Correction of the sterility defect in homozygous obese female mice by treatment with the human recombinant leptin

The sterility of male and female homozygous ob/ob mice is a recognized feature of the ob mutation (1). Whereas ob/ob males can occasionally reproduce if maintained on a restricted diet, ob/ob females are always sterile (2). Thinning of the ob/ob females to normal weight by diet-restriction failed to correct their sterility. Early sexual development is normal in ob/ob females; however, ovulation never follows and the mice remain prepuberal indefinitely with no occurrence of oestrus cycles. Reproductive hormones are reduced in ob/ob females (3) demonstrating a functional defect from the hypothalamic-pituitary axis (4-6). The ovaries of ob/ob females are capable of producing viable eggs when transplanted into lean female recipients (7). Reconstitution of reproductive functions in the ob/ob female necessitates delivery of hypothalamic extracts to the third ventricle (8) and administration of pituitary extract (9), gonadotropic hormones (10), progesterone (11) and relaxin (12). These previous findings demonstrate that the sterility of ob/ob females is caused by an insufficiency of hormones at the hypothalamic-pituitary level rather than physical hindrance of copulatory activity, pregnancy and parturition caused by excess adipose tissue. We show here that repeated administration of only the recombinant human ob protein, leptin, into homozygous female ob/ob mice can correct their sterility, thus resulting in ovulation, pregnancy and parturition.

NRF2, a member of the NFE2 family of transcription factors, is not essential for murine erythropoiesis, growth, and development

The locus control region of the beta-globin gene is composed of four erythroid-specific hypersensitive sites. Hypersensitive site 2 has been shown to be a powerful enhancer and contains a tandem repeat sequence for the transcription factors AP1 and NFE2 (activating protein 1 and nuclear factor erythroid 2, respectively). The human NRF2 (NFE2 related factor 2) has been isolated by bacterial expression screening using this core sequence as a probe. p45-NFE2, NRF1, and NRF2 belong to the CNC ("cap 'n' collar") subfamily of the basic region-leucine zipper transcription factors, which exhibits strong homology at specific regions such as the "CNC" and the DNA binding and leucine zipper domains. Although the erythroid-specific p45-NFE2 has been implicated in globin gene regulation, p45-NFE2 null mice succumb to bleedings due to lack of platelets and those that survive exhibit only a mild anemia. To determine the function of NRF2, which we found to be widely expressed in vivo, we have characterized the genomic structure of the mouse NRF2 gene, disrupted the Nrf2 gene by homologous recombination in mouse embryonic stem cells (ES cells), and generated NRF2-/- mice. Homozygous mutant mice developed normally, were not anemic, reached adulthood, and reproduced. Our studies indicate that NRF2 is dispensable for mouse development.

Early onset of reproductive function in normal female mice treated with leptin

Numerous studies have revealed an association between nutritional status, adiposity, and reproductive maturity. The role of leptin, a hormone secreted from adipose tissue, in the onset of reproductive function was investigated. Normal prepubertal female mice injected with leptin grew at a slower rate than controls as a result of the hormone's thinning effects, but they reproduced up to 9 days earlier than controls and showed earlier maturation of the reproductive tract. These results suggest that leptin acts as a signal triggering puberty, thus supporting the hypothesis that fat accumulation enhances maturation of the reproductive tract.

Animal virus replication and RNAi-mediated antiviral silencing in Caenorhabditis elegans

The worm Caenorhabditis elegans is a model system for studying many aspects of biology, including host responses to bacterial pathogens, but it is not known to support replication of any virus. Plants and insects encode multiple Dicer enzymes that recognize distinct precursors of small RNAs and may act cooperatively. However, it is not known whether the single Dicer of worms and mammals is able to initiate the small RNA-guided RNA interference (RNAi) antiviral immunity as occurs in plants and insects. Here we show complete replication of the Flock house virus (FHV) bipartite, plus-strand RNA genome in C. elegans. We show that FHV replication in C. elegans triggers potent antiviral silencing that requires RDE-1, an Argonaute protein essential for RNAi mediated by small interfering RNAs (siRNAs) but not by microRNAs. This immunity system is capable of rapid virus clearance in the absence of FHV B2 protein, which acts as a broad-spectrum RNAi inhibitor upstream of rde-1 by targeting the siRNA precursor. This work establishes a C. elegans model for genetic studies of animal virus-host interactions and indicates that mammals might use a siRNA pathway as an antiviral response.

