Heterogeneity within the gram-positive anaerobic cocci demonstrated by analysis of 16S-23S intergenic ribosomal RNA polymorphisms

Peptostreptococci are gram-positive, strictly anaerobic bacteria which, although regarded as members of the commensal human microflora, are also frequently isolated from sites of clinical infection. The study of this diverse group of opportunist pathogens has been hindered by an inadequate taxonomy and the lack of a valid identification scheme. Recent re-classification of the Peptostreptococcus family into five distinct genus groups has helped to clarify the situation. However, this has been on the basis of 16S rRNA sequence determinations, which are both time-consuming and expensive. The aim of the present study was to evaluate the use of PCR-amplified ribosomal DNA spacer polymorphisms for the rapid differentiation of the currently recognised taxa within the group of anaerobic gram-positive cocci. A collection comprising 19 reference strains with representatives of each of the 15 species, two close relatives and two of the well-characterised groups, together with 38 test strains was studied. All strains were identified to species group level by phenotypic means. Amplification of the 16S-23S intergenic spacer region (ISR) with universal primers produced distinct banding patterns for all the 19 reference strains and the patterns could be differentiated easily visually. However, of the 38 test strains, less than half could be speciated from ISR analysis alone. Only five groups produced correlating banding patterns for all members tested (Peptoniphilus lacrimalis, P. ivorii, Anaerococcus octavius, Peptostreptococcus anaerobius and Micromonas micros). For other species, either the type strain differed significantly from other species members (e.g., A. hydrogenalis) or there appeared to be considerable intra-species variation (e.g., A. vaginalis). Partial 16S rRNA gene sequences for the 'trisimilis' and 'betaGAL' groups showed that both are most closely related to the Anaerococcus group. This work highlights the heterogeneous nature of a number of Peptostreptococcus species and hence the need for still further revision of the taxonomy of this important group of pathogens.

Strain persistence of invasive Candida albicans in chronic hyperplastic candidosis that underwent malignant change

OBJECTIVES

The aim of this study was to assess persistence and tissue invasion of Candida albicans strains isolated from a 65 year-old patient with chronic hyperplastic candidosis (CHC), that subsequently developed into squamous cell carcinoma (SCC).

MATERIALS AND METHODS

C. albicans (n=7) were recovered from the oral cavity of the patient over seven years. Confirmation of CHC and SCC in this patient was achieved by histopathological examination of incisional biopsy tissue. DNA fingerprinting was performed on the seven isolates from the CHC patient together with a further eight isolates from patients with normal oral mucosa (n=2), chronic atrophic candidosis (n=1), SCC (n=1) and CHC (n=4). Genotyping involved the use of inter-repeat PCR using the eukaryotic repeat primer 1251. Characterisation of the tissue invasive abilities of the isolates was achieved by infecting a commercially available reconstituted human oral epithelium (RHE; SkinEthic, Nice, France). After 24 h, C. albicans tissue invasion was assessed by histopathological examination.

RESULTS

DNA fingerprinting demonstrated strain persistence of C. albicans in the CHC patient over a seven year period despite provision of systemic antifungal therapy. The strain of C. albicans isolated from this patient was categorised as a high invader within the RHE compared to other isolates.

CONCLUSIONS

Candidal strain persistence was evident in a patient with CHC over seven years. This persistence may be due to incomplete eradication from the oral cavity following antifungal therapy or subsequent recolonisation from other body sites or separate exogenous sources. The demonstration of enhanced in vitro tissue invasion by this particular strain may, in part, explain the progression to carcinoma.

Leukocyte receptor complex-encoded immunomodulatory receptors show differing specificity for alternative HLA-B27 structures

We studied recognition of the disease-associated HLA-B27 allele by immunomodulatory receptors encoded within the leukocyte receptor complex. HLA class I are ligands for members of the killer Ig receptor (KIR) and Ig-like transcript (ILT)/LIR/LILR families (the new LILR nomenclature is described at www. gene.ucl.ac.uk/nomenclature/genefamily/lilr.html). Members of these families bound HLA-B27 in both classical and beta(2) microglobulin-independent forms. Classical complexes bound ILT2, ILT4, and LIR6 transfectants but not ILT1, ILT3, or ILT5. A free H chain form of HLA-B27 bound ILT4 and LIR6. Both forms of HLA-B27 bound KIR3DL1 transfectants. HLA-B27 free H chain bound CD14(+) cells in PBL from healthy controls, consistent with ILT4 expression on monocytes. Alternative recognition of different forms of HLA-B27 by KIR or ILT could influence their immunomodulatory function and may imply a role in inflammatory disease.

