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Biomedical subjects

M Singh

Publications and source records attributed to M Singh.

At least 649 records · Page 36Linked to original sources
PubMed1994

One year outcome of babies with severe neonatal hyperbilirubinemia and reversible abnormality in brainstem auditory evoked responses.

Brainstem auditory evoked responses (BAER) were longitudinally recorded prospectively in 18 term infants with neonatal hyperbilirubinemia (NHB) (total serum bilirubin > 15 mg/dl). Seven neonates had abnormal BAER. Wave complex IV-V was absent in eight recordings in NHB group while they were normal in the control group (p < 0.001). Prolongation of latency of waves I and V and interwave conduction time (wave I-V) occurred in jaundiced infants especially when unconjugated serum bilirubin level rose above 22 mg/dl. The abnormalities in BAER reversed to normal in all seven neonates after exchange blood transfusion indicating transient nature of bilirubin toxicity to the brain. All seven neonates in the study and control group had normal hearing, development quotient and were free of neurological sequelae on follow up for one year.

Audiometry, Evoked Response↗
PubMed1994

Chlamydial serology and laparoscopic findings in infertile women.

Fifty-seven infertile women were studied for presence of chlamydial infection by detecting antichlamydial antibodies using indirect immunoperoxidase assay technique. Laparoscopy was performed in all of them. Inflammatory changes in fallopian tubes were present irrespective of serological status. Thus no rigid criteria for carrying out laparoscopy can be made. A high index of suspicion is required for detection of chlamydial infection as it runs an indolent course with no specific symptoms.

Antibodies, Bacterial↗
PubMed1993

The host response in graft versus host disease. I. Radiosensitive T cells of host origin inhibit parental anti-F1 cytotoxicity in murine chronic graft versus host disease.

Murine graft versus host (GVH) disease takes two forms depending on the parental/F1 strain combination employed. Acute lethal GVH disease is characterized by anemia, lymphopenia, hypogammaglobulinemia, profound anti-F1 cytotoxicity, and the loss of cytotoxic potential against third-party alloantigen. In contrast to this, chronic GVH disease is characterized by polyclonal B cell activation, auto-antibody production, no anti-F1 cytotoxicity, and retained cytotoxicity against allotargets. We now report that this marked disparity in disease expression results from a radio-sensitive host mechanism which protects the F1 mouse from parental anti-F1 cytotoxicity in mice undergoing chronic GVH disease. Cellular analysis revealed that protection in chronic GVH disease is mediated by a phenotypically complex system of genetically unrestricted radiosensitive T cells of F1 origin. These cells fail to functionally emerge in mice undergoing acute lethal GVH disease.

Acute Disease↗
PubMed1993

The host response in graft versus host disease. II. The emergence of host protective cells is in part determined by background genomic compatibility.

Murine graft versus host (GVH) disease takes two forms depending on the parental/F1 strain combination employed. In an accompanying paper (Singh et al., Clin. Immunol. 151, 1993) many of the clinical features of these two forms of GVH disease are described. In addition to these clinical characteristics, acute lethal GVH (ALGVH) disease is characterized by diminished natural killer cell activity, whereas chronic GVH disease is characterized by normal or increased natural killer cell activity. Previously we have reported that this marked disparity in disease expression can be attributed to radiosensitive host cells which protect the F1 mouse from parental anti-F1 cytotoxicity (CTX) in mice undergoing chronic GVH (CGVH) disease. These cells fail to functionally emerge in mice undergoing ALGVH disease. We now report that the background genome, presumably the minor lymphocyte stimulatory loci, of the donor cells determines whether these host cells emerge and thereby dictates the form of GVH disease which is induced. C57BL/6 (B6) cells (H-2b, minor lymphocyte stimulatory locus (Mls)b) and B10.D2 cells (H-2d, Mlsb) were found to induce ALGVH disease when adoptively transferred to [C57BL/6xDBA/2]F1 (B6D2) (H-2b/d, Mls-1a/b, Mls-2a/b) recipient mice. DBA/2 cells (H-2d, Mls-1a, Mls-2a) and Balb/c cells (H-2d, Mls-1a, Mls-2b) induced CGVH disease in B6D2 mice. Using Mls congenic strains we have demonstrated that donor cell reactivity against Mls-2a was necessary and sufficient to induce ALGVH disease as determined by anemia, lymphopenia, anti-F1 cytotoxicity, and loss of cytotoxicity against allogeneic targets. Such Mls-2a reactivity correlated with the impaired induction of a host protective cell capable of vetoing self-directed CTX. Failure of this host protective cell to emerge in turn correlated with donor anti-host CTX and the emergence of ALGVH disease.