Identification and characterization of a prostaglandin transporter

Carrier-mediated prostaglandin transport has been postulated to occur in many tissues. On the basis of sequence homology, the protein of unknown function encoded by the rat matrin F/G complementary DNA was predicted to be an organic anion transporter. Expression of the matrin F/G complementary DNA in HeLa cells or Xenopus oocytes conferred the property of specific transport of prostaglandins. The tissue distribution of matrin F/G messenger RNA and the sensitivity of matrin F/G-induced prostaglandin transport to inhibitors were similar to those of endogenous prostaglandin transport. The protein encoded by the matrin F/G complementary DNA is thus preferably called PGT because it is likely to function as a prostaglandin transporter.

Characterization of multiple-antimicrobial-resistant salmonella serovars isolated from retail meats

A total of 133 Salmonella isolates recovered from retail meats purchased in the United States and the People's Republic of China were assayed for antimicrobial susceptibility, the presence of integrons and antimicrobial resistance genes, and horizontal transfer of characterized antimicrobial resistance determinants via conjugation. Seventy-three (82%) of these Salmonella isolates were resistant to at least one antimicrobial agent. Resistance to the following antibiotics was common among the United States isolates: tetracycline (68% of the isolates were resistant), streptomycin (61%), sulfamethoxazole (42%), and ampicillin (29%). Eight Salmonella isolates (6%) were resistant to ceftriaxone. Fourteen isolates (11%) from the People's Republic of China were resistant to nalidixic acid and displayed decreased susceptibility to ciprofloxacin. A total of 19 different antimicrobial resistance genes were identified in 30 multidrug-resistant Salmonella isolates. The bla(CMY-2) gene, encoding a class A AmpC beta-lactamase, was detected in all 10 Salmonella isolates resistant to extended-spectrum beta-lactams. Resistance to ampicillin was most often associated with a TEM-1 family beta-lactamase gene. Six aminoglycoside resistance genes, aadA1, aadA2, aacC2, Kn, aph(3)-IIa, and aac(3)-IVa, were commonly present in the Salmonella isolates. Sixteen (54%) of 30 Salmonella isolates tested had integrons ranging in size from 0.75 to 2.7 kb. Conjugation studies demonstrated that there was plasmid-mediated transfer of genes encoding CMY-2 and TEM-1-like beta-lactamases. These data indicate that Salmonella isolates recovered from retail raw meats are commonly resistant to multiple antimicrobials, including those used for treating salmonellosis, such as ceftriaxone. Genes conferring antimicrobial resistance in Salmonella are often carried on integrons and plasmids and could be transmitted through conjugation. These mobile DNA elements have likely played an important role in transmission and dissemination of antimicrobial resistance determinants among Salmonella strains.

Resveratrol, a natural product derived from grape, exhibits antiestrogenic activity and inhibits the growth of human breast cancer cells

Resveratrol is a natural phytoalexin compound found in grapes and other food products. In this study, the effect of resveratrol on the growth of human breast cancer cells was examined. Results show that resveratrol inhibits the growth of estrogen receptor(ER)-positive MCF-7 cells in a dose-dependent fashion. Detailed studies with MCF-7 cells demonstrate that resveratrol antagonized the growth-promoting effect of 17-beta-estradiol (E2) in a dose-dependent fashion at both the cellular (cell growth) and the molecular (gene activation) levels. At 5 x 10(-6) M, resveratrol abolished the growth-stimulatory effect mediated by concentrations of E2 up to 10(-9) M. The antiestrogenic effect of resveratrol could be observed at a concentration of 10(-6) M and above. The antiestrogenic effect of resveratrol was also demonstrated at the molecular level. Resveratrol in a dose-dependent fashion antagonized the stimulation by E2 of progesterone receptor gene expression in MCF-7 cells. Moreover, expression of transforming growth factor-alpha and insulin-like growth factor I receptor mRNA was inhibited while the expression of transforming growth factor beta2 mRNA was significantly elevated in MCF-7 cells cultivated in the presence of resveratrol (10(-5) M). In summary, our results show that resveratrol, a partial ER agonist itself, acts as an ER antagonist in the presence of estrogen leading to inhibition of human breast cancer cells.

