Phosphorylation of elF-4E and initiation of protein synthesis in P19 embryonal carcinoma cells

Mitogenic stimulation of protein synthesis is accompanied by an increase in elF-4E phosphorylation. The effect on protein synthesis by induction of differentiation is less well known. We treated P19 embryonal carcinoma cells with the differentiating agent retinoic acid and found that protein synthesis increased during the first hour of addition. However, the phosphorylation state, as well as the turnover of phosphate on elF-4E, remained unchanged. Apparently, the change in protein synthesis after RA addition is regulated by another mechanism than elF-4E phosphorylation. By using P19 cells overexpressing the EGF receptor, we show that the signal transduction pathway that leads to phosphorylation of elF-4E is present in P19 cells; the EGF-induced change in phosphorylation of elF-4E in these cells is likely to be regulated by a change in elF-4E phosphatase activity. These results suggest that the onset of retinoic acid-induced differentiation is triggered by a signal transduction pathway which involves changes in protein synthesis, but not elF-4E phosphorylation. © 1995 Wiley-Liss, Inc.     

Disentangling the link between leaf photosynthesis and turgor in fruit growth

Despite the importance of understanding plant growth, the mechanisms underlying how plant and fruit growth declines during drought remain poorly understood. Specifically, it remains unresolved whether carbon or water factors are responsible for limiting growth as drought progresses. We examine questions regarding the relative importance of water and carbon to fruit growth depending on the water deficit level and the fruit growth stage by measuring fruit diameter, leaf photosynthesis, and a proxy of cell turgor in olive (Olea europaea). Flow cytometry was also applied to determine the fruit cell division stage. We found that photosynthesis and turgor were related to fruit growth; specifically, the relative importance of photosynthesis was higher during periods of more intense cell division, while turgor had higher relative importance in periods where cell division comes close to ceasing and fruit growth is dependent mainly on cell expansion. This pattern was found regardless of the water deficit level, although turgor and growth ceased at more similar values of leaf water potential than photosynthesis. Cell division occurred even when fruit growth seemed to stop under water deficit conditions, which likely helped fruits to grow disproportionately when trees were hydrated again, compensating for periods with low turgor. As a result, the final fruit size was not severely penalized. We conclude that carbon and water processes are able to explain fruit growth, with importance placed on the combination of cell division and expansion. However, the major limitation to growth is turgor, which adds evidence to the sink limitation hypothesis.     

Conscious Brain-to-Brain Communication in Humans Using Non-Invasive Technologies

Human sensory and motor systems provide the natural means for the exchange of information between individuals, and, hence, the basis for human civilization. The recent development of brain-computer interfaces (BCI) has provided an important element for the creation of brain-to-brain communication systems, and precise brain stimulation techniques are now available for the realization of non-invasive computer-brain interfaces (CBI). These technologies, BCI and CBI, can be combined to realize the vision of non-invasive, computer-mediated brain-to-brain (B2B) communication between subjects (hyperinteraction). Here we demonstrate the conscious transmission of information between human brains through the intact scalp and without intervention of motor or peripheral sensory systems. Pseudo-random binary streams encoding words were transmitted between the minds of emitter and receiver subjects separated by great distances, representing the realization of the first human brain-to-brain interface. In a series of experiments, we established internet-mediated B2B communication by combining a BCI based on voluntary motor imagery-controlled electroencephalographic (EEG) changes with a CBI inducing the conscious perception of phosphenes (light flashes) through neuronavigated, robotized transcranial magnetic stimulation (TMS), with special care taken to block sensory (tactile, visual or auditory) cues. Our results provide a critical proof-of-principle demonstration for the development of conscious B2B communication technologies. More fully developed, related implementations will open new research venues in cognitive, social and clinical neuroscience and the scientific study of consciousness. We envision that hyperinteraction technologies will eventually have a profound impact on the social structure of our civilization and raise important ethical issues.     

Elicitation of Necrosis in Vigna unguiculata Walp. by Homogeneous Aspergillus niger Endo-Polygalacturonase and by alpha-d-Galacturonate Oligomers

Endo-polygalacturonase (PG) was purified from a commercial preparation of Aspergillus niger pectinase by means of carboxymethylcellulose chromatography, preparative isoelectric focusing, and gel permeation through Sephadex G-50. The enzyme was electrophoretically homogeneous and consisted of a single polypeptide chain with a molecular weight of 33,500. The enzyme exhibited a specific activity significantly higher than those of purified polygalacturonases from phytopathogenic fungi. Galacturonate oligomers with a degree of polymerization higher than four appeared quickly as products of the enzymic hydrolysis of Napolygalacturonate. The oligomers were later degraded to di- and monogalacturonate. The homogeneous enzyme and growing mycelium of Aspergillus niger separately elicited a necrotic response in cowpea (Vigna unguiculata Walp.) pods. Heat-inactivated PG and PG inactivated with specific antibodies did not elicit necrosis, suggesting that the catalytic activity of the enzyme is necessary for its function as an elicitor. The PG-released oligosaccharides from Vigna cell wall and the galacturonides with a degree of polymerization greater than four separately elicited necrosis, whereas di- and monogalacturonate did not.     

