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Biomedical subjects

R Villegas

Publications and source records attributed to R Villegas.

At least 19 recordsLinked to original sources
PubMed2005

Pediatric renal transplantation: 13 years of experience--report from the Chilean Cooperative Multicenter Group.

Between 1989 and 2002, 178 renal transplants were performed in 168 pediatric patients in Chile. The mean age was 10.9 +/- 3.7 years (range 1 to 17.9). End-state renal disease etiologies were: congenital renal hypoplasia/dysplasia, chronic glomerulonephritis, and reflux nephropathy. Seventy received a graft from a living donor (LD), and 108 from a cadaveric donor (CD). Only 9% received antibody induction. Acute rejection episodes were reported in 76 patients: 38% in LD recipients and 48% in CD recipients (P = NS). One-, 3-, and 5-year graft survivals were 88%, 84%, and 76%, respectively, for LD and 86%, 79%, and 68% for CD recipients. Actuarial graft survival was significantly better among those patients with serum creatinine < 1 mg/dL at 1 year posttransplant compared with those with creatinine > 1 mg/dL (P < .05). The graft survival rate has improved from the first period (1989 to 1996) to the second period (1997 to 2002); (P = .05). Patient survival rates at 1, 3, and 5 years were 98%, 98%, and 98%, respectively, for LD, and 95%, 94%, and 94% for CD. Global height/age Z-score decreased from -0.7 at birth to -1.5 when dialysis started, and to -2.4 at the time of transplantation. The Z-score height/age at 1, 3, and 5 years posttransplantation was -2.25, -2.24, and -2.5. No significant differences were observed in transplant outcomes comparing patients younger than 7 years with those older ones. In conclusion, pediatric renal transplant has been performed in Chile with acceptable morbidity. The patient and graft survivals are similar to the reported international experience. In the last period there was a significant improvement in graft survival.

Adolescent↗
PubMed2005

Comparison of cyclosporine concentrations 2 hours post-dose determined using 3 different methods and trough level in pediatric renal transplantation.

Immunosuppression has been one of the great challenges in pediatric recipients of kidney allografts. Cyclosporine (CsA) has evolved during the past 25 years of transplantation. It requires frequent blood level monitoring because of its narrow therapeutic window and interpatient and intrapatient variability. Neoral (Novartis) is no exception. Ideally, monitoring of blood levels should also include determination of the area under the time-concentration curve (AUC) to better target the therapeutic window, thus avoiding underdosing or overdosing, especially in pediatric patients. A single blood concentration measurement 2 hours after Neoral administration (C2) has been shown to be a more for accurate predictor of drug exposure than trough levels (C0). Therefore, its use may lead to reduction in the incidence and severity of cellular rejection and of CsA toxicity. Some studies have shown that the metabolites/CsA ratio is substantially lower using C2 than C0, however, the between-assay differences for C2 monitoring have not been considered. The purpose of this study was to evaluate CsA C0 and C2 levels, determined using monoclonal fluorescence polarization immunoassay (FPIA)/TDx and enzyme multiplied immunoassay (EMIT). CsA levels were determined using a radioimmunoassay (RIA) in 30 pediatric transplant recipients with stable renal function within 42.7 mean months follow-up. Mean age was 13.4 years; 15 children were girls; 23 patients were recipients of cadaveric kidneys. The mean CsA microemulsion dose was 5.7 mg/kg/d. The 3 methods showed a high correlation between C0 and C2 (r > or = 0.97). A linear regression slope was significantly higher for C0 than C2 (P < .001). The CsA concentrations both at C0 and C2 were significantly higher with FPIA than with RIA (P < .009) but no differences were found for EMITT (P = .2). The mean C0 level for FPIA was 22% and 26% higher than RIA and EMIT, respectively. The mean C2, for FPIA was 7% and 12% higher than RIA and EMIT, respectively. In conclusion, CsA levels determined using RIA or EMIT are better than using FPIA/Tx; also, C2 CsA levels are more accurate than C0 in pediatric transplantation patients.

Area Under Curve↗
PubMed2005

Clustering of protective factors for glucose intolerance and insulin resistance: a cross-sectional study.

