two with atrial fibrillation and one with sinus rhythm) who showed no TSH response to TRH at presentation exhibited a return of TSH response to TRH at follow up six weeks later. In conclusion, reduced or absent TSH responses to TRH are common in sick elderly patients whether they have atrial fibrillation or sinus rhythm and whether they are euthyroid or hyperthyroid biochemically. An absence of response is therefore an uncertain marker of hyperthyroidism in these groups of patients, and diagnosis and ablative treatment should be based at least on the presence of raised circulating free triiodothyronine or free thyroxine concentrations, or both.

Aged↗
PubMed1985

Prolactinomas.

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Humans↗
PubMed1985

The genital tract in female children with imperforate anus.

A retrospective study was undertaken to determine the type and frequency of genital tract anomalies that occur in female children with imperforate anus. The functional outcome and optimal management of the genital tract anomalies were also studied. Primary vaginal anomalies occurred in 22 of 72 patients assessed, and uterine anomalies occurred in 18 of 51 patients assessed. For 17 patients, who were 13 years of age or older, information was available on genital tract function. Of these 17 patients, five had severe vaginal scarring. A previous vaginoplasty or cloacal abnormality was a predictor of poor vaginal function. It is suggested that vaginoplasty, in cases in which it is possible, be delayed until puberty.

Abnormalities, Multiple↗