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Biomedical subjects

M McMillan

Publications and source records attributed to M McMillan.

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

The association of H-2Ld with human beta-2 microglobulin induces localized conformational changes in the alpha-1 and -2 superdomain.

We have analyzed changes in the antigenicity of major histocompatibility complex class I molecules resulting from the association of human beta-2 micro-globulin (B2m) with the mouse class I heavy chain. In particular, the H-2Ld molecule exhibited enhanced cross-reactivity for the 34-1-2 monoclonal antibody. In order to assess the nature of this structural alteration induced by human B2m, we utilized H-2 class I hybrid molecules in the mapping of the 34-1-2 determinant to the helical region of the alpha-1 domain. H-2Ld class I hybrid molecules were then used to establish the importance of the alpha-2 and -3 domains in the observed increase of 34-1-2 cross-reactivity following exchange with human B2m. The H-2Ld hybrids suggest that alterations in interdomain contact are responsible for enhanced 34-1-2 cross-reactivity on the H-2Ld molecule. It is likely that this alteration arises through changes in class I conformation at regions of the molecule distant from points of contact between B2m and the class I molecule. This suggests that perturbations induced by association of human B2m with H-2Ld can affect the conformation of the alpha-1 and -2 superdomain. That class I antigenic determinants are altered by the association of human B2m with mouse class I further suggests that the class I molecule is structurally flexible and may reflect the ability of the class I molecule to bind and present a vast array of disparate peptides to the T-cell receptor.

Amino Acid Sequence↗
PubMed1989

Creation of H-2 class I epitopes using synthetic peptides: recognition by alloreactive cytotoxic T lymphocytes.

A major role that cytotoxic T lymphocytes (CTLs) play in the immune response is the specific destruction of viral-infected cells and tissue from foreign grafts. Class I molecules encoded within the major histocompatibility complex are the target structures for these CTLs. Recently, viral-restricted CTLs have been shown to recognize viral peptides in association with class I molecules, while several studies with cloned alloreactive CTLs have indicated that these T cells can recognize class I-derived peptides in association with class I molecules. Together, these observations suggest that peptide binding is an important function of class I molecules. In this paper, we show that the recognition of a particular class I molecule by a bulk population of alloreactive CTLs can be altered by incubating with it a peptide derived from another class I molecule. Specifically, we used the hybrid D/Ldm1 molecule as a target structure together with the peptide Ld61-85, and we have shown that their associative recognition by Ld-specific CTLs depends on sequence and configuration of the peptide and is specific for Ld using a cold-target inhibition assay. Our results are discussed in light of three possible models for the target structure(s) that can be recognized by alloreactive CTLs and in terms of the role peptides may play during allorecognition.

Amino Acid Sequence↗
PubMed1988

Molecular characterization of the C3HfB/HeN H-2Kkm2 mutation. Implications for the molecular basis of alloreactivity.

The C3HfB/HeN (C3Hf) mouse strain expresses an H-2Kk molecule, previously denoted H-2Kkv1, that is structurally and functionally distinct from H-2Kk of the parental C3H strain. By molecular genetic analysis, we demonstrate that the C3Hf H-2K gene carries a homozygous coding region mutation relative to the C3H allele, revealing that C3Hf meets the requirements for assignment of a mutant haplotype, H-2km2. C3Hf H-2Kkm2 bears a single clustered substitution of four nucleotides within 14 contiguous nucleotides in exon 3. Since this sequence also is present intact at the homologous position in H-2Dk of both C3H and C3Hf, the origin of the H-2Kkm2 mutation is consistent with a nonreciprocal sequence transfer from the H-2Dk donor gene, analogous to the mechanism proposed for generation of the H-2Kb mutations. The H-2Kkm2 mutation encodes three clustered amino acid substitutions, at positions 95, 98, and 99, that map to one of the large beta strands at the bottom of the peptide antigen binding cleft of the H-2Kkm2 molecule. The nature and location of these amino acid substitutions are unique relative to any other known H-2 mutant or HLA variant, and underscore the importance of the beta-pleated sheet in influencing CTL recognition. These results indicate that H-2Kkm2 alloantigenicity may derive largely from altered presentation of self cellular peptides.

