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Biomedical subjects

C J Cohen

Publications and source records attributed to C J Cohen.

At least 37 records · Page 2Linked to original sources
PubMed1999

WIN 17317-3, a new high-affinity probe for voltage-gated sodium channels.

The iminodihydroquinoline WIN 17317-3 was previously shown to inhibit selectively the voltage-gated potassium channels, K(v)1.3 and K(v)1.4 [Hill, R. J., et al. (1995) Mol. Pharmacol. 48, 98-104; Nguyen, A., et al. (1996) Mol. Pharmacol. 50, 1672-1679]. Since these channels are found in brain, radiolabeled WIN 17317-3 was synthesized to probe neuronal K(v)1 channels. In rat brain synaptic membranes, [(3)H]WIN 17317-3 binds reversibly and saturably to a single class of high-affinity sites (K(d) 2.2 +/- 0.3 nM; B(max) 5.4 +/- 0.2 pmol/mg of protein). However, the interaction of [(3)H]WIN 17317-3 with brain membranes is not sensitive to any of several well-characterized potassium channel ligands. Rather, binding is modulated by numerous structurally unrelated sodium channel effectors (e.g., channel toxins, local anesthetics, antiarrhythmics, and cardiotonics). The potency and rank order of effectiveness of these agents in affecting [(3)H]WIN 17317-3 binding is consistent with their known abilities to modify sodium channel activity. Autoradiograms of rat brain sections indicate that the distribution of [(3)H]WIN 17317-3 binding sites is in excellent agreement with that of sodium channels. Furthermore, WIN 17317-3 inhibits sodium currents in CHO cells stably transfected with the rat brain IIA sodium channel with high affinity (K(i) 9 nM), as well as agonist-stimulated (22)Na uptake in this cell line. WIN 17317-3 interacts similarly with skeletal muscle sodium channels but is a weaker inhibitor of the cardiac sodium channel. Together, these results demonstrate that WIN 17317-3 is a new, high-affinity, subtype-selective ligand for sodium channels and is a potent blocker of brain IIA sodium channels.

Animals↗
PubMed1999

Laparoscopic lymphadenectomy for gynecologic malignancies.

OBJECTIVE: The purpose of our study was to detail our 5-year experience with laparoscopic lymphadenectomy for gynecologic malignancies. METHODS: From 11/5/92 to 3/9/98, we performed laparoscopic lymphadenectomies on 94 patients with various gynecologic malignancies. Pelvic, paraaortic, and combinations of both pelvic and paraaortic lymphadenectomies were performed depending on the primary site of disease and indication for lymph node dissection. Data were prospectively collected on all patients. RESULTS: From 11/5/92 to 3/9/98 we performed 94 laparoscopic lymphadenectomies for gynecologic malignancies. The distribution included 64 patients with cervical cancer, 14 with ovarian cancer, 12 with endometrial cancer, 2 with fallopian tube cancer, 1 with a uterine malignant mixed mesodermal tumor, and 1 with a metastatic neuroendocrine tumor. Fifty-five patients had only pelvic lymph node dissections, 9 patients had paraaortic dissections only, and 30 had both pelvic and paraaortic dissections performed. Among 30 patients having laparoscopic lymphadenectomy only, the mean hospital stay was 3.6 days. Included in this group were 19 patients who received postoperative neoadjuvant chemotherapy for cervical cancer as inpatients prior to ambulatory radiation therapy. The mean length of stay for this group was 4.6 days versus 1.7 days for the 11 patients who did not receive postoperative chemotherapy (P = 0.0025). The mean number of pelvic nodes was 11.9 (range 0-57), with a mean of 4. 5 between 11/5/92 and 12/31/95 and a mean of 19.1 from 1/1/96 to 3/9/98. The mean number of paraaortic nodes obtained was 3.7 (range 0-14), with a mean of 3.4 from 11/5/92 to 12/31/95 and a mean of 4.1 from 1/1/96 to 3/9/98. A total of 3 patients required conversions to laparotomy. One was for a vascular injury to the vena cava, 1 for a large tumor extending to both sidewalls, and the third for removal of densely matted lymph nodes. CONCLUSIONS: Laparoscopic lymphadenectomy is a technically feasible procedure for patients with gynecologic malignancies requiring lymph node dissections, with an acceptable safety profile and nodal yield. The number of nodes obtained increased in direct proportion to operator experience. In addition, patients may benefit from a decrease in hospital stay compared to conventional lymphadenectomy via laparotomy.

