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Biomedical subjects

S Prakash

Publications and source records attributed to S Prakash.

At least 289 records · Page 16Linked to original sources
PubMed1983

Molecular cloning and characterization of the RAD1 gene of Saccharomyces cerevisiae.

We have cloned the RAD1 gene of Saccharomyces cerevisiae and physically mapped it to a 4.0-kb DNA fragment from chromosome XVI. The RAD1 gene determines a transcript of 3.1 kb, and the direction of transcription was found to be leftwards, from EcoRI towards Bg/II (Fig. 1). Deletions of the RAD1 gene were made and were found to have no effect on viability of vegetative cells or spores, or on sporulation.

Chromosome Mapping↗
PubMed1983

Isolation and characterization of the RAD3 gene of Saccharomyces cerevisiae and inviability of rad3 deletion mutants.

The RAD3 gene of Saccharomyces cerevisiae is required for nicking of DNA containing pyrimidine dimers or interstrand crosslinks. We have cloned the RAD3 gene and physically mapped it to 2.6 kilobase of DNA. A DNA segment of the cloned RAD3 insert was ligated into plasmid YIp5, which transforms yeast by homologous integration, and shown to integrate at the RAD3 site in chromosome V, thus verifying the cloned DNA segment to be the RAD3 gene and not a suppressor. The RAD3 gene encodes a 2.5-kilobase mRNA, extending between the Kpn I site and the Sau3A1/BamHI fusion junction in plasmid pSP10, and the direction of transcription has been determined. The 2.5-kilobase transcript could encode a protein of about 90,000 daltons. We also show the deletions of the RAD3 gene to be recessive lethals, indicating that the RAD3 gene plays an important role in other cellular processes in addition to incision of damaged DNA.

Journal Article↗
PubMed1983

Immunological studies in seronegative spondyloarthropathies.

Immunological parameters including the serum levels of major classes of immunoglobulins and complement C3, screening of six commonly encountered autoantibodies (including rheumatoid factor) and screening for circulating immune complexes were carried out in patients with different presentations of seronegative spondyloarthropathies. Compared with 27 controls, the mean serum levels of IgG were significantly elevated (p less than 0.001) in 19 patients with ankylosing spondylitis (AS), 15 with Reiter's disease (RD) and nine with 'unclassified' seronegative spondarthritis. Serum IgA was significantly elevated (p less than 0.01) in Reiter's disease but not in the other two groups of patients. One patient with 'unclassified' seronegative spondarthritis showed complete absence of IgA and IgM in his serum. Serum C3 levels were estimated in 26 AS patients, 14 RD patients and nine unclassified seronegative spondarthritis patients. The values did not differ significantly from those in 27 controls. Autoantibodies were not detected in any of 29 patients with AS, 15 with RD and 10 patients with unclassified seronegative spondarthritis. Circulating immune complexes were detected by latex agglutination-inhibition technique in 5.9% of 85 controls, 61% of 18 patients with ankylosing spondylitis (p less than 0.001), 67% of 15 patients with Reiter's disease (p less than 0.05) and 78% of nine patients with unclassified seronegative spondarthritis (p less than 0.001). The findings would suggest an ongoing antigenic challenge in these diseases in which tissues may be damaged by deposits of antigen-antibody complexes.

Antigen-Antibody Complex↗
PubMed1983

HLA B27 related 'unclassifiable' seronegative spondyloarthropathies.

Twenty-five patients (22 males and 3 females) are described who had 'unclassifiable' seronegative peripheral arthritis affecting mainly the large joints of the lower limbs with other typical features of spondyloarthropathies such as heel pain, low back pain, and mucosal ulcers. But their disorders could not be diagnosed as any specific spondyloarthropathy such as ankylosing spondylitis, Reiter's disease, etc. The mean age of onset of disease was 21.4 years and 60% of them had mono- or oligoarthritis; 60% had arthritis of only lower limb joints. Knee, ankle, and hip joints were most commonly involved, often asymmetrically (mean degree of asymmetry = 0.28). Minimal radiographic sacroiliitis was present in 4 patients, though 13 had low back pain. HLA B27 antigen was detected in 21 (84%) of these patients and only 5.9% of 118 controls (relative risk 83). In addition to these 25 patients there were 4 others whose only symptom was severe bilateral heel pain: 3 of them were positive for HLA B27.

Achilles Tendon↗
PubMed1982

Defective excision of pyrimidine dimers and interstrand DNA crosslinks in rad7 and rad23 mutants of Saccharomyces cerevisiae.

