Localization of the disulfide bridges of human histocompatibility antigens.

Both papain-solubilized and detergent-solubilized human histocompatibility antigens have been treated with NTCB (2-nitro-5-thiocyanatobenzoic acid) which cleaves these molecules at cysteine residues. A study of the fragment produced has made it possible to deduce the size and location of the two disulfide loops in these molecules. The sizes of the two loops in HLA-B7 and in the mixture HLA-B7 + 12 are about 5100 and 6600 daltons, a size similar to that of the disulfide loops found in immunoglobulins. The disulfide loops in HLA-A2 may be smaller in size. The two loops are located in middle regions of these molecules; neither the N-terminal nor the C-terminal regions contain disulfide loops.     

Apoptosis, tolerance, and regulatory T cells – old wine, new wineskins

Summary: Antigen‐specific unresponsiveness (or tolerance) has always been an important area of research. Interest in the fate of apoptotic cells and their ability to tolerize has revived interest in some of the older models involving hapten‐modified self. Recently, we have examined the mechanisms by which intravenous injection of trinitrophenol‐coupled spleen cells leads to systemic tolerance. These studies have revealed an important role for Fas/Fas ligand interactions, caspases, CD40/CD40L, and regulatory CD4⁺ and CD8⁺ T cells. Extension of these studies to peripheral deletion of T‐cell antigen receptor transgenic T cells has shown that deletion and active regulation of immune responses may be important mechanisms for the control of potentially damaging autoimmune responses.     

Differentiation of Campylobacter species by protein banding patterns in polyacrylamide slab gels.

Soluble protein extracts of 37 catalase-positive strains of Campylobacter species were examined by polyacrylamide slab gel electrophoresis (PAGE). Electrophoretic banding patterns showed good correlation with biochemical tests and with available DNA homology data in distinguishing species of Campylobacter but did not differentiate subspecies or biotypes. PAGE patterns indicated that Campylobacter coli is a distinct species. Furthermore, the PAGE patterns indicated that C. jejuni and nalidixic acid-resistant thermophilic Campylobacter species (C. laridis) are each distinct species. The protein banding patterns of C. fetus subsp. venerealis and C. fetus subsp. fetus strains were distinctly different from those of the three thermophilic species.     

Expression of collagen, interstitial collagenase, and tissue inhibitor of metalloproteinases-1 in restenosis after carotid endarterectomy.

Extracellular matrix is the principal component of the fibrous caps of atherosclerotic plaques and intimal hyperplastic lesions of reconstructed arteries. Interstitial collagen form an important part of the matrix, and the balance between collagen synthesis and degradation by interstitial collagenase (matrix metalloproteinase-1, MMP-1) may determine whether plaques rupture or vessels develop stenosis. We examined type I procollagen gene expression in human atherosclerotic and restenotic carotid arteries using in situ messenger RNA (mRNA) hybridization and the expression of MMP-1 and its endogenous inhibitor (tissue inhibitor of metalloproteinases-1, TIMP-1) by immunohistochemistry. Compared with normal arteries, atherosclerotic plaques bed increased expression of immunoreactive MMP-1 and TIMP-1 with modest increase of type 1 procollagen mRNA. Early restenotic lesions (< 1.5 years) contained abundant type I procollagen mRNA but little immunoreactive MMP-1 and TIMP-1. Late restenotic lesions (> 4 years) resembled atheroma and exhibited increased immunoreactive MMP-1 and TIMP-1 as well as abundant type I procollagen mRNA. Compared with atherosclerotic plaques, type I procollagen is increased and MMP-1 is decreased in early restenotic lesions. MMP-1 and TIMP-1 expressions are upregulated in lesions with a clear atheroma. These findings suggest that the balance between proteolysis and matrix synthesis may influence both the stability of atheromatous plaques and the development of restenotic lesions.     