Adult↗
PubMed1999

Laparoscopic management of adnexal masses in premenopausal and postmenopausal women.

OBJECTIVE: To evaluate the feasibility and safety of laparoscopic adnexal mass removal in patients without preselection for benign pathology and assess the operative complications and findings. METHODS: All patients presenting to the gynecologic oncology service between April 1992 and April 1996 with adnexal masses were candidates for laparoscopic management. Patients underwent preoperative radiological studies and office pelvic examination. Laparoscopic management was attempted on patients without evidence of gross metastatic disease or masses that extended above the umbilicus. Laparotomy was performed if indicated by pathologic findings or technical difficulty. All removed adnexal masses were sent for immediate pathologic diagnosis. The type of procedure, intraoperative findings, and complications were all recorded at the time of procedure. RESULTS: One hundred sixty patients underwent laparoscopic evaluation for an adnexal mass. Benign pathology was discovered in 139 (87%, 95% confidence interval [CI] 84, 90) patients, and 141 (88%, 95% CI 86, 91) patients were managed laparoscopically. Reasons for laparotomy included technical difficulty, operative complications, or malignancy. Frozen section diagnosis was concordant with the final pathology reports in all but five patients (97% concordance), and no discrepancies resulted in treatment delays. CONCLUSION: Laparoscopic management of adnexal masses can be successful in a gynecologic oncology population if there is expertise in operative laparoscopy, availability of immediate accurate pathologic examination, and appropriate further treatment where indicated.

Adnexal Diseases↗
PubMed1998

Results of selective use of operative laparoscopy in gynecologic oncology.

OBJECTIVE: To evaluate the impact of integration of operative laparoscopy on length of stay (LOS) and complication rates on an academic gynecologic oncology service. METHODS: Retrospective analysis of all admissions to our gynecologic oncology service was performed for the academic years 1990/1991 and 1993/1994. Primary endpoints were frequency of complications and LOS. RESULTS: In 1990/1991, there were 785 total admissions, of which 287 were surgical and 3% were approached laparoscopically. In 1993/1994, there were 973 admissions of which 436 were surgical and 23% were approached laparoscopically. Operative laparoscopy was applied equally regardless of age and reproductive status; the utilization of laparoscopy was increased by 14-fold for patients with cancer, 4. 5-fold for patients with benign disease, and 12-fold for patients with adnexal masses. No change in the mean LOS of nonsurgical admissions was noted, yet overall LOS for all patients decreased from 6.3 to 4.8 days (P < 0.0001). Mean LOS in surgical patients decreased from 9.4 to 6.0 days (P < 0.0001). After correction for complications, decreases in LOS only occurred in procedures for which laparoscopy was significantly integrated. No reductions in LOS were noted with like surgical approaches; i.e., there was no change in the LOS of patients undergoing laparotomy in both years. Surgical complications were not increased by laparoscopy. CONCLUSIONS: Aggressive utilization of operative laparoscopy, even only for selected patients, into the surgical practice of a gynecologic oncology service demonstrates significant improvements in LOS without adversely affecting surgical complication rates.

Adult↗
PubMed1998

A national HIV community cohort: design, baseline, and follow-up of the AmFAR Observational Database. American Foundation for AIDS Research Community-Based Clinical Trials Network.

This article describes the design, methodology, baseline distributions, and general follow-up characteristics of the American Foundation for AIDS Research (AmFAR) National Observational Database (ODB) Project including the benefits and limitations of collecting information on a large simple cohort in the HIV community setting. The study prospectively followed 15,611 HIV-positive men and women and collected longitudinal and cross-sectional data on demographics, medical conditions, drug therapies, laboratory parameters, and survival. Participants were followed between October 1990 and December 1993 by 252 community-based sites coordinated by 22 centers in the Community-Based Clinical Trials Network (CBCT Network) throughout the United States (including Puerto Rico) and Toronto, Canada. The ODB provided quantitative information on a national level needed to track the HIV epidemic and plan clinical trials conducted through the Network, and to provide sites with local databases to monitor patients and facilitate access to therapies in clinical trials. Overall, the ODB contains information on 1,925 women (12%) and 13,686 men (88%), 60% white, 20% African American, 17% Latino/Hispanic, with 56,254 baseline and follow-up forms, a median follow-up of about 12 months, a 16% loss-to-follow-up, and an 11% mortality rate. AmFAR plans to place the ODB in the public domain.

