Showing papers by "University of Tübingen published in 1992"

Role of octreotide in the prevention of postoperative complications following pancreatic resection.

Abstract: Though morbidity and mortality rates following pancreatic resection have improved in recent years, they are still around 35% and 5%, respectively. Typical complications, such as pancreatic fistula, abscess, and subsequent sepsis, are chiefly associated with exocrine pancreatic secretion. In order to clarify whether the perioperative inhibition of exocrine pancreatic secretion prevents complications, we assessed the efficacy of octreotide, a long-acting somatostatin analogue. We conducted a randomized, double-blind, placebo-controlled, multicenter trial in 246 patients undergoing major elective pancreatic surgery. Patients were stratified into a high-risk stratum (limited to patients with pancreatic and periampullary tumors) or low-risk stratum (patients with chronic pancreatitis). Patients received octreotide (3 x 100 micrograms) or placebo subcutaneously for 7 days perioperatively. Eleven complications were defined: death, leakage of anastomosis, pancreatic fistula, abscess, fluid collection, shock, sepsis, bleeding, pulmonary insufficiency, renal insufficiency, and postoperative pancreatitis. Two hundred patients underwent pancreatic head resection, 31 patients underwent left resection, and 15 patients had other procedures. The overall mortality rate within 90 days was 4.5%, with 3.2% in the octreotide group and 5.8% in the placebo group. The complication rate was 32% in the patients receiving octreotide (40 of 125 patients) and 55% in patients receiving placebo (67 of 121 patients) (p less than 0.005). In the patients in the high-risk stratum, complications were observed in 26 of the 68 (38%) patients treated with octreotide and in 46 of 71 (65%) patients given placebo (p less than 0.01). Whereas in patients in the low-risk stratum, the complication rate was 25% (14 of 57 patients) in those treated with octreotide and 42% (21 of 50 patients) in patients given placebo (p = NS). The perioperative application of octreotide reduces the occurrence of typical postoperative complications after pancreatic resection, particularly in patients with tumors.

Autophagy and other vacuolar protein degradation mechanisms

Abstract: Autophagic degradation of cytoplasm (including protein, RNA etc.) is a non-selective bulk process, as indicated by ultrastructural evidence and by the similarity in autophagic sequestration rates of various cytosolic enzymes with different half-lives. The initial autophagic sequestration step, performed by a poorly-characterized organelle called a phagophore, is subject tofeedback inhibition by purines and amino acids, the effect of the latter being potentiated by insulin and antagonized by glucagon. Epinephrine and other adrenergic agonists inhibit autophagic sequestration through a prazosin-sensitive α1-adrenergic mechanism. The sequestration is also inhibited by cAMP and by protein phosphorylation as indicated by the effects of cyclic nucleotide analogues, phosphodiesterase inhibitors and okadaic acid.

Vendobionta and Psammocorallia: lost constructions of Precambrian evolution

Abstract: The non-availability of biomineralized skeletons and low levels of predation led Vendian evolution along strange avenues. The Ediacara-type Vendobionta appear to represent a kingdom, in which foliate shapes, large sizes and the necessary compartmentalization were achieved by quilting of the skin rather than by multicellularity. Psammocorallia, in contrast, are interpreted as coelenterates that constructed an internal sand skeleton. Both were immobile soft-bottom dwellers that had high population densities, and both became preserved by obrutional accidents; thus they render ‘fossil snap shots’, in which the original distributional patterns, age structures and standing biomasses of populations are accurately recorded.

Boswellic acids: novel, specific, nonredox inhibitors of 5-lipoxygenase.

Abstract: Isomers (alpha- and beta-) of boswellic acids (BAs), 11-keto-beta-BA and their acetyl derivatives were isolated from the gum resin of Boswellia serrata. BA and derivatives concentration dependently decreased the formation of leukotriene B4 from endogenous arachidonic acid in rat peritoneal neutrophils. Among the BAs, acetyl-11-keto-beta-BA induced the most pronounced inhibition of 5-lipoxygenase (5-LO) product formation with an IC50 of 1.5 microM. In contrast to the redox type 5-LO inhibitor nordihydroguaiaretic acid, BA in concentrations up to 400 microM did not impair the cyclooxygenase and 12-lipoxygenase in isolated human platelets and the peroxidation of arachidonic acid by Fe-ascorbate. The data strongly suggest that BAs are specific, nonreducing-type inhibitors of the 5-LO product formation either interacting directly with the 5-LO or blocking its translocation.

