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Biomedical subjects

A Cohen

Publications and source records attributed to A Cohen.

At least 505 records · Page 28Linked to original sources
PubMed1991

Differential regulation of gamma and delta T cell antigen receptor gene expression by phorbol esters and Ca2+ ionophores in the acute lymphocyte leukemia DND41 cell line.

We have investigated the role of two signal transduction pathways on the regulation of the gamma and delta T cell antigen receptor (TcR) gene expression, in the acute lymphocytic leukemic cell line DND41. Protein kinase C (PKC) activation, and intracellular free Ca2+ mobilization, initiated by phorbol esters and calcium ionophores, respectively, not only acted independently but, more interestingly, their effects were antagonistic, suggesting a role for these signals during T cell differentiation. The Ca2+ ionophore, ionomycin, increased the levels of intracellular free Ca2+ and induced the expression of the gamma and delta chains of the T cell antigen receptor in a concentration-dependent manner. The phorbol ester 12-myristate 13-acetate down-regulated the basal gamma TcR expression with marginal effect on delta TcR mRNA, but diminished the induction of both gamma and delta TcR, initiated by the Ca2+ ionophore. These antagonistic effects of the two arms of the phospholipase C-mediated signal transduction pathways, i.e. PKC activation and increased intracellular free Ca2+, were specific to the regulation of the gamma and delta TcR, since the same signals exerted a synergistic effect on the mRNA levels of interleukin 2 receptor. These data confirm our hypothesis that the antagonistic regulation on the gamma and delta TcR gene expression by phorbol esters and calcium ionophores occurs in the same cell, and stresses the biological significance of PKC activation and intracellular free calcium mobilization during intrathymic differentiation and selection.

Blotting, Northern↗
PubMed1991

Soluble factor(s) produced in injured fish optic nerve regulate the postinjury number of oligodendrocytes: possible role of macrophages.

Mammalian central nervous system (CNS) axons are virtually incapable of regenerating after injury. However, CNS neurons of lower vertebrates, such as fish and amphibians, are endowed with a high regenerative capacity. Lately, the glial cells have been credited with the regenerative ability of any specific CNS. We have previously demonstrated that many oligodendrocytes are recovered in cultures of injured rat optic nerve, while only a few oligodendrocytes are recovered from injured fish optic nerve in culture. We further demonstrated that medium conditioned by regenerating fish optic nerves (CM), which has been shown to cause axonal elongation in injured rabbit optic nerves, causes a decrease in the number of oligodendrocytes in rat glial cultures. In the present study, we demonstrate that soluble factors in the CM are capable of reducing the number of fish oligodendrocytes in fish optic nerve cultures. In addition, an inverse relationship was found between the number of macrophages and the number of oligodendrocytes. These results thus suggest that macrophages and/or activated resident microglial cells are directly or indirectly responsible for the presence of these soluble factor(s) that regulate the postinjury number of oligodendrocytes in the fish optic nerves.

Animals↗
PubMed1991

Functional enuresis: pharmacological versus behavioral treatment.

Treatment of childhood enuresis requires a careful anamnesis, physical examination, urinalysis, and urine culture to determine if a subject is affected with functional or organic enuresis. Functional enuresis (FE) was present in the majority of our patients (168/204). These 168 subjects, aged from 6 to 11 years, were randomly divided into three therapy groups (pharmacological therapy, behavioral therapy, and behavioral therapy with the aid of a personal computer). Our study shows that behavioral therapy gave better results in FE than did pharmacological therapy. We point out the usefulness of combining bladder retention training and behavioral therapy to improve the general maturity and autonomous behavior of the child, and the resultant positive effects on his personality.

Behavior Therapy↗
PubMed1991

Cesarean section by local anesthesia in patients with familial dysautonomia.

We describe a 29-year-old patient with familial dysautonomia who underwent cesarean section because of severe intrauterine fetal growth retardation. The surgery was done after induction of local anesthesia to avoid the critical and sometimes fatal complications of general anesthesia known in patients with familial dysautonomia. Surgery was uneventful and almost painless. The postoperative period was without complications. Induction of local anesthesia for cesarean section may constitute a suitable alternative in patients with familial dysautonomia.

