A novel membrane glycoprotein, SHPS-1, that binds the SH2-domain-containing protein tyrosine phosphatase SHP-2 in response to mitogens and cell adhesion

Protein tyrosine phosphatases (PTPases), such as SHP-1 and SHP-2, that contain Src homology 2 (SH2) domains play important roles in growth factor and cytokine signal transduction pathways. A protein of approximately 115 to 120 kDa that interacts with SHP-1 and SHP-2 was purified from v-src-transformed rat fibroblasts (SR-3Y1 cells), and the corresponding cDNA was cloned. The predicted amino acid sequence of the encoded protein, termed SHPS-1 (SHP substrate 1), suggests that it is a glycosylated receptor-like protein with three immunoglobulin-like domains in its extracellular region and four YXX(L/V/I) motifs, potential tyrosine phosphorylation and SH2-domain binding sites, in its cytoplasmic region. Various mitogens, including serum, insulin, and lysophosphatidic acid, or cell adhesion induced tyrosine phosphorylation of SHPS-1 and its subsequent association with SHP-2 in cultured cells. Thus, SHPS-1 may be a direct substrate for both tyrosine kinases, such as the insulin receptor kinase or Src, and a specific docking protein for SH2-domain-containing PTPases. In addition, we suggest that SHPS-1 may be a potential substrate for SHP-2 and may function in both growth factor- and cell adhesion-induced cell signaling.

Are Short Chain Fatty Acids in Gut Microbiota Defensive Players for Inflammation and Atherosclerosis?

Intestinal flora (microbiota) have recently attracted attention among lipid and carbohydrate metabolism researchers. Microbiota metabolize resistant starches and dietary fibers through fermentation and decomposition, and provide short chain fatty acids (SCFAs) to the host. The major SCFAs acetates, propionate and butyrate, have different production ratios and physiological activities. Several receptors for SCFAs have been identified as the G-protein coupled receptor 41/free fatty acid receptor 3 (GPR41/FFAR3), GPR43/FFAR2, GPR109A, and olfactory receptor 78, which are present in intestinal epithelial cells, immune cells, and adipocytes, despite their expression levels differing between tissues and cell types. Many studies have indicated that SCFAs exhibit a wide range of functions from immune regulation to metabolism in a variety of tissues and organs, and therefore have both a direct and indirect influence on our bodies. This review will focus on SCFAs, especially butyrate, and their effects on various inflammatory mechanisms including atherosclerosis. In the future, SCFAs may provide new insights into understanding the pathophysiology of chronic inflammation, metabolic disorders, and atherosclerosis, and we can expect the development of novel therapeutic strategies for these diseases.

Butyrate attenuates inflammation and lipolysis generated by the interaction of adipocytes and macrophages

AIM

Paracrine interaction between macrophages and adipocytes in obese visceral fat tissues is thought to be a trigger of chronic inflammation. The immunomodulatory effect of the short chain fatty acid, butyric acid, has been demonstrated. We hypothesize that sodium butyrate (butyrate) attenuates inflammatory responses and lipolysis generated by the interaction of macrophages and adipocytes.

METHODS

Using contact or transwell co-culture methods with differentiated 3T3-L1 adipocytes and RAW264.7 macrophages, we investigated the effects of butyrate on the production of tumor necrosis factor alpha (TNF-α), monocyte chemoattractant protein 1 (MCP-1), interleukin 6 (IL-6), and the release of free glycerol, free fatty acids (FFAs) into the medium. We also examined the activity of nuclear factor-kappaB (NF-κB) and the phosphorylation of mitogen-activated protein kinases (MAPKs) in co-cultured macrophages, as well as lipase activity and expression in co-cultured adipocytes.

RESULTS

We found increased production of TNF-α, MCP-1, IL-6, and free glycerol, FFAs in the co-culture medium, and butyrate significantly reduced them. Butyrate inhibited the phosphorylation of MAPKs, the activity of NF-κB in co-cultured macrophages, and suppressed lipase activity in co-cultured adipocytes. Lipase inhibitors significantly attenuated the production of TNF-α, MCP-1 and IL-6 in the co-culture medium as effectively as butyrate. Butyrate suppressed the protein production of adipose triglyceride lipase, hormone sensitive lipase, and fatty acid-binding protein 4 in co-cultured adipocytes. Pertussis toxin, which is known to block GPR41 completely, inhibited the antilipolysis effect of butyrate.

