Combining 3D human in vitro methods for a 3Rs evaluation of novel titanium surfaces in orthopaedic applications

In this study, we report on a group of complementary human osteoblast in vitro test methods for the preclinical evaluation of 3D porous titanium surfaces. The surfaces were prepared by additive manufacturing (electron beam melting [EBM]) and plasma spraying, allowing the creation of complex lattice surface geometries. Physical properties of the surfaces were characterized by SEM and profilometry and 3D in vitro cell culture using human osteoblasts. Primary human osteoblast cells were found to elicit greater differences between titanium sample surfaces than an MG63 osteoblast-like cell line, particularly in terms of cell survival. Surface morphology was associated with higher osteoblast metabolic activity and mineralization on rougher titanium plasma spray coated surfaces than smoother surfaces. Differences in osteoblast survival and metabolic activity on titanium lattice structures were also found, despite analogous surface morphology at the cellular level. 3D confocal microscopy identified osteoblast organization within complex titanium surface geometries, adhesion, spreading, and alignment to the biomaterial strut geometries. Mineralized nodule formation throughout the lattice structures was also observed, and indicative of early markers of bone in-growth on such materials. Testing methods such as those presented are not traditionally considered by medical device manufacturers, but we suggest have value as an increasingly vital tool in efficiently translating pre-clinical studies, especially in balance with current regulatory practice, commercial demands, the 3Rs, and the relative merits of in vitro and in vivo studies. Biotechnol. Bioeng. 2016;113: 1586-1599. © 2015 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

Polychlorinated biphenyl (PCB) and dioxin concentrations in residential dust of pregnant women

Polychlorinated biphenyls (PCBs) and dioxins are well known for their persistence in the environment. PCBs can be found in the residential environment long after the use of these chemicals in domestic products and industrial processes has ceased. Dioxins have been assessed in Australia as being of very low concentrations. Despite concerns about residential dust as a source of human exposure to persistent chemicals, there has been limited testing of PCBs and dioxins in dust in Australia. As part of an assessment of maternal exposure to a variety of persistent toxic substances, we analysed 30 residential dust samples from a variety of geographical settings for their dioxin and PCB concentrations. PCBs were found in most samples, the median and range concentrations (pg g(-1)) of dominant congeners of PCB were as follows: PCB118 (315; <35.0-29 000), PCB105 (130; 14.0-16 000) and PCB156 (440; <5.00-2800). Dioxin concentrations were generally low with median concentrations for the total sum of dioxin-like polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) of 3.75 pg g(-1) each. There was a very high percentage of non-detects. Concentrations of both PCBs and dioxins were low compared with most studies reporting residential dust concentrations internationally. Age of dwelling was the only factor observed to influence both PCB congener concentrations and dioxin isomers in multivariate regression analyses. No other housing or sociodemographic variables, including proximity to industry, were important predictors in multivariate linear regression models.

A Mental Health Assessment and Support Team for Community Elders in Fife (EAST)

Background

The aging population combined with the increased recognition of the need to assess elderly patients with mental health difficulties in their own environment encouraged service redesign in Fife with the focus on community assessment of older people with mental health needs.

Aims

To establish and assess the functioning of a joint Health and Social Services enhanced assessment and support team (EAST) for community-dwelling elders with significant mental health needs living in a Scottish health region, and to determine the impact of this team on the requirement for acute psychogeriatric hospital services.

Methods

Prospective three-year data collection of service activity involving EAST and the local psychogeriatric acute inpatient and day hospital facilities.

Results

EAST assessed 111 patients during the study, 83% with a diagnosis of dementia. The mean duration of assessment was six weeks with 9% of patients receiving an overnight home assessment and 6% requiring hospital admission. Overall there was a substantial reduction in utilization of both acute psychogeriatric admission beds and day hospital placements.

Conclusions

Multi-agency community assessment of elders with mental health problems can be addressed effectively without recourse to hospital admission, which may allow resource release for further service developments.

Treatment of post-transplant lymphomas with anti-B-cell monoclonal antibodies

The treatment of post-transplant lymphomas still needs major improvements in order to put the patient in remission and to retain graft function. Chemotherapy is far too toxic in these patients. A more specific treatment such as anti-B-cell monoclonal antibody is very promising. The cytotoxic effect of antibody relies mainly on complement-induced and antibody-dependent cellular cytotoxicity; apoptosis may also induce tumor cell death. B-cell antigens expressed on the cell surface are the targets of antibody attack; some specificities may be chosen because of their level of expression or because of signaling induced within the cell. Anti-B-cell antibodies can be produced by genetic engineering in order to be humanized or to carry bispecific Fabs. The efficacy and safety of anti-B-cell monoclonal antibodies (mAbs) in transplant patients have been proven with different antibodies such as anti-CD21/CD24 mAb, anti-CD38 mAb and anti-CD20 mAb. In a retrospective analysis of different centers in France, rituximab (anti-CD20 mAb, Roche Products) achieved an overall 69% remission rate in 34 organ and bone-marrow transplant patients. But the conditions of use of antibody must be better defined, particularly with regard to the immunosuppressive therapy, the type of tumor and the dose of antibody. We must also improve our understanding of the in vivo mechanisms of action of antibody to develop more efficient antibody constructs.