Technique and results of transanal endoscopic microsurgery in early rectal cancer.

Abstract: The anatomy of the pelvis makes it difficult to perform local excisions in the rectum when the tumor is some distance from the anal verge. We have, therefore, developed a new minimally invasive technique for tumor resection. A rectoscope with a 40-mm diameter permits tumor resection under stereoscopic control in the gas-dilated rectal cavity. Excisions in full-thickness technique up to segmental resections with end-to-end anastomosis can be performed. In selected cases, local excision of a small rectal cancer can be regarded as appropriate treatment. However, most local resections of carcinomas are performed when removal of an adenoma is planned, and the postoperative histology shows a carcinoma. Since 1983, we have operated on 326 patients, 274 who have been enrolled in a prospective clinical trial. Definitive histologic examination proved that 74 of these tumors were carcinomas. The rate of severe complications in patients with carcinomas was 9%, and the mortality rate was 0%. The advantages of this new technique are: The stereoscopic magnified view in the gas-dilated rectum allows precise surgery in an operative field that is otherwise difficult to reach. During the postoperative period, minimal discomfort and pain result in a short hospitalization.

Hemin uptake system of Yersinia enterocolitica: similarities with other TonB-dependent systems in gram-negative bacteria.

Abstract: The hemin receptor HemR of Yersinia enterocolitica was identified as a 78 kDa iron regulated outer membrane protein. Cells devoid of the HemR receptor as well as cells mutated in the tonB gene were unable to take up hemin as an iron source. The hemin uptake operon from Y. enterocolitica was cloned in Escherichia coli K12 and was shown to encode four proteins: HemP (6.5 kDa), HemR (78 kDa), HemS (42 kDa) and HemT (27 kDa). When expressed in E.coli hemA aroB, a plasmid carrying genes for HemP and HemR allowed growth on hemin as a porphyrin source. Presence of genes for HemP, HemR and HemS was necessary to allow E.coli hemA aroB cells to use hemin as an iron source. The nucleotide sequence of the hemR gene and its promoter region was determined and the amino acid sequence of the HemR receptor deduced. HemR has a signal peptide of 28 amino acids and a typical TonB box at its amino-terminus. Upstream of the first gene in the operon (hemP), a well conserved Fur box was found which is in accordance with the iron-regulated expression of HemR.

Genetic analysis of epidermin biosynthetic genes and epidermin‐negative mutants of Staphylococcus epidermidis

Abstract: Epidermin is produced by Staphylococcus epidermidis Tu3298 which harbors the 54-kb plasmid, pTu32. The plasmid contains not only the epidermin structural gene epiA, but also a flanking DNA region which is necessary for epidermin biosynthesis. The DNA sequence of this region revealed, in addition to epiA, five additional open reading frames, epiB, C, D, Q and P [Schnell, N., Engelke, G., Augustin J., Rosenstein, R., Ungermann, V., Gotz, F. & Entian, K.-D. (1992) Eur. J. Biochem. 204, 57-68]. We isolated a number of stable mutants from strain Tu3298 which are unable to produce biologically active epidermin. Complementation studies using the newly constructed staphylococcal plasmid vectors pT181mcs and pCU1 led to their classification as epiA, epiB, epiC or epiD mutants. Furthermore, evidence is presented that epiB lacks its own promoter and is co-transcribed from the epiA promoter. There is evidence that epiC and D possess their own promoters. Although epiQ and epiP mutants were not isolated, it could be shown by heterologous gene expression in S. carnosus and S. xylosus that the corresponding DNA region is involved in epidermin biosynthesis. We can not exclude the possibility that, in addition to the four open reading frames, epiA, B, C, D, and the DNA region comprising epiQ and P, host-encoded functions are necessary for epidermin production. Thus, the genetic information for epidermin biosynthesis in S. carnosus and S. xylosus is located on an 8-kb DNA fragment of pTu32. A further characterization of the two epiA mutants revealed that in both mutants, the preepidermin nucleotide sequence was changed. In one mutant, the mutation led to a substitution of Ser3 by Asn; in the other of Gly10 by Glu.

