Inhibition of gap junctional intercellular communication in heptachlor- and heptachlor epoxide-treated normal human breast epithelial cells

Based on the concern of organochlorides in the environment and in human tissue, this study was designed to determine whether various noncytotoxic levels of heptachlor and heptachlor epoxide could inhibit, reversibly, gap junctional intercellular communication in human breast epithelial cells (HBEC). Cytotoxicity and gap junctional intercellular communication (GJIC) were evaluated by lactate dehydrogenase assay and fluorescence redistribution after photobleaching analysis, respectively. Both heptachlor and heptachlor epoxide were noncytotoxic up to 10 μg/ml. At this concentration, heptachlor and heptachlor epoxide inhibited GJIC of normal human breast epithelial cells after 1 h treatment. Within a 24 h treatment with heptachlor and heptachlor epoxide at 10 μg/ml, recovery of GJIC had not returned. GJIC completely recovered after a 12 h treatment of 1 μg/ml heptachlor epoxide, but it did not recover after a 24 h treatment of 1 μg/ml heptachlor. RT-PCR and Western blots were analyzed to determine whether the heptachlor or heptachlor epoxide might have altered the steady-state levels of gap junction mRNA and/or connexin protein levels or phosphorylation state. No significant difference in the level of connexin 43 (Cx43) message between control and heptachlor-treated cells was observed. Western blot analyses showed hypophosphorylation patterns in cells treated with 10 μg/ml heptachlor and heptachlor epoxide for 1 h with no recovery within 24 h. Immunostaining of Cx43 protein in normal HBEC indicated that heptachlor and heptachlor epoxide caused a loss of Cx43 from the cell membranes at noncytotoxic dose levels. Taken together, these results suggest that heptachlor and heptachlor epoxide can alter GJIC at the post-translational level, and that, under the conditions of exceeding a threshold concentration in the breast tissue containing ‘initiated’ cells for a long time and not being counteracted by anti-tumor-promoting chemicals, they could act as breast tumor promoters.     

USE OF RIBOSOMAL DNA INTERNAL TRANSCRIBED SPACERS FOR PHYLOGENETIC STUDIES IN DIATOMS1

Sequence variation of ribosomal DNA internal transcribed spacers (ITS) among populations, species, and genera of the diatom genus Stephanodiscus was investigated. ITS 1 and ITS 2, including the 5.8S gene, were sequenced from geographically distant and nearby populations of S. niagarae Ehrenberg. In addition, repeats from S. hantzschii Grunow and Cyclotella meneghiniana Kützing were sequenced to determine the taxonomic range over which the ITS region could be used for diatom systematics. The morphologically distinct S. yellowstonensis Theriot & Stoermer, thought to have evolved from S. niagarae in Yellowstone Lake between 12,000 and 8000 years ago, also was sequenced to assess its relationship to nearby S. niagarae populations. The organization and relative sizes of ITS 1 and ITS 2 in Stephanodiscus species were similar to those reported for other eukaryotes. In general, ITS 2 was slightly larger and more variable than ITS 1. Cladistic analysis of ITS sequences did not resolve relationships of nearby S. niagarae and S. yellowstonensis populations. However, central North American S. niagarae populations were in a clade supported by two nucleotide changes. For Cyclotella, much of the ITS region was not alignable with that for Stephanodiscus species; therefore, generic-level comparison within the Thalassiosiraceae may not be possible. The variation (95–96% similarity) between S. hantzschii and other Stephanodiscus species suggests that interspecific relationships could be assessed with ITS sequences. Although S. yellowstonensis is morphologically distinct from S. niagarae, no autapomorphic nucleotide sites were identified. Two S. niagarae populations (Heart and Lewis Lakes), however, did possess autapomorphic ITS sites.     

Cortical Cytochrome Oxidase Activity Is Reduced in Alzheimer's Disease

Abstract: A defect in energy metabolism may play a role in the pathogenesis of neurodegenerative diseases, such as Alzheimer's disease. In the present study, we examined the activities of the enzymes that catalyze oxidative phosphorylation in frontal, temporal, parietal, and occipital cortex from Alzheimer's disease patients and age-matched controls. Complex I and complex II–III activities showed a small decrease in occipital cortex, but were unaffected in the other cortical areas. The most consistent change was a significant decrease of cytochrome oxidase (complex IV) activity of 25–30% in the four cortical regions examined. These results provide further evidence of a cytochrome oxidase defect in Alzheimer's disease postmortem brain tissue. A deficiency in this key energy-metabolizing enzyme could lead to a reduction in energy stores and thereby contribute to the neurodegenerative process.     

