Id1 and Id3 are required for neurogenesis, angiogenesis and vascularization of tumour xenografts

Id proteins may control cell differentiation by interfering with DNA binding of transcription factors. Here we show that targeted disruption of the dominant negative helix-loop-helix proteins Id1 and Id3 in mice results in premature withdrawal of neuroblasts from the cell cycle and expression of neural-specific differentiation markers. The Id1-Id3 double knockout mice also display vascular malformations in the forebrain and an absence of branching and sprouting of blood vessels into the neuroectoderm. As angiogenesis both in the brain and in tumours requires invasion of avascular tissue by endothelial cells, we examined the Id knockout mice for their ability to support the growth of tumour xenografts. Three different tumours failed to grow and/or metastasize in Id1+/- Id3-/- mice, and any tumour growth present showed poor vascularization and extensive necrosis. Thus, the Id genes are required to maintain the timing of neuronal differentiation in the embryo and invasiveness of the vasculature. Because the Id genes are expressed at very low levels in adults, they make attractive new targets for anti-angiogenic drug design.

Rescue of embryonic lethality in Mdm4-null mice by loss of Trp53 suggests a nonoverlapping pathway with MDM2 to regulate p53

The p53 protein can inhibit cell cycling or induce apoptosis, and is thus a critical regulator of tumorigenesis. This protein is negatively regulated by a physical interaction with MDM2, an E3 ubiquitin ligase. This interaction is critical for cell viability; loss of Mdm2 causes cell death in vitro and in vivo in a p53-dependent manner. The recently discovered MDM2-related protein MDM4 (also known as MDMX) has some of the same properties as MDM2. MDM4 binds and inhibits p53 transcriptional activity in vitro. Unlike MDM2, however, MDM4 does not cause nuclear export or degradation of p53 (refs. 9,10). To study MDM4 function in vivo, we deleted Mdm4 in mice. Mdm4-null mice died at 7.5-8.5 dpc, owing to loss of cell proliferation and not induction of apoptosis. To assess the importance of p53 in the death of Mdm4-/- embryos, we crossed in the Trp53-null allele. The loss of Trp53 completely rescued the Mdm4-/- embryonic lethality. Thus, MDM2 and MDM4 are nonoverlapping critical regulators of p53 in vivo. These data define a new pathway of p53 regulation and raise the possibility that increased MDM4 levels and the resulting inactivation of p53 contribute to the development of human tumors.

Corin, a transmembrane cardiac serine protease, acts as a pro-atrial natriuretic peptide-converting enzyme

Atrial natriuretic peptide (ANP) is a cardiac hormone essential for the regulation of blood pressure. In cardiac myocytes, ANP is synthesized as a precursor, pro-ANP, that is converted to biologically active ANP by an unknown membrane-associated protease. Recently, we cloned a transmembrane serine protease, corin, that is highly expressed in the heart. In this study, we examine effects of corin on pro-ANP processing. Our results show that recombinant human corin converts pro-ANP to ANP and that the cleavage in pro-ANP by corin is highly sequence specific. Our findings suggest that corin is the long-sought pro-ANP-converting enzyme and that the corin-mediated pro-ANP activation may play a role in regulating blood pressure.

Comparative human salivary and plasma proteomes

The protein compositions, or the proteomes, found in human salivary and plasma fluids are compared. From recent experimental work by many laboratories, a catalogue of 2290 proteins found in whole saliva has been compiled. This list of salivary proteins is compared with the 2698 proteins found in plasma. Approximately 27% of the whole-saliva proteins are found in plasma. However, despite this apparent low degree of overlap, the distribution found across Gene Ontological categories, such as molecular function, biological processes, and cellular components, shows significant similarities. Moreover, nearly 40% of the proteins that have been suggested to be candidate markers for diseases such as cancer, cardiovascular disease, and stroke can be found in whole saliva. These comparisons and correlations should encourage researchers to consider the use of saliva to discover new protein markers of disease and as a diagnostic non-proximal fluid to detect early signs of disease throughout the body.

