Arrangement of actin filaments and cytoplasmic granules in the sea urchin egg after TPA treatment

Elongation of microvilli and formation of actin filaments after treatment with a phorbol ester, TPA, were investigated in unfertilized eggs of Hemicentrotus pulcherrimus. Microvilli on the egg surface were examined by scanning electron microscopy. Actin filaments in the cortical layer of the eggs were observed by fluorescence microscopy using rhodamine-labeled phalloidin. The actin molecules were polymerized and bundled to form long filaments inside the cortical layer of eggs after TPA treatment. Arrangement of the actin filaments was followed by spiral elongation of microvilli. Transmission electron microscopic studies showed that the cortical granules under the cell membrane of sea urchin eggs were transferred after TPA treatment from the surface to the interior of the cell [Ciapa et al., 1988: Dev. Biol. 128:142-149]. This movement of the cortical granules was inhibited by cytochalasin B, but not by nocodazole. Furthermore, the distribution of clear granules was changed following TPA treatment. From these results we conclude that intracellular actin filaments may cause the transport of cortical granules and clear granules into the central area of the egg by the activation of protein kinase C. The possible involvement of actin in the inward displacement of granules might be the result of the rearrangement of actin filaments in the cortical layer.

Cytoplasmic Ca2+ oscillation coordinates the formation of actin filaments in the sea urchin eggs activated with phorbol ester

Changes in the intracellular Ca2+ concentration ([Ca2+]i) and the formation of actin filaments were investigated in unfertilized eggs of the sea urchin Hemicentrotus pulcherrimus after activation with a phorbol ester, 12-O-tetradecanoyl phorbol13-acetate (TPA). Intracellular Ca2+ oscillation was observed using a fluorescent Ca2+ indicator dye, calcium green dextran. From about 20 to 80 min after the addition of TPA to 100 microM, there was a rise in [Ca2+]i, which was followed by Ca2+ oscillation. A change in [Ca2+]i in response to TPA was not observed in eggs that had been injected with heparin, an inositol 1,4,5-triphosphate (IP3) receptor antagonist. Therefore, long-term exposure to a high concentration of TPA seems to induce Ca2+ release via the IP3 pathway, as well as causing the release of diacylglycerol from membrane lipids. Moreover, the elongation of actin filaments occurred in the cytoplasm during the rise in [Ca2+]i. Actin filaments also formed when TPA-induced cytoplasmic alkalization was inhibited by exposure to Na(+)-free sea water. These results suggest that the observed cytoplasmic formation of actin filaments may be related to change in the cytoplasmic [Ca2(+)]i, and not intracellular pH, induced by TPA. These phenomena may be similar to the changes in actin construction that occur during cell cycle events.

Detection of mononuclear cells as the source of the increased tissue factor mRNA in the liver from lipopolysaccharide-treated rats

Tissue factor (TF) triggers the coagulation cascade reaction in vivo. Overexpression of TF mRNA is one leading cause of disseminated intravascular coagulation and thrombosis-related organ failure. In response to lipopolysaccharide (LPS) stimulation, various cell types can produce TF mRNA in vitro. However, there is currently no agreement on what types of cells in the liver overexpress TF mRNA after LPS treatment. For the first report, we found the increased TF mRNA with reverse transcription-polymerase chain reaction (RT-PCR), and confirmed a fourfold increase (p<0.001 vs. control, t-test) of the TF mRNA level with RT-competitive PCR in the liver of LPS-treated (2.0 mg/kg i.v. injection) rats. There was no significant difference in the glyceraldehyde-3-phosphate dehydrogenase mRNA level between LPS-treated rats and control rats. To clarify the localization and cellular source of LPS-induced TF mRNA, we performed in situ hybridization analysis with [35S]-labeled oligonucleotides probes, which we originally designed. We detected intense signals of TF mRNA in mononuclear cells but not in endothelial cells around the hepatic vein of LPS-treated rats. In this study, we showed that the TF mRNA level induced by LPS treatment, which may indicate mononuclear cells associated, significantly increased in the liver of rats. These results will provide circumstantial support for the therapeutic strategy that mononuclear cell should be one of the target cells to be treated in the early phase of disseminated intravascular coagulation in the liver, and that the need to suppress its overexpression of TF mRNA is essential for preventing hypercoagulable condition.

