Protective effect of Ninjin-yoei-to on damage to isolated hepatocytes following transient exposure to tert-butyl hydroperoxide

To establish a simple screening system for estimating efficacy of an agent for an oxidative-related lesion, we investigated the damage in isolated rat hepatocytes exposed to 75 microM tert-butyl hydroperoxide (t-BuOOH) and then subsequently incubated the cells in fresh medium. By electron spin resonance spectroscopy analysis using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), DMPO adducts of tert-butoxyl radicals and carbon center radicals were detected during the t-BuOOH exposure, and DMPO-OH formation was detected after t-BuOOH removal. In t-BuOOH-exposed cells, the level of phosphatidylcholine hydroperoxide (PCOOH), a peroxidative product of biomembranes in the hepatocytes, and the leakage of enzymes into the culture medium were significantly increased. An increase in acid phosphatase (AP) activity representing lysosome destabilization preceded the aspartate oxoglutarate aminotransferase (AST), alanine oxoglutarate aminotransferase (ALT) and lactate dehydrogenase (LDH) leakage. Ninjin-yoei-to added to the culture medium following the t-BuOOH exposure significantly inhibited the PCOOH formation and the leakage of AP, AST, ALT and LDH, concentration-dependently. Ninjin-yoei-to at 1 mg/ml in culture medium completely diminished these increases in enzyme activities down to the background levels found in control experiments and this reduction was greater than the most effective alpha-tocopherol concentration of 20 micromol/ml. Considering all of these results, it is likely Ninjin-yoei-to may exert its protective effect by antioxidative action and membrane stabilization.

EGF family ligand-dependent phenotypic modulation of smooth muscle cells through EGF receptor

The phenotypic modulation of smooth muscle cells (SMCs) is closely associated with the development and progression of various SMC diseases. We investigated the molecular mechanism of phenotypic modulation triggered by EGF family ligands using a primary culture system of differentiated SMCs. Among four EGF-receptor (EGFR) family members, the EGFR was solely activated by EGF, heparin-binding EGF (HB-EGF), transforming growth factor alpha (TGF alpha), epiregulin (ER), and betacellulin (BTC), resulting in induction of phenotypic modulation of SMCs. This effect was mediated through the coordinated activation of the extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38MAPK) pathways. These results suggest that EGF family ligand- and EGFR-triggered signaling pathways are critically involved in the phenotypic modulation of SMCs.

[Parkinsonism induced by MPTP and free radical generation]

Oxygen free radical formation has been implicated in dopaminergic toxicity caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and iron. Although MPTP produces a parkinsonian syndrome after its conversion to 1-methyl-4-phenylpyridine (MPP+) by type B monoamine oxidase (MAO-B) in the brain, the etiology of this disease remains obscure. MPP+ is one of the most potent dopamine (DA)-releasing agents. Iron-catalyzed DA autoxidation and oxidative stress may be involved in the pathogenesis of Parkinson's disease. If indeed the effect of MPP+ on hydroxyl radical (.OH) formation is due to DA release, reserpine-induced DA depletion may reduce MPP(+)-induced .OH formation. Imidapril, an angiotensin converting enzyme (ACE) inhibitor, can resist MPP(+)-induced .OH formation via suppression of release of DA by angiotensin. Histidine, a singlet oxygen (1O2) scavenger, protects MPP(+)-induced .OH formation. Fluvastatin, an inhibitor of low-density lipoprotein (LDL) oxidation, can resist MPP(+)-induced .OH formation. The inhibitory effect on the susceptibility of LDL oxidation can reduce .OH generation. These drugs may be applied as antiparkinsonian agents. Further clinical investigation is necessary in the future.

