Showing papers by "University of Lausanne published in 1985"

Evoked mechanical responses of isolated cochlear outer hair cells

Abstract: Intracellular current administration evokes rapid, graded, and bidirectional mechanical responses of isolated outer hair cells from the mammalian inner ear. The cells become shorter in response to depolarizing and longer in response to hyperpolarizing currents in the synaptic end of the cell. The cells respond with either an increase or decrease in length to transcellular alternating current stimulation. The direction of the movement with transcellular stimuli appears to be frequency dependent. Iontophoretic application of acetylcholine to the synaptic end of the cell decreases its length. The microarchitecture of the organ of Corti permits length changes of outer hair cells in a manner that could significantly influence the mechanics of the cochlear partition and thereby contribute to the exquisite sensitivity of mammalian hearing.

A limiting dilution assay for quantifying Leishmania major in tissues of infected mice

Abstract: Summary A limiting dilution assay for the quantification of Leishmania major in infected mouse tissue was developed. The assay was found to be both sensitive and reliable, and, due to its design, could be scored either visually or following the incorporation of 3H-thymidine by the growing parasites. Results are presented in which the assay was employed to enumerate L. major in the tissues of susceptible (BALB/c) and resistant (CBA) mice at intervals after infection with L. major. It was found that parasites could be detected at the site of injection with L. major as early as 3 days after infection. By day 8, a substantial increase in the number of parasites at the lesion site had occurred in both strains of mice. Subsequently, whereas the number of parasites decreased in the lesions of CBA mice, their number steadily increased in the lesions of BALB/c mice. Parasites were detected in lymph nodes draining the lesion site in both BALB/c and CBA mice by 28 days after infection. Interestingly, a low number of L. major was found in the lymph nodes of CBA mice at 100 days after infection, a time when no parasites could be detected at the lesion site. Previous results from this laboratory have demonstrated that the adoptive transfer of L. major-specific L3T4-positive T-cell populations exacerbated cutaneous lesions induced by L. major in BALB/c mice. Experiments presented here indicate that the adoptive transfer of L. major-specific T-cells also exacerbated cutaneous leishmaniasis in CBA mice. Using the sensitive limiting dilution assay presently described, it was found that this unexpected exacerbative effect of L. major-specific T-cells on lesion development was accompanied by a substantial increase in the number of parasites in the lesions of the adoptively transferred mice.

Dissociation between components of spatial memory in rats after recovery from the effects of retrohippocampal lesions.

Abstract: 1. A series of 4 experiments examined the performance of rats with retrohippocampal lesions on a spatial water-maze task. 2. The animals were trained to find and escape onto a hidden platform after swimming in a large pool of opaque water. The platform was invisible and could not be located using olfactory cues. Successful escape performance required the rats to develop strategies of approaching the correct location with reference solely to distal extramaze cues. 3. The lesions encompassed the entire rostro-caudal extent of the lateral and medial entorhinal cortex, and included parts of the pre- and para-subiculum, angular bundle and subiculum. Groups ECR 1 and 2 sustained only partial damage of the subiculum, while Group ECR+S sustained extensive damage. These groups were compared with sham-lesion and unoperated control groups. 4. In Expt 1A, a profound deficit in spatial localisation was found in groups ECR 1 and ECR+S, the rats receiving all training postoperatively. In Expt 1B, these two groups showed hyperactivity in an open-field. In Expt 2, extensive preoperative training caused a transitory saving in performance of the spatial task by group ECR 2, but comparisons with the groups of Expt 1A revealed no sustained improvement, except on one measure of performance in a post-training transfer test. All rats were then given (Expt 3) training on a cueing procedure using a visible platform. The spatial deficit disappeared but, on returning to the normal hidden platform procedure, it reappeared. Nevertheless, a final transfer test, during which the platform was removed from the apparatus, revealed a dissociation between two independent measures of performance: the rats with ECR lesions failed to search for the hidden platform but repeatedly crossed its correct location accurately during traverses of the entire pool. This partial recovery of performance was not (Expt 4) associated with any ability to discriminate between two locations in the pool. 5. The apparently selective recovery of aspects of spatial memory is discussed in relation to O'Keefe and Nadel's (1978) spatial mapping theory of hippocampal function. We propose a modification of the theory in terms of a dissociation between procedural and declarative sub-components of spatial memory. The declarative component is a flexible access system in which information is stored in a form independent of action. It is permanently lost after the lesion. The procedural component is “unmasked” by the retrohippocampal lesion giving rise to the partial recovery of spatial localisation performance.

