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Biomedical subjects

R Kapoor

Publications and source records attributed to R Kapoor.

At least 91 records · Page 5Linked to original sources
PubMed1998

Effects of intravenous methylprednisolone on outcome in MRI-based prognostic subgroups in acute optic neuritis.

Treatment of acute optic neuritis with steroids has been shown to hasten visual recovery without affecting the final degree of recovery. However, MRI-clinical studies indicate that patients with long optic nerve lesions, particularly those that involve the nerve within the optic canal, may have a worse prognosis for recovery of vision. Partly because such lesions could lead to swelling and subsequent ischemic optic nerve damage, steroids could have a selective beneficial effect on this subgroup of patients. The present randomized trial was designed to test this possibility. Sixty-six patients with acute optic neuritis received IV saline or IV methylprednisolone. The clinical, psychophysical, electrophysiologic, and MRI outcomes were assessed after 6 months. Patients with short lesions presented earlier than those with long lesions (involving three or more 5-mm-thick slices of any part of the optic nerve, as well as its intracanalicular portion), and lesion length was significantly less in patients presenting within a week of onset of symptoms. Lesions also tended to lengthen during follow-up in individual patients. Treatment did not limit lesion length in either the long or short lesion subgroup and had no significant effect on final visual outcome. We conclude that steroids do not improve visual outcome or lesion length in patients with acute optic neuritis.

Acute Disease↗
PubMed1997

Immuno-localization of kynurenine aminotransferase (KAT) in the rat medulla and spinal cord.

In the mammalian brain, kynurenine aminotransferase (KAT) is pivotal to the synthesis of kynurenic acid, a preferential antagonist at the strychnine-insensitive NMDA-glycine site. As NMDA receptors are involved in autonomic function, we have examined the immunohistochemical localization of KAT in the medulla and spinal cord of the rat. KAT immunoreactivity (KAT-li) was found throughout these areas, in both glia and neurons. Unlike the mainly astrocytic localization in forebrain structures, KAT-li was predominantly neuronal, notably in areas important for blood pressure and heart rate regulation: ventral medulla, nucleus ambiguus, nucleus of the solitary tract and intramediolateral cell column of the spinal cord. The presence of KAT in these nuclei supports a neuromodulatory role for kynurenic acid in NMDA-mediated autonomic function.

Animals↗
PubMed1997

Sphincteric incontinence: the primary cause of post-prostatectomy incontinence in patients with prostate cancer.

Post-prostatectomy incontinence in patients with cancer of the prostate is often the result of sphincteric injury. However, recent studies have emphasized the role of detrusor instability and decreased bladder compliance in the etiology of post-prostatectomy incontinence. To further clarify the primary cause of incontinence, we reviewed the urodynamic studies of 39 patients referred for evaluation of incontinence after prostatectomy (35 radical, 4 TURP and radiation) for prostate cancer. Multichannel videourodynamic studies were performed to characterize bladder function, and sphincteric incontinence was assessed by Valsalva leak point pressure (VLPP). Flexible cystourethroscopy was used to evaluate the vesicourethral anastomosis. A pad scoring system was used to measure symptom severity. Sphincteric damage was found to be the sole cause of urinary incontinence in 23 patients (59%) and a major contributor in 14 others (36%). Twenty-seven patients (69%) had VLPP less than 103 cmH2O (mean = 55) with a urethral urodynamic catheter in place. An additional 10 (26%) had VLPP less than 150 cmH2O (mean = 63) upon removal of the catheter. VLPP is an indication of the severity of sphincteric damage. The importance of removing the urodynamic catheter during measurement of the VLPP is emphasized. Urethral fibrosis was confirmed by cystourethroscopy in 26 (67%) patients. Bladder dysfunction characterized by detrusor instability and/or decreased bladder compliance was seen in 15 patients (39%). In contrast to previous studies, our results indicate that sphincteric damage, and not bladder dysfunction, accounts for the vast majority of post-prostatectomy incontinence in patients with prostate cancer. However, it is essential to identify and treat bladder dysfunction in order to optimize the outcome of treatment for sphincteric incontinence.

