Solution binding of an antigenic peptide to a major histocompatibility complex class I molecule and the role of beta 2-microglobulin.

The major histocompatibility complex-encoded class I molecule, a noncovalent dimer of a polymorphic 45-kDa heavy chain and a nonpolymorphic 12-kDa beta 2-microglobulin (beta 2m) light chain, binds peptide antigen prior to its interaction with T-cell antigen receptors. We report here that the binding in aqueous solution at 37 degrees C of a soluble purified murine major histocompatibility complex class I protein, H-2Lds (a soluble analogue of H-2Ld consisting of the alpha 1 and alpha 2 domains of H-2Ld, the alpha 3 domain and the C terminus of Q10b), to an antigenic peptide is controlled by the light-chain subunit beta 2m. Analysis of the equilibrium binding data favors a model in which two classes of peptide binding sites exist, the high-affinity class having an equilibrium constant for dissociation, KH, of 3.

Patterns of E74A RNA and protein expression at the onset of metamorphosis in Drosophila.

Metamorphosis in Drosophila is triggered by a pulse of the steroid hormone ecdysone at the end of larval development. Ecdysone initiates a genetic hierarchy that can be visualized as a series of puffs in the larval salivary gland polytene chromosomes. The E74 gene is responsible for the early ecdysone-inducible puff at position 74EF and encodes two related DNA-binding proteins which appear to play a regulatory role in the hierarchy.

Characterization of an Escherichia coli gene encoding betaine aldehyde dehydrogenase (BADH): structural similarity to mammalian ALDHs and a plant BADH.

An open reading frame of 1476 nucleotides, cloned from a region of the Escherichia coli genome encoding betaine biosynthesis functions, was shown to encode a betaine aldehyde dehydrogenase (BADH; EC 1.2.1.

Magnitude and time course of extracellular potassium inhomogeneities during acute ischemia in pigs. Effect of verapamil.

Prior studies have demonstrated the presence of inhomogeneities in myocardial [K+]e after serial 10-minute occlusions of the left anterior descending coronary artery in the pig, even within restricted locations of an ischemic zone. These inhomogeneities are thought to underlie the electrophysiological abnormalities responsible for lethal ventricular arrhythmias through reentrant and nonreentrant pathways, but a clear association has not been demonstrated. As a prerequisite to establishing this association, these studies were performed to establish measurement standards for [K+]e inhomogeneity, to quantify the magnitude and time course of these inhomogeneities, to determine whether the inhomogeneities are greater in the ischemic border where lethal ventricular arrhythmias are known to originate, and to assess the effect of a known antifibrillatory drug on [K+]e inhomogeneities.

Excess beta 2 microglobulin promoting functional peptide association with purified soluble class I MHC molecules.

T lymphocytes expressing alpha beta receptors recognize antigenic peptide fragments bound to major histocompatibility complex class I or class II molecules present on the surface membranes of other cells. Peptide fragments are present in the two available HLA crystal structures and recent data indicate that peptide is required for the stable folding of the class I heavy chain and maintenance of its association with the class I light chain, beta 2-microglobulin (beta 2m), at physiological temperature. To explain how the exogenous peptide used to create targets for cytotoxic cells bearing CD8 antigen could associate with apparently peptide-filled extracellular class I molecules, we hypothesized that stable binding of exogenous peptide to mature class I molecules reflects either the replacement of previously bound peptide during the well documented beta 2m exchange process or the loading of 'empty' class I heavy chains dependent on the availability of excess beta 2m.

An investigation of skin deformation around percutaneous devices.

According to the literature one of the primary failure models of percutaneous devices (PDs) in soft tissue implantation sites is that of mechanically induced trauma along the implant/tissue interface. In order to avoid such avulsion, subcutaneous flanges have been incorporated into PD designs to provide a better distribution of stresses along the implant/tissue interface. Tissue necrosis and inflammation were then observed to be most pronounced around the rim of the subcutaneous flange.

Pyomyositis in an HIV-positive premature infant: case report and review of the literature.

Pyomyositis is a purulent infection of skeletal muscle caused predominantly by Staphylococcus aureus. Although not often encountered in the continental United States, pyomyositis is frequently seen in tropical areas. Pyomyositis is difficult to diagnose as it may mimic other diseases.

Giant mitochondria distinct from enlarged mitochondria in secretory and ciliated cells of gerbil trachea and bronchioles.

Numerous mitochondria ranging from slightly larger than normal to several micrometers in diameter (giant) were found in about one-half the serous secretory cells in the surface epithelium of the normal gerbil trachea and proximal bronchi. Tracheal serous cells of mice also were found to contain numerous giant mitochondria. Clara cells of gerbil bronchioles contained abundant giant mitochondria in addition to normal tubular mitochondria and the second population of enlarged spherical mitochondria that have been described in Clara cells of several genera.

The extracellular domains of MHC class II molecules determine their processing requirements for antigen presentation.

We have evaluated the relative contributions of the extracellular and cytoplasmic domains of MHC class II molecules in determining the Ag-processing requirements for class II-restricted Ag presentation to T cells. Hybrid genes were constructed to encode a heterodimeric I-Ak molecule in which the extracellular portion of the molecule resembled wild type I-Ak but where the connecting stalk, transmembrane and cytoplasmic domains of both the alpha- and beta-chain were derived from the class I molecule H-2Dd. Mutant I-Ak molecules were expressed as heterodimeric membrane glycoproteins reactive with mAb specific for wild type I-Ak.

