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Biomedical subjects

P Kumar

Publications and source records attributed to P Kumar.

At least 307 records · Page 17Linked to original sources
PubMed1997

Impedance of a goat eye lens.

The complex electrical impedance of a goat eye lens is studied in the frequency range 10 mHz-10 Hz at room temperature, using a computer-controlled AC impedance system. AC impedance software (model 368, version 2.2) is employed to determine the total impedance and capacitance of the eye lens at various frequencies. A Cole-Cole plot of the eye lens material is drawn between the real component of impedance Z' and the imaginary component Z" for each excitation frequency that shows a perfect arc of a-semicircle, with its centre lying below the abscissa at an angle of 35 degrees. The half-angle phi between R(0) and R infinity is found to be 55 degrees, which mathematically demonstrates the selective permeability of the eye lens. Using graphical analysis of the Cole-Cole plot, characteristic frequency fc and distribution factor alpha are observed to be 1 Hz and 0.77, respectively. At characteristic frequency, capacitance and total impedance are found to be 1.14 microF and 9.08 k omega. The effect of electrode polarisation on capacitance is corrected, based on Fricke's power function. The observed electrical parameters are then used to explain the multiple current path through various tissue compartments. Further, an attempt is made to explain the results on the basis of a possible dipolar model.

Animals↗
PubMed1997

The predictive value of tumor regression rates during chemoradiation therapy in patients with advanced head and neck squamous cell carcinoma.

OBJECTIVE: The value of tumor regression rates in predicting survival outcome during chemoradiation therapy was prospectively evaluated. METHODS AND MATERIALS: Sixty-two patients diagnosed with locally advanced stage III/IV unresectable head and neck squamous cell carcinoma underwent weekly clinical and endoscopic serial assessment of primary and nodal tumor sizes during chemoradiation therapy between July 1993 and September 1995. Chemoradiation therapy consisted of protocol treatment using supradose intra-arterial targeted cisplatin (SIT-P) at 150 mg/m2 four times at weekly intervals along with intravenous sodium thiosulfate at 9 g/m2 and concurrent conventionally fractionated radiotherapy at 1.8 to 2.0 Gy/fraction (fx) to a total dose of 68 to 74 Gy. Tumor reduction was serially measured as a percentage of the original pretreatment size at weekly intervals by the same team of surgical and radiation oncologists. Correlations were then made between tumor regression rates and survival. RESULTS: Complete or near complete regression of disease during chemoradiation therapy as compared with nonresponsive/partially responsive disease was associated with better survival outcome (P = 0.001 and P = 0.013, respectively). Among patients exhibiting complete or near complete regression of disease, rapid tumor reduction (median = 4.2 weeks) was associated with inferior survival outcome when compared with slower disease regression (median = 6.4 weeks, P = 0.007). CONCLUSIONS: Our findings fail to support the "traditional" hypothesis that rapid tumor regression during treatment is predictive of an improved survival outcome. Treatment strategies that alter ongoing therapy based upon initial tumor regression rates should be avoided.

Antidotes↗
PubMed1997

Esophageal leiomyomatosis involving trachea: surgical resection and repair.

We report the case of a 26-year-old man with diffuse esophageal leiomyomatosis involving the trachea. The tumor was resected by total esophagectomy and partial resection of the trachea and the left main bronchus. The tracheobronchial defect was repaired with a free forearm skin graft with satisfactory outcome. This approach offers good long-term prospects.

Adult↗
PubMed1997

Hypocholesterolaemic effects of Terminalia arjuna tree bark.

