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Biomedical subjects

P Kumar

Publications and source records attributed to P Kumar.

At least 217 records · Page 12Linked to original sources
PubMed2000

Development of artificial articular cartilage.

Attempts have been made to develop an artificial articular cartilage on the basis of a new viewpoint of joint biomechanics in which the lubrication and load-bearing mechanisms of natural and artificial joints are compared. Polyvinyl alcohol hydrogel (PVA-H), 'a rubber-like gel', was investigated as an artificial articular cartilage and the mechanical properties of this gel were improved through a new synthetic process. In this article the biocompatibility and various mechanical properties of the new improved PVA-H is reported from the perspective of its usefulness as an artificial articular cartilage. As regards lubrication, the changes in thickness and fluid pressure of the gap formed between a glass plate and the specimen under loading were measured and it was found that PVA-H had a thicker fluid film under higher pressures than polyethylene (PE) did. The momentary stress transmitted through the specimen revealed that PVA-H had a lower peak stress and a longer duration of sustained stress than PE, suggesting a better damping effect. The wear factor of PVA-H was approximately five times that of PE. Histological studies of the articular cartilage and synovial membranes around PVA-H implanted for 8-52 weeks showed neither inflammation nor degenerative changes. The artificial articular cartilage made from PVA-H could be attached to the underlying bone using a composite osteochondral device made from titanium fibre mesh. In the second phase of this work, the damage to the tibial articular surface after replacement of the femoral surface in dogs was studied. Pairs of implants made of alumina, titanium or PVA-H on titanium fibre mesh were inserted into the femoral condyles. The two hard materials caused marked pathological changes in the articular cartilage and menisci, but the hydrogel composite replacement caused minimal damage. The composite osteochondral device became rapidly attached to host bone by ingrowth into the supporting mesh. The clinical implications of the possible use of this material in articular resurfacing and joint replacement are discussed.

Aluminum Oxide↗
PubMed2000

Impact of anemia in patients with head and neck cancer.

Head and neck squamous cell carcinoma, which is comprised of a heterogeneous group of tumors arising from the epithelial lining of the oral cavity, pharynx, and larynx, is a locoregional disease. Tumor hypoxia and anemia are known to adversely effect the efficacy of radiation therapy, a local treatment modality. Therefore, head and neck cancers represent an ideal model for assessing the impact of anemia following treatment with radiation therapy. Various treatment strategies aimed at increasing tumor oxygenation in head and neck cancer patients (including hyperbaric oxygen and hypoxic cell radiosensitizers) have been studied. These studies have been fueled by evidence that hypoxia adversely effects the radiosensitivity of cells. Although the exact mechanism of action of the oxygen effect is not known, in vitro studies with conventional photon radiation therapy under normoxic conditions have shown an effectiveness of 2.5-3.0 times greater than that achieved under anoxic conditions. Recent studies, including large retrospective analyses, have demonstrated the dramatic adverse impact of anemia upon locoregional tumor control and survival. These studies, which have revealed hemoglobin levels as a powerful prognostic factor, provide compelling evidence for the value of reversing anemia and hence tumor hypoxia in head and neck cancer patients.

Anemia↗
PubMed2000

Neonatal autopsies: a 10-year experience.

OBJECTIVES: To identify trends in neonatal autopsy rates at a tertiary care hospital during the last decade, to determine the concordance between antemortem and post-mortem diagnoses, and to describe patient characteristics that influenced diagnostic yield on autopsy. DESIGN: Retrospective review of medical records. SETTING: Tertiary care children's hospital. PATIENTS: All neonatal deaths between January 1, 1984, and December 31, 1993. MAIN OUTCOME MEASURES: For those with autopsies, data included length of stay, diagnostic imaging studies, antemortem diagnoses, and autopsy findings. Autopsy diagnoses were compared with antemortem findings and classified according to concordance. RESULTS: Of 487 neonatal deaths, autopsies were performed in 296 (61%). The autopsy rate declined significantly during 10 years from 71.2% (1984-1988) to 47.7% (1989-1993). New diagnoses were made at autopsy in 44% of cases. Major discordancies were identified in 35 infants (12%); minor discordancies in 95 (32%). Autopsies were more likely to reveal new diagnoses in infants born at 28 to 36 weeks' gestation and in those whose mothers had no prenatal care. Major findings at autopsy were more likely in infants whose mothers had no prenatal care and in infants who died within 6 hours of birth. There was no relationship between new findings at autopsy and age, length of hospital stay, or antemortem imaging studies. CONCLUSIONS: This study reveals a significant decline in neonatal autopsies during a 10-year period. This study also demonstrates that neonatal autopsy continues to provide clinically significant data and remains a valuable tool in perinatal medicine.

Adult↗
PubMed2000

Impact of Anemia in Patients With Head and Neck Cancer.

