Biomedical subjects

Y Cohen

Publications and source records attributed to Y Cohen.

At least 73 records · Page 4Linked to original sources

PubMed2000

Assignment of the water slow-diffusing component in the central nervous system using q-space diffusion MRS: implications for fiber tract imaging.

Diffusion-weighted NMR spectroscopy (MRS) was performed on isolated bovine optic nerve and rat brain (in vitro) to characterize the multiexponential water signal decay in diffusion experiments. q-Space analysis of the diffusion data was used to obtain structural information about the investigated neuronal tissues. This analysis provided displacement distribution profiles of the water in the sample. Two diffusing components were identified from these profiles, thus enabling us to obtain the following information about the slow decaying component: 1) displacement of this component is restricted to a diffusing distance of approximately 2 microm; 2) it has a longer T2 than the rapidly diffusing component; and 3) the population fraction of this component depends on the orientation of the nerve fiber. When the diffusion was measured perpendicular to the long axis of the bovine optic nerve, the weighting of this population was 41 +/- 2%, whereas parallel to the long axis of the nerve it was found to be 14 +/- 2%. In the randomly oriented brain tissue, the population of this component was only 7 +/- 3%. These observations led to the conclusion that the slow-decaying component originates mainly from restricted water diffusion in the neuronal fibers. In view of these findings, in vitro and in situ diffusion-weighted images with high b values (with long delta) were acquired to obtain highly detailed images of white matter fiber tracts in the central nervous system. These images provide detailed information on white matter fiber tract location and allow spinal cord maturation to be followed with high accuracy.

Aging↗

PubMed2000

Displacement imaging of spinal cord using q-space diffusion-weighted MRI.

Displacement MR images of water in in vitro rat spinal cord were computed from q-space analysis of high b value diffusion-weighted MRI data. It is demonstrated that q-space analysis of heavily diffusion-weighted MRI (qs-DWI) provides MR images in which physical parameters of the tissues such as the mean displacement and the probability for zero displacement of the water molecules are used as contrasts. It is shown that these MR images provide structural information surpassing the spatial resolution of conventional MRI by several orders of magnitude. This imaging methodology was used to follow spinal cord maturation in the rat. It was found that changes in the diffusion characteristics of white matter upon maturation are responsible for the emergence of gray/white matter contrast. The mean displacement of water molecules in the white and gray matter of the mature rat spinal cord was found to be 2-3, and 8-10 microns, respectively. The potential and the limitations of this new imaging methodology for early detection of white matter disorders are discussed.

Animals↗

PubMed2000

Recombinant prolactin receptor extracellular domain of rainbow trout (Oncorhynchus mykiss): subcloning, preparation, and characterization.

The cDNA of the extracellular domain of rainbow trout (Oncorhynchus mykiss) prolactin receptor (trPRLR-ECD) was cloned in the prokaryotic expression vector pMON to enable its expression in Escherichia coli after induction with nalidixic acid. The bacterially expressed trPRLR-ECD protein, contained within the refractile body pellet, was solubilized in 4.5 M urea, refolded, and purified on a Q-Sepharose column, pH 8, by stepwise elution with NaCl. The bioactive monomeric 26-kDa fraction was eluted in 0.2 M NaCl, yielding 20 mg/2.5 L of induced culture. The purified protein was over 98% homogeneous, as shown by SDS-PAGE in the presence or absence of reducing agent and by chromatography on a Superdex column. Binding experiments using [125I]ovine placental lactogen (oPL) as a ligand revealed that human growth hormone (hGH), oPL, and ovine prolactin (oPRL) were the most effective competitors, with respective IC50 values of 1.32, 2.27, and 2.70 nM. Chicken (ch) PRL did not compete at all, and homologous trPRL was much less effective, with a corresponding IC50 value of 1826 nM. Gel-filtration was used to determine the stoichiometry of trPRLR-ECD's interaction with oPL, hGH, and oPRL. Only oPL yielded a 2:1 complex, whereas hGH and oPRL formed only 1:1 complexes, with excess trPRLR-ECD being seen at the initial 2:1 trPRLR-ECD:hGH or trPRLR-ECD:oPRL ratios. No studies were performed with chPRL because of its inability to compete with [125I]oPL or with trPRL because of its low affinity toward trPRLR-ECD. The present results agree with previous findings indicating, as in mammals, that homologous PRL interacts transiently with its receptor and suggest that transient homologous PRL-induced homodimerization of the receptor is sufficient to initiate a biological signal, despite the fact that, in classical binding experiments, only low specific binding can be detected.

