A meta-analysis on continuous versus interrupted skin closure following appendicectomy.

BACKGROUND: The aim of this review was to analyse RCTs comparing wound-related outcomes between continuous subcuticular and interrupted transdermal wound closures for open appendicectomies in all age groups. METHODS: A systematic literature search was conducted in April 2020 (MEDLINE, Embase, CENTRAL, Web of Science, PROSPERO, Google Scholar, WHO International Clinical Trials Registry Platform). RCTs without restrictions on study language, year, status of publication, and patient age were included. The risk of bias was assessed using the risk-of-bias tool for RCTs. Pooled risk ratios (RRs) and mean differences (MDs) for binary and continuous variables were calculated using random-effects models. A summary-of-findings table was generated to assess the level of evidence. RESULTS: Eleven trials were included (1781 patients analysed, 891 in continuous and 890 in interrupted groups). The overall rate of wound infection was 7.1 per cent. There was no significant difference in the risk of wound infection (11 trials, 1781 patients; RR 1.13, 95 per cent c.i. 0.77 to 1.66; P = 0.530) or wound exploration (7 trials, 1129 patients; RR 0.74, 0.41 to 1.34, P = 0.320) between the two groups. Continuous wound closure had a significantly reduced risk of wound dehiscence (6 trials, 865 patients; RR 0.16, 0.05 to 0.50; P = 0.002) and smaller wound scar (3 trials, 417 patients; MD -2.11 (95 per cent c.i. -2.57 to -1.66) mm; P < 0.001). The absolute risk reduction and number needed to treat for wound dehiscence were 6.1 per cent and 16 respectively. There was no significant statistical heterogeneity for all outcomes (I2 0-15 per cent, χ2 P > 0.100). Most RCTs had a high risk of bias. CONCLUSION: Continuous subcuticular open appendicectomy wound closure is not associated with an increased risk of wound infection and exploration. This method of closure has a reduced risk of wound dehiscence and better cosmetic outcomes.

Wound infection after open appendicectomy remains a significant problem around the world. As such, wounds with infection frequently require exploration, leading to poor cosmetic outcomes. This study investigated whether the method of skin closure (continuous versus interrupted) used after this surgery has any bearing on wound-related outcomes, including wound infection. Patient satisfaction, quality of life, cost, and length of hospital stay were also compared between the two common methods of skin closure. Evidence from a multitude of published works in all languages from around the world was analysed. The evidence suggests that continuous skin closure is not associated with an increased risk of infection and wound opening, but has better wound integrity, cosmetic outcome, and patient satisfaction. The length of hospital stay is no different between these two types of wound closure.

Transcranial Doppler Ultrasound Detection of Microemboli as a Predictor of Cerebral Events in Patients with Symptomatic and Asymptomatic Carotid Disease: A Systematic Review and Meta-Analysis.

OBJECTIVE: Identification of patients who will benefit from carotid endarterectomy is not entirely effective, primarily utilising degree of carotid stenosis. This study aimed at determining if microembolic signals (MES) detected by transcranial Doppler ultrasound (TCD) can provide clinically useful information regarding stroke risk in patients with carotid atherosclerosis. METHODS: A meta-analysis of prospective studies was performed. Three analyses were proposed investigating MES detection as a predictor of: stroke or TIA, stroke alone, and stroke or TIA but with an increased positivity threshold. Subgroup analysis was used to compare pre-operative (symptomatic or asymptomatic) patients and peri- or post-operative patients. RESULTS: Twenty-eight studies reported data regarding both MES status and neurological outcome. Of these, 22 papers reported data on stroke and TIA as an outcome, 19 on stroke alone, and eight on stroke and TIA with increased positivity threshold. At the median pre-test probability of 3.0%, the post-test probabilities of a stroke after a positive and negative TCD were 7.1% (95% CI 5-10.1) and 1.2% (95% CI 0.6-2.5), respectively. In addition, the sensitivities and specificities of each outcome showed that increasing the threshold for positivity to 10 MES per hour would make TCD a more clinically useful tool in peri- and post-operative patients. CONCLUSION: TCD provides clinically useful information about stroke risk for patients with carotid disease and is technically feasible in most patients. However, the generally weak level of evidence constituting this review means definitive recommendations cannot be made.

