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High-strength steels are increasingly used in deep drawing for automotive parts due to their improved strength properties. To increase the formability and thus extend the process limits, a deep drawing process with additional force transmission has been developed. For a numerical optimisation of the considered process, an exact modelling of the failure behaviour is essential. The forming limit curve (FLC) is widely used to predict the onset of necking in sheet metal forming. However, the validity of the FLC is limited to the case of linear strain paths. Therefore, the scope of past investigations has been on failure modelling depending on the stress state. This article presents the experimental-numerical characterisation of the failure behaviour of the high-strength steels HCT600X and HX340LAD. Tensile tests with butterfly specimens were carried out under varying stress states and simulated with ABAQUS to parametrise the stress-based models Johnson-Cook (JC), Modified Mohr-Coulomb (MMC) and DF2016. An additional experiment was carried out to evaluate the models in terms of predicted outcome accuracies by comparing the onset of fracture in the simulation with the experimental findings. In future investigations, the improved damage modelling will be applied in a deep drawing simulation with additional force transmission to optimise the process design.

Effective risk management of a portfolio demands accurate and succinct models which explain the main risk factors. Since portfolios have detailed individual records, an ideal approach is to use survival models. We look at a case study of how the administrator of a large multi-employer pension scheme created its own mortality tables. In addition to looking at statistical tests of fit, we consider a process for checking the suitability of a model for financial purposes. We also illustrate how a given scheme can test whether its experience is significantly different from other schemes, even after allowing for various known risk factors.

ABSTRACTNewly recognized Fic family virulence proteins may be important in many bacterial pathogens. To relate cellular mechanisms to pathogenesis and immune protection, we studied the cytotoxicity of the Histophilus somniimmunoglobulin-binding protein A (IbpA) direct repeat 2 Fic domain (DR2/Fic) for natural host target cells. Live virulent IbpA-producing H. somnistrain 2336, a cell-free culture supernatant (CCS) of this strain, or recombinant DR2/Fic (rDR2/Fic) caused dramatic retraction and rounding of bovine alveolar type 2 (BAT2) epithelial cells. IbpA-deficient H. somnistrain 129Pt and a Fic motif His298Ala mutant rDR2/Fic protein were not cytotoxic. The cellular mechanism of DR2/Fic cytotoxicity was demonstrated by incubation of BAT2 cell lysates with strain 2336 CCS or rDR2/Fic in the presence of [α-32P]ATP, which resulted in adenylylation of Rho GTPases and cytoskeletal disruption. Since IbpA is not secreted by type III or type IV secretion systems, we determined whether DR2/Fic entered the host cytoplasm to access its Rho GTPase targets. Although H. somnidid not invade BAT2 cells, DR2/Fic was internalized by cells treated with H. somni, CCS, or the rDR2/Fic protein, as shown by confocal immunomicroscopy. Transwell bacterial migration assays showed that large numbers of strain 2336 bacteria migrated between retracted BAT2 cells, but IbpA-deficient strain 129Pt did not cross a monolayer unless the monolayer was pretreated with strain 2336 CCS or rDR2/Fic protein. Antibody to rDR2/Fic or passively protective convalescent-phase serum blocked IbpA-mediated cytotoxicity and inhibited H. somnitransmigration across BAT2 monolayers, confirming the role of DR2/Fic in pathogenesis and corresponding to the results for in vivoprotection in previous animal studies.