Animals↗

PubMed2000

Characterization of glucose-sensitive insulin release systems in simulated in vivo conditions.

We studied the glucose-responsive insulin controlled release system based on the hydrogel poly(2-hydroxyethyl methacrylate-co-N,N-dimethylaminoethyl methacrylate), also called poly(HEMA-co-DMAEMA), with entrapped glucose oxidase, catalase and insulin. When exposed to physiological fluids, glucose diffuses into the hydrogel, glucose oxidase catalyzes the glucose conversion to gluconic acid, causing swelling of the pH-sensitive hydrogel and subsequently increased insulin release. The higher the glucose concentration in the medium, the higher and faster the swelling and release rates. The effects of polymer morphology and oxygen availability on hydrogel swelling and on insulin release kinetics were tested. Polymer morphology was modified by changing the crosslinking agent (tetraethylene glycol dimethacrylate) concentration (0-0.95 vol%). Oxygen availability was modified by changing the immobilized catalase concentration (0-15 units catalase per unit glucose oxidase) and by bubbling oxygen through the medium. The results indicated that: (i) Hydrogels without crosslinking agent were found to be stable in water, and their sensitivity to pH and glucose was higher than the chemically crosslinked hydrogels. (ii) Immobilization of catalase in addition to glucose oxidase in hydrogels prepared without crosslinking agent, resulted in enhanced swelling kinetic. In addition, we carried out primary in vivo experiments on rats, which demonstrated that at least some of the entrapped insulin retains its active form and is effective in reducing blood glucose levels. Moreover, no tissue encapsulation was observed around matrices implanted in the peritoneum. In conclusion, the pH-sensitive hydrogel poly(HEMA-co-DMAEMA) can be manipulated to produce glucose-responsive insulin release system that is effective in reducing blood glucose levels.

Animals↗

PubMed2000

Neural network based quantitative structural property relations (QSPRs) for predicting boiling points of aliphatic hydrocarbons

Quantitative structural property relations (QSPRs) for boiling points of aliphatic hydrocarbons were derived using a back-propagation neural network and a modified Fuzzy ARTMAP architecture. With the back-propagation model, the selected molecular descriptors were capable of distinguishing between diastereomers. The QSPRs were obtained from four valance molecular connectivity indices (1chiv,2chiv,3chiv,4chiv), a second-order Kappa shape index (2kappa), dipole moment, and molecular weight. The inclusion of dipole moment proved to be particularly useful for distinguishing between cis and trans isomers. A back-propagation 7-4-1 architecture predicted boiling points for the test, validation, and overall data sets of alkanes with average absolute errors of 0.37% (1.65 K), 0.42% (1.73 K), and 0.37% (1.54 K), respectively. The error for the test and overall data sets decreased to 0.19% (0.81 K) and 0.31% (1.30 K), respectively, using the modified Fuzzy ARTMAP network. A back-propagation alkene model, with a 7-10-1 architecture, yielded predictions with average absolute errors for the test, validation, and overall data sets of 1.96% (6.79 K), 1.83% (6.45 K), and 1.25% (4.42 K), respectively. Fuzzy ARTMAP reduced the errors for the test and overall data sets to 0.19% (0.73 K) and 0.25% (0.95 K), respectively. The back-propagation composite model for aliphatic hydrocarbons, with a 7-9- architecture, yielded boiling points with average absolute errors for the test, validation, and overall set of 1.74% (6.09 K), 1.25% (4.68 K), and 1.37% (4.85 K), respectively. The error for the test and overall data sets using the Fuzzy ARTMAP composite model decreased to 0.84% (1.15 K) and 0.35% (1.35 K), respectively. Performance of the QSPRs, developed from a simple set of molecular descriptors, displayed accuracy well within the range of expected experimental errors and of better accuracy than other regression analysis and neural network-based boiling points QSPRs previously reported in the literature.

Journal Article↗

PubMed2000

Metoclopramide induced akathisia during cesarean section.