Tomographic Small-Animal Imaging Using a High-Resolution Semiconductor Camera

We have developed a high-resolution, compact semiconductor camera for nuclear medicine applications. The modular unit has been used to obtain tomographic images of phantoms and mice. The system consists of a 64 x 64 CdZnTe detector array and a parallel-hole tungsten collimator mounted inside a 17 cm x 5.3 cm x 3.7 cm tungsten-aluminum housing. The detector is a 2.5 cm x 2.5 cm x 0.15 cm slab of CdZnTe connected to a 64 x 64 multiplexer readout via indium-bump bonding. The collimator is 7 mm thick, with a 0.38 mm pitch that matches the detector pixel pitch. We obtained a series of projections by rotating the object in front of the camera. The axis of rotation was vertical and about 1.5 cm away from the collimator face. Mouse holders were made out of acrylic plastic tubing to facilitate rotation and the administration of gas anesthetic. Acquisition times were varied from 60 sec to 90 sec per image for a total of 60 projections at an equal spacing of 6 degrees between projections. We present tomographic images of a line phantom and mouse bone scan and assess the properties of the system. The reconstructed images demonstrate spatial resolution on the order of 1-2 mm.

Health and housing: a historical examination of alternative perspectives

The deleterious effect of low-quality housing and related environmental factors on the physical and mental health of its residents is a widely accepted phenomenon. Yet low-quality housing continues to exist, partly because of the nature of housing as a commodity in a capitalist system. This paper defines three political-analytic perspectives within which the housing-health relationship can be seen: individualistic, reformist, and dialectical-materialist. These approaches incorporate perspectives on the nature of the relationship as well as strategic implications arising from them. In this context, the housing-health relationship is examined in fact and interpretation from the 1840s to the present. All three perspectives are illustrated by various popular analyses of changes in urban form and housing as well as the housing-health relationship. The dependence of housing quality on the mode of production is shown, demonstrating the weaknesses of the individualistic and reformist perspectives, which assume housing quality to be independent of the mode of production. The different strategic implications of the three perspectives are illustrated in the conclusion in a discussion of the case of lead paint poisoning.

A survey of methohexitone use by anesthetists in the clinical practice of ECT in Edinburgh

The dosage of methohexitone (methohexital) administered by anesthetic staff was surveyed in a consecutive series of 52 patients referred for electroconvulsive therapy (ECT) in routine clinical practice in Edinburgh. Patients were weighed before the first treatment, and the ratio of administered dose to weight in kilograms calculated. Anesthesia was administered by three consultant staff and six nonconsultant staff. In only one patient (2%) was the administered dose within the range recommended by the Royal College of Psychiatrists (0.75-0.9 mg/kg), and in only four patients (8%) were the doses within the range recommended by the American Psychiatric Association (0.75-1.0 mg/kg). In all other patients the dose exceeded these recommended ranges; the average dose was 1.5 (+/- 0.3) mg/kg. The possible implications of these findings are discussed.

The colanic acid gene cluster of Salmonella enterica has a complex history

The colanic acid gene cluster of Salmonella enterica LT2 was sequenced and compared with that of Escherichia coli K-12. The two clusters are similar with divergence slightly higher than average for genes of the two species. The cluster was divided into four blocks by GC content and seems likely to have transferred from a higher GC content species to the ancestor of E. coli and S. enterica. All 19 genes of K-12 and 13 genes of LT2 appear to have undergone random genetic drift with amelioration of the GC content. However, in the case of S. enterica, we believe that the six genes of the GDP-fucose pathway group were replaced relatively recently by genes closely related to those of the original donor species. Two repetitive elements were observed: a bacterial interspersed mosaic element in the intergenic region between wzx and wcaK in K-12 only and a RSA (repetitive sequence element) sequence between wcaJ and wzx in LT2 only.