Comparison of VivaSight double-lumen tube with a conventional double-lumen tube in adult patients undergoing video-assisted thoracoscopic surgery.

The efficiency of a double-lumen tube depends on its position in the airways, which can be verified by fibreoptic bronchoscopy. The VivaSight DL is a single-use double-lumen tube with a camera embedded in the tube's right side. The view from the camera appears continuously on a monitor. In this prospective study of 71 adult patients, we compared intubation times using either the VivaSight DL or a conventional double-lumen tube. Median (IQR [range]) duration of intubation with visual confirmation of tube position was significantly reduced using the VivaSight DL compared with the conventional double-lumen tube (51 (42-60 [35-118]) s vs 264 (233-325 [160-490]) s, respectively, p < 0.0001). None of the patients allocated to the VivaSight DL required fibreoptic bronchoscopy during intubation or surgery. The VivaSight DL enables significantly more rapid intubation compared with the conventional double-lumen tube.

Epidemiology and genetic determinants of progressive deterioration of glycaemia in American Indians: the Strong Heart Family Study.

AIMS/HYPOTHESIS: Type 2 diabetes is a chronic, heterogeneous disease and a major risk factor for cardiovascular diseases. The underlying mechanisms leading to progression to type 2 diabetes are not fully understood and genetic tools may help to identify important pathways of glycaemic deterioration. METHODS: Using prospective data on American Indians from the Strong Heart Family Study, we identified 373 individuals defined as progressors (diabetes incident cases), 566 individuals with transitory impaired fasting glucose (IFG) and 1,011 controls (normal fasting glycaemia at all visits). We estimated the heritability (h(2)) of the traits and the evidence for association with 16 known variants identified in type 2 diabetes genome-wide association studies. RESULTS: We noted high h(2) for diabetes progression (h(2) = 0.65 ± 0.16, p = 2.7 × 10(-6)) but little contribution of genetic factors to transitory IFG (h(2) = 0.09 ± 0.10, p = 0.19) for models adjusted for multiple risk factors. At least three variants (in WFS1, TSPAN8 and THADA) were nominally associated with diabetes progression in age- and sex-adjusted analyses with estimates showing the same direction of effects as reported in the discovery European ancestry studies. CONCLUSIONS/INTERPRETATION: Our findings do not exclude these loci for diabetes susceptibility in American Indians and suggest phenotypic heterogeneity of the IFG trait, which may have implications for genetic studies when diagnosis is based on a single time-point measure.

A dual action of saturated fatty acids on electrical activity in rat pancreatic ß-cells. Role of volume-regulated anion channel and KATP channel currents.

Free fatty acids (FFAs) exert complex actions on pancreatic ß-cells. Typically, an initial potentiation of insulin release is followed by a gradual impairment of ß-cell function, the latter effect being of possible relevance to hyperlipidaemia in type 2 diabetes mellitus. The molecular actions of FFAs are poorly understood. The present study investigated the acute effects of saturated FFAs on electrophysiological responses of rat pancreatic ß-cells. Membrane potential and KATP channel activity were recorded using the perforated patch technique. Volume-regulated anion channel (VRAC) activity was assessed from conventional whole-cell recordings. Cell volume regulation was measured using a video-imaging technique. Addition of octanoate caused a transient potentiation of glucose-induced electrical activity, followed by a gradual hyper-polarisation and a prolonged inhibition of electrical activity. Octanoate caused an initial increase in VRAC activity followed by a secondary inhibition coinciding with increased KATP channel activity. Similar effects were observed with palmitate and 2-bromopalmitate whereas butyrate was virtually ineffective. Octanoate and palmitate also exerted a dual effect on electrical activity evoked by tolbutamide. Octanoate significantly attenuated cell volume regulation in hypotonic solutions, consistent with VRAC inhibition. It is concluded that medium and long chain FFAs have a dual action on glucose-induced electrical activity in rat pancreatic ß-cells: an initial stimulatory effect followed by a secondary inhibition. These effects appear to be the result of reciprocal actions on VRAC and KATP channel currents, and could contribute towards the stimulatory and inhibitory actions of FFAs on pancreatic ß-cell function.

