Showing papers by "University of Lausanne published in 1991"

Influence of surface characteristics on bone integration of titanium implants. A histomorphometric study in miniature pigs.

Abstract: The purpose of the present study was to evaluate the influence of different surface characteristics on bone integration of titanium implants. Hollow-cylinder implants with six different surfaces were placed in the metaphyses of the tibia and femur in six miniature pigs. After 3 and 6 weeks, the implants with surrounding bone were removed and analyzed in undecalcified transverse sections. The histologic examination revealed direct bone-implant contact for all implants. However, the morphometric analyses demonstrated significant differences in the percentage of bone-implant contact, when measured in cancellous bone. Electropolished as well as the sandblasted and acid pickled (medium grit; HF/HNO3) implant surfaces had the lowest percentage of bone contact with mean values ranging between 20 and 25%. Sandblasted implants with a large grit and titanium plasma-sprayed implants demonstrated 30-40% mean bone contact. The highest extent of bone-implant interface was observed in sandblasted and acid attacked surfaces (large grit; HCl/H2SO4) with mean values of 50-60%, and hydroxylapatite (HA)-coated implants with 60-70%. However, the HA coating consistently revealed signs of resorption. It can be concluded that the extent of bone-implant interface is positively correlated with an increasing roughness of the implant surface.

Methanol and Formic Acid Toxicity: Biochemical Mechanisms

Abstract: Metabolism of methanol, methyl ethers, esters and amides give rise to formic acid This acid is an inhibitor of the mitochondrial cytochrome oxidase causing histotoxic hypoxia Formic acid is a weaker inhibitor than cyanide and hydrosulphide anions The body burden of formate in methanol poisoning is high enough to cause acidosis, and other clinical symptoms Part of the protons can be attributed to formic acid whereas the most significant acid load results from the hypoxic metabolism The acidosis causes eg dilatation of cerebral vessels, facilitation of the entry of calcium ions into cells, loss of lysosomal latency and deranged production of ATP The latter effect seems to impede parathormone-dependent calcium reabsorption in the kidney tubules Besides, urinary acidification is affected by formic acid Its excretion causes continuous recycling of the acid by the tubular cell Cl-/formate exchanger This sequence of events may partially explain an accumulation of formate in urine Occupational exposure to vapours of methanol and formic acid can be quantitatively monitored by urinary formic acid determinations Formic acid toxicity may prove a suitable model for agents causing histotoxic hypoxia

A bioautographic agar overlay method for the detection of antifungal compounds from higher plants

Abstract: A simple bioautographic agar overlay assay using Candida albicans as the indicator organism for the detection and activity-guided fractionation of antifungal compounds by thin layer chromatography has been developed. Inhibition of fungal growth was assessed by the detection of dehydrogenase activity with thiazolyl blue (methylthiazolyltetrazolium chloride; MTT). A series of clinically used antimycotic agents were tested in order to determine the sensitivity of the assay. The compatibility of the agar overlay technique with chemically modified silica gel (Diol and RP-18) plates and with various organic solvents was evaluated. The methodology is also applicable to the search for antibacterial compounds, as shown with Bacillus subtilis as a test organism.

Risk theory for the compound Poisson process that is perturbed by diffusion

Abstract: The classical model of collective risk theory is extended in that a diffusion process is added to the compound Poisson process. It is shown that the probabilities of ruin (by oscillation or by a claim) satisfy certain defective renewal equations. The convolution formula for the probability of ruin is derived and interpreted in terms of the record highs of the aggregate loss process. If the distribution of the individual claim amounts are combinations of exponentials, the probabilities of ruin can be calculated in a transparent fashion. Finally, the role of the adjustment coefficient (for example, for the asymptotic formulas) is explained.

Structure-function relationship of Na,K-ATPase.

Abstract: In animal cells, the major ionmotive ATPase is the ouabain-inhibitable sodium pump, a membrane-bound enzyme that couples the free energy contained within the ATP molecule to the translocation of N a + and K + across the plasma membrane. The enzyme consists of a heterodimer of an a and {3 subunit (Figure la), which constitutes the minimal functional unit able to hydrolyze ATP and to undergo E1-E2 transition (Figure Ib), a conformational change characteristic of the P-type ATPase (57). Na+,K+ -coupled transport has evolved in higher eukaryotes (vertebrate and invertebrate) to accomplish functions specific to these multicellular organisms (64). Ubiquitous distribu­ tion of Na,K-ATPase in all cells insures the primary control of cell volume and the maintenance of the gradients of Na+ and K+ across the cell mem­ brane. Asymmetric distribution of Na,K-ATPase to the basolateral membrane of epithelial cells allows the vectorial trahsport of salt and water from one side of the cell layer (as occurs in the kidn, ey and the intestine), thereby con­ trolling the extracellular volume and the osmotic balance between the in­ traand extracellular compartments. In excitable cells, the Na+ and K+

Superfamily of steroid nuclear receptors: positive and negative regulators of gene expression.