L-685,458, an aspartyl protease transition state mimic, is a potent inhibitor of amyloid beta-protein precursor gamma-secretase activity

Progressive cerebral amyloid beta-protein (A beta) deposition is believed to play a central role in the pathogenesis of Alzheimer's disease (AD). Elevated levels of A beta(42) peptide formation have been linked to early-onset familial AD-causing gene mutations in the amyloid beta-protein precursor (A beta PP) and the presenilins. Sequential cleavage of A beta PP by the beta- and gamma-secretases generates the N- and C-termini of the A beta peptide, making both the beta- and gamma-secretase enzymes potential therapeutic targets for AD. The identity of the A beta PP gamma-secretase and the mechanism by which the C-termini of A beta are formed remain uncertain, although it has been suggested that the presenilins themselves are novel intramembrane-cleaving gamma-secretases of the aspartyl protease class [Wolfe, M. S., Xia, W., Ostaszewski, B. L., Diehl, T. S., Kimberly, W. T., and Selkoe, D. J. (1999) Nature 398, 513-517]. In this study we report the identification of L-685,458 as a structurally novel inhibitor of A beta PP gamma-secretase activity, with a similar potency for inhibition of A beta(42) and A beta(40) peptides. This compound contains an hydroxyethylene dipeptide isostere which suggests that it could function as a transition state analogue mimic of an aspartyl protease. The preferred stereochemistry of the hydroxyethylene dipeptide isostere was found to be the opposite to that required for inhibition of the HIV-1 aspartyl protease, a factor which may contribute to the observed specificity of this compound. Specific and potent inhibitors of A beta PP gamma-secretase activity such as L-685,458 will enable important advances toward the identification and elucidation of the mechanism of action of this enigmatic protease.

Effects of storage conditions and hemolysis on vitamin E concentrations in porcine serum and liver

Vitamin E (alpha-tocopherol) is an antioxidant vitamin important in protecting unsaturated fatty acids in lipid membranes from peroxidation. Variation in collection, storage, and shipping conditions of samples can potentially lead to breakdown of vitamin E prior to analysis. Therefore, the purposes of this project were 1) to determine the stability of vitamin E in refrigerated and frozen porcine liver and serum and 2) to evaluate the effects of red blood cell (RBC) hemolysis on porcine serum vitamin E concentrations. Porcine liver and nonhemolyzed serum were collected and stored refrigerated or frozen. Samples were analyzed for vitamin E immediately or on days 2, 3, 7, or 14. In addition, porcine RBCs were added to normal serum at concentrations from 1 x 10(6) to 1 X 10(9) RBC/ml and hemolyzed by freeze-thaw prior to analysis for vitamin E or products of lipid peroxidation.

Polycyclic aromatic hydrocarbons in fuel-oil contaminated soils, Antarctica

Where fuel oil spills have occurred on Antarctic soils polycyclic aromatic hydrocarbons (PAH) may accumulate. Surface and subsurface soil samples were collected from fuel spill sites up to 30 years old, and from nearby control sites, and analysed for the 16 PAHs on the USEPA priority pollutants list, as well as for two methyl substituted naphthalenes, 1-methylnaphthalene and 2-methylnaphthalene. PAH levels ranged from 41-8105 ng g-1 of dried soil in the samples from contaminated sites and were below detection limits in control site samples. PAH were detected in surface soils and had migrated to lower depths in the contaminated soil. The predominant PAH detected were naphthalene and its methyl derivatives.

Nursing implications of a vancomycin resistant enterococcus outbreak in a renal unit

Vancomycin Resistant Enterococcus is a difficult organism to treat and is becoming more prevalent world-wide. When it was identified in a busy renal unit, radical and expensive measures were taken to try and control the outbreak. Although these had costs to both patients and staff, the organism was eradicated from the unit.

Towards filmless and distance radiology

To many people radiology is synonymous with films. For 20 years or so, however, it has been possible to capture digitally data traditionally displayed on film, and that was true from the beginning of computed tomography and magnetic resonance imaging too. There is more to picture archiving and communication systems (PACS) than the economies of filmlessness and the ability to modify images. To realise the full potential of PACS requires huge and expensively equipped networks linking the radiology department, hospital wards, outpatient clinics, laboratories, family doctors' clinics, and so on, permitting simultaneous consultations on different sites and almost instant reporting from specialist radiologists at a distance. The data sets that need to be transferred are huge but some of the technical obstacles are now being overcome and the past few years have seen some hospitals move to a filmless state. The more common pattern, though, will be a piecemeal approach. PACS and teleradiology certainly provide a quicker imaging service. How soon a total PACS will save money for a hospital operating budget is less clear.

Outcome of patients discharged from a coronary care unit with a diagnosis of "chest pain not yet diagnosed"

OBJECTIVE

To determine the outcome and 3-year mortality rate among patients discharged from a coronary care unit (CCU) with a diagnosis of "chest pain not yet diagnosed."

DESIGN

Prospective observational cohort study.

SETTING

CCU in a university teaching hospital.

PATIENTS

All 158 eligible patients discharged from the CCU between August 1986 and December 1988. Of them, 27 refused to participate and 31 did not meet the inclusion criteria because of significant co-morbidity or transportation difficulties.

INTERVENTIONS

Evaluation with maximal and thallium exercise stress testing and four major gastrointestinal (GI) investigations: 24-hour intraesophageal pH monitoring, upper GI endoscopy with biopsy, esophageal motility studies and an upper GI barium series.

