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Biomedical subjects

K Kumar

Publications and source records attributed to K Kumar.

At least 91 records · Page 5Linked to original sources
PubMed1987

Cerebral endothelial microvilli following global brain ischemia in dogs.

Cerebral blood vessels (BVs) of dogs subjected to global brain ischemia by complete cardiac arrest of 15 min followed by 8 h of reperfusion, were studied in neocortex and hippocampus by means of transmission electron microscopy. Widespread endothelial microvilli were present in the postischemic animals. The number of endothelial microvilli in the postischemic animals (mean/BV in the neocortex = 3.26 and in the hippocampus = 2.54) was significantly larger than that in the non-ischemic controls (mean/BV in the neocortex = 1.39 and in the hippocampus = 0.84), P for both regions being less than 0.05. Arterioles, venules and capillaries, all were equally affected. Endothelial pinocytotic vesicles were also observed frequently in the postischemic dogs. Marked pericapillary swelling of astrocytic foot processes was present in the surrounding neuropil. It is concluded that the prominent cerebral endothelial microvilli recognized after 8 h of reperfusion following cardiac arrest in this experimental model of global brain ischemia, may play a significant role in the development of delayed postischemic hypoperfusion.

Animals↗
PubMed1987

Ultrastructural and ionic studies in global ischemic dog brain.

A time course of tissue ionic changes, and their relation to ultrastructural findings during reperfusion following a 15-min global ischemic brain insult was studied in a dog model. Parietal cortex was analyzed for Ca, Na, K, Mg and Fe in controls and after 10 min, 2, 4, and 8 h of reperfusion. After 8 h of reperfusion, the mean values (mumol/g tissue wet wt.) for Ca (control = 1.43, 8 h = 2.76) and Na (control 60.4, 8 h = 107.4) doubled and K (control = 90.4, 8 h = 48.5) decreased to half that of the control. Ultrastructural studies and subcellular localization of calcium in parietal cortex of in situ-fixed brains after 8 h showed cortical neurons with clumping of nuclear chromatin, dilatation of endoplasmic reticulum and disruption of plasma membranes. Large amounts of electron-dense precipitates of calcium were present within dilated astrocytic processes, synaptic vesicles, cytoplasm of edematous dendrites and mitochondria. Cortical neurons from postischemic dogs without reperfusion showed only slight chromatin clumping and edema of astrocytic processes, but no calcium accumulation. The large ionic shifts noted between 4 and 8 h of reperfusion, indicate a progressive inability of the cells to maintain normal transmembrane gradients of these ions and may reflect a membrane destructive process, as demonstrated ultrastructurally at 8 h. Enhanced calcium entry into the neuron during reperfusion appears to be a part of the cytotoxic mechanism leading to neuronal necrosis.

Animals↗
PubMed1987

Effect of flunarizine on global brain ischemia in the dog: a quantitative morphologic assessment.

The effects of flunarizine, a calcium antagonist, were evaluated in an experimental model of global brain ischemia produced by 15 min of cardiac arrest followed by resuscitation and reperfusion. One group of dogs received flunarizine (0.1 mg/kg intravenously during a 10-min period) at the onset of resuscitation. Another group of dogs underwent cardiac arrest, resuscitation, and reperfusion but did not receive flunarizine. A third group served as nonischemic control. In situ-fixed brains of all animals (nonischemic controls and the postischemic dogs after 8 h of reperfusion) were examined for anoxic ischemic injury. Quantitation of the ischemic neurons was carried out in parietal cortex, hippocampus, and cerebellum by using an image analysis system. Significant difference in the number of necrotic neurons between the flunarizine-treated group and the ischemic controls was noted in the hippocampus only; the mean percentage of necrotic neurons in the two groups being 14.8 +/- 9.6 and 29.3 +/- 12.1, respectively (P less than 0.05). These results indicate that flunarizine has an ameliorating effect on neuronal injury in the hippocampus that follows cardiac arrest in this experimental model of global brain ischemia. However, flunarizine was not found to be effective in reducing the ischemic neuronal damage in the cortex or the cerebellum.

Animals↗
PubMed1987

Brain cortex tissue Ca, Mg, Fe, Na, and K following resuscitation from cardiac arrest in dogs.

Recent evidence suggests that ultimate neurologic injury following cardiac arrest and resuscitation may be largely determined by biochemical events occurring during reperfusion. To test this hypothesis and further characterize the time course of some of these events, we examined tissue samples from the parietal cortex for their total content of calcium (Ca), magnesium (Mg), iron (Fe), sodium (Na), and potassium (K) after 10 minutes, two hours, four hours, and eight hours of reperfusion following a 15-minute cardiac arrest in dogs. After 10 minutes of reperfusion, there were relatively small, but significant, increases in the total tissue content of Ca and Na, as compared to nonischemic controls. All values had returned to normal at two hours and remained normal at four hours of reperfusion. However, at eight hours of reperfusion, Ca and Na content approximately doubled and K content was reduced by half. There were no significant changes at any time in the tissue content of Fe or Mg. We conclude that with between four and eight hours of reperfusion following a 15-minute cardiac arrest, a major defect occurs in many cells of the cortex with respect to their ability to control ionic balances of Ca, Na, and K. This might be explained either by failure of the energy-dependent ionic pumps or by more generalized damage to the membrane permeability barrier by a process such as lipid peroxidation.

Animals↗
PubMed1987

Single-dose gentamicin therapy of recurrent urinary tract infection in patients with normal urinary tracts.

