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Biomedical subjects

M Johnson

Publications and source records attributed to M Johnson.

At least 721 records · Page 40Linked to original sources
PubMed1984

Prostaglandin E2 excretion in spinal cord injury patients.

Hyponatremia has proven to be a common finding in spinal cord injured (SCI) patients. Mechanisms exist whereby SCI patients with either normal or impaired renal function may develop it. One such mechanism may be an impairment in prostaglandin (PGE2) excretion resulting in unopposed activity of antidiuretic hormone (ADH). Paired 24-hour urine collections for PGE2 were collected from SCI patients with varying degrees of renal dysfunction. There was a wide interpatient variability in the excretion of PGE2, with no significant correlation of PGE2 excretion in respect to either urine volume, urine sodium concentration, or the degree of renal dysfunction.

Adult↗
PubMed1984

Some new developments in the rheology of bone.

Bone has been shown to be a viscoelastic material which is thermorheologically complex. This implies that multiple mechanisms determine the viscoelastic response of bone. New calculations of the contribution of fluid flow to the viscoelastic behavior of bone have been made. The calculation of the relaxation time was based on Biot's model for the relaxation of fluid flow in porous materials while the relaxation strength was estimated from simple composite models. These models together with recent measurements of the permeability of bone predict that part of the relaxation due to fluid flow will occur at fairly high frequencies, perhaps above 10 kHz for in vitro samples. Measurements of ultrasonic wave propagation and attenuation in wet bone have been performed from 0.5 MHz to 15 MHz and the mechanical damping was measured from 100 Hz to 1 kHz with fluid viscosities ranging from 10(-3) to 5 X 10(-2) (MKS). However, a complete understanding of the rheological properties of bone will require additional experiments to bridge the gap between the low frequency measurements and the ultrasonic measurements.

Animals↗
PubMed1984

Attitudes toward nursing as expressed by nursing and non-nursing college males.

One way to address the increasingly critical shortage of nurses in the health care system is to recruit more men into nursing. To do so effectively one must understand the attitudes that potential male recruits have toward nursing as a career. This investigation was undertaken to determine differences in attitudes toward nursing as a career held by men in various majors. The Attitudes Toward Nursing Scale (ATNS), developed by the investigators, was used to measure five categories of attitudes toward selecting nursing as a career frequently cited in the literature. A sample of 247 male non-nursing and 94 male nursing community college students completed the scale. Analysis of demographic variables revealed that the nursing students were more likely to be older, married, and have military corpsman experience than were the non-nursing students. Additional statistical analysis revealed that communication majors (i.e., English, Drama, Speech) were most similar and mathematics majors were least similar to nursing majors in various attitudes. Also, a substantial percentage of non-nursing majors were potential recruits for nursing in that they indicated interest in nursing as an alternative career. Recruitment of men into nursing programs will not solve the current shortage of nurses. However, men as a viable source should not be treated lightly. Recruitment efforts should focus on recognizing interested students, and recruiting those who have attitudes toward nursing as a career which are similar to those of nursing majors.

Attitude↗
PubMed1984

Effect of clonidine therapy on renal hemodynamics in renal transplant hypertension.

Antihypertensive medications have a variable effect on renal hemodynamics and may contribute to renal insufficiency in some patients. Since clonidine has actually been found to improve renal hemodynamics in patients with essential hypertension, we studied the effects of clonidine therapy in patients with renal transplant hypertension. Baseline measurements of BP and renal hemodynamics were made in six patients after two weeks of therapy with furosemide. Clonidine was then added and titrated until BP was controlled. Repeated measurements of renal hemodynamics were made four and 16 weeks after clonidine therapy was begun. Glomerular filtration and effective renal plasma flow as assessed by inulin and aminohippurate sodium clearances were preserved during prolonged clonidine therapy.

Adult↗
PubMed1984

Calcium chelation and calcium-channel blockade in anesthetized acute renovascular hypertensive dogs.

Acute animal studies were conducted to explore the effect of calcium manipulation on blood pressure and in the blood pressure response to angiotensin blockade under conditions of renovascular hypertension in anesthetized mongrel dogs. Ethylenediaminetetraacetic acid (EDTA) was used to lower serum calcium (SCa) levels, while nifedipine was infused intravenously to antagonize calcium at the cellular level. Angiotensin blockade was accomplished by infusion of the competitive inhibitor of angiotensin, saralasin. Following renal artery clamping, mean arterial pressure (MAP) increased a mean of 21 +/- 3 mm Hg from 116 +/- 5 to 137 +/- 6 mm Hg (p less than 0.001) in 23 studies. Lowering of SCa by 30 min of EDTA infusion in 9 of these animals resulted in a mean fall of -21 +/- 4 mm Hg from 127 +/- 7 to 105 +/- 7 mm Hg (p less than 0.005). A 30 min infusion of nifedipine solution in 5 animals did not significantly affect blood pressure. In 9 normocalcemic hypertensive animals, saralasin reduced MAP from 138 +/- 8 to 127 +/- 8 mm HG (p less than 0.001). In 9 animals with lowered SCa (6.9 +/- 0.2 mg/dl) due to 30 min of EDTA infusion, the same dose of saralasin resulted in a greater reduction of MAP from 127 +/- 7 to 78 +/- 9 mm Hg (p less than 0.001). Nifedipine and saralasin used together in 5 hypertensive animals resulted in the reduction of MAP from 155 +/- 14 to 131 +/- 14 mm Hg (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1984

Micropipette aspiration of human blood platelets: a defect in Bernard-Soulier's syndrome.