Acute Disease↗
PubMed1993

DNA regions flanking the mouse Ig 3' alpha enhancer are differentially methylated and DNAase I hypersensitive during B cell differentiation.

Two B cell-specific enhancer elements are associated with the IgH gene cluster. One enhancer is located within the J-C mu intron (E mu), whereas a second enhancer (3' alpha E) is approximately 12.5 kb 3' of the C alpha membrane exon. In an attempt to understand the function of 3' alpha E, we have characterized its surrounding structural milieu during various stages of B cell differentiation through analysis of methylation patterns and the identification of DNAse I-hypersensitive sites. We observed a correlation between the chromatin structure of this region and the differentiation state of the cell. Compared to liver and brain, the region 3' of alpha was hypermethylated in pre-B and T cell lines and became progressively demethylated as B cell differentiation continued. A DNAse I-hypersensitive site was present in pre-B cell lines about 17 kb 3' of 3' alpha E. In fully differentiated myeloma cell lines, a second cluster of DNAse I-hypersensitive sites was present immediately 5' of 3' alpha E. Our data indicate that the 3' alpha enhancer is relatively sequestered during early stages of B cell differentiation and becomes increasingly accessible at later stages.

Animals↗
PubMed1993

Potentiation of antitumor immunotoxins by liposomal monensin.

BACKGROUND: The cytotoxicity of specific ricin A-chain immunotoxins is greatly enhanced in vitro by the carboxylic ionophore monensin. However, the highly lipophilic nature of monensin, which is reflected in its poor solubility and short half-life, has restricted its use in in vivo animal studies. PURPOSE: The purpose of this study was to assess the ability of monensin incorporated in unilamellar vesicles (liposomes) to potentiate antitumor immunotoxins in vitro and in vivo. METHODS: Monensin was incorporated into liposomes and used in combination with specific immunotoxins against human tumor cell lines in vitro and in vivo. Inhibition of [3H]leucine incorporation was used to evaluate the cytotoxic action of immunotoxin with or without monensin in vitro on the following human tumor cell lines: H-MESO-1 malignant mesothelioma, LS174T colorectal carcinoma, and U373, U87, and MG-1 glioblastomas. For the in vivo studies of immunotoxins and liposomal monensin, BALB/c nu/nu mice were inoculated intraperitoneally with H-MESO-1 cells. RESULTS: Liposomal monensin potentiated the cytotoxic action of cell-specific anti-human transferrin receptor immunotoxin on H-MESO-1 target cells at a molar concentration of monensin that was 160-fold lower than the concentration of monensin in buffer that produced the same effect (0.3 nM versus 0.05 microM). Moreover, immunotoxin plus 0.1 microM liposomal monensin was fivefold more toxic for H-MESO-1 cells and 1000-fold and 2200-fold more toxic for human glioblastoma U373 and U87 cells, respectively, than immunotoxin plus 0.1 microM free monensin in buffer. Liposomal monensin produced similar effects when it was combined with different specific immunotoxins and other target cell lines (i.e., LS174T, U87, and CEM). Immunotoxin specificity was preserved with liposomal monensin, as shown by the absence of effect with non-cell-binding immunotoxins or on antigen-negative cell lines. In mice, liposomal monensin in combination with specific immunotoxin substantially prolonged survival, and three (21%) of 14 mice bearing H-MESO-1 xenografts treated with the liposomes showed no evidence of tumor at day 160 after treatment. Treatment with control immunotoxin plus liposomal monensin was ineffective. CONCLUSION: These findings suggest that encapsulation of monensin into liposomes increased the capacity of monensin to enhance the potency of cell-specific immunotoxin in vitro and in vivo.

