Work interest as a predictor of competitive employment: policy implications for psychiatric rehabilitation

Consumers with serious mental illness (N = 166) enrolling in two community-based mental health programs, a vocational Program of Assertive Community Treatment and a clubhouse certified by the International Center for Clubhouse Development (ICCD), were asked about their interest in work. About one third of the new enrollees expressed no interest in working. Equivalent supported employment services were then offered to all participants in each program. Stated interest in work and receipt of vocational services were statistically significant predictors of whether a person would work and how long it would take to get a job. Two thirds of those interested in work and half of those with no initial interest obtained a competitive job if they received at least one hour of vocational service. Once employed, these two groups held comparable jobs for the same length of time. These findings demonstrate the importance of making vocational services continuously available to all people with serious mental illness, and the viability of integrating these services into routine mental health care.

[Recommended algorithms of prescription in the diagnosis of iron deficiency and overload]

In view of the recent development of new tests of biochemistry and molecular biology the assessment of iron status should be reconsidered and updated. The French Society of Clinical Biology (SFBC) and the French Society of Hematology (Cellular Hematology Group) recommend algorithms in the diagnosis of iron deficiency and iron overload bearing in mind the best efficiency and health economy. These recommendations are based on the known sensibility and specificity of each test. The analytical requirements for the determination of the tests as well as the clinical and biological signs evoking an iron deficiency or overload are recalled.

Search for mitochondrial A3243G tRNA(Leu) mutation in Polish patients with type 2 diabetes mellitus

BACKGROUND

The influences of genetic and environmental factors form a clinical picture of type 2 diabetes mellitus. Genetic studies of type 2 diabetes mellitus become increasingly important. The knowledge of the molecular background of type 2 diabetes has been growing rapidly over recent years. One of the forms of the disease defined on the molecular level is maternally inherited type 2 diabetes mellitus. This diabetes, which is frequently accompanied by hearing impairment of deafness (maternally inherited diabetes with deafness-MIDD), was linked with sequence differences in mitochondrial DNA. The most frequent cause of MIDD is A3243G substitution in a mitochondrial tRNA(Leu) gene. While this mutation was identified in different races in several populations, it is still important and valuable to evaluate its prevalence in various ethnic groups. The aim of the project was to determine the prevalence of A3243G substitution in a mitochondrial tRNA(Leu) gene among Polish diabetic subjects.

MATERIAL AND METHODS

In total 129 individuals, with type 2 diabetes and 12 with gestational diabetes were selected for this study. Two techniques based on restriction fragment length polymorphism (RFLP) method were used to screen for A3243G mutation. In the first approach, non-radioactive PCR reactions of mitochondrial DNA region of interest were performed using DNA of the study participants. This was followed by Apa I restriction enzyme digestion of the PCR product. Subsequently an electrophoretic separation was done on 2% agarose gel with ethidium bromide staining. In the second, more sensitive, modification of RFLP, [alpha 32P]dCTP was used for internal primer labeling and the electrophoresis was done on acrylamide gel. A positive sample was used to control the quality of the genotyping.

RESULTS

In both approaches none of the samples, except for the positive control, showed the evidence of the G variant.

CONCLUSIONS

In summary, the A3243G mutation in mitochondrial tRNA(Leu) gene is not a frequent cause of diabetes in the Polish population. Further screening of enlarging study group is necessary to fully determine the prevalence of this mutation in our population. This, together with the search for other mitochondrial mutations, should allow to fully determine the prevalence of MIDD and its specific molecular background in the Polish population.

A randomized, controlled trial of remacemide for motor fluctuations in Parkinson's disease

BACKGROUND

Preclinical studies suggest that glutamate antagonists help ameliorate motor fluctuations in patients with PD treated with levodopa.