On convex principles of premium calculation

Abstract: The classical definition of a principle of premium calculation is generalized: risks with identical distributions do not necessarily lead to the same premium. In the first part (Sections 1–3) the theoretical properties of convexity are discussed; in particular, the gradient of a principle is introduced. It is noted that the more common principles are all convex. In the second part these notions are applied to solve two problems under rather general assumptions: (1) Optimal purchase of reinsurance: If the first insurer knows how the reinsurer determines his premium, what form and degree of reinsurance should he choose? (2) Optimal cooperation: How should n companies split up a given risk to minimize the total premium? The case where the optimal decompostion consists of constant quotas is described in detail. In general, there is a close connection with Pareto optimality on the one hand, and no trade equilibria on the other.

Monoclonal antibodies recognizing a neoantigen of poly(C9) detect the human terminal complement complex in tissue and plasma.

Abstract: The terminal complement complex (TCC), consisting of C5b, C6, C7, C8, and C9, contains neoantigens that are absent from the individual native components. Neoantigens are present both in the membrane-bound (MAC) and the fluid-phase (SC5b-9) complex. The present study describes production of monoclonal antibodies against neoantigens of both forms of the TCC. A convenient screening and detection system, based mainly on enzyme-linked immunosorbent assays, crossed immunoelectrophoresis with autoradiography, and affinity chromatography with subsequent sodium dodecyl sulphate-polyacrylamide gel electrophoresis including immunoblotting, is described in detail. Two monoclonal antibodies were specific for a neoantigen located in the poly(C9) moiety of the TCC. One of these antibodies, MCaE11, was used for immunohistochemical detection of MAC in tissue and for quantification of the fluid-phase TCC in ethylenediaminetetraacetic acid plasma.

Whole body protein synthesis and energy expenditure in very low birth weight infants.

Abstract: The aim of the present work was to study whole body protein synthesis and breakdown, as well as energy metabolism, in very low birth weight premature infants (< 1500 g) during their rapid growth phase. Ten very low birth weight infants were studied during their first and second months of life. They received a mean energy intake of 114 kcal/kg day and 3 g protein/kg day as breast milk or milk formula. The average weight gain was 15 g/ kg day. The apparent energy digestibility was 88%, i.e. 99 kcal/kg-day. Their resting postprandial energy expenditure was 58 kcal/kg-day, indicating that 41 kcal/kg day was retained. The apparent protein digestibility was 89%, i.e. 2.65 g/kg-day. Their rate of protein oxidation was 0.88 g/kg-day so that protein retention was 1.76 g/kg-day. There was a linear relationship between N retention and N intake (r = 0.78, p < 0.001). The slope of the regression line indicates a net efficiency of N utilization of 67%. Estimates of body composition from the energy balance, coupled with N balance method, showed that 25% of the gain was fat and 75% was lean tissue. Whole body protein synthesis and breakdown were determined using repeated oral administration of 15N glycine for 60–72 h, and 15N enrichment in urinary urea was measured. Protein synthesis averaged 11.2 g/kg-day and protein breakdown 9.4 g/ kg day. Muscular protein breakdown, as estimated by 3-methylhistidine excretion, contributed to 12% of the total protein breakdown. There was a positive correlation (r = 0.68, p < 0.05) between protein synthesis and protein gain, as well as between resting energy expenditure and protein gain (r = 0.58, p < 0.01). The slope of the regression line indicated that 1 g of protein gain required the synthesis of five times more protein (5 g) and resulted in an extra energy expenditure of 10 kcal. Thus, the net cost of protein synthesis in these very low birth weight infants was 2 kcal/ g.

