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Biomedical subjects

S Srinivas

Publications and source records attributed to S Srinivas.

At least 37 records · Page 2Linked to original sources
PubMed1999

Tool support for authoring eligibility criteria for cancer trials.

A critical component of authoring new clinical trial protocols is assembling a set of eligibility criteria for patient enrollment. We found that clinical protocols in three different cancer domains can be categorized according to a set of clinical states that describe various clinical scenarios for that domain. Classifying protocols in this manner revealed similarities among the eligibility criteria and permitted some standardization of criteria based on clinical state. We have developed an eligibility criteria authoring tool which uses a standard set of eligibility criteria and a diagram of the clinical states to present the relevant eligibility criteria to the protocol author. We demonstrate our ideas with phase-3 protocols from breast cancer, prostate cancer, and non-small cell lung cancer. Based on measurements of redundancy and percentage coverage of criteria included in our tool, we conclude that our model reduces redundancy in the number of criteria needed to author multiple protocols, and it allows some eligibility criteria to be authored automatically based on the clinical state of interest for a protocol.

Breast Neoplasms↗
PubMed1998

Methotrexate tolerance in patients with ileal conduits and continent diversions.

BACKGROUND: Methotrexate is readily absorbed from the intestinal tract. When given to patients with urinary diversion to the intestinal tract, methotrexate may be reabsorbed into the circulation, thus increasing its serum concentration and potentially increasing its toxicity. METHODS: Forty-eight patients with transitional cell carcinoma of the urinary tract who had undergone cystectomy and either an ileal conduit or a continent diversion were evaluated for their tolerance of chemotherapy. Of the 42 evaluable patients, 23 had a continent diversion and 19 had an ileal conduit. None of the patients with the continent diversion had an indwelling Foley catheter during the course of chemotherapy. RESULTS: There were no statistically significant differences in incidence of fever or neutropenia, mucositis, dose modification, or delay in chemotherapy between the two groups. When compared with a group of patients with native bladders who received the same chemotherapy, patients with continent diversions did not have increased incidence or severe toxicity from chemotherapy. CONCLUSIONS: Patients with continent diversions tolerated chemotherapy as well as patients with ileal conduits.

Antimetabolites, Antineoplastic↗
PubMed1998

Retinal oxygen consumption during hyperglycemia in patients with diabetes without retinopathy.

OBJECTIVE: This study aimed to determine whether retinal oxygen consumption in patients with diabetes without retinopathy is affected by acute changes in blood glucose. DESIGN: The study design was a nonrandomized, interventional clinical study. PARTICIPANTS: The study consisted of 12 patients with diabetes without ophthalmoscopically visible diabetic retinopathy whose ages were 20 to 59 years (mean, 33.7 years). INTERVENTION: Retinal vessel oximetry was performed on subjects during normoglycemia and during acutely induced hyperglycemia. Hyperglycemia was achieved with the ingestion of an oral glucose load. MAIN OUTCOME MEASURES: Changes in retinal arterial and venous blood oxygen saturation resulting from systemic blood glucose changes were measured. Measurements were made using a noninvasive, two-wavelength digital imaging retinal vessel oximeter. RESULTS: In each subject, the measured retinal venous blood oxygen saturation decreased significantly during hyperglycemia. The amount of decrease in venous oxygen saturation associated with hyperglycemia was positively correlated with the duration of diabetes. The measured retinal arterial oxygen saturation did not change significantly during hyperglycemia. CONCLUSIONS: These results, taken with the observations of numerous other investigators that show increased blood flow during acute hyperglycemia, provide evidence of substantially increased retinal oxygen consumption during hyperglycemia. The results also complement previous observations of the effect of diabetes on retinal autoregulation.

Adult↗
PubMed1998

Characterization of the roles of hemolysin and other toxins in enteropathy caused by alpha-hemolytic Escherichia coli linked to human diarrhea.

