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Biomedical subjects

R Reddy

Publications and source records attributed to R Reddy.

At least 109 records · Page 6Linked to original sources
PubMed1997

A simplified sequence for observing deoxymyoglobin signals in vivo: myoglobin excitation with dynamic unexcitation and saturation of water and fat (MEDUSA).

This paper describes a new, simplified pulse sequence for observing NMR signals from deoxymyoglobin in vivo. Paramagnetically shifted resonances from deoxymyoglobin can be exploited to noninvasively calculate intracellular oxygen tension in striated muscle. However, special sequences are required to observe these weak signals against the larger water and fat signals encountered in vivo. The pulse sequence described here, which is based on inversion recovery sequences, efficiently suppresses both water and fat resonances and can be implemented with short repetition rates. Moreover, it is perfectly suited for studies with surface coils, where RF inhomogeneities render other popular suppression sequences ineffective.

Humans↗
PubMed1997

T1rho-relaxation in articular cartilage: effects of enzymatic degradation.

Spin-lattice relaxation in the rotating frame (T1rho) dispersion spectroscopy and imaging were used to study normal and enzymatically degraded bovine articular cartilage. Normal specimens demonstrate significant T1rho "dispersion" (approximately 60 to approximately 130 ms) in the 100 Hz to 9 kHz frequency range. Proteoglycan-degraded specimens have 33% greater T1rho values than collagen-degraded or normal samples. T1rho-weighted images reveal structure not found in conventional T1- or T2-weighted images. Our results suggest that T1rho measurements are selectively sensitive to proteoglycan content. The potential of this method in distinguishing the early degenerative changes in cartilage associated with osteoarthritis is discussed.

Animals↗
PubMed1997

17O-decoupled proton MR spectroscopy and imaging in a tissue model.

17O-decoupled proton MR spectroscopy and imaging were implemented at 2 T. Their sensitivity and accuracy in vitro were examined using semisolid tissue phantoms doped with H2(17)O. A double-tuned solenoidal coil was used to irradiate the same volume of 17O and 1H nuclei, as well as to facilitate direct calibration of the decoupling power. Decoupling efficiency was optimized as was 17O detection sensitivity. Decoupling was most efficient at RF amplitudes below 2.5 kHz (expressed as gamma [17O] x H1), which is within the limits of the acceptable specific absorption rate. Propagation of error analysis demonstrated that 17O detection sensitivity is optimal at a TE equal to the T2 of 17O-depleted water protons. Based on Meiboom's work, a simple theory was formulated for estimating the transverse relaxivity of H2(17)O and the proton signal enhancement produced by decoupling. There was excellent agreement between theory and experiment. Overall, 17O-decoupled spectroscopy and imaging were highly sensitive and accurate in quantifying H2(17)O in vitro.

Calibration↗
PubMed1997

Reproducibility of exercise-induced modulation of cardiovascular responses to cold stress.

The modulation of cardiovascular responses to the cold pressor test (CPT) as produced by exercise was studied in 13 volunteers. The reproducibility of the measurements selected for the study, i.e. heart rate (HR), blood pressure (BP), blood flow (BF) and skin temperature (ST), was investigated through repeat experiments in the fall of 1994 and the winter of 1995. HR was monitored before, during and after a 10-min period of bicycling at 70% of reserve HR. BP, cutaneous BF and ST were measured before and after exercise. Two CPTs (hand into ice-cold water for 1 min) were performed: one preceding exercise and another at 3 min after exercise. The results obtained allow us to conclude that in non-hypertensive volunteers (1) the pronounced cardiovascular responses (ST, BF and BP) induced by CPT are reproducible (p > 0.2) when compared to basal level values and (2) cardiovascular responses to cold stress are significantly attenuated by exercise (p < 0.03). Our study, therefore, supports and validates the use of our coupled exercise-CPT method in ongoing epidemiological studies attempting to identify individuals at risk for the development of hypertension as well as those most likely to benefit from preventative exercise programs.