Aged↗
PubMed1997

Postural hypotension in a patient with cervical myelopathy due to craniovertebral anomaly.

We report a patient with craniovertebral anomaly leading to cervical cord compression who presented with disabling postural hypotension. A 60-year-old electrician presented with progressive weakness of the upper and lower limbs, which had started 7 years previously. He had difficulty in holding urine for the previous year and had blacked out on standing for the past 3 months. He had upper limb wasting and lower limb spasticity, with impaired joint position sense. Autonomic dysfunctions included postural hypotension, absence of sinus arrhythmia, impaired Valsalva ratio, and lack of increase in blood pressure on cold immersion and isometric contraction. Cervical spine radiograph and magnetic resonance imaging revealed atlantoaxial dislocation, Klippel-Feil syndrome and osteophytes, resulting in cord compression at C2-C4. Partial and selective damage to the descending autonomic fibres may be responsible for postural hypotension in this patient.

Arrhythmia, Sinus↗
PubMed1997

Nitric oxide donors reversibly block axonal conduction: demyelinated axons are especially susceptible.

Diseases such as multiple sclerosis and Guillain-Barré syndrome are characterized not only by widespread loss of myelin from nerve fibres, but also by widespread inflammation in the central and peripheral nervous systems, respectively. While the demyelination alone is sufficient to block conduction and thereby cause symptoms, there is increasing evidence that the inflammation may also contribute significantly to the conduction block, although the mechanisms are not understood. Nitric oxide is an important inflammatory mediator which is elevated within the central nervous system in multiple sclerosis and which can be experimentally applied to tissues using nitric oxide donors. We report that such compounds cause reversible conduction block in both normal and demyelinated axons of the central and peripheral nervous systems. Notably, conduction in demyelinated and early remyelinated axons is particularly sensitive to block by nitric oxide, so that at lower concentrations, including those expected at sites of inflammation, demyelinated axons are selectively affected. We therefore propose that inflammation may directly cause symptoms via nitric oxide release, and that the inhibition of such release may open a new therapeutic avenue for demyelinating disease.

Animals↗
PubMed1997

Slow sodium-dependent potential oscillations contribute to ectopic firing in mammalian demyelinated axons.

Ectopic action potentials can arise at regions of axonal demyelination, and are believed to contribute to a range of symptoms in patients with demyelinating conditions such as multiple sclerosis. The mechanism(s) by which the ectopic impulses are generated are uncertain. We have previously shown that such ectopic activity can result from inward potassium currents. Paradoxically, the potassium channel blocking agent 4-aminopyridine (4AP) can sometimes cause ectopic activity in demyelinating lesions. To study this phenomenon we have made intra-axonal recordings of ectopic activity in demyelinated axons, both in the presence and absence of 5 mM 4AP. 4AP promoted a pattern of firing which was observed, albeit less frequently, in demyelinated axons in the absence of this drug, namely trains of single impulses, or trains of short, high-frequency bursts of impulses. When recorded close to the demyelinated lesion, the impulses were generated by an underlying, almost sinusoidal oscillation of the membrane potential. This oscillation was abolished by the sodium channel blocking agent tetrodotoxin (0.1-1 microM). We conclude that the ectopic spiking induced by 4AP is generated by membrane potential oscillations associated with the site of demyelination. The sodium-dependent current underlying these oscillations, together with the prolonged inward potassium currents which we have previously described, may contribute to the generation of ectopic discharges in a range of disorders of myelinated axons.

4-Aminopyridine↗
PubMed1997

Mitrofanoff principle for continent urinary diversion.