Results of single-dose therapy of urinary tract infections in pediatric patients have been contradictory mainly because of selection criteria. We evaluated the efficacy of a single dose of gentamicin in patients with normal urinary tracts and in whom urinary tract infections were recurrent. Twenty-one patients were included in the study, and a similar number in a conventional group given treatment for 10 days. Cure rate was 100% in both groups. The recurrence rates of 67% in the study and 52% in the conventional group were comparable. Single-dose therapy seems to have a role in the treatment of urinary tract infection in the absence of urinary tract malformation.

Adolescent↗
PubMed1987

Role of neutrophil chemotaxis in the pathogenesis of urinary tract infection.

Status of neutrophil chemotaxis was evaluated in seventeen infants and children with acute urinary tract infection. Four different chemotactic factors including those generated by patient's own invading pathogens were studied against patient cells. Chemotactic migration was found to be depressed during active infection and gradually returned to normal after successful eradication of the organisms. During a second episode of UTI chemotaxis again became defective. Inhibition of neutrophil chemotaxis seems to be at least one mechanism in the pathogenesis of UTI. Counteracting the suppression may play a role in modifying the inflammatory process and/or enhancing recovery during therapy.

Adolescent↗
PubMed1986

Caprine beta-mannosidosis: phenotypic features.

The clinical features of caprine beta-mannosidosis were evaluated in 10 newborn goats, one stillborn goat and one goat fetus. The phenotypic abnormalities observed in all 10 live affected animals included an inability to rise from a recumbent position, moderate to marked intention tremor, eye movements resembling pendular nystagmus, clinical deafness, bilateral Horner's syndrome, carpal contractures, pastern joint hyperextension, thickened skin and to a varying degree, a dome-shaped skull. Subjective evaluation suggested that most animals had a decreased muscle mass. Together, these characteristics represent a common phenotype which is expressed at birth in caprine beta-mannosidosis.

Animals↗
PubMed1986

The pattern of muscle involvement in poliomyelitis of the upper limb.

The pattern of muscle paralysis and paresis in the upper limb has been studied in 31 children with poliomyelitis. The incidence of involvement of the upper limb alone is the same as of the upper and lower limbs together, and of the spine and upper limb. The left arm was more commonly affected than the right. The muscle most frequently paralysed was the deltoid. When complete paralysis of the whole deltoid occurred and was associated with paralysis of the rotator cuff muscles, the shoulder often subluxed downwards. The next most commonly affected muscles were the elbow flexors and extensors. In the hand the opponens pollicis was most often involved. As far as the spinal segments are concerned, C5 involvement was usually associated with paralysis and C7 with paresis.

Adolescent↗
PubMed1986

Ischemia, resuscitation, and reperfusion: mechanisms of tissue injury and prospects for protection.

Since its introduction in 1960, CPR has evolved into a complex program involving not only the medical community but also the lay public. Currently, program activities include instruction of the lay public in basic life support techniques, development and deployment of emergency medical systems, recommendations for drug protocols for advanced cardiac life support and, most recently, introduction of new methods for tissue protection following resuscitation. After 25 years of experience, we are beginning to understand the pathophysiology of tissue ischemia during cardiac arrest and the interventions required to improve chances of survival and quality of life of the cardiac arrest victim. Recent data in the literature suggest that modification of certain interventions in the resuscitation program may be needed. The poor neurologic outcomes with prolonged standard CPR show that it is not protective after 4 to 6 minutes of cardiac arrest. Modifications to this technique, including SVC-CPR or IAC-CPR, have not been shown to increase resuscitability or hospital discharge rates. Human studies of open-chest cardiac massage are needed to evaluate this option. Defibrillation is the definitive treatment for ventricular fibrillation. Greater emphasis should be placed on the earliest possible delivery of this treatment modality. Computerized defibrillators may provide greater and earlier access to defibrillation in the homes of patients at high risk of ventricular fibrillation. They may also be applicable by untrained public service personnel (police and firemen), individuals in geographically inaccessible areas (aircraft), or emergency medical technicians in rural areas where skill retention is a significant problem. Calcium has no proved benefit in cardiac resuscitation. There is biochemical evidence that it may be harmful in brain resuscitation. Its use in resuscitation should be discontinued. The dose of epinephrine currently advocated in the ACLS protocols may be inadequate to increase aortic diastolic pressure and coronary and cerebral perfusion pressures and thus aid resuscitation. Animal studies indicate that substantial increases in the current dosage are needed to achieve these effects. Human studies are needed to verify these results. A role for calcium antagonists in the treatment of postarrest encephalopathy has been demonstrated in animals and is currently undergoing clinical trials. Iron-dependent lipid peroxidative cell membrane injury may be important in the pathogenesis of postarrest encephalopathy. Animal studies suggest that the iron chelator deferoxamine may have a significant therapeutic role in the treatment of postarrest encephalopathy.

Animals↗
PubMed1986

Malathion toxicity: effect on the liver of the fish Brachydanio rerio (Cyprinidae).

Four-month-old siblings of zebra fish, Brachydanio rerio, were exposed to 0.5, 0.7, 0.9, and 1.1 mg/liter of malathion for 7 days. DNA, RNA, protein, and free amino acid contents and the activities of acid and alkaline phosphatases were monitored in the liver. There was marked inhibition in DNA, RNA, and protein contents and the activities of acid and alkaline phosphatase. Total free amino acid content, however, significantly increased. Seven days withdrawal to freshwater indicated a recovery trend. The probable reasons for various changes are discussed.

Acid Phosphatase↗