Co-engagement of CD8 with the T cell receptor is required for negative selection.

Although it is established that the CD8 and CD4 co-receptors are involved in T-lymphocyte recognition and activation in the periphery, it is less clear whether these molecules participate in thymic selection events. Analysis of thymic selection in mice transgenic for T cell-receptor genes or for major histocompatibility complex (MHC) genes, or mice injected with antibodies against CD8, CD4 or MHC molecules, is consistent with the participation of CD8 and CD4 in thymic selection. But antibody-mediated crosslinking of surface receptors in thymic organ cultures has indicated that CD8 is not involved in thymic deletion.

The role of beta 2-microglobulin in peptide binding by class I molecules.

Efficient transport of class I major histocompatibility complex molecules to the cell surface requires association of the class I heavy chain with endogenous peptide and the class I light chain, beta 2-microglobulin (beta 2M). A mutant cell line deficient in beta 2M transports low amounts of nonpeptide-associated heavy chains to the cell surface that can associate with exogenously provided beta 2M and synthetic peptide antigens. Normal beta 2M-sufficient cells grown in serum-free media devoid of beta 2M also require an exogenous source of beta 2M to efficiently bind synthetic peptide.

Isolation and localization of a slow troponin (TnT) gene on chromosome 19 by subtraction hybridization of a cDNA muscle library using myotonic dystrophy muscle cDNA.

Subtraction hybridization techniques were used to isolate 91 cDNA clones which are overexpressed in normal control skeletal muscle relative to muscle from patients with myotonic muscular dystrophy. The gene responsible for myotonic dystrophy (DM) has been localized to the 19q13.2-13.

Cuticular lipid differences between the malaria vector and non-vector forms of the Anopheles maculatus complex.

Two chromosomal forms (E and F) of the Anopheles maculatus Theobald complex were distinguished by gas-liquid chromatographic (GC) analysis of cuticular lipids in association with a multivariate principal component analysis. The GC chromatogram obtained from n-hexane extracts of individual specimens showed no consistent qualitative differences in normalized peak areas between forms. Of the seventeen consistent peaks, five were found to be quantitatively different between forms at a high (99.

A real way forward in A&E. Developing the nurse-practitioner role.

The development of nurse-practitioners offers real scope for improvement in A&E services. However, if it is to be successful, the education must be properly established.

A comparison of magnetic and electrical stimulation of facial nerve at the cerebello-pontine angle in the dog.

Magnetic stimulation is a painless, non-invasive technique which allows an alternative method for testing cranial nerves which were previously inaccessible. We compared the latency of muscle responses obtained by electrical stimulation of the facial nerve at the cerebello-pontine angle (CPA) to high intensity transcranial magnetic stimulation (TMS) in 6 dogs. Evoked muscle response from the levator nasolabialis during electrical stimulation had a mean latency of 6.

Effects of cholinergic agonists on the dorsal immobility response.

The effects of pilocarpine, arecoline, and physostigmine on the dorsal immobility response in ovariectomized female rats were tested. The effect of pretreatment with the cholinergic antagonist scopolamine was also tested. Pilocarpine, arecoline, and physostigmine all significantly decreased the duration of the dorsal immobility response in a dose-dependent way.

Recognition by CD8 on cytotoxic T lymphocytes is ablated by several substitutions in the class I alpha 3 domain: CD8 and the T-cell receptor recognize the same class I molecule.

The CD8 molecule on class I-reactive cytotoxic T lymphocytes (CTLs) is believed to function as a coreceptor along with the alpha beta T-cell receptor. Whereas the alpha beta T-cell receptor recognizes polymorphic residues in the alpha 1/alpha 2 domains of the class I molecule, the CD8 molecule is believed to recognize monomorphic class I residues. Our previous experiments suggested that residue 227 in the alpha 3 domain of major histocompatibility complex class I molecules contributes to the determinant recognized by CD8.

Synergistic increases in IL-1 synthesis by the human monocytic cell line THP-1 treated with PAF and endotoxin.

The capacity to stimulate cytokine release may be important to the long-term effects of platelet-activating factor (PAF), which has a very short half-life. Previous studies have shown that PAF stimulates interleukin 1 (IL-1) release by human monocytes. IL-1 and other cytokines produced in response to PAF may be important to the long-term effects of this short-lived lipid.

Effect of proviral insertion on transcription of the murine B2mb gene.

We describe three B2mb mutants caused by integration of retroviral proviruses into the B2m gene. All three insertions occurred within 500 base pairs of each other in the 5' end of the first intron of the B2mb gene. Mutant cell line i1 contained a nonfunctional Abelson murine leukemia virus-initiated transcript that spliced into B2mb exon II; mutant cell lines i7 and i18 contained transcripts complementary to B2mb exon 1.

Substitution at residue 227 of H-2 class I molecules abrogates recognition by CD8-dependent, but not CD8-independent, cytotoxic T lymphocytes.

The CD8 (Lyt 2) molecule is a phenotypic marker for T lymphocytes that recognize and react with major histocompatibility complex (MHC) class I molecules. Antibody blocking experiments and gene transfection studies indicate that CD8 binds to a determinant on MHC class I molecules on the target cells, facilitating interaction between effector T lymphocytes and the target cell. The CD8 molecule may also be involved in transmembrane signalling during T-cell activation.

The Lyt-2 molecule recognizes residues in the class I alpha 3 domain in allogeneic cytotoxic T cell responses.