Plasma membrane association of cathepsin B in human prostate cancer: biochemical and immunogold electron microscopic analysis

BACKGROUND

Cathepsin B (CB), a cysteine protease, is usually found in perinuclear lysosomes of epithelial cells of normal organs and non-malignant tumors, but is associated with the plasma membranes of many solid organ malignant tumors. Plasma membrane localized CB facilitates degradation of extracellular matrix proteins and progression of tumor cells from one biological compartment to another. The activities of CB and its subcellular distribution have not been investigated in malignant prostate. Our objective was to examine the subcellular distribution of CB by determining the activities of CB in lysosome and plasma membrane/endosome subcellular fractions and its subcellular localization by immunogold electron microscopy.

METHODS

Prostate tissue pieces obtained immediately after prostatectomy were homogenized and fractionated into subcellular components for determining biochemical activities of CB and cysteine protease inhibitors (CPIs). Distribution of CB was compared with that of prostate specific antigen (PSA, a serine protease), which is abundant in secretory vesicles and granules of normal prostate, benign prostatic hyperplasia (BPH) and malignant prostate cells. Localization of CB was investigated in resin embedded lysosomes and plasma membrane/endosome subcellular fractions and in prostate tissue sections by immunogold electron microscopy.

RESULTS

We have demonstrated the specificity of CB activity in human prostate homogenates by using a variety of inhibitors in our assay. We did not find any difference in the specific activity of CB based on protein or DNA content in homogenates of malignant prostate (Gleason histologic scores 5-7) and BPH (no histological evidence of cancer) whether it was measured by chromogenic or fluorogenic peptide substrate assay techniques. We found significantly higher activities of CB in the plasma membrane/endosome fractions of malignant prostate than in BPH. In contrast, CPI activity was increased relative to CB activity in plasma membrane/endosome fraction of BPH versus prostate cancer. Our data indicated a shift in the balance of enzyme to inhibitor that would favor increased activities of CB in prostate cancer. The immunogold microscopic study showed specific localization of CB in plasma membrane. They also showed localization of CB in lysosomes that were often adjacent to luminal and/or basal surfaces of malignant cells in contrast to the usual perinuclear distribution of lysosomes in hyperplastic prostate glands. PSA was localized in secretory granules and vesicles, including the plasma membranes and secretory blebs in malignant prostate cells. Occasional PSA positive secretory vesicles or membrane profiles were seen in the plasma membrane/endosomal and lysosomal fractions.

CONCLUSIONS

The increased activity of CB in plasma membrane/endosomal fractions is associated with malignant prostate and not with BPH or normal prostate. Morphologic distribution CB is associated with the plasma membranes or lysosomes adjacent to apical and basal cell surfaces. This distribution is characteristic feature prostate cancer cells, but not in BPH or normal prostate cells. Subcellular distribution of PSA occurs in secretory vesicles and granules of the cytoplasm, but not in lysosomes. Our biochemical and morphological data could be used to distinguish malignant prostates from non-malignant tumors.

PCR fingerprinting of Candida albicans associated with chronic hyperplastic candidosis and other oral conditions

The purpose of this study was to genotype strains of Candida albicans to determine whether specific types were associated with chronic hyperplastic candidosis (CHC). A total of 67 candidal isolates from CHC patients (n = 17) and from patients with other oral conditions (n = 21) were genotyped by PCR fingerprinting employing two interrepeat primer combinations (1245 and 1246 primers or 1251 primer) and a single minisatellite-specific M13 primer. The most suitable primer for fingerprint analysis was found to be primer 1251, yielding well-resolved banding patterns. For the 67 isolates tested, PCR fingerprinting delineated 25 (1245 and 1246 primers), 27 (1251 primer), and 25 (M13 primer) profiles. The majority of C. albicans isolates from multiple sites within the mouth produced identical profiles (six out of nine subjects examined). For patients for whom a series of longitudinal isolates was available, strain persistence for up to 7 years was evident for five out of eight individuals, despite episodes of antifungal therapy. Computer-assisted comparison of the interrepeat PCR fingerprints identified seven distinct profiles that were shared among isolates from different individuals. However, no association was evident among isolates of C. albicans from specific clinical conditions. Eight isolates that were initially identified as C. albicans but having atypical PCR profiles were later confirmed as Candida dubliniensis. In conclusion, the genotypic data do not indicate clonal restriction of C. albicans with respect to CHC. Furthermore, these results have demonstrated that in the majority of individuals, colonizing populations of C. albicans are clonal in nature and exhibit strain persistence.