Adult↗
PubMed1991

Primary cardiac valve tumors.

To investigate the characteristics of primary cardiac valve tumors, we retrospectively analyzed our multiinstitutional experience from 1932 through 1990. We encountered 56 valvular tumors in 53 patients. The average age of these patients was 52 years (range, 2 to 88 years) and 79% (42/53) were male. Symptoms were present in 38% (20/53) and were neurological in 15% (8/53). Four patients experienced sudden death. Each of the four valves was affected with approximately equal frequency: 16 aortic, 15 mitral, 13 pulmonary, and 12 tricuspid. All but four tumors were benign. The most common histological type was papillary fibroelastoma (41), followed by myxomas (5), fibromas (4), sarcomas (2), hamartoma (1), hemangioma (1), histiocytoma (1), and undifferentiated (1). Average tumor size was 1.15 cm (range, 3 mm to 7 cm), and the average size of fibroelastomas was 8 mm (range, 3 to 15 mm). Mitral valve tumors were more likely than aortic valve tumors to produce serious neurological symptoms or sudden death (8/15 versus 3/16; p less than 0.05). Six patients underwent echocardiography, and results were positive in each. All 6 underwent uncomplicated valve repair or replacement. Compared with a series of 407 nonvalvular tumors, cardiac valve tumors are more likely to occur in male patients (p less than 0.001) and adults (p less than 0.001). Valve tumors are also more commonly benign (p less than 0.001) and asymptomatic (p less than 0.001). These tumors demonstrate somewhat less aggressive behavior compared with non-valvular tumors, but their distinct propensity to produce serious clinical sequelae argues in favor of surgical resection for all cardiac valve tumors.

Female↗
PubMed1991

Expression of the human T cell receptor V beta repertoire.

We have used a sensitive assay, based on amplification of cDNA by the polymerase chain reaction, to determine in a variety of human tissues the relative levels of expression of the genes coding for each of the twenty families of human TcR V beta. We have determined the diversity of the expressed TcR V beta repertoire early in the development of the immune system. We have shown that the full TcR V beta repertoire is expressed early into the second trimester; the expressed repertoire is as diverse at this point, in both fetal thymus and spleen, as it is in mature thymus and peripheral blood lymphocytes. In addition the relative expression in the fetal thymus of each V beta gene is conserved to a large extent in the fetal spleen.

Adult↗
PubMed1991

Density effects in conjunction search: evidence for a coarse location mechanism of feature integration.

Four experiments used the visual search paradigm to examine feature integration mechanisms. Reaction time to determine the presence or absence of a conjunctive target is relatively fast and exhaustive for low-density displays. Search rate is slow and self-terminating for high-density displays. Density effects do not arise when the target is defined by a unique feature. Two mechanisms are proposed for feature integration. A fast mechanism integrates features on the basis of coarse location information coded with the initial registration of the features. This coarse location mechanism requires that display items be spaced apart. A second, slower mechanism is used when objects are clumped together. The 2-mechanism hypothesis provides a resolution to conflicting findings in the visual search and illusory-conjunction literature. A possible interpretation of the findings with a single guided search mechanism for feature integration is also discussed.

Adult↗
PubMed1991

Traumatic atlanto-occipital dislocation in children: review and report of five cases.

Traumatic atlanto-occipital dislocation has usually been considered incompatible with life. However, reports on survivors stress the need for early clinical diagnosis of this condition, particularly in the context of multiple trauma, in order to avoid life-threatening diagnostic manipulations and to provide adequate treatment. Five instances of atlanto-occipital dislocation in children observed during the last two years prompted this report, since four of them survived only temporarily. The radiologic and computed tomographic (CT) findings have been reevaluated. Use of metrizamide CT is advised in clinically suspected cases with inconclusive radiologic workup.

Atlanto-Occipital Joint↗
PubMed1991

Nucleotide sequence and spatial expression pattern of a drought- and abscisic Acid-induced gene of tomato.

