[Management of multiresistant bacteria in urology]

Contamination and infection with extensive drug resistant (XDR) bacteria are increasing in urology with the exception of methicillin resistant Staphylococcus aureus (MRSA) (stabilization). They often lead to logistic and therapeutical problems. Only 30-50% of XDR cases are of exogenous origin. To slow this trend, screening, hygiene programs, isolation, decontamination, targeted therapy of symptomatic infections, education programs, and success controls should be applied. Furthermore, all regulatory and legal instructions should be followed. Local hygiene networks help to find apt measures for XDR control. It is important to balance hygiene measures against hygiene hysteria. To prepare urological instruments, a local instrument preparation plan that takes into consideration all legal instructions should be followed. The efforts in health system general prophylactic measures should be supported. Only with consistent implementation in all areas of daily life (health care, local environment, animal husbandry, and soil contaminated within the framework of animal husbandry) can a substantial reduction of XDR bacteria be achieved in the long term.

Synthese und Kristallstruktur von Pentakis(dimethylsulfoxid)- oxo-titan(IV)chlorid / Synthesis and Crystal Structure of Pentakis(dimethylsulfoxide)-oxo-titanium(IV) Chloride

Pentakis(dimethylsulfoxide)-oxo-titanium(IV) chloride is obtained by reaction of titanium tetrachloride with a stoichiometric amount of water in dimethylsulfoxide. A single crystal structure determination (P1̄, a = 9.564(6), b = 10.504(7), c = 12.510(8) Å, α = 70.21(5), β = 83.48(5), γ = 89.82(5)°, V = 1174 Å3, Z = 2) shows a dicationic titanium(IV) complex with five dimethylsulfoxide ligands and one oxygen atom. The two chlorine anions are not bonded to the complex cation. The TiO6-fragment is a distorted octahedron, where five of the six oxygen atoms belong to the coordinated dimethylsulfoxide molecules.

[Asymptomatic Renal Stones: Do they really Exist?]

BACKGROUND

Asymptomatic renal calculi without any history of colic, hematuria or infection can be found as an incidental finding during preven-tive check-ups. The aim of our study was to eval-uate whether these stones provoke symptoms with the need for further treatment during the follow-up and whether they cause cortical defects which may consecutively affect the renal func-tion.

PATIENTS AND METHODS

In a prospective study we evaluated 104  patients with renal calculi. The -medical history, radiological findings and functional imaging as well as urine and blood analyses were recorded and evaluated. The influence of stone size and localisation on the development of acute stone-related symptoms, renal function and renal scarring were evaluated. Furthermore, we analysed whether localised pathological findings in radiographic or functional imaging may influence the creatinine level. The follow-up was be-tween 12 and 48  months (median: 25  months).

RESULTS

During the study period 27 / 104 of our patients (26 %) developed symptomatic events (renal colic, hematuria, infection) in which patients with middle pole calculi with a mean -cumulative stone diameter of 9.8  mm had the -highest risk. A localised renal scarring could be found in 36.6 %. These patients had a significantly higher risk in presenting an increased creatinine level. Increasing stone size was diagnosed in 39  cases (37.5 %).

CONCLUSIONS

Asymptomatic renal stones have to be controlled regularly in order to prevent the -patient from loss of renal function and hypertension caused by increasing stones or urinary tract infection.

The development of stimulus control with and without a lighted key

In two experiments, the effect of an illuminated response key on the acquisition of stimulus control by an airflow stimulus was assessed. In the first experiment, pigeons were given nondifferential training with airflow emerging from behind the response key in one of three conditions of illumination: trained to peck a lighted key, trained to peck an unlighted key with a houselight present, trained to peck a key in total darkness. After 10 days of training on a variable-interval schedule of reinforcement, all subjects were given a generalization test on airflow velocity. The gradients for subjects trained in the dark were sharp, while those for subjects trained in lighted conditions were shallow. In the second experiment, the effect of an irrelevant keylight on the acquisition of an airflow velocity discrimination was assessed. Two groups of pigeons were trained to discriminate two airflow velocities. One group was trained with a lighted response key and the other was trained to peck the response key in total darkness. The dark-trained subjects acquired the discrimination more rapidly. The results demonstrate that the acquisition of stimulus control by airflow with either a differential or nondifferential training procedure can be overshadowed by keylight.