Ratio of cathepsin B to stefin A identifies heterogeneity within Gleason histologic scores for human prostate cancer

BACKGROUND

Cathepsin B (CB), a lysosomal cysteine protease, is involved in degradation of extracellular matrix proteins and progression of tumor cells from one biological compartment to another in many solid organ cancers, including prostate cancer. Our objective was to identify patterns of distribution of CB and its endogenous cellular inhibitor stefin A in cryostat sections of frozen BPH and prostate cancer tissue samples and to define these patterns in relation to Gleason histologic scores, clinical stages, and serum total PSA levels.

METHODS

We localized CB and stefin A in the same sections using polyclonal and monoclonal antibody immunoglobulin G (IgGs) against CB and stefin A using immunofluorescence and confocal microscopic techniques. Only cryostat sections of frozen prostates were used in localizations of CB and stefin A.

RESULTS

Benign prostatic hyperplasia (BPH) showed similar localization patterns for CB and stefin A and a ratio of 1 was indicated by CB = stefin A. Confocal studies indicated that most CB and stefin A sites in BPH glandular cells overlapped as shown by the yellow fluorescence of their co-localization. We found considerable variability in individual localization of CB and stefin A within and between Gleason histologic scores for prostate cancers. This variability was also found in Gleason score 6 tumors that are otherwise considered similar histologically and morphologically. Negative control sections did not show localization of CB by FITC, stefin A by Cy3 or yellow fluorescence for co-localization. Our analysis of the ratio of CB to stefin A showed three patterns, namely CB = stefin A, CB > stefin A, and CB < stefin A, within each Gleason score evaluated by us. Confocal microscopy showed more sites of yellow fluorescence when the ratio was CB = stefin A than those found in CB > stefin A or CB < stefin A. Statistical analyses showed prostate cancer cases with ratios of CB > stefin A (P < 0.05) and CB < stefin A (P < 0.05) significantly different from normal prostate and BPH which had ratios of CB = stefin A. Regression analysis did not show any specific relationship between the ratio of CB to stefin A and Gleason scores, clinical stages, and serum total prostate specific antigen (PSA) levels in prostate cancers. Analysis of our data indicates that the homeostatic balance between the enzyme and inhibitor was altered even in Gleason histologic score 6 tumors that are usually considered histologically similar by glandular differentiation.

CONCLUSIONS

We have shown that prostate cancer is a heterogeneous tumor within each Gleason histological score regardless of the progression indicated by lower to higher Gleason score tumors. The ratio of CB > stefin A would indicate a preponderance of enzyme that would favor degradation of extracellular matrix proteins and progression of tumor cells in biological compartments. These tumors are expected to be aggressive prostate cancers. In contrast, prostate tumors showing ratios of CB < stefin A and CB = stefin A are expected to be less aggressive prostate cancers. This is the first report to define heterogeneity within any Gleason score for prostate cancers by the ratios of CB to stefin A.

Use of molecular techniques to study microbial diversity in the skin: chronic wounds reevaluated

The skin is colonized by an array of microorganisms which form its natural microflora. Disruption to the normal barrier function of the skin (due to trauma or disease) may result in invasion of the dermis by opportunistic bacteria. To date, these organisms, which may contribute to the chronicity of skin wounds, have been analyzed solely by culture methods. It is increasingly realized that standard culture methods of analysis do not accurately reflect the full diversity of complex microflora. This review discusses the limitations of traditional culture approaches and reviews recent advances in molecular microbiological techniques which facilitate a more comprehensive characterization of the microflora within clinical samples. The currently available technologies and techniques are described, as is their use in clinical practice and their potential for diagnostic screening. Chronic venous ulceration of the lower limbs is an important skin disorder in which the microflora invading the dermal tissues contribute to the observed delayed healing. Using chronic leg ulcers as a working example, we show how strict culture and molecular microbiological techniques may be employed, for the first time in combination, to definitively characterize the invading microbial community of the dermis.