OUTCOME MEASURES

Results of investigations and incidence of recurrent chest pain, CCU readmission, coronary angiography, coronary artery bypass surgery, myocardial infarction and death at 6, 12, 24 and 36 months after the index visit.

RESULTS

Of the patients enrolled in the study 79% (79/100) had a normal exercise thallium stress test result, 74% (68/92) had an abnormal result from the 24-hour pH monitoring, 87% (82/94) had abnormal endoscopic results, 90% (84/93) had abnormal manometric results, and 89% (83/93) had signs of reflux with the barium series. At 3 years 50 patients had recurrent chest pain and 3 underwent coronary artery bypass surgery. Three patients died over the 3 years, all of noncardiac causes.

CONCLUSION

Many patients discharged from the CCU with a diagnosis of chest pain not yet diagnosed have a high incidence of esophageal disorders and a very low 3-year mortality rate. More research into the early and effective identification and management of patients with such a diagnosis is needed.

Organization of the Escherichia coli K-12 gene cluster responsible for production of the extracellular polysaccharide colanic acid

Colanic acid (CA) is an extracellular polysaccharide produced by most Escherichia coli strains as well as by other species of the family Enterobacteriaceae. We have determined the sequence of a 23-kb segment of the E. coli K-12 chromosome which includes the cluster of genes necessary for production of CA. The CA cluster comprises 19 genes. Two other sequenced genes (orf1.3 and galF), which are situated between the CA cluster and the O-antigen cluster, were shown to be unnecessary for CA production. The CA cluster includes genes for synthesis of GDP-L-fucose, one of the precursors of CA, and the gene for one of the enzymes in this pathway (GDP-D-mannose 4,6-dehydratase) was identified by biochemical assay. Six of the inferred proteins show sequence similarity to glycosyl transferases, and two others have sequence similarity to acetyl transferases. Another gene (wzx) is predicted to encode a protein with multiple transmembrane segments and may function in export of the CA repeat unit from the cytoplasm into the periplasm in a process analogous to O-unit export. The first three genes of the cluster are predicted to encode an outer membrane lipoprotein, a phosphatase, and an inner membrane protein with an ATP-binding domain. Since homologs of these genes are found in other extracellular polysaccharide gene clusters, they may have a common function, such as export of polysaccharide from the cell.

Radiology in the detection and prevention of colorectal cancer

Imaging techniques available for detection of colorectal cancer include barium enema, endoscopy, computed tomography (CT), ultrasound, magnetic resonance (MR) and immunoscintigraphy. Technical advances continue rapidly and prompt frequent re-evaluation of the optimal approach to management of these patients. Barium enema and colonoscopy are the main techniques for evaluation of symptomatic patients, although CT may well assume the predominant role within a few years. Variation in quality of barium enemas and colonoscopy poses a challenge for continuing medical education (CME) activities. Screening of asymptomatic individuals has to be considered separately for high, moderate and low risk population. Recommendations have to be made at present in the absence of evidence of effectiveness. Staging of disease pre-operatively is of limited value. Follow-up after surgery should be primarily clinical although endoscopy, CT, MR, ultrasound and immunoscintigraphy all have specific roles in the evaluation of patients suspected of harbouring recurrent disease.

Radiology in screening for colorectal cancer

This paper is in two sections. The first reports our own experience at McMaster University with screening for colorectal cancer (CRC), and the second discusses some general aspects of screening, and problems with the methods that are available.

A plasmid-borne O-antigen chain length determinant and its relationship to other chain length determinants

We identify a function-controlling O antigen chain length for a plasmid-borne gene, cldpHS-2, harboured by Flexneri strains of Escherichia coli known to cause reactive arthritis. The predicted amino acid sequence of the gene product is very similar to those of other cld genes and that of fepE, thought to be part of the enterobactin iron uptake system of E. coli. The predicted proteins are compared with rfb-associated chain length determinants as a family of related genes.

Structure of the O antigen of Escherichia coli K-12 and the sequence of its rfb gene cluster