AIMS: A cluster of interrelated factors: a body mass index (BMI) < 25 kg/m(2), moderate exercise and alcohol intake, non-smoking and a favourable dietary pattern has been linked with markedly reduced risk of Type 2 diabetes. The aim of this study was to estimate the prevalence of a similar low-risk group in a sample of middle-aged Irish men and women, and determine whether this cluster is associated with a reduced risk of glucose intolerance (IFG and Type 2 diabetes according to ADA/WHO criteria) and insulin resistance [homeostasis model assessment (HOMA) score in upper quartile of distribution]. METHODS: A cross-sectional study involving a stratified random sample of 1018 general practice patients, aged 50-69 years. We defined a low-risk group based on the following variables: BMI < 25 kg/m(2); waist-hip ratio < 0.85 for women and 0.90 for men; never smoking status; participation in medium to high level of physical activity; light drinking (3.5-7 units of alcohol per week) and a 'prudent' dietary pattern. Valid data were available for glucose tolerance status and HOMA score and all exposure variables from 684 and 671 participants, respectively. RESULTS: A total of 7.5% of participants had none of the 'protective factors', 24.9% had one, 31.0% two, 23.3% three, 10.0% four, 3.0% five and 0.3% had six protective factors. In multivariate analyses the odds ratios for insulin resistance were 0.59, 0.48, 0.14 and 0.04 in persons with one, two, three and four or more low-risk factors, respectively, relative to those with none. Similar linear inverse trends were observed for glucose intolerance. CONCLUSIONS: The findings are consistent with an inverse linear relation between a cluster of core protective, lifestyle-related factors and the prevalence of both glucose intolerance and insulin resistance.

Aged↗
PubMed2004

A real-time quantitative PCR comparative study between rat optic and sciatic nerves: determination of neuregulin-1 mRNA levels.

Injured axons from peripheral nervous system (PNS) possess the ability to regenerate. In contrast, regeneration of injured axons does not occur in the central nervous system (CNS) or occurs to a limited extent. Previous works have shown that rat sciatic nerve conditioned medium (CM) produced PC12 cells neuronal-like differentiation and neurite outgrowth. In the present work, we compared the expression of neuregulin-1s (NRG-1s) from rat sciatic and optic nerves as members of the PNS and CNS, respectively. Sciatic nerve CM showed a higher neurotrophic activity on PC12 cells than rat optic nerve CM. RT-PCR analysis verified the presence of all three types of NRG-1 mRNAs and their receptors in both types of nerves. Real-time quantitative PCR (QPCR) assays showed that the relative expression levels of all three types of NRG-1 mRNAs were higher in optic nerves than in sciatic nerves. Eleven-day cultured optic nerves showed an increased in NDF and SMDF when compared to freshly isolated optic nerves, whereas GGF decreased. However, 11-day-cultured sciatic nerves only showed an increase in SMDF mRNA. Western blots corroborated the differences in NRG-1 expression profile for both types of nerves and their CMs. Incubation of both CMs with the anti-pan-NRG-1 antibody showed that the neurotrophic activity of the optic nerve CM increased, whereas the sciatic nerve CM remained unchanged. These results indicated that different NRG-1 levels are expressed upon nerve degeneration and the balance between those levels and other neurotrophic factors could have an important role on nerve regeneration.

Animals↗
PubMed2004

Prudent diet and the risk of insulin resistance.

BACKGROUND AND AIM: Diet is a potentially modifiable risk factor for diabetes. Dietary patterns may exert greater effects on health than individual foods, nutrients or food groups. Data on associations between dietary patterns and the risk of insulin resistance and type 2 diabetes are sparse. The aim of the study was to examine associations between dietary patterns and the risk of insulin resistance. METHODS AND RESULTS: We performed a cross sectional study involving a group of 1018 men and women, sampled from 17 general practice lists in the South of Ireland, with a response rate of 69%. Participants completed a detailed health and lifestyle questionnaire and provided fasting blood samples for analysis of glucose, insulin and lipids. Dietary intake was assessed using a food frequency questionnaire. The food frequency questionnaire was a modification of the UK arm of the European Prospective Investigation into cancer, EPIC study, which was based on that used in the US Nurses' Health Study. Dietary patterns were assessed by K cluster analysis. Insulin resistance was estimated on the basis of fasting glucose and insulin, using the glucose homeostasis model (HOMA scores). Insulin resistance was defined as the upper quartile of the HOMA scores. Three dietary patterns were identified by cluster analysis (traditional Irish diet, a prudent diet and an alcohol and convenience foods diet). Participants in clusters 1 (traditional Irish diet) and 3 (high alcohol and convenience foods) had a lower intake of more 'healthy' food groups (such as fruit, vegetables, low fat dairy products, poultry, fish and whole grain products) and higher intake of foods richer in total and SFA content (such as high fat dairy products, butter, meat and meat products). Cluster 2 (prudent dietary pattern) was characterized by a higher intake of food groups that are typically recommended in health promotion programs and a lower intake of meat (read meat), meat products, sweets, high fat dairy and white bread (white bread and unrefined cereal). The prudent diet had the lowest HOMA scores in analysis of covariance. The prevalence of insulin resistance in the prudent diet was lower than that in the traditional diet (OR=0.53; 95%CI, 0.33-0.85 in fully adjusted analysis). CONCLUSION: A prudent diet may be associated with enhanced insulin sensitivity and a lower risk of type 2 diabetes.