Unactivated leukocyte expression of C-reactive protein is minimal and not dependent on rs1205 genotype.

C-reactive protein (CRP), a prominent component of the innate immune system, is implicated in the pathophysiology of many conditions. CRP production primarily occurs in the liver; but contributions from other tissues is unclear. The Genotype-Tissue Expression Portal shows essentially no expression in whole blood and reports in the literature are conflicting. Multiple genomic variants influence serum levels of CRP. We measured CRP mRNA expression in leukocytes and sought to determine if rs1205 genotype influences leukocyte expression. Leukocytes were obtained from 20 women differing by genotype. Quantitative, real-time PCR (RT-qPCR) detected CRP and reference gene (GAPDH) mRNA. Leukocyte expression was calculated by the 2ΔCT method, and against a standard curve. Digital drop PCR was also used to calculate expression ratios. Student's t test and linear regression methods examined possible differences between genotypes. During 32 runs (10 replicates each), the RT-qPCR mean (SD) CRP/GAPDH ratio was 3.39 × 10-4 (SD 1.73 × 10-4) and 3.15 × 10-4 (SD 1.64 × 10-4) for TT and CC genotypes respectively, p = 0.76; and digital drop PCR results were similar. Serum CRP was not significantly different between genotypes, nor correlated with leukocyte expression. CRP is minimally expressed in unactivated leukocytes and this expression is not likely influenced by rs1205 genotype.

Pleural fluid analysis of lung cancer vs benign inflammatory disease patients.

BACKGROUND: Correct diagnosis of pleural effusion (PE) as either benign or malignant is crucial, although conventional cytological evaluation is of limited diagnostic accuracy, with relatively low sensitivity rates. METHODS: We identified biological markers accurately detected in a simple PE examination. We analysed data from 19 patients diagnosed with lung cancer (nine adeno-Ca, five non-small-cell Ca (not specified), four squamous-cell Ca, one large-cell Ca) and 22 patients with benign inflammatory pathologies: secondary to trauma, pneumonia or TB. RESULTS: Pleural effusion concentrations of seven analysed biological markers were significantly lower in lung cancer patients than in benign inflammatory patients, especially in matrix metalloproteinase (MMP)-9, MMP-3 and CycD1 (lower by 65% (P<0.000003), 40% (P<0.0007) and 34% (P<0.0001), respectively), and in Ki67, ImAnOx, carbonyls and p27. High rates of sensitivity and specificity values were found for MMP-9, MMP-3 and CycD1: 80 and 100%; 87 and 73%; and 87 and 82%, respectively. CONCLUSION: Although our results are of significant merit in both the clinical and pathogenetic aspects of lung cancer, further research aimed at defining the best combination for marker analysis is warranted. The relative simplicity in analysing these markers in any routine hospital laboratory may result in its acceptance as a new diagnostic tool.

Genome-wide linkage scan for plasma high density lipoprotein cholesterol, apolipoprotein A-1 and triglyceride variation among American Indian populations: the Strong Heart Family Study.

BACKGROUND: Recent studies have identified chromosomal regions linked to variation in high density lipoprotein cholesterol (HDL-C), apolipoprotein A-1 (apo A-1) and triglyceride (TG), although results have been inconsistent and previous studies of American Indian populations are limited. OBJECTIVE: In an attempt to localise quantitative trait loci (QTLs) influencing HDL-C, apo A-1 and TG, we conducted genome-wide linkage scans of subjects of the Strong Heart Family Study. METHODS: We implemented analyses in 3484 men and women aged 18 years or older, at three study centres. RESULTS: With adjustment for age, sex and centre, we detected a QTL influencing both HDL-C (logarithm of odds (LOD) = 4.4, genome-wide p = 0.001) and apo A-1 (LOD = 3.2, genome-wide p = 0.020) nearest marker D6S289 at 6p23 in the Arizona sample. Another QTL influencing apo A-1 was found nearest marker D9S287 at 9q22.2 (LOD = 3.0, genome-wide p = 0.033) in the North and South Dakotas. We detected a QTL influencing TG nearest marker D15S153 at 15q22.31 (LOD = 4.5 in the overall sample and LOD = 3.8 in the Dakotas sample, genome-wide p = 0.0044) and when additionally adjusted for waist, current smoking, current alcohol, current oestrogen, lipid treatment, impaired fasting glucose, and diabetes, nearest marker D10S217 at 10q26.2 (LOD = 3.7, genome-wide p = 0.0058) in the Arizona population. CONCLUSIONS: The replication of QTLs in regions of the genome that harbour well known candidate genes suggest that chromosomes 6p, 9q and 15q warrant further investigation with fine mapping for causative polymorphisms in American Indians.