Diet-induced hyperlipidaemic rabbits were given 50% ethanolic extract of Terminalia arjuna tree bark in doses of 100 mg/kg (Group B, n = 6) and 500 mg/kg (Group C, n = 6) and compared with controls (Group A). At 60 days of intervention in Groups A, B and C mean +/- S.E.M. total cholesterol was 574 +/- 61, 320 +/- 29 and 217 +/- 44 mg/dl, respectively (P < 0.01); LDL cholesterol was 493 +/- 57, 271 +/- 30 and 162 +/- 44 mg/dl (P < 0.01); HDL cholesterol was 59 +/- 7, 36 +/- 3 and 35 +/- 4 mg/dl (P = n.s.); triglyceride was 108 +/- 13, 67 +/- 6 and 101 +/- 26 mg/dl (P = n.s.); cholesterol/HDL ratio was 10.1 +/- 1.3, 9.2 +/- 1.1 and 6.1 +/- 1.0 (P = n.s.); and LDL/HDL ratio was 8.7 +/- 1.3, 7.8 +/- 1.1 and 4.5 +/- 1.0 (P < 0.01). The extract did not adversely affect biochemical tests of liver and renal function and haematological parameters.

Animals↗
PubMed1997

Exchange interaction between nuclear spins.

We describe the developments in the determination of exchange interaction between nuclear moments in a metal. We discuss two techniques, the isotopic interference and higher harmonics of Larmor precession, both techniques determine the sign as well as the magnitude of the exchange constant. In addition, we briefly discuss the possibility of experiments at negative temperatures providing additional information about the space dependence of the exchange interaction.

Copper↗
PubMed1997

Phosphatidylcholine coated chest drains: are they better than conventional drains after open heart surgery?

INTRODUCTION: Inadequate thoracic drainage after open heart surgery has serious deleterious consequences. Thrombus formation within the chest drains is primarily responsible for the occlusion of chest drains. Chest drains coated with derivatives of phosphatidylcholine (PC), commonest phospholipid on cell membranes, potentially have a less thrombogenic surface. MATERIALS AND METHODS: In a prospective randomised double blind study, we compared PC-coated drains (Group I, n = 25) with non coated drains (Group II, n = 26) after open heart surgery. Drain performance, post-operative complications and clinical course were compared. RESULTS: PC-coated drains had a significantly shorter period of drainage, 20.4 +/- 1.0 versus 28.9 +/- 3.7 h (P < 0.05). Otherwise, mean volume drained, number clots removed from drain and the ease of drainage of the two types of drains were similar. There were no significant differences in the incidence of post-operative pericardial effusions, dysrhythmias, ambulation time and hospital stay. CONCLUSIONS: We conclude that the PC coated drains may be of importance in cases where prolonged drainage is anticipated otherwise they have no significant advantage.

Adult↗
PubMed1997

Successful resection of obstructing airway granulation tissue following lung transplantation using endobronchial laser (Nd:YAG) therapy.

OBJECTIVE: Airway obstruction due to an excessive growth of granulation tissue at the level of the anastomosis is an important complication following lung transplantation which requires early diagnosis and treatment. We report encouraging experience in the management of this condition using endobronchial Nd:YAG laser therapy. METHODS: Four adult lung transplant recipients developed airway anastomotic obstruction secondary to granulation tissue formation at 9, 10, 32 and 32 days following bilateral sequential lung transplantation (2 patients), en bloc double lung transplantation (1 patient) and single lung transplantation (1 patient). The diameter of the airways at the level of the anastomoses was reduced by 75, 30, 60, 60, 50 and 90%, respectively. Endobronchial Nd:YAG laser was applied via a fiberoptic bronchoscope introduced through a rigid bronchoscope. The granulation tissue was visualised and resected with photocoagulation with the laser using between 1000-2000 J depending on the amount of tissue present. Necrotic tissue was removed with large forceps. If the obstruction extended to the orifice of a lobar bronchus resection was undertaken in a staged fashion. RESULTS: Airway patency was fully restored at two anastomotic sites, and restored to 90% patency at two and 80 and 75% at one each, respectively. This was associated with a significant improvement in pulmonary function in 3 patients. One patient had a subsequent bougie dilatation of a stenotic area and 2 patients received an endobronchial stent for tracheo or broncho-malacia. One patient died from a gastrointestinal haemorrhage. Three patients are well at 10, 17 and 18 months following transplantation and have no further granulation tissue recurrence. There were no complications directly attributable to laser therapy. CONCLUSION: Our encouraging early experience leads us to suggest that Endobronchial Nd-YAG laser therapy should be considered in the management of airway anastomotic obstruction due to excessive granulation tissue formation after lung transplantation.

