Understanding topological symmetry: a heuristic approach to its determination.

An algorithm based on heuristic rules for topological symmetry perception of organic structures having heteroatoms, multiple bonds, and any kind of cycle, and configuration, is presented. This algorithm identifies topological symmetry planes and sets of equivalent atoms in the structure, named symmetry atom groups (SAGs). This approach avoids both the need to explore the entire graph automorphism groups, and to encompass cycle determination, resulting in a very effective computer processing. Applications to several structures, some of them highly symmetrical such as dendrimers, are presented.

El nuevo tratamiento legal de las enfermedades profesionales en comparación con lo derogado y con la recomendación sobre el tema / No disponible

Los avances producidos en los procesos industriales,la introducción de nuevos elementos y sustancias,el progreso en el ámbito científico y la necesidad de ajustarse a las recomendaciones europeas han desembocado en la aprobación del nuevo Real Decreto 1299/2006 de enfermedades profesionales.Conocer y manejar de forma adecuada la lista deenfermedades profesionales vigente es paso indispensablepara proceder a declarar todas y cada una de estas enfermedades.Nuestro trabajo se centra en el análisis de laestructura y los cambios que muestra el nuevo cuadrorespecto al ya derogado y comparación con las recomen-daciones europeas acerca del temaLa infradeclaración de EP a la que hemos estadoasistiendo podría explicarse en parte por la vigenciahasta hace poco de una lista obsoleta.La reciente publicación del nuevo cuadro de EPha generado muchas expectativas aunque no faltanopiniones críticas que ponen en duda su eficacia enla consecución del objetivo de subsanar esta infradeclaración.En general el nuevo Real Decreto se ajusta a lasRecomendaciones Europeas y aporta importantescambios estructurales y de contenido, ajustándose aun modelo mixto. Si bien carece del enfoque preventivoque incentivaba la Unión Europea y deja a un lado las enfermedades por riesgos psicosociales

The advances produced in the industrial processes,introduction of new elements and substances,progress in the scientific scope and the need to harmonize the national regulation to the Europeanrecommendations have ended at the approval of thenew Real Decree 1299/2006 of professional diseases.To know and to handle in a suitable way theeffective professional diseases list it is an indispensable step in order to notify all and each one of these diseases.Our study is focused in the analysis of the structureand the changes that the new list shows with respectto the precedent one and the comparison with theEuropean recommendation concerning this subjet.The infra- notification of professional diseases,we have been attending, could be explained, partly,by the use, of a obsolete list, until recently.The recent publication of the new list has generatedmany expectations, although there are opinionsthat put in doubt its effectiveness in the attainment ofthe objective to correct this infra notification.In general, the new Real Decree adjust to theEuropean recommendation and include importantchanges at bough levels: structure and contents,adjusting to a mixed model. Although its preventiveapproaches lacks , that was stimulated from theEuropean Union. Nevertheless the new regulationleaves to a side the diseases by psycho-social risks atworkplace

Algorithm for exhaustive and nonredundant organic stereoisomer generation.

Generation of organic stereoisomers with R/S, Z/E, and/or M/P configurations that may contain heteroatoms, multiple bonds, and any kind of cycle (isolated, spiro, condensed, and nested) is described. Inputs for processing are molecular structures in a N_tuple format resident on an automatic (canonical) or manual (non canonical) generated file which are processed by doing internal molecular graph construction, a weighted bipartite tree construction for all atoms and bonds to detect stereocenters, and symmetrical atom groups (SAG) with some specific SAG parameters that constitute a novel way for redundancy elimination of meso structures. Finally, determination of ligand CIP priorities allows for writing the output N_tuples with stereoisomer description. Several examples showing application of this methology to a wide number of structures are also presented.

Respiratory system of Gluconacetobacter diazotrophicus PAL5. Evidence for a cyanide-sensitive cytochrome bb and cyanide-resistant cytochrome ba quinol oxidases.