Aged↗
PubMed2004

Alcohol intake and insulin resistance. A cross-sectional study.

BACKGROUND AND AIM: The development of insulin resistance is a critical step in the pathogenesis of type 2 diabetes. The effect of alcohol intake on insulin sensitivity/resistance is not well defined. The aim of this study was to examine the association between alcohol intake and insulin resistance in a sample of middle-aged men and women with data on a wide range of potential confounding factors, including diet. METHODS: We performed a cross sectional study involving a group of 1018 men and women, sampled from 17 general practice lists in the South of Ireland, with a response rate of 69%. Participants completed a detailed health and lifestyle questionnaire and a food frequency questionnaire and provided fasting blood samples for analysis of glucose and insulin. Insulin resistance was estimated on the basis of fasting glucose and insulin, using the glucose homeostasis model (HOMA scores). Insulin resistance was defined as the upper quartile of the HOMA scores. RESULTS: We found evidence of a U-shaped relationship between alcohol intake and insulin resistance fitted as a continuous variable (HOMA scores) with lowest levels in light drinkers (between 0.5 to 0.99 units per day) relative to the other drinking categories. However no significant association between alcohol intake and HOMA score was observed in fully adjusted analyses, including adjustment for dietary saturated fat and fruit and vegetables intake. In logistic regression analysis with insulin resistance (categorical) as the dependent variable, we observed that ex-drinkers were at higher risk of insulin resistance compared to occasional drinkers independently of age, sex, BMI and waist circumference, (OR=2.4, 95% CI, 1.1-5.7, p=0.04). On further adjustment for potential confounders including diet this association was also attenuated and was non-significant. CONCLUSIONS: The reported effects of alcohol intake on insulin resistance may be confounded by other aspects of lifestyle, especially diet.

Alcohol Drinking↗
PubMed2004

Dietary patterns in middle-aged Irish men and women defined by cluster analysis.

OBJECTIVES: To identify and characterise dietary patterns in a middle-aged Irish population sample and study associations between these patterns, sociodemographic and anthropometric variables and major risk factors for cardiovascular disease. DESIGN: A cross-sectional study. SUBJECTS AND METHODS: A group of 1473 men and women were sampled from 17 general practice lists in the South of Ireland. A total of 1018 attended for screening, with a response rate of 69%. Participants completed a detailed health and lifestyle questionnaire and provided a fasting blood sample for glucose, lipids and homocysteine. Dietary intake was assessed using a standard food-frequency questionnaire adapted for use in the Irish population. The food-frequency questionnaire was a modification of that used in the UK arm of the European Prospective Investigation into Cancer study, which was based on that used in the US Nurses' Health Study. Dietary patterns were assessed primarily by K-means cluster analysis, following initial principal components analysis to identify the seeds. RESULTS: Three dietary patterns were identified. These clusters corresponded to a traditional Irish diet, a prudent diet and a diet characterised by high consumption of alcoholic drinks and convenience foods. Cluster 1 (Traditional Diet) had the highest intakes of saturated fat (SFA), monounsaturated fat (MUFA) and percentage of total energy from fat, and the lowest polyunsaturated fat (PUFA) intake and ratio of polyunsaturated to saturated fat (P:S). Cluster 2 (Prudent Diet) was characterised by significantly higher intakes of fibre, PUFA, P:S ratio and antioxidant vitamins (vitamins C and E), and lower intakes of total fat, MUFA, SFA and cholesterol. Cluster 3 (Alcohol & Convenience Foods) had the highest intakes of alcohol, protein, cholesterol, vitamin B(12), vitamin B(6), folate, iron, phosphorus, selenium and zinc, and the lowest intakes of PUFA, vitamin A and antioxidant vitamins (vitamins C and E). There were significant differences between clusters in gender distribution, smoking status, physical activity, body mass index, waist circumference and serum homocysteine concentrations. CONCLUSION: In this general population sample, cluster analysis methods yielded two major dietary patterns: prudent and traditional. The prudent dietary pattern is associated with other health-seeking behaviours. Study of dietary patterns will help elucidate links between diet and disease and contribute to the development of healthy eating guidelines for health promotion.