We report a case of akathisia developed after administration of 2.5 mg metoclopramide for treatment of nausea during cesarean section. The relevant literature as well as options for prevention and treatment of this phenomenon are reviewed.

Journal Article↗

PubMed2000

Bell palsy complicating pregnancy: a review.

UNLABELLED: The aim of the present work was to review the published evidence on the association of Bell palsy (BP), an acute idiopathic peripheral facial paralysis of unknown etiology, with pregnancy. Reports have shown that women of reproductive age are affected two to four times more often than men of the same age, and pregnant women 3.3 times more often than nonpregnant women. The apparent predisposition of pregnant women to Bell palsy has been attributed to the high extracellular fluid content, viral inflammation, and immunosuppression characteristic of pregnancy, but findings are controversial. Most cases of Bell palsy occur in the third trimester or the puerperium. Onset is acute and painful. Some authors suggest that Bell palsy increases the risk of hypertension and toxemia of pregnancy, whereas the pregnant state, in turn, may affect the course and severity of disease. Recovery is usually good; poor prognostic markers are recurrence in subsequent pregnancy and bilateral disease, both of which are rare. Neonatal outcome is apparently unaffected, although this has been studied rarely. The preferred mode of management remains undecided; it is usually confined to supportive care. Corticosteroids in pregnancy are controversial. We think clinicians should be aware of these findings to avoid unnecessary testing and treatment and to help the patient cope with this acute, painful disease. TARGET AUDIENCE: Obstetricians & Gynecologists, Family Physicians LEARNING OBJECTIVES: After completion of this article, the reader will be able to identify the potential etiologies of Bell palsy associated with pregnancy and to describe the clinical presentation of this condition in pregnancy and its likelihood for recovery.

Adrenal Cortex Hormones↗

PubMed2000

Transition from anaerobic to aerobic growth conditions for the sulfate-reducing bacterium Desulfovibrio oxyclinae results in flocculation.

A chemostat culture of the sulfate-reducing bacterium Desulfovibrio oxyclinae isolated from the oxic layer of a hypersaline cyanobacterial mat was grown anaerobically and then subjected to gassing with 1% oxygen, both at a dilution rate of 0.05 h(-1). The sulfate reduction rate under anaerobic conditions was 370 nmol of SO(4)(2-) mg of protein(-1) min(-1). At the onset of aerobic gassing, sulfate reduction decreased by 40%, although viable cell numbers did not decrease. After 42 h, the sulfate reduction rate returned to the level observed in the anaerobic culture. At this stage the growth yield increased by 180% compared to the anaerobic culture to 4.4 g of protein per mol of sulfate reduced. Protein content per cell increased at the same time by 40%. The oxygen consumption rate per milligram of protein measured in washed cell suspensions increased by 80%, and the thiosulfate reduction rate of the same samples increased by 29% with lactate as the electron donor. These findings indicated possible oxygen-dependent enhancement of growth. After 140 h of growth under oxygen flux, formation of cell aggregates 0.1 to 3 mm in diameter was observed. Micrometer-sized aggregates were found to form earlier, during the first hours of exposure to oxygen. The respiration rate of D. oxyclinae was sufficient to create anoxia inside clumps larger than 3 microm, while the levels of dissolved oxygen in the growth vessel were 0.7 +/- 0.5 microM. Aggregation of sulfate-reducing bacteria was observed within a Microcoleus chthonoplastes-dominated layer of a cyanobacterial mat under daily exposure to oxygen concentrations of up to 900 microM. Desulfonema-like sulfate-reducing bacteria were also common in this environment along with other nonaggregated sulfate-reducing bacteria. Two-dimensional mapping of sulfate reduction showed heterogeneity of sulfate reduction activity in this oxic zone.

Aerobiosis↗

PubMed2000

Sulfate reduction and possible aerobic metabolism of the sulfate-reducing bacterium Desulfovibrio oxyclinae in a chemostat coculture with Marinobacter sp. Strain MB under exposure to increasing oxygen concentrations.

