Search PubMed⌕ Search

Biomedical subjects

M Singh

Publications and source records attributed to M Singh.

At least 577 records · Page 32Linked to original sources
PubMed1995

Digoxigenin-labelled cDNA probes for the detection of potato virus Y in dormant potato tubers.

An isolate (Y139) of the potato virus Y strain PVYO, common in the potato-growing regions of eastern Canada, was cloned and segments of about 1800 bases from the 3'-end of the PVY-genome were sequenced. These clones were used to prepare molecular detection probes by labelling with digoxigenin. Five methods reported to yield nucleic acid preparations from tuber tissue were compared. Two of the methods failed to yield nucleic acids from tubers suitable for use in dot-blot hybridization. The other three methods yielded satisfactory nucleic acids which could be successfully detected with the PVYO probes. A method of nucleic acid extraction from tuber tissues was selected which is simple, reproducible and does not use phenol. Using this standardized procedure, PVY was detected in freshly harvested, greenhouse-grown tubers of 8 potato cultivars; the probe was specific to PVY; and the sensitivity of detection using purified viral RNA was down to 10 pg. The sensitivity of detection in tuber extracts was down to a dilution of 1:64, while that from potato leaves was to a dilution of 1:1024. Nucleic acids prepared by the standardized procedure and denatured prior to storage at 4 degrees C, -20 degrees C or at -70 degrees C remained suitable for hybridization for over 2 weeks.

DNA Probes↗
PubMed1995

Synthetic delivery system for tuberculosis vaccines: immunological evaluation of the M. tuberculosis 38 kDa protein entrapped in biodegradable PLG microparticles.

Tuberculosis remains a major public health burden which could be ameliorated by effective and well-defined subunit vaccines, particularly because the protective efficacy of current M. bovis BCG vaccines is both unpredictable and variable. The immunodominant 38 kDa antigen from Mycobacterium tuberculosis was entrapped in biodegradable poly (DL-lactide co-glycolide) (PLG) microparticles which served as a delivery system. Both cellular and humoral immune responses were assessed and compared with those obtained after immunization with the 38 kDa protein emulsified in incomplete Freund's adjuvant (IFA). Vaccination of mice with a single dose of antigen-loaded microparticles resulted in specific IgG titres peaking after five weeks comparable to those achieved after vaccination with protein emulsified in incomplete Freund's adjuvant (IFA). T-cell responses were found to be superior to those induced with antigen/IFA. The T- and B-cell epitope specificities ad judged with synthetic peptides were identical following immunization with antigen in microparticles or IFA. Differences in adjuvanticity were revealed by measuring antigen-specific IgG1, IgG2a and antigen-induced IFN-gamma secretion in vitro: substantially higher titres of IgG2a were observed following immunization with antigen/microparticles than with 38 kDa protein/IFA. This was paralleled by a tenfold higher secretion of IFN-gamma in mice injected with antigen/microparticles. Reduction in colony-forming units was not consistent in mice immunized with 38 kDa protein entrapped in microparticles which were subsequently infected with live tubercle bacilli. Taken together these results indicate that biodegradable PLG microparticles constitute a favorable candidate vaccine delivery system worthy of further assessment in the quest to develop better and defined agents protecting against tuberculosis.

Amino Acid Sequence↗
PubMed1995

Analysis of aggregation mechanism of erythrocytes under normal- and microgravity conditions.

Aggregation mechanism of erythrocytes under normal and microgravity conditions is analyzed from their recorded images. The video data is analyzed by PC/AT based image processing system. The results show that the shape of individual erythrocytes and their formed aggregates changes significantly which may affect the formation process of aggregates under microgravity conditions.

Cell Size↗
PubMed1995

A prospective study on the association between red hair color and endometriosis in infertile patients.

