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Biomedical subjects

D Silva

Publications and source records attributed to D Silva.

At least 19 recordsLinked to original sources
PubMed2006

Steroids and bone density in patients with functioning kidney allografts.

INTRODUCTION: Osteopenia and osteoporosis after renal transplantation have been associated with factors related to the cause of end-stage renal disease, as well as to clinical events and therapeutic factors in the posttransplant period. We studied the prevalence of low bone density (LBD) according to WHO criteria. METHODS: A cross-sectional study was performed in a cohort of 106 patients (54 men and 52 women) with functioning renal allografts, who underwent bone densitometry (DEXA) of the lumbar spine and femoral neck. Patients were grouped according to DEXA into those with normal bone density (NBD) or LBD. We studied clinical, analytical, and therapeutic variables. RESULTS: Thirtysix patients (34%) had NBD and 70 patients (66%) LBD. Weight was the only parameter showing a significant difference (P = .034), namely, among NBD it was 80.44+/-15.13 versus LBD 73.94 +/- 14.54 kg, respectively. Creatinine clearance (CCr) tended to be lower among patients with LBD 59.62 +/- 22.73 versus 69.59 +/- 28.15 mL/min in patients with NBD (P = .052). PTHi levels were higher in patients with LBD (149.39 +/- 110.75) than those with NBD (110.94 +/- 82.61) (P = .069). In the multivariate analysis the important determinants were weight Exp(ss) = 0.967 [CI = 0.939 to 0.996] (P = .036); CCr Exp(ss) = 0.982 [CI = 0.965 to 1.000] (P = .055); and PTHi levels Exp(ss) = 1.003 [CI = 0.932 to 0.994] (P = .059). CONCLUSIONS: Osteopenia and osteoporosis are frequent among kidney transplant patients (66%), with a similar distribution between the lumbar spine and femoral neck. Excess weight and possibly better renal function may be protective factors. The cumulative steroid dose showed a significant effect on bone density. As expected, secondary hyperparathyroidism in patients with renal impairment seemed to be a risk factor for LBD.

Absorptiometry, Photon↗
PubMed2004

Quenching of the intrinsic fluorescence of bovine serum albumin by chlorpromazine and hemin.

The binding of chlorpromazine (CPZ) and hemin to bovine serum albumin was studied by the fluorescence quenching technique. CPZ is a widely used anti-psychotic drug that interacts with blood components, influences bioavailability, and affects function of several biomolecules. Hemin is an important ferric residue of hemoglobin that binds within the hydrophobic region of albumin with high specificity. Quenching of the intrinsic fluorescence of bovine serum albumin (BSA) was observed by selectively exciting tryptophan residues at 290 nm. Emission spectra were recorded in the range from 300 to 450 nm for each quencher addition. Stern-Volmer graphs were plotted, and the quenching constant estimated for BSA solution titrated with hemin at 25 masculine C was 1.44 (+/- 0.05) x 10(5) M(-1). Results showed that bovine albumin tryptophans are not equally accessible to CPZ, in agreement with the idea that polar or charged quenchers have more affinity for amino acid residues on the outer wall of the protein. Hemin added to albumin solution at a molar ratio of 1:1 quenched about 25% of their fluorescence. The quenching effect of CPZ on albumin-hemin solution was stronger than on pure BSA. This increase can be the result of combined conformational changes in the structure of albumin caused firstly by hemin and then by CPZ. Our results suggest that the primary binding site for hemin on bovine albumin may be located asymmetrically between the two tryptophans along the sequence formed by subdomains IB and IIA, closer to tryptophan residue 212.

Animals↗
PubMed2004

Development of a nasal vaccine for chronic hepatitis B infection that uses the ability of hepatitis B core antigen to stimulate a strong Th1 response against hepatitis B surface antigen.