CONCLUSION

Butyrate suppresses inflammatory responses generated by the interaction of adipocytes and macrophages through reduced lipolysis and inhibition of inflammatory signaling.

Oxygen free radicals and lipid peroxidation in the pathogenesis of gastric mucosal lesions induced by indomethacin in rats. Relation to gastric hypermotility

The relationship of gastric hypermotility to mucosal hemodynamics, lipid peroxidation and vascular permeability changes was investigated in the pathogenesis of indomethacin-induced gastric lesions in rats. Subcutaneous administration of indomethacin (25 mg/kg) produced an increase in both the amplitude and frequency of stomach contraction from 30 min after treatment, resulting in hemorrhagic damage 2 h later. Gastric mucosal blood flow measured by a Laser flowmetry showed oscillatory fluctuations under hypercontractile states: a decrease during contraction followed by an increase during relaxation. Mucosal lipid peroxidation and vascular permeability were significantly increased with time after indomethacin treatment, and these changes preceded the appearance of hemorrhagic damage. All these events were prevented when gastric hypermotility was inhibited by atropine or 16,16-dimethyl prostaglandin E2. Pretreatment of the animals with allopurinol and hydroxyurea or continuous infusion of superoxide dismutase and dimethyl sulfoxide during a test period also attenuated these functional changes and mucosal lesions induced by indomethacin, without affecting the motility response. We conclude that oxygen free radicals may play a role in the development of mucosal lesions associated with gastric hypermotility in indomethacin-treated rats.

Integrin-mediated tyrosine phosphorylation of SHPS-1 and its association with SHP-2. Roles of Fak and Src family kinases

SHPS-1 is a receptor-like glycoprotein that undergoes tyrosine phosphorylation and binds SHP-2, an Src homology 2 domain containing protein tyrosine phosphatase, in response to various mitogens. Cell adhesion to extracellular matrix proteins such as fibronectin and laminin also induced the tyrosine phosphorylation of SHPS-1 and its association with SHP-2. These responses were markedly reduced in cells overexpressing the Csk kinase or in cells that lack focal adhesion kinase or the Src family kinases Src or Fyn. However, unlike Src, focal adhesion kinase did not catalyze phosphorylation of the cytoplasmic domain of SHPS-1 in vitro. Overexpression of a catalytically inactive SHP-2 markedly inhibited activation of mitogen-activated protein (MAP) kinase in response to fibronectin stimulation without affecting the extent of tyrosine phosphorylation of focal adhesion kinase or its interaction with the docking protein Grb2. Overexpression of wild-type SHPS-1 did not enhance fibronectin-induced activation of MAP kinase. These results indicate that the binding of integrins to the extracellular matrix induces tyrosine phosphorylation of SHPS-1 and its association with SHP-2, and that such phosphorylation of SHPS-1 requires both focal adhesion kinase and an Src family kinase. In addition to its role in receptor tyrosine kinase-mediated MAP kinase activation, SHP-2 may play an important role, partly through its interaction with SHPS-1, in the activation of MAP kinase in response to the engagement of integrins by the extracellular matrix.