Escherichia coli K-12 has long been known not to produce an O antigen. We recently identified two independent mutations in different lineages of K-12 which had led to loss of O antigen synthesis (D. Liu and P. R. Reeves, Microbiology 140:49-57, 1994) and constructed a strain with all rfb (O antigen) genes intact which synthesized a variant of O antigen O16, giving cross-reaction with anti-O17 antibody. We determined the structure of this O antigen to be -->2)-beta-D-Galf-(1-->6)-alpha-D-Glcp- (1-->3)-alpha-L-Rhap-(1-->3)-alpha-D-GlcpNAc-(1-->, with an O-acetyl group on C-2 of the rhamnose and a side chain alpha-D-Glcp on C-6 of GlcNAc. O antigen synthesis is rfe dependent, and D-GlcpNAc is the first sugar of the biological repeat unit. We sequenced the rfb (O antigen) gene cluster and found 11 open reading frames. Four rhamnose pathway genes are identified by similarity to those of other strains, the rhamnose transferase gene is identified by assay of its product, and the identities of other genes are predicted with various degrees of confidence. We interpret earlier observations on interaction between the rfb region of Escherichia coli K-12 and those of E. coli O4 and E. coli Flexneri. All K-12 rfb genes were of low G+C content for E. coli. The rhamnose pathway genes were similar in sequence to those of (Shigella) Dysenteriae 1 and Flexneri, but the other genes showed distant or no similarity. We suggest that the K-12 gene cluster is a member of a family of rfb gene clusters, including those of Dysenteriae 1 and Flexneri, which evolved outside E. coli and was acquired by lateral gene transfer.

Identification of L-tryptophan derivatives with potent and selective antagonist activity at the NK1 receptor

As part of a program of screening the Merck sample collection, N-ethyl-L-tryptophan benzyl ester was identified as a weak antagonist at the substance P (NK1) receptor. Structure-activity studies showed that the indole ring system could be replaced by 3,4-dichlorophenyl, alpha- or beta-naphthyl, or benzthiophene with retention or only small loss of affinity. It was found that acylation of the tryptophan nitrogen gave compounds with higher affinity than N-ethyl or other basic amines. Optimization of substitution on the benzyl ester led to the identification of the 3,5-bis-(trifluoromethyl)benzyl ester of N-acetyl-L-tryptophan 26 as a potent and selective substance P receptor antagonist. Compound 26 blocked substance P induced dermal extravasation in vivo and was the most potent compound from this structurally novel class of antagonists which further adds to the diversity of small molecules that bind to the (NK1) receptor.

Pneumatic reduction of intussusception using carbon dioxide

Pneumatic reduction using air has recently become popular for the initial non-surgical management of intussusception. Since carbon dioxide (CO2) is rapidly absorbed from body surfaces, it should theoretically result in less cramping and distension following reduction. We reviewed our recent experience with the pneumatic reduction of intussusception using CO2 in 26 children. In 22 of these the intussusception was reduced (85%). There was one performation with CO2; the patient did not suffer any postoperative complications. Five additional children who had been treated unsuccessfully with barium had intussusception subsequently reduced with CO2. Following CO2 reduction, most children were fed within hours, and there were no instances of significant abdominal distension or cramping. We conclude that pneumatic reduction of intussusception using CO2 is safe and effective, and has the theoretical advantage of more rapid absorption from the gastrointestinal tract than air.

Repeat unit polysaccharides of bacteria: a model for polymerization resembling that of ribosomes and fatty acid synthetase, with a novel mechanism for determining chain length

We report the identification and sequence from Escherichia coli and Salmonella enterica strains of the cld gene, encoding the chain-length determinant (CLD) which confers a modal distribution of chain length on the O-antigen component of lipopolysaccharide (LPS). The distribution of chain lengths in the absence of this gene fits a model in which as the chain is extended there is a constant probability of 0.165 of transfer of growing chain to LPS core, with termination of chain extension. The data for E. coli O111 fit a model in which the CLD reduces this probability for short chains and increases it to 0.4 for longer chains, leading to a reduced number of short chain molecules but an increase in numbers of longer molecules and transfer of essentially all molecules by chain length 21. We put forward a model for O-antigen polymerase which resembles the ribosome and fatty acid synthetase in having two sites, with the growing chain being transferred from a D site onto the new unit at the R site to extend the chain and then back to the D site to repeat the process. It is proposed that the CLD protein and polymerase form a complex which has two states: 'E' facilitating extension and 'T' facilitating transfer to core. The complex is postulated to enter the E state as O-antigen polymerization starts, and to shift to the T state after a predetermined time, the CLD acting as a molecular clock. The CLD is not O-antigen or species-specific but the modal value does depend on the source of the cld gene.

Delayed perforation of a duodenal diverticulum by a biliary endoprosthesis

A 73-year-old woman with cholangitis due to stricture of the bile duct and the presence of stones was treated by the placement of a biliary endoprosthesis. However, 8 weeks later the lower end of the stent had retracted into a duodenal diverticulum and penetrated its inferior wall. The patient was readmitted to hospital for treatment of a retroperitoneal abscess.

