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Biomedical subjects

R Reddy

Publications and source records attributed to R Reddy.

At least 253 records · Page 14Linked to original sources
PubMed1981

Primary and secondary structure of U2 snRNA.

With the improved rapid sequencing techniques, the earlier sequence of U2 RNA of Novikoff hepatoma (Shibata et al, J. Biol. Chem. 250, 3909-3920, 1975) was reanalyzed and modified. The improved sequence of U2 RNA is 188 (or 189) nucleotides long and is in register with a characterized U2 RNA pseudogene (Denison et al, PNAS 78, 810-814, 1981) except for an 11 nucleotide sequence (nucleotides 147-157) which is absent from the pseudogene. From these results, a secondary structure of U2 RNA is proposed which is supported by the preferred cleavage sites with T1-RNase, RNase A and S1 nuclease. Isolated U2 RNA was cleaved by T1-RNase preferentially at positions 64 and 164, whereas U2 RNA in U2-snRNP was cleaved only at position 64, indicating that position 164 is protected in U2-snRNP. As with U1 RNA (Epstein et al, PNAS 78, 1562-1566, 1981) the 5'-end of isolated U2 RNA was not preferentially cleaved by T1-RNase.

Animals↗
PubMed1981

The primary nucleotide sequence of U4 RNA.

U4 RNA is one of the "capped" nuclear snRNAs recently found to be precipitable by anti-Sm antibodies as ribonucleoprotein particles. U4 RNA, along with other snRNAs, has been implicated in hnRNA processing, mRNA transport, or both (Lerner, M. R., Boyle, J., Mount, S., Wolin, S., and Steitz, J. A. (1980) Nature 283, 220-224). Since the proteins bound to different snRNAs appear to be the same, the functions of different snRNPs might be dependent on the RNA components. To help understand the function of U4 RNP, the nucleotide sequence of U4 RNA was determined. The sequence is (formula see text) In addition to the modified nucleotides in the "cap," U4 RNA contains Am at position 63 and m6A at position 98. It also exhibited A-C microheterogeneity at position 97.

Animals↗
PubMed1981

Placenta accreta and percreta: a review of 5 cases.

Five cases of placenta accreta and percreta are reviewed. Three cases, one a recurrence in the same patient, presented with acute abdominal pain; in one case perforation resulting from placenta percreta was discovered at laparotomy. In another case, placenta accreta was recognized during cesarean delivery. Total or subtotal hysterectomy was performed in three cases; piecemeal removal of placental tissue and closure of the tear was performed in two of the patients. There were no maternal deaths, but the infants were stillborn in three cases of perforation or uterine rupture.

Adolescent↗
PubMed1981

Site-specific cleavage by T1 RNase of U-1 RNA in u-1 ribonucleoprotein particles.

The structures and functions of small nuclear ribonucleoprotein particles have become of interest because of their suggested role in processing heterogeneous nuclear RNA [Lerner, M. R., Boyle, J. A., Mount, S. M., Wolin S. L. & Steitz, J. A. (1980) Nature (London) 283, 220-224]. To determine the conformation of U-1 RNA in U-1 ribonucleoprotein particles and whether proteins of these particles protect segments of U-1 RNA, intact particles and isolated U-1 RNA were digested with T1 RNase. The digested particles were immunoprecipitated with anti-Sm antibodies. A 5'-end fragment containing nucleotides 1-107 and 3'-end fragments containing nucleotides 108-165 and 108-153 were recovered in nearly quantitative yield from digestion of the particles, suggesting that position 107 is the principal cleavage site in them. At the same T1 RNase concentrations, deproteinized U-1 RNA was cleaved into many fragments. At low T1 RNase concentrations, major cleavage site of deproteinized U-1 RNA was at nucleotide 69. Comparison of the cleavage sites of free U-1 RNA and of U-1 RNA in U-1 ribonucleoprotein particles suggested similar secondary structures. The resistance of the 5' end of U-1 RNA to T1 RNase was unexpected inasmuch as this region has been implicated in hydrogen bonding with heterogeneous nuclear RNA splice junctions.