A chemostat coculture of the sulfate-reducing bacterium Desulfovibrio oxyclinae together with a facultative aerobe heterotroph tentatively identified as Marinobacter sp. strain MB was grown under anaerobic conditions and then exposed to a stepwise-increasing oxygen influx (0 to 20% O(2) in the incoming gas phase). The coculture consumed oxygen efficiently, and no residual oxygen was detected with an oxygen supply of up to 5%. Sulfate reduction persisted at all levels of oxygen input, even at the maximal level, when residual oxygen in the growth vessel was 87 microM. The portion of D. oxyclinae cells in the coculture decreased gradually from 92% under anaerobic conditions to 27% under aeration. Both absolute cell numbers and viable cell counts of the organism were the same as or even higher than those observed in the absence of oxygen input. The patterns of consumption of electron donors and acceptors suggest that aerobic incomplete oxidation of lactate to acetate is performed by D. oxyclinae under high oxygen input. Both organisms were isolated from the same oxic zone of a cyanobacterial mat where they have to adapt to daily shifts from oxic to anoxic conditions. This type of syntrophic association may occur in natural habitats, enabling sulfate-reducing bacteria to cope with periodic exposure to oxygen.

Aerobiosis↗

PubMed2000

Oxygen-dependent growth of the sulfate-reducing bacterium Desulfovibrio oxyclinae in coculture with Marinobacter sp. Strain MB in an aerated sulfate-depleted chemostat.

A chemostat coculture of the sulfate-reducing bacterium Desulfovibrio oxyclinae and the facultatively aerobic heterotroph Marinobacter sp. strain MB was grown for 1 week under anaerobic conditions at a dilution rate of 0.05 h(-1). It was then exposed to an oxygen flux of 223 micromol min(-1) by gassing the growth vessel with 5% O(2). Sulfate reduction persisted under these conditions, though the amount of sulfate reduced decreased by 45% compared to the amount reduced during the initial anaerobic mode. After 1 week of growth under these conditions, sulfate was excluded from the incoming medium. The sulfate concentration in the growth vessel decreased exponentially from 4.1 mM to 2.5 microM. The coculture consumed oxygen effectively, and no residual oxygen was detected during either growth mode in which oxygen was supplied. The proportion of D. oxyclinae cells in the coculture as determined by in situ hybridization decreased from 86% under anaerobic conditions to 70% in the microaerobic sulfate-reducing mode and 34% in the microaerobic sulfate-depleted mode. As determined by the most-probable-number (MPN) method, the numbers of viable D. oxyclinae cells during the two microaerobic growth modes decreased compared to the numbers during the anaerobic growth mode. However, there was no significant difference between the MPN values for the two modes when oxygen was supplied. The patterns of consumption of electron donors and acceptors suggested that when oxygen was supplied in the absence of sulfate and thiosulfate, D. oxyclinae performed incomplete aerobic oxidation of lactate to acetate. This is the first observation of oxygen-dependent growth of a sulfate-reducing bacterium in the absence of either sulfate or thiosulfate. Cells harvested during the microaerobic sulfate-depleted stage and exposed to sulfate and thiosulfate in a respiration chamber were capable of anaerobic sulfate and thiosulfate reduction.

Colony Count, Microbial↗

PubMed2000

Distribution and diversity of archaea corresponding to the limnological cycle of a hypersaline stratified lake (Solar lake, Sinai, Egypt).

The vertical and seasonal distribution and diversity of archaeal sequences was investigated in a hypersaline, stratified, monomictic lake, Solar Lake, Sinai, Egypt, during the limnological development of stratification and mixing. Archaeal sequences were studied via phylogenetic analysis of 16S rDNA sequences as well as denaturing gradient gel electrophoresis analysis. The 165 clones studied were grouped into four phylogenetically different clusters. Most of the clones isolated from both the aerobic epilimnion and the sulfide-rich hypolimnion were defined as cluster I, belonging to the Halobacteriaceae family. The three additional clusters were all isolated from the anaerobic hypolimnion. Cluster II is phylogenetically located between the genera Methanobacterium and Methanococcus. Clusters III and IV relate to two previously documented groups of uncultured euryarchaeota, remotely related to the genus Thermoplasma. No crenarchaeota were found in the water column of the Solar Lake. The archaeal community in the Solar Lake under both stratified and mixed conditions was dominated by halobacteria in salinities higher than 10%. During stratification, additional clusters, some of which may possibly relate to uncultured halophilic methanogens, were found in the sulfide- and methane-rich hypolimnion.

