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Biomedical subjects

J W Cox

Publications and source records attributed to J W Cox.

At least 55 records · Page 3Linked to original sources
PubMed1982

Studies of the effects of essential fatty acid deficiency in the rat.

We report a model of prostaglandin depletion induced in rats by fasting for 11 days, followed by institution of an essential fatty acid-deficient diet. Urinary prostaglandin E, 2 weeks after this diet had been implemented, was 22 +/- 2 ng/24 hours compared to 113 +/- 8.5 ng/24 hours in controls (P less than 0.01). There was no difference in 24-hour urine volume or solute excretion in controls and essential fatty acid-deficient rats. Five hours after administration of NaCl, 10 mM/kg, essential fatty acid-deficient diet rats excreted 1.85 +/- 0.78 ml urine compared to 6.42 +/- 2.26 ml in control (p less than 0.01) with Na+ excretion 447 +/- 273 muEq in essential fatty acid-deficient rats vs 1483 +/- 366 muEq in control (P less than 0.01). Intravenous isotonic NaCl, 1.5% body weight, resulted in increased urine flow rate in control rats from 8.3 +/- 2 microliter/min to 28.7 +/- 8.8 microliter/min with sodium excretion increasing from 0.19 +/- 0.2 to 3.3 +/- 0.9 muEq/min. In the essential fatty acid-deficient diet animals, there was no significant change in flow rate, 6.07 +/- 2.43 to 9.85 +/- 4.29 microliter/min, or sodium excretion, 0.09 +/- 0.03 to 0.40 +/- 0.24 muEq, after saline infusion. There was no difference in the glomerular filtration rate of plasma aldosterone in the two groups after the salt load. When given a water load, 3 ml/100 g body weight, essential fatty acid-deficient diet rats excreted 2.5 +/- 0.7 ml in 5 hours compared to 6.3 +/- 1.4 ml in controls (P less than 0.01). The defect in water excretion was not due to increased sensitivity to antidiuretic hormone, since similar sensitivity to this hormone was demonstrated in the essential fatty acid-deficient diet and control rats during a water diuresis. When isotonic saline was substituted for drinking water, there was an increase in systolic blood pressure in essential fatty acid-deficient diet rats from 124 +/- 2 to 142 +/- 3 mm Hg over 9 days (P less than 0.01) compared to 122 +/- 2 before and 122 +/- 2 mm Hg after saline drinking in controls. The administration of linoleic acid for 4 days increased urinary prostaglandin E excretion to 114 +/- 15 ng/24 hours from 23 +/- 4 (P less than 0.01), and the alterations in the ability to excrete a sodium and water load were reversed. In essential fatty acid-deficient diet animals made hypertensive by 9 days of saline drinking, the institution of linoleic acid to the diet normalized the blood pressure despite the continued administration of saline. These studies demonstrate that essential fatty acid-deficient diet animals develop salt-sensitive hypertension with a combined defect in both sodium and water excretion which is reversed following correction of the essential fatty acid deficiency.

Animals↗
PubMed1982

Urinary concentrating ability and antidiuretic hormone responsiveness in the potassium-depleted dog.

The effects of potassium depletion on urine concentration ability, renal PGE2 excretion, and ADH release were studied in 28 female dogs made K depleted by oral K-exalate and a K-free diet. After K depletion was established (serum K 2.9 +/- 0.1 mEq/L), urine volume increased from control measurements, 596.4 +/- 34.0 to 1201.5 +/- 96.9 ml/24 hr (p less than 0.001); urine PGE2 excretion increased, 985.4 +/- 91.1 to 2122.0 +/- 328.5 ng/24 hr, (p less than 0.001); and Umax decreased, 2006 +/- 74.0 to 1186 +/- 71.9 mOsm/kg H2) (p less than 0.001). Indomethacin (5 mg/kg/day, s.c.) administered on 3 consecutive days after K depletion had been established, resulted in no significant improvement in Umax, 1186.8 +/- 71.9 to 1341.8 +/- 105.6 mOsm/kg H2O. Release of ADH from the neurohypophysis was evaluated by measuring plasma ADH during graded increases in serum tonicity with intravenous hypertonic saline before and after K depletion. Although ADH increased with increasing serum tonicity during both control and K depletion periods, there was a blunting of ADH release during K depletion. The regression coefficient of plasma ADH and serum tonicity was significantly lower during K depletion, 0.24, than in the control period, 0.65, (p less than 0.01). After 3 days of indomethacin (5 mg/kg/day, s.c.) ADH release from the neurohypophysis in response to graded increases in serum tonicity was partially normalized in the K-depleted animals without changes in serum K (regression coefficient, 0.53). K depletion in dogs therefore leads to an increase in the urine volume and an increase in renal PGE synthesis associated with a decrease in Umax. The increase in PGE2 synthesis is not responsible for the defect in Umax, since it is not corrected with indomethacin. The release of ADH in response to raising serum tonicity is blunted during K depletion, which is partially corrected by indomethacin. These data suggest an inhibiting role for PGE2 in the release of ADH from the neurohypophysis during K depletion.

Animals↗
PubMed1981

The antenatal and perinatal characteristics of socio-economically depressed Caucasians.

Many studies have shown that Aborigines have an above average obstetric risk, but the results are not clear as to whether this is a racial characteristic or attributable to social circumstances. The co-existence of sufficient numbers of unemployed and unskilled Caucasians and Aborigines living in similar social circumstances in a Western Queensland town enabled a valid evaluation of this problem. It was found that the incidence of obstetrical problems and resulting morbidity amongst Caucasians of low socio-economic standing and Aborigines were almost identical. As low socio-economic status seems to be more closely linked with antenatal, obstetrical and neonatal risk than race, it seems prudent to expand the present health projects catering for Aborigines to encompass all underprivileged people.