Growth condition-dependent synchronized changes in transcript levels of type II hexokinase and type 1 glucose transporter in tumor cells

Transcript levels of hexokinase (HK) isozymes and glucose transporter (GLUT) isoforms in RNA samples of AH130 cells obtained from dish cultures and ascites were evaluated in a quantitative manner. In AH130 cells cultured in dishes, HKI and HKII were expressed at a similar level, but HKIII and HKIV were not. GLUT1 and GLUT3 were also expressed, and messages of these two isoforms represented 27% and 71%, respectively, of the total GLUT messages. A faint signal of GLUT2 was also observed. On the contrary, in cells grown as ascites, the transcript of HKII was dominant, and its level was about 15-fold over that of dish-cultured AH130 cells. Transcript levels of GLUT1 and GLUT3 were 4.5- and 2-fold, respectively, higher than those in dish-cultured cells. Thus, GLUT1 was more susceptible to changes in culture conditions than GLUT3. Based on these results, we concluded that the change in growth conditions caused synchronized changes in the transcript levels of HKII and GLUT1 in AH130 cells. However, such marked changes in the transcript levels of HKII and GLUT1 were not observed when AH130 cells were cultured in dishes under a hypoxic condition, indicating that the observed changes were not solely attributable to the difference in oxygen concentration between the ascites and cell culture conditions. Accordingly, other factors such as growth factors may be responsible for this difference in levels of HKII and GLUT1 between the two growth conditions.

Protective effect of histidine on potassium chloride depolarization enhances 1-methyl-4-phenylpyridinium ion-induced hydroxyl radical generation in the rat striatum

The present study examined the antioxidant effect of histidine on extracellular potassium ion concentration, [K+]o-induced depolarization enhances 1-methyl-4-phenylpyridinium ion (MPP+)-induced hydroxyl radical (*OH) generation in the rat striatum. Rats were anesthetized and sodium salicylate in Ringer's solution (0.5 nmol/M microl/min) was infused through a microdialysis probe to detect the generation of *OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. Induction of [K+]o (20, 70 and 140 mM) significantly increased the level of 2,3-DHBA by the action of MPP+ (5 mM) in a concentration-dependent manner. However, histidine (25 mM) reduced the [K+]o-induced *OH formation. Although the level of MPP+-induced dopamine (DA) and 2,3-DHBA formation after [K+]o (70 mM) treatment increased, [K+]o failed to increase either the level of MPP+-induced DA and 2,3-DHBA in the reserpinized group. When iron (II) was administered to [K+]o (70 mM)-pretreated rats, iron (II) clearly produced a dose-dependent increase in the level of 2,3-DHBA, as compared with MPP+-only treated rats. However, in the presence of histidine (25 mM), the effect of [K+]o was abolished. These results indicated that histidine may reduce the [K+]o-induced depolarization enhanced *OH formation by the action of MPP+ in the rat striatum.

Evidence for existence of immobilization stress-inducible semicarbazide-sensitive amine oxidase inhibitor in rat brain cytosol

An endogenous inhibitor of semicarbazide-sensitive amine oxidase (SSAO) was separated by gel filtration from 105000xg supernate in rat brain cytosol following immobilization stress (IMMO). The molecular weight of this inhibitor was estimated to be 500-700 by gel filtration. This inhibitor was proved to be heat-stable resistant to protease treatment. These results suggest that this inhibitor is induced by IMMO. SSAO activity in rat brain might be regulated by the level of this inhibitor.

Growth hormone therapy in achondroplasia

Achondroplasia is one of the most common causes of severe rhizomelic dwarfism. We have previously reported the growth-promoting effect of growth hormone (GH) in this disorder. In this expanded clinical study, dose dependency and the long-term effect of GH were also investigated. Prepubertal children with achondroplasia (82 males and 63 females) were randomly divided into 2 groups. Patients were treated with 0.5 IU/kg per week or 1.0 IU/kg per week subcutaneous recombinant human GH. Of 75 patients, the mutational analysis of fibroblast growth factor receptor-3 revealed that G1138A was detected in 70 and G1138C was found in 2. GH increased growth rate and height z score in a dose-dependent manner. GH also increased serum insulin-like growth factor (IGF)-I, IGF-binding protein-3 and osteocalcin. No adverse effects were observed in either group. We conclude that GH therapy is a useful method for improvement of severe growth retardation of achondroplasia.

