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Biomedical subjects

G Prabhakar

Publications and source records attributed to G Prabhakar.

At least 19 recordsLinked to original sources
PubMed1999

Evaluation of radioiodination of meta-iodobenzylguanidine (MIBG) catalysed by in situ generated Cu(I) and directly added Cu(II).

A reliable method of labelling MIBG with 131I is reported. Radioiodination involved nucleophilic exchange reaction (160 degrees C, 30 min) catalysed by directly added Cu(II) or by Cu(I) generated in situ by addition of Na2S2O5 to CuSO4. An additional step of purification of the radiolabelled MIBG by anion exchange chromatography is recommended. The radiochemical (RC) yield was over 90%, while the typical RC purity of 131I-MIBG was not less than 98%. Higher labelling yield was achieved with Cu(I) than when using Cu(II), and with 125I (commercial product) than with 131I obtained by wet radiochemical processing method in-house. The purity and stability of MIBG-131I was confirmed by biodistribution studies in monkeys with 0.03% and 0.8% uptake in adrenals and myocardium, respectively. It is concluded that Cu(I) or Cu(II) catalysed radioiodination method is well suited for production of MIBG-131I.

3-Iodobenzylguanidine↗
PubMed1998

Right atrial metastatic melanoma in a patient with transient ischemic attacks.

A 65-year-old-man was admitted for evaluation of a transient ischemic attack. A 4.5 x 5.3-cm right atrial mass and a patent foramen ovale were identified by echocardiography. A 0.5-cm lesion was identified in the left temporal lobe of the brain by magnetic resonance imaging. Positron emission tomography was used to differentiate a tumor from an infarct in the brain. The cardiac and the brain lesions were successfully resected. Histopathologic study of the atrial and cerebral tissue demonstrated that these were metastases from a previously excised scalp desmoplastic malignant melanoma. The patient remains well at 14 months' follow-up.

Aged↗
PubMed1998

The safety of cardiac operations in the liver transplant recipient.

BACKGROUND: Advances in surgical techniques and immunosuppressive drugs have improved the survival of patients after orthotopic liver transplantation. Enhanced survival has resulted in an increased number of patients who require medical as well as surgical management of diseases. METHODS: To contribute to the sparse literature on the surgical aspects, we reviewed our experience with 15 patients who underwent cardiac operation (1.25%) from a total of 1,200 liver transplant recipients at our center. The variables studied included the pretransplant cardiac evaluation, the interval from transplantation to cardiac operation, postoperative complications, the management of immunosuppression, and follow-up. The patients had a mean age of 52.9 years (range, 39 to 69 years) and 13 of them (86.6%) were men. Multiple cardiac risk factors were present in all 15 patients and chronic renal insufficiency was present in 7 patients. Cardiac operation was undertaken a mean of 30.4 months (range, 9 days to 62 months) after myocardial ischemia and valvular regurgitation had been ruled out at the time of transplantation. Myocardial revascularization was performed in 12 patients, 2 of whom underwent concurrent valve operation and 3 of whom underwent valve repair or replacement. Most patients had their immunosuppression regimen continued at baseline levels. RESULTS: There were no early deaths. Three patients had major complications and 4 had minor complications. There were no bleeding, infection, or healing complications. Postoperative renal parameters were persistently elevated in 5 patients and transiently elevated in 3. Liver function parameters were transiently elevated in 6 patients after the cardiac operation. No patient had hepatic rejection. A transient elevation or decrease in immunosuppressive drug levels was seen in 3 patients. Follow-up, obtained on all 15 patients, ranged from 6 to 83 months (mean, 26.5 months). There were 2 late deaths (13.3%), and 3 patients (25%) who underwent myocardial revascularization had recurrent angina. CONCLUSIONS: Cardiac operations can be undertaken safely in liver transplant recipients with good intermediate-term results. The immunosuppression regimen can be continued at preoperative levels with no need for stress-dose steroids. There were no hepatic complications among our patients, although some patients can experience worsening of renal failure.

Adult↗
PubMed1998

Reconstruction of supravalvar aortic stenosis with autologous pulmonary artery.