SP-22 is a thioredoxin-dependent peroxide reductase in mitochondria

SP-22 is a mitochondrial antioxidant protein in bovine adrenal cortex. The protein is homologous to thioredoxin peroxidase and other antioxidant proteins. It protects radical-sensitive enzymes from oxidative damage by a radical-generating system (Fe2+/dithiothreitol) in the presence of a small amount of serum. In this study we purified a second mitochondrial protein with Mr 11,777, which cooperates with SP-22 to protect glutamine synthetase and other proteins from Fe2+/dithiothreitol-mediated damage. Without SP-22, the protein had no protecting activity. We determined amino acid and nucleotide sequences of the protein and its cDNA, respectively, and found that it was a protein of the thioredoxin family. The protein, designated as mt-Trx (mitochondrial thioredoxin), had a presequence composed of 59 amino acids that seemed to be a mitochondrial targeting signal. Mitochondrial extract prepared from adrenal cortex contained NADPH-dependent 5,5'dithiobis(2-nitrobenzoic acid) (Nbs2) reductase activity. The enzyme was thought to have thioredoxin reductase activity, since the Nbs2-reducing activity was stimulated by mt-Trx. We partially purified the Nbs2 reductase from bovine adrenocortical mitochondria. In the presence of the partially purified reductase, mt-Trx, and NADPH, SP-22 showed the activity to protect oxyhemoglobin against ascorbate-induced damage. Furthermore, with the three protein components (Nbs2 reductase, mt-Trx, and SP-22) NADPH was oxidized in the presence of hydrogen peroxide or tert-butyl hydroperoxide. The oxidation of NADPH was concomitant with the disappearance of an equimolar amount of hydrogen peroxide. Without any one of the protein components no hemoglobin-protecting and peroxide-dependent NADPH-oxidizing activities were observed. From these results we concluded that SP-22 is thioredoxin-dependent peroxide reductase or so-called thioredoxin peroxidase in mitochondria from the adrenal cortex.

Facilitated nitration and oxidation of LDL in cigarette smokers

BACKGROUND

Cigarette smoking increases the risk of developing atherosclerosis and ischaemic heart disease. Smoking-induced oxidative stress is considered to favour oxidation of low-density lipoprotein (LDL) and subsequently promotes the atherogenic process. We investigated whether peroxynitrite, a reaction product of cigarette smoke, is involved in facilitated oxidation of LDL in smokers.

MATERIALS AND METHODS

Plasma LDL was obtained from 10 healthy asymptomatic cigarette smokers and 10 healthy nonsmokers. The state of enhanced oxidative stress in the plasma was assessed by LDL subfraction assay using anion-exchange high-performance liquid chromatography (AE-HPLC) and measurements of thiobarbituric acid-reactive substances (TBARS), 8-hydroxydeoxyguanosine (8-OHdG), vitamin E, 3-nitrotyrosine and 3-chlorotyrosine.

RESULTS

Smokers showed a significantly higher level of TBARS and 8-OHdG as well as a significantly lower level of vitamin E than nonsmokers, even after stopping smoking for 10 h or more. The LDL subfraction assay demonstrated an increase in oxidatively modified LDL, as expressed by lower levels of LDL1 and higher levels of LDL2. The 3-nitrotyrosine levels in apolipoprotein B in LDL were significantly higher in smokers than nonsmokers, while the 3-chlorotyrosine levels remained unchanged. In addition, these changes observed in the smokers were further accelerated within 30 min after resumption of cigarette smoking when compared with the levels before smoking resumption.

CONCLUSION

The present study suggests that peroxynitrite plays a significant role in oxidative modification of plasma LDL induced by cigarette smoking.

Remnant lipoproteins as strong key particles to atherogenesis

Recent epidemiologic studies have revealed that hypertriglyceridemia is associated with atherosclerosis independent of other coronary risk factors. However, it is difficult to select patients at high risk for coronary artery disease using only serum triglyceride levels compared with low-density lipoprotein cholesterol levels since multiple factors are associated with elevating triglycerides. Atherosclerotic diseases with high triglyceride levels can be found in patients with familial combined hyperlipidemia, diabetes mellitus, and metabolic syndrome, in which remnant lipoproteins accumulate in the circulating blood. Recent researches have paid attention to remnant lipoproteins as atherogenic particles with the development of methods for measuring remnant cholesterol levels and apolipoprotein B-48 levels directly from human serum. Measurement of these parameters in addition to serum triglycerides may help to distinguish high-risk patients and enable us to prevent or suppress the progression of atherosclerotic diseases in those patients. However, questions remain to be answered to evaluate the significance of remnant lipoproteins. Here, we focus on three issues: the underlying problems in measuring remnant lipoprotein cholesterol, the assessment of postprandial hyperlipidemia as an atherogenic condition, and finally a review of our experimental and clinical findings about the mechanisms by which remnant lipoproteins induce atherosclerosis.