Safety and efficacy of high kV biliary lithotripsy: preliminary experience

Despite intense interest in laparoscopic cholecystectomy, biliary lithotripsy (BL), by avoiding the need for general anesthesia, could remain a useful alternative in approximately 10% of patients with symptomatic gallstones. The poor stone clearance rates reported by the Dornier National Biliary Lithotripsy Study has led to disenchantment with biliary lithotripsy. However, the results may reflect the relatively low kV (18.7 +/- 1.7) used. We have compared symptomatic gallbladder stone/cholecystolithiasis patients with one to five stones of aggregate diameter < 60 mm treated with one to three sessions on an MPLS 9000 (Dornier) lithotripter at moderate kV (22.7 +/- 1.7 kV; mean number of shocks 1473 +/- 356) with a similar group treated with high kV (26 kV, mean number of shocks 1357 +/- 507). Ultrasound stone diameter measurements were made pre- and post-BL; 12-wk results are reported. Treatment safety was assessed by recording adverse experiences and serum, urine, hematology, and chemistry. For patients with single stones, the high kV treatment took significantly (p < 0.05) less time (74 +/- 30 min) than moderate kV treatment (118 +/- 33 min). At 3 months, the moderate kV-treated single-stone group had a residual maximum fragment size of 3.2 +/- 3.3 mm versus 1.8 +/- 2.3 mm in the high kV-treated single-stone group. The 3-month stone-free rate for patients with single stones treated at high kV was 44% compared with 46% for the moderate kV-treated group (NS). At 1 wk, 11 patients had microscopic or macroscopic hematuria and six patients had mildly elevated liver function tests. At 6 wk, however, all urine and hematological measurements had returned to normal. Two patients suffered pancreatitis, one in each group. High kV BL appears to be safe and, for patients with single stones, gives better fragmentation and takes less time to administer than moderate kV. Whether a high kV treatment protocol can achieve improved long-term stone-free rates remains to be assessed.

4-Amido-2-carboxytetrahydroquinolines. Structure-activity relationships for antagonism at the glycine site of the NMDA receptor

trans-2-Carboxy-5,7-dichloro-4-amidotetrahydroquinolines, evolved from the lead 5,7-dichlorokynurenic acid, have been synthesized and tested for in vitro antagonist activity at the glycine site on the N-methyl-D-aspartate (NMDA) receptor. Optimization of the 4-substituent has provided antagonists having nanomolar affinity, including the urea trans-2-carboxy-5,7-dichloro-4[[(phenylamino)carbonyl]amino]-1,2,3, 4-tetrahydroquinoline (35; IC50 = 7.4 nM vs [3H]glycine binding; Kb = 130 nM for block of NMDA responses in the rat cortical slice), which is one of the most potent NMDA antagonists yet found. The absolute stereochemical requirements for binding were found to be 2S,4R, showing that, in common with other glycine-site NMDA receptor ligands, the unnatural configuration at the alpha-amino acid center is required. The preferred conformation of the trans-2,4-disubstituted tetrahydroquinoline system, as shown by X-ray crystallography and 1H NMR studies, places the 2-carboxyl pseudoequatorial and the 4-substituent pseudoaxial. Modifications of the 4-amide show that bulky substituents are tolerated and reveal the critical importance for activity of correct positioning of the carbonyl group. The high affinity of trans-2-carboxy-5,7-dichloro-4-[1-(3-phenyl-2-oxoimidazolidinyl)]- 1,2,3,4-tetrahydroquinoline (55; IC50 = 6 nM) suggests that the Z,Z conformer of the phenyl urea moiety in 35 is recognized by the receptor. Molecular modeling studies show that the 4-carbonyl groups of the kynurenic acids, the tetrahydroquinolines, and related antagonists based on N-(chlorophenyl)glycine, can interact with a single putative H-bond donor on the receptor. The results allow the establishment of a three-dimensional pharmacophore of the glycine receptor antagonist site, incorporating a newly defined bulk tolerance/hydrophobic region.

Comparative efficiencies of bispecific F(ab'gamma)2 and chimeric mouse/human IgG antibodies in recruiting cellular effectors for cytotoxicity via Fc gamma receptors

The three forms of Fc gamma receptor carried by monocytes (Fc gamma RI, II) and natural killer (NK) cells (Fc gamma RIII) are all capable of mediating cell lysis. Here we compare the use of F(ab'gamma)2 bispecific antibodies, specifically targetting individual Fc gamma R, and chimeric IgG mouse/human antibodies which are capable of targetting all Fc gamma R, for their ability to mediate target cell destruction. The derivatives are prepared by linking hinge sulphydryl residues via tandem thioether bonds, using a bismaleimide crosslinker: Fab' from an anti-Fc gamma R mAb linked to Fab' from a common anti-target mAb (BsAb), or Fab' from the common anti-target mouse antibody linked to human Fc gamma (FabFc or bisFabFc). All the derivatives targetting chick red blood cells gave efficient lysis, although different effector cell donors yielded differences in both the lytic levels achieved and the comparative efficiencies of derivatives. In contrast, significant lysis of the guinea pig lymphoblastic leukaemia, L2C, regularly resulted only via the anti-Fc gamma RIII BsAb and the chimeric derivatives. These results suggest that the chimeric, Fc-containing derivatives mediate tumour cell lysis principally through Fc gamma RIII on NK cells. This is in contrast to the situation with the chick red blood cells where the chimeric derivatives appear capable of lysing erythrocytes by utilizing either monocytes or NK cells, because significant (approximately 50%) lysis occurred with effector cell populations magnetically depleted through either Fc gamma RII or Fc gamma RIII. A major difference between these two types of antibody derivative was their ability to function in the presence of high concentrations of normal human Fc gamma. The lysis mediated by BsAb reactive with Fc gamma RI or II was unaffected by the presence of human Fc gamma at 2.5 mg/ml (a concentration comparable with that yielded by IgG in plasma) whereas the BsAb recognizing Fc gamma RIII and all the Fc-containing derivatives were completely inhibited.