Ggamma13 colocalizes with gustducin in taste receptor cells and mediates IP3 responses to bitter denatonium

Gustducin is a transducin-like G protein selectively expressed in taste receptor cells. The alpha subunit of gustducin (alpha-gustducin) is critical for transduction of responses to bitter or sweet compounds. We identified a G-protein gamma subunit (Ggamma13) that colocalized with alpha-gustducin in taste receptor cells. Of 19 alpha-gustducin/Ggamma13-positive taste receptor cells profiled, all expressed the G protein beta3 subunit (Gbeta3); approximately 80% also expressed Gbeta1. Gustducin heterotrimers (alpha-gustducin/Gbeta1/Ggamma13) were activated by taste cell membranes plus bitter denatonium. Antibodies against Ggamma13 blocked the denatonium-induced increase of inositol trisphosphate (IP3) in taste tissue. We conclude that gustducin heterotrimers transduce responses to bitter and sweet compounds via alpha-gustducin's regulation of phosphodiesterase (PDE) and Gbetagamma's activation of phospholipase C (PLC).

Swim pressure: stress generation in active matter

We discover a new contribution to the pressure (or stress) exerted by a suspension of self-propelled bodies. Through their self-motion, all active matter systems generate a unique swim pressure that is entirely athermal in origin. The origin of the swim pressure is based upon the notion that an active body would swim away in space unless confined by boundaries-this confinement pressure is precisely the swim pressure. Here we give the micromechanical basis for the swim stress and use this new perspective to study self-assembly and phase separation in active soft matter. The swim pressure gives rise to a nonequilibrium equation of state for active matter with pressure-volume phase diagrams that resemble a van der Waals loop from equilibrium gas-liquid coexistence. Theoretical predictions are corroborated by Brownian dynamics simulations. Our new swim stress perspective can help analyze and exploit a wide class of active soft matter, from swimming bacteria to catalytic nanobots to molecular motors that activate the cellular cytoskeleton.

Corin, a mosaic transmembrane serine protease encoded by a novel cDNA from human heart

A novel cDNA has been identified from human heart that encodes an unusual mosaic serine protease, designated corin. Corin has a predicted structure of a type II transmembrane protein and contains two frizzled-like cysteine-rich motifs, seven low density lipoprotein receptor repeats, a macrophage scavenger receptor-like domain, and a trypsin-like protease domain in the extracellular region. Northern analysis showed that corin mRNA was highly expressed in the human heart. In mice, corin mRNA was detected by in situ hybridization in the cardiac myocytes of the embryonic heart as early as embryonic day (E) 9.5. By E11.5-13.5, corin mRNA was most abundant in the primary atrial septum and the trabecular ventricular compartment. Expression in the heart was maintained through the adult. In addition, mouse corin mRNA was also detected in the prehypertrophic chrondrocytes in developing bones. By fluorescent in situ hybridization analysis, the human corin gene was mapped to 4p12-13 where a congenital heart disease locus, total anomalous pulmonary venous return, had been previously localized. The unique domain structure and specific embryonic expression pattern suggest that corin may have a function in cell differentiation during development. The chromosomal localization of the human corin gene makes it an attractive candidate gene for total anomalous pulmonary venous return.

High incidence of T-cell tumors in E2A-null mice and E2A/Id1 double-knockout mice

The basic-helix-loop-helix (bHLH) proteins encoded by the E2A gene are broadly expressed transcription regulators which function through binding to the E-box enhancer sequences. The DNA binding activities of E2A proteins are directly inhibited upon dimerization with the Id1 gene product. It has been shown that disruption of the E2A gene leads to a complete block in B-lymphocyte development and a high frequency of neonatal death. We report here that nearly half of the surviving E2A-null mice develop acute T-cell lymphoma between 3 to 10 months of age. We further show that disruption of the Id1 gene improves the chance of postnatal survival of E2A-null mice, indicating that Id1 is a canonical negative regulator of E2A and that the unbalanced ratio of E2A to Id1 may contribute to the postnatal death of the E2A-null mice. However, the E2A/Id1 double-knockout mice still develop T-cell tumors once they reach the age of 3 months. This result suggests that E2A may be essential for maintaining the homeostasis of T lymphocytes during their constant renewal in adult life.