Newly recognized Fic family virulence proteins may be important in many bacterial pathogens. To relate cellular mechanisms to pathogenesis and immune protection, we studied the cytotoxicity of the Histophilus somni immunoglobulin-binding protein A (IbpA) direct repeat 2 Fic domain (DR2/Fic) for natural host target cells. Live virulent IbpA-producing H. somni strain 2336, a cell-free culture supernatant (CCS) of this strain, or recombinant DR2/Fic (rDR2/Fic) caused dramatic retraction and rounding of bovine alveolar type 2 (BAT2) epithelial cells. IbpA-deficient H. somni strain 129Pt and a Fic motif His298Ala mutant rDR2/Fic protein were not cytotoxic. The cellular mechanism of DR2/Fic cytotoxicity was demonstrated by incubation of BAT2 cell lysates with strain 2336 CCS or rDR2/Fic in the presence of [-32P]ATP, which resulted in adenylylation of Rho GTPases and cytoskeletal disruption. Since IbpA is not secreted by type III or type IV secretion systems, we determined whether DR2/Fic entered the host cytoplasm to access its Rho GTPase targets. Although H. somni did not invade BAT2 cells, DR2/Fic was internalized by cells treated with H. somni, CCS, or the rDR2/Fic protein, as shown by confocal immunomicroscopy. Transwell bacterial migration assays showed that large numbers of strain 2336 bacteria migrated between retracted BAT2 cells, but IbpA-deficient strain 129Pt did not cross a monolayer unless the monolayer was pretreated with strain 2336 CCS or rDR2/Fic protein. Antibody to rDR2/Fic or passively protective convalescent-phase serum blocked IbpA-mediated cytotoxicity and inhibited H. somni transmigration across BAT2 monolayers, confirming the role of DR2/Fic in pathogenesis and corresponding to the results for in vivo protection in previous animal studies.

Since the CMP process depends on chemical and mechanical effects, the interaction with the physical and chemical properties of the GST alloy play very important roles during the CMP process. In this paper, the impact of the CMP process on a soft GST alloy will be discussed. In addition, the paper addresses how major chemical properties of the GST alloy affect the GST CMP process. For example, in order to remove the three different elements of GST material during the CMP process, it is critical to understand how the alloy's chemical behavior changes when interacting with the CMP slurries. A fully characterized GST CMP baseline process, including its process and defect results, will be presented. The methods used to optimize the CMP process and reduce post-CMP defects will also be discussed.

Studies on the origin of aneuploid conceptions have indicated that many chromosomal abnormalities arise during maternal meiosis. Therefore, the direct cytogenetic analysis of female gametes is of interest to evaluate underlying mechanisms. Human oocytes failing to fertilize after the application of assisted reproductive technologies have predominantly been used for this purpose. In addition, indirect data can be obtained from the examination of the first polar body that reflects the chromosomal constitution of the oocyte. Both approaches have been conducted with different methods and provided substantial information on the incidence of aneuploidy originating from errors during first meiotic division. However, the results reported so far display great variability, most probably due to technical problems and heterogeneity of the study population. Notwithstanding these limitations, it was unequivocally shown that two aneuploidy-causing mechanisms exist: non-disjunction, resulting in the loss or gain of whole chromosomes, and predivision, resulting in the loss or gain of single chromatids in mature oocytes. All chromosome groups are affected by aneuploidy but abnormalities in groups D, E, and G exceed the expected values. Considering only abnormal complements with one extra or missing chromosome/chromatid reveals a slight increase in predivision compared with non-disjunction. Chromosome and chromatid abnormalities are positively correlated to maternal age. The simultaneous analysis of oocytes and first polar bodies suggests that some cases of aneuploidy are caused by gonadal mosaicism instead of meiotic errors.

The preservative treatabilities of C. pachyceras and G. brevis sapwood and heartwood were examined using a modified European pre-norm (prCEN/TR14734). Treatability was assessed by measuring depth of penetration of treating fluid and uptake along different planes. C. pachyceras sapwood and heartwood were found to be difficult to treat and G. brevis sapwood and heartwood easy to treat using the classification methods in the pre-norm. Fungal staining of G. brevis was found to reduce penetration of the treatment fluid.

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Fractures remain the no. 1 failure reason with ceramic inlays. Bulk fractures still require complete rerestoration, however chippings in ceramic may be repaired. 40 IPS Empress inlays (MO) were inserted in extracted molars and stored in water for 2 years. Repair cavities in ceramic were prepared (n = 8), having been pretreated prior to restoration with resin composite as follows: A: Hydrofluoric acid (5 %) + silane coupling agent (SCA), B: CoJet + SCA, C: Air-abrasion (50 ?m) + SCA, D: Phosphoric acid (36 %) + SCA, E: SCA only. After restoration and water storage, thermomechanical loading was performed (TML: 100000 x 50 N, 2500 x 5 C/55 C). Before and after TML, epoxy replicas were made and investigated for marginal quality under a SEM. Results after TML exhibit the following significant differences: (p < 0,05): A = B > C > D = E. Hydrofluoric acid as well as CoJet pretreatment show nearly perfect margins even after TML.

