Genetic diversity and identification of human infection by amplification of the chlamydial 60-kilodalton cysteine-rich outer membrane protein gene.

The 60-kDa cysteine-rich outer membrane protein genes of Chlamydia psittaci, Chlamydia pneumoniae, and Chlamydia trachomatis have very different 5' ends, but two areas flanking this variable region show absolute sequence conservation. This observation permitted differentiation of the three species of Chlamydia by the polymerase chain reaction (PCR), forming the basis of a diagnostic test for chlamydial infections. The PCR product containing the variable region of the respective 60-kDa CrP genes was also subjected to restriction endonuclease digestion, enabling differentiation of individual type strains of C. psittaci. Differentiation was possible between lymphogranuloma venereum and trachoma isolates of C. trachomatis. The PCR-based diagnostic test was successful with all strains of chlamydiae studied. The PCR primers showed high specificity and did not produce any product with common bacterial pathogens that may share the same sites of infection.     

Immunity to type IX collagen in rodents: a study of type IX collagen for autoimmune and arthritogenic activities

Type IX collagen (CIX), a cartilage-specific glycoprotein, constitutes ≤ 10% of cartilage collagen. To ascertain whether CIX can induce arthritis as shown for type II and XI collagen (CII and CXI), outbred rats were sensitized with bovine, chick and human CIX; inbred rats, mice, and guinea pigs were sensitized with bovine CIX. Mice and guinea pigs proved resistant to arthritis, as did rats sensitized with CIX/Freund's incomplete adjuvant (FIA). Arthritis was seen in rats when 100 μg of Mycobacterium tuberculosis (Mtb) were added to FIA, but seldom with smaller doses of Mtb, suggesting the arthritis was adjuvant-induced. High levels of antibodies to rat CIX, containing complement-fixing subclasses, were detected in rat sera in addition to DTH and lymphocyte proliferation responses to rat CIX. Given the potential for CIX-induced disease, CIX-sensitized rats were injected intraperitoneally with lipopolysaccharide (LPS) to stimulate proinflammatory cytokine release, and intra-articularly with rat CIX to stimulate arthritis. LPS stimulation was ineffective; however, intra-articularly injected CIX produced transient synovitis. When rats with stable adjuvant arthritis were sensitized with CIX/FIA, significant increases in paw volume were measured compared with controls given CI/FIA. Immunohistochemical studies of actively and passively sensitized rats revealed deposits of CIX antibody, but not C3, at the joint margins where proteoglycan staining was weak. Together, these findings suggest that autoimmunity to CIX, in contrast to CII and CXI, is not directly pathogenic but may contribute to joint injury provided arthritis is initiated by an independent disease process.     

Population studies of the fragile X: a molecular approach.

The fragile X mutation can now be recognised by a variety of molecular techniques. We report a pilot screening survey of a population of children with mental impairment in which we used Southern blotting methods to detect the fragile X mutation, augmented by cytogenetic studies on children whose phenotype suggested a possible chromosome abnormality. There were 873 children with special educational needs in our survey and 310 fulfilled our criteria for testing. A sample was obtained from 254, of whom four were found to have a full fra(X) mutation (delta L) and none to have a premutation. The number of CGG repeats in our population of X chromosomes was measured by PCR analysis and the genotype at the closely linked polymorphic locus FRAXAC1 established. The distribution of CGG repeat numbers was very similar to that of the control population reported by Fu et al and the distribution of FRAXAC1 alleles almost identical to that of the control population reported by Richards et al. Among the non-fragile X chromosomes, we found a very significant correlation between the size of the CGG repeat and the FRAXAC1 genotype. There was a dearth of A and D genotypes in subjects with a small number of CGG repeats and an excess of the A genotype in those with a large number of CGG repeats. These observations are considered in the light of the reported disequilibrium between the A (and possibly also the D) genotype and the fra(X) mutation.     