The role of interpretation processes and parental discussion in the media's effects on adolescents' use of alcohol

OBJECTIVE

The process that connects media use with alcohol-related beliefs and behaviors has not been well documented. To address this issue, we examined adolescents' viewing patterns, beliefs about alcohol and media messages, and parental discussion of media messages in the context of a theoretical model of message interpretation processes. Measures included the degree to which adolescents found portrayals desirable, realistic, and similar to their own lives; the degree to which they wanted to be like (identify with) the portrayals; and the degree to which they associated positive outcomes with drinking alcohol (expectancies).

DESIGN

Cross-sectional survey.

SETTING

Two public high schools in the California central coastal area that include a diverse population in terms of ethnic origin, income level, and education level.

PARTICIPANTS

Ninth-grade students (n = 252) and 12th-grade students (n = 326).

OUTCOME MEASURES

Students reported the number of days within the past week watching various genres of television content, along with perceptions of realism of content, desirability of portrayals, identification with portrayals, expectancies toward alcohol use, personal norms for alcohol use, desire for products with alcohol logos, current alcohol use, frequency of parental reinforcement, and counter-reinforcement of television messages. Associations were examined via hierarchical multiple regression analysis.

RESULTS

Effects of media exposure on drinking behavior, controlling for grade level, ethnicity, gender, household income, and education levels were primarily positive and indirect, operating through a number of intervening beliefs, especially expectancies (beta =.59; r(2) =.33). Direct associations, primarily with exposure to late-night talk shows (beta =.12; r(2) =.01), were small. Parental discussion also affected behavior indirectly, operating through expectancies, identification, and perceived realism. The appeal of products with alcohol logos, which was higher among the younger students (t = 3.44) and predicted by expectancies (beta =. 37; r(2) =.13), sports viewing (beta =.17; r(2) =.03) and late-night talk shows (beta =.10; r(2) =.01), predicted actual drinking behavior (beta =.22; r(2) =.04). Drinking behavior was higher among the older students (t = -2.515).

CONCLUSIONS

Adolescents make drinking decisions using a progressive, logical decision-making process that can be overwhelmed by wishful thinking. The potential risk of frequent exposure to persuasive alcohol portrayals via late-night talk shows, sports, music videos, and prime-time television for underage drinking is moderated by parental reinforcement and counter-reinforcement of messages. Interventions need to acknowledge and counter the appeal of desirable and seemingly realistic alcohol portrayals in the media and alert parents to their potential for unintended adverse effects.

Roles of the complex formation of SHPS-1 with SHP-2 in insulin-stimulated mitogen-activated protein kinase activation

SHPS-1 is a receptor-like protein that undergoes tyrosine phosphorylation and binds SHP-2, an SH2 domain-containing protein tyrosine phosphatase, in response to insulin and other mitogens. The overexpression of wild-type SHPS-1, but not of a mutant SHPS-1 in which all four tyrosine residues in its cytoplasmic region were mutated to phenylalanine, markedly enhanced insulin-induced activation of mitogen-activated protein kinase in Chinese hamster ovary cells that overexpress the human insulin receptor. Mutation of each tyrosine residue individually revealed that the major sites of tyrosine phosphorylation of SHPS-1 in response to insulin are Tyr449 and Tyr473. In addition, mutation of either Tyr449 or Tyr473 abolished the insulin-induced tyrosine phosphorylation of SHPS-1 and its association with SHP-2. Surface plasmon resonance analysis showed that glutathione S-transferase fusion proteins containing the NH2-terminal or COOH-terminal SH2 domains of SHP-2 bound preferentially to phosphotyrosyl peptides corresponding to the sequences surrounding Tyr449 or Tyr473, respectively, of SHPS-1. Furthermore, phosphotyrosyl peptides containing Tyr449 or Tyr473 were effective substrates for the phosphatase activity of recombinant SHP-2 in vitro. Together, these results suggest that insulin may induce phosphorylation of SHPS-1 at Tyr449 and Tyr473, to which SHP-2 then binds through its NH2-terminal and COOH-terminal SH2 domains, respectively. SHPS-1 may play a crucial role both in the recruitment of SHP-2 from the cytosol to a site near the plasma membrane and in increasing its catalytic activity, thereby positively regulating the RAS-mitogen-activated protein kinase signaling cascade in response to insulin.