Golgi and Nissl studies of the visual cortex of the bottlenose dolphin

Abstract: Nissl, Golgi and fibre preparations were made of the cerebral cortex of the lateral gyrus of the bottlenose dolphin (Tursiops truncatus)in the region where visual evoked potentials have been reported (Sokolov et al., '72; Ladygina et al., '78). In the adult the visual cortex is relatively thin (average about 1,300 μm) for so large a brain (fixed brain weight for a typical adult in our series was 1,330 g). Layers I, III, and VI are wide and represent three-quarters of the total cortical thickness. Layer I contains few cell bodies, while III and VI have a variety of pyramidal and nonpyramidal neurons. Layers II and V are narrow and contain striking palisades of darkly staining pyramidal cells that are particularly large in layer V. No clearly demarcated layer IV is present in the adult dolphin visual cortex. Many of the neurons identified with the Golgi technique are typical of pyramids in other mammals, with a single apical dendrite and a bouquet of basal dendrites, mostly highly spiny. Others are unusual in having bifurcated or oblique apical dendrites. Typical large and small spiny and nonspiny stellates are also found, mainly in layers III and VI. In addition various forms of spindle-shaped, bipolar and multipolar neurons are found in most layers. An 18-day-old brain shows signs of immaturity in its visual cortex. It is thinner (970 μm) and on average its neurons are smaller, paler, and more densely packed. Especially the pyramids of layer V are much smaller than in the adult. Also, a distinct “granular” band occurs between layers III and V and seems to be a rudimentary layer IV. At 3 years of age most of the adult features have developed, but layer IV is still detectable. No striking differences were observed in cell and fibre architecture between the cortex of the lateral gyrus and that of the so-called “calcarine” area that has also been considered as “visual.” We conclude that, although different in many respects from other mammalian visual cortices, that of the dolphin is apparently well developed and differentiated.

Water Exchange on Hexaaquavanadium(III): a Variable-Temperature and Variable-Pressure 17O-NMR Study at 1.4 and 4.7 Tesla

Abstract: Water exchange on hexaaquavanadium (III) has been studied as a function of temperature (255 to 413 K) and pressure (up to 250 MPa, at several temperatures) by 17O-NMR spectroscopy at 8.13 and 27.11 MHz. The samples contained V3+ (0.30–1.53 m), H+ (0.19–2.25 m) and 17O-enriched (10–20%) H2O. The trifluoromethanesulfonate was used as counter-ion, and, contrary to the previously used chloride or bromide, CF3SO is shown to be non-coordinating. The following exchange parameters were obtained: k = (5.0 ± 0.3) · 102 s−1, ΔH* = (49.4 ± 0.8) kJ mol−1, ΔS* = −(28 ± 2) JK−1 mol−1, ΔV* = −(8.9 ± 0.4) cm3 mol−1 and Δβ* = −(1.1 ± 0.3) · 10−2 cm3 mol−1 MPa−1. They are in accord with an associative interchange mechanism, Ia. These results for H2O exchange are discussed together with the available data for complex formation reactions on hexaaquavanadium(III). A semi-quantitative analysis of the bound H2O linewidth led to an estimation of the proportions of the different contributions to the relaxation mechanism in the coordinated site: the dipole-dipole interaction hardly contributes to the relaxation (less than 7%); the quadrupolar relaxation, and the scalar coupling mechanism are nearly equally efficient at low temperature (∼ 273 K), but the latter becomes more important at higher temperature (75–85% contribution at 360 K).

Variable-Temperature and Variable-Pressure 17O-NMR Study of Water Exchange of Hexaaquaaluminium(III)†‡

Abstract: The transverse relaxation rate of H2O in Al(H2O) has been measured as a function of temperature (255 to 417 K) and pressure (up to 220 MPa) using the 17O-NMR line-broadening technique, in the presence of Mn(II) as a relaxation agent. At high temperatures the relaxation rate is governed by chemical exchange with bulk H2O, whereas at low temperatures quadrupolar relaxation is prevailing. Low-temperature fast-injection 17O-NMR was used to extend the accessible kinetic domain. The samples studied contained Al3+ (0.5 m), Mn2+ (0.2–0.5 m), H+ (0.2–3.1 m) and 17O-enriched (20–40%) H2O. Non-coordinating perchlorate was used as counter ion. The following H2O exchange parameters were obtained: k = (1.29 ± 0.04) s−1, ΔH* = (84.7 ± 0.3) kJ mol−1, ΔS* = +(41.6 ± 0.9) J K−1 mol−1, and ΔV = +(5.7 ± 0.2) cm3 mol−1, indicating a dissociative interchange, Id, mechanism. These results of H2O exchange on Al(H2O) are discussed together with the available complex-formation rate data and permit also the assignment of Id mechanisms to these latter reactions.

