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Biomedical subjects

P Ahmed

Publications and source records attributed to P Ahmed.

At least 19 recordsLinked to original sources
PubMed1998

Diversity of hemagglutination phenotypes among P-fimbriated wild-type strains of Escherichia coli in relation to papG allele repertoire.

Data regarding the hemagglutination (HA) patterns of the three variants (classes I, II, and III) of the Escherichia coli adhesin PapG are conflicting. These HA patterns usually have been assessed for each papG allele separately with recombinant strains in slide HA assays. We rigorously evaluated an alternative microtiter tray HA assay and then used it to assess the HA of four erythrocyte types (human A1P1 and OP1, rabbit, and sheep erythrocytes) by multiple wild-type E. coli strains representing the four naturally occurring combinations of the papG alleles, i.e., class I plus III, class III only, class II plus III, and class II only. The microtiter tray HA assay displayed significantly better reproducibility of intraobserver (83%) and interobserver (86%) results than did slide HA assays (39 and 73%, respectively). Novel findings from the study of 32 wild-type P-fimbriated strains included reproducible determinations of phenotypic diversity among different papG categories, among strains within each papG category, and from day to day for individual strains. There was also substantial overlap of phenotypes between papG categories I plus III and III only and between II plus III and II only. A class III papG recombinant strain's HA pattern differed significantly from that of the wild-type class III strains. These data demonstrate that HA phenotypes of wild-type P-fimbriated E. coli strains can be reproducibly assessed by a microtiter HA assay and that they correspond broadly to papG genotype but in a more complex and varied fashion than previously recognized.

Adhesins, Escherichia coli↗
PubMed1994

Effect on cardiovascular function and iron metabolism of the acute removal of 2 units of red cells.

BACKGROUND: The collection from a donor of 2 red cell units at one time would decrease recipient exposure to viruses and alloantigens. If the donor is a large person, the blood volume lost and the postdonation hemoglobin and/or hematocrit should be within acceptable limits. If the donor is a large person, the blood volume lost and the postdonation hemoglobin and/or hematocrit should be within acceptable limits. The effect on cardiovascular function and iron metabolism requires description. STUDY DESIGN AND METHODS: Manual 2-unit erythropheresis was performed on eight donors, with the plasma returned. Donors had treadmill testing of maximum aerobic power (VO2max) before donation, 24 hours after, and 8 to 11 weeks after. Serial samples were drawn for iron metabolism studies. RESULTS: Donors weighed 61.2 to 74.8 kg, and 9.6 to 11.4 percent of their blood volume was removed. Mean VO2max decreased from 84 percent of that predicted before donation to 74 percent 24 hours afterward. By 8 to 11 weeks, hemoglobin returned to acceptable donor levels and mean VO2max was 92 percent of that predicted. Mean hemoglobin fell from 14.4 to 11.7 g per dL (144 to 117 g/L) and rose to 13.9 g per dL (139 g/L) at 16 weeks. At 16 weeks, serum iron (120 +/- 47 vs. 83 +/- 33 micrograms/dL [21 +/- 8 vs. 15 +/- 6 mumol/L]), ferritin (40 +/- 24 vs. 18 +/- 10 ng/mL [40 +/- 20 vs. 20 +/- 10 micrograms/L]), and free erythroprotoporphyrin (19 +/- 5 vs. 28 +/- 5 micrograms/dL [0.34 +/- 0.09 vs. 0.50 +/- 0.09 mumol/L]) differed significantly from baseline levels. No major donor symptoms occurred. CONCLUSION: Two-unit erythropheresis was done with blood volume loss and postdonation hemoglobin no worse than those that would occur in a 50-kg donor donating 450 mL. Cardiovascular effects and donor symptoms were mild. Two-unit red cell donations would be clinically advantageous, and they warrant further studies of both utility and donor safety.

Adult↗
PubMed1989

Multiple plasma exchanges successfully maintain a young adult patient with Crigler-Najjar syndrome type I.

Plasmapheresis has been shown to reduce total and free bilirubin levels in acute exacerbations of Crigler-Najjar syndrome, type I (CNS-TI), but its effectiveness in long-term management has not been reported. An 18-year-old (yo) male with CNS-TI, who required prolonged daily high-intensity phototherapy to prevent cerebral nervous system symptoms, developed increasingly frequent bouts of confusion, nausea, and vomiting associated with free bilirubin concentrations (fbcs) greater than 10-15 nmol/L. Pending consideration of orthotopic liver transplantation, plasma exchange (approximately 3 liters per procedure) was begun in 12/84 using the IBM/COBE 2997 with 5% albumin as replacement fluid. Frequency of treatments was guided by twice weekly fbcs, with plasma exchange for fbc greater than 10-15 nmol/L. Pre-exchange and postexchange fbcs ranged from 27.5 to 11 nmol/L and 9.2 to 2 nmol/L, respectively. Seventy-two exchanges were performed over a 28 month period. Irreversible CNS damage did not occur, and the patient underwent successful liver transplantation in April of 1987, with complete correction of his metabolic disorder. He remains well 18 months following transplantation.

