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P S Ramanujam

Publications and source records attributed to P S Ramanujam.

18 recordsLinked to original sources
PubMed2005

Photodimerization in pyrimidine-substituted dipeptides.

Ten N(epsilon)-glycylornithineamide derivatives have been synthesized containing various N(alpha)-linked pyrimidine-1-ylacetyl groups which can undergo (2pi + 2pi) photodimerization on irradiation with UV light at 254 nm. The dimerization efficiency of the free and bound pyrimidine groups was compared in aqueous solution: it was dependent on the substitution of the pyrimidine ring. N(alpha),N(alpha')-bis-(uracil-1-ylacetyl)-(N(epsilon)-glycylornithineamide) and N(alpha),N(alpha')-bis-(5-bromouracil-1-ylacetyl)-(N(epsilon)-glycylornithineamide) were identified as possible candidates for optical data storage.

Acetates↗
PubMed2003

Evanescent polarization holographic recording of sub-200-nm gratings in an azobenzene polyester.

I demonstrate high-resolution polarization holographic recording with evanescent waves in a thin film of an azobenzene polyester deposited directly on the hypotenuse of a highly refractive prism. A spatial frequency greater than 7000 lines/mm and diffraction efficiency greater than 1% have been achieved. It was found that diffraction efficiency increases in the dark after the writing beams have been switched off. The biphotonic effect found in other azobenzene polymers, which converts cis states of the azobenzene to trans states followed by an ordering process that is due to aggregation, is proposed as the reason for this increase in diffraction efficiency.

Journal Article↗
PubMed2003

Photoinduced anisotropy in a family of amorphous azobenzene polyesters for optical storage.

We investigate parameters associated with optical data storage in a variety of amorphous side-chain azobenzene-containing polyesters denoted as E1aX. The polyesters possess a common cyano-substituted azobenzene chromophore as a side chain, but differ in their main-chain polyester composition. Seventeen different polymers from the E1aX family divided into four classes, depending on the type of the main-chain substituent (one-, two-, and three-ring aromatic or alicyclic) have been thoroughly investigated. Various parameters characterizing the photoinduced birefringence in these materials, such as the response time, thermal and light stability, and long-term stability under ambient light at room temperature have been measured. Each of these parameters is quantitatively represented and therefore it is possible to make a clear comparison between the properties of the polymers. The results indicate that the long-term stability at ambient temperature is closely related to the thermal stability of the photoinduced birefringence. A strong correlation has also been found between the response time and the stability of the induced anisotropy toward illumination with unpolarized white light. One of the classes of E1aX polymers characterized by two-ring aromatic substituent in the main chain is a good candidate for optical data storage media. A recording energy of approximately 2 J/cm2 is sufficient to induce high refractive-index modulations of deltan = 0.13 in these materials, which is retained even at elevated temperatures (>130 degrees C). Long-term stability of greater than one year for the induced anisotropy has also been achieved.

Journal Article↗
PubMed2003

Polarization holographic and surface-relief gratings at 257 nm in an amorphous azobenzene polyester.

Polarization holographic and surface-relief gratings have been recorded in an amorphous azobenzene polyester by use of a frequency-doubled argon-ion laser beam at 257 nm. Higher excited states of azobenzene in the trans and cis configurations contribute to the formation of a diffraction grating in this experiment. A combination of right and left circularly polarized writing beams has been found to give the highest diffraction efficiency. The contributions to the total phase difference that arise from anisotropy and surface relief have been separated experimentally, and it is shown that the surface-relief grating contributes a larger phase difference than that which is due to anisotropy.

Journal Article↗
PubMed1997

The effect of wheat bran fiber and calcium supplementation on rectal mucosal proliferation rates in patients with resected adenomatous colorectal polyps.