There are estimated to be 350 million chronic carriers of hepatitis B infection worldwide. Patients with chronic hepatitis B are at risk of liver cirrhosis with associated mortality because of hepatocellular carcinoma and other complications. An important goal, therefore, is the development of an effective therapeutic vaccine against chronic hepatitis B virus (HBV). A major barrier to the development of such a vaccine is the impaired immune response to HBV antigens observed in the T cells of affected patients. One strategy to overcome these barriers is to activate mucosal T cells through the use of nasal vaccination because this may overcome the systemic immune downregulation that results from HBV infection. In addition, it may be beneficial to present additional HBV epitopes beyond those contained in the traditional hepatitis B surface antigen (HbsAg) vaccine, for example, by using the hepatitis B core antigen (HBcAg). This is advantageous because HBcAg has a unique ability to act as a potent Th1 adjuvant to HbsAg, while also serving as an immunogenic target. In this study we describe the effect of coadministration of HBsAg and HBcAg as part of a strategy to develop a more potent and effective HBV therapeutic vaccine.

Administration, Intranasal↗
PubMed2004

Systematic genome-wide approach to positional candidate cloning for identification of novel human disease genes.

BACKGROUND: Recent large-scale genome projects afford a unique opportunity to identify many novel disease genes and thereby better understand the genetic basis of human disease. Functional Annotation of Mouse (FANTOM) 2, the largest mouse transcriptome project yet, provides a wealth of data on novel genes, splice variants and non-coding RNA, and provides a unique opportunity to identify novel human disease genes. AIMS: To demonstrate the power of combining the FANTOM 2 cDNA dataset with a positional candidate approach and bioinformatics analysis to identify genes underlying human genetic disease. RESULTS: By mapping all FANTOM 2 cDNA to the human genome, we were able to identify mouse clones that co-localised on the human genome with mapped but uncloned human disease loci. By this method we identified mouse and corresponding human genes mapping within the loci of 100 different human genetic diseases (mapped interval of <5 cM). Of particular interest was the elucidation through FANTOM 2 novel mouse gene data of candidate human genes for the following: (i) developmental -disorders: neural tube defect, Meckel syndrome, Wolf--Hirschhorn syndrome and keratosis follicularis spinulosa decalvans cum ophiasi; (ii) neurological disorders: benign familial infantile convulsions 3, early-onset cerebellar ataxia with retained tendon reflexes, infantile-onset spinocerebellar ataxia and vacuolar neuro-myopathy and (iii) cancer-related syndromes: tylosis with oesophageal cancer and low-grade B-cell chronic lymphatic leukaemia. CONCLUSIONS: The FANTOM 2 data will dramatically accelerate efforts to identify genes underlying human disease. It will also facilitate the creation of transgenic mouse models to help elucidate the function of potential human disease genes.

Animals↗
PubMed2003

The role of endoplasmic reticulum stress in nonimmune diabetes: NOD.k iHEL, a novel model of beta cell death.

The final common pathway in diabetes development is beta cell apoptosis. We herein describe a novel diabetes model based on transgenic NOD.k iHEL mice, wherein male mice develop diabetes due to nonimmune-mediated beta cell death. Histology and electron microscopy confirm endoplasmic reticulum (ER) abnormalities that are consistent with endoplasmic stress caused by the HEL transgene. The NOD.k iHEL model may be particularly useful for studying mechanisms of beta cell death secondary to ER stress and also for testing potential therapies designed to protect beta cells from stress-induced apoptosis. The observation that only male NOD.k iHEL mice develop diabetes and exhibit ER abnormalities is intriguing and suggests these mice may be useful in deciphering the link between hyperandrogenism, insulin resistance, and diabetes.

Animals↗
PubMed2002

The role of Fas ligand in beta cell destruction in autoimmune diabetes of NOD mice.

