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Biomedical subjects

A Cohen

Publications and source records attributed to A Cohen.

At least 793 records · Page 44Linked to original sources
PubMed1984

Purine metabolism in human T lymphocytes: role of the purine nucleoside cycle.

Human intrathymic T lymphocytes were separated by a bovine serum albumin density gradient into a population of G1-phase small thymocytes and a population of S-phase-enriched large thymocytes. Purine metabolism was studied in these thymocyte populations, representing immature T lymphocytes, and compared with the metabolism of mature T lymphocytes isolated from the peripheral blood. De novo purine biosynthesis was highly cell cycle dependent; i.e., de novo purine biosynthetic activity was found only in large S-phase thymocytes, whereas both G1 T-cell populations lacked any significant activity. Thus G1-phase small thymocytes and G1-phase peripheral blood T lymphocytes have only salvage pathways to maintain their purine nucleotide pools. Despite the similarity of purine salvage activities in G1 thymocytes and in peripheral blood T lymphocytes, small thymocytes have fourfold lower levels of purine nucleoside triphosphates. The decreased levels of purine nucleotides in G1 thymocytes may be the result of increased purine efflux. It was found that an unusually large proportion (24-48%) of hypoxanthine incorporated by G1 thymocytes is excreted into the medium in the form of inosine.

Cell Separation↗
PubMed1984

Elliptocytosis preceding myelofibrosis in a patient with polycythemia vera.

A patient with polycythemia vera showed marked elliptocytosis in the peripheral blood, 2 years after the diagnosis was established. 4 years later on, the patient developed myelofibrosis. The significance of elliptocytosis, which appears during the course of polycythemia vera, as an early indicator for the development of myelofibrosis is discussed.

Aged↗
PubMed1984

Solcoderm treatment of epidermal growths including intradermal nevi.

Solcoderm was used in the management of various epidermal growths in 372 patients with 1,002 lesions, including condyloma acuminatum, verruca plana, basal cell epithelioma, intradermal nevus, seborrheic and solar keratosis. No antiseptic precautions or local anesthesia were used during the treatment. The results seem promising and suggest that Solcoderm is a simple, safe, and efficient method for the management of these tumors. Cosmetic results were excellent. It is especially recommended when the lesions are in difficult to manage locations for surgical or other known chemical or physical methods, when the patient is not fit for surgical procedures, and when local anesthesia is contraindicated.

Acetates↗
PubMed1984

Quantitative assessment of growth and function of the cardiac chambers in the normal human fetus: a prospective longitudinal echocardiographic study.

We assessed the changes in cardiac chamber size, architecture and function in the normal fetus in a prospective, longitudinal, two-dimensional, and two-dimensionally directed M mode echocardiographic study. Serial echocardiograms were recorded in 16 normal fetuses at 4 week intervals from 20 weeks gestation to parturition. Fetal gestational age was assessed by biparietal diameter. Left ventricular, right ventricular, and left atrial chamber sizes and aortic diameter all increased linearly with age. The ratios of right and left ventricular diameter, left atrial to aortic diameters, and relative left ventricular wall thickness that we used as an index of short-axis left ventricular architecture remained constant. Fractional right ventricular and left ventricular wall thicknesses were similar both on echocardiograms and in postmortem hearts over the same range of gestational ages. In addition, postmortem right ventricular and left ventricular free wall weights were indistinguishable and contributed the same proportion to total heart weight throughout gestation. Left ventricular echocardiographic mass increased linearly from a mean of 0.86 +/- 0.09 to 7.47 +/- 2.43 g at term and corresponded closely with postmortem left ventricular weight. We conclude that (1) fetal cardiac chamber dimensions, wall thicknesses, and left ventricular mass increased with gestational age, (2) cardiac architecture in terms of the ratios of right ventricular/left ventricular diameters, left atrial/aortic diameters, and relative wall thickness remained constant, (3) right and left ventricular fractional shortening did not change with age, (4) left ventricular mass assessed echocardiographically corresponded closely with postmortem left ventricular weights in fetal hearts of similar gestational ages, and (5) the similarities between right and left ventricular sizes, wall thicknesses, and free wall weights in this study do not support the theory of right ventricular dominance in the human fetus.

Echocardiography↗
PubMed1984

A destructive maxillary cemento-ossifying fibroma following maxillofacial trauma.

The cemento-ossifying fibroma, a mesodermal type of non-odontogenic tumor, is rarely discussed in the otolaryngologic literature. It is a tumor that is seen more in blacks than in whites, appears largely in the elderly, is chiefly located in the mandibular molar or premolar area and is generally neither aggressive nor excessively destructive. The triggering mechanism for its derivation from aberrant periodontal membrane growth or development from endosteal fibrous tissue remains controversial. We report a case of cemento-ossifying fibroma in a 26-year-old Hispanic male which was located in the posterior portion of the maxilla which destroyed the maxillary bone, orbital floor, and the lateral wall of the nose. One year prior to discovery of the lesion the patient sustained severe facial trauma resulting in facial bone fractures. It may be speculated that the trauma sustained was the critical triggering factor allowing for unchecked growth and destruction associated with an otherwise non-aggressive tumor, which may have been present prior to the traumatic incident.

