Modulation of the mutagenicity and metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by phenolic compounds

NNK is a potent environmental carcinogen generated during tobacco processing and smoking. The carcinogenic response to tobacco smoking is modulated by nutritional factors. In this study, liver microsomes from phenobarbital and beta-naphthoflavone-treated or control hamsters were used to assay the mutagenicity (Salmonella typhimurium TA1535) of NNK. Western analysis of these microsomal preparations revealed an increased expression of protein recognized by polyclonal antibodies specific for P-450 1A2 in beta-naphthoflavone-induced microsomes and P-450 2B1/2B2 in phenobarbital-induced microsomes. Both inducers significantly increased the mutagenicity of NNK. Metabolism of NNK by the three microsomal preparations was compared. Metabolites formed by methyl-hydroxylation of NNK by microsomes from control animals were significantly greater than those formed by alpha-methylene hydroxylation. Phenobarbital treatment had the greatest effect on alpha-methylene hydroxylation while beta-naphthoflavone had the greatest effect on methyl hydroxylation. The antimutagenic action of the polyphenolic compounds ellagic acid, esculetin and propyl gallate correlated with an inhibition of the metabolism of NNK. There were, however, differences in the effects of these compounds on specific pathways of NNK metabolism depending upon the microsomal enzyme induction treatment. This suggests that phenolic compounds have selective affinity for specific P-450 isozymes activating NNK.

Cholinergic inhibition of muscle fibres isolated from Schistosoma mansoni (Trematoda:Digenea)

Cholinergic compounds inhibit FMRFamide-induced contractions in dispersed muscle fibres isolated from adult Schistosoma mansoni. Acetylcholine (ACh) was the most effective cholinergic agonist tested with an EC50 < 100 nM. Less effective were propionylcholine and arecoline with EC50 < 1 microM and butyrylcholine and carbachol with EC50 < 10 microM. Choline, muscarine, pilocarpine, nicotine, DMPP (1,1-dimethylphenylpiperazine) and levamisole were all ineffective. Amongst tested antagonists, d-tubocurarine (100 microM), mecamylamine (1 mM), scopolamine (1 mM) and quinuclidinyl benzilate (10 microM) were all ineffective. Bicuculline, picrotoxin and strychnine were also ineffective. However alpha-bungarotoxin, at 100 nM, was able to block the inhibitory ACh effect. From these data it appears that the cholinergic receptor on the schistosome muscle fibres may be of the nicotinic type, but that its pharmacology is different from that of nicotinic receptors of vertebrates as well as of nematodes or a variety of other invertebrates.

Functional regions of the homeodomain protein IDX-1 required for transactivation of the rat somatostatin gene

The insulin-, glucagon- and somatostatin-producing cells (beta, alpha, and delta, respectively) in the pancreatic islets derive from a common precursor stem cell and differentiate sequentially during embryonic development. The homeodomain protein islet duodenum HOX (IDX)-1 [insulin promoter factor (IPF)-1/somatostatin transactivating factor (STF)-1)] is a transcription factor critically required for both the development of the pancreas and the transcriptional expression of the insulin gene. IDX-1 may also act to determine the differentiation of the common pancreatic precursor to beta, alpha, and delta cells. Although IDX-1 is detected in most adult mouse islet beta-cells and regulates insulin gene transcription, it is also found in 15% of the delta-cells and transactivates the rat somatostatin gene. The roles of different domains of IDX-1 involved in the transactivation of the somatostatin gene are unclear. In this study, we have created a series of amino- and carboxy-terminal deletions, as well as point substitution mutations to delineate functional domains within the IDX-1 protein. We find that deletions amino-proximal to the homeodomain enhance DNA-binding to the TAAT-1 transcriptional control element within the somatostatin gene promoter. However, these amino-terminal deletions result in substantial decreases in transactivation of a transcriptional reporter containing the TAAT-1 element. Paradoxically, coexpression of the transcriptionally inactive, amino-terminally deleted IDX-1 mutant proteins, either with the wild-type IDX-1 or with themselves, results in a marked enhancement of transactivation of the transcriptional TAAT-1 element reporter. We provide evidence that this synergistic enhancement of transactivation is mediated by protein-protein interactions among the regions of IDX-1 located carboxyl-proximal to the homeodomain. Although successive deletions into the carboxy-terminal region do not alter DNA-binding, these deletions result in a biphasic enhancement and diminution of transactivation. The IDX-1 homeodomain mediates sequence- specific DNA-binding because substitution mutations within this region abolish DNA-binding. All of the amino- and carboxy-terminal deletion proteins were present in nuclear extracts of transfected cells, suggesting that nuclear localization signals reside within the IDX-1 homeodomain. The mapping of the functional domains of IDX-1 may facilitate understanding of IDX-1-mediated gene regulation and islet cell development.