Role of SH-PTP2, a protein-tyrosine phosphatase with Src homology 2 domains, in insulin-stimulated Ras activation

SH-PTP2 is a nontransmembrane human protein-tyrosine phosphatase that contains two Src homology 2 (SH2) domains and binds to insulin receptor substrate 1 (IRS-1) via these domains in response to insulin. The expression of a catalytically inactive mutant of SH-PTP2 (containing the mutation Cys-459-->Ser) in Chinese hamster ovary cells that overexpress human insulin receptors (CHO-IR cells) markedly attenuated insulin-stimulated Ras activation. Expression of mutant SH-PTP2 also inhibited MAP kinase activation in response to insulin but not in response to 12-O-tetradecanoyl phorbol-13-acetate. In contrast, the insulin-induced association of phosphoinositide 3-kinase activity with IRS-1 was not affected by the expression of inactive SH-PTP2. Furthermore, the expression of mutant SH-PTP2 had no effect on the binding of Grb2 to IRS-1, on the tyrosine phosphorylation of Shc, or on the formation of the complex between Shc and Grb2 in response to insulin. However, the amount of SH-PTP2 bound to IRS-1 in insulin-treated CHO-IR cells expressing mutant SH-PTP2 was greater than that observed in CHO-IR cells overexpressing wild-type SH-PTP2. Recombinant SH-PTP2 specifically dephosphorylated a synthetic phosphopeptide corresponding to the sequence surrounding Tyr-1172 of IRS-1, a putative binding site for SH-PTP2. Additionally, phenylarsine oxide, an inhibitor of protein-tyrosine phosphatases, inactivated SH-PTP2 in vitro and increased the insulin-induced association of SH-PTP2 with IRS-1. These results suggest that SH-PTP2 may regulate an upstream element necessary for Ras activation in response to insulin and that this upstream element may be required for the Grb2- or Shc-dependent pathway. Furthermore, these results are consistent with the notion that SH-PTP2 may bind to IRS-1 through its SH2 domains in response to insulin and dephosphorylate the phosphotyrosine residue to which it binds, thereby regulating its association with IRS-1.

Augmented diurnal variations of the cardiac renin-angiotensin system in hypertensive rats

There are several controversies concerning the enhanced gene expression of cardiac renin-angiotensin system components in spontaneously hypertensive rats (SHR) compared with their normotensive control Wistar-Kyoto (WKY) rats. We hypothesized that these discrepancies arise from circadian fluctuations in gene expression. We examined the circadian mRNA expression of renin, angiotensinogen, ACE, and angiotensin type 1a (AT1a) and type 2 (AT2) receptors in the hearts of SHR and WKY rats by real-time quantitative reverse transcription-polymerase chain reaction. The cardiac mRNA expression of the renin-angiotensin system components showed circadian oscillations in both SHR and WKY rats. The amplitudes of these circadian fluctuations were greater in the SHR than in the WKY rats. The mRNA levels of the renin-angiotensin system components were also increased in the SHR compared with the WKY rats at many time points (especially during the dark phase). However, the levels of ACE, AT1a receptor, and AT2 receptor mRNA in the SHR and WKY rats were almost the same during the late light phase. In contrast to mRNA expression, ACE activity was similar both at the time of maximum and minimum mRNA expression. The AT1 receptor antagonist candesartan upregulated AT1a receptor mRNA and downregulated ACE mRNA at specific time points only in the SHR group. Our findings of differential diurnal expression of cardiac renin-angiotensin system genes in SHR and WKY rats appear to explain the discrepancies between prior studies. However, the physiological relevance of the differential circadian mRNA expression of the renin-angiotensin system components remains to be elucidated.