Use of autologous tissue in corrective cardiac operations offers many advantages including the potential for growth. We report a surgical technique using autologous pulmonary artery in the repair of supravalvar aortic stenosis in a 6-year-old child. At 30 months' follow-up, the pulmonary arterial tissue shows no evidence of calcification or dilatation and appears to be growing with the aorta.

Aortic Valve Stenosis↗
PubMed1997

Pulmonary artery augmentation with autologous aortic tissue.

OBJECTIVE: To assess durability and viability of autologous aortic tissue used to augment severe branch pulmonary artery stenosis with a novice surgical technique. PATIENTS AND METHODS: Seven patients underwent corrective surgery for complex cyanotic congenital heart disease. Their age ranged from 3-6 years, and their weight 11-17.4 kg. All had concomitant branch pulmonary artery stenosis repaired utilizing an autologous patch, harvested from the patient's own aorta by excising a ring and opening it to form the patch. The aorta is reconstructed directly by end to end anastomosis. RESULTS: One patient died in hospital. Another patient died at 18 months at home. The surviving five patients have remained well in the follow up period of mean 31 months (range 10-52). All patients were restudied by follow up echocardiography and remain with no evidence of the aortic autograft tissue calcification or stenosis. The reconstructed aorta showed no stenosis at the site of anastomosis. CONCLUSION: The intermediate term results of this novice surgical technique appear encouraging and justify the technique. However, longer follow up will be required to confirm the continued growth of this patch material.

Aorta↗
PubMed1997

Presentation and treatment of spontaneous aortocaval fistula.

BACKGROUND: Spontaneous rupture of abdominal aortic aneurysm into the inferior vena cava is rare. The clinical presentation is highly variable, and the diagnosis can be difficult, often being made only at operation. The aortocaval fistula results in a large left-to-right shunt, which can cause cardiac failure. Once the diagnosis is made, treatment is by surgical closure of the fistula and repair of the aneurysm with a graft. METHODS: This is a retrospective review of a single surgeon's experience with aortocaval fistula complicating abdominal aortic aneurysms. RESULTS: Over a 15-year period, we had five patients with spontaneous aortocaval fistula who were treated operatively. Preoperative diagnosis was made in two, suspected in one, and not made in two, one of whom died (the only perioperative death in the series). CONCLUSIONS: Spontaneous aortocaval fistulas are uncommon, and their preoperative recognition is difficult. Hematuria in association with an abdominal aortic aneurysm should raise the suspicion of an aortocaval fistula. Surgical correction is possible, with survival rates comparable to those associated with rupture of aneurysms into the retroperitoneum. Early operative control of the fistula is important to optimize the preload to the heart.

Aged↗
PubMed1997

Utility of a bedside Doppler in tracking left ventricular dysfunction related to hemorrhagic shock.

Treatment of hemorrhagic shock with fluid resuscitation alone results in diastolic dysfunction as measured by peak systolic pressure/end systolic volume ratio (PSP/ESV). The purpose of this study was to test the ability of a simple Doppler device to track diastolic dysfunction in hemorrhagic shock. In this prospective, controlled crossover study, five adult swine were resuscitated from hemorrhagic shock using fluids. Diastolic dysfunction was confirmed using PSP/ESV ratio. The effect of nitroprusside and dobutamine on this diastolic dysfunction was evaluated. Data (PSP/ESV, Doppler-derived acceleration, and oxygen transport parameters) were collected at each stage of the model. Arterial pressure and oxygen transport parameters corrected to baseline values; however, the PSP/ESV and Doppler-derived acceleration failed to correct with fluid resuscitation alone. Treatment with nitroprusside and dobutamine increased oxygen transport parameters, PSP/ESV ratio, and Doppler-derived acceleration significantly. Doppler-derived acceleration tracks left ventricular dysfunction seen in hemorrhagic shock.

Animals↗
PubMed1995

Aortic translocation for D-TGA associated with LVOTO and VSD.

Aortic translocation is a useful surgical option in certain difficult subsets of transposition of great arteries with ventricular septal defect and left ventricular outflow tract obstruction. We report here the use of this technique with pulmonary homograft reconstruction of right ventricular pulmonary artery continuity in a child with transposition of the great arteries, left ventricular outflow tract obstruction, and restrictive ventricular septal defect.