METHODS

In a multicenter, randomized, double-blind, placebo-controlled, parallel-group, dose-ranging study, the authors assessed the safety, tolerability, and efficacy of the glutamate receptor blocker remacemide hydrochloride in 279 patients with motor fluctuations treated with levodopa. The primary objective was to assess the short-term tolerability and safety of four dosage levels of remacemide during 7 weeks of treatment. Patients were also monitored with home diaries and the Unified PD Rating Scale (UPDRS) to collect preliminary data on treatment efficacy.

RESULTS

Remacemide was well tolerated up to a dosage of 300 mg/d on a twice daily schedule and 600 mg/d on a four times daily schedule. The most common dosage-related adverse events were dizziness and nausea, as observed in previous studies of remacemide. The percent "on" time and motor UPDRS scores showed trends toward improvement in the patients treated with 150 and 300 mg/d remacemide compared with placebo-treated patients, although these improvements were not significant.

CONCLUSION

Remacemide is a safe and tolerable adjunct to dopaminergic therapy for patients with PD and motor fluctuations. Although this study had limited power to detect therapeutic effects, the observed improvement is consistent with studies of non-human primates with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonian signs and symptoms. Additional studies are warranted to confirm these results over an extended period of observation, and to explore the potential neuroprotective effects of remacemide in slowing the progression of PD.

Genetic and biochemical characterization of glycerol uptake in mycoplasma mycoides subsp. mycoides SC: its impact on H(2)O(2) production and virulence

Highly virulent strains of Mycoplasma mycoides subsp. mycoides SC belonging to the African cluster contain an operon with the genes gtsA, gtsB, and gtsC, encoding membrane ATP binding cassette transporter proteins GtsA, GtsB, and GtsC, which are involved in glycerol transport. Strain Afadé from the African cluster incorporated [U-(14)C]glycerol with a time-dependent increase. The less virulent strain L2 of the European cluster, which lacks gtsB and gtsC, failed to incorporate glycerol. Antibodies against GtsB noncompetitively inhibited glycerol uptake. L-alpha-Glycerophosphate was not transported by M. mycoides subsp. mycoides SC. It is postulated to be synthesized by phosphorylation of glycerol during transport and subsequently metabolized further to dihydroxyacetone phosphate accompanied by release of H(2)O(2). Peroxide production in glycerol-containing growth medium was high for the African strain Afadé but very low for the European strain L2. Virtually no H(2)O(2) was produced by both strains without glycerol. Hence, the efficient glycerol uptake system found in the virulent strain of the African cluster leads to a strong release of peroxide, a potential virulence factor which is lacking in the less virulent European strains. M. mycoides subsp. mycoides SC might have adopted, as a strategy for virulence, a highly efficient uptake system for glycerol which allows the production of an active metabolic intermediate that damages host cells.

The inositol 5-phosphatase SHIP is expressed as 145 and 135 kDa proteins in blood and bone marrow cells in vivo, whereas carboxyl-truncated forms of SHIP are generated by proteolytic cleavage in vitro

The inositol polyphosphate 5-phosphatase SHIP plays an important role in negative signalling in B cells and mast cells and in the down-regulation of cytokine receptor-mediated signals in myeloid cells. SHIP is expressed as a 145 kDa full-length protein and an isoform of 135 kDa due to alternative splicing. Additional smaller forms of SHIP which are truncated at the carboxy terminus have been described in bone marrow and peripheral blood mononuclear cells (PBMC). Our data demonstrate that human bone marrow cells and PBMC from healthy donors and patients with acute myeloid leukemia express the 145 kDa form of SHIP and low amounts of a 135 kDa form of SHIP in vivo whereas C-terminal-truncated SHIP proteins are generated by a PMSF-sensitive protease during the preparation of cell lysates in vitro. We have further characterized this protease and identified a proteolytic cleavage site in the human SHIP protein C-terminal to tryptophan residue 941. These data support a physiological role for the 145 and 135 kDa forms of SHIP in bone marrow and peripheral blood cells from normal donors and patients with acute myeloid leukemia.