Microchip capillary electrophoresis using on-line chemiluminescence detection

Chemiluminescence detection was used in capillary electrophoresis integrated on a microchip. Quartz microchips have two main channels and four reservoirs. Dansyl-lysine and -glycine were separated and detected with bis[(2-(3,6,9-trioxadecanyloxycarbony)-4-nitrophenyl]oxalate as peroxyoxalate chemiluminescent reagent. These dansyl amino acids came into contact with the chemiluminescence reagent to produce visible light at the interface between the separation channel and chemiluminescence reagent-containing reservoir. The detection limit (S/N = 3) for dansyl-lysine was 1 x 10(-5) M, which corresponded to the very small mass detection limit of ca. 0.4 fmol. However, the concentration sensitivity in the present system was approximately two orders of magnitude lower than that in the conventional capillary electrophoresis-chemiluminescence detection system. The relative standard deviations of migration time and peak height for dansyl-lysine were 4.2 and 4.5%, respectively. A channel conditioning before every run and an appropriate control of voltages were needed for the reproducible results. The present system had advantages in rapid separation time (within 40 s), small (several 10 pI) and accurate sample injection method using a cross-shaped injector, and simplification and miniaturization of the detection device.

Fast separation of oligonucleotide and triplet repeat DNA on a microfabricated capillary electrophoresis device and capillary electrophoresis

A laser-induced fluorescence detection system coupled with a highly sensitive silicon-intensified target (SIT) camera is successfully applied to the imaging of a band for DNA fragment labeling by fluorescence dye in a microchannel, and to the visualizing of the separation process on a microfabricated chip. We demonstrated that an only 6 mm separation channel is sufficient for the separation of triplet repeat DNA fragment and DNA molecular marker within only 12 s. The separation using the microfabricated capillary electrophoresis device is confirmed to be at least 18 times faster than the same separation carried out by conventional capillary electrophoresis with 24.5 cm effective length. The use of a short capillary with 8.5 cm effective length is also efficient for fast separation of DNA; however, the microchip technology is even faster than capillary electrophoresis using a short capillary.

Positive modulation of AMPA receptors increases neurotrophin expression by hippocampal and cortical neurons

This study investigated whether positive modulators of AMPA-type glutamate receptors influence neurotrophin expression by forebrain neurons. Treatments with the ampakine CX614 markedly and reversibly increased brain-derived neurotrophic factor (BDNF) mRNA and protein levels in cultured rat entorhinal/hippocampal slices. Acute effects of CX614 were dose dependent over the range in which the drug increased synchronous neuronal discharges; threshold concentrations for acute responses had large effects on mRNA content when applied for 3 d. Comparable results were obtained with a second, structurally distinct ampakine CX546. Ampakine-induced upregulation was broadly suppressed by AMPA, but not NMDA, receptor antagonists and by reducing transmitter release. Antagonism of L-type voltage-sensitive calcium channels blocked induction in entorhinal cortex but not hippocampus. Prolonged infusions of suprathreshold ampakine concentrations produced peak BDNF mRNA levels at 12 hr and a return to baseline levels by 48 hr. In contrast, BDNF protein remained elevated throughout a 48 hr incubation with the drug. Nerve growth factor mRNA levels also were increased by ampakines but with a much more rapid return to control levels during chronic administration. Finally, intraperitoneal injections of CX546 increased hippocampal BDNF mRNA levels in aged rats and middle-aged mice. The present results provide evidence of regional differences in mechanisms via which activity regulates neurotrophin expression. Moreover, these data establish that changes in synaptic potency produce sufficient network level physiological effects for inducing neurotrophin genes, indicate that the response becomes refractory during prolonged ampakine exposure, and raise the possibility of using positive AMPA modulators to regulate neurotrophin levels in aged brain.