Alcohol Drinking↗
PubMed2001

Ionic currents in PC12 cells differentiated into neuron-like cells by a cultured-sciatic nerve conditioned medium.

The present work deals with the identification of the ionic currents found in PC12 cells differentiated into neuron-like cells by a 9-11-day cultured-sciatic nerve conditioned medium (CM). PC12 whole-cell currents were measured after chronic exposure to CM. The results obtained in these CM-treated cells reveal that the functional expression of Ca(2+) currents is increased, that Na+ currents are not affected, and that a transient K+ current and a K+ delayed rectifier (K+ dr) current are increased. The combination of nifedipine and omega-conotoxin GVIA (omega-CgTX) does not block completely the increased functional expression of the Ca(2+) current. The remaining current is blocked by omega-agatoxin TK indicating that P/Q-type channels are additionally contributing to the increase in Ca(2+) current. NGF-treated PC12 cells, used as positive controls, confirm that NGF increases the expression of voltage-dependent Na+ currents and of Ca(2+) currents. In addition, we found that NGF also increases a K+ dr-type current in these cells. The results obtained with the CM might be due to a molecule or a mixture of molecules released into the medium by the 9-11-day cultured sciatic nerves.

Animals↗
PubMed2001

Vertical dimension. Part 1: comparison of clinical freeway space.

This study was conducted in order to compare the clinical freeway space measurements using three simple methods commonly used by dentists in their practices. The study was performed in 15 young healthy subjects with natural dentition and bilateral molar support. Artificial landmarks (adhesive tape) were placed on the more prominent parts of the nose and chin of each subject. Vertical dimension of occlusion (VDO) was measured in the intercuspal position. Postural vertical dimension (PVD) was measured in the following functional conditions: after swallowing saliva, after pronouncing the word "Mississippi", and in a relaxed postural mandibular position (RPMP). Then, the clinical freeway space value in each functional condition was obtained by subtracting VDO from PVD value. Significant differences among clinical freeway space values using three different methods were observed (ANOVA). A significantly higher clinical freeway space value was found using phonetics method than after swallowing and with the mandible in a relaxed postural position (Bonferroni multiple comparison test). No significant differences between swallowing and relaxed methods were found. These results seem to suggest that the measures of clinical freeway space depend upon the method used.

Adult↗
PubMed2000

A second locus for an axonal form of autosomal recessive Charcot-Marie-Tooth disease maps to chromosome 19q13.3.

Autosomal recessive Charcot-Marie-Tooth disease (CMT) represents a heterogeneous group of disorders affecting the peripheral nervous system. The axonal form of the disease is designated as "CMT type 2" (CMT2), and one locus (1q21.2-q21.3) has been reported for the autosomal recessive form. Here we report the results of a genomewide search in an inbred Costa Rican family (CR-1) affected with autosomal recessive CMT2. By analyzing three branches of the family we detected linkage to the 19q13.3 region, and subsequent homozygosity mapping defined shared haplotypes between markers D19S902 and D19S907 in a 5.5-cM range. A maximum two-point LOD score of 9.08 was obtained for marker D19S867, at a recombination fraction of.00, which strongly supports linkage to this locus. The epithelial membrane protein 3 gene, encoding a PMP22 homologous protein and located on 19q13.3, was ruled out as being responsible for this form of CMT. The age at onset of chronic symmetric sensory-motor polyneuropathy was 28-42 years (mean 33.8 years); the electrophysiological data clearly reflect an axonal degenerative process. The phenotype and locus are different from those of demyelinating CMT4F, recently mapped to 19q13.1-13.3; hence, the disease affecting the Costa Rican family constitutes an axonal, autosomal recessive CMT subtype (ARCMT2B).

Adult↗
PubMed2000

Neuregulin found in cultured-sciatic nerve conditioned medium causes neuronal differentiation of PC12 cells.