Adult↗
PubMed1984

The "urge to classify" the narcotic addict: a review of psychiatric classification. II.

Attempts to classify drug addicts are divided into three main groups: (1) psychiatric classifications, (2) psychosocial classifications, and (3) classifications by pattern of abuse. An extensive literature review of the psychiatric classifications of narcotic addicts suggests that there is no one diagnosis that fits all narcotic addicts and that the importance of psychopathology in drug addiction has been exaggerated. It is concluded that theoretical psychiatric classifications of narcotic addicts have failed to stimulate empirical research and that empirical classifications have not demonstrated their utility for treatment and prognosis.

Humans↗
PubMed1984

[Not Available].

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Demography↗
PubMed1984

Absence of lymphocyte ecto-5'-nucleotidase in infants with reticuloendotheliosis and eosinophilia (Omenn's syndrome).

Lymphocytes from three infants with reticuloendotheliosis and eosinophilia ( Omenn 's syndrome) and immunodeficiency were assayed for 5'-nucleotidase activity. B and T lymphocytes from all three patients were totally deficient in ecto-5'-nucleotidase activity, but had normal levels of cytoplasmic 5'-nucleotidase. In contrast, cultured lymphocytes expressed normal ectoplasmic and cytoplasmic activities, suggesting that the lymphocyte-restricted enzyme deficiency was not likely a primary genetic defect. The deficiency of lymphocyte ecto-5'-nucleotidase was not associated with any abnormality of deoxynucleoside metabolism. The absence of lymphocyte ecto-5'-nucleotidase may be a characteristic feature of this syndrome and may help to distinguish this disease from others with similar manifestations.

5'-Nucleotidase↗
PubMed1984

Deferoxamine: a reversible S-phase inhibitor of human lymphocyte proliferation.

Deferoxamine is widely used therapeutically as a chelator of ferric ion in disorders of iron overload. This study demonstrates that this drug is a potent inhibitor of DNA synthesis by human B and T lymphocytes in vitro, but has relatively little effect on the synthesis of RNA and protein. The inhibitory effects of deferoxamine are completely reversible by washing or by adding stoichiometric amounts of Fe3+. Micromolar concentrations of deferoxamine decrease intracellular levels of deoxyribonucleoside triphosphates, which is similar to the effects of hydroxyurea. The binding of iron by deferoxamine likely causes an inhibition of ribonucleotide reductase activity, thereby preventing cells from completing the S phase of the cell proliferation cycle. As a reversible and nontoxic S-phase inhibitor, it may have important experimental and therapeutic applications.

Adolescent↗
PubMed1984

Methadone plasma levels and persistent drug abuse in high dose maintenance patients.

Methadone maintenance patients who maintained on a high daily dose were divided into good performers and poor performers based on whether they demonstrated persistent use of heroin, non-prescription diazepam, and/or excessive alcohol consumption. Mean methadone plasma levels 24 hours after an oral dose of 80 mg were found to be 410.4 ng/ml in good performers compared to 101.8 ng/ml in poor performers (P less than .05). Seven of nine (77.8%) poor compared to two of 15 (13.3%) good performers had 24-hour methadone plasma levels under 50 ng/ml (P less than .01). High dose methadone patients who show evidence of persistent drug or alcohol abuse should have their 24-hour methadone plasma level determined to help assess whether the patient should receive more methadone or find an alternative treatment.

Alcohol Drinking↗
PubMed1984

Primary ventricular fibrillation complicating acute myocardial infarction: an assessment of predictability and prognosis.

In order to identify patients with a high risk of developing primary ventricular fibrillation (PVF) following acute myocardial infarction (AMI) and to examine the prognostic significance of this arrhythmia, 46 patients who developed PVF were compared to a group of 80 patients who had AMI without PVF. A computerized, multivariate discriminant analysis identified several significant correlates of PVF. Higher rates of hypokalemia, complete left bundle branch block, 3rd-degree AV block and a lower frequency of diabetes were found in the PVF group. No difference was found with respect to the frequency of warning arrhythmias. A discriminant function constructed on the basis of the significant variables had a 4.3% false-negative rate in predicting PVF. Recurrent ventricular fibrillation occurred in nine patients, four of whom died. In-hospital mortality was significantly higher in the PVF than in the control group. As PVF is associated, in part, with treatable derangements and increased mortality, every endeavor should be made to prevent its occurrence.

Aged↗
PubMed1984

Thalassemia.

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Blood Transfusion↗
PubMed1984

Functional characterization of human thymocyte subpopulations separated by density gradient centrifugation.