A mammalian DNA repair enzyme that excises oxidatively damaged guanines maps to a locus frequently lost in lung cancer

BACKGROUND

Guanine residues in the genome are vulnerable to attack by free radicals and reactive oxygen species. A major lesion thus produced, 8-oxoguanine (OG), causes mutations by mis-pairing with adenine during replication. In bacteria and budding yeast, OG is removed from the genome through the action of base-excision DNA repair (BER) enzymes, which catalyze expulsion of the aberrant base and excision of its sugar moiety from the DNA backbone. Although OG is known to be produced in and cleansed from mammalian genomes, the enzymes responsible for OG repair in these cells have remained elusive.

RESULTS

Here, we report the cloning and biochemical characterization of mammalian BER enzymes that specifically target OG residues in DNA. These 8-oxoguanine DNA glycosylases, hOgg1 (human) and mOgg1 (murine), are homologous to each other and to yeast Ogg1. They also contain an active site motif - the Helix-hairpin-Helix, Gly/Pro-rich-Asp motif - characteristic of a superfamily of BER proteins with a similar core fold and active site geometry. Both hOgg1 and mOgg1 exhibit exquisite selectivity for the base opposite OG in DNA, operating with high efficiency only on OG base-paired to cytosine. Furthermore, hOgg1 and mOgg1 are unable to process a panel of alternative lesions, including 8-oxoadenine, yet bind with high affinity to synthetic abasic site analogs. The proteins operate through a classical glycosylase/lyase catalytic mechanism; mutation of a catalytically essential lysine residue results in loss of catalytic potency but retention of binding to OG-containing oligonucleotides. The hOGG1 gene is localized on the short arm of chromosome 3 (3p25/26) in a region commonly deleted in cancers.

CONCLUSIONS

These results conclusively establish the existence and identity of an 8-oxoguanine DNA glycosylase/lyase in human and murine cells, completing the triad of proteins that together protect mammals from the genotoxic effects of guanine oxidation. The observation that at least one allele of hOGG1 is commonly deleted in cancer cells suggests that such cells may possess a reduced capacity to counter the mutagenic effects of reactive oxygen species, a deficiency that could increase their overall genomic instability. This speculation is fueled by recent observations that cells constitutively active for the Ras/Raf pathway constitutively produce high levels of superoxide, a known generator of OG.

Leptin treatment rescues the sterility of genetically obese ob/ob males

Leptin, a hormone secreted from white adipose tissue, has been shown to normalize the body weight of ob/ob but not db/db mice as postulated by Coleman in his classical parabiosis experiments. The major effect of leptin is therefore to decrease food intake, thus resulting in a breakdown of fat stores. Recently, we have suggested that leptin plays a role in reproductive physiology based on the observation that leptin treatment but not food restriction rescues the sterility of ob/ob females. In the present communication, we treated sterile ob/ob males with leptin and asked whether fertility could be induced, thus selecting their reproductive ability as the endpoint of the experiment. Our results show that all food-restricted ob/ob males are unable to impregnate normal C57BL/6J females. However, all leptin-treated ob/ob males fertilized normal females mice that carried out normal pregnancies and deliveries, demonstrating that the reproductive capacity of ob/ob males was corrected only with leptin treatment. Furthermore, reproductive indices such as testicular weight and histology are normalized in leptin-treated animals. Therefore, as in ob/ob females, leptin plays a significant role in the male mouse reproductive pathways.