In highly aerobic environments, Gluconacetobacter diazotrophicus uses a respiratory protection mechanism to preserve nitrogenase activity from deleterious oxygen. Here, the respiratory system was examined in order to ascertain the nature of the respiratory components, mainly of the cyanide sensitive and resistant pathways. The membranes of G. diazotrophicus contain Q(10), Q(9) and PQQ in a 13:1:6.6 molar ratios. UV(360 nm) photoinactivation indicated that ubiquinone is the electron acceptor for the dehydrogenases of the outer and inner faces of the membrane. Strong inhibition by rotenone and capsaicin and resistance to flavone indicated that NADH-quinone oxidoreductase is a NDH-1 type enzyme. KCN-titration revealed the presence of at least two terminal oxidases that were highly sensitive and resistant to the inhibitor. Tetrachorohydroquinol was preferentially oxidized by the KCN-sensitive oxidase. Neither the quinoprotein alcohol dehydrogenase nor its associated cytochromes c were instrumental components of the cyanide resistant pathway. CO-difference spectrum and photodissociation of heme-CO compounds suggested the presence of cytochromes b-CO and a(1)-CO adducts. Air-oxidation of cytochrome b (432 nm) was arrested by concentrations of KCN lower than 25 microM while cytochrome a(1) (442 nm) was not affected. A KCN-sensitive (I(50)=5 microM) cytochrome bb and a KCN-resistant (I(50)=450 microM) cytochrome ba quinol oxidases were separated by ion exchange chromatography.

Regression of papilloma high-grade lesions (CIN 2 and CIN 3) is stimulated by therapeutic vaccination with MVA E2 recombinant vaccine.

Human papillomavirus (HPV) is the etiologic agent for cervical cancer. In Mexico, a women dies every 2 h, and since 1990 the statistics have shown that the numbers of deaths are increasing. We conducted a phase II clinical trial to evaluate the potential use of the MVA E2 recombinant vaccinia virus in treating high-grade lesions (CIN 2 and CIN 3) associated with oncogenic papillomavirus. Fifty-four female patients with high degree lesions were treated either with an MVA E2 therapeutic vaccine or with conization. Thirty-four women received the therapeutic vaccine, at a total of 10(7) virus particles per dose injected directly into the uterus once every week over a 6-week period. Twenty control patients were treated with conization. By colposcopy, 19 patients out of 34 showed no lesion, in three patients the lesions were reduced by 85-90%, in eight other lesions had reduced by 60%, and in four more patients, they were reduced by 25%. Histological analysis showed total elimination of high-grade lesions in 20 out of 34 patients after treatment with MVA E2. Eleven patients had a 50% reduction in lesion size. In two other patients, the lesion was reduced to CIN 2 and in one more patient the lesion was reduced to low grade (CIN 1). All patients developed antibodies against the MVA E2 vaccine, and generated a specific cytotoxic response against papilloma-transformed cells. DNA viral load was significantly reduced in MVA E2-treated patients. Conization eliminated the lesions in 80% of the patients, but patients did not develop cytotoxic activity specific against cancer cells and did not eliminate the papillomavirus. In addition, three patients treated with conization had recurrence of lesions 1 year later. These results show that therapeutic vaccination with MVA E2 proved to be very effective in stimulating the immune system against papillomavirus, and in generating regression of high-grade lesion.

Partial bioenergetic characterization of Gluconacetobacter xylinum cells released from cellulose pellicles by a novel methodology.

AIMS: Gluconacetobacter xylinum is well known for its ability to produce large amounts of cellulose, however, little is known about its cell physiology. Our goal was to study the respiratory metabolism and components of the respiratory system of this bacterium in static cultures. To reach our goal, a medium formulation had to be designed to improve cell growth and cellulose production together with a novel method for the recovery of cells from cellulose pellicles. METHODS AND RESULTS: Successive modifications of a nutrient medium improved G. xylinum cell growth 4.5-fold under static culture conditions. A blender homogenization procedure for the releasing of cells from the cellulose matrix gave a high yield of cells recovered. Respiratory activities of purified cells were greatly stimulated by exogenous substrates and showed to be resistant to KCN. Unexpectedly, exogenous NADH was oxidized at high rates. Cytochromes a, b, c and d were identified after spectral analyses. CONCLUSIONS: Partial bioenergetic characterization of G. xylinum cells allowed us to propose a scheme for its respiratory system. In addition, the growth medium for biomass production and the procedure for the efficient recovery of cells from cellulose pellicles were significantly improved. SIGNIFICANCE AND IMPACT OF THE STUDY: This work provides the first-ever bioenergetic characterization of G. xylinum grown in static cultures. In addition, a novel methodology to obtain purified cells in suitable quantities for biochemical research is described.