Animals↗
PubMed1981

Comparison of RNase T1 fingerprints of U1, U2, and U3 small nuclear RNA's of HeLa cells, human normal fibroblasts, and Novikoff hepatoma cells.

To determine whether there are differences between the U1, U2, and U3 small nuclear RNA's of human cancer cells (HeLa cells) and human normal fibroblasts (IMR-90 cells), and between these uridine-rich small nuclear RNA's of human and Novikoff hepatoma cells, the cells were first incubated in Eagle's medium with [32P]Pi to label these RNA's uniformly. No differences were found between the RNase T1 fingerprints of the purified U1, U2, and U3 RNA's of HeLa cells and IMR-90 cells. The RNase T1 fingerprints of U1 RNA's from human tissues were very similar to that of the U1 RNA of Novikoff hepatoma cells. The RNase T1 fingerprints of U2 and U3 RNA's from human tissues had many similarities to those of Novikoff hepatoma cells, but a few differences were found, such as a point mutation of the U-U-Gp in the rat U2 RNA to A-U-Gp (U leads to A) in human U2 RNA. Unlike the three U3 RNA's of Novikoff hepatoma cells, U3 RNA from human tissues appears to be only one species. These results indicate that U1, U2, and U3 RNA's of human cancer cells are essentially the same as those of human normal cells. In addition, the uridine-rich small nuclear RNA's appear to be conserved through evolution.

Animals↗
PubMed1980

The nucleotide sequence of nuclear U6 (4.7 S) RNA.

The low molecular weight RNA species which have been purified and characterized in this laboratory (T.S. Ro-Choi and H. Busch (1974) in The Cell Nucleus, Vol. 3, pp 151-208; Academic Press, New York) are now of interest because of their suggested role in processing of heterogeneous nuclear RNAs (Lerner, M.R., Boyle, J.A., Mount, S.M., Wolin, S.L., and Steitz, J.A. (1980) Nature, 283, 220-224). A previously uncharacterized RNA, U6 (4.7 S) nuclear RNA, which is 106 nucleotides long, was extracted from Novikoff hepatoma ascites cell nuclei and purified by polyacrylamide gel electrophoresis. The primary nucleitde sequence of U6 RNA was determined by subjecting the RNA to several types of enzymatic digestions and gel-sequencing techniques. The sequence is: (formula: see text). U6 RNA contains three pseudouridylic acid residues, four alkali-stable dinucleotides, two alkali-stable trinucleotides, one m6adenosine, and one m2guanosine and is notable for the high concentration of modified nucleotides in the center of the molecule. U6 RNA has an unusual 5' terminus which has not yet been fully characterized.

Animals↗
PubMed1980

Substitutions, insertions, and deletions in two highly conserved U3 RNA species.

In view of the increasing interest in low molecular weight ribonucleoprotein particles in exon-intron binding and cleavage reactions (Lerner, M. R., Boyle, J. A., Mount, S. M., Wolin, S. L., and Steitz, J. A. (1980) Nature 283, 220--224), the complementarity of the conserved regions to HnRNAs, or protein binding sites, or both, is of potential importance. U3A, U3B, and U3C are three RNA species localized to the nucleolus of Novikoff hepatoma cells. The nucleotide sequence of U3A RNA determined in this study was compared to that of U3B RNA (Reddy, R., Henning, D., and Busch, H. (1979) J. Biol. Chem. 254, 11097--11105). Both U3A and U3B RNAs contained 5' "caps" and were 216 nucleotides long. The nucleotide sequence 1 to 87 was identical in both U3A and U3B, but differences were found at 18 positions in the remainder of the sequence. Of these differences, 11 were single base replacements, two were dinucleotide replacement AU leads to GG at positions 93 to 94, UC leads to GG at positions 173 to 174, and one was a trinucleotide replacement, UCG leads to CUU at positions 179 to 181. Of the total 18 base replacements, 11 (61%) were purine leads to purine or pyrimidine leads to pyrimidine. Interestingly, two base insertions/deletions were found in each RNA when both RNA sequences were compared for maximum sequence similarity. These data establish that the heterogeneity of some low molecular weight nuclear and nucleolar RNA species resulted from a small number of mutations but much of the sequence was conserved.