Amino Acid Sequence↗
PubMed1988

Allospecific cytotoxic T lymphocytes recognize an H-2 peptide in the context of a murine major histocompatibility complex class I molecule.

We have isolated cytotoxic T lymphocytes (CTL) preferentially reactive with the alpha 1 external domain of the H-2Ld antigen by selecting for T cells capable of recognizing a variant major histocompatibility complex (MHC) class I antigen sharing alpha 1 sequences with H-2Ld. Using these CTL, we demonstrate that a synthetic alpha 1 peptide corresponding to one of the helices derived from the H-2Ld molecule can be presented by a class I restriction element to reconstitute a CTL determinant borne by intact H-2Ld. Moreover, several other H-2L-reactive CTL generated independently were also able to recognize H-2Ld either as an intact alloantigen or as a peptide in conjunction with appropriate class I restriction elements. These data demonstrate that an H-2 peptide can reconstitute a CTL target structure and suggest that some alloreactive T cells in fact might be directed against allogeneic class I peptides in the context of a class I framework.

Amino Acid Sequence↗
PubMed1988

Direct demonstration of critical amino acid residues required for cytotoxic T-lymphocyte allorecognition of H-2 class I antigens.

To identify critical amino acid residues recognized by alloreactive cytolytic T lymphocytes (CTL) generated between H-2Kb and H-2Kbm1, we have derived a series of cloned L-cell lines expressing the following mutant H-2Kb class I genes. Cell line L-KbTyr-Tyr expresses a mutant gene in which positions 155-156 of the Kb molecule have been changed from Arg-Leu to Tyr-Tyr, leaving position 152 unchanged. Cell line L-KbAla expresses the reciprocal mutant gene that has position 152 of the Kb molecule mutated from glutamic acid to alanine, leaving positions 155-156 unchanged. Electrophoretic mobilities of the mutant Kb molecules reflect only those changes predicted by the mutations. Mutant-specific (anti-Kbm1) and native-specific (anti-Kb) CTL lyse L-KbTyr-Tyr and L-KbAla target cells equally well. Unlabeled target inhibition of lysis revealed a pattern of recognition and inhibition that suggests that the amino acid differences between Kbm1 and Kb create at least two discrete determinants that can be recognized by different populations of CTL. The results suggest that these determinants consist, at least in part, of a linear amino acid sequence from which critical amino acid residues can be identified.

Amino Acid Sequence↗
PubMed1988

Plasma clearance and effects of alpha-hANP infused in patients with end-stage renal failure.

The effects and clearance of synthetic atrial natriuretic peptide (alpha-hANP) were investigated in eight patients with end-stage renal failure and six normal volunteers. ANP or vehicle was infused for 1 h at 10 pmol.kg-1.min-1 in random order on two separate occasions. During ANP infusions in end-stage renal patients, microhematocrit rose by 9.8 +/- 2% (P less than 0.005, n = 8), from base-line values of 0.24 +/- 0.02. Serum protein and albumin rose consistently. In contrast, during placebo infusions, no significant changes were seen. Blood pressure, heart rate, plasma renin concentration, serum creatinine, and electrolytes did not change significantly during either study phase. In end-stage renal failure patients, metabolic clearance rate of infused ANP was 1.04 +/- 0.095 l/min and its plasma half-life was 4 min 34 s. In normal volunteers, metabolic clearance rate was 2.6 l/min and its plasma half-life 3 min 30 s. The data suggest that ANP promotes contraction of plasma volume via a mechanism independent of renal function and also indicate that the kidney is not the only organ involved in the ANP metabolism.

Adult↗
PubMed1986

Phosphorylation of the mouse hepatitis virus nucleocapsid protein.

