Biomedical subjects

R L Klein

Publications and source records attributed to R L Klein.

At least 37 records · Page 2Linked to original sources

PubMed1996

Gastric tube as the primary procedure for pure esophageal atresia.

Long gap esophageal atresia occurs in approximately 5% of patients with tracheoesophageal anomalies. A small group of such patients have a rudimentary or diverticular distal esophagus that is not amenable to primary repair. These children usually require staged procedures and esophageal replacement using other parts of the intestinal tract. To circumvent the morbidity and delayed repair associated with cervical esophagostomy, colon interposition, or delayed gastric tube interposition, the authors propose the use of a primary gastric tube for early establishment of esophageal continuity in the neonate. Three cases of early esophageal replacement using a gastric tube are described. All three patients were born prematurely, with comorbid conditions, and had a rudimentary distal esophagus. The results of the operation were successful. The authors believe that primary repair of the esophagus, when possible, is the gold standard.

Esophageal Atresia↗

PubMed1996

Regulation of GABAA receptor structure and function by chronic drug treatments in vivo and with stably transfected cells.

In this article, we review the use of stably transfected cells to study the regulation of receptor structure and function by chronic drug treatments and compare results from these cells to results obtained from other systems, including neuronal cultures and intact animals. We focus on the gamma-aminobutyric acid type A (GABAA) receptor complex. Sedative/hypnotic drugs such as benzodiazepines, barbiturates and alcohol that potentiate GABAA receptor function produce tolerance and dependence. Chronic treatment of GABAA receptor preparations from brain and neuronal cultures with GABAA agonists, as well as these other three classes of drugs, results in regulation of several properties of the receptor. Drug treatments may regulate levels of binding sites, allosteric binding interactions, receptor function, levels of receptor subunit mRNA and levels of receptor subunit protein. Some or all of these effects may comprise the molecular mechanisms of tolerance to these GABAA-modulatory drugs. The use of cells stably transfected with neurotransmitter receptors provides a homogeneous population that can be cultured under controlled conditions. As most preparations contain mixed populations of GABAA receptor subunits, stably transfected cells offer the advantage of the expression of receptors with a defined subunit composition. We conclude that chronic drug treatments regulate allosteric coupling and function of GABAA receptors in stably transfected cells. This regulation does not appear to be due to decreases in the expression of alpha 1- or beta 1-receptor subunits or to expression of subunits other than alpha 1, beta 1, gamma 2L. Therefore, it is unlikely to be due to changes in receptor subunit composition and probably represents post-translational changes. The rapid regulation of allosteric coupling and function by drug treatment of the stably transfected cells should provide insights to the mechanisms of coupling between GABAA and benzodiazepine receptors as well as tolerance and dependence of benzodiazepines and ethanol.

Animals↗

PubMed1996

LDL from patients with well-controlled IDDM is not more susceptible to in vitro oxidation.

Increased susceptibility of LDL to oxidation has been shown to be associated with the presence of coronary heart disease and may account for the accelerated vascular disease seen in diabetes. The response of LDL to in vitro oxidative stress has been proposed as a measure of the predisposition of LDL to the in vivo subendothelial oxidative stress. Increased susceptibility to oxidation has been demonstrated recently in diabetic patients with poorly controlled IDDM. Thus, we conducted studies to determine whether the increased susceptibility of LDL to oxidation was secondary to diabetes per se or to the level of glycemic control. Fifteen IDDM patients with good glycemic control and with no evidence of macrovascular disease or proteinuria were compared with healthy age-, sex-, race-, and BMI-matched nondiabetic subjects. Fasting blood glucose levels averaged 12.1 +/- 1.1 (mean +/- SE) vs. 4.9 +/- 0.1 mmol/l in the diabetic versus the control groups, respectively. HbA1c levels averaged 7.7 +/- 0.5 vs. 4.4 +/- 0.2%, reflecting well-controlled diabetes (P < 0.0001). Total, LDL, VLDL, and HDL cholesterol, triglyceride, and lipoprotein(a) levels did not differ between the groups. The particle size, lipid composition, fatty acid content, antioxidant content, and glycation were similar for LDL isolated from both groups. A rapid LDL preparation technique was used to compare LDL susceptibility to oxidation under the following conditions: final LDL cholesterol concentration of 100 microg/ml, 5 micromol/l of CuCl2 at 25 degrees C. There was no difference in the susceptibility to in vitro oxidation of LDL isolated from IDDM patients compared with control subjects. There was no correlation of glycemic control with any of the parameters of the in vitro oxidation of LDL. LDL from patients with well-controlled IDDM does not differ in composition or in susceptibility to in vitro oxidative stress compared with LDL from nondiabetic subjects.