Fungal elicitors induce a transient release of active oxygen species from cultured spruce cells that is dependent on Ca(2+) and protein-kinase activity.

Abstract: Cell-wall components from the ectomycorrhizal fungi Amanita muscaria and Hebeloma crustuliniforme and from the spruce pathogen Heterobasidion annosum elicited a transient release of active oxygen species from cultured spruce cells (Picea abies (L.) Karst.). Since the detection of active oxygen was suppressed by catalase, H2O2 was assumed to be the prevailing O2 species. On the other hand, superoxide dismutase enhanced the concentration of detectable H2O2 indicating that the superoxide anion was formed before dismutating to H2O2. The elicitors induced the formation of active oxygen in a dose-dependent manner. Interestingly, elicitors from mycorrhizal fungi had a lower H2O2-inducing activity than equal amounts of cell-wall preparations from the pathogen H. annosum. In Ca2+-depleted medium the production of active oxygen by elicitor-treated spruce cells was suppressed. Additionally, the ionophore A 23187 induced active oxygen formation in a medium with Ca2+ but not in a Ca2+-depleted medium. Furthermore, the protein-kinase inhibitor staurosporine inhibited the oxidative burst. At a concentration of 34 nM the effect was diminished to 50%. From these results it is suggested that the release of active oxygen species from cultured spruce cells triggered by cell-wall-derived fungal elicitors depends on external Ca2+ and a protein-kinase activity. In these respects the effect shows similarities with the well-studied respiratory burst of mammalian neutrophils.

Proteases and proteolysis in the lysosome

Abstract: Proteins sequestered by a non-selective bulk process within the lysosomes turn over with an apparent half-life of about 8 minutes and this rapid lysosomal proteolysis is initiated by endopeptidases, in particular by the cathepsins D and L. We describe also the cathepsins B and H which show mainly exopeptidase and only low endopeptidase activity. Especially cathepsin H is most probably the only lysosomal aminopeptidase in many cell types. Additionally, the properties of other mammalian lysosomal endo- and exopeptidases are compared. Finally, we discuss some of the conditions for the action of lysosomal proteases as the low intralysosomal pH, the high part of lysosomal thiol groups and the absence of intralysosomal proteinase inhibitors.

General-relativistic celestial mechanics. II. Translational equations of motion.

Abstract: The translational laws of motion for gravitationally interacting systems of {ital N} arbitrarily composed and shaped, weakly self-gravitating, rotating, deformable bodies are obtained at the first post-Newtonian approximation of general relativity. The derivation uses our recently introduced multi-reference-system method and obtains the translational laws of motion by writing that, in the local center-of-mass frame of each body, relativistic inertial effects combine with post-Newtonian self- and externally generated gravitational forces to produce a global equilibrium (relativistic generalization of d'Alembert's principle). Within the first post-Newtonian approximation (i.e., neglecting terms of order ({ital v}/{ital c}){sup 4} in the equations of motion), our work is the first to obtain complete and explicit results, in the form of infinite series, for the laws of motion of arbitrarily composed and shaped bodies. We first obtain the laws of motion of each body as an infinite series exhibiting the coupling of all the (Blanchet-Damour) post-Newtonian multipole moments of this body to the post-Newtonian tidal moments (recently defined by us) felt by this body. We then give the explicit expression of these tidal moments in terms of post-Newtonian multipole moments of the other bodies.

Organization of medullary adrenergic and noradrenergic projections to the periaqueductal gray matter in the rat.