Antimicrobial therapy continues to be important in reducing losses due to pneumonic forms of Mycoplasma bovisdisease in beef and dairy calves. Although M. bovisdiseases have been documented as frequent and economically important in the United States, there are no published reports on the antimicrobial activity of approved compounds against US strains. In this study, the authors report on the activity of 9 different antimicrobials against 223 recently recovered isolates of M. bovis. These isolates represent accessions from 5 geographic regions of the United States and were grouped by 4 tissues of origin (milk, respiratory, joint, or ear and eye). A broth microdilution test was used to determine minimum inhibitory concentration (MIC) values by reading redox changes detected in broth with alamarBlue (resazurin) indicator. For each antimicrobial, the median, MIC50, MIC90, mode, and range were calculated, and the values used for comparisons. In the absence of accepted breakpoint values, published MIC cutoff values for animal mycoplasmas as well as Clinical Laboratory Standards Institute interpretive criteria were used as a reference to define in vitro activity. The MIC values from active antimicrobials were found to distribute independently of region of origin of the isolates or of tissue of origin. Enrofloxacin, florfenicol, and spectinomycin were found to be active compounds in vitro. Oxytetracycline and chlortetracycline were active against more than half of the isolates. Very few isolates were inhibited by tilmicosin and none by erythromycin, ampicillin, or ceftiofur. The antimicrobial profiles determined for these US strains were remarkably similar to those reported for European isolates. However, unlike in Europe, there appears to be no diversity of profiles when US isolates are grouped by region or tissue of origin.

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In order to assess the role of binucleate giant oocytes for generating digynic triploidy, we studied their frequency, maturation patterns and chromosomal complements at metaphase II (MII) or after fertilization.

Es wurde eine Spannungs‐Dehnungbeziehung für Stahlfaserbeton entwickelt, die unabhängig von Einflußfaktoren wie Bauteilhöhe, Fasergeometrie und Langzeitbeanspruchungen ist. Der Beitrag stellt sie vor und zeigt, daß damit ein nahtloser Übergang zur Bemessung nach DIN 1045‐1 möglich ist.

High stability is a prominent characteristic of integral membrane proteins of known atomic structure. But rather than being an intrinsic property, it may be due to a selection exerted by biochemical procedures prior to structure determination, since solubilization results in the transient exposure of membrane proteins to solution conditions. This may cause structural perturbations that interfere with 3D crystallization and hence with X-ray analysis. This problem also affects the preparation of samples for electron crystallography and NMR studies and may account for the fact that high-resolution structures of representatives of whole groups, such as transport proteins and signal transducers, have not been elucidated so far by any method. A knowledge of the proportion of labile proteins among membrane proteins, and of the kinetics of their denaturation, is therefore necessary. Establishing stability profiles, developing methods to maintain lateral pressure, or preventing contact with water (or both) should prove significant in establishing the structures of conformationally flexible proteins.

BACKGROUND: Digynic zygotes with three pronuclei and one polar body obtained after intracytoplasmic sperm injection (ICSI) were studied cytogenetically to elucidate the frequency and origin of chromosomal abnormalities at the earliest stage of conception. METHODS: Uncleaved, single-cell zygotes were incubated with podophyllotoxin and vinblastine and fixed by a gradual fixation air drying method. The chromosomes were stained with Giemsa. RESULTS: Twenty-two (50%) out of 44 informative zygotes revealed cytogenetic alterations, including aneuploidy (six cells, 13.6%), structural aberrations (10 cells, 22.7%) and combinations of numerical and structural abnormalities (two cells, 4.5%). In one case (2.3%), double aneuploidy or an effect of chromosomal translocation could not be distinguished and one zygote (2.3%) turned out tetraploid due to injection of a diploid spermatozoon. Two zygotes (4.5%) showed an irregular chromatid segregation between the two maternal complements. In completely analysable cells, the sex chromosome ratio XXX:XXY was 17:15. CONCLUSIONS: Digynic ICSI zygotes carry a high rate of cytogenetic abnormalities that obviously have been transmitted by the participating oocytes and spermatozoa. We also confirmed the previously reported, possibly ICSI-induced irregular oocyte chromatid segregation. The results suggest that aneuploidy in the oocytes must have been caused by predivision instead of non-disjunction.

