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Biomedical subjects

V Sharma

Publications and source records attributed to V Sharma.

At least 109 records · Page 6Linked to original sources
PubMed1998

Carbohydrate specificity and quaternary association in basic winged bean lectin: X-ray analysis of the lectin at 2.5 A resolution.

The structure of basic Winged Bean Agglutinin (WBAI) with two dimeric molecules complexed with methyl-alpha-D-galactopyranoside in the asymmetric unit, has been determined by the molecular replacement method and refined with 2.5 A X-ray intensity data. The polypeptide chain of each monomer has the characteristic legume lectin tertiary fold. The structure clearly defines the lectin-carbohydrate interactions. It reveals how the unusually long variable loop in the binding region endows the lectin with its characteristic sugar specificity. The lectin forms non-canonical dimers of the type found in Erythrina corallodendron lectin (EcorL) even though glycosylation, unlike in EcorL, does not prevent the formation of canonical dimers. The structure thus further demonstrates that the mode of dimerisation of legume lectins is not necessarily determined by the covalently bound carbohydrate but is governed by features intrinsic to the protein. The present analysis and our earlier work on peanut lectin (PNA), show that legume lectins are a family of proteins in which small alterations in essentially the same tertiary structure lead to wide variations in quaternary association. A relationship among the non-canonical modes of dimeric association in legume lectins is presented.

Amino Acid Sequence↗
PubMed1998

Studies on an affinity label for the sulfuryl acceptor binding site in an aryl sulfotransferase.

Active site-directed affinity labeling was utilized to elucidate peptide sequences at the binding site for sulfuryl acceptors in rat hepatic aryl sulfotransferase (AST) IV (also known as tyrosine-ester sulfotransferase, EC 2.8.2.9). The affinity labeling reagent, N-bromoacetyl-4-hydroxyphenylamine, was designed on the basis of substrate specificity studies with para-substituted phenols, utilization of a bromoacetamido group for reactivity with active site amino acid residues and its similarity to acetaminophen, a known substrate for aryl (phenol) sulfotransferases. AST IV utilized N-bromoacetyl-4-hydroxyphenylamine as a substrate with kinetic constants that compared favorably to those obtained with acetaminophen. Incubation of AST IV with N-bromoacetyl-4-hydroxyphenylamine at pH 7.0 in the absence of PAPS and other substrates resulted in an irreversible inactivation of the enzyme that was both time- and concentration-dependent. [14C]-N-bromoacetyl-4-hydroxyphenylamine was synthesized and used to analyze the regions of protein sequence that were involved in the binding of the affinity label. AST IV was incubated with [14C]-N-bromoacetyl-4-hydroxyphenylamine, hydrolyzed with endoproteinase Lys-C and the labeled peptides were purified by HPLC. Control incubations of AST IV with the affinity label in the presence of 4-propylphenol and PAP were utilized to ascertain the specificity of the interaction. Sequence analysis of the labeled peptides, carried out by automated Edman degradation, revealed labeling sites on cysteine (Cys-232, Cys-283 and Cys-289) and lysine (Lys-286) residues near the C-terminus of the protein. The locations of these labeling sites were further evaluated both by sequence-alignment with other sulfotransferases and by theoretical calculations on predicted secondary structure.

Affinity Labels↗
PubMed1998

An expression map from human chromosome 14q24.3.

We have constructed an expression map of chromosome 14q24.3 between markers D14S42 and D14S63. cDNA selection with YACs from 14q24.3 was used to generate expressed sequence tags (ESTs). The localization of ESTs was confirmed on a YAC contig. PCR products of ESTs were used as probes to screen cDNA libraries leading to the isolation of transcripts for known and unknown genes. In total, the expression map contains 7 known genes previously mapped to 14q24.3, 6 cDNA transcripts, and 15 anonymous ESTs. The addition of 21 unique transcribed loci from an approximately 5- to 7-Mb region of chromosome 14q24.3 will facilitate future efforts to identify human disease genes from this region.