Abstract: The periaqueductal or midbrain central gray matter (CG) in the rat contains a dense network of adrenergic and noradrenergic fibers. We examined the origin of this innervation by using retrograde and anterograde axonal tracers combined with immunohistochemistry for the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and phenylethanolamine N-methyltransferase (PNMT). Following injections of the fluorescent tracers Fast Blue or Fluorogold into the CG, double-labeled neurons in the medulla were identified mainly in the noradrenergic A1 group in the caudal ventrolateral medulla (VLM) and A2 group in the medial part of the nucleus of the solitary tract (NTS); and in the adrenergic C1 group in the rostral ventrolateral medulla and C3 group in the rostral dorsomedial medulla. Injections of Phaseolus vulgaris-leucoagglutinin (PHA-L) into these cell groups resulted in a distinct pattern of axonal labeling in various subdivisions of the CG. Anterogradely labeled fibers originating in the medial NTS were predominantly found in the lateral portion of the dorsal raphe nucleus and in the adjacent part of the lateroventral CG (CGlv). Following PHA-L injections into the C3 region the anterogradely labeled fibers were diffusely distributed in the CGlv and the dorsal raphe nucleus at caudal levels, but rostrally tended to be located laterally in the CGlv. In contrast, ascending fibers from the caudal and rostral VLM terminated in the rostral dorsal part of the CGlv and in the dorsal nucleus of the CG, whereas ventral parts of the CG, including the dorsal raphe nucleus, contained few afferent fibers. Double-label studies with antisera against DBH and PNMT confirmed that noradrenergic neurons in the A1 and A2 groups and adrenergic neurons in the C1 and C3 groups contributed to these innervation patterns in the CGlv. Noradrenergic and adrenergic projections from the medulla to the CG may play an important role in a variety of autonomic, sensory and behavioral processes.

Multilevel logic synthesis based on functional decision diagrams

Abstract: The authors introduce an efficient data structure for Boolean function representation and present a new algorithm for the synthesis of multilevel logic. Other algorithms represent Boolean functions in the operational domain using Sum-of-Products representations. The authors prefer the synthesis in the functional domain using the less complex Reed-Muller Expansion. The algorithm bases on a new efficient representation, the so-called functional decision diagrams, which are herewith presented. The authors implemented this algorithm, the results are encouraging. >

Transanal endoscopic microsurgery

Abstract: Transanal endoscopic microsurgery (TEM) has emerged as a minimally invasive means of resecting rectal tumors. Developed in Germany and now being used with increasing frequency in the United States, TEM utilizes a 40-mm operating rectoscope, which is sealed with an airtight facepiece. Carbon dioxide is constantly infused, thereby distending the rectum and maintaining visibility. A variety of instruments, such as tissue graspers, a high-frequency knife, suction, and needle holders, are inserted through the facepiece. Adenomas that are small, large, or even circumferential, as well as selected carcinomas up to 24 cm, can be removed with TEM instrumentation. The optics provide sixfold magnification, and this, combined with the constantly distended operative field, allows for a precise excision of the tumor as well as closure of the wound. For lesions in the mid and upper rectum, TEM is an alternative to a transsacral or transabdominal approach, with subsequently shorter hospital stay and fewer complications.

Tonotopic Order in the Adult and Developing Auditory System of the Rat as Shown by c-fos Immunocytochemistry.

Abstract: Immediate early genes such as the proto-oncogene c-fos can be expressed in neurons following synaptic excitation by sensory stimulation. C-fos immunocytochemistry has subsequently been shown to be a very sensitive marking technique for neuronal activity. Here, antibodies against the c-fos protein product Fos were used to map the tonotopic organization in the auditory system of adult and developing rats. After stimulating adult rats with pure-tone pulses, bands of Fos-immunoreactive neurons revealed the frequency representation in seven brainstem nuclei: all three subdivisions of the cochlear nucleus, the lateral superior olive, the medial nucleus of the trapezoid body, the ventral nucleus of the trapezoid body, the rostral periolivary nucleus, the dorsal nucleus of the lateral lemniscus and the inferior colliculus. With the exception of the dorsal cochlear nucleus and the inferior colliculus, tonotopicity has not been previously demonstrated in the brainstem nuclei of the rat. During development two striking results were obtained. First, beginning at postnatal day 14 (i.e. approximately 2 days after physiological hearing begins in rats), not only low but also high frequencies were able to induce strong Fos immunoreactivity, indicating that gradual recruitment of formerly unresponsive high-frequency sites does not occur in the rat. Second, a gradual age-related shift of the position of isofrequency bands was not seen in any of the nuclei, suggesting that changes in frequency - place code do not occur after 2 weeks postnatally. These results indicate that the rat's auditory brainstem nuclei achieve their adult-like tonotopic organization early on, implying a somewhat different developmental time course than is found in other mammalian species.