Primary non-Hodgkin's lymphoma of the mandible treated with radiotherapy, chemotherapy, and autologous peripheral blood stem cell transplantation

Extranodal presentation in non-Hodgkin's lymphoma (NHL) is uncommon, and the mandible is very rarely involved. Primary NHL of the mandible, for the most part, has intermediate or high malignancy and has a much greater incidence of local recurrence compared with other sites of involvement. A 48-year-old Japanese man with NHL of the mandible received radiotherapy, followed by high-dose chemotherapy supported with peripheral blood stem cell transplantation (PBSCT). High-dose cyclophosphamide, Adriamycin, and vincristine were used for pretransplant conditioning. He achieved complete remission and has survived in continuous complete remission for more than 72 months to date. Marrow-ablative chemotherapy facilitated by PBSCT is thought to be useful as part of the primary therapy for patients with NHL who have poorer prognoses.

Expression of the zinc finger gene fez-like in zebrafish forebrain

Anterior-posterior (A-P) patterning in the neuroectoderm is established during gastrulation in zebrafish and amphibians. We isolated a novel zinc-finger gene fez-like (fezl) from zebrafish, which displays sequence similarities to Xenopus Fez. The fezl transcripts were detected in the anterior edge of neuroectoderm, the prospective dorsal forebrain, from the late gastrula (80% epiboly stage) to the mid-segmentation period. fezl was also expressed in the ventral forebrain overlying the prechordal plate at these stages. The expression of fezl was enhanced in embryos expressing the Wnt inhibitor Dkk1 and reduced in embryos expressing Wnt8b. The expression in the ventral forebrain was eliminated in the one-eyed pinhead mutant and the antivin RNA-injected embryos, which lack the prechordal plate. Radiation hybrid mapping revealed that the fezl gene is localized to linkage group 11.

Styrene inhibits monoamine oxidase A, but not monoamine oxidase B in monkey brain mitochondria

The effects of styrene on mitochondrial monoamine oxidase (MAO) activity in rat and monkey brains were compared in vitro. After preincubation at 25 degrees C for 20 min with 1 mM styrene monomer MAO-A activity in monkey brain was inhibited potently using 5-HT (for MAO-A substrate), but MAO-B activity in monkey brain and platelets were slightly inhibited using beta-PEA (for MAO-B substrate). Styrene monomer also competitively inhibited MAO-A activity in a dose-dependent manner. MAO-A in monkey brain was inhibited by styrene in ascending order of potency: styrene trimer>styrene dimer>styrene monomer. In contrast styrene monomer slightly inhibited both MAO-A and MAO-B activities in rat brain mitochondria. In the present study styrene monomer potently inhibits MAO-A activity, but not MAO-B activity, in monkey brain mitochondria in vitro. These results indicate the inhibiting action of styrene differs depending on animal species and MAO isoforms.

Methamphetamine enhances 1-methyl-4-phenylpyridinium ion-induced hydroxyl radical generation in the rat striatum

We determined the methamphetamine (MA), a potent dopamine (DA) releaser, enhances 1-methyl-4-phenylpyridinium ion (MPP(+))-induced hydroxyl radical (&z.rad;OH) generation in the rat striatum. Rats were anesthetized, and sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was infused through a microdialysis probe to detect the generation of .OH as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. After administration of MA (5 mg/kg i.v., every 2 h, four times), MA drastically increased DA release and the &z.rad;OH formation. When iron (II) was administered to the MA-treated animals, a marked elevation of DHBA was observed, compared with MPP(+)-only treated animals, that showed a positive linear correlation between DA and .OH formation trapped as DHBA (R(2)=0.985) in the dialysate. These results suggest that MA enhances the &z.rad;OH products of efflux/oxidation due to MPP(+).

Day/night variation of 5-hydroxyindole acetic acid concentration in rat cerebrospinal fluid after acute and long-term administration of a selective serotonin reuptake inhibitor, fluvoxamine

When 30 mg/kg, p.o. of fluvoxamine, a selective serotonin reuptake inhibitor, was administered, significant increases of 3-methoxy-4-hydroxyphenylglycol (MHPG) and 5-hydroxy indole-3-acetic acid (5-HIAA) contents in rat cerebrospinal fluid (CSF) were observed from two days after administration of fluvoxamine in both the light and dark periods and in the dark period of the light/dark cycle, respectively. In long-term treatment with 15 mg/kg, p.o. of fluvoxamine, the level of MHPG in CSF exhibited no difference, whereas the levels of 5-HIAA showed a significant increase during the light periods. These results suggest that fluvoxamine enhances the 5-HT system, but only with long-term treatment.

