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Biomedical subjects

J Cohen

Publications and source records attributed to J Cohen.

At least 397 records · Page 22Linked to original sources
PubMed1998

Nefazodone and REM sleep: how do antidepressant drugs decrease REM sleep?

In previous uncontrolled studies, nefazodone, a new antidepressant drug, increased REM sleep or had no effect on REM sleep. We report a double-blind, placebo-controlled, parallel group study on effects of nefazodone (N) on polysomnographic sleep variables in healthy human volunteers. Nefazodone was administered for 16 consecutive days, and nocturnal sleep, as well as multiple sleep latency test (MSLT), was monitored before, during, and after N administration. We found that N had no effect on any measured REM sleep variable including REM sleep duration, REM density, and nocturnal REM sleep distribution. Nefazodone also had no significant effect on nocturnal total sleep time or NREM variables, but increased daytime alertness measured by the MSLT. Since N is a potent serotonin reuptake blocker, the present findings that N had no effect on REM sleep cast doubt on the hypothesis that antidepressant drugs decrease REM sleep by increasing serotonergic neurotransmission. A review of other relevant work also casts doubt on this hypothesis.

Adolescent↗
PubMed1998

Detrimental effects of sodium during mouse oocyte cryopreservation.

Cryopreservation is an established way of storing embryos, but effective methods are not available for freezing eggs. Most freezing damage is caused by high solute concentration (solution effects) and intracellular ice. Sodium salts are the major components of cryopreservation media, and the main contributor to the solution effects. The present experiments examine the effect of substituting choline for sodium as the major extracellular cation in the cryopreservation of mouse eggs. The effects of serum and various cryoprotectants were also examined. Survival, fertilization, and development were inversely related to the concentration of sodium in the freezing medium. Oocytes frozen in a choline-based medium had the highest (p < 0.001) survival and development rates. The absence of serum during thawing inhibited fertilization, whereas exposure to serum or opening the zona allowed fertilization to reach the control level. Dimethyl sulfoxide was as effective as 1,2 propanediol for obtaining high survival and fertilization rates. These results support the hypothesis that the high concentration of sodium in conventional freezing media is detrimental to cells and show that choline is a promising replacement for sodium. Reducing or eliminating sodium may allow oocytes and other cells to be frozen more efficiently.

Animals↗
PubMed1998

Early postoperative calcium levels as predictors of hypocalcemia.

OBJECTIVE: Early, safe postoperative hospital discharge has become a priority in the current environment of cost containment and managed care. One determinant for this following operations of the thyroid or parathyroid glands is a stable postoperative calcium level. This study sought to determine whether early postoperative calcium levels could safely predict hypocalcemia following operations of the thyroid or parathyroid glands. STUDY DESIGN: A retrospective chart review of 197 patients undergoing such operations was undertaken. METHODS: The study population was divided into patients undergoing parathyroid exploration with removal of one or more glands for parathyroid disease ("parathyroid" group) and patients undergoing bilateral thyroid operations ("nonparathyroid" group). Postoperative calcium levels were plotted as a function of time, and the slope between the first two postoperative calcium levels examined. RESULTS: A positive slope predicted normocalcemia in 100% of "nonparathyroid" and 90% of "parathyroid" surgeries. A negative slope was predictive in its magnitude. The nonparathyroid patients who developed postoperative hypocalcemia had an average slope significantly more negative (-0.84% change/h) than patients remaining normocalcemic (-0.49% change/h) (P = .03). Similarly, the parathyroid patients who became hypocalcemic had an average initial slope nearly twice as negative (-1.4% change/h) as patients remaining normocalcemic (-0.78% change/h) (P = .005). CONCLUSIONS: These results indicate that an initial upsloping postoperative calcium curve based on two early postoperative calcium measurements is strongly predictive of a stable postoperative calcium level, and a steeply downsloping initial calcium curve is worrisome for eventual hypocalcemia.

Calcium↗
PubMed1998

The N terminus of rotavirus VP2 is necessary for encapsidation of VP1 and VP3.

The innermost core of rotavirus is composed of VP2, which forms a protein layer that surrounds the two minor proteins VP1 and VP3, and the genome of 11 segments of double-stranded RNA. This inner core layer surrounded by VP6, the major capsid protein, constitutes double-layered particles that are transcriptionally active. Each gene encoding a structural protein of double-layered particles has been cloned into baculovirus recombinants and expressed in insect cells. Previously, we showed that coexpression of different combinations of the structural proteins of rotavirus double-layered particles results in the formation of virus-like particles (VLPs), and each VLP containing VP1, the presumed RNA-dependent RNA polymerase, possesses replicase activity as assayed in an in vitro template-dependent assay system (C. Q.-Y. Zeng, M. J. Wentz, J. Cohen, M. E. Estes, and R. F. Ramig, J. Virol. 70:2736-2742, 1996). This work reports construction and characterization of VLPs containing a truncated VP2 (VPdelta2, containing amino acids [aa] Met-93 to 880). Expression of VPdelta2 alone resulted in the formation of single-layered delta2-VLPs. Coexpression of VPdelta2 with VP6 produced double-layered delta2/6-VLPs. VLPs formed by coexpression of VPdelta2 and VP1 or VP3, or both VP1 and VP3, resulted in the formation of VLPs lacking both VP1 and VP3. The presence of VP6 with VPdelta2 did not result in encapsidation of VP1 and VP3. To determine the domain of VP2 required for binding VP1, far-Western blot analyses using a series of truncated VP2 constructs were performed to test their ability to bind VP1. These analyses showed that (i) full-length VP2 (aa 1 to 880) binds to VP1, (ii) any N-terminal truncation lacking aa 1 to 25 fails to bind VP1, and (iii) a C-terminal 296-aa truncated VP2 construct (aa 1 to 583) maintains the ability to bind VP1. These analyses indicate that the N terminus of rotavirus VP2 is necessary for the encapsidation of VP1 and VP3.