Fitting ordinary differential equations to chaotic data.

Abstract: We address the problem of estimating parameters in systems of ordinary differential equations which give rise to chaotic time series. We claim that the problem is naturally tackled by boundary value problem methods. The power of this approach is demonstrated by various examples with ideal as well as noisy data. In particular, Lyapunov exponents can be computed accurately from time series much shorter than those required by previous methods.

The scalp distribution of the fractal dimension of the EEG and its variation with mental tasks

Abstract: The insights gained by the concept of deterministic chaos for the EEG is that this seemingly disordered process may be governed by relatively few simple laws which could be determined. One of the quantitative measures of a complex dynamical system is that of its dimension. The term ‘dimension’ refers to the ability of a space to contain a set of points. We estimated the correlational dimension of the EEG and compared the outcome to traditional Fourier analyses. In addition, we tested the hypothesis that the EEG can be described as filtered noise. Data from 15 electrode sites and 31 subjects are reported in the present study. We have utilized a variety of tasks that cut across sensory modalities including touch, vision, and imagery which reflect neuropsychological processes that differentially engage areas of the cortex in the first part of the study. In the second part, the differences between the perception of an object and the imagination of the same object were evaluated. The outcome shows variations between scalp sites for all measures and also variations between tasks in terms of dimensionality of the EEG. The hypothesis of a higher dimensionality ("complexity") of imagery compared to actual perceptual processing was confirmed. A statistical comparison between the maps generated by means of the various measures shows that different informations are extracted when using the different measures. There is also statistical evidence that the EEG cannot completely be described by the model of filtered noise.

Nitrido Complexes of Transition Metals

Abstract: In the past decade new syntheses and numerous structural determinations have enlivened studies in the still relatively young field of nitrido-transition-metal complexes. Aside from the terminal function of the nitrido ligand MN:, this group also occurs as linear μ2-bridging ligand in symmetric and asymmetric coordination; examples are known with almost right-angled bridge function; and, finally, it also functions as μ3-bridging ligand. Accordingly, the fresh impulses given to synthetic chemistry by nitrido complexes are also many-sided: such complexes are used, inter alia, for the preparation of phosphaniminato and thionitrosyl complexes as well as for the synthesis of metallaheterocycles of the type MN3S2 and MN3P2 with delocalized π-systems. In technetium chemistry complexes with terminal nitrido group are employed as radiopharmaceuticals, and, owing to the strong trans influence of the MN: group, nitrido complexes of molybdenum are suitable as catalysts in olefin metathesis. Finally, nitrido complexes are also of wide interest in theoretical studies.

Determination of cytokines in synovial fluids: correlation with diagnosis and histomorphological characteristics of synovial tissue.

Abstract: In a study aimed at correlating cytokine levels in synovial fluid with the pathology of rheumatoid arthritis (RA), tumour necrosis factor alpha, interleukin 1 beta and interferon gamma were immunoassayed in 27 patients with RA, 16 patients with other arthritides, 23 with osteoarthritis, 13 patients with trauma, and 18 patients at necropsy without inflammatory disease and not known to have had joint disease (median 27 hours after death). The results for interleukin 1 beta clearly show higher cytokine levels in patients with RA and other arthritides than in patients with osteoarthritis, trauma, or the patients at necropsy. Interferon gamma levels in patients with osteoarthritis and the patients at necropsy, however, were significantly greater than in patients with RA, and tumour necrosis factor alpha levels were also greater in the patients at necropsy compared with patients with RA. This study also correlated histomorphological patterns of synovitis and indicators of local inflammatory activity with synovial fluid cytokine levels, showing, for example, a positive association of interleukin 1 beta titre and a negative association of interferon gamma titre with ulcerogranulomatous synovitis (itself associated with RA). Taken together, these results extend and strengthen data suggesting a possible part played by increased synovial fluid levels of interleukin 1 beta in joint destruction in RA, but provide no evidence for increases in levels of tumour necrosis factor alpha or interferon gamma affecting the disease pathology.