Characterization of an endoprotease (PrpL) encoded by a PvdS-regulated gene in Pseudomonas aeruginosa

The expression of many virulence factors in Pseudomonas aeruginosa is dependent upon environmental conditions, including iron levels, oxygen, temperature, and osmolarity. The virulence of P. aeruginosa PAO1 is influenced by the iron- and oxygen-regulated gene encoding the alternative sigma factor PvdS, which is regulated through the ferric uptake regulator (Fur). We observed that overexpression of PvdS in strain PAO1 and a DeltapvdS::Gm mutant resulted in increased pyoverdine production and proteolytic activity compared to when PvdS was not overexpressed. To identify additional PvdS-regulated genes, we compared extracellular protein profiles from PAO1 and the DeltapvdS::Gm mutant grown under iron-deficient conditions. A protein present in culture supernatants from PAO1 but not in supernatants from DeltapvdS::Gm was investigated. Amino acid sequence analysis and examination of the genomic database of PAO1 revealed that the N terminus of this 27-kDa protein is identical to that of protease IV of P. aeruginosa strain PA103-29 and is homologous to an endoprotease produced by Lysobacter enzymogenes. In this study, the gene encoding an endoprotease was cloned from PAO1 and designated prpL (PvdS-regulated endoprotease, lysyl class). All (n = 41) but one of the strains of P. aeruginosa, including clinical and environmental isolates, examined carry prpL. Moreover, PrpL production among these strains was highly variable. Analysis of RNase protection assays identified the transcription initiation site of prpL and confirmed that its transcription is iron dependent. In the DeltapvdS::Gm mutant, the level of prpL transcription was iron independent and decreased relative to the level in PAO1. Furthermore, transcription of prpL was independent of PtxR, a PvdS-regulated protein. Finally, PrpL cleaves casein, lactoferrin, transferrin, elastin, and decorin and contributes to PAO1's ability to persist in a rat chronic pulmonary infection model .

Light chains of mammalian cytoplasmic dynein: identification and characterization of a family of LC8 light chains

Cytoplasmic dynein is a large multisubunit motor protein that moves various cargoes toward the minus ends of microtubules. In addition to the previously identified heavy, intermediate, and light intermediate chains, it has recently been recognized that cytoplasmic dynein also has several light chain subunits with apparent molecular weights between 8-20 kDa. To systematically identify the light chains of purified rat brain cytoplasmic dynein, peptide sequences were obtained from each light chain band resolved by gel electrophoresis. Both members of the tctex1 light chain family, tctex1 and rp3, were identified in a single band. Only one member of the roadblock family, roadblock-2, was found. Two members of the LC8 family were resolved as separate bands, the previously identified LC8 subunit, and a second novel cytoplasmic dynein family member, LC8b. The tissue distribution of these two dynein LC8 subunits differed, although LC8b was the major family member in brain. Database searches found that both LC8a and LC8b were also present in several mammalian species, and a third mammalian LC8 sequence, LC8c was found in the human database. The amino acid sequences of both LC8a and LC8b were completely conserved in mammals. LC8a and LC8b differ in only six of the 89 amino acids. The amino acid differences between LC8a and LC8b were located near the N-terminus of the molecules, and most were in the outward facing alpha-helices of the LC8 dimer. When the mammalian LC8a sequence was compared to the LC8 sequences found in six other animal species including Xenopus and Drosophila, there was, on average, 94% sequence identity. More variation was found in LC8 sequences obtained from plants, fungi, and parasites. LC8c differed from the other two human LC8 sequences in that it has amino acid substitutions in the intermediate chain binding domain at the C-terminal of the molecule. The position of amino acid substitutions of the three mammalian LC8 family members is consistent with the hypothesis that they bind to different proteins.