Adult↗

PubMed1996

Employee sabotage in the workplace: a biopsychosocial model.

Recently, there has been an increased interest in workplace violence. However, the psychiatric literature has paid little, if any attention to the specific subject area of workplace property harm or sabotage by employees. The specific psychology and/or psychopathology of the individual worker may be relevant in the evaluation of sabotage behavior. However, psychosocial factors associated with behavior within organizations and originating in part from the job itself are not likely to be considered in the initial assessment. We therefore introduce concepts from the organizational behavior literature that may facilitate and complement psychiatric evaluation of sabotage in the workplace. These concepts will fill the gap in a biopsychosocial assessment of sabotage in the workplace and provide a nexus for future interdisciplinary studies of workplace property violence.

Forensic Psychiatry↗

PubMed1995

Ethanol increases GABAA responses in cells stably transfected with receptor subunits.

Ethanol enhancement of GABAA receptor function has been found in some, but not all, studies. These results suggest the existence of ethanol-sensitive and -resistant receptors that may differ in subunit composition, although methodological differences (e.g., 36Cl- flux versus membrane currents) could also contribute to the different results. To examine these possibilities, we used mouse L(tk-) cells stably transfected with alpha 1 + beta 1 or alpha 1 + beta 1 + gamma 2L GABAA receptor subunit DNAs and compared 36Cl- flux with whole-cell, patch-clamp measurements of GABAA receptor function. Both techniques detected a similar modulation of the GABA receptor by ethanol, flunitrazepam, and pentobarbital. The potentiating action of ethanol required the gamma-subunit and was maximal at a concentration of 10 mM. Similar ethanol potentiation was obtained with brief (20 msec) or long (2 sec) applications of GABA. Analysis of data obtained from individual cells expressing alpha 1 beta 1-gamma 2L subunits showed considerable variability in sensitivity to ethanol, particularly with concentrations of 30 and 100 mM. Ethanol potentiated GABA action if the cells were grown on coverslips coated with polylysine, but had no effect on GABAA receptors of cells grown on uncoated coverslips. Thus, ethanol action was influenced by the growth matrix. Taken together, these data indicate that a gamma-subunit is necessary, but not sufficient, for ethanol sensitivity in this cell system. We suggest that posttranslational processing, particularly receptor phosphorylation, may also be important and that stably transfected cells will be useful in elucidating these events.

Animals↗

PubMed1995

GABAA receptor function and binding in stably transfected cells: chronic ethanol treatment.

Effects of chronic ethanol exposure on GABAA receptors may contribute to tolerance and dependence to alcohol. Ethanol treatment of mice and rats can produce alterations of GABAA receptor binding, function, and subunit mRNA and protein levels. We treated a cell line (PA3 cells) that stably expresses GABAA receptors chronically with ethanol. Expression of bovine alpha 1, beta 1, and gamma 2L GABAA receptor subunits genes in these cells is controlled by a dexamethasone-sensitive promoter, and this provides an excellent system to study the regulation by chronic ethanol treatment of receptors with a defined subunit composition. The actions of the GABA agonist muscimol on receptor function (36Cl- uptake) were not affected by 100 mM ethanol treatment for 4 days, but the actions of flunitrazepam (1 microM) were decreased in cells treated with ethanol. The functional coupling between benzodiazepine and GABA sites on the receptors was affected by chronic ethanol treatment in a manner consistent with results from mice. Ethanol treatments (50 or 100 mM) for 4 days did not affect the affinity (Kd) or receptor density (Bmax) of [3H]flunitrazepam binding, or the levels of alpha 1 subunit mRNA, or alpha 1 or beta 1 subunit proteins. These results demonstrate that the regulation of the stably expressed GABAA receptors by chronic ethanol, in the absence of neuronal receptor gene promoters, is posttranscriptional and likely posttranslational.

