Biomedical subjects
N Khan
Publications and source records attributed to N Khan.
A histopathologic study of cerebral malaria in a rhesus monkey model.
Explore the source record for details and available documents.
Inhibition of DNA polymerase alpha by aphidicolin derivatives.
17-Acetylaphidicolin was 10-fold weaker and two derivatives lacking hydroxyl groups at the 16 and 17 positions were 100-fold weaker than aphidicolin as inhibitors of DNA polymerase alpha from HeLa and Chinese hamster ovary cells. 17,18-Diacetyl, 3,17,18-triacetyl and 3-epi derivatives of aphidicolin were inactive. Active compounds were, like aphidicolin, competitive with dCTP and did not inhibit aphidicolin-resistant DNA polymerases.
Entamoeba histolytica antigens as possible vaccinogens? A short review.
A few key papers which have recently been published on the characterization of amoeba antigens are reviewed. Immunofluorescence tests and immunoelectron microscopy have demonstrated the localization of certain surface antigens on axenically cultured trophozoites. Most of the surface antigens have largely been shown to elicit a humoral response. The elicitation of cellular response has not been well illustrated. The localization of a large number of antigens in cytoplasmic vacuoles and plasma membrane indicates that a greater stimulus to the host would be provided by intracellular antigens than by those located on the surface of amoeba trophozoites. In a few inoculation studies, amoeba antigens, in combination with several adjuvants, have been successfully employed for inducing protective immunity in various animal model systems. These and other results clearly demonstrate that amoeba antigens are fully capable of generating humoral and as well as CMI responses. A combination of these two effector limbs of immunity can be fully exploited through effective use of future vaccines.
Masquerading as coronary artery disease: idiopathic hypertrophic subaortic stenosis.
Explore the source record for details and available documents.
"Study of immune responsiveness in adult asymptomatic sickle cell haemoglobinopathy in rural central India".
Explore the source record for details and available documents.
Anterior ST segment depression in first inferior myocardial infarction: echocardiographic analysis of extent of left ventricular wall motion abnormality.
Explore the source record for details and available documents.
Protein loss across burn wounds.
One factor contributing to negative nitrogen balance in burned patients is protein loss through the burn wound. There is, however, little information on the amount and type of protein lost by this route. This study was designed to quantitate protein loss through burn wounds. Multiple full- and partial-thickness burns on 29 patients were studied. Sampled burn sites were dried and occlusive sponge dressings (2'' X 2'') were applied and left in place for 1 hour. The central 1 square-inch portion of the dressing was then removed, rinsed in distilled water, and total protein, albumin, and globulin were measured in the water wash. Considerable protein losses were measured. These losses were greatest in the first 3 postburn days, being somewhat greater in full-thickness burns (0.98 +/- 0.82 mg/cm2/hr) compared to partial-thickness burns (0.59 +/- 0.41 mg/cm2/hr) during this period mean +/- SD). Subsequent to the first 3 postburn days, protein loss in all burn types decreased to a relatively steady rate of loss of approximately 0.25 mg/cm2/hr. Based upon these data, average daily protein losses during the first postburn week can be estimated by the following equation: 24-hour protein loss through burn surface (gm) = 1.2 X body surface area (m2) X % burn (%). On subsequent days, protein is lost at approximately half this rate. These data demonstrate significant protein losses through burn wounds greater than recent studies have considered. It is possible that inadequate nutritional replacement of these protein losses is partly responsible for the marked negative nitrogen balance of the early postburn period.
Atrial activity during cardioplegia and postoperative arrhythmias.
