Characterization of a water-soluble glucan from angelica acutiloba

A water-soluble glucan, AR-Glucan, from the roots of Angelica acutiloba was obtained homogeneous as determined by ultracentrifugal analysis, electrophoresis, and gel filtration. AR-Glucan was composed Of d-glucose, and its MW was estimated to be 13 500. Methylation analysis indicated that AR-Glucan contained 4-O- and 4,6-di-O-substituted glucosyl residues. ¹H and ¹³C NMR data accorded with the results of methylation analysis, and the glycosidic linkages in AR-Glucan were shown to have the α-configuration. The results of β-amylase, α-amylase, and pullulanase treatments of AR-Glucan showed that it contained (1 → 4) linked α-d-glucosyl side chains of long chain length such as amylopectin. Thus, AR-Glucan is a (1 → 4) linked α-d-glucan to which are attached glucosyl side chains at O-6 of the glucosyl residues of the main chain.     

Cell Growth Suppression of Astrocytoma C6 Cells by Glial Fibrillary Acidic Protein cDNA Transfection

Abstract: The cellular functions of the intermediate filament family including glial fibrillary acidic protein (GFAP) are not well known yet beyond their roles as structural elements of cells. Expression of GFAP, which is specific in astrocytes and regulated developmentally, suggests its involvement in cell growth and differentiation of astrocytes. We transfected murine GFAP cDNA into a rat astrocytoma C6 cell line to assess the specific effect of GFAP on cells. Two stable GFAP-transfected cell lines, GFC6-5 and GFC6-6, exhibited a series of morphological and growth characteristics that distinguish them from their counterparts, i.e., NeoC6 cells transfected only with the neomycin-resistant gene, and native C6 cells. Both GFC6-5 and GFC6-6 cells showed elongated cell shapes with extended processes rich in GFAP, markedly suppressed cell growth, and decreased bromodeoxyuridine uptake. Western blot analysis revealed a remarkable increase of GFAP expression in GFC6-5 and GFC6-6 compared with that in NeoC6 and C6, in contrast to similar vimentin expression in all cell lines. The results indicate that the expression of GFAP has dramatic effects on cell morphology and cell growth suppression in C6 cells, suggesting that GFAP may function as a tumor suppressor in astrocytoma.     

Silicon-accumulating idioblasts in leaves of Cecropiaceae (Urticales)

A survey of the structure and mineral composition of leaf idioblasts in the Cecropiaceae was conducted. In all six genera of the family, idioblasts usually occur as trichomes or enlarged epidermal cells and nearly always accumulate Si, in marked contrast to the idioblasts of other members of the Urticales, which mostly possess cystoliths containing abundant Ca and Si. The horizontally elongate, mineralized structures ofPoikilospermum, reported formerly as “cystoliths” also contain mainly Si and little Ca. Six genera of Cecropiaceae share a common character in accumulating abundant Si in idioblasts of the leaf epidermis, while lacking cystoliths composed of abundant Ca and Si.     

Partial hydatidiform mole in a pregnant chimpanzee (Pan troglodytes)

Until now, the occurrence of hydatidiform mole in non-human primates has not been documented. This report presents a case in which a stillborn fetus, associated with a partial hydatidiform mole, was found at necropsy in the uterus of a pregnant chimpanzee (Pan troglodytes) which had suddenly died. Hydropic swelling of the chorionic villi and proliferation of trophoblastic cells were present. The trophoblast was stained enzyme-immunohistochemically with human chorionic gonadotropin (hCG) and pregnancy-specific-β1-glycoprotein (SP1). The concentrations of hCG and SP1 in maternal serum were high, 1,350 mIU/ml and 1,000 ng/ml, respectively. The distribution of DNA content of the cytotrophoblast in the molar villi shifted from diploid to an aneuploid pattern. © 1993 Wiley-Liss, Inc.     

Intrinsic or acquired drug resistance and metastasis: Are they linked phenotypes?

