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Biomedical subjects

R Padmanabhan

Publications and source records attributed to R Padmanabhan.

At least 145 records · Page 8Linked to original sources
PubMed1983

High efficiency DNA-mediated transformation of primate cells.

Tissue culture cells from several mammalian species, including three primate lines, were transfected with recombinant vectors carrying Escherichia coli xanthine-guanine phosphoribosyltransferase or Tn5 aminoglycoside phosphotransferase dominant selectable markers. Human HeLa and SV40-transformed xeroderma pigmentosum cells exhibited stable transformation frequencies of at least 10(-3) (0.1 percent). CV-1, an African green monkey kidney cell line, could be stably transformed with the exceptionally high frequency of 6 X 10(-2) (6 percent).

Animals↗
PubMed1983

Comparative sequence analysis of the inverted terminal repetition in the genomes of animal and avian adenoviruses.

The nucleotide sequences at the inverted terminal repetitions from two animal adenoviruses, infectious canine hepatitis virus and equine adenovirus, and from one avian adenovirus, CELO, were analyzed. DNAs from infectious canine hepatitis virus and equine adenovirus contain a homologous region which is 23 nucleotides long from the terminus. The first 17 nucleotides of this region are identical to the ones in human adenovirus type 2 DNA. The striking homologous sequence of 14 nucleotides, conserved in the inverted terminal repetitions of several human adenovirus strains and in simian adenovirus type 7, is only partially conserved in the two animal and one avian adenoviruses reported here.

Adenoviridae↗
PubMed1983

Axial skeletal malformations associated with cranioschisis aperta and exencephaly. The result of experimental intervention after the neural tube closure in rats.

Maternal administration of a single dose of cyclophosphamide (20 mg/kg) after the neural tube closure (on day 12) resulted in exencephaly and cranioschisis in 100% of rat fetuses at term. Extensive hemorrhages and edema were regularly associated with these defects. Alizarin-red stained skeletal preparations revealed absence of skull vault, premature closure of basicranial synchondroses, exaggeration of the craniovertebral angle, and agencies and hypoplasia of the vertebrae, ribs and sternum. It is suggested that failure of the neural tube to close is not the primary cause of axial skeletal malformations and even after closure, the axial skeletal anlagen remains susceptible to teratogenic insult.

Abnormalities, Drug-Induced↗
PubMed1982

Teratogenic effects of acetaldehyde in the rat.

Acetaldehyde, the proximal metabolite of ethanol, was administered intraperitoneally in single and triple doses (50, 75, 100 mg/kg) to pregnant CF rats on days 10, 11 and 12 of gestation and fetuses were collected on day 21. Besides significant fetal resorptions, malformations were found which included edema, microcephaly, micrognathia, micromelia, hydrocephaly, exencephaly, hemorrhages etc. Somatometric measurements of fetuses (i.e. crown rump length, transumbilical distance and tail length) revealed significant growth retardation. Alizarin red-stained skeletal preparations showed considerable stunting. The placental weight and umbilical cord length were also significantly reduced. The close similarity of the pattern of acetaldehyde-induced fetal malformations with those resulting from maternal alcohol consumption during pregnancy is suggestive of the possible implication of acetaldehyde in the fetal alcohol syndrome.

Abnormalities, Drug-Induced↗
PubMed1982

Physical mapping of human adenovirus type 7 DNA using a simple and sensitive method of terminal labeling.

The tyrosine-containing peptide covalently attached to each 5'-terminus of adenovirus type 7 (Ad 7; Greider) DNA was labeled with 125I. The 5'-labeled DNA was subjected to digestion with several restriction endonucleases and the size of the labeled terminal fragments was determined. Partial hydrolysis by these endonucleases generated a series of labeled fragments which were fused to the terminal fragments and could, therefore, be detected by autoradiography. From the sizes of the partial products the location of the cleavage sites of the enzymes on Ad7 DNA could be determined. The subgenomic DNA extracted from incomplete particles by protease treatment could also be labeled with 125I, since it was found to contain the tyrosine-containing peptide covalently attached to the preferentially packaged left end of the genome.