Animals↗
PubMed1998

Crystallization and preliminary X-Ray analysis of rotavirus protein VP6.

As a first step to gain insight into the structure of the rotavirus virion at atomic resolution, we report here the expression, purification, and crystallization of recombinant rotavirus protein VP6. This protein has the property of polymerizing in the form of tubular structures in solution which have hindered crystallization thus far. Using a combination of electron microscopy and small-angle X-ray scattering, we found that addition of Ca2+ at concentrations higher than 100 mM results in depolymerization of the tubes, leading to an essentially monodisperse solution of trimeric VP6 even at high protein concentrations (higher than 10 mg/ml), thereby enabling us to search for crystallization conditions. We have thus obtained crystals of VP6 which diffract to better than 2.4 A resolution and belong to the cubic space group P4132 with a cell dimension a of 160 A. The crystals contain a trimer of VP6 lying along the diagonal of the cubic unit cell, resulting in one VP6 monomer per asymmetric unit and a solvent content of roughly 70%.

Animals↗
PubMed1998

Chromosome identification in human oocytes and polar bodies by spectral karyotyping.

Sixty unfertilized human oocytes and two fresh polar bodies were karyotyped by spectral karyotyping (SKY). The oocytes were provided by 29 women ranging from 30 to 42 yr of age. The mean hybridization efficiency for oocytes was 95.2% (60/63). Nondisjunction of bivalent chromosomes (13.3%) and predivision of sister chromatids at meiosis I (3.3%) were unequivocally determined by analysis first with SKY and then fluorescence in situ hybridization. Four oocytes (6.7%) were hyperhaploid, six (10.0%) were hypohaploid, one (1.7%) showed balanced predivision, and another (1.7%) was diploid. No specific structural rearrangements were detected. This study demonstrates that the SKY technique can be used successfully as an alternative method of karyotyping second meiotic metaphase chromosomes from human oocytes and polar bodies in appropriate spreads.

Chromatids↗
PubMed1998

Reference typing report for complement receptor 1 (CR1).

A total of 100 Chinese blood donors (50 from Shen-Zhen and 50 from Taiwan) were studied by the participants in addition to 9 reference samples. A new nomenclature for the CR1 structural alleles was recommended by the participants which would use a numbering system, e.g. CR1*1. The structural allele frequencies in the Chinese were: CR1*1 (190 kD) 0.96, CR1*2 (220 kD) 0.03, CR1*3 (160 kD) 0.01 and CR1*4 (250 kD) 0.00. The HindIII expression polymorphism was also studied and the high expressing allele had a gene frequency of 0.71 while the low expressor gene frequency was 0.28. Erythrocyte copy numbers were quantified and compared between laboratories with good correlation (R = 0.55-0.88). The mean (+/- SD) erythrocyte copy number was 463 (+/- 229) in the Taiwan donors and 446 (+/- 207) in the Mainland Chinese.

Alleles↗
PubMed1998

Risk factors for stroke and type of stroke in persons with isolated systolic hypertension. Systolic Hypertension in the Elderly Program Cooperative Research Group.

BACKGROUND AND PURPOSE: We sought to determine risk factors for stroke and stroke type in persons with isolated systolic hypertension (ISH). METHODS: We performed proportional hazards analyses of data from the Systolic Hypertension in the Elderly Program, a double-blind, randomized, placebo-controlled trial of 4736 persons aged > or =60 years with ISH (systolic blood pressure, 160 to 219 mm Hg; diastolic blood pressure, <90 mm Hg). One treatment group received chlorthalidone (12.5 to 25 mg/d) with step-up to atenolol (25.0 to 50.0 mg/d) or reserpine (0.05 to 0.10 mg/d), if needed. The other treatment group received matching placebo. The main outcome measures were stroke, stroke or transient ischemic attack [TIA], and stroke types: ischemic (including lacunar, atherosclerotic, and embolic) and hemorrhagic. RESULTS: During an average follow-up of 4.5 years, 384 strokes or TIAs and 262 strokes (including 217 ischemic, 66 lacunar, 26 atherosclerotic, and 25 embolic strokes) were documented. In multivariate analyses, placebo treatment, older age, smoking, history of diabetes, higher systolic blood pressure, lower HDL cholesterol, and ECG abnormality were significantly associated (P<0.05) with increased incidence of stroke or TIA, stroke, or ischemic stroke. Greater lacunar stroke risk was significantly related to placebo treatment, older age, history of diabetes (relative risk [RR] = 3.03; 95% confidence interval [CI], 1.70 to 5.40), and smoking (RR = 3.04; 95% CI, 1.73 to 5.37). Greater atherosclerotic and embolic stroke risk were significantly related to presence of carotid bruit (RR = 5.75; 95% CI, 2.50 to 13.24) and older age (RR = 1.65 per 5 years; 95% CI, 1.25 to 2.18), respectively. CONCLUSIONS: In older persons with ISH, history of diabetes and smoking are important risk factors for lacunar stroke, whereas carotid bruit and age are important risk factors for atherosclerotic and embolic stroke, respectively.

