gamma-Aminobutyric acid (GABA)- and barbiturate-mediated 36Cl- uptake in rat brain synaptoneurosomes: evidence for rapid desensitization of the GABA receptor-coupled chloride ion channel

"Desensitization" of the gamma-aminobutyric acid (GABA) receptor-coupled chloride ion channel was studied using an in vitro method for measuring chloride (Cl-) permeability in brain vesicles (synaptoneurosomes). Muscimol, a GABA agonist, stimulated 36Cl- uptake in rat cerebral cortical synaptoneurosomes in a concentration-dependent manner (EC50 7.3 +/- 0.5 microM), whereas pentobarbital stimulated 36Cl- uptake in a biphasic manner, indicated by a bell-shaped concentration-response relationship, with a maximal response at 500 microM (EC50 271 +/- 17 microM). Higher concentrations of pentobarbital led to progressively smaller stimulation of 36Cl- uptake and blocked muscimol-stimulated 36Cl- uptake. Lower concentrations of pentobarbital (100-200 microM), when added with muscimol, produced an additive effect in stimulating 36Cl- uptake, whereas even lower (subthreshold) concentrations of pentobarbital (50 microM) potentiated muscimol-stimulated 36Cl- uptake. Following continuous exposure of synaptoneurosomes (up to 20 min) to muscimol (50 microM) or pentobarbital (500 microM), the 36Cl- uptake response diminished to a new steady state level with a t1/2 of approximately 6 sec and 30 sec, respectively. The decrement in response to these agonists was dependent on both concentration and length of exposure. No decrement was observed in the ability of subthreshold concentrations of pentobarbital to enhance muscimol-stimulated 36Cl- uptake following prolonged (20 min) incubation. "Heterologous desensitization" between muscimol and pentobarbital was observed in experiments where either muscimol or pentobarbital was added to the vesicles following pretreatment with the other. These findings suggest that "desensitization" of the GABA receptor/Cl- ion channel may involve both the GABA and barbiturate recognition sites or a common effector component such as the ionophore itself.     

Raising the ambient potassium ion concentration enhances carbachol stimulated phosphoinositide hydrolysis in rat brain hippocampal and cerebral cortical miniprisms

Summary The influence of the ambient potassium ion concentration ([K⁺]_ upon agonist stimulated hydrolysis of phosphoinositides (PI) has been studied in isolated miniprisms of rat hippocampus and cerebral cortex. When the external [K⁺] was raised from 6 to 18 mmol/l, there was little or no increase in the hydrolysis of PI in the absence of agonist, however, carbachol (100 mol/l) stimulated hydrolysis was greatly enhanced in both brain regions studied. Thus, carbachol stimulated the hydrolysis of PI to 146% and 386% of control levels at potassium concentrations of 5.8 and 18.2 mmol/l, respectively, in the rat hippocampus. A similar enhancement of muscarine (100 mol/l) stimulation was observed in cortical miniprisms with 18 mmol/l [K⁺]. A further enhancement was seen at higher ambient [K⁺], although basal hydrolysis of PI was then also increased. The carbachol-stimulated hydrolysis of PI found at both 6 and raised [K⁺] was prevented by atropine (1 and 10 mol/l) and tetraethylammonium (20 mmol/l), but not by 10 mmol/l Mg²⁺. Pirenzepine (50 nmol/l) also reduced this response. The ions Cs⁺ and Rb⁺ (but not Li⁺ or Tris⁺) produced a similar enhancement of the carbachol stimulation to that found with K⁺. At a buffer [K⁺] of 6 mmol/l, noradrenaline (100 mol/l) produced a 2-fold increase in the hydrolysis of PI whereas 5-hydroxytryptamine (100 mol/l) and histamine (500 mol/l) had little or no effect. However, histamine and 5-hydroxytryptamine did stimulate the hydrolysis of PI when [K⁺] was increased. Miniprism ATP content was not changed by a rise in [K⁺] to 18 mmol/l. The significance of these results is discussed in terms of the postsynaptic cellular events following cholinergic stimulation.     

