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M M Chan

Publications and source records attributed to M M Chan.

At least 55 records · Page 3Linked to original sources
PubMed1989

Bacterial expression of human cysteine proteinase inhibitor stefin A.

Stefin A, a cysteine proteinase inhibitor of the cystatin superfamily, has been found to be most abundant in epidermal cells. In order to determine its cellular function, we have expressed human stefin A in Escherichia coli using plasmid expression vectors under the control of bacteriophage T7 RNA polymerase. The heat-stable, antibody-positive bacterial product was isolated using a papain-Sepharose affinity column and was shown to inhibit two cysteine proteinases, papain and human cathepsin B. Recombinant stefin A may have commercial and therapeutic potential in situations requiring inhibition of cysteine proteinase activities, and in cosmetics, as an ingredient in skin creams.

Blotting, Western↗
PubMed1988

Expression of human cathepsin B protein in Escherichia coli.

A cDNA fragment containing the coding sequence for the mature enzyme of human lysosomal proteinase cathepsin B was inserted in the pET plasmid expression vectors, so that it was placed under the control of transcription and translation signals from bacteriophage T7. Upon induction, cathepsin B antigen was detected by in situ immunoscreening of lysed E. coli and by Western blot analysis of bacterial lysates. To our knowledge this is the first report of abundant synthesis of cloned cathepsin B in any expression system. Subfragments of cathepsin B can also be generated by this technique and will be used to study cathepsin B structure and function.

Base Sequence↗
PubMed1988

Identification of the avian homologues of mammalian CD4 and CD8 antigens.

Two mAb were produced against chicken T cells. The CT4 antibody precipitated a polypeptide of Mr 64,000 under both reducing and non-reducing conditions. The CT8 antibody precipitated a molecule of Mr 63,000 under non-reducing conditions and polypeptide chains of Mr 34,000 under reducing conditions, suggesting that the CT8 molecule is a disulfide-linked homodimer. Tissue distribution studies by immunofluorescence revealed that the CT4 and CT8 Ag were expressed by the majority of thymocytes and by subpopulations of CT3+ cells in peripheral tissues. The CT4 reactive molecule was found on approximately 70% of thymocytes, 10% splenocytes, and 45% of lymphoid cells in blood. The CT8 reactive molecule was expressed on approximately 80% of thymocytes, 50% of spleen cells, and 15% of blood lymphocytes. Two-color immunofluorescence indicated that the CT4 and CT8 Ag were expressed together on most thymocytes and on mutually exclusive subsets of cells in the spleen and blood. Ontogenic studies revealed a sharp increase in the frequencies of CT4+ and CT8+ cells in the thymus between days 13 and 16 embryonic life. Both CT4 and CT8 antibodies inhibited PHA- and Con A-induced proliferative responses of splenocytes, and the degree of inhibition correlated with the frequencies of CT4+ and CT8+ lymphoblasts. Treatment of spleen cells with CT4 antibody and inhibited PWM-induced IL-2 production, and removal of CT8+ cells inhibited the cytolytic activity induced by allogeneic lymphocyte stimulation. Macrophages did not express detectable CT4 reactivity. These results suggest that the CD4 and CD8 molecules and their tissue-restricted patterns of expression are highly conserved in birds and mammals.

Animals↗
PubMed1988

A large subpopulation of avian T cells express a homologue of the mammalian T gamma/delta receptor.

This report describes an avian TCR molecule, TCR1, whose molecular characteristics, signal-transducing property, and tissue distribution suggest that it is a homologue of the mammalian TCR-gamma/delta. TCR1+ cells are the first to be generated in the thymus during ontogeny, preceding other T3+ cells by approximately 3 d. Unlike their mammalian counterpart, TCR1+ cells constitute a relatively large subpopulation of peripheral T cells in mature chickens. These results suggest a phylogenetically important role for this receptor in T cell development and function.

Animals↗
PubMed1988

The Ly-10 antigen is a marker of mouse-activated T lymphocytes.