Archaea↗

PubMed2000

Multicenter prospective study of ventilator-associated pneumonia during acute respiratory distress syndrome. Incidence, prognosis, and risk factors. ARDS Study Group.

We investigated the incidence, risk factors for, and outcome of ventilator-associated pneumonia (VAP) in patients with acute respiratory distress syndrome (ARDS). We compared 134 patients with ARDS with 744 patients without ARDS on mechanical ventilation. Fiberoptic bronchoscopic examination and quantitative bacterial cultures (protected brush or catheter sampling [threshold: 10(3) cfu/ml], or bronchoalveolar lavage [threshold: 10(4) cfu/ml]) were used to diagnose pneumonia. VAP occurred in 49 patients (36.5%). The incidence of pneumonia was 23% (173 of 744 patients) among patients without ARDS (p < 0.002). Nonfermenting gram-negative rods caused significantly more pneumonia in ARDS patients. Mortality rates were identical in ARDS patients with (28 of 49 patients, 57%) and without (50 of 85 patients, 59%) pulmonary infection (p = 0.8). VAP resulted in a considerable increase in attributable time on mechanical ventilation of both the overall population of ARDS patients and of survivors. Both the use of sucralfate (adjusted odds ratio [OR]: 4. 42; 95% confidence interval [CI]: 2.01 to 9.7, p = 0.0002) and the duration of exposure to sucralfate (adjusted OR: 1.206; 95% CI: 1. 095 to 1.328, p = 0.0002) were associated with an increased risk of VAP during ARDS. VAP considerably prolongs the time on mechanical ventilation without affecting survival. Patients given sucralfate may be at greater risk of developing pulmonary infection during ARDS.

Adult↗

PubMed2000

Who needs individual bioequivalence studies for narrow therapeutic index drugs? A case for warfarin.

Warfarin is, among drugs, considered to have a narrow therapeutic index for which individual bioequivalence has been suggested. To establish the propriety of "switching," an individual bioequivalence study involving a replicate-design study and three "switchings" in healthy subjects was undertaken using the U.S.-brand warfarin sodium tablet and a generic product. A randomized, single-center, open-label, single-dose, four-way crossover replicate bioequivalence study was performed in 24 healthy male volunteers in which each subject received the same 5 mg warfarin test and reference tablets twice on different occasions under fasting conditions. Concentrations of warfarin in plasma were measured by a validated specific HPLC method. The individual pharmacokinetic parameters obtained with test and reference products were compared using pooled data and Liu's method. Bioequivalence was shown with both average and individual bioequivalence methods. The individual bioequivalence assessment did not show a subject-by-formulation interaction, nor did it add value to the bioequivalence assessment of warfarin.

Adolescent↗

PubMed2000

Phase II study of weekly high dose fluorouracil in previously treated patients with metastatic colorectal cancer.

UNLABELLED: The purpose of this study was to evaluate the efficacy, toxicity, and safety of outpatient chemotherapy with weekly high-dose 5-fluorouracil (HD-5FU) in previously treated patients (pts) with metastatic colorectal cancer. Previously treated and failed pts with histologically confirmed, measurable metastatic colorectal cancer, performance status (WHO) 0-2 and adequate bone marrow function were eligible for treatment. Patients received 5FU (2.6 g/m2) as a 24-hour continuous infusion. Treatment was repeated weekly. A total of 202 cycles were given. Eighteen pts were enrolled. No pts achieved objective response. In 6 pts (33%), after 4 weeks of treatments, CEA level decreased 25% or more, and after 8 weekly treatments it rose again. Mild myelosuppression rarely occurred. Grade I nausea and vomiting occurred in 2 pts and Grade I diarrhea occurred in 2 pts. Mucositis was not observed. CONCLUSION: In our experience single agent, weekly, high dose 5-FU is well tolerated, but is ineffective as second-line treatment for metastatic colorectal cancer, and has only a marginal effect on CEA level.

Adenocarcinoma↗

PubMed2000

The Japanese need travel vaccinations.

