Retrovirus-mediated immunosuppression. II. FeLV-UV alters in vitro murine T lymphocyte behavior by reversibly impairing lymphokine secretion

Murine splenocytes and cloned murine T cells were used to study the in vitro immunosuppressive effects of UV-inactivated feline leukemia virus (FeLV-UV) on lymphokine secretion. FeLV-UV can significantly depress the accumulation of IL 2 in cultures of Con A-stimulated C57BL/6 splenocytes and in cultures containing the alloreactive helper T cell clone B6D/2-2m plus Con A. Inhibition of lymphokine accumulation in these cultures could not be attributed to absorption or inactivation of IL 2 by the FeLV-UV or to the FeLV-UV-induced production of substances which interfere with the IL 2 bioassay. Thus, FeLV-UV appears to block production and/or secretion of IL 2 by a direct inhibitory effect on IL 2-secreting murine T lymphocytes. Additional studies indicate that FeLV-UV impairs IL 2 production only if added very soon after lymphocyte contact with lymphokine-inducing agents and that IL 2 secretion resumes when FeLV-UV is removed from the culture. FeLV-UV also impairs accumulation of MAF (interferon-gamma?) in cultures of Con A-stimulated C57BL/6 splenocytes and in cultures containing the alloreactive cytotoxic T lymphocyte clone B6D/2-7c plus Con A. The latter observation again suggests that FeLV-UV impairs lymphokine secretion by a direct effect on lymphokine-producing T lymphocytes. Furthermore, it suggests that FeLV-UV does not selectively impair production of IL 2 nor does it have selective inhibitory effects on helper T cells. Rather, FeLV-UV appears to have a general inhibitory effect on lymphokine production by T lymphocytes. Finally, concentrations of FeLV-UV which suppress MAF production by the CTL clone have little influence on the cytolysis mediated by the same cloned T cell population. Thus, the immunosuppressive influence of FeLV-UV is selective for phenomena associated with induction of new T lymphocyte functions, such as lymphokine secretion, and spares other immune functions already expressed by the same cells.     

Protein diffusion in crowded electrolyte solutions

We report on a combined cold neutron backscattering and spin-echo study of the short-range and long-range nanosecond diffusion of the model globular protein bovine serum albumin (BSA) in aqueous solution as a function of protein concentration and NaCl salt concentration. Complementary small angle X-ray scattering data are used to obtain information on the correlations of the proteins in solution. Particular emphasis is put on the effect of crowding, i.e. conditions under which the proteins cannot be considered as objects independent of each other. We thus address the question at which concentration this crowding starts to influence the static and in particular also the dynamical behaviour. We also briefly discuss qualitatively which charge effects, i.e. effects due to the interplay of charged molecules in an electrolyte solution, may be anticipated. Both the issue of crowding as well as that of charge effects are particularly relevant for proteins and their function under physiological conditions, where the protein volume fraction can be up to approximately 40% and salt ions are ubiquitous. The interpretation of the data is put in the context of existing studies on related systems and of existing theoretical models.     

A fasciocutaneous flap for vaginal and perineal reconstruction

A skin and fascia flap from the medial thigh is proposed for vaginal and perineal reconstruction. Dissection, vascular injection, and radiographs of 20 fresh cadaver limbs uniformly demonstrated the presence of a communicating suprafascial vascular plexus in the medial thigh. Three to four nonaxial vessels were consistently found to enter the proximal plexus from within 5 cm of the perineum. Preservation of these vessels permitted reliable elevation of a 9 X 20 cm fasciocutaneous flap without using the gracilis muscle as a vascular carrier. Fifteen flaps in 13 patients were used for vaginal replacement and coverage of vulvectomy, groin, and ischial defects. Depending on the magnitude of the defect, simultaneous and independent elevation of the gracilis muscle provided additional vascularized coverage as needed. Our experience indicates that the medial thigh fasciocutaneous flap is a durable, less bulky, and potentially sensate alternative to the gracilis musculocutaneous flap for vaginal and perineal reconstruction.     

