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Biomedical subjects

A Gupta

Publications and source records attributed to A Gupta.

At least 181 records · Page 10Linked to original sources
PubMed2002

Potentiation of spermicidal activity of 2',4'-dichlorobenzamil by lidocaine.

The present investigation was designed to study the spermicidal activity of lidocaine, a membrane stabilizer, and its combination with 2',4'-dichlorobenzamil hydrochloride, a Na+-Ca2+ exchange inhibitor, on human semen and spermatozoa separated from semen. Both drugs per se produced dose- and time-dependent reduction in motility of ejaculated human sperm. Lidocaine was found to potentiate the spermicidal activity of benzamil resulting in significant decrease in time for producing complete loss of ejaculated sperm motility. Sperm revival test revealed irreversible loss of sperm viability indicating a spermicidal rather than spermiostatic action by both the drugs. Furthermore, both benzamil (10-40 mM) per se and benzamil-lidocaine combination (0.5 and 16 mM) produced contraception in rabbit model.

Amiloride↗
PubMed2001

Attenuation of catalase activity in the malignant phenotype plays a functional role in an in vitro model for tumor progression.

We have developed an in vitro model to study the molecular mechanisms of tumor progression. Using repeated treatments with ionizing radiation or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), we caused malignant progression of a papilloma producing mouse keratinocyte cell line, 308 cells. In a previous study we have shown that the malignant variants of 308 cells have elevated reactive oxygen species (ROS) levels, and have established a functional role for the pro-oxidant state in the progressed phenotype (Carcinogenesis 20 (1999) 2063). In this study, we have evaluated the status of intracellular defense mechanisms for ROS scavenging in the progressed phenotype to identify sources that contribute to their pro-oxidant state. Our results demonstrate that a reduction in several anti-oxidant defense mechanisms, including catalase and glutathione S-transferase mu, correlates with the emergence of the malignant phenotype. We provide evidence that attenuation of catalase activity may play a functional role in the malignant progression of mouse keratinocytes.

Animals↗
PubMed2001

Dynamic compression nail: a preliminary report.

BACKGROUND: Interlocking nailing, which has become the method of choice for treating fractures of the femoral and tibial shafts, still lacks ability to provide the important contact-compression at the fracture. An intramedullary compression nail is described, which provides axial compression at the fracture site with tightening of the specially designed distal interlocking screw. This uses the same principle as dynamic compression plating. METHODS: The study included 11 femoral and tibial nailings performed for various clinical applications such as acute fractures, non-unions and malunions. RESULTS: All the fractures attained radiological union, with good skeletal continuity across the fracture, within an average time of 13 weeks in fresh fractures and 18 weeks in non-unions. CONCLUSIONS: Active compression through intramedullary compression nailing has great utility for treating non-unions where it provides greater degree of impaction of its irregular ends. This may prove greatly advantageous to the fracture union through increased stability and the osteogenic potential, particularly when utilized in combination with the small diameter unreamed nails.

Journal Article↗
PubMed2001

In vitro beta-hematin formation assays with plasma of mice infected with Plasmodium yoelii and other parasite preparations: comparative inhibition with quinoline and endoperoxide antimalarials.

Formation of beta-hematin in vitro could be catalyzed in the presence of various preparations related to the malaria parasite viz., the cell free homogenate of Plasmodium yoelii, lipid extract of the parasite homogenate, purified malarial hemozoin and synthetic beta-hematin. Plasma from mice infected with P. yoelii also catalyzed in vitro beta-hematin formation with highly significant efficiency. The plasma based beta-hematin formation assay was highly sensitive, as the background absorbance was almost negligible due to absence of any preformed hemozoin. The plasma beta-hematin synthesizing activity was recovered in the lipid extract. The quinoline and endoperoxide antimalarials act by inhibiting hemozoin biosynthesis in the malaria parasite. Therefore, the in vitro beta-hematin formation assay is useful for the screening and identification of blood schizontocidal antimalarials acting through interruption of heme detoxification in the parasite. Quinoline and endoperoxide antimalarials showed about three fold greater inhibition of beta-hematin synthesizing activity in the plasma-based assays as compared to that of P. yoelii homogenate-based assays. The specificity of the inhibition was similar in both preparations. The plasma-based assay therefore provides a better alternative than the parasite homogenate-based assay for in vitro screening and identification of novel inhibitors of hemozoin biosynthesis as potential blood schizontocidal antimalarials.

