Liver tumor-promoting effect of beta-naphthoflavone, a strong CYP 1A1/2 inducer, and the relationship between CYP 1A1/2 induction and Cx32 decrease in its hepatocarcinogenesis in the rat

Interrelationships among induction of cytochrome P-450 (CYP) 1A1/2, decrease in connexin 32 (Cx32), and liver tumor-promoting activity by beta-naphthoflavone (BNF) in the promotion stage were examined in a 2-stage liver carcinogenesis model. A total of 20 male Fischer 344 rats were initiated with a single intraperitoneal injection of 150 mg/kg of diethylnitrosamine (DEN) or were given the saline vehicle alone. Starting 2 weeks later, they were fed a diet containing 2%, 1%, or 0% BNF for 6 weeks. All animals were subjected to a two-thirds partial hepatectomy at week 3 and were sacrificed at week 8. Absolute and relative liver weights were significantly increased in the DEN+BNF groups as compared to the DEN-alone group. Diffuse hepatocellular hypertrophy with cytoplasmic eosinophilia, sometimes accompanied by development of adenoma-like hepatic foci, was observed in the BNF-treated rats. Remarkable induction of cytochrome CYP 1A1/2 and significant increase in CYP 2E1 were noted in the DEN+BNF groups, and positive immunohistochemical staining for both was observed diffusely. The areas of Cx32-positive spots per hepatocyte in the centrilobular areas of livers of the BNF-treated rats were significantly decreased, but no changes were observed in periportal areas. The numbers and areas of foci positive for glutathione S-transferase placental form were increased in the BNF-treated groups. These results suggest that BNF is a liver tumor promoter that, unlike phenobarbital, does not induce CYP 2B1/2 isozymes, and there seems to be no direct relationship between CYP 1A1/2 induction and Cx32 reduction in BNF hepatocarcinogenesis.     

Vinyl polymerization with dimethylaniline/cupric nitrate system

A study of vinyl polymerizations initiated with the system of dimethylaniline (DMA) and cupric [Cu(II)] nitrate has been made. This initiator system was found to induce the polymerization of vinyl monomers having an electron-attracting substituent such as methyl methacrylate (MMA) and acrylonitrile, but it does not initiate the styrene and vinyl acetate polymerizations. The rate of polymerization (R_p) of MMA with this system was expressed by the following Eqs., depending upon the Cu(II) concentration used: The apparent activation energy for this polymerization was found to be 16.5 and 14.4 kcal/mole for the above two Cu(II) concn. ranges, respectively. The polymer of MMA obtained by this system was found to contain an endgroup similar to dimethylaniline, probably a methylanilinomethyl group, from the determination of its UV spectrum.     

Mechanisms of integrin-mediated virus attachment and internalization process

Viruses that propagate within vertebrate hosts have adapted many strategies to infect host cells. One of the first steps in a viral infection is the binding of the virus to cell surface molecules. This interaction between a virus and its receptors plays a key role in the multiplication cycle. Entry of viruses into cells is a complex, multistep process, and for several viruses, cell attachment and internalization are distinct steps. A number of virus receptors have been identified; a common family of viral receptors is the integrin family. Integrins are a widely expressed family of cell adhesion receptors, by which cells attach to extracellular matrices; they also mediate important cell-cell adhesion events. Integrins are involved in a number of tissue remodeling events, including embryogenesis, angiogenesis, wound repair, and bone resorption. In addition, several integrins are used by manyviruses in theirinfectious cycle. Virus-integrin interactions maybe more complex than previously thought because several viruses can interact with unique integrin regions or can activate distinct signaling pathways. This article will discuss the strategies devised by many viruses in their integrin-mediated attachment or cell entry.     

Radioimmunoassay for activin A/EDF. Method and measurement of immunoreactive activin A/EDF levels in various biological materials

A radioimmunoassay (RIA) for the measurement of activin A, which is identical to erythroid differentiation factor (EDF), has been developed. A specific antiserum against activin A/EDF was raised in rabbits using a mixture of recombinant EDF and polyvinyl pyrrolidone. Of the compounds tested this polyclonal antibody cross-reacted only with bovine inhibin (3.2%) and human TGF-beta (4.2%). The least detectable value in this assay was 0.06 ng/tube. The within- and between-assay coefficients of variation at three different concentrations were 3.6-9.8% and 3.4-7.7%, respectively. Using this RIA, immunoreactive activin A/EDF levels in various biological fluids and tissues were examined. The dose-response curves of porcine follicular fluid and ovarian extract were parallel to the standard curve, and porcine follicular fluid contained high activin A/EDF immunoreactivity (1050 ng/ml). On gel chromatography of porcine follicular fluid, the major immunoreactivity was eluted in the same position as authentic activin A/EDF. Human placental extract and amniotic fluid had relatively high immunoreactive activin A/EDF levels (174 ng/g wet wt. and 63.9 ng/ml, respectively), but the dose-response curve of amniotic fluid was not parallel to the standard curve. Among rat tissues, the ovary showed the highest activin A/EDF immunoreactivity (163 ng/g wet wt.) much lower than that of porcine ovary (1020 ng/g wet wt.). Low immunoreactive activin A/EDF levels were detected in most parts of rat brain (8.7-14.2 ng/g wet wt.), except for the pituitary gland (70.0 ng/g wet wt.). The initial plasma half clearance time (t1/2) of exogenous activin A/EDF was 14 min in the rat and the plasma FSH concentration did not change significantly during this period. These results suggest that this RIA system has sufficient sensitivity and specificity to measure activin A/EDF concentrations in biological materials, and that the reproductive tissues are the main sources of activin A/EDF.     