Stoichiometry of Na+-Ca2+ exchange in inside-out patches excised from guinea-pig ventricular myocytes

1. The stoichiometry (nx) of cardiac Na+-Ca2+ exchange was examined by measuring the reversal potential of the Na+-Ca2+ exchange current (INa-Ca) in large inside-out patches, 'macro patches', excised from intact guinea-pig ventricular cells. 2. Cytoplasmic application of Na+ (Na+i) or Ca2+ (Ca2+i) induced INa-Ca which showed properties similar to INa-Ca in the giant membrane patch. The outward INa-Ca was depressed by an exchanger inhibitory peptide, XIP. 3. The reversal potential of the XIP-sensitive current indicated that nx was approximately 4 (3.6-4.2) at 9-40 mM Na+i, and nx tended to increase as Na+i was increased. Proteolysis by trypsin did not significantly affect the stoichiometry. Similar results were obtained from the reversal potential of INa-Ca that was induced by application of both Na+i and Ca2+i. 4. At 0.1 microM Ca2+i, nx was approximately 4 (3.7-4. 4) at 6-25 mM Na+i and tended to increase as Na+i was increased. When Ca2+i was changed from 0.1 to 1 and 1000 microM at constant 50 mM Na+i, the value was approximately 4 (3.6-4.4). 5. When the extracellular Na+ (Na+o) and Ca2+ (Ca2+o) concentrations were varied in the presence of 25 or 9 mM Na+i and 1 microM Ca2+i, nx was almost constant ( approximately 4) over the range 0.3-20 mM Ca2+o and 10-145 mM Na+o. 6. These results indicated that the stoichiometry of Na+-Ca2+ exchange is different from generally accepted 3Na+:1Ca2+, and suggested that the stoichiometry is either 4Na+:1Ca2+ or variable depending on Na+i and Ca2+i.

Trichostatin A, an inhibitor of histone deacetylase, inhibits smooth muscle cell proliferation via induction of p21(WAF1)

The proliferation of vascular smooth muscle cells (VSMCs) can contribute to a variety of pathological states, including atherosclerosis and post-angioplasty restenosis. The p21(WAF1) cyclin-dependent kinase inhibitor regulates cell-cycle progression, senescence, and differentiation in injured blood vessels. Histone deacetylase (HDAC) inhibitors have shown utility in controlling proliferation in a wide range of tumor cell lines, possibly by inducing the expression of p21(WAF1). Our goal was to investigate the effect of trichostatin A (TSA), a specific and potent HDAC inhibitor, on the proliferation of vascular smooth muscle cells (VSMCs) isolated from rat thoracic aorta. TSA suppressed the HDAC activity of VSMCs in a dose-dependent manner and inhibited VSMC proliferation as demonstrated by cell number counting and the degree of [3H] thymidine incorporation. Further, TSA reduced the phosphorylation of Rb protein, a regulator of cell-cycle progression. TSA treatment also induced the expression of p21(WAF1) but not of p16(INK4), p27(KIP1) or p53. Finally, TSA inhibited HDAC activity of VSMCs from p21(WAF1) knock-out mice but had no effect on VSMC proliferation in these animals. In conclusion, TSA inhibits VSMC proliferation via the induction of p21(WAF1) expression and subsequent cell-cycle arrest with reduction of the phosphorylation of Rb protein at the G1-S phase.

Determination of R(+)- and S(-)-lansoprazole using chiral stationary-phase liquid chromatography and their enantioselective pharmacokinetics in humans

PURPOSE

Stereoselective and sensitive methods employing chiral stationary phase columns for HPLC determination of enantiomers of lansoprazole in the human serum were developed and pharmacokinetic behaviors of the enantiomers were evaluated in seven subjects.

METHODS

Five chiral stationary phase columns: Chiralcel OD (cellulose tris(3,5-dimethyl-phenylcarbamate)), OF (cellulose tris(4-chlorophenylcarbamate)), OG (cellulose tris(4-methylphenylcarbamate)) and OJ (cellulose tris(4-methylbenzoate)), and Chiralpak AS (amylose tris ((S)-1-phenylethylcarbamate)) were investigated.

RESULTS

Chiralcel OD and Chiralpak AS columns gave a good resolution of R(+)- and S(-)-enantiomers from racemic lansoprazole, but Chiralcel OF, OG, and OJ did not. The mean Cmax and the AUC values of R(+)-enantiomer were 3-5 times greater than those of S(-)-enantiomer following oral administration of 30 mg of racemic lansoprazole. The CLtot values of R(+)-enantiomer were significantly smaller than those of S(-)-enantiomer. Binding of R(+)-enantiomer to human serum proteins was significantly greater than that of S(-)-enantiomer. The mean metabolic ratio (metabolites/parent compound) in human liver microsomes of S(-)-enantiomer was significantly greater than that of R(+)-enantiomer.

