Search PubMed⌕ Search

Biomedical subjects

J Cohen

Publications and source records attributed to J Cohen.

At least 901 records · Page 50Linked to original sources
PubMed1992

Problem drug use in a central London general practice.

OBJECTIVE: To describe the profile of problem drug users presenting in general practice and to determine whether they can be cared for in general practice. DESIGN: Study of consultations by problem drug users. SETTING: Central London general practice. SUBJECTS: 150 problem drug users presenting over two years. MAIN OUTCOME MEASURES: Stopping drug use, alterations in lifestyle, obtaining paid work, and stopping drug related crime. RESULTS: Of the 150 patients, 111 were men and 39 women, and 106 were unemployed. 121 patients used heroin, 112 of whom injected. 145 patients accepted a methadone reduction programme and 81 completed it. A further 25 were stabilised on reducing doses of methadone, until places became available for them as inpatients at drug dependency units or rehabilitation projects. CONCLUSION: Withdrawal programmes for patients who misuse drugs can be successfully managed in general practice.

Family Practice↗
PubMed1992

Slow, tight binding to human renin of some nonpeptidic renin inhibitors containing a 4-methoxymethoxypiperidinylamide at the P4 position.

A series of nonpeptidic human renin inhibitors with a 4-methoxymethoxypiperidinylamide at the P4 position of the molecule exhibited slow tight binding to the enzyme. Replacement of the methoxymethoxy moiety on the piperidine ring with H, OH, methoxyethyl, propyloxy or n-butyl eliminated the effect. The inhibition was partially reversed by prolonged dialysis at 4 degrees C, arguing against formation of a covalent bond in the tightened complex.

Binding Sites↗
PubMed1992

Undifferentiated (embryonal) sarcoma of the liver. Pathologic findings and long-term survival after complete surgical resection.

Undifferentiated (embryonal) sarcoma of liver is a rare tumor with a reputed poor prognosis. Four patients with this tumor are reported, of whom three were alive without recurrence 1.5, 2.5, and 12 years after initial complete surgical resection, and two of whom received no adjuvant therapy. The fourth patient, in whom complete surgical resection of tumor was not achieved, died with recurrent tumor at 13 months. The latter tumor differed histologically and consisted mainly of closely packed smaller undifferentiated cells with a higher mitotic and apoptotic rate. Eosinophilic globules, characteristic of embryonal sarcoma, were found in some cases to contain condensed nuclear chromatin, evidence of origin from tumor cells dying by apoptosis. One tumor mainly contained large cysts lined by biliary-type epithelium; this suggested an origin from a multipotent precursor cell able to differentiate along both stromal and epithelial lines.

Adolescent↗
PubMed1992

Combining discrepant diagnostic information from multiple sources: are complex algorithms better than simple ones?

Optimizing methods of combining discrepant diagnostic information from multiple sources is one of the more daunting tasks facing the field of child psychopathology. Several researchers have asserted that complex information-combining schemes, those in which certain information or sources of information are weighted differently from others, are preferable. This study provides theoretical and empirical evidence that simple information-combining schemes, those in which all information from all sources is weighted equally, will as a rule work as well as complex schemes and may even work better. The implications of these findings for diagnostic instrument and algorithm design are discussed. A two-step diagnostic procedure utilizing a simple information-combining scheme is presented.

Algorithms↗
PubMed1992

Subzonal sperm insertion and the frequency of gamete fusion.

The subzonal sperm insertion technique was applied to assess the potential of motile human spermatozoa to form pronuclei. In 184 mature human oocytes, subzonal sperm insertion was used as the primary mode of insemination in cases with abnormal semen analyses. Oocytes (n = 131) that failed to fertilize in vitro in cases with normal semen profiles were also micromanipulated for secondary insemination. The frequency of sperm fusion, expressed as a percentage, was defined as the total number of male pronuclei formed divided by the total number of spermatozoa inserted subzonally. Our results indicate that 37% of spermatozoa from men with normal semen are able to fuse with the oolemma and decondense within the ooplasm, when placed in the perivitelline space of the oocyte. Excluding the oocytes that appeared morphologically abnormal (presence of cytoplasmic inclusions such as refractile bodies within the ooplasm), the frequency of sperm fusion increased to nearly 60%. Moreover, 14% of subzonally inserted spermatozoa from men with abnormal semen analyses demonstrated an ability to form a pronucleus. The incidence of polyspermy was high, ranging from 30 to 80% in the different groups studied. It is therefore concluded that the human oolemma provides little protection against multiple sperm fusion and that the frequency of gamete fusion is unexpectedly high, even when the spermatozoa are derived from infertile men.

Evaluation Studies as Topic↗
PubMed1992

Microsurgical fertilization procedures: the absence of stringent criteria for patient selection.

Subzonal sperm insertion and partial zona dissection were applied in 250 in vitro fertilization cycles in couples (n = 200) with abnormal semen analyses; 61 clinical pregnancies were established (24% per egg retrieval). Patients were selected without using minimal cutoff criteria. The study included patients with 0% normal sperm forms (strict criteria), no motile sperm (but some live cells), and sperm counts which could be assessed only after centrifugation. Patients were categorized into three subsets. Group A (n = 116 cycles) failed to fertilize in a previous cycle. Group B (n = 40) was excluded from IVF due to the severity of sperm profiles, such as a maximum of 2% normal forms. Group C (n = 94) constitutes those patients for whom a standard cycle could possibly result in failure. Monospermic fertilization rates were 18% (A), 19% (B), and 24% (C). The incidences of embryo replacement were 63% (A), 53% (B), and 69% (C). Rates of clinical pregnancy were 22% (A), 23% (B), and 28% (C). The presence of one, two, or three semen abnormalities did not correlate with the outcome of microsurgical fertilization. Twenty-two percent of patients with combined oligoasthenoteratozoospermia became pregnant. Moreover, ongoing pregnancies were established in instances with 0% normal sperm forms and no progressively motile spermatozoa. It is concluded that stringent cutoff criteria may not be necessary when both partial zona dissection and subzonal sperm insertion are performed efficiently.