[Clinical value of urinary biochemical parameters]

Twelve of the urine parameters, namely sodium, potassium, chloride, urea, creatinine, uric acid, calcium, phosphate, protein, microalbumin, amylase and glucose, routinely measured in a biochemistry laboratory were chosen to revalue their interest in clinical practice. For each parameter, urinary collection method, physiologic review and specific indications were set out. The clinical interest of chloride, urea, phosphate or uric acid measurement seem limited to specific pathological conditions. The measurement of urine amylase is out of interest.

Differential modulation of stimulatory and inhibitory Fc gamma receptors on human monocytes by Th1 and Th2 cytokines

Immune complex-mediated inflammatory responses are initiated by Fc gamma R on phagocytes. We report in this study that an inhibitory receptor, Fc gamma RIIb2, is expressed on circulating human monocytes, and when co-cross-linked with stimulatory Fc gamma R it down-regulates effector function. Fc gamma RIIb2 expression is increased by IL-4 and decreased by IFN-gamma, in contrast to the activating receptor, Fc gamma RIIa, which is increased by IFN-gamma and decreased by IL-4. Thus, Th1 and Th2 cytokines differentially regulate the opposing Fc gamma R systems, altering the balance of activating and inhibiting Fc gamma R. The detection and cytokine modulation of Fc gamma RIIb2 in human myeloid cells provide evidence of a negative regulator of immune complex-mediated responses in human phagocytes and offer a new approach to limit Ab-triggered inflammation in autoimmune disease.

Monitoring of ascorbate at a constant rate in cell culture: effect on cell growth

Ascorbic acid (vitamin C) is a primary antioxidant for cells. But, ascorbic acid added to culture medium is not readily available to cells in culture, because it is unstable in aqueous media. We determined the conditions required to obtain and maintain a constant concentration of ascorbate in the culture medium using ascorbate and ascorbate-phosphate. The study was carried out with human fibroblasts and the amounts of ascorbate in the culture medium were determined by high performance liquid chromatography. A mixture of 0.25 mmol/L ascorbate and 0.45 mmol/L ascorbate-phosphate provided a constant concentration of ascorbate in the culture medium. This constant ascorbate concentration proved to be nontoxic for cells and stimulated cell growth in the short term and long term.

Phylogenetic analysis of Pasteurella multocida subspecies and molecular identification of feline P. multocida subsp. septica by 16S rRNA gene sequencing

Pasteurella multocida is commonly found in the oral cavity of cats and dogs. In humans it is known as an opportunistic pathogen after bites from these animals. Phenotypic identification of P. multocida based on biochemical reactions is often limited and usually only done on a species level, even though 3 subspecies are described. For molecular taxonomy and diagnostic purposes a phylogenetic analysis of the three subspecies of P. multocida based on their 16S rRNA (rrs) gene sequence was therefore carried out. We found P. multocida subsp. septica on a distinguished branch on the phylogenetic tree of Pasteurellaceae, due to a 1.5% divergence of its rrs gene compared to the two other, more closely related subspecies multocida and gallicida. This phylogenetic divergence can be used for the identification of P. multocida subsp. septica by rrs gene determination since they form a phylogenetically well isolated and defined group as shown with a set of feline isolates. Comparison to routine phenotypic identification shows the advantage of the sequence-based identification over conventional methods. It is therefore helpful for future unambiguous identification and molecular taxonomy of P. multocida as well as for epidemiological investigations.

Elevated expression of membrane type 1 metalloproteinase (MT1-MMP) in reactive astrocytes following neurodegeneration in mouse central nervous system

Reactive astrocytes occurring in response to neurodegeneration are thought to play an important role in neuronal regeneration by upregulating the expression of extracellular matrix (ECM) components as well as the ECM degrading metalloproteinases (MMPs). We examined the mRNA levels and cellular distribution of membrane type matrix metalloproteinase 1 (MT1-MMP) and tissue inhibitors 1-4 of MMPs (TIMPs) in brain stem and spinal cord of wobbler (WR) mutant mice affected by progressive neurodegeneration and astrogliosis. MT1-MMP, TIMP-1 and TIMP-3 mRNA levels were elevated, whereas TIMP-2 and TIMP-4 expression was not affected. MT1-MMP was expressed in reactive astrocytes of WR. In primary astrocyte cultures, MT1-MMP mRNA was upregulated by exogeneous tumor necrosis factor alpha. Increased plasma membrane and secreted MMP activities were found in primary WR astrocytes.

