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Biomedical subjects

A Ahmad

Publications and source records attributed to A Ahmad.

At least 19 recordsLinked to original sources
PubMed1992

Change of speciation of Cu(II) in growth medium due to uptake of ammonia by Pseudomonas testosteroni during growth.

Growth of Pseudomonas testosteroni in a medium containing 1 mM Cu(II) causes a color change from blue to green. The spectrum of the supernatant solution from the blue culture shows an absorption at 660 nm, identical to that of 1 mM [Cu(II)] in the medium. The green supernatant solution shows a UV absorption, which tails into the visible and so is responsible for the green color, and a d-d absorption at 720 nm. The absorption at 660 nm for the blue supernatant solution is probably due to [Cu(NH3)3(H2O)3]2+. Growth of the organism causes loss of ammonia and a speciation change to [CU(NH3)2(H2O)4]2+, with a shift in absorption maximum from 660 to 720 nm. These conclusions are based upon the spectra of known aquaammine complexes of Cu(II) and calculations of the speciation of Cu(II) before and after growth. Change in metal speciation owing to nutrient uptake by an organism does not appear to have been recognized previously.

Ammonia↗
PubMed1992

Inadequate internal mammary artery graft as a cause of postoperative ischemia: incidence, diagnosis and management.

Inadequate left internal mammary artery (LIMA) graft to the left anterior descending artery (LAD) was encountered in 10 of 3,076 patients between 1984 and July 1990. The mean number of bypass grafts was 2.9 per patient. All patients with inadequate LIMA grafts were stable preoperatively with normal to moderately reduced left ventricular function. No technical difficulties were encountered during surgery. All patients were weaned off cardiopulmonary bypass with minimal or no inotropic support. Each patient developed myocardial ischemia of the LAD territory and/or circulatory collapse or recurrent ventricular dysrhythmia during the first 24 h postoperatively. Six patients, who were immediately re-operated on and had an additional saphenous graft to the LAD, recovered with no infarction and good functional results. Four patients, who were medically treated, developed myocardial infarction. In cases of refractory circulatory collapse and/or ventricular dysrhythmia, inadequate LIMA flow should be suspected. We recommend urgent re-operation with additional saphenous vein graft to the LAD.

Aged↗
PubMed1992

Biopharmaceutical studies of spirobishexahydropyrimidine.

Oral administration of spirobishexahydropyrimidine showed an increase in the activity of serum transaminases, lactate dehydrogenase and alkaline phosphatase. Biological half life and other pharmacokinetic parameters showed rapid absorption and slow elimination of the drug.

Alanine Transaminase↗
PubMed1992

The HID50 (hypothermia-inducing dose 50): an alternative to the LD50 for measurement of bacterial virulence.

A group of 40 mice involved in bacterial LD50 estimations was monitored over a period of 4 days by two teams of observers. One team measured the colonic temperature of the mice, the other assessed them clinically and killed those they judged terminally ill. The temperatures of all mice considered terminally ill dropped before this judgement was made. Measurement of such infection-induced hypothermia provides a more objective, reproducible, and earlier endpoint than that used in conventional LD50 estimation.

Animals↗
PubMed1991

A role for IgE in intestinal immunity. Expression of rapid expulsion of Trichinella spiralis in rats transfused with IgE and thoracic duct lymphocytes.

In these experiments we characterize the protective antibodies in immune serum that interact synergistically with immune thoracic duct lymphocytes (TDL) to induce rapid expulsion (RE) of Trichinella spiralis in adult rats. Antibodies with both reaginic and nonreaginic activity mediated RE upon passive transfer to adult rats that had been adoptively transfused with immune TDL 7 days earlier. In serum collected 28 days after a primary infection, the most important antibody was homocytotropic IgE. Native IgE produced by active infection was isolated from 28-day immune serum by salt precipitation and/or by sequential affinity chromatography. The murine mAb A2 and B5 (anti-rat IgE) were conjugated separately to Sepharose 4B affinity columns for affinity separations. IgE was shown to be pure by gel electrophoresis and Western blots and its m.w. was estimated at approximately 190,000. As little as 183 micrograms of purified IgE could induce RE after passive transfer to adult rats. The IgE was shown to be functional by PCA activity, Ag-binding on Western blots, and skin sensitization; the latter could be blocked by pretreatment with 1R162, a rat myeloma IgE. Monoclonal IgG of any isotype transferred in amounts up to 35 mg/rat could not transfer RE to rats previously transfused with TDL cells. Immune serum collected 3 mo after the primary infection contained insufficient IgE to transfer RE, but complex non-IgE fractions were protective. The data thus demonstrate that IgE is a functional Ig in the rat capable of mediating the rejection of challenge nematode infections of the gut in the absence of other specific Ig. Secondly, other Ig may also play a role, in particular, several weeks after the primary infection when specific IgE levels in serum have declined.