Synthesis and metal complexation of poly(ethyleneimine) and derivatives

Abstract: This article surveys the research work on the synthesis and modification reactions of poly(ethyleneimine) as well as its applications to metal complexation processes. Poly(ethyleneimine), one of the most simple heterochain polymers exists in the form of two different chemical structures: one of them is branched, which is a commercially available and the other one linear which is synthesized by cationic polymerization of oxazoline monomers and subsequent hydrolysis of poly[(N-acylimino)ethylene]. The most salient feature of poly(ethyleneimine) is the simultaneous presence of primary, secondary, and tertiary amino groups in the polymer chain which explains its basic properties and gives access to various modification reactions. A great number of synthetic routes to branched and linear poly(ethyleneimine)s and polymer-analogous reactions are described. In addition, the complexation of poly(ethyleneimine) and its derivatives with metal ions is investigated. Homogeneous and heterogeneous metal separation and enrichment processes are reviewed.

Do women develop alcoholic brain damage more readily than men

Abstract: Chronic alcoholism is related to brain damage (i.e., volume changes) in both men and women. There is an open question whether the brains of women are more vulnerable than those of men to alcohol toxicity. The present follow-up study focuses on a direct comparison of sex-related differences in alcoholic brain shrinkage and its reversibility. In a prospective design, a random sample of 65 alcoholics of both sexes (51 males and 14 females) was studied. Computerized tomography brain scans before and after a 6-week inpatient treatment program with controlled abstinence revealed a significant re-expansion of the brain as assessed by linear measurements. By controlling for moderating variables such as age, mean daily alcohol consumption, liver dysfunction, etc. the degree of brain shrinkage was found to be similar in men and women despite significantly shorter ethanol expositions in the women. These findings corroborate the hypotheses of other investigators about basic biological differences between the two sexes as to the effects of alcohol. The hypothesis of an enhanced vulnerability of women to acute and chronic complications of alcoholism is supported.

Clinical significance of antibodies against neutrophils in patients with inflammatory bowel disease and primary sclerosing cholangitis.

Abstract: The presence of perinuclear antibodies against neutrophils (pANCA) has been detected recently in sera of patients with inflammatory bowel disease and primary sclerosing cholangitis. In order to evaluate their clinical significance, sera from 126 patients with inflammatory bowel disease (80 Crohn's disease and 46 ulcerative colitis and 22 patients with primary sclerosing cholangitis were examined for pANCA by indirect immunofluorescence on liver sections and cytocentrifuge slides of neutrophils and by immunoblot. Perinuclear antibodies against neutrophils were found in 83% of patients with ulcerative colitis in 88% of patients with primary sclerosing cholangitis and inflammatory bowel disease, in 40% of patients with primary sclerosing cholangitis but without inflammatory bowel disease, and in 25% of patients with Crohn's disease using the immunofluorescence test. Titres of pANCA ranged from 1:10 to 1:1000 in ulcerative colitis and primary sclerosing cholangitis (median 1:100), whereas in Crohn's disease only four patients had titres of more than 1:10. The occurrence of pANCA did not correlate with clinical activity of Crohn's disease and primary sclerosing cholangitis whereas in ulcerative colitis high titres of pANCA were found mainly in active disease. Using an immunoblot system with sonified neutrophils as antigen, 82% of sera from patients with primary sclerosing cholangitis reacted with up to five different determinants, whereas only 12% of sera from patients with Crohn's disease and 11% of sera with ulcerative colitis detected one of the determinants, suggesting different antigens involved in pANCA reaction.

Expression and regulation of the antimonite, arsenite, and arsenate resistance operon of Staphylococcus xylosus plasmid pSX267.

Abstract: The arsenate, arsenite, and antimonite resistance region of the Staphylococcus xylosus plasmid pSX267 was subcloned in Staphylococcus carnosus. The sequenced DNA region revealed three consecutive open reading frames, named arsR, arsB, and arsC. Expression studies in Escherichia coli with the bacteriophage T7 RNA polymerase-promoter system yielded three polypeptides with apparent molecular weights of 8,000, 35,000, and 15,000, which very likely correspond to ArsR, ArsB, and ArsC, respectively. ArsB was distinguished by its overall hydrophobic character, suggesting a membrane association. The arsenate, arsenite, and antimonite resistance was shown to be inducible by all three heavy metal ions. Inactivation of the first gene, arsR, resulted in constitutive expression of resistance. Similar results were obtained with transcriptional fusions of various portions of the ars genes with a lipase reporter gene, indicating a function of ArsR as a negative regulator of a putative promoter in front of arsR. The inactivation of arsR also resulted in reduction of resistance to arsenite and antimonite, while arsenate resistance was unaffected. The three ars genes conferred arsenite resistance in E. coli and arsenite as well as arsenate resistance in Bacillus subtilis. Images