Summation of punishment suppression

In two experiments, eight rats were trained to lever press with food on a variable-interval schedule. Bar pressing produced shock on a variable-interval schedule in the presence of two independently presented stimuli, a light and a tone. Two rats in each experiment received alternative presentations of the light and the tone and were consequently always in the presence of a stimulus that signalled variable-interval punishment. The other two rats in each experiment were treated similarly except that they received periods in which neither light nor tone was present. During these periods, bar pressing was not punished. The two stimuli that signalled punishment were then presented simultaneously to evaluate the effect of stimulus compounding on response suppression. The subjects trained without punishment-free periods did not show summation to the compound stimulus; the subjects trained with punishment-free periods showed summation of suppression. The major difference between the two experiments was the longer mean interval of variable-interval punishment used in the second experiment. This manipulation made the summation effect more resistant to extinction and thus increased its magnitude.

A novel TWO-STEP renaturation procedure for efficient production of recombinant BMP-2

Bone morphogenetic proteins (BMPs) stimulate bone formation and thus constitute important protein therapeutics. Here, a novel procedure is presented which allows fast and efficient production of biologically active BMP-2 via a TWO-STEP procedure: the conditions are designed such that the first step favors formation of monomeric species with the correct intramolecular disulfide bridges, the conditions of the second folding reaction stimulate the formation of the intermolecular disulfide bridge. The short processing times and increased yields compared to previously published procedures allow low-cost production of this important protein drug.

Safety and feasibility of long-term temozolomide treatment in patients with high-grade glioma

We surveyed neuro-oncologists regarding patients treated with temozolomide for at least 12 cycles or 12 months. Patients receiving first-line temozolomide for a median 13 cycles had a median progression-free survival (PFS) of 14 months. Patients with recurrent disease receiving a median 14 cycles had a median PFS of 15.5 months. A small percentage of patients experienced grade III to IV toxicity. These results suggest that long-term treatment with temozolomide is feasible and well tolerated.

Assessment of cytological criteria for diagnosing osteosarcoma in dogs

OBJECTIVES

To evaluate the specific cytological criteria of osteosarcomas in dogs.

METHODS

Significant cytological characteristics of osteosarcoma and benign mesenchymal bone proliferations were determined from imprint smears of 25 dogs with osteosarcoma (group 1) and 20 dogs admitted for removal of surgical bone implants after uncomplicated healing of bone fractures (group 2).

RESULTS

Mild to moderate cellular necrosis occurred frequently in patients with osteosarcoma. The cytoplasm of osteoblasts was pale blue to blue with a more pronounced basophilia in group 2. In 48 per cent of the patients in group 1, but none in group 2, osteoblasts showed a slight to moderate eosinophilic cytoplasmic granulation. In both groups, osteoblasts contained one red to pale blue nucleus with one or two grey-red to blue nucleoli in group 2. Forty-four per cent of animals in group 1 had osteoblasts with more than two nucleoli per nucleus. The median nuclear:cytoplasmic ratio was higher in group 1 (1:2.0) than in group 2 (1:3.5). Osteoblasts in group I were frequently seen to have a clumped chromatin pattern and showed significantly more criteria of malignancy (median six criteria per patient) than those in group 2 (median two criteria per patient). In group 1, mitoses of osteoblasts were detectable in 23 of 25 dogs, whereas only one dog in group 2 had evidence of mitotic osteoblasts.

CLINICAL SIGNIFICANCE

Cytological criteria can be helpful in the diagnosis of canine osteosarcoma.

Portal vein thrombosis after hematopoietic cell transplantation: frequency, treatment and outcome

Patients who develop veno-occlusive disease (VOD) of the liver may have low plasma levels of the natural anticoagulants protein C and antithrombin III, but large vessel thromboses are not commonly reported in these patients. We reviewed the records of 1847 consecutive patients for evidence of portal vein thrombosis. Eight patients (0.4%) developed portal vein thrombosis (PVT) at a median of day +28 (range 3-58). All patients had clinical evidence of VOD with ascites, a median total serum bilirubin 11.9 mg/dl, and median weight gain from baseline of 7.9%. Median plasma levels of antithrombin III and protein C were low (36% and 21%, respectively). Four patients with PVT died of severe VOD and multi-organ failure, but PVT did not contribute to death. We conclude that PVT is a rare complication of hematopoietic cell transplant and is associated with hepatic VOD. We speculate that PVT resulted from diminished portal venous flow (related to hepatic sinusoidal obstruction to blood flow) and a hypercoagulable state (related to low circulating antithrombin III and protein C levels). Prognosis depended on the severity of the underlying VOD and not PVT per se, suggesting that treatments directed solely toward dissolution of portal vein thrombi should be used with caution in this setting.