Health service use among low-risk newborns after early discharge with and without nurse home visiting

BACKGROUND

To examine the potential benefits of routine nurse home visiting after early discharge, we compared health service use among low-risk newborns with and without a nurse home visit and telephone follow-up after short hospital stays.

METHODS

Records of newborns discharged routinely before (n = 83) and after (n = 91) implementation of a universal postpartum home visiting program were reviewed retrospectively. Acute care visits, rehospitalizations, and well-baby visits for newborns up to 74 days of age were compared between the groups.

RESULTS

Acute care visits, rehospitalizations, and missed well-baby visits consistently appeared less likely among newborns receiving home visiting services, in both unadjusted and adjusted analyses. Adjusting for insurance, parity, and breast-feeding, a twofold reduction in acute care visits by 14 days was significant. Although not statistically significant, adjusted analyses of acute care and missed well-baby visits revealed apparently similar patterns at all time intervals. There were too few rehospitalizations for multivariate analysis.

CONCLUSIONS

Despite the limitations of this small retrospective study, the consistency of the findings suggests potentially important benefits of home visiting services after early discharge of low-risk newborns, with substantial implications for clinical and reimbursement policy. Effects could be greater with more vulnerable populations and shorter stays than those in this study.

Employee age and perceptions of work in self-managing and traditional work groups

Self-managing work groups are a form of work design in which employees take responsibility for the group's tasks and have discretion over decisions which impact group performance. To explore the impact of age and work teams on job attitudes, data from 477 employees suggested that self-managed work group members differed from traditional job holders regarding perceived general job satisfaction, perceived control by supervisors, as well as a number of specific dimensions of the work environment. Moreover, while there was evidence of an age effect on attitudes toward supervisory control, there was no joint effect of age by work design on job attitudes, i.e., one's perceived general job satisfaction. Older employees who were members of self-managed work groups were however, more impacted by this form of work design in reporting more positive perceptions of their access to information essential to the performance of their work. These findings suggest that an "older" work force should not be considered a barrier to implementing a work teams approach to job design.

CSF of neuroleptic-naive first-episode schizophrenic patients: levels of biogenic amines, substance P, and peptides derived from chromogranin A (GE-25) and secretogranin II (secretoneurin)

Lumbar cerebrospinal fluid (CSF) was collected from controls and neuroleptic-naive patients with their first acute schizophrenic episode. The CSF was analyzed for several biogenic amines and their metabolites [dopamine,dihydroxyphenylacetic acid (DOPAC), noradrenaline, 5-hydroxytryptamine (5-HT), 5-hydroxyindolacetic acid (5-HIAA)]. For these transmitters, which are stored and secreted from synaptic vesicles, there was no significant difference between controls and schizophrenic patients. As constituents of large dense-core vesicles substance P (SP) and GE-25 (derived from chromogranin A)-and secretoneurin (derived from secretogranin 11)-immunoreactivities were determined. SP-like immunoreactivity levels did not differ between controls and patients; however, GE-25 was elevated and especially the GE-25/secretoneurin ratio was significantly (p < .001) higher in patients. Characterization of the immunoreactivities by high-performance liquid chromatography did not reveal any difference between patients (n = 3) and controls in the processing of the two proproteins chromogranin A and secretogranin II. These data indicate that proteolytic processing of the two widespread constituents of large dense-core vesicles, i.e., chromogranin A and secretogranin II, is not altered in schizophrenic patients. The increase in the chromogranin A /secretoneurin ratio in schizophrenic patients deserves further investigation in order to elucidate its possible pathogenetic significance.

A symmetry-driven search for electrostatic interaction partners in charybdotoxin and a voltage-gated K+ channel

A structural model of charybdotoxin bound to a Shaker K+ channel has emerged from mechanistic and mutagenic analysis of toxin-channel interactions. We test this model by predicting through-space electrostatic interactions between specific pairs of channel-toxin residues. Dissociation constants of channel-toxin variants, determined by radiolabeled toxin binding to Shaker-transfected COS membrane fragments, were used to identify pairs of residues located closely enough to interact electrostatically. The results further refine the structural model of the bound complex and produce a more detailed view of the vestibule of the Shaker channel.

A comparative study of psychological aspects of recurring and non-recurring functional aphonias

The present study is based on the hypothesis that patients with recurrent attacks of aphonia differ from those with non-recurring attacks of aphonia in their anxiety levels, social assertiveness and stress-coping strategies. A comparison was made between 21 women with recurring aphonia and 19 women with non-recurring aphonia with respect to these three factors. Seventeen healthy women served as volunteers. Compared to patients with non-recurring aphonias, patients with recurring aphonias exhibited a significantly higher level of anxiety and significantly more respect for social norms and codes of propriety. Their coping was also characterized by a higher escape tendency. Patients with recurring aphonias also reported a significantly higher number of problems in their private lives within the preceding 5-year period. In therapy patients should be encouraged to reflect upon a possible rigidity toward social norms and better understand fears regarding conflicts in personal relationships.