Production and characterization of monoclonal anti-thy-1 antibodies that stimulate lymphokine production by cytolytic T cell clones

Abstract: In an effort to derive monoclonal antibodies (mAb) which can induce production of macrophage-activating factor (MAF) by cloned murine cytolytic T lymphocyte (CTL) lines, we have fused spleen cells from a rat immunized with a CTL clone with the nonsecreting mouse myeloma X63-Ag8.653. Three mAb (designated I-22, III-5 and V-8) were found to stimulate MAF production by the immunizing CTL clone and (with a single exception) two other unrelated CTL clones. However, none of these mAb inhibited the cytolytic activity of the clones. Immunoprecipitation studies indicated that the three mAb reacted primarily with a 25-30-kDa protein which could not be distinguished from that precipitated by either a reference anti-Thy-1.2 mAb or a polyclonal rabbit anti-Thy-1 antiserum. Moreover, competition binding experiments demonstrated that the three mAb competed with each other and with the reference anti-Thy-1.2 mAb. Flow cytofluorometric analysis of the strain distribution of the molecules defined by the mAb revealed that two of the antibodies (I-22 and III-5) were directed against nonpolymorphic determinants of Thy-1, whereas V-8 mAb reacted only with Thy-1.2+ lymphocytes. One of the mAb (III-5) was also able to stimulate proliferation and interleukin 2 secretion by normal splenic T cells. Since mAb directed against a number of other surface structures on CTL clones did not stimulate MAF production, it thus appears that Thy-1 (or molecules associated with Thy-1) may play a functional role in T lymphocyte triggering.

Biochemical Differentiation in Serum-Free Aggregating Brain Cell Cultures

Abstract: The basic methodology of rotation-mediated aggregating cell culture was introduced by Moscona (1961), who took advantage of the finding that dissociated immature cells in vitro reassemble spontaneously to form histotypic, three-dimensional structures (Moscona, 1960). Subsequent morphological investigations have revealed that such cell aggregates prepared from fetal brain form patterns of cell alignment similar to those in vivo (Moscona, 1965; DeLong, 1970; DeLong and Sidman, 1970; Garber and Moscona, 1972; Levitt et al., 1976; Garber 1977), and undergo extensive morphological differentiation, including synaptogenesis and myelination (Seeds and Vatter, 1971; Kozak et al.,1977; Matthieu et al., 1978,1981; Seeds and Haffke, 1978; Honegger et al.,1979; Matthieu and Honegger, 1979; Trapp et al., 1979, 1982; Lu et al., 1980).

The prevalence of accentuated palmoplantar markings and keratosis pilaris in atopic dermatitis, autosomal dominant ichthyosis and control dermatological patients.

Abstract: The prevalence of keratosis pilaris and accentuated palmoplantar marking was evaluated in 61 patients with atopic dermatitis, 35 patients with dominant ichthyosis vulgaris and 247 other dermatological cases taken as controls. Our data showed that (1) these features are of no diagnostic significance for atopic dermatitis and (2) they are significantly more frequent in patients with ichthyosis vulgaris without associated eczema than in those with atopic dermatitis. Consequently, they should be considered as part of the phenotype of ichthyosis vulgaris rather than attributed to a concomitant atopic dermatitis as suggested by some. These findings should be taken into account when evaluating atopic dermatitis or ichthyosis. To assess the frequency of scaling under winter weather conditions, 155 control subjects were also examined for evidence of visible desquamation and 25.8% showed slight but definite scaling.

Antibody-independent activation of C1, the first component of complement, by cardiolipin.

Abstract: Lipid vesicles containing phospholipids known to be present in substantial amounts in mitochondrial membranes were tested for their capacity to activate C1. Among them, only cardiolipin (CL) was highly efficient in C1 activation; no such effect was observed with phosphatidylcholine, phosphatidylethanolamine, or phosphatidylinositol. CL was shown to bind specifically C1q, because only unlabeled C1q competed with 125I-C1q for binding to CL. The requirement for C1q was confirmed by the finding that only fully reconstituted macromolecular C1, containing C1q, was activated by CL. The specificity of CL-induced activation of C1 was also demonstrated by introducing adriamycin, an agent known to interact with CL. Whereas adriamycin did not decrease C1 activation induced by immune complexes, it abrogated C1 activation by CL. The latter was shown to be a strong nonimmune activator of C1, because C1-INH did not inhibit CL-induced activation. When the concentration of CL in vesicles was decreased in the presence of phosphatidylcholine, C1 activation was detected only above a critical level of 35 mol% CL, compatible with a minimal density or clustering of CL molecules in the plane of the membrane. Moreover, C1 activation by CL was modulated by the addition of cholesterol. The threshold of CL required for C1 activation was lowered by the incorporation of more than 35 mol% cholesterol into the vesicles. These results show that CL incorporated into liposomes can be a potent nonimmune activator of C1. The negatively charged phosphate groups in CL are likely candidates for Clq-binding.