Polylysine binding to unphosphorylated smooth muscle myosin enhances formation and stabilizes myosin filaments in vitro

Previously, we demonstrated that positively charged polylysine, our model for biological polyamines, activates the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin and shifts the myosin conformation from the folded 10S to linear 6S form. These effects of polylysine were reversed by the oppositely charged heparin (Szymanski et al. (1993) Am J Physiol 265, C379). In the present report, we provide further information on polylysine binding to smooth muscle myosin, and test the hypothesis that polylysine binding to unphosphorylated myosin involves filament formation. To relate the effects of polylysine on contractility in smooth muscle to physiologically relevant material, we investigated the ability of naturally occurring positively charged polyamines, histones, cadaverine, putrescine and spermidine to activate the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin. Our data show that polylysine binding to individual unphosphorylated myosin molecules stimulates formation of myosin filaments. Polylysine also interacts with myosin filaments, causing enhancement of their size and the numbers, and this could be reversed by heparin. Polylysine binding to myosin filaments made them more resistant to disassembly by high salt concentrations (KCl) or ATP. Naturally occurring polyamines in millimolar concentrations activate the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin. We suggest that the electrostatic interactions between naturally occurring positively charged polyamines and unphosphorylated smooth muscle myosin may play a role in stabilization of thick filament structurein situ.     

The incidence of thyroglobulin antibodies and thyroid enlargement in a general practice in north-east England

Antibodies to thyroglobulin in a titre of 1:25 or more were found in 16·2% of women and 4·3% of men between the ages of 21 and 80 years in a random sample of the population from a general practice in the north-east of England. The incidence of antibodies was highest in the seventh decade in both sexes. High antibody titres (1:78125 or more) were found in 4·6% of women and 1·6% of men and it is suggested that this may represent the incidence of diffuse thyroiditis in the population.

Significant thyroid enlargement was found in 12% of women and 0·9% of men, the corrected incidence of goitre obtained by averaging the frequency of goitres in each decade between 21 and 80 years was 8·9% and 0·9% respectively.

     

High prevalence of Helicobacter pylori in saliva demonstrated by a novel PCR assay.

AIMS--To investigate the prevalence of Helicobacter pylori in the saliva of patients infected with this bacterium. METHODS--A novel polymerase chain reaction (PCR) assay was developed to detect H pylori in saliva and gastric biopsy specimens from patients undergoing endoscopy. RESULTS--Our PCR assay amplified a 417 base pair fragment of DNA from all 21 DNAs derived from H pylori clinical isolates but did not amplify DNA from 23 non-H pylori strains. Sixty three frozen gastric biopsy and 56 saliva specimens were tested. H pylori specific DNA was detected by PCR in all 39 culture positive biopsy specimens and was also identified from another seven biopsy specimens which were negative by culture but positive by histology. H pylori specific DNA was identified by PCR in saliva specimens from 30 (75%) of 40 patients with H pylori infection demonstrated by culture or histological examination, or both, and in three patients without H pylori infection in the stomach. CONCLUSION--The results indicate that the oral cavity harbours H pylori and may be the source of infection and transmission.     

Ectopic production of human chorionic gonadotrophin-like material by breast cancer

Human chorionic gonadotrophin (hCG) is a placental protein whose ectopic secretion by nontrophoblast tumors has been claimed to be of clinical relevance. Serum levels of hCG were measured in 570 patients with breast disease. A double-antibody radioimmunoassay (RIA) using antisera to hCG-beta was employed. Approximately 14% of patients with breast cancer were found to have elevated serum hCG levels. Such raised titers were not stage- or tumor-type-related, but occurred only in postmenopausal subjects. Further study showed that those patients with elevated hCG levels also had raised levels of human luteinizing hormone (hLH). Assay cross-reactivity was shown to account for the "spurious" hCG elevations. An immunocytochemical study also failed to find hCG an ectopic breast tumor constituent and/or product. It is concluded that hCG is not produced by breast tumors and has no clinical utility.