Adolescent↗
PubMed1997

Laparoscopic evaluation of liver disease in chronic renal failure prior to renal transplantation.

BACKGROUND: Diagnostic laparoscopy with liver biopsy has been shown to be safe and effective in the evaluation of patients with chronic liver disease. Patients with end-stage renal disease may be more prone to bleeding complications secondary to liver biopsy as a result of multiple factors directly related to their underlying renal condition. METHODS AND PATIENTS: From January 1994 to June 1996, 16 patients with end-stage renal disease and hepatic dysfunction (6 women and 10 men) underwent diagnostic laparoscopy with liver biopsy prior to renal transplantation at the University of Miami School of Medicine. Laparoscopy was performed using a 5 mm video laparoscope with a left paramedian approach. The mean patient age was 46 years. Fourteen patients had chronic hepatitis C with a reactive anti-HCV by ELISA; one patient had chronic hepatitis B with reactive HBsAg, and one patient was co-infected with both hepatitis B and C viruses. RESULTS: Two patients developed hypotension related to the procedure and one patient developed an intra-abdominal hemorrhage 5 days after laparoscopy that did not require surgical intervention. Biopsy findings were as follows: 13 patients had mild chronic hepatitis; 2 patients had chronic hepatitis with bridging fibrosis; and 1 patient was cirrhotic. Prior kidney transplantation or peritoneal dialysis did not preclude the performance of laparoscopy. CONCLUSION: Diagnostic laparoscopy can be safety performed in patients with end-stage renal disease with acceptable morbidity and mortality.

Abdomen↗
PubMed1997

Expression of MAGE genes in ocular melanoma during progression from primary to metastatic disease.

Primary melanomas that form within the eye have a unique pattern of disease progression as compared with melanomas that form within the skin. A high percentage of patients (approximately 50%) develop metastatic tumors that occur predominately in the liver. An unusual characteristic of ocular melanomas is the prolonged disease-free interval that extends for many years between the development of primary and metastatic tumors. It is estimated that the shortest interval between dissemination of tumor cells from the eye and the appearance of clinically detectable metastases is 6 years. A recent report indicated that fresh uveal melanoma tissue and metastatic tumor biopsies failed to express melanoma antigen gene (MAGE)-1, MAGE-2, or MAGE-3. In the present study, we examined the expression of MAGE genes on fresh and cultured tumor cells obtained from an ocular melanoma patient during different stages of progressive disease. MAGE gene expression was determined by reverse transcription-polymerase chain reaction using MAGE-1, MAGE-2 and MAGE-3 specific primers. Our results demonstrate that primary ocular tumor tissue and cultured tumor cells both express significant levels of MAGE-1, 2, and 3 at the time of enucleation. A high percentage of tumor cells within the primary tumor appear to express MAGE as demonstrated by consistent MAGE expression in 16 tumor cell clones. Metastatic liver tumors that developed 3 years after enucleation and 18 years after the initial formation of the primary tumor also expressed high levels of MAGE-1, -2, and -3. MAGE was expressed on fresh tumor tissue from a single biopsy and cultured tumor cells obtained from three of four different metastatic tumor nodules. When the MAGE-negative metastatic tumor cells were treated with the demethylating agent 5-Aza-2-Deoxycytidine (5-Aza-dC), transcription of MAGE-1 was restored, indicating the MAGE genes were not deleted. Our results demonstrate that in some patients, MAGE genes are expressed on primary and metastatic ocular melanomas.

Antigens, Neoplasm↗
PubMed1997

Point mutations in the 23S rRNA gene of Helicobacter pylori associated with different levels of clarithromycin resistance.

