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Biomedical subjects

M Misra

Publications and source records attributed to M Misra.

At least 73 records · Page 4Linked to original sources
PubMed1997

Computer simulation of cerebral blood flow in moyamoya and the results of surgical therapies.

Moyamoya is the disease which involves the terminal portions of the internal carotid or origins of the middle or anterior cerebral arteries. The posterior communicating arteries are also involved, but not the vertebrals or the basilar artery. The disease occurs more commonly in females than males and it has two age peaks at less than 10 and 40 years. Over the years many treatment options or procedures have been advocated for this disease either with direct bypasses or indirect revascularization procedures or both in combination. Whether one procedure is better than another is a matter of question and still to be determined. Along with it, there are various diagnostic and research work have been done for the etiology and the management of this disease. We have tried to implement a computer model of cerebral blood flow in order to assess and predict the flow in this disease process. At this time to know and predict the effectivity of certain types of offered treatment of Moyamoya disease is only to evaluate patients clinically with long term follow ups and at some interval after surgery with angiography or blood flow determinations. This study tries to focus on the use of computerized model of predicting cerebral blood flow which tries to assess the cerebral flow and decide which treatment option would be the best for a particular patient. After various computer simulations the blood flow following each treatment option is detected and the situation which offers the best treatment in a particular case is offered to the patient. To confirm the use of utility of this computer model a larger population of patients with Moyamoya disease need to be evaluated.

Adult↗
PubMed1997

Post-cranioplasty cerebrospinal fluid hydrodynamic changes: magnetic resonance imaging quantitative analysis.

The syndrome of the trephined has been described in many patients with cranial defects as an indication for cranioplasty. Cerebral blood flow changes, the effect of the atmospheric pressure on the brain, as well as cerebrospinal fluid hydrodynamic changes have been postulated as the possible reasons for this syndrome. Using dynamic phase-contrast magnetic resonance imaging we measured arterial, venous, and cerebrospinal fluid flow into and out of the skull, before and after cranioplasty in one patient whose bone flap was removed because of osteomyelitis. We report significant changes in the oscillatory CSF flow after cranioplasty. A moderate increase in venous outflow as well as a two-fold increase in craniocaudal cerebrospinal fluid systolic flow velocity was measured after the skull closure. The changes in the cerebrospinal fluid oscillatory flow at the level of the craniovertebral junction could reflect changes in the compliance of the craniospinal system produced by closure of the cranial defect.

Adult↗
PubMed1997

Evaluation of cerebral autoregulation following diffuse brain injury in rats.

The normal cerebral circulation has the ability to maintain a stable cerebral blood flow over a wide range of cerebral perfusion pressures and this is known as cerebral autoregulation. This autoregulation may be impaired in the injured brain. Closed head injury was induced in 28 Sprague-Dawley rats weighing 400-450 g. Four groups were studied: control group, head injured rat from meter height using 350 g, 400 g and 450 g respectively. CBF, volume velocity was monitored using laser-Doppler flowmetry together with monitoring of ICP and arterial blood pressure. Correlation to assess the relationship between CBF and CPP was done in each animal every hour. If correlation coefficient was > 0.85 and CPP was within normal range, loss of autoregulation was hypothesized. Chi square test, ANOVA test and unpaired Student's t-test were done and significant level of p < 0.05 was established. Mean CBF in injured rats was significantly lower than controls (p = 0.028) at the fifth hour. CBV was lower in the group of 450 g 1 m impact than in controls at 3 h (p = 0.04). Velocity in the group of all injured rats, was significantly lower than in controls at 3 h (p = 0.032) and at 4 h (p = 0.027). Loss of autoregulation was seen during first four hours after trauma in all groups of rats who sustained injury. Statistical significant difference (p = 0.041) in loss of autoregulation between injured and control animals was seen. No loss of autoregulation was observed in the control group. In conclusion CBF and CPP provide information about loss of autoregulation in diffuse brain injury. Decrease in CBF and increase of ICP is observed as a result of loss of cerebral autoregulation. Knowledge of loss of autoregulation could give important information and help in the management of head injured patients.

Animals↗
PubMed1997

Intraventricular atrial natriuretic peptide for acute intracranial hypertension.