OBJECTIVE: To determine if red-haired infertile women have an increased prevalence of endometriosis. DESIGN: Prospective, nonblinded. SETTING: Large, metropolitan, private hospital, associated with a university. Subspeciality care provided by reproductive endocrinologists. PATIENTS: One hundred forty-three consecutive women undergoing laparoscopy or laparotomy for infertility. INTERVENTIONS: Laser ablation of any endometriosis present. MAIN OUTCOME MEASURE: Presence of endometriosis. RESULTS: Of 143 women entered into the study, 12 had natural red hair. The ages of these women ranged between 23 and 41 years. Ten of 12 (83%) of the red-haired women were found to have endometriosis compared with 55 of 131 (42%) of nonredheads. By statistical analysis, the 95% confidence intervals for the presence of endometriosis in redheads was 55% to 100% versus 34% to 51% for nonredheads. CONCLUSION: The results suggest an association between the occurrence of natural red hair and those factors that lead to the development of endometriosis.

Adult↗
PubMed1995

Quantitative synthesis and formation of cyclopenta[cd]pyrene 3,4-oxide under simulated atmospheric conditions.

Cyclopenta[cd]pyrene 3,4-oxide (2) has been synthesized in a one-step, quantitative reaction using dimethyldioxirane. The oxide, or its thermal rearrangement products cyclopenta[cd]-pyren-3(4H)-one and cyclopenta[cd]pyren-4(3H)-one, is formed from cyclopenta[cd]pyrene (1) under simulated environmental conditions. In one case these products are formed when 1 is adsorbed on model particulates and then exposed to the reaction products of tetramethylethylene and ozone in the gas phase.

Atmosphere↗
PubMed1995

Biodegradable delivery system for a birth control vaccine: immunogenicity studies in rats and monkeys.

PURPOSE: The purpose of this study was to develop a single administration delivery system for a model birth control vaccine, in order to reduce the need for multiple injections and enhance immunogenicity. METHODS: The immunogen-loaded microspheres were prepared by solvent evaporation method and characterized for loading levels, size distribution and in vitro release kinetics. The microspheres were immunized intramuscularly in wistar rats and bonnet monkeys, and the antibody response was compared to that obtained with the same total dose of the immunogen on alum given at a monthly interval. RESULTS: Results indicated that a single injection of the immunogen entrapped in the microspheres generated a response comparable to that obtained by the same immunogen on alum injected at a monthly interval. The antibodies generated by the microspheres in the monkeys also had a good bioneutralization capacity indicating immunogen integrity during the microencapsulation process. CONCLUSIONS: Biodegradable microspheres served as an effective delivery system for a model immunogen used in this study to reduce the need for frequent immunizations and enhance immunogenicity.

Animals↗
PubMed1995

Effect of immunization with lutropin-receptor on the ovarian function of rabbits.

Three New Zealand white adult female rabbits, designated as A, B, and C, were immunized to produce lutropin receptor antibodies. Antisera inhibited the binding of 125I-hCG to the lutropin receptor and the production of testosterone by hCG stimulated rat Leydig cells. During the study period of, approximately 10 months after the last immunization, rabbits did not ovulate in response to an injection of 75 IU of human chorionic gonadotropin or mating as revealed by laparotomy. As the antibody titers declined, induction of ovulation and laparotomy revealed restoration of ovulation and corpus luteum formation. However, no pregnancy occurred when rabbits A and B were mated and artificially inseminated. These observations indicate that lutropin receptor antibodies can cause infertility in female rabbits.

Animals↗
PubMed1995

Rapid induction of mammary intraductal proliferations, ductal carcinoma in situ and carcinomas by the injection of sexually immature female rats with 1-methyl-1-nitrosourea.