Ly-10.1 is a lymphocyte surface antigen controlled by a gene linked to the Ly-1.1 locus and expressed on activated T helper, T suppressor (Ts), and cytotoxic T lymphocytes (CTL). In this report, we describe the following: 1) Ly-10 is a heterodimeric glycoprotein consisting of a 80,000 heavy and a 34,000 light chain. 2) Although mature CTL are Ly-10+ by negative selection with anti-Ly-10.1 and complement (C), CTL precursors reactive to allogeneic cells are Ly-10-. 3) Similarly, IL-2-producing effector T cells induced by Mls-incompatible cells and semiallogeneic stimulation are eliminated by anti-Ly-10.1 and C after activation but are not eliminated as precursors before activation. 4) In mixed lymphocyte culture with semiallogeneic cells, the frequency of Ly-10.1+ cells was highest on the 2nd to 5th day after stimulation, decreased by the 12th day, and increased after restimulation with fresh antigen as demonstrated by immunofluorescence, C-mediated lysis, and IL-2 production. 5) When spleen cells were treated with anti-Ly-10 and C before concanavalin A (Con A) activation, the suppressive activity in the Con A T blasts was reduced, suggesting that in normal mice, some Ts preexist in a Ly-10+ activated state. These results indicate that Ly-10 is a marker of activation of T cells, not expressed on precursor T cells and whose expression is both transient and dependent on the presence of antigen. The similarities in biochemical and cellular characteristics suggest that Ly-10 is a mouse homologue of the human lymphocyte activation marker 4F2.

Animals↗
PubMed1986

Evaluation of a pediatric multiple vitamin preparation for total parenteral nutrition. II. Blood levels of vitamins A, D, and E.

This study represents the first attempt to evaluate the American Medical Association Nutrition Advisory Group (NAG) recommendations for intravenous vitamin A, D, and E dosages for infants and children. Patients studied included 18 preterm infants (group 1) and 26 term infants and children (group 2A) receiving total parenteral nutrition for 2 to 4 weeks and eight infants and children receiving total parenteral nutrition for 3 to 6 months (group 2B). Term gestation infants and children up to 11 years of age all received the same dosages (those that were recommended by the NAG for children weighing more than 10 kg). Preterm infants received 65% of these doses. In group 1, cord blood alpha-tocopherol levels were less than 0.22 mg/dL in seven preterm infants (reference value = 0.29 +/- 0.04), but mean levels increased to 1.65 +/- 0.17 mg/dL after four days of treatment. Eight infants consistently received additional vitamin E orally (80 to 150 mg daily), and their levels increased to 2.18 +/- 0.26 mg/dL by four days of study and to 3.49 +/- 0.57 mg/dL after 3 weeks. Oral supplementation in the preterm infants appeared to be unnecessary because intravenous vitamins alone maintained levels above 1.1 mg/dL. In group 2, alpha-tocopherol levels were maintained within the reference range. Patients receiving lipid emulsions containing substantial quantities of alpha-tocopherol had significantly higher blood levels than patients receiving lipid emulsions containing little alpha-tocopherol (P less than .01). Mean 25-OH vitamin D levels were maintained above or within the reference range in groups 2A and 2B.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1985

The relationship between the human sperm hypoosmotic swelling test, routine semen analysis, and the human sperm zona-free hamster ovum penetration assay.

The functional integrity of sperm membranes of 270 semen samples collected from fertile men and the male partners in couples with infertile marriages was assessed by the hypoosmotic swelling test and the results correlated with routine semen analysis and the human sperm zona-free hamster ovum penetration assay. Semen samples with abnormal semen parameters had lower values of percentage of swollen sperm after hypoosmotic treatment in comparison with those with normal semen parameters. A weak positive correlation was observed between sperm swelling and sperm morphologic features (r = 0.32, P less than 0.05) and between sperm swelling and sperm motility (r = 0.22, P less than 0.05). Insignificant correlation was observed between sperm swelling and in vitro sperm fertilizing capacity, as assessed by the zona-free hamster ovum penetration assay. The results indicate that the sperm swelling test and the zona-free hamster ovum penetration assay are evaluating different functional qualities of sperm that are apparently not associated with each other.

Animals↗
PubMed1985

Genetic control of immune response to the L-Glu, L-Lys, L-Phe terpolymer in man.