Cell fate analysis of teloblasts in the Tubifex embryo by intracellular injection of HRP

As in other clitellate annelids, embryonic development in the oligochaete Tubifex is characterized by the generation of five bilateral pairs of teloblasts (designated M, N, O, P and Q), which serve as embryonic stem cells to produce germ bands on either side of the embryo. A large part of the tissues comprising body segments has been assigned to the progenies of the teloblasts; however, the developmental fate of each teloblast has been inferred only from its initial position in the embryo. In the present study, the fate of the progenies of each teloblast was followed by means of intracellular injection of a tracer enzyme, horseradish peroxidase. Cell fate maps for teloblasts in the Tubifex embryo were constructed. M teloblasts gave rise to nearly all of the mesodermal tissues, which included circular and longitudinal muscles, coelomic walls, nephridia (in segments VII and VIII) and primordial germ cells (in segments X and XI). Although few in number, M teloblasts also contributed cells to the ventral ganglion. Similarly, each of the ectoteloblasts, N, O, P and Q, made a topographically characteristic contribution to the ectodermal tissues such as the nervous system (i.e. ganglionic cells and peripheral neurones) and epidermis, all of which exhibited a segmentally repeated distribution pattern. The P and Q teloblasts uniquely gave rise to additional ectodermal tissues, namely ventral and dorsal setal sacs, respectively. Furthermore, O teloblasts made a contribution to the nephridiopores in segments VII and VIII as well. These results confirm the previously held view that ectoteloblasts and mesoteloblasts are the main source of ectodermal and mesodermal segmental tissues, respectively, but also suggest that all of the teloblasts produce more types of tissue than has previously been thought.

CrkL mediates Ras-dependent activation of the Raf/ERK pathway through the guanine nucleotide exchange factor C3G in hematopoietic cells stimulated with erythropoietin or interleukin-3

CrkL is an SH2 and SH3 domain-containing adaptor protein implicated in pathogenesis of chronic myelogenous leukemia. Here, we demonstrate that overexpression of CrkL enhances the erythropoietin (Epo)- or interleukin (IL)-3-induced activation of Elk-1 and the c-fos gene promoter activity in 32D/EpoR-Wt cells. Moreover, the Epo-induced activation of ERK1 and ERK2 was augmented and prolonged in cells inducibly overexpressing CrkL. A moderate increase in Epo-induced activation of JNK was also observed in cells overexpressing CrkL. Overexpression of C3G enhanced the Elk-1 activation synergistically with CrkL, while a C3G mutant lacking the guanine nucleotide exchange domain showed an inhibitory effect. Studies using a dominant negative Ha-Ras mutant demonstrated that the Elk-1 and ERK2 activation enhanced by CrkL and C3G was dependent on Ras. Consistent with this, the Epo-induced activation of Ras was augmented in cells inducibly overexpressing CrkL. Most importantly, a CrkL mutant defective in the SH2 or N-terminal SH3 domain showed an inhibitory effect on the Epo-induced activation of ERK2. These data indicate that the CrkL-C3G complex plays a role in Epo- or IL-3-induced, Ras-dependent activation of the Raf/ERK pathway leading to the activation of Elk-1 and the c-fos gene transcription.