Pyrosequencing assay to rapidly detect clarithromycin resistance mutations in Canadian Helicobacter pylori isolates.

BACKGROUND: Mutations at positions 2142 or 2143 in the twocopy 23S ribosomal RNA gene of Helicobacter pylori are highly predictive of in vitro clarithromycin resistance and failure of clarithromycin-containing treatment regimens. OBJECTIVE: To design an assay to rapidly detect these mutations using rapid polymerase chain reaction and pyrosequencing, a novel method of 'sequencing by synthesis', and to test this assay with a collection of Canadian H pylori isolates. METHODS: Forty-two H pylori isolates (24 clarithromycin-resistant, 18 clarithromycin-susceptible) were studied. A target region in the 23S gene was rapidly amplified and sequenced by pyrosequencing. RESULTS: Mutations at one of the two positions studied were present in 20 of the 24 (83%) clarithromycin-resistant isolates; 13 had double- copy A2143G mutations, four had double-copy A2142G mutations and three had single-copy A2143G mutations. There were no mutations in 17 of the 18 (94%) susceptible isolates. A single-copy A2142G mutation was detected in one susceptible isolate. CONCLUSIONS: The pyrosequencing assay developed was able to detect and differentiate mutations at positions 2142 and 2143 in either one or both copies of the H pylori 23S ribosdomal RNA gene. Further study is needed to determine whether this pyrosequencing assay can be used to determine H pylori susceptibility to clarithromycin from clinical specimens such as stools or gastric biopsies.

The role of RAP1 in the regulation of the MAT alpha locus.

The RAP1 gene of Saccharomyces cerevisiae encodes an abundant DNA-binding protein, also known as GRF1, TBA, or TUF, that binds to many sites in the yeast genome in vitro. These sites define a consensus sequence, [sequence: see text], and deletion analyses of genes that contain this sequence have implicated the involvement of RAP1 in numerous cellular processes, including gene activation and repression. The MAT alpha locus, required for determination of the alpha cell type in yeast cells, contains a RAP1 binding site; this site coincides with the MAT alpha upstream activating sequence (UAS) and is necessary for expression of the two genes encoded by the MAT alpha locus, MAT alpha 1 and MAT alpha 2. We show that the MAT alpha UAS is sufficient to activate transcription from a promoterless gene fusion of the yeast CYC1 upstream region and the lacZ gene. Constructs containing only the MAT alpha UAS generated elevated levels of beta-galactosidase activity which were indistinguishable from those of constructs containing the entire MAT alpha intergenic region. Further, the MAT alpha UAS has an intrinsic polarity of transcriptional activation; transcription of CYC1-lacZ was six- to sevenfold higher when the UAS was oriented in the direction normally associated with MAT alpha 2 transcription. Point mutations in the MAT alpha UAS that reduce MAT alpha expression three- to fivefold resulted in a bi-mating phenotype, while a mutation that reduced MAT alpha expression still further resulted in an a-mating phenotype. We isolated plasmids from a high-copy-number yeast library that suppressed the bi-mating defect of point mutations in the MAT alpha UAS, and the most effective dosage suppressor contained the gene encoding RAP1. A temperature-sensitive rap1 mutant bi-mates at the semipermissive temperature. Double mutants at rap1 and mat alpha mate exclusively as a cells, at all temperatures, and do not express detectable levels of MAT alpha RNA. These data provide evidence that the RAP1 gene product functions at the MAT alpha UAS in vivo.

Immuno-chemotherapy in metastatic renal cell carcinoma: long-term results from the rambam and linn medical centers, Haifa, Israel.

