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Biomedical subjects

D J Jones

Publications and source records attributed to D J Jones.

At least 181 records · Page 10Linked to original sources
PubMed1970

Effects of parathyroid hormone on plasma and urinary adenosine 3',5'-monophosphate in man.

The effects of parathyroid hormone (PTH) on plasma and urinary adenosine 3',5'-monophosphate (cyclic AMP) levels were studied in normal subjects. Under basal conditions normal adults have plasma concentrations of cyclic AMP ranging from 10 to 25 nmoles/liter and excrete from 1.5 to 5 mumoles of cyclic AMP per g of urinary creatinine. About one-half to two-thirds of the cyclic AMP excreted in the urine is derived from the plasma by glomerular filtration, and the remainder is produced by the kidney. Renal production of cyclic AMP is partly under the control of PTH. It can be suppressed by infusions of calcium and stimulated by infusions of the calcium chelating agent, EDTA. Infusions of PTH in doses up to 10 mU/kg per min were associated with dose-related increases both in urinary cyclic AMP and phosphate. Infusions of PTH in doses ranging from 20 to 80 mU/kg per min did not lead to any further increase in phosphaturia but did lead to further marked increases in urinary cyclic AMP. A modest increase in plasma cyclic AMP was noted when PTH was infused at 40 mU/kg per min. Anephric patients failed to show appreciable increases in plasma cyclic AMP in response to large doses of PTH but did show expected increases in response to glucagon. Surgical removal of parathyroid adenomas from nine patients with primary hyperparathyroidism was invariably followed by a decrease in urinary cyclic AMP, PTH, in large doses, and calcium infusion produced up to 2-fold increases in the other known naturally occurring cyclic nucleotide, guanosine 3',5'-monophosphate (cyclic GMP).

Adenine Nucleotides↗
PubMedDate not supplied

Determination of quercetin in human plasma by HPLC with spectrophotometric or electrochemical detection.

A reversed-phase high-performance liquid chromatographic method for the determination of quercetin in human plasma following intravenous infusion is described. Quercetin in plasma was extracted with methanol-dimethyl sulphoxide (4:1 v/v) and separated on a C18 Hypersil-BDS column with 44% (v/v) methanol in 0.1 M ammonium acetate (pH 5.15) containing 0.27 mM EDTA as the mobile phase. The drug was detected specifically and sensitively at its absorption maximum of 375 nm, or electrochemically, with a detection limit of 80 ng/mL and 2 ng/mL, respectively.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Current status of tumor markers in large bowel cancer.

The aim of a primary screening system is to detect premalignant lesions and carcinomas when amenable to "curative" surgery. Although a number of "classical" tumor markers have acquired potential for clinical management, none is presently adequate for presymptomatic diagnosis or screening. In colorectal carcinoma, the screening potential of carcinoembryonic antigen (CEA), the gastrointestinal-related antigen, CA19-9, and other more recently characterized "biochemical markers" is virtually nonexistent, even in patients at high risk to develop the disease. Promising new leads are beginning to emerge from somatic cell genetic and molecular biological approaches. In common with other epithelial neoplasms, perturbations in oncogene expression have been demonstrated in colorectal cancers, and probably reflect important events in malignant transformation and progression. Studies of oncogene expression have, however, not yet yielded clinically useful information. Recently, an intensive search for specific chromosomal and gene abnormalities in the hereditary colon cancer syndromes led to the location of the familial adenomatous polyposis (FAP) gene at chromosome 5q21-q22. Significant is that the loss of alleles on chromosome 5 has also been observed in the tumor cells of at least 20% of sporadic colon cancer patients. This type of association between constitutional genetic change and genetic aberration in the cells of sporadic tumors is reminiscent of other malignant diseases with a genetic component (e.g., retinoblastoma and Wilms' tumor).(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers, Tumor↗
PubMedDate not supplied

Beta-adrenergic receptor changes in learned helplessness may depend on stress and test parameters.

Behavioral deficits following inescapable stress (learned helplessness) may serve as an animal model of depression. Previous studies using foot-shock stress to induce learned helplessness and a bar-press test for the stress-induced behavioral deficit have found increased beta-adrenergic receptor density in the hippocampus of learned helpless rats. We replicated these experiments using a tail-shock stress and the shuttle-box test. In our experiments, rats that developed learned helplessness after inescapable stress did not demonstrate any significant differences in beta-adrenergic receptor density or affinity in the frontal cortex, cerebellum, or hippocampus compared to the nonhelpless rats, nor to the tested control rats. These results suggest that beta-adrenergic receptor changes in learned helplessness may depend on the specific stress and test procedures used.

Animals↗
PubMedDate not supplied

Mild hemophilia in children: prevalence, complications, and treatment.

PURPOSE: To review the natural history of mild hemophilia (factor VIII or IX level >5% and <50%), including presentation and diagnosis, characteristics of bleeding episodes, and therapy, at two hemophilia treatment centers. METHODS: Inpatient and outpatient records of 55 patients <17 years old with factor VIII or IX levels of 5 to 50% were reviewed and bleeding episodes for which medical attention was sought were analyzed. RESULTS: Five of the 55 patients were girls. Girls and patients with no family history of hemophilia were diagnosed at 5.5 and 5.3 years of age, respectively, compared to 2.8 years overall. Thirty-five patients were diagnosed because of a positive family history. No bleeding occurred in 18 patients; 190 bleeding episodes occurred in 37 patients. Most bleeding occurred in muscle/soft tissue (101 episodes) or joints (57 episodes) and were associated with trauma (174 episodes). CONCLUSIONS: Mild hemophilia may affect females more often than is appreciated. Delays in diagnosis and treatment may occur unless the variability in presentation is recognized.

Adolescent↗
PubMedDate not supplied

Age-associated reduction in pineal beta-adrenergic receptor density is prevented by life-long food restriction in rats.

At 28 months of age (old rats), male Fisher 344 rats which had been fed 40% of the ad libitum food intake since they were 6 months old, had a similar beta-adrenergic receptor density (Bmax) in their pineal gland as young, 3-month-old rats. In contrast, old rats which had been fed ad libitum for the same period had approximately 50% of the Bmax value compared to that of young rats. The beta-receptor density of cerebral cortical tissue and the beta-receptor affinity (Kd) of both the cortex and the pineal gland did not decline with age and was not affected by food restriction. The reduction in pineal beta-receptor density with age may be casually related to the concurrent age-associated decline in pineal production of melatonin.

Aging↗
PubMedDate not supplied

Enflurane and uterine contractility in rabbits.

The effect of enflurane on uterine contractility was studied in sexually mature rabbits in which intrauterine balloon catheters had been implanted. Three animal groups were studied: untreated; treated with estrogen-progesterone; and 27 to 28 days pregnant. The effects of 1.5 percent or 3.0 percent enflurane were quantitated by measuring contraction frequency and amplitude during an anesthetically steady state. The effects of prior anesthesia with 1.5 percent enflurane on uterine responses to 1.5 IU oxytocin IV were also evaluated. Neither 1.5 percent of 3.0 percent enflurane altered contraction amplitude or frequency in the 3 groups of rabbits. However, the amplitude of the contractile response to oxytocin 30 minutes following enfluane was significantly depressed. The results indicate that, while the intact rabbit uterus under different hormonal influences is not depressed by 1.5 or 3.0 percent enflurane, its response to oxytocin following enflurane is decreased.

Animals↗