Fas ligand (FasL), a type 2 membrane protein belonging to the TNF family, plays an important role in the induction of cell death. Ligation of Fas receptors by FasL results in apoptosis of the Fas-expressing cell. Autoimmune diabetes results from beta cell destruction by islet-reactive T cells, a process that involves beta cell apoptosis. This raises the question of whether the FasL-Fas pathway plays a major role in beta cell death. To address this issue it is important to know whether beta cells express Fas and/or FasL and, if so, whether induction of these molecules leads to beta cell death. In fact, both Fas and FasL have been demonstrated to be expressed by beta cells in response to cytokine stimulation, although there remains an argument in the literature as to whether beta cells truly express FasL. This is largely because FasL expression has only been demonstrable by immunohistochemistry and not by flow cytometry. Transgenic NOD mice with beta cells expressing a FasL transgene develop an accelerated form of diabetes. We show here that beta cells from FasL transgenic NOD mice are more susceptible to cytokine-induced apoptosis than wild-type beta cells, consistent with the hypothesis that if beta cells express FasL then Fas-FasL interaction on the beta cell surface is able to mediate beta cell self-death in the absence of T cells. Interventions that block the Fas-FasL pathway may be useful, therefore, in the prevention or treatment of type 1 diabetes.

Animals↗
PubMed2001

Effects of chronic nicotine and methylphenidate in adults with attention deficit/hyperactivity disorder.

Acute nicotine treatment has been found to reduce symptoms of attention deficit/hyperactivity disorder in adults (E. D. Levin, C. K. Conners, et al., 1996). In this study, chronic nicotine effects were compared with placebo and methylphenidate. Acute and chronic nicotine treatment significantly attenuated the rise in hit reaction time standard error over session blocks on the Conners Continuous Performance Test (C. K. Conners et al., 1996). Acute nicotine significantly reduced severity of clinical symptoms on the Clinical Global Impressions scale (National Institute of Mental Health, 1985). Nicotine caused a significant decrease in self-report of depressive mood as measured by the Profile of Mood States test (D. M. McNair, M. Lorr, & L. F. Droppleman, 1981). This small study (40 participants) provided evidence that nicotine treatment can reduce severity of attentional deficit symptoms and produce improvement on an objective computerized attention task.

Adult↗
PubMed2001

Lipid profile and redox status in high performance rhythmic female teenagers gymnasts.

BACKGROUND: The aim of the present study is to evaluate the lipid profile and some parameters of oxi-redox status in a group of teenage female athletes. All gymnasts of the Portuguese National Team of Rhythmic (n=20) were included in the study. A group of untrained healthy female adolescents, matched for age, was also included (n=28). METHODS: Auxology, nutritional status and body composition were evaluated as well as biological parameters, dietary and training habits. Statistics included descriptive analysis, t-Student and Mann-Whitney for comparative study, and Pearson and Spearman correlations, according to variable distribution. RESULTS: Chronological age was 14.3+/-1.7 and 14.6+/-1,7 years, respectively for gymnasts and untrained adolescents. Gymnasts showed lower body mass index (p<0.001) and fat mass (p<0.001) and also a hypoenergetic diet, with higher supply in protein (p<0.05) and saturated fat (p<0.01). Lipid profile showed higher HDL-cholesterol (p<0.01) and lower apo B values (p<0.001) in gymnasts, compared to untrained. Red blood cell's enzymes studied were higher for transmembrane NADH reductase of ferricyanide (TMR), (p<0.01), methaemoglobin reductase (MetHbRed), (p<0.01), and low-molecular weight protein tyrosine phosphatase (LMW-PTP), (p<0.0001) in untrained adolescents. Susceptibility of LDL to peroxidation (LDL-TBARS) were higher in gymnasts (76.3+/-20.3 microM/l versus 35+/-21.7 microM/l), (p<0.001). Correlations were positive and significant in both gymnasts and untrained, between LDL-TBARS and LDL-cholesterol (r=0.674, p<0.01 and r=0.544, p<0.05 respectively) and apolipoprotein B (r=0.721, p<0.001 and r=0.659, p<0.01, respectively). LDL-TBARS were negative and significatively correlated to TMR (t=-0.608; p<0.01) only in gymnasts. CONCLUSIONS: The authors conclude that the practice of intense physical exercise in rhythmic gymnasts induces a compromise of nutritional status and unbalanced food habits. The intensive exercise also induces not only a protective lipid profile, but also a higher lipid peroxidation. Further prospective studies are important to evaluate the influence of intensive training on atherosclerosis development.