Aorta↗
PubMed1995

Extended transseptal versus conventional left atriotomy: early postoperative study.

BACKGROUND: Mitral valve operations require excellent exposure. The description of an extended vertical transseptal atriotomy by Guiraudon and associates promises to provide optimal exposure of the mitral valve. A prospective study was carried out to evaluate the merits of the extended vertical transseptal atriotomy in comparison with the conventional left atriotomy for mitral valve operations. METHODS: Conventional atriotomy was performed in 24 patients (group I) whereas 65 patients underwent the extended vertical transseptal offroach (group II). They were similar in age, sex, cause of disease, New York Heart Association functional class, left atrial size, and left ventricular function. The early postoperative rhythm changes in these two groups were compared. Statistical studies to analyze the significance of incidence of junctional arrhythmia in these two groups were carried out. RESULTS: Of the 24 patients in group I, 3 had development of transient junctional rhythm after operation, lasting less than 24 hours. None had this arrhythmia at the time of discharge. Of the 65 patients in group II, junctional rhythm was documented in 25, with a rate of occurrence of 38% (95% confidence interval, 27.6% to 52.2%). At the 6-week follow-up, 3 patients still had this junctional rhythm, with a failure to recover rate of 12% (3 of 25). CONCLUSIONS: The surgical exposure was considered excellent and closure of the atriotomy was thought to be easy in group II. However, this should be balanced against a significant (38%) incidence of transient junctional rhythm in the early postoperative period in group II, probably from injury to sinus node artery or atrial conduction pathways.

Adolescent↗
PubMed1995

Characterization of lymphocyte beta-adrenoceptor activity and Gs-protein in patients with rheumatic heart valvular disease.

In order to test whether the beta-adrenoceptor activity in rheumatic heart valvular disease depends on the ventricular load conditions, we determined their density and binding affinity to [125I]-iodocyanopindolol in lymphocytes, as well as plasma catecholamine and cAMP levels in 69 patients with regurgitant and stenotic lesions of the aortic and mitral valves. The patients were classified as having left ventricular pressure overload (LVP), left ventricular volume overload (LVV), mixed lesions (MOL) or right ventricular pressure overload (RVP). The beta-adrenoceptor activity was determined by radioligand binding methods, catecholamines by high performance liquid chromatography using an electrochemical detector and cAMP by radioimmunoassay. The mean beta-adrenoceptor density (Bmax) of the control group was 60.1 +/- 9.5 fmol (n = 29) per 10(6) lymphocytes. In the study population, the density was decreased by 83% in LVP, 78% in LVV, 87% in MOL and 86% in RVP. Plasma norepinephrine was elevated by 89% in LVP and 60% in MOL, epinephrine by 43% in LVP, 50% in VOL, 115% in MOL and 20% in RVP, while dopamine was not significantly changed, and cAMP was slightly elevated in all four groups. Screening for activating mutational changes in the Gs alpha-protein gave negative results, possibly dissociating the elevation in plasma cAMP from stimulatory effects of such abnormalities in the Gs-protein signaling.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Comparison of fresh and glutaraldehyde-treated autologous stented pericardium as pulmonary valve replacement.

The use of fresh autologous pericardium in valve surgery has shown poor results in the past mainly due to thickening and retraction. Recently, it has been suggested that a short treatment with glutaraldehyde might radically change its behavior. In an attempt to determine whether this disparity in results is due to the glutaraldehyde treatment or to a better present-day surgical technique, fresh and glutaraldehyde-treated autologous pericardium was mounted in a frame and implanted in the pulmonary position of adult sheep. Six survivors obtained in each group were sacrificed between 2 and 8 months in the "fresh" group and between 2 and 6 months in the "glutaraldehyde-treated" group. Macroscopically, the fresh pericardium became thickened and retracted in all specimens, eventually resulting in severe regurgitation, while the glutaraldehyde-treated, although slightly thickened, retained its pliability without significant retraction. Microscopically, viability of the central core of the collagen was more often preserved in the fresh pericardium. Endothelialization was irregular. In conclusion, short glutaraldehyde treatment seems to improve the results of autologous pericardium mounted on a valve stent. Its effect on calcification remains to be ascertained.