Epidemiological and microbiological study of an outbreak of infectious keratoconjunctivitis in sheep

After several thousand sheep had been imported from Australia and New Zealand to Croatia during 1995, many native sheep that had been in contact with the imported animals acquired a severe ocular disease closely resembling infectious keratoconjunctivitis. In affected flocks glucose-fermenting mycoplasma were isolated from 48 per cent of conjunctival swabs and Branhamella ovis from 58 per cent. Twelve of 42 culturally and biochemically identical isolates were identified as Mycoplasma conjunctivae by polymerase chain reaction. From the conjunctivae of two animals M conjunctivae and M arginini were isolated in mixed culture. For many reasons most farmers removed the imported animals from their flocks and only sporadic cases of the disease were recognised in 1996. At the end of 1997, six flocks which were clinically free of the disease but had been affected during 1995, and five flocks with no history of the severe ocular disease were examined clinically and microbiologically, and were found to be free of M conjunctivae infection. At the time, B ovis was cultured almost exclusively from sheep originating from flocks which had been affected during 1995 and/or 1996. It was usually isolated in pure culture or as the predominant bacterial species, and was often accompanied by mild conjunctivitis. There were no microbiologically confirmed new cases of infectious keratoconjunctivitis during 1998 and 1999.

Immunoblot assays using recombinant antigens for the detection of Mycoplasma hyopneumoniae antibodies

The 36kDa L-lactate dehydrogenase (LDH) and a 29kDa partial fragment of an ABC transporter ATP-binding protein analogue/multidrug resistance protein homologue (PR2) of Mycoplasma hyopneumoniae were tested for their potential as diagnostic antigens. Recombinant LDH was genetically engineered to contain six histidine residues at its C-terminal end, expressed in Escherichia coli and purified to a high degree using Ni(2+)-chelate affinity chromatography. A partial 262 amino acid segment representing the C-terminal end of the PR2 protein was cloned as a glutathione S-transferase (GST) fusion protein, expressed in E. coli and purified by urea extraction. Purified recombinant LDH-6xHis and PR2-GST were then reacted with pig sera in immunoblot assays. Our immunoblots showed that both proteins detected anti-M. hyopneumoniae antibodies in field and experimentally infected pig sera but not in any of the SPF control sera. The two proteins were specific for M. hyopneumoniae as they did not react with sera of pigs infected with the closely related Mycoplasma flocculare and Mycoplasma hyorhinis which are frequently isolated in pigs but are not of particular concern.

Antigenic and genetic characterization of lipoprotein LppQ from Mycoplasma mycoides subsp. mycoides SC

Lipoprotein LppQ, a predominant 48-kDa antigen, and its corresponding gene, lppQ, were characterized in Mycoplasma mycoides subsp. mycoides SC, the etiological agent of contagious bovine pleuropneumonia. The lppQ gene is specific to M. mycoides subsp. mycoides SC and was found in the type strain and in field strains isolated in Europe, Africa, and Australia, as well as in vaccinal strains. LppQ is encoded as a precursor with a consensus sequence for prokaryotic signal peptidase II and a lipid attachment site. The leader sequence shows significant prominent transmembrane helix structure with a predicted outside-to-inside helix formation capacity. The N-terminal domain of the mature LppQ was shown to be surface exposed. It induced a strong, specific, early, and persistent immune response in naturally and experimentally infected animals. The C-terminal domain of LppQ possesses an integral membrane structure built up of repeated units, rich in hydrophobic and aromatic amino acids, which have a pore formation potential. A recombinant peptide representing the N-terminal domain of LppQ was obtained by site-directed mutagenesis of nine Mycoplasma-specific TGA (Trp) codons into universal TGG (Trp) codons and expression in Escherichia coli hosts. It was used for serodetection of cattle infected with M. mycoides subsp. mycoides SC, in which it was detected postinfection for significantly longer than conventional serological test reactions.