Adult↗
PubMed1997

Activity profile of placental superoxide-superoxide dismutase system in pregnant mice and its possible relation with placental steroidogenesis.

Placenta in mouse generate increasing quantities of superoxide dismutase from day 13 of pregnancy until parturition. This is associated with a concomitant reduction in the activity of superoxide radical. This findings points to the steroidogenic control of the later half of pregnancy by the placental axis. Parturition is associated with an abrupt spurt in superoxide radical. This is a novel finding and could be a consequence of the estrogen surge at labour. It is suggested that this abrupt increase in superoxide radical level at parturition may remould the placental membrane fluid at the point of its attachment with uterine membranes so as to facilitate the separation of placenta from uterus.

Animals↗
PubMed1997

Primary cutaneous zygomycosis due to Saksenaea vasiformis and Apophysomyces elegans.

We report three cases of primary cutaneous zygomycosis due to either Saksenaea vasiformis (two patients) or Apophysomyces elegans (one patient). Extensive surgical debridement helped two patients recover from their infections. The underlying disease in the one patient who died was diabetes mellitus. We reviewed the literature on primary cutaneous zygomycosis and found that S. vasiformis and A. elegans were the etiologic agents in 16 and 13 earlier cases, respectively.

Adult↗
PubMed1997

Linkage analysis of candidate regions for coeliac disease genes.

A strong HLA association is seen in coeliac disease [specifically to the DQ(alpha1*0501,beta1*0201 heterodimer], but this cannot entirely account for the increased risk seen in relatives of affected cases. One or more genes at HLA-unlinked loci also predispose to coeliac disease and are probably stronger determinants of disease susceptibility than HLA. A recent study has proposed a number of candidate regions on chromosomes 6p23 (distinct from HLA), 6p12, 3q27, 5q33.3, 7q31.3, 11p11, 15q26, 19p13.3, 19q13.1, 19q13.4 and 22cen for the location of a non-HLA linked susceptibility gene. We have examined these regions in 28 coeliac disease families by linkage analysis. There was excess sharing of chromosome 6p markers, but no support for a predisposition locus telomeric to HLA. No significant evidence in favour of linkage to coeliac disease was obtained for chromosomes 3q27, 5q33.3, 7q31.3, 11p11, 19p13.3, 19q13.1, 19q13.4 or 22cen. There was, however, excess sharing close to D15S642. The maximum non-parametric linkage score was 1.99 (P = 0.03). Although the evidence for linkage of coeliac disease to chromosome 15q26 is not strong, the well established association between coeliac disease and insulin dependent diabetes mellitus, together with the mapping of an IDDM susceptibility locus (IDDM3) to chromosome 15q26, provide indirect support for this as a candidate locus conferring susceptibility to coeliac disease in some families.

Celiac Disease↗
PubMed1997

Acute myocardial infarction after intravenous radiographic contrast medium.

Acute myocardial infarction after the use of intravenous radiographic contrast medium (RCM) is rare. There is only one reported case in the literature; this is the second case. A 65-year-old woman complained of pain in the right costovertebral area, and abdominal ultrasonography showed hydronephrosis. She had insulin-dependent diabetes and hypertension. Intravenous pyelogram, using renographin, was performed. Within 5 minutes, she felt bad and became hypotensive and diaphoretic. Laboratory studies and electrocardiography confirmed the diagnosis of acute myocardial infarction. Generally, elderly and diabetic patients with abnormal renal function are considered to be at high risk for adverse reactions to RCM. Renal function was normal. It has also been reported that high R osmolality RCM such as renographin, is associated with a greater risk of adverse reactions compared with the use of low-osmolar RCM. This case should raise awareness regarding acute myocardial infarction as a complication after the use of intravenous RCM.

Aged↗
PubMed1997

Secondary colony formation after long-term bone marrow culture using peripheral blood and bone marrow of HIV-infected patients.