Escherichia coli strains producing alpha-hemolysin have been associated with diarrhea in several studies, but it has not been clearly demonstrated that these strains are enteropathogens or that alpha-hemolysin is an enteric virulence factor. Such strains are generally regarded as avirulent commensals. We examined a collection of diarrhea-associated hemolytic E. coli (DHEC) strains for virulence factors. No strain produced classic enterotoxins, but they all produced an alpha-hemolysin that was indistinguishable from that of uropathogenic E. coli strains. DHEC strains also produced other toxins including cytotoxic necrotizing factor 1 (CNF1) and novel toxins, including a cell-detaching cytotoxin and a toxin that causes HeLa cell elongation. DHEC strains were enteropathogenic in the RITARD (reversible intestinal tie adult rabbit diarrhea) model of diarrhea, causing characteristic enteropathies, including inflammation, necrosis, and colonic cell hyperplasia in both small and large intestines. Alpha-hemolysin appeared to be a major virulence factor in this model since it conferred virulence to nonpathogenic E. coli strains. Other virulence factors also appear to be contributing to virulence. These findings support the epidemiologic link to diarrhea and suggest that further research into the role of DHEC and alpha-hemolysin in enteric disease is warranted.

Animals↗
PubMed1998

In vitro effects of a high-molecular-weight heat-labile enterotoxin from enteroaggregative Escherichia coli.

The pathogenic mechanisms of enteroaggregative Escherichia coli (EAggEC) infection are not fully elucidated. In this work we show that an ammonium sulfate precipitate of culture supernatant of EAggEC strain 049766 increased the potential difference (PD) and the short-circuit current (Isc) in rat jejunal preparations mounted in Ussing chambers. The precipitate contained two major proteins of 108 and 116 kDa, which were partially copurified by chromatography in DEAE-cellulose. This chromatographic fraction (peak I) increased jejunal PD and Isc in a dose-dependent manner, accompanied by a decrease in tissue electrical resistance. These effects were inhibited by incubation of peak I at 75 degreesC for 15 min or for 1 h with proteinase K at 37 degreesC. Rabbit polyclonal antibodies against peak I containing both the 108- and 116-kDa proteins inhibited the enterotoxic effect. Specific polyclonal antibodies raised against the 108-kDa but not against the 116-kDa protein inhibited the enterotoxic effect, suggesting that the 108-kDa protein is the active toxic species. Moreover, another EAggEC strain (065126) producing the 116-kDa protein but not the 108-kDa protein had no effect on rat jejunal mucosa in the Ussing chamber. The >100-kDa fraction derived from prototype EAggEC strain 042, which also expressed both 108- and 116-kDa proteins, also produced an enterotoxic effect on rat jejunal preparations in Ussing chambers; however, the same strain cured of its 65-MDa adherence plasmid did not. A subclone derived from the 65-MDa plasmid expressing the 108-kDa toxin (and not the 116-kDa protein) elicited rises in Isc. Tissue exposed to any preparation containing the 108-kDa toxin exhibited similar histopathologic changes, characterized by increased mucus release, exfoliation of cells, and development of crypt abscesses. Our data suggest that some EAggEC strains produce a ca. 108-kDa enterotoxin/cytotoxin which is encoded on the large virulence plasmid.

Animals↗
PubMed1998

Optical Doppler tomography: imaging in vivo blood flow dynamics following pharmacological intervention and photodynamic therapy.

A noninvasive optical technique has been developed for imaging in vivo blood flow dynamics and vessel structure with high spatial resolution. The technique is based on optical Doppler tomography, which combines Doppler velocimetry with optical coherence tomography to measure blood flow velocity at discrete spatial locations in turbid biological tissue. Applications of this technique for monitoring changes in blood flow dynamics and vessel structure following pharmacological intervention and photodynamic therapy are demonstrated.

Allantois↗
PubMed1997

Parenteral gene therapy with p53 inhibits human breast tumors in vivo through a bystander mechanism without evidence of toxicity.

Mutations of the p53 tumor suppressor gene are the most frequently observed genetic lesion in human cancer. Previously, we found that multiple intravenous injections of a liposome:p53 complex inhibited the growth of a malignant human breast cancer cell line that was implanted into nude mice. In the present study, we evaluated the toxicity of the liposome:p53 complex and the mechanism of this in vivo treatment in reducing tumor growth. Intravenously delivered liposome:p53 complex at dosages sufficient to inhibit human breast cancer in nude mice showed no evidence of toxicity. Clinical chemistries, complete blood counts, and histopathologic examination of various organs from the p53-treated groups did not demonstrate any difference from the control groups. To elucidate the mechanism by which the liposome:p53 complex inhibits cancer, the transfection efficiency of a liposome:chloramphenicol acetyltransferase (CAT) complex into the tumor was determined. Interestingly, less than 5% of the tumor was transfected with a liposome:CAT complex. A mechanism that could account for p53 reduction of tumor size and a low transfection efficiency is inhibition of angiogenesis. After one treatment, we found that the liposome:p53 complex reduced the number of blood vessels in the p53-treated group by approximately 60% compared to the control group (p < 0.001). The close correlation between the antitumor effect of p53 and the reduction of blood vessel density in the tumor suggests that p53 effects are mediated, at least in part, by an antiangiogenesis mechanism.