Colorectal cancers continue as the second most common cause of death from cancer in the United States. Only a few prospective, randomized clinical trials have been performed to evaluate the potential preventive effects of dietary fiber or calcium in patients with an increased risk for the development or recurrence of colorectal cancer. We designed and conducted a double-blinded, placebo-controlled randomized trial involving supplementation of fiber and calcium intake and measurements of [3H]thymidine labeling index (LI) percentages in rectal mucosal biopsies obtained from patients with resected colorectal adenomas to examine the potential mechanisms by which dietary interventions might reduce colorectal cancer risk. We performed a randomized, double-blinded, Phase II study, using a factorial design to measure the effects of supplemental dietary wheat bran fiber (2.0 or 13.5 g/day) and calcium carbonate (250 or 1500 mg/day elemental calcium) supplementation on [3H]thymidine LI percentages in rectal mucosal crypts and 24-h in vitro outgrowth cultures. Measurements were made at baseline randomization (i.e., after a 3-month placebo run-in period using 2.0 g of wheat bran fiber plus 250 mg of calcium carbonate) and after 3 and 9 months on treatment in 100 randomized participants who had a history of colon adenoma resection. Neither the wheat bran fiber nor the calcium carbonate supplements significantly reduced [3H]thymidine LI percentages in rectal mucosal crypts (total or compartmental analysis) or 24-h in vitro outgrowth cultures at either 3 or 9 months of daily supplementation in the 93 evaluable participants. We conclude that 9 months of high-dose wheat bran fiber and calcium carbonate supplementation in study participants with a history of recently resected colorectal adenomas does not have a significant effect on cellular proliferation rates in rectal mucosal biopsies, comparing 3- and 9-month results to baseline results. Ultimately, there is great need for the evaluation of these two different nutrient interventions in the setting of Phase III studies wherein adenomatous polyp recurrence, rather than a rectal mucosal biomarker, serves as the primary end point.

Adenomatous Polyps↗
PubMed1996

Randomized, double-blinded, placebo-controlled study of effect of wheat bran fiber and calcium on fecal bile acids in patients with resected adenomatous colon polyps.

BACKGROUND: Ongoing epidemiologic and nutritional studies suggest that colorectal carcinogenesis is consistent with complex interactions between genetic susceptibility and environmental and dietary factors. Among the dietary components found to reduce colon cancer risk are high intakes of dietary fiber and calcium. PURPOSE: We designed and conducted a randomized, double-blinded, placebo-controlled trial involving supplementation of the customary dietary intake with fiber and calcium and measurements of fecal bile acids to examine the potential mechanisms by which added dietary interventions might reduce colorectal cancer risk. METHODS: In a randomized, double-blinded, phase II study, we used a factorial design to measure the effects of dietary wheat bran fiber (2.0 or 13.5 g/day) in the form of cereal and supplemental calcium carbonate (250 or 1500 mg/day elemental calcium) taken as a tablet on fecal bile acid concentrations and excretion rates. Measurements were made at base-line randomization (i.e., after a 3-month placebo run-in period using 2.0 g wheat bran fiber plus 250 mg calcium carbonate) and after 3 and 9 months on treatment in a randomly selected 52-patient subsample of the 95 fully assessable study participants who had a history of colon adenoma resection. Concentrations of fecal bile acids, total, primary (i.e., chenodeoxycholic and cholic), and secondary (i.e., deoxycholic, lithocholic, and ursodeoxycholic), were measured in 72-hour stool samples by gas-liquid chromatography. All P values resulted from two-sided tests. RESULTS: All geometric mean fecal bile acid concentrations and excretion rates were lower at 9 months than at 0 months or 3 months on treatment in the high-dose fiber, high-dose calcium, and high-dose fiber/high-dose calcium treatment groups. The high-dose fiber effect at 9 months of supplementation was statistically significant with respect to virtually all geometric mean fecal bile acid concentrations and excretion rates. For example at 9 months versus 0 months, high-dose fiber supplementation caused a reduction in fecal concentrations of total bile acids (52% reduction; P = .001) and deoxycholic acid (48% reduction; P = .003). High-dose calcium supplementation also had a significant, but lower, effect at 9 months versus 0 months on the geometric mean total bile acid (35% reduction; P = .044) and deoxycholic fecal bile acid (36% reduction; P = .052) concentrations. CONCLUSIONS: High-dose wheat bran fiber and calcium carbonate supplements given for 9 months are associated with statistically significant reductions in both total and secondary fecal bile acid concentrations and excretion rates in patients with resected colon adenomas. This study supports the hypothesis that one of the important ways in which a high intake of wheat bran fiber and calcium may reduce the risk of colorectal neoplasia and cancer is by reduction of the concentrations of fecal bile acids. IMPLICATION: Phase III studies of these agents in the prevention of adenoma recurrence are necessary to confirm this hypothesis and have now been initiated at multiple institutions.

Adenomatous Polyposis Coli↗
PubMed1996

Study of human papillomavirus infection in patients with anal squamous carcinoma.