OBJECTIVE: To determine if defective bone marrow function in HIV infection is associated with decreased numbers of progenitor cells or defective stromal cell function. DESIGN: Defective bone marrow function may in part be responsible for the cytopenias so frequently seen in patients with AIDS. Although a number of investigators have reported impaired growth of committed hematopoietic progenitor cells in HIV-1-infected patients, few studies have examined the most primitive hematopoietic stem cells. Our study was designed to determine the function and quality of the most immature hematopoietic progenitor and stem cells in the peripheral blood and bone marrow of HIV-1-infected patients and to assess stromal cell function. METHODS: For quantification of these cells we used a modified long-term culture-initiating cell (LTCIC) assay in which the number of secondary colony-forming cells after 5 weeks of stromal culture served as a measure of LTCIC. Stromal cells from normal controls and HIV-1-infected patients were used for cross-matching experiments. Normal CD34+ cells or those derived from HIV-infected patients were plated and colony growth assessed. RESULTS: We found that HIV-1-infected patients had a mean of 0.8 secondary colony-forming cells/10(5) peripheral blood mononuclear cells (PBMC), whereas normal controls showed 1.2 secondary colony-forming cells/10(5) PBMC (P = not significant) after long-term culture. Asymptomatic patients showed well preserved numbers of secondary colony-forming cells after long-term culture of PBMC, but a significant reduction was seen in patients with a history of opportunistic infections (P < 0.01), low CD4+ cell count (< 200 x 10(6)/l; P < 0.05), or leukopenia (P < 0.05). Decreased numbers of secondary colony-forming cells have also been found in bone marrow of HIV-1-infected patients with advanced disease. When normal CD34+ cells were cultured on stromal layers from bone marrow of HIV-1-infected patients or normal controls, no differences in the numbers of surviving progenitor cells were found. CONCLUSIONS: Our data indicate that the hematopoietic defect in HIV-1 infection involves the most immature hematopoietic cells and becomes evident in advanced disease. Stromal function of HIV-infected patients appears normal.

Bone Marrow↗
PubMed1997

Gastrin effects on growth and exocrine secretion in the neonatal rat pancreas.

In adult rats, cholecystokinin (CCK) binds to pancreatic CCK-A receptors and stimulates exocrine secretion and pancreatic growth. In newborn rats there is very little mature intestinal CCK and few pancreatic CCK-A receptors. However, there is an abundant source of the related peptide gastrin, and in addition, there are pancreatic CCK-B/gastrin receptors. In this study, we have explored the hypothesis that gastrin may "deputise" for CCK in the neonate and cause pancreatic exocrine secretion, growth, and maturation. Newborn rats were injected intraperitoneally with the gastrin antagonist, C1-988, or placebo for 5 days and sacrificed on day 6. Body weight (CI-988, 8.25 +/- 0.48 g; placebo, 10.17 +/- 0.93 g) and pancreatic weight (19.41 +/- 1.5 vs. 21.58 +/- 1.72 mg) were the same. Protein (1,202 +/- 78 vs. 1,254 +/- 56 micrograms), amylase (22.3 +/- 0.9 vs. 19.2 +/- 1.00 U), RNA (117 +/- 7 vs. 126 +/- 5 micrograms), and DNA (95 +/- 8 vs. 100 +/- 7 micrograms) contents of the pancreas were similar in the two groups. The weight of the stomach was reduced (p = 0.04) in the treated group (50.8 +/- 2.5 mg) compared to the placebo group (59.8 +/- 3.7 mg). In both neonates and adults, CCK-8 was approximately 1,000 times more potent than gastrin-17 in stimulating amylase release from isolated pancreatic acini. This suggests that enzyme release is probably mediated by the same receptors in both adults and neonates, and in adults previous work has shown this to be the CCK-A receptor. In conclusion, these data show that gastrin has very weak effects on neonatal pancreatic exocrine secretion, and furthermore, gastrin is not essential for growth and maturation of the neonatal pancreas. The role of gastrin and CCK-B/gastrin receptors in the neonatal pancreas remains speculative.

Amylases↗