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Biomedical subjects

E Tucker

Publications and source records attributed to E Tucker.

At least 37 records · Page 2Linked to original sources
PubMed1987

Results of screening a large group of intercollegiate competitive athletes for cardiovascular disease.

To determine the feasibility of detecting cardiovascular disease in a large group of young competitive athletes, a prospective screening evaluation of intercollegiate student athletes was undertaken at the University of Maryland. Initial clinical screening (including personal and family history, physical examination and 12 lead electrocardiogram) was performed in 501 athletes. Ninety of these subjects had positive findings on one or more of the three studies and agreed to further cardiologic evaluation. The vast majority (75 [84%] of 90) had no definitive evidence of cardiovascular disease, although 1 athlete had mild systemic hypertension and 14 (15%) had echocardiographic evidence of relatively mild mitral valve prolapse that had not been previously suspected. In three athletes with relatively mild ventricular septal hypertrophy (14 to 15 mm), it was not possible to discern with absolute certainty whether the wall thickening was a manifestation of hypertrophic cardiomyopathy or secondary to athletic conditioning ("athlete heart"). Therefore, this screening protocol identified no athletes with definite evidence of hypertrophic cardiomyopathy, Marfan's syndrome or other cardiovascular diseases that convey a significant potential risk for sudden death or disease progression during athletic activity. This failure to identify such diseases could have been due to a lack of sensitivity of the screening tests or to the low frequency with which these diseases occur in youthful healthy athletes. A systematic preparticipation screening program (such as the present one) does not appear to be an efficient means of detecting clinically important cardiovascular disease in young athletes.

Adolescent↗
PubMed1987

Inducible polymorphic ventricular tachycardia and ventricular fibrillation in a subgroup of patients with hypertrophic cardiomyopathy at high risk for sudden death.

This investigation was undertaken to elucidate the underlying electrophysiologic substrate in hypertrophic cardiomyopathy and to identify possible predictors of sudden death in this patient population. Programmed stimulation was performed in 18 patients aged 14 to 64 years (mean 36) believed to be at high risk for sudden death on the basis of prior cardiac arrest or syncope, nonsustained ventricular tachycardia on Holter ambulatory electrocardiographic (ECG) monitoring or a family history of frequent sudden death. Polymorphic ventricular tachycardia that deteriorated to ventricular fibrillation was reproducibly induced in 8 (44%) of the 18 patients (Group A). This rhythm was induced in all three patients with a history of cardiac arrest. No sustained monomorphic ventricular tachycardia was induced. Group B comprised the 10 patients in whom a sustained arrhythmia could not be reproducibly initiated. The electrophysiologic substrate was distinctly different in patients with, than in those without, inducible sustained arrhythmia. The refractory period was shorter at the right ventricular outflow tract (232 +/- 22 ms) compared with the apex (264 +/- 12 ms) in Group A (p less than 0.005) whereas there was no difference in Group B (271 +/- 25 ms versus 271 +/- 13 ms). The local ventricular electrogram of most patients in both groups was prolonged and markedly multiphasic. However, 5 of the 8 Group A patients exhibited a double electrogram (V-V') with premature stimulation compared with 1 of the 10 patients in Group B (p less than 0.02). A positive R wave in lead aVR of the scalar ECG and poor R wave progression in the precordial leads were more common in Group A than in Group B (p less than 0.001 and p less than 0.001, respectively). The reason for the distinctly different electrophysiologic substrate and the high prevalence of inducible polymorphic arrhythmia is unclear. It may relate to the underlying myocardial architecture in these patients, characterized by myocardial cellular disarray and fibrosis.

Adolescent↗
PubMed1987

Heterodimers and homodimers of inhibin subunits have different paracrine action in the modulation of luteinizing hormone-stimulated androgen biosynthesis.