The effect of intraventricular atrial natriuretic peptide (ANP) on elevated intracranial pressure (ICP) was evaluated in a rodent model of global ischemia and reperfusion. ANP administration into the lateral ventricle 30 minutes after reperfusion statistically significantly reduced ICP compared with both vehicle treated animals (p < 0.001) and pretreatment pressures (p < 0.001). The ICP effects of ANP did not coincide with specific changes in regional perfusion parameters measured by laser-Doppler flowmetry. Two different vehicles for ANP were used to verify that the changes in ICP observed were independent of the sodium content administered in the vehicle. Based on the reductions observed in ICP, ANP deserves further evaluation as a treatment modality for the acute elevations in ICP associated with ischemic brain injury.

Acute Disease↗
PubMed1997

Comparative microanatomy of the lateral wall of the 'cavernous sinus' in humans and the olive baboon.

Despite many studies of the 'cavernous sinus' lateral wall, the anatomy of this area remains controversial. We performed a comparative microanatomical and histoarchitectural study in 14 humans and in 10 nonhuman primates (Papio cynocephalus anubis). Venous channels and cranial nerves were embedded in the 'interperiosteodural space'. The dura propria of the lateral wall could be removed without entering the venous compartment. The oculomotor and trochlear nerves were accompanied by an arachnoidal and dural sheath. The oculomotor nerve sheath stopped under the anterior clinoid process in baboons. The trigeminal ganglion was covered posteriorly with an arachnoid membrane and adhered firmly to the dura propria on lateral and anterior sections. The three branches of the trigeminal nerve had no arachnoid covering, except for arachnoid granulations in humans. In baboons, the oculomotor and trochlear nerves were thicker than in humans, while the ophthalmic nerve was thinner. The abducens nerve belonged to the lateral wall of the sinus in baboons and had no arachnoidal sheath except in the first millimeters of Dorello's canal. After leaving their arachnoidal and dural sheath, the intracavernous cranial nerves acquired a typical peripheral sheath. The venous channels in both species were true dural sinuses. Willis cords and adipose tissue were identified.

Abducens Nerve↗
PubMed1997

High power drill systems in neurosurgery.

Neurosurgical drill systems have evolved enormously over the centuries, from the early tools of trephination to the latest motor powered drills. The Midas Rex III Motor system and the Midas Rex driver motor are the newest systems, incorporating features that allow convenient operation by surgeons.

Craniotomy↗
PubMed1997

Aneurysm clips: magnetic quantification and magnetic resonance imaging safety. Technical note.

Knowledge of the magnetic properties of cerebral aneurysm clips in patients undergoing magnetic resonance (MR) imaging is imperative. The authors quantified in electromagnetic units the magnetic properties of 13 different types of aneurysm clips by using a vibrating sample magnetometer. Their results showed that the magnetic moment of these clips ranged from 0.15 EMU/g to as high as 152.7 EMU/g. Based on these results and tests of the movement of the clips during MR imaging, they conclude that aneurysm clips with a magnetic moment less than 1 EMU/g may be safely used during MR imaging. The quantification of magnetic properties into electromagnetic units by using a vibrating sample magnetometer is a reliable method applicable to any testing field gradient. This method can be used as a standard to measure and label the magnetic properties of aneurysm clips.

Aneurysm↗
PubMed1997

The effect of change of renal replacement therapy on serum lipoprotein (a) concentration.