Nephrectomy, immuno-chemotherapy and resection of residual disease have been the treatment of choice for patients with metastatic renal cell carcinoma during the past decades. The aim of this study was to report the long-term results of this treatment approach. Sixty-two patients with metastatic renal cell carcinoma participated in a Phase II study. At diagnosis, 32 patients had localized disease, 30 had metastatic disease and 53 underwent nephrectomy. Metastatic sites were lungs, lymph nodes, bones and liver. Immuno-chemotherapy consisted of: interleukin-2, interferon alpha, 5-fluorouracil and vinblastine. All patients were evaluated for toxicity and response to treatment. CR was achieved in 4 patients and PR in 14. Seven patients, with maximum response to immuno-chemotherapy underwent resection of residual tumor and reached CR. Therefore, CR was achieved in 11 patients (18%) with a median survival of +67 months. Flu-like symptoms were the common side effects. Performance status and histology type significantly affected survival. Nephrectomy, immuno-chemotherapy and resection of residual disease are recommended for patients with metastatic renal cell carcinoma.

The role of personality in body image dissatisfaction and disordered eating: discrepancies between men and women.

BACKGROUND: Body image and disordered eating research has focused mostly on the female experience. The present study examined gender differences in the relationship between personality, disordered eating, and body image dissatisfaction. METHODS: Participants were 238 female and 85 male undergraduates (Mage = 20.52 years, SD = 4.22) at a Canadian university. Materials included a battery of self-report questionnaires pertaining to personality, body image, and disordered eating. RESULTS: As expected, females reported more body dissatisfaction and disordered eating than males. Personality factors were found to be significantly related to the experience of body dissatisfaction in both genders. Further, several personality traits significantly contributed to the prediction of male (high Neuroticism, low Conscientiousness) and female (high Neuroticism) body dissatisfaction beyond the influence of body mass index (BMI). Interestingly, and contrary to findings with female participants, personality traits were not significantly related to disordered eating scores in men. Among women, disordered eating scores were significantly predicted by high Neuroticism and Extraversion, and low Conscientiousness. CONCLUSIONS: Although the relationship between disordered eating, body image dissatisfaction, and personality is well-documented in females, this relation may differ for males. The focus on male body image has been increasing in Western society; exploring how males view their bodies may be beneficial to researchers and clinicians alike.

Plasminogen activator inhibitor-1 is associated with leukocyte telomere length in American Indians: findings from the Strong Heart Family Study.

Essentials Plasminogen activator inhibitor-1 (PAI-1) advanced cellular senescence in experiment studies. No population study exists on the association between PAI-1 and biological aging in American Indians. We found cross-sectional and longitudinal associations between higher PAI-1 and shorter telomere length. Our findings suggest a pathway linking PAI-1 with biological aging beyond metabolic factors. SUMMARY: Background Plasminogen activator inhibitor-1 (PAI-1) promotes cellular aging both in vitro and in vivo. Telomere length is a marker of biological aging. Objectives To examine the cross-sectional and longitudinal associations between plasma PAI-1 and leukocyte telomere length in a large-scale epidemiological study of American Indians. Methods We measured leukocyte telomere length (LTL) and plasma PAI-1 in 2560 American Indians who were free of overt cardiovascular disease (CVD) and participated in the Strong Heart Family Study (SHFS) clinical examination in 2001-2003. LTL and PAI-1 were repeatedly measured in 475 participants who attended SHFS clinical visits in both 2001-2003 and 1998-1999. A generalized estimating equation model was used to examine the cross-sectional and longitudinal associations between PAI-1 and LTL, adjusting for known risk factors. Results A higher level of plasma PAI-1 was negatively associated with shorter age-adjusted LTL (ß = -0.023; 95% CI, -0.034 to -0.013). This association was attenuated (ß = -0.015; 95% CI, -0.029 to -0.002) after adjustments for demographics, study site, lifestyle (smoking, drinking and physical activity) and metabolic factors (obesity, blood pressure, fasting glucose, insulin, lipids and kidney function). Further adjustment for hsCRP did not change this association (ß = -0.015; 95% CI, -0.029 to -0.001). Longitudinal analysis revealed that change in plasma PAI-1 was also inversely associated with change in LTL after adjusting for demographics, follow-up years, lifestyle factors, changes in metabolic factors, baseline levels of PAI-1 and LTL (ß = -0.0005; 95% CI, -0.0009 to -0.0001). Conclusions A higher level of plasma PAI-1 was associated with shorter LTL in American Indians. This finding may suggest a potential role of PAI-1 in biological aging among American Indians.