Functional interaction of cytosolic hsp70 and a DnaJ-related protein, Ydj1p, in protein translocation in vivo

In order to analyze the in vivo role of the SSA class of cytosolic 70-kDa heat shock proteins (hsps) of Saccharomyces cerevisiae, we isolated a temperature-sensitive mutant of SSA1. The effect of a shift of mutant cells (ssa1ts ssa2 ssa3 ssa4) from the permissive temperature of 23 degrees C to the nonpermissive temperature of 37 degrees C on the processing of several precursor proteins translocated into the endoplasmic reticulum or mitochondria was assessed. Of three mitochondrial proteins tested, the processing of only one, the beta subunit of the F1F0 ATPase, was dramatically affected. Of six proteins destined for the endoplasmic reticulum, the translocation of only prepro-alpha-factor and proteinase A was inhibited. The processing of prepro-alpha-factor was inhibited within 2 min of the shift to 37 degrees C, suggesting a direct effect of the hsp70 defect on translocation. More than 50% of radiolabeled alpha-factor accumulated in the precursor form, with the remainder rapidly reaching the mature form. However, the translocation block was complete, as the precursor form could not be chased through the translocation pathway. Since DnaJ-related proteins are known to interact with hsp70s and strains containing conditional mutations in a dnaJ-related gene, YDJ1, are defective in translocation of prepro-alpha-factor, we looked for a genetic interaction between SSA genes and YDJ1 in vivo. We found that a deletion mutation of YDJ1 was synthetically lethal in a ssa1ts ssa2 ssa3 ssa4 background. In addition, a strain containing a single functional SSA gene, SSA1, and a deletion of YDJ1 accumulated the precursor form of alpha-factor. However, no genetic interaction was observed between a YDJ1 mutation and mutations in the SSB genes, which encode a second class of cytosolic hsp70 chaperones. These results are consistent with SSA proteins and Ydj1p acting together in the translocation process.

Binding of high molecular weight kininogen to human endothelial cells is mediated via a site within domains 2 and 3 of the urokinase receptor

The urokinase receptor (uPAR) binds urokinase-type plasminogen activator (u-PA) through specific interactions with uPAR domain 1, and vitronectin through interactions with a site within uPAR domains 2 and 3. These interactions promote the expression of cell surface plasminogen activator activity and cellular adhesion to vitronectin, respectively. High molecular weight kininogen (HK) also stimulates the expression of cell surface plasminogen activator activity through its ability to serve as an acquired receptor for prekallikrein, which, after its activation, may directly activate prourokinase. Here, we report that binding of the cleaved form of HK (HKa) to human umbilical vein endothelial cells (HUVEC) is mediated through zinc-dependent interactions with uPAR. These occur through a site within uPAR domains 2 and 3, since the binding of 125I-HKa to HUVEC is inhibited by vitronectin, anti-uPAR domain 2 and 3 antibodies and soluble, recombinant uPAR (suPAR), but not by antibody 7E3, which recognizes the beta chain of the endothelial cell vitronectin receptor (integrin alphavbeta3), or fibrinogen, another alphavbeta3 ligand. We also demonstrate the formation of a zinc-dependent complex between suPAR and HKa. Interactions of HKa with endothelial cell uPAR may underlie its ability to promote kallikrein-dependent cell surface plasmin generation, and also explain, in part, its antiadhesive properties.

The study and clinical application of the osteocutaneous flap of fibula

In this article, four cases of free fibular osteocutaneous flap transfer are reported. The advantages of the bone-attached flap, its microsurgical anatomy, and its design and method of isolation are discussed in detail. Postoperative follow-up showed success in all four cases with satisfactory functional recovery.

Corticofugal modulation of the midbrain frequency map in the bat auditory system

The auditory system, like the visual and somatosensory systems, contains topographic maps in its central neural pathways. These maps can be modified by sensory deprivation, injury and experience in both young and adult animals. Such plasticity has been explained by changes in the divergent and convergent projections of the ascending sensory system. Another possibility, however, is that plasticity may be mediated by descending corticofugal connections. We have investigated the role of descending connections from the cortex to the inferior colliculus of the big brown bat. Electrical stimulation of the auditory cortex causes a downward shift in the preferred frequencies of collicular neurons toward that of the stimulated cortical neurons. This results in a change in the frequency map within the colliculus. Moreover, similar changes can be induced by repeated bursts of sound at moderate intensities. Thus, one role of the mammalian corticofugal system may be to modify subcortical sensory maps in response to sensory experience.