The present work deals with the search and identification of the molecule or combination of molecules, present in a medium conditioned by cultured rat-sciatic nerves (CM), able to cause neuronal differentiation of PC12 cells. The molecular mass range of the active fraction, as well as the thermostability and heparin affinity of the active component found in previous work, all characteristics shared with neuregulin (NRG) family members, led us to search for a NRG protein in the CM. Nerves were previously cultured for 8 days and the CM collected every 24 h, the following 3 days. The CM was concentrated (30,000 NMWL) and fractionated by quaternary ammonium chromatography and Cibacron blue affinity chromatography. The most active fraction B1.2 was further characterized by heparin affinity chromatography, size exclusion HPLC, Western blotting and immunoprecipitation. Results reveal abundance of NRG mRNA in the cultured nerves, presence of a 54 kDa NRG protein in the CM that increases along fractionation, and progressive diminution of fraction B1.2 differentiation activity on PC12 cells by gradual removal of the NRG protein by immunoprecipitation. The abundance of Schwann cells and the lack of axons in the cultured nerves suggest Schwann cells as the main NRG source, to which fibroblasts and perineurial cells might contribute.

Animals↗
PubMed2000

Effects of head and neck inclination on bilateral sternocleidomastoid EMG activity in healthy subjects and in patients with myogenic cranio-cervical-mandibular dysfunction.

This study was conducted in order to determine the effect of head and neck position on bilateral electromyographic (EMG) activity of the sternocleidomastoid muscles. The study was performed on 16 patients with myogenic cranio-cervical-mandibular dysfunction (CMD) and 16 healthy subjects. EMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing surface electrodes on the right and left sternocleidomastoid muscles. EMG activity was recorded in the left lateral decubitus position, in a darkened room and with the individual's eyes closed, under the following experimental conditions: 1. Head, neck, and body horizontally aligned; 2. Head and neck upwardly inclined with respect to the body, simulating the effect of a thick pillow, 3. Head and neck downwardly inclined with respect to the body, simulating the effect of a thin pillow. Variation of head and neck positions was determined by measuring the distance from the angle of neck and shoulder and the apex of the shoulder (SND = shoulder-neck distance) of each individual. Then, head and neck were forward or downwardly inclined with respect to the body at one-third of SND. A significantly higher contralateral EMG activity and a more asymmetric EMG activity were observed in the CMD group than in the healthy subjects (Kruskal-Wallis Test). These results suggest a different behavior of bilateral sternocleidomastoid EMG activity in CMD patients than in healthy subjects depending on the positioning of the head and neck.

Adult↗
PubMed1999

[Angioplasty in acute myocardial infarction. Early and late results].

BACKGROUND: The usefulness of angioplasty in the first hours of an acute myocardial infarction is widely demonstrated. However, its long term effects are less well known. AIM: To report the effects of coronary angioplasty on early and late outcome of patients with acute myocardial infarction. PATIENTS AND METHODS: A non-randomized, consecutive and retrospective analysis of the hospital and late outcome of 70 patients, aged 35 to 85 years, subjected to coronary angioplasty during an acute myocardial infarction. Patients were followed during 12 to 60 months. RESULTS: Angioplasty was performed 5.3 +/- 5 hours after the initial symptoms. Anterior descendent artery was occluded in 63% of patients with a 99.5% luminal occlusion and TIMI 0-1 anterograde flow. An angiographic success was achieved in 83% of procedures with a residual stenosis of 32.3%. Recurrent ischemia was observed in 6% of patients, that were treated with a new revascularization procedure. Thirteen percent of patients died, all due to cardiogenic shock. Severe ventricular failure and failure of revascularization influenced mortality. During the first year of follow up there was a 3.3% mortality and 3.3% of patients required a new revascularization procedure. Eighty percent of patients were asymptomatic and event-free. CONCLUSION: Angioplasty was a useful therapeutic procedure in this group of patients.

Adult↗
PubMed1998

Lectin-binding sites in uterus and oviduct of normal and Campylobacter fetus subspecies venerealis-infected heifers.

