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Biomedical subjects

E L Robinson

Publications and source records attributed to E L Robinson.

At least 19 recordsLinked to original sources
PubMed2001

Effect of a selective aldosterone receptor antagonist in myocardial infarction.

Myocardial infarction (MI) initiates adaptive tissue remodeling, which is essential for heart function (such as infarct healing) but is also important for maladaptive remodeling (for example, reactive fibrosis and left ventricular dilation). The effect of aldosterone receptor antagonism on these processes was evaluated in Sprague-Dawley rats using eplerenone, a selective aldosterone receptor antagonist. Infarct healing and left ventricular remodeling were evaluated at 3, 7, and 28 days after MI by determination of the diastolic pressure-volume relationship of the left ventricle, the infarct-thinning ratio, and the collagen-volume fraction. Eplerenone did not affect reparative collagen deposition as was evidenced by a similar collagen volume fraction in the infarcted myocardium between eplerenone and vehicle-treated groups at 7 and 28 days post-MI. In addition, the thinning ratio, which is an index of infarct expansion, was comparable between the eplerenone and vehicle-treated animals at 7 and 28 days post-MI. A protective effect of eplerenone was demonstrated at 28 days post-MI, where reactive fibrosis in the viable myocardium was reduced in eplerenone-treated animals compared with vehicle-treated animals. Thus aldosterone receptor antagonism does not retard infarct healing but rather protects against maladaptive responses after MI.

Animals↗
PubMed2000

Gravity and thermoregulation: metabolic changes and circadian rhythms.

Gravity appears to alter thermoregulation through changes in both the regulated level of body temperature and the rhythmic organization of temperature regulation. Gravity has been hypothesized to have an associated metabolic cost. Increased resting energy expenditure and dietary intake have been observed in animals during centrifuge experiments at hypergravity. Thus far, only animals have shown a corresponding reduction in metabolism in microgravity. Altered heat loss has been proposed as a response to altered gravitational environments, but remains documented only as changes in skin temperature. Changes in circadian timing, including the body temperature rhythm, have been shown in both hypergravity and microgravity, and probably contribute to alterations in sleep and performance. Changes in body temperature regulation may result from circadian disturbance, from the direct or indirect actions of gravity on the regulated temperature, or from changes in thermoregulatory effectors (heat production and heat loss) due to altered gravitational load and convective changes. To date, however, we have little data on the underlying thermoregulatory changes in altered gravity, and thus the precise mechanisms by which gravity alters temperature regulation remain largely unknown.

Animals↗
PubMed1999

Light masking of circadian rhythms of heat production, heat loss, and body temperature in squirrel monkeys.

Whole body heat production (HP) and heat loss (HL) were examined to determine their relative contributions to light masking of the circadian rhythm in body temperature (Tb). Squirrel monkey metabolism (n = 6) was monitored by both indirect and direct calorimetry, with telemetered measurement of body temperature and activity. Feeding was also measured. Responses to an entraining light-dark (LD) cycle (LD 12:12) and a masking LD cycle (LD 2:2) were compared. HP and HL contributed to both the daily rhythm and the masking changes in Tb. All variables showed phase-dependent masking responses. Masking transients at L or D transitions were generally greater during subjective day; however, L masking resulted in sustained elevation of Tb, HP, and HL during subjective night. Parallel, apparently compensatory, changes of HL and HP suggest action by both the circadian timing system and light masking on Tb set point. Furthermore, transient HL increases during subjective night suggest that gain change may supplement set point regulation of Tb.

Animals↗
PubMed1999

Endogenous thermoregulatory rhythms of squirrel monkeys in thermoneutrality and cold.

Whole body heat production (HP) and heat loss (HL) were examined to determine if the free-running circadian rhythm in body temperature (Tb) results from coordinated changes in HP and HL rhythms in thermoneutrality (27 degrees C) as well as mild cold (17 degrees C). Squirrel monkey metabolism (n = 6) was monitored by both indirect and direct calorimetry, with telemetered measurement of Tb and activity. Feeding was also measured. Rhythms of HP, HL, and conductance were tightly coupled with the circadian Tb rhythm at both ambient temperatures (TA). At 17 degrees C, increased HP compensated for higher HL at all phases of the Tb rhythm, resulting in only minor changes to Tb. Parallel compensatory changes of HP and HL were seen at all rhythm phases at both TA. Similar time courses of Tb, HP, and HL in their respective rhythms and the relative stability of Tb during both active and rest periods suggest action of the circadian timing system on Tb set point.