In 1980 Mitrofanoff described a method to achieve continent urinary diversion by surgically closing the bladder neck and creating a continent catheterizable stoma from the appendix which had been implanted in a nonrefluxing manner into the bladder or from a nonrefluxing distal ureter. The Mitrofanoff principle (MP) serves well as a continence mechanism for either the native bladder or intestinal reservoirs. We review 17 patients, including 10 children, who were treated with the MP and received a continent catheterizable channel. For the MP, appendix was used in 16 patients and ureter in 1. The continuity between the urinary reservoir and urethra was maintained wherever possible. Bladder neck suspension was preferred to bladder neck closure in incontinent females and boys. Complications and their management have been discussed at length. Stable renal functions, ease of catheterization and urinary continence were achieved in 93.8% of the patients.

Adolescent↗
PubMed1997

Endoscopic management of traumatic posterior urethral stricture: early results and followup.

PURPOSE: We assessed the outcome of core through internal urethrotomy for traumatic posterior urethral stricture, and reviewed the followup results of these patients. MATERIALS AND METHODS: During the last 4 years 13 patients with a stricture up to 2 cm. long underwent core through internal urethrotomy with C-arm fluoroscopy guidance and an orientation in 2 planes. Retrograde urethrotomy was performed and an 18F Foley catheter was left indwelling for 4 weeks, after which urethrotomy was repeated. All patients were advised to perform clean intermittent self-catheterization for urethral calibration and dilation. Outcome was defined as class 1-3 patients who required 2 or fewer urethrotomies with clean intermittent self-catheterization discontinued after the primary procedure, class 2-5 who required 2 or fewer urethrotomies with clean intermittent self-catheterization and class 3-5 who required 3 or more urethrotomies. RESULTS: Of the 13 patients 8 (61%) did well after a mean followup of 17.7 months. The 3 patients with a class 1 outcome did well, while 2 of 5 with a class 2 outcome required repeat urethrotomy during followup. Of the 5 patients (39%) with a class 3 outcome in whom core through internal urethrotomy failed 3 required open surgery and 2 were lost to followup. Recurrence rate was 69% at 3 months and 25% at 12 months after the initial procedure. No patient was incontinent at last followup. Two patients had significant hematuria postoperatively, which resolved with conservative treatment. CONCLUSIONS: Endoscopic treatment should be considered the first line procedure for all post-traumatic posterior urethral strictures. The morbidity of open surgery can be avoided in 61% of patients. Hospital stay, loss of work, morbidity and related complications are also markedly decreased with endoscopic therapy.

Adult↗
PubMed1997

Chronic renal failure and nephrolithiasis in a solitary kidney: role of intervention.

PURPOSE: We determined the role of intervention and its outcome in patients with a solitary kidney, nephrolithiasis and chronic renal insufficiency, as well as the role of clearance in these patients compared to those with a solitary kidney, nephrolithiasis and normal renal function. MATERIALS AND METHODS: A total of 36 records was evaluable, including 16 from patients with normal (group 1) and 20 from those with abnormal (group 2) renal function. Group 2 was further subdivided into those with mild to moderate (group 2A) and advanced (group 2B) renal failure. Patients with acute renal failure were excluded from the study. Glomerular filtration rate was calculated by the Cockcroft and Gault formula. The reciprocal of serum creatinine was used to determine outcome. RESULTS: Groups 1 and 2 were comparable demographically except for serum creatinine, stone bulk and hospital stay. Of 36 patients 8 with normal renal function and 15 with chronic renal failure underwent percutaneous nephrolitholapaxy, 6 underwent extracorporeal shock wave lithotripsy and 7 underwent open surgery. Total clearance was achieved in 25 of 36 patients (72%). Glomerular filtration rate improved in 24 patients, remained stable in 8 and deteriorated in 4. However, 3 patients had less than 20% deterioration and 1 had significant deterioration in function after intervention. Improvement in glomerular filtration rate after intervention was significantly greater in cases of advanced renal failure. Patients with residual stones did worse than those without residual calculi. Mean hospital stay, deterioration in glomerular filtration rate and major morbidity rate were significantly greater in patients with residual calculi than in those with total clearance. CONCLUSIONS: Intervention should be contemplated in patients with a solitary kidney, stone disease and renal failure as in any other patient with stone disease, with the aim being total clearance. Stone eradication delays deterioration, and decreases the requirement for dialysis and renal replacement.