Inhibin, a gonadal hormone capable of preferential suppression of pituitary follicle-stimulating hormone (FSH) secretion, has recently been purified. The major form of this protein is an alpha beta heterodimer encoded by two separate genes. In contrast to the FSH-suppressing action of the alpha beta heterodimer, the beta beta homodimer stimulates FSH secretion. Luteinizing hormone (LH)-secreting pituitary cells and gonadal androgen-producing cells have long been shown to form a closed-loop feedback axis. Based on recent studies demonstrating the FSH stimulation of inhibin biosynthesis by ovarian granulosa and testis Sertoli cells, an additional closed-loop feedback axis exists between pituitary FSH- and gonadal inhibin-producing cells. Because uncharacterized Sertoli cell factors have been suggested to either stimulate or inhibit androgen production by testicular Leydig cells, we have tested the intragonadal paracrine actions of heterodimers and homodimers of inhibin subunits. In primary cultures of testis cells, the alpha beta heterodimer of inhibin enhances Leydig cell androgen biosynthesis stimulated by LH, whereas the beta beta homodimer suppresses androgen production. Furthermore, similar modulatory actions of inhibin-related proteins were found in cultured ovarian theca-interstitial cells and theca explants treated with LH. In contrast, treatment with the inhibin-related proteins alone did not affect gonadal steroidogenesis. Our data indicate that the inhibin-related gene products synthesized by Sertoli and granulosa cells may form heterodimers or homodimers to serve as intragonadal paracrine signals in the modulation of LH-stimulated androgen biosynthesis and allow cross-communication between the two feedback loops.

Androgens↗
PubMed1986

Cardiovascular changes after bilateral upper dorsal sympathectomy. Short- and long-term effects.

The effect of bilateral upper dorsal sympathectomy (UDS) on cardiac function was investigated in two groups of young healthy patients who underwent bilateral excision of T2 and T3 ganglia for palmar hyperhidrosis. In ten patients echocardiography of left ventricular function (LVF) was performed before operation and 2 weeks after operation. Electrocardiograms (ECG) were done before operation, during operation immediately after sectioning each sympathetic chain, and at 2 weeks after operation. The mean pulse rate decreased significantly in patients after they underwent bilateral UDS. There were no clinical arrhythmias or changes in LVF in any patient. Submaximal exercise testing and ECG tracings done at rest and after effort were obtained for 29 patients before undergoing bilateral UDS, 30 days after operation, and 1-3 more times within a 2-year postoperative period. Pulse rates taken at rest and after effort were significantly lower than those taken after operation, and the blood pressure response to exercise was blunted. ECG tracings showed a significant change in the electrical frontal plane axis and shortening of the QTc interval. These changes were evident 30 days after operation and persisted for 2 years. In conclusion, bilateral UDS has no overt arrhythmogenic effect in the young, healthy heart and its beta-blocker-like effect persists for at least 2 years.

Adolescent↗
PubMed1983

Relative potencies of gonadotropin-releasing hormone agonists and antagonists on ovarian and pituitary functions.

The abilities of various agonistic and antagonistic analogs of GnRH to modulate ovarian estrogen production were compared with their relative potencies to regulate pituitary LH release. Granulosa cells from immature hypophysectomized rats were cultured for 2 days in the presence of FSH and aromatase substrate (delta 4-androstenedione), with or without various concentrations of GnRH agonists or 10(-8) M GnRH plus various concentrations of selected GnRH antagonists. FSH treatment increased estrogen production, whereas concomitant treatment with various GnRH agonists resulted in dose-dependent decreases in estrogen production. des-Gly10-[D-Ser(TBu)6] Pro9-NHEt-GnRH proved most potent at both the ovarian and pituitary levels, being 170- and 190-fold greater than those values for the GnRH decapeptide, respectively. In general, the ovarian and pituitary potencies of all 10 agonists studied were comparable, with a correlation coefficient of 0.98. When added together with 10(-8) M GnRH, the GnRH antagonists caused dose-dependent blockage of the inhibitory effect of GnRH. Among 7 antagonists tested, [Ac-D-Phe1,D-p-cl-Phe2,D-TYrp3,6]GnRH was shown to be most potent at the pituitary level (half maximal inhibitory dose ratio: IDR50 antagonist/GnRH = 0.17) and blocked the GnRH inhibition at the ovarian level with an IDR50 value of 4.4. The potencies of the antagonists to block the GnRH effect at the pituitary and ovarian levels were comparable, yielding a correlation coefficient of 0.97. Although one cannot rule out subtle differences in the specificities of the respective GnRH target tissues due to minor disparities between pituitary and ovarian potencies of some analogs, the present results demonstrate an overall agreement of responsiveness between ovarian granulosa cells and pituitary gonadotrophs to GnRH agonists and antagonists.

Animals↗
PubMed1979

Primary pure insular ovarian carcinoids.

Ovarian carcinoids are generally found in association with teratomatous elements. Reported are the 23rd and 24th primary pure insular ovarian carcinoids. One of the cases presented initially with carcinoid heart disease.

Aged↗
PubMed1977

Total infrarenal aortic occlusion.