CrkL activates integrin-mediated hematopoietic cell adhesion through the guanine nucleotide exchange factor C3G

CrkL is a member of the Crk family of adapter proteins consisting mostly of SH2 and SH3 domains. CrkL is most abundantly expressed in hematopoietic cells and has been implicated in pathogenesis of chronic myelogenous leukemia. However, its function has not been precisely defined. Here, we show that overexpression of CrkL enhances the adhesion of hematopoietic 32D cells to fibronectin. The CrkL-induced increase in cell adhesion was blocked by antibodies against VLA-4 (alpha4beta1) and VLA-5 (alpha5beta1) but was observed without changes in surface expression levels of these integrins. Studies using CrkL mutants demonstrated that the SH2 domain is partially required for enhancing cell adhesion, whereas the C-terminal SH3 domain as well as the tyrosine phosphorylation site (Y207) is dispensable. In contrast, the N-terminal SH3 domain, involved in binding C3G and other signaling molecules, was showed to play a crucial role, because a mutant defective of this domain showed an inhibitory effect on the cell adhesion to fibronectin. Furthermore, overexpression of C3G also increased the adhesion of hematopoietic cells to fibronectin, whereas a C3G mutant lacking the guanine nucleotide exchange domain abrogated the CrkL-induced increase in cell adhesion. On the other hand, a dominant negative mutant of H-Ras or that of Raf-1 enhanced the basal and CrkL-induced cell adhesion and that of R-Ras modestly decreased the adhesion. Taken together, these results indicate that the CrkL-C3G complex activates VLA-4 and VLA-5 in hematopoietic cells, possibly by activating the small GTP binding proteins, including R-Ras, through the guanine nucleotide exchange activity of C3G.

[Renin-angiotensin-aldosterone system in the reproductive system]

Besides the circulating renin-angiotensin-aldosterone (R-A-A) system, the tissue R-A-A system has been elucidated to play important roles as autocrines and/or paracrines. The components of R-A-A system are expressed in the ovary, uterus and placenta, indicating the existence of the tissue R-A-A system in these organs. The data indicating the involvement of R-A-A system of these tissues into reproduction have been accumulated. AT2 receptors might modulate the initiation and progression of follicle atresia involving granulosa cell apoptosis. AT2 receptors are expressed abundantly in the uterus and decreased during pregnancy. The placental renin are shown to be secreted into the maternal circulation and elevate blood pressure. It is expected to elucidate the significance of the R-A-A system in the reproductive system.

Synergistic interactions between ampakines and antipsychotic drugs

Tests were made for interactions between antipsychotic drugs and compounds that enhance synaptic currents mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid-type glutamate receptors ("ampakines"). Typical and atypical antipsychotic drugs decreased methamphetamine-induced hyperactivity in rats; the effects of near or even subthreshold doses of the antipsychotics were greatly enhanced by the ampakines. Interactions between the ampakine CX516 and low doses of different antipsychotics were generally additive and often synergistic. The ampakine did not exacerbate neuroleptic-induced catalepsy, indicating that the interaction between the different pharmacological classes was selective. These results suggest that positive modulators of cortical glutamatergic systems may be useful adjuncts in treating schizophrenia.

A clinical study on the magnetic stimulation of the facial nerve

OBJECTIVES

A clinical study on the usefulness of magnetic stimulation of the facial nerve, with special attention paid to the selection of the coil shape and stimulation procedures.

STUDY DESIGN

The subjects consisted of 55 patients with Bell's palsy, 1 patient with a cerebellopontine angle (CPA) tumor, 1 patient with multiple sclerosis (MS), and 30 normal subjects. Three types of coils were used in this study; a 90-mm large single coil, a 40-mm small single coil, and a 20-mm small double coil.

METHODS

The compound muscle action potentials (CMAPs) and long latency response were evoked by transcranial magnetic stimulation (TMS) with a 90-mm large single coil. The 40-mm small single coil was used to test blink reflex by aiming it at the supraorbital nerve as the target site. The subcutaneous activation of the infra-auricular facial nerve was performed with the 20-mm double coil.

RESULTS

The reproducible CMAP and long latency responses were obtained from normal subjects with TMS. However, responses were observed only in patients with relatively mild Bell's palsy. The magnetic stimulation-evoked responses reflected the brainstem function in the patients with a CPA tumor and MS.