Exhaustive generation of organic isomers. 6. Stereoisomers having isolated and spiro cycles and new extended N_tuples.

A new stereoisomer generation system named CAMGEC2 for generation of stereoisomers containing isolated and spiro cycles with one or more descriptors among R, S, Z, E, M, and P is developed using Graph Theory. It includes new approaches for symmetry analysis, cycle detection processes in molecular graphs in a modular way, and also an extension of the N_tuple format for linear representation of molecular graphs that keeps graph topographical information.

Mucosal immune response of spotted sand bass Paralabrax maculatofasciatus (Steindachner, 1868) orally immunised with an extracellular lectin of Aeromonas veronii.

To assess the immunogenic and immunoprotective role of the extracellular lectin from Aeromonas veronii (MCBP), which has affinity for mucosal constituents such as mucin, lactoferrin, immunoglobulins and collagen, spotted sand bass (Paralabrax maculatofasciatus) were orally immunised either with soluble MCBP, adjuvant-conjugated MCBP or immobilised MCBP on latex microspheres. The results suggest that the MCBP is capable of eliciting protective immunity against A. veronii infections when administered orally. The highest mucosal immune response was elicited in fish immunised with MCBP covalently linked to cholera toxin B subunit (CTB) or to Escherichia coli heat-labile toxin (hLT). MCBP-CTB was found to elicit immunoprotection against a challenge with live Aeromonas cells with a relative percent survival of almost 70% and without the expression of the severe histopathological alterations induced by A. veronii.

Interaction between Aeromonas veronii and epithelial cells of spotted sand bass (Paralabrax maculatofasciatus) in culture.

An in vitro fish model to study the interaction between Aeromonas veronii and skin, gill and intestinal epithelial cells was developed using primary cultures of mucosal cells (isolated from healthy organisms). Primary cultures were exposed to Aeromonas veronii strain A186 isolated from a patient with severe gastrointestinal disease. Microbial adherence was assessed by a spectrophotometric evaluation of an enzyme-linked, biotin-streptavidin Aer. veronii cell-adhesion assay to confluent monolayers of epithelial cells on 96-well tissue culture plates. The three primary-culture cells are susceptible to Aer. veronii attachment, with the greatest binding affinity found in gills, and to a lesser extent, in skin and intestine epithelial cells. Aer. veronii adherence was dependent on bacterial load and incubation time. The effect of glycoconjugates on Aer. veronii adhesion was investigated by pre-incubating Aer. veronii cells with monosaccharides, sialic acid-rich glycoproteins and sulphated polysaccharides. In addition, the participation of a 48-kDa Aer. veronii lectin (MCBP - mucosal constituents binding protein), with affinity for mucosal constituents, was evaluated as a putative adhesion factor of Aer. veronii to the mucosal epithelial cells of spotted sand bass by pre-incubating bacterial cells with rabbit polyclonal antibodies to Aer. veronii MCBP. Our study shows that primary-culture fish mucosal cells provide a suitable model for the study of the interactions between Aer. veronii and epithelial cells of the fish mucosa, and to study putative virulence factors of fish pathogens.

[The validity and reliability of a questionnaire for assessing the functional capacity of older persons]. / Validez y fiabilidad de un cuestionario para valorar la capacidad funcional de las personas mayores.