Extraction of DNA from oral cytological samples by scraping and smear method suitable for restriction site mutation analysis: a pilot study

The restriction site mutation assay (RSM) can be used to measure base changes which occur in the DNA coding for bacterial restriction enzymes. The aim of this study was to investigate whether DNA, of sufficient quantity and quality for analysis by RSM, could be extracted from cells collected from precancerous lesions using a cytological smear technique. Six smears were collected from each of five lesions of leukoplakia displaying a variety of clinical appearances. Three methods for the extraction of DNA were compared. The commercial extraction method was shown to be most convenient and reproducible, routinely providing 1-5 microg of DNA per sample. Cell populations collected by a cytological smear technique can provide DNA of sufficient quantity and quality for analysis of RSM.

The genomic context of natural killer receptor extended gene families

The two sets of inhibitory and activating natural killer (NK) receptor genes belong either to the Ig or to the C-type lectin superfamilies. Both are extensive and diverse, comprising genes of varying degrees of relatedness, indicative of a process of iterative duplication. We have constructed gene maps to help understand how and when NK receptor genes developed and the nature of their polymorphism. A cluster of over 15 C-type lectin genes, the natural killer complex is located on human chromosome 12p13.1, syntenic with a region in mouse that borders multiple Ly49 loci. The equivalent locus in man is occupied by a single pseudogene, LY49L. The immunoglobulin superfamily of loci, the leukocyte receptor complex (LRC), on chromosome 19q13.4, contains many polymorphic killer cell immunoglobulin-like receptor (KIR) genes as well as multiple related sequences. These include immunoglobulin-like transcript (ILT) (or leukocyte immunoglobulin-like receptor genes), leukocyte-associated inhibitory receptor genes (LAIR), NKp46, Fc alphaR and the platelet glycoprotein receptor VI locus, which encodes a collagen-binding molecule. KIRs are expressed mostly on NK cells and some T cells. The other LRC loci are more widely expressed. Further centromeric of the LRC are sets of additional loci with weak sequence similarity to the KIRs, including the extensive CD66(CEA) and Siglec families. The LRC-syntenic region in mice contains no orthologues of KIRs. Some of the KIR genes are highly polymorphic in terms of sequence as well as for presence/absence of genes on different haplotypes. Some anchor loci, such as KIR2DL4, are present on most haplotypes. A few ILT loci, such as ILT5 and ILT8, are polymorphic, but only ILT6 exhibits presence/absence variation. This knowledge of the genomic organisation of the extensive NK superfamilies underpins efforts to understand the functions of the encoded NK receptor molecules. It leads to the conclusion that the functional homology of human KIR and mouse Ly49 genes arose by convergent evolution. NK receptor immunogenetics has interesting parallels with the major histocompatibility complex (MHC) in which some of the polymorphic genes are ligands for NK molecules. There are hints of an ancient genetic relationship between NK receptor genes and MHC-paralogous regions on chromosomes 1, 9 and 19. The picture that emerges from both complexes is of eternal evolutionary restlessness, presumably in response to resistance to disease.

Removal of tightly bound endotoxin from biological products

The method for endotoxin removal described in this paper is useful for separation of tightly bound endotoxin from biological products, particularly those produced in Escherichia coli in the form of inclusion bodies for which a denaturation step is required to solubilise the product. We employed guanidine hydrochloride and ammonium sulphate in combination with hydrophobic interaction chromatography (HIC). These conditions enable binding of the endotoxin to the matrix, giving unbound product in the column flow-through. This makes the method generally applicable to biological products. An endotoxin reduction of about 3.7 logs was achieved; from as much as 1,100,000 EU mg(-1) in the solubilised material to about 200 EU mg(-1) in the product purified by this method. The method was developed for a cervical dysplasia vaccine, a fusion protein comprising L2, E7 and E6 from Human Papilloma Virus type 16, because both conventional and commercially available methods of endotoxin removal were ineffective in removing the tightly bound endotoxin from this product.

