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Biomedical subjects

M A Nelson

Publications and source records attributed to M A Nelson.

At least 91 records · Page 5Linked to original sources
PubMed1984

Metabolic and blood pressure effects of 6 alpha-methylprednisolone in the conscious sheep.

Methylprednisolone has been reported to be produce hypertension in the rat but to have no effect on blood pressure in the dog. In this study, methylprednisolone infused to conscious sheep for up to 10 days at either 20 micrograms/kg/hr or 100 micrograms/kg/hr, failed to induce a hypertensive response. Metabolic effects characteristic of glucocorticoid activity, such as increased water intake and urine volume, were observed in all animals. No consistent decrease in plasma potassium concentration was observed with either rate of infusion, indicating a lack of in-vivo mineralocorticoid activity. In the conscious sheep, like the dog, methylprednisolone exhibits only glucocorticoid activity and does not increase blood pressure.

Animals↗
PubMed1984

The blood pressure and metabolic effects of 19-nor-deoxycorticosterone and 19-nor-progesterone in sheep.

The present study examines the blood pressure and metabolic effects of 5 day infusions of 19-nor-deoxycorticosterone (19-nor-DOC) and 19- nor-progesterone (19-nor-PROG) in the intact conscious sheep. Both these steroids raise blood pressure in the rat. 19-nor-DOC (5 mg/d) produced a significant increase in mean arterial pressure (MAP) of 17 mmHg on day 5 (p less than 0.001), associated with 'mineralocorticoid' effects hypokalaemia, hypernatraemia and an initial urinary sodium retention. In contrast 19-nor-PROG (5 mg/d and 50 mg/d) had no effect on MAP and displayed no 'mineralocorticoid' activity.

Animals↗
PubMed1984

The influence of potassium loading on the pressor and metabolic effects of 9-alpha-fluoro-cortisol in sheep.

9 alpha-Fluorocortisol (9 alpha FF) is an analogue of cortisol with 'mineralocorticoid', 'glucocorticoid' and 'hypertensinogenic' activity. 9 alpha FF was infused at 2 mg/day for 5 days to sheep receiving a normal Na intake (100 mmol/d) and a high K intake (congruent to 800 mmol/d). K loading modified the Na retaining effects of 9 alpha FF but had no effect on the development of the hypertension. These experiments suggest that the effects of K loading on the development of 9 alpha-FF hypertension are not related simply to the effects that K has on modifying the Na retaining effects of the steroid.

Animals↗
PubMed1984

The effect of potassium on the hypertensive and electrolyte responses to ACTH administration in sheep.

This study examines the blood pressure and electrolyte response to adrenocorticotrophic hormone (ACTH) in K loaded sheep to test the hypothesis that ACTH-induced hypertension is blunted in K loaded sheep. ACTH treatment in sheep on a 'normal' Na (70-100 mmol/day) and high K intake (congruent to 800 mmol/day) increased mean arterial pressure (MAP) by upto 17 mmHg over 5 days. Cardiac rate and urinary Na excretion also increased. Plasma [Na] and [K] fell with ACTH. On a lower Na (30 mmol/day) and high K intake (congruent to 800 mmol/day) ACTH raised MAP by upto 16 mmHg over 5 days. Cardiac rate, urinary Na and K excretion also increased. Plasma [Na] fell and plasma [K] was unchanged. Thus, ACTH hypertension is not modified in chronically K loaded sheep, although electrolyte responses are different from normal.

Adrenocorticotropic Hormone↗
PubMed1984

"How do adrenocortical steroid hormones produce hypertension?".

ACTH dependent and independent adrenocortical steroid hypertension in experimental animals is thought to be due to the 'mineralocorticoid' and/or 'glucocorticoid' activity of the steroid/s. Studies in sheep examining ACTH and adrenocortical steroid hypertension have provided evidence for a 'hypertensinogenic' class of steroid activity. A hypothesis is proposed to explain how the 'hypertensinogenic' actions of a steroid may produce hypertension. It is suggested that effects mediated via 'mineralocorticoid' and 'glucocorticoid' receptors may modulate or amplify the 'hypertensinogenic' activity. Individual steroids may express any, all or none of these three types of steroid hormone activity.

Adrenal Cortex Hormones↗
PubMed1984

The effect of intracerebroventricular infusions of CRF, sauvagine, ACTH (1-24) and ACTH (4-10) on blood pressure in sheep.

This study reviews the effects of intracerebroventricular (i.c.v.) infusion of corticotrophin releasing factor (CRF) and adrenocorticotrophic hormone (ACTH) (1-24) on blood pressure in conscious sheep. The effects of sauvagine, a peptide with 50% homology with CRF and ACTH (4-10) and other analogues of ACTH were studied. Intracerebroventricular infusion of CRF for 24 h at 10 and 100 micrograms/h increased blood pressure and heart rate. Sodium (Na) excretion also increased. Sauvagine at 10 micrograms/h also increased blood pressure. Both peptides raised body temperature and produced 'arousal' behaviour. ACTH (1-24) at 0.8 microgram/h for 48 h raised blood pressure and body temperature but had no significant effect on Na excretion or behavior. ACTH (4-10) and other related analogs (alpha-MSH, alpha gamma 1-MSH) at up to 10 micrograms/h for 48 h had no effects. These studies show that neuropeptides involved in the physiological response to 'stress' may have central effects on blood pressure.