CONCLUSIONS

The stereoselective pharmacokinetics of lansoprazole enantiomers is likely due to its stereoselective protein binding and/or metabolism.

Effect of molecular charges on renal uptake of 111In-DTPA-conjugated peptides

The effect of molecular charges on renal accumulation of 111In-DTPA-labeled low molecular weight (LMW) peptides was investigated using 111In-DTPA-octreotide derivatives as models to design radiolabeled peptides that are taken up less by renal cells. The N-terminal D-phenylalanine (Phe) of 111In-DTPA-D-Phe(1)-octreotide was replaced with L-aspartic acid (Asp), L-lysine (Lys), L-methionine (Met) or L-Phe. Cellulose acetate electrophoresis indicated that both 111In-DTPA-L-Phe(1)-octreotide and 111In-DTPA-L-Met(1)-octreotide showed similar net charges, whereas 111In-DTPA-L-alphaLys(1)-octreotide and 111In-DTPA-L-Asp(1)-octreotide had more positive and negative charges, respectively, at pH values similar to those in blood and glomerular filtrate. When injected into mice, significant differences were observed in the renal radioactivity levels. 111In-DTPA-L-alphaLys(1)-octreotide showed the highest radioactivity levels from 10 min to 6 h postinjection, whereas the lowest radioactivity levels were observed with 111In-DTPA-L-Asp(1)-octreotide at all the postinjection intervals. These findings indicated that the replacement of only one amino acid in 111In-DTPA-D-Phe(1)-octreotide significantly altered net molecular charges of the resulting peptides and that the net charges of the 111In-DTPA-octreotide derivatives significantly affected their renal uptake. Thus, an increase of negative charges in peptide molecules may constitute a strategy for designing 111In-DTPA-conjugated LMW peptides with low renal radioactivity levels.

The NSY mouse: a new animal model of spontaneous NIDDM with moderate obesity

The NSY (Nagoya-Shibata-Yasuda) mouse was established as an inbred strain of mouse with spontaneous development of diabetes mellitus, by selective breeding for glucose intolerance from outbred Jcl:ICR mice. NSY mice spontaneously develop diabetes mellitus in an age-dependent manner. The cumulative incidence of diabetes is 98% in males and 31% in females at 48 weeks of age. Neither severe obesity nor extreme hyperinsulinaemia is observed at any age in these mice. Glucose-stimulated insulin secretion was markedly impaired in NSY mice after 24 weeks of age. In contrast, fasting plasma insulin level was higher in male NSY mice than that in male C3H/He mice (545 +/- 73 vs 350 +/- 40 pmol/l, p < 0.05, at 36 weeks of age). Pancreatic insulin content was higher in male NSY mice than that in male C3H/He mice (76 +/- 8 vs 52 +/- 5 ng/mg wet weight, p < 0.05, at 36 weeks of age). Morphologically, no abnormal findings, such as hypertrophy or inflammatory changes in the pancreatic islets, were observed in NSY mice at any age. These data suggest that functional changes of insulin secretion in response to glucose from pancreatic beta cells may contribute to the development of non-insulin-dependent diabetes mellitus (NIDDM) in the NSY mouse. Although insulin sensitivity was not measured, fasting hyperinsulinaemia in NSY mice suggests that insulin resistance may also contribute to the pathogenesis of NIDDM. Since these findings are similar to the pathophysiologic features of human NIDDM patients, the NSY mouse is considered to be useful for investigating the pathogenesis and genetic predisposition to NIDDM.