Our experience from 1960 to 1976 with total infrarenal aortic thrombosis (Leriche syndrome) was reviewed. Sixteen heavy smokers (14 men and 2 women) with an average age of fifty-four years underwent thrombectomy with aortoiliac (12 patients) or aortofemoral (4) Dacron bypasses. The last ten patients were hydrated for 12 hours preoperatively with 3,000 ml of Ringer's solution containing supplemental potassium. Mannitol (25 g), furosemide (20 mg), and heparin (120 u/kg) were given intraoperatively. Thrombectomy was accomplished by transection of the aorta, with proximal manual control of the aorta after the renal arteries were occluded. With this technic there were no deaths or renal complications, whereas previously, three of the six patients developed renal complications and one died. Ninety-two per cent of the grafts have remained open. We recommend that the direct transabdominal approach be continued rather than the extraanatomic bypass (axillobilateral-femoral), since further propagation of the aortic thrombosis may then lead to infarction of the kidneys or other viscera.

Adult↗
PubMed1975

Perinatal infection and vaginal flora.

Vaginal cultures were obtained from 1, 083 mothers on admission to the labor floor. The additional bacteriologic information gained from this survey was not sufficient to warrant continued use of the admission vaginal culture as a screening procedure.

Amnion↗
PubMedDate not supplied

A single and multiple dose pharmacokinetic and metabolism study of meclofenamate sodium.

A single and multiple oral dose administration study of meclofenamate sodium (Meclomen) was conducted in ten healthy male volunteers. An initial 300 mg oral dose on day 1 was followed by a 100 mg every 8 h dosage regimen on study days 4 through 18. Intensive plasma and urine sample collection was carried out over the first three study days, and for 120 h following administration of the final dose on day 18. Plasma and urine specimens were analyzed by a specific HPLC assay for unconjugated meclofenamic acid and metabolites I and II of meclofenamic acid before and after sample incubation with beta-glucuronidase. Meclofenamic acid was rapidly absorbed following oral dose administration. Concentrations of meclofenamic acid existed primarily as unconjugated drug in plasma, with only a small amount present in the conjugated form. Meclofenamic acid was rapidly eliminated, with an elimination half-life of approximately 1.3 h. This resulted in no detectable accumulation upon multiple dose administration. Metabolite I, which is one-fifth as active as meclofenamic acid in in vitro inhibition of cyclooxygenase, was present in unconjugated form at steady state in concentrations approximately 50 per cent of those of meclofenamic acid, as unconjugated drug. The majority of metabolite I in plasma existed as glucuronide conjugate. Metabolite II, which is inactive, was present in very significant concentrations in unconjugated form. Plasma protein binding determinations conducted on meclofenamic acid and metabolite I indicated that the free fraction of metabolite I was 8.7 to 10.9 times higher than that of meclofenamic acid. When the lower activity and lower steady state concentrations, but higher free fraction, are considered, it would appear that metabolite I may contribute significantly to the in vivo inhibition of cyclooxygenase activity seen after administration of meclofenamic acid.

Adult↗
PubMedDate not supplied

MR virtual angioscopy of thoracic aortic atherosclerosis in homozygous familial hypercholesterolemia.

PURPOSE: The thoracic aorta is an important site of atherosclerotic disease in patients with homozygous familial hypercholesterolemia (HFH). Thoracic aortic atherosclerosis in patients with HFH was assessed with contrast-enhanced MR angiograms using exoscopic and endoscopic virtual angioscopy reconstructions and maximum intensity projections (MIPs). METHOD: Contrast-enhanced MR angiograms of the thoracic aorta of 15 patients with HFH and 8 normal volunteers were obtained. Perspective surface reconstructions of the MR angiograms including virtual angioscopy views were evaluated by three radiologists blinded to the diagnosis. RESULTS: Thoracic wall irregularity was depicted on 8 of 15 (53%) patient scans and only 1 of 8 (13%) normal subject scans using surface reconstructions. Wall irregularity scores of patients with HFH were significantly increased compared with controls (2.0 +/- 0.9 vs. 1.0 +/- 0.6; p = 0.008). There was excellent interobserver agreement (weighted kappa = 0.82 +/- 0.12). Virtual endoscopy views added diagnostic confidence compared with exoscopic surface renderings alone. MIP reconstructions were unable to depict wall irregularity. CONCLUSION: MR angiography with virtual angioscopy of the thoracic aorta depicts nonstenotic wall irregularity of thoracic aortic atherosclerosis in patients with HFH. This may be important for assessing disease progression and response to treatment and may be generalizable to routine (non-HFH) atherosclerosis.

Adult↗