Analysis of the radiolabeled tryptic peptides derived from the nucleocapsid proteins of two serotypes of mouse hepatitis virus showed each to have a small number of unique peptides; however, two biologically distinct variants of the JHM strain appeared identical. Analysis of [32P]-labeled nucleocapsid-derived peptides showed that phosphorylation occurs at only a few sites and that all three viruses differed in the sites of phosphorylation. No differences in the sites of phosphorylation were found between the nucleocapsid proteins derived from purified virions and the membranes or the cytosol of infected cells, suggesting that post-translational phosphorylation plays no role in the regulation of viral assembly. These data show unequivocal evidence that the nucleocapsid proteins of mouse hepatitis virus strains differ in the sites of phosphorylation.

Capsid↗
PubMed1986

Phorbol esters inhibit alpha 1-adrenergic receptor-stimulated phosphoinositide hydrolysis and contraction in rat aorta: evidence for a link between vascular contraction and phosphoinositide turnover.

We investigated the actions of two biologically active phorbol esters, phorbol dibutyrate (PDB) and phorbol myristate acetate (PMA), on receptor-stimulated phosphoinositide hydrolysis in rat aorta. We found both PDB and PMA potently inhibited norepinephrine (NE) stimulated PI hydrolysis in rat aortic rings. The biologically inactive phorbol, 4-alpha-phorbol was ineffective. In the presence of the calcium channel antagonist nitrendipine, PDB potently inhibited both the phasic and tonic components of NE-induced contraction. These results suggest a functional coupling between receptor-stimulated PI turnover and vascular contraction. They also suggest a mode of feed-back regulation in vascular tissue involving phorbol esters in receptor-stimulated PI hydrolysis.

Animals↗
PubMed1986

Preliminary observations on the effect of dietary brussels sprouts on thyroid function.

Brassica vegetables are the major source of glucosinolates in the human diet. Certain glucosinolates are readily converted into goitrogenic species, notably 5-vinyloxazolidine-2-thione and thiocyanate ion. The effect of dietary Brussels sprouts, a particularly rich source of such glucosinolates, on thyroid function has been examined. Inclusion of cooked Brussels sprouts (150 g daily for 4 weeks) into a normal diet of 10 volunteer subjects had no effect on thyroid function as determined by measurement of thyrotrophic hormone, thyroxine and tri-iodothyronine even though the sprouts contained high concentrations (220 mg/100 g) of glucosinolates. In view of the reported antithyroid activity of 5-vinyloxazolidine-2-thione it is suggested that this lack of activity of cooked Brussels sprouts is due to inactivation during cooking of myrosinase, the specific glucosinolate-degrading enzyme.

Antithyroid Agents↗
PubMed1986

Potato steroidal alkaloids and neural tube defects: serum concentrations fail to demonstrate a causal relation.

Spoiled potatoes and, in particular, steroidal alkaloids have been proposed as an aetiological factor in the pathogenesis of neural tube defect (NTD). The present study involves the measurement of potato (solanum) steroidal alkaloid concentrations in serum by radioimmunoassay. Serum solanidine and total potato alkaloid concentrations were measured in two groups of women: one group pregnant with a fetus, subsequently shown to be affected by a NTD, the other with a healthy fetus. Serum alkaloid concentrations were, contrary to expectations, lower in the NTD group. They lend no weight therefore to the theory that potato alkaloids are responsible for NTD, but are consistent with the opinion that some water-soluble vitamins lessen the risk.

Diosgenin↗
PubMed1986

Pulmonary involvement in Sweet's syndrome (acute febrile neutrophilic dermatosis). Preleukemic and leukemic phases of acute myelogenous leukemia.

A 60-year-old man developed histologic lesions characteristic of acute febrile neutrophilic dermatosis in skin and lung during preleukemic and leukemic phases of acute myeloid leukemia. These lesions showed improvement and resolution during oral prednisone therapy, requiring higher doses during each relapse. The response to prednisone therapy was enhanced by concomitant administration of effective antileukemic chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1986

Hepatic alpha 1-adrenergic receptor alteration in a rat model of chronic sepsis.