Animals↗
PubMed1996

A dotted line assimilates in visibility to a solid line.

This study tested the theory that a context-produced increase in visibility of a target is due to its assimilation in visibility to the context. A context + target and a context are discriminated better than are a target and background. This occurs for two different context + targets in which the context is a solid line and the target is a dotted line. But it does not occur when solid lines replace these dotted lines. The dotted lines are much less visible than the solid lines. Therefore, the dotted lines increase in similarity in visibility to the solid lines, which is assimilation, but for visibility, rather than for a typical part. Assimilation does not occur between perceptually equal parts. Consequently, the reason why the two context + targets with only solid lines do not result in increases in visibility may be that these lines are sufficiently equal in visibility that assimilation in visibility is precluded. So, the theory is supported. This theory is consistent with evidence that one group (phenomenal whole) is associated with both assimilation and an increase in visibility. Accordingly, a stimulus with a relatively large distance between its solid and dotted lines is apprehended as a relatively weak group, and does not result in an increase in visibility.

Adult↗
PubMed1995

Effects of racist provocation and social support on cardiovascular reactivity in African American women.

It has been speculated that exposure to the chronic stress of racism contributes to the high rates of hypertension among African Americans. Social support may buffer the effects of stress on cardiovascular (CV) health by attenuating stress-induced CV responses that have been linked to hypertension. In this study we investigated the effects of racism and social support on CV reactivity in African American women. Participants showed greater increases in CV and emotional responses while responding and listening to racist provocation. Augmented blood pressure (BP) persisted through recovery following racial stress. Participants receiving no support showed the greatest increases in anger during racist provocation. No significant effects were seen for support on CV reactivity. These results provide some of the first evidence that interactive confrontation with racism elicits significant increases in CV reactivity and emotional distress. Furthermore, individuals receiving less support may be at greater risk for the potentially health-damaging effects of racial stress. These findings may have significant implications for the health of African Americans.

Journal Article↗
PubMed1993

Serum immunoreactive and bioactive lactogenic hormones in advanced breast cancer patients treated with bromocriptine and octreotide.

6 patients with advanced breast cancer who had failed first and second line endocrine therapies received bromocriptine (1.25-2.5 mg twice daily per os) and octreotide (Sandostatin) via a continuous subcutaneous infusion (200-400 micrograms/24 h) until disease progression. Pre-treatment 24-h profiles of serum lactogenic hormones and their response to standard provocative tests were established and repeated at 2 weeks, and 3 and 6 months (or at tumour progression). Immunoreactive prolactin (ir-PRL), growth hormone (ir-GH) and insulin-like growth factor I (IGF-I) were measured by radioimmunoassay and bioactive lactogenic hormone levels (BLH) were estimated using the Nb2 rat lymphoma cell bioassay. Before treatment all patients showed episodic secretion of ir-PRL, ir-GH and BLH and provocative stimuli resulted in a peak of ir-GH and BLH maximal between 60 and 90 min after injection but no change in ir-PRL. After 2 weeks of treatment, ir-PRL levels were reduced to below the limit of detection in all 6 patients. Peaks of ir-GH and BLH were still apparent, although much reduced. Immunoreactive PRL continued to be profoundly suppressed in 3 of the 4 patients who remained on treatment for 3 to 6 months. Small pulses of ir-GH were still detectable in these patients with which BLH was, again, well correlated. After 2 weeks of treatment, serum IGF-I levels were reduced by 9-54% of the pretreatment values and generally remained suppressed throughout treatment. Clinically, 4 patients did not show disease progression for periods of up to 6 months and side-effects were minimal.

Aged↗
PubMed1993

Circadian rhythms of thermoregulation in the squirrel monkey (Saimiri sciureus).