Animals↗
PubMed1979

Nucleotide sequence of nucleolar U3B RNA.

U3A, U3B, and U3C are three distinct molecular weight nucleolar RNAs present in Novikoff hepatoma ascites cells. The primary nucleotide sequence of U3B, the most prominent of these U3 species, was determined. Purified U3B RNA was subjected to various enzymatic digestion procedures, including digests of 32P-labeled U3B RNA, RNA ligase, and polynucleotide kinase labeling, for determination of its primary sequence which is: (formula: see text). The 5'-terminus of the RNA has a "cap" and localized purine-rich regions were found near the 3'-terminus, which have been incorporated into a hydrogen-bonded region in a proposed secondary structure of the molecule.

Animals↗
PubMed1979

Electrophysiologic properties of nitroprusside in man.

The effects of nitroprusside on His bundle electrograms, when given intravenously for 10 minutes, were studied in 14 patients with heart disease. Recordings were made at varied heart rates using atrial and ventricular pacing. Nitroprusside significantly reduced the AH interval, but it had no effect on the HV interval. Functional and effective refractory periods were measured by the extrastimulus technique. The functional refractory period of the AV node as well as the effective refractory period of the ventriculoatrial conduction system significantly decreased after nitroprusside infusion. This improvement in conduction can probably be explained by the systemic hypotension produced by nitroprusside, which reflexly will increase sympathetic drive to the heart and decrease vagal tone.

Adult↗
PubMed1979

Electrophysiologic properties of methyldopa in man.

There is little information on the effects of methyldopa on the human conduction system. His bundle ECGs were obtained in 11 patients before and after the intravenous infusion of 100 mg of methyldopa. Antegrade refractory periods were obtained with the extrastimulus method. The significant results were as follows: the sinus rate was 71 +/- 4 beats per minute before, and 65 +/- 3 beats per minute after methyldopa (P less than 0.01). The mean A-H interval at a paced rate of 120 beats per minute was 113 +/- 14 msec before, and 135 +/- 18 msec after, methyldopa (P less than 0.05). The mean atrioventricular nodal functional refractory period was 430 +/- 23 msec before and 452 +/- 24 msec after methyldopa administration (P less than 0.001). The mean effective refractory period was 385 +/- 29 msec before, and 388 +/- 27 msec after methyldopa (P less than 0.01). The sinus node recovery time in the control state was 989 +/- 55 msec and 1102 +/- 66 msec after methyldopa infusion (P less than 0.05). Thus, methyldopa can impair conduction through the atrioventricular node and depress the sinus node.

Adult↗
PubMed1978

Lower limb angiography in leprosy.

Bilateral lower limb angiography was performed on 58 patients with leprosy and compared with bilateral lower limb angiography performed on 63 non-leprosy patients. The vessels in leprosy were narrow and constricted. Decreased blood flow through arteries in the distal third of the lower limb was present. Abnormal AV fistula formation in the thigh and calf muscles and in trophic ulcers of the feet was also seen. Deep inflammatory granulomatous reaction surrounding the arteries as a result of leprosy is a possible explanation for these angiographic findings and is felt to be related to trophic ulceration. These findings were specific for leprosy, precede clinical manifestations, and are helpful in management.

Adult↗
PubMed1978

Severe mitral regurgitation with a normal-sized left atrium.

The syndrome of severe mitral regurgitation with a normal-sized left atrium may or may not be associated with pulmonary hypertension and prominent left atrial V waves. To explain these pressure alterations by a single pressure-volume relationship is probably not adequate. It would appear that, whatever the clinical circumstances, normal pulmonary vascular pressures cannot exclude the diagnosis of mitral regurgitation.

Adult↗