Effects of brain ischemia on intermediate filaments of rat hippocampus

Neurofilaments subunits (NF-H, NF-M, NF-L) and glial fibrillary acidic protein (GFAP) were investigated in the hippocampus of rats after distinct periods of reperfusion (1 to 15 days) following 20 min of transient global forebrain ischemia in the rat. In vitro [¹⁴Ca]leucine incorporation was not altered until 48 h after the ischemic insult, however concentration of intermediate filament subunits significantly decreased in this period. Three days after the insult, leucine incorporation significantly increased while the concentration NF-H, NF-M, and NF-L were still diminished after 15 days of reperfusion. In vitro incorporation of³²P into NF-M and NF-L suffered immediately after ischemia, but returned to control values after two days of reperfusion. GFAP levels decreased immediately after ischemia but quickly recovered and significantly peaked from 7 to 10 days after the insult. These results suggest that transient ischemia followed by reperfusion causes proteolysis of intermediate filaments in the hippocampus, and that proteolysis could be facilitated by diminished phosphorylation levels of NF-M and NF-L.     

Glycosyl transferases in mouse and human milk fat globule membranes

Summary Membranes isolated from mouse and human milk fat globules were found to contain the enzymes responsible for the synthesis of dolichol monophosphate mannose and dolichol monophosphate glucose as well as those involved in the transference of the glycosyl residues from the two dolichol derivatives to dolichol diphosphate oligosaccharides. The levels of most of the enzymes were comparable to those found in mouse mammary gland microsomes. The presence of enzymes involved in protein glycosylation via dolichol derivatives in the milk fat globule membrane provides evidence in favor of an outward flow of membrane components from the rough endoplasmic reticulum, where these enzymes are active in vivo, towards the cell surface.     

Oncofetal antigen-I (OFA-I) relative antigenicity on melanoma cells

Summary The oncofetal antigen-I (OFA-I) has been defined as an immunogenic antigen that is expressed on human cancer cells and is cross reactive with fetal brain tissue. Quantitative variations in the expression of OFA-I among different cultured melanoma cell lines were determined by absorption techniques based on functionally monospecific anti-OFA-I serum. Allo-antibodies were removed by absorption with lymphoblasts autologous to an OFA-I-positive target cell. Functional monospecificity toward OFA-I was confirmed by complete absorption with a specimen of fetal brain but not by liver from the same fetus.Of 14 melanoma cell lines tested, two did not express OFA-I, whereas 12 expressed the antigen to varying degrees. Five of the cell lines were highly antigenic, and serum absorbed with 5×10⁵ of any of these cell lines could reduce the anti-OFA-I titer (1 : 96) at least four-fold. OFA-I was detected on biopsied melanomas autologous to the antigenic cultured cells. The ability to select highly antigenic cell lines could be useful in further attempts to characterize OFA-I and to monitor tumor immunity in vitro. Antigenic cell lines may improve the response of patients treated in trials of immunotherapy.     

Synthesis of dolichol derivatives in human erythrocyte membranes

Summary Human erythrocyte membranes contain the enzymes responsible for the synthesis of dolichol-P-glucose, dolichol-P-mannose, dolichol-PP-N-acetylglucosamine, dolichol-PP-NN diacetylchitobiose and of dolichol-PP-oligosaccharides containing NN diacetylchitobiose and mannose or the same sugar residues plus glucose. The transfer of the oligosaccharide moieties from the dolichol-PP-oligosaccharides to endogenous proteins could not be detected. These enzymes appeared to be integral membrane proteins.Abbreviation Dol dolichol Dedicated to ProfessorLuis f. Leloir on the occasion of his 70th birthday.     