Abstract: The nuclear hormone receptor superfamily is characterized by an impressive functional diversity of its members despite a remarkable overall structural unity. A variety of ligands bind specifically to them and these receptors control gene networks that have profound effects on growth, development, and homeostasis. The ligand-receptor complexes recognize transcriptional enhancer DNA sequences, the hormone response elements, resulting in induction or repression of gene activity. The similarity between all these hormone response enhancer elements, as well as between the receptors themselves, indicates a conserved general strategy for the hormonal control of transcription by steroids. The activated receptors bind to responsive promoters and most likely mediate the assembly of stage- and tissue-specific transcription factor complexes that stimulate or inhibit gene expression.

Stable transformation of the moss Physcomitrella patens.

Abstract: We report the stable transformation of Physcomitrella patens to either G418 or hygromycin B resistance following polyethylene glycol-mediated direct DNA uptake by protoplasts. The method described in this paper was used successfully in independent experiments carried out in our two laboratories. Transformation was assessed by the following criteria: selection of antibiotic-resistant plants, mitotic and meiotic stability of phenotypes after removal of selective pressure and stable transmission of the character to the offspring; Southern hybridisation analysis of genomic DNA to show integration of the plasmid DNA; segregation of the resistance gene following crosses with antibiotic-sensitive strains; and finally Southern hybridisation analysis of both resistant and sensitive progeny. In addition to stable transformants, a heterogeneous class of unstable transformants was obtained.

CD8+ cytolytic T cell clones derived against the Plasmodium yoelii circumsporozoite protein protect against malaria

Abstract: Immunization of BALB/c mice with radiation-attenuated Plasmodium yoelii sporozoites induces cytotoxic T lymphocytes (CTL) specific for an epitope located within the amino acid sequence 277-288 of the P. yoelii circumsporozoite (CS) protein. Several CD8+ CTL clones were derived from the spleen cells of sporozoite-immunized mice, all displaying an apparently identical epitope specificity. All the clones induced high levels of cytolysis in vitro upon exposure to peptide-incubated MHC-compatible target cells. The adoptive transfer of two of these clones conferred complete protection against sporozoite challenge to naive mice. This protection is species and stage specific. Using P. yoelii specific ribosomal RNA probes to monitor the in vivo effects of the CTL clones, we found that their target was the intrahepatocytic stage of the parasite. The protective clones completely inhibited the development of the liver stages of P. yoelii. Some CTL clones were only partially inhibitory in vivo, while others failed completely to alter liver stage development and to confer any detectable degree of protection. The elucidation of the effector mechanism of this CTL mediated protection against rodent malaria should facilitate the design of an effective malaria vaccine. From a broader perspective this model may provide further insight into the mechanism(s) of CTL mediated killing of intracellular non-viral pathogens in general.

Auditory corticocortical interconnections in the cat: evidence for parallel and hierarchical arrangement of the auditory cortical areas.