Head and neck squamous cell carcinoma, which is comprised of a heterogeneous group of tumors arising from the epithelial lining of the oral cavity, pharynx, and larynx, is a locoregional disease. Tumor hypoxia and anemia are known to adversely effect the efficacy of radiation therapy, a local treatment modality. Therefore, head and neck cancers represent an ideal model for assessing the impact of anemia following treatment with radiation therapy. Various treatment strategies aimed at increasing tumor oxygenation in head and neck cancer patients (including hyperbaric oxygen and hypoxic cell radiosensitizers) have been studied. These studies have been fueled by evidence that hypoxia adversely effects the radiosensitivity of cells. Although the exact mechanism of action of the oxygen effect is not known, in vitro studies with conventional photon radiation therapy under normoxic conditions have shown an effectiveness of 2.5-3.0 times greater than that achieved under anoxic conditions. Recent studies, including large retrospective analyses, have demonstrated the dramatic adverse impact of anemia upon locoregional tumor control and survival. These studies, which have revealed hemoglobin levels as a powerful prognostic factor, provide compelling evidence for the value of reversing anemia and hence tumor hypoxia in head and neck cancer patients.

Journal Article↗
PubMed2000

Acute inhalation toxicity study of 2-fluoroacetamide in rats.

One of the most potent rodenticides is 2-fluoroacetamide (2-FA). Toxicity of this chemical is well documented. However, its inhalation toxicity data is not available in the literature. Hence, acute inhalation toxicity study was carried out by exposing male and female rats to aerosols of 2-FA at different concentrations for 4 h in a dynamically operated whole body inhalation exposure chamber. During and after the inhalation exposure the rats were less active, and showed mild tremors and convulsions. At higher concentrations the rats died after 2-3 days. The estimated 4-h LC50 for male and female rats was 136.6 and 144.5 mg.m-3 respectively. Exposure to 0.7 LC50 for 4 h duration showed an increase in the liver weight of male and female rats 7 days after exposure. Various haematological and biochemical variables determined were within the normal limits. However, histological findings showed injured lung as indicated by desquamation and necrosis of the epithelium of the respiratory tract. Marked hypertrophy of hepatocytes displaying strong acidophilic granulated cytoplasm was observed. Focal dilatation of renal proximal tubules in kidney with cytoplasmic vacuolation, and irregularly placed pyknotic nuclei were seen. The present study shows that 2-FA is a highly toxic chemical through the inhalation route based on the LC50 value. Consequently necessary precautions should be taken during its handling.

Animals↗
PubMed2000

Substance abuse by medical students and doctors.

The doctors are vulnerable to substance abuse/addiction due to their ready accessibility to the substances of abuse. There is higher percentage use of alcohol, tranquillisers and psychedelics among medical students, and dependence rates are 5% for medical students and 3% for doctors. Majority of the substance-abusing doctors are graduates, belong to medicine speciality (21%) and majority of them prescribe drugs to themselves (37%). The consultants experience more substance related complications, despite having late age of onset of alcohol and substance dependence, less number of concomitant substance abuse and less career handicap. Stress (situational, personal and professional), medical student abuse and family history of alcoholism are the major risk factors. Despite paucity of studies in Indian population, substance use is reported between 32.5% to as high as 81.2% among medical students, intems and house physicians. In spite of the treatment dilemmas, the physicians do respond favourably to treatment. These findings have implications in planning preventive and interventional strategies for this professional group.

Alcohol-Related Disorders↗
PubMed2000

Acquired immunodeficiency syndrome presenting as testicular tuberculosis.

A 50 year old heterosexual male presented with fever and cough with expectoration of months duration, and swelling in the right testis. The serological tests showed positivity for HIV 1 and 11 antibodies. Testicular biopsy from the right testis showed epitheloid cell granulomas with central caseous necrosis and peripheral mantle of lymphocytes and plasma cells. Zeihl-Neelsen stain on tissue sections showed AFB positivity. To the best of our knowledge this is the second reported case of acquired immunodeficiency syndrome presenting as testicular tuberculosis.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Ovarian strumal carcinoid--report of a case that matastasized.

Ovarian teratomas are known for their ability to form a wide variety of tissues. One unusual example of this potential is the strumal carcinoid in which the thyroid tissue is found in intimate association with carcinoid tumor. Although considered as a malignant transformation of struma ovarii, it is almost always benign. We report a rare case of strumal carcionid in a 44 year old lady who had metastasis in the contralateral ovary, myometrium and lungs.

Adult↗
PubMed2000

Subacute (90 days) oral toxicity studies of Kombucha tea.

