Coding Region Polymorphisms of Human T-Cell Receptor Vβ6.9 and Vβ21.4

Two new TCRV beta coding region polymorphisms were identified: V beta 6.9a/b and V beta 21.4a/b. In both cases, a single nucleotide difference gives rise to an amino acid exchange. Genomic typing by the PCR/sequence-specific oligonucleotide probing technique was performed to study a possible contribution of these two new polymorphisms in susceptibility to autoimmune diseases. However, there was no association with insulin-dependent diabetes mellitus, rheumatoid arthritis, juvenile rheumatoid arthritis, multiple sclerosis, myasthenia gravis or coeliac disease. On the other hand, significant differences were found between Caucasoid and Oriental populations in frequencies of the V beta 6.9 and V beta 21.4 alleles.     

Activities of various β-lactams and β-lactam/β-lactamase inhibitor combinations against Acinetobacter baumannii and Acinetobacter DNA group 3 strains

Acinetobacter baumannii and Acinetobacter DNA group 3 are members of the so-called A. calcoaceticus-A. baumannii complex and are important nosocomial pathogens. Multiresistance in these organisms is increasingly frequent, and alternative treatment options are needed. The beta-lactamase inhibitors clavulanate, sulbactam and tazobactam have intrinsic activity against Acinetobacter strains. In the present study, broth microdilution was used to assess the in-vitro activities of currently available beta-lactam/beta-lactamase inhibitor combinations and sulbactam alone against 469 Acinetobacter isolates (A. baumannii, n=395; Acinetobacter DNA group 3, n=74) collected from various laboratories in Germany. Fixed concentrations and fixed ratios of beta-lactamase inhibitors were used. Sulbactam-containing combinations (susceptibility rates of 90.4-92.7% for A. baumannii and 97.3-100% for Acinetobacter DNA group 3) and sulbactam alone were superior to clavulanate- and tazobactam-containing combinations. The activity of sulbactam-containing combinations against members of the A. calcoaceticus-A. baumannii complex was conferred exclusively by the intrinsic activity of the beta-lactamase inhibitor and did not result from enhanced beta-lactam activity. Testing with the inhibitor added at a fixed ratio of inhibitor to beta-lactam appeared to give more reliable results than testing at a fixed concentration of the inhibitor. Resistance to carbapenems (0.3%) remains low in Germany.     

Bactericidal activity of three β-lactams alone or in combination with a β-lactamase inhibitor and two aminoglycosides against Klebsiella pneumoniae harboring extended-spectrum β-lactamases

Objective: To study the bactericidal activity of β-lactam antibiotics (imipenem, cefepime, cefpirome) alone or in combination with a β-lactamase inhibitor (sulbactam) in the presence or absence of aminoglycoside (amikacin or isepamicin) against Klebsiella pneumoniae strains producing extended-spectrum β-lactamases (ESBLs).
Methods: We characterized 10 strains by means of analytic isoelectric focusing and pulsed-field gel electrophoresis. The ESBLs produced by these strains were derived from either TEM (TEM-1, TEM-2) or SHV-1. The killing-curve method was used for this bacterial investigation. Bacteria (final inoculum 5×10 ⁵ CFU/mL) were incubated with antibiotics at clinical concentrations obtained in vivo.
Results: All the combinations with cefepime or cefpirome + sulbactam were bactericidal, with a 4 log₁₀ decrease being obtained within 6 h without regrowth at 24 h, whereas imipenem alone, and combinations, gave a bactericidal effect within 6 h. The two cephalosporins alone decreased the inoculum of 4 log₁₀ at 6 h but regrowth was observed at 24 h. When the aminoglycoside was added, this bactericidal effect was obtained within 3 h with amikacin and within 1 h with isepamicin.
Conclusions: Cefepime + sulbactam or cefpirome + sulbactarn may be an alternative to imipenem for the treatment of patients with ESBL-producing K. pneumoniae. Aminoglycosides are often associated in nosocomial infections due to ESBL-producing K. pneumoniae: isepamicin acted faster than amikacin, but both worked well. To conclude, it may be prudent to avoid extended-spectrum cephalosporins as single agent when treating serious infections due to ESBL-producing K. pneumoniae. Addition of a β-lactamase inhibitor such as sulbactam ± aminoglycoside is advisable to avoid failure of treatment.     

β-Thalassaemia mutations and their linkage to β-haplotypes in Tamil Nadu in Southern India

A study for screening of beta-thalassaemia mutations by the Amplification Refractory Mutation System (ARMS) and haplotyping by Polymerase Chain Reaction (PCR) was undertaken because there was a paucity of data in Tamil Nadu in Southern India and to initiate a comprehensive prenatal diagnosis programme. A total of 294 alleles were analysed to study the nature of the mutations, of which 146 were beta-thalassaemia alleles. Only four types of beta-thalassaemia mutations were recorded. Of these, 128 alleles were of the variant IVS-1 nt 5 (G-->C). Thirteen had the mutation codon 41/42 (del TCTT), four had the mutation codon 8/9 (insert G) and one had the 619 bp deletion at the 3' end of the gene. The most common mutation, IVS-1 nt 5 (G-->C), was strongly associated with a single haplotype although the association was not absolute. The population of Tamil Nadu in Southern India seems to be ideal for initiating a prenatal diagnosis programme based on direct detection of mutation by ARMS coupled with RFLP linkage analysis.     