CONCLUSION

Although magnetic stimulation remains inferior to conventional electric stimulation in some sense and requires further study, this method is potentially useful because it can stimulate the facial nerve continuously from the cortex to the periphery and can effectively evoke responses reflecting the brainstem function.

beta-adrenergic modulation of L-type Ca2+-channel currents in early-stage embryonic mouse heart

Little information is available concerning the modulation of cardiac function by beta-adrenergic agonists in early-stage embryonic mammalian heart. We have examined the effects of isoproterenol (Iso) on the spontaneous beating rate and action potential (AP) configuration in embryonic mouse hearts at 9.5 days postcoitum (dpc), just 1 day after they started to beat. Iso (3 microM) increased the spontaneous beating rate in whole hearts, dissected ventricles, and isolated ventricular myocytes. In ventricular myocytes, Iso also increased the slope of the pacemaker potential and the action potential duration but decreased the maximum upstroke velocity. In whole cell voltage-clamp experiments, the Ca2+-channel currents were measured as Ba2+ currents (IBa). In 9.5-dpc myocytes, IBa was enhanced significantly from -4.7 +/- 0.9 to -6.7 +/- 1.2 pA/pF (by 52.4 +/- 14.8%, n = 10) after the application of Iso. Propranolol (3 microM) reversed the effect of Iso. Forskolin (For, 10 microM) produced an increase in IBa by 95.5 +/- 18.8% (n = 8). In ventricular myocytes at a late embryonic stage (18 dpc), 3 microM Iso caused an appreciably greater increase in IBa from -6.2 +/- 0.5 to -14.5 +/- 2.2 pA/pF (by 137.8 +/- 33.0%, n = 8), whereas the increase in IBa by 10 microM For (by 120.0 +/- 23.0%, n = 7) was comparable to that observed in the early stage (9.5 dpc). These results indicate that the L-type Ca2+-channel currents are modulated by beta-adrenergic receptors in the embryonic mouse heart as early as 9.5 dpc, probably via a cAMP-dependent pathway.

DNA analysis by microfabricated capillary electrophoresis device

The LIGA (Lithographie Galvanoformung Abformung) process using synchrotron radiation lithography is applied to the microfabrication of capillary array electrophoresis (CAE) device. Laser-induced fluorescence detection system for the CAE device has been constructed by the modification of laser confocal fluorescence microscopy. DNA molecules were detected during migrating in the microchannels filled with polymer separation matrices under electric field to optimize the separation conditions for DNA analysis. Based on this observation, we demonstrated that microfabricated CAE device is realized the fast separation of DNA.

Cardiac malignant pheochromocytoma with bone metastases

A patient with malignant cardiac pheochromocytoma with bone metastases is described. The primary tumor was located between the pulmonary trunk and the left atrium, while metastatic lesions were found in the iliac bones. Treatments with antihypertensive agents, alpha-methylparatyrosine, and combination chemotherapy with cyclophosphamide, vincristine, and dacarbazine partially improved the patient's symptoms, catecholamine levels, and the metastatic lesion of the iliac bones. However, the primary tumor in the heart progressively increased in size and the patient died of disseminated intravascular coagulation and other various complications about 4 years after the diagnosis of the disease.

