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Biomedical subjects

K A Siddiqui

Publications and source records attributed to K A Siddiqui.

At least 19 recordsLinked to original sources
PubMed2000

Avirulent mutants of Macrophomina phaseolina and Aspergillus fumigatus initiate infection in Phaseolus mungo in the presence of phaseolinone; levamisole gives protection.

To evaluate the role of phaseolinone, a phytotoxin produced by Macrophomina phaseolina, in disease initiation, three nontoxigenic avirulent mutants of the fungus were generated by UV-mutagenesis. Two of them were able to initiate infection in germinating Phaseolus mungo seeds only in the presence of phaseolinone. The minimum dose of phaseoli-none required for infection in 30% seedlings was 2 5 mg/ml. A human pathogen, Aspergillus fumigatus was also able to infect germinating seeds of P. mungo in the presence of 5 mg/ml concentration of phaseolinone. Phaseolinone seemed to facilitate infection by A. fumigatus, which is not normally phytopathogenic, by reducing the immunity of germinating seedlings in a nonspecific way. Levamisole, a non-specific immunopotentiator gave protection against infection induced by A. fumigatus at an optimum dose of 50 mg/ml. Sodium malonate prevented the effects of levamisole.

Adjuvants, Immunologic↗
PubMed1998

Study of efficacy and tolerance of ketoprofen and diclofenac sodium in the treatment of acute rheumatic and traumatic conditions.

A comparative, multi-centre study, was conducted during June to December, 1996 to evaluate the efficacy and tolerance of Ketoprofen 100 mg Enteric Coated (EC) tablet and 100 mg intra-muscular injection; with that of Diclofenac Sodium 50 mg tablet and 75 mg intra-muscular injection in acute rheumatic and traumatic disorders. Total of 180 patients (90 per drug), were studied, 82 men and 98 women, between the ages of 18 and 75 years. The symptoms and the number of patients were backache 50, arthritis 64, frozen shoulder 32 and sprains 34. Pain was qualitatively assessed by visual analogue scale (VAS), XY pain index, pain at mobilization and the level of pain handicap. For pain (VAS 75-100) the treatment was initiated with an injectable bid, followed by tablets bid or tid. If the pain score on VAS was less than 75, tablets were given in a bid dosage. The duration of treatment was 15 days in each case. The overall complete relief of symptoms occurred in 25% (23/90) patients with Ketoprofen and in 10% (9/90) diclofenac sodium. Moderate to mild relief was found in 75% (67/90) cases with Ketoprofen and 87% (78/90) with diclofenac sodium. No pain relief was seen in 3% (3/90) with diclofenac sodium, as against no failure in pain relief in the ketoprofen group. Tolerance was found as excellent-good for ketoprofen in 72% (65/90) with diclofenac sodium in 50%, moderate to poor for ketoprofen in 28% (35/90) and with diclofenac sodium in 50% (45/90). Our results indicate that ketoprofen compared to diclofenac sodium is efficacious in acute rheumatic and traumatic injuries. Ketoprofen injection, compared to diclofenac sodium was found to be more effective in providing analgesia.

Adolescent↗
PubMed1996

E. coli growth inhibition by a high copy number derivative of plasmid pBR322.

We have observed that plasmid pKH47, a pBR322-derivative containing a 100bp poly(dA)-poly(dT) insertion, causes growth inhibition of host E. coli cells harboring it. In this paper we show that this inhibitory effect is due to an increased copy number property of this plasmid, which is turn leads to an over expression of the plasmid-encoded tet gene. Our work also indicates that contrary to other pleiotropic effects caused by the tet gene product, which solely depend on the expression of the 5' end of the gene, growth inhibition requires an intact tet gene. In addition we present the isolation of an E. coli mutant that is refractive to the inhibitory effect of pKH47 and shares some properties with the parental bacteria containing plasmid pKH4.

Base Composition↗
PubMed1996

High expression of plasmid-encoded tetracycline resistance gene in E. coli causes a decrease in membrane-bound ATPase activity.

Expression of the plasmid pBR322-encoded tetracycline-resistant gene (tet) is known to cause other pleiotropic effects in addition to mediating the efflux of tetracycline from bacterial host cells. We have recently reported that expression of the tet gene in plasmid pKH47, a high-copy-number derivative of pBR322, causes growth inhibition of Escherichia coli cells harboring this plasmid. In this paper we report that reduced membrane-bound ATPase activity is found in E. coli cells containing plasmid pKH47. This effect is dependent on the presence of an intact tet gene and reduces the ability of the cells to grow in a minimum medium containing succinate as the sole carbon source. The same effect is more dramatically observed in cells containing an unrelated plasmid in which tet gene expression is under the control of the tac promoter.

Adenosine Triphosphatases↗
PubMed1995

Kinetoplast DNA minicircle binding proteins in a Leishmania Spp: interference of protein DNA interaction by berenil.

A kinetoplast DNA minicircle of a Leishmania Spp. binds to several proteins of the kinetoplast Lysates of kinetoplasts of Leishmania grown in the presence of berenil show complete disappearance of some of these protein bands, while the rest of the proteins present appear as much less intense bands in South Western blots when probed with either the conserved or variable regions of the minicircle or whole minicircle DNA. The conserved region of minicircle DNA complexed with berenil in vitro also fails to interact with the DNA binding proteins of kinetoplast of untreated cell in South Western blots. Since berenil induces dyskinetoplasty of kinetoplastidae, the results indicate that interference of protein-DNA interaction in the presence of berenil may be the primary event in making organisms dyskinetoplastic.

Animals↗
PubMed1991

Catenated dimers and knotted DNA structures: putative intermediates in the replication of T. cruzi kinetoplast minicircle DNA.

