Changes in the relationship between cerebrospinal fluid and blood composition produced by ACTH treatment in conscious sheep

It has been proposed that an increase in CSF osmolality could be involved in the genesis of hypertension by activation of central nervous system receptors involved in cardiovascular regulation. ACTH induced hypertension in the sheep is an adrenally dependent model of steroid induced hypertension. This study reports the effect of ACTH administration (20 g/kg/day) for 5 days on the composition of cerebrospinal fluid (CSF) and blood (plasma) in conscious sheep. ACTH increased CSF and plasma osmolality within 24 h associated with parallel increases in both blood and CSF glucose concentrations and plasma and CSF sodium concentration. Plasma potassium fell within 24 h, but CSF potassium did not change over the 5 days of ACTH treatment. Neither calcium nor magnesium changed in either plasma or CSF. CSF phosphate increased and plasma phosphate decreased. CSF and plasma bicarbonate were elevated with ACTH. Plasma chloride decreased after 5 days of ACTH treatment but was not associated with a change in CSF. The relevance of the measured changes in CSF osmolality and composition to the mechanisms involved in the production of ACTH-induced hypertension will be subject of further experimentation.     

A-KinaseAnchoringProteins: a key to selective activation of cAMP-responsive events?

The cAMP-dependent protein kinase (PKA) regulates a variety of diverse biochemical events through the phosphorylation of target proteins. Because PKA is a multifunctional enzyme with a broad substrate specificity, its compartmentalization may be a key regulatory event in controlling which particular target substrates are phosphorylated. In recent years it has been demonstrated that differential localization of the type II holoenzyme is directed through interaction of the regulatory subunit (RII) with a family ofA-KinaseAnchoringProteins (AKAPs). In this report, we review evidence for PKA compartmentalization and discuss the structural and functional properties of AKAPs.     

Electrostatic interactions stabilizing ferredoxin electron transfer complexes. Disruption by "conservative" mutations.

Mitochondrial ferredoxins mediate electron transfer from NADPH:ferredoxin oxidoreductase to cytochrome P450 enzymes. Previous studies on human ferredoxin, in which acidic residues were replaced with neutral amino acids, established that Asp-76 and Asp-79 are are important for binding to both reductase and P450 (Coghlan, V. M., and Vickery, L. E. (1991) J. Biol. Chem. 266, 18606-18612). Here we report that replacement of Asp----Glu at position 76 or 79, whereas maintaining negative charge at these positions also results in dramatic decreases in binding affinity for both electron transfer partners (5-100-fold, delta(delta G) approximately 1.0-2.8 kcal/mol). These results imply that the active electron transfer complexes in these systems are dominated by a stable form which requires specific pairwise electrostatic interactions of fixed geometry for recognition and binding. This mechanism contrasts with that proposed for other electron transfer systems (as exemplified by cytochrome c) in which electrostatic interactions are believed to function primarily in precollisional orientation leading to "encounter complexes" having multiple geometries of similar free energy.     

Human secreted carbonic anhydrase: cDNA cloning, nucleotide sequence, and hybridization histochemistry

Complementary DNA clones coding for the human secreted carbonic anhydrase isozyme (CA VI) have been isolated and their nucleotide sequences determined. These clones identify a 1.45-kb mRNA that is present in high levels in parotid submandibular salivary glands but absent in other tissues such as the sublingual gland, kidney, liver, and prostate gland. Hybridization histochemistry of human salivary glands shows mRNA for CA VI located in the acinar cells of these glands. The cDNA clones encode a protein of 308 amino acids that includes a 17 amino acid leader sequence typical of secreted proteins. The mature protein has 291 amino acids compared to 259 or 260 for the cytoplasmic isozymes, with most of the extra amino acids present as a carboxyl terminal extension. In comparison, sheep CA VI has a 45 amino acid extension [Fernley, R. T., Wright, R. D., & Coghlan, J. P. (1988b) Biochemistry 27, 2815]. Overall the human CA VI protein has a sequence identity of 35% with human CA II, while residues involved in the active site of the enzymes have been conserved. The human sheep secreted carbonic anhydrases have a sequence identity of 72%. This includes the two cysteine residues that are known to be involved in an intramolecular disulfide bond in the sheep CA VI. The enzyme is known to be glycosylated and three potential N-glycosylation sites (Asn-X-Thr/Ser) have been identified. Two of these are known to be glycosylated in sheep CA VI. Southern analysis of human DNA indicates that there is only one gene coding for CA VI.     