Chromosome Mapping↗
PubMed1998

Chemical modification of titanium surfaces for covalent attachment of biological molecules.

The surface of implantable biomaterials is in direct contact with the host tissue and plays a critical role in determining biocompatibility. In order to improve the integration of implants, it is desirable to control interfacial reactions such that nonspecific adsorption of proteins is minimized and tissue-healing phenomena can be controlled. In this regard, our goal has been do develop a method to functionalize oxidized titanium surfaces by the covalent immobilization of bioactive organic molecules. Titanium first was chemically treated with a mixture of sulfuric acid and hydrogen peroxide to eliminate surface contaminants and to produce a consistent and reproducible titanium oxide surface layer. An intermediary aminoalkylsilane spacer molecule was then covalently linked to the oxide layer, followed by the covalent binding of either alkaline phosphatase or albumin to the free terminal NH2 groups using glutaraldehyde as a coupling agent. Surface analyses following coating procedures consisted of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Enzymatic activity of coupled alkaline phosphatase was assayed colorimetrically, and surface coverage by bound albumin was evaluated by SEM visualization of colloidal gold immunolabeling. Our results indicate that the linkage of the aminoalkylsilane to the oxidized surface is stable and that bound proteins such alkaline phosphatase and albumin retain their enzymatic activity and antigenicity, respectively. The density of immunolabeling for albumin suggests that the binding and surface coverage obtained is in excess of what would be expected for inducing biological activity. In conclusion, this method offers the possibility of covalently linking selected molecules with known biological activity to oxidized titanium surfaces in order to guide and promote the tissue healing that occurs during implant integration in bone and soft tissues.

Biological Factors↗
PubMed1998

Missense mutations in the chromosome 14 familial Alzheimer's disease presenilin 1 gene.

Mutations in the presenilin genes (PS-1 and PS-2) cause early onset autosomal dominant Alzheimer's disease (AD). Eight early-onset, autopsy-documented familial AD kindreds were screened for mutations in PS-1, and seven different mutations were identified. Three of these were new mutations (G209V, A426P, and E120D), two were previously reported mutations in new families, and three mutations were confirmed in previously published families. Two of these new mutations are found within predicted transmembrane domains (TMDs 4, 7, and 8). The A426P mutation is the most C-terminal PS-1 mutation identified to date.

Adult↗
PubMed1998

The reduction in electroporation voltages by the addition of a surfactant to planar lipid bilayers.

The effects of a nonionic surfactant, octaethyleneglycol mono n-dodecyl ether (C12E8), on the electroporation of planar bilayer lipid membranes made of the synthetic lipid 1-pamitoyl 2-oleoyl phosphatidylcholine (POPC), was studied. High-amplitude ( approximately 100-450 mV) rectangular voltage pulses were used to electroporate the bilayers, followed by a prolonged, low-amplitude ( approximately 65 mV) voltage clamp to monitor the ensuing changes in transmembrane conductance. The electroporation thresholds of the membranes were found for rectangular voltage pulses of given durations. The strength-duration relationship was determined over a range from 10 micros to 10 s. The addition of C12E8 at concentrations of 0.1, 1, and 10 microM to the bath surrounding the membranes decreased the electroporation threshold monotonically with concentration for all durations (p < 0.0001). The decrease from control values ranged from 10% to 40%, depending on surfactant concentration and pulse duration. For a 10-micros pulse, the transmembrane conductance 150 micros after electroporation (G150) increased monotonically with the surfactant concentration (p = 0.007 for 10 microM C12E8). These findings suggest that C12E8 incorporates into POPC bilayers, allowing electroporation at lower intensities and/or shorter durations, and demonstrate that surfactants can be used to manipulate the electroporation threshold of lipid bilayers.

Detergents↗
PubMed1998

Integration of local orientation in strabismic amblyopia.