Catecholamine therapy is often ineffective in reversing the peripheral vasodilatation and hypotension of septic shock. This suggests that catecholamines might not be able to activate alpha 1-adrenergic receptors to cause vasoconstriction. Despite elevations in endogenous catecholamines, hypoglycemia is also a complication of human sepsis, suggesting that among many other causes, hepatic alpha 1-receptors might be altered. To better understand the pathophysiologic basis for this pharmacologic dilemma, we studied the effect of experimental sepsis on alpha 1-adrenergic receptors in hepatic tissue, a rich source of alpha 1-receptors, from septic and control Sprague-Dawley rats. alpha 1-adrenergic receptors were measured with [3H]-prazosin and data analyzed by a computerized nonlinear least-square regression algorithm. Twenty-four hours following cecal ligation with puncture, a decreased number of alpha 1-adrenergic receptors was noted in crude and purified plasma membrane fractions (23 and 40% reductions respectively) from septic animals. No changes in either agonist or antagonist affinity for receptors from septic animals were noted. These data indicate that the catecholamine refractoriness seen in septic shock may be a result of alterations in alpha 1-adrenergic receptor number or receptor-effector coupling.

Animals↗
PubMed1985

Expression and T cell recognition of hybrid antigens with amino-terminal domains encoded by Qa-2 region of major histocompatibility complex and carboxyl termini of transplantation antigens.

Coding potential of the Q6 gene from the Qa-2a region of BALB/c Crgl mice was analyzed by a combination of hybrid class I gene construction and DNA-mediated gene transfer. Recombinant genes were created by exon shuffling of the 5' coding region of the Q6 gene and the 3' coding region of a gene encoding a transplantation antigen (Kd, Dd, or Ld), or the inverse. Some of these hybrid class I genes were expressed in the transfected mouse fibroblasts (L cells). The hybrid class I molecules encoded by the 5' end of the Q6 gene and the 3' end of the Ld gene precipitated as 45,000 mol wt molecules associated with beta 2-microglobulin. The expression of the hybrid proteins indicates that 926 basepairs of the 5' flanking region upstream of the structural Q6 gene contain a promoter that functions as a transcription initiation site in L cells. The 3' portion of the Q6 gene appears to be responsible for the lack of cell surface expression of the intact Q6 and the hybrid Ld/Q6 genes in mouse fibroblasts. Accordingly, this portion of the Q6 class I gene may play a regulatory role in tissue-specific expression. Serological analyses of hybrid Q6 proteins suggested that Q6 may be a structural gene for CR (H-2 crossreactive) antigen found normally on subpopulations of lymphocytes. If this identification is correct, Q6 gene will define a new category of class I genes encoding approximately 40,000 mol wt molecules and carrying a characteristic truncated cytoplasmic tail. Analysis of L cells transfected with Q6 hybrid genes demonstrated also that the cytotoxic T cells specific for Qa-2a region-coded antigens recognize the amino-terminal alpha 1-alpha 2 domain of Q6 fusion products. This recognition can be blocked by anti-Qa-2a alloantiserum and monoclonal antibodies reactive with the alpha 3-beta 2-microglobulin portion of the Q6 hybrids. We propose that the structural requirements for the anti-Qa-2a cytotoxic T lymphocyte-specific epitopes on target molecules are the same as for anti-H-2-alloreactive cytotoxic T lymphocyte determinants on transplantation antigens and that the mechanism of target recognition is similar in both cases. This interpretation is consistent with the following structural similarities found in both categories of class I molecules: (a) Kd and Q6 alpha 1-alpha 2 domains share serologically defined epitopes.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Identification of a unique tumor-specific antigen as a novel class I major histocompatibility molecule.