Adolescent↗
PubMed2000

The health and nutritional status of school children in two rural communities in Sri Lanka.

There is growing evidence of considerable burden of morbidity and mortality due to infectious diseases and undernutrition in school children. This study describes the nutritional status and parasitic infections of school children in two areas of rural Sri Lanka. All children in four primary schools in the Moneragala district of Sri Lanka were included in the study. The height and weight of children were measured and anthropometric indices calculated. Stool and blood samples were examined for evidence of intestinal helminthiasis, malaria and anaemia. A greater proportion of boys than girls were underweight, wasted and stunted. Over 80% of the children were anaemic but did not apparently have iron deficiency anaemia according to their blood picture. The prevalence of parasitic infections such as hookworm and Plasmodium spp that may contribute to anaemia was low.

Body Weight↗
PubMed2000

Ascertainment of birth defects: the effect on completeness of adding a new source of data.

BACKGROUND: The Western Australian (WA) Birth Defects Registry aims for complete ascertainment of birth defects in WA, but the proportions of birth defects in rural areas and in Aboriginal children are lower than in metropolitan and non-Aboriginal children. The effect on ascertainment of adding data from the Rural Paediatric Service (RPS) was investigated. METHOD: A file of all cases of birth defects for children born 1980-1997 and recorded on the RPS database was linked to the Registry. RESULTS: The addition of this new data source had little effect on the overall prevalence of birth defects (an increase from 5.38 to 5.41%). There was a slightly greater effect on the prevalence of birth defects in rural residents (4.67%-4.76%) and Aboriginal children (4.55-4.78%), although the prevalence for each of these groups is still less than for metropolitan residents and non-Aboriginal infants, respectively. All major categories of birth defects were represented in the new cases and, in general, their addition made little difference to the prevalence of each category. The exception was fetal alcohol syndrome, which increased from 0.13 per 1000 to 0.18 per 1000 once the 21 new cases from the RPS were added. CONCLUSION: Complete ascertainment of birth defects is important in developing and evaluating preventive programs, and in investigating clusters of birth defects.

Congenital Abnormalities↗
PubMed2000

Importance of zinc in the central nervous system: the zinc-containing neuron.

Zinc is essential to the structure and function of myriad proteins, including regulatory, structural and enzymatic. It is estimated that up to 1% of the human genome codes for zinc finger proteins. In the central nervous system, zinc has an additional role as a neurosecretory product or cofactor. In this role, zinc is highly concentrated in the synaptic vesicles of a specific contingent of neurons, called "zinc-containing" neurons. Zinc-containing neurons are a subset of glutamatergic neurons. The zinc in the vesicles probably exceeds 1 mmol/L in concentration and is only weakly coordinated with any endogenous ligand. Zinc-containing neurons are found almost exclusively in the forebrain, where in mammals they have evolved into a complex and elaborate associational network that interconnects most of the cerebral cortices and limbic structures. Indeed, one of the intriguing aspects of these neurons is that they compose somewhat of a chemospecific "private line" of the mammalian cerebral cortex. The present review outlines (1) the methods used to discover, define and describe zinc-containing neurons; (2) the neuroarchitecture and synaptology of zinc-containing neural circuits; (3) the physiology of regulated vesicular zinc release; (4) the "life cycle" and molecular biology of vesicular zinc; (5) the importance of synaptically released zinc in the normal and pathological processes of the cerebral cortex; and (6) the role of specific and nonspecific stressors in the release of zinc.

Alzheimer Disease↗
PubMed2000

Oral health and hospitalization in Western Australian children.