We have demonstrated that human lymphocytes can respond to the synthetic polypeptide GLPhe upon in vitro challenge by the antigen similar to that of (H,G)-A--L, (T,G)-A--L, (Phe,G)-A--L, and GAT. Family studies further support our postulation that responses to these synthetic polymers are under dual gene control. Three families with intra-HLA-A/B recombinants provided mapping information for Ir-GLPhe genes. The response phenotype of the recombinant of family 21 localized the Ir-GLPhe genes toward the HLA-B of D regions, whereas recombinants of family 24 and 27 placed the Ir-GLPhe genes distal to HLA-B, toward the A region. This discrepant gene assignment can be explained by assuming that recombination occurred at different positions between HLA-A and HLA-B. In family 21, crossover occurred distal to the Ir genes, while for the other two, proximal to them. A second possibility is that as in the mouse the two complementing genes are situated in different regions of the human major histocompatibility complex (MHC) and all three of the crossovers occurred between them with the putative Ir-GLPhe-1 located near the HLA-A region and Ir-GLPhe-2 on the HLA-D region or vice versa. A third possibility is that immune response required interaction between a complete HLA-D-like molecule encoded in the A region and another encoded elsewhere, perhaps in HLA-D.

Chromosome Mapping↗
PubMed1984

Genetic control of major histocompatibility complex-linked immune responses to synthetic polypeptides in man: poly(L-phenylalanine, L-glutamic acid)-poly (DL-alanine)--poly(L-lysine) and L-glutamic acid, L-alanine, L-tyrosine (60:30:10).

Vigorous lymphoproliferative responses to synthetic polypeptides poly(L-phenylalanine, L-glutamic acid)-poly(DL-alanine)--poly(L-lysine) [( Phe,G)-A--L], and L-glutamic acid, L-alanine, L-tyrosine (60:30:10) (GAT) were observed in cells from 92 unrelated subjects. Thirty-three percent responded to (Phe,G)-A--L and 77% to GAT. No HLA association was observed with responses to these two antigens. Family studies indicated that two complementary immune response (Ir) genes are required for response to each antigen. Eleven matings were informative for linkage analysis between HLA and these Ir genes. Families in which the complementary genes are in coupling gave maximal lod scores (log of the odds) of 4.50 for (Phe,G)-A--L and 7.57 for GAT for 0 = 0. In a HLA-B/D recombinant family, the Ir- PheGAL genes are mapped towards the HLA-D region. The localization of Ir-GAT genes close to HLA-B was provided by a HLA-A/B recombinant.

Genes, MHC Class II↗
PubMed1983

Characterization of T lymphocyte subsets with monoclonal antibodies: discovery of a distinct marker, Ly-m22, of T suppressor cells.

The study of cell surface antigens has accelerated in the few years since the advent of hybridoma technology to the point where many dozens of such markers have now been described. The functional heterogeneity of post-thymic T cells in the immune response, however, still exhibit complexities beyond the resolving power of our current repertoire of marker antigens. In this study, we investigated the surface phenotype of three types of effector T cells: helper cells, nonspecific suppressor cells, and cytotoxic T cells, using four recently discovered alloantigen systems of T cells: Ly-m10, Ly-m18, Ly-m19, and Ly-m22. SRBC-primed spleen cells were used as a source of specific helper T cells, and they were tested by their ability to promote antibody synthesis by B lymphocytes. Concanavalin A-activated suppressor cells were assayed by their ability to inhibit that response. Cytotoxic T cells were activated by alloantigen. We found Ly-m10 to be expressed on all three cell types tested, whereas Ly-m18 and Ly-m19 were absent from all three. Ly-m22, whose controlling locus is closely linked to the Mls region, had a unique distribution, being present solely on suppressor cells. Thus Ly-m22 emerged as a new marker that distinguishes nonspecific T suppressor cells (Ly-m22+) from T helper as well as cytotoxic T cells (Ly-m22-). Ly-m22 is the only antigen besides I-J so far known to be restricted to suppressor cells.

Animals↗
PubMed1981

Genetic heterogeneity of DR4 in the Old Order Amish and two new HLA-D specificities.

