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Biomedical subjects

A K Patel

Publications and source records attributed to A K Patel.

At least 37 records · Page 2Linked to original sources
PubMed1988

Formation of the Ca2+-activated photoprotein obelin from apo-obelin and mRNA inside human neutrophils.

1. A method has been developed to incorporate the apoprotein of the Ca2+-activated photoprotein obelin, and mRNA purified from the hydroid Obelia, into the cytoplasm of intact human neutrophils. This was based on internal release from pH-sensitive immunoliposomes taken up initially by phagocytosis. 2. Addition of the prosthetic group of obelin, coelenterazine, to these cells containing apo-obelin or Obelia mRNA resulted in formation of active Ca2+-activated obelin. 3. The obelin formed within the neutrophils responded to the chemotactic peptide N-formylmethionyl-leucyl-phenylalanine (1 microM) and to the membrane attack complex of complement (C5B6789n). 4. The formation of the apo-obelin from mRNA within neutrophils was inhibited by over 80% in the absence of added amino acids, and by over 90% by the protein-synthesis inhibitor puromycin (100 micrograms/ml). 5. The translation of Obelia mRNA inside cells provides a method for circumventing consumption of Ca2+-activated photoproteins during cell activation or injury, and for monitoring protein synthesis in living cells.

Apoproteins↗
PubMed1987

Threshold responses in production of reactive oxygen metabolites in individual neutrophils detected by flow cytometry and microfluorimetry.

1. The fluorescent compound 2',7'-dichlorofluorescein was used as an indicator of intracellular H2O2 production by neutrophils in order to compare the response of the cell population with that observed with individual cells determined by flow cytometry and quantitative fluorescence microscopy. 2. 2',7'-Dichlorofluorescein diacetate was deacetylated by intracellular esterases to form reduced 2',7'-dichlorofluorescein. The polar non-fluorescent intermediate remained trapped within both intracellular granules and the cytoplasm. Reduced dichlorofluorescein was oxidized by H2O2, a product of the oxidative burst, to yield the highly fluorescent product dichlorofluorescein. 3. A population of neutrophils stimulated by suboptimal concentrations of fMet-Leu-Phe (N-formylmethionyl-leucyl-phenylalanine) or phorbol ester (phorbol 12-myristate 13-acetate) resulted in an oxidation of 45-50% of the cellular dichlorofluorescein (non-fluorescent) to oxidized dichlorofluorescein within 30 min. Subcellular fractionation showed that, although dichlorofluorescein (non-fluorescent) occurred both in the cytoplasm and the granules, oxidation of dichlorofluorescein (non-fluorescent) occurred predominantly in the granules of stimulated neutrophils. 4. Flow cytometry showed that unstimulated cells consisted of a single population of cells with low cellular fluorescence. Activation of neutrophils (to produce reactive oxygen metabolites) resulted in the appearance of a second population of cells, with high fluorescence. The number of cells in this new population increased with time. fMet-Leu-Phe (0.1 microM) or phorbol ester (1 ng/ml) activated 45% of the cells within 8 min and 42% within 30 min respectively. 5. Analysis of individual cells by quantitative fluorescence microscopy demonstrated that, in the presence of a suboptimal concentration of stimulus, cells either failed to respond or were activated after different time delays, 4-120 s (39 +/- 18.4 s) by fMet-Leu-Phe or 12-200 s (59 +/- 17.4 s) by phorbol ester. Furthermore the oxidative bursts were of different magnitudes. 6. It is concluded that, in order for an individual cell to cross the activation threshold for the 'end response', a critical concentration of stimulus together with the necessary changes in intracellular signals are required.

Cells, Cultured↗
PubMed1987

Catheter drainage of the pericardium. Practical method to maintain long-term patency.