Block of cardiac ATP-sensitive K(+) channels reduces hydroxyl radicals in the rat myocardium

The present study examined whether opening of an ATP-sensitive K(+) (K(ATP)) channel can induce hydroxyl free radical ((*)OH) generation in the rat myocardium. Sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was infused directly through a microdialysis probe to detect the generation of (*)OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA). Induction of cromakalim (100 microM), a K(ATP) channel opener, through the microdialysis probe significantly increased the level of 2,3-DHBA. Another K(ATP) channel opener, nicorandil, also increased the level of 2,3-DHBA. When iron(II) was administered to cromakalim-pretreated animals, a marked elevation of DHBA was observed, compared with iron(II) only-treated animals. A positive linear correlation between iron(II) and formation of (*)OH, trapped as DHBA in the dialysate, was shown (r(2) = 0.988). When corresponding experiments were performed with nicorandil-treated animals, a positive linear correlation between iron(II) and DHBA in the dialysate was shown (r(2) = 0.988). However, the presence of glibenclamide (1-50 microM) decreased the cromakalim-induced 2,3-DHBA formation in a concentration-dependent manner (IC(50) = 9.1 microM). 5-Hydroxydecanoate (5-HD; 100 microM), another K(ATP) channel antagonist, also decreased cromakalim-induced (*)OH formation. The IC(50) value for 5-HD against cromakalim-evoked increase in 2,3-DHBA was 107.2 microM. In the presence of glibenclamide (10 microM), the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery (LAD). When the heart was reperfused, the normal elevation of 2,3-DHBA in the heart dialysate was not observed in animals pretreated with glibenclamide (10 microM). When corresponding experiments were performed with 5-HD (100 microM) pretreated animals, the same results were obtained. These results suggest that opening of cardiac K(ATP) channels may cause (*)OH generation.

Inhibition of monkey brain semicarbazide-sensitive amine oxidase by various antidepressants

We examined whether the antidepressant drugs, such as the dicyclic drug zimeldine, the tricyclic drug imipramine, tetracyclic drug maprotiline, and the non-cyclic drug nomifensine, inhibit in vitro semicarbazide-sensitive amine oxidase (SSAO) activity in monkey brain. The deamination of 1 microM benzylamine was not inhibited at high concentrations of clorgyline or deprenyl, while it was highly sensitive for semicarbazide. When corresponding experiments were performed with 100 microM benzylamine, the opposite results were obtained. The most potent of inhibition of SSAO was observed by imipramine, followed by maprotiline, zimeldine and nomifensine. Inhibition of SSAO was not enhanced by varying the time of preincubation of the enzyme and various antidepressant drugs, indicating direct action on and reversible inhibition of SSAO. We found the tricyclic antidepressant drug to be the most selective inhibitors of SSAO activity in monkey brain, as compared with other type of antidepressant drugs.

Novel mix-family homeobox genes in zebrafish and their differential regulation

We report the isolation of two novel zebrafish mix-type homeobox genes, mtx1 and mtx2. The homeodomains of both Mtx1 and Mtx2 exhibited a 50% amino acid identity to other Mix-family protein homeodomains. mtx1 was expressed throughout the yolk syncytial layer (YSL), an extraembryonic structure in teleosts, from the late-blastula to the mid-gastrula period. mtx2 was first expressed in the dorsal blastomeres soon after the mid-blastula transition, and slightly later in the entire blastoderm margin. After the late blastula period, mtx2 transcripts were detected in the YSL, and they were restricted to the dorsal YSL by the early gastrula period. The expression of mtx2 was dependent on Wnt signals but not on Nodal signals. mtx1 expression was not regulated by either Wnt or Nodal signals. This is in complete contrast to the Nodal signal-dependent expression of mixer. These results indicate the complexity of the regulation of mix-type homeobox genes.