Animals↗
PubMed1995

In situ mitral valve stabilization with glutaraldehyde.

Mitral valve repair in the young rheumatic patient carries a high reoperation rate due to progression of the disease. In an attempt to halt or at least slow down this process, the possibility of fixing in situ the valve tissues with glutaraldehyde was explored. Six weanling sheep underwent tanning of their anterior mitral leaflet for two minutes with 0.5% buffered glutaraldehyde. The non-treated posterior mitral leaflet served as control. The animals were sacrificed at varying intervals between 2.5 and 6 months. At sacrifice, Doppler echocardiography and hemodynamic studies were done. The leaflets were subjected to histopathologic examination and calcium and glutaraldehyde contents were estimated. Glutaraldehyde treatment of the anterior leaflet caused thickening of the cusp and chordae associated with partial devitalization of its core tissue, partial loss of endothelium and intense fibrocellular reaction with abundant elastic fibers without altering its functional integrity. It did not induce calcification. There were no detectable levels of glutaraldehyde at explantation. The posterior mitral leaflets were normal. Although the absence of calcification and partial viability of the tissue are encouraging, it does not necessarily follow that this treatment would arrest progression of the underlying disease. This process may have clinical application in the future, but it is not yet recommended.

Animals↗
PubMed1994

Complex karyotypic mosaicism as a result of non-disjunction and subsequent centromere fission.

Karyotypic discrepancy among four different cell types is described in tissues derived from a pregnancy terminated because of chromosomal anomalies. Chorionic villus cells demonstrated 46,XX (direct preparation) and 46,XX/47,XX,+mar1 (cultured cells) karyotypes, while fetal skin fibroblasts had a karyotype of 47,XX,+18 and the placenta showed a triple mosaicism of 47,XX,+18/47,XX,+mar1/48,XX,+18,+mar2. The origin of this complex chromosomal distribution and its significance are discussed in comparison with findings in similar cases.

Abortion, Induced↗
PubMed1994

Unilateral renal hypoplasia and contralateral renal agenesis: a new association with 45,X/46,XY mosaicism.

The association of urinary anomalies with Turner's syndrome is well established. This report describes an unusual antenatal presentation of this cytogenetic disorder and the first reported case of unilateral renal hypoplasia and contralateral renal agenesis in a 45,X/46,XY fetus. The fetus presented with severe third trimester oligohydramnios and symmetrical intrauterine growth retardation at 29 weeks and 2 days' gestation. Chorionic villus cultures revealed a 45,X karyotype. A phenotypically male infant weighing 1833 g was delivered at 35 weeks and 2 days. Chromosomal analysis of the newborn showed a 45,X/46,XY mosaicism, and surgical exploration revealed absence of the left kidney and a hypoplastic right kidney. The infant died at 11 months of age from renal failure and peritonitis. This case demonstrates that monosomy X may be encountered in fetuses with marked growth delay and oligohydramnios. The etiology of the oligohydramnios in this case was a fetal renal malformation not previously described in Turner's syndrome. Antenatal cytogenetic findings should be confirmed postnatally, with a search for mosaicism, when monosomy X is encountered.

Female↗
PubMed1994

Complex chromosomal rearrangements: some breakpoints may have cellular adaptive significance.

Cytogenetic study of a 3-year-old girl with developmental delay and some minor abnormalities revealed a complex chromosome rearrangement (CCR) involving seven chromosomes with eight breakpoints, leading to monosomy of segment 5q15-q22. According to breakpoint distribution, CCRs may be classified as those with primary intrachromosomal abnormalities (including inversions, insertions, duplications, etc.) and those without them. Only the latter group of CCRs was used in this analysis. Comparison of theoretical and observed breakpoint distributions in 33 cases demonstrated that recurrent involvement of some chromosome(s) ("re-entry") occurs more frequently than expected. One possible explanation for this observation suggests that the initial event leads to an unstable provisional rearrangement, and subsequent breaks are necessary to stabilize the karyotype.

Child, Preschool↗