Viral escape from the neutralizing antibody response: the lymphocytic choriomeningitis virus model

In addition to CD8+ cytotoxic T lymphocyte (CTL) responses, neutralizing antibodies contribute substantially to the long-term immune control of noncytopathic viruses, as demonstrated during infection with the lymphocytic choriomeningitis virus (LCMV). The high virus load during the initial phase of an infection and the ability of this RNA virus to spontaneously acquire mutations are important prerequisites for escaping an ongoing immune response. In this context, LCMV escape from the humoral response by single point mutations in neutralizing envelope protein determinants may occur, particularly during conditions of CTL deficiency, leading to virus persistence.     

Thrombin (PAR-1)-induced proliferation in astrocytes via MAPK involves multiple signaling pathways

Protease-activated receptors (PARs), newlyidentified members of G protein-coupled receptors, are widelydistributed in the brain. Thrombin evokes multiple cellular responsesin a large variety of cells by activating PAR-1, -3, and -4. Incultured rat astrocytes we investigated the signaling pathway ofthrombin- and PAR-activating peptide (PAR-AP)-induced cellproliferation. Our results show that PAR activation stimulatesproliferation of astrocytes through the ERK pathway. Thrombinstimulates ERK1/2 phosphorylation in a time- andconcentration-dependent manner. This effect can be fully mimicked by aspecific PAR-1-AP but only to a small degree by PAR-3-AP and PAR-4-AP.PAR-2-AP can induce a moderate ERK1/2 activation as well.Thrombin-stimulated ERK1/2 activation is mainly mediated by PAR-1 viatwo branches: 1) the PTX-sensitive Gprotein/(-subunits)-phosphatidylinositol 3-kinase branch, and2) the G_q-PLC-(InsP₃receptor)/Ca²⁺-PKC pathway. Thrombin- or PAR-1-AP-inducedERK activation is partially blocked by a selective EGF receptorinhibitor, AG1478. Nevertheless, transphosphorylation of EGF receptoris unlikely for ERK1/2 activation and is certainly not involved inPAR-1-induced proliferation. The metalloproteinase mechanism involvingtransactivation of the EGF receptor by released heparin-binding EGF wasexcluded. EGF receptor activation was detected by the receptorautophosphorylation site, tyrosine 1068. Our data suggest thatthrombin-induced mitogenic action in astrocytes occurs independently ofEGF receptor transphosphorylation.

     

Citrate,Beneficial or Deleterious in the CNS?

Cerebellar granule neurons were incubated with or without glucose (3 mM) in the presence or absence of citrate (20 mM) using normoxic and/or hypoxic incubation conditions. During 4 h of hypoglycemia and also during hypoxia plus hypoglycemia, citrate increased lactate dehydrogenase (LDH) leakage from the cells and decreased mitochondrial activity, the latter was also the case in the presence of glucose. After 24 h of hypoglycemia, however, citrate decreased LDH leakage slightly, possibly due to its metabolism in the tricarboxylic acid cycle under these conditions. It should be noted that during mild hypoxia plus hypoglycemia a reduced LDH leakage was observed when compared to hypoglycemia alone. The 4 h low oxygen period did protect the neurons also during the 20 h re-oxygenation period. The present study might indicate that incubation of brain cell cultures in an atmosphere of air (30% oxygen) and 5% CO₂, which is used in most laboratories, can be toxic and that oxygen concentration should be lowered considerably to mimic conditions in the brain.     

Intranasal volume and olfactory function

The aim of this exploratory study was to identify the volume intranasal segments as they relate to parameters of olfactory function. Fifty healthy male volunteers (age range 22-59 years, mean age 28.5 years) were included. Olfactory function was measured by lateralized phenyl ethyl alcohol odor thresholds and odor discrimination, and by bilateral odor identification. Magnetic resonance imaging of the nasal cavity was performed immediately following olfactometry. To correlate the results of olfactometry with intranasal volume, each nasal cavity was divided into 11 segments. Significant correlations were found between the odor thresholds and volumes of the anterior part of the lower and upper meatus of the right nasal cavity. These results reveal that two nasal segments are important for inter-individual differences of odor thresholds in healthy subjects: (i) the segment in the upper meatus below the cribriform plate and (ii) the anterior segment of the inferior meatus. The latter finding is of special interest for nasal surgery, which allows modification of this volume through resection of the inferior turbinate and/or septoplasty.     