Seven Old Order Amish families were D and DR typed using the Eighth International Workshop HTC and Dr antisera. Four different DR4 haplotypes were identified in five families, two of which were negative for Dw4 as well as all other known HLA-D alleles. These two "new" D/DR types reacted with all 8W antisera submitted as anti-DRf4, but could be distinguished by their differential reactivity with three non-DR4 antisera 8W1207, 572, and 1074. We have designated these new specificities as DR-Am4.1 and 4.2 Sera 8W1207 and 572 were positive with DR-Am4.1 cells, while 8W1074 defined DR-Am4.2. The complete haplotypes of the new HLA-D/DR specificities were Aw32, Cw5, Bw44, D-Am4,1, DR-Am4.1 and A2, Cw4, Bw35, D-Am4.2, Dr-Am4.2. Homozygous cells of these new variants stimulated each other strongly in MLC. D-Am4.1/DR-Am4.1 represents a new D region allele possibly showing linkage disequilibrium with Bw4.2/DR-Am4.2, the second new variants, was not found in a screening of 31 non-Amish unrelated subjects. It, therefore, appears to have a low gene frequency in the population.

Alleles↗
PubMed1981

Genetic control of major histocompatibility complex-linked immune responses to synthetic polypeptides in man.

Vigorous lymphocyte proliferative response to synthetic polypeptides was observed in cells from 50 normal volunteers. Results indicated that 64% responded to poly(LHis, LGlu)-poly(DLAla)--poly(LLys) [(H, G)-A--L] and 54% to poly(LTyr, LGlu)-poly(DLAla)--poly(LLys) [(T, G)-A--L]. Subjects could be classified into high-, intermediate-, and non-responder phenotypes according to their stimulation indices. Family studies indicated that high responses to these antigens are inherited as histocompatibility antigen gene (HLA)-linked dominant traits. Two matings suggested gene complementation in response to (T, G)-A--L and (H, G)-A--L. One, with an intra-HLA recombinant offspring, provided evidence localizing the immune response gene(s) controlling lymphocyte proliferation to (T, G)-A--L and (H, G)-A--L, presumably the homologue to Ir-1 of mouse, closer to the HLA-B than to the HLA-D region.

Adult↗
PubMed1980

Metabolic responses of folic acid and related compounds to thyroxine in rats.

This study deals with the effects of thyroidectomy and feeding thyroid powder on histidine and folic acid metabolism. Normal rats maintained on a soy protein diet, low in methionine but supplemented with vitamin B-12, oxidize approx. 10% of an injected dose of [2-14C]histidine in 3 h and excrete low levels of formiminoglutamic acid. Addition of methionine increases histidine oxidation to approx. 20%. The feeding of thyroid powder or the injection of high levels of thyroxine decreases histidine oxidation and increases formiminoglutamic acid excretion. Surgical thyroidectomy at weaning increases histidine oxidation to approx. 45% and, thus, resembles the effect of methionine in promoting histidine oxidation and decreasing formiminoglutamic acid excretion. The feeding of methionine to the thyroidectomized animal further increases histidine oxidation to 65%. The distribution of folate forms in the liver was determined by column chromatography following administration of a dose of tritiated folic acid. In the normal animal, tetrahydrofolate accounts for 38% of the total folate present. The feeding of methionine increases this to 48%, which is consistent with the observed increase in histidine metabolism. Thyroidectomy increases the percentage of tetrahydrofolate to 63% and the feeding of methionine further increases it to 68%. The percentage of tetrahydrofolate relative to total folate is in proportion to the observed rate of histidine metabolism. The action of thyroidectomy in increasing histidine oxidation may be accounted for by its effect in increasing the proportion of tetrahydrofolate.

Animals↗
PubMed1979

Effect of vitamin B-6 deficiency on preference for several taste solutions in the rat.

The effect of dietary-induced vitamin B-6 (B-6) deficiency on the intake of the taste solutions, sodium chloride (NaCl), sodium saccharin (NaSacc), quinine sulfate (QS), and hydrochloric acid (HCl) was studied using a 48 hour, two-bottle choice technique. The B-6 deficient group demonstrated increased preference to 1.5 X 10(-1) and 3.0 X 10(-1) M NaCl compared to control ad libitum fed and control pair-fed groups. Total fluid intake on NaCl test days was also elevated in the B-6 deficient rats. There was no significant difference in the mean preference to NaSacc, QS, or HCl among the three groups. Adrenal hypertrophy was observed in the deficient rats. There was no change in the plasma level of Na and Zn but there was a reduction in urinary Na excretion. When the deficient rats were replenished by intraperitoneal injection of pyridoxine.HCl and feeding with the control diet containing adequate B-6, the increased preference for NaCl was extinguished, suggesting that the preference alteration was reversible. Urinary Na excretion also returned to normal.

Adrenal Glands↗