Animals↗
PubMed1991

Aortic valve replacement in patients over 80 years of age: a comparative standard for balloon valvuloplasty.

Elderly patients who develop symptomatic aortic valvular malfunction have a grave prognosis. Until recently they have not been seriously considered for active treatment, such as valvular surgery or balloon valvuloplasty. Between January 1972 and July 1989, 88 patients over the age of 80 years underwent aortic valve replacement and have been prospectively followed for a total of 185 patient-years. The majority were in New York Heart Association functional class III (48%) or IV (48%) preoperatively. Valvular pathology was pure aortic stenosis in 81%, regurgitation alone in 6%, and mixed lesions in 13% of the cases. Before 1982 the majority of patients received mechanical valves, whereas tissue valves have predominated since then (76% of total). Forty-three percent of the patients had concomitant coronary artery bypass grafting. The overall operative mortality was 16%. Emergency surgery, isolated aortic valve replacement, advanced preoperative functional class, and female gender carried a statistically higher operative mortality. The overall actuarial survival (standard error) at 5 years was 64(7)%. Survival was significantly higher at 5 years for concomitant coronary bypass grafting than for isolated aortic valve replacement, 70 (11)% versus 59(8%), and for males compared to females, 73(9)% versus 55(9)%. The 5-year event-free rates for valve-related death and valve re-replacement were 97(2)% and 93(5)%, respectively. These data provide a firm basis for aortic valve replacement as the standard form of treatment in patients over 80.

Actuarial Analysis↗
PubMed1991

Characterization of the thoracic duct T-helper cells that co-mediate, with antibody, the rapid expulsion of Trichinella spiralis in adult rats.

Thoracic duct cells that act synergistically with immune serum or antibody to transfer rapid expulsion of a challenge infection with Trichinella spiralis muscle larvae were characterized as OX38+, OX8-, OX22- T helper cells. Protective capacity was confined to the dividing T helpers that appeared on days 3-5 in the thoracic duct of rats during a T. spiralis infection. To realize their intestinal priming potential in recipient rats. MHC-compatibility between donor and recipient rat was required. Fractionation of immune serum with 40% saturated ammonium sulphate left transferable protective activity in both the precipitate and supernatant fractions. Absorption of immune serum with muscle larvae antigen removed the capacity to transfer protection.

Animals↗
PubMed1990

Intraintestinal migration to the epithelium of protective, dividing, anti-Trichinella spiralis CD4+ OX22- cells requires MHC class II compatibility.

We have measured the intraintestinal migration of activated Th cells belonging to the OX8- OX22- and OX8- OX22+ subsets derived from thoracic duct lymph of rats infected with Trichinella spiralis. Cells in S-phase were labeled with 125I-UdR or 3H-TdR in vitro and transfused i.v. Identical proportions of both helper cell subsets localized in the small intestine but three to four times as many OX22- cells as OX22+ cells migrated to the intestinal epithelium. Experiments using MHC class I and II recombinant rats indicated that localization of OX8- OX22- cells in the lower lamina propria (LP) and muscularis was reduced by 50% in MHC class II incompatible rats as assessed by total gamma-counts but by a factor of three when labeled cells were counted. Movement of labeled OX8- OX22- cells to the epithelium was reduced by a factor of five to seven when assessed by the same methods. Quantitative cellular localization in the gut and further movement to the epithelium were normal in class I-mismatched rats. The movement from the lower-mid LP to the epithelium was undertaken principally by dividing cells as indicated by a progressive loss of grain counts in labeled cells and the appearance of doublet-cells in mitosis. In allogeneic combinations, extravasating cells remained localized close to their primary site of exit in the muscularis and lower-mid LP. The results suggest that the requirement for MHC class II compatibility for adoptive transfer of immunity in rats to T. spiralis is functionally related to localization of the protective OX22- cell subset in the epithelium.

Animals↗
PubMed1990

Treatment of adenocarcinoma of the cardia with synchronous chemotherapy and radiotherapy.

Twenty-nine evaluable patients with adenocarcinoma of the cardia were treated with synchronously administered chemotherapy (two cycles of 5-fluouracil and cisplatin and 30-36 Gy of radiation to determine whether these tumours are responsive to such treatment. Complete regression of tumour was observed endoscopically in 19 patients, and partial regression in four. Fourteen patients had their tumours resected and in six no microscopic tumour was found in the specimen. Nine patients received additional radiotherapy to a total dose of 54-60 Gy instead of surgery. Tumour response was associated with rapid reversal of dysphagia. Only one patient required subsequent intervention for relief of dysphagia due to fibrous stricture. Enhanced survival was associated with a complete endoscopic response to initial chemotherapy and radiotherapy, and a tumour of less than 5 cm in length. The median survival of responding patients was 15 months. Synchronous chemotherapy and radiotherapy was of major palliative benefit in this series and merits further evaluation.