Adolescent↗
PubMed1981

Preparation of thioester substrates and development of continuous spectrophotometric assays for phospholipase A1 and monoacylglycerol lipase.

Current assays of phospholipase A1 (EC 3.1.1.32) and monoacylglycerol lipase (EC 3.1.1.23) activities in tissues are discontinuous, laborious, and expensive. Some spectrophotometric substrates were synthesized to alleviate this problem. Thioester analogs of phosphatidylcholine and phosphatidylethanolamine. rac-1,2-S,O-didecanoyl-3-phosphocholine-1-mercapto-2,3-propanediol and rac-1,2-S,O-didecanoyl-3-phosphoethanolamine-1-mercapto-2,3-propanediol, were synthesized from the diacylglycerol analog, rac-1,2-S,O--didecanoyl-1-mercapto-2,3-propanediol. The latter was prepared from triacylmercaptoglycerol by lipolysis and separation by chromatography on silica gel. Monoacylglycerol thioester analogs, 1-S-hexadecanoyl-1-mercapto-2,3-propanediol and 1-S-decanoyl-1-mercapto-2,3-propanediol, were synthesized by selective acylation of mercaptoglycerol. All of the substrates were hydrolyzed by Rhizopus delemar lipase to release sulfhydryl groups reactive towards 4,4'-dithiobispyridine. The hydrolysis could be followed continuously in a spectrophotomer with 0.1 absorbance unit corresponding to 5 nmol product. The structure and isomeric purity of the phospholipid analogs were verified by their behavior on thin-layer chromatography, elemental analyses, infrared spectra, and by the specificity of the colorimetric reaction with lipolytic enzymes. Whereas phospholipase A1 activity hydrolyzed both phospholipid analogs to release the theoretical amount of free thiol, neither phospolipases C nor A2 promoted thio release. The pH optimum, heat stability, and Ca2+ ion dependency were determined for the hydrolysis of each substrate by R. delemar lipase. The results indicate that the phospholipase A1 and monoacylglycerol lipase activities in R. delemar lipase are due to separate enzymes, and that these enzyme specific assays will be of general utility for enzyme characterization and purification studies. These substrates are useful for sensitive, convenient, and specific spectrophotometric assays for phospholipase A1 and monoacylglycerol lipase over the pH range 3 to 8.

Calcium↗
PubMed1979

Infant mortality in 12 Aboriginal settlements: Queensland, 1972--1976.

The infant mortality rate amongst Aborigines from 12 Queensland Aboriginal settlements and missions over the years 1972 to 1976 was 72 per 1000 live births. This rate is comparable with that for Queensland of 60 years ago. The Aboriginal infants had twice the present-day Queensland risk of neonatal death and eight times the risk of postneonatal death. Prematurity was the major cause of neonatal deaths; gastroenteritis and pneumonia were the major causes of infant deaths. These rates emphasise the need for community and preventive health care for the Aboriginal children, particularly during the postneonatal period.

Australia↗
PubMed1979

Synthesis of choline and ethanolamine phospholipids with thiophosphoester bonds as substrates for phospholipase C.

Spectrophotometric assays of esterases are sensitive, rapid, and quite specific when thioester substrates are used. Glycerophospholipids with thiophosphoester bonds may be useful as substrates for phospholipase C (EC 3.1.4.3). These have been made from mercaptoglycerol and mercaptoethanol. The thiols were oxidized to disulfides, acylated, and reduced with dithiothreitol. Phosphocholine derivatives were made by the classical methods for oxyphosphoesters. The phosphatidyl choline analogue was converted to the phosphatidyl ethanolamine analogue by transphosphatidylation with cabbage phospholipase D and ethanolamine. Structures were proved with enzymic hydrolysis, infrared spectra, TLC behavior, and elemental analyses. The synthesized compounds were rac-1-S-phosphocholine-2,3-O-didecanoyl-1-mercapto-2,3-propanediol, 1-S-phosphoethanolamine-2,3-O-didecanoyl-1-mercapto-2,3-propanediol, and 1-S-phosphocholine-2-O-hexadecanoyl-1-mercapto-2-ethanol.

Bacillus cereus↗
PubMed1979

A system oriented electrocardiographic amplifier.

A low noise, programmable gain amplifier has been developed for acquiring ECG data from a variety of recording environments. Features include: low noise (4muV peak-to-peak) differential inputs; digitally programmable gains (range 100 to 16000) and output DC offsets (range -3.5 to +4 V) controlled via a serial interface; externally selectable low frequency response (0.04 or 0.08 Hz); and an on-board output monitor multiplexer controlled via a second serial interface.

Amplifiers, Electronic↗
PubMed1979

Factors influencing the time of introduction of steroidal contraception in the breast-feeding mother.

To ensure infertility whilst breast feeding many mothers ingest steroidal contraceptives. Animal experiments have shown how sexual differentiation of the brain occurs during perinatal life and can be affected by exogenous steroids. The amount of sex steroid secreted in the milk of lactating mothers is very small and dependent on the type of steroid chosen. "On demand" breast feeding is associated with a longer period of lactational amenorrhoea, obviating the necessity for early usage of contraceptives. In view of the possibility that sexual differentiation may be disturbed, it is suggested that, where steroidal contraception is required, the progesterone with the minimal amount of oestrogenic metabolite be used.

Animals↗