Similar, and similar concepts

This paper analyzes English symmetrical predicates such as collide and match. Its point of departure is an analysis of the concept 'similar' from Tversky (1977) that appears to show that similarity is psychologically asymmetrical. One basis for this claim from Tversky is that the sentences North Korea is similar to Red China and Red China is similar to North Korea are assessed as differing in meaning by experimental subjects; this seems to imply that the symmetrical entailment (R x, y <--> R y, x) fails for this concept. Five experiments are presented that show: (1) the apparent asymmetry of similar is reproduced for 20 predicates that are intuitively thought to be symmetrical, including equal and identical; (2) unique linguistic-interpretative properties hold for these symmetrical words, such as reciprocal interpretation when they appear intransitively, for example, North Korea and Red China are similar; (3) the asymmetrical interpretation of subject-complement constructions containing the symmetrical words is a consequence of general linguistic-interpretive principles. On the basis of the experimental findings, we offer an analysis of symmetrical predication. One major claim of the analysis is that symmetry is a property of lexical items and has no special syntax, that is, that John meets is semantically but not syntactically anomalous. A second claim is that the structural positioning of noun phrases in sentences containing symmetricals--rather than inherent semantic properties of the noun phrases themselves--sets their status as Figure and Ground (as described by Talmy, 1985) or Variant and Referent (as described by Tversky, 1977) in the comparison, even if the nouns are nonsense items. Finally, the behavior of symmetrical predicates is shown to vary as a function of their differing lexical class assignments and collateral semantic designations, such as activity versus state. Most generally, it is claimed that a deeper understanding of symmetrical terms comes from analyzing the semantics of syntactic structures in which they appear.

p53 in lymphomas of mucosal-associated lymphoid tissues

Lymphomas of mucosal-associated lymphoid tissues (MALT) constitute a distinct clinicopathologic entity comprised of centrocyte-like cells with a characteristic morphologic appearance and immunophenotype. The origin of these cells is still undetermined, although evidence suggests that they might derive from marginal zone lymphocytes present in normal lymph nodes and spleens. Recently, marginal zone lymphomas have been shown to have a high rate of p53 mutation. To determine whether p53 mutations were also present in MALT lymphoma, we evaluated specimens from eight patients (six gastric specimens, one parotid, and one from the small bowel) for p53 mutations using polymerase chain reaction and single strand conformational polymorphism analysis. Exon-4 through exon-8 were evaluated, because these are common sites of p53 mutation. In addition, tissues from 15 patients with MALT (including seven studied by single strand conformational polymorphism analysis) were examined for expression of p53 gene protein product by immunohistochemical techniques. All specimens were negative for p53 mutations, suggesting that mechanisms of lymphomagenesis are different for MALT than for splenic marginal zone lymphomas. Despite the absence of p53 point mutations, p53 gene product was localized in tissues from three of 15 patients with MALT. Staining was restricted to nuclei of neoplastic cells and was present in less than 10% of the cells. In summary, low-grade MALT lymphomas differ from marginal zone lymphomas in lacking p53 point mutations, although some patients express low levels of p53 gene product.

mdm-2 oncogene expression in non-Hodgkin's lymphomas

The mdm-2 protein is a 90-kD protein that forms a complex with the p53 protein, enabling cells from some human neoplasms to overcome the growth-suppressing activity of p53. Most non-Hodgkin's lymphomas lack p53 mutations, and the mechanism of inactivation of tumor suppressive function remains obscure. To assess the role of mdm-2 in lymphomagenesis, 22 cases were evaluated for mdm-2 gene amplification or rearrangement in Southern blots. Localization of the mdm-2 protein was performed on cryostat sections and compared with expression of the p53 gene product. No case exhibited mdm-2 gene amplification or rearrangement, but overexpression of nuclear mdm-2 gene protein product was found in three of six diffuse large cell (B-cell immunoblastic) lymphomas (30-70% of the tumor cells stained). The mdm-2 protein was absent from low- and intermediate-grade lymphomas with the exception of a few cells (5% or less) in four cases. The mdm-2-positive cases stained negative for p53. Southern blot analysis showed that samples overexpressing mdm-2 did not have amplification or rearrangement of the gene. In summary, amplification of the mdm-2 gene does not appear to play a prominent role in the pathogenesis of non-Hodgkin's lymphomas, although overexpression of the protein gene product occurs, particularly in high-grade neoplasms.