Alcoholism↗

PubMed1995

Isolation, characterization, and metabolism of the glycated and nonglycated subfractions of low-density lipoproteins isolated from type I diabetic patients and nondiabetic subjects.

The total low-density lipoprotein (LDL) fraction was isolated from 21 patients with type I diabetes and 7 nondiabetic normolipemic subjects. The LDL was separated into two subfractions, one glycated (G-LDL) and one nonglycated (N-LDL), using affinity chromatography. G-LDL comprised 21.1 +/- 3.6 and 5.2 +/- 0.6% of the total LDL in diabetic patients and normal subjects, respectively. G-LDL isolated from both diabetic patients and normal subjects was significantly more glycated than N-LDL isolated from the same subject. G-LDL isolated from both diabetic patients and normal subjects was enriched in triglycerides. The metabolism of N-LDL and G-LDL was investigated in human fibroblasts, which express only the classical LDL receptor, and in human monocyte-derived macrophages, which also express a receptor for G-LDL. In fibroblasts, the rates of receptor-mediated accumulation of N-LDL isolated from normal subjects and diabetic patients were significantly greater (P < 0.01) than those of G-LDL. In contrast, when the same LDL subfractions were incubated with human monocyte-derived macrophages, the rates of receptor-mediated accumulation of G-LDL isolated from both groups were significantly greater (P < 0.01) than those of N-LDL. Rates of degradation of G-LDL by human macrophages were not significantly different from those of N-LDL during short-term incubations but reached statistical significance (P < 0.05) when LDL subfractions were incubated with cells for 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Release of platelet plasminogen activator inhibitor 1 in whole blood is increased in patients with type II diabetes.

OBJECTIVE: To compare platelet plasminogen activator inhibitor 1 (PAI-1) release in type II diabetic patients and healthy control subjects. RESEARCH DESIGN AND METHODS: We studied a group of 27 diabetic patients and a group of 16 nondiabetic control subjects. Whole-blood platelet aggregation, defined as a decrease in platelet count during shaking (180 rpm) of blood samples at 37 degrees C, and plasma PAI-1 antigen concentrations were measured in parallel at time 0, 7.5, 15, 30, 60, 120, and 180 min. RESULTS: Platelet aggregation did not differ significantly between the two groups at any time period. However, the increase in plasma PAI-1 antigen concentration over basal levels at time 0 was higher for the group of diabetic patients when compared with their matched control subjects. The increment of PAI-1 antigen was 61.8 +/- 29.4 vs. 35.9 +/- 13.4 ng/ml (P < 0.005, means +/- SD) after 180 min for the diabetic and control subjects, respectively. Platelet PAI-1 release was correlated to very-low-density lipoprotein cholesterol and triglyceride plasma levels, but not to HbA1c levels. CONCLUSIONS: Platelets of patients with type II diabetes release significantly more PAI-1 than platelets of healthy subjects at the same level of platelet aggregation. This may contribute to enhanced thrombosis in diabetes.

Adult↗

PubMed1995

Regulation of allosteric coupling and function of stably expressed gamma-aminobutyric acid (GABA)A receptors by chronic treatment with GABAA and benzodiazepine agonists.

