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Biomedical subjects

M S Gordon

Publications and source records attributed to M S Gordon.

At least 73 records · Page 4Linked to original sources
PubMed1989

Angiotensin-mediated renin suppression is altered in non-modulating hypertension.

Plasma renin activity (PRA) suppression by angiotensin II (Ang II), the "short feedback loop," has been shown to be blunted in essential hypertension. Non-modulators comprise 50% of normal- and high-renin essential hypertensive individuals and are defined by their abnormal adrenal and renal responses to infused Ang II. This study sought to determine if the abnormal Ang II suppression of PRA in essential hypertension is specific to non-modulators. We measured PRA suppression during infusion of Ang II in 22 normotensive and 32 hypertensive (16 modulators and 16 non-modulators) subjects. A significant correlation between basal PRA and the fall in PRA in response to Ang II infusion was seen in the normotensives (r = -0.934, p less than 0.001) and modulators (r = -0.831, p less than 0.001) but not in the non-modulators (r = -0.275, p = 0.304). However, after 3 days of converting enzyme inhibition therapy, the correlation between basal PRA and decrement in PRA was significant in the non-modulators (r = -0.762, p less than 0.01). Thus, the abnormal PRA suppression documented previously in hypertensive individuals is a defect specific to non-modulators and is corrected with converting enzyme inhibition therapy.

Adult↗
PubMed1989

The role of dopamine in nonmodulating hypertension.

Dopamine may exert a tonic inhibitory effect on aldosterone secretion and enhance renal sodium excretion. Nonmodulating hypertension in part is characterized by decreased aldosterone secretion in response to angiotensin II (AII) as well as a decreased natriuretic response to a saline load. This study assesses whether an abnormally increased dopaminergic inhibition of aldosterone secretion underlies the adrenal defect in nonmodulating hypertension and whether abnormalities of renal dopamine formation contribute to sodium retention. We measured the plasma dopamine concentration in 39 patients with nonmodulating hypertension and in 32 patients with normal modulation on a 10-meq sodium intake. Dopamine levels were significantly higher (P less than 0.05) in nonmodulators. The aldosterone response to AII (3 ng/kg.min) was assessed before and during administration of the dopamine antagonist metoclopramide in 13 patients. Metoclopramide did not change the adrenal response to AII in either hypertensive subgroup. In 12 normal subjects mean urinary dopamine levels were higher in a sodium-replete state (200-mmol intake) than in a low sodium state (10-mmol intake; 1.68 +/- 0.28 vs. 0.92 +/- 0.22 mumol/day; P less than 0.01) as expected. Modulators demonstrated this same effect, while nonmodulators did not [modulators, 3.66 +/- 0.82 and 1.37 +/- 0.14 mumol/day; nonmodulators, 1.33 +/- 0.28 and 1.68 +/- 0.90 mumol/day; P less than 0.02]. The sodium-retaining tendency of nonmodulators may reflect, at least in part, reduced intrarenal dopamine production in the sodium-replete state, but the adrenal defect in aldosterone release in nonmodulators is not mediated by excess dopaminergic inhibition of aldosterone secretion.

Adrenal Glands↗
PubMed1989

Tissue-specific regulation of rat estrogen receptor mRNAs.

The estrogen receptor (ER) is present in a wide variety of mammalian tissues and is required for physiological estrogen responses, including estrogen-induced tissue-specific changes in gene expression. We studied the estrogen regulation of the mRNAs encoding the ER in rat uterus, liver, and pituitary. Ovariectomized (21-28 day post surgery) female CD-1 rats were injected daily with 17 beta-estradiol (E2, 10 micrograms/100 g BW) for 0, 1, or 4 h, 1, 3, or 7 days and compared with intact controls. Steady-state levels of ER mRNA were quantified using a human ER cDNA probe. Only one hybridizing species of approximately 6.2 kilobase (kb) was detected in uterine and liver RNA, similar to that observed in MCF7 human breast cancer cells. However, the ER mRNA regulation by E2 differed in direction depending on the tissue examined. In uterus, ER mRNA increased 3- to 6-fold after ovariectomy, and returned to intact levels within 24 h of E2 replacement. In contrast, liver ER mRNA declined 1.5- to 3-fold after ovariectomy and returned to intact levels after 1-3 days of E2. In pituitary tissue two hybridizing forms of ER mRNA were observed, with one species migrating at 6.2 kb, equivalent to the form in other tissues, and a second smaller species at approximately 5.5 kb. The lower molecular weight species varied somewhat in abundance from animal to animal, averaging about 20% of the intensity of the 6.2 kb band. The ER mRNA forms were regulated positively with E2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Management of invasive carcinoma in pedunculated colorectal polyps.