Adenocarcinoma↗
PubMed1990

Synergistic interaction between immune serum and thoracic duct cells in the adoptive transfer of rapid expulsion of Trichinella spiralis in adult rats.

Rapid expulsion of Trichinella spiralis could be transferred to naive adult rats with thoracic duct lymphocytes and immune serum. Thoracic duct cells collected from Days 3-5 and immune serum collected on Day 28, respectively, after infection were effective. Both cells and serum were unable to transfer rapid expulsion when given alone, even in large volumes. Recipients of immune serum and cells eliminated a significantly higher number of larvae than control rats by 1 hr after challenge with muscle larvae. Rapid expulsion produced 30-80% larval worm rejection but could not be increased by the transfer of more cells or immune serum. Mucus trappings did not appear to play a role in the rejection process. After transfer of 2 x 10(8) cells and 4.0 ml immune serum, rapid expulsion persisted for less than 1 week. However, after adoptive transfer of cells alone, the gut remained functionally receptive to the passive transfer of immune serum for 7 weeks. Therefore, the changes effected by transfer of cells were long lived in contrast to the 1 week, or less, of functional persistence by transferred immune serum. The data indicate that two separate processes, one cell mediated and the other immune serum mediated, interact synergistically in the intestine and lead to the expression of rapid expulsion.

Animals↗
PubMed1990

Sequential release of antigens from chloroform-treated Staphylococcus epidermidis: application towards a possible vaccine.

This study describes the properties of two potential Staphylococcus epidermidis vaccines prepared by chloroform treatment of bacteria and release of antigen from these chloroform-treated organisms. Both vaccines were antigenic on testing with homologous hyperimmune serum and induced immune reactivity in immunized rabbits. There was protective efficacy in mice against intraperitoneal challenge by Staph. epidermidis.

Animals↗
PubMed1990

Recombinant targeted proteins for biotherapy.

In an effort to improve existing biotherapies, researchers have used recombinant techniques to alter the structure of toxins, monoclonal antibodies, and other receptor and effector molecules. Experimental research has demonstrated that the extent of problems such as nonspecific toxicity and rapid clearance by the immune system are not as great with genetically engineered toxins as opposed to native toxins. Fusion proteins, which combine portions of toxins, antibodies, or various effector molecules, exhibit the preferred biologic properties of their constituents. Unlike their murine counterparts, chimeric antibodies have the ability to invoke cell-mediated immunity and are less immunogenic to humans. Because they display different antigen-binding specificities on the same molecule, hybrid hybridomas are a potential means of juxtaposing effector cells or toxins to tumor cells. These and other positive features of recombinant proteins offer a decided advantage over previous biotherapeutic agents, and these molecules are expected to find application in the treatment of cancer, the acquired immunodeficiency syndrome, and autoimmune diseases.

Animals↗
PubMed1990

Effects of reduced dietary magnesium on platelet production and function in hamsters.

The increased vulnerability of animals fed a magnesium (Mg)-deficient (MD) diet to ischemia-induced myocardial necrosis has been attributed to changes in myocardial electrolyte metabolism. However, a variety of hematologic changes have also been reported in MD and some of these, such as an increase in platelet aggregability, may contribute to the increased myocardial vulnerability. In the present study, we quantified the effect of MD on platelet and megakaryocyte abundance as well as on platelet aggregability with and without an administered calcium channel blocker (nifedipine). Hamsters were fed either a "minimal Mg" diet, in which the level of Mg was kept just high enough to prevent seizures, or a "preset Mg" diet containing precisely known amounts of Mg. Animals fed the minimum Mg diet showed an initial increase in the platelet count, which returned to control range when the dietary Mg was increased to 9 mmoles/kg. Animals on the preset Mg diet showed an increased platelet count if the Mg level was 10 mmoles/kg or less. In addition to the increase in number, platelets from MD animals were less responsive to the aggregation-inhibiting effect of nifedipine than were platelets from control animals, although MD itself did not result in an increased aggregability under the conditions used here. Animals with an increase in circulating platelets showed decreased megakaryocyte abundance in the femoral marrow, but megakaryocytes that were present were larger than those in control animals. These results indicate a profound effect of dietary Mg deficiency on platelet biology. The observed changes could contribute to the increase in myocardial vulnerability to injury found in MD animals.

Animals↗