Fifty-four of 59 (91.5%) clarithromycin-resistant isolates of Helicobacter pylori from different patients possessed either the A2143G (formerly A2058G) or the A2144G (formerly A2059G) mutation in the gene encoding 23S rRNA. The A2143G mutation was significantly more likely to occur in isolates with MICs exceeding 64 mg/L (65% versus 30% with the A2144G mutation; P = 0.01). The majority (26 of 31; 83.9%) of isolates with the A2143G mutation had MICs exceeding 64 mg/L. Peptic ulcer disease recurred in a substantial proportion of patients infected with H. pylori strains containing either the A2143G or the A2144G mutation.

Anti-Bacterial Agents↗
PubMed1997

Malignant sustained ventricular tachyarrhythmias in women: characteristics and outcome of treatment with an implantable cardioverter defibrillator.

Clinical rhythm, heart disease, ejection fraction, defibrillation threshold, recurrent arrhythmias, and mortality were compared in 268 consecutive recipients (213 men and 55 women) of their first implantable cardioverter defibrillator for life-threatening ventricular tachycardia or fibrillation. Women were younger than men, less likely to have structural heart disease, and more likely to have clinical ventricular fibrillation, a higher ejection fraction, and a lower defibrillation threshold. Complications of defibrillator placement were similar in both sexes. Unadjusted survival tended to be higher in women than in men (97% vs 90%, respectively, at 2 years, P = 0.08), largely due to fewer deaths from noncardiac causes or cardiac causes other than arrhythmia (P = 0.04). Women also tended to be at lower, albeit still substantial, risk for recurrent arrhythmias during follow-up (37% vs 52% in men at 2 years, P = 0.11). After adjustment for baseline differences, overall survival, arrhythmia death-free survival, nonarrhythmia death-free survival, and frequency of recurrent arrhythmias were not found to be gender related. Despite their apparent "lower risk" status on initial presentation, women remained at substantial risk for recurrent arrhythmias. This underscores the need to avoid being unduly biased by the "appearance" of health in managing women with malignant arrhythmias. That survival and other clinical endpoints were all ultimately independent of gender emphasizes the importance of other clinical variables in assessing risk from ventricular tachyarrhythmias.

Adult↗
PubMed1997

Peripheral fibroma with calcification--a case report.

A female patient aged 10 years reported with an intra oral swelling on the labial aspect of 32 & 33, appearing to originate from the marginal gingiva & interdental papilla. The swelling was pedunculated, mobile, non-tender, firm in consistency with an irregular surface. The colour of the gingiva was normal with slight ulceration. The swelling was excised & diagnosed histopathologically as peripheral cementifying/ossifying fibroma.

Child↗
PubMed1997

A strategy for the development of secure telemedicine applications.

Healthcare applications based on computer-supported collaboration technologies have the potential to improve the quality of care delivered to patients. Such applications can help overcome barriers to quality healthcare in the small, scattered populations of rural areas enabling telemedicine to be a part of the practice of medicine. However the growing concern about the potential for abuse through disclosure of personal health information to unauthorized parties has restricted the deployment and adoption of these potentially valuable tools. The authors, who built ARTEMIS--an Intranet healthcare collaboration facility, now describe their approach to develop secure telemedicine applications for rural healthcare practitioners.

Computer Security↗
PubMed1996

Multicenter comparison of truncated biphasic shocks and standard damped sine wave monophasic shocks for transthoracic ventricular defibrillation. Transthoracic Investigators.