Digynic zygotes with three pronuclei and one polar body obtained after intracytoplasmic sperm injection (ICSI) were studied cytogenetically to elucidate the frequency and origin of chromosomal abnormalities at the earliest stage of conception.

Crystals of transmembrane proteins may be grown from detergent solutions or in a matrix of membranous lipid bilayers existing in a liquid crystalline state and forming a cubic phase (in cubo). While crystallization in micellar solutions appears analogous to that for soluble proteins, crystallization in lipidic matrices is poorly understood. As this method was shown to be applicable to several membrane proteins, understanding its mechanism will facilitate a rational design of crystallization, minimizing the laborious screening of a large number of parameters. Using polarization microscopy and low‐angle X‐ray diffraction, experimental evidence is provided to support a mechanistic model for the in cubo crystallization of bacteriorhodopsin in a lipid matrix. Membrane proteins are thought to reside in curved lipid bilayers, to diffuse into patches of lower curvature and to incorporate into lattices which associate to form highly ordered three‐dimensional crystals. Critical testing of this model is necessary to generalize it to other membrane proteins.

In den letzten Jahren hat sich im Bereich der technischen Regelwerke für den Stahlbau und den Stahlfaserbeton viel getan. Die DIN 1045 (88) wird abgelöst werden durch die DIN 1045‐1, der EC 2‐1 (92) liegt als Entwurf in der 2. Überarbeitung vom Januar 2001 vor. Die Forschung und Entwicklung im Bereich des Stahlfaserbetons ist auf einem Stand, der ein technisches Regelwerk überfällig werden läßt. Die Bestrebungen, ein solches Regelwerk zu erstellen sind sowohl auf europäischer als auch nationaler Ebene in vollem Gang. Ein Vergleich der Regelwerke zeigt erhebliche Unterschiede in der Querkrafttragfähigkeit auf, und läßt insbesondere für gering beanspruchte Bauteile den Stahlfaserbeton als sinnvolle Alternative erscheinen. Für den planenden Ingenieur wird in Zukunft die Auseinandersetzung mit diesen Konzepten sowohl in bemessungstechnischer als auch wirtschaftlicher Hinsicht unumgänglich sein.

Control of mycoplasmal mastitis requires individual cow milk sampling for culture and identification of Mycoplasma bovis. This sampling is time-consuming and expensive. Currently, some herds sample cows monthly with the dairy herd improvement (DHI) program, but a preservative is added to this milk that kills M. bovis. In this paper, a nested polymerase chain reaction (PCR) procedure that allows for rapid testing of preservative-treated milk is validated. The specificity of the nested PCR assay was confirmed by testing isolated nucleic acids of other organisms phylogenetically related to M. bovisor common to milk. A comparison against blind-passage culture on 53 field milk samples determined its sensitivity. Exposure of seeded milk samples to the procedure resulted in a sensitivity of 5.1 cfu equivalents per milliliter. Analysis of these results proved that the nested PCR assay was as sensitive as traditional culture and can be used on preservative-treated milk.

Three different methods are currently used for the study of high-resolution structures of membrane proteins: X-ray crystallography, electron crystallography, and nuclear magnetic resonance (NMR) spectroscopy. Thus far, all methods combined have yielded a rather modest number of crystal structures that have been solved at the atomic level. It is hypothesized here that different methods may select different populations of proteins on the basis of various properties. Thus, protein stability may be a significant factor in the formation of three-dimensional (3D) crystals from detergent solutions, since exposure of hydrophobic protein zones to water may cause structural perturbation or denaturation in conformationally labile proteins. This is different in the formation of two-dimensional (2D) crystals where a protein remains protected in its native membrane environment. A biological selection mechanism may therefore be operative in that highly ordered lattices may form only if strong protein–protein interactions are relevant in vivo, thereby limiting the number of proteins that are amenable to electron crystallography. Keeping a protein in a bilayer environment throughout 3D crystallization maintains the lateral pressure existing in native membranes. This can be accomplished by using lipidic cubic phases. Alternatively, the hydrophobic interface of a membrane protein may be spared from contact with water by crystallization from organic solvents where the polar caps are protected in reverse micelles by using appropriate detergents. Some of the criteria that are useful in optimizing the various approaches are given. While the usefulness of complementary methods seems obvious, the results presented may be particularly critical in recognizing key problems in other structural approaches.

van den Berg JC, Go PMNYH, de Valois JC, et al. Preoperative and postoperative assessment of laparoscopic inguinal hernia repair by dynamic MRI. Invest Radiol 2000;35694–697.

