Biomedical subjects

E J Baas

Publications and source records attributed to E J Baas.

8 recordsLinked to original sources

PubMed1992

Peptide-induced stabilization and intracellular localization of empty HLA class I complexes.

The human cell line T2 has been reported to be class I assembly deficient, and accordingly expresses reduced amounts of HLA-A2 and no HLA-B5 at the cell surface. By immunoblotting we observe the steady-state class I heavy chain levels of T2 to be near normal when compared with the identical class I alleles of the wild-type cell line T1. In pulse chase experiments, formation of heavy chain beta 2-microglobulin complexes is observed for both HLA-A2 and HLA-B5. Culture at reduced temperatures (26 or 20 degrees C) does not increase the amount of class I molecules transported, unlike what has been reported for the class I assembly-deficient mouse mutant cell line RMA-S. The HLA-B5 and the HLA-A2 complexes formed by T2 are thermolabile in cell lysates, albeit to different degrees. The thermolability of HLA-B5 can be overcome by addition of HLA-B5-presentable peptides, obtained by trifluoroacetic acid extraction from an HLA-B5-positive cell line, underlining the necessity of peptide for class I stability and indicating that T2-derived class I complexes are devoid of peptide. Cytoplast fusion of T2 cells with RMA-S cells shows the defect in class I assembly of RMA-S to be similar to that of T2. Localization of class I molecules observed by immuno-electron microscopy reveals the accumulation in the T2 cell line of both HLA-B5 and HLA-A2 in the endoplasmic reticulum (ER). Class I molecules are present in all the cisternae of the Golgi complex of T2, but the ratio of HLA-A and -B locus products in the Golgi area differs significantly from that at the cell surface. We conclude that the requirement for peptide in transport of class I molecules manifests itself at a stage beyond the ER, most likely the Golgi area.

Cell Line↗

PubMed1988

Molecular analysis of HLA-DP specificities HLA-DPw1, -DPw2 and -DPw4: DP beta chain heterogeneity correlates with PLT subtyping.

HLA-DP molecules were isolated from Epstein-Barr virus transformed B cell lines by immunoprecipitation with monoclonal antibody B7/21.2 and subsequently analysed by two-dimensional gel electrophoresis. The results obtained demonstrate that the HLA-DP molecules that can be isolated from cells positive for the HLA-DP specificities HLA-DPw1, -DPw2 and -DPw4 display DP beta chain isoelectric point differences, whereas no DP alpha chain polymorphism was observed. These results suggest that the PLT defined HLA-DP specificities (HLA-DPw1, -DPw2 and -DPw4) are probably DP beta chain structures.

Cell Line↗

PubMed1987

Molecular diversity of HLA-DQ. DQ alpha and beta chain isoelectric point differences and their relation to serologically defined HLA-DQ allospecificities.

HLA-DQ molecules were isolated from a panel of HLA-DR-DQ homozygous cell lines, partially of consanguineous origin, derived by the use of monoclonal antibody SPV-L3, and subsequently analyzed by gel electrophoretic techniques. It is demonstrated that both the DQ alpha and beta chain exhibit an extensive isoelectric point polymorphism. Within a panel of 29 B-cell lines tested, at least 5 distinct alpha and 6 distinct DQ beta chain gene products were observed. Of the 30 theoretically possible DQ alpha-beta dimers, only 10 could be identified within the panel: 5 different dimers are associated with the DQw1 allospecificity; HLA-DQw2 and -DQw3 are associated with 2 types of dimers, whereas another DQ alpha-beta combination was expressed by a cell line with a so-called DQ-blank specificity. The relation between the specificities 2B3 and TA10 appeared to be complicated as far as DQ beta chain isoelectric point differences are concerned: monoclonal antibody IIB3 seems to be reactive with four distinct DQ beta chain alleles whereas monoclonal antibody TA10 only reacted with one type of DQ beta chain. These results suggest that the polymorphic DQ alpha and beta chains may both contribute to the definition of the HLA-DQ allospecificity. A particular DQ beta chain was present in two types of HLA-DQw1 molecules, as well as in one type of HLA-DQw2 and -DQw3 (2B3 positive) molecule, and formed dimers with electrophoretic distinct DQ alpha chains. On the other hand, HLA-DQw2 molecules isolated from HLA-DR3-positive cells and one type of HLA-DQw3 (TA10 positive) molecule were found to be constructed of identical alpha chains but appeared to differ in the composition of their DQ beta chain gene products. The implications of these findings will be discussed.