In order to investigate the processes which integrate local orientation information in observers with strabismic amblyopia, we measured contrast thresholds for discriminating the global orientation of a pattern (3 "bars") comprised of Gabor patches. We found that in both eyes of amblyopic observers, as has been reported for normal observers [Saarinen, Levi & Shen (1997) Proceedings of the National Academy of Sciences USA, 94, 8267-8271], there is an approximately two-fold enhancement of contrast sensitivity when the global and local orientations are aligned (relative to mixed orientations), and a smaller enhancement when the global and local orientations are orthogonal. This orientation dependent enhancement occurs despite substantial losses of contrast sensitivity. These results suggest that the integration processes in the amblyopic eye that operate to enhance detection are essentially intact.

Adult↗
PubMed1998

A closer look at inpatient suicide.

BACKGROUND: We examined the risk factors for suicide among inpatients in an Ontario provincial psychiatric hospital. METHODS: Forty-four inpatients who had committed suicide during their hospital stay from 1969 to 1995 were compared with a group of inpatient controls matched for sex, age and date of admission. The diagnosis for each patient was reviewed by the authors. RESULTS: Suicide victims were more likely to have had a mood disorder, family history of psychiatric problems, mention of suicide risk in chart notes and a previous suicide attempt. Two findings necessitated further scrutiny: The most common diagnosis among inpatients who committed suicide in this study was a mood disorder and not schizophrenia as previously reported. A large proportion of patients (24) had experienced a rapidly fluctuating clinical course prior to the time of suicide. CONCLUSIONS: The implications of these findings, including the possible role of antidepressants in the induction of cycling prior to suicide, are discussed.

Adult↗
PubMed1998

Serotonin function and risk for alcoholism in boys with attention-deficit hyperactivity disorder.

Data in animals and adults indicate that central serotonergic (5-HT) function may be involved in the development of alcohol abuse. Despite this, studies exploring this mechanism in individuals at risk for alcoholism are scant. This study used a fenfluramine (FEN) challenge procedure to investigate the relationship between risk for alcoholism and 5-HT function in 7- to 11-year-old boys with attention-deficit hyperactivity disorder (ADHD). The prolactin (PRL) and cortisol (CORT) responses to FEN were examined in 10 sons of alcoholic fathers (FA+) and 30 sons of nonalcoholic fathers (FA-). The FA+ group had a significantly greater CORT, but not PRL, response to FEN relative to the FA- group. The discrepancy between the CORT and PRL responses may be due to the different mechanisms that underlie their 5-HT stimulated release. This suggests that, among ADHD boys, those at familial risk for alcohol abuse may differ from those who are not at risk in 5-HT function.

Alcoholism↗
PubMed1998

Identification of antibodies directed against O-acetylated sialic acids in visceral leishmaniasis: its diagnostic and prognostic role.

A significantly increased O-acetylated sialic acid (O-AcSA) binding fraction was purified from serum of visceral leishmaniasis (VL) patients by affinity chromatography on immobilized bovine submaxillary mucin (BSM) and found to be immunoglobulin in origin. The serodiagnostic and prognostic potential of BSM as a capture antigen was established by ELISA with no cross reactivity with coendemic diseases like malaria, tuberculosis, leprosy, chagas disease and cutaneous leishmaniasis; however, a strong cross reactivity was present with trypanosomiasis patients. In 56 clinically diagnosed VL patients, the BSM-ELISA was compared with diagnosis by microscopy using Giemsa stained tissue smears and direct ELISA using crude parasite antigen (parasite-ELISA); 49/56(87.5%) and 5/56(9.0%) were positive and negative respectively by all 3 methods. The BSM-ELISA failed to diagnose 2/56(3.5%) patients which were biopsy and parasite-ELISA positive. The prognostic potential of the BSM-ELISA in 18 longitudinally monitored VL patients before and after conventional antimonial treatment showed a significant decrease in anti O-AcSA titres in drug responsive patients whereas anti O-AcSA levels persisted in drug unresponsive patients. The IgG subclass distribution of antibodies directed against O-AcSA showed increased IgG2 levels in VL patients as compared to healthy controls. The BSM-based ELISA holds great promise as a serodiagnostic and prognostic assay for VL.

