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Biomedical subjects

Y M Yang

Publications and source records attributed to Y M Yang.

At least 91 records · Page 5Linked to original sources
PubMed1985

Cobalamin malabsorption in three siblings due to an abnormal intrinsic factor that is markedly susceptible to acid and proteolysis.

Three siblings presented in their second year of life with megaloblastic anemia that responded to parenteral cobalamin (Cbl). Schilling tests were less than 1%, correcting to 5 to 15% after addition of hog intrinsic factor (IF). Gastric acid analysis and gastric biopsies were normal by light and electron microscopy. Gastric juice contained less than 3 pmol/ml of Cbl-binding ability due to IF (normal, 10-34 pmol/ml) and less than 2 pmol/ml of IF when measured with a radioimmunoassay (RIA) using normal human IF-[57Co]Cbl and rabbit anti-human IF serum (normal, 17-66 pmol/ml). However, RIA employing rabbit anti-hog IF serum gave values of 4-13 pmol/ml of IF (normal, 11-33 pmol/ml). This material had an apparent molecular weight of 40,000 (normal IF = 70,000). The IF from gastric biopsies appeared normal in terms of Cbl-binding ability, ileal binding, molecular weight, and both RIAs. This IF differed from normal mucosal IF, in that it lost its Cbl-binding ability when incubated at 37 degrees C at acid pH or in the presence of pepsin or trypsin. This loss was retarded when [57Co]Cbl was bound to the IF before these incubations. The stabilizing effects of neutralization and Cbl were also demonstrated in vivo. Schilling tests for the siblings of 0.4, 0.5, and 1.0% increased to 2.7, 5.7, and 4.3% (P less than 0.05), respectively, when the Schilling tests were repeated with the addition of NaHCO3 and cobinamide (which allows Cbl to bind immediately to IF). We conclude that Cbl malabsorption in these children is due to an abnormal IF that is markedly susceptible to acid and proteolytic enzymes which cause a decrease in its molecular weight and Cbl-binding ability and a loss of antigenic determinants that are recognized by the anti-human IF serum.

Anemia, Megaloblastic↗
PubMed1975

Healthy blood donors with selective absence of immunoglobulin A: prevention of anaphylactic transfusion reactions caused by antibodies to IgA.

Gel diffusion analysis of sera from 73,569 healthy volunteer blood donors revealed apparent lack of IgA in 113 (1:650) samples, all with normal levels of IgG and IgM. Of these, 30 sera had low levels of IgA, while the remaining 83 had no IgA detectable by a more sensitive hemagglutination inhibition assay. The frequency of absent IgA (algA) was 1:886. High-titer anti-IgA was detected in the sera of 13 algA donors; only two had any known history of parenteral injection of IgA. Passive transfusion of high-titer anti-IgA in the units of blood elicited no clinical reaction in the recipients. Precipitating antibodies to ruminant IgM were present in 14 of the 83 donors. The incidence of hepatitis B surface antigen (HB-sAg), anti-HB-sAG, and antinuclear antibodies was the same in IgA-deficient and control sera. The algA donors form a unique resource for blood components for the clinical management of patients with anapylactic reactions caused by anti-IgA.

Anaphylaxis↗
PubMedDate not supplied

Analysis of a repeat-containing family of Giardia lamblia variant-specific surface protein genes: diversity through gene duplication and divergence.

Giardia lamblia trophozoites express on their surfaces one of a set of cysteine-rich antigenically variant proteins, called variant-specific surface proteins, which comprise the majority of proteins detected by surface labeling. While these VSP proteins may be immunodominant proteins important in the host immune response to G. lamblia, the ability to switch expression from one VSP to another may provide a means for the trophozoites to avoid the host immune response. The first VSP characterized, VSPA6 (from the A6 clone of the WB isolate, originally termed CRP170), contains 18-23 copies of a 65 amino acid repeat. We have now used the repeat as a probe to isolate from a WBA6 genomic library two genes related to vspA6 (called vspA6-S1, vspA6-S2). Sequence analysis of the vspA6-S1 gene revealed nearly two complete copies of the 195 bp repeat and substantial nucleotide and translated amino acid similarity in the coding regions 5' and 3' to the repeats. The vspA6-S2 gene, while still related, showed greater divergence from vspA6 than vspA6-S1 in the nonrepeat coding region and contained nearly four copies of a 201 bp repeat that was 75% identical to the 195 bp vspA6 repeat. These results suggest that gene duplication followed by divergence has played a key role in the generation of the vsp gene repertoire.