Stoichiometry, organisation and catalytic function of protein X of the pyruvate dehydrogenase complex from bovine heart

Mammalian pyruvate dehydrogenase complex (PDC) contains a subunit, protein X, which mediates high-affinity binding of dihydrolipoamide dehydrogenase (E3)to the dihydrolipoamide acetyltransferase (E2) core. Precise stoichiometric determinations on bovine heart PDC, by means of two approaches, indicate the presence of 12 mol protein X/mol PDC and 60 mol E2/mol PDC. Studies of the organisation of collagenase-modified PDC by means of covalent cross-linking of N,N'-1,2-phenylenedimaleimide to lipoamide thiols on protein X, reveal that the main cross-linked products have Mr values corresponding to homodimers of protein X. However, significant formation of higher-Mr aggregates indicates that lipoyl domains of protein X can form an interacting network independent of E2 lipoyl domains. These data suggest that either 12 interacting X monomers or 6 interacting X dimers are involved in the binding of six E3 homodimers to the E2/X core. The presence of 60 E2 subunits/complex also supports proposals for a non-integrated external position of protein X. Collagenase-treated PDC possesses residual activity (15 %), indicating that protein-X-linked lipoamide groups can substitute for the lipoyl domains of E2 in overall complex catalysis. Protein-X-mediated diacetylation of dihydrolipoamide moieties is also performed by the modified complex which raises the possibility of a unique catalytic function for protein X.

Correlation between biomarkers of omega-3 fatty acid consumption and questionnaire data in African American and Caucasian United States males with and without prostatic carcinoma

Results from animal studies suggest that omega-3 fatty acids from marine sources are protective against cancer. To determine whether adipose tissue and erythrocyte membrane fatty acid composition could serve as biomarkers of essential fatty acid consumption in subjects with prostate cancer, we compared fish consumption, which was estimated using a food frequency survey, to the omega-3 fatty acid content of adipose tissue and erythrocyte membranes. The study was conducted using 127 men who had undergone a prostate biopsy. All subjects were recruited from a university hospital urology clinic. African Americans comprised 23% of the subjects, and 70% were diagnosed with prostate cancer. We found a correlation of 0.44 with 95% confidence intervals (CIs) = 0.29-0.57 between reported fish consumption and the omega-3 fatty acid eicosapentaenoic acid composition in erythrocyte membranes and 0.38 with 95% CI = 0.21-0.53 when the dietary survey was compared to eicosapentaenoic acid in adipose tissue. The survey/biomarker correlations in cases were not significantly different from the correlations in controls. The study had 90% power to detect a 0.35 difference between correlations. These results suggest that the presence of prostate cancer does not affect the adipose tissue or erythrocyte membrane biomarkers of fatty acid consumption, and that erythrocyte membranes are as useful as biomarkers as is adipose tissue. Our findings corroborate previous studies that found that tissue biomarkers can reflect past fatty acid consumption and support the use of biomarkers in case-control studies using cancer patients.

A strongly interacting pair of residues on the contact surface of charybdotoxin and a Shaker K+ channel

Charybdotoxin, a peptide neurotoxin of known molecular structure, blocks Shaker K+ channels by binding to a receptor at the outer opening of the ion conduction pathway. Analysis of variants of CTX at position 29 and of Shaker at position 449 shows that these two residues interact closely in the channel-toxin complex. The CTX mutation M29I leads to a slight strengthening of block when tested on Shaker-449T; the same CTX mutation weakens block 1700-fold when tested on Shaker-449F. The known position of CTX-29 on the toxin's interaction surface thus locates Shaker-449 within 5 A of the pore axis of the closed channel. All four subunits must carry the 449F mutation to produce a highly toxin-insensitive channel.

Interaction of Ca2(+)-activated K+ channels with refolded charybdotoxins mutated at a central interaction residue

Charybdotoxin is a small peptide blocker of K+ channels, rigidly held in active conformation by three disulfide bonds. The toxin blocks K+ channels by binding to a receptor site located at the external "vestibule", and thus physically occluding the outer opening of the K+ conduction pore. In the blocked complex, K27, a residue on the toxin's molecular surface, projects its epsilon-amino group into the K(+)-selective pore. The results here show that CTX, produced by heterologous expression in E. coli, may be manipulated to place unnatural positively charged residues at position 27. The toxin folds faithfully to its native conformation when the crucial lysine at position 27 is replaced by a cysteine residue, a maneuver that allows specific chemical modification of this side-chain. Replacements of K27 by side-chains slightly shorter or slightly longer than lysine yield active toxins. The toxin variant with ornithine at this position interacts much less strongly with K+ ions in the pore of slowpoke-type Ca2(+)-activated K+ channels than does wild-type toxin. This result argues that the epsilon-amino group of K27 in bound toxin lies only a few ångstroms away from a K+ ion occupying the blocked pore. The peptide folds with high efficiency to form the correct disulfides even in the presence of strong denaturants.