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Biomedical subjects

P Ramanujam

Publications and source records attributed to P Ramanujam.

11 recordsLinked to original sources
PubMed1991

Sequence requirements for activation of replication by the SV40 transcriptional promoter or enhancer elements.

Previous studies have demonstrated that the 21- or the 72-bp repeat transcriptional control elements enhance the efficiency of SV40 DNA replication in vivo, provided either of these repeats is located near the end of the core replication origin containing the 17-bp A + T-containing sequence. Using two sets of point mutants we have investigated the contributions of the various sequence motifs present in the 21- or the 72-bp repeats toward activation of replication. Regarding the contribution of the six GC motif components of the 21-bp repeats, we find that GC motif I, located closest to the core origin, is dispensable for activation of replication. A mutation in GC-I in fact causes an increase in replication efficiency. We also find that GC motifs I and II present in the nontandem copy of the 21-bp repeats are not sufficient to activate replication. Our present study indicates that a combination of three GC motifs such as II, III, and IV (including one of the two perfect, tandem copies of the 21-bp repeats) is important for activation of replication. Regarding the 72-bp repeat transcriptional enhancer region, we find mutations in a number of its individual motifs to have a negative consequence on replication, with mutations in the GT-I*/TC-II and Sph-II/octamer motifs exhibiting the most negative effects. Overall, we find that the replication activation effects of the 21- and the 72-bp repeats require the participation of multiple motifs present in them. Cellular factors binding to these motifs are expected to mediate their replication activation effects. For the most part, the motifs required for activation of replication are the same as those reported in earlier studies to be important for efficient early and late viral mRNA transcription.

Base Sequence↗
PubMed1990

Effects of dietary wheat bran fiber on rectal epithelial cell proliferation in patients with resection for colorectal cancers.

A preponderance of carcinogenesis studies in rodents and epidemiologic studies in humans suggests a potential role of dietary fiber in the prevention of colorectal cancer. Recently, wheat bran fiber used as a dietary supplement has been shown to decrease the growth of rectal adenomatous polyps in patients with familial polyposis; however, few studies of high-risk human populations have been attempted to determine the effects of dietary fiber supplementation on markers of carcinogenesis in the colon or rectum. We have designed a one-arm study to evaluate the effects of dietary supplementation with wheat bran fiber [i.e., 13.5 g/day for 8 wk; after 1 mo, 2 g/day (compliance evaluation period)] on [3H]thymidine rectal mucosa cell labeling (i.e., percent of epithelial cells incorporating [3H]thymidine into DNA in intact rectal crypt cells over a 90-min exposure as well as in minced rectal biopsy tissue over a 24-hr exposure) in rectal biopsy specimens. The biopsy specimens were obtained at sigmoidoscopy in 17 compliant patients with a history of resected colon or rectal cancer. We categorized patients as having initially low or initially high [3H]thymidine-labeling indices (i.e., percent of mucosa cells that incorporate [3H]thymidine into DNA during 1.5- or 24-hour in vitro incubations) by using the median baseline labeling index as a cutoff between high and low values. On the basis of a chi-square test used to identify patients with a statistically significant (P less than .001) change, six of the eight patients who initially had high 24-hour outgrowth labeling indices showed a significant decrease in the rectal mucosa biopsy specimens obtained after treatment. An overall 22% decrease was observed in rectal mucosa cell biopsy specimens obtained at study termination (P less than .001). Of the eight patients with initially high total [3H]thymidine-labeling indices in crypt organ culture, four had a significant (P less than .001) decrease from baseline values, one had a significant increase, and three showed no change following the fiber intervention. The wheat bran fiber dietary supplement of 13.5 g/day was well tolerated by this group of older (54-70 yr) patients. Although the [3H]-thymidine labeling index data suggest that the wheat bran fiber supplement can inhibit DNA synthesis and rectal mucosa cell proliferation in high-risk patients, the results of this small pilot study should not be overinterpreted vis à vis the potential role of wheat bran fiber as a chemopreventive agent for colorectal cancer.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1990

Fast gel electrophoresis to analyze DNA-protein interactions.

A rapid method for electrophoresis of DNA-protein complexes is described. Popular "gel-shift" assays are performed using Pharmacia PhastSystem with its convenience of pre-cast gels and buffer strips and microprocessor-controlled high-resolution separation. Using this system, the products of a DNA binding reaction (DNA-protein complexes) can be separated from "free" DNA in less than one hour. DNA fragments as well as oligonucleotides have been used as targets with partially purified extracts containing sequence-specific DNA binding proteins. We present here a comparison of results of gel-shift assays obtained by conventional techniques and by our rapid "PhastShift" method which reduces the time, effort and technical expertise necessary to obtain reproducible results.

Antigens, Viral↗
PubMed1983

Unusual manifestations of gallstone migration into the gastrointestinal tract.

Eighty-one cases of mechanical small bowel obstruction were seen at our hospital in the three year period 1978 to 1980. Four (5%) were due to gallstone ileus, three of them in women. All four patients were more than 75 years of age. Because most patients with biliary-enteric fistulas and gallstone ileus are elderly and in poor general condition, simple removal of the obstruction gallstone is usually adequate, but interval cholecystectomy is recommended in patients with a long life expectancy, because recurrence of calculi and symptoms increases with time.

Aged↗
PubMed1982

Hepatobiliary scanning in cholecystitis.

To validate the use of 99mTc-PIPIDA in the diagnosis of biliary tract disease, 117 patients with clinical symptoms of acute cholecystitis were prospectively scanned as an initial screening test. The accuracy of the test was evaluated on the basis of surgical pathology in 59 patients. Three groups were defined: cystic duct obstruction, common duct obstruction, and normal scan. The diagnostic accuracy of the test for acute cholecystitis was 97%. Complete common duct obstruction was confirmed at surgery in 12 patients (100%). A normal scan helped to rule out acute cholecystitis. Jaundice did not influence the reliability of the method. Hepatobiliary scanning is an accurate, safe, and rapid diagnostic test for acute cholecystitis.

Acute Disease↗