Acetylation↗
PubMed1998

Molecular basis of recognition by Gal/GalNAc specific legume lectins: influence of Glu 129 on the specificity of peanut agglutinin (PNA) towards C2-substituents of galactose.

The ability to discriminate between galactose and N- acetylgalactosamine, observed in some lectins, is crucial for their biological activity as well as their usefulness as tools in biology and medicine. However, the molecular basis of differential binding of lectins to these two sugars is poorly understood. Peanut agglutinin (PNA) is one of the few galactose-specific legume lectins which does not bind N- acetylgalactosamine at all and is, therefore, ideal for the study of the basis of specificity towards C-2 substituted derivatives of galactopyranosides. Examination of the three-dimensional structure of PNA in complex with lactose revealed the presence of both a longer loop and bulkier residues in the region surrounding the C-2 hydroxyl of the galactopyranoside ring, which can sterically prevent the accommodation of a bulky substituent in this position. One such residue, is a glutamic acid at position 129 which protrudes into the binding site and perhaps directly obstructs any substitution at the C-2 position. Two mutants in bacterially expressed PNA were therefore constructed. These were E129D and E129A, in which Glu129 was replaced by Asp and Ala, respectively. The specificity of the mutants for galactose, galactosamine, and N- acetylgalactosamine was examined through observing the inhibition of hemagglutination and binding of the lectin to immobilized asialofetuin. The results showed that the affinity of E129A and E129D for C-2-substituted derivatives of the galactose varies. The mutant E129D showed significant binding towards N- acetylgalactosamine, suggesting that the residue Glu 129 is crucial in imparting exclusive galactose-specificity upon PNA. This study not only attempts to provide an explanation for the inability of PNA to accommodate C-2-substituted derivatives at its primary subsite, but also seeks to present a basis for engineering lectins with altered specificities.

Acetylgalactosamine↗
PubMed1998

Term delivery in a woman with severe congenital neutropenia, treated with growth colony stimulating factor.

The patient was diagnosed in childhood as having severe congenital neutropenia and had recurrent admissions with severe infections. In 1987, prior to getting married, she was sterilized. She continued to require i.v. antibiotics when she contracted a severe infection. On one occasion, she was treated with growth colony stimulating factor (G-CSF). Her increased neutrophil count was sustained following this treatment. In June 1993, she wished to start a family and underwent in-vitro fertilization (IVF) treatment. G-CSF was given prior to oocyte retrieval. She conceived on her first cycle and an ultrasound scan revealed a singleton pregnancy. Throughout the course of the pregnancy, her white cell count was monitored closely and remained at <1.0x10(9)/l. The pregnancy progressed uneventfully and at 37 weeks gestation she was admitted for G-CSF injections. At 38 weeks she was delivered of a boy weighing 3350 g, by elective Caesarean section. His white cell count was normal. This is the first case of G-CSF being used before conception and during pregnancy in a patient with congenital neutropenia. It shows that advances in cytokine therapy and close interdisciplinary liaison can lead to a successful outcome and help patients, who would otherwise remain childless, to achieve a family.

Adult↗
PubMed1998

The relationship between follicular fluid aspirate volume and oocyte maturity in in-vitro fertilization cycles.

As a consequence of multiple follicular growth during ovarian stimulation for in-vitro fertilization (IVF), follicles of varying sizes often yield oocytes that vary in maturity and morphology of the oocyte-cumulus-corona complex. The objective of this prospective study was to explore the relationship between follicular fluid aspirate volume and the oocyte's developmental potential in an IVF treatment cycle. In total 9933 follicles were studied from 400 patients who underwent 535 consecutive IVF treatment cycles at St James's University Hospital, Leeds, UK, between February 1995 and February 1996. The volume of each individual follicle aspirated was recorded and related to the probability of obtaining an oocyte, its fertilizing capacity, the cleavage rate and the quality of embryos derived. We found no statistically significant difference in oocyte recovery rates between follicles with an aspirate volume < or = 1 ml and follicles with a volume > 1 ml. Although oocytes obtained from follicles with an aspirate volume > or = 1 ml showed a significantly lower fertilization rate, they went on to cleave at the same rate as oocytes obtained from larger follicles and resulted in embryos of comparable quality. Furthermore, there was no statistically significant difference in the implantation, clinical pregnancy or live birth rates per cycle between embryos derived from follicles with an aspirate volume < or = 1 ml and those derived from follicles with an aspirate volume > 1 ml. We conclude that follicular size and the oocyte's developmental potential in the stimulated ovary are not closely related and can be independent. This is in contrast to the Graafian follicle and the pre-ovulatory oocyte in the natural cycle.