Effects of cadmium exposure on zinc and copper distribution in neonatal rats

Tissue zinc and copper concentrations undergo marked changes in the neonatal rat during the first several weeks of life and it was of considerable interest to study the effect of cadmium exposure on these ontogenic changes. Long evans rats received either 2 or 10 mol cadmium chloride per kg SC at 9 days of age and were sacrificed at 20 or 36 days of age. Tissue copper and zinc concentrations in cadmium-treated rats were compared to those of age-matched controls for statistically significant changes. The tissue affected, the element altered and the direction of change in concentration, increased (+) or decreased (-), are summarized for the two dosing groups (age at dosing, age at sacrifice in days): 2 mol/kg (9, 20): kidney Zn (+), blood Zn (-), cerebral Cu (-), cerebellar Cu (+); 2 mol/kg (9, 36): blood Zn (-); 10 mol/kg (9, 20); liver, kidney, cerebral and cerebellar and blood Zn (-), cerebellar Cu (+); 10 mol/kg (9, 36]: liver and heart Zn (+), blood Zn (-); liver and heart Zn (+), blood Zn (-); kidney, cerebral, cerebellar and heart Cu (+). Changes in tissue zinc or copper concentrations produced by cadmium treatment could not be accounted for by the direct replacement of these elements by cadmium and may be due to alterations in transport of these elements. These results indicate that early life exposure to low levels of camium can have large and persistent effects on the distribution of the essential metals, copper and zinc.     

CB 1954 revisited

Summary Although it has been the subject of considerable interest for 15 years, originally as a cytotoxic agent and more recently as a radiosensitizer, there is very little pharmacokinetic information on CB 1954 (2,4-dinitro-5-aziridinylbenzamide). We have developed a rapid high-performance liquid chromatography assay for the drug and its metabolites and applied it to detailed examination of the pharmacokinetics of CB 1954 in mice and dogs. With IV administration a dose of 50 mg/kg gave peak blood concentrations of 100 g/ml in mice, while 25 mg/kg gave peak palsma concentrations of 27 g/ml in dogs. Peak concentrations were 3 to 5-fold lower for the IP route in mice and the oral route in dogs, and the bioavailabilities were 85% and 40%, respectively. Elimination t_1/2 values were 1.4–2 h in mice and 2.5–4 h in dogs and were independent of route of administration. Plasma protein binding was 57% but tissue penetration in mice was generally good. Tumour: plasma ratios were 50%–90%, while brain: plasma ratios were lower, at 37%–50%. The parent drug and several metabolites were identified and quantified in mouse urine, the total recovery being 24%–29%, of which 16%–25% was parent drug. The metabolites were also found in the circulation and in tissues. No changes in pharmacokinetics were seen with repeated dosing in mice or with administration of the protective agent phenyl AIC. Phenobarbitone pretreatment produced a small reduction in elimination t_1/2, mainly by accelerating aziridine ring removal. Allopurinol increased the blood levels of the 5-amino nitroreduction product. These studies provide a pharmacokinetic basis for interpreting the antitumour activity and toxicity of CB 1954, as well as for the development of new mixed-function sensitizers.     

Autocrine growth of human blymphocytes: Maintained response to autostimulatory factors is the special feature of immortalization by Epstein-Barr virus—A hypothesis

The autocrine growth profile of human B lymphocytes transformed with Epstein-Barr virus (EBV) was found to comprise three distinct components: a B-cell growth factor (BCGF); an interleukin-1 (IL-1)-like activity; an activity requiring cell-to-cell contact for its action. Observations on the inhibition of the EBV-carrying Daudi lymphoma line by α-interferon indicated that loss of response to these autostimulatory factors was underlying growth cessation. Furthermore, a putative for BCGF was found to be down-regulated on B cells stimulated with non-transforming mitogens but constitutively expressed following EBV-transformation. Taken together with recent evidence that normal B cells produce autostimulatory factors, these findings suggest that the special feature of autocrine growth by EBV-immortalized cells is a maintenance of what should normally be a transient phenotype, possibly through deregulation of receptor expression. This hypothesis is discussed.     