Excision of pyrimidine dimers and interstrand DNA crosslinks was examined in the deletion mutants rad7-delta 1, rad23-delta 1, and rad7-delta 1 rad23-delta 1. These mutants remove pyrimidine dimers and crosslinks much less efficiently than the RAD+ strains; only 30-60% of pyrimidine dimers and 25-40% of crosslinks are removed even after prolonged incubation. The rad7 and rad23 mutations may represent defects in protein factors which increase the efficiency of the nicking enzyme complex or make chromatin more accessible to the nicking activity.

Biological Evolution↗
PubMed1982

Genetic control of excision of Saccharomyces cerevisiae interstrand DNA cross-links induced by psoralen plus near-UV light.

Excision of interstrand DNA cross-links induced by 4,5',8-trimethyl psoralen plus 360-nm light was examined in wild type (RAD+) and various radiation-sensitive (rad) mutants of Saccharomyces cerevisiae known to be defective in the excision of UV light-induced pyrimidine dimers. Alkaline sucrose sedimentation of DNA after incubation of psoralen-plus-light-treated cells indicated little or no nicking of cross-linked DNA in rad1-2, rad2-5, rad3-2, rad4-4, rad10-2, and mms19-1 mutants. In the rad14-2 mutant, substantial nicking was observed but to a much lesser extent than in the RAD+ strains, whereas the rad16-1 mutant was as proficient in nicking as the RAD+ strain. Removal of cross-links was also examined in RAD+, rad3-2, and rad14-2 strains by determining the sensitivity of alkali-denatured and -neutralized DNA to hydrolysis by S1 nuclease. No cross-link removal was observed in the rad3-2 mutants, and the rad14-2 mutant was much less efficient than the RAD+ strain in removing cross-links.

DNA Repair↗
PubMed1981

Morphological features of Jat dentition.

Observations on morphological characters of milk and permanent teeth, based on 648 pairs of dental casts of 356 male and 292 female Jat children of Haryana (India) are reported. Deciduous teeth show high frequencies of bilateral winging of maxillary central incisor, Carabelli's cusp of maxillary second molar, and deflecting wrinkle of mandibular second molar. Reduction of maxillary molar cusps is more marked in males than in females. Y pattern is very common in deciduous molars. Permanent teeth have high frequencies of grooved cingulum of incisors, cingular nodule of lateral incisors and canines, and distal accessory ridge of canines. Low frequencies of Carabelli's cusp and winging are also common. The tendency towards faintly developed shovelling in milk incisors occurs more often than in the permanent teeth.

Adolescent↗
PubMed1981

Recombination and mutagenesis in rad6 mutants of Saccharomyces cerevisiae: evidence for multiple functions of the RAD6 gene.

The rad6-1 and rad6-3 mutants are highly UV sensitive and show an increase in spontaneous and UV induced mitotic heteroallelic recombination in diploids. Both rad6 mutants are proficient in spontaneous and UV induced unequal sister chromatid recombination in the reiterated ribosomal DNA sequence and are deficient in UV induced mutagenesis. In contrast to the above effects where both mutants appear similar, rad6-1 mutants are deficient in sporulation and meiotic recombination whereas rad6-3 mutants are proficient. The differential effects of these mutations indicate that the RAD6 gene is multifunctional. The possible role of the RAD6 gene in error prone excision repair of UV damage during the G1 phase of the cell cycle in addition to its role in postreplication repair is discussed.

Alleles↗
PubMed1981

a/alpha-specific effect on the mms3 mutation on ultraviolet mutagenesis in Saccharomyces cerevisiae.

A new gene involved in error-prone repair of ultraviolet (UV) damage has been identified in Saccharomyces cerevisiae by the mms3-1 mutation. UV-induced reversion is reduced in diploids that are homozygous for mms3-1, only if they are also heterozygous (MATa/MAT alpha) at the mating type locus. The mms3-1 mutation has no effect on UV-induced reversion either in haploids or MATa/MATa or MAT alpha/MAT alpha diploids. The mutation confers sensitivity to UV and methyl methane sulfonate in both haploids and diploids. Even though mutation induction by UV is restored to wild-type levels in MATa/MATa mms3-1/mms3-1 or MAT alpha/MAT alpha mms3-1/mms3-1 diploids, such strains still retain sensitivity to the lethal effects of UV. Survival after UV irradiation in mms3-1 rad double mutant combinations indicates that mms3-1 is epistatic to rad6-1 whereas non-epistatic interactions are observed with rad3 and rad52 mutants. When present in the homozygous state in MATa/MAT alpha his1-1/his1-315 heteroallelic diploids, mms3-1 was found to lower UV-induced mitotic recombination.