Apx toxins in Pasteurellaceae species from animals

Pasteurellaceae species particularly of porcine origin which are closely related to Actinobacillus pleuropneumoniae were analyzed for the presence of analogues to the major A. pleuropneumoniae RTX toxin genes, apxICABD, apxIICA and apxIIICABD and for their expression. Actinobacillus suis contains both apxICABD(var.suis) and apxIICA(var. suis) operons and was shown to produce ApxI and ApxII toxin. Actinobacillus rossii contained the operons apxIICA(var.rossii) and apxIIICABD(var.rossii). However, only the toxin ApxII and not ApxIII could be detected in cultures of A. rossii. The Apx toxins found in A. suis and A. rossi may play a role in virulence of these pathogens. Actinobacillus lignieresii, which was included since it is phylogenetically very closely related to A. pleuropneumoniae, was found to contain a full apxICABD(var.lign.) operon which however lacks the -35 and -10 boxes in the promoter sequences. As expected from these results, no expression of ApxI was detected in A. lignieresii grown under standard culture conditions. Actinobacillus seminis, Actinobacillus equuli, Pasteurella aerogenes, Pasteurella multocida, Haemophilus parasuis, and also Mannheimia (Pasteurella) haemolytica, which is known to secrete leukotoxin, were all shown to be devoid of any of the apx toxin genes and did not produce ApxI, ApxII or ApxIII toxin proteins. However, proteins of slightly lower molecular mass than ApxI, ApxII and ApxIII which showed limited cross-reactions with monospecific, polyclonal anti-ApxI, anti-ApxII and anti-ApxIII were detected on immunoblot analysis of A. equuli, A. seminis and P. aerogenes. The presence of Apx toxins and proteins that imunologically cross react with Apx toxins in porcine Actinobacillus species other than A. pleuropneumoniae can be expected to interfere with serodiagnosis of porcine pleuropneumonia.

Practice of a testing bench to study the effects of cyclic stretching on osteoblast-orthopaedic ceramic interactions

A new experimental method has been used to study the behaviour of human osteoblasts cultured on bioceramics subjected to mechanical strains. The ceramics were alumina, hydroxyapatite (HA) and a duplex system composed of hydroxyapatite-covered alumina. The system applied 400 microdeformations for a 6-h period with a cycle frequency of 0.5 Hz to osteoblasts growing on ceramic-covered disks. The effects of strains on short-term cell viability, cell growth, alkaline phosphatase (ALP) activity, and collagen biosynthesis were assessed. When possible, the parameters (lactate dehydrogenase) were studied along the experiment in samples of the culture medium, in the other cases by comparison of stretched and unstretched cultures on the same ceramics with the same cell line. In relationship with the coating, mechanical strains resulted in a decrease in DNA corresponding to cell number, an LDH release during straining, an unchanged (alumina) or decreased (HA and duplex) ALP activity, a decrease (HA and duplex) of collagen and total protein synthesis or an increase of it (alumina). The stress-producing device and its associated protocol are shown to be suitable for investigating the behaviour of cells, cultured on biomaterials subjected to mechanical strain.

Resting metabolic rate, body composition, and serum leptin concentrations in a free-living elderly population

OBJECTIVE

The present study investigated the relationship between serum leptin concentrations and resting metabolic rate (RMR) in a large study group of elderly individuals with special consideration of body composition and body fat distribution as possible confounders.

DESIGN AND METHODS

The subjects were 122 women (age: 69+/-6 years, body mass index (BMI): 26.3+/-3.6 kg/m(2)) and 82 men (age: 69+/-5 years, BMI: 26.0+/-2.6 kg/m(2)). RMR was measured by indirect calorimetry and body composition by the bioelectrical impedance method. Serum leptin levels were determined by radioimmunoassay.