Animals↗
PubMed2001

Recombinant fusion proteins for haemagglutination-based rapid detection of antibodies to HIV in whole blood.

Recombinant fusion proteins, consisting of a monovalent anti-human RBC monoclonal antibody B6, and conserved immunodominant peptide of HIV-1 envelope glycoprotein gp41 or HIV-2 envelope glycoprotein gp36, have been designed and purified after over-expression in E. coli. These fusion proteins are Fab-based and were obtained by assembling the light chain with Fd (variable domain and the first constant domain of the heavy chain) or Fd fusions containing HIV-derived peptide, and following a protocol of in vitro denaturation of inclusion bodies and subsequent renaturation to assemble functional Fab. Using a multistep column chromatographic procedure, monomeric Fab and Fab fusion proteins containing HIV-derived peptide were purified to high degree, free of aggregates. The yield of various proteins on the laboratory scale (1-2 l of shake flask culture) was in the range of tens of milligram. Purified anti-human RBC Fab fusion proteins containing sequences derived from HIV-1 gp41 and HIV-2 gp36 were highly specific for detection of antibodies to HIV-1 and HIV-2, respectively. The described design, expression and purification protocols will make it possible to produce specific recombinant reagents in large quantities for agglutination-based rapid detection of antibodies to HIV in whole blood.

Agglutination Tests↗
PubMed2001

Methioninase cancer gene therapy with selenomethionine as suicide prodrug substrate.

In this study, we report a novel approach to gene-directed enzyme prodrug therapy for cancer. This gene therapy strategy exploits the toxic pro-oxidant property of methylselenol, which is released from selenomethionine (SeMET) by cancer cells with the adenoviral-delivered methionine alpha,gamma-lyase (MET) gene cloned from Pseudomonas putida. In MET-transduced tumor cells, the cytotoxicity of SeMET is increased up to 1000-fold compared with nontransduced cells. A strong bystander effect occurred because of methylselenol release from MET gene-transduced cells and uptake by surrounding tumor cells. Methylselenol damaged the mitochondria via oxidative stress and caused cytochrome c release into the cytosol, thereby activating the caspase cascade and apoptosis. Adenoviral MET-gene/SeMET treatment also inhibited tumor growth in rodents and significantly prolonged their survival. Recombinant adenovirus-encoding MET gene-SeMET treatment thereby offers a new paradigm for cancer gene therapy.

Adenoviridae↗
PubMed2001

Crystal structure of Rv2118c: an AdoMet-dependent methyltransferase from Mycobacterium tuberculosis H37Rv.

Rv2118c belongs to the class of conserved hypothetical proteins from Mycobacterium tuberculosis H37Rv. The crystal structure of Rv2118c in complex with S-adenosyl-l-methionine (AdoMet) has been determined at 1.98 A resolution. The crystallographic asymmetric unit consists of a monomer, but symmetry-related subunits interact extensively, leading to a tetrameric structure. The structure of the monomer can be divided functionally into two domains: the larger catalytic C-terminal domain that binds the cofactor AdoMet and is involved in the transfer of methyl group from AdoMet to the substrate and a smaller N-terminal domain. The structure of the catalytic domain is very similar to that of other AdoMet-dependent methyltransferases. The N-terminal domain is primarily a beta-structure with a fold not found in other methyltransferases of known structure. Database searches reveal a conserved family of Rv2118c-like proteins from various organisms. Multiple sequence alignments show several regions of high sequence similarity (motifs) in this family of proteins. Structure analysis and homology to yeast Gcd14p suggest that Rv2118c could be an RNA methyltransferase, but further studies are required to establish its functional role conclusively.