Pericardiocentesis with catheter insertion and drainage is widely used in management of large pericardial effusions and cardiac tamponade. Two potential problems with an indwelling pericardial catheter system are catheter blockage and infection. We have utilized slow infusion of heparinized saline solution (3 ml/hr) via a continuous flush device to maintain catheter patency for up to seven days (mean 3.6) in 16 patients. Pericardial effusions were secondary to malignancy, uremia, and cardiac surgery. This article describes practical aspects of the technique. Most pericardial effusions can be successfully treated with pericardiocentesis and catheter drainage, provided the drainage is continued reliably and safely for several days. Surgical treatment such as subxiphoid pericardiostomy or partial pericardiectomy should be reserved for loculated effusions, clotted blood, subacute effusive-constrictive pericarditis, or significant recurrences after initial drainage.

Adult↗
PubMed1987

The membrane attack complex of complement induces permeability changes via thresholds in individual cells.

Flow cytometry was used to quantify the fluorescence of propidium iodide in rat polymorphonuclear leucocytes (PMN) attacked by the membrane attack complex (MAC) in order to establish the existence of permeability and lytic thresholds in individual cells, a 'threshold' being defined as a cellular event involving the rapid transition of cells from one state to another under physiological conditions. Activation of the complement pathway resulted in PMN being attacked by MAC within 5 min. Approximately 30-40% of the cell population subsequently became permeable to small molecules and macromolecules. Individual PMN passed through 'thresholds' of cell permeability and cell lysis, or recovered from complement attack at different times. In the flow cytometer, three distinct populations of PMN were identified: cells that had recovered before the permeability 'threshold', cells that had recovered after the permeability 'threshold' but before the lytic 'threshold', and cells that failed to recover from complement attack. Individual PMN attacked by MAC passed through permeability and lytic thresholds at different times after an initial lag of 7.5 +/- 2.5 min and 11.5 +/- 1.0 min, respectively. Adenosine, an activator of adenylate cyclase, inhibited removal of MAC from the cell surface. Consequently, more cells passed through the permeability and lytic 'thresholds', resulting in an increased percentage of lysed cells.

2-Chloroadenosine↗
PubMed1983

Detection and estimation of rheumatic mitral regurgitation in the presence of mitral stenosis by pulsed Doppler echocardiography.

The sensitivity and specificity of pulsed Doppler echocardiography (PDE) in diagnosis and estimation of the severity of mitral regurgitation in the presence of rheumatic mitral stenosis was studied in 34 patients (18 women and 16 men) ranging in age from 33 to 70 years (mean 55). Definitive diagnosis of mitral regurgitation was confirmed in all patients by angiography and in 20 patients also by indicator dilution technique. Mitral regurgitation was detected by PDE in all patients with angiographically proven severe mitral regurgitation and in 7 of 8 patients with moderate mitral regurgitation. In patients with trace to mild mitral regurgitation, PDE was positive in only 7 of 13 patients. When subdivided for mild, moderate and severe mitral regurgitation, PDE sensitivity for diagnosis was 54, 88, and 100%, respectively; overall accuracy was 79% and specificity was 100%. Average systolic dispersion on time-interval histogram was 59% for mild, 89% for moderate, and 100% for severe mitral regurgitation. Groups of patients with mild mitral regurgitation could be differentiated from those with moderate (p less than 0.05) and severe (p less than 0.01) mitral regurgitation. A significant overlap of individual values, however, occurred. In 7 of 11 patients with moderate to severe mitral regurgitation, systolic turbulence also was detected in the left atrium. PDE was sensitive and specific in diagnosing moderate to severe mitral regurgitation in the presence of mitral stenosis. Assessment of precise severity of mitral regurgitation is still a problem in individual patients.

Adult↗
PubMed1983

Multiple calcified thrombi (rocks) in the right ventricle.

Large, organized right ventricular thrombi are rare. This report describes a 51 year old man with a history of recurrent pulmonary emboli treated with inferior vena cava ligation who subsequently developed multiple mobile calcified thrombi in the right ventricle. He was treated successfully by surgical resection. Unusual clinical presentation on admission consisted of a two component friction rub secondary to calcified masses rubbing against each other in systole and diastole. Cardiac catheterization showed a constrictive-restrictive pattern that persisted after surgery. The role of noninvasive studies in the diagnosis and long-term follow-up of the patient is emphasized.

Calcinosis↗
PubMed1983

Estimation of absolute left ventricular volume from gated radionuclide ventriculograms. A method using phase image assisted automated edge detection and two-dimensional echocardiography.