Chemical and biological properties of a peptidoglycan isolated from Treponema pallidum kazan.

A peptidoglycan layer of Treponema pallidum kazan was isolated by solubilization of whole cells with 1% warm sodium dodecyl sulfate and subsequent digestion of an insoluble residue with proteases. Electron microscopy revealed that the peptidoglycan was isolated as a single-layered sacculus of less than 5 nm in thickness, freed from axial filaments and an envelope sheath. An isolated peptidoglycan fraction was mainly composed of glucosamine, muramic acid, alanine, glutamic acid, ornithine, and glycine in molar ratios of 0.65:0.68:1.63:1.00:0.75:1.03. Amino (N)- and carboxyl (C)-terminal amino acid analyses suggested the involvement of at least a part of the glycine residue in cross-linking between the amino group of ornithine residue at one strand of the stem peptide subunit and the carboxyl group of alanine of the neighboring strand. The treponemal peptidoglycan lacked the immunoadjuvant activity both to stimulate antibody production and to induce delayed-type hypersensitivity against ovalbumin, as well as the properties necessary to stimulate guinea pig and mouse splenocytes and guinea pigs peritoneal macrophages, unlike the cell walls or peptidoglycans (group A type of Schleifer and Kandler's classification, Bacteriol. Rev. 36:407-477, 1972) isolated from many bacterial species parasitic to the mammal. However, the peptidoglycan activated the human complement system through the alternative pathway, as well as the classical one, and caused a liberation of 5-hydroxytryptamine in rabbit blood platelets in a similar manner to the cell wall peptidoglycans of both group A and B types.     

Corticostriatal projections from the somatic motor areas of the frontal cortex in the macaque monkey: segregation versus overlap of input zones from the primary motor cortex, the supplementary motor area, and the premotor cortex

It is an important issue to address the mode of information processing in the somatic motor circuit linking the frontal cortex and the basal ganglia. In the present study, we investigated the extent to which corticostriatal input zones from the primary motor cortex (MI), the supplementary motor area (SMA), and the premotor cortex (PM) of the macaque monkey might overlap in the putamen. Intracortical microstimulation was performed to map the MI, SMA, and dorsal (PMd) and ventral (PMv) divisions of the PM. Then, two different anterograde tracers were injected separately into somatotopically corresponding regions of two given areas of the MI, SMA, PMd, and PMv. With respect to the PMd and PMv, tracer injections were centered on their forelimb representations. Corticostriatal input zones from hindlimb, forelimb, and orofacial representations of the MI and SMA were, in this order, arranged from dorsal to ventral within the putamen. Dense input zones from the MI were located predominantly in the lateral aspect of the putamen, whereas those from the SMA were in the medial aspect of the putamen. On the other hand, corticostriatal inputs from forelimb representations of the PMd and PMv were distributed mainly in the dorsomedial sector of the putamen. Thus, the corticostriatal input zones from the MI and SMA were considerably segregated though partly overlapped in the mediolateral central aspect of the putamen, while the corticostriatal input zone from the PM largely overlapped that from the SMA, but not from the MI. Received: 30 June 1997 / Accepted: 2 October 1997     

Wnt signaling plays an essential role in neuronal specification of the dorsal spinal cord

In the developing spinal cord, signals from the roof plate are required for the development of three classes of dorsal interneuron: D1, D2, and D3, listed from dorsal to ventral. Here, we demonstrate that absence of Wnt1 and Wnt3a, normally expressed in the roof plate, leads to diminished development of D1 and D2 neurons and a compensatory increase in D3 neuron populations. This occurs without significantly altered expression of BMP and related genes in the roof plate. Moreover, Wnt3a protein induces expression of D1 and D2 markers in the isolated medial region of the chick neural plate, and Noggin does not interfere with this induction. Thus, Wnt signaling plays a critical role in the specification of cell types for dorsal interneurons.     

Bilateral tectal projection of single nigrostriatal dopamine cells in the rat

Employing fluorescent retrograde double/triple labeling techniques, we found that a substantial population of substantia nigra pars reticulata cells send divergent axon collaterals to both the ipsilateral striatum and bilateral superior colliculi in the rat. These multi-collateralized neurons were localized predominantly in the ventrolateral portion of the substantia nigra pars reticulata at its rostral level. Furthermore, tyrosine hydroxylase immunofluorescence histochemistry combined with fluorescent retrograde tracing techniques showed that the vast majority (more than 85%) of such specifically branched cells are dopaminergic. This novel nigral cell population seems to be in a strategic position to evoke dopamine-mediated motor impairments (i.e. abnormal saccadic eye movements in Parkinsonism) and/or behavioral syndromes (i.e. compulsive turning behavior) through the GABA-containing nigrotectal pathway.