Impact of coexpression and coamplification of sICAM and antiapoptosis determinants bcl-2/bcl-x(L) on productivity,cell survival,and mitochondria number in CHO-DG44 grown in suspension and serum-free media

We have engineered dihydrofolate reductase-negative (dhfr-/-) Chinese hamster ovary (CHO) DG44 cells adapted for growth in serum-free suspension cultures for simultaneous expression of the common cold therapeutic, the soluble intercellular adhesion molecule 1 (sICAM), and the antiapoptosis determinants bcl-2 or bcl-x(L). Detailed analyses of titer and antiapoptosis characteristics of these production cell lines included an independent (sICAM; bcl-2/bcl-x(L)) as well as a cocistronic (sICAM-(bcl-2/bcl-x(L))) expression set-up in which translation-initiation of the survival cistron is driven by an internal ribosome entry site (IRES) of the encephalomyocarditis virus (EMCV). In transient transfections or stable mixed populations and in comparison to isogenic sICAM-only control vectors, both bcl-x(L)-encoding configurations achieved higher sICAM yields while bcl-2 over-expression resulted in decreased product levels. Overall, the death-protective impact of bcl-2 and bcl-x(L) in engineered CHO-DG44 was not significant under typical batch-mode operation, an observation that was confirmed by clonal analysis. bcl-2 and bcl-x(L) displayed their antiapoptosis potential only following dhfr-based amplification in sICAM-producing CHO-DG44 cell lines. In all cases, bcl-x(L) outperformed bcl-2 in its cell death-protective capacity. Amplification-dependent high-level expression of mitochondria-localized bcl-2 family members required for successful antiapoptosis engineering may be essential to compensate for increased mitochondria numbers found to be associated with production cell lines grown in serum-free medium.     

Magnesium supplementation and deoxycorticosterone acetate--salt hypertension: effect on arterial mechanical properties and on activity of endothelin-1

The aim of this study was to show whether the decrease in blood pressure induced by Mg supplementation in deoxycorticosterone acetate - salt (DOCA-salt) hypertensive rats is associated with mechanical modifications of blood vessels and (or) changes in tissular production and (or) vasoconstrictor activity to endothelin-1. DOCA-salt treatment increased blood pressure, media thickness, cross-sectional area, and lumen diameter of carotid arteries. Distensibility and incremental elastic modulus versus stress were not altered in carotid arteries, suggesting that the DOCA-salt vessel wall adapts structurally to preserve its blood pressure buffering capacity. Magnesium supplementation attenuated DOCA-salt hypertension. In comparison with normotensive rats, systolic, mean, and pulse pressures were higher whereas diastolic pressure was not different in Mg-supplemented DOCA-salt rats. Magnesium supplementation did not significantly modify the elastic parameters of carotid arteries. In resistance mesenteric arteries, DOCA-salt hypertension induces an inward hypertrophic remodeling. Magnesium supplementation attenuates wall hypertrophy and increases lumen diameter to the normotensive diameter, suggesting a decrease in peripheral resistance. Magnesium supplementation normalizes the altered vasoconstrictor activity of endothelin-1 in mesenteric arteries and attenuates endothelin-1 overproduction in kidney, left ventricle, and aorta of DOCA-salt rats. These findings suggest that Mg supplementation prevents blood pressure elevation by attenuating peripheral resistance and by decreasing hypertrophic effect of endothelin-1 via inhibition of endothelin-1 production.     

Splitting p63

Causative TP63 mutations have been identified in five distinct human developmental disorders that are characterized by various degrees of limb abnormalities, ectodermal dysplasia, and facial clefts. The distribution of mutations over the various p63 protein domains and the structural and functional implications of these mutations establish a clear genotype-phenotype correlation.