ApoAI deficiency results in marked reductions in plasma cholesterol but no alterations in amyloid-beta pathology in a mouse model of Alzheimer's disease-like cerebral amyloidosis

Epidemiological studies suggest links between cholesterol metabolism and Alzheimer's disease (AD), with hypercholesterolemia associated with increased AD risk, and use of cholesterol-lowering drugs associated with decreased risk. Animal models using cholesterol-modifying dietary or pharmacological interventions demonstrate similar findings. Proposed mechanisms include effects of cholesterol on the metabolism of amyloid-beta (Abeta), the protein that deposits in AD brain. To investigate the effect of genetic alterations in plasma cholesterol on Abeta pathology, we crossed the PDAPP transgenic mouse model of AD-like cerebral amyloidosis to apolipoprotein AI-null mice that have markedly reduced plasma cholesterol levels due to a virtual absence of high density lipoproteins, the primary lipoprotein in mice. Interestingly and in contrast to models using non-physiological high fat diets or cholesterol-lowering drugs to modify plasma cholesterol, we observed no differences in Abeta pathology in PDAPP mice of the various apoAI genotypes despite robust differences in plasma cholesterol levels between the groups. Absence of apoAI also resulted in reductions in brain but not cerebrospinal fluid cholesterol, but had no effect on brain apolipoprotein E levels. These and other data suggest that it is perhaps the level of brain apolipoprotein E, not cholesterol per se, that plays a primary role in brain Abeta metabolism.     

Antibiotic prescribing and admissions with major suppurative complications of respiratory tract infections: a data linkage study.

BACKGROUND: Systematic reviews of antibiotic treatment of common acute respiratory tract infections (RTIs) suggest modest symptomatic benefit, but provide limited evidence that prescribing prevents complications. AIM: To assess the relationship between penicillin prescribing (the most commonly used group of antibiotics for RTIs) and hospital admission with complications. DESIGN OF STUDY: Data linkage study. SETTING: Ninety-six health authorities of England for the year 1997-1998. METHOD: Hospital admissions related to RTIs were linked with prescribing analysis and cost (PACT) data. RESULTS: There was close correlation between items of penicillin use and total antibiotic use (r = 0.96). After controlling for SMR, age, sex, and Townsend score, a one-unit increase in penicillin use (items dispensed per capita) was associated with a reduction in annual incidence per 10,000 of admissions for quinsy (-3.55 admissions, 95% confidence interval [CI] = -6.85 to -0.26), and mastoiditis (square root of incidence of admissions = -1.05, 95% CI = -1.82 to -0.27). This does not represent lower referral thresholds among higher prescribers as higher prescribing was associated with more admissions for tonsillectomy and overall admissions. Increasing prescribing by 2000 items of penicillin for a practice of 10,000 patients could possibly prevent one admission for either mastoiditis or quinsy. CONCLUSION: Higher antibiotic prescribing is associated with significantly fewer admissions with major complications. However, the overall size of the effect is modest and it is difficult to advocate an overall increase in prescribing to prevent complications. Future research should concentrate on finding better methods of targeting antibiotics to individuals at risk of poor outcome.     

Development of suppressor T cells in mice heavily infected with mycobacteria

Specific pathogen-free B6D2 mice were infected intravenously with 10(8) viable BCG, M. habana or M. simiae and the level of tuberculin hypersensitivity to 2.5 micrograms PPD or cytoplasmic protein antigens (CPA) prepared from the other organisms was determined using the footpad swelling test with increasing time after infection. This was correlated with the growth or persistence of mycobacterial populations within the liver. Spleen cells were removed from these infected mice and the level of blast transformation following exposure to PHA, PPD or M. habana or M. simiae CPA was measured in vitro. Early in the mycobacterial infections (day 14) thymidine incorporation by the spleen cells was significantly enchanced followed by a profound depression in incorporation rates as the infection progressed. The mechanism of this depressed response involved the production of suppressor T cells in the spleen. In the case of the M. simiae or M. habana infection, cells capable of mediating suppression were still present even after 12 months of infection. In the BCG infection, suppressor T cells declined with time so that by 4 months incorporation rates were back to normal and suppressor cells were no longer detectable in the spleens of the infected animals.     