Animals↗
PubMed1996

Epstein-Barr Virus DNA recombination and loss in sporadic Burkitt's lymphoma.

Epstein-Barr virus (EBV) antigens in tumor tissue define associations of virus with human malignancies and provide clues as to mechanisms of viral oncogenesis. In Burkitt's lymphoma, EBV markers are absent from 85% of sporadic cases and 4% of endemic (African) cases, raising questions as to the exact role EBV in the disease. Standard screening criteria may be insufficient to determine the EBV status of all tumors. One of 9 tumors from American patients expressed EBV nuclear antigen 1 (EBNA1) and contained standard episomal EBV DNA, making this series consistent with the 15% EBV association traditionally ascribed to sporadic Burkitt's lymphoma. Surprisingly, 3 tumors without detectable EBNA1 contained partial EBV genomes. Identification of defective, integrated viral DNA in some tumors indicates greater involvement of virus in sporadic Burkitt's lymphoma than previously documented and suggests a process of viral DNA rearrangement and loss during malignant progression most consistent with an initiating role for EBV in tumorigenesis.

Adolescent↗
PubMed1996

Review of a computer based telephone Helpline in an A&E department.

OBJECTIVE: An audit of use of the telephone Helpline in the accident and emergency (A&E) department was conducted to establish the type of call, time, by whom the calls were made, appropriateness of advice given, and whether callers attended or not as advised, and also to obtain feedback from callers as to the degree of satisfaction with the advice given. METHODS: All calls over a four week period were included in the study. The information logged comprised name, age, telephone number, date and time of call, nature of query, advice given, and name of advisor. Callers whose telephone number had been noted were contacted for feedback. RESULTS: There were 300 calls over the four week period, and 150 callers were available for feedback. Most calls were received between 12.00 and 20.00 hours. The majority of callers were parent or self, 52% of calls were for problems concerning adults, and 40% for children; no age was recorded in 8%. Nursing staff answered 90.7% of the calls. Queries were wide ranging but commonly involved open and closed wounds and head injuries, with 29.3% being advised to attend A&E, 32.3% to ring or see their GP, and 38.4% were reassured or given other advice; 4% of callers attended A&E despite being advised otherwise, 97% were judged to have received appropriate advice, and 91.3% of callers were satisfied with the advice given. CONCLUSION: The Helpline has proved of benefit to the public. It is necessary and important to have protocols for common problems and to document all details carefully. It is also necessary that nursing staff are trained in handling the telephone queries and using the protocols. The use of a PC based system has improved data collection and also allows immediate access to protocols.

Adult↗
PubMed1996

Doxorubicin and dose-escalated cyclophosphamide with granulocyte colony-stimulating factor for the treatment of hormone-resistant prostate cancer.

PURPOSE: The goals of this study were to define the efficacy and toxicity of doxorubicin and dose-escalated cyclophosphamide (Cy) along with granulocyte colony-stimulating factor (G-CSF) in the treatment of hormone-refractory prostate cancer (HRPC), to determine the maximal-tolerated dose (MTD) of Cy in this regimen, and to evaluate the impact of prior pelvic irradiation (XRT) on MTD and toxicity. PATIENTS AND METHODS: Thirty-five patients were treated every 21 days with fixed-dose doxorubicin (40 mg/m2) and Cy 800 to 2,000 mg/m2 (in a cohort dose-escalation schema) along with G-CSF. RESULTS: Five of 15 patients (33%) with measurable disease obtained an objective response. Sixteen of 35 patients (46%) had a greater than 50% decrease in prostate-specific antigen (PSA) level (95% confidence interval [CI], 28.8% to 63.4%). Ten of 35 patients (28.6%) had a greater than 75% decrease in PSA level. The median survival time was 11 months. The median survival duration of patients with a greater than 50% decrease in PSA level was 23 months, versus a median survival time of 7 months in patients without a PSA response (P = .02). Although 33% of cycles were associated with grade 4 neutropenia, febrile neutropenia occurred in only 7.8% of all cycles. Thrombocytopenia and anemia were rare. Nonhematologic toxicity was minimal. Patients who had received prior pelvic XRT had a lower Cy MTD, but their hematologic toxicity was not appreciably different. CONCLUSION: This is a well-tolerated, active regimen for the treatment of HRPC. Toxicity was not different in patients with prior pelvic XRT, although these patients had a lower MTD.