Cloning and characterization of a human beta,beta-carotene-15,15'-dioxygenase that is highly expressed in the retinal pigment epithelium

Retinoids play a critical role in vision, as well as in development and cellular differentiation. beta,beta-Carotene-15,15'-dioxygenase (Bcdo), the enzyme that catalyzes the oxidative cleavage of beta,beta-carotene into two retinal molecules, plays an important role in retinoid synthesis. We report here the first cloning of a mammalian Bcdo. Human BCDO encodes a protein of 547 amino acid residues that demonstrates 68% identity with chicken Bcdo. It is expressed highly in the retinal pigment epithelium (RPE) and also in kidney, intestine, liver, brain, stomach, and testis. The gene spans approximately 20 kb, is composed of 11 exons and 10 introns, and maps to chromosome 16q21-q23. A mouse orthologue was also identified, and its predicted amino acid sequence is 83% identical with human BCDO. Biochemical analysis of baculovirus expressed human BCDO demonstrates the predicted beta,beta-carotene-15,15'-dioxygenase activity. The expression pattern of BCDO suggests that it may provide a local supplement to the retinoids available to photoreceptors, as well as a supplement to the retinoid pools utilized elsewhere in the body. In addition, the finding that many of the enzymes involved in retinoid metabolism are mutated in retinal degenerations suggests that BCDO may also be a candidate gene for retinal degenerative disease.

Molecular characterization of the novel basic helix-loop-helix protein DEC1 expressed in differentiated human embryo chondrocytes

The differentiation of human embryo chondrocytes was markedly induced by the addition of Bt2cAMP to the culture medium. Using this culture system, a novel human cDNA for a basic helix-loop-helix (bHLH) protein (named DEC1) expressed primarily in the chondrocytes in response to Bt2cAMP was cloned by the subtractive hybridization method. DEC1 protein consists of 412 amino acids and exhibits structural similarities to the mammalian HES family, Drosophila hairy, and Enhancer of split m7 in the bHLH region. Northern blot analysis showed that DEC1 mRNA was expressed in various tissues including the cartilage, lung, spleen, and intestine, but not in the brain. These findings suggest that the bHLH factor DEC is involved in the control of cell differentiation in several tissues including cartilage.

The glycine-phenylalanine-rich region determines the specificity of the yeast Hsp40 Sis1

Hsp40s are ubiquitous, conserved proteins which function with molecular chaperones of the Hsp70 class. Sis1 is an essential Hsp40 of the cytosol of Saccharomyces cerevisiae, thought to be required for initiation of translation. We carried out a genetic analysis to determine the regions of Sis1 required to perform its key function(s). A C-terminal truncation of Sis1, removing 231 amino acids but retaining the N-terminal 121 amino acids encompassing the J domain and the glycine-phenylalanine-rich (G-F) region, was able to rescue the inviability of a Deltasis1 strain. The yeast cytosol contains other Hsp40s, including Ydj1. To determine which regions carried the critical determinants of Sis1 function, we constructed chimeric genes containing portions of SIS1 and YDJ1. A chimera containing the J domain of Sis1 and the G-F region of Ydj1 could not rescue the lethality of the Deltasis1 strain. However, a chimera with the J domain of Ydj1 and the G/F region of Sis1 could rescue the strain's lethality, indicating that the G-F region is a unique region required for the essential function of Sis1. However, a J domain is also required, as mutants expected to cause a disruption of the interaction of the J domain with Hsp70 are inviable. We conclude that the G-F region, previously thought only to be a linker or spacer region between the J domain and C-terminal regions of Hsp40s, is a critical determinant of Sis1 function.

Epigenetics as a mechanism linking developmental exposures to long-term toxicity

A variety of experimental and epidemiological studies lend support to the Developmental Origin of Health and Disease (DOHaD) concept. Yet, the actual mechanisms accounting for mid- and long-term effects of early-life exposures remain unclear. Epigenetic alterations such as changes in DNA methylation, histone modifications and the expression of certain RNAs have been suggested as possible mediators of long-term health effects of environmental stressors. This report captures discussions and conclusions debated during the last Prenatal Programming and Toxicity meeting held in Japan. Its first aim is to propose a number of criteria that are critical to support the primary contribution of epigenetics in DOHaD and intergenerational transmission of environmental stressors effects. The main criteria are the full characterization of the stressors, the actual window of exposure, the target tissue and function, the specificity of the epigenetic changes and the biological plausibility of the linkage between those changes and health outcomes. The second aim is to discuss long-term effects of a number of stressors such as smoking, air pollution and endocrine disruptors in order to identify the arguments supporting the involvement of an epigenetic mechanism. Based on the developed criteria, missing evidence and suggestions for future research will be identified. The third aim is to critically analyze the evidence supporting the involvement of epigenetic mechanisms in intergenerational and transgenerational effects of environmental exposure and to particularly discuss the role of placenta and sperm. While the article is not a systematic review and is not meant to be exhaustive, it critically assesses the contribution of epigenetics in the long-term effects of environmental exposures as well as provides insight for future research.