Amino Acid Motifs↗
PubMed2001

Molecular mechanisms for aberrant expression of the human breast cancer specific gene 1 in breast cancer cells: control of transcription by DNA methylation and intronic sequences.

Breast cancer specific gene 1 (BCSG1), also referred as synuclein gamma, is the third member of a neuronal protein family synuclein. BCSG1 is not expressed in normal breast tissues but highly expressed in advanced infiltrating breast carcinomas. When over expressed, BCSG1 significantly stimulates breast cancer metastasis. To elucidate the molecular mechanisms underlying the abnormal transcription of BCSG1 in breast cancer cells, in this study, we isolated a 2195 base pair fragment of human BCSG1 gene. This fragment includes 1 kb 5'-flanking region, exon 1, and intron 1. By analysing the promoter activity and the methylation status of the exon 1 region, we show that (1) Intron 1 plays critical roles in the control of BCSG1 gene transcription through cis-regulatory sequences that affect BCSG1 transcription in cell type-specific and cell type-nonspecific manners. (2) The activator protein-1 (AP-1) is functionally involved in BCSG1 transcription in breast cancer cells through its binding to an AP-1 motif located in the intron 1. (3) The exon 1 region of BCSG1 gene contains a CpG island that is unmethylated in BCSG1-positive SKBR-3 and T47D cells but densely methylated in BCSG1-negative MCF-7 cells. (4) Treating MCF-7 cells with a demethylating agent 5-Aza-2'-deoxycytidine specifically activated BCSG1 transcription. Thus, our results suggest that while the cellular content of transcription activators and repressors that interact with the cis-regulatory sequences present in the intron 1 contribute prominently to the tissue-specific expression of BCSG1, demethylation of exon 1 is an important factor responsible for the aberrant expression of BCSG1 in breast carcinomas.

Amino Acid Motifs↗
PubMed2001

Chemoprevention of esophageal tumorigenesis by dietary administration of lyophilized black raspberries.

Fruit and vegetable consumption has consistently been associated with decreased risk of a number of aerodigestive tract cancers, including esophageal cancer. We have taken a "food-based" chemopreventive approach to evaluate the inhibitory potential of lyophilized black raspberries (LBRs) against N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumorigenesis in the F344 rat, during initiation and postinitiation phases of carcinogenesis. Anti-initiation studies included a 30-week tumorigenicity bioassay, quantification of DNA adducts, and NMBA metabolism study. Feeding 5 and 10% LBRs, for 2 weeks prior to NMBA treatment (0.25 mg/kg, weekly for 15 weeks) and throughout a 30-week bioassay, significantly reduced tumor multiplicity (39 and 49%, respectively). In a short-term bioassay, 5 and 10% LBRs inhibited formation of the promutagenic adduct O(6)-methylguanine (O(6)-meGua) by 73 and 80%, respectively, after a single dose of NMBA at 0.25 mg/kg. Feeding 5% LBRs also significantly inhibited adduct formation (64%) after NMBA administration at 0.50 mg/kg. The postinitiation inhibitory potential of berries was evaluated in a second bioassay with sacrifices at 15, 25, and 35 weeks. Administration of LBRs began after NMBA treatment (0.25 mg/kg, three times per week for 5 weeks). LBRs inhibited tumor progression as evidenced by significant reductions in the formation of preneoplastic esophageal lesions, decreased tumor incidence and multiplicity, and reduced cellular proliferation. At 25 weeks, both 5 and 10% LBRs significantly reduced tumor incidence (54 and 46%, respectively), tumor multiplicity (62 and 43%, respectively), proliferation rates, and preneoplastic lesion development. Yet, at 35 weeks, only 5% LBRs significantly reduced tumor incidence and multiplicity, proliferation indices and preneoplastic lesion formation. In conclusion, dietary administration of LBRs inhibited events associated with both the initiation and promotion/progression stages of carcinogenesis, which is promising considering the limited number of chemopreventives with this potential.