The nucleotide sequence of le16, a tomato (Lycopersicon esculentum Mill.) gene induced by drought stress and regulated by abscisic acid specifically in aerial vegetative tissue, is presented. The single open reading frame contained within the gene has the capacity to encode a polypeptide of 12.7 kilodaltons and is interrupted by a small intron. The predicted polypeptide is rich in leucine, glycine, and alanine and has an isoelectric point of 8.7. The amino terminus is hydrophobic and characteristic of signal sequences that target polypeptides for export from the cytoplasm. There is homology (47.2% identity) between the amino terminus of the LE 16 polypeptide and the corresponding amino terminal domain of the maize phospholipid transfer protein. le16 was expressed in drought-stressed leaf, petiole, and stem tissue and to a much lower extent in the pericarp of mature green tomato fruit and developing seeds. No expression was detected in the pericarp of red fruit or in drought-stressed roots. Expression of le16 was also induced in leaf tissue by a variety of other abiotic stresses including polyethylene glycol-mediated water deficit, salinity, cold stress, and heat stress. None of these stresses or direct applications of abscisic acid induced the expression of le16 in the roots of the same plants. The unique expression characteristics of this gene indicates that novel regulatory mechanisms, in addition to endogenous abscisic acid, are involved in controlling gene expression.

Journal Article↗
PubMed1991

Organ-Specific and Environmentally Regulated Expression of Two Abscisic Acid-Induced Genes of Tomato : Nucleotide Sequence and Analysis of the Corresponding cDNAs.

The cDNAs, pLE4 and pLE25, represent mRNAs that accumulate in response to water deficit and elevated levels of endogenous abscisic acid in detached leaves of drought-stressed tomato (Lycopersicon esculentum Mill., cv Ailsa Craig) (A Cohen, EA Bray [1990] Planta 182: 27-33). DNA sequence analysis of pLE4 and pLE25 showed that the deduced polypeptides were 13.9 and 9.3 kilodaltons, respectively. Each polypeptide was hydrophilic, cysteine- and tryptophan-free, and found to be similar to previously identified proteins that accumulate during the late stages of embryogenesis. pLE4 and pLE25 mRNA accumulated in a similar organ-specific pattern in response to specific abiotic stresses. Yet, expression patterns of the corresponding genes in response to developmental cues were not similar. pLE25 mRNA accumulated to much higher levels in developing seeds than in drought-stressed vegetative organs. pLE4 mRNA accumulated predominantly in drought-stressed leaves. The similarities and differences in the accumulation characteristics of these two mRNAs indicates that more than one mechanism exists for the regulation of their corresponding genes.

Journal Article↗
PubMed1991

Acoustic transmission of the respiratory system using speech stimulation.

Two methods for the analysis of the acoustic transmission of the respiratory system are presented. Continuous speech utterance is used as acoustic stimulation. The transmitted acoustic signal is recorded from various sites over the chest wall. The AR method analyzes the power spectral density function of the transmitted sound, which heavily depends on the microphone assembly and the utterance. The method was applied to a screening problem and was tested on a small database that consisted of 19 normal and five abnormal patients. Using the first five AR coefficients and the prediction error of an AR(10) model, as discriminating features, the system screened all abnormals. An ARMA method is suggested, which eliminates the dependence on microphone and utterance. In this method, the generalized least squares identification algorithm is used to estimate the ARMA transfer function of the respiratory system. The normal transfer function demonstrates a peak at the range of 130-250 Hz and sharp decrease in gain for higher frequencies. A pulmonary fibrotic patient demonstrated a peak at the same frequency range, a much higher gain in the high frequency range with an additional peak at about 700 Hz.

Adult↗
PubMed1991

Percutaneous dilational tracheostomy. A bedside procedure on the intensive care unit.

Tracheostomy is performed commonly to aid weaning from assisted ventilation in patients who require intensive care. The procedure carries a significant mortality and morbidity, in part due to problems in moving unstable patients. We report the use of a bedside percutaneous tracheostomy technique for use in adult patients who require intensive care. The procedure was successful in 19 of 20 cases. The one failure, in the first case, resulted from transection of a superficial midline vein. The lack of significant haemorrhage was notable in all other cases. The procedure has proved to be efficient and cost-effective in this unit and has now replaced conventional surgical tracheostomy in this group of patients.

Adult↗
PubMed1991

Adenosine deaminase and thymocyte maturation.