Abstract: The origin and laminar arrangement of the homolateral and callosal projections to the anterior (AAF), primary (AI), posterior (PAF) and secondary (AII) auditory cortical areas were studied in the cat by means of electrophysiological recording and WGA-HRP tracing techniques The transcallosal projections to AAF, AI, PAF and AII were principally homotypic since the major source of input was their corresponding area in the contralateral cortex Heterotypic transcallosal projections to AAF and AI were seen, originating from the contralateral AI and AAF, respectively PAF received heterotypic commissural projections from the opposite ventroposterior auditory cortical field (VPAF) Heterotypic callosal inputs to AII were rare, originating from AAF and AI The neurons of origin of the transcallosal connections were located mainly in layers II and III (70–92%), and less frequently in deep layers (V and VI, 8–30%) Single unit recordings provided evidence that both homotypic and heterotypic transcallosal projections connect corresponding frequency regions of the two hemispheres The regional distribution of the anterogradely labeled terminals indicated that the homotypic and heterotypic auditory transcallosal projections are reciprocal The present data suggest that the transcallosal auditory interconnections are segregated in 3 major parallel components (AAF-AI, PAF-VPAF and AII), maintaining a segregation between parallel functional channels already established for the thalamocortical auditory interconnections For the intrahemispheric connections, the analysis of the retrograde tracing data revealed that AAF and AI receive projections from the homolateral cortical areas PAF, VPAF and AII, whose neurons of origin were located mainly in their deep (V and VI) cortical layers The reciprocal interconnections between the homolateral AAF and AI did not show a preferential laminar arrangement since the neurons of origin were distributed almost evenly in both superficial (II and III) and deep (V and VI) cortical layers On the contrary, PAF received inputs from the homolateral cortical fields AAF, AI, AII and VPAF, originating predominantly from their superficial (II and III) layers The homolateral projections reaching AII originated mainly from the superficial layers of AAF and AI, but from the deep layers of VPAF and PAF The laminar distribution of anterogradely labeled terminal fields, when they were dense enough for a confident identification, was systematically related to the laminar arrangement of neurons of origin of the reciprocal projection: a projection originating from deep layers was associated with a reciprocal projection terminating mainly in layer IV, whereas a projection originating from superficial layers was associated with a reciprocal projection terminating predominantly outside layer IV This laminar distribution indicates that the homolateral auditory cortical interconnections have a feed-forward/feed-back organization, corresponding to a hierarchical arrangement of the auditory cortical areas, according to criteria previously established in the visual system of primates The principal auditory cortical areas could be ranked into 4 distinct hierarchical levels The tonotopically organized areas AAF and AI represent the lowest level The second level corresponds to the non-tonotopically organized area AII Higher, the tonotopically organized areas VPAF and PAF occupy the third and fourth hierarchical levels, respectively

Morphine 6-glucuronide and morphine 3-glucuronide as molecular chameleons with unexpected lipophilicity

Abstract: Morphine 6-glucuronide, but not morphine 3-glucuronide, is a highly potent opiate receptor agonist. In fact, there is converging evidence that much of the analgesic effect occurring after morphine treatment in humans is due to this metabolite rather than to the parent drug. Yet glucuronides as a rule are considered as highly polar metabolites unable to cross the blood-brain barrier and rapidly excreted by the urinary and/or biliary routes. Here, we report that morphine 6-glucuronide, and to a lesser extent morphine 3-glucuronide, are far more lipophilic than predicted, and in fact not much less lipophilic than morphine itself. Force-field and quantum mechanical calculations indicate that the two glucuronides can exist in conformational equilibrium between extended and folded forms. The extended conformers, because they efficiently expose their polar groups, must be highly hydrophilic forms predominating in polar media such as water; in contrast, the folded conformers mask part of their polar groups, thus being more lipophilic and likely to predominate in media of low polarity such as biological membranes.

Mycobacterial heat-shock proteins as carrier molecules.

Abstract: We have previously shown that the priming of mice with live Mycobacterium tuberculosis var. bovis (Bacillus Calmette-Guerin, BCG) and immunization with the repetitive malaria synthetic peptide (NANP)40 conjugated to purified protein derivative (PPD), led to the induction of high and long-lasting titers of anti-peptide IgG antibodies, overcoming the requirement of adjuvants and the genetic restriction of the antibody response to the peptide (Lussow et al., Proc. Natl. Acad. Sci. USA 1990. 87:2960). This initial work led us to the following observations. BCG had to be live for priming to lead to the induction of anti-peptide antibodies. Surprisingly, priming with other living microorganisms which chronically infect the macrophage (e.g. Salmonella typhimurium and Leishmania major) also induced anti-peptide antibodies in mice immunized with PPD-(NANP)40 conjugate. It was, thus, hypothesized that molecules expressed during active infection and also known to be highly conserved between species, namely the heat-shock proteins (hsp), could mediate the T cell sensitization required for the production of anti-peptide antibodies. In fact, when the PPD protion of the conjugate was replaced by a highly purified recombinant protein corresponding to the 65-kDa (GroEL-type) hsp of M. bovis, this resulted in the production of anti-(NANP) IgG antibodies in BCG-primed mice, irrespective of the major histocompatibility complex-controlled responsiveness to the (NANP) sequence itself. Further, similar induction of anti-peptide antibody response was also obtained with a recombinant 70-kDa (DnaK-type) hsp of M. tuberculosis, but not with a small molecular mass (18 kDa) of M. leprae. Finally, an adjuvant-free carrier effect for anti-peptide IgG antibody production in BCG-primed mice, was also exerted by the GroEL hsp of Escherichia coli. This finding that hsp can act as carrier molecules without requiring conventional adjuvants is of potential importance in the development of vaccine strategies.

A controlled study of inhaled pentamidine for primary prevention of Pneumocystis carinii pneumonia.