Genetic and Environmental Effects on the Expression of Peptidases and Larval Viability in Drosophila Melanogaster

The peptidase system in Drosophila melanogaster, consisting of dipeptidase-A, dipeptidase-B, dipeptidase-C and the leucine aminopeptidases, was used as a model to study the adaptive significance of enzyme activity variation. The involvement of the peptidases in osmoregulation has been suggested from the ubiquitous distribution of peptidase activities in nearly all tissues and the high concentration of amino acids and oligopeptides in the hemolymph. Under this hypothesis, larvae counteract increases in environmental osmotic stress by hydrolyzing peptides into amino acids both intra- and extracellularly to increase physiological osmotic concentration. The expression of the peptidases was studied by assaying for peptidase activities in third instar larvae of isogenic lines, which were reared under increasing levels of environmental osmotic stress using either D-mannitol or NaCl. Second and third chromosome substitution isogenic lines were used to assess the relative contribution of regulatory and structural genes in enzyme activity variation. Results indicate that: (1) genetic variation exists for peptidase activities, (2) the effect of osmotic stress is highly variable among peptidases, (3) changes in peptidase activities in response to osmotic stress depend on both genetic background and osmotic effector and (4) peptidase activities are correlated with each other, but these phenotypic correlations depend on genetic background, osmotic effector, and level of osmotic stress. Osmotic concentration in the larval hemolymph is correlated with leucine aminopeptidase activity, but changes in hemolymph osmotic concentration in response to environmental osmotic stress depend on the osmotic effector in the environment. Although these findings suggest that genetic and environmental factors contribute significantly toward the expression of enzymes with similar functions, a relative larval viability study of genotypes that differed significantly in dipeptidase-B (DIP-B) activity revealed that low DIP-B activity did not confer any measurable reduction in larval viability under increasing levels of environmental osmotic stress. These negative results suggest that, either DIP-B does not play a major role in osmoregulation or differential osmoregulation is not related to egg to adult viability in these tests.     

Attenuation of Eph Receptor Kinase Activation in Cancer Cells by Coexpressed Ephrin Ligands

The Eph receptor tyrosine kinases mediate juxtacrine signals by interacting “in trans” with ligands anchored to the surface of neighboring cells via a GPI-anchor (ephrin-As) or a transmembrane segment (ephrin-Bs), which leads to receptor clustering and increased kinase activity. Additionally, soluble forms of the ephrin-A ligands released from the cell surface by matrix metalloproteases can also activate EphA receptor signaling. Besides these trans interactions, recent studies have revealed that Eph receptors and ephrins coexpressed in neurons can also engage in lateral “cis” associations that attenuate receptor activation by ephrins in trans with critical functional consequences. Despite the importance of the Eph/ephrin system in tumorigenesis, Eph receptor-ephrin cis interactions have not been previously investigated in cancer cells. Here we show that in cancer cells, coexpressed ephrin-A3 can inhibit the ability of EphA2 and EphA3 to bind ephrins in trans and become activated, while ephrin-B2 can inhibit not only EphB4 but also EphA3. The cis inhibition of EphA3 by ephrin-B2 implies that in some cases ephrins that cannot activate a particular Eph receptor in trans can nevertheless inhibit its signaling ability through cis association. We also found that an EphA3 mutation identified in lung cancer enhances cis interaction with ephrin-A3. These results suggest a novel mechanism that may contribute to cancer pathogenesis by attenuating the tumor suppressing effects of Eph receptor signaling pathways activated by ephrins in trans.     