Animals↗
PubMed2001

Neuroprotective effects of an adenoviral vector expressing the glucose transporter: a detailed description of the mediating cellular events.

Considerable knowledge exists concerning the events mediating neuron death following a necrotic insult; prompted by this, there have now been successful attempts to use gene therapy approaches to protect neurons from such necrotic injury. In many such studies, however, it is not clear what sequence of cellular events connects the overexpression of the transgene with the enhanced survival. We do so, exploring the effects of overexpressing the Glut-1 glucose transporter with an adenoviral vector in hippocampal cultures challenged with the excitotoxin kainic acid (KA). Such overexpression enhanced glucose transport, attenuated the decline in ATP concentrations, decreased the release of excitatory amino acid neurotransmitters, and decreased the total free cytosolic calcium load. Commensurate with these salutary effects, neuronal survival was enhanced with this gene therapy intervention. Thus, the neuroprotective effects of this particular gene therapy occurs within the known framework of the mechanisms of necrotic neuronal injury.

Adenosine Triphosphate↗
PubMed2001

Effects of dietary N-(4-hydroxyphenyl)retinamide on N-nitrosomethylbenzylamine metabolism and esophageal tumorigenesis in the Fischer 344 rat.

BACKGROUND: 9-cis-Retinoic acid (9-cis-RA) and N-(4-hydroxyphenyl)retinamide (4-HPR) are effective chemopreventive agents against epithelial tumors in the oral cavity, breast, and prostate. We tested the inhibitory activity of these retinoids against N-nitrosomethylbenzylamine (NMBA)-induced tumorigenesis in the rat esophagus. METHODS: Male Fischer 344 rats were randomly assigned to receive diets either lacking or containing 9-cis-RA or 4-HPR for 1 week before tumor initiation with NMBA and then for the duration of the study. NMBA metabolism, O(6)-methylguanine adduct formation, and cytochrome P450 messenger RNA (mRNA) expression in the esophagi of the rats were studied to investigate the mechanisms by which dietary 4-HPR affects tumorigenesis. All statistical tests were two-sided. RESULTS: Dietary 4-HPR resulted in a dose-dependent and statistically significant enhancement (P<.05) of tumorigenesis in response to NMBA. In two different tumor bioassays, the mean tumor multiplicity for rats fed the highest concentration of dietary 4-HPR (0.8 g/kg diet) was increased by 5.9 tumors (95% confidence interval [CI] = 1.7 to 10.1 tumors) and 6.7 tumors (95% CI = 5.6 to 7.8 tumors) compared with the mean tumor multiplicity for rats that received the control diet lacking 4-HPR. Animals fed diets containing 9-cis-RA displayed no statistically significant increase in tumorigenesis. Compared with animals fed a diet lacking 4-HPR, animals fed 4-HPR had increased NMBA metabolism in esophageal explant cultures and had higher levels of O(6)-methylguanine DNA adducts and CYP2A3 mRNA in their esophagi. CONCLUSIONS: Dietary 4-HPR enhances tumorigenesis in response to NMBA in the rat esophagus by increasing tumor initiation events. Dietary 4-HPR may exert paradoxical effects at some sites, such as the aerodigestive tract, by modulating the bioactivation of carcinogens in target tissues.

Alitretinoin↗
PubMed2001

Enhanced immunogenicity of a contraceptive vaccine using diverse synthetic carriers with permissible adjuvant.

A vaccine directed against human chorionic gonadotropin (hCG) has previously undergone clinical testing demonstrating the feasibility of the approach in preventing pregnancy in women. Some individuals, however, did not respond adequately despite employing highly immunogenic bacterial toxoids as carriers. We investigated the potential of three promiscuous pathogen-derived Th peptides as carriers, employing alum as the adjuvant. While conjugation with each peptide improved the antibody response against hCG in mice of different haplotypes, immunisation with a combination of these peptide-conjugates generated anti-hCG responses higher than those achieved with the individual peptides or tetanus toxoid (TT). Antibodies were of high affinity and capable of neutralising the bioactivity of hCG but were devoid of anti-peptide reactivity. These results have implication for the design of hCG vaccine with improved immunogenicity for diverse population.