Abstract: BACKGROUND: Current recommendations for prophylaxis of Pneumocystis carinii pneumonia (PCP) are based on data from patients who have had at least one episode of PCP (secondary prevention). We designed a study to determine the efficacy and side effects of inhaled pentamidine in the primary prevention of PCP. METHODS: Two hundred twenty-three patients sero-positive for human immunodeficiency virus (HIV) who had the acquired immunodeficiency syndrome (AIDS) but not PCP, who had advanced AIDS-related complex, or who had less than 0.2 x 10(9) CD4-positive lymphocytes per liter received either 300 mg of pentamidine isethionate or 300 mg of sodium isethionate every 28 days by inhaler. The proportion of patients surviving without PCP was analyzed with the log-rank test as a function of time spent in the trial, according to the intention to treat with either placebo or pentamidine. RESULTS: The third of five planned interim analyses showed a significant difference in the occurrence of PCP, with 8 cases in pentamidine group and 23 in the placebo group (nominal P value = 0.0021). There were no deaths within 60 days of the diagnosis of PCP and no significant differences in survival between groups. Approximately 53 inhalations were needed to prevent one episode of pneumonia. Thirty-eight of 114 patients given pentamidine (33 percent) and 7 of 109 given placebo (6 percent) had moderate-to-severe coughing during inhalations (two-tailed P less than 0.00001), which caused 4 patients given pentamidine (3.5 percent) to discontinue taking it. CONCLUSIONS: A dose of 300 mg of aerosolized pentamidine given every four weeks was well tolerated and 60 to 70 percent effective in preventing a first episode of PCP in patients with HIV infection.

Corticofugal modulation of the information processing in the auditory thalamus of the cat.

Abstract: Single unit activity of 355 cells was recorded in the auditory thalamus of anesthetized cats before, during, and after the inactivation by cooling of the ipsilateral primary auditory cortex (AI). Most of the units (n = 288) showed similar functional characteristics of firing before and after the cryogenic blockade of AI. The spontaneous firing rate remained unchanged by cooling in 20% of the units and decreased in the majority of them (60%). In some regions, i.e. dorsal division of the medial geniculate body (MGB), lateral part of the posterior group of the thalamus, and auditory sector of the reticular nucleus of the thalamus, the maximum firing rate evoked by white noise bursts was generally affected by cooling in the same direction and to the same extent as the spontaneous activity. Units in the ventral division of MGB showed a characteristic increase of signal-to-noise ratio during cortical cooling. The corticofugal modulation led to the appearance or disappearance of the best frequency of tuning in 51 units and changed it by more than 0.5 octave in 34 units. The bandwidths of different response patterns to pure tones stimulation were used to define a set of functional properties. During cryogenic blockade of AI, two cortically modulated sub-populations of units were usually distinguished that exhibited changes for a given functional property. The complexity and diversity of the effects of cortical inactivation suggest that the corticothalamic projection may be the support for selective operations such as an adaptive filtering of the incoming acoustic signal at the thalamic level adjusted as a function of cortical activity.

Ultrastructure of giant and small thalamic terminals of cortical origin : a study of the projections from the barrel cortex in mice using Phaseolus vulgaris leuco-agglutinin (PHA-L)

Abstract: By means of tracing with the lectin Phaseolusvulgaris leucoagglutinin (PHA-L), we examined in the thalamus of the mouse, the axon terminals of fibers originating in the barrel cortex. Vibratome sections of the brain were subjected to PHA-L immunocytochemistry and processed for light and electron microscopy. We observed small (0.5–0.8 μm in diameter) varicosities of labeled fibers in the nucleus ventrobasalis (VB) and the nucleus posterior (PO) as well as labeled giant terminals (3–5 μm in diameter) in PO. The analysis involved examination of serial sections and computer-aided reconstruction of several terminals. The small varicosities in VB appear to be small axon terminals forming distinct asymmetric synapses with small dendritic profiles. Some labeled terminals are apposed to, but not synaptically related with, the cell bodies of neurons in VB that are retrogradely labeled with PHA-L. The small varicosities seen with the light microscope in PO are terminals forming asymmetric synapses with dendritic shafts. The giant terminals in PO appear as large, vesicle-filled profiles forming part of synaptic glomeruli, i.e. complexes of one corticothalamic terminal engulfing several excrescences of a single dendrite. A giant terminal forms several asymmetric synapses (about 8) with these excrescences, as well as numerous (up to 15) puncta adhaerentia. The glomeruli are enveloped in glial lamellae, and they are often found at the bifurcations of primary dendritic segments. We suggest that the small terminals in VB are in the service of feedback signalling from the barrel cortex to its principal thalamic relay nucleus; the functional importance of this projection may reside in increased spatio-temporal discrimination. We interpret the giant terminals in PO as elements serving feed-forward processing, allowing the barrel cortex to influence, via PO, parts of the motor pathway modulating the animal's ongoing behavior.