Chronic treatments with drugs that stimulate or potentiate gamma-aminobutyric acid (GABA)A receptor function cause uncoupling of allosteric sites and downregulation of the GABAA receptors expressed in neurons. To study these effects on receptors having a defined subunit composition, we treated stably transfected mouse Ltk- cells (PA3 cells) with drugs known to uncouple GABAA receptors. Because dexamethasone controls the expression of bovine alpha-1, beta-1 and gamma 2L GABAA receptor subunit genes in PA3 cells, this expression system provides a way to study receptors in the absence of neuronal subunit gene promoters. We assayed binding of [3H]flunitrazepam to measure allosteric coupling and uptake of 36Cl- to measure GABAA receptor function. Chronic (4 day) treatment of PA3 cells with muscimol, GABA or flunitrazepam reduced the GABA enhancement of binding of [3H]flunitrazepam to PA3 cells. Chronic flurazepam or muscimol treatments also caused downregulation of benzodiazepine potentiation of muscimol-stimulated 36Cl- uptake. Chronic treatment with muscimol did not affect levels of subunit mRNAS and alpha 1- or beta 1-subunit protein of GABAA receptors and chronic flunitrazepam did not affect subunit mRNAs or alpha 1 protein. We conclude that chronic drug treatments regulate allosteric coupling and function of GABAA receptors in stably transfected cells and this regulation cannot be attributed to decreases in the expression of receptor subunits or to expression of subunits other than alpha 1 beta 1 or gamma 2L.

Allosteric Regulation↗

PubMed1995

Psychiatric factors associated with dangerous misidentification delusions.

The delusional misidentification syndromes are characterized by misidentification delusions of others or of the self. Aggressive ideas or behaviors often accompany these delusions. The relationship between delusional misidentification and dangerousness remains for the most part poorly understood. In the present article, we compare a group of dangerous individuals suffering from dangerous misidentification delusions with a group of dangerous individuals suffering from other types of delusions. Individuals with dangerous misidentification delusions were more likely to experience grandiose ideation, thought disorder, generalized hostility, excitement, general psychopathology, and a previous history of violence than dangerous delusional individuals with no delusional misidentification. The group with dangerous delusional misidentification syndromes was less likely to attack others with weapons than were the dangerous delusional group with no delusional misidentification.

Adult↗

PubMed1995

Actions of the general anesthetic propofol on recombinant human GABAA receptors: influence of receptor subunits.

The intravenous general anesthetic 2,6-diisopropylphenol (propofol) potentiates GABAA receptor function, but the precise mechanisms and specificity of this action are still unclear. To study the influence of receptor subunit composition on the action of propofol, 18 different combinations of cloned cDNAs coding for human brain subunit isoforms of the GABAA receptor, as well as mRNAs from mouse brain, were expressed in Xenopus oocytes, and effects of this anesthetic were investigated by the voltage-clamp technique. We found that low concentrations (1-10 microM) of propofol dramatically potentiated GABA-evoked Cl- currents in all GABAA receptor constructs tested. This action did not require specific subunits but was correlated inversely with the GABA sensitivity of each receptor construct. Larger concentrations (10-25 microM) of propofol produced direct activation of Cl- currents, and this action was dependent on the expression of the beta-subunit of the GABAA receptor and did not correlate with the GABA sensitivity of the receptors. These results suggest that propofol exerts a dual effect on GABAA receptors: a positive modulation of the GABA-mediated action on GABAA receptors that is not influenced by the receptor subunit composition, and a specific interaction with the beta-subunit that directly activates the GABAA receptor-coupled Cl- channel.

Animals↗

PubMed1994

A single amino acid of the human gamma-aminobutyric acid type A receptor gamma 2 subunit determines benzodiazepine efficacy.

Incorporation of the gamma 2 subunit into gamma-aminobutyric acid type A (GABAA) receptors is required for the expression of benzodiazepine pharmacology, but the regions of the subunit responsible for benzodiazepine actions have not been defined. Using mutagenesis, we identified a single amino acid of the gamma 2 subunit of the human GABAA receptor that profoundly alters the nature of this pharmacology. When threonine 142 was mutated to serine, the benzodiazepine receptor antagonist, flumazenil, and the weak inverse agonist, Ro 15-4513, both acted as potent partial agonists. Further, potentiation of GABA responses by diazepam, alprazolam, clonazepam, or flunitrazepam doubled in receptors containing the Ser-142 gamma 2 subunit. In contrast, responses to the Type I benzodiazepine receptor selective ligands, zolpidem, alpidem, and CL218,872, were roughly halved. This change in pharmacology appears to occur at a stage following ligand binding, i.e. the mutation affects benzodiazepine efficacy. There was no effect on GABA affinity or efficacy or pentobarbital, Ro 5-4864, or alphaxalone modulation of GABA responses. These findings demonstrate that very minor changes in receptor structure can profoundly affect the efficacy of receptor ligands. Thus, agonism is determined not only by the structure of the drug, but also by the structure of the receptor, or protein complex, with which it interacts.