Lipoprotein (a) [Lp(a)] is an independent atherogenic risk factor. Lp(a) levels are elevated in patients on renal replacement therapy (RRT). This study looked at the effect of change of RRT on serum lipid and Lp(a) levels. Three groups were identified: (1) patients on dialysis who were transplanted; (2) those who had lost their transplants through immunorejection; (3) those who changed from continuous ambulatory peritoneal dialysis (CAPD) to hemodialysis (HD). All Lp(a) measurements were taken at least 3 months after the change of therapy. Our results were as follows: Group A (n = 21): 8 CAPD and 13 HD patients were transplanted. Median Lp(a) levels fell posttransplantation in the CAPD group (15.6 mg/dL vs 11.4 mg/dL, p = 0.04). The HD group showed a rise in cholesterol, low-density (LDL) and high-density lipoprotein (HDL) levels, with no change in Lp(a) levels. Group B (n = 11): 7 patients started CAPD and 4 HD. Overall, there was a marked increase in Lp(a) levels: median 38.2 mg/dL vs 55.9 mg/dL (p = 0.04), reflecting an increase in those starting CAPD (27.8 mg/dL vs 60.0 mg/dL, p = 0.01), with little change in the HD group (40.45 mg/dL vs 40.05 mg/dL). However, there was a decrease in cholesterol (7.4 mmol/L vs 5.1 mmol/L, p = 0.002) and LDL (5.5 mmol/L vs 3.3 mmol/L, p = 0.004). Group C (n = 16): 16 patients changed from CAPD to HD. Lp(a) levels were higher while on CAPD, as compared to when on HD (58.9 mg/dL vs 49 mg/dL, p = 0.03). Cholesterol (6.62 mmol/L vs 5.26 mmol/L, p = 0.006) and LDL (4.48 mmol/L vs 3.40 mmol/L, p = 0.004) were also higher when on CAPD. In conclusion, serum Lp(a) levels are clearly affected by the mode of the RRT, being highest in CAPD, and decline after transplantation or conversion to HD. Atherogenic risk is thus likely to differ between the modes of RRT and may be greatest for those on CAPD.

Adult↗
PubMed1997

Effect of liposome-encapsulated meso-2,3-dimercaptosuccinic acid on mice exposed to lead through drinking water.

Liposomes are the potent carriers of therapeutic drugs for their targeted delivery to the intracellular sites specially when the drug is hydrophilic in nature and is unable to cross the cell membrane. Lead, a major source of environmental pollution, is accumulated in the body system of both animals and humans through reticuloendothelial system, the site where liposomes also get engulfed upon their entry into the body. In view of these considerations, meso-2,3 dimercaptosuccinic acid (DMSA), a potent chelating drug used in heavy metals intoxication, specially lead, was encapsulated in small unilamellar liposomes composed of phosphatidyl-choline and cholesterol (1:1) and used to evaluate its efficacy in lead intoxication. DMSA either in free form or encapsulated in liposomes was administered intravenously (2,62 mumoles/kg, three injections at a gap of 48 hours each, total 7.85 mumoles/kg) to mice which were pre-fed with lead in drinking water (500 micrograms/ml) for one month. It was found that only DMSA encapsulated in liposomes was significantly effective in reducing the level of lead in liver, kidneys and spleen at the dose administered. DMSA either in free form or encapsulated in liposomes also restored the inhibition in blood delta-aminolevulinic acid dehydratase (delta-ALAD) activity. The results suggest that liposome encapsulated DMSA may be preferred over free DMSA for reducing the body burden of lead.

Animals↗
PubMed1996

Relative susceptibilities of C57BL/6, (C57BL/6 x C3H/He)F1, and C3H/He mice to acute toxicity and carcinogenicity of nickel subsulfide.

The aim of this study was to compare susceptibility of mice of different strains to the toxicity and carcinogenicity of nickel subsulfide (Ni3S2), a water insoluble compound suspected to damage cells through oxidative mechanisms. Groups of 30 male mice of each strain, C57BL/6 (C57BL), (C57BL x C3H/He)F1 (B6C3F1), and C3H/He (C3H), were injected with single doses of 0.5-10 mg of Ni3S2/site into the thigh muscle and observed for up to 78 weeks. The highest Ni3S2 dose was lethal within 1 week to C57BL (93%) > B6C3F1 (80%) > C3H (53%) mice. The most susceptible C57BL mice also had the most severe necrotic/inflammatory kidney damage, compared with that in the other mice. The final incidence of local sarcomas at the 5 mg Ni3S2 dose was: C3H (97%) > B6C3F1 (76%) > C57BL (40% of mice at risk, i.e. those surviving at least 25 week; P < 0.05 or better as compared to the incidence in C3H mice). The relatively highest acute toxicity of Ni3S2 in C57BL mice observed in the present study, concurred with the weakest antioxidant response to systemic water-soluble nickel(II), resulting in reduction in glutathione (GSH) level and increased lipid peroxidation (LPO) in their kidneys and livers, two main targets of acute nickel toxicity, reported by us previously (Toxicol. Lett. 1991, 57, 269; ibid. 1991, 58, 121). Ni3S2 deposited in the muscle, therefore, constitutes a source of soluble nickel that can reach and damage distant organs. THe strongest tumor response in C3H mice relative to other strains did, in turn, concur with the lowest base levels of GSH and highest LPO in their muscle, the target for Ni3S2 carcinogenesis. Thus, the acute toxicity and carcinogenicity of Ni3S2 and Ni3S2-derived soluble nickel(II) in mice seem to depend, at least in part, on antioxidant capacity of target organs, which varies among different strains.