An increase of the native interstitial adenosine concentration during histidine application

We examined whether histidine can increase the production of interstitial adenosine via noradrenaline (NA) release-mediated activation of ecto-5'-nucleotidase in the ventricular myocardium, with use of microdialysis techniques in in situ rat hearts. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rat hearts and the tissue was perfused with Tyrode's solution containing adenosine 5'-monophosphate (AMP) through the dialysis probe at a rate of 1.0 microl/min. Adenosine in the dialysate collected during perfusion with Tyrode's solution containing 100 microM AMP (through the probe) originated from the hydrolysis of AMP catalyzed by endogenous ecto-5'-nucleotidase, so that the level of adenosine reflected the activity of ecto-5'-nucleotidase in this tissue. In the presence of NA (10 microM), histidine, a scavenger of highly active singlet oxygen (1O2), significantly increased concentration of adenosine. Histidine (5-50 mM) increased the level of AMP-primed dialysate adenosine in a concentration-dependent manner. When histidine (25 mM) was infused to rat myocardium, small increase in the levels of adenosine were observed. However, when corresponding experiments were performed with NA (10 microM)-pretreated animals, a marked elevation of the level of adenosine in rat heart dialysate was obtained. To confirm the possible mechanism of interaction between 1O2 and NA, we examined the effect of histidine in ischemic-reperfused rat hearts. In the presence of histidine (25 mM), a marked elevation of NA and adenosine was observed. However, when corresponding experiments were performed with reserpinized rat hearts, the elevation of both NA and adenosine was not observed in ischemia-reperfused rat hearts. These results indicate that histidine increases interstitial adenosine concentration via NA release-mediated activation of ecto-5'-nucleotidase.

Fluvastatin, a new inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, resists hydroxyl radical generation in the rat myocardium

The aim of this study was to determine whether fluvastatin, an inhibitor of low-density lipoprotein (LDL) oxidation, can resist Cu (II)-induced hydroxyl radical generation (*OH) in the extracellular fluid of rat myocardium. Rats were anaesthetized and sodium salicylate in Ringer's solution (0.5 nmol microL(-1) min(-1)) was infused through a microdialysis probe to detect the generation of *OH as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (2,3-DHBA) in the myocardium. When Cu (II) (0, 10, 25 or 50 microM) was administered to 1 mM tyramine-pretreated rats, a marked elevation in the levels of 2,3-DHBA was found, indicating a positive linear correlation between Cu (II) and the increase in *OH formation trapped as 2,3-DHBA in the dialysate (r2 = 0.977). In the presence of fluvastatin (100 microM), a marked decrease in the levels of 2,3-DHBA was found. Corresponding experiments performed with iron (II) (0, 10, 25 or 50 microM), showed a marked elevation in the levels of 2,3-DHBA, indicating a positive linear correlation between iron (II) and the increase in *OH formation trapped as 2,3-DHBA in the dialysate (r2 = 0.986). However, in the presence of fluvastatin (100 microM) a small decrease in the level of 2,3-DHBA was found. The results show that iron (II) against LDL oxidation may be insensitive compared with Cu (II). Cu (II)-induced *OH formation may be reduced by inhibiting LDL with fluvastatin.

Protective effect of fluvastatin, a new inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on MPP(+)-induced hydroxyl radical in the rat striatum

We examined whether fluvastatin, an inhibitor of low-density lipoprotein (LDL) oxidation, can resist 1-methyl-4-phenylpyridine (MPP(+))-induced hydroxyl radical generation (.OH) in the extracellular fluid of rat striatum. Rats were anesthetized and sodium salicylate in Ringer's solution (0.5 nmol/microliter/min) was infused through a microdialysis probe to detect the generation of.OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the striatum. MPP(+) (5 mM; total dose 75 nmol) clearly produced an increase in.OH formation. However, fluvastatin (100 microM) reduced the.OH formation by the action of MPP(+). These results indicated that fluvastatin, a potent inhibitor of LDL oxidation, may resist the formation of.OH products of MPP(+).