Assessment of cytological criteria for diagnosing basal cell tumours in the dog and cat

A retrospective study was undertaken in which cytological features of basal cell tumours from 18 dogs and 12 cats were examined. Fine-needle aspiration biopsy was performed for cytological examination and diagnosis was confirmed on histopathological examination of excised tumour specimens. Cytological smears were analysed for occurrence of cystic areas, as well as frequencies of squamous cells, fibrocytes, fibroblasts, neutrophils, lymphocytes, mast cells, melanocytes and basal cells. Basal cell aggregates were examined for indicators of malignancy, evidence of basaloid cell structure, well defined cellular borders and cell aggregation patterns. Cellularity and quality of smears was moderate to good, although, in six aspirates, cellularity was poor due to a high amount of degenerate material within the tumours. Fifteen of the smears revealed between one and three nuclear criteria of malignancy. However, despite the less well differentiated appearance of basal cells that was sometimes seen, the tumours were considered benign based on histopathological examination. Basal cell tumours are therefore likely to be underdiagnosed on cytological examination due to non-specific features. The occurrence of other cell populations and lack of cells with basaloid structures and linear aggregation patterns might further confuse the tumour diagnosis. The authors conclude that the cytological diagnosis of basal cell tumours can be based on the criteria described in the present study.

Increased production of human proinsulin in the periplasmic space of Escherichia coli by fusion to DsbA

The production of human proinsulin in its disulfide-intact, native form in Escherichia coli requires disulfide bond formation and the periplasmic space is the favourable compartment for oxidative folding. However, the secretory expression of proinsulin is limited by its high susceptibility to proteolysis and by disulfide bond formation, which is rate-limiting for proinsulin folding. In this report we describe a method for the production of high amounts of soluble, native human proinsulin in E. coli. We fused proinsulin to the C-terminus of the periplasmic disulfide oxidoreductase DsbA via a trypsin cleavage site. As DsbA is the main catalyst of disulfide bond formation in E. coli, we expected increased yields of proinsulin by intra- or intermolecular catalysis of disulfide bond formation. In the context of the fusion protein, proinsulin was found to be stabilised, probably due to an increased solubility and faster disulfide bond formation. To increase the yield of DsbA-proinsulin in the periplasm, several parameters were optimised, including host strains and cultivation conditions, and in particular growth medium composition and supplement of low molecular weight additives. We obtained a further, about three-fold increase in the amount of native DsbA-proinsulin by addition of L-arginine or ethanol to the culture medium. The maximum yield of native human proinsulin obtained from the soluble periplasmic fraction after specific cleavage of the fusion protein with trypsin was 9.2 mg g(-1), corresponding to 1.8% of the total cell protein.

Polyionic fusion peptides function as specific dimerization motifs

The de novo design of a molecular adapter for directed association and covalent linkage of two polypeptides is presented. Using peptides containing charged amino acid residues and an additional cysteine residue (AlaCysLys(8) and AlaCysGlu(8)) we demonstrate that the electrostatic interaction promotes the association of two synthetic peptides and, subsequently, disulfide bond formation. The reaction depends on both the redox potential and on the ionic strength of the buffer. Varying the redox potential, the interaction of the peptides was quantified by a Delta G(0') of 6.6 +/- 0.2 kcal/mol. Heterodimerization of the peptides is highly specific, a competition of association by other cysteine containing compounds could not be observed. Two proteins comprising cysteine-containing polyionic fusion peptides, a modified Fab fragment and an alpha-glucosidase fusion, could be specifically conjugated by directed association and subsequent disulfide bond formation. Both proteins retain their functional characteristics within the bifunctional conjugate: enzymatic activity of the alpha-glucosidase and antigen-binding capacity of the Fab fragment are equivalent to the non-conjugated components.

Binding of external ligands onto an engineered virus capsid

The development of novel delivery systems for therapeutic substances includes targeting of the carriers to a specific site or tissue within the body of the recipient. This can be accomplished by appropriate receptor-binding domains and requires linking of these domains to the carrier. We have used recombinantly expressed polyomavirus-like particles as a model system and inserted the sequence of a WW domain into different surface loops of the viral capsid protein VP1. In one variant, the WW domain maintained its highly selective binding properties of proline-rich ligands and showed an increased affinity but also an accelerated association/dissociation equilibrium compared to the isolated WW domain, thus allowing a short-term coupling of external ligands onto the surface of the virus-like particles.