Adenocarcinoma↗
PubMed1995

The antiandrogen withdrawal syndrome. Experience in a large cohort of unselected patients with advanced prostate cancer.

BACKGROUND: Flutamide withdrawal has been reported to be therapeutically efficacious for patients with hormone-refractory prostate cancer, with a reported prostate specific antigen (PSA) response rate of 29%. METHODS: to evaluate the results of flutamide withdrawal in a large group of unselected patients, the medical records of 107 consecutive patients with metastatic prostate cancer who developed progressive disease while receiving flutamide therapy were reviewed retrospectively. Flutamide withdrawal was undertaken at the time of disease progression. RESULTS: Eighty-two patients were evaluable. Of these, three had a > 80% fall in PSA value, and another nine had a > 50% decrease, for a response proportion of 14.6% (95% confidence interval 7.8%-24.2%). The median response duration was 3.5 months (range, 1-12+ months). Eight of patients treated with combined androgen blockade at the time of diagnosis of metastatic disease had a response (14%), whereas 4/25 responses (16%) were noted in patients in whom flutamide was added later, at the time of first progression. When patients who responded were compared with patients who did not respond, there was not a significant difference in age, pretreatment PSA level, type of gonadal androgen deprivation, or the likelihood of prior combined androgen blockade versus late addition of flutamide. The duration of prior therapy with flutamide was longer in patients who responded (21.5 vs. 12.0 months). CONCLUSIONS: These findings confirm the flutamide withdrawal phenomenon in a large group of unselected patients, although its frequency is not as high as previously reported. In contrast to earlier reports, whether patients have had initial hormonal therapy with combined androgen blockade or monotherapy does not appear to be predictive of the likelihood of response to antiandrogen withdrawal.

Adult↗
PubMed1995

Isolation and characterization of a chicken homolog of the c-ret proto-oncogene.

The c-ret proto-oncogene encodes a receptor tyrosine kinase that plays important roles in human disease and in normal mammalian development. Mutations in the human RET gene are associated with multiple endocrine neoplasia syndromes and Hirschsprung's disease in humans, while targeted mutagenesis of murine c-ret resulted in severe developmental abnormalities affecting the excretory and peripheral nervous systems. To examine the evolutionary conservation of the ret protein sequence and its developmental expression pattern, we isolated and sequenced cDNA clones of chicken c-ret and examined its expression in chick embryos and adult tissues. The cytoplasmic domains of chicken and human ret were relatively well conserved (91% similar), but the extracellular domains were more divergent (68% similar), although the conservation of cysteine residues in this region suggests a conserved secondary structure. As in mouse and human, chicken c-ret encodes two protein isoforms. The number and sizes of the transcripts were similar to those in human and mouse cells, and during chick embryogenesis, c-ret mRNA was observed in many of the same sites as in the mouse, including the Wolffian duct and ureteric bud, the enteric, dorsal root, sympathetic and facioacoustic ganglia, and the ventral spinal cord. Evolutionary differences in expression were observed in the trigeminal ganglion, the ventral roots of the spinal cord, the mesenchymal cells of the branchial arches and the adult testes. The results are discussed with regard to the role of the ret receptor in normal development and disease.

Amino Acid Sequence↗
PubMed1994

Polyomavirus middle-sized tumor antigen modulates c-Jun phosphorylation and transcriptional activity.