Adjuvants, Immunologic↗
PubMed1993

Structure of the nifQ gene from Enterobacter agglomerans 333 and its overexpression in Escherichia coli.

The nifQ gene, involved in early stages of iron-molybdenum cofactor (FeMo-co) biosynthesis, was identified downstream of the nifB and nifF genes of Enterobacter agglomerans. This gene was cloned and its nucleotide sequence determined. The amino acid sequence, as deduced from the nucleotide sequence, revealed an accumulation of cysteine amino acid residues at the C-terminal end of the protein. The cysteine cluster showed the following consensus sequence Cys-X4-Cys-X2-Cys-X5-Cys, which is a typical characteristic of metal-binding proteins. Further, the nifQ gene was cloned downstream of strong transcriptional (bacteriophage lambda PLPR) and translational (atpE) signals of the expression vector pCYTEXP1 and expressed as an unfused, soluble protein in Escherichia coli. The molecular mass of 19 kDa, as deduced by SDS-PAGE, is in good agreement with the molecular mass deduced from the nucleotide sequence. The availability of high-level expression clones should facilitate purification of large quantities of the recombinant NifQ protein and elucidation of its properties.

Amino Acid Sequence↗
PubMed1993

Haploid and diploid expression of a Brassica campestris anther-specific gene promoter in Arabidopsis and tobacco.

The anther-specific cDNA clone Bcp1 from Brassica campestris is expressed in both the haploid pollen and diploid tapetum, as shown by in situ hybridization. We have isolated Bgp1, a genomic clone homologous to Bcp1. The coding region and extensive 5' flanking sequences of Bgp1 have been sequenced, and the coding region shows 88% identity with Bcp1. RNA gel blot analysis confirmed the expression of Bgp1-specific transcripts in B. campestris pollen. A 767 bp 5' DNA fragment was fused to the reporter gene beta-glucuronidase (gus) and introduced into both Arabidopsis thaliana and Nicotiana tabacum by transformation. This 5' fragment directed high-level expression in the pollen and tapetum of transgenic Arabidopsis. In transgenic tobacco however, the same construct was expressed only in pollen. A series of 5' deletion constructs has been created and used to transform A. thaliana to analyse the 5' region of Bgp1. The results indicate that Bgp1 expression in the tapetum and pollen of Arabidopsis requires the presence of different 5' DNA sequences.

Amino Acid Sequence↗
PubMed1993

Characterization of expression of a mitochondrial gene region associated with the Brassica "Polima" CMS: developmental influences.

The mitochondrial genome of the Polima (pol) male-sterile cytoplasm of Brassica napus contains a chimeric 224-codon open reading frame (orf224) that is located upstream of, and co-transcribed with, the atp6 gene. The N-terminal coding region of orf224 is derived from a conventional mitochondrial gene, orfB, while the origin of the remainder of the sequence is unknown. We show that an apparently functional copy of orfB is present in the pol mitochondrial genome, indicating that the pol CMS is not caused by the absence of an intact, expressed orfB gene. The 5' termini of orf224/atp6 transcripts present in both sterile and fertility-restored (Rf) pol cytoplasm plants are shown to map to sequences resembling mitochondrial transcription-initiation sites, whereas the 5' termini of two transcripts specific to restored lines map to sequences which resemble neither one another nor mitochondrial promoter motifs. It is suggested that the complex orf224/atp6 transcript pattern of Rf plants is generated by a combination of multiple transcription initiation and processing events and that the nuclear restorer gene acts to specifically alter orf224/atp6 transcripts by affecting RNA processing. Northern analyses demonstrate that the effect of the restorer gene on orf224/atp6 transcripts is not tissue or developmental-stage specific. However, the expression of the atp6 region is developmentally regulated in pol plants, resulting in decreased levels of monocistronic atp6 transcripts in floral tissue relative to seedlings. It is suggested that this developmental regulation may be related to the absence of overt phenotypic effects of the CMS mutation in vegetative tissues.