While most data in the literature indicate that chemically-induced mammary carcinogenesis in the rat proceeds through morphologically identifiable stages, little quantitative data exist on the frequency of their occurrence. A carcinogen induction protocol is reported that defines conditions under which approximately 38% of detectable lesions in the abdominal-inguinal mammary glands were histologically classified as either intraductal proliferations or ductal carcinoma in situ. The remainder of the lesions were classified as carcinomas. This response was observed in a group of 30 female Sprague-Dawley rats injected i.p. with 50 mg 1-methyl-1-nitrosourea (MNU)/kg body wt at 21 days of age. The experiment was terminated 35 days following carcinogen administration. The methods used to prepare whole mounts and to identify, excise and process lesions in the whole mounts to permit histological classification are described in detail. This carcinogenesis protocol also induced a significant palpable tumor response. The first palpable tumor, histologically classified as an adenocarcinoma, was observed 30 days post carcinogen administration. When the experiment was terminated (35 days post MNU), the cumulative incidence of palpable carcinomas was 60%. The rapidity of the carcinogenic response was remarkable. Unlike the i.v. administration of 7,12-dimethylbenz[a]anthracene (DMBA) to rats of this age, MNU injection resulted in > 99% incidence of palpable mammary gland tumors that were malignant. The data reported in this paper confirm and support the pathogenetic pathway described for the induction of mammary tumors in the rat by DMBA. The induction of mammary carcinogenesis in immature animals described in this paper may be of value in the investigation of early morphologically identifiable stages of this disease process as well as providing an extremely rapid method for tumor induction.

Aging↗
PubMed1995

Exercise intensity dependent inhibition of 1-methyl-1-nitrosourea induced mammary carcinogenesis in female F-344 rats.

The objective of this experiment was to evaluate the effects of treadmill exercise on tumor induction in an experimental model for breast cancer. Female F-344 rats were injected i.p. with 50 mg MNU/kg body wt at 50 and 57 days of age. Animals were assigned to one of five groups: sham exercise or 35% or 70% maximal treadmill running intensity for 20 or 40 min/day, 5 days per week. These work rates represent an exercise intensity level generally considered insufficient to improve cardiovascular fitness (35% maximal intensity) or an aerobic level of exercise sufficient to improve cardiovascular fitness in humans (70% maximal intensity). Rats were exercised for 3 months following carcinogen administration at which time the experiment was terminated. Mammary cancer incidence was reduced by as much as 37% and cancer multiplicity by < 60% at the highest exercise intensity. Unexpectedly, the degree of protection against cancer was proportional to the intensity but not to the duration of exercise.

Animals↗
PubMed1995

Treatment with chemopreventive agents, difluoromethylornithine and retinyl acetate, results in altered mammary extracellular matrix.

The effect of treatment with D-L-2-difluoromethylornithine (DFMO) plus retinyl acetate (RA) on the promotion stage of 1-methyl-1-nitrosourea (MNU)-induced mammary carcinogenesis was evaluated in female Sprague-Dawley rats. Combined treatment was more effective than single agent treatment in decreasing cancer incidence and multiplicity and in prolonging cancer latency. Increased efficacy was associated with reduced morphological complexity of the gland and increased mammary extracellular matrix. Using ovarian hormones to model mitogen stimulation in the mammary gland, DFMO plus RA treatment reduced mammary gland complexity in the absence of an effect on bromodeoxyuridine (BrDU) labeling index measured immunohistochemically. Morphological and biochemical evaluation of these glands revealed increased levels of extracellular matrix in rats treated with chemopreventive agents. Tenascin expression and fibronectin levels were elevated and laminin levels were decreased. The fact that matrix degrading proteinase activity was also increased indicated that tissue remodeling was modulated by these chemopreventive agents. These data provide evidence of alterations in epithelial cell-extracellular matrix interactions that could account in part for the chemopreventive effects of DFMO plus RA.

Animals↗
PubMed1995

The nature of the immunogen determines the specificity of antibodies and T cells to selected peptides of the 38 kDa mycobacterial antigen.