Cosecretion of chaperones and low-molecular-size medium additives increases the yield of recombinant disulfide-bridged proteins

Attempts were made to engineer the periplasm of Escherichia coli to an expression compartment of heterologous proteins in their native conformation. As a first approach the low-molecular-size additive L-arginine and the redox compound glutathione (GSH) were added to the culture medium. Addition of 0.4 M L-arginine and 5 mM reduced GSH increased the yield of a native tissue-type plasminogen activator variant (rPA), consisting of the kringle-2 and the protease domain, and a single-chain antibody fragment (scFv) up to 10- and 37-fold, respectively. A variety of other medium additives also had positive effects on the yield of rPA. In a second set of experiments, the effects of cosecreted ATP-independent molecular chaperones on the yields of native therapeutic proteins were investigated. At optimized conditions, cosecretion of E. coli DnaJ or murine Hsp25 increased the yield of native rPA by a factor of 170 and 125, respectively. Cosecretion of DnaJ also dramatically increased the amount of a second model protein, native proinsulin, in the periplasm. The results of this study are anticipated to initiate a series of new approaches to increase the yields of native, disulfide-bridged, recombinant proteins in the periplasm of E. coli.

Conjugation of an antibody Fv fragment to a virus coat protein: cell-specific targeting of recombinant polyoma-virus-like particles

The development of cell-type-specific delivery systems is highly desirable for gene-therapeutic applications. Current virus-based vector systems show broad cell specificity, which results in the need to restrict the natural tropism of these viral systems. Here we demonstrate that tumour-cell-specific virus-like particles can be functionally assembled in vitro from recombinant viral coat protein expressed in Escherichia coli. The insertion of a negatively charged peptide in the HI loop of polyoma VP1 interferes with the binding of VP1 to the natural recognition site on mammalian cells and also serves as an adapter for the coupling of antibody fragments that contain complementary charged fusion peptides. A recombinant antibody fragment of the tumour-specific anti-(Lewis Y) antibody B3 could be coupled to the mutant VP1 by engineered polyionic peptides and an additional disulphide bond. With this system an entirely recombinant cell-specific delivery system assembled in vitro could be generated that transfers genes preferentially to cells presenting the tumour-specific antigen on the cell surface.

The pro-sequence facilitates folding of human nerve growth factor from Escherichia coli inclusion bodies

Nerve growth factor (beta-NGF), a neurotrophin required for the development and survival of specific neuronal populations, is translated as a prepro-protein in vivo. While the presequence mediates translocation into the endoplasmic reticulum, the function of the pro-peptide is so far unknown. As the pro-sequences of several proteins are known to promote folding of the mature part, the renaturation behaviour of recombinant human beta-NGF pro-protein was compared to that of the mature form. Expression of rh-pro-NGF in Escherichia coli led to the formation of inclusion bodies (IBs). The presence of the covalently attached pro-sequence significantly increased the yield and rate of refolding with concomitant disulfide bond formation when compared to the in vitro refolding of mature NGF (rh-NGF). Physicochemical characterization revealed that rh-pro-NGF is a dimer. The pro-peptide could be removed by limited proteolysis with trypsin yielding biologically active, mature rh-NGF. Furthermore, rh-pro-NGF exhibited biological activity in the same concentration range as rh-NGF.

Pro-sequence assisted folding and disulfide bond formation of human nerve growth factor

Nerve growth factor (NGF) is a member of the neurotrophin family. These growth factors support neuronal survival and differentiation. Neurotrophins are synthesized as pre-pro-proteins. Whereas the pre-sequences mediate secretion, the function of the pro-peptides is largely unknown. To test the role of the pro-sequence as a folding enhancer, recombinant human pro-NGF (rh-pro-NGF) was produced in Escherichia coli. The oxidative refolding of rh-pro-NGF and rh-NGF was studied using electrospray mass spectrometry (ESIMS) time-course analysis. This analysis permitted both the identification and quantification of intermediates present during the process. The disulfide bonds formed at different times of the refolding processes were characterized by proteolytic digestion followed by matrix assisted laser desorption ionization mass spectrometry (MALDIMS) analysis. Folding yields and kinetics of rh-pro-NGF were significantly enhanced when compared to the in vitro refolding of mature rh-NGF. These results suggest that the pro-sequence of NGF promotes folding of the mature part.