Over the past 20 years, the prevalence of dental disease in Western Australian children has diminished. The causes of this significant improvement in health are associated with better care models, water fluoridation and changes in lifestyle. In this study, the authors examine the reasons for hospitalization for oral health conditions in Western Australia for the calendar year 1995 using the Health Department of WA database. A total of 3,754 episodes of care (4,395 bed days) was recorded for dental conditions. Dental caries resulted in the fifth and sixth highest number of episodes of hospitalization in preschool (1-4 years) and primary-school age (5-12 years) children respectively. Abnormal tooth eruption resulted in the highest number of episodes of hospitalization in high-school age (13-17 years) children. From the age-stratified rates of hospitalization (per 1000), non-Aboriginal children were more than twice as likely to enter hospital for dental related conditions. The primary cause of this is the 15 times higher rate of hospitalization for high-school age non-Aboriginal children which clearly reflects the greater use of services for impacted third molars by the metropolitan non-Aboriginal community. Examination of the distribution by health service region revealed the hospitalization rate was significantly less than the state average for the Kimberley, Pilbara, Northern Goldfields and Wanneroo regions. These data reflect the paucity of oral health care available to residents of these regions, particularly the northwest, and does not reflect a diminished burden of disease. Similarly, the rate of hospitalization for Aboriginal children reflects population and service delivery differences particularly in regional and remote WA. These data highlight the need to develop new strategies in oral health care to target 'at risk' groups in the community, particularly new parents of young children. The preventive measures associated with good oral health in children are clearly aligned with those for good general health and can be integrated into existing health messages.

Adolescent↗
PubMed2000

Importance of lipoprotein metabolism parameters in the clinical and angiographic severity of coronary artery disease.

Coronary artery disease that is clinically and angiographically significant is associated to important biochemical parameters with direct interference in lipoprotein and apoprotein metabolism. The purpose of our study was to evaluate the importance of several lipoprotein metabolic parameters in the clinical and angiographic severity of chronic coronary artery disease. In a population with the diagnosis of ischemic coronary artery disease, we assessed the degree of angiographic (single- versus multivessel disease) and clinical (C.C.S. I-IV classification) severities. In each patient, we determined the value of total cholesterol, triglycerides, HDL and LDL cholesterol, HDL 2 and 3, apoprotein AI and B, lipoprotein (a), anti-phospholipid antibodies and C reactive protein. Our results showed that some parameters were significant in the comparison between a normal group and the global coronary artery disease population, such as the value of total cholesterol, HDL cholesterol, HDL 2, apoprotein AI and B lipoprotein (a) and anti-phospholipid antibodies. In the distinction of coronary artery disease subgroups, in relation to C.C.S. < or = 2 and > or = 3 classes, some factors could be discriminated, such as HDL cholesterol, HDL 2, total cholesterol/HDL, lipoprotein (a), anti-phospholipid antibodies and C reactive protein. In the distinction between classes C.C.S. < or = 2 and AMI, the levels of triglycerides, HDL cholesterol, HDL 2, total cholesterol/HDL, lipoprotein (a) and anti-phospholipid antibodies were significant. In the division between single vessel versus multivessel coronary artery disease we found significant values of HDL cholesterol, HDL 2, total cholesterol/HDL, apoprotein AI, lipoprotein (a), anti-phospholipid antibodies and C reactive protein. In conclusion, our present study endorses the clinical role of lipids and plasma lipoproteins in the determination of several cardiovascular risk factors, but introduction of new parameters such as lipoprotein (a) and the anti-phospholipid antibodies can be very useful for a better and global understanding of the pathophysiological processes and distinction of higher risk subgroups for extension and degree of severity of ischemic coronary artery disease.

Aged↗
PubMed2000

Acid phosphatase, genetic polymorphism and cardiovascular risk factors in a pediatric population.

