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Biomedical subjects

M Singh

Publications and source records attributed to M Singh.

At least 739 records · Page 41Linked to original sources
PubMed1991

Tumor localization of monoclonal antibodies against human renal carcinoma in a xenograft model.

We investigated the localization of intravenously injected DAL K45 and DAL K29, two monoclonal antibodies (MABs) against human renal cell carcinoma (RCC), and their F(ab)2 fragments in nude mice bearing intrarenal transplants of the RCC line Caki-1. More of the MABs or their F(ab)2s specifically localized in the tumor than in any normal tissue with the exception of blood. Compared to parent MABs, F(ab)2s were cleared faster from all tissues. In serum, the MABs and F(ab)2s showed a single radioactive peak retaining partial immunoreactivity. DAL K45-F(ab)2 showed the highest tumor:normal tissue localization ratios and the most distinct gamma-camera image at 24 h.

Adult↗
PubMed1991

Human immunodeficiency virus type 1 regulator of virion expression, rev, forms nucleoprotein filaments after binding to a purine-rich "bubble" located within the rev-responsive region of viral mRNAs.

The human immunodeficiency virus type 1 rev protein binds with high affinity (Kd less than 1-3 nM) to a purine-rich "bubble" containing bulged GG and GUA residues on either side of a double-helical RNA stem-loop located toward the 5' end of rev-response element RNA. High-affinity rev binding is maintained when the bubble is placed in heterologous stem-loop structures, but rev binding is reduced when either the bulged residues or flanking base pairs in the stem are altered. Rev binding to the purine-rich bubble nucleates assembly of long filamentous ribonucleoprotein structures containing polymers of rev bound to flanking RNA sequences. It is proposed that rev regulates human immunodeficiency virus RNA expression by selectively packaging viral transcripts carrying the rev-response element sequence into rod-like nucleoprotein complexes that block splicing of the packaged mRNAs.

Base Sequence↗
PubMed1991

Thermophilic actinomycetes associated with agro-environment of Punjab state (India).

Thermophilic actinomycetes (TAs) are unique high temperature aerobic bacteria which belong to the group actinomycetes. While working on hypersensitivity pneumonitis (HP), an immunological disorder, resulting from the inhalation of spores of thermophilic actinomycetes, it was considered worthwhile to record their occurrence in the environment of Punjab. Thermophilic actinomycetes isolated by spread plate method from nine different substrates of the Punjab environment were identified as 8 different species. Atmospheric occurrence of TAs was detected by exposing Petri dishes containing soy agar medium which were exposed in six different environments of the state. Seven thermophilic species were recorded. Thermoactinomyces vulgaris was the predominant species with 87.5, 87.1, and 100% prevalence in the soil, natural manure and the wheat field, respectively. The study is the first report of its kind from this region.

Actinomycetaceae↗
PubMed1991

Characterization of transcription initiation sites on the soybean mitochondrial genome allows identification of a transcription-associated sequence motif.

Transcription initiation sites on the soybean mitochondrial genome have been characterized by sequence analysis of in vitro-capped soybean mtRNAs and corresponding mtDNA regions. The most abundant, discrete soybean mtRNA species labeled by guanylyltransferase and [alpha-32P]GTP are shown to correspond to the major transcript of the atp9 gene and to a group of small RNAs consisting of a discrete 80 nucleotide (nt) species plus heterogeneous species ranging in size from 133 to 148 nt. The 133-148 nt RNAs represent a set of transcripts with a common 5' terminus and ragged 3' ends, while the 80 nt RNA corresponds to positions 53-133 of the 133 nt species. The major, discrete in vitro-capped RNA species thus correspond to primary transcripts originating at three sites located in two regions of the soybean mitochondrial genome. The sequences extending from 13 nucleotides upstream to 8 nucleotides downstream of the initiation sites for the atp9 and 133-148 nt transcripts are identical at 18 of 21 positions. Sequences closely resembling this motif are located at some other 5' transcript termini of dicot plant mitochondria. Less closely related sequences are found at transcription initiation sites of wheat and maize mitochondria.

Base Sequence↗
PubMed1991

Regression of human melanoma xenografts in nude mice injected with methotrexate linked to monoclonal antibody 225.28 to human high molecular weight-melanoma associated antigen.