Adolescent↗
PubMed1989

Chemoattractant activity of Entamoeba histolytica for human polymorphonuclear neutrophils.

The ability of axenic Entamoeba histolytica trophozoites and amoebic protein preparations to stimulate chemotaxis of human polymorphonuclear neutrophils (PMN) was evaluated. Virulent E. histolytica (strain HM1:IMSS) stimulated chemotaxis (delta distance = 0.55 +/- 0.02 mm, P less than 0.01 vs. control medium). Sonicated (100 micrograms protein/ml) or homogenized (500 micrograms protein/ml) virulent amoebae also significantly stimulated PMN chemotaxis, whereas preparations of the nonpathogenic "Entamoeba-like" Laredo strain did not stimulate chemotaxis. Preparations of subcellular fractions of E. histolytica demonstrated maximal stimulation of PMN chemotaxis existed in nonvesiculated membranes and the supernatant from plasma membranes.

Animals↗
PubMed1988

Deletion of antigens of the Lewis a/b blood group family in human prostatic carcinoma.

The expression of antigens of the blood group Lewis a/b family were studied in a series of 42 prostatectomy specimens from patients with adenocarcinoma clinically confined to the prostate; 19 of these were later reclassified as pathologic Stage C. Staining of normal or hyperplastic versus neoplastic epithelium was assessed in routinely processed, paraffin-embedded tissue using murine monoclonal antibodies and an avidin-biotin immunoperoxidase technique. Antigens screened and the antibodies used to recognize them were Lewis a (CF4C4), Lewis b and Type 1 H (NS10), monosialosyl Lewis a I (19.9), and disialosyl Lewis a and monosialosyl Lewis a II (FH7). FH7 strongly stained the benign epithelium of all 39 Lewis positive cases, suggesting that the sialyltransferase responsible for synthesis of FH7-reactive determinants is highly active in benign prostatic tissue. When compared to the reactivity of benign epithelium in Lewis positive cases, the staining of the carcinomas was markedly reduced in 18 cases (46%) and absent in 16 cases (41%). This reduction or loss of staining of the malignant epithelium was observed for all antibodies that stained the corresponding benign epithelium of each case. In only five of the cases (13%) was the intensity of staining in the carcinoma equal to that of the surrounding benign epithelium. No cases in this latter group had recurrence of disease, whereas in the other staining groups 25-33% of the cases had recurrences; median follow-up for the entire group was 78 months. No correlation was apparent between Gleason score and the staining pattern with these antigens. In summary, antigens of the Lewis a/b family are deleted in a high percentage of cases of prostatic adenocarcinoma.

Antibodies, Monoclonal↗
PubMed1986

A new polymorphic determinant on HLA-DQ molecules.

In man, the immune response genes are located within the HLA-D/DR region, and the gene products, the Ia antigens, are expressed on B lymphocytes, monocytes, and a percentage of null cells and activated T lymphocytes. We recently identified a human Ia antigen, K19, which appeared to be limited in its expression to B lymphocytes, and to be preferentially expressed on the more mature cells within this population. This work was facilitated by a monoclonal antibody. HK-19, which recognized a monomorphic determinant of this Ia molecule. We now report the characterization of a second monoclonal antibody, HK-13, which recognized the same molecule as HK-19, but only on cells from some individuals. The greater affinity of HK-13 allowed more complete characterization of the K19/K13 molecule. This characterization included cytofluorography, two-dimensional gel electrophoresis, tryptic peptide mapping, and partial N-terminal amino acid sequencing, and indicated that K19 and K13 were epitopes on HLA-DQ (DC) molecules. The pattern of reactivity of HK-13 on a panel of typing cells did not correlate with any of the known HLA-DQ polymorphic determinants. Thus, HK-13 is a new polymorphic determinant of the HLA-DQ series.

Amino Acid Sequence↗
PubMed1983

A unique DR-related B cell differentiation antigen.

The Ia or class II molecules in both mouse and man are the basis for the genetic control of the immune response. In addition to DR, other class II antigens have been described in man. We describe a new human Ia antigen K19, recognized by three monoclonal antibodies (HK-9, HK-19, and HK-20). This antigen has the general biochemical characteristics of an Ia antigen but is different from a DR antigen. Further, this antigen is found only on mature B lymphocytes and not on monocytes and activated T cells. Thus, this antigen may represent a new Ia-like molecule that is preferentially expressed on mature B cells.

Animals↗