The cps gene cluster of Salmonella strain LT2 includes a second mannose pathway: sequence of two genes and relationship to genes in the rfb gene cluster

We report the presence in Salmonella enterica strain LT2 (serovar thyphimurium) of duplicate genes for two steps in the synthesis of GDP-mannose. The previously known genes, rfbK (phosphomannomutase) and rfbM (mannose-1-phosphate guanyltransferase), are part of the gene cluster for the O antigen. The two new genes, cpsB and cpsG, respectively, are thought to be part of the gene cluster for the M antigen capsular polysaccharide, present in many Enterobacteriaceae. The two genes have been sequenced and have a GC content of 0.61, suggesting an origin outside of Salmonella. Comparison of the inferred protein sequences for cpsB and rfbM shows 57% identity of amino acids whereas for cpsG and rfbK there is only 19% identity. It is suggested that the greater divergence between cpsG and rfbK may be due to a period of accelerated evolution, perhaps precipitated by transfer of the genes from another species.

Novel 5-HT3 antagonists. Indole oxadiazoles

The synthesis and biochemical evaluation of a series of indole oxadiazole 5-HT3 antagonists are described. The key pharmacophoric elements have been defined as a basic nitrogen, a linking group capable of H-bonding interactions, and an aromatic moiety. The steric limitations of the aromatic binding site have been determined by substitution about the indole ring. Variation of the heterocyclic linking group has shown that while two hydrogen-bonding interactions are possible, only one is essential for high affinity. The environment of the basic nitrogen has been investigated and shown to be optimal when constrained within an azabicyclic system. These results have been incorporated into a proposed binding model for the 5-HT3 antagonist binding site, in which the optimum distance between the aromatic binding site and the basic amine is 8.4-8.9 A and the steric limitations are defined by van der Waals difference mapping.

Cloning and nucleotide sequence of the Salmonella typhimurium LT2 gnd gene and its homology with the corresponding sequence of Escherichia coli K12

The complete nucleotide sequence of the Salmonella strain LT2 gnd gene for 6-phosphogluconate dehydrogenase was determined. The gene contains 1404 bases and encodes a 468 amino acid polypeptide, which is the same as for Escherichia coli K12. The DNA sequence shows 14.8% difference between the two and the amino acid sequence 3.6% difference. Changes are mostly in the third codon base and most of the amino acid changes are conservative.

Impaired humoral immune response in complement C3-deficient guinea pigs: absence of secondary antibody response

A recently described genetically controlled C3 deficiency (C3D) in guinea pigs (GP) provided a unique model for studying the role of C3 in the afferent limb of the humoral immune response in a direct manner. These C3D animals, which have only 5-7% of normal serum C3 level, were immunized with the bacteriophage phi chi 174, a T cell-dependent antigen, followed by a booster injection after 4 weeks (1.5 X 10(9) plaque-forming units/kg). The formation of IgM and IgG antibody in the course of the primary and secondary response was determined and compared with a control group of inbred strain 2 GP. The C3D animals showed a markedly diminished antibody response to this antigen. Amplification of the antibody titer as well as regular isotype switching from IgM to IgG was absent in the secondary response. Increasing the amount of antigen to a high dose (1 X 10(10) plaque-forming units/kg) led to a normalization of the antibody response. The impairment in antibody formation resembles closely the impaired antibody response in C4-deficient or C2-deficient GP, which both have a block in activation of C3 via the classical pathway. However, in contrast to C4D GP or C2D GP the C3D GP do not exhibit serological characteristics of immune complex disease. They have normal levels of total serum IgM, of IgM anti-2,4-dinitrophenyl antibodies and of IgM rheumatoid factors.