Perioperative transfusions associated with colorectal cancer surgery : Clinical judgment versus the hematocrit

We prospectively studied 123 patients with colorectal cancer in order to identify determinants of perioperative blood transfusions and unnecessary transfusions. Transfusions were considered unnecessary if the preoperative hematocrit reading exceeded 36% or the discharge hematocrit level exceeded 33%. Age, sex, admission hematocrit reading, operative procedure, specimen length, duration of surgery, estimated blood loss, tumor size, tumor differentiation, nodal status, Dukes' staging, and attending surgeon were evaluated in relation to perioperative blood transfusion using stepwise logistic regression. Fifty-one (41%) of the 123 patients in the study were transfused and 35 patients (28%) received at least 1 unnecessary unit of blood. Advanced age, low admission hematocrit reading, high estimated operative blood loss, prolonged procedures, and lengthy specimens were significantly related to the administration of blood. Excessive intraoperative transfusions and the practice of administering blood in pairs of units accounted for the unnecessary transfusions. This study indicates that factors that influence clinical judgment and thereby the decision to transfuse a patient are not accurate indicators of when blood should be given. Greater use of pre-transfusion hematocrit testing, especially in the operating room and before transfusing a second unit of blood, will dramatically reduce blood usage in elective colorectal cancer surgery.

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Resumen Hemos estudiado en forma prospectiva 123 pacientes con cáncer colorrectal con el objeto de identificar factores determinantes de transfusiones sanguíneas perioperatorias y de transfusiones innecesarias. Se consideró que las transfusiones eran innecesarias si el hematocrito preoperatorio excedía 36% o si el hematocrito de egreso excedía 33%. La edad y sexo, el hematocrito de admisión, el tipo de procedimiento operatorio, la longitud del especimen resecado, la duración de la operación, la magnitud estimada de la pérdida de sangre, el tamaño del tumor, el grado de la diferenciación del tumor, el estado de los ganglios, la clasificación Dukes del tumor y el cirujano, fueron valorados en relación con el volumen de transfusión perioperatoria utilizando el método de regresión logística escalonada. Cincuenta y uno (41%) de los 123 pacientes fueron transfundidos y 35 (28%) recibieron por lo menos una unidad de sangre innecesaria. La edad avanzada, un hematocrito bajo en el momento de la admisión, la escimación de una alta pérdida de sangre, los procedimientos prolongados y los especimenes de gran longitud aparecieron como factores significativamente relacionados con la administracion de sangre. Las transfusiones intraoperatorias excesivas y la práctica de administrar sangre en pares de unidades fueron responsables de las transfusiones innecesarias. Este estudio indica que los factores que influencian el juicio clínico, y por consiguiente la decisión de transfundir a un paciente, no son indicadores precisos de cuando se debe administrar sangre. Una mayor utilización del hematocrito pretransfusión, especialmente dentro de la sala de operaciones y antes de transfundir una segunda unidad de sangre, logrará disminuir en forma dramática el uso de sangre en cirugía electiva para cáncer colorrectal.

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Résumé Les auteurs se sont livrés à une étude prospective de 123 malades atteints de cancer colorectal dans le but d'identifier les facteurs qui ont été à l'origine de transfusions pré-, per-, et postopératoires et de transfusions inutiles. Les transfusions ont été considérées comme inutiles lorsque l'hématocrite préopératoire dépassait 36 pour cent ou qu'il excédait 33 pour cent au moment de la sortie de l'opéré. Pour apprécier la valeur de la transfusion périopératorie ont été pris en compte les divers facteurs suivants : l'âge, le sexe, le taux de l'hématocrite à l'admission, le type de l'intervention, la longueur du spécimen, la durée de l'opération, la quantité de sang perdu, la taille de la tumeur, le degré de différenciation du cancer, l'état des ganglions, le stade évolutif (classification de Dukes), la qualification du chirurgien. Cinquante et un des malades (41%) furent transfusés et 35 parmi eux (28%) reçurent inutilement au moins une unité de sang. L'ae avancé de l'opéré, le taux bas de l'hématocrite à l'admission, la perte importante de sang au cours de l'intervention, la longue durée de l'opération, l'importance de la pièce opératoire réséquée furent en rapport de manière significative avec l'administration de sang. Les transfusions inutiles furent le fait de l'administration excessive de sang au cours de l'opération ou de l'emploi d'unités doubles de sang. Cette étude indique que les facteurs cliniques ne constituent pas des éléments de valeur pour déterminer l'indication de la transfusion de sang. C'est le taux de l'hématocrite avant et au cours de l'intervention qu'il faut prendre en compte. L'observation de cette règle est appelée à réduire considérablement l'emploi du sang au cours de la chirurgie colorectale élective.