Animals↗
PubMed1996

Metal-independent putative superoxide dismutase mimics in chemistry, biology, and medicine.

The excessive generation of superoxide radicals O2-. with inadequate available defence provided by the enzyme superoxide dismutase (SOD) may result in the development and exacerbation of many of mankind's common illnesses. The native SOD proves too problematic to be used for the prevention and cure of such diseases. A number of metal-independent synthetic SOD mimics, based on organic nitroxides, have been tried as therapeutic interventions. Among the widely studied mimics, 2-ethyl-2,5,5-trimethyl-3-oxazolidinanyl, 2,2,6,6-tetramethyl-1-piperidimyloxy, nitrosoureas, and triazene derivatives have indicated promising results with possible future applications in chemistry, biology, and medicine.

Cyclic N-Oxides↗
PubMed1996

Evidence for the involvement of nitric oxide in cisplatin-induced toxicity in rats.

Cisplatin treatment of rats results into a significant increase in the activity of Ca(2+)-independent nitric oxide synthase (NOS) in kidneys and liver. Significant enhancement of lipid peroxidation in gastric mucosa, kidneys and liver was also observed. The administration of NG-nitro-L-arginine methyl ester, an inhibitor of NOS, markedly reduced renal and gastrointestinal toxicity, and also decreased the content of blood urea nitrogen, serum creatinine, and incidence of diarrhoea along with a significant inhibition in lipid peroxidation in the target organs. The present report, while demonstrating the beneficial effect of the blockade of NO pathways during cisplatin chemotherapy, may be helpful in developing strategies for combating some of the toxic side-effects of the drug.

Animals↗
PubMed1996

Transcranial cerebral oximetry in endovascular treatment of carotid-cavernous fistula.

The transcranial cerebral oximeter is a reliable, low-cost, noninvasive device that provides real-time evaluation of regional brain oxygen saturation during endovascular treatment of cerebrovascular diseases. We discuss three patients with carotid-cavernous fistulae treated by endovascular balloon occlusion, each monitored continuously before, during, and after the procedure with transcranial cerebral oximetry. The cerebral oxygen saturation measured was directly related to the side of the venous drainage of the fistula, being 15-20% higher on that side. Following endovascular occlusion of the fistula, oxygen saturation gradually became equal on the two sides.

Adult↗
PubMed1996

Transverse sinus dural fistula: combined surgical and endovascular approach: a case report.

BACKGROUND: The treatment of a large dural sinus fistula can be very difficult and complicated. The very extensive and complex nature of these malformations may require a combination therapy in the form of surgery and multistaged embolization. The transverse sinus fistula in our patient was fed by multiple large high-flow feeders and was draining retrograde into the superior sagittal sinus (SSS) and the cortical veins. The SSS did not fill in the late venous phase of the carotid angiogram, suggesting increased venous pressure. METHODS: A case of transverse sinus dural fistula is described that was managed by a combination of surgery and embolization. The complex nature of this malformation encouraged us to adopt a combination of multistaged embolization and surgery for the management and clinical control. The patient underwent embolization of multiple feeders from the branches of the external carotid artery. After this procedure, the patient underwent endovascular occlusion of the transverse sinus via the SSS. Throughout the endovascular treatment, the patient had concomitant intracranial pressure monitoring and SSS pressure monitoring, along with transcranial cerebral oximetry (TCCO). Despite this aggressive endovascular intervention, the fistula could not be completely closed. The patient then underwent surgical excision of the transverse sinus along with duraplasty and cranioplasty. RESULTS: The patient had a good recovery and posttreatment angiogram revealed normal antegrade flow in the SSS with no evidence of the fistula. The combined surgical and endovascular techniques are described and their use in clinical practice is discussed. CONCLUSIONS: The complexity of certain large dural sinus fistulae should not be underestimated. They may require a prolonged multistaged treatment for their total obliteration. Also, despite the large size and complexity of the disease, complete cure can be achieved.

Adult↗