BACKGROUND: The most important factor for improving out-of-hospital ventricular fibrillation survival rates is early defibrillation. This can be achieved if small, lightweight, inexpensive automatic external defibrillators are widely disseminated. Because automatic external defibrillator size and cost are directly affected by defibrillation waveform shape and because of the favorable experience with truncated biphasic waveforms in implantable cardioverter-defibrillators, we compared the efficacy of a truncated biphasic waveform with that of a standard damped sine monophasic waveform for transthoracic defibrillation. METHODS AND RESULTS: The principal goal of this multicenter, prospective, randomized, blinded study was to compare the first-shock transthoracic defibrillation efficacy of a 130-J truncated biphasic waveform with that of a standard 200-J monophasic damped sine wave pulse using anterior thoracic pads in the course of implantable cardioverter-defibrillator testing. Pad-pad ECGs were also examined after transthoracic defibrillation. After the elimination of data for 24 patients who did not meet all protocol criteria, the results from 294 patients were analyzed. The 130-J truncated biphasic pulse and the 200-J damped sine wave monophasic pulse resulted in first-shock efficacy rates of 86% and 86%, respectively (P = .97). ST-segment levels measured 10 seconds after the shock in 151 patients in sinus rhythm were -0.26 +/- 1.58 and -1.86 +/- 1.93 mm for the 130- and 200-J shocks, respectively (P < .0001). CONCLUSIONS: We found that 130-J biphasic truncated transthoracic shocks defibrillate as well as the 200-J monophasic damped sine wave shocks that are traditionally used in standard transthoracic defibrillators and result in fewer ECG abnormalities after the shock.

Adolescent↗
PubMed1996

Early graft loss secondary to massive hemorrhagic necrosis following orthotopic liver transplantation. Evidence for cytokine-mediated univisceral Shwartzman reaction.

Massive hemorrhagic necrosis (MHN) of the liver following orthotopic liver transplantation (OLT) occurs infrequently during an otherwise uneventful recovery 1 week after OLT. It is characterized by fever and sudden deterioration of allograft function leading to failure in the absence of vascular thrombosis. The etiology is unknown, although it is usually preceded by some degree of allograft rejection. Between 6 and 8 days after OLT, four patients (out of 150) became febrile, hypotensive, and experienced a rapid rise in transaminases within 48 hr. Two patients had evidence of mild rejection; the other two had moderate to severe acute cellular rejection. All patients were ABO identical, crossmatch negative. Bolus steroids were given followed by OKT3 in the two patients with severe rejection. Although sepsis was suspected, antibiotic therapy did not ameliorate the clinical course. Each patient progressed to MHN with severe centrilobular necrosis and variable portal infiltrate. High levels of interferon-gamma and tumor necrosis factor-alpha occurred prior to the rise in transaminases in each MHN patient (155 +/- 39 pg/ml and 414 +/- 201 pg/ml, respectively) compared with levels in OLT patients with severe rejection (14 +/- 4 pg/ml and 26 +/- 5 pg/ml, respectively, P < 0.05). These data support the concept of a cytokine-mediated inflammatory response leading to a univisceral Shwartzman reaction in the transplanted liver. Early recognition of this syndrome and retransplantation are critical for survival.

Adult↗
PubMed1996

Small RNA database.

The small RNA database is a compilation of all the small size RNA sequences available to date from prokaryotic and eukaryotic organisms. About 500 small RNA sequences are in our database currently. The sources of individual RNAs and their GenBank accession numbers are also included. The small RNA database can be accessed through the World Wide Web(WWW). Our WWW URL is http://mbcr.bcm.tmc.edu/smallRNA/smallrna. html. The new small RNA sequences published since our last compilation are listed in this paper.

Animals↗
PubMed1996

Disease in the scurfy (sf) mouse is associated with overexpression of cytokine genes.

The murine X-linked lymphoproliferative disease scurfy is similar to the Wiskott-Aldrich syndrome in humans. Disease in scurfy (sf) mice is mediated by CD4+ T cells. Based on similarities in scurfy mice and transgenic mice that overexpress specific cytokine genes, we evaluated the expression of cytokines in the lesions of sf mice by Northern blotting, quantitative reverse-transcription polymerase chain reaction (RT-PCR) and by hybridization in situ. Overall, the phenotypic characteristics of scurfy disease correlated well with increased interleukin (IL)-4 (lymphadenopathy), IL-6 (B cell proliferation, hypergammaglobulinemia), IL-7 (dermal inflammatory cell infiltration), and high levels of tumor necrosis factor-alpha (wasting).