A hyperthermostable bacterial histone-like protein as an efficient mediator for transfection of eukaryotic cells

Gene delivery has shown potential in a variety of applications, including basic research, therapies for inborn genetic defects, cancer, AIDS, tissue engineering, and vaccination. Most available systems have serious drawbacks, such as safety hazards, inefficiency under in vivo-like conditions, and expensive production. When using naked DNA, for instance, a large amount of ultrapure DNA has to be applied as a result of degradation by nucleases. Similarly, the use of eukaryotic histones, synthetic peptides, or peptide nucleic acids may be limited by high production costs. We have demonstrated a biotechnologically feasible and economical approach for gene delivery using the histone-like protein from the hyperthermostable eubacterium Thermotoga maritima, TmHU as an efficient gene transfer reagent. HU can be easily isolated from recombinant Escherichia coli, is extraordinarily stable, and protects dsDNA from thermal denaturation. This study demonstrates its use as an inexpensive tool for gene delivery.

Fibrin encapsulated liposomes as protein delivery system. Studies on the in vitro release behavior

The efficacy of biologically active proteins in medical therapy depends on the development of suitable drug delivery systems. These delivery systems need to overcome the severe problems connected with the use of proteins such as their usually short half lives in body fluids and their susceptibility to proteolysis and denaturation. Our delivery system combines two widespread devices by encapsulating liposomes containing the model protein horseradish peroxidase (HRP) inside the biopolymer fibrin. The liposomes enable the protein to remain in its preferred aqueous environment and protect it during the polymerization process. Further encapsulation of the liposomes inside fibrin was carried out in order to achieve a depot system with sustained protein release. In vitro experiments showed that the protein filled liposomes were absolutely stable within the fibrin network. In contrast to 'free' HRP, enzyme entrapped in liposomes was completely retained by the fibrin network and wasn't released from the device unless the fibrin was degraded by plasmin.

Refolding, purification, and characterization of human recombinant PDE4A constructs expressed in Escherichia coli

A 5'-truncated PDE4A-cDNA corresponding to the amino acid positions 200-886 of the "full-length" sequence (Accession No. L20965) was generated from human leukocyte mRNA by RT-PCR. Several PDE4A constructs containing the catalytic region and differing in their degree of N- and/or C-terminal truncation (amino acid positions 200-886, 200-704, 342-886, and 342-704) were expressed in Escherichia coli to investigate the effect of truncations on purification characteristics, long-term stability, and aggregation. All peptides accumulated as inclusion bodies, necessitating refolding prior to purification by dye and metal chelate affinity chromatography. The constructs differed in long-term stability due to variable levels of protease contamination. The position of the His-tag also influenced the purification results. The best results were obtained with the N- and C-truncated form C-terminally His-tagged, appropriate quantities of which were obtained in pure form and was found to be stable against proteolysis at 4 degrees C for at least 6 weeks. The comparison of the molecular mass of the investigated PDE4A constructs obtained by SDS electrophoresis, size-exclusion chromatography, and analytical ultracentrifugation indicated that C-terminal truncated PDE4A forms dimers whereas PDE4A constructs with a complete C-terminus tend to form larger aggregates.

The N-terminal fragment of human parathyroid hormone receptor 1 constitutes a hormone binding domain and reveals a distinct disulfide pattern

The N-terminal extracellular parts of human G-protein coupled receptor class B, for example, receptors for secretin, glucagon, or parathyroid hormone, are involved in ligand binding. To obtain structural and functional information on the N-terminal receptor fragment of human parathyroid hormone receptor 1 (PTHR1), the truncated receptor was expressed in the cytosol of Escherichia coli in the form of inclusion bodies. Oxidative refolding of inclusion body material resulted in stable, soluble, monomeric protein. Ligand binding was proved by surface plasmon resonance spectroscopy and isothermal titration calorimetry. Refolded receptor fragment was able to bind parathyroid hormone with an apparent dissociation constant of 3-5 microM. Far-UV circular dichroism spectra showed that the refolded polypeptide contained approximately 25% alpha-helical and 23% beta-sheet secondary structures. Analysis of the disulfide bond pattern of the refolded receptor fragment revealed disulfide bonds between Cys170 and Cys131, Cys148 and Cys108, and Cys117 and Cys48. These results demonstrate that the extracellular N-terminal domain of the parathyroid hormone receptor (PTHR1) possesses a well-defined, stable conformation, which shows a significant ligand binding activity.