Cadmium body burden and increased blood pressure in middle-aged American Indians: the Strong Heart Study.

Cadmium (Cd) is an environmental pollutant that has been associated with cardiovascular disease in populations, but the relationship of Cd with hypertension has been inconsistent. We studied the association between urinary Cd concentrations, a measure of total body burden, and blood pressure in American Indians, a US population with above national average Cd burden. Urinary Cd was measured using inductively coupled plasma mass spectrometry, and adjusted for urinary creatinine concentration. Among 3714 middle-aged American Indian participants of the Strong Heart Study (mean age 56 years, 41% male, 67% ever-smokers, 23% taking antihypertensive medications), urinary Cd ranged from 0.01 to 78.48 µg g-1 creatinine (geometric mean=0.94 µg g-1) and it was correlated with smoking pack-year among ever-smokers (r2=0.16, P<0.0001). Participants who were smokers were on average light-smokers (mean 10.8 pack-years), and urinary Cd was similarly elevated in light- and never-smokers (geometric means of 0.88 µg g-1 creatinine for both categories). Log-transformed urinary Cd was significantly associated with higher systolic blood pressure in models adjusted for age, sex, geographic area, body mass index, smoking (ever vs never, and cumulative pack-years) and kidney function (mean blood pressure difference by lnCd concentration (ß)=1.64, P=0.002). These associations were present among light- and never-smokers (ß=2.03, P=0.002, n=2627), although not significant among never-smokers (ß=1.22, P=0.18, n=1260). Cd was also associated with diastolic blood pressure among light- and never-smokers (ß=0.94, P=0.004). These findings suggest that there is a relationship between Cd body burden and increased blood pressure in American Indians, a population with increased cardiovascular disease risk.

Gene expression and cell proliferation in rat liver after 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure.

Recently 4 genes (plasminogen activator inhibitor 2, interleukin 1 beta, clone 1, and clone 141) that are transcriptionally or posttranscriptionally responsive to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have been cloned from a human skin keratinocyte cell line. We determined whether these genes were expressed in the livers of Sprague-Dawley rats following exposure to TCDD and whether there was a relationship between expression and hepatic cell proliferation. TCDD was administered by using a dose loading/maintenance regimen to achieve rapid quasi-steady-state TCDD liver concentrations of 0.03, 30, or 150 ng/g of liver. Gene expression was determined by Northern analysis using polyadenylated mRNA isolated from liver tissue of male and female animals exposed to TCDD for 1 or 14 days and hybridized with the human complementary DNA clone corresponding to one of the four human TCDD-responsive genes. Under low-stringency hybridization conditions, only the expression of clone 1 could be detected. A dose- and time-dependent expression of this gene was observed in the liver of both male and female rats. Expression of clone 1 was not detected in rats subjected to either a two-thirds partial hepatectomy or exposure to a single administration of the hepatic tumor promoters Wy-14643, carbon tetrachloride, or phenobarbital at doses that induce hepatic cell proliferation. Liver:body weight ratios were elevated in rats exposed to the middle and high TCDD doses. Histopathological observation and analysis of serum enzyme levels indicated no evidence of TCDD-induced liver necrosis. Cell proliferation was evaluated immunohistochemically after 7-day 5-bromo-2'-deoxyuridine administration. No increase in total hepatic labeling index was observed for any of the TCDD-exposed treatment groups compared to controls at week 1 or week 2. An increase in the periportal hepatocyte proliferation labeling pattern was observed in TCDD-treated animals. While these results demonstrate that a human TCDD-responsive gene is expressed in the liver of TCDD-treated male and female Sprague-Dawley rats, the expression of this gene is not linked to hepatic cell proliferation or the sex-specific tumor-promoting activity of TCDD.

Glucose-sensitive conductances in rat pancreatic beta-cells: contribution to electrical activity.