Characterization of a cartilage-derived 66-kDa protein (RGD-CAP/beta ig-h3) that binds to collagen

A 66-kDa collagen fiber-associated protein (RGD-CAP) was isolated from a fiber-rich fraction of pig cartilage by ultrafiltration and collagen-affinity chromatography. Amino acid sequencing and cDNA cloning indicated that the RGD-CAP is identical or closely related to beta ig-h3 protein which is induced in human adenocarcinoma cells by transforming growth factor-beta (TGF-beta) (Skonier, J., Neubauer, M., Madisen, L., Bennett, K., Plowman, G.D., and Purchio, A.F. (1992) DNA Cell. Biol. 11, 511-522). The RGD-CAP, as well as beta ig-h3, has the RGD sequence in the C-terminal region. The native RGD-CAP bound to type I, II, and IV collagens even in the presence of 1 M NaCl. A recombinant preparation of RGD-CAP expressed in Escherichia coli cells also bound to collagen but not to gelatin. The RGD-CAP mRNA was expressed in chondrocytes throughout all stages, although the expression level was highest during the prehypertrophic stage. In addition, TGF-beta increased the RGD-CAP mRNA level in chondrocyte cultures. Since RGD-CAP transcripts were found in most tissues, this novel collagen-binding protein may play an important role in cell-collagen interactions in various tissues including developing cartilage.

Zuotin, a ribosome-associated DnaJ molecular chaperone

Correct folding of newly synthesized polypeptides is thought to be facilitated by Hsp70 molecular chaperones in conjunction with DnaJ cohort proteins. In Saccharomyces cerevisiae, SSB proteins are ribosome-associated Hsp70s which interact with the newly synthesized nascent polypeptide chain. Here we report that the phenotypes of an S.cerevisiae strain lacking the DnaJ-related protein Zuotin (Zuo1) are very similar to those of a strain lacking Ssb, including sensitivities to low temperatures, certain protein synthesis inhibitors and high osmolarity. Zuo1, which has been shown previously to be a nucleic acid-binding protein, is also a ribosome-associated protein localized predominantly in the cytosol. Analysis of zuo1 deletion and truncation mutants revealed a positive correlation between the ribosome association of Zuo1 and its ability to bind RNA. We propose that Zuo1 binds to ribosomes, in part, by interaction with ribosomal RNA and that Zuo1 functions with Ssb as a chaperone on the ribosome.

A testis-specific androgen receptor coregulator that belongs to a novel family of nuclear proteins

We have characterized a novel partner for androgen receptor (AR), termed ARIP3, that interacts with the DNA-binding domain/zinc finger region of AR and is predominantly expressed in the testis. Rat ARIP3 is a nuclear protein comprising 572 amino acids. It modulates AR-dependent but not basal transcription, suggesting that ARIP3 acts as an AR transcriptional coregulator. Except for the C-terminal AR-interacting domain, ARIP3 contains distinct regions that are also present in two recently described proteins, a protein inhibitor of activated Stat3 and an RNA helicase II-interacting protein (Gu/RH-II binding protein). Conserved structural features of these proteins indicate the existence of a gene family involved in the regulation of various transcription factors. Collectively, ARIP3 belongs to a novel nuclear protein family and is perhaps the first tissue-specific coregulator of androgen receptor.