Management of patients with endoscopically removed pedunculated colorectal polyps found to contain invasive carcinoma is controversial. When the endoscopist is confident that the polyp has been completely removed and the margins are pathologically clear, the salient issue which should guide subsequent management is the likelihood of lymph node metastases. Analysis of several institutional reviews has led the authors to conclude that the incidence of lymph node metastases is negligible in those patients in whom careful pathologic examination discloses free margins of resection, absence of lymphatic invasion, and well-differentiated or moderately well differentiated histology. Adhering to these criteria, pedunculated polyps containing invasive carcinoma can be safely managed by endoscopic polypectomy alone.

Adenocarcinoma↗
PubMed1987

Effect of tablet solubility and hygroscopicity on disintegrant efficiency in direct compression tablets in terms of dissolution.

The effect of tablet composite solubility and hygroscopicity on the dissolution efficiency of three "super disintegrants", sodium starch glycolate, crospovidone, and croscarmellose sodium, was investigated. Lactose, dicalcium phosphate dihydrate, and sorbitol, alone or in combination, provided varying degrees of solubility and hygroscopicity to the direct compression tablet formulations. To monitor in vitro dissolution, 1% p-aminobenzoic acid was added to the formulation as a tracer. The results indicate that hygroscopic ingredients decrease the effectiveness of super disintegrants in promoting in vitro dissolution. The greater the overall hygroscopicity of the tablet formulation, the larger the decrease in the efficiency of the super disintegrant. Composite tablet solubility did not influence the effectiveness of the super disintegrants. Super disintegrants that complied with the same compendial specifications, but were manufactured by different companies, behaved similarly in promoting tablet dissolution.

Chemistry, Pharmaceutical↗
PubMed1986

Computer modeling of estradiol interactions with the estrogen receptor.

Two computer models for the binding of estradiol to estrogen receptors were constructed, based solely upon the thermodynamic constraints of the most likely equilibria involved and known equilibrium constants. Previous data had suggested that the positive cooperativity of the system was dependent upon a monomer-dimer equilibrium (Notides et al., Proc. natn. Acad. Sci., U.S.A. 78 (1981) 4926-4930). Using computer modeling, we confirmed that the thermodynamic constraints of a monomer-dimer equilibrium system result in convex Scatchard plots in agreement with experimental data, including the progression to linearity at low receptor concentrations. This technique yielded estimates of the equilibrium constant for dimerization (approx. 10(10) to 10(14) M-1). The dose-response characteristics of the monomer-dimer equilibrium system revealed steep dose-response curves that were sensitive to the receptor concentration. In contrast, the dose-response curves that did not undergo a monomer-dimer equilibrium system and had a single step equilibrium process were more gradual.

Computers↗
PubMed1981

A cardiology patient simulator for continuing education of family physicians.

"Harvey," the cardiology patient simulator (CPS), is the result of a new type of simulation technology that allows for repetitive practice of bedside cardiology skills and provides feedback to the learner. "Harvey" is able to realistically simulate an essentially unlimited number of both common and rare cardiac disease. This report describes the use of the CPS in continuing medical education programs conducted for members of the American Academy of Family Physicians. Cardiovascular disorders constitute a significant percentage of the practice of family physicians. The CPS teaching system has great potential for helping them keep their cardiovascular diagnostic skills current and for promoting better understanding of recent advances in the diagnosis and treatment of heart disease. The participants in this study were nearly unanimous in their feeling that the CPS accurately simulates cardiology bedside findings and is a valuable teaching tool with which they would like to again be taught in the future.

Cardiovascular Diseases↗