Factors affecting health club attendance: a comparison of simple and elaborate settings.

Changes in physical fitness associated with two types of health clubs over a three month period were investigated. Factors associated with attendance at a "complex" club and a "simple" club were examined. Ten apparently healthy women were selected randomly from women joining each of these health clubs.

T cell activation by purified, soluble, class I MHC molecules. Requirement for polyvalency.

To examine the nature of the interaction of the TCR with the MHC class I Ag, we have studied the stimulation requirements of an H-2Dd-reactive T cell hybridoma, using a homogeneous, purified preparation of a molecularly engineered soluble counterpart of the class I Ag, H-2Dd/Q10b. We demonstrate that this monovalent, soluble MHC Ag is incapable of stimulating the release of IL-2 from this T cell hybridoma. However, the same preparation of the purified protein can elicit a dose-dependent response when made multivalent either by covalent coupling to soluble, high m.

Cell surface expression of the amino-terminal domain of A kappa alpha. Recognition of an isolated MHC antigenic structure by allospecific T cells but not alloantibodies.

To evaluate the relationship between structure and function of the alpha 1 and beta 1 domains of class II MHC molecules, a strategy has been developed whereby isolated alpha 1 or beta 1 domains can be expressed on the surface of transfected mouse L cells as a part of a hybrid class II/class I molecule. The construction and expression of a chimeric class II/class I gene encoding the first two exons of A kappa alpha linked to the C2, TM and cytoplasmic exons of H-2Dd (A kappa alpha 1/DdC2) are described. High levels of A kappa alpha 1/DdC2 protein were detected on transfected L cells with a DdC2-specific mAb.

The outcome of fractures of the distal radius in young adults.

Fractures of the distal radius in young adults are not uncommon, but have received little attention in the literature. This paper reports a series of 40 fractures of the distal radius. The quality of reduction was found to relate directly to the final result.

Scanning electron microscopy of the substructure of smear layers in human dentine.

Smear-layer debris was sonicated from dentine surfaces and trapped on microfilters for microscopy, which showed that the layers are composed, in part, of aggregates of globular subunits approx. 0.05-0.

Readability of computer display print enlarged for low vision.

A letter counting task was presented on a Macintosh computer screen using two different versions of 24 point Times Roman print. One version, called "grainy," had 12 matrix units per font height and the other, called "smooth," had 24. A mixed group of low vision subjects and a normally sighted group had speed and accuracy measured as they performed the test task from two different viewing distances.

Disinfection of metal and plastic pelvic specula in general practice.

One hundred and sixteen general practices in Wellington were surveyed about their use and disinfection of gynaecological specula. Two thirds of the practices used metal specula which were adequately disinfected by boiling for at least one hour. Of the 46 practices that used plastic specula, only four always disposed of them, as recommended, after use.

Analysis of positional isomers of monounsaturated fatty acids by high performance liquid chromatography of 2,4-dinitrophenylhydrazones of reduced ozonides.

A method is described for quantifying the positional isomers in monounsaturated fatty acid methyl ester (FAME) fractions. The procedure involves the preparation of 2,4-dinitrophenylhydrazones (DNPH) of the fragments generated during reductive ozonolysis of FAME, class isolation of the aldehyde and aldehyde ester DNPH, and separation of the aldehyde ester derivatives by high performance liquid chromatography (HPLC). The high extinction coefficient of the DNPH provides for a sensitive assay which is linear for a large range of components over a concentration range of 0.

Analysis of hybrid H-2D and L antigens with reciprocally mismatched aminoterminal domains: functional T cell recognition requires preservation of fine structural determinants.

Studies of immune recognition of hybrid class I antigens expressed on transfected cells have revealed an apparent general requirement that the N(alpha 1) and C1(alpha 2) domains be derived from the same gene in order to preserve recognition by virus-specific H-2-restricted and allospecific T cells. One exception has been the hybrid DL antigen in which the N domain of H-2Ld has been replaced by that of H-2Dd. Cells bearing this molecule serve as targets for some virus and allospecific CTL.

Behavior problems of equids in zoos.

Behavior problems in zoo equids commonly result from a failure to provide for needs basic to equine nature. Equids are gregarious, and failure to provide companions may result in pacing. Wild equids spend 60 to 70 per cent of their time grazing, and failure to provide ad libitum roughage contributes to the problems of pacing, cribbing, wood chewing, and coprophagia.

Alternative processing of H-2Dd pre-mRNAs results in membrane expression of differentially phosphorylated protein products.

Two distinct mRNA species encoding the mouse major histocompatibility antigen H-2Dd have been identified in BALB/c spleen cells as well as in cultured cell lines expressing this cell surface glycoprotein. The alternate transcripts of H-2Dd arise from either removal or inclusion of exon VII (encoding I2) during pre-mRNA processing. The relative levels of each kind of H-2Dd transcript varied considerably between different cell types, and in all cells examined both forms of alloantigen were expressed on the cell membrane.

Genetic engineering of an H-2Dd/Q10b chimeric histocompatibility antigen: purification of soluble protein from transformant cell supernatants.

We have constructed a recombinant class I gene in which 5' sequences of H-2Dd are linked to the 3' half of a Qa subregion gene, Q10b. This hybrid gene would be expected to direct the synthesis of a protein containing the N and C1 domains of H-2Dd covalently linked to the C2 domain of the secreted, nonpolymorphic, Q10b antigen. Following DNA-mediated gene transfer into mouse L cells, transformants were analyzed by radiolabeling and immunoprecipitation.