Aged↗
PubMed1998

Efficient allocation of patients to treatment cells in clinical trials with more than two treatment conditions.

OBJECTIVE: Clinical trials generally allocate patients to equal-sized treatment groups. The authors propose that it may be more efficient to allocate unequal proportions of the total sample size to treatments when more than two treatments are being compared. METHOD: This proposal is illustrated with two examples. One involved a comparison of three treatments and used a dichotomous categorical outcome. The other involved comparison of three treatments and used a continuous measure. RESULTS: In both examples, a considerable increase in efficiency was realized by reducing the number of patients assigned to the placebo cell. CONCLUSIONS: Unequal allocation of patients to treatments should be considered when more than two groups are compared.

Antidepressive Agents↗
PubMed1998

Smoking in the home: changing attitudes and current practices.

OBJECTIVES: Trends in attitudes and current practices concerning smoking in the home were examined. METHODS: Data from population-based surveys of adults in Ontario, Canada, were analyzed. RESULTS: Between 1992 and 1996, the percentage of respondents who agreed that parents spending time at home with small children should not smoke increased from 51% to 70%. In 1996, 34% of the homes surveyed were smoke-free. Smoke-free homes were associated with nonsmoking respondents and with the presence of children and no daily smokers in the home. Only 20% of homes with children and any daily smokers were smoke-free. CONCLUSIONS: Efforts are needed to assist parents in reducing children's exposure to environmental tobacco smoke in the home.

Adolescent↗
PubMed1998

Transforming the curriculum while serving the community: strategies for developing community-based sites.

Developing community-based clinical opportunities for students is a challenge. At San Jose State University (SJSU) School of Nursing, faculty transformed the curriculum by developing community-based experiences directed by faculty and delivered by students during clinical practice. These innovative clinical experiences provide a structure to educate students and enhance the ability to bring health care to underserved people in a community. This article describes the structure and processes for implementing the new experiences and offers strategies to guide other faculty interested in developing community-based experiences.

Community Health Nursing↗
PubMed1998

Role of organic acids during processing to improve quality of channel catfish fillets.

A microbial preparation derived from aquacultured channel catfish fillets (Ictalurus punctatus) was acidified with 0, 1, 2 and 4% (vol/vol) weak organic and held in an ice bath at 0 degree C to simulate the chilling process. Additionally, catfish fillets were sprayed under varying pressures at 15 degrees C with organic acids to evaluate the efficacy of concentrations of organic acids and spray pressures to ameliorate the microbiological quality. To determine plate counts, the dilution fluid was neutralized to pH 7.2 with 1.0 M NaOH. The aerobic plates counts of microorganisms in the chilling water were monitored over a 20-min interval. Aerobic plate counts were found on the channel catfish fillets before and after spray washing with organic acids. Plates were incubated at 35 degrees C for 48 h. The addition of organic acids tot he microbial preparation used in simulating the chilling process significantly (P < 0.05) reduced the number of bacterial surviving. The number of surviving bacteria in the chilled water decreased with increasing concentration and time of exposure to organic acids. Propionic acid had the most detrimental effect on organisms present in the microfloral preparation followed by acetic and lactic acids. Spray washing of catfish fillets with water did not significantly (P < 0.05) affect the microbial quality of fillets. However, catfish fillets sprayed with organic (lactic and propionic) acids significantly (P < 0.05) reduced the microbial counts by 10-fold. Lactic and propionic acids were not significantly (P > 0.05) different in influencing the aerobic counts of the catfish fillets.

Animals↗
PubMed1998

The fragile X syndrome.

Fragile X syndrome (FXS) is the most common cause known of inherited developmental disability. New and widely available techniques in DNA analysis allow both affected individuals and carriers to be tested from a simple blood sample. It is now recognised that a wide range of clinical severity occurs in both sexes. Specific treatment and interventional strategies are now available and of great benefit to individuals, families and carers. Genetic counselling allows families to make informed decisions. General practitioners can play a central role in detection and management of this syndrome.

Fragile X Syndrome↗