BACKGROUND: Although the clinical expression of cardiovascular disease usually occurs in adulthood, it is unanimously accepted that atherosclerosis begins in the pediatric age. Because of the early onset of the disease, it is of great importance to screen for major risk factors since pre-school age, especially in risk families. Recent investigations have shown a great interest not only in studying the classic risk factors, but also in the evaluation of oxidative stress and the main antioxidant defense systems. The major cause of this interest is the knowledge of the deleterious effect of reactive oxygen species on lipids, the endothelial membrane of arteries and, finally, on the occurrence of cardiovascular disease. POPULATION AND METHODS: 51 children of both genders, aged 9-12 years, randomly selected from a rural community, were observed. A possible association between low molecular acid phosphatase genetic polymorphism of the erythrocyte and the prooxidant status markers (epinephrine oxidase and low molecular protein phosphotyrosine phosphatase from the erythrocyte), some enzymatic systems of the body antioxidant defense (transmembranar reductase of ferricyanide and metahemoglobin reductase) and finally some intermediate phenotypes of cardiovascular disease (lipid profile and blood pressure) were studied. RESULTS: The study of prooxidant status markers and antioxidant enzymes shows significant differences for acid phosphatase and epinephrine oxidase activities in relation to low molecular acid phosphatase genetic polymorphism, the highest values observed being in those homozygous to the B allele (p < 0.05). The inter-relation study between variables showed, among other things, a significant inverse correlation between acid phosphatase and transmembrane reductase and a direct correlation between apolipoprotein B, acid phosphatase and metahemoglobin reductase. A positive family history for cardiovascular disease also showed a direct and significant correlation to total cholesterol, LDL-cholesterol and apolipoprotein B. CONCLUSIONS: The polymorphic variants of low molecular acid phosphatase and protein phosphotyrosine phosphatase with greater activity are strongly associated, not with the classic parameters of cardiovascular risk factors, but with oxidative stress indicators, such as low molecular protein phosphotyrosine phosphatase and epinephrine oxidase. Family history indicators of cardiovascular risk are clearly associated, since early ages, to some conventional risk factors, such as lipid profile and blood pressure.

Acid Phosphatase↗
PubMed2000

LDL peroxidation in adolescent female gymnasts.

UNLABELLED: Physical exercise may in vivo promote an increase of free radical formation. Low-density lipoproteins (LDL) are highly susceptible to oxidation, probably because of their high polyunsaturated fatty acid content, since lipid oxidation is an important factor in the genesis and development of atherosclerosis. The aim of the present study is to evaluate the effect in a group of adolescent gymnasts, of intense and regular physical exercise on lipid profile and redox status. POPULATION: All members of the Portuguese National Team of Rhythm Gymnastics (1996) (n = 20). METHODS: 1. Clinical evaluation 1.1 Anthropometric evaluation: weight, height, triceps, biceps, subscapular and supra- and supra-iliac skinfolds. NCHS were used as the standard of reference for weight and height, and Frisancho for the sum of skinfolds; 1.2. Evaluation of nutritional status (Quetelet body mass index) and body composition (Durnin and Siri). 2. Evaluation of biological parameters: a blood sample was collected after 12 hours fasting and 24 hours detraining, to evaluate: 2.1 Lipid profile: total cholesterol, high (HDL) and low (LDL) density lipoproteins, triglycerides, apolipoproteins A1 and B, were measured using internationally recommended laboratory methods; 2.2. Plasma trace elements: zinc, copper and selenium, by atomic absorption; 2.3 Red blood cell enzymes; transmembranar reductase (TMR), metahemoglobin reductase (MethaHbRed) and acid phosphatase, by spectrophotometry; 2.4. Redox status: MDA and MDA-LDL were evaluated by spectrophotometry. 3. Evaluation of eating habits: 24 hr recall. RESULTS: Chronological age is 14.3 +/- 1.7 years. Nutritional assessment shows a mean value for height near the 50th percentile (99% +/- 3.8), and low mean values respectively for BMI (89.3% +/- 9) and sum of triceps and subscapular skinfolds (51.9% +/- 14). Study of lipid profile shows low mean values for total cholesterol (162.3 mg/dl +/- 27.7) LDL-cholesterol (87.6 mg/dl +/- 22.6) and Apo B (64.4 mg/dl +/- 11.5), but high values for HDL-cholesterol (61.3 mg/dl +/- 14.5) and Apo A1 (173.1 mg/dl +/- 25.1). We observe higher values for total cholesterol and LDL-cholesterol in those with lower Cu plasmatic levels. We also observe a negative significative correlation between MDA-LDL and Zn (r = -0.469), Cu (r = -0.524) and RTM (r = -0.608). CONCLUSIONS: The AA concluded that in this group of gymnasts intense physical exercise induces, a favorable lipid profile, but a clear susceptibility to LDL peroxidation in those with lower plasma Cu and Zn values. It is possible that the negative correlation observed between MDA-LDL and TMR is caused by higher consumption of TMR induced by the action of exercise on the oxidative system.