A bovine serum albumin gradient was used to separate two populations of human thymocytes--a minority population (8%) of large thymocytes (LT) and a majority population (92%) of small thymocytes (ST). Fifty per cent of LT cells were in the S, G2 or M phases of the cell cycle compared to 5% of ST cells and 15% of unfractionated thymocytes. LT cells proliferated in response to T cell mitogens and included all of the T colony precursor cells (TCPC). In contrast, ST cells proliferated with mitogens only in the presence of added T cell growth factors and contained none of the thymocyte TCPC. ST cells neither helped nor suppressed the function of LT cells in any assay. This separation technique has provided a rapid method for isolating functionally distinct thymic lymphocyte subpopulations and permitted a further definition of the TCPC in the human thymus. Furthermore it should prove useful in studies of thymocytes at different stages of the cell cycle.

Adolescent↗
PubMed1984

"Second wind" during inspiratory loading.

Five human volunteers breathed through an inspiratory register to achieve a transdiaphragmatic pressure (Pdi) of 42-45% of the maximum, until fatigue. During the period of resistive breathing all subjects experienced at least one episode of a sudden feeling of relaxation and relief from dyspnea, i.e., "second wind." These episodes were accompanied by a sudden decrease in the neural stimulation to the diaphragm as reflected in the electromyogram (EMG). Changes in lung volume or chest configuration were eliminated as was recruitment of accessory muscles of inspiration during the "second wind"; thus, there appeared to be a change in the contractile function of the diaphragm such that the same force (Pdi) was achieved with less neural input. These results indicate that the phenomenon of "second wind" has physiologic correlates and may be subject to experimental verification and manipulation.

Adult↗
PubMed1983

Sequential accumulation of mRNAs encoding different myosin heavy chain isoforms during skeletal muscle development in vivo detected with a recombinant plasmid identified as coding for an adult fast myosin heavy chain from mouse skeletal muscle.

In order to study developmental transitions of myosin heavy chain gene expression, we have cloned from newborn mouse skeletal muscle a recombinant plasmid (plasmid MHC 32) that contains an insertion coding for the COOH-terminal portion of an adult fast myosin heavy chain isoform of mouse skeletal muscle. By Northern blots and dot blots, it has been shown that the MHC 32 sequence reveals a broad cross-hybridization with RNA from different mammalian striated muscle tissues. Southern blots with mouse genomic DNA show only one homologous gene, but cross-hybridization at lower stringency to seven to eight different bands, some containing multiple genomic fragments, among which are probably the genes encoding the different striated muscle isoforms. S1 protection experiments with RNA from mouse skeletal muscle before and after birth demonstrate that plasmid MHC 32 is homologous to a major mRNA species of adult skeletal muscle. This adult mRNA is a predominant sequence within 5-6 days after birth. It begins to accumulate at 1-3 days; at the 18th day fetal stage, another major mRNA species is detected as partially homologous with the adult MHC 32 sequence. This fetal myosin heavy chain mRNA is still predominant at 1-3 days after birth, but is rapidly (by 5-6 days) replaced by the adult MHC sequence. There is thus a rapid transition after birth from fetal to adult skeletal muscle myosin heavy chain mRNA sequences.

Amino Acid Sequence↗
PubMed1983

Purine and pyrimidine metabolism in human T lymphocytes. Regulation of deoxyribonucleotide metabolism.

Purine and pyrimidine deoxyribonucleoside metabolism was studied in G1 and S phase human thymocytes and compared with that of the more mature T lymphocytes from peripheral blood. Both thymocyte populations have much higher intracellular deoxyribonucleoside triphosphate (dNTP) pools than peripheral blood T lymphocytes. The smallest dNTP pool in S phase thymocytes is dCTP (5.7 pmol/10(6) cells) and the largest is dTTP (48 pmol/10(6) cells), whereas in G1 thymocytes, dATP and dGTP comprise the smallest pools. While both G1 and S phase thymocytes have active deoxyribonucleoside salvage pathways, only S phase thymocytes have significant ribonucleotide reduction activity. We have studied ribonucleotide reduction and deoxyribonucleoside salvage in S phase thymocytes in the presence of extracellular deoxyribonucleosides. Based on these studies, we propose a model for the interaction of deoxyribonucleoside salvage and ribonucleotide reduction in S phase thymocytes. According to this model, extracellular deoxycytidine at micromolar concentrations is efficiently salvaged by deoxycytidine kinase. However, due to feedback inhibition of deoxycytidine kinase by dCTP, the maximal level of dCTP which can be achieved is limited. The salvage of both deoxyadenosine and deoxyguanosine (up to 10(-4) M) is completely inhibited in the presence of micromolar concentrations of deoxycytidine, whereas the salvage of thymidine is unregulated resulting in large increases in dTTP levels. Moreover, significant amounts of the salvaged deoxycytidine is used for dTTP synthesis resulting in further increase of dTTP pools. The accumulated dTTP inhibits the reduction of UDP and CDP while stimulating GDP reduction and subsequently also ADP reduction. The end result of the proposed model is that S phase thymocytes in the presence of a wide range of extracellular deoxyribonucleoside concentrations synthesize their pyrimidine dNTP by the salvage pathway, whereas purine dNTPs are synthesized primarily by ribonucleotide reduction. Using the proposed model, it is possible to predict the relative intracellular dNTP pools found in fresh S phase thymocytes.

Cell Cycle↗