Cancers induced by physical or chemical carcinogens express tumor-specific antigens that are uniquely specific for any given tumor; therefore, there is a seemingly endless variety of these unique antigens. We have studied a UV-induced fibrosarcoma, designated 1591, to elucidate the obscure molecular nature and genetic origins of unique tumor-specific antigens. A monoclonal antibody raised against syngeneic 1591 tumor cells has unique tumor specificity. This tumor-specific monoclonal antibody precipitated from the tumor a 45-kDa molecule associated with a 12-kDa molecule having the pI of beta2-microglobulin. This and other evidence indicated that the 1591 tumor expresses a novel class I molecule. A 1591 variant selected for the absence of binding to the monoclonal antibody lacked the novel class I MHC molecule as well as reactivity with cytotoxic T lymphocytes specific for the 1591 tumor. Furthermore, tumor cells bearing the antigen are rejected while variants that have lost the antigen grow progressively. Fourteen of 14 host-selected progressor tumor variants lost reactivity with the monoclonal antibody and provided further evidence that this novel class I molecule is a transplantation antigen on the parental 1591 tumor required for immune rejection. The identification of a unique tumor-specific antigen as a novel class I major histocompatibility complex gene product allows us to search for the possible genetic mechanisms involved and to explore further the role such molecules play in tumor immunity and malignancy.

Animals↗
PubMed1985

Molecular characterization of novel H-2 class I molecules expressed by a C3H UV-induced fibrosarcoma.

Two novel class I-like molecules expressed on tumor 1591, a C3H UV-induced fibrosarcoma, are biochemically characterized using two-dimensional gel electrophoresis, a cross-blocking RIA, and tryptic peptide mapping. One novel molecule that reacts with CP28, a syngeneic tumor-specific monoclonal antibody, appears mosaic because it possesses characteristics of both Kk and Dk class I molecules. The second molecule is closely related but not identical to the bona fide Ld molecule expressed on BALB/c spleen. Thus 1591 expresses at least two novel class I molecules and is vigorously rejected by normal C3H mice, while a variant tumor derived from 1591, termed AS7, does not express these two class I molecules although it still expresses Kk and Dk. The significance of these observations to the immunobiology and genetics of the UV-induced fibrosarcoma system is discussed. Speculations on the role that the major histocompatibility complex may play in the immunosurveillance of neoplasms are also presented.

Animals↗
PubMed1985

Solanidine is present in sera of healthy individuals and in amounts dependent on their dietary potato consumption.

Solanidine, a steroidal alkaloid, and its glycosides have been reported to have caused poisoning in man and animals. These alkaloids are normally present in small amounts in potatoes. Measurement of solanidine in body fluid would be expected to establish the real incidence of acute toxicity and help to resolve the question of any chronic toxicity including teratogenicity. We report the detection of solanidine in the serum of 57 normal healthy volunteer subjects in whom it measured 4.0-56.3 nmol/l (1.6-22.5 ng/ml) before the midday meal. There was a significant correlation between serum solanidine concentration and normal dietary intake of potato by the individual concerned. When two subjects abstained from potato and its products serum solanidine fell markedly and became minimal after the second week onwards.

Adolescent↗
PubMed1985

Measurement of potato steroidal alkaloids in human serum and saliva by radioimmunoassay.

Radioimmunoassay methods are described for measuring potentially toxic potato glycoalkaloids and the aglycone solanidine in human serum and saliva. Solanidine and total alkaloid concentrations in serum and saliva during the summer are given for a group of subjects from the UK and a group from Sweden. Serum concentrations ranged from 3.2 to greater than 125 nmol/l for total alkaloid and 2.5 to 92.5 nmol/l for solanidine and were comparable in the two populations. Salivary total alkaloid concentrations were only about 10% of serum values. Salivary solanidine concentrations did not exceed 20% of the serum levels. Good correlation was found between serum and salivary alkaloid concentrations (r = 0.734, for solanidine; r = 0.892 for total alkaloid). Serum and salivary alkaloid concentrations were significantly raised in a group of Swedish subjects eating potatoes containing unusually high concentrations of alkaloids when compared with those in a group of subjects eating their normal diets.

Adult↗