Expression of myelin-associated glycoprotein by small neurons of the dorsal root ganglion in chickens.

Abstract: Biochemical and immunocytochemical investigations have shown that myelin-associated glycoprotein (MAG) is exclusively related to myelin and myelin-forming cells in mammals In the present study it was found that dorsal root ganglia in young chickens display MAG-immunoreactive material in most small sensory neurons The presence of MAG at the surface of small sensory neurons raises the question of whether this glycoprotein acts as a cell adhesion molecule in lower vertebrates

Mononuclear cells infiltrating human mammary carcinomas: immunohistochemical analysis with monoclonal antibodies.

Abstract: Breast carcinomas were examined by the immunoperoxidase technique using antisera specific for lymphocyte subsets, monocytes, NK cells and major histocompatibility antigens (HLA-A, -B, -C; Ia-like). Sixty-four per cent of the patients had a moderate or strong mononuclear cell infiltration, 77% of the patients without mononuclear cell infiltration had receptors for estrogens as compared to 51% of the patients with infiltration. The majority of the infiltrating mononuclear cells were T cells; generally the OKT8 cells were predominant. The Leu 3A/OKT8 cell ratio was not related to histological type, tumor size, age of the patient or presence of metastases. Some of the T cells had the Ia antigen and were thus probably activated. The B cells were either absent or less numerous than the T cells. There was no relation between their distribution and the various parameters studied. A few monocytes were heterogeneous according to their markers (OKM I and acid phosphatase). In 6 cases only there was a strong infiltration of mononuclear cells positive for acid phosphatase. The number of the natural killer cells was also low. Only a few mononuclear infiltrating cells had receptors for transferrin. There was a positive correlation between the inflammatory infiltration and the presence of HLA class-I antigens on tumor cells. Some of the antisera specific for lymphocyte subsets also stained the breast carcinoma cells. The great variations in the subsets of mononuclear cells in breast carcinomas may correspond to various systems of defense against neoplasm.

Comparison of the distributions of ipsilaterally and contralaterally projecting corticocortical neurons in cat visual cortex using two fluorescent tracers

Abstract: Using the retrograde fluorescent tracers Fast Blue and Diamidino Yellow we have studied the callosal and ipsilateral corticocortical connections between the cat9s area 17/18 border region and the posteromedial lateral suprasylvian visual area (PMLS), as well as the callosal connections of each of these regions with its contralateral homologue. The main goal was to determine whether single cortical neurons project with branching axons to more than one cortical target. In addition, the double-labeling technique enabled us to examine, within a single section of cortical tissue, the relative distributions of neurons with different cortical targets. Most corticocortical neurons labeled in the area 17/18 border region and in area PMLS projected to only one of the cortical injection sites tested. When two callosal neuron types were labeled in the same area, no double-labeled neurons were found. When ipsilateral corticocortical and callosal neurons were labeled in combination, a few double-labeled neurons were found in both cortical regions examined. The most common type of double- labeled neuron was located in area PMLS and projected bilaterally to the area 17/18 border region. Our findings regarding the laminar distributions of ipsi- and contralaterally projecting neurons are in agreement with previous studies. In addition, we have found that, for callosal neurons within the upper layers of areas 17 and 18, neurons projecting to the contralateral area 17/18 border are located in the lower half of layer II/III and in upper layer IV, whereas neurons projecting to contralateral area PMLS are restricted to the lower portion of layer II/III. In addition, for callosal neurons within the deep layers of area PMLS, neurons projecting to contralateral area PMLS are located throughout layers V and VI, whereas neurons projecting to the contralateral area 17/18 border are restricted to layer VI. There are numerous other possible targets for axon collaterals not examined in this paper. However, the scarcity of neurons with multiple projections demonstrated in this study reflects the high degree of specificity of cortical connectivity. This anatomical organization may be the basis for a precise channeling of differential information at the single neuron level.