Positive Facial Affect – An fMRI Study on the Involvement of Insula and Amygdala

Imitation of facial expressions engages the putative human mirror neuron system as well as the insula and the amygdala as part of the limbic system. The specific function of the latter two regions during emotional actions is still under debate. The current study investigated brain responses during imitation of positive in comparison to non-emotional facial expressions. Differences in brain activation of the amygdala and insula were additionally examined during observation and execution of facial expressions. Participants imitated, executed and observed happy and non-emotional facial expressions, as well as neutral faces. During imitation, higher right hemispheric activation emerged in the happy compared to the non-emotional condition in the right anterior insula and the right amygdala, in addition to the pre-supplementary motor area, middle temporal gyrus and the inferior frontal gyrus. Region-of-interest analyses revealed that the right insula was more strongly recruited by (i) imitation and execution than by observation of facial expressions, that (ii) the insula was significantly stronger activated by happy than by non-emotional facial expressions during observation and imitation and that (iii) the activation differences in the right amygdala between happy and non-emotional facial expressions were increased during imitation and execution, in comparison to sole observation. We suggest that the insula and the amygdala contribute specifically to the happy emotional connotation of the facial expressions depending on the task. The pattern of the insula activity might reflect increased bodily awareness during active execution compared to passive observation and during visual processing of the happy compared to non-emotional facial expressions. The activation specific for the happy facial expression of the amygdala during motor tasks, but not in the observation condition, might reflect increased autonomic activity or feedback from facial muscles to the amygdala.     

Beautiful,complicated—and intelligent? Novel aspects of the thigmonastic stamen movement in Loasaceae

In a recent study we investigated the complex mechanisms regulating the pollen release via thigmonastic stamen movement found exclusively in Loasaceae subfamily Loasoideae. We demonstrated that stamen movement is modulated by abiotic (light and temperature) as well as biotic stimuli (pollinator availability and visitation frequency). This is explained as a mechanism to adjust the rate of stamen movement and thus pollen dispensation to different environmental conditions in order to optimize pollen transfer. Stamen movement is rapid and thus a near-immediate response to pollinator visits. However, Loasaceae flowers also show a response to biotic stimuli on a longer time scale, by adjusting the duration of both the staminate and the carpellate phase of the anthesis. We here present two additional data sets on species not previously studied, underscoring the shortening of the staminate phase in the presence of pollinator visits vs. their absence and the shortening of the carpellate phase after pollination. Overall, the plant shows not only a rapid but an “intelligent” reaction to its environment in adjusting anthesis and pollen presentation to a range of factors. The physiological and morphological bases of the stamen movement are poorly understood. Our previous study showed that there is no direct spatial relationship between the place of stimulation in the flower and the stamen bundle activated. We here further show the morphological basis for stamen movement from a reflexed into an erect position: Only the basal part of the filament curves around the receptacle, while the upper part of the filament retains its shape. We hypothesize that the stimulus is transmitted over the entire receptacle and the place of reaction is determined by stamen maturity, not the location of the stimulus.     

Relatively Recent Evolution of Pelage Coloration in Colobinae: Phylogeny and Phylogeography of Three Closely Related Langur Species

To understand the evolutionary processes leading to the diversity of Asian colobines, we report here on a phylogenetic, phylogeographical and population genetic analysis of three closely related langurs, Trachypithecus francoisi, T. poliocephalus and T. leucocephalus, which are all characterized by different pelage coloration predominantly on the head and shoulders. Therefore, we sequenced a 395 bp long fragment of the mitochondrial control region from 178 T. francoisi, 54 T. leucocephalus and 19 T. poliocephalus individuals, representing all extant populations of these three species. We found 29 haplotypes in T. francoisi, 12 haplotypes in T. leucocephalus and three haplotypes in T. poliocephalus. T. leucocephalus and T. poliocephalus form monophyletic clades, which are both nested within T. francoisi, and diverged from T. francoisi recently, 0.46-0.27 (T. leucocephalus) and 0.50-0.25 million years ago (T. poliocephalus). Thus, T. francoisi appears as a polyphyletic group, while T. leucocephalus and T. poliocephalus are most likely independent descendents of T. francoisi that are both physically separated from T. francoisi populations by rivers, open sea or larger habitat gaps. Since T. francoisi populations show no variability in pelage coloration, pelage coloration in T. leucocephalus and T. poliocephalus is most likely the result of new genetic mutations after the split from T. francoisi and not of the fixation of different characters derived from an ancestral polymorphism. This case study highlights that morphological changes for example in pelage coloration can occur in isolated populations in relatively short time periods and it provides a solid basis for studies in related species. Nevertheless, to fully understand the evolutionary history of these three langur species, nuclear loci should be investigated as well.