1H NMR spectra of vertebrate [2Fe-2S] ferredoxins. Hyperfine resonances suggest different electron delocalization patterns from plant ferredoxins

We report the observation of paramagnetically shifted (hyperfine) proton resonances from vertebrate mitochondrial [2Fe-2S] ferredoxins. The hyperfine signals of human, bovine, and chick [2Fe-2S] ferredoxins are described and compared with those of Anabaena 7120 vegetative ferredoxin, a plant-type [2Fe-2S] ferredoxin studied previously [Skjeldal, L., Westler, W. M., & Markley, J. L. (1990) Arch. Biochem. Biophys. 278, 482-485]. The hyperfine resonances of the three vertebrate ferredoxins were very similar to one another both in the oxidized state and in the reduced state, and slow (on the NMR scale) electron self-exchange was observed in partially reduced samples. For the oxidized vertebrate ferredoxins, hyperfine signals were observed downfield of the diamagnetic envelope from +13 to +50 ppm, and the general pattern of peaks and their anti-Curie temperature dependence are similar to those observed for the oxidized plant-type ferredoxins. For the reduced vertebrate ferredoxins, hyperfine signals were observed both upfield (-2 to -18 ppm) and downfield (+15 to +45 ppm), and all were found to exhibit Curie-type temperature dependence. This pattern and temperature dependence are distinctly different from those found with reduced plant-type ferredoxins which have signal centered around +120 ppm with Curie-type temperature dependence, assigned to cysteines which interact with Fe(III), and signals centered around +20 ppm with anti-Curie temperature dependence, assigned to cysteines which interact with Fe(II) [Dugad, L. B., La Mar, G. N., Banci, L., & Bertini, I. (1990) Biochemistry 29, 2263-2271].(ABSTRACT TRUNCATED AT 250 WORDS)     

拐芹根化学成分研究Ⅱ

从伞型科当归属植物拐芹(Angelica polymorpha Maxim)的根及根茎中又分得4个结晶性化合物。经物理常数测定、光谱分析,分别鉴定为欧前胡素Ⅰ,异氧化前胡内酯Ⅱ,Pabulenol Ⅲ,Phellopterin Ⅳ。     

Assessment of DNA damage and its modulation by dietary and genetic factors in smokers using the Comet assay: a biomarker model

Methods are needed to assess exposure to genotoxins in humans and to improve understanding of dietary cancer prevention. The Comet assay was used to detect smoking-related exposures and dietary modulations in target tissues. Buccal scrapings, blood and faeces were collected from 38 healthy male volunteers (smokers and non-smokers) during a dietary intervention study with bread supplemented with prebiotics±antioxidants. GSTM1-genotype was determined with PCR. Buccal and peripheral lymphocytes were analysed for DNA damage using the Comet assay. Genotoxicity of faecal water (FW) was assayed in human colon HT29 clone 19A cells. 'Tail intensity' (TI) was used as a quantitative indicator of DNA damage in the Comet assay. Intervention with bread reduced DNA damage in lymphocytes of smokers (8.3±1.7% TI versus 10.2±4.1% TI, n=19), but not of non-smokers (8.6±2.8% TI versus 8.3±2.7% TI, n=15). Faecal water genotoxicity was reduced only in non-smokers (9.4±2.9% TI versus 18.9±13.1% TI, n=15) but not in smokers (15.5±10.7% TI versus 20.4±14.1% TI, n=13). The Comet assay was efficient in the detection of both smoking-related exposure (buccal cells) and efficacy of dietary intervention (faecal samples). Smokers and non-smokers profited differently from the intervention with prebiotic bread±antioxidants. Stratification of data by genotype enhanced specificity/sensitivity of the intervention effects and contributed important information on the role of susceptibility.     

Hansemann, Boveri, chromosomes and the gametogenesis-related theories of tumours

Theodor Boveri (1862-1915) is often credited with suggesting (in 1914) the first chromosomal theory of cancer, especially in terms of abnormal numbers of chromosomes arising in cells by multipolar mitoses in adult cells. However, multipolar mitoses in animal cells had been described as early as 1875, and Hansemann (1858-1920), in publications between 1890 and 1919, included this mechanism among various ways by which abnormal chromosome numbers might arise in cells and cause tumour formation. Both theories were conceived in a period when gametogenic ideas of tumour formation were current. Boveri based his theory on the observation that some cells in early sea urchin embryos having abnormal chromosome complements wander from their usual developmental paths. His observation may have been seen by other authors at the time as support for Cohnheim's "embryonic cell rest" theory of cancer. Hansemann's contribution is seen as both the original, and the more significant of the chromosomal theories of cancer.