Discard milk from sick or antibiotic-treated cows is often used as an economical alternative to milk replacer at dairy farms. This practice poses a health risk to calves if the discard milk is from cows with mycoplasma mastitis. Mycoplasma bovis, Mycoplasma californicum, and Mycoplasma canadenseare among the agents known to cause contagious mastitis in cattle and occasionally pneumonia, otitis media, or arthritis in calves. This report describes a recent outbreak of calf polyarthritis and respiratory disease on a midwest dairy farm. The farm fed discard mycoplasma mastitic milk to its calves. On-the-farm pasteurization of the discard milk to 65°C for 1h before feeding prevented additional illness in the calves. Discard milk samples were collected before and after heating and tested for mycoplasma by culture. Only samples collected before pasteurization yielded live cultures. Common mastitic mycoplasma agents were also tested for sensitivity to heat. It was determined that 65°C killed M. bovisand M. californicumafter 2min of exposure, while M. canadenseremained viable for up to 10min. Exposure to 70°C inactivated M. bovisand M. californicumafter 1min, but M. canadensesamples were positive for up to 3min. Thus, M. canadenseappears to be more heat resistant than M. bovisand M. californicum. Heat treatment that results in the destruction of M. canadenseshould be used for the pasteurization of discard mycoplasma mastitic milk.

A fast simulator for e-beam lithography called SELID, is presented. For the exposure part, an analytical solution based on the Boltzmann transport equation is used instead of Monte Carlo. All-important phenomena (backscattering, generation of secondary electrons) are included in the calculation. The reaction/diffusion effects occurring during post exposure bake in the case of chemically amplified resists (CARs) are taken into account. The results obtained by the simulation are compared successfully with experimental ones for conventional and CARs. The case of substrates consisting of more than one layer is considered in depth as being of great importance in e-beam pattering. By using SELID, forecast of resist profile with considerable accuracy for a wide range of resists, substrates and energies is possible as long as the evaluation of proximity effect parameters.

The preponderance of structural data of the purple membrane from X-ray diffraction (XRD), electron crystallography (EC), and atomic force microscopy (AFM) allows us to ask questions about the structure of bacteriorhodopsin itself, as well as about the information derived from the different techniques. The transmembrane helices of bacteriorhodopsin are quite similar in both EC and XRD models. In contrast, the loops at the surfaces of the purple membrane show the highest variability between the atomic models, comparable to the height variance measured by AFM. The excellent agreement of the AFM topographs with the atomic models from XRD builds confidence in the results. Small technical difficulties in EC lead to poorer resolution of the loop structures, although the combination of atomic models with AFM surfaces allows clear interpretation of the extent and flexibility of the loop structures. While XRD remains the premier technique to determine very-high-resolution structures, EC offers a method to determine loop structures unhindered by three-dimensional crystal contacts, and AFM provides information about surface structures and their flexibility under physiological conditions.

An enzyme-linked immunoabsorbent assay (ELISA) was used to evaluate the levels of antibodies to Mycoplasma ovipneumoniaeand M. argininiin lambs with chronic respiratory disease. Sera were obtained from lambs in several flocks at various stages of the clinical disease and tested with sodium dodecyl sulfate (SDS)-treated M. ovipneumoniaeand M. argininiwhole cells and a crude capsular extract of M. ovipneumoniaeas the antigens. There were low levels of antibody to M. ovipneumoniaein flocks sampled at the early stages of infection, whereas increased levels of antibody were present in lambs from flocks that had apparently recovered from the clinical disease. Slowly rising titers of circulating antibodies to M. ovipneumoniaewere confirmed by sequential bleeding of lambs during the course of the clinical disease. However, antibody levels of M. argininiwere more likely to increase earlier in the disease process. There was significant cross-reactivity between the 2 SDS-treated antigens in both the ELISA test and western immunoblotting. In contrast, the crude capsular extract was specific for detecting antibodies to M. ovipneumoniae.

Abstract.: We report on a couple with complete fertilization failure in three consecutive trials of intracytoplasmic sperm injection. Some of the unfertilized oocytes were fixed and decondensed sperm heads were found in all of them. It is not clear whether specific defects of the oocyte, abnormalities of sperm chromatin, or a combination of factors are responsible for the observed failure to develop pronuclei.