Interferon alpha-2a and 13-cis-retinoic acid in patients with metastatic renal cell cancer

Treatment of patients with metastatic renal cell cancer (RCC) with interferon-alpha-2a (IFN) and 13-cis-retinoic acid (CRA) was first reported to be tolerable on an outpatient basis and to yield a 30% objective response rate. We sought to confirm these preliminary results by conducting a phase II trial of therapy with IFN/CRA in patients with bidimensionally measurable RCC. Twenty-five patients were enrolled. The median age was 58 (range, 47-75 years) and the median Karnofsky performance status was 90 (range 60-100). Seventeen patients (60%) had undergone prior nephrectomy and none had received prior systemic therapy. Treatment consisted of oral CRA at 1 mg/kg/day and IFN self-administered by subcutaneous injection at 3 MU/day with weekly escalation to 6 and 9 MU/day. Treatment was well tolerated, with cheilitis, influenza-like symptoms, and fatigue the most common toxicities. Severe toxicity was reversible and consisted of grade 4 cheilitis in one patient and grade 3 malaise/fatigue in two patients. One complete and four partial responses were observed, for an objective response rate of 20% (95% confidence interval, 4-36%). We conclude that treatment with CRA/IFN for RCC is tolerable on an outpatient basis and induces objective responses in some patients. The contribution, if any, of CRA to the responses observed will be determined in ongoing randomized phase III trials.

Folding of a synthetic parallel beta-roll protein

Recently, the design of beta-sheet proteins and concomitant folding studies have attracted increasing attention. A unique natural all-beta domain occurs in a family of cytolytic bacterial toxins, the so-called RTX toxins. This domain consists of a variable number (about 6-45) of tandem repeats of a glycine-rich nine-residue motif with the consensus sequence GGXGXDX(L/I/F)X. The analysis of the three-dimensional structure of alkaline protease from Pseudomonas aeruginosa which possesses six of these repeats revealed that they fold into a novel 'parallel beta-roll' where calcium is bound within the turns connecting the beta-strands. A 75-mer peptide of the sequence NH(2)-WLS-[GGSGNDNLS](8)-COOH was chemically synthesised. Circular dichroism spectroscopy showed that this polypeptide folds in the presence of Ca(2+) and polyethylene glycol into a beta-structure which is presumably identical with the parallel beta-roll. This synthetic beta-roll behaves similarly to the isolated beta-roll domains from Escherichia coli haemolysin or Bordetella pertussis cyclolysin in terms of calcium binding and polymerisation behaviour.

Mechanism of assembly of recombinant murine polyomavirus-like particles

VP1 is the major viral coat protein of murine polyomavirus and can be used for the generation of virus-like particles in vitro. Here, we demonstrate that capsid assembly is an equilibrium reaction followed by oxidation of intracapsomere disulfide bonds, which are not essential for the formation of virus-like particles but enable complete particle assembly and prevent capsid disassembly.

Purification of a viral coat protein by an engineered polyionic sequence

Virus-like particles composed of the polyoma coat protein VP1 were produced as a central building block of an artificial vector system for gene therapy. For this purpose, recombinant VP1 was expressed in E. coli. Classical purification schemes resulted only in low yields of protein. Therefore, we developed a new affinity purification procedure. We decided to use a polyionic sequence containing eight glutamic acid residues which allows efficient purification using ion-exchange chromatography. This peptide was inserted in a solvent exposed loop on the surface of VP1. After recombinant expression and cell lysis the first purification and concentration step consisted of a fractionated ammonium sulfate precipitation. The resuspended VP1 was loaded on an anion-exchange column. Elution with ca. 600 mM NaCl yielded almost homogeneous protein. Subsequently a size exclusion chromatography was performed to separate the pentameric VP1 from higher oligomeric and aggregated material. In contrast to wildtype VP1 the highly charged mutant form showed no significant tendency to aggregate. To demonstrate the functional state of the VP1 mutant, the in vitro assembly was investigated. At conditions similar to those for wildtype VP1 assembly, the mutant protein could form homogeneous virus-like particles.