Targeted disruption of the ubiquitous CNC-bZIP transcription factor, Nrf-1, results in anemia and embryonic lethality in mice

The CNC-basic leucine zipper (CNC-bZIP) family is a subfamily of bZIP proteins identified from independent searches for factors that bind the AP-1-like cis-elements in the beta-globin locus control region. Three members, p45-Nf-e2, Nrf-1 and Nrf-2 have been identified in mammals. Expression of p45-Nf-e2 is largely restricted to hematopoietic cells while Nrf-1 and Nrf-2 are expressed in a wide range of tissues. To determine the function of Nrf-1, targeted disruption of the Nrf-1 gene was carried out. Homozygous Nrf-1 mutant mice are anemic due to a non-cell autonomous defect in definitive erythropoiesis and die in utero.

Cloning, in vitro expression, and tissue distribution of a human prostaglandin transporter cDNA(hPGT)

We recently identified a cDNA in the rat that encodes a broadly expressed PG transporter (PGT). Because PGs play diverse and important roles in human health and disease, we cloned human PGT (hPGT) from an adult human kidney cDNA library. A consensus sequence (4.0 kb) derived from several clones, plus 3' polymerase chain reaction amplification, exhibited 74% nucleic acid identity and 82% amino acid identity compared to rat PGT. When transiently expressed in HeLa cells, a full-length clone catalyzed the transport of PGE1, PGE2, PGD2, PGF2alpha, and, to a lesser degree, TXB2. Northern blotting revealed mRNA transcripts of many different sizes in adult human heart, placenta, brain, lung, liver, skeletal muscle, pancreas, kidney, spleen, prostate, ovary, small intestine, and colon. hPGT mRNAs are also strongly expressed in human fetal brain, lung, liver, and kidney. The broad tissue distribution and substrate profile of hPGT suggest a role in the transport and/or metabolic clearance of PGs in diverse human tissues.

Functional Organogel Based on a Salicylideneaniline Derivative with Enhanced Fluorescence Emission and Photochromism

A new organogelator based on a salicylideneaniline derivative with cholesterol moieties was synthesized, and it was proposed that it could gelate various organic solvents, such as 1-butanol, 1-octanol, butyl acetate, tetrachloromethane, benzene, toluene through combination with a gelation test. From the results of analysis by UV/Vis absorption, circular dichroism (CD), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies and semiempirical (AM1) calculations, we believed that the gelator molecules could self-assemble into left-handed helical nanofibers through unimolecular layer packing, which further twisted into the thicker fibers and constructed 3D networks in the gel phase. Interestingly, the organogel exhibited strong fluorescence enhancement relative to a solution of the same concentration because of the formation of J aggregations. Meanwhile, photochromism of the organogel could take place under UV-light irradiation. Both strong fluorescence emission and photochromism properties were concurrent in one system based on a salicylideneaniline derivative. It was suggested that the self-assembly of the functional organogelator could lead to unique photophysical properties.

Luman, a new member of the CREB/ATF family, binds to herpes simplex virus VP16-associated host cellular factor

The human host cell factor (HCF) is expressed in a variety of adult and fetal tissues, and its gene is conserved in animals as diverse as mammals and insects. However, its only known function is to stabilize the herpes simplex virus virion transactivator VP16 in a complex with the cellular POU domain protein Oct-1 and cis-acting regulatory elements in promoters of immediate-early viral genes. To identify a cellular function for HCF, we used the yeast two-hybrid system to identify a cellular ligand for HCF. This protein, Luman, appears to be a cyclic AMP response element (CRE)-binding protein/activating transcription factor 1 protein of the basic leucine zipper superfamily. It binds CREs in vitro and activates CRE-containing promoters when transfected into COS7 cells. This activation of transcription was synergistically enhanced by the presence of CCAAT/enhancer-binding protein elements and inhibited by AP-1 elements in the promoter. In addition to a basic DNA binding domain, Luman possesses an unusually long leucine zipper and an acidic amino-terminal activation domain. These features in Luman are also present in what appear to be homologs in the mouse, Drosophila melanogaster, and Caenorhabditis elegans. Luman and VP16 appear to have similar mechanisms for binding HCF, as in vitro each competitively inhibited the binding of the other to HCF. In transfected cells, however, while VP16 strongly inhibited the ability of GAL-Luman to activate transcription from a GAL4 upstream activation sequence-containing promoter, Luman was unable to inhibit the activity of GAL-VP16. Luman appears to be a ubiquitous transcription factor, and its mRNA was detected in all human adult and fetal tissues examined. The possible role of HCF in regulating the function of this ubiquitous transcription factor is discussed.