Maltoporin, a protein spanning Escherichia coli outer membranes, modifies electrical conductance of membranes due to its channel‐forming properties. This observation was made by conductance measurements across planar bilayers which were derived from unextracted, isolated outer membrane vesicles using a porin‐deficient E. coli strain. Alternatively, proteoliposomes reconstituted with detergent‐solubilized homogeneous maltoporin and phospholipids were used. With either membrane preparation, channel conductance was observed, although no discrete conductance levels were detected. The presence of lipopolysaccharide, a bacterial glycolipid, was not required, nor did it affect channel activity. In the presence of the water‐soluble periplasmic maltose‐binding protein, conductance fluctuations occurred in discrete steps, demonstrating opening and closing events of channels. Multiple step sizes (1/3, 2/3 and 1 ns in 1 M KCl) in single channel traces suggest cooperative opening and closing of up to three channels. The action of maltose‐binding protein is highly asymmetrical, and its affinity to maltoporin is very high (KD = 1.5 X 10(‐7) M). Association of maltose‐binding protein to maltoporin shifts, for a given polarity, the equilibrium between open and closed states in favour of closed states. This result matches earlier in vivo studies, and supports the physiological significance of the observations made.

Phosphoporin, an Escherichia coli outer membrane‐spanning protein re‐incorporated in phospholipid planar bilayers generates aqueous channels similar to those of matrix porin. One phosphoporin trimer contains three pores which are induced simultaneously but fluctuate separately between open and closed states. Membrane potential shifts this two‐state equilibrium in favour of closed channels. This negative resistance occurs at lower potentials than with matrix porin channels. The phosphoporin channel is poorly anion selective for small solutes. Polyphosphates and other phosphorylated molecules specifically inhibit phosphoporin pore conductance to small ions, a property which is specific to phosphoporin. There is an excellent correlation between the effect of such solutes measured in planar bilayers and their inhibitory effect on beta‐lactam antibiotic uptake in vivo by phosphoporin. It is concluded that the phosphoporin channel contains a selectivity filter which is only efficient for larger molecules, most probably through basic residues.

Two dimensional crystals of maltoporin (or phage lambda receptor) were obtained by reconstitution of purified maltoporin trimers and Escherichia coli phospholipids by detergent dialysis. Two different trimer packing forms were observed. One was hexagonal (a = 7.8 nm) and one rectangular (a = 7.8 nm, b = 13.6 nm). In this paper we describe the three‐dimensional structure of maltoporin, deduced from the study of the rectangular form by electron microscopy and image processing. At a resolution of approximately 2.5 nm, maltoporin trimers form aqueous channel triplets which appear to merge into a single outlet at the periplasmic surface of the outer membrane. The pore defined by maltoporin has a similar structure to that outlined by the matrix protein. From the results of functional studies by conductance measurement, it is concluded that the three channels defined by maltoporin act, contrary to those formed by the porin (OmpF protein), as a single conducting unit. A tentative outline of the maltoporin promoter is given. Maltoporin appears to be constituted by three different domains: a major rod‐like domain spanning the membrane, a minor domain located near the periplasmic surface of the membrane and finally a central domain responsible for the splitting of the channel.

Porin spans the outer membrane of Escherichia coli with most of the protein embedded within the membrane. It lacks pronounced hydrophobic domains and consists predominantly of beta‐pleated sheet. These observations require the accommodation of polar and ionizable residues in an environment that has a low dielectric constant. Owing to a currently limited understanding of the constraints governing membrane protein structure, a minimal approach to structure prediction is proposed that identifies segments causing polypeptides to reverse their direction (turn identification). The application of this procedure avoids hydrophobicity parameters and yields a model of porin which is in good agreement with all experimental data available. The presence of polar and ionizable residues within membrane boundaries implies a dense (saturating) network of hydrogen bond donor and acceptor groups. Application to a paradigm of hydrophobic membrane proteins, bacteriorhodopsin, reveals a pattern consistent with its alpha‐helical folding. The postulated structure includes significantly more polar residues in the membrane domain than have been assumed previously, suggesting that there are also hydrogen bonding networks in bacteriorhodopsin. Extensive networks permeating protein interior and surfaces would explain the extraordinary stability and the tight interactions between functional units in the formation of crystalline arrays of both proteins.