Adjuvants, Immunologic↗
PubMed2001

Helium and other alternative insufflation gases for laparoscopy.

BACKGROUND: Carbon dioxide (CO(2)) is currently the insufflation gas of choice for laparoscopy. It fulfills most of the requirements for an ideal insufflation gas, being colorless, noninflammable, and rapidly excreted from the circulation. However, its use is associated with adverse cardiorespiratory effects, especially in patients with preexisting cardiorespiratory compromise. METHODS: The descriptive review of relevant literature, moreover, has been proposed that it increases the incidence of port site (wound) metastases from abdominal cancers when used during oncological surgery. In addition, it may cause postoperative pain due to peritoneal irritation, and its use is associated with physiological and immunological impairment. Hence, there is scope for the investigation of alternative insufflation gases. Other possibilities include gasless laparoscopy, helium, nitrous oxide, (N(2)O), and argon. Helium insufflation has been used extensively in animal models but only to a limited extent in humans. In experimental studies, it has been shown to produce fewer changes in cardiorespiratory and intraperitoneal immunological status than CO(2) insufflation, and its use is associated with less spread of tumors to port sites in a variety of small animal tumor models. However, helium also has the potential for some adverse effects. Helium pneumothorax probably resolves more slowly than CO(2) pneumothorax, and helium gas embolism is tolerated poorly in animal models. The clinical significance of these potential problems has yet to be determined. CONCLUSIONS: Although the use of alternative gases appears to be promising, further evaluation is needed within both clinical and laboratory settings before their routine clinical use can be supported.

Abdominal Neoplasms↗
PubMed2001

Investigation of the enhancement of N-nitrosomethylbenzylamine-induced esophageal tumorigenesis by 6-phenylhexyl isothiocyanate.

Previous studies in our laboratory have shown that 6-phenylhexyl isothiocyanate (PHITC), enhances N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumorigenesis in F344 rats while the shorter chain analogs, phenylethyl isothiocyanate (PEITC), and 3-phenylpropyl isothiocyanate (PPITC), inhibit NMBA-induced esophageal tumorigenesis. To test the hypothesis that PHITC influences the promotional stage of esophageal tumorigenesis, groups of 22-27 rats were dosed with vehicle or NMBA three times a week for 5 week, and fed a modified AIN-76A diet containing PHITC at concentrations of 0.0, 1.0, and 2.5 micromol/g. At the 25th week, the rats were killed, esophagi harvested and tumors counted. In the groups that received NMBA+PHITC, apparent but statistically insignificant increases in tumor multiplicity of 32 and 42% were found in comparison to rats treated with NMBA alone. A higher frequency of dysplastic lesions was found in rats treated with NMBA+2.5 micromol/g PHITC (71%) when compared to rats treated with NMBA only (12%). To test whether PHITC increased cellular proliferation, we evaluated proliferating cell nuclear antigen (PCNA) expression by immunohistochemistry. While there were no significant increases in PCNA staining in rats treated with NMBA+PHITC compared to rats treated with NMBA only, rats treated with PHITC only had a significantly higher PCNA index compared to untreated controls. Expression of cyclin D1, another biomarker of proliferation, was analyzed by semi-quantitative reverse transcription-polymerase chain reaction. There were no significant increases in cyclin D1 expression in groups treated with NMBA+PHITC compared to the group treated with NMBA only. Thus, while the data suggest a promotional effect by PHITC as manifested by a significant increase in dysplastic leukoplakia by the high dose of PHITC and an increase in the PCNA index by PHITC alone, PHITC does not appear to have a significant effect on esophageal cell proliferation.

Animals↗