Adolescent↗
PubMed1998

Chemotherapy in advanced ovarian cancer: four systematic meta-analyses of individual patient data from 37 randomized trials. Advanced Ovarian Cancer Trialists' Group.

The purpose of this systematic study was to provide an up to date and reliable quantitative summary of the relative benefits of various types of chemotherapy (non-platinum vs platinum, single-agent vs combination and carboplatin vs cisplatin) in the treatment of advanced ovarian cancer. Also, to investigate whether well-defined patient subgroups benefit more or less from cisplatin- or carboplatin-based therapy. Meta-analyses were based on updated individual patient data from all available randomized controlled trials (published and unpublished), including 37 trials, 5667 patients and 4664 deaths. The results suggest that platinum-based chemotherapy is better than non-platinum therapy, show a trend in favour of platinum combinations over single-agent platinum, and suggest that cisplatin and carboplatin are equally effective. There is no good evidence that cisplatin is more or less effective than carboplatin in any particular subgroup of patients.

Antineoplastic Agents↗
PubMed1997

Prophylaxis for disseminated Mycobacterium avium complex (MAC) infection in patients with AIDS: a cost-effectiveness analysis.

OBJECTIVE: To determine the effectiveness and costs of prophylaxis for disseminated Mycobacterium avium complex (MAC) infection in patients with AIDS. DESIGN: A decision analysis model was constructed to compare rifabutin (300 mg/day), azithromycin (1200 mg/week), and clarithromycin (500 mg twice per day) with no prophylaxis. Sensitivity analysis was done on all model parameters, including initial CD4 count for beginning prophylaxis. SETTING: The setting was hypothetical for the cost-effectiveness model. Clinical data were taken from published prospective randomized controlled trials. MAIN OUTCOME MEASURES: Outcomes were measured in terms of projected life expectancy, quality-adjusted life expectancy, direct medical costs, and cost-effectiveness in U.S. dollars per quality-adjusted life-year saved ($/QALY). RESULTS: For patients with AIDS and those having CD4 counts <75 cells/mm3, azithromycin, clarithromycin, and rifabutin prophylaxis increased lifetime per person MAC-related costs by $994, $2,117, and $2,185 U.S., respectively. Quality-adjusted life expectancy increased from 1.6068 QALYs to between 1.6186 and 1.6255 QALYs. The cost-effectiveness ratios were $58,200, $116,000, and $179,100/QALY saved for azithromycin, clarithromycin, and rifabutin prophylaxis, respectively, each compared with no prophylaxis. Results were most dependent on the annual cost of prophylaxis, the initial CD4 count when starting prophylaxis, and any survival benefit with prophylaxis. For each type of prophylaxis, strategies beginning with CD4 counts <25 or 50 cells/mm3 were substantially more cost-effective than those beginning in patients with higher CD4 counts. CONCLUSIONS: MAC prophylaxis is likely to cost society an additional $99 to $219 million U.S. per 100,000 patients treated. In the context of Centers for Disease Control and Prevention (CDC) recommendations to use prophylaxis in patients with CD4 counts <75 cells/mm3, azithromycin represents the best value and is most cost-effective when used in patients with CD4 counts <25 cells/mm3.

AIDS-Related Opportunistic Infections↗
PubMed1997

Functional expression of Drosophila para sodium channels. Modulation by the membrane protein TipE and toxin pharmacology.

The Drosophila para sodium channel alpha subunit was expressed in Xenopus oocytes alone and in combination with tipE, a putative Drosophila sodium channel accessory subunit. Coexpression of tipE with para results in elevated levels of sodium currents and accelerated current decay. Para/TipE sodium channels have biophysical and pharmacological properties similar to those of native channels. However, the pharmacology of these channels differs from that of vertebrate sodium channels: (a) toxin II from Anemonia sulcata, which slows inactivation, binds to Para and some mammalian sodium channels with similar affinity (Kd congruent with 10 nM), but this toxin causes a 100-fold greater decrease in the rate of inactivation of Para/TipE than of mammalian channels; (b) Para sodium channels are >10-fold more sensitive to block by tetrodotoxin; and (c) modification by the pyrethroid insecticide permethrin is >100-fold more potent for Para than for rat brain type IIA sodium channels. Our results suggest that the selective toxicity of pyrethroid insecticides is due at least in part to the greater affinity of pyrethroids for insect sodium channels than for mammalian sodium channels.