Animals↗

PubMed1994

Effects of 5-HT3 receptor antagonists on binding and function of mouse and human GABAA receptors.

Both 5-HT3 receptor antagonists and benzodiazepine receptor ligands have effects on anxiety, and alter the behavioral action of ethanol. For these reasons, we tested the ability of several 5-HT3 receptor antagonists to inhibit the ligand binding and function of the gamma-aminobutyric acidA/benzodiazepine receptor Cl- channel complex of mouse brain membranes. MDL 72222 (1-a-H-3-a-5-aH-optropan-3yl-3,5-dichlorobenzoate) and LY 278584 (1-methyl-N-(8-methyl-8-azabicyclo[3.2.1.]oct-3-yl)-1H-indazole-3- carboxamide) inhibited [3H]flunitrazepam binding with Ki values of approximately 20 microM; ICS 205-930 (3 alpha-tropanyl-1H-indole-3-carboxylic acid ester) was more potent with a Ki of 0.8 microM. ICS 205-930 (50 microM) had no effect on [3H]muscimol binding. ICS 205-930, MDL 72222, and LY 278584 all inhibited the binding of [35S]TBPS (tert-butylbicyclophosphorothionate) with Ki values of approximately 10 microM and reduced muscimol-dependent 36Cl- flux into mouse cortical microsacs by 30-45% at a concentration of 10 microM. ICS 205-930, MDL 72222, and LY 278584 (at micromolar concentrations) reduced GABA-gated chloride currents studied in Xenopus oocytes expressing human alpha 1 beta 1 gamma 2S GABAA receptor subunits. ICS 205-930 differed from the other two 5-HT3 receptor antagonists in that it induced a biphasic effect on GABA-gated currents: at concentrations from 0.1 to 5 microM it potentiated GABA responses, whereas at higher concentrations (50-100 microM) it produced inhibition. The stimulatory action induced by ICS 205-930 was due to interaction at the benzodiazepine recognition site because expression of the gamma 2 subunit was required and Ro 15-1788 (1 microM) completely prevented the potentiation caused by ICS 205-930. Thus, several 5-HT3 receptor antagonists inhibit benzodiazepine binding and affect GABAA receptor function. These actions are most pronounced for ICS 205-930 and likely involve direct affects on the GABA/benzodiazepine complex rather than interactions with 5-HT3 receptors.

Animals↗

PubMed1994

Differential effects of GABAergic ligands in mouse and rat hippocampal neurons.

Previous electrophysiological studies suggested that GABAA receptors in rat hippocampal neurons might be less sensitive to ethanol than mouse neurons. Therefore, we examined the effects of ethanol (0.5-850 mM) in cultured mouse (C57BL/6) and rat (Sprague-Dawley) neurons. In 35% of the mouse neurons, the Cl- current was potentiated by ethanol starting at 0.5 mM. In all of the rat neurons examined, on the other hand, the current was potentiated by concentrations starting at 200 mM. We also studied the effects of GABA and other GABAergic ligands. GABAA receptors in rat and mouse neurons displayed EC50s for GABA of 9 +/- 0.3 and 17 +/- 0.8 microM, respectively and ethanol did not significantly change these values. The EC50 for diazepam was 92 +/- 3 and 120 +/- 8 nM in rat and mouse, respectively. Pentobarbital enhanced the current with EC50s of 84 +/- 3 and 106 +/- 6 microM in rat and mouse, respectively. The sensitivity for Cl-218,872, which binds preferentially to the Type I benzodiazepine receptor, was similar in all the neurons. RO 15-4513, an inverse partial agonist to the benzodiazepine receptor, was not effective in reversing the potentiation of the Cl- current in rat neurons and only slightly reduced the potentiation in mouse neurons. The receptors in rat neurons were more sensitive to external Zn2+; the current was inhibited by 50% with a concentration of 93 +/- 3 and 244 +/- 9 microM in rat and mouse, respectively. Analysis of mRNA encoding for the gamma 2L receptor subunit showed similar levels in rat and mouse neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Pulmonary blastoma in children: report of two cases and review of the literature.

