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Biomedical subjects

R M Jones

Publications and source records attributed to R M Jones.

At least 289 records · Page 16Linked to original sources
PubMed1981

Role of arginine vasopressin on fluid and electrolyte balance in rats exposed to high altitude.

Normal rats (N) and rats with hereditary hypothalamic diabetes insipidus (DI) were employed to examine the role of arginine vasopressin (AVP) in the reduction of water intake and urine output during hypoxic exposure. The pattern of reduced water intake followed by recovery was similar in both N and DI rats during 7 days of hypobaric hypoxia (inspired O2 pressure of 75 Torr). Water intake was markedly reduced during the first 6 h of hypoxic exposure in both groups, whereas urine output did not decrease significantly until after 6 h in DI rats and after 18 h in N rats. Total urinary excretion of AVP in N rats decreased and remained depressed during 7 days of hypoxia. (AVP excretion corrected for osmolar clearance was unchanged.) Plasma AVP of conscious N rats was 2.7 +/- 0.40 pg/ml plasma during normoxia and 2.4 +/- 0.74 pg/ml plasma after 2 h of exposure to inspired O2 fractional concentrations of 0.105 (paired samples). We conclude that AVP is not a major factor in the decreased water intake and urine output observed during hypoxia, and that the initial disturbance is a reduced water intake that leads to negative water balance, reduced urine volume, increased urine concentration, and hyperosmotic volume contraction. The reduced or unchanged AVP release in normal rats during hypoxia appears to be inappropriate.

Adaptation, Physiological↗
PubMed1981

Mechanism of reduced water intake in rats at high altitude.

Water intake was reduced during the 1st day of hypobaric hypoxia (inspired O2 pressure of 75 Torr) to 35-40% of the normoxic level in both normal rats (N) and rats with diabetes insipidus (DI). Analysis of water intake under graded saline loads at several inspired O2 levels (inspired O2 fractional concentrations of 0.105, 0.120, and 0.2095) indicated that hypoxia increased the threshold for osmotic stimulation of drinking without changing the sensitivity of the response in both N and DI rats. Nephrectomized N rats reduced water intake during hypoxia to 33% of the nephrectomized normoxic level of intake, and nephrectomized DI rats reduced intake to 47% of the nephrectomized normoxic intake. From these results it is concluded that reduced angiotensin II formation was not the factor responsible for reduced water intake during hypoxia. Polyethylene glycol-induced hypovolemia resulted in increased water intake during normoxia, but during hypoxia it was reduced to 29% of the normoxic rate. Reduced body temperature and hyperventilation were not the source of hypoxic attenuation of thirst. The mechanism may reside beyond the central integration of osmotic and nonosmotic information, or at the osmotic sensing mechanism itself.

Adaptation, Physiological↗
PubMed1981

Incidence of choledochoduodenal sphincter spasm during fentanyl-supplemented anesthesia.

One hundred patients were studied prospectively to assess the incidence of spasm of the choledochoduodenal sphincter during biliary tract surgery performed under a fentanyl-supplemented anesthetic technique. The incidence of failure of passage of contrast medium into the duodenum was 3%. In each of the three patients with cholangiographic evidence of sphincter spasm, contrast medium flowed freely into the duodenum after the intravenous administration of 2 mg of glucagon. It is concluded that spasm of the choledochoduodenal sphincter is an uncommon occurrence during fentanyl-supplemented anesthesia and that this method of anesthesia is suitable for biliary tract surgery.

Ampulla of Vater↗
PubMed1981

Cardiovascular responses and changes in plasma cation levels associated with infusion of hyperosmolar urea solutions.

In four patients, infusion of a hyperosmolar solution of urea to decrease brain volume was associated with hypotension and a decreasing of plasma levels of ionized calcium. This prompted a further study into the effects of intravenous hyperosmolar urea solutions on cardiovascular function and plasma levels of cations in the anesthetized dog. Using an infusion rate of 250 mg/kg/min, significant (p less than 0.05) reductions in mean arterial pressure, systemic vascular resistance, hematocrit, and levels of plasma sodium and ionized calcium were found. These changes were associated with significant (p less than 0.05) increases in cardiac output, right atrial pressure, arterial PO2 and PCO2, and levels of plasma potassium. It is concluded that rapid infusions of hyperosmolar urea may have important effects of hemodynamic status and plasma cation concentrations.