Upon centrifugation of gently lysed T. cruzi cells through a sucrose gradient, a free DNA fraction was shown to contain catenated dimers and knotted DNA structures. Southern hybridization and electron microscopic studies indicated that both of these structures derived from minicircle DNA, the major component of T. cruzi kinetoplast DNA. Partial denaturation analysis of a random population of catenated dimers suggests that these structures may have arisen from a late stage in the replication of minicircle DNA. On the other hand, the T. cruzi knotted minicircles we have isolated appear to be very similar to trefoil structures recently reported and implicated as replicative intermediates in two other trypanosoma species.

Animals↗
PubMed1990

A new antileishmanial compound, phaseolinone.

Inclusion of phaseolinone, a newly described mycotoxin, at 20 micrograms per ml in a solid culture medium (blood agar overlay) and at 50 micrograms per ml in a liquid culture (medium 199) inhibited the growth of L. donovani promastigotes. About 90% of the motile promastigotes lost motility after exposure to 50 micrograms per ml of phaseolinone for 6-7 h and here 3-day-old culture was more sensitive than 7-day-old culture. In an in vitro assay, DNA dependent RNA polymerase activity of 3-day-old promastigotes was considerably inhibited in the presence of this toxin. Therefore, this key enzyme was suggested to be one of the sites of action of phaseolinone.

Animals↗
PubMed1989

Spacetime representation of global electrocortical activity.

A model for global electrocortical activity is developed by considering telencephalonic structures as mass of linked oscillators generating activity with a number of resonant modes. Equations for the signals are written in the comoving frame and then transformed into the laboratory frame. The state transition matrix is obtained in the presence of electric and magnetic fields.

Animals↗
PubMed1989

Bidirectional sequencing of supercoiled plasmid DNA.

In this paper we show that restriction DNA fragments can prime DNA synthesis of a homologous supercoiled plasmid DNA. Using the dideoxyribonucleotide chain terminator method, newly synthesized truncated chains can be detached from the primers by restriction enzyme digestion. Therefore, by choosing DNA fragments flanked by two different restriction enzymes sites, nucleotide sequence information can be simultaneously obtained on both regions of the DNA surrounding the restriction fragment. The advantage of this sequencing approach over current methods is that no prior knowledge of the primary sequence is needed to find the nucleotide sequence of a given DNA fragment. Thus, synthetic primers are not required and internal sequences of a given clone can be easily accessed without the need of fragmenting the original construct. The method has been used with rapid plasmid preparations, thus considerable time and effort can be saved in the gathering of nucleotide sequence information.

Base Sequence↗
PubMed1989

Chromosomal mapping and nucleotide sequence of a human DNA autonomously replicating sequence.

A 1.1-kb human DNA fragment (ARSH1) capable of functioning as a putative origin of replication in yeast cells has been characterized both by in situ hybridization to human metaphase chromosomes and by DNA sequencing. Our hybridization studies show a preferential localization of ARSH1 in chromosome regions 1p34-36 and 2q34-37. DNA sequence analysis indicates that in addition to the consensus sequence required for ARS function in yeast cells, nuclear matrix-associated DNA motifs are also present in the 1.1-kb fragment. These results suggest that ARSH1 sequences may serve as points of anchorage to the nuclear matrix for chromosomes 1 and 2.

Amino Acid Sequence↗
PubMed1987

Phage-induced change of toxigenesis in Vibrio cholerae.

A temperate phage coding for constitutive hypertoxigenicity has been constructed in Vibrio cholerae strain 569B and used to lysogenise the low-toxin-producing strain MAK 757; 18% of lysogens showed 10-100-fold increase in toxin production. This property was also transmitted at low frequency to second generation lysogens. Thus temperate phage can increase toxin production in a low-toxin-producing strain.

Bacteriophages↗
PubMed1985

Evidence that a system similar to the recA system of Escherichia coli exists in Vibrio cholerae.

Two lines of evidence suggest that a gene analogous to the recA gene of Escherichia coli exists in Vibrio cholerae and that its product serves a proteolytic function in the SOS response. Firstly, Southern blot hybridization using the recA gene of E. coli as a probe revealed a genomic sequence in V. cholerae which hybridized with the probe. Secondly, the SOS-like response in V. cholerae (as measured by beta phage induction) triggered by DNA damaging agents like Furazolidone could be blocked by Antipain, a protease inhibitor known to inhibit RecA protease action in E. coli. Maximal blocking effect of Antipain on beta phage induction occurred at 1 mM. At this concentration neither the viability of the host bacterium nor the lytic growth of a clear plaque mutant of the phage was affected by Antipain.

Antipain↗
PubMed1984

Phage beta interaction with Vibrio cholerae.

The role of temperate phage beta in determining the serology and eltor-lytic phage sensitivity in Vibrio cholerae was investigated. The only serological change found in six host strains was a change to roughness. This was accompanied by failure to adsorb several of the lytic phages. Various phage-sensitivity changes were induced by phage beta in two hosts at the post-adsorption level. In strain HP47, three types of progeny were obtained of which one was universally resistant to lytic phages. These untypable lysogens were culturally stable but gave rise to segregants of the rare phage-type 6 on single colony selection.

Bacteriophage Typing↗
PubMed1983

Temperate phage induction and filament formation in Vibrio cholerae by furazolidone.

Furazolidone a synthetic nitrofuran used in the treatment of cholera, was found to cause prophage induction and filament formation in Vibrio cholerae. Maximum induction of phage beta was obtained at a drug concentration of 0.5 microgram/ml. Neither induction of prophage nor filamentation took place if the drug treatment was carried out in the presence of 2.5 micrograms/ml chloramphenicol, indicating a requirement for de novo protein synthesis. Our results strongly suggest the existence of "SOS" type functions in Vibrio cholerae.

Chloramphenicol↗