Species composition,similarity, and structure of mayan homegardens in tixpeual and tixcacaltuyub,yucatan, Mexico

We studied species composition, similarity, and structure of homegardens in two Yucatecan Maya communities, Tixpeual and Tixcacaltuyub, Yucatan, Mexico. The number of gardens sampled per village was 20 and 22; total area sampled was very similar, 45,265 m² and 40,150 m²; the number of trees and shrubs present was 5651 and 5603; and number of species was 135 and 133, respectively. Diversity was low for both sites (H′= 1.6), as were the correlation coefficients (r) for the species-area and individuals-area correlations. The relatively low values obtained for the structural parameters reflect the random pattern of plant incorporation to the gardens, the variability in the proportion of constantly used and not constantly used garden area, and a certain uniformity in the number of species used and number of individuals present, and the relationship between these parameters and garden size. All these reflect the uniqueness of each homegarden, which depends upon the cultural background of the owner. We noticed a trend towards a change in homegarden structure and function in response to the modernization process. Homegardens in villages in the outskirts of cities tend to have more ornamental species and commercial fruit plants than homegardens in isolated villages.     

Optogenetic actuator – ERK biosensor circuits identify MAPK network nodes that shape ERK dynamics

Combining single‐cell measurements of ERK activity dynamics with perturbations provides insights into the MAPK network topology. We built circuits consisting of an optogenetic actuator to activate MAPK signaling and an ERK biosensor to measure single‐cell ERK dynamics. This allowed us to conduct RNAi screens to investigate the role of 50 MAPK proteins in ERK dynamics. We found that the MAPK network is robust against most node perturbations. We observed that the ERK‐RAF and the ERK‐RSK2‐SOS negative feedback operate simultaneously to regulate ERK dynamics. Bypassing the RSK2‐mediated feedback, either by direct optogenetic activation of RAS, or by RSK2 perturbation, sensitized ERK dynamics to further perturbations. Similarly, targeting this feedback in a human ErbB2‐dependent oncogenic signaling model increased the efficiency of a MEK inhibitor. The RSK2‐mediated feedback is thus important for the ability of the MAPK network to produce consistent ERK outputs, and its perturbation can enhance the efficiency of MAPK inhibitors.     

The RAGE/multiligand axis: a new actor in tumor biology

The receptor for advanced glycation end-products (RAGE) is a multiligand binding and single-pass transmembrane protein which actively participates in several chronic inflammation-related diseases. RAGE, in addition to AGEs, has a wide repertoire of ligands, including several damage-associated molecular pattern molecules or alarmins such as HMGB1 and members of the S100 family proteins.Over the last years, a large and compelling body of evidence has revealed the active participation of the RAGE axis in tumor biology based on its active involvement in several crucial mechanisms involved in tumor growth, immune evasion, dissemination, as well as by sculpturing of the tumor microenvironment as a tumor-supportive niche. In the present review, we will detail the consequences of the RAGE axis activation to fuel essential mechanisms to guarantee tumor growth and spreading.     

CD38 expression enhances sensitivity of lymphoma T and B cell lines to biochemical and receptor-mediated apoptosis

CD38 has been widely characterised both as an ectoenzyme and as a receptor. In the present paper, we investigated the role of CD38 as possible modulator of apoptosis. CD38-positive (CD38(+)) and negative (CD38(-)) fractions, obtained by sorting CD38(+) cells from lymphoma T (Jurkat) and lymphoma B (Raji) and by transfecting lymphoma LG14 and myeloid leukemia K562 cell lines, were used. Cellular subpopulations were exposed to different triggers (H(2)O(2), UV-B, alpha-TOS and hrTRAIL) and the extent of apoptosis was determined by Annexin V-FITC/PI assay. Our data showed that, in lymphoma cells, propensity to apoptosis was significantly linked to CD38 expression and that, remarkably, such response was independent of the nature of the trigger used. Inhibition of CD38 expression by antisense oligonucleotides treatment resulted in CD38-silenced fractions which were as prone to apoptosis as CD38(-) ones. Notably, susceptibility of K562 to apoptosis-inducing challenges was not affected by CD38 expression.