Adult↗
PubMed1997

Cholecystectomy under regional anesthesia in a patient with total Kartagener's syndrome.

A 41-year-old woman with complete Kartagener's syndrome developed cholecystitis in a left-sided gall bladder. Bilateral diffuse bronchiectasis ruled her unfit for general anesthesia; chronic cough, copious expectoration and dyspnea prevented her from lying down supine for more than a few minutes. Successful cholecystectomy was performed in a semi-reclined position using thoracic epidural anesthesia, the anatomy being the mirror image of that of a gall bladder in normal position. The gall bladder was full of stones and operative cholangiogram revealed a normal but transposed biliary system.

Adult↗
PubMed1997

Cystadenoma with mesenchymal stroma mistaken for hepatic hydatid cyst.

Hepatobiliary cystadenoma with mesenchymal stroma occurs uniquely in women, can be associated with other hepatobiliary anomalies, and has the potential for malignant transformation. We describe a case of hepatobiliary cystadenoma with mesenchymal stroma which was initially treated as hepatic hydatid cyst.

Adenoma, Bile Duct↗
PubMed1997

Cardiac depression and cellular injury in hemorrhagic shock and reinfusion: role of free radicals.

We investigated the effect of hemorrhagic shock and reinfusion on the cardiac function and contractility, plasma CK and CK-MB activity and lactate concentration, oxyradical-producing activity of polymorphonuclear leukocytes (PMNL-CL), cardiac chemiluminescence (LV-CL), antioxidant enzyme activity [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-PX)] and malondialdehyde (MDA) concentration in anesthetized dogs to determine the role of oxyradicals in cardiac depression and cellular injury in hemorrhagic shock and reinfusion. The dogs were assigned into three groups: I (sham), 4 h duration; II (S + R), 2 h of shock followed by reinfusion for 2 h; III (SOD + S + R), as II but pretreated with PEG-SOD. Hemorrhagic shock was produced by withdrawal of blood to maintain the mean arterial pressure at 50 +/- 5 mm Hg. Cardiac function and contractility were depressed during hemorrhagic shock. Plasma CK, CK-MB and lactate increased during shock. Following reinfusion after 2 h of shock hemodynamic parameters and plasma lactate tended to return towards control values. Plasma CK and CK-MB, PMNL-CL and cardiac MDA, total-, Mn- and CuZn-SOD activity increased while LV-CL decreased. In spite of the increase in the antioxidant reserve, there was oxidative damage. Pretreatment with SOD attenuated the deleterious effects of shock and reinfusion on the cardiovascular function, plasma CK, and CK-MB, PMNL-CL, cardiac MDA, SOD, and LV-CL. Protection was incomplete for cardiovascular function and plasma CK and CK-MB. These results suggest that oxyradicals may partly be involved in the deterioration of cardiovascular function and cellular injury during hemorrhagic shock and reinfusion.

Animals↗
PubMed1996

Altered responsiveness of medullary depressor neurones to L-glutamate and D-serine in SHR rats.

We have investigated the effects of microinjection of L-glutamate, D-serine and glycine into the caudal ventrolateral medulla (CVLM) of spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats. In SHR the depressor responses to L-glutamate were significantly enhanced compared to WKY rats, while those to the NMDA-glycine site agonists, D-serine and glycine (in the presence of strychnine) were significantly diminished. Depressor responses to NMDA and D-serine could be blocked with 5-fluro-indole-2-carboxylic acid (FICA, an NMDA-glycine site antagonist). In support of our previous findings, the larger responses of NMDA-glutamate site agonists and smaller responses of NMDA-glycine site agonists in SHR, may suggest that SHR have reduced levels of the endogenous glutamate antagonist, kynurenic acid.

Animals↗