Zonula occludens toxin structure-function analysis. Identification of the fragment biologically active on tight junctions and of the zonulin receptor binding domain

Zonula occludens toxin (Zot) is an enterotoxin elaborated by Vibrio cholerae that increases intestinal permeability by interacting with a mammalian cell receptor with subsequent activation of intracellular signaling leading to the disassembly of the intercellular tight junctions. Zot localizes in the bacterial outer membrane of V. cholerae with subsequent cleavage and secretion of a carboxyl-terminal fragment in the host intestinal milieu. To identify the Zot domain(s) directly involved in the protein permeating effect, several zot gene deletion mutants were constructed and tested for their biological activity in the Ussing chamber assay and their ability to bind to the target receptor on intestinal epithelial cell cultures. The Zot biologically active domain was localized toward the carboxyl terminus of the protein and coincided with the predicted cleavage product generated by V. cholerae. This domain shared a putative receptor-binding motif with zonulin, the Zot mammalian analogue involved in tight junction modulation. Amino acid comparison between the Zot active fragment and zonulin, combined with site-directed mutagenesis experiments, confirmed the presence of an octapeptide receptor-binding domain toward the amino terminus of the processed Zot.

Neutrophil differentiation into a unique hybrid population exhibiting dual phenotype and functionality of neutrophils and dendritic cells

Neutrophils have been reported to acquire surface expression of MHC class II and co-stimulatory molecules as well as T-cell stimulatory activities when cultured with selected cytokines. However, cellular identity of those unusual neutrophils showing antigen presenting cell (APC)-like features still remains elusive. Here we show that both immature and mature neutrophils purified from mouse bone marrow differentiate into a previously unrecognized "hybrid" population showing dual properties of both neutrophils and dendritic cells (DCs) when cultured with granulocyte macrophage-colony-stimulating factor but not with other tested growth factors. The resulting hybrid cells express markers of both neutrophils (Ly6G, CXCR2, and 7/4) and DCs (CD11c, MHC II, CD80, and CD86). They also exhibit several properties typically reserved for DCs, including dendritic morphology, probing motion, podosome formation, production of interleukin-12 and other cytokines, and presentation of various forms of foreign protein antigens to naïve CD4 T cells. Importantly, they retain intrinsic abilities of neutrophils to capture exogenous material, extrude neutrophil extracellular traps, and kill bacteria via cathelicidin production. Not only do our results reinforce the notion that neutrophils can acquire APC-like properties, they also unveil a unique differentiation pathway of neutrophils into neutrophil-DC hybrids that can participate in both innate and adaptive immune responses.

The critical active-site amine of the human 8-oxoguanine DNA glycosylase, hOgg1: direct identification, ablation and chemical reconstitution

BACKGROUND

Base-excision DNA repair (BER) is the principal pathway responsible for the removal of aberrant, genotoxic bases from the genome and restoration of the original sequence. Key components of the BER pathway are DNA glycosylases, enzymes that recognize aberrant bases in the genome and catalyze their expulsion. One major class of such enzymes, glycosylase/lyases, also catalyze scission of the DNA backbone following base expulsion. Recent studies indicate that the glycosylase and lyase functions of these enzymes are mechanistically unified through a common amine-bearing residue on the enzyme, which acts as both the electrophile that displaces the aberrant base and an electron sink that facilitates DNA strand scission through imine (Schiff base)/conjugate elimination chemistry. The identity of this critical amine-bearing residue has not been rigorously established for any member of a superfamily of BER glycosylase/lyases.

RESULTS

Here, we report the identification of the active-site amine of the human 8-oxoguanine DNA glycosylase (hOgg1), a human BER superfamily protein that repairs the mutagenic 8-oxoguanine lesion in DNA. We employed Edman sequencing of an active-site peptide irreversibly linked to substrate DNA to identify directly the active-site amine of hOgg1 as the epsilon-NH2 group of Lys249. In addition, we observed that the repair-inactive but recognition-competent Cys249 mutant (Lys249-->Cys) of hOgg1 can be functionally rescued by alkylation with 2-bromoethylamine, which functionally replaces the lysine residue by generating a gamma-thia-lysine.