The perforated patch technique was used to assess the relative contribution of K(ATP) channel activity, assessed from input conductance (G(input)), and volume-sensitive anion channel activity to the induction of electrical activity in single isolated rat pancreatic beta-cells by glucose, 2-ketoisocaproate and tolbutamide. In cells equilibrated in the absence of glucose, the membrane potential was -71 mV and G(input) 3.66 nS. Addition of 8 mM glucose resulted in depolarisation, electrical activity and a reduction in G(input), reflecting an inhibition of K(ATP) channels. Cells equilibrated in 4 mM glucose had a membrane potential of -59 mV and a G(input) of 0.88 nS. In this case, a rise in glucose concentration to 8-20 mM again resulted in depolarisation and electrical activity, but caused a small increase in G(input). 2-Ketoisocaproate also evoked electrical activity and an increase in G(input), whereas electrical activity elicited by addition of tolbutamide was accompanied by reduced G(input). Increasing the concentration of glucose from 4 to 8-20 mM generated a noisy inward current at -70 mV, reflecting activation of the volume-sensitive anion channel. The mean amplitude of this current was glucose-dependent within the range 4-20 mM. Addition of 2-ketoisocaproate or a 15% hypotonic solution elicited similar increases in inward current. In contrast, addition of tolbutamide failed to induce the inward current. It is concluded that K(ATP) channel activity is most sensitive to glucose within the range 0-4 mM. At higher glucose concentrations effective in generating electrical activity, activation of the volume-sensitive anion channel could contribute towards the nutrient-induced increase in G(input).

Cell-attached recordings of the volume-sensitive anion channel in rat pancreatic beta-cells.

The cell-attached configuration of the patch-clamp technique was used to study the volume-sensitive anion conductance in isolated rat pancreatic beta-cells at the single-channel level. In unstimulated cells, current level was close to zero. Exposure of cells to a 33% hypotonic solution resulted in the generation of an inward current at 0 mV pipette potential. A similar inward current was elicited by a rise in glucose concentration or by addition of alpha-ketoisocaproate. In contrast, the sulphonylurea tolbutamide was ineffective. The inward current evoked by hypotonic solutions consisted of occasional discreet channel events interspersed with periods of current noise which could not be clearly resolved into unitary channel events. Stimulation with glucose resulted in a predominantly noisy pattern of current. With a reduced [Cl(-)] pipette solution, regular channel openings could be resolved in the presence of a stimulatory glucose concentration, with a calculated conductance of 215 pS. Channel activity could also be recorded in excised inside-out patches, though rapid 'rundown' occurred under such conditions. It is concluded that hypotonic solutions and glucose activate the volume-sensitive anion channel in the cell-attached configuration by increasing channel open probability. This generates an inward current in non-voltage-clamped cells. The channel showed complex kinetics which depended in part upon extracellular [Cl(-)].

Phosphatidylinositol and phosphatidic acid metabolism in rat pancreatic islets in response to neurotransmitter and hormonal stimuli.

Carbamylcholine produced a concentration-dependent stimulation of labelling of phosphatidylinositol and phosphatidic acid in rat islets of Langerhans following preincubation with 32PO43(-). The time course of these effects suggested that the initial action of carbamylcholine was to stimulate phosphatidic acid production, presumably by causing hydrolysis of phosphatidylinositol. This conclusion was substantiated by experiments in which islet phospholipids were pre-labelled with [3H]arachidonic acid. Under these conditions, carbamylcholine caused a loss of radioactivity from phosphatidylinositol, together with an increase in labelling of phosphatidic acid. The effects of carbamylcholine on islet phospholipid labelling were not dependent upon the presence of added Ca2+, but were abolished by EDTA and by atropine. An apparent stimulation of phosphatidylinositol and phosphatidic acid metabolism was also induced by cholecystokinin-pancreozymin, whereas glucagon, arginine, glibenclamide and thyrotropin had no significant effect. The data suggest that enhanced activity of the so-called phosphatidylinositol cycle may be an important event in regulating secretory activity of islets in response to certain neurotransmitter and hormonal stimuli. Furthermore, the results are compatible with the hypothesis that increased phospholipid metabolism may play a role in the modulation of ionic fluxes during stimulation by such agents.