The HU protein from Thermotoga maritima: recombinant expression, purification and physicochemical characterization of an extremely hyperthermophilic DNA-binding protein

The histone-like protein TmHU from the hyperthermophilic eubacterium Thermotoga maritima was cloned, expressed to high levels in Escherichia coli, and purified to homogeneity by heat precipitation and cation exchange chromatography. CD spectroscopical studies with secondary structure analysis as well as comparative modeling demonstrate that the dimeric TmHU has a tertiary structure similar to other homologous HU proteins. The Tm of the protein was determined to be 96 degrees C, and thermal unfolding is nearly completely reversible. Surface plasmon resonance measurements for TmHU show that the protein binds to DNA in a highly cooperative manner, with a KD of 73 nM and a Hill coefficient of 7.6 for a 56 bp DNA fragment. It is demonstrated that TmHU is capable to increase the melting point of a synthetic, double-stranded DNA (poly[d(A-T)]) by 47 degrees C, thus suggesting that DNA stabilization may be a major function of this protein in hyperthermophiles. The significant in vitro protection of double-helical DNA may be useful for biotechnological applications.

Correlation of haemostatic abnormalities with tumour stage and characteristics in dogs with mammary carcinoma

Sixty female dogs with untreated mammary carcinoma, comprising equal numbers of dogs in tumour stages I to IV, were evaluated for haemostatic abnormalities using the following tests: platelet count, prothrombin time, activated partial thromboplastin time, thrombin time, plasma activity of factor V, VIII and X, plasma concentration of fibrinogen, fibrin monomers and fibrinogen degradation products, and plasma antithrombin III activity. Two-thirds of all dogs had one or more haemostatic test abnormality of which the likelihood and frequency was increased in those with stage III and IV neoplasia. Haemostatic abnormalities were more frequently observed in dogs which had mammary tumours with distant metastases, extended tumour necrosis, inflammatory carcinomas, tumours fixed to underlying structures, or tumours in which there was penetration of the tumour capsule by tumour cells. As in humans with mammary carcinoma, these haemostatic abnormalities might be used as prognostic indicators, but their clinical importance remains unknown.

A gene for inherited cutaneous venous anomalies ("glomangiomas") localizes to chromosome 1p21-22

Venous malformations (VMs) are localized defects of vascular morphogenesis. They can occur in every organ system, most commonly in skin and muscle. They can cause pain and bleeding, and in some critical locations they can be life threatening. Usually venous anomalies occur sporadically, but families with dominant inheritance have been identified. Using linkage analysis, we have established in earlier reports that some families with inherited VMs show linkage to chromosome 9p21; the mutation causes ligand-independent activation of an endothelial cell-specific receptor tyrosine kinase, TIE-2. Here we show that VMs with glomus cells (known as "glomangiomas"), inherited as an autosomal dominant trait in five families, are not linked to 9p21 but, instead, link to a new locus, on 1p21-p22, called "VMGLOM" (LOD score 12.70 at recombination fraction.00). We exclude three known positional candidate genes, DR1 (depressor of transcription 1), TGFBR3 (transforming growth factor-beta receptor, type 3), and TFA (tissue factor). We hypothesize that cutaneous venous anomalies (i.e., glomangiomas) are caused by mutations in a novel gene that may act to regulate angiogenesis, in concert with the TIE-2 signaling pathway.

Maintenance treatment with medroxyprogesterone acetate in patients with advanced breast cancer responding to chemotherapy: results of a randomized trial. Essen Breast Cancer Study Group

The purpose of this randomized phase III trial was to study whether medroxyprogesterone acetate (MPA) maintenance treatment prolongs the time to progression in advanced breast cancer patients responding to an induction chemotherapy. Patients with progressive advanced breast cancer previously untreated with anthracylines and progestins were given epirubicin (30 mg/m2) and ifosfamide (2 g/m2) on days 1 and 8 at 3-weekly intervals. Patients without disease progression after 6 cycles of chemotherapy were randomly assigned to receive, until progression, either no treatment or MPA at a daily total dose of 500 mg. Ninety patients were randomized: 46 to the MPA arm and 44 to the observation arm. Median time to progression was longer in the MPA arm: 4.9 months versus 3.7 months in the intent-to-treat analysis (p = 0.02), and 4.9 months versus 3.0 months in the secondary efficacy analysis (p = 0.012). Seven patients were removed from MPA due to side effects. The changes in patient-rated quality of life scores were similar in both groups. The median length of survival from randomization was 17.4 months for patients receiving MPA and 18.3 months for patients randomized to observation (p = 0.39). In conclusion, in patients with advanced breast cancer achieving remission or non-progression with 6 cycles of epirubicin and ifosfamide chemotherapy, MPA maintenance treatment led to a significant, though modest, prolongation of the time to progression without affecting overall survival of the study patients.