Polyomavirus middle-sized tumor antigen (MT) increases the expression of c-jun through a phorbol 12-O-tetradecanoate 13-acetate response element in the c-jun promoter. To investigate the cellular signaling pathways affected by MT, we studied the role of the c-Ras and Raf-1 proteins in MT-induced transactivation of c-jun and cell transformation. There was an increase in GTP complexed to Ras in MT-expressing cells, indicating an increase in Ras activity. Coexpression of dominant inhibitory mutants of Ha-ras and raf-1 with MT inhibited MT-mediated transactivation and focus formation. Studies of the phosphorylation of c-Jun showed that MT expression increased the phosphorylation of Ser-63 and Ser-73 in the transactivation domain and decreased the phosphorylation of a peptide containing Ser-243, Ser-249, and Thr-231 in the DNA binding domain. MT increased the transcriptional activating ability of c-Jun but failed to increase the transcriptional activating ability of c-Jun mutants with Ser-63 and Ser-73 changed to nonphosphorylatable Ala, indicating that MT modulates c-Jun activity through phosphorylation. The dominant inhibitory mutants of Ha-ras and raf-1 interfered with the ability of MT to activate c-Jun. The results indicate that MT induces a phosphorylation cascade through the activation of c-Ras and Raf-1 and that c-Jun is one of the downstream targets that may cause changes in gene expression leading to cell transformation.

3T3 Cells↗
PubMed1993

The weight-based heparin dosing nomogram compared with a "standard care" nomogram. A randomized controlled trial.

OBJECTIVE: To determine whether an intravenous heparin dosing nomogram based on body weight achieves therapeutic anticoagulation more rapidly than a "standard care" nomogram. DESIGN: Randomized controlled trial. SETTING: Two community teaching hospitals in Phoenix, Arizona, and Rochester, New York. PARTICIPANTS: One hundred fifteen patients requiring intravenous heparin treatment for venous or arterial thromboembolism or for unstable angina. INTERVENTION: Patients were randomized to the weight-based nomogram (starting dose, 80 units/kg body weight bolus, 18 units/kg per hour infusion) or the standard care nomogram (starting dose, 5000-unit bolus, 1000 units per hour infusion). Activated partial thromboplastin time (APTT) values were monitored every 6 hours, and heparin dose adjustments were determined by the nomograms. MEASUREMENTS: Activated partial thromboplastin times were measured using a widely generalizable laboratory method. The primary outcomes were the time to exceed the therapeutic threshold (APTT > 1.5 times the control) and the time to achieve therapeutic range (APTT, 1.5 to 2.3 times the control). Bleeding complications and recurrent thromboembolism were also compared. RESULTS: Kaplan-Meier curves for the primary outcomes favored the weight-based nomogram (P < 0.001 for both). In the weight-based heparin group, 60 of 62 patients (97%) exceeded the therapeutic threshold within 24 hours, compared with 37 of 48 (77%) in the standard care group (P < 0.002). Only one major bleeding complication occurred (in a standard care patient). Recurrent thromboembolism was more frequent in the standard care group; relative risk, 5.0 (95% CI, 1.1 to 21.9). CONCLUSIONS: The weight-based heparin nomogram is widely generalizable and has proved to be effective, safe, and superior to one based on standard practice.

Angina, Unstable↗
PubMed1993

Intravenous heparin dosing: patterns and variations in internists' practices.

OBJECTIVE: To characterize internists' dosing practices when administering and adjusting intravenous heparin regimens. DESIGN: A survey administered by physician-investigators. SETTING: Two community teaching hospitals and one Veterans Affairs Medical Center. SUBJECTS: Sixty-one attending physicians in internal medicine. MEASUREMENTS: Physicians' choices of therapeutic activated partial thromboplastin time (APTT) range, initial heparin bolus, initial infusion dose, and dose/infusion adjustments when APTT levels are < 1.2 x control (< 35 seconds), 1.2-1.5 x control (35-45 seconds), 1.5-2.3 x control (46-70 seconds), 2.3-3.0 x control (71-90 seconds), and > 3.0 x control (> 90 seconds). RESULTS: Physicians' dosing decisions and therapeutic ranges during heparin treatment varied widely. Responses to nontherapeutic APTT levels had especially high coefficients of variation (0.67-0.81). Two groups of physicians, together comprising a majority of all respondents, use mutually exclusive therapeutic ranges (mean 44-56 seconds and 60-83 seconds). These two groups differ significantly in several types of dosing decisions. CONCLUSION: In the absence of generalizable standard guidelines for intravenous heparin therapy, internists' dosing practices vary widely. Because such practices may impede timely, effective anticoagulation, experimental studies comparing standardized dosing protocols are needed.

Adult↗