Elevated abeta42 in skeletal muscle of Alzheimer disease patients suggests peripheral alterations of AbetaPP metabolism

The levels of amyloid-beta40 (Abeta40) and Abeta42 peptides were quantified in temporalis muscles and brain of neuropathologically diagnosed Alzheimer disease (AD) and of nondemented individuals. This was achieved by using a novel analytical approach consisting of a combination of fast-performance liquid chromatographic (FPLC) size exclusion chromatography developed under denaturing conditions and europium immunoassay on the 4.0- to 4.5-kd fractions. In the temporalis muscles of the AD and nondemented control groups, the average values for Abeta42 were 15.7 ng/g and 10.2 ng/g (P = 0.010), and for Abeta40 they were 37.8 ng/g and 29.8 ng/g (P = 0.067), respectively. Multiple regression analyses of the AD and control combined populations indicated that 1) muscle Abeta40 and muscle Abeta42 levels were correlated with each other (P < 0.001), 2) muscle Abeta40 levels were positively correlated with age (P = 0. 036), and 3) muscle Abeta42 levels were positively correlated with Braak stage (P = 0.042). Other forms of the Abeta peptide were discovered by mass spectrometry, revealing the presence of Abeta starting at residues 1, 6, 7, 9, 10, and 11 and ending at residues 40, 42, 44, 45, and 46. It is possible that in AD the skeletal muscle may contribute to the elevated plasma pool of Abeta and thus indirectly to the amyloid deposits of the brain parenchyma and cerebral blood vessels. The increased levels of Abeta in the temporalis muscles of AD patients suggest that alterations in AbetaPP and Abeta metabolism may be manifested in peripheral tissues.     

Mouse T-cell tumour immunoglobulin. I. Antigenic properties and effects on T-cell responses.

The mouse T-cell tumours E1-4 and WEHI-22 produce an immunoglobulin (TCT Ig) which suppresses the antibody response to T- dependent antigens in vitro while having no effect on responses to T-independent antigens. TCT Ig also augments IgG responses to both kinds of antigen. TCT Ig appears to be a new class of mouse Ig because its effects on in vitro antibody responses can be absorbed by antisera to mouse Kappa chains but not with antisera to any of the known classes of mouse Ig. Furthermore, TCT Ig activity cannot be duplicated by free light chains, Fab2 fragments, several mouse serum Ig preparations of Ig made from B cells. TCT Ig affects only T-cell function in antibody responses. It has no effect on the ability of the different subclasses of T cells to respond to mitogens or to alloantigens. Furthermore, it does not block T-T cell co-operation suggesting that the molecular basis for T-T co-operation differs from that of T-B co-operation.     

Ureaplasma urealyticum intrauterine infection: role in prematurity and disease in newborns.

Ureaplasma urealyticum, a common commensal of the urogenital tract of sexually mature humans, is gaining recognition as an important opportunistic pathogen during pregnancy. While its etiologic significance in many aspects of adverse pregnancy remains controversial, recent evidence indicates that U. urealyticum in the absence of other organisms is a cause of chorioamnionitis. Furthermore, ureaplasmal infection of the chorioamnion is significantly associated with premature spontaneous labor and delivery. In at least some cases, it appears to be causal. Present evidence indicates that U. urealyticum is a cause of septicemia, meningitis, and pneumonia in newborn infants, particularly those born prematurely. There is strong but not definitive evidence that ureaplasmal infection of the lower respiratory tract can lead to development of chronic lung disease in very low-birth-weight infants. Although risk factors for colonization of the lower genitourinary tract have been identified, little information is available concerning risk factors for intrauterine infection and host immune responses to invasive infection. Recent establishment of animal models of respiratory and central nervous system diseases should provide an opportunity to evaluate risk factors, pathogenic mechanisms, and operative immune mechanisms. However, the most critical need is additional information concerning indications for diagnosis and treatment as well as efficacy of treatment.