Adult↗
PubMed1998

Rapid diagnosis of Indian visceral leishmaniasis using achatininH, a 9-O-acetylated sialic acid binding lectin.

We have developed a rapid, accurate, and inexpensive hemagglutination assay (HA) for diagnosis of Indian visceral leishmaniasis (VL) using achatininH, a 9-O-acetylated sialic acid binding lectin. The assay is based on the selective binding of achatininH to 9-O-acetylated derivatives of sialic acid (9-O-AcSA), which appears exclusively on the erythrocytes of patients with VL. Blood samples from 35 patients with demonstrable splenic or bone marrow amastigotes were assayed by HA and compared with an ELISA. All cases were correctly diagnosed by HA, and were in concordance with the ELISA. The increase in 9-O-AcSA was corroborated by direct fluorimetric estimation of sialic acid and its 9-O-acetylated derivative. Therefore, 9-O-acetylated derivatives of sialic acid, absent in normal erythrocytes, serve as an important biomarker, and indirectly reflect the presence of the parasite. Accordingly, this assay can be used for detection of active kala-azar cases and merits clinical consideration.

Biomarkers↗
PubMed1998

Emergency drugs in dental practice.

An increase in the life expectancy of medically compromised patients has resulted in greater numbers of these individuals within our ageing population. As dental surgeons are increasingly expected to provide care for such patients, the likelihood of a medical emergency occurring within the dental surgery may increase. This article reviews the more common emergency drugs that a dentist may have to administer in the event of a medical emergency. The indications, mode of action, method of administration and dose of each agent are discussed.

Dental Care for Chronically Ill↗
PubMed1998

The summer penile syndrome: seasonal acute hypersensitivity reaction caused by chigger bites on the penis.

OBJECTIVE: To describe the seasonal acute hypersensitivity reaction of the penis due to chigger bites, known as the summer penile syndrome. DESIGN: A consecutive series of patients. SETTING: The emergency department of an urban academic children's hospital in the midwestern United States. PARTICIPANTS: Male pediatric patients with an acute hypersensitivity reaction of the penis. RESULTS: Ninety-four patients were treated for summer penile syndrome during the four-month period from June through September. Patients ranged in age from seven months to 11 years (mean = 5.1, SD = 2.5). Twenty-one percent of patients had also experienced a similar prior episode of penile swelling. Symptoms included pruritus in 84% of cases, dysuria in 33%, and decreased strength of urine stream in 8% of patients. Eighty-four percent of patients had recent exposure to the woods, park, lawn, or poison ivy. In addition to edema, findings on physical examination included a papule or bite puncture mark in 50% of patients, erythema in 32%, and excoriation in 6% of patients. Fifty-six percent of patients had bites on other areas of the body. The emergency physician attributed the penile edema to an insect or chigger bite in 98% of cases. Treatment consisted of an oral antihistamine and cold compresses in most cases. The reported duration of penile swelling ranged from one to 18 days with a mean of 4.1 days (SD = 3.5), and the reported duration of pruritus ranged from 0 to 14 days with a mean of 3.0 days (SD = 2.6). CONCLUSION: This study provides an understanding of the summer penile syndrome for pediatric care providers. To our knowledge, this study is the first to describe this seasonal syndrome in the medical literature.

Acute Disease↗