CONCLUSIONS

This study provides the first direct identification of the active-site amine for any DNA glycosylase/lyase belonging to the BER superfamily, members of which are characterized by the presence of a helix-hairpin-helix-Gly/Pro-Asp active-site motif. The critical lysine residue identified here is conserved in all members of the BER superfamily that exhibit robust glycosylase/lyase activity. The ability to trigger the catalytic activity of the Lys249-->Cys mutant of hOgg1 by treatment with the chemical inducer 2-bromoethylamine may permit snapshots to be taken of the enzyme acting on its substrate and could represent a novel strategy for conditional activation of catalysis by hOgg1 in cells.

Regulation of the promoter activity of interferon regulatory factor-7 gene. Activation by interferon snd silencing by hypermethylation

The molecular mechanism by which virus induces expression of the early inflammatory genes has not yet been completely elucidated. Previous studies indicated that the virus-mediated transcription of type I interferon (IFN) genes required activation of two members of IFN regulatory factor (IRF) family, IRF-3 and IRF-7, where the expression of IRF-7 was found to be indispensable for the induction of IFNA genes. To determine the factors that regulate expression of IRF-7 gene, as well as its inducibility by type I IFNs, we have isolated and characterized the promoter and first intron of the human IRF-7 gene. This region shows a presence of two potential interferon-sensitive response elements (ISRE/IRF-E). However, only the ISRE present in the first intron was functional and conferred interferon inducibility in a transient transfection assay. Using a pull-down assay with an oligodeoxynucleotide corresponding to this ISRE immobilized to magnetic beads, we have demonstrated that this ISRE binds ISGF3 complex and IRF-1 from the extract of IFN-treated cells but not from the untreated cells. We have further shown that the previously observed lack of expression of IRF-7 in 2fTGH fibrosarcoma cell line, correlated with hypermethylation of the CpG island in the human IRF-7 promoter. The repression of the promoter activity was relieved by treatment with DNA methyltransferase inhibitor 5-aza-deoxycytidine. In vitro methylation of IRF-7 promoter silenced IRF-7 directed expression of luciferase gene in HeLa cells that express endogenous IRF-7 gene. Whether silencing of IRF-7 by methylation is instrumental for the process of tumorigenesis remains to be determined.

Adeno-associated viral vector-mediated vascular endothelial growth factor gene transfer induces neovascular formation in ischemic heart

Vascular endothelial growth factor (VEGF) plays important roles in physiological and pathological angiogenesis. Recent studies have demonstrated that direct injection of VEGF protein, plasmid DNA, or an adenoviral vector encoding the VEGF gene into ischemic myocardium or limb can induce collateral blood vessel formation and improve perfusion of the ischemic areas. However, these approaches have limitations ranging from a short-lasting effect to angioma formation. In this study, we investigated the feasibility of using adeno-associated viral (AAV) vectors to deliver VEGF genes to mouse myocardium. A cytomegalovirus promoter was used to drive genes for a human VEGF isoform, VEGF(165), and LacZ. A mouse myocardial ischemic model was generated by ligation of the anterior descending coronary artery. Approximately 10(11) copies of the AAV-VEGF vector mixed with 10(10) copies of AAV-LacZ were injected to one site of normal myocardium and a total of 10(11) copies of AAV-VEGF were injected to multiple sites of myocardium around the ischemic region. LacZ gene expression was observed up to 3 months after the vector inoculation. After AAV-VEGF inoculation, neoangiogenesis was observed in the ischemic heart model but not in normal heart tissue. An inflammatory-cell infiltration was not observed in the AAV-VEGF- and AAV-LacZ-inoculated hearts, and angioma-like structure was not observed. These results indicated that injection of the AAV vector directly to myocardium could mediate efficient gene transfer and transgene expression and that VEGF gene delivered by AAV vector can induce angiogenesis in ischemic myocardium.