Animals↗
PubMed1996

Changes in adenine nucleotides during hemorrhagic shock and reperfusion.

Certain tissues are known to be susceptible to shock-induced damage: liver, small bowel mucosa, and small bowel wall. This study was done to assess the changes in adenine nucleotides induced by hemorrhagic shock. Male Sprague-Dawley rats (n = 21; 300-350 g) were anesthetized with sodium pentobarbital (50 mg/kg, ip) and mechanically ventilated. The external jugular vein and common carotid artery were cannulated. Laparotomy was done. Hemorrhagic shock was induced by withdrawing blood into a heparinized syringe until a mean arterial blood pressure of 40 mm Hg was obtained and was maintained for 30 min by continued withdrawals. Shed blood was then reinfused through the venous catheter. No additional fluid was administered. The animals were observed for another 60 min. Throughout the procedure, biopsies were taken of liver and small bowel. The small bowel biopsies were separated into mucosal and wall fractions. Nucleotides were extracted. ATP, ADP, AMP, adenosine, inosine, xanthine, and hypoxanthine were measured with gradient HPLC. Cellular ATP concentrations decreased significantly during shock (P < 0.05). Liver ATP dropped from 8.93 +/- 0.55 to 2.91 +/- 0.16 micromol/g dry tissue (mean +/- SEM) (33%), small bowel mucosal ATP from 9.40 +/- 1.04 to 3.26 +/- 0.21 (35%), and small bowel wall ATP from 5.47 +/- 0.36 to 2.74 +/- 0.18 (50%). The nucleotide response to shock in small bowel mucosa was closer to that of liver than to that of small bowel wall. After reperfusion, ATP levels were partially restored in liver, small bowel mucosa, and small bowel wall, but not to preshock values. All of the metabolites (adenosine, inosine, hypoxanthine, and xanthine) increased during shock (P < 0.05), and did not return to preshock levels after reperfusion. The abnormalities in ATP and its metabolites, and their persistence after reperfusion, suggest a possible mechanism for the production of postshock damage.

Adenine Nucleotides↗
PubMed1996

Antimicrobial susceptibility testing of Helicobacter pylori. Comparison of E-test, broth microdilution, and disk diffusion for ampicillin, clarithromycin, and metronidazole.

The optimal method for the determination of the minimum inhibitory concentration (MIC) of antimicrobials against Helicobacter pylori has not been established. The epsilometer agar diffusion gradient test (E-Test; AB Biodisk, Solna, Sweden) was compared with broth microdilution, the reference method, and disk diffusion for the antimicrobial susceptibility testing of 122 clinical isolates of H. pylori to ampicillin, clarithromycin, and metronidazole. Isolates were considered to be resistant when the MIC values was > 8 micrograms/ml for either ampicillin or metronidazole and > 2 micrograms/ml for clarithromycin. For an individual isolate, the MICs for ampicillin and clarithromycin determined by broth microdilution and the E-test were highly reproducible, with replicate results being within +/- 1 log2 dilution. The correlation between the MICs determined by E-test and broth microdilution was excellent for both ampicillin and clarithromycin (90.1% and 88.5% were within +/- log2 dilution, and 98.3% and 96.7% of the values were within +/- 2 log2 dilution, respectively). In no instance did the interpretation of "sensitive" or "resistant" differ. Conversely, only 70.5% of the E-test results of metronidazole were within +/- 1 log2 dilution of the broth microdilution results. In addition, 15 (12.3%) of the H. pylori isolates interpreted as resistant by the E-test were sensitive by the broth microdilution method. All discrepancies occurred when the E-test MIC values fell between 8 and 32 micrograms/ml. The results of the ampicillin and clarithromycin disk diffusion assay correlated 100% with the results of the broth microdilution. However, these data suggest that when the E-test MIC results of metronidazole yield values between 8 and 32 micrograms/ml, the MIC should be reevaluated by another method.

Ampicillin↗