Cardioplegia provides excellent protection for the left ventricle, but the right atrium may be poorly protected. Myocardial temperatures, right atrial electrical activity, and postoperative arrhythmias were assessed in 103 patients participating in two consecutive randomized trials comparing blood cardioplegia (n = 36), crystalloid cardioplegia (n = 38), and diltiazem crystalloid cardioplegia (n = 29). Both right atrial and right ventricular temperatures were significantly warmer (p less than 0.05) during delivery of the blood cardioplegic solution than during delivery of either the crystalloid or the diltiazem crystalloid cardioplegic solutions; the aortic root temperatures were 9 degrees +/- 2 degrees C with blood cardioplegia and 5 degrees + 1 degrees C with both crystalloid and diltiazem crystalloid cardioplegia. Atrial activity during cardioplegic arrest was greatest with blood cardioplegia (12 +/- 3 beats/min), lower with crystalloid cardioplegia (10 +/- 2 beats/min), and minimal with diltiazem crystalloid cardioplegia (5 +/- 1 beats/min, p less than 0.05). Perioperative ischemic injury (by creatine kinase MB isoenzyme analysis) was greatest with crystalloid cardioplegia (p less than 0.05). Postoperative supraventricular arrhythmias (both treated and untreated) were more frequent after crystalloid cardioplegia (crystalloid, 63%; blood, 40%; diltiazem, 47%; p less than 0.05). Patients in whom supraventricular arrhythmias developed had significantly more postoperative ischemic injury (by creatinine kinase MB isoenzyme analysis, p less than 0.05). Blood cardioplegia reduced supraventricular arrhythmias by reducing ischemic injury despite warmer intraoperative temperatures and more right atrial activity. Diltiazem crystalloid cardioplegia reduced postoperative arrhythmias by improving intraoperative myocardial protection and suppressing intraoperative and postoperative atrial activity. Crystalloid cardioplegia cooled but did not arrest the right atrium intraoperatively, resulted in the most perioperative ischemic injury, and yielded the highest incidence of postoperative supraventricular arrhythmias.
Diagnostic significance of serum cholinesterase and lactate dehydrogenase in skin malignancy.
Explore the source record for details and available documents.
Cloning and expression of a cDNA encoding a catalytically active fragment of calf thymus DNA polymerase alpha.
A calf thymus cDNA expression library was constructed in the EcoRI site of lambda gt11 and probed with an antibody raised against calf thymus DNA polymerase alpha. Three classes of antibody-reactive clones were isolated. The largest class carried a 1.9 kilobase calf cDNA insert and expressed a 165-175 kilodalton beta-galactosidase:calf fusion protein which displayed DNA polymerase activity. The characteristic responses of the polymerase activity to alpha-specific inhibitors and antibodies identified the 1.9 kilobase cDNA as a sequence specifically derived from the structural gene encoding the pol alpha catalytic core.
The natural history of acute rheumatic fever in Kuwait: a prospective six year follow-up report.
One hundred and twenty-six children with the initial attack of acute rheumatic fever were followed up prospectively for 6 years. Sixty-six children maintained regular secondary prophylaxis (regular group) and 60 were irregular (irregular group). Two recurrences developed in the regular group with a recurrence rate of 0.005/patient/year follow-up, and 71 recurrences developed in the irregular group with a recurrence rate of 0.2/patient/year follow-up. These findings demonstrate the effect of secondary prophylaxis in reducing the frequency of recurrences. The prevalence rate of rheumatic heart disease in children who had carditis in the initial attack was 42% in the regular group vs 70% in the irregular group (p less than 0.05). These findings demonstrate the deleterious effect of recurrences in the evolution of rheumatic heart disease. The prevalence rate of rheumatic heart disease in children who maintained regular secondary prophylaxis, was 42% in those children who had carditis in the initial attack and 6% in those who had no carditis (p less than 0.05). These findings demonstrate the prognostic significance of presence or absence of carditis during the initial attack, in the subsequent evolution of rheumatic heart disease. The prevalence rate of rheumatic heart disease in the 66 children who maintained regular prophylaxis was 23%. Comparison of these data with those of similarly designed studies shows that the evolution of rheumatic heart disease following the initial attack of acute rheumatic fever, seems to behave similarly in the tropics and subtropics as it did in temperate climates.
Radionuclide findings in arteriovenous fistula between left pulmonary artery and vein.