Evidence is reviewed which suggests a linkage may exist between certain forms of de novo or acquired drug resistance and metastasis. This includes finding that expression of certain dominantly acting mutant oncogenes or tumor suppressor genes, e.g. genes which normally act to “drive” tumor progression and metastasis, can also affect the expression of drug resistance. Moreover, this can be accompanied by altered expression of certain cellular genes thought to be involved in expression of drug resistance. A direct linkage between acquired drug resistance and metastasis would suggest that tumor sublines selected for drug resistance should manifest more aggressive malignant properties than their drug-sensitive counterparts. While this does not appear to be true for drug resistant sublines selected in vitro, indeed such cell lines frequently manifest diminished in vivo tumorigenic and/or metastatic competence, there is some evidence to support such a correlation exists for tumor cell lines that are selected in vivo for drug resistance. Attention is also drawn to the fact that new linkages between metastasis and drug resistance may be uncovered by analyzing the ability of tumor subpopulations to acquire drug resistance after one or several previous exposures to chemotherapeutic drugs, as opposed to examining intrinsic drug resistance only. Furthermore, ability to detect induced or acquired drug resistance in vitro may be strongly influenced by the types of assay used to detect and monitor drug resistanc. In particular, three-dimensional cell culture systems may reveal acquired or induced “multicellular” drug resistance in situations where conventional two-dimensional culture systems may therefore reveal as yet undiscovered associations between the phenotypes of metastasis and drug resistance.     

A computational model of four regions of the cerebellum based on feedback-error learning

We propose a computationally coherent model of cerebellar motor learning based on the feedback-error-learning scheme. We assume that climbing fiber responses represent motor-command errors generated by some of the premotor networks such as the feedback controllers at the spinal-, brain stem- and cerebral levels. Thus, in our model, climbing fiber responses are considered to convey motor errors in the motor-command coordinates rather than in the sensory coordinates. Based on the long-term depression in Purkinje cells each corticonuclear microcomplex in different regions of the cerebellum learns to execute predictive and coordinative control of different types of movements. Ultimately, it acquires an inverse model of a specific controlled object and complements crude control by the premotor networks. This general model is developed in detail as a specific neural circuit model for the lateral hemisphere. A new experiment is suggested to elucidate the coordinate frame in which climbing fiber responses are represented.     

Stimulation of Cultured Cerebellar Granule Cells via Glutamate Receptors Induces TRE- and CRE-Binding Activities Mediated by Common DNA-Binding Complexes

By use of nuclear mini-extracts prepared from cultured cerebellar granule cells in a gel-mobility assay, exogenous N-methyl-D-aspartate (NMDA) or kainate was shown to increase both 12-O-tetradecanoylphorbol 13-acetate-responsive element (TRE)- and cyclic AMP-responsive element (CRE)-binding activity. These increases were specifically prevented by the NMDA receptor antagonist D,L-2-amino-5-phosphonovalerate and the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione, respectively. The increase of TRE-binding activity was dependent on de novo protein synthesis, and its inductions by both NMDA and kainate required extracellular Ca2+. TRE-binding activity was competitively inhibited by the CRE, and vice versa, showing higher DNA-binding affinity to the CRE than to the TRE. A proteolytic clipping bandshift assay demonstrated that the increase in CRE-binding activity could be mediated by the TRE-binding activity. Thus, the TRE-binding activity cross-binding to the CRE could be activated by NMDA or kainate stimulation. The involvement of c-Fos or Fos-related proteins in the TRE- and CRE-binding complexes was shown by a supershift gel-mobility assay using anti-c-Fos antiserum.     

Inhibition of Ischemia-Induced Dopamine Release by ω-Conotoxin, a Calcium Channel Blocker, in the Striatum of Spontaneously Hypertensive Rats: In Vivo Brain Dialysis Study

The effect of omega-conotoxin GVIA (CgTX), an N-and L-type voltage-sensitive calcium channel (VSCC) blocker, on the release of dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum before and during transient cerebral ischemia in spontaneously hypertensive rats was studied using an in vivo brain dialysis technique. Continuous perfusion of CgTX in the striatum was started 20 min before ischemia and concentrations of dopamine and DOPAC in the dialysate were measured using HPLC with an electro-chemical detector. Before ischemia, both 10 and 100 microM CgTX significantly lowered the concentration of dopamine, to 49% of the basal values. DOPAC concentrations also decreased significantly, by 28 and 17%, respectively. Forebrain ischemia, produced by bilateral carotid artery occlusion, reduced striatal blood flow to less than 6% of the resting value in each group. During 20 min of ischemia, the vehicle group showed a marked increase in dopamine (175 times the basal concentration). In the 10 or 100 microM CgTX perfusion group, in contrast, dopamine release was significantly attenuated, to 38 or 29% of the vehicle group, respectively. DOPAC concentrations decreased during ischemia to 58% of the basal value in the vehicle group and 49% in both CgTX groups. These results indicate that the massive release of striatal dopamine during ischemia depends largely on the influx of extracellular calcium via CgTX-sensitive VSCCs.