Phase or amplitude differences between rhythms in heat production (HP) and heat loss (HL) have been suggested to account for the circadian rhythm in body temperature (Tb). To describe the relationships among these rhythms in a primate, five unrestrained squirrel monkeys (1.0-1.3 kg) were studied using combined direct and indirect calorimetry, with telemetry of Tb and activity, in a 24-h light-dark cycle (LD 12:12) at 25 +/- 0.5 degrees C. Dry (D; sensible) HL, evaporative (E) HL, HP (oxygen consumption and CO2 production), Tb, and activity were measured at 10-min intervals for a week. Tb, activity, HP, and HL displayed daily rhythms, peaking during the light period. Although the timing of peaks was not significantly different, the diurnal increase in Tb was seen to result from a delayed increase in DHL, and possibly, EHL, relative to increased HP. The nocturnal decrease in Tb was due to different time courses of decrease in HP and HL, with no clear lag in HL. The rhythm in Tb therefore resulted from both phase and time course differences in HP and HL rhythms.

Animals↗
PubMed1990

The effect of captopril on the membrane properties of central neurons in-vitro.

Captopril, a potent antihypertensive that acts via inhibition of angiotensin converting enzyme also has apparent central actions. Its effects on membrane properties on particular central neurons in-vitro has therefore been investigated. In the substantia nigra, where there is a high concentration of angiotensin converting enzyme, captopril caused a dose-dependent depolarization without any apparent change in conductance, but possibly requiring the integrity of the dendritic arbour. A similar effect occurred when captopril was applied to neurons in either the thalamus or hippocampus, where levels of angiotensin converting enzyme are relatively low. Further studies with homologues of captopril revealed that the -SH group on the molecule was a prerequisite of the effect observed. It is concluded that the -SH group on the captopril molecule has an electrogenic effect on diverse central neurons, independent of inhibition of angiotensin converting enzyme, but preferentially manifest at the level of the dendrite.

Animals↗
PubMed1989

Radiation-induced hypopituitarism is dose-dependent.

Radiation-induced hypopituitarism has been studied prospectively for up to 12 years in 251 adult patients treated for pituitary disease with external radiotherapy, ranging in dose from 20 Gy in eight fractions over 11 days to 45 Gy in 15 fractions over 21 days. Ten further patients were studied 2-4 years after whole-body irradiation for haematological malignancies using 12 Gy in six fractions over 3 days and seven patients were studied 3-11 years after whole-brain radiotherapy for a primary brain tumour (30 Gy, eight fractions, 11 days). Five years after treatment, patients who received 20 Gy had an incidence of TSH deficiency of 9% and in patients treated with 35-37 Gy, 40 Gy and 42-45 Gy, the incidence of TSH deficiency (22, 35 and 52% respectively) increased significantly (P less than 0.001) with increasing dose. A similar relationship was observed for both ACTH and gonadotrophin deficiencies when the 20 Gy group was compared to patients treated with 35-45 Gy (P less than 0.01 and P less than 0.05 respectively). Growth hormone deficiency was universal by 5 years over the dose range 35-45 Gy. In seven patients who were treated with 30 Gy in eight fractions over 11 days, deficiencies were observed at a similar frequency to the 40 Gy group (15 fractions, 21 days). No evidence of pituitary dysfunction was detected in the ten patients who received 12 Gy (six fractions, 3 days). Both total radiation dose and fractionation schedule may determine the incidence of pituitary hormone deficiencies. The dose below which deficiencies do not occur is probably irrelevant to therapeutic irradiation of pituitary and other intracranial neoplasms.

Adolescent↗
PubMed1988

Adrenocorticotrophin (ACTH) deficiency undetected by standard dynamic tests of the hypothalamic-pituitary-adrenal axis.