The congenital absence of adenosine deaminase in humans results in severe combined immunodeficiency. To clarify the process whereby thymocytes are destroyed in the absence of adenosine deaminase activity, we induced a parallel condition in mice through the injection of an inhibitor of adenosine deaminase, deoxycoformycin. We have observed that deoxycoformycin, in addition to maintaining high levels of dATP in thymocytes, blocks the progression of thymocyte differentiation at two points. As a result of the first block, the cortex is depleted of immature cortical thymocytes while CD4+CD8+ thymocytes with functionally rearranged T-cell receptors survive. As a result of the second block, the CD4+CD8+ thymocytes are prevented from further differentiation to mature CD4+CD8- or CD4-CD8+ T lymphocytes and accumulate at the corticomedullar junction and in the medulla. These observations suggest that the maintenance of dNTP pools by adenosine deaminase is critical to at least two stages of thymocyte differentiation.

Adenosine Deaminase↗
PubMed1991

Crescentic IgA nephropathy as a manifestation of human immune deficiency virus infection.

A 37-year-old Caucasian male homosexual presented with hematuria and rapidly progressive acute renal failure. He was found to have proteinuria and microscopic hematuria as well as RBC casts. Investigations revealed polyclonal gammopathy with five times normal serum IgA levels as well as elevated serum IgG. Renal biopsy showed evidence of crescentic IgA nephropathy with ultrastructural changes of tubuloreticular inclusions described in HIV nephropathy. He was found to be positive for human immunodeficiency viral antibodies. Renal function improved during follow-up after two doses of 1 g each of methylprednisone. In our opinion, this is the first case of HIV-related crescentic IgA nephropathy. HIV testing should be performed more frequently in patients presenting with acute glomerular diseases.

AIDS-Associated Nephropathy↗
PubMed1991

Myotonic heart disease: a clinical follow-up.

We followed 37 patients with myotonic dystrophy for a mean of 6 years. Two developed atrial flutter or fibrillation, 6 developed a new bundle branch block, 1 developed complete heart block requiring a pacemaker, and another with progressive 1st-degree heart block and a widening QRS interval had a sudden death. Most patients had predictable, gradually progressive disease of their cardiac conduction system. We recommend that patients with progressive atrioventricular block or widening QRS interval due to myotonic heart disease have yearly ECGs and be questioned about syncope or presyncope to determine the need for a cardiac pacemaker.

Adolescent↗
PubMed1991

Effect of monomeric immunoglobulin G (IgG) on the clearance of soluble aggregates of IgG in man.

Serum concentrations of IgG may influence Fc receptor-mediated clearance of immune complexes. For instance, when 123I-labeled aggregates of human IgG (123I-AIgG), used as a model for soluble immune complexes, are administered to patients with systemic lupus erythematosus (SLE), there is an inverse correlation between the serum concentrations of IgG and the clearance and volume of distribution in steady state (Vss) of 123I-AIgG. To answer the question whether IgG has a direct effect on the clearance of immune complexes, we measured the elimination of 123I-AIgG in eight patients with hypogammaglobulinemia, before and after substitution with intravenous gammaglobulin (IVIG). As expected, raising IgG concentrations in these patients (by 6 g/l) caused a significant decrease of the Vss of 123I-AIgG. However, clearance of 123I-AIgG remained unchanged by IVIG. Thus, the results of this study offer no experimental evidence that raising concentrations of IgG influences the clearance of soluble immune complexes.

Adult↗
PubMed1991

[Outcome of immediate management of severe head injuries].

Immediate management of severe head injuries still poses a serious challenge. 50 patients with severe head injuries (Glasgow Coma Scale, 8 or less) were treated from February 1, 1989 to April 30, 1990. The effects of age, Glasgow Coma Score at admission, CT findings, pupillary reactivity to light and intracranial pressure on outcome, were evaluated. The results of the present series match those of other studies and in some aspects the results are even superior. We attribute the high incidence of good outcome to the direct referral of the severe head injury patients, thus excluding delays at peripheral hospitals. In addition, aggressive management in the intensive care units and a broader range of indications for operation were also correlated with favorable outcome.

Brain Injuries↗