Alleles↗

PubMed1977

Epidemic caprine keratoconjunctivitis: recovery of Mycoplasma conjunctivae and its possible role in pathogenesis.

Clinical, microbiological, serological, histological, and therapeutic aspects of two separate outbreaks of caprine keratoconjunctivitis are described. The disease was characterized by a high rate of contagion, rapid onset, intense lacrimation, conjunctival hyperemia, and corneal opacity with neovascularization. In addition, many of the animals developed respiratory illness during the second epidemic. The only organism consistentlyisolated was Mycoplasma conjunctivae. A total of 23 strains were isolated from 18 inflamed conjunctivae, one normal conjunctiva, and the nasal secretions of four goats with concomitant respiratory illness. The convalescent sera of goats in the first outbreak had neutralizing antibody titers to M. conjunctivae that ranged from 1:32 to 1:256. In the milder second outbreak the antibody titers ranged from 1:4 to 1:32 in animals with only ocular disease and from 1:4 to 1:64 in animals with only respiratory disease. Whereas little change was noted in antibody titers of goats with only localized eye disease, 43% of the goats with respiratory disease showed significant fourfold rises. The histological picture was consistent with acute corneal infection. Animals requiring antibiotic treatment appeared to respond favorably to a combination of oxytetracycline and polymyxin B, but not to penicillin. These findings suggest that M. conjunctivae is one cause of epidemic caprine keratoconjunctivitis.

Animals↗

PubMed1977

Epidemic caprine keratoconjunctivitis: experimentally induced disease with a pure culture of Mycoplasma conjunctivae.

The induction of caprine keratoconjunctivitis by the subconjunctival inoculation of a cloned culture of Mycoplasma conjunctivae is described. The clinical course of the experimental disease was similar to that noted in naturally occurring outbreaks of "pink-eye" among goats, and biopsies of inflamed conjunctivae showed similar histological response. M. conjunctivae was consistently recovered from the inflamed conjunctival tissues of inoculated animals that developed ocular disease, thus fulfilling Koch's postulates and establishing this organism as an etiological agent of caprine keratoconjunctivitis. Immunological studies suggested that cellular immune mechanisms may play a role in protecting animals from disease produced by this mycoplasma.

Animals↗

PubMed1976

An evaluation of sedatives and anesthetics in the agouti (Dasyprocta sp).

Seven drugs administered im were evaluated to determine their efficacy in immobilizing captive agoutis. Ketamine HCl (63-83 mg/kg) and phencyclidine HCl (16.5-22.0 mg/kg) produced immobilization and analgesia. Phencyclidine administration was accompanied by numerous side effects and prolonged recovery. Xylazine HCl (3-70 mg/kg) and fentanyl-droperidol (0.28-1.11 ml/kg( produced varying degrees of ataxia and intermittent recumbency. Acetylpromazine, chlorpromazine, and promazine HCl were ineffective. Surgical anesthesia was successfully induced and maintained with halothane.

Analgesia↗

PubMed1976

The agouti (Dasyprocta sp) in biomedical research and captivity.

Agoutis (Dasyprocta sp) are hystricomorph rodents belonging to the family Dasyproctidae. Utilization of agoutis in a research program of the National Institutes of Health necessitated the development of suitable methods for feeding, housing and collecting blood. The rodents were maintained successfully in conventional dog cages and kennels, and thrived on a diet of primate diet and apples. Physical examinations and periodic blood collections were best performed while agoutis were sedated with ketamine HCl (42-83 mg/kg, intramuscularly). Satisfactory sites for blood sampling were the cephalic, saphenous and jugular veins. Hematologic and serum chemical values established for the agouti were similar to those found in other rodents. Experimentally induced and naturally occurring diseases of agoutis were reviewed.

Anesthesia↗

PubMed1972

Agar block technique for identification of mycoplasmas by use of fluorescent antibody.

A procedure for staining mycoplasmata colonies directly on agar blocks for examination by fluorescent microscopy is described. Areas of the agar surface appropriate for staining were demarcated by use of Lucite cylinders. Direct fluorescent-antibody staining was superior to indirect staining. The technique was very useful for determining whether cultures were mixed and for identification of mycoplasmas in either pure or mixed cultures.

Acrylic Resins↗