A simple, accurate, and sensitive assay method of dehydroepiandrosterone sulfate: application for quantitative determination in human breast cyst and duct fluids

Radioimmunoassay (RIA) is the most prevalent method for measuring small amounts of hormones, peptides, and other compounds in human body fluids. The method, however, has several problems, such as cross reactions or non-specific reactions of the antibody used. In order to establish an improved method for assaying dehydroepiandrosterone sulfate (DHEAS) and cholesterol, which are the largest components of human breast cyst and duct fluids, we describe a simple, accurate, and sensitive method using high-performance liquid chromatography (HPLC). The samples were treated with cholesterol oxidase for quantitation of dehydroepiandrosterone (DHEA) and free cholesterol, and the respective oxidized substances, 4-androstene-3,17-dione and 4-cholesten-3-one, were extracted with n-hexane. The extracts were analyzed by straight phase HPLC. Effluents were monitored by measuring absorption at 240 nm, where a newly introduced chromophoric group, an alpha,beta-unsaturated ketone, showed intense absorption (epsilon = 16,000). When the total amount of DHEA (DHEAS plus DHEA) was measured, the sample had been solvolyzed by sulfatase beforehand. The amounts of DHEAS were quantified by comparing the amounts of DHEA before and after solvolysis. Levels of free cholesterol, DHEAS, and DHEA in human breast cyst fluids (n = 30) were 1.77 +/- 1.12 mmol/dl, 8.27 +/- 10.24 micromol/dl, and 0.02 +/- 0.02 micromol/dl (means +/- SD), respectively. The levels of sterol and steroid measured in breast duct fluids that were turbid, brown, dark green, or milky in color (n = 9) (mean levels, 3.20 +/- 2.97 mmol/dl for free cholesterol and 14.77 +/- 13.75 micromol/dl for DHEAS) were significantly (P < 0.01) higher than the levels in clear or serous breast fluids (n = 21) (mean levels, 0.14 +/- 0.13 mmol/dl for free cholesterol and 0.04 +/- 0.07 micromol/dl for DHEAS).     

Partially folded structure of flavin adenine dinucleotide-depleted ferredoxin-NADP+ reductase with residual NADP+ binding domain

Maize ferredoxin-NADP(+) reductase (FNR) consists of flavin adenine dinucleotide (FAD) and NADP(+) binding domains with a FAD molecule bound noncovalently in the cleft between these domains. The structural changes of FNR induced by dissociation of FAD have been characterized by a combination of optical and biochemical methods. The CD spectrum of the FAD-depleted FNR (apo-FNR) suggested that removal of FAD from holo-FNR produced an intermediate conformational state with partially disrupted secondary and tertiary structures. Small angle x-ray scattering indicated that apo-FNR assumes a conformation that is less globular in comparison with holo-FNR but is not completely chain-like. Interestingly, the replacement of tyrosine 95 responsible for FAD binding with alanine resulted in a molecular form similar to apo-protein of the wild-type enzyme. Both apo- and Y95A-FNR species bound to Cibacron Blue affinity resin, indicating the presence of a native-like conformation for the NADP(+) binding domain. On the other hand, no evidence was found for the existence of folded conformations in the FAD binding domains of these proteins. These results suggested that FAD-depleted FNR assumes a partially folded structure with a residual NADP(+) binding domain but a disordered FAD binding domain.     

Increased gene expression of endothelin-1 and vasoactive intestinal contractor/endothelin-2 in the mammary gland of lactating mice

In an attempt to understand the roles of endothelin-1 (ET-1) and vasoactive intestinal contractor/endothelin-2 (VIC/ET-2), we have studied the genes for both peptides to be expressed in the mammary gland of lactating mice. We observed through real-time PCR analysis that ET-1 and VIC/ET-2 gene expression gradually increase after parturition and that ET-1 gene expression is significantly higher than that of VIC/ET-2. The distribution of ET-1 peptide was found to be localized mainly in the epithelial cells of the mammary gland at 14th day of lactation. ET-1 gene expression increases significantly, parallel to the increase in beta-casein gene expression, in epithelial cell lines (HC11) of mouse mammary gland after hormonal stimulation by addition of dexamethazone and prolactin. The observed increase in ET-1 expression in differentiated epithelial cells suggests physiological roles for ET-1, including milk production and secretion in the mammary gland of lactating mice.     

Requirement for Activation of the Serine-Threonine Kinase Akt (Protein Kinase B) in Insulin Stimulation of Protein Synthesis but Not of Glucose Transport

A wide variety of biological activities including the major metabolic actions of insulin is regulated by phosphatidylinositol (PI) 3-kinase. However, the downstream effectors of the various signaling pathways that emanate from PI 3-kinase remain unclear. Akt (protein kinase B), a serine-threonine kinase with a pleckstrin homology domain, is thought to be one such downstream effector. A mutant Akt (Akt-AA) in which the phosphorylation sites (Thr³⁰⁸ and Ser⁴⁷³) targeted by growth factors are replaced by alanine has now been shown to lack protein kinase activity and, when overexpressed in CHO cells or 3T3-L1 adipocytes with the use of an adenovirus vector, to inhibit insulin-induced activation of endogenous Akt. Akt-AA thus acts in a dominant negative manner in intact cells. Insulin-stimulated protein synthesis, which is sensitive to wortmannin, a pharmacological inhibitor of PI 3-kinase, was abolished by overexpression of Akt-AA without an effect on amino acid transport into the cells, suggesting that Akt is required for insulin-stimulated protein synthesis. Insulin activation of p70 S6 kinase was inhibited by ~75% in CHO cells and ~30% in 3T3-L1 adipocytes, whereas insulin-induced activation of endogenous Akt was inhibited by 80 to 95%, by expression of Akt-AA. Thus, Akt activity appears to be required, at least in part, for insulin stimulation of p70 S6 kinase. However, insulin-stimulated glucose uptake in both CHO cells and 3T3-L1 adipocytes was not affected by overexpression of Akt-AA, suggesting that Akt is not required for this effect of insulin. These data indicate that Akt acts as a downstream effector in some, but not all, of the signaling pathways downstream of PI 3-kinase.     