AMPA receptor desensitization modulates synaptic responses induced by repetitive afferent stimulation in hippocampal slices

In patches excised from CA1 pyramidal cells, peak amplitudes of currents evoked by brief glutamate pulses grew progressively smaller over a series of high-frequency pulses. This decline was eliminated by cyclothiazide, a drug previously shown to block AMPA receptor desensitization. In hippocampal slices, synaptically evoked bursts exhibited an increase from the first to the second response, presumably due to facilitation of transmitter release, but the subsequent responses gradually declined in amplitude. Cyclothiazide attenuated or reversed this decline; after normalization to the first response, the amplitudes of the later responses to a 50 Hz series of afferent stimulation were increased by 20-25% in regular recording medium and by as much as 40% when transmitter release was enhanced in a high-calcium medium. The effect of cyclothiazide was greatly diminished when the stimulation frequency was reduced to 33 or 25 Hz. Comparable results were obtained in slices in which NMDA, GABAA, and GABAB receptors were blocked. The ampakine drug CX516 which has only a minor influence on desensitization kinetics did not differentially facilitate the later responses to high-frequency afferent stimulation. These results suggest that the desensitization of AMPA receptors contributes importantly to synaptic activity when afferents are repetitively activated at high-frequency.

The waveform of synaptic transmission at hippocampal synapses is not determined by AMPA receptor desensitization

Relationships between the kinetic properties of AMPA receptors and the decay phase of fast excitatory transmission were investigated using modulatory drugs. The benzothiadiazide compound cyclothiazide blocked receptor desensitization in patches excised from hippocampus but had only a weak influence on receptor deactivation, i.e., on the decay of responses produced by a 1-ms pulse of glutamate. The ampakine drug CX516 (BDP-12) produced an opposite pattern of effects: a fourfold slowing of deactivation with little change in desensitization. A structurally related drug (CX554 or BDP-20) had prominent effects on both desensitization and deactivation. The halfwidth of field EPSPs measured in the CA1 region of hippocampal slices increased 50-100% in the presence of CX516 or CX554 but by less than 15% at concentrations of cyclothiazide that fully blocked desensitization in patch experiments. These results indicate that receptor deactivation plays a substantially greater role than receptor desensitization in determining the duration of synaptic responses.

[Hemolytic uremic syndrome after bone marrow transplantation]

One hundred and thirteen patients who underwent autologous or allogeneic bone marrow transplantation (BMT) were investigated for the subsequent development of hemolytic uremic syndrome (HUS). HUS developed in seven patients (four males and three females, five acute lymphocytic leukemia (ALL), one acute myelogenous leukemia, one non-Hodgkin's lymphoma) between 36-196 days after BMT. Four patients were recipients of autologous BMT and three were those of allogeneic BMT. Six patients were preconditioned with the regimens including fractionated total body irradiation (TBI). ALL and preconditioning regimen with TBI were suspected to be the risk factors for the development of HUS. Cyclosporin A (CSP) administration was discontinued in three patients who had been given CSP for graft-versus-host disease prophylaxis. Predonisolone was given to the three patients and plasma exchange was performed in one patient. Both hemolytic anemia and thrombocytopenia were resolved in virtually all patients, while creatinine elevation has persisted along with hypertension in one patient.

Lyn physically associates with the erythropoietin receptor and may play a role in activation of the Stat5 pathway

Protein tyrosine phosphorylation plays a crucial role in signaling from the receptor for erythropoietin (Epo), although the Epo receptor (EpoR) lacks the tyrosine kinase domain. We have previously shown that the Jak2 tyrosine kinase couples with the EpoR to transduce a growth signal. In the present study, we demonstrate that Lyn, a Src family tyrosine kinase, physically associates with the EpoR in Epo-dependent hematopoietic cell lines, 32D/EpoR-Wt and F36E. Coexpression experiments in COS7 cells further showed that Lyn induces tyrosine phosphorylation of the EpoR and that both LynA and LynB, alternatively spliced forms of Lyn, bind with the membrane-proximal 91-amino acid region of the EpoR cytoplasmic domain. In vitro binding studies using GST-Lyn fusion proteins further showed that the Src homology (SH)-2 domain of Lyn specifically binds with the tyrosine-phosphorylated EpoR in lysate from Epo-stimulated cells, whereas the tyrosine kinase domain of Lyn binds with the unphosphorylated EpoR. Far-Western blotting and synthetic phosphopeptide competition assays further indicated that the Lyn SH2 domain directly binds to the tyrosine-phosphorylated EpoR, most likely through its interaction with phosphorylated Y-464 or Y-479 in the carboxy-terminal region of the EpoR. In vitro binding studies also demonstrated that the Lyn SH2 domain directly binds to tyrosine-phosphorylated Jak2. In vitro reconstitution experiments in COS7 cells further showed that Lyn induces tyrosine phosphorylation of Stat5, mainly on Y-694, and activates the DNA-binding and transcription-activating abilities of Stat5. In agreement with this, Lyn enhanced the Stat5-dependent transcriptional activation when overexpressed in 32D/EpoR-Wt cells. In addition, Lyn was demonstrated to phosphorylate the EpoR and Stat5 on tyrosines in vitro. These results suggest that Lyn may play a role in activation of the Jak2/Stat5 and other signaling pathways by the EpoR.