RESULTS

There was a strong correlation between fat mass (FM) and serum leptin levels in both sexes. An age-related decline in leptin levels adjusted for FM was observed only in the women. After adjustment of RMR for both fat-free mass (FFM) and FM, leptin levels were not associated with RMR. In stepwise multiple regression analysis, FFM was the main predictor of RMR, explaining 35.8% and 47.6% of the variance of RMR in men and women respectively. FM did not explain variance in RMR in men, but accounted for 2.6% of the variance in RMR in women. Waist-hip-ratio and age influenced RMR only in males, explaining 5.7% and 4.0% of the variance in RMR respectively.

CONCLUSION

Leptin is not a significant predictor of RMR in the elderly, but body composition and distribution of body fat are significantly associated with RMR.

Isolation and characterization of a capsule-deficient mutant of Actinobacillus pleuropneumoniae serotype 1

The capsular polysaccharides (CPS) play a major role in pathogenicity of Actinobacillus pleuroIpneumoniae, the causative agent of porcine pleuropneumonia. The purpose of the present study was to isolate a mutant in CPS biosynthesis by using a mini-Tn 10 transposon mutagenesis system and evaluate its adherence to host cells. One mutant apparently did not possess CPS as it did not react with a monoclonal antibody against A. pleuropneumoniae serotype 1 capsular antigen. Absence of capsule was confirmed by flow cytometry and also by transmission electron microscopy after polycationic ferritin labelling. The site of insertion of the mini-Tn 10 was determined and found to be in the cpxC gene. Its gene product, CpxC, is a protein involved in polysaccharide transport across the cytoplasmic membrane during CPS biosynthesis. Use of piglet tracheal frozen sections indicated that the CPS mutant adhered significantly (P=0.0001) more than the parent strain. The non-capsular mutant was less virulent in pigs compared to the parent strain and showed no mortality in experimentally infected pigs. The CPS mutant was however resistant to pig serum. This CPS mutant is the first A. pleuropneumoniae mutant in a CPS transport gene. It is also the first time that adherence of a CPS mutant of A. pleuropneumoniae is evaluated. Our observations indicate that capsular polysaccharides of A. pleuropneumoniae serotype 1 are not involved in adherence to piglet tracheal frozen sections but rather mask, at least in part, the adhesive functions.

Immune responses to Mycoplasma conjunctivae in alpine ibex, alpine chamois, and domestic sheep in Switzerland

The humoral immune response of three alpine chamois (Rupicapra rupicapra rupicapra), two alpine ibex (Capra ibex ibex) and three domestic sheep naturally affected with infectious keratoconjunctivitis (IKC), and four ibex and two sheep experimentally infected with Mycoplasma conjunctivae was analysed. In addition, the local immune response to M. conjunctivae was analysed using conjunctival washes from chamois and sheep. Immunoblot analysis of sera using whole cell antigens of M. conjunctivae revealed the major immunogenic proteins which had molecular masses of 175, 83, 68, 60, 50, 42, 36, and 33 kDa. Major antigens were found at 83, 68, 60, and 42 kDa in both sera and conjunctival washes from naturally infected animals of all three Caprinae species. In experimentally infected animals, antibodies to the 68 and 60 kDa antigens were dominant. Naturally infected animals showed much stronger immune reactions than those experimentally infected, and specific antibodies appeared 2 to 4 wk after experimental infection. To evaluate possible cross-reactions, whole cell antigen of M. conjunctivae was analysed by immunoblot against hyperimmune sera of closely related Mycoplasma spp. Antibodies to the 175, 73, 68, 60, and 33 kDa antigens appeared to be specific to M. conjunctivae. Cross-reactions mainly with 83, 50, and 42 kDa antigens were detected, in particular with M. ovipneumoniae and M. bovoculi hyperimmune sera, but also with antisera against M. capricolum capricolum and M. putrefaciens.