Age-Dependent Impairment of Mitochondrial Function in Primate Brain

Abstract: It has been hypothesized that some of the functional impairments associated with aging are the result of increasing oxidative damage to mitochondrial DNA that produces defects in oxidative phosphorylation. To test this hypothesis, we examined the enzymes that catalyze oxidative phosphorylation in crude mitochondrial preparations from frontoparietal cortex of 20 rhesus monkeys (5-34 years old). Samples were assayed for complex I, complex II-III, complex IV, complex V, and citrate synthase activities. When enzyme activities were corrected for citrate synthase activities (to account for variable degrees of mitochondrial enrichment), linear regression analysis demonstrated a significant negative correlation of the activities of complex I (p < 0.002) and complex IV (p < 0.03) with age but no significant change in complex II-III or complex V activities. Relative to animals 6.9 ± 0.9 years old (n = 7), the citrate synthase-corrected activity of complex I was reduced by 17% in animals 22.5 ± 0.9 years old (n = 6) (p < 0.05) and by 22% in animals 30.7 ± 0.9 years old (n = 7) (p < 0.01). Similar age-related reductions in the activities of complexes I and IV were obtained when enzyme activities were corrected for complex II-III activity. These findings show an age-associated progressive impairment of mitochondrial complex I and complex IV activities in cerebral cortices of primates.     

Ecto-Protein Kinase and Surface Protein Phosphorylation in PC12 Cells: Interactions with Nerve Growth Factor

Abstract: The phosphorylation of surface proteins by ectoprotein kinase has been proposed to play a role in mechanisms underlying neuronal differentiation and their responsiveness to nerve growth factor (NGF). PC 12 clones represent an optimal model for investigating the mode of action of NGF in a homogeneous cell population. In the present study we obtained evidence that PC12 cells possess ectoprotein kinase and characterized the endogenous phosphorylation of its surface protein substrates. PC12 cells maintained in a chemically defined medium exhibited phosphorylation of proteins by [γ-³²P]ATP added to the medium at time points preceding the intracellular phosphorylation of proteins in cells labeled with ³²P_i. This activity was abolished by adding apyrase or trypsin to the medium but was not sensitive to addition of an excess of unlabeled P_i. As also expected from ecto-protein kinase activity, PC12 cells catalyzed the phosphorylation of an exogenous protein substrate added to the medium, dephospho-α-casein, and this activity competed with the endogenous phosphorylation for extracellular ATP. Based on these criteria, three protein components migrating in sodium dodecyl sulfate gels with apparent molecular weights of 105K, 39K, and 20K were identified as exclusive substrates of ecto-protein kinase in PC12 cells. Of the phosphate incorporated into these proteins from extracellular ATP, 75–87% was found in phosphothreonine. The phosphorylation of the 39K protein by ecto-protein kinase did not require Mg²⁺, implicating this activity in the previously demonstrated regulation of Ca²⁺-dependent, high-affinity norepinephrine uptake in PC12 cells by extracellular ATP. The protein kinase inhibitor K-252a inhibited both intra- and extracellular protein phosphorylation in intact PC12 cells. Its hydrophilic analogue K-252b, had only minimal effects on intracellular protein phosphorylation but readily inhibited the phosphorylation of specific substrates of ecto-protein kinase in PC12 cells incubated with extracellular ATP, suggesting the involvement of ecto-protein kinase in the reported inhibition of NGF-induced neurite extension by K-252b. Preincubation of PC12 cells with 50 ng/ml of NGF for 5 min stimulated the activity of ecto-protein kinase toward all its endogenous substrates. Exposure of PC12 cells to the same NGF concentration for 3 days revealed another substrate of ecto-protein kinase, a 53K protein, whose surface phosphorylation is expressed only after NGF-induced neuronal differentiation. In the concentration range (10–100 μM) at which 6-thioguanine blocked NGF-promoted neurite outgrowth in PC12 cells, 6-thioguanine effectively inhibited the phosphorylation of specific proteins by ecto-protein kinase. This study provides the basis for continued investigation of the involvement of ecto-protein kinase and its surface protein substrates in neuronal differentiation, neuritogenesis, and synaptogenesis.     