Amino Acid Sequence↗
PubMedDate not supplied

Pharmacologic induction of fetal hemoglobin synthesis: cellular and molecular mechanisms.

The switch from embryonic to fetal then to adult hemoglobin synthesis is a unique phenomenon during early human development. Fetal hemoglobin (Hb F) is known to interfere with polymerization of Hb S in erythrocytes. Several pharmacologic agents such as 5-azacytidine, myleran, hydroxyurea, erthropoietin, and butyrates enhance fetal hemoglobin production and have been used in hemoglobinopathy patients to ameliorate severe pain episodes and reduce severe anemia. Among these, hydroxyurea is the agent of choice because of its safety and ease of administration. One of the primary cellular mechanisms involved in pharmacologic induction of Hb F synthesis is rapid regeneration of erythroid precursors following the cytoreduction phase of certain pharmacologic agents. Molecular mechanisms involving changes in chromatin structure and/or transcription factor binding have been demonstrated for gamma gene induction by butyrate. Identifying the proteins involved in gamma gene activation by various compounds may offer a new strategy for gene therapy to cure hemoglobinopathy disorders.

Anemia, Sickle Cell↗
PubMedDate not supplied

Hierarchical distribution analysis for computer-assisted classifications of patient records.

The many existing hierarchical classifications present opportunities for computer-aided classification of medical data. The authors evaluate lexical term mapping followed by hierarchical node activation to determine the semantic locality of diagnoses in the American College of Radiology (ACR) classification. The activated hierarchy exposes conceptual structures behind lexically matched categories and markedly narrows the alternatives for human review. Several distribution analyses are evaluated for narrowing the candidate search space, to reduce ambiguity. The methods were tested on a prototype system, using a set of 78 samples of Mayo radiology diagnoses; their relative effectiveness is illustrated.

Classification↗
PubMedDate not supplied

T cell subsets in glomerulonephritis.

Abnormal lymphocyte function has been postulated to have a pathogenetic role in nephrotic syndrome. In an attempt to investigate the pathogenetic role of lymphocyte subsets in human glomerular disease, we studied 110 children suffering from nephritis during the acute nephrotic phase or nephritis without steroid treatment, 4 weeks later after steroid treatment, in remission and relapse. These patients included minimal change nephrotic syndrome (MCNS) 15 cases, focal segmental glomerular sclerosis (FGS) 6 cases, mesangial cell proliferative nephropathy (MesPGN) 42 cases, membranoproliferative glomerulonephritis (MPGN) 2 cases, hepatitis B surface antigenemia associated with membranous nephropathy (HBVMN) 10 cases, IgA mesangial nephropathy (IgAN) without nephrotic syndrome 7 cases, poststreptococcal glomerulonephritis (PSGN) 24 cases and chronic glomerulonephritis (CGN) 4 cases. There was no significant difference in the total lymphocyte count of each different pathological group of nephritis except that lymphopenia was noted in the CGN patients. When the lymphocyte phenotypic profile was examined, OKT8 cells were significantly increased in the MesPGN patients and both OKT4 and OKT8 cells were significantly increased in HBVMN. Comparison of MCNS and MesPGN during the acute nephrotic phase showed the OKT4/OKT8 ratio decreased significantly in MesPGN. Four weeks after steroid treatment, OKT4 cells decreased both in MCNS and MesPGN being pronounced in MCNS. In the remission stage with steroid treatment the OKT4/OKT8 ratio decreased in MCNS and was mildly elevated in MesPGN. In relapse, the OKT4/OKT8 ratio was the same as it was during the onset of nephrotic phase. MCNS cases were steroid responsive whereas in MesPGN there were frequent relapses or partial steroid response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