Apoptotic process of cerebellar degeneration in experimental methylmercury intoxication of rats

This report deals with the mechanism involved in the cerebellar degeneration following experimental methylmercury poisoning of male Wistar rats. The cerebellar granule cells of animals that exhibited typical hind leg paresis were shrunken and displayed marked nuclear pyknosis. At the ultrastructural level, the nuclei of these cells were condensed and fragmented, features which are characteristic of apoptosis. In situ staining for DNA strand breaks revealed that the pyknotic nuclei were positively labeled. DNA fragmentation was confirmed by agarose gel electrophoresis; a ladder pattern of multiples of approximately 200-base pair fragments, typical of apoptosis, was observed with the cerebellar DNA of the methylmercury-treated animals. These observations suggest that the degeneration of cerebellar granule cells by alkyl mercury compounds involves an apoptotic process.

MM-1, a c-Myc-binding protein, is a candidate for a tumor suppressor in leukemia/lymphoma and tongue cancer

The c-myc oncogene product (c-Myc) is a transcription factor that dimerizes with Max and recognizes the E-box sequence, and it plays key functions in cell proliferation, differentiation, and apoptosis. We previously showed that MM-1 bound to myc box II within the transactivation domain of c-Myc and repressed the E-box-dependent transcriptional activity of c-Myc. Here we report that MM-1 showed features of a tumor suppressor. In an EST data base search for cDNAs homologous to MM-1, we found a frequent substitution of amino acid 157 of MM-1, from alanine to arginine (A157R), and the substitution was observed more in tumor cells than in normal cells. A survey of the A157R mutation of MM-1 in 57 cultured cancer cells and 90 tissues from cancer patients showed that the A157R was present in about 50-60% of leukemia/lymphoma cells and in more than 75% of squamous cell carcinoma of tongue cancer. Although both the A157R and the wild-type MM-1 bound to c-Myc, only A157R lost the activities to repress both the E-box-dependent transcriptional activity of c-Myc and the myc/ras cooperative transforming activity in rat 3Y1 cells. Furthermore, the wild-type MM-1, but not A157R, arrested the growth of 3Y1 cells. The human MM-1 gene was mapped at chromosome 12q12-12q13, where many chromosome abnormalities in cancer cells have been reported. The results suggest that MM-1 is a novel candidate for a tumor suppressor that controls the transcriptional activity of c-Myc.

Role of angiotensin II in high fructose-induced left ventricular hypertrophy in rats

Recent studies suggest the linkage of hypertension and insulin resistance. High fructose diet is known to induce hyperinsulinemia and hypertension in rats. In a previous study, however, high fructose (66%) diet failed to elevate blood pressure but increased left ventricular weight in Sprague-Dawley rats. In the present study, we investigated the precise mechanism of high fructose diet-induced changes in the cardiovascular system in rats. Intake of fructose-enriched diet for 2 weeks increased serum insulin and plasma angiotensin II levels. Urinary excretion of sodium and norepinephrine was not changed. Blood pressure measured directly through an indwelling catheter was not increased, but left ventricular weight and protein content were increased by high fructose diet. To further elucidate the role of the renin-angiotensin system, an angiotensin II type 1 receptor antagonist, TCV-116, was given orally at 1 mg/kg per day with either normal or high fructose diet. Concomitant administration of TCV-116 did not affect plasma glucose or serum insulin levels. Plasma angiotensin II was increased, but neither urinary sodium nor norepinephrine was changed by TCV-116. TCV-116 similarly decreased blood pressure in rats on normal and high fructose diets. Increase in left ventricular weight induced by high fructose diet was prevented by the concomitant administration of TCV-116. On the other hand, left ventricular weight in control rats was not changed by TCV-116. In conclusion, increased plasma angiotensin II may account for the left ventricular hypertrophy induced by high fructose diet, whereas hemodynamic change, sodium retention, and the sympathetic nervous system do not play an important role.

Kikuchi's disease and the skin: case report and review of the literature

We report scattered indurated erythematous lesions that presented in an 18-year-old Japanese man with Kikuchi's disease (KD; histiocytic necrotizing lymphadenitis). A skin biopsy showed a proliferation of histiocytes and abundant nuclear debris without the presence of neutrophils, which is characteristic of KD. The specific dermatological and pathological details of KD have been yet to be fully described. In order to assess the typical skin features of KD better, we have reviewed all the previously well-documented reports of such lesions. As the clinical and histopathological cutaneous findings in KD are so heterogeneous, it is important that scattered indurated erythematous lesions should be included as one of the possible cutaneous manifestations of this disease.