Reserpine attenuates interstitial adenosine-mediated activation of ecto-5'-nucleotidase in rat hearts in vivo

We examined whether reserpine-induced norepinephrine (NE) depletion attenuated the products of adenosine in rat heart. A flexibly mounted microdialysis technique was used to measure the concentration of interstitial adenosine and to assess the activity of ecto-5'-nucleotidase in rat hearts in situ. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and perfused with Tyrode solution containing adenosine 5'-monophosphate (AMP) at rate of 1.0 microliter/min. The baseline level of dialysate adenosine was 0.51 +/- 0.09 microM. The introduction of AMP (100 microM) through the probe increased markedly the dialysate adenosine to 8.95 +/- 0.86 microM, and this increase was inhibited by ecto-5'-nucleotidase inhibitor, alpha, beta-methyleneadenosine 5'-diphosphate (AOPCP, 100 microM), to 0.66 +/- 0.38 microM. Thus, the level of dialysate adenosine is a measure of the ecto-5'-nucleotidase activity in the tissue in situ. AMP concentration for the half-maximal effect of adenosine release (EC(50)) was 107.3 microM. The maximum attainable concentration of dialysate adenosine (E(max)) by AMP was 21.1 microM. However, the EC(50) and E(max) values with reserpinized animals were 106.9 and 7.1 microM, respectively. Electrical stimulation of the left stellate ganglion increased significantly dialysate adenosine concentration, from the control level of 8.66 +/- 0.96 microM to 12.38 +/- 1.11 microM. After stimulation, dialysate adenosine returned to near the prestimulation level. When corresponding experiments were performed with reserpinized animals, the effect of electrical stimulation was abolished. Tyramine (endogenous catecholamine trigger) increased the adenosine concentration in a concentration-dependent manner. However, the elevation of adenosine concentration with reserpinized animals was not observed. These results suggest that reserpine attenuates NE-induced adenosine via stimulation of alpha(1)-adrenoceptor and protein kinase C mediated activation of ecto-5'-nucleotidase in rat heart.

Cooperative roles of Bozozok/Dharma and Nodal-related proteins in the formation of the dorsal organizer in zebrafish

In vertebrates, specification of the dorso-ventral axis requires Wnt signaling, which leads to formation of the Nieuwkoop center and the Spemann organizer (dorsal organizer), through the nuclear accumulation of beta-catenin. Zebrafish bozozok/dharma (boz) and squint (sqt), which encode a homeodomain protein and a Nodal-related protein, respectively, are required for the formation of the dorsal organizer. The zygotic expression of boz and sqt in the dorsal blastoderm and dorsal yolk syncytial layer (YSL) was dependent on the maternally derived Wnt signal, and their expression at the late blastula and early gastrula stages was dependent on the zygotic expression of their own genes. The dorsal organizer genes, goosecoid (gsc) and chordin (din), were ectopically expressed in wild-type embryos injected with boz or sqt RNA. The expression of gsc strictly depended on both boz and sqt while the expression of din strongly depended on boz but only partially depended on sqt and cyclops (cyc, another nodal-related gene). Overexpression of boz in embryos defective in Nodal signaling elicited the ectopic expression of din but not gsc and resulted in dorsalization, implying that boz could induce part of the organizer, independent of the Nodal proteins. Furthermore, boz; sqt and boz;cyc double mutants displayed a severely ventralized phenotype with anterior truncation, compared with the single mutants, and boz;sqt;cyc triple mutant embryos exhibited an even more severe phenotype, lacking the anterior neuroectoderm and notochord, suggesting that Boz/Dharma and the Nodal-related proteins cooperatively regulate the formation of the dorsal organizer.

Conformational behavior of C alpha,alpha-diphenyl glycine: extended conformation in tripeptides containing consecutive D phi G residues

Recent studies on the conformational preferences of the Dphig (C(alpha,alpha)-diphenylglycine) residue showed that this C(alpha,alpha)-disubstituted glycine has a structural versatility. In fact, depending on the nature of the following or preceding residue, Dphig can assume either folded or extended conformations. We have carried out the analysis of the conformational preferences of the Dphig residue in tripeptides containing consecutive Dphig residues. The crystal structures of Z-Dphig-Dphig -Dphig-OMe (a; Z = benzyloxycarbonyl; OMe = methyl ester), Z-Aib-Dphig-Dphig-OMe (b; Aib = alpha-aminoisobutyric acid), and Z-Ac(3)c-Dphig-Dphig-OMe (c; Ac(3)c = alpha-amino-cyclopropan carboxylic acid), are here reported. The Dphig residues adopt the fully extended conformation in the three tripeptides examined. Together with our previous findings on Dphig containing peptides, the structures of the peptides here examined, indicate that the presence of adjacent Dphig residue in the sequence further stabilizes the extended conformation.