Animals↗
PubMed1997

Tamoxifen and endometrial cancer: tamoxifen effects on the human female genital tract.

An association between the administration of tamoxifen in patients with breast cancer and the development of endometrial cancer has been suggested in a number of clinical studies, none of which was designed prospectively to study the endometrial effects of tamoxifen. Because of this observation, some have equated tamoxifen with "estrogen," and inferences have been drawn about its possible carcinogenic effect. This presentation analyzes the effect of tamoxifen on the lower genital tract in the adult human female, compares it with the effect of estradiol, and compares and contrasts the effect of these substances on the end organs of laboratory animals, cell lines, transplants, and their differential effects in the human uterus, cervix, and vagina. Of note is the fact that in patients who have not had breast cancer, there is no report of the development of endometrial cancer in women taking tamoxifen. Careful monitoring of this population may define with better precision the mechanism of action of tamoxifen as well as the process of oncogenesis in the human endometrium.

Animals↗
PubMed1996

Lack of effect of cimetidine on lymphocyte subsets in patients infected with human immunodeficiency virus type 1.

Cimetidine, widely used for peptic ulcer disease, blocks type 2 histamine receptors present on immune cells, including T cells, B cells, and monocytes. As an earlier published study showed evidence of increases in CD4 cell counts due to this drug, we conducted a randomized, placebo-controlled, 8-week trial of oral cimetidine (400 mg p.o. t.i.d.) in a study involving 182 patients infected with human immunodeficiency virus (HIV). Overall, cimetidine-treated patients had a decline in CD4+ cell counts that was no different from the decline for placebo-treated persons, neither during the first 8 weeks of the trial (mean drop, 7.1% [standard error, 12.1-1.8] vs. 6.7% [standard error, 11.6-1.5]) nor during the subsequent 8 weeks of open-label administration of cimetidine. No differences were evident between the treatment groups in terms of the percentage reactive to p24 antigen at baseline, and p24 antigen concentrations did not change from baseline to the end of week 8. In summary, cimetidine is well tolerated by HIV-infected individuals but alters neither CD4+ cell counts nor at least one quantitative measure of viral load, HIV p24 antigen levels.

Adult↗
PubMed1996

Angiotensin II stimulates T-type Ca2+ channel currents via activation of a G protein, Gi.

Angiotensin II (ANG II) is the most potent and the most physiologically important stimulator of aldosterone synthesis and secretion from the adrenal zona glomerulosa. Because steroidogenesis by adrenal glomerulosa (AG) cells is mediated in part by Ca2+ influx through T- and L-type Ca2+ channels, we evaluated whether T-type Ca2+ channels are regulated by ANG II. We observe that ANG II enhances T-type Ca2+ current by shifting the voltage dependence of channel activation to more negative potentials. This shift is transduced by the ANG II type 1 receptor. The effect of the hormone is not mediated by Ca2+/calmodulin-dependent protein kinase II (CaMKII) as it is not prevented by CaMKII(281-302), a peptide inhibitor of the catalytic region of the kinase. Rather, this shift is mediated by the activation of a G protein, Gi, because it is abolished by cell pretreatment with pertussis toxin and by cell dialysis with a monoclonal antibody generated against recombinant Gi alpha. This effect of ANG II on T-type Ca2+ channels should increase Ca2+ entry in AG cells at physiologically relevant voltages and result in a sustained increase in aldosterone secretion.

Angiotensin II↗
PubMed1996

Modulation of pulsatile GH release through a novel receptor in hypothalamus and pituitary gland.