BRCA1 maps proximal to D17S579 on chromosome 17q21 by genetic analysis

Previous studies have demonstrated linkage between early-onset breast cancer and ovarian cancer and genetic markers on chromosome 17q21. These markers define the location of a gene (BRCA1) which appears to be inherited as an autosomal dominant susceptibility allele. We analyzed five families with multiple affected individuals for evidence of linkage to the BRCA1 region. Two of the five families appear to be linked to BRCA1. One apparently linked family contains critical recombinants, suggesting that the gene is proximal to the marker D17S579 (Mfd188). These findings are consistent with the maximum-likelihood position estimated by the Breast Cancer Linkage Consortium and with recombination events detected in other linked families. Linkage analysis was greatly aided by PCR-based analysis of paraffin-embedded normal breast tissue from deceased family members, demonstrating the feasibility and importance of this approach. One of the two families with evidence of linkage between breast cancer and genetic markers flanking BRCA1 represents the first such family of African-American descent to be reported in detail.     

The stimulatory effect of chronic lithium treatment on basal thyrotropin secretion in rats: In vivo antagonism by methylparaben

Chronic treatment of rats with lithium chloride was examined in order to determine its effect on hypothalamic monoamine and metabolite content, basal thyrotropin (TSH) secretion and thyroid function. The hypothalamic concentrations of noradrenaline (NA), dopamine (DA) and its metabolites, dihydroxyphenylacetic acid. (DOPAC) and homovanillic acid (HVA) in the lithium treated rats remained unaltered when compared to control levels. NA turnover and the NA metabolite, 3-methoxy-4-hydroxyphenylglycol (total MHPG), were significantly lower (p<0.01), whereas both serotonin (5-HT) and its metabolite, 5-hydroxyindole-3-acetic acid (5-HIAA), were significantly higher (p<0.01 and p<0.02, respectively) in the lithium treated rat hypothalami than in controls. Chronic lithium treatment significantly elevated basal TSH levels (p<0.05). This effect was antagonized by methylp-hydroxybenzoate (methylparaben, p<0.01), which did not itself affect basal TSH levels. Free serum T₃ and T₄ levels were not significantly affected by chronic lithium treatment, although T₄ tended to be slightly lower than control levels. The monoamine changes observed in the hypothalamus of lithium treated rats did not appear to account for the elevated TSH levels observed in these rats since NA activity which is generally regarded as stimulatory was decreased and 5-HT which has an inhibitory effect on TSH secretion, was increased. The elevated TSH levels may have been due to a reduced negative feedback inhibition of TSH release by the mildly reduced circulating T₄ levels caused by chronic lithium treatment. A further possibility is that the pituitary cGMP (and hence TSH) response to TRH may have been enhanced by chronic lithium treatment and methylparaben may have antagonized this effect.     

Inhibition of Bordetella pertussis filamentous hemagglutinin-mediated cell adherence with monoclonal antibodies

Abstract Filamentous hemagglutinin (FHA), a 220-kDa protein located on the surface of Bordetella pertussis , is one of the major cell adhesins of this bacterium. We have produced three hybridoma cell lines that express monoclonal antibodies (mAbs) against FHA: X3C, X3E and X4B. The anti-FHA mAbs X3C and X3E reacted with 220-kDa FHA protein bands on Western blots. The mAb X4B, which reacted with FHA in ELISA, did not bind to FHA in a Western blot assay. All three mAbs seemed to be directed to the same epitope or to epitopes in close proximity as suggested by competition ELISAs. All three mAbs were able to inhibit the adherence of Chinese hamster ovary cells to purified FHA, and they could also inhibit the FHA-mediated agglutination of goose red blood cells. The attachment of B. pertussis to epithelial cell monolayers was inhibited by the mAb X3C. These antibodies are very useful probes to identify the presence of FHA in bordetellae species and in clinical reagents such as pertussis vaccines, and to characterize the functional domains of this important bacterial adhesin.