Pulmonary blastoma is a rare primary neoplasm of the lung. Approximately 25% of the reported cases have occurred in pediatric patients. The authors found 45 cases of these tumors in children aged < or = 16 years, and report two more cases of pulmonary blastoma--in a 3 1/2-year-old boy and a 22-month-old girl. Because these tumors are considered malignant, surgical excision is recommended.

Child, Preschool↗

PubMed1994

Benzodiazepine treatment causes uncoupling of recombinant GABAA receptors expressed in stably transfected cells.

GABAA and benzodiazepine receptors are allosterically coupled, and occupation of either receptor site increases the affinity of the other. Chronic exposure of primary neuronal cultures to benzodiazepine agonists reduces these allosteric interactions. Neurons express multiple GABAA receptor subunits, and it has been suggested that uncoupling is due to changes in the subunit composition of the receptor. To determine if uncoupling could be observed with expression of defined subunits, mouse Ltk- cells stably transfected with GABAA receptors (bovine alpha 1, beta 1, and gamma 2L subunits) were treated with flunitrazepam (Flu) or clonazepam. The increase in [3H]Flu binding affinity caused by GABA (GABA shift or coupling) was significantly reduced in cells treated chronically with the benzodiazepines, whereas the KD and Bmax of [3H]Flu binding were unaffected. The uncoupling caused by clonazepam treatment occurred rapidly with a t1/2 of approximately 30 min. The EC50 for clonazepam treatment was approximately 0.3 microM, and cotreatment with the benzodiazepine antagonist Ro 15-1788 (5.6 microM) prevented the effect of clonazepam. The uncoupling observed in this system was not accompanied by receptor internalization, is unlikely to be due to changes in receptor subunit composition, and probably represents post-translational changes. The rapid regulation of allosteric coupling by benzodiazepine treatment of the stably transfected cells should provide insights to the mechanisms of coupling between GABAA and benzodiazepine receptors as well as benzodiazepine tolerance.

Allosteric Site↗

PubMed1994

Delusional misidentification syndromes and dangerousness.

Dangerousness in the delusional misidentification syndromes is studied by reviewing a sample of 82 cases defined by either verbal threats or physical violence caused by misidentification delusion. Eighty cases were obtained from a review of the anglophone psychiatric literature in which the patients exhibited some degree of dangerousness, to which we added 2 previously unreported cases.

Adult↗

PubMed1994

Platelet plasminogen activator inhibitor 1 in patients with type II diabetes.

OBJECTIVE: To compare platelet plasminogen activator inhibitor 1 (PAI-1) concentration in type II diabetic patients and healthy control subjects. RESEARCH DESIGN AND METHODS: We studied a group of 12 diabetic patients whose disease was controlled by diet or sulfonylurea therapy and a group of 17 nondiabetic control subjects. All subjects were free of clinically advanced vascular disease. PAI-1 antigen concentrations were measured in 5 x 10(8) isolated platelets, which were lysed by 1% Triton X-100. RESULTS: Mean platelet PAI-1 was significantly higher in diabetic patients (264 +/- 83 ng/5 x 10(8) platelets) compared with control subjects (202 +/- 71 ng/5 x 10(8) platelets) (P < 0.05). A significant independent positive correlation was found between platelet PAI-1 concentrations and fasting plasma specific insulin levels in the diabetic patients (r = 0.63, P = 0.03). CONCLUSIONS: These findings suggest that 1) a higher platelet PAI-1 concentration may contribute to enhanced thrombosis in type II diabetes and 2) megakaryocyte PAI-1 synthesis may be under the control of insulin.

Blood Platelets↗