Changes in the Cytoskeletal and Nuclear Matrix Proteins in Rat Hepatocyte Neoplastic Nodules in Their Relation to the Process of Transformation

In a previous paper (Barboroet al.,1993,Biophys. J.65, 1690–1699) we have shown that cancer development in the resistant hepatocyte model of Solt and Farber is characterized by the progressive unfolding of the higher-order structure of chromatin. A possible functional role of decondensation phenomena in cell transformation cannot be ruled out. Genetic activation involves the relaxation of the superstructure of chromatin, which may be, at least in part, modulated by its interaction with the nuclear matrix. Moreover, recent observations suggest that gene expression can be stimulated by alterations in the organization of the cytoskeleton. Therefore, we have characterized the changes in composition that the nuclear matrix–intermediate filament complex undergoes during the evolution of rat hepatocyte nodules. Dramatic changes in the expression of both the nuclear matrix and intermediate filament proteins occur during transformation; they are, however, related in a different way to the stages of carcinogenesis. Several new nuclear matrix proteins appear in early nodules, isolated 9 weeks after initiation. The subsequent evolution of persistent nodules is also characterized by discrete changes in the composition. Thus, the new synthesis of nuclear matrix proteins reflects the emergence of successive cellular populations, in line with the recent finding that a subset of components of the nuclear matrix is cell type-specific. In contrast, intermediate filament proteins undergo continuing changes. A new keratin with apparent molecular weight of 39 kDa, analogous to human keratin 19, appears in early nodules, and its expression steadily increases up to the 32nd week from initiation; at the same time, the amount of the proteolytic fragments of keratins A and D increases sharply. These findings suggest that the inappropriate expression of keratin 19 may be involved in the epigenetic activation of new cellular programs, through the rearrangement of the cytoskeleton which in turn may perturb nuclear matrix function.     

Thermostable chemotaxis proteins from the hyperthermophilic bacterium Thermotoga maritima.

An expressed sequence tag homologous to cheA was previously isolated by random sequencing of Thermotoga maritima cDNA clones (C. W. Kim, P. Markiewicz, J. J. Lee, C. F. Schierle, and J. H. Miller, J. Mol. Biol. 231: 960-981, 1993). Oligonucleotides complementary to this sequence tag were synthesized and used to identify a clone from a T. maritima lambda library by using PCR. Two partially overlapping restriction fragments were subcloned from the lambda clone and sequenced. The resulting 5,251-bp sequence contained five open reading frames, including cheA, cheW, and cheY. In addition to the chemotaxis genes, the fragment also encodes a putative protein isoaspartyl methyltransferase and an open reading frame of unknown function. Both the cheW and cheY genes were individually cloned into inducible Escherichia coli expression vectors. Upon induction, both proteins were synthesized at high levels. T. maritima CheW and CheY were both soluble and were easily purified from the bulk of the endogenous E. coli protein by heat treatment at 80 degrees C for 10 min. CheY prepared in this way was shown to be active by the demonstration of Mg(2+)-dependent autophosphorylation with [32P]acetyl phosphate. In E. coli, CheW mediates the physical coupling of the receptors to the kinase CheA. The availability of a thermostable homolog of CheW opens the possibility of structural characterization of this small coupling protein, which is among the least well characterized proteins in the bacterial chemotaxis signal transduction pathway.     

Expression of Native GABAA Receptors in Xenopus Oocytes Injected With Rat Brain Synaptosomes

Abstract: Oocytes from the frog Xenopus laevis were shown recently to express native nicotinic acetylcholine receptors after injection with purified Torpedo electroplaque membrane vesicles. Injection of Xenopus oocytes with rat cortical or nigral synaptosomes has now been shown to result in the expression of γ-aminobutyric acid type A (GABA_A) receptor-mediated Cl⁻ currents. Electrophysiological characterization of the responses of these receptors to GABA and other agents revealed that they were incorporated into the oocyte membrane and that they retained their original pharmacological properties, such as sensitivity to Cl⁻ channel blockers, benzodiazepines, and general anesthetics. These results suggest that this approach to the expression of heterologous proteins in Xenopus oocytes may facilitate the study of native synaptic proteins derived from brain tissue.     

The genetic and environmental effects on depressive symptoms among older female twins.

The aim of the present study was to examine the contribution of genetic and environmental factors to depressive symptoms among older women. The participants were 102 monozygotic and 115 dizygotic female twin pairs aged 64 to 76 years. Depressive symptoms were assessed by the Center for the Epidemiologic Studies Depression Scale. The contribution of genetic and environmental effects was estimated for the constructed depressiveness factor and for the subscales which were depressed mood, psychomotor retardation, lack of wellbeing and interpersonal difficulties. Of the variance in depressiveness, shared environmental influences accounted for 39% and nonshared environmental influences 61%. For the subscales, 24% to 62% of the variance was explained by individual, and 13% to 23% by shared, environmental factors. Lack of wellbeing had its own moderate additive genetic effect explaining 30% of the variance. This study showed that in older women predominantly environmental factors underlay individual differences in depressiveness; however, the factors varied to some extent between dimensions measured by the subscales.     