Identification of Candida dubliniensis, based on ribosomal DNA sequence analysis

Differentiation of Candida albicans and the recently described C. dubliniensis has proven difficult due to the high degree of phenotypic similarity of these species. The present study examines sequence variations in the ribosomal DNA (rDNA) intergenic transcribed spacer (ITS) regions of C. albicans (n = 5) and C. dubliniensis (n = 7) strains, with a view to identifying sequence differences that would enable consistent differentiation of these two species by restriction fragment length polymorphism (RFLP) analysis. The ITS1 and ITS2 regions, together with the entire 5.8S rRNA gene of the strains, were amplified by the polymerase chain reaction (PCR), using primers ITS1 and ITS4, PCR products from both C. albicans and C. dubliniensis were of similar size (around 540 bp); however, sequence analysis revealed over 20 consistent base differences between the products of the two species. On the basis of sequence variation, the restriction enzyme MspA1 I was selected and used to differentiate the PCR products of C. albicans and C. dubliniensis by RFLP analysis. MspA1 I yielded two discernible fragments from C. albicans PCR products, whilst those from C. dubliniensis appeared undigested, thereby providing an approach to differentiate the two species.

A molecular epidemiological study of sequential oral isolates of Candida albicans from terminally ill patients

The pattern of candidal colonisation was studied in a group of terminally ill patients receiving antifungal treatment for oral candidosis. A total of 43 isolates of C. albicans was collected pre- and post-antifungal treatment from patients up to a maximum period of 4 weeks. Isolates were analysed by electrophoretic karyotyping (EK) and by inter-repeat polymerase chain reaction (IR-PCR). Fifteen electrophoretic karyotypes and 17 IR-PCR profiles were identified. Sequential isolates from 10 patients yielded identical profiles in both EKs and IR-PCR analyses. In the case of four patients, minor differences in the profiles were obtained by either EK or IR-PCR. The findings suggest that antifungal treatment in this patient group fails to eradicate the original C. albicans strain, thereby allowing recolonisation of the oral cavity. The present study has also shown that either EK or IR-PCR is a useful typing approach in such epidemiological investigations.

Analysis of promoters recognized by PvdS, an extracytoplasmic-function sigma factor protein from Pseudomonas aeruginosa

The alternative sigma factor PvdS is required by Pseudomonas aeruginosa for initiation of transcription from pyoverdine (pvd) promoters. Two divergent PvdS-dependent promoters (pvdE and pvdF) were characterized by deletion analysis, and the minimal promoter region for each included a sequence element, the iron starvation (IS) box, that is present in other pvd promoters. Site-directed mutagenesis showed that the IS box elements were essential for promoter activity in vivo. Band shift assays and in vitro transcription experiments showed that a complex of PvdS and core RNA polymerase required the presence of an IS box in order to bind to and initiate transcription from pvd promoters. These results indicate that IS box elements participate in sequence-specific recognition by PvdS to enable initiation of transcription from pvd promoters and are likely to represent a -35 sequence element for this sigma factor.

DAP12 and KAP10 (DAP10)-novel transmembrane adapter proteins of the CD3zeta family

Transmembrane adapter proteins are molecules that associate with receptors and mediate intracellular signals following interaction of the receptor with its ligand. Many such molecules have been characterized in detail, particularly the small TM adapters of the CD3zeta class at the core of the T cell receptor. Recently, two new genetically linked members of this class of transmembrane adapters have been identified called DAP12 (KARAP) and KAP10 (DAP10), respectively. In this review, we discuss this new class of TM adapters using the wealth of knowledge concerning CD3zeta and FcRgamma to highlight similarities and differences with DAP12 and KAP10. In addition, novel receptor families which interact with these TM adapters have also been identified. The role of these receptors and their inhibitory isoforms are discussed.

Divergent and convergent evolution of NK-cell receptors

Natural killer (NK)-cell receptors specific for major histocompatibility complex (MHC) class I molecules have been identified in humans and mice. Some of the most important receptors are structurally unrelated in the two species: the murine Ly-49 receptors are C-type lectins, while human killer-cell inhibitory receptors (KIRs) belong to the immunoglobulin superfamily. Here, Roland Barten and colleagues describe the divergent and convergent evolution of NK-cell receptors.