Intravenous injections into nude mice of 5 mg/kg methotrexate (MTX) linked to the antibody to human high molecular weight-melanoma associated antigen (HMW-MAA), monoclonal antibody (mAb) 225.28, an IgG2a, on days 1, 4, 7, 10 and 14, starting 24 h after subcutaneous inoculation of 2 x 10(6) cultured human M21 melanoma cells inhibited mean tumor volume by 90% on day 14 and by 65% on day 50 after the beginning of the treatment. Injections of equimolar amounts of free MTX and MTX linked to normal mouse IgG or to an isotype-matched myeloma protein did not inhibit tumor growth significantly. MTX linked to mAb 225.28 did not inhibit the xenograft of a subline of human melanoma cell line M21 without detectable expression of HMW-MAA. In a clonogenic assay, the MTX-225.28 conjugate was three times more potent in inhibiting the growth of M21 melanoma cells than free MTX, but did not inhibit the growth of kidney carcinoma cells Caki-1, which do not express high-Mr MAA. In contrast, MTX linked to the mAb DAL K29, reacting with kidney carcinoma cells Caki-1, inhibited their growth but did not affect that of melanoma cells. M21 melanoma cells isolated from the residual tumor of a mouse treated with the MTX-225.28 conjugate did not differ in their reactivity with mAb 225.28 and in their sensitivity to MTX when compared with M21 cells from an untreated mouse.

Animals↗
PubMed1991

Inhibition of human renal cancer by monoclonal-anti-body-linked methotrexate in an ascites tumor model.

The monoclonal antibody DAL K29 against a cell-surface antigen associated with a human renal cell carcinoma was covalently linked to the antifolate methotrexate with full retention of antibody activity and partial retention of drug activity. Using an ascites tumor model, developed after intraperitoneal (i.p.) inoculation of 5 x 10(6) cells of the human kidney cancer line Caki-1 per pristane-primed nude mouse, we showed that the methotrexate-Dal-K29 conjugate was a more potent tumor inhibitor (P less than 0.0005) of human renal cell carcinoma (which is resistant to currently available modalities including chemotherapy) than the drug or mAb alone, the drug linked to an isotype-matched nontumor-specific IgG or a mixture of the drug and the mAb. Only the conjugate could produce tumor-free survival in a proportion of the mice during the period of observation (i.e. 150 days after tumor inoculation).

Animals↗
PubMed1991

Percutaneous ultrasound-guided fetal skin biopsy: a new approach.

Our preliminary experience with this unreported percutaneous ultrasound guided method using a fine needle system showed 100% success (seven cases) in obtaining fetal skin biopsies. The fetal scalp was chosen for biopsy. This technique is easy, less invasive, simple, has minimum procedural difficulties and complications and thus it may replace fetoscopy for obtaining fetal skin biopsy.

Biopsy, Needle↗
PubMed1991

A Blastocystis species from the sea-snake, Lapemis hardwickii (Serpentes: Hydrophiidae).

Observations were made on Blastocystis isolated from the sea-snake, Lapemis hardwickii. Exponential growth of the organism was observed between 2 and 4 days of culture. Vacuolated, amoeboid and granular forms were observed in cultures, similar to B. hominis. The optimal growth temperature for the sea-snake Blastocystis was 24 degrees C compared with 37 degrees C for B. hominis. The karyotypic patterns of B. hominis and the sea-snake Blastocystis were studied in the clamped homogeneous electric field (CHEF) technique and found to be different. Based on the above differences, the sea-snake Blastocystis was designated as Blastocystis lapemi sp. nov.

Animals↗
PubMed1991

A fully modular vector system for the optimization of gene expression in Escherichia coli.

The new expression vector system CYTEXP is designed to facilitate the optimization of both transcription and translation in Escherichia coli, while at the same time allowing the exchange of its major components using unique restriction sites. In vitro mutagenesis can be performed in situ using single-stranded DNA generated from the bacteriophage f1 ORI sequence. The basic vector pCYTEXP1 bears a synthetic copy of the intercistronic sequence that enhances the translation of the E. coli atpE gene. Reading frames can be inserted directly downstream of this sequence. The bacteriophage lambda promoters, the atpE sequence, the bacteriophage fd transcriptional terminator, the f1 ORI, and the amp antibiotic resistance gene are all borne on exchangeable "modules." Thus, both the efficiency and the conditions of expression of cloned genes can be readily optimized.

Antigens, Bacterial↗
PubMed1991

Inhibition of human renal cancer by monoclonal antibody targeted methotrexate-containing liposomes in an ascites tumor model.

The monoclonal antibody DAL K29 against a human renal cell carcinoma associated cell surface antigen was covalently linked to small unilamellar lipid vesicles (SUV) containing the antifolate, methotrexate (MTX), with full retention of antibody activity. In an ascites tumor model developed after intraperitoneal inoculation of 5 x 10(6) cells of the human kidney cancer line Caki-1 per pristane primed nude mouse, the DAL K29 linked MTX-containing SUV was a more potent tumor inhibitor (P less than 0.0005) than the drug or MAB alone, MTX-containing SUV, a mixture of DAL K29 and MTX-containing SUV or MTX-containing SUV linked to an isotype matched nontumor specific IgG.

Animals↗
PubMed1991

Sudden unexplained death syndrome--a new manifestation in melioidosis?