Previous reports have suggested that platelets from patients with Bernard-Soulier's syndrome (BSS) are not giant cells. Rather, they are normal-sized in suspension, but spread out on glass slides more readily than control cells, yielding the impression of being giant. The present study has used cell sizing techniques, electron microscopy, and micropipette aspiration to evaluate platelets from three patients with BSS. Cell sizing techniques revealed that BSS platelets were considerably larger than normal. The increased size was confirmed in electron microscopic studies of BSS platelets fixed in suspension. However, the BSS platelets did not contain increased amounts of internalized surface membrane considered to be the source of membrane necessary for excessive spreading. A possible explanation for increased spreading of BSS platelets was found in studies of their resistance to deformation in micropipettes. BSS platelets were much less resistant to deformation than normal cells or other abnormal platelets when aspirated under the same negative pressure. Their unusual deformability may explain the tendency of BSS platelets to spread more readily than normal cells on glass slides.

Blood Platelet Disorders↗
PubMed1983

Protective effect of vitamin E (DL-alpha-tocopherol) against intraventricular haemorrhage in premature babies.

Forty four babies, of less than 32 weeks' gestation, were either randomly given 25 mg/kg vitamin E (DL-alpha-tocopherol acetate) intramuscularly after birth (day 0) and on days 1, 2, and 3 or served as controls. Frequent real time ultrasound examinations of the brain were made in each baby during the first week and less frequently thereafter. In babies under 32 weeks' gestation the incidence of intraventricular haemorrhage was lower in supplemented babies (18.8%) compared with the controls (56.3%). On days 0, 1, 2, and 3 median plasma vitamin E concentrations in babies without haemorrhage and in those with subependymal haemorrhage only were similar. Babies with intraventricular haemorrhage had lower median concentrations on day 1 (p less than 0.002) and day 2 (p less than 0.05) compared with those with subependymal haemorrhage and lower concentrations on day 0 (p less than 0.02) and day 1 (p less than 0.05) compared with those without haemorrhage. These findings suggest that in premature babies vitamin E, an antioxidant, protects endothelial cell membranes from oxidative damage and disruption and limits the magnitude of haemorrhage and its spread from the subependyma into the ventricles.

Cerebral Hemorrhage↗
PubMed1983

Protective effect of vitamin E on intraventricular haemorrhage in the newborn.

Forty-four consecutively born babies of birth weights under 1751 g were randomly selected to receive a daily intramuscular injection of vitamin E (all-rac-alpha-tocopheryl acetate) from the day of birth (Day 0) until Day 3, or were allocated to a non-supplemented control group. Frequent ultrasound examinations of the brain were made during the first week of life and babies were classified as having 'no haemorrhage', 'subependymal haemorrhage (SEH) only' or 'intraventricular haemorrhage' (IVH). The incidence of SEH or IVH was similar in supplemented (42.9%) and control babies (43.5%). SEH or IVH was observed only in babies of less than 32 weeks gestation; when only babies under 32 weeks were considered, IVH was less common in those supplemented (18.8%) than in the controls (56.3%). Babies with IVH had lower median plasma vitamin E concentrations when compared with babies without any haemorrhage and compared with those with only SEH. Three supplemented babies suffered IVH and they were the three with the lowest plasma vitamin E concentrations among the babies supplemented with vitamin E from Day 0 to Day 3. We speculate that vitamin E protects endothelial cell membranes of capillaries in the subependymal layer of the brain against oxidative damage and disruption and thereby limits the magnitude of haemorrhage in the subependymal layer, and reduces the risk of extension into the ventricles.

Cerebral Hemorrhage↗
PubMed1983

A physiological appraisal of polyethylene glycol and a balanced electrolyte solution as bowel preparation.

Seventy-seven patients undergoing bowel preparation with either sennosides and rectal washout (S + RWO; n = 26) or polyethylene glycol and a balanced electrolyte solution (PEG + E) given orally (n = 25) or by nasogastric infusion (n = 26) have been studied. PEG + E was not associated with significant physiological change in electrolytes or blood gases. Patients tolerated PEG + E well and it provided a moderate to good bowel preparation in over 80 per cent of cases. PEG + E was not associated with a change in colonic microflora and was not associated with explosive mixtures of colonic gas due to hydrogen. It is therefore a safe, quick and efficient bowel preparation and provides a safer alternative to mannitol. The solution (PEG + E) man be used orally or by nasogastric infusion and does not require an accompanying intravenous infusion.

Adult↗
PubMed1983

Direct binding of radioiodinated monoclonal antibody to tumor cells: significance of antibody purity and affinity for drug targeting or tumor imaging.

For MoAb to be used efficiently for drug targeting and tumor imaging, the fraction of antibody binding to tumor cells must be maximized. We have studied the binding of 125I MoAb in three different tumor systems. The fraction of antibody that could be bound to the cell surface was directly proportional to the antibody purity. The affinity constant also limits the fraction of antibody that can bind to cells at a given antigen concentration. Rearrangement of the standard expression for univalent equilibrium binding between two reactants shows that in antigen excess, the maximum fraction of antibody that can bind (formula; see text). Binding data using four different MoAb with three cell systems confirm this relationship. Estimates for reasonable concentrations of tumor antigens in vivo indicate that antibodies with binding constants less than 10(8) M-1 are not likely to be useful for drug targeting or tumor imaging.

Animals↗