Kombucha tea (KT) is a popular health beverage and is used as an alternative therapy. KT is prepared by placing the kombucha culture in solution of tea and sugar and allowing to ferment. The inoculum is a fungus consisting of symbiotic colony of yeast and bacteria. KT is consumed in several countries and is believed to have prophylactic and therapeutic benefits in a wide variety of ailments, viz., intestinal disorders, arthritis, ageing and stimulation of immunological system. Though KT is used in several parts of the world its beneficial effects and adverse effects have not been scientifically evaluated. Since there are no animal toxicological data on KT, subacute oral toxicity study was carried out. Five groups of rats were maintained: (a) control group given tap water orally, (b) KT given 2 ml/kg orally, (c) plain tea (PT) given 2 ml/kg orally, (d) KT given in drinking water, 1% (v/v) and (e) PT given in drinking water, 1% (v/v). The rats were given this treatment daily for a period of 90 days. Weekly records of weight, feed intake, water intake and general behaviour were monitored. There was no significant difference in the growth of the animals as evidenced by the progressive body weight change. The organ to body weight ratio and histological evaluation did not show any toxic signs. The haematological and biochemical variables were within the clinical limits. The study indicates that rats fed KT for 90 days showed no toxic effects.

Administration, Oral↗
PubMed2000

Seropositivity for intracellular bacterial infections among abattoir associated personnels.

Studies were carried out to detect the antibodies against zoonotic intracellular bacterial infections viz., brucellosis, listeriosis and tuberculosis in abattoir associated personnel employing dot-ELISA. Out of 165 serum samples tested 25.5, 40.0 and 10.9 per cent were detected as positive for brucellosis, listeriosis and tuberculosis, respectively. Immunodetection of these occupationally exposed persons for IgM as well as IgG antibodies revealed positivity for IgM, IgG and IgM + IgG in 8.5, 17.6 and 13.9 per cent for listeriosis and 5.5, 2.4 and 3.0 for tuberculosis respectively. Antibodies against brucellosis and listeriosis both were detected in 10.9 per cent persons, while 6.7 per cent persons were positive for both listeriosis and tuberculosis. No person was found positive with both brucellosis and tuberculosis. All the three infections were detected in 3.6 per cent persons.

Abattoirs↗
PubMed1999

Properties of mixed backbone oligonucleotides containing 3'-O-methyl ribonucleosides.

Oligonucleotides containing 3'-O-methyl ribonucleosides were synthesized, and their thermal stabilities and global conformations with RNA and DNA have been studied. The duplexes displayed lower T(m) values as compared to the unmodified ones, and adopted A-conformations. Furthermore, they are not a substrate for RNase H, are slightly resistant to snake venom phosphodiesterase, and are not cleaved by nuclease S 1.

Base Sequence↗
PubMed1999

Selenium effects on gallium arsenide induced biochemical and immunotoxicological changes in rats.

The influence of selenium (6.3 and 12.6 micromol/kg, intraperitoneally) on the disposition of gallium and arsenic and a few gallium arsenide (GaAs) sensitive biochemical variables was studied in male rats. Concomitant administration of Se and GaAs (70 micromol/kg, orally, 5 days a week for 4 weeks) significantly prevented the accumulation of arsenic while, the gallium concentration reduced moderately in the soft organs. The biochemical (haematopoietic and liver) and immunological variables however, responded less favorably to selenium administration. Most of the protection was however observed with the dose of 12.6 micromol rather than at 6.3 micromol. The results thus suggest a few beneficial effects of selenium in preventing the appearance of signs of GaAs toxicity like preventing inhibition of blood delta-aminolevulinic acid dehydratase (ALAD), hepatic malondialdehyde (MDA) formation and the accumulation of gallium and arsenic concentration.

Animals↗
PubMed1999

Radiation-induced normal tissue injury: role of adhesion molecules in leukocyte-endothelial cell interactions.

The late onset of necrosis and fibrosis in normal tissues can be a serious consequence of radiotherapy in cancer patients. Because radiation-induced vascular injury precedes the tissue damage, vascular injury is regarded as crucial in the pathogenesis of tissue damage. An understanding of the processes responsible is essential to develop strategies for the amelioration of radiation-induced normal tissue damage. Leukocyte infiltration is commonly observed at sites of irradiation and is likely to lead to the acceleration and/or induction of parenchymal atrophy, fibrosis and necrosis in normal tissues following radiotherapy. The molecular mechanisms mediating leukocyte infiltration of tissues during inflammation have been studied extensively. It is now well established that cell adhesion molecules (CAMs) expressed on leukocytes and endothelial cells control the trafficking of leukocytes from the blood vessel lumen in these conditions. CAMs including E (endothelial), P (platelet) and L (leukocyte)-selectins, intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), beta1 and beta2 integrins and CD31 are involved in the cascade of events resulting in rolling, arrest and transmigration of leukocytes through the inflamed endothelium. Whether a similar sequence of molecular events induces leukocyte sequestration in irradiated normal tissues is not known. This review is focussed on the role of CAMs in radiation-induced leukocyte infiltration of normal tissues and the therapeutic implications of these findings.

Animals↗