Hormone replacement should provide a serum hormone profile similar to that found in normal physiology. This is generally impractical because hormones are usually released episodically and therefore require frequent administration. However, rather than replacing the hormone directly, in theory, one could administer a mimic or amplifier of the pulse generator that controls pulsatile release of the particular hormone. Using growth hormone (GH) as a paradigm we sought such a mimetic that would provide episodic GH release when administered by the oral route. A GH secretagogue MK0677, is described that has these ideal properties; following oral administration MK0677 amplifies episodic GH release. Mechanistically, it synergizes with growth hormone releasing hormone (GHRH) through a receptor and signal transduction pathway distinct from that of GHRH and is a functional antagonist of somatostatin (SRIF). MK0677 also acts on the arcuate nucleus and appears to stimulate GHRH release. By using 35S-MK0677, a new G-protein coupled receptor for MK0677 was characterized in the plasma membrane fraction of pituitary and hypothalamic tissue. The receptor is present in very low abundance and couples to phospholipase C. Other ligands selective for this receptor also cause synchronization of well-defined pathways leading to GH release. Repeated oral treatment of dogs once daily with MK0677 initiates amplified pulsatile GH release accompanied by increases in IGF-1 that are sustained. The unique biological properties of MK0677 and other synthetic ligands that bind to the same receptor force us to predict that these ligands mimic a naturally occurring hormone that regulates pulsatile GH release. Understanding the regulatory mechanisms involved in this paradigm has broad implications for the control of pulsatile rhythms in the endocrine system.

Amino Acid Sequence↗
PubMed1996

Managed care in gynecologic oncology.

We review the recent literature on managed care and its application to gynecologic oncology. Although the literature is limited, we discuss professional agreement contracts, the role of primary care physicians and specialists in gynecologic cancer screening, changes in health care distribution, changes in physician-patient relationships, and cancer research.

Contract Services↗
PubMed1995

Endometrial cancer. Management of high risk and recurrence including the tamoxifen controversy.

Risk factors for endometrial cancer include obesity, nulligravidity, late menopause, and anovulatory states. Although diabetes is highly associated with endometrial cancer, hypertension is not an independent variable when correction is made for other factors. Exogenous estrogen increases the risk by at least four times, and smoking is a significant factor. Screening of asymptomatic women may be useful among high risk patients. In addition, racial influence on virulence has recently been identified. Most recurrences of endometrial cancer are identified within 3 years of initial diagnosis. Predictors include ploidy, histologic grade, histologic type, receptor status, and stage. Treatment of recurrence is individualized based on tumor location and receptor status and may involve surgery, radiation therapy, hormonal therapy, or cytotoxic chemotherapy. Tamoxifen has been shown to improve survival among subsets of patients with breast cancer in all stages. A comprehensive literature review and meta-analyses, however, verified an increased risk of endometrial cancer among tamoxifen-treated patients compared with control subjects that may equal the cancer risk from exogenous estrogen exposure. Screening techniques include sonographic assessment of endometrial thickening and vascular patterns, hysteroscopy, and endometrial sampling. A subendometrial cystic proliferation can confuse radiographic evaluation of endometrium, leading to unindicated curettage. A disproportionate incidence of high grade lesions has been reported; however, tamoxifen should not be withheld from patients with breast cancer.

Breast Neoplasms↗
PubMed1995

Voltage-gated calcium currents have two opposing effects on the secretion of aldosterone.

Using Ca2+ channel blockers with different specificities for L- and T-type Ca2+ channels, we have investigated the roles of these two channel types in K(+)-induced aldosterone secretion. In whole cell voltage-clamp experiments, the spider toxin omega-agatoxin-IIIA (omega-Aga-IIIA) completely blocks L-type Ca2+ channels but has no effect on T-type Ca2+ channels. In contrast, Ni2+ and 1,4-dihydropyridines block both L- and T-type Ca2+ channels. Secretion induced by 7 mM extracellular K+ concentration ([K+]o) is unaffected by omega-Aga-IIIA but is strongly inhibited by Ni2+ or the 1,4-dihydropyridine, nitrendipine. This suggests that physiological increases in [K+]o stimulate aldosterone secretion primarily by enhancing Ca2+ entry through T-type Ca2+ channels. Surprisingly, secretion induced by 60 mM [K+]o is enhanced by omega-Aga-IIIA or Ni2+ and is inhibited by the L-type Ca2+ channel activator BAY K 8644. Nitrendipine (1 nM) also stimulates such secretion, although higher concentrations are inhibitory (concentration inhibiting 50% of maximal response approximately 30 nM). If extracellular Ca2+ concentration is reduced from 1.25 to 0.5 mM, secretion induced by 60 mM [K+]o is enhanced, and Ni2+ or low nitrendipine become inhibitory. Together, these results that L-type Ca2+ currents can reduce steroidogenesis and that the role of these currents was previously misconstrued because 1,4-dihydropyridines modify secretion by multiple mechanisms. Thus Ca2+ entry can function as a negative modulator of steroid secretion.

Agatoxins↗