At a travel clinic in Kathmandu we reviewed the vaccination records from March 1997 to March 1998 for all travelers to developing countries like Nepal, for two important vaccines, namely, typhoid and hepatitis A. These travelers visited the clinic for various medical problems. One of the reasons for doing this study was that in previous years we saw a disproportionate number of Japanese travelers with hepatitis A, who had not taken the hepatitis A vaccine or immune gamma globulin for prevention of this illness. We hypothesized, therefore, that one of the reasons that Japanese patients visiting our clinic had higher rates of hepatitis A was because they were not vaccinated against this disease. There were 765 tourists for that time period out of which about 10% were Japanese. The rest were Americans, British, Israelis, Canadians, Australians, Danish and a small miscellaneous group from other countries.

Health Promotion↗

PubMed2000

Prolactin serum level in patients with breast cancer.

BACKGROUND: Previous studies have suggested that prolactin may serve as an indicator of disease progression in breast cancer. OBJECTIVES: To evaluate the use of PRL as a serum tumor marker in patients with breast cancer. METHODS: PRL serum level was determined in 99 breast cancer patients and compared with CA 15-3 serum level. RESULTS: Elevated serum level of PRL (> 20 ng/ml) was found in 8 of 99 patients (8.1%). A stratified analysis of prolactin levels according to therapy revealed that PRL levels was increased in 8 of 55 untreated patients (14.5%), but not in patients who received hormonal or chemotherapy in the 3 months preceding the test (0/42 patients, P = 0.009). However, mean PRL level was similar in patients with no evidence of disease activity and in patients with active disease (10.2 vs. 8.2 ng/ml, NS). In comparison, CA 15-3 mean level was significantly lower in patients with no evidence of disease as compared to patients with active disease (18.2 vs. 144.7 units/ml, P < 0.001). PRL level was increased in 6 of 60 patients (10%) with no evidence of disease and in 2 of 39 (5.2%) with active disease (NS). In comparison, CA 15-3 level was increased in 3 of 60 patients (5%) with no evidence of disease and in 24 of 39 (61.5%) with active disease (P < 0.001). CONCLUSIONS: PRL levels are decreased following hormonal or chemotherapy in patients with breast cancer and there is no correlation between PRL serum level and the state of disease. Further studies are needed to clarify a possible clinical significance of hyperprolactinemia in a subset of patients with breast cancer.

Adult↗

PubMed2000

[Attachment theory as the basic principle for understanding psychopathological development and inpatient treatment].

There seems to be an as yet unresolved question as to whether attachment behavior is an innate factor or whether it is an outcome of primary social relations. On the basis of Bowlby's researches as well as on Emde's, the author argues that attachment is an innate developmental factor that needs external impact, meaning parental care, to evolve and develop. The two cases presented here reflect similar expressions of alienation and detachment as well as essential differences. In the first case, the child has lost his innate ability and urge for social attachment due to severely defective care during early infancy, mainly desertion. In the second case, the child expresses clear attachment ability, yet, due to the deviant care, this ability has developed into disturbed attachment patterns. In both cases, it is claimed that only comprehensive treatment, which is in a way removed from reality, may "rekindle" the innate attachment ability of the first child and lead the second child unimpaired attachment behavior.

Adolescent↗

PubMed1999

Extensive venous and arterial thrombosis associated with an inhibitor to activated protein C.

Activated protein C resistance (APCR) in the absence of alterations in the factor V gene has been observed during pregnancy, in patients on oral contraceptives, in the presence of antiphospholipid antibodies, and in patients with ischemic stroke. We report a 49-year-old woman with recurrent major venous and arterial thromboses who displayed pronounced APCR, yet no changes in the activated protein C (APC) cleavage sites of factor V. The APCR values determined by four different assays were similar to those obtained in plasma from a homozygote for factor V Q506. Addition of IgG isolated from the patient's serum to normal plasma lowered the APCR ratio from 2.4 to 1.6. Incubation of patient's IgG with normal APC resulted in a profound change in the mobility of APC in crossed immunoelectrophoresis. APC was also shown to bind to patient's IgG immobilized on a protein A agarose column. Factor Va inactivation by APC was inhibited by patient's IgG, but not by control IgG in the presence or absence of either phospholipids or protein S. These results provide evidence for the existence of an acquired antibody against APC in the patient's plasma, which gave rise to the APCR phenotype and was probably responsible for the major thrombotic events. We suggest that acquired APCR due to anti-APC antibodies be considered a potential cause for severe venous and arterial thromboses.

Autoantibodies↗