Twenty-four patients underwent gated cardiac blood pool (GBP) imaging, two-dimensional echocardiography (2-D echo), and single-plane contrast ventriculography (within 24 hours). Variable left ventricular (LV) regions of interest on GBP images were identified by an automated threshold radial search. To avoid excluding LV counts we indexed the search threshold to the threshold identified by a phase image generated by Fourier analysis. LV depth calculated by 2-D echo was used for attenuation correction of LV counts. LV end-diastolic volume (EDV) and end-systolic volume (ESV) were calculated by dividing attenuation, background and deadtime corrected LV count rates by the background corrected count rate/ml of venous blood drawn during the study. Correlations between radionuclide and contrast volumes were good (EDV + ESV r = 0.97, EDV r = 0.94, ESV r = 0.95). Regression lines were close to the lines of identity. This method, in which GBP imaging and automated LV edge finding are complemented by 2-D echo for count attenuation correction, demonstrated reliable and reproducible noninvasive estimates of absolute LV volume.

Adult↗
PubMed1981

Cardiac arrhythmias due to oral aminophylline in patients with chronic obstructive pulmonary disease.

The effect of orally-administered aminophylline on cardiac arrhythmias was studied in 15 patients with stable chronic obstructive pulmonary disease by continuous 24-hour ambulatory electrocardiographic recordings. During the control period, the mean frequency of ventricular ectopic beats (VEBs) per hour was 43 +/- 26 (range 0.3 to 401), and heart rate was 80 +/- 3 beats per minute. All grades of ventricular arrhythmias were seen with occasional VEBs in five patients, frequent in three, multifocal in four, coupled beats in two, and short runs of ventricular tachycardia in one patient. Seven patients had occasional atrial premature contractions, six paroxysmal atrial tachycardia, and one patient had stable atrial fibrillation. Mean frequency of VEBs per hour and heart rate were statistically similar in patients undergoing two 24-hour control recordings. Mean grade of atrial and ventricular arrhythmias also remained similar on two control recordings. After oral aminophylline, the mean frequency of VEBs per hour increased to 72 +/- 41 (P = 0.006). Heart rate increased to 88 +/- 4 beats per minutes (P = less than 0.01). The mean grade of ventricular or atrial arrhythmias remained unchanged. We conclude that orally-administered aminophylline has both arrhythmogenic and chronotropic effects, but does not change the grade of arrhythmia.

Administration, Oral↗
PubMed1979

Improved pacing tolerance of the ischemic human myocardium after administration of carnitine.

The possibility that DL-carnitine has a protective effect during myocardial ischemia was evaluated by performing two rapid coronary sinus pacing studies 15 minutes apart in 21 patients with coronary artery disease. Eleven patients received DL-carnitine (20 or 40 mg/kg) before the second pacing study. The treated group had a significant increase in mean heart rate (12.5 beats/min, P less than 0.001), pressure-rate product (1,912 units, P less than 0.01) and pacing duration (3.2 minutes, P less than 0.001) after the administration of carnitine. The treated group also had improvements in percent myocardial lactate extraction (8.8 percent increase, P less than 0.001) and left ventricular end-diastolic pressure (a decrease of 5.3 mm Hg, P less than 0.05). There was significantly less S-T segment depression during the second pacing period in both the untreated and treated groups. The results of this study suggest that in ischemic human hearts with reasonably well preserved left ventricular function, DL-carnitine may improve the tolerance for stress associated with an increase in heart rate and pressure-rate product.

Carbon Dioxide↗
PubMed1979

Carotid sinus syncope induced by malignant tumors in the neck. Emergence of vasodepressor manifestations following pacemaker therapy.

Three patients had carotid sinus syncope secondary to malignant neoplasms in the neck. Pacemaker therapy controlled the cardioinhibitory reflex with bradycardia, but the patients manifested varying episodes of hypotension due to a vasodepressor reflex that most likely resulted from persistent irritation of the carotid sinus by the tumor. These episodes seemed to be self-limiting. Surgical treatment in resistant cases is a possibility.

Carcinoma, Squamous Cell↗