Adolescent↗
PubMed1999

Detection of pathological zinc accumulation in neurons: methods for autopsy, biopsy, and cultured tissue.

It has been repeatedly shown that synaptically released zinc contributes to excitotoxic neuronal injury in ischemia, epilepsy, and mechanical head trauma. Such zinc-induced injury leaves an unmistakable "footprint" in the injured neurons, allowing an easy and unambiguous postmortem diagnosis. This footprint is the presence of weakly bound, histochemically reactive zinc in the cytoplasm of the perikaryon and proximal dendrites. Such staining appears to be a necessary and sufficient marker for zinc-induced neuronal injury. Here we show how to prepare and stain tissue from biopsy, autopsy, or experimental animal sources for maximal contrast and visibility of zinc-injured neurons.

Animals↗
PubMed1998

Peripheral versus central potencies of N-type voltage-sensitive calcium channel blockers.

The ability of a series of synthetic analogues of omega-conopeptides MVIIA (SNX-111) and TVIA (SNX-185) to prevent electrically-evoked norepinephrine release from rat tail artery and hippocampal slice preparations was determined in an effort to identify voltage-sensitive calcium channel (VSCC) blockers that selectively target N-type VSCCs in central nervous system tissue. Electrical field stimulation (3 Hz, 1 ms in duration. 80 V for 1 min) caused a high and consistent tritium outflow from rat tail artery and hippocampal slice preparations preloaded with [3H]-norepinephrine. All conopeptides, chosen for their selective affinities for high-affinity SNX-111 binding sites (i.e., N-type VSCCs) over high-affinity omega-conopeptides MVIIC (SNX-230) binding sites (i.e., P/Q-type VSCCs), produced a concentration-dependent inhibition of calcium dependent electrically-evoked tritium outflow from both tail arteries and hippocampal slices: IC50s ranged from 1.2 nM to 1.2 microM. Blocking potencies (IC50s) in the tail artery assay were significantly correlated with those measured in the hippocampal slice preparation (r = 0.91, P = 0.00000012). There was a significant correlation between IC50s for blockade of hippocampal norepinephrine release and the inhibition of high-affinity [125I]-SNX-I11 binding in rat brain synaptosomes (r = 0.76, P = 0.00028). Blockade of hippocampal norepinephrine release was not significantly correlated with the inhibition of high-affinity SNX-230 binding (r = 0.46, P = 0.056). Maximum inhibition of tritium outflow in the tail artery assay was 22+/-1.4% of control, approximating the value (20.9+/-16.0% of control) obtained in the absence of extracellular Ca2+. In contrast, the maximum inhibition of tritium release from hippocampal slices was 36.8+/-2.5% of control (P < 0.05, compared to that of the tail artery assay). These results suggest that (1) N-type VSCCs alone mediate low frequency electrical stimulation-evoked neurotransmitter release from peripheral sympathetic efferents (tail artery) while both N-type and non-N type(s) mediate neurotransmitter release from CNS neurons (hippocampus); and (2) analogues of omega-conopeptides MVIIA and TVIA do not differentiate between N-type VSCCs mediating norepinephrine release from central and peripheral neural tissues.

Animals↗