Plant hydraulics as a central hub integrating plant and ecosystem function: meeting report for ‘Emerging Frontiers in Plant Hydraulics’ (Washington,DC, May 2015)

Water plays a central role in plant biology and the efficiency of water transport throughout the plant affects both photosynthetic rate and growth, an influence that scales up deterministically to the productivity of terrestrial ecosystems. Moreover, hydraulic traits mediate the ways in which plants interact with their abiotic and biotic environment. At landscape to global scale, plant hydraulic traits are important in describing the function of ecological communities and ecosystems. Plant hydraulics is increasingly recognized as a central hub within a network by which plant biology is connected to palaeobiology, agronomy, climatology, forestry, community and ecosystem ecology and earth‐system science. Such grand challenges as anticipating and mitigating the impacts of climate change, and improving the security and sustainability of our food supply rely on our fundamental knowledge of how water behaves in the cells, tissues, organs, bodies and diverse communities of plants. A workshop, ‘Emerging Frontiers in Plant Hydraulics’ supported by the National Science Foundation, was held in Washington DC, 2015 to promote open discussion of new ideas, controversies regarding measurements and analyses, and especially, the potential for expansion of up‐scaled and down‐scaled inter‐disciplinary research, and the strengthening of connections between plant hydraulic research, allied fields and global modelling efforts.     

Antagonistic Effect of a Salivary Proline-Rich Peptide on the Cytosolic Ca2+ Mobilization Induced by Progesterone in Oral Squamous Cancer Cells

A salivary proline-rich peptide of 1932 Da showed a dose-dependent antagonistic effect on the cytosolic Ca²⁺ mobilization induced by progesterone in a tongue squamous carcinoma cell line. Structure-activity studies showed that the activity of the peptide resides in the C-terminal region characterized by a proline stretch flanked by basic residues. Furthermore, lack of activity of the retro-inverso peptide analogue suggested the involvement of stereospecific recognition. Mass spectrometry-based shotgun analysis, combined with Western blotting tests and biochemical data obtained with the Progesterone Receptor Membrane Component 1 (PGRMC1) inhibitor AG205, showed strong evidence that p1932 performs its modulatory action through an interaction with the progesterone receptor PGRMC1, which is predominantly expressed in this cell line and, clearly, plays a role in progesterone induced Ca²⁺ response. Thus, our results point to p1932 as a modulator of the transduction signal pathway mediated by this protein and, given a well-established involvement of PGRMC1 in tumorigenesis, highlight a possible therapeutic potential of p1932 for the treatment of oral cancer.     

Evidence for a Selective Localization of Voltage-Sensitive Ca2+ Channels in Nerve Cell Bodies of Corpus Striatum

Specific binding sites for [3H]nitrendipine, an organic Ca2+ channel antagonist, were abolished in crude synaptosomal membranes of kainic acid-lesioned caudate nuclei. In contrast, specific lesions of dopaminergic or serotonergic axon terminals in caudate nuclei failed to alter the density or the affinity of [3H]nitrendipine binding sites. In addition, the basal and veratridine-stimulated 45Ca2+ accumulations were greatly impaired in slices prepared from kainic acid-lesioned caudate nuclei. The veratridine-elicited accumulation of 45Ca2+ in control slices was attenuated by addition of tetrodotoxin in the incubation medium. The present data provide evidence that most of the [3H]nitrendipine binding sites and the voltage-dependent Ca2+ channels are located in intrinsic neurons or interneurons in caudate nucleus. In contrast, destruction of dopaminergic or serotonergic nerve terminals emanating from other brain areas and innervating the caudate nucleus failed to change the apparent Bmax value for [3H]nitrendipine binding.     

Foot-shock stress enhances the increase of [35S]TBPS binding in the rat cerebral cortex and the convulsions induced by isoniazid

We report earlier that isoniazid and foot-shock stress individually increase the maximal number of [³⁵S]TBPS binding sites (B_max) measured ex vivo in unwashed membranes from rat cerebral cortex and that the increase due to both treatments are prevented by pretreatment in vivo with diazepam which alone induced a significant decrease in the total number of [³⁵S]TBPS binding sites. In the present paper, the effect of stress was studied on both the increase in [³⁵S]TBPS binding and the convulsant activity induced by isoniazid in unstressed rats. Isoniazid induced a time dependent increase in [³⁵S]TBPS binding. The isoniazid-induced increase in [³⁵S]TBPS binding was markedly potentiated by foot-shock stress. Moreover, foot-shock stress markedly reduced the latency to the appearance of generalized seizures induced by isoniazid (300 mg/kg s.c.). The results provide evidence that the in vivo inhibition of GABAergic transmission elicited by isoniazid results in an increase of [³⁵S]TBPS binding in the rats cerebral cortex. The finding that stress, like isoniazid, enhances [³⁵S]TBPS binding suggests that this treatment also inhibits the function of GABAergic synapses.     

Changes of the liver UDP-glucuronosyltransferase activity in trout (Salmo gairdneri Rich.) acutely exposed to selected aquatic toxicants

Rainbow trout were exposed for 4 or 8 days to various types of toxicants, each applied to the test water at a high sublethal concentration. The activity of liver UDP-glucuronosyltransferase (UDP-GT) was assayed from the submitochondrial fraction using p-nitrophenol as an aglycone. Activity of UDP-GT was inhibited by 2,4,6-trichlorophenol, pentachlorophenol and dehydroabietic acid, all toxicants regularly found in effluents of the pulp and paper industry. The heavy metals cadmium and zinc, the polychlorinated biphenyl, Pyralene 3010, and chloroform did not affect UDP-GT activity. The slimicide N-methyl-dithiocarbamate (Vapam) significantly increased the enzyme activity.