Axin, an inhibitor of the Wnt signalling pathway, interacts with β-catenin, GSK-3β and APC and reduces the β-catenin level

Background:

The Wnt/Wingless signalling pathway plays an important role in both embryonic development and tumorigenesis. β-Catenin and Axin are positive and negative effectors of the Wnt signalling pathway, respectively.

Results:

We found that Axin interacts with β-catenin and glycogen synthase kinase-3β (GSK-3β). Furthermore, the regulation of the G-protein signalling (RGS) domain of Axin is associated with the colorectal tumour suppressor adenomatous polyposis coli (APC). Overexpression of Axin in the human colorectal cancer cell line SW480 induced a drastic reduction in the level of β-catenin. Interaction with β-catenin and GSK-3β was required for the Axin-mediated β-catenin reduction.

Conclusion:

Axin interacts with β-catenin, GSK-3β and APC, and negatively regulates the Wnt signalling pathway, presumably by regulating the level of β-catenin.

     

β-Lactamase-producing bacteria in mixed infections

Beta-lactamase-producing bacteria (BLPB) can play an important role in polymicrobial infections. They can have a direct pathogenic impact in causing infections, as well as an indirect effect through their ability to produce the beta-lactamase. BLPB may not only survive penicillin therapy themselves, but can also protect other penicillin-susceptible bacteria from penicillin by releasing free beta-lactamase into their immediate environment. This phenomenon occurs in upper respiratory tract, skin, soft tissue, surgical and other infections. The in-vitro and in-vivo clinical evidence supporting the role of BLPB in the increasing failure of penicillin to resolve such infections, and the implications of this phenomenon for the management of infections, are discussed.     

Emergence of α5β1 fibronectin- and αvβ3 vitronectin-receptor expression in melanocytic tumour progression

Cell adhesion is crucial in the process of tumour progression. As integrins are important receptor molecules involved in cell adhesion, we studied the distribution of the α1-6, αv, αIIb, β1, β3, and β4 integrin subunits in tissue sections of common naevocellular naevi ( n =22), dysplastic naevi (16), thin (24) and thick primary cutaneous melanomas (28), and melanoma metastases (25). We found correlated expression of α1/α2, of α4/α5/β3, and of α6/β4. Decrease of α6 and β4, and increase of α4 and αv were found to be correlated with melanoma progression. Furthermore, expression of α5 and β3 was detected only in primary melanoma and melanoma metastasis. Our findings indicate that during melanoma progression alterations in integrin expression occur, the most striking being emergence of α5β1 fibronectin and αvβ3 vitonectin receptor.     

Cerebroside-β-glucosidase activity in Gaucher brain

Cerebroside-beta-glucosidase (acid beta-glucosidase) activity was determined in the forebrain from three patients with the infantile type of Gaucher disease, six patients with the Norrbottnian type and one patient with a mixed infantile/Norrbottnian type. The forebrain from ten subjects, aged 3 months to 20 years, served as controls. The activity was assayed with the natural substrate, (glucose-6-3H) nervonoylglucosylsphingosine and the artificial fluorogenic 4-methyl-umbelliferyl-beta-glucoside. The average residual activities of beta-glucosidase were 12% in the Norrbottnian type and 5% in the infantile type when determined with natural or artificial substrate. Optimum discrimination of the two types of Gaucher disease was obtained with the natural substrate.     

Physiological roles for amyloid β peptides

Alzheimer's disease is recognized post mortem by the presence of extracellular senile plaques, made primarily of aggregation of amyloid β peptide (Aβ). This peptide has consequently been regarded as the principal toxic factor in the neurodegeneration of Alzheimer's disease. As such, intense research effort has been directed at determining its source, activity and fate, primarily with a view to preventing its formation or its biological activity, or promoting its degradation. Clearly, much progress has been made concerning its formation by proteolytic processing of the amyloid precursor protein, and its degradation by enzymes such as neprilysin and insulin degrading enzyme. The activities of Aβ, however, are numerous and yet to be fully elucidated. What is currently emerging from such studies is a diffuse but steadily growing body of data that suggests Aβ has important physiological functions and, further, that it should only be regarded as toxic when its production and degradation are imbalanced. Here, we review these data and suggest that physiological levels of Aβ have important physiological roles, and may even be crucial for neuronal cell survival. Thus, the view of Aβ being a purely toxic peptide requires re-evaluation.     

Human NK Cells Expressing α4β1/β7 Adhere to VCAM-1 Without Preactivation

The authors demonstrate that resting CD56⁺/CD3⁻ NK cell adhesion to the endothelial VCAM-1 is over three-fold higher than CD56⁻/CD3 ⁺ T-cell adhesion. T-cell, but not NK-cell adhesion, to VCAM-1 is enhanced significantly by stimulation. The expression of VCAM-I receptor subunits α4 and β1 on both effector cells remains unchanged upon stimulation. A subpopulation of NK cells, as well as of T cells, was found to express β7, whose expression was not altered upon stimulation. The authors conclude that the adhesive properties of the same receptor structures on these distinct cell populations are regulated in a different manner, according to the specific functions of the effector cells of the immune system.