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Supported by the Frieda and George Zinberg Foundation and NCI-NIH grant 1 RO1-CA-35558-01.     

Psychosocial Working Conditions Play an Important Role in the Return-to-Work Process After Total Knee and Hip Arthroplasty

Journal of Occupational Rehabilitation - Purpose Both personal and work-related factors affect return to work (RTW) after total knee arthroplasty (TKA) and total hip arthroplasty (THA). Little is...     

Effects of Bovine Colostrum with or without Egg on In Vitro Bacterial-Induced Intestinal Damage with Relevance for SIBO and Infectious Diarrhea

Small intestinal bacterial overgrowth (SIBO) occurs commonly, is difficult to treat, and frequently recurs. Bovine colostrum (BC) and chicken eggs contain immunoglobulins and other components that possess antimicrobial, immunoregulatory, and growth factor activities; however, it is not known if they have the ability to reduce injury caused by the presence of bacteria associated with SIBO (Streptococcus, Escherichia coli, Staphylococcus, Bacteroides, Klebsiella, Enterococcus, and Proteus) and infectious diarrhea (enteropathogenic Escherichia coli, Salmonella). We examined the effects of BC, egg, or the combination, on bacterial growth and bacteria-induced changes in transepithelial electrical resistance (TEER) and bacterial translocation across confluent Caco-2 monolayers. BC, egg, or the combination did not affect bacterial growth. Adding bacteria to monolayers reduced TEER and (with minor variations among species) increased bacterial translocation, increased monolayer apoptosis (increased caspase-3 and Baxα, reduced Bcl2), increased intercellular adhesion molecule 1 (ICAM-1), and reduced cell adhesion molecules zonulin1 (ZO1) and claudin-1. BC, egg, or the combination reduced these effects (all p < 0.01) and caused additional increases in vascular endothelial growth factor (VEGF) and Heat Shock Protein 70 (Hsp70) expression. We conclude that BC ± egg strengthens mucosal integrity against a battery of bacteria relevant for SIBO and for infectious diarrhea. Oral BC ± egg may have clinical value for these conditions, especially SIBO where eradication of precipitating organisms may be difficult to achieve.     

Unhealthy Diet Pattern Mediates the Disproportionate Prevalence of Obesity among Adults with Socio-Economic Disadvantage: An Australian Representative Cross-Sectional Study

The role of unhealthy dietary pattern in the association between socio-economic factors and obesity is unclear. The aim was to examine the association between socio-economic disadvantage and obesity and to assess mediation effect of unhealthy dietary pattern defined using the Mediterranean diet criteria. The data source was the Australian National Nutrition and Physical Activity Survey. The study sample included 7744 participants aged 18 years and over, 28% of whom had obesity. We used the Australian Socio-Economic Indexes for Areas (SEIFA) classification system for categorizing socio-economic disadvantage; calculated the Mediterranean Diet Score (MDS) using standard criteria; and used measured body mass index to define obesity. We conducted a mediation analysis using log–binomial models to generate the prevalence ratio for obesity and the proportion mediated by the MDS. The most disadvantaged group was associated with higher level of obesity after controlling for covariates (1.40, 95% CI 1.25, 1.56) compared to the least disadvantaged group, and in a dose–response way for each decreasing SEIFA quintile. The relationship between socio-economic disadvantage and obesity was mediated by the MDS (4.0%, 95% CI 1.9, 8.0). Public health interventions should promote healthy dietary patterns, such as the Mediterranean diet, to reduce obesity, especially in communities with high socio-economic disadvantage.