Culture Techniques↗
PubMed1992

Improved pregnancy outcome with gonadotropin releasing hormone agonist (GnRH-a) stimulation is due to the improvement in oocyte quantity rather than quality.

The impact of gonadotropin releasing hormone agonist (GnRH-a) on the quality and quantity of oocytes harvested in in vitro fertilization-embryo transfer (IVF-ET) patients was studied by comparing the results for patients stimulated with gonadotropin alone and with gonadotropin plus GnRH-a. Adding GnRH-a significantly improved the viable pregnancies per transfer and reduced the spontaneous abortions, which seemed to improve oocyte quality. However, when oocyte quality was evaluated by the fertilization rate and the implantation and delivery rates per embryos transferred, there were no significant difference in the results, indicating that GnRH-a did not improve the oocyte quality. On the other hand, GnRH-a significantly increased the average number of oocytes harvested, fertilized, and transferred, and this increased number of oocytes transferred has been demonstrated to increase pregnancy and multiple-pregnancy rates. Multiple pregnancy with more embryos implanted would significantly reduce the abortion rate. Abortion rates decreased inversely to the number of embryos implanted. Our data strongly suggest that the efficacy of GnRH-a on IVF-ET patients was due more to the quantity increase than the quality of embryos transferred.

Embryo Implantation↗
PubMed1992

Portal vein thrombosis: a review.

Portal vein thrombosis (PVT) is a rare condition that affects both children and adults. This article reviews the existing literature on PVT, with an emphasis on recent developments. A comprehensive description of etiologic factors and clinical aspects is presented. Treatment issues that remain unresolved are addressed and a framework for the diagnostic work-up and management of patients with PVT is provided.

Humans↗
PubMed1992

Sequences of the four larger proteins of a porcine group C rotavirus and comparison with the equivalent group A rotavirus proteins.

The sequences of the four larger proteins of rotavirus group C (Cowden strain) are presented and compared with the sequences of the corresponding group A proteins. They exhibit a significant level of homology, allowing gene coding assignment for the group C rotavirus. The coding strategy of the group C virus RNA segment is the same as that for the group A large segments as one long open reading frame is present in each segment. The genome segment 1 encodes the structural protein VP1 which presents the RNA-dependent RNA polymerase consensus motifs. The VP1 protein is the most highly conserved between the rotaviruses of groups A and C. The genome segment 2 encodes the VP2 protein. The deduced protein sequence does not present the putative leucine zippers identified in the group A protein but its amino terminal is hydrophilic and highly charged as previously noted for the group A protein. The genome segment 3 encodes for a protein homologous to the group A outer capsid protein VP4. As observed among the various group A sequences, the amino terminal is the region presenting the fewest similarities. A cleavage region and a putative fusion motif similar to those present in the group A viruses have been identified. For this protein the comparison has been extended to the IDIRV [corrected] VP3 previously sequenced and indicates that groups A and C VP4 proteins are much more related to each other than to the group B equivalent. The genome segment 4 encodes for a protein showing an approximate 40% sequence identity to the minor core protein, VP3, of the group A rotavirus. This remarkable conservation of primary structures argues for severe functional constraint on the evolution of these proteins.

Amino Acid Sequence↗
PubMed1992

Characterization of an oligomerization domain and RNA-binding properties on rotavirus nonstructural protein NS34.

Intermolecular interactions between polypeptide chains often play essential roles in such biological phenomena as replication, transcription, translation, transport, ligand binding, and assembly. We have initiated studies of the functions of the rotavirus SA114F gene 7 product by sequence analysis and expression in insect cells. This nonstructural protein, NS34, is a slightly acidic protein, and its secondary structure is predicted to be 78% alpha-helix, with several heptad repeats of hydrophobic amino acids being present in its carboxy half. NS34 was found in oligomers when analyzed in insect cells, in SA11-infected MA104 cells, and in cell-free translation reactions. Investigation of the multiple electrophoretically distinct forms of NS34 showed they were all composed of homooligomers. Deletion mutants constructed and tested for oligomerization showed that the carboxy terminus of the protein, containing the predicted heptad repeats, was responsible for oligomerization. A basic region present in NS34 of group A rotaviruses, found to be 40% conserved in NS34 of group C rotavirus, is a candidate for a functional domain of this protein. NS34, which was found to be associated with the cytoskeleton fraction of cells, also interacts with viral RNA. These results make it likely that NS34 plays a central role in the replication and assembly of genomic RNA structures.

Amino Acid Sequence↗
PubMed1992

Raised intracranial pressure and visual complications in AIDS patients with cryptococcal meningitis.

The clinical course of cryptococcal meningitis in AIDS shows some important differences from the features of the illness in non-AIDS patients. Complications such as raised intracranial pressure and visual impairment that are recognised in non-AIDS patients may be less frequent in those with AIDS. Persistent intracranial hypertension should be managed actively to prevent visual impairment. In AIDS patients, in whom ventriculo-peritoneal shunts carry additional risks, acetazolamide can be used successfully to lower the CSF pressure and prevent visual loss.

Acquired Immunodeficiency Syndrome↗