Incidence of Prevotella intermedia and Prevotella nigrescens in Periodontal Health and Disease

The incidence of black-pigmented rods (BPRs), especially Prevotella intermedia and Prevotella nigrescens, in periodontal health and disease were examined. Furthermore, the degradative enzyme activities of P. intermedia were compared among the strains from periodontal health and disease. Microbiological specimens were collected from subgingival crevice or periodontal pocket by paper point. The BPRs were found in 71.1% of periodontally healthy subjects (n = 45), and in 47.1% of healthy sites (n = 34) and 87.8% of active sites (n = 41) among periodontally diseased patients. Porphyromonas gingivalis was detected only in active sites of periodontally diseased patients (17.8% of 180 strains). P. intermedia was the predominant BPR in both healthy and active sites (37.3 and 41.7%, respectively) of the patients. However, P. nigrescens was the predominant BPR (70.5% of 173 strains) in periodontally healthy subjects. The enzyme activities of esterase, esterase-lipase, acid-phosphatase and α-fucosidase of P. intermedia strains isolated from active sites in patients were significantly higher (P < 0.05) than those of healthy subjects. The results suggest that P. intermedia might increase the activity of degradative enzymes under a certain condition and support the progression of periodontitis.     

Involvement of Receptor-like Protein Tyrosine Phosphatase ζ/RPTPβ and Its Ligand Pleiotrophin/Heparin-binding Growth-associated Molecule (HB-GAM) in Neuronal Migration

Pleiotrophin/heparin-binding growth-associated molecule (HB-GAM) is a specific ligand of protein tyrosine phosphatase ζ (PTPζ)/receptor-like protein tyrosine phosphatase β (RPTPβ) expressed in the brain as a chondroitin sulfate proteoglycan. Pleiotrophin and PTPζ isoforms are localized along the radial glial fibers, a scaffold for neuronal migration, suggesting that these molecules are involved in migratory processes of neurons during brain development. In this study, we examined the roles of pleiotrophin-PTPζ interaction in the neuronal migration using cell migration assay systems with glass fibers and Boyden chambers. Pleiotrophin and poly-l-lysine coated on the substratums stimulated cell migration of cortical neurons, while laminin, fibronectin, and tenascin exerted almost no effect. Pleiotrophin-induced and poly-l-lysine–induced neuronal migrations showed significant differences in sensitivity to various molecules and reagents. Polyclonal antibodies against the extracellular domain of PTPζ, PTPζ-S, an extracellular secreted form of PTPζ, and sodium vanadate, a protein tyrosine phosphatase inhibitor, added into the culture medium strongly suppressed specifically the pleiotrophin-induced neuronal migration. Furthermore, chondroitin sulfate C but not chondroitin sulfate A inhibited pleiotrophin-induced neuronal migration, in good accordance with our previous findings that chondroitin sulfate constitutes a part of the pleiotrophin-binding site of PTPζ, and PTPζ-pleiotrophin binding is inhibited by chondroitin sulfate C but not by chondroitin sulfate A. Immunocytochemical analysis indicated that the transmembrane forms of PTPζ are expressed on the migrating neurons especially at the lamellipodia along the leading processes. These results suggest that PTPζ is involved in the neuronal migration as a neuronal receptor of pleiotrophin distributed along radial glial fibers.     

Nitrite-Specific Active Transport System of the Cyanobacterium Synechococcus sp. Strain PCC 7942

Studies on the nitrite uptake capability of a mutant of Synechococcus sp. strain PCC 7942 lacking the ATP-binding cassette-type nitrate-nitrite-bispecific transporter revealed the occurrence of a nitrite-specific active transport system with an apparent K_m (NO₂⁻) of about 20 μM. Similar to the nitrate-nitrite-bispecific transporter, the nitrite-specific transporter was reversibly inhibited by ammonium in the medium.     

Effects of soy protein diet on the expression of adipose genes and plasma adiponectin.

Many studies have reported the cholesterol-lowering, anti-lipogenic, anti-obesity and anti-hypertensive effects of soy protein. Adipose tissue-specific plasma protein, adiponectin, has anti-atherogenic and anti-insulin-resistance properties. Here, we investigated the effects of soy protein diet on body fat composition, plasma glucose, lipid and adiponectin levels and expression of genes involved in glucose and fatty acid metabolism in obese KK-A y mice. Body weights and adipose tissue weights of mesenteric, epididymal, and brown fat were lower in mice on calorie-restricted diet containing soy protein isolate. Plasma cholesterol, triglyceride, free fatty acid, and glucose levels were also decreased by this diet. Body fat content and plasma glucose levels in mice on a soy protein isolate diet were still lower than those treated with an isocaloric casein-protein-diet. Among the genes related to glucose and fatty acid metabolism, adiponectin mRNA levels in adipose tissue and adiponectin plasma concentrations were elevated in mice on a calorie-restricted diet, although there were no significant differences between soy protein and casein protein groups. Our results indicate that that soy protein diet decreased body fat content and plasma glucose levels more effectively than isocaloric casein-protein diet in obese mice.