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Biomedical subjects

C Moon

Publications and source records attributed to C Moon.

43 records · Page 3Linked to original sources
PubMed1985

Main and interaction effects of metallic toxins on classroom behavior.

This study investigated the relationships of metal levels and metal combinations to children's classroom behavior. Hair-metal concentrations of lead, arsenic, mercury, cadmium, and aluminum were determined in 80 randomly selected elementary-age children, who were also rated by their classroom teacher on the Walker Problem Behavior Identification Checklist (WPBIC). Parents were interviewed to control for confounding variables that may have affected behavioral development. Regression analysis indicated that the set of metals was significantly related to increased scores on four of the five WPBIC subscales and on the total scale, with lead being a major contributor to four of the six dependent measures. Metal combinations were significantly related to increased scores on the WPBIC subscales measuring acting-out, disturbed peer relations, and immaturity, and on the total scale. A continuing reexamination of metal poisoning concentrations is needed because metal levels and metal combinations previously thought harmless may be associated with nonadaptive classroom behavior.

Aluminum↗
PubMed1977

Plasma renin and "prorenin" in essential hypertension during sodium depletion, beta-blockade, and reduced arterial pressure.

An inactive form of renin is activated by incubating human plasma at -5 degrees C. The relative proportions of active renin and this cryoactivatable "prorenin" in plasmas of untreated hypertensive patients varied widely. However, prorenin increased in parallel with active renin after sodium deprivation or diuretic therapy in 36 patients; the increases were similar whether or not blood-pressure fell. In contrast, propranolol administration in 22 patients lowered active renin in all, but it increased prorenin by 98% in 15 in whom systolic pressure fell. In the other 7 blood-pressure did not change, and beta-blockade produced a fall in total renin (active renin plus prorenin) while prorenin was unchanged. For all 22 there was an inverse relationship between propranolol-induced changes in plasma-prorenin and systolic pressure (r=-0-77, P less than 0-001). The fraction of active plasma-renin fell during propranolol administration from 43% to 18%, regardless of the blood-pressure response. Clonidine produced similar changes in 10 patients. Thus, sodium depletion stimulates total renin release, while propranolol and clonidine produce divergent responses of active renin and prorenin, the changes in prorenin depending on the changes induced in blood-pressure. These observations suggest that propranolol may block intrarenal conversion of prorenin to active renin while also suppressing total renin release. But the latter effect may be offset by concurrent baroreceptor-mediated release of total renin (mostly prorenin) when blood-pressure is lowered.

Adult↗
PubMed1977

Plasma prorenin in normal, hypertensive, and anephric subjects and its effect on renin measurements.

We have previously shown that a cryoactivatable inactive form of renin, which we have tentatively termed prorenin, occurs in human plasma. Plasma prorenin is measured by subtracting the endogenous plasma renin activity (PRA) from the total renin activity measured after cryoactivation. Cryoactivation is accomplished by shaking plasma at -5 degrees C for 4 days. Circulating prorenin averaged 5.6 +/- 0.8 (SE) ng/ml per hour in a group of 30 normal subjects and 5.1 +/- 1.0 ng/ml per hour in 25 hypertensive subjects during random sodium intake. In these two groups, prorenin ranged from zero to 36 times the endogenous renin level, averaging 2.5-fold in normal subjects and 3.4-fold in hypertensive subjects. During sodium deprivation prorenin more than doubled in 12 hypertensive subjects from a mean of 2.8 to 6.3 ng/ml per hour. In 25 anephric subjects, circulating prorenin was slightly lower than in normal subjects, averaging 3.4 +/- 0.9 ng/ml per hour (P less than 0.05). In contrast to our findings in nephric subjects, the low level of PRA measured in anephric subjects ((0.26 +/- 0.04 ng/ml per hour) was almost always a constant fraction of the measured prorenin. This led to the demonstration that prorenin can be inadvertently activated by chilling blood during processing for renin measurement and this often accounts for the small amount of renin measured in plasmas from anephric subjects. The error in routine PRA measurements due to inadvertent activation averaged +48% in anephric subjects and +17% in those with kidneys. Evaluation of the effect of processing bloods at room temperature revealed that net angiotensin I accumulation is less than 2% of that generated during incubation and can be ignored. Accordingly, to avoid the inadvertent activation of prorenin which can at times lead to a sizable and variable overestimation of PRA we recommend collecting and processing blood samples at room temperature and then storage of plasma completely frozen until the time for analysis.

Adolescent↗
PubMed1976

Plasma prorenin: cryoactivation and relationship to renin substrate in normal subjects.

We previously demonstrated an inactive form of renin, termed prorenin, in the plasma of normal, hypertensive and anephric patients. Prorenin activity can be determined in plasma from the total renin activity after activation, minus the prior endogenous plasma renin activity. In the present study, conditions for cryoactivation of prorenin have been defined. Plasma prorenin is slowly converted to active renin-like material at -5 degrees C at pH 7.4. Activation takes four days and does not occur at pH 5.0. The degree of activation increases above pH 5 and is greatest between pH 7 and pH 9. Thus, almost no cryoactivation of prorenin occurs at the pH optimum for renin (5.7) in contrast to maximum activation at pH 7.4. No activation has been observed in the frozen state, but it does occur with decreasing rapidity at temperatures from -5 degress to +4 degress C. Since blood samples obtained for the determination of plasma renin activity are routinely chilled upon collection by most laboratories, some activatin of prorenin most likely occurs in all routine renin assays. The pH optimum of the enzymatic reaction of the activated prorenin in plasma is 5.8, the same as for renal renin, and the shape of the pH optimum curve is similar to that of renal renin added to human plasma. In a group of 23 normal subjects with plasma renin activity of 3.5 +/- 2.9 (SD), the activated prorenin increment was found to be significantly higher, 6.3 +/- 5.0 (SD) ng/ml/hour. Unlike plasma renin activity, prorenin activity in these normal subjects was directly related to the concentration of renin substrate (p less than 0.001). When the actual "concentration" of prorenin was calculated using renal renin as the reference standard, a direct relationship was also found between the concentration of prorenin and renin substrate (p less than 0.01). The observed relationship between prorenin and renin substrate concentrations might be a consequence of their regulation by common factors.

Angiotensin II↗
PubMedDate not supplied

Evaluation of plant extracts for sweetness using the Mongolian gerbil.

Extracts of Thladiantha grosvenorii fruits, Stevia rebaudiana leaves, and Abrus precatorius leaves were investigated using Mongolian gerbil electrophysiological and conditioned taste aversion procedures, which were designed to respond to sucrose. A close correlation was observed between extracts of these sweet plants known to contain sweet principles and those extracts indicated as being sweet by a combination of these gerbil bioassays. The methods employed seem to be suitable for use in aiding the purification of highly sweet compounds of plant origin.

Animals↗
PubMedDate not supplied

Main and interaction effects of metal pollutants on visual-motor performance.

This study investigated possible relationships of metal levels and metal combinations with children's visual-motor performance. Hair-metal concentrations of lead, arsenic, methylmercury, cadmium, and aluminum were determined in 69 randomly selected elementary age children. They were also administered the Bender Visual-Motor Gestalt Test. Parents of subjects were interviewed to control for confounding variables that might affect cognitive development. Regression data indicated that increases in aluminum and the interaction of aluminum with lead were significantly related to decreased visual-motor performance. Because metal levels and metal combinations previously thought harmless may be associated with visual-motor deficits, a continuing reexamination of metal poisoning concentrations is needed.

Age Factors↗