Adult↗
PubMed1981

Abnormal electro-oculograms from eyes with a malignant melanoma of the choroid.

Electro-oculograms (EOGs) were recorded from 14 patients with a malignant melanoma of the choroid, nine of which were histologically verified. Twelve of the 14 eyes (86%) with a malignant melanoma of the choroid had an EOG value that was considered borderline. One eye studied had a normal EOG value and a histologically verified malignant melanoma. EOGs were also recorded from a group of eight patients with a choroidal nervus. Five of these eight eyes had normal EOG values, two eyes had borderline EOG values, and one eye had an abnormal EOG value. The EOG value in eyes with a malignant melanoma of the choroid was inversely related to the size of the melanoma. Abnormal EOG values were obtained, however, from eyes lesions occupying only a few square millimeters.

Adult↗
PubMed1980

A cardioactive factor in human plasma with positive inotropic and positive chronotropic activities.

A cardioactive factor with a molecular weight of about 100,000 and that exhibits positive inotropic and positive chronotropic activity on isolated guinea pig atria has been found in human plasma. The positive inotropic activity is less stable than the positive chronotropic activity. The two activities move together in cation- and anion-exchange chromatography, gelfiltration chromatography, and polyethylene glycol precipitation. They may be associated with a single large polypeptide or with different subunits of a complex protein.

Journal Article↗
PubMed1980

Anaesthesia and demyelinating disease.

The demyelinating diseases are classified and the current concepts of the aetiology and pathophysiology of the most common of these diseases, multiple sclerosis, are described. The effects of the impaired function, local responses and known complications of the disease on the choice of anaesthetic, drugs and techniques are discussed.

Anesthesia, General↗
PubMed1980

Phase selectivity of spatial frequency channels.

The phase selectivity of spatial frequency channels was measured, using an adaptation technique. Subjects first adapted to a grating of a given spatial frequency; subsequent threshold measurements were made at various spatial frequencies and phase shifts. Changes in the phase relationship between the test and adaptation gratings due to eye movements were circumvented by viewing the grating through an image stabilization apparatus. Local retinal adaptation was minimized by using an adaptation grating whose contrast flickered sinusoidally as a function of time. We were able to demonstrate channel-like frequency tuning for all conditions studied, but the threshold elevations following adaptation were always independent of the phase shift between the test and adaptation gratings. Our results imply that the channels which are selectively tuned to spatial frequency are not selectively tuned to spatial phase.

Adaptation, Ocular↗
PubMed1980

Contrast sensitivity measures and accuracy of image stabilization systems.

Recently, it has been argued that the precision of image stabilization is reflected in the magnitude of the differences in contrast sensitivity measures obtained with and without image stabilization. Here we present two sets of data, one showing large and the other small differences in contrast sensitivity to sinusoidal gratings viewed under stabilized and unstabilized, normal conditions. Both sets of data were obtained by the use of the same apparatus optimized for image stabilization. Large differences occur between unstabilized and stabilized measures of sensitivity only when the observer is allowed to scan the unstabilized test grating, or to prolong inspection of the stabilized target thus allowing for disappearance of the stabilized image. On the other hand, when the target is presented for a few seconds and the observer fixates on it, normal image motion, which results from eye movements of fixation, is found to enhance contrast sensitivity by only a small amount. It would appear, therefore, that the extent of reduction of sensitivity for a stabilized grating cannot be used as an index of the precision of image stabilization.

Adult↗
PubMed1979

Teamwork, planning keys to success.

To ensure a successful psychiatric unit in a general hospital, the hospital must determine needs, plan with all involved parties, and follow up with sensible control measures.

Health Services Needs and Demand↗