The involvement of the different domains of the MHC class I molecule in CTL recognition was investigated. mAbs specific for the alpha 1/alpha 2 domains of H-2Ld interfered with both the primary and secondary generation and effector function of in vitro Ld-specific CTL. mAbs specific for the alpha 3 domain of H-2Ld interfered with the generation and function of primary in vitro Ld-specific CTL; however, there was no effect on the in vitro generation of secondary CTL and only partial inhibition of their function.

Effect of bombesin and gastrin-releasing peptide on canine sphincter of Oddi.

This study reports the effects of bombesin and gastrin-releasing peptide (GRP) on the canine sphincter of Oddi using a method that allows repeated cannulation of the biliary sphincter in the unanesthetized animal through a Thomas cannula placed opposite the biliary papilla. Immediately after intravenous administration of bombesin or GRP, phasic sphincter contractions disappeared, basal sphincter pressures fell, and common bile duct pressures rose. Because bombesin releases cholecystokinin (CCK) and CCK resulted in a similar pattern to that of bombesin, the bombesin effect on the sphincter of Oddi may have been secondary to CCK's effect on the sphincter.

A single amino acid substitution in the alpha 3 domain of an H-2 class I molecule abrogates reactivity with CTL.

We previously described a somatic cell expressing a variant H-2Dd molecule that did not serve as a target for alloreactive anti-Dd CTL. The mutant cell line had been isolated by its failure to express a serological epitope present on the H-2Dd alpha 3 domain. In the present study the alpha 3 domain of the Dd molecule of this somatic cell variant was sequenced and a single nucleotide change resulting in a glutamic acid to lysine substitution at residue 227 was identified.

Expression of hemopoietic histocompatibility antigens on H-2-loss variants of F1 hybrid lymphoma cells: evidence consistent with trans gene regulation.

H-2 heterozygous marrow stem cells, lymphoid progenitor cells, and leukemia/lymphoma cells do not express hemopoietic or hybrid histocompatibility (Hh) antigens, which are important transplantation antigens recognized during the rejection of normal or neoplastic hemopoietic cells. The Hh-1b determinant of the H-2b haplotype maps to the D region of H-2. We have tested the hypothesis that gene(s) at or near H-2D of the H-2d haplotype down-regulate the expression of Hh-1b in the trans configuration.

Mitotic recombination between homologous chromosomes generates H-2 somatic cell variants in vitro.

A spontaneously arising variant clone that does not express the H-2Dd and H-2Ld molecules was isolated by immunoselection from an (H-2b X H-2d)F1 cell line. This variant clone expresses H-2Kb, H-2Db, and H-2Kd molecules. Southern blot analysis demonstrated that the variant was heterozygous at the H-2K, I, and S loci but had lost the H-2Dd and H-2Ld genes.

Spontaneous deletion at the B2m locus: evidence for site-specific genetic rearrangement.

We have isolated 20 independent spontaneous mutants in the B2mb allele from a B2ma/b heterozygous murine cell line by immunoselection in vitro with a monoclonal antibody directed against the product of the B2mb allele. One class of mutants has undergone a deletion in the 5' end of the B2mb gene. The deletions appear to be identical in all of the independent clones, and extend an unknown distance upstream of the B2m gene from a region in the first intron.

Retroviral insertional mutagenesis of a target allele in a heterozygous murine cell line.

A clonal murine cell line that is heterozygous at the beta 2-microglobulin locus (B2m) was obtained by Abelson murine leukemia virus (Ab-MuLV) transformation of liver cells from (C57BL/6 X BALB/c) F1 fetuses. To obtain proviral insertional mutants, we superinfected a subclone of these cells, which does not express the env surface protein of the Moloney leukemia virus (Mo-MuLV, the helper virus that was used to transmit the defective Ab-MuLV genome during transformation), with Mo-MuLV. Mutant clones that fail to express the C57BL/6 allele of B2m (B2mb) were then immunoselected by using a monoclonal antibody that specifically recognizes the B2mb gene product and not that of the B2ma allele.

Molecular analysis of an EL4 cell line that expresses H-2Db but not H-2Kb or beta 2-microglobulin.

EL4/Mar is a variant cell line that expresses H-2Db but neither H-2Kb nor beta 2-microglobulin (beta 2m). Southern and RNA blot analysis and immunoprecipitation of metabolically labeled proteins established that the B2m gene(s), beta 2m mRNA, and beta 2m protein are normal in this cell line. Somatic cell hybridization showed that the defect in this cell line was in the synthesis of H-2Kb, and RNA blot analysis with an H-2Kb specific oligonucleotide established that the H-2Kb gene(s) in this cell line was not transcribed into a stable mRNA species.

Genetic control of natural resistance to Trypanosoma rhodesiense: transfer of resistance with bone marrow or spleen cells.

Inbred strains of mice differ greatly in their innate resistance to Trypanosoma rhodesiense, the etiologic agent of African sleeping sickness. BALB/c mice are very susceptible to this organism, whereas C57BL/6 mice are highly resistant. This difference is regulated by at least three distinct genes.

Activated charcoal: in vivo and in vitro studies of effect on gas formation.

It has been reported that activated charcoal reduces intestinal gas production after ingestion of beans as evidenced by decreased breath hydrogen excretion and decreased passage of flatus. In the present study we assessed the ability of activated charcoal to reduce intestinal gas production by in vitro and in vivo methods. In vitro studies were performed using human fecal homogenates incubated with or without additional carbohydrate.