Time-resolved fluorescent X-ray interference

A fluorescent X-ray interference method can effectively measure nanometer-level conformational changes for non-crystallized molecules and proteins in aqueous conditions. The time-resolved technique can be used to obtain information about the dynamics of molecules and proteins. Instrumentation for time-resolved fluorescent X-ray interference has been designed. A typical interference-fringe pattern was observed with approximately 3 s of X-ray exposure time from K-fluorescent X-rays emitted from a Zn monoatomic layer on an Rh substrate. The primary X-ray beam was polychromed with a mirror for total external reflection of X-rays and was tuned to an energy level at which only Zn K radiation became optimally excited. The glancing angle of the primary X-ray beam was fixed at a glancing angle at which the total intensity of K-fluorescent X-rays emitted from Zn atoms corresponded to the maximum value. The fluorescent X-ray interference fringes were monitored with an imaging plate (IP) as a non-energy-dispersive two-dimensional detector. The exposed interference fringes on the IP were integrated along the direction of the fringes. The integrated fringes were in close agreement with a theoretical estimate based on the interference among transmitted and reflected waves at interfaces in the sample.

Molecular cloning and nucleotide sequence of the pyruvate kinase gene of an actinomycete Microbispora thermodiastatica

The gene for the thermostable pyruvate kinase of Microbispora thermodiastatica IFO 14046, a moderate thermophilic actinomycete, was cloned in Escherichia coli. This gene consists of an open reading frame of 1422 nucleotides and encodes a protein of 474 amino acids with molecular mass of 50,805 Da. The open reading frame was confirmed as the pyruvate kinase gene by comparison with the N-terminal amino acid sequence of the purified pyruvate kinase from M. thermodiastatica.

Murine cardiac progenitor cells require visceral embryonic endoderm and primitive streak for terminal differentiation

Cardiac progenitor cells in avian and amphibian embryos are known to commit to cardiac lineage during gastrulation or early neurulation. These cells require cell interaction with anterior endoderm for their differentiation into cardiomyocytes. However, little is known about cell interaction in mammalian cardiogenesis. We investigated the staging of murine cardiomyocyte commitment and the role of cell interaction in differentiation of cardiac progenitor cells into cardiomyocytes, using cultures of various embryonic regions at 7.25 and 7.5 days post coitum (p.c.), respectively. To evaluate the terminal differentiation of cardiac progenitor cells, we employed three parameters; expression of spontaneous beating, myosin heavy chain (MHC) protein, and cardiac-specific genes (alpha myosin heavy chain, Csx/Nkx2.5 and myosin light chain 2V genes). mRNAs of cardiac-specific genes were detected in 7.25-day p.c. mesoderm by RT-PCR, suggesting that the genetic specification to cardiac lineage initiated in the mesoderm by 7.25 days p.c. The 7.25-day p.c. isolated mesoderm in 48 hr culture, however, failed to differentiate into spontaneous beating cardiomyocytes and exhibited non-organized MHC protein in 19% of these culture. In contrast, all of the 7.5-day p.c. isolated mesoderm differentiated into beating cardiomyocytes even in 24 hr culture. The 7.25-day p.c. mesoderm associated with primitive streak increased MHC protein expression in 93% of these cultures, although they formed beating foci in 3%. The 7.25-day p.c. explants containing both visceral embryonic endoderm and primitive streak succeeded in terminal differentiation into spontaneous beating cardiomyocytes. Our study suggests that cardiac progenitor cells obtain the potency to complete terminal differentiation autonomously at 7.5 days p.c., as a consequence of the multistep induction by cell interactions with both the primitive streak and visceral embryonic endoderm, following the genetic specification to cardiac lineage in the early gastrula stage.