Adrenocorticotropic Hormone↗
PubMed1984

Isokinetic muscle imbalance and knee-joint injuries. A prospective blind study.

One hundred and seventy-two randomly selected high-school football players underwent pre-season isokinetic muscle-testing to determine if there was any relationship between an imbalance in thigh-muscle function and the occurrence of knee injuries. Strength, power, power-endurance, and time to maximum tension were measured for the quadriceps and hamstring muscle groups for both lower extremities of each athlete. The resulting values were utilized to see if a difference of 10 per cent or more between the right and left extremities or between the mean and actual hamstring-to-quadriceps ratio of the individual extremity would result in more knee injuries. No such relationship was found.

Adolescent↗
PubMed1983

Simultaneous very fast liquid-chromatographic analysis of ethosuximide, primidone, phenobarbital, phenytoin, and carbamazepine in serum.

We describe a sensitive, specific, and very fast liquid-chromatographic assay for simultaneously determining five anticonvulsants (ethosuximide, primidone, phenobarbital, phenytoin, and carbamazepine) by using commercially available 5- or 3-microns particle size reversed-phase columns and a microflow-cell-equipped ultraviolet detector. The anticonvulsant drugs are extracted from 200 microL of serum containing 50 mg of cyclopal per liter as an internal standard, by elution from a Bond-Elut (Analytichem International, Harbor City, CA 90710) column with 300 microL of methanol. A 5-microL aliquot of the eluate is applied to an analytical column and eluted with a mobile phase of acetonitrile/methanol/phosphate buffer, 20 mmol/L, pH 3.7 (13.5/35/51.5 by vol), at a flow rate of 3.0 mL/min and at 50 degrees C. Detection is at 210 or 195 nm. The chromatography is complete in less than 2.5 min with the 5-microns-particle column, and in less than 1.4 min with the 3-microns-particle column. The sensitivity of the method for all drugs is less than 1 mg/L. Analytical recovery of drugs added to serum ranged from 92 to 109% for concentrations up to 200 mg/L. Between-run precision (CV) ranged from 1.3 to 4.1%.

Carbamazepine↗
PubMed1983

Liquid-chromatographic determination of tobramycin in serum with spectrophotometric detection.

We describe a simple, precise, accurate, and specific liquid-chromatographic procedure for determination of tobramycin in 50 microL of serum. Tobramycin and the internal standard (sisomicin) are quantitatively converted into their trinitrophenyl derivatives by reaction with a water-soluble derivatizing agent (2,4,6-trinitrobenzenesulfonic acid) at 70 degrees C for 30 min. The derivatives are extracted from the crude reaction mixture by using a reversed-phase Bond-Elut C18 column, and separated on a reversed-phase octyl column with a mobile phase consisting of an acetonitrile/phosphate buffer (70/30 by vol) at a flow rate of 3.0 mL/min. The eluted compounds are detected at 340 nm, and quantified from their peak areas. Chromatography is complete in less than 4.5 min at the optimum column temperature of 50 degrees C. The lower limit of detection for tobramycin is less than 0.2 mg/L. Analytical recoveries for tobramycin varied from 94 to 99%, linearity extended to 25 mg/L, and day-to-day precision (CV) was between 4.6 and 5.1%. Numerous drugs and antibiotics tested do not interfere. Results correlate well (r greater than 0.95) with those by radioimmunoassay and EMIT.

Anti-Bacterial Agents↗
PubMed1982

A comparison of the effects of two angiotensin converting enzyme inhibitors, SQ 14 225 and MK 422 in Na-restricted sheep.

1. The effects of angiotensin converting enzyme inhibition (CEI) using an intravenous infusion of either SQ 14 225 or MK 422 on blood pressure, plasma renin concentration, blood aldosterone concentration and urinary Na excretion, were studied in sodium-restricted sheep. 2. After 7 days of infusion of either drug mean arterial pressure had decreased and plasma renin concentration had increased. 3. Urinary sodium excretion and blood aldosterone concentration were not altered by infusion of either compound. 4. This study confirms a role for angiotensin II in the control of blood pressure in the Na-restricted sheep but suggests that urinary Na excretion in the sheep is not as dependent on angiotensin II as has been reported in other species.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1981

Backache.

Explore the source record for details and available documents.

Back Pain↗
PubMed1980

Suprathreshold processing of complex visual stimuli: evidence for linearity in contrast perception.

Magnitude estimation experiments show that perceived contrast for both sine and square waves is a linear function of stimulus contrast. The suprathreshold sine:square ratio required for equal perceived contrast derived from these data was verified by contrast matching experiments. These findings imply a high degree of linearity in suprathreshold visual processing of contrast.

Form Perception↗