Right-to-left extra cardiac shunts are usually congenital and are rarely due to trauma or complicating thoracic or vascular surgery. A case of a right-to-left cardiac shunt due to an arteriovenous fistula between the left pulmonary artery and the left pulmonary vein is reported. This may be the first report of this abnormality. The etiology is not clear. The case was investigated only by radionuclide procedures because the general condition of the patient was so poor that invasive procedures could not be undertaken.
Internal carotid artery occlusion in a young female with mitral valve prolapse.
A healthy 28 year old housewife presented with sudden right hemiplegia and aphasia. No predisposing factors could be ascertained apart from posterior cusp mitral value prolapse on two dimensional echocardiography. Extensive investigations confirmed the presence of cerebral infarction and persistent occlusion of the left internal carotid artery near its origin.
Asymptomatic severe aortic regurgitation in the young. Hemodynamic and angiographic data in 37 patients with echocardiographic correlation.
The aim of this study was to evaluate from hemodynamic and angiocardiographic (ACG) data the extent of left ventricular (LV) systolic dysfunction in a group of predominantly young (mean age 29 years) asymptomatic patients with severe aortic regurgitation (AR). In addition, echocardiography was performed and these data were correlated with ACG data and the value of these parameters in predicting LV dysfunction was tested. Thirty-seven patients were catheterized and 18 demonstrated LV dysfunction with an ejection fraction (EF) of less than 50%. These patients were classified as group A and the remaining 19 patients with EF greater or equal to 50% formed group B. While there was no difference between the 2 groups with regard to age or regurgitant fraction, the end-diastolic pressure was raised (p less than 0.01) and cardiac index depressed (p less than 0.05) significantly in group A. Of the echocardiographic parameters, the end-systolic diameter (ESD) correlated best with the EF (coefficient of correlation = -0.7 and p less than 0.001). In addition, the ESD was significantly higher in group A (p less than 0.001). When an ESD greater than or equal to 48 mm was used as a predictor of an EF less than 50% (group A) the sensitivity was 89% and the specificity 79%. In conclusion, many young asymptomatic patients with severe AR may have severe LV systolic dysfunction and an ESD greater than or equal to 48 mm is a good predictor of such a subgroup.
Macrophage spreading inhibition test as an alternate method for in vitro assessment of cell-mediated immunity against Entamoeba histolytica.
During cellular immune responses sensitized lymphocytes release a number of mediators collectively known as 'lymphokines'. The assaying of macrophage spreading inhibition (MSI) factor released by sensitized lymphocytes was employed as an alternative procedure for in vitro detection of cell-mediated immunity (CMI) in animals immunized with amoeba antigen preparation. The MSI test was compared with macrophage migration inhibition test. A well defined CMI was detectable in animals immunized by amoebic antigen in combination with Freund's complete adjuvant (FCA). Macrophage spreading was found greatly inhibited when peritoneal exudate cells from these animals were cultured in the presence of specific antigen. The optimal time for the development of typical reaction was 30 min. Incubation for a longer time resulted in macrophage clumping.
Tricuspid stenosis and regurgitation in rheumatic heart disease: a prospective cardiac catheterization study in 525 patients.
Cardiac catheterization (CC) was done in 525 symptomatic patients. Tricuspid regurgitation (TR) was graded from right ventricular (RV) angiography (RVA) and compared with RV indicator curves (IC). Tricuspid stenosis (TS) was diagnosed from the mean diastolic gradient (MDG). Organic (O) disease was diagnosed from TS or from thickening of the tricuspid valve (TV) on angiography. TR was found in 137 patients (26%), of whom 46 (33.5%) had additional TS. All of the patients with TS had significant TR. OTR was more frequent (70.4%) and more severe (p less than 0.0001) than functional TR (FTR). There was no difference in pulmonary artery pressure between FTR and OTR except when associated with TS. The TV was explored in 56 patients. A MDG greater than or equal to 2 mm Hg correctly predicted TS in 91% of the patients and right atrial angiography in 100% of the patients. Organic thickening of the TV was predicted in 84%.