PURPOSE: The purpose of this study was to determine the incidence of human papillomavirus deoxyribonucleic acid (HPV DNA) in anal squamous carcinoma. METHODS: HPV DNA in situ hybridization for HPV Types 6, 11, 16, 18, 31, 33, and 35 was performed on the formalin-fixed, paraffin-embedded tissue from 53 perianal and anal squamous carcinomas and 10 controls. RESULTS: HPV DNA sequences were identified in 18 of 53 anal squamous carcinomas (34 percent). All 10 controls were negative for HPV DNA. Of the 18 positive patients, 10 were perianal squamous carcinomas, and 8 were anal canal squamous carcinomas. Six of the perianal carcinomas were positive for HPV Types 6 and 11. The remaining four perianal carcinomas and all eight of the anal canal carcinomas were positive for HPV Types 16 and 18. CONCLUSION: HPV DNA sequences can be identified in anal squamous carcinomas. Anal squamous epithelium is another site where HPV infection may carry a risk for malignant transformation. One-third of anal squamous carcinomas may be associated with prior HPV infection. Patients with anogenital HPV infection should be routinely screened for anal squamous lesions.

Aged↗
PubMed1995

The diagnostic value of exercise echocardiography in ischemic heart disease in relation to quantitative coronary arteriography.

The aim of the study was to assess the diagnostic value of bicycle exercise echocardiography using quantitative coronary arteriography as a reference. Exercise echocardiography was performed in 70 consecutive patients referred for coronary angiography. Digital loops were obtained at rest, peak, and immediately after exercise in the standard views (parasternal long and short axis, apical two and four chamber views). Wall motion analysis was made on the basis of the 16 segment model, scoring each segment from 3 (hyperkinesia) to -1 (hypokinesia). Exercise echocardiography was considered positive when wall motion in at least one segment decreased at least one score from rest to peak or post exercise. Cinefilms were evaluated using automated quantitative coronary arteriography software. Transstenotic pressure gradients were calculated based on flow assumptions at the maximal stenosis flow reserve. Pressure losses > 30 mmHg and quantitatively measured percent diameter stenosis of > 50% were considered clinically significant. Stenoses in the equivocal range of 40-69% were subjected to separate analysis. Exercise echocardiography was superior to exercise-induced ST-segment depression in the diagnosis of coronary artery disease. In the overall sample of 70 patients, the sensitivity of exercise echocardiography against percent diameter stenosis was 84%, against pressure gradient 86%. The specificity against these two parameters was 86% and 84%, respectively. When analysing the subgroup of 40-69% stenoses (N = 14), sensitivity of exercise echocardiography against percent diameter stenosis was 67%, against pressure gradient 88%. The specificity against these two parameters was 100% and 84%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Hemangioma of the small intestine: case report and literature review.

One case of small bowel polypoid hemangioma of the jejunum presenting as recurrent gastrointestinal blood loss is reported. The presenting symptoms and diagnostic methods are discussed. The importance of intraoperative enteroscopy in diagnosing and treating this condition is emphasized.

Aged↗
PubMed1994

Perineal excision of rectal procidentia in elderly high-risk patients. A ten-year experience.

PURPOSE: This report presents a ten-year experience with perineal excision and posterior levator ani repair in elderly, high-risk patients with complete rectal procidentia. METHODS: Seventy-two patients with rectal prolapse were treated with perineal excision. Nine presented with acute incarcerated rectal prolapse. Mortality, morbidity, recurrence rates, and improvement of anal continence were assessed. RESULTS: Recurrence rate was 5.5 percent. Improvement in anal continence was seen in 66.7 percent of patients. Morbidity and mortality was low. CONCLUSIONS: Perineal excision of rectal prolapse is safe and has a low recurrence rate. Posterior levator ani repair seems to improve anal continence.

Acute Disease↗
PubMed1994

Assessment of coronary artery stenosis pressure gradient by quantitative coronary arteriography in patients with coronary artery disease.