OBJECTIVES: Our aim was to evaluate the validity and reliability of a questionnaire to measure the functional capacity in older people. DESIGN: Observational cross-sectional study. SETTING: Community level. Three basic health areas. PARTICIPANTS: 519 individuals over 64 selected by systematic random sampling taking as sampling units a list of household living at least an individual over 64 years. MEASUREMENTS AND MAIN RESULTS: A new questionnaire was developed starting from the OARS-MFAQ, the CVA. This new questionnaire is shorter but it maintains the same structure. Ten interviews were recorded in a videotape and subsequently analyzed and marked by four different observers to evaluate the inter-observer agreement. To assess the criterion validity the rates of 40 individuals in the CVA were compared with the rates assigned to the same individuals by experts in each area of the questionnaire (physical health, mental health, daily activities, economic resources, and social support). The criterion validity of the version to proxies of CVA (CVA-I) was studied comparing the answers in the CVA of 31 individuals and the answers given in the CVA-I by proxies of the same 31 individuals. The internal consistency in both versions of the questionnaire was studied in 519 individuals, agreement showed values of kappa coefficient between 0.43 and 0.69. Correlation coefficients Interobserver between expert's rates showed values between 0.54 and 0.74. Correlation coefficients between CVA and CVA-I showed values between 0.60 and 0.74 except in the social support dimension (0.16). The Cronbach alpha coefficient were 0.73 for CVA and 0.62 for CVA-I. CONCLUSIONS: The CVA questionnaire showed an acceptable validity and reliability except in the social support dimension of the CVA-I.

Interactions between nerve growth factor binding and estradiol in early development of the zebra finch telencephalon.

The zebra finch telencephalon exhibits rapid and substantial development in the first few weeks after hatching. In parallel, the rate of estradiol synthesis is very high in the zebra finch forebrain, and estradiol can have potent neurotrophic effects in specific telencephalic regions, including those that control the learning and production of song. In an attempt to elucidate mechanisms regulating telencephalic development, potentially including a role for the large capacity for estrogen production, (125)I-nerve growth factor (NGF) binding was measured in homogenates of telencephalon from zebra finches age 3, 15, 30, 60, and 120 days. The highest density of low- and high-affinity (125)I-NGF binding sites was observed in 3-day-old finches. Using an aromatase inhibitor, Fadrozole, to reduce estradiol levels in 1 to 4-day-old zebra finches significantly decreased both high- and low-affinity (125)I-NGF binding sites. Conversely, treating adult or 8 to 14-day-old hatchlings with estradiol increased high-affinity (125)I-NGF binding sites. These results are consistent with the hypothesis that estradiol influences the level of NGF receptors, and suggest one mechanism through which the steroid could affect brain development. The data also indicate that estradiol and NGF activity may be important for very early development of the telencephalon.

[Changes in plasma concentrations of lipids and lipoproteins in students from 1992 to 1996: Cuenca study]. / Evolución de las concentraciones plasmáticas de lípidos y lipoproteínas en los escolares entre los años 1992 y 1996: estudio de Cuenca.

BACKGROUND: The aims of this study were to analyze the evolution of plasma lipid and lipoprotein levels in school children of Cuenca city, Spain, between 1992 and 1996; and to study pubertal changes in 1992 cohort. SUBJECTS AND METHODS: A longitudinal observational study was made in 642 schoolchildren 9-16 years old recruited in three public schools of Cuenca city. In 1992, 307 schoolchildren 9-16 years old were examined. On a second examination made in 1996 were examined children of the cohort of 1992 as well as other children who were 9-11 years old in 1996; and belonged to the same schools were recruited. Socio-demographics variables, weight, height, body mass index, systolic blood pressure, diastolic blood pressure and fasting plasma total cholesterol, LDL-C, HDL-C and triglyceride concentrations were determined (and in addition, the apoproteins A-I and B100 and lipoprotein (a) were determined in the second examination). RESULTS: Between the years 1992 and 1996 there has been a falling in total cholesterol concentrations of schoolchildren of the cohort of 1992 due to a decreasing in LDL-C and HDL-C levels, the levels total cholesterol ranged from 183.0 mg/dl to 163.3 mg/dl. Comparing the lipid concentrations of the schoolchildren who were 9 to 11 years old in the cohort of 1992 with the lipid concentrations who were 9 to 11 years old in the cohort of 1992 with the lipid concentrations of 1996 it has been found evidence of an important decreasing of total cholesterol and LDL-C, and a moderate increasing in the HDL-C, whereas triglycerides are stable. CONCLUSIONS: Due to the decreasing of total cholesterol and LDL-C levels and the increasing of HDL-C, the lipid profile in schoolchildren of Cuenca city has improved during the 1992-1996 years. Total cholesterol and HDL-C concentrations of 1992 cohort have been a falling during the puberty.