Porin from Escherichia coli outer membranes has been analysed by high angle diffuse X‐ray diffraction, and by attenuated total reflection infrared spectroscopy. These methods demonstrate independently that the majority of the polypeptide backbone is arranged in anti‐parallel beta‐pleated sheet structure. The average length of the beta‐strands, which are oriented nearly normal to the membrane plane, is estimated to be 10‐12 residues, independent of the method used. Although the details of strand arrangement (beta‐barrels or stacked sheets) are not as yet known, porin represents the first transmembrane protein for which beta‐structure has been established unequivocally.

The authors determine the feasibility of dynamic magnetic resonance (MR) imaging in the diagnosis of groin hernia.

Background/Aims:Bombesin-stimulated plasma cholecystokinin levels decrease after an initial increase despite continuous infusion of bombesin. The aim of this study was to determine if a feedback mechanism, mediated by bile salts or proteolytic enzymes, is responsible for this decline. Methods:Bombesin (1.0 ng · kg−1· min−1) was infused into volunteers for 180 minutes on separate occasions. Cholestyramine, colestipol, camostate, or saline were perfused intraduodenally during the second hour of the tests. Cholestyramine was also administered without infusion of bombesin. Results:Colestipol and cholestyramine, dependent on their bile salt-binding capacity, markedly enhanced (P< 0.05) bombesin-stimulated plasma cholecystokinin from 2.1 ± 0.5 pmol/L to 6.4 ± 2.2 pmol/ L and 12.1 ± 3.3 pmol/L (P< 0.05 vs. colestipol), respectively, and further decreased gallbladder volume (P< 0.05) from 9.4 ± 1.6 mL to 2.0 ± 0.4 mL and 2.2 ± 0.5 mL, respectively. The protease inhibitor camostate had no effect. Bile salt precipitation also enhanced plasma pancreatic polypeptide responses (P< 0.01) but did not alter gastrin responses. Plasma cholecystokinin responses to cholestyramine without bombesin infusion varied considerably, but increments were highly correlated to decreases in gallbladder volume (r= 0.91; P< 0.005). Conclusions:Bile salt sequestration but not protease inactivation enhances plasma cholecystokinin and gallbladder responses to bombesin infusion in humans.

Elongation factor Tu is present in a fourfold excess over the amount seemingly involved in protein synthesis. It is identical to a major protein which we have found associated with the plasma membrane. The possibility of a specific role in that location is considered.

The sole histidine residue in OmpF porin was replaced by threonine using site-directed mutagenesis. This exchange affected neither channel properties nor channel structure, as determined by X-ray analysis to 3.2 Å. Conductance and critical voltage (Vc) were observed in the pH range 4.3–9.4, with results indistinguishable from those observed in the wild-type protein. The validity of these observations is supported by the independence of the methods used, and by the fact that mutants in residues located in the channel constriction yielded significantly different values from wild-type protein. The binding of a glycolipid molecule might be affected.

Homogeneous detergent-solubilized B873 light-harvesting complexes from a carotenoid-less mutant of the purple non-sulfur bacterium, Rhodospirillum rubrum G9, were reassembled spontaneously into two-dimensional (2D) hexagonal arrays during extensive and controlled dialysis. As the complexes contain only 1 to 2 mol phospholipid per mol αβ dimer, the arrays formed by a self assembly process are primary due to protein-protein interactions. The hexagonal lattices were analyzed by negative stain electron microscopy and digital image processing. They exhibited a unit cell size of 12·3 nm, in close agreement with the particle diameter of the active photo-unit in native chromatophore membranes. The unit cell contains a central 15 nm stain-filled depression, embraced by a ring with an outer diameter of 10 nm. Copyright 1993, 1999 Academic Press

Myelin basic protein has been isolated from bovine brain using the nonionic detergent n-octyl-polydisperse oligooxyethylene. The purified basic protein contains large amounts of heterogeneous lipids.

We suggest the term “speaking stomach syndrome” for persistent gurgling sounds in the gastric region, synchronous with breathing. The therapy of this syndrome has so far been a question of trial and error. In three patients respiration modification by a behavior therapist proved successful.