Epistasis, Genetic↗
PubMed1981

Spontaneous mitotic recombination in mms8-1, an allele of the CDC9 gene of Saccharomyces cerevisiae.

The methyl methane sulfonate (MMS)-sensitive mutation mms8-1 increases the rate of spontaneous mitotic intragenic recombination at five heteroallelic loci on three chromosomes. Complementation, segregation, and mapping studies indicate that mms8-1 is allelic to cdc9, known to be defective in deoxyribonucleic acid ligase. Both mms8-1 and cdc9 mutants are lethal in combination with the recombination-defective mutant rad52-1. Genetic analysis of spontaneous red/white sectors in an ade2-1/ade2-1 ade5/+ mms8-1/mms8-1 strain shows nonreciprocal recombinational events involving long chromosome segments. We also observe greater than expected rates of simultaneous recombination at loci on different chromosomes in both wild-type and mms8-1 mutants.

Alleles↗
PubMed1980

Variation in activities of amylase allozymes associated with chromosome inversions in Drosophila pseudoobscura, D. persimilis and D. miranda.

Different electrophoretic alleles of amylase show associations with particular chromosome 3 inversions in D. pseudoobscura and D. persimilis. Relative adult amylase activities were compared in 37, 37 and 10 strains of D. pseudoobscura, D. persimilis and D. miranda, respectively. Strains carrying the same electrophoretic allele were compared by crossing these lines individually to a reference strain carrying a different electrophoretic mobility allele. This procedure allows comparisons among species, inversions, electromorphs and strains for genetic variation in amylase activity. F2 analysis established that the activity variation co-segregates with the structural amylase locus. This type of variation could be due to either structural gene differences or differences in closely linked, cis-acting regulatory regions. Variation has been detected among and within electrophoretic mobility classes. Moreover, this variation is clearly nonrandom and reveals more of the genetic structure associated with the chromosomal inversion phylogeny of D. pseudoobscura and D. persimilis. ----Some of the findings are: (1) Similar electromorphs in D. pseudoobscura and D. persimilis usually show different activities. These species show nearly complete differentiation of amylase alleles, based on activities. (2) D. persimilis has the broadest range of variation in amylase activity, about four-fold between the highest and lowest alleles. D. pseudoobscura and D. miranda are also polymorphic for activity, but have more constrained ranges of variation. D. miranda alleles show on the average about four times the activity of D. pseudoobscura alleles. (3) Some association of electrophoretic mobility and activity has been found. Alleles 1.09 of D. persimilis, as well as 1.43 and 1.55 of D. miranda, have relatively high activity. It may be that these high activity alleles are part of an adaptation to cooler habitats. (4) Within electrophoretic classes, associations of activities with inversions have been found. These are especially strong in D. persimilis. The 1.00 alleles in the ST, KL, MD and WT inversions, the 0.92 allele in the ST and MD inversions and the 1.09 allele in the WT and KL inversions have levels of activities that depend upon the arrangement in which they are located. These results demonstrate that suppression of recombination in inversion heterokaryotypes can result in extensive genic divergence between inversions.

Amylases↗
PubMed1980

Developmental variation in amylase allozyme activity associated with chromosome inversions in Drosophila persimilis.

The amylase locus in Drosophila persimilis is polymorphic for allozymes, two of which show associations with naturally occurring chromosome 3 inversions. Amy1.09 occurs at high frequencies only in Whitney (WT), while the other common arrangements-Standard (ST), Klamath (KL) and Mendocino (MD)-are predominantly Amy 1.00. We have examined numerous strains, representing various electromorphs and inversions, for variation in cis-specific activity expression in both third-instar larvae and adults. Comparisons of these two life stages also allows the survey of developmental variation in amylase activities. The amount of activity variation exceeds electrophoretic variation at this locus. Moreover, this variation is largely nonrandom and reveals more genic divergence among inversions. The 1.00 allozyme of MD is more active than 1.00 KL in larvae and adults and shows a different developmental pattern. The activity of the 1.00 allozyme of KL is greater than 1.00 allozyme of ST in larvae and adults, but these two arrangements have similar developmental patterns. WT 1 with a 1.00 allele is dramatically different from the 1.00 allozymes of other arrangements in its developmental pattern. The 1.09 allozymes has high activity in WT and KL, but these arrangements differ in their developmental pattern of expression, WT being more active in adults. F2 segregational analyses are consistent with the variation being due to either structural enzyme variants or closely linked cis-acting regulatory elements. We argue that the suppression of recombination between arrangements has allowed the divergence in amylase activity among inversions.

Amylases↗