Inhibition of L-aromatic amino acid decarboxylase by polychlorinated biphenyls.

PC12 cells were used to examine the mechanisms by which polychlorinated biphenyls (PCBs) reduce cellular levels of dopamine (DA). In cells treated 3 days with Aroclor 1254, 2,2',5,5'-tetrachlorobiphenyl (2,2',5,5'-TCB), or 2,2',3,3',4,4'-hexachlorobiphenyl (2,2',3,3',4,4'-HCB), the PCB-mediated reduction in 3H-tyrosine uptake was observed only at high PCB concentrations that produced a reduction in DNA levels. The PCB congener, 2,2',4,4',5,5'-hexachlorobiphenyl (2,2',4,4',5,5'-HCB) did not produce a reduction in 3H-tyrosine uptake at any concentration tested. Thus, there were PCB concentrations at which a reduction in DA levels did not coincide with a decrease in 3H-tyrosine uptake, suggesting that inhibition of tyrosine uptake was not the primary mechanism by which PCBs reduce DA levels. Aroclor 1254-treated cells also exhibited elevated levels of DOPA, further supporting the conclusion that tyrosine levels were not limiting. Incubation of Aroclor 1254-pretreated cells with 3H-tyrosine resulted in a dose-dependent increase in cellular levels of 3H-DOPA and decrease in cellular levels of 3H-DA, suggesting a PCB-mediated inhibition of the conversion of 3H-DOPA to 3H-DA. When the media was supplemented with DOPA, Aroclor 1254-treated cells still exhibited reduced levels of DA, compared to control cells, even though the control and PCB-treated cells had similar cellular levels of DOPA. Thus, one mechanism by which PCBs may reduce cellular levels of DA is by inhibiting L-aromatic amino acid decarboxylase-mediated conversion of DOPA to DA. The PCB congeners, 2,2',4,4'-TCB, 2,2',5,5'-TCB, and 2,2',4,4',5,5'-HCB, also produced dose-dependent increases in DOPA levels. The congener 2,2',3,3',4,4'-HCB did not produce an increase in DOPA levels, although it did mediate reductions in cellular DA levels. However, when PC12 cells were supplemented with DOPA, all four PCB congeners produced a similar reduction in DA levels, suggesting that the conversion of DOPA to DA was inhibited by the PCBs.

Haem O and a putative cytochrome bo in a mutant of Bacillus cereus impaired in the synthesis of haem A.

In a spontaneous mutant (PYM1) of Bacillus cereus impaired in the synthesis of haem A, no haem-A-containing cytochromes were detected spectroscopically. The haem A deficiency was compensated by high levels of haem O and a CO-reactive cytochrome o in membranes; no other oxidases were detected. In contrast, the wild-type strain had considerable amounts of haem A and negligible levels of haem O. The mutant PYM1 exhibited normal colony morphology, growth, and sporulation in nonfermentable media, whereas on fermentable media, the mutant overproduced acid, which led to poor growth and inhibition of sporulation. External control of the pH of the medium in fermentable media allowed close-to-normal growth and massive sporulation of the mutant. The presence of membrane-bound cytochrome caa3-OII and aa3-II subunits in strain PYM1 was confirmed by Western blots and haem C staining (COII subunit). Western blotting also revealed that in contrast to the wild-type - strain PYM1 contained the membrane-bound subunits caa3-COI and aa3-I, but in low amounts. The effect of several respiratory inhibitors on the respiratory system of strain PYM1 suggested that the terminal oxidase is highly resistant to KCN and CO and that a c-type cytochrome might be involved in the electron transfer sequence to the putative cytochrome bo.

Effects of polychlorinated biphenyls on dopamine release from PC12 cells.