We report in this study that the nature of the injected immunogen or infection of mice can change the specificity of antibodies against different epitopes of the mycobacterial 38 kDa antigen. Following immunization with a selection of 14 peptides, only p65-83 and p285-304 resulted in antibodies binding to the whole antigen, whereas the recombinant antigen induced antibodies to p201-220 and p230-249, which are non-immunogenic following peptide immunization. Killed tubercle bacilli stimulated antibodies exclusively against the N-terminal 1-20 peptide, whilst infection with live tubercle bacilli led to antibodies recognizing non-continuous epitopes, demonstrable by binding to the 38 kDa protein, but to none of the tested peptides. The most striking finding is that protein immunization failed to induce antibodies to p65-83, although this epitope is immunodominant for T cells, irrespective of the mode of sensitization. Since this peptide contains non-overlapping B (69-75) and T (75-81) cell stimulatory cores, it appears that T help dedicated to the adjacent B epitope following peptide immunization may have shifted in favour of B cells reacting either with distantly located linear epitopes p1-20 and p201-220 following immunization with the whole protein, or to conformational epitopes following tuberculous infection of mice. The mechanisms which can deviate T help from one to another B cell specificity could involve regulation of antigen processing, liable to the nature of the immunogen. The described results suggesting distinct functional pairing between T and B epitopes, but with limited fidelity, may have general implications for the design of subunit vaccines.

Amino Acid Sequence↗
PubMed1995

Decreased expression of functional human chorionic gonadotropin/luteinizing hormone receptor gene in human uterine leiomyomas.

Human myometrium contains functional hCG/LH receptors. The purpose of this study was to determine whether or not leiomyomas that arise from myometrium also contain these receptors. Northern blotting demonstrated that leiomyomas and normal adjacent myometria contained hCG/LH receptor mRNA transcripts. Western immunoblotting showed that leiomyomas and corresponding normal myometria also contained 60- and 50-kDa receptor proteins. Ligand blotting revealed that only the 50-kDa receptor protein in leiomyomas and corresponding normal myometria could bind 125I-hCG and that this binding inhibited by excess unlabeled hCG. In situ hybridization and immunocytochemistry revealed that smooth muscle cells in leiomyomas and corresponding normal myometria contained the hCG/LH receptor mRNA transcripts and receptor proteins. The receptor levels were lower in leiomyomas than in corresponding normal myometria. However, the receptors were functional, as treatment with hCG resulted in a decrease of connexin-43 protein levels in leiomyomas as in normal myometria. In summary, human uterine leiomyomas express a functional hCG/LH receptor gene at a reduced level compared with that for normal corresponding myometria. This finding could be relevant to an understanding of the growth control mechanisms in leiomyomas and the manner in which medical therapy for leiomyomas might work.

Adult↗
PubMed1995

Expression of Shigella dysenteriae serotype 1 O-antigenic polysaccharide by Shigella flexneri aroD vaccine candidates and different S. flexneri serotypes.

The potential utility of Shigella flexneri aroD vaccine candidates for the development of bi- or multivalent vaccines has been explored by the introduction of the genetic determinants rfp and rfb for heterologous O antigen polysaccharide from Shigella dysenteriae serotype 1. The serotype Y vaccine strain SFL124 expressed the heterologous antigen qualitatively and quantitatively well, qualitatively in the sense of the O antigen polysaccharide being correctly linked to the S. flexneri lipopolysaccharide R3 core oligosaccharide and quantitatively in the sense that typical yields were obtained, with ratios of homologous to heterologous O antigen being 4:1 for one construct and 1:1 for another. Moreover, both polysaccharide chains were shown to be linked to position O-4 of the subterminal D-glucose residue of the R3 core. In contrast to the hybrid serotype Y SFL124 derivatives, analogous derivatives of serotype 2a vaccine strain SFL1070 did not elaborate a complete heterologous O antigen. Such derivatives, and analogous derivatives of rough, O antigen-negative mutants of SFL1070, formed instead a hybrid lipopolysaccharide molecule consisting of the S. flexneri lipid A R3 core with a single repeat unit of the S. dysenteriae type 1 O antigen. Introduction of the determinants for the S. dysenteriae type 1 O antigen into a second serotype 2a strain and into strains representing other serotypes of S. flexneri, revealed the following for the expression of the heterologous O antigen: serotypes 1a, 1b, 2a, and 5a did not produce the heterologous O antigen, whereas serotypes 2b, 3a, 3b, 4a, 4b, 5b, and X did.

Bacterial Proteins↗
PubMed1995

Serum antibodies to Trichomonas vaginalis in invasive cervical cancer patients.