Adenosine Triphosphatases↗
PubMed1993

In vitro encystment and experimental infections of Blastocystis hominis.

Cultures of Blastocystis hominis were induced to encyst using three encystation media: (a) an encystation medium (EM) comprising yeast extract in buffered saline containing 50% horse serum, (b) an encystation medium (CEM) comprising EM conditioned with bacterial soluble products and (c) an encystation medium (TEM) containing 0.5% trypticase in EM. Two isolates of B. hominis were studied, an axenized isolate C and a non-axenized isolate MS. In EM, isolate C did not encyst, whereas 6.1% of isolate MS had encysted by day 1. However, in CEM and TEM, 17.4% and 25.7% of isolate C, respectively, had encysted by day 5. In all three media, isolate MS encysted more readily than isolate C, with as much as 91.7% of the former encysting in TEM. As viewed by phase-contrast microscopy, cyst-like stages appeared highly refractile. Direct stool examination of juvenile Wistar rats infected with 10,000 cyst-like stages of both C and MS isolates showed Blastocystis at day 2 post-infection. At autopsy on day 7, large numbers of Blastocystis were seen in the cecum, with smaller numbers being observed in the large intestine. In contrast, rats fed with various inocula of the vacuolar stages of isolates C and MS did not become infected, indicating the importance of the encysted stages in the transmission of the parasite.

Animals↗
PubMed1993

The effect of superoxide dismutase alleles on aging in Drosophila.

The effects of superoxide dismutase on aging were tested using two different experimental approaches. In the first, replicated populations with postponed aging were compared with their controls for frequencies of electrophoretic alleles at the SOD locus. Populations with postponed aging had consistently greater frequencies of the allele coding for more active SOD protein. This allele was not part of a segregating inversion polymorphism. The second experimental approach was the extraction of SOD alleles from different natural populations followed by the construction of different SOD genotypes on hybrid genetic backgrounds. This procedure did not uncover any statistical effect of SOD genotype on longevity or fecundity. There were large effects on longevity and fecundity due to the family from which a particular SOD genotype was derived. To detect the effects of SOD genotypes on longevity with high probability would require a ten-fold increase in the number of families used.

Aging↗
PubMed1993

Edaphological characteristics of unweathered and weathered fly ashes from Gondwana and lignite coal.

Naturally weathered and unweathered samples of fly ashes produced from Gondwana and lignite coals were characterized for their edaphological properties. The particle size distribution in these fly ashes varied widely, and the percentage of [Formula: see text] size particles governed their water holding capacity. All fly ashes were noncoherent in the dry state and had lower particle density than quartz and mulite. The fly ashes were low in available N, but were sufficient in available P, K, Ca, Mg, S, Cu, Fe, Mn, Zn and B. Among the fly ashes, unweathered lignite fly ash was the richest source of K, Ca, Mg, S and Fe, while weathered lignite fly ash had the highest amounts of Mn, Zn and B. The pH of the fly ashes was closely related to the ratio of exchangeable Ca to exchangeable Al. The fly ashes were high in soluble salt, but were poor in cation exchange capacity. As an amendment to correct soil pH, the fly ashes had a poor buffering capacity. Weathering decreased the total Fe, available S and exchangeable Na percentages, but increased the organic C content of the fly ashes. Invariably, an excess of soluble salts and exchangeable Na could limit plant growth on fly ash dumps. Toxic levels of B and Al existed in only some fly ashes.

Journal Article↗
PubMed1993

Melanotic neuro-ectodermal tumour of infancy arising from the squamous and occipital bone.

The melanotic neuro-ectodermal tumour of infancy is an uncommon benign tumour of neural crest origin occurring in infants with a predilection for the anterior maxilla. This lesion shows a good response to conservative surgical excision with few recurrences but it should be followed up for long periods of time because of the rare malignant change possible in the tumour.

Humans↗