Characterization of a predominant immunogenic outer membrane protein of Riemerella anatipestifer

The ompA gene, encoding the 42-kDa major antigenic outer membrane protein OmpA of Riemerella anatipestifer, the etiololgical agent of septicemia anserum exsudativa, was cloned and expressed in Escherichia coli. Recombinant OmpA displayed a molecular mass similar to that predicted from the nucleotide sequence of the ompA gene but lower than that observed in total cell lysates of R. anatipestifer. The ompA gene showed a conserved C-terminal region comprising the OmpA-like domain and a variable N-terminal region. This structure is similar to those of the analogous outer membrane proteins of several gram-negative bacteria. However, OmpA of R. anatipestifer contains six EF-hand calcium-binding domains and two PEST regions, which distinguish it from other outer membrane proteins. The occurrence of these motifs in OmpA suggests a possible role in virulence for this protein. The ompA gene is present in the R. anatipestifer type strain and in all serotype reference strains. However, it exhibits some minor genetic heterogeneity among different serotypes, which seems not to affect the strong antigenic characteristics of the protein. OmpA is a conserved and strong antigenic determinant of R. anatipestifer and hence is suggested to be a valuable protein for the serodetection of R. anatipestifer infections, independent of their serotype.

Detection of the ADP-ribosyltransferase toxin gene (cdtA) and its activity in Clostridium difficile isolates from Equidae

Clostridium difficile is an antibiotic-associated emerging pathogen of humans and animals. Thus far three toxins of C. difficile have been described: an enterotoxin (ToxA), a cytotoxin (ToxB) and an ADP-ribosyltransferase (CDT). In the present work we describe the first isolation of CDT producing C. difficile from Equidae with gastro-intestinal disease. Out of 17 C. difficile strains isolated from Equidae, 11 were positive for the genes tcdA and tcdB encoding ToxA and ToxB. In addition four of these 11 isolates were positive for the cdtA gene encoding the catalytic subunit of the ADP-ribosyltransferase CDT. Interestingly none of the isolates derived from canines (41 isolates) and felines (4 isolates) harboured the cdtA gene. In C. difficile field isolates which contained the cdtA gene, ADP-ribosyltransferase activity could also be detected in culture supernatants indicating expression and secretion of CDT. All strains were associated with intestinal disorders, but no association was found for the occurrence of toxins with a specific clinical diagnosis.

Mineralization and alkaline phosphatase activity in collagen lattices populated by human osteoblasts

Adult human osteoblastic cells were grown in a native type I collagen gel. Proliferation and viability analyses showed that cells rapidly stopped dividing and became blocked in the G0G1 phase (91% on day 13). Carboxyfluorescein diacetate cell staining and flow cytometry showed that osteoblasts were viable for the first 16 days and then viability decreased (58% viable cells on day 22). Osteoblasts were able to retract the matrix. Betaglycerophosphate (betaGP) stimulated the deposition of mineral particles in the collagen network, and electron probe microanalysis showed that they were principally calcium and phosphorus, with a Ca/P ratio of about 1.7. Various times of betaGP supply were tested. We compared 10 mM betaGP added only once at day 0, or continuously from day 0, day 8, or day 21. Mineralization was observed in conditions where betaGP was added at day 0. Furthermore, 10 mM betaGP added once during gel preparation was sufficient to induce mineralization with mineral accumulation up to day 15 whereas the speed of the gel contraction decreased. In every condition, cultures expressed high alkaline phosphatase (ALP) levels as early as day 3, which decreased afterwards. These kinetics might explain why the other conditions did not prove favorable to the mineralization process. The model was used to study the influence of blocking gel retraction. Blocking retraction delayed the ALP activity decrease, but had no effect on mineralization. In conclusion, human adult osteoblasts cultured in native collagen gel stopped proliferation and underwent mineralization very early. This model should be used to investigate the influence of effectors on the early stages of culture.