OBJECTIVE: To evaluate, by seroepidemiology, the possible role of the sexually-transmitted flagellate, Trichomonas vaginalis, in invasive cervical cancer. SUBJECTS AND METHOD: Sera from 121 invasive cervical cancer patients and 242 random age-matched female controls. Antibodies to T. vaginalis were detected by the western blot technique. RESULTS: Antibodies to T. vaginalis were detected in the sera of 41.3% (50/121) of invasive cervical cancer patients compared with only 5.0% (12/242) of female controls. All the reactive sera reacted strongly with the immunogenic surface membrane proteins of T. vaginalis of molecular weights of about 92 and 115 kDa, with variable reactivity to other immunogenic proteins of T. vaginalis. CONCLUSION: The significantly increased relative risk, RR = 3.42 (95% CI = 1.73-6.78), is comparable to the RRs derived in seroepidemiological studies of human papillomavirus, suggesting that T. vaginalis may be even more closely associated with invasive cervical cancer than previously realized.

Adult↗
PubMed1995

Effect of cooling on oxygen consumption in febrile critically ill patients.

Hyperthermic critically ill patients are commonly cooled to reduce their oxygen consumption (VO2). However, no previous studies in febrile humans have measured VO2 during cooling. We cooled 12 febrile, critically ill, mechanically ventilated patients while measuring VO2 and CO2 production (VCO2) by analysis of inspired and expired gases. All patients were mechanically ventilated for hypoxemic, hypercapneic, or shock-related respiratory failure and had a mean APACHE II score of 22.4 +/- 7.7. As temperature was reduced from 39.4 +/- 0.8 to 37.0 +/- 0.5 degrees C, VO2 decreased from 359.0 +/- 65.0 to 295.1 +/- 57.3 ml/min (p < 0.01) and VCO2 decreased from 303.6 +/- 43.6 to 243.5 +/- 37.3 ml/min (p < 0.01). The respiratory quotient (RQ) did not change significantly, and calculated energy expenditure decreased from 2,481 +/- 426 to 1,990 +/- 33 kcal/day (p < 0.01). In 7 patients with right heart catheters, cardiac output decreased from 8.4 +/- 3.2 to 6.5 +/- 1.8 L/min (p < 0.01) as the oxygen extraction fraction also tended to decrease from a mean of 28.2 +/- 6.8 to 23.4 +/- 4.7% (p = 0.12) during cooling. Accordingly, cooling the febrile patient unloads the cardiorespiratory system and, in situations of limited oxygen delivery or hypoxemic respiratory failure, may thus facilitate resuscitation and minimize the potential for hypoxic tissue injury.

APACHE↗
PubMed1995

Continuities between psychiatric disorders in adolescents and personality disorders in young adults.

OBJECTIVE: Personality disorders are a major mental health problem, but little information about their etiology and natural history is available. This study examined continuities between axis I disorders in adolescents and personality disorders in young adults. METHOD: The authors interviewed 145 young adults (mean age, 19.6 years) who had been diagnosed with a variety of DSM-III emotional and disruptive disorders during adolescence (mean age, 13.7 years). The Personality Disorder Examination was used to establish whether the subjects currently suffered from personality disorders. RESULTS: Subjects who had had disruptive disorders during adolescence showed high rates of all types of personality disorders (40% had a personality disorder at follow-up), while subjects who had had emotional disorders had a lower rate of personality disorders (12%). Men were more likely to have cluster A personality disorders, and women were more likely to have cluster C personality disorders. Disruptive diagnoses were associated with cluster B personality disorders, but emotional disorders did not show an association with cluster C personality disorders. Oppositional disorder did not increase the likelihood of passive-aggressive personality disorder. There was an association between attention deficit disorder with hyperactivity and borderline personality disorder. CONCLUSIONS: The rate of personality disorders was lower among young adults who had had emotional disorders during adolescence than among those who had had disruptive disorders, suggesting either that treatment for emotional disorders is more effective or that the personality psychopathology in these adolescents is not as severe as that in adolescents with disruptive disorders.

Adolescent↗