Immunohistochemistry in the differential diagnosis of liver carcinomas.

Abstract: Immunohistochemical techniques were used to study 177 hepatic tumors (hepatocarcinoma, cholangiocarcinoma, hepatocholangiocarcinoma, adenocarcinoma of unknown origin, and metastatic carcinoma). Phenotypes suggestive of hepatocarcinoma included keratins 8 and 18, factor XIII a, alpha-fetoprotein. C-reactive protein, carcinoembryonic antigen (CEA) cross-reacting antigen; those in effect that excluded hepatocarcinoma were keratins 1, 5, 10, 11, 19, true CEA. C-reactive protein, used for the first time, proved to be a fairly sensitive and specific marker. Factor XIII a, which was thought to be synthesized only by histiocytes, was also present in hepatocytes. Immunohistochemistry appears to be an important tool in the diagnosis of hepatic tumors. As a result of this study, 32 cases were reclassified; several were found to be intermediate between hepatocarcinoma and cholangiocarcinoma. Sixteen cases apparently were true hepatocholangiocarcinomas. In 12 cases of hepatocarcinoma, some tumor cells expressed keratins of bile duct type. It was impossible to differentiate immunohistochemically cholangiocarcinoma from metastatic carcinoma, except in two cases with breast tissue markers.

Antibody-fluorescein conjugates for photoimmunodiagnosis of human colon carcinoma in nude mice.

Abstract: To improve the detectability of tumors by light-induced fluorescence, the use of monoclonal antibodies (MoAb) as carriers of fluorescent molecules was studied. As a model for this approach, the biodistribution of an anticarcinoembryonic antigen (CEA) MoAb coupled to fluorescein was studied in mice bearing a human colon carcinoma xenograft. In vitro, such conjugates with fluorescein-MoAb molar ratios ranging from four to 19, doubly labeled with 125I, showed more than 82% binding to immobilized CEA. In vivo, conjugates with a fluorescein-MoAb molar ratio of ten or less resulted in a tumor uptake of more than 30% of the injected dose of radioactivity per gram tumor at 24 hours. Tumor to liver, kidney, and muscle ratios of 20, 30 and 72, respectively, were obtained 48 hours after injection of the 125I-MoAb-(fluorescein)10 conjugate. The highest fluorescence intensity was always obtained for the tumor with the anti-CEA MoAb conjugate; whereas in control mice injected with fluoresceinated control immunoglobulin G1, no detectable increase in tumor fluorescence was observed. To compare these results with a classically used dye, mice bearing the same xenografts received 60 micrograms of Photofrin II. The intensity of the fluorescence signal of the tumor with this amount of Photofrin II was eight times lower than that obtained after an injection of 442 ng of fluorescein coupled with 20 micrograms of MoAb, which gave an absolute amount of fluorescein localized in the tumor of up to 125 ng/g of tumor. These results illustrate the possibility of improving the specificity of in vivo tumor localization of dyes for laser-induced fluorescence photodetection and phototherapy by coupling them to MoAb directed against tumor markers.

Dietary Indicators of Oral and Pharyngeal Cancer

Abstract: The relationship between frequency of consumption of a selected number of indicator foods and oral and oropharyngeal cancer risk was analysed in a case-control study conducted in Northern Italy on 105 cases of oral and pharyngeal cancer and 1169 controls in hospital for acute, non-neoplastic or digestive diseases. Besides significant and strong direct associations with tobacco (relative risk, RR = 11.0 for current versus never smokers) and alcohol (RR = 5.8 for upper versus lower consumption tertile), consumption of six food items (milk, meat, cheese, carrots, green vegetables and fruit) were inversely and significantly related to oral and pharyngeal cancer risk. The strongest protection was apparently related to frequent fruit consumption, with RRs of 0.8 and 0.2 in the two highest tertiles. Allowance for major potential confounding factors, including tobacco, alcohol and social class indicators explained only part of the dietary correlates observed. The two items remaining significant after multivariate analysis were fruit (RR = 0.3 for the upper tertile) and alcohol (RR = 3.8 for the upper tertile). The associations observed may simply reflect a generally poorer nutritional status in the cases, although the observation that fruit consumption appears to be a particularly important protective factor against oropharyngeal cancer is of potential interest, in terms of aetiological clues and preventive implications.