Adenoviruses, Human↗
PubMed1982

Physical mapping of the genome and sequence analysis at the inverted terminal repetition of adenovirus type 4 DNA.

The genome of adenovirus type 4 (Ad4), the unique member of Ad group E, has been mapped with nine restriction endonucleases. Comparison of the occurrence of restriction endonuclease cleavage sites on Ad2, Ad7, Ad12 and Ad4 indicates that there is very little homology between these serotypes. Sequence analysis at the ITR of Ad4 showed that the "CAT" box which is present in all the ITRs of Ad's so far sequenced is absent in Ad4. The length of 116 bp for the ITR of Ad4 is also different from that of other Ad subgroups.

Adenoviruses, Human↗
PubMed1981

Malformations of the eye resulting from maternal hypervitaminosis A during gestation in the rat.

Vitamin A (1--1.5 lac IU) was administered orally to pregnant Wistar rats on days 8--14 of gestation (sperm + = day 0). Fetuses collected on day 21 revealed several anomalies including those of the eyes, e.g. open eyelids, exophthalmia, cataractous lens, microphthalmia and anophthalmia. Histological examination of treated eyes revealed degenerative changes in the cornea, lens and retina; shallowness or obliteration of anterior and vitreous chambers, and complete fusion of various structures with each other in some cases of microphthalmia. Anophthalmic cases showed no trace of any ocular structure. Retinae showed remarkable infoldings. The degenerative changes in retinae were associated with degeneration of optic nerve fibres. Eye malformations induced by hypervitaminosis A were stage dependent and mostly found in groups treated on day 8 and 9 of gestation. Reported cases of anomalies in humans associated with hypervitaminosis A during pregnancy warn us against the uncritical use of high doses of vitamin A during pregnancy.

Abnormalities, Drug-Induced↗
PubMed1981

Effect of experimental cryptorchidism on the testis in the rat--a histological study.

Cryptorchidism in adult male rats was induced by pushing testes of either side into abdomen and suturing the inguinal canals. Histological examination of such tests revealed impeded mitosis and loosening of seminiferous epithelium within 24 hours. Giant cells appeared initially on the luminal side and became progressively larger and numerous subsequently. The epithelial height was gradually reduced. By day 6 some tubules contained only Sertoli cells while others had Sertoli cells, a few spermatogonia and several giant cells. Edema of peritubular space progressed with time and by day 13 lymphocytic infiltration was obvious. These degenerative changes became intense, and by day 21, giant cells started disappearing. By day 25 the degenerated tubules were replaced by an acidophilic substance. There was no evidence of any regeneration.

Animals↗
PubMed1980

Purification and properties of a DNA ligase from a soluble DNA replication complex.

A DNA ligase has been purified from a subnuclear soluble replication complex isolated from adenovirus type 2-infected human KB cells. DNA ligase activity could not be demonstrated using an exogenous template until the complex was dissociated, suggesting that the ligase activity may be a component of the complex. The purified enzyme was free of endonuclease, exonuclease, 5'-nucleotidase, and phosphatase activities, and had a molecular weight of 105 000, as estimated by sedimentation in a glycerol gradient. The ligase requires ATP and a divalent cation for activity. The optimum of the reaction is at pH 7.8 in 50--100 mM Tris-HCl buffer and 10--20 mM MgCl2. Monovalent salts greatly stimulate ligase activity and the optimum was found at 150 mM. The reaction is very sensitive to high temperature; maximum activity was observed at 25--30 degrees C. ATP is the sole required cofactor and NAD, dATP and GTP could not replace the requirement for ATP. The Km for ATP is 60 microM. The Km for DNA is 250 microgram/ml or 1.6 nmol of terminal phosphate/ml and thus the enzyme shows relatively weak affinity for exogenous DNA. The maximum conversion of 32P into a phosphatase-resistant form is approximately 1.3% of the total, whereas T4 ligase, under the same conditions, can convert more than 25% of phosphate into a resistant form.

Adenoviruses, Human↗