Gallbladder emptying in man related to fasting duodenal migrating motor contractions

Animal studies have shown that the gallbladder (GB) empties partially during fasting in relation to phase II of the interdigestive motor cycle (IDMC). It has been assumed that in man the GB remains inert during fasting, although there have been no studies in which repeated sequential measurements of gallbladder volume have been made and related to the IDMC. In this study the possibility of linkage between the IDMC and GB volume has been examined in nine fasting human volunteers (five males/four females). A multilumen constantly perfused manometry catheter was positioned in the duodenum and motor activity recorded continuously. Phase III of the IDMC was characterized by phasic contractions, with a frequency of 10-12/min for at least 2 min, which had a distal propagative pattern and were followed by a motor quiescence (Phase I). GB volume was calculated at 15 min intervals from ultrasound measurements of the maximal length and diameter of the GB by the summation of cylinders method, and related to the time of onset of each phase III of the IDMC. In all nine subjects GB volume decreased prior to the onset of phase III and increased following its passage (P less than 0.01). GB volume decrease ranged between 6 and 56% of maximal GB volume (median 18%) and subsequent filling ranged from 14 to 53% (median 27%). The maximal volume decrease occurred 30 min prior to the onset of phase III (P less than 0.02). These studies have demonstrated that the human GB empties partially during phase II of the IDMC.(ABSTRACT TRUNCATED AT 250 WORDS)

An inherited deficiency of the third component of complement, C3, in guinea pigs

Hereditary deficiency of the third component of complement, C3, is found very seldom in the human. C3 deficiency is associated with severe bacterial infections revealing the central role of C3 in complement activation via the classical or alternative pathway. We describe a new hereditary C3 deficiency in strain 2 guinea pigs. Serum from these animals had a markedly reduced lytic activity in a standard assay for complement-dependent, antibody-mediated cytotoxicity. In functional assays of individual components, the hemolytic activity of the components C4, C2, C5 and of factors B, D and H was in the normal range. The functional C3 titer, and similarly C3 antigenic activity in the serum of these C3-deficient animals (C3D) was on average only 5.7% of normal activity. Typing the animals with alloantisera or monoclonal antibodies to guinea pig Ia-antigens revealed that the C3D animals had the major histocompatibility complex-haplotype of inbred strain 2 guinea pigs (B.1, Ia.2,4). The C3 defect is not linked to the major histocompatibility complex and, in addition, is not linked to a C3a receptor deficiency. Macrophages and hepatocytes of the C3D animals have an unimpaired capacity for synthesis and secretion of C3 as measured by enzyme-linked immunosorbent assay. There was no indication for hypercatabolism of normal C3 by the animals as shown by plasma clearance of 125I-radiolabeled C3. Thrombocytes of the C3D animals responded normally to stimulation with purified C3a in an ATP-release assay without an indication for a desensitization in vivo. Possibly the fault resides in an enhanced susceptibility of their own C3 to proteolysis. However, C3 partially purified from the plasma of the C3D animals or secreted by hepatocytes exhibited no obvious structural differences to purified normal C3 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis or in immunoblotting. The C3D serum had a reduced bactericidal activity compared to normal or to C4-deficient serum. Nevertheless, the animals are apparently healthy without an indication for increased frequency of bacterial infections. These guinea pigs provide an unique model for analysis of the biological functions of C3 in vivo and in vitro without the need for artificial C3-depletion procedures with all their known and unknown side-effects.

Colonization factor antigen II (CFA/II) of enterotoxigenic Escherichia coli: molecular cloning of the CS3 determinant

The genes for the cell surface associated antigen CS3, produced by CFA/II type enterotoxigenic Escherichia coli, have been cloned in the plasmid vector pBR322 to produce a family of recombinant plasmids. These plasmids contain a series of HindIII fragments of which a fragment of 4.6 kb is common to all those expressing CS3. One of these plasmids, pPM474, has been subjected to mutagenesis with Tn1725 and deletions generated using Bal31. This has defined a minimum region of 3.75 kb necessary for the production of CS3 on the cell surface and implying genetic complexity as has been observed with other fimbrial antigens. Analysis of the plasmid encoded proteins in E. coli K-12 minicells has confirmed this complexity.

Purification of the 25-kDa Vibrio cholerae major outer-membrane protein and the molecular cloning of its gene: ompV

The 25-kDa peptidoglycan-associated outer-membrane protein and most likely porin of Vibrio cholerae is a major immunogenic species. It has been purified by ion-exchange elution on hydroxyapatite followed by gel filtration on Bio-Gel P150 both in the presence of sodium dodecyl sulfate. This protein, of greater than 90% purity as judged by Western blotting, has been used to raise antibodies in rabbits. The antisera were then used to screen V. cholerae gene banks, constructed in Escherichia coli K12, and this has enabled us to isolate several colonies harbouring the cloned gene. The plasmids in these colonies have been designated pPM451, pPM455 and pPM472. These plasmids have a 5.3 X 10(3)-base BamHI fragment of V. cholerae DNA in common. Restriction endonuclease mapping of these plasmids has been performed and the protein identified both by Western blot analysis and in E. coli K12 minicells. The protein is not efficiently expressed in E. coli K12. It is proposed to use the name ompV to describe the structural gene, present in the cloned DNA, for this V. cholerae outer membrane protein.