Application of extended Kalman filter to identification of enzymatic deactivation

A recursive estimation scheme, the Extended Kalman Filter (EKF) technique, was applied to study enzymatic deactivation in the enzymatic hydrolysis of pretreated cellulose using a model previously developed by the authors. When no deactivation model was assumed, the results showed no variation with time for all the model parameters except for the maximum rate of cellobiose-to-glucose conversion (r'(m)).The r'(m) variation occurred in two zones with a grace period. A new model of enzymatic hydrolysis of pretreated cellulose deactivation was proposed and validated showing better behavior than the old deactivation model. This approach allows one to study enzyme deactivation without additional experiments and within operational conditions.     

Mathematical modelization of a packed-bed reactor performance with immobilized yeast for ethanol fermentation

The performance of a continuous vertical packed-bed reactor with yeast immobilized in carrageenan gel beads is reported. The study focuses on the mathematical modelling of the steady-state fermentor behavior by means of a tanks-in-series model which includes the intrinsic kinetic model and the external mass transfer and internal diffusion-reaction conditions in the beads.     

Different effects of duration on prevalence of anti-adrenal medullary and pancreatic islet cell antibodies in type I diabetes mellitus

Autoimmunity is a known factor in the pathogenesis of islet cell destruction, but little is known of its role in the pathogenesis of the neuronal complications of diabetes. We carried out a cross-sectional study of 94 subjects with Type I diabetes mellitus (DM) to examine the relationship between duration and presence of complement fixing anti-adrenal medullary antibodies (CF-ADM). CF-ADM were present in 19% of subjects (n = 62) with duration of DM less than or equal to 16 years and 3% of subjects (n = 32) with duration of DM greater than 16 years. All subjects with CF-ADM+ and duration of DM 0-5 years (n = 7) were islet cell antibody positive (ICA+). Among subjects with duration of DM 6-16 years who were CF-ADM+, 4 of 5 subjects were ICA- and 1 of 5 subjects was ICA+. The only CF-ADM+ subject with duration of DM greater than 16 years was ICA-. Absorption of ADM+ and ICA+ sera with upper phase glycolipid extract blocks ICA but not ADM binding to tissue. This study suggests: 1) CF-ADM positivity is associated with ICA positivity in subjects with duration of DM 0-5 years. CF-ADM positivity persists after 5 years duration of DM when islet cell antibodies have disappeared. Therefore, the antigenic target of the adrenal medulla and pancreatic islets may be different. 2) There is an increased prevalence of CF-ADM in subjects with duration of DM 0-16 years (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Shutoff on Neuroblastoma Cell Protein Synthesis by Semliki Forest Virus: Loss of Ability of Crude Initiation Factors to Recognize Early Semliki Forest Virus and Host mRNA's

A crude ribosomal wash containing the initiation factors of protein synthesis was isolated from mouse neuroblastoma cells 8 h after infection with Semliki Forest virus (SFV). The activity of this wash was compared with that of a wash from control cells in a cell-free protein-synthesizing “pH5” system, with early SFV mRNA (42S), late SFV mRNA (26S), encephalomyocarditis virus (EMC) mRNA, or neuroblastoma polyadenylated mRNA templates. A pronounced loss of activity (±80%) of the crude ribosomal wash from infected cells was observed with host mRNA (neuroblastoma polyadenylated mRNA) and early SFV mRNA, messengers which contain a cap structure at the 5′ terminus. However, these washes were only slightly less active in systems programmed with (noncapped) EMC mRNA and late SFV mRNA. Although late SFV mRNA (26S) is capped, the synthesis of late (= structural) proteins in infected lysates was insensitive to inhibition by cap analogs. Purified initiation factors eIF-4B (M_r, 80,000) and cap-binding protein (M_r, 24,000) from reticulocytes (but none of the others) were able to restore the activity of infected factors to about 90% of control levels in systems programmed with early SFV mRNA and host mRNA. These observations indicate that infection-exposed crude initiation factors have a decreased level of eIF-4B and cap-binding protein activity. However, after partial purification of these and other initiation factors from infected and control cells, we found no significant difference in activity when model assay systems were used. Furthermore, both eIF-4B and cap-binding protein from infected cells were able to restore the activity of these infection-exposed factors to the same level obtained when these factors isolated from control cells or reticulocytes were added. A possible mechanism for the shutoff of host cell protein synthesis is discussed.