Histone deacetylase inhibitors suppress mutant p53 transcription via histone deacetylase 8

Mutation of the p53 gene is the most common genetic alteration in human cancer and contributes to malignant process by enhancing transformed properties of cells and resistance to anticancer therapy. Mutant p53 is often highly expressed in tumor cells at least, in part, due to its increased half-life. However, whether mutant p53 expression is regulated by other mechanisms in tumors is unclear. Here we found that histone deacetylase (HDAC) inhibitors suppress both wild-type and mutant p53 transcription in time- and dose-dependent manners. Consistent with this, the levels of wild-type and mutant p53 proteins are decreased upon treatment with HDAC inhibitors. Importantly, we found that upon knockdown of each class I HDAC, only HDAC8 knockdown leads to decreased expression of wild-type and mutant p53 proteins and transcripts. Conversely, we found that ectopic expression of wild-type, but not mutant HDAC8, leads to increased transcription of p53. Furthermore, we found that knockdown of HDAC8 results in reduced expression of HoxA5 and consequently, attenuated ability of HoxA5 to activate p53 transcription, which can be rescued by ectopic expression of HoxA5. Because of the fact that HDAC8 is required for expression of both wild-type and mutant p53, we found that targeted disruption of HDAC8 expression remarkably triggers proliferative defect in cells with a mutant, but not wild-type, p53. Together, our data uncover a regulatory mechanism of mutant p53 transcription via HDAC8 and suggest that HDAC inhibitors and especially HDAC8-targeting agents might be explored as an adjuvant for tumors carrying a mutant p53.

Arg-Gly-Asp peptide increases endothelial hydraulic conductivity: comparison with thrombin response

The contribution of integrin receptors to the regulation of endothelial permeability was studied using cultured bovine pulmonary microvascular endothelial cell (BPMVEC) monolayers by the measurement of hydraulic conductivity (Lp). Treatment of monolayers with a peptide containing the sequence Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) (0.85 mM) to compete for the RGD sequence of extracellular matrix (ECM) proteins increased endothelial Lp threefold, whereas the control peptide Gly-Arg-Gly-Glu-Ser-Pro had no effect on Lp. This action of GRGDSP on Lp was not significantly altered by dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP; 0.5 mM). Endothelial Lp increased twofold when the monolayers were challenged with alpha-thrombin (5 x 10(-8) M for 10 min), and this response was completely reversed by DBcAMP. The strength of adhesion of endothelial cells was estimated by evaluating the ability of endothelial cells to remain attached to ECM after treating the monolayers with 0.05% trypsin plus 0.5 mM EDTA. Exposure of the monolayers to either GRGDSP or alpha-thrombin significantly reduced the strength of adhesion to the ECM. DBcAMP prevented the antiadhesive effect of alpha-thrombin but not that of GRGDSP. Treatment of the monolayers with either alpha-thrombin or GRGDSP caused formation of intercellular gaps, but only the thrombin-induced intercellular gaps were accompanied by reorganization of actin filaments. These results indicate that integrin binding to ECM proteins regulates an important determinant of endothelial permeability and that alpha-thrombin and GRGDSP increase endothelial cell monolayer permeability by different mechanisms.

Trypanosoma cruzi contains major pyrophosphate stores, and its growth in vitro and in vivo is blocked by pyrophosphate analogs

High field (31)P nuclear magnetic resonance spectroscopy showed that inorganic pyrophosphate (P(2)O(7)(4-)) is more abundant than ATP in Trypanosoma cruzi, the causative agents of Chagas' disease. These results were confirmed by specific analytical assays, which showed that in epimastigotes, the concentrations of inorganic pyrophosphate and ATP were 194.7 +/- 25.9 and 37.6 +/- 5.5 nmol/mg of protein, respectively, and for the amastigote form, the corresponding concentrations were 358.0 +/- 17.0 and 36.0 +/- 1.9 nmol/mg of protein. High performance liquid chromatographic analysis of perchloric acid extracts of epimastigotes labeled for 3 h with (32)P-orthophosphate showed a significant incorporation of the precursor into inorganic pyrophosphate. Inorganic pyrophosphate was not uniformly distributed in T. cruzi but was shown by (31)P-NMR and chemical analysis to be particularly associated with acidocalcisomes, organelles shown previously to contain large amounts of phosphorus and various elements. Electron microscopy analysis of pyrophosphatase-treated permeabilized epimastigotes showed disappearance of the electron density of the acidocalcisomes. Nonmetabolizable analogs of pyrophosphate, currently used for the treatment of bone resorption disorders, selectively inhibited the proliferation of intracellular T. cruzi amastigotes and produced a profound suppression in the number of circulating trypomastigotes in mice with an acute infection of T. cruzi, offering a potentially new route to chemotherapy.