Six patients (four females, two males; aged 18-65 years), previously treated by external pituitary irradiation (2000-4000 cGY in 8-15 fractions over 10-20 days) for pituitary tumours, presented with the symptoms of excessive and inappropriate tiredness suggestive of ACTH deficiency, despite a normal peak cortisol response to an insulin tolerance test (four cases) or to a glucagon stimulation test (two cases). These six patients were found to have significantly lower mean 24 h urinary free cortisol levels (100 +/- 40 nmol; mean +/- SD) compared with the mean value of 31 normal controls (210 +/- 70.8 nmol; P less than 0.01). In addition serum cortisol profiles based on a series of four timed samples between 0900-2300 h were subnormal (mean 130 nmol/l) in comparison with profiles obtained from 12 normal controls (mean 270 nmol/l) (P less than 0.001). Glucocorticoid replacement therapy promptly abolished their symptoms. These results suggest that a discordance between ACTH secretion under basal circumstances and ACTH response to pharmacological tests may exist in patients with ACTH deficiency. We speculate that defective endogenous corticotrophin-releasing hormone (CRF) secretion, due to radiation-induced damage at hypothalamic level, is one cause of this phenomenon.

Adolescent↗
PubMed1987

Treatment with oral piperazine oestrone sulphate for genuine stress incontinence in postmenopausal women.

The use of oestrogens in the treatment of genuine stress incontinence was assessed by a double-blind prospective trial in 36 postmenopausal women with genuine stress incontinence who received 3 months of cyclical treatment with either piperazine oestrone sulphate or a matching placebo. Patients were assessed subjectively and objectively before and after treatment by 7-day bladder charts, urethral pressure profiles (UPP), the Urilos nappy test, vaginal cytology and hormone assays (plasma oestrogens and gonadotrophins). There was no statistical difference in the subjective response to treatment between the two groups. After 6 weeks of treatment there was a greater reduction in the number of pad changes/24 h in the oestrogen-treated patients that approached statistical significance but, because of a marked response in the placebo group, this difference was not significant after 3 months of treatment. There were also no significant differences between the two groups with respect to the UPP or Urilos measurements but the vaginal cytology and hormone profiles were significantly affected by oestrogens. In view of the possible risks of oestrogen therapy its use in genuine stress incontinence is limited.

Aged↗
PubMed1984

Antagonism of xylazine plus chloral hydrate loss of the righting reflex in mice. A simple in vivo procedure for the evaluation of selective alpha 2-adrenoceptor antagonists.

Xylazine causes a dose-related loss of the righting reflex (LRR) in mice when combined with a subanesthetic dose of chloral hydrate. Compounds that preferentially block alpha 2-adrenoceptors antagonize this xylazine plus chloral hydrate LRR at low doses and in a dose-related manner. This action of these compounds appears related to their alpha 2-adrenoceptor blocking properties insofar as their activity in this test correlates reasonably well with their activity in other in vivo and in vitro procedures thought to reflect alpha 2-antagonism. Also, compounds without any appreciable alpha blocking properties or without selectivity for blocking alpha 2-adrenoceptors are not active in this procedure. At higher doses, the alpha 2-blockers antagonize the reversal of the LRR caused by low doses. This action may be indicative of the in vivo alpha 1 blocking properties of these compounds, which may in turn be related to their sedating properties. In any event, antagonism of xylazine plus chloral hydrate LRR in mice appears to be a simple, rapid, and quantitative procedure for the in vivo evaluation and comparison of selective alpha 2-adrenoceptor antagonists.

Adrenergic alpha-Antagonists↗
PubMed1984

The importance of urinary immunoglobulin light chain isoelectric point (pI) in nephrotoxicity in multiple myeloma.

There is clinical and experimental evidence to imply that urinary immunoglobulin light chains are nephrotoxic yet some patients pass large amounts for years with little renal damage. Animal experiments suggest that a light chain is more nephrotoxic if it has a high isoelectric point (i.e. is cationic in relation to urine pH). We studied 23 patients with multiple myeloma, measuring light chain excretion rate, light chain isoelectric point (pI) and creatinine clearance. Light chain excretion rate was independent of light chain isoelectric point and did not correlate with creatinine clearance. Light chain isoelectric point correlated with creatinine clearance, suggesting that this characteristic may be an important determinant of the nephrotoxic effect of these immunoglobulin constituents.

Aged↗