Regulation of adenylyl cyclase from Paramecium by an intrinsic potassium conductance

Abstract: Hyperpolarization of the cell membrane of Paramecium stimulates adenosine 3',5'-monophosphate (cAMP) formation. Manipulations of the K+ resting conductance of the ciliate by adaptation in different buffers affected excitability of the cAMP generating system. Blockade of K+ channels inhibited hyperpolarization-stimulated cAMP formation. A mutant of Paramecium that is unable to control its K+ resting conductance had a defect in cAMP formation. Purified adenylyl cyclase, when incorporated into an artificial lipid bilayer membrane, revealed properties of a voltage-independent K+ channel. This indicates that the adenylyl cyclase of Paramecium has a secondary function as carrier of the K+ resting conductance. A hyperpolarization-activated K+ efflux appears to directly regulate adenylyl cyclase activity in vivo.

Analysis of genes involved in the biosynthesis of lantibiotic epidermin.

Abstract: The structural gene of the lanthionine-containing peptide antibiotic epidermin is located on a 54-kb plasmid of Staphylococcus epidermidis [Schnell et al. (1988) Nature 333, 276-278]. A 13.5-kb DNA region neighbouring the epidermin structural gene (epiA) was subcloned and its sequencing revealed five additional open reading frames. Three of these reading frames, epiB, epiC and epiD shared no homology with previously described proteins stored in data bases. They were located 3' adjacent to epiA. Using epiB as a probe, a 5-kb mRNA was identified indicating that three or all four reading frames are transcribed as an operon. Additionally, a 0.3-kb mRNA specific for epiA was identified. Two open reading frames (epiP and epiQ) were located 3' to epiA, epiB, epiC and epiD, but in the reverse orientation. The epiQ gene product shows similarity to the positive regulatory factor PhoB. This might indicate a regulatory function of epiQ in epidermin biosynthesis. The epiP gene product shows striking similarity to several serine proteases which makes epiP a likely candidate for processing the epidermin prepeptide. Heterologous epidermin synthesis in the non-producing organism Staphylococcus carnosus finally proved that these reading frames are necessary for epidermin biosynthesis.

The illusion of group effectivity.

Abstract: The illusion of group effectivity refers to the belief, persistent despite contradictory empirical evidence, that groups can stimulate creativity. This article uses unpublished data from the authors' research on brainstorming to illustrate the illusion of group effectivity and then presents a theoretical interpretation of this illusion based on two assumptions: (a) People are motivated to view their own performance in a positive light. (b) People who generate ideas in groups have difficulty in differentiating between own and others' ideas. They are therefore more prone to this self-serving bias than persons who work individually. In an experiment conducted to test these hypotheses, subjects who had brainstormed either in groups or individually were presented with the set of ideas produced by their nominal or real groups and asked to identify the ideas they had suggested and those that had occurred to them. Results were generally consistent with the hypotheses.

Speech deficits in ischaemic cerebellar lesions.

Abstract: Twelve patients with cerebellar infarction, 8 in the region supplied by the posterior inferior cerebellar artery (PICA) and 4 in the territory of the superior cerebellar artery, underwent formal perceptual examination for speech deficits. With respect to topography the results firstly underline the significance of the paravermal region of the superior cerebellar portion for speech functions. In all patients with dysarthric impairment the lesion extended to this area, whereas patients with PICA infarction sparing the superior portion of the cerebellum showed no speech deficits. Secondly the findings do not corroborate the notion of an exclusively left-sided cerebellar speech motor control, since 3 of the 4 dysarthric subjects had unilateral right-sided ischaemia. This study thirdly demonstrates that lesions of the cerebellar cortex without involvement of the dentate nucleus can cause dysarthric impairment. Phonetic analysis revealed irregularly distributed articulatory deficits and slowed speech tempo as the most common dysarthric features.