Site-specific fluorescence labelling of recombinant polyomavirus-like particles

For the development of gene therapy protocols based on polyomavirus-like particles, we describe a method for fluorescence labelling of virions in order to study virus-cell interactions preceding gene delivery. Site-specific fluorescence labelling of polyomavirus-like particles is achieved via a single cysteine residue and maleimide conjugates of fluorescence dyes (fluorescein, Texas Red). Polyomavirus-like particles can be assembled in vitro from recombinant capsomers produced in E. coli. Since the assembly process is independent of disulfide bond formation, all cysteine residues of the wild-type protein were replaced by serines, and a new unique cysteine residue was introduced for the attachment of the fluorescence marker.

Diagnosis of myocardial infarction: integration of serum markers and clinical descriptors using information theory

OBJECTIVE

We examine the use of information theory applied to a single cardiac troponin T (cTnT) (first generation monoclonal; Boehringer Mannheim Corp., Indianapolis, Indiana) used with the character of chest pain, electrocardiography (ECG) and serial ECG changes in the evaluation of acute myocardial infarction (AMI). We combined a single measure of cTnT (blinded to the investigators) with a creatine kinase MB isoenzyme (CK-MB) measurement to discover the best decision value for this test in a study of 293 consecutive patients presenting to the emergency department with symptoms warranting exclusion of AMI.

METHODS

The decision value for determining whether cTnT is positive or negative was determined independently of the final diagnosis by examining the information in the cTnT and CKMB data. Using information theory, an autocorrelation matrix with a one-to-one pairing of the CKMB and troponin T was constructed. The effective information, also known as Kullback entropy, assigned the values for troponin T and for CKMB that have the lowest frequency of misclassification error. The Kullback entropy is determined by subtracting the data entropy from the maximum entropy of the data set in which the information has been destroyed. The assignment of the optimum decision values was made independently of the clinical diagnoses without the construction of a receiver-operator characteristic curve (ROC). The final diagnosis of AMI was independently determined by the clinicians and entered into the medical record.

RESULTS

The decision value for cTnT was 0.1 ng/ml as determined by the the information in the data. The method was validated within the same study by mapping the results so obtained into the diagnoses obtained independently by the clinicians using all of the methods at their disposal. The cTnT was different in AMI (n = 60) compared with non-AMI patients (n = 233) (2.08 +/- 0.21 vs. 0.07 +/- 0.10; p < .0001).

CONCLUSION

Information theory provides a strong framework and methodology for determining the decision value for cTnT which minimizes misclassification errors at 0.1 ng/ml. The result has a strong correlation with other features in detecting AMI in patients presenting with chest pain.

Expression and renaturation of the N-terminal extracellular domain of torpedo nicotinic acetylcholine receptor alpha-subunit

The N-terminal extracellular region (amino acids 1-209) of the alpha-subunit of the nicotinic acetylcholine receptor (nAChR) from Torpedo marmorata electric tissue was expressed as inclusion bodies in Escherichia coli using the pET 3a vector. Employing a novel protocol of unfolding and refolding, in the absence of detergent, a water-soluble globular protein of 25 kDa was obtained displaying approximately 15% alpha-helical and 45% beta-structure. The fragment bound alpha-[3H]bungarotoxin in 1:1 stoichiometry with a KD value of 0.5 nM as determined from kinetic measurements (4 nM from equilibrium binding). The kinetics of association of toxin and fragment were of second order, with a similar rate constant (8.2 x 10(5) M-1 s-1) as observed previously for the membrane-bound heteropentameric nAChR. Binding of small ligands was demonstrated by competition with alpha-[3H]bungarotoxin yielding the following KI values: acetylcholine, 69 microM; nicotine, 0.42 microM; anatoxin-a, 3 miroM; tubocurarine, 400 microM; and methyllycaconitine, 0.12 microM. The results demonstrate that the N-terminal extracellular region of the nAChR alpha-subunit forms a self-assembling domain that functionally expresses major elements of the ligand binding sites of the receptor.