In PC12 cells, Aroclor 1254 produced a concentration-dependent decrease in basal and K(+)-evoked dopamine (DA) release, and cellular DA levels. Aroclor 1254 did not alter the fraction of cellular DA released, suggesting that the decreased release of DA was solely due to decreased cellular levels of DA, and not to decreased packaging of DA or inhibition of neurotransmitter release. The coplanar congener 3,3',4,4',5-pentachlorobiphenyl decreased cellular DA levels and release of DA at levels that produced cytotoxicity. Absent of any apparent cytotoxicity, the ortho-substituted PCB congeners 2,2',5,5'-tetrachlorobiphenyl, 2,2',3,3',4,4'-hexachlorobiphenyl, 2,3',4,4',5-pentachlorobiphenyl, and 2,2',4,4',5,5'-hexachlorobiphenyl were effective in decreasing the amount of DA released from PC12 cells. These results suggest that ortho-chlorinated PCBs can cause decreased K(+)-evoked DA release through non-Ah receptor-mediated mechanisms. Furthermore, the PCB-mediated decrease in DA release was not due to impairment of DA packaging or release, but only due to decreased cellular DA levels.

Aroclor 1254 alters the binding of 125I-labeled nerve growth factor in PC12 cells.

The effects of Aroclor 1254, a mixture of polychlorinated biphenyls (PCBs), on nerve growth factor (NGF) receptors and neurite outgrowth in PC12 cells were examined. Aroclor 1254 enhanced the NGF-stimulated neurite elongation and decreased the Kd value for binding of 125I-labeled NGF to the high-affinity NGF receptors. The NGF dose-response curve for neurite outgrowth was also shifted to the left in cells pretreated with Aroclor 1254, suggesting that NGF was more potent in the presence of PCBs. Thus, one mechanism by which PCBs may enhance NGF-stimulated neurotrophic effects is in increasing the affinity of binding of NGF to the high-affinity NGF receptors, which are believed to mediate the neurotrophic effects of NGF. The data suggest that PCBs have the potential to influence the NGF neurotrophic system.

Aroclor 1242 stimulates the production of inositol phosphates in polymorphonuclear neutrophils.

Exposure in vitro to the mixture of polychlorinated biphenyls (PCBs), Aroclor 1242, stimulates superoxide anion (O2-) production and degranulation in rat polymorphonuclear neutrophils (PMNs). The mechanism by which PCBs activate PMNs is unknown. Phospholipase C-dependent hydrolysis of membrane phosphoinositides is an important early event in PMN activation in response to several agonists including N-formyl-methionyl-leucyl phenylalanine (fMLP); therefore, the present study was undertaken to determine whether Aroclor 1242 stimulates the production of inositol phosphates in isolated rat PMNs. PMNs elicited with glycogen from rat peritoneum were labeled with myo-[2-3H]inositol, and the effect of fMLP and Aroclor 1242 on accumulation of [3H]inositol phosphates was determined. Both fMLP (in the presence of cytochalasin B) and Aroclor 1242 induced rapid breakdown of inositol-containing phospholipids. Peak accumulation of [3H]inositol phosphates occurred within 5 sec in response to Aroclor 1242 and within 15-30 sec in response to fMLP. In cytochalasin B-treated PMNs, significant O2- generation occurred within 5 min of exposure to fMLP or Aroclor 1242. 2,2',4,4'-Tetrachlorobiphenyl (TCB), but not 3,3',4,4'-TCB, stimulates O2- production and degranulation in isolated rat PMNs. To determine whether inositol phosphate accumulation parallels PMN activation, [3H]inositol monophosphate (IP) production was measured in response to Aroclor 1242, 2,2'4,4'-TCB, and 3,3'4,4'-TCB in LiCl-treated cells. Both Aroclor 1242 and 2,2',4,4'-TCB, but not 3,3',4,4'-TCB, caused significant accumulation of [3H]IP. Previous reports indicate that cytochalasin B enhances PMN activation in response to fMLP by increasing the production of inositol phosphates. Pretreatment of PMNs with cytochalasin B significantly enhanced O2- production in cells exposed to Aroclor 1242 but did not alter [H]IP accumulation. These data suggest that treatment of rat PMNs with Aroclor 1242 stimulates PI turnover and are consistent with the hypothesis that hydrolysis of membrane phospholipids is important in PMN activation by PCBs. The enhancing effect of cytochalasin B on PCB-induced O2- production, however, likely involves other mechanisms.

The effects of Aroclor 1254 on undifferentiated and NGF-stimulated differentiating PC12 cells.

