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Biomedical subjects

A Ansari

Publications and source records attributed to A Ansari.

At least 145 records · Page 8Linked to original sources
PubMed1988

In vitro functional characterization of SAG-3--a naturally occurring monoclonal antibody in NZB mice: specificity toward functional T cell subsets.

Natural thymocytotoxic autoantibodies (NTA) have been suggested to contribute to the T cell mediated immune dysfunction prevalent in NZB mice. However, direct studies to confirm these suggestions have been difficult to perform due to the absence of large amounts of pure NTA. To overcome this problem, we generated a naturally occurring monoclonal antibody from an NZB mouse which possesses the serological characteristics of serum-NTA. Herein, we report the in vitro functional characteristics of this monoclonal antibody designated SAG-3. In vitro treatment of spleen and lymph node cells from BALB/c mice with SAG-3 and complement eliminated most of the proliferative response to Con-A and moderately reduced the response of these cells to PHA-P and PWM. Complement mediated cytolysis of SAG-3 reactive cells significantly reduced the capacity of unprimed lymph node cells to generate primary CTL responses in vitro against allogeneic cells. However, only a partial decrease in CTL activity was observed when primed secondary CTL effector cells were treated, due primarily to the depletion of CTL's specific towards MHC class I antigens. Furthermore, a moderate reduction in antigen-specific helper T cell function was observed. Pretreatment of responder cells with SAG-3 + C' did not appear to reduce the proliferative MLR response to a wide range of stimulator cells. In addition, contrary to previous reports on serum-NTA, SAG-3 appears not to be reactive against Con-A induced suppressor T cells. Finally, by FACS analysis SAG-3+ thymocytes constitute an overlapping population of Lyt-2+ and L3T4+ thymocytes. These findings are discussed in comparison to previous reports on NTA.

Animals↗
PubMed1988

Early evening ranitidine administration promotes faster duodenal ulcer healing.

In a prospective double-blind clinical trial, 141 patients with endoscopically diagnosed duodenal ulcer were randomly assigned to treatment with ranitidine 300 mg, taken either at 6 PM or at 10 PM. After 2 wk of treatment, 52 of 70 patients (74%) in the 6 PM treatment group had healed, compared with 32 of 64 patients (50%) taking ranitidine at 10 PM (p less than 0.01). After 4 wk, the cumulative healing rates were 100% and 94%, respectively, for the 6 PM and 10 PM treatment regimens. These results suggest that ranitidine, taken as a single daily 300-mg dose at 6 PM after dinner, provides more rapid duodenal ulcer healing than the same dose of the drug taken at 10 PM.

Adolescent↗
PubMed1987

Rebinding and relaxation in the myoglobin pocket.

The infrared stretching bands of carboxymyoglobin (MbCO) and the rebinding of CO to Mb after photodissociation have been studied in the temperature range 10-300 K in a variety of solvents. Four stretching bands imply that MbCO can exist in four substates, A0-A3. The temperature dependences of the intensities of the four bands yield the relative binding enthalpies and and entropies. The integrated absorbances and pH dependences of the bands permit identification of the substates with the conformations observed in the X-ray data (Kuriyan et al., J. Mol. Biol. 192 (1986) 133). At low pH, A0 is hydrogen-bonded to His E7. The substates A0-A3 interconvert above about 180 K in a 75% glycerol/water solvent and above 270 K in buffered water. No major interconversion is seen at any temperature if MbCO is embedded in a solid polyvinyl alcohol matrix. The dependence of the transition on solvent characteristics is explained as a slaved glass transition. After photodissociation at low temperature the CO is in the heme pocket B. The resulting CO stretching bands which are identified as B substates are blue-shifted from those of the A substates. At 40 K, rebinding after flash photolysis has been studied in the Soret, the near-infrared, and the integrated A and B substates. All data lie on the same rebinding curve and demonstrate that rebinding is nonexponential in time from at least 100 ns to 100 ks. No evidence for discrete exponentials is found. Flash photolysis with monitoring in the infrared region shows four different pathways within the pocket B to the bound substates Ai. Rebinding in each of the four pathways B----A is nonexponential in time to at least 10 ks and the four pathways have different kinetics below 180 K. From the time and temperature dependence of the rebinding, activation enthalpy distributions g(HBA) and preexponentials ABA are extracted. No pumping from one A substate to another, or one B substate to another, is observed below the transition temperature of about 180 K. If MbCO is exposed to intense white light for 10-10(3) s before being fully photolyzed by a laser flash, the amplitude of the long-lived states increases. The effect is explained in terms of a hierarchy of substates and substate symmetry breaking. The characteristics of the CO stretching bands and of the rebinding processes in the heme pocket depend strongly on the external parameters of solvent, pH and pressure. This sensitivity suggests possible control mechanisms for protein reactions.