A comparison of performance of three gamma camera systems for positron emission tomography

The development of coincidence positron imaging using a gamma camera should significantly increase PET utilization. This study has compared the performance of three such systems with each other and with an equivalent single photon emission computed tomography (SPECT) measurement. A Carlson phantom, which consisted of a 20 cm diameter cylinder containing areas of uniform activity, hot lesions, cold lesions and orthogonal alternate hot and cold lines, was filled with an activity of 18F chosen to try and best exploit each camera and imaged for a fixed time (27 min). The image quality of 9 mm thick slices in each section of the phantom was compared visually. Several image quality parameters were also compared including line source resolution and noise equivalent count rate. There were considerable differences in PET image quality between the three cameras but all were at least as good as the SPECT image. The full width at half maximum (FWHM) resolution of all systems was similar (approximately 4.5 mm) but the maximum noise equivalent count rates in a 20 cm cylinder were significantly different (6.3, 2.6 and 1.6 kcps) (where cps is counts per second) and correlated with the phantom image quality.

Arrangement of the ILT gene cluster: a common null allele of the ILT6 gene results from a 6.7-kbp deletion

The leukocyte receptor cluster (LRC) is a highly polymorphic region of human chromosome 19q13.4 that encompasses at least 24 members of the immunoglobulin superfamily (Ig-SF). The centromeric end of the LRC contains eight Ig-SF loci, namely LAIR1 and seven ILT genes. All ILT genes conform to prototypic ILT gene structures. ILT6 is the only member of the ILT family that lacks a transmembrane and cytoplasmic domain. Close examination of the ILT6 genomic sequence reveals high similarity of this locus with the organization of activating ILT genes. However, the ILT6 transcript runs through the putative splice site of exon 8 that encodes for an extracellular stalk region, leading to a premature in-frame stop codon. Downstream of exon 8 are three pseudo exons that are not included in any of the known ILT6 transcripts, but share high homology to the equivalent region in activating ILT loci, suggesting that these genes have evolved from a common ancestral sequence. Comparison of two haplotypes over this region revealed a remarkable polymorphism with respect to the ILT6 gene which lacks exons 1-7 in one allele, reminiscent of the presence/absence variation displayed by the closely related and genetically linked KIR loci. Detailed sequence analysis of the two LAIR/ILT clusters suggests that the two complexes may have evolved from an inverted duplication.

Glutathione loading prevents free radical injury in red blood cells after storage

We have previously demonstrated that the loss of glutathione (GSH) and GSH-peroxidase (GSH-PX) in banked red blood cells (RBCs) is accompanied by oxidative modifications of lipids, proteins and loss of membrane integrity. The objective of this study was to determine whether artificial increases in antioxidant (GSH) or antioxidant enzyme (catalase) content could protect membrane damage in the banked RBCs following an oxidant challenge. RBCs stored at 1-6 degrees C for 0, 42 and 84 days in a conventional additive solution (Adsol) were subjected to oxidative stress using ferric/ascorbic acid (Fe/ASC) before and after enriching them with GSH or catalase using a hypotonic lysis-isoosmotic resealing procedure. This lysis-resealing procedure in the presence of GSH/catalase raised intracellular GSH and catalase concentrations 4-6 fold, yet produced only a small reduction in mean cell volume (MCV), mean cell hemoglobin (MCH) and mean cell hemoglobin concentrations (MCHC). Indicators of oxidative stress and membrane integrity were measured, including acetylcholinesterase (AChE) activity, GSH concentration, phosphatidylserine (PS) externalization (prothrombin-converting activity) and transmembrane lipid movements (14C-lyso phosphatidylcholine flip-flop and PS transport). GSH-enrichment protected AChE activity in fresh (0 day) and stored (42 and 84 days) RBCs from Fe/ASC oxidation by 10, 23 and 26%, respectively, compared with not-enriched controls. Following oxidative stress, the rate of transbilayer lipid flip-flop did not increase in fresh cells, but increased 9.3% in 42-day stored cells. Phosphatidylserine exposure, as measured by prothrombinase activity, increased 2.4-fold in fresh and 5.2-fold in 42-day stored cells exposed to Fe/ASC. Previous studies have shown that 42-day storage causes a moderate decrease in PS transport (approximately 50%), whereas transport rates declined by up to 75% in stored RBCs when challenged with Fe/ASC. GSH-enrichment prevented the increase in passive lipid flip-flop and the increase in prothrombinase activity, but offered no protection against oxidative damage of PS transport. In contrast to these effects, catalase-enrichment failed to protect GSH levels and AChE activity upon oxidative stress. Membrane protein thiol oxidation was assessed by labeling reactive protein thiols with 5-acetalamidofluorescein followed by immunoblotting with antifluorescein antibodies. Significant oxidation of membrane proteins was confirmed by a greater loss of thiols in stored RBCs than in fresh RBCs. These results demonstrate that it may be possible to prevent storage-mediated loss of AChE, increased lipid flip-flop, and increased PS exposure, by maintaining or increasing GSH levels of banked RBCs.