The indirect haemagglutination (IHA) test using sensitized turkey erythrocytes and the indirect immunofluorescence assay (IgM-IFA) was confirmed to be sensitive in the detection of a recent or current Pseudomonas pseudomallei infection in 19 culture-confirmed Singapore melioidosis patients. All were found to have antibody titres from 4 to 32768 in the IHA test and 10 to 320 in the IgM-IFA test. When these tests were employed on sera from 16 immigrant Thai construction workers who died of sudden unexplained death syndrome (SUDS) and 73 healthy Thai fellow workers, 93.8% and 68.8% of SUDS cases had IHA titre of greater than or equal to 4 and IgM-IFA titre of greater than or equal to 10 respectively, in contrast to 39.7% and 12.3% found among healthy Thai workers. These data indicate that at the time of death, most of the SUDS patients had an active infection with P. pseudomallei, possibly resulting from reactivation of a latent infection. The aetiological role of P. pseudomallei as the major cause of SUDS is discussed.

Adult↗
PubMed1991

Controlled delivery of diphtheria toxoid using biodegradable poly(D,L-lactide) microcapsules.

Diphtheria toxoid, which is an important vaccine in the expanded program of immunization (EPI) in the developing countries, was microencapsulated using poly(D,L,-lactide) of 49,000 molecular weight and the in-water drying technique. The microcapsules were subjected to an in vitro antigen release study using a sensitive enzyme-linked immunosorbent assay (ELISA) developed in the laboratory. Antibody titers in immunized Balb/C mice were also determined using direct ELISA. The antibody units in the immunized group till day 75 were quite comparable to those in the group receiving conventional three-dose injection of diphtheria toxoid with calcium phosphate as an adjuvant. SEM photographs of the microcapsules during in vitro degradation demonstrated the erosion kinetics of the polymer, leading to controlled release of the antigen.

Animals↗
PubMed1991

Isomeric DNA ladder formation of a plasmid encoding tobramycin resistance from Escherichia coli.

During a 20-month survey of resistance to three aminoglycosides (gentamicin, tobramycin, and amikacin) in Escherichia coli at a university hospital, six tobramycin-, kanamycin-resistant isolates containing a 50 kilobase conjugative R-plasmid which encoded an aminoglycoside phosphotransferase (APH-(3')) were isolated. The APH-(3') conferred resistance to kanamycin (MIC = 100 mg/L) but not to tobramycin (MIC = 20 mg/L). In both the original isolates and transconjugants the six R-plasmids demonstrated an isomeric ladder in the range of 50-112 kb, which was enhanced by exposure of the bacterial cultures to tobramycin. pJFJ2522 is the prototype for this group of plasmids. Bacterial DNA gyrase reversed the isomeric DNA ladder in pJFJ25222 by increasing the supercoiling of the plasmid DNA. Regardless of the level of supercoiling, the plasmids produced indistinguishable restriction endonuclease fragment patterns. The clinical isolates containing these plasmids demonstrated different restriction fragment length polymorphism (RFLP) of their EcoRI digested genomic DNA using E. coli rRNA as a probe. Ladder formation was plasmid specific since other tobramycin R-plasmids did not form a ladder, but it was not host specific. pJFJ25222 formed a ladder in a recA- host and displayed the same restriction pattern in a recA- as in a recA+ environment. In conclusion, pJFJ2522 contains a new tobramycin resistance gene whose mechanism of resistance is not known and whose product probably influences the isomerization of the plasmid.

Conjugation, Genetic↗
PubMed1991

Suppression of cytoplasmic male sterility by nuclear genes alters expression of a novel mitochondrial gene region.

To identify regions of the mitochondrial genome that potentially could specify the "Polima" (pol) cytoplasmic male sterility (CMS) of Brassica napus, transcripts of 14 mitochondrial genes from nap (male fertile), pol (male sterile), and nuclear fertility-restored pol cytoplasm plants were analyzed. Transcriptional differences among these plants were detected only with the ATPase subunit 6 (atp6) gene. Structural analysis of the atp6 gene regions of pol and nap mitochondrial DNAs showed that rearrangements in the pol mitochondrial genome occurring upstream of atp6 have generated a chimeric 224-codon open reading frame, designated orf224, that is cotranscribed with atp6. In CMS plants, most transcripts of this region are dicistronic, comprising both orf224 and atp6 sequences. Nuclear restorer genes at either of two distinct loci appear to specifically alter this transcript pattern such that monocistronic atp6 transcripts predominate. The differences in expression of this region appear to result, in part, from differential processing of a tRNA-like element comprising a tRNA pseudogene present immediately upstream of atp6 in both the sterile and fertile mitochondrial DNAs. Possible mechanisms by which expression of the orf224/atp6 locus and the Polima CMS trait may be specifically related are considered.

Adenosine Triphosphatases↗