Identification of allelopathy in the USDA-ARS rice germplasm collection

Field experiments in 1988 and 1989 identified rice accessions from the USDA-ARS rice germplasm collection for allelopathic effects to ducksalad [Heteranthera limosa (Sw.) Willd.]. About 10000 accessions were evaluated; 347 accessions had apparent allelopathic activity. Accessions that had demonstrated allelopathic activity to ducksalad in 1988 or 1989 were evaluated further for allelopathic activity in 1990 (67 accessions) and 1991 (47 accessions). In 1990, 12 accessions had a radius of activity of 0.18-0.20 m and 80-90% weed control within the area of activity. In 1991, 12 different accessions had a radius of activity of 0.13-0.18 m and 50-85% weed control in the area of activity.

Stem cell factor protects germ cells from apoptosis in vitro

Stem cell factor (SCF) plays an important role in migration, adhesion, proliferation, and survival of primordial germ cells and spermatogonia during testicular development. However, the function of SCF in the adult testis is poorly described. We have previously shown that, in the presence of SCF, there were more type A spermatogonia incorporating thymidine at stage XII of rat seminiferous tubules cultured in vitro than in the absence of SCF, implying that the increased DNA synthesis might result from enhanced survival of spermatogonia. To explore the potential pro-survival function of SCF during spermatogenesis, the seminiferous tubules from stage XII were cultured in the presence or absence of SCF (100 ng/ml) for 8, 24, 48, and 72 hours, respectively, and apoptosis was analyzed by DNA laddering and in situ 3′-end labeling (ISEL) staining. Surprisingly, not only spermatogonia, but also spermatocytes and spermatids, were protected from apoptosis in the presence of SCF. Apoptosis took place much later and was less severe in the SCF-treated tubules than in the controls. Based on previous studies showing that FSH prevents germ cells from undergoing apoptosis in vitro, and that SCF level is increased dramatically in response to FSH stimulation, we also tested if the pro-survival effect of FSH is mediated through SCF by using a function-blocking monoclonal antibody, ACK-2, to block SCF/c-kit interaction. After 24 hours of blockade, the protective effect of FSH was partially abolished, as manifested by DNA laddering and ISEL analyses. The present study demonstrates that SCF acts as an important survival factor for germ cells in the adult rat testis and FSH pro-survival effect on germ cells is mediated partially through the SCF/c-kit pathway.

Drug targeting Mycobacterium tuberculosis cell wall synthesis: genetics of dTDP-rhamnose synthetic enzymes and development of a microtiter plate-based screen for inhibitors of conversion of dTDP-glucose to dTDP-rhamnose

An L-rhamnosyl residue plays an essential structural role in the cell wall of Mycobacterium tuberculosis. Therefore, the four enzymes (RmlA to RmlD) that form dTDP-rhamnose from dTTP and glucose-1-phosphate are important targets for the development of new tuberculosis therapeutics. M. tuberculosis genes encoding RmlA, RmlC, and RmlD have been identified and expressed in Escherichia coli. It is shown here that genes for only one isotype each of RmlA to RmlD are present in the M. tuberculosis genome. The gene for RmlB is Rv3464. Rv3264c was shown to encode ManB, not a second isotype of RmlA. Using recombinant RmlB, -C, and -D enzymes, a microtiter plate assay was developed to screen for inhibitors of the formation of dTDP-rhamnose. The three enzymes were incubated with dTDP-glucose and NADPH to form dTDP-rhamnose and NADP(+) with a concomitant decrease in optical density at 340 nm (OD(340)). Inhibitor candidates were monitored for their ability to lower the rate of OD(340) change. To test the robustness and practicality of the assay, a chemical library of 8,000 compounds was screened. Eleven inhibitors active at 10 microM were identified; four of these showed activities against whole M. tuberculosis cells, with MICs from 128 to 16 microg/ml. A rhodanine structural motif was present in three of the enzyme inhibitors, and two of these showed activity against whole M. tuberculosis cells. The enzyme assay was used to screen 60 Peruvian plant extracts known to inhibit the growth of M. tuberculosis in culture; two extracts were active inhibitors in the enzyme assay at concentrations of less than 2 microg/ml.