This study was carried out to investigate the effect of infection with Campylobacter fetus subsp. venerealis (Cfv) on the pattern of lectin binding in the uterus and oviduct of heifers. Cfv persistence was demonstrated by bacterial isolation and immunofluorescence. Infected animals showed variations in the lectin binding pattern when compared with control animals. Cfv-infected heifers showed an increased expression of galactose and N-acetyl-galactosamine in the endometrial glands (PNA and SBA binding, respectively). The oviductal epithelium of infected heifers was strongly positive for Con A, which indicated the presence of alpha-D-mannose and alpha-D-glucose. The results of this study showed that Cfv-infection modifies the lectin binding pattern in the reproductive system of heifers. Modifications in glycoconjugates may be involved in failures of fertility and/or implantation.

Animals↗
PubMed1995

Neuronal differentiation of PC12 and chick embryo ganglion cells induced by a sciatic nerve conditioned medium: characterization of the neurotrophic activity.

The present work deals with the finding and characterization of a neurotrophic factor present in serum-free Dulbecco's modified Eagle's medium in which rat sciatic nerves previously cultured for 9 days were maintained for 24 h. This sciatic nerve conditioned medium (SNCM) produced neuronal differentiation and neurite outgrowth on PC12 cells, as well as survival and differentiation of eight-day old chick embryo dorsal root ganglion (E8-DRG) and ciliary ganglion (E8-CG) neurons. SNCM activity was decreased by dilution, heating and trypsin treatment; it was not inhibited by anti-NGF and anti-bFGF antibodies; and it was not mimicked by CNTF, laminin and fibronectin. By utilizing its neurite-promoting activity on PC12 cells, experiments oriented to purify the factor were carried out. Ultrafiltration, heparin-affinity chromatography and size-exclusion high pressure liquid chromatography (HPLC) were employed. The ability of SNCM to induce PC12 cell, E8-DRG and E8-CG neuronal differentiation, the heparin affinity of the active SNCM protein, and the size-exclusion HPLC elution characteristics of the active protein suggest that the active component of the SNCM is, in all probability, a novel sciatic nerve neurotrophic factor (SNTF).

Animals↗
PubMed1994

Expression of sodium channels with different saxitoxin affinity during rat forebrain development.

This work characterizes the development of the saxitoxin (STX)-sensitive Na+ channels from rat whole forebrain between embryonic day 15 (E15) and postnatal day 90 (P90), both with binding studies and with single channel studies. The Na+ channel total mRNA and the individual mRNAs encoding Na+ channels I, II and III were also determined. The total STX binding rose about 40-fold from E15 to reach a plateau at P30 and its temporal course correlated with the expression of Na+ channel total mRNA. Low affinity and high-affinity STX binding sites, predominant in embryonic and postnatal forebrains, respectively, were found. The single channel studies of batrachotoxin-modified channels also revealed two main populations. In E15 only low-affinity channels (KD = 32.7 nM; 200 mM NaCl) and in P30 only high affinity ones (KD = 1.6 nM) were present. At P0 channels with intermediate affinity (KD range 3-34 nM) were observed. The increase in affinity was due to a gradual increase in the STX association rate.

Animals↗
PubMed1992

Reconstitution of sodium channels in large liposomes formed by the addition of acidic phospholipids and freeze-thaw sonication.

Phosphatidylcholine (PC) alone or with phosphatidylethanolamine (PE) are sufficient for the reconstitution of Na+ channels in planar lipid bilayers. However, when Na+ channels were first reconstituted into liposomes using the freeze-thaw-sonication method, addition of acidic phospholipids, such as phosphatidylserine (PS), to the neutral phospholipids was necessary to obtain a significant toxin-modulated 22Na uptake. To further investigate the acidic phospholipid effect on reconstitution into liposomes, Na+ channels purified from Electrophorus electricus electrocytes were reconstituted into liposomes of different composition by freeze-thaw sonication and the effect of batrachotoxin and tetrodotoxin on the 22Na flux was measured. The results revealed that, under our experimental conditions, the presence of an acidic phospholipid was also necessary to obtain a significant neurotoxin-modulated 22Na influx. Though neurotoxin-modulated 22Na fluxes have been reported in proteoliposomes made with purified Na+ channels and PC alone, the 22Na fluxes were smaller than those found using lipid mixtures containing acidic phospholipids. Electron microscopy of negatively stained proteoliposomes prepared with PC, PC/PS (1:1 molar ratio), and PS revealed that the acidic phospholipid increases the size of the reconstituted proteoliposomes. The increment in size caused by the acidic phospholipid, due to the associated increase in internal volume for 22Na uptake and in area for Na+ channel incorporation, appears to be responsible for the large neurotoxin-modulated 22Na fluxes observed.

Animals↗