Down-regulation of inhibition following unilateral deafening

Physiological and neurochemical experiments described here suggest that unilateral deafening causes a reduction in inhibition in the adult gerbil inferior colliculus (IC) contralateral to the deafened ear. Multiple-unit recordings were made from single electrode penetrations in the IC prior to and directly after contralateral cochlear ablation. These recordings showed up to 60% increases in the proportion of sampled loci at which neural activity excited by ipsilateral stimulation was observed after the ablation. Novel excitatory responses were evident within minutes of the ablation. Western blotting for glutamic acid decarboxylase protein levels showed significant decreases in the IC contralateral to cochlear ablation, relative to those in the ipsilateral IC, at 24 h and 7 days survival after the ablation. Four hour or 1 year survival post-ablation did not produce significant contralateral/ipsilateral differences in relation to the control group. Taken together, these results suggest the presence of at least two, short-term mechanisms involved in the central response to cochlear removal, both of which appear to implicate a decreased inhibitory influence. One is a very rapid, stimulus-related, functional unmasking. The other is a more delayed reduction in the capacity of gamma-aminobutyric acid synthesis in the IC.

Microbial Biomass and Community Structure in a Sequence of Soils with Increasing Fertility and Changing Land Use

The microbial biomass and community structure of eight Chinese red soils with different fertility and land use history was investigated. Two community based microbiological measurements, namely, community level physiological profiling (CLPP) using Biolog sole C source utilization tests and phospholipid fatty acid (PLFA) profiles, were used to investigate the microbial ecology of these soils and to determine how land use alters microbial community structure. Microbial biomass-C and total PLFAs were closely correlated to organic carbon and total nitrogen, indicating that these soil microbial measures are potentially good indices of soil fertility in these highly weathered soils. Metabolic quotients and C source utilization were not correlated with organic carbon or microbial biomass. Multivariate analysis of sole carbon source utilization patterns and PLFAs demonstrated that land use history and plant cover type had a significant impact on microbial community structure. PLFAs showed these differences more than CLPP methods. Consequently, PLFA analysis was a better method for assessing broad-spectrum community differences and at the same time attempting to correlate changes with soil fertility. Soils from tea orchards were particularly distinctive in their CLPP. A modified CLPP method, using absorbance readings at 405 nm and different culture media at pH values of 4.7 and 7.0, showed that the discrimination obtained can be influenced by the culture conditions. This method was used to show that the distinctive microbial community structure in tea orchard soils was not, however, due to differences in pH alone.

Evaluation of a phenotypic scheme for identification of the 'butyrate-producing' Peptostreptococcus species

Gram-positive anaerobic cocci (GPAC) are isolated from approximately one quarter of all infections involving anaerobic bacteria. However, studies of the significance of this group of pathogens have been hindered by an inadequate taxonomy and the lack of a valid identification scheme. In the present study, a phenotypic scheme for the identification of 'butyrate-producing' GPAC based on the analysis of volatile fatty acid profiles by gas-liquid chromatography, biochemical profiles (including the use of the rapid ID 32 A commercial kit) and carbohydrate fermentation reactions, was evaluated. The identity of 68 clinical isolates of GPAC was determined by application of the scheme published by Murdoch. The scheme was found to be easy to apply and only four of the test isolates could not be readily assigned to a species or well-defined group. The species most frequently identified in the test collection were Peptostreptoccoccus vaginalis, P. tetradius and the betaGAL group. A large number of strains was assigned to the heterogeneous 'prevotii/tetradius' group. Some species regarded as being restricted to particular clinical sites were shown to be more widespread than previously thought. The clinical source of the isolates did not show any consistent correlation with species identity.