Erythropoietin and IL-3 induce tyrosine phosphorylation of CrkL and its association with Shc, SHP-2, and Cbl in hematopoietic cells

The present study demonstrates that erythropoietin (Epo) and IL-3 induce tyrosine phosphorylation of the SH2/SH3-containing adapter protein CrkL and its transient association with tyrosine-phosphorylated SHP-2, Shc, and Cbl in a murine IL-3-dependent cell line, 32D, expressing the Epo receptor (EpoR). In these cells, CrkL was constitutively complexed with the guanine nucleotide exchange factor C3G, which was found to coimmunoprecipitate with Shc from Epo- or IL-3-stimulated cells. Studies using cells expressing mutant EpoRs showed that the Epo-induced tyrosine phosphorylation of CrkL is dependent on the membrane-proximal EpoR cytoplasmic region involved in the activation of Jak2 as well as the C-terminal 145 amino acid region which is required for tyrosine phosphorylation of SHP-2 and Shc. It was further revealed that CrkL is recruited to the tyrosine-phosphorylated EpoR, most likely through its interaction with tyrosine-phosphorylated Shc and SHP-2. These results suggest that CrkL is involved in the signaling pathways from the receptors for Epo and IL-3, most likely by modulating the activity of the Ras family GTPases through its interaction with C3G.

Cerebellar ataxia and peripheral neuropathy due to chronic bromvalerylurea poisoning

A patient with chronic bromvalerylurea poisoning showed cerebellar ataxia and peripheral neuropathy. The patient was a 42-year-old Japanese man who developed consciousness disturbance, diplopia, slurred speech, ataxia and gait disturbance after having taken bromvalerylurea for ten years. Magnetic resonance imaging revealed atrophy of the cerebellum and pontine tegmentum. An electrophysiological study revealed decreased motor nerve conduction velocity and amplitude of compound muscle action potentials of the right tibial nerve. Histological findings of the left sural nerve indicated a slightly decreased large myelinated fiber diameter, which suggested chronic axonal damage.

A profile of the behavioral changes produced by facilitation of AMPA-type glutamate receptors

A newly developed group of benzoylpiperidine drugs that enhance AMPA-receptor-gated currents ("ampakines") has been shown to improve memory encoding in rats across a variety of experimental paradigms. The present experiments were intended to i) provide a partial profile of the behavioral changes produced by ampakines, ii) test if two ampakines (BDP-12 and BDP-20) that differ significantly in their effects on AMPA receptor kinetics produce similar behavioral profiles, and iii) determine if physiological potency is reflected in behavioral potency. BDP-20 reduced two measures of exploratory activity in aged rats but increased speed of performance in a radial maze; the drug also caused substantially improved retention of spatial information. These results are similar to those obtained with BDP-12, an analog that differs from BDP-20 in its effects on ligand binding to the AMPA receptor and on the physiological responses of the receptors to glutamate. BDP-20 was approximately ten-fold more potent in behavioral effects than BDP-12, which agrees with the relative potencies of the two drugs as assessed with excised patches and excitatory synaptic responses. These findings indicate that ampakines, though differing in their effects on AMPA-receptor-mediated responses, have similar effects at the behavioral level.