Carbon Monoxide↗
PubMed1986

Ligand binding to heme proteins: relevance of low-temperature data.

Binding of carbon monoxide to the beta chain of adult human hemoglobin has been studied by flash photolysis over the time range from about 100 ps to seconds and the temperature range from 40 to 300 K. Below about 180 K, binding occurs directly from the pocket (process I) and is nonexponential in time. Above about 180 K, some carbon monoxide molecules escape from the pocket into the protein matrix. Above about 240 K, escape into the solvent becomes measurable. Process I can be observed up to 300 K. The low-temperature data extrapolate smoothly to 300 K, proving that the results obtained below 180 K provide functionally relevant information. The experiments show again that the binding process even at physiological temperatures is regulated by the final binding step at the heme iron and that measurements at high temperatures are not sufficient to fully understand the association process.

Carbon Monoxide↗
PubMed1986

Acute and chronic pulmonary thromboembolism: current perspectives. Part I: Glossary of terms, historic evolution and prevalence.

Despite considerable medical as well as surgical advances, the problem of pulmonary thromboembolism, both acute and chronic, continues to plague clinicians of all medical disciplines. Approximately 650,000 to 700,000 patients per year suffer from acute pulmonary thromboembolism in the United States. Of these, approximately 60,000-70,000 die as a direct result of it. Our knowledge of the etiology, pathology, pathogenesis of pulmonary infarction, pathophysiology, accurate diagnosis, proper management (including both primary and secondary prophylaxis) of deep vein thrombi and pulmonary thromboemboli has advanced considerably during the past 15 years. These advances, which have now been adopted in the clinical practice, have already begun to indicate that not only more cases of acute and chronic pulmonary thromboembolism are being recognized than before, but also the morbidity and mortality of this disease process is declining. This is likely to improve further as our quest for safe, accurate, noninvasive and inexpensive diagnostic methods continues. Medical thromboembolectomy using thrombolytic therapy is fast replacing the surgical thromboembolectomy for patients with acute massive pulmonary thromboembolism. Better thrombolytic agents, such as tissue plasminogen activator, which selectively lyses the thromboemboli without producing significant systemic lytic state and now undergoing clinical investigation, is likely to revolutionize the management of both acute and chronic pulmonary thromboembolism because of its propensity to dissolve plasminogen-bound thrombi of any age. The majority of the patients who suffer from acute pulmonary thromboembolism recover most of their lost lung function unless cardiopulmonary reserve was compromised prior to the onset of the acute episode.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1986

Pseudopericardial effusion: echocardiographic and computed tomographic correlations.

The findings of small anterior and posterior relatively echo-free spaces adjacent to the epimyocardium by echocardiography is more often indicative of pseudopericardial effusion due to subepicardial fat deposition rather than true pericardial effusion (PE), at least in older obese and Type II diabetic patients. This conclusion was based on the echo and computed tomography (CT) correlation performed in 10 consecutive patients (8 women, 2 men). The mimicry of various extracardiac and cardiac causes resulting in confusion with anterior and posterior PE is emphasized. Subepicardial fat deposition is one of the most common causes which mimic presence of small PE on echo and can be confirmed easily by limited CT of the chest. Age, sex, obesity, and diabetes mellitus (Type II) appear to be the most common predisposing factors for the accumulation of excess subepicardial fat.

Adipose Tissue↗
PubMed1986

Childhood familial pheochromocytoma. Conflicting results of localization techniques.

Childhood familial pheochromocytoma was investigated in four patients by abdominal computed tomographic scan, [131I]metaiodobenzylguanidine scan, and vena caval catecholamine sampling. Results conflicted with surgical findings. Computed tomographic scan identified all four adrenal tumors but missed two midline tumors in one patient. [131I]metaiodobenzylguanidine scan identified two of three adrenal tumors but also suggested extra-adrenal tumors not confirmed at operation in two of three patients. Vena caval sampling for catecholamines confirmed all adrenal tumors but suggested additional tumors not verified at operation in two of three patients. All patients are asymptomatic and have normal urinary catecholamines 15 to 51 months after operation. Because of the frequency of multiple tumors in familial pheochromocytoma, different diagnostic techniques were employed. False-positive results were more frequent with [131I]metaiodobenzylguanidine and vena caval sampling. Reinterpretation of the [131I]metaiodobenzylguanidine scans at a later date led to less false-positive interpretation, although the false-negative rate remained unchanged. More pediatric experience with [131I]metaiodobenzylguanidine scans and vena caval sampling in familial pheochromocytoma is needed. Confirmation of tumor and its localization rest with meticulous surgical exploration.

3-Iodobenzylguanidine↗