Luminescence switching of a persistent room-temperature phosphorescent pure organic molecule in response to external stimuli

A metal- and heavy atom-free nonplanar organic molecule with persistent RTP was successfully fabricated and exhibited a multicolour phosphorescence-to-fluorescence switching property in response to mechanical force stimuli.

Helical Stacking Tuned by Alkoxy Side Chains in π-Conjugated Triphenylbenzene Discotic Derivatives

We report on the synthesis and self-assembly of a new series of discotic molecules containing triphenylbenzene as the core and alkoxy side chain with varying length. It was found that compounds 3 a-c, 4 b and 5 b could form stable gels in several apolar solvents. Transmission electron microscopy (TEM) images revealed that their morphologies were very different for the different alkoxy-substituted organogels. In toluene or hexane, 3 b and 3 c resulted in both left- and right-handed helical fibers, whereas 3 a resulted in straight rigid fibers; 4 b and 5 b resulted in most straight fibers with a few twisted fibers. The results from FT-IR and UV/Vis absorption spectroscopy indicated that the hydrogen bonding and pi-pi interactions were the main driving forces for the formation of the self-assembled gels. Further detailed analysis of their aggregation modes were conducted by UV-visible absorption spectra and X-ray diffraction (XRD) measurements. Based on these findings, the influence of these peripheral alkoxy substituents on the gel formation and the aggregation mode were discussed. The special enhanced fluorescent emissions, which resulted from aggregation, were also found in the gel phase.

Olig bHLH proteins interact with homeodomain proteins to regulate cell fate acquisition in progenitors of the ventral neural tube

BACKGROUND

Organizing signals such as Sonic hedgehog are thought to specify neuronal subtype identity by regulating the expression of homeodomain proteins in progenitors of the embryonic neural tube. One of these, Nkx2.2, is necessary and sufficient for the development of V3 interneurons.

RESULTS

We report that Olig genes, encoding basic helix-loop-helix (bHLH) proteins, are expressed in a subset of Nkx2.2 progenitors before the establishment of interneurons and oligodendroglial precursors. Gain-of-function analysis in transgenic mouse embryos indicates that Olig genes specifically inhibit the establishment of Sim1-expressing V3 interneurons. Moreover, coexpression of Olig2 with Nkx2.2 in the chick neural tube generated cells expressing Sox10, a marker of oligodendroglial precursors. Colocalization of Olig and Nkx2.2 proteins at the dorsal extent of the Nkx2.2 expression domain is consistent with regulatory interactions that define the potential of progenitor cells in the border region.

CONCLUSIONS

Interactions between homeodomain and Olig bHLH proteins evidently regulate neural cell fate acquisition and diversification in the ventral neural tube. In particular, interactions between Olig and Nkx2.2 proteins inhibit V3 interneuron development and promote the formation of alternate cell types, including those expressing Sox10.

Synthesis and biological activity of highly potent octapeptide analogs of somatostatin

In the search for selective and long-acting analogs of somatostatin, nearly 200 compounds were synthesized by solid-phase methods, purified, and tested biologically. Among these octapeptides, some contained N-terminal (Formula: see text) were 177 times and 113 times more potent, respectively, than somatostatin in tests for inhibition of growth hormone release. These two octapeptides containing tyrosine and valine in positions 3 and 6, respectively, were more active and more selective than their Phe-3 and Thr-6 counterparts, D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH2 and D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Trp-NH2. D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH2 was also about 6 times more potent than its L-Trp-4 diastereoisomer. The analogs D-Phe-Cys-Tyr-Lys-Val-Cys-Thr-NH2 and D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2 showed a prolonged duration of action and were able to inhibit growth hormone release for at least 3 hr. Analogs of both Phe-3/Thr-6 and Tyr-3/Val-6 classes also suppressed the release of insulin and glucagon in rats and pentagastrin-induced secretion of gastric acid in dogs, but their potencies in these tests were much smaller than the growth-hormone-release inhibitory activity. Some of these analogs possessed antitumor activities as shown by the inhibition of growth of animal models of prostate, mammary, and ductal pancreatic tumors.