The aim of the study described here was to correlate coronary artery (CA) stenosis pressure gradients calculated by quantitative coronary arteriography (QCA) to invasively measured transstenotic pressure drops in patients with anginal symptoms and with known or suspected coronary artery disease. Furthermore, the known mathematical models are improved by introducing (1) pressure catheter-corrected minimal stenosis area, (2) modification of flow assumptions, and (3) stenosis exit angle. Included in the study were 45 patients with 61 stenoses. The visually estimated CA lesion severity in these non-complex stenoses was in the equivocal range of 40-70%. All measurements were performed after intracoronary administration of nifedipine and nitroglycerin. Stenosis dimensions were assessed from magnified cinefilms, using hand-held calipers. Highly significant overall correlation was found between measured and calculated pressure gradients with correction for the impact of the intracoronary catheter (P < 0.00001, r = 0.84). In particular, a substantial number of stenoses with haemodynamically-insignificant pressure gradients were identified by hydrodynamic calculations. In conclusion, the great majority of the coronary artery stenoses could be classified reliably by QCA as being haemodynamically insignificant or significant, respectively.

Blood Pressure↗
PubMed1992

Hydrostatic balloon dilatation of benign colonic anastomotic strictures.

From 1985 to 1990, 25 patients with benign colorectal anastomotic strictures were treated. The majority of the patients presented with decreasing stool caliber and abdominal cramps. Most of the strictures were secondary to anastomosis utilizing the EEA stapling device (United States Surgical Corp., Norwalk, CT) for malignant neoplasm. Under IV sedation, strictures were dilated endoscopically with the TTS balloon (Microvasive). No complications were encountered in this series. Hydrostatic balloon dilatation is a safe and effective modality for treatment of anastomotic strictures.

Aged↗
PubMed1992

Management of acute incarcerated rectal prolapse.

Perineal excision was used to treat eight elderly patients with acute incarcerated prolapse: four showed signs of strangulation with areas of gangrene, six made an uneventful recovery without colostomy, and two developed anastomotic leak, needing diverting colostomy with a complete recovery. There were no mortalities. There were no recurrences of rectal prolapse.

Acute Disease↗
PubMed1989

Anorectal complications of vaginal delivery.

The incidence of anorectal complications following vaginal delivery was studied in 20,500 women. One thousand forty (5 percent) of all normal vaginal deliveries resulted in episiotomy with third- and fourth-degree extension or a fourth-degree perineal tear. Of these fourth-degree lacerations, 101 patients (10 percent) experienced wound disruption after primary repair. Sixty-seven patients (66 percent) experienced wound disruption that required surgical correction. Anorectal complications were anal ulcer, anorectal abscess, sphincteric disruption, and rectovaginal fistula. Surgical correction of these complications resulted in satisfactory outcome.

Adult↗
PubMed1988

Perineal excision of rectal prolapse with posterior levator ani repair in elderly high-risk patients.

Perineal excision of rectal prolapse with simultaneous posterior levator ani repair was used to treat 41 elderly patients with rectal procidentia. The majority of the patients had significant associated risk factors. This procedure was performed with minimal morbidity and no mortality. A significant improvement in anal continence was seen in 78 percent of patients. The recurrence rate of rectal prolapse was 4.8 percent.

Aged↗
PubMed1984

Perianal abscesses and fistulas. A study of 1023 patients.

In a five and one-half year period, 1023 patients with anorectal abscesses and fistulas were treated. Under regional anesthesia the abscesses were unroofed and debrided and a primary fistulotomy was performed whenever a low fistula was identified. In 355 (34.7 per cent) an internal fistulous opening was demonstrated at the time of abscess drainage. Thirty-two patients had suprasphincteric fistulas and underwent two-stage fistulotomy using a seton. Perianal abscesses were encountered in 42.7 per cent of the patients, followed by ischiorectal (22.7 per cent), intersphincteric (21.4 per cent), and supralevator (7.33 per cent). The patients with supralevator and intersphincteric abscesses had a high incidence of fistula identified during abscess drainage. The recurrence rates were 3.7 per cent in the group with abscess drainage only and 1.8 per cent in the group that had primary fistulotomy along with abscess drainage. The follow-up period averaged 36 months. To accomplish adequate drainage and identify the deeper components and associated fistulous opening (34.7 per cent of the entire group), careful examination under regional anesthesia is recommended. Early aggressive treatment of an anorectal abscess and fistula significantly reduces the possibility of recurrent abscesses and/or the need for further surgery.

Abscess↗
PubMed1983

The role of seton in fistulotomy of the anus.

A five year experience with 45 patients who underwent two stage fistulotomies using seton has been reviewed. The use of seton in suprasphincteric fistulas yields excellent anatomic and physiologic results. It is recommended that a seton be used in all high, complex and suprasphincteric fistulas or when there is doubt as to the extent of the sphincter muscle involved in the fistulous process.

Abscess↗