Rat pheochromocytoma [PC12] cells were used as models of a dopaminergic system to examine the effects of subchronic exposure to Aroclor 1254 on levels of cellular dopamine in undifferentiated and nerve growth factor (NGF)-stimulated differentiating cells. Either in the absence, or simultaneously in the presence of NGF, exposure to Aroclor 1254 resulted in dose-dependent decreases in levels of cellular dopamine, which with increasing time of exposure, up to 3 days, became increasingly sensitive to lower concentrations of PCBs as evidenced by shifts of the dose-response curves to the left. Pretreatment of PC12 cells with NGF for 7 or 14 days prior to exposure to Aroclor 1254 afforded partial protection from the PCB-mediated decreases in cellular dopamine, consistent with the hypothesis that the cells have different sensitivities to the dopamine decreasing effects of PCBs, depending on the state of differentiation that they are in when exposure to PCBs occurs. Exposure to Aroclor 1254 did not block the morphological aspects of NGF-induced neuronal differentiation, but rather enhanced the NGF-stimulated elongation of neurites in a dose-dependent manner. These results suggest that Aroclor 1254 reduces the levels of cellular dopamine, in both undifferentiated and differentiating PC12 cells, and that pretreatment with NGF may partially prevent PCB-mediated decreases in cellular dopamine. These results also suggest that Aroclor 1254 may enhance neurite elongation.

Nerve growth factor stimulates the production of inositol 1,3,4- and 1,4,5-trisphosphate and inositol 1,3,4,5-tetrakisphosphate in PC12 cells.

In PC12 cells, preincubated with [3H]inositol, nerve growth factor (NGF) stimulated an approximately 100% increase in the levels of [3H]inositol 1,3,4-trisphosphate ([3H]-Ins(1,3,4)P3], [3H]inositol 1,4,5-trisphosphate ([3H]Ins(1,4,5)P3], and [3H]inositol 1,3,4,5-tetrakisphosphate ([3H]Ins(1,3,4,5)P4] as early as 5-15 s after addition of NGF. This NGF-mediated response was apparent only when the cells had been cultured in the absence of fetal bovine serum (FBS). PC12 cells cultured in FBS-containing medium did not display NGF-mediated increases in [3H]Ins(1,3,4)P3, [3H]Ins(1,4,5)P3, and [3H]Ins(1,3,4,5)P4 levels. Using cells cultured in the absence of FBS, epidermal growth factor (EGF) and fibroblast growth factor also stimulated production of [3H]Ins(1,3,4)P3, [3H]Ins(1,4,5)P3, and [3H]Ins(1,3,4,5)P4. Lavendustin A, a tyrosine kinase inhibitor, inhibited both the EGF- and NGF-stimulated increases in the levels of these tritiated inositol phosphates. These results suggest that NGF stimulates the production of Ins(1,3,4)P3, Ins(1,4,5)P3, and Ins(1,3,4,5)P4 and that this response is dependent on tyrosine kinase activity. Furthermore, although the production of Ins(1,3,4)P3, Ins(1,4,5)P3, and Ins(1,3,4,5)P4 may be a common response to factors stimulating neuronal differentiation, it is not sufficient for stimulation of neuronal differentiation.

Nerve growth factor binding sites on hepatic parenchymal cells.

Nerve growth factor (NGF) binding sites on rat hepatocytes (HCs) in culture for 24 to 48 h were characterized using 125I-NGF. Specific binding of 125I-NGF to HCs was saturable. Scatchard analysis indicated a single population of binding sites with a Kd of 5.5 nM and a Bmax of 540 fmol/mg protein. In isolated hepatocyte membranes, specific binding of 125I-NGF was also apparent with Kd and Bmax values of 10.8 nM and 3740 fmol/mg protein, respectively. Specific binding of 125I-NGF to HCs was displaced by excess, unlabeled NGF but not by up to 1000-fold excess of either insulin or epidermal growth factor. Internalization/sequestration of 125I-NGF into HCs was measured as radioactivity present in solubilized cells after exposure to high salt and acid. These studies indicated 83 +/- 11% of 125I-NGF was accumulated by internalization/sequestration at a concentration of 1 nM 125I-NGF. Internalization was reduced to 43 +/- 4% when incubations were carried out at 4 degrees C. These results indicate the presence of a specific, low-affinity binding site for NGF on hepatocytes in culture.