High-yield expression, purification and characterization of tumor-targeted IFN-alpha2a

BACKGROUND

IFN-alpha has been shown to be effective against hematologic malignancies. However, it is ineffective against most solid tumors and has not been satisfactory because of its toxicity.

METHODS

The NGR (Asn-Gly-Arg) peptide is a tumor-homing peptide. In order to increase the anti-tumor activity of IFN-alpha2a and lower the dose, we coupled a cyclic NGR peptide with the C terminus of IFN-alpha2a (named IFN-alpha2a-NGR).

RESULTS

The fusion protein was expressed in E. coli and purified by ion-exchange chromatography. The purity of IFN-alpha2a-NGR was >98% and the final purification yield of IFN-alpha2a-NGR was approximately 18 mg/L. The anti-tumor efficacy and the binding ability of IFN-alpha2a-NGR with tumor vasculature were investigated in vitro and in vivo.

DISCUSSION

Our study has demonstrated that the anti-tumor efficacy of IFN-alpha2a-NGR is significantly increased in comparison with IFN-alpha2a, and IFN-alpha2a-NGR could selectively target tumor vessels. These data indicate that the tumor-homing peptide (NGR) can enhance the therapeutic efficacy of IFN-alpha2a against tumors.

Ultraviolet photoalteration of late Na+ current in guinea-pig ventricular myocytes

UV irradiation has multiple effects on mammalian cells, including modification of ion channel function. The present study was undertaken to investigate the response of membrane currents in guinea-pig ventricular myocytes to the type A (355, 380 nm) irradiation commonly used in Ca(2+) imaging studies. Myocytes configured for whole-cell voltage clamp were generally held at -80 mV, dialyzed with K(+)-, Na(+)-free pipette solution, and bathed with K(+)-free Tyrode's solution at 22 degrees C. During experiments that lasted for approximately 35 min, UVA irradiation caused a progressive increase in slowly-inactivating inward current elicited by 200-ms depolarizations from -80 to -40 mV, but had little effect on background current or on L-type Ca(2+) current. Trials with depolarized holding potential, Ca(2+) channel blockers, and tetrodotoxin (TTX) established that the current induced by irradiation was late (slowly-inactivating) Na(+) current (I(Na)). The amplitude of the late inward current sensitive to 100 microM: TTX was increased by 3.5-fold after 20-30 min of irradiation. UVA modulation of late I(Na) may (i) interfere with imaging studies, and (ii) provide a paradigm for investigation of intracellular factors likely to influence slow inactivation of cardiac I(Na).

Effects of adenosine triphosphate on the vase life of cut carnation flowers

The addition of adenosine triphosphate (ATP) to vase solutions at a concentration of 0.01−0.50 mmol/L markedly extended the vase life of cut carnation flowers at 25°C and 80−90% relative humidity. The most beneficial effect on vase life was observed at 0.1 mmol/L ATP, with a 28% extension over non-ATP-treated flowers. Furthermore, the addition of ATP at 0.1 mmol/L increased flower size by 12% by the end of the vase-holding period and significantly extended the time to maximum flower expansion by 1.7 days, compared with non-ATP-treated flowers held in distilled water. Our data suggest that exogenous ATP supply is an effective method to extend the vase life of cut carnation flowers.

Gene profiling involved in immature CD4+ T lymphocyte responsible for systemic lupus erythematosus

We attempted to characterize the genes expression of CD4+ T lymphocytes for the pathogenesis of systemic lupus erythematosus (SLE). Genomewide gene expression profiles of CD4+ T cells, which were isolated from the disease severe activity (T4-1s) and nonactivity (T4-2s) with an SLE patient by using long serial analysis of gene expression (LongSAGE). We picked out 289 genes matching to Unigene cluster with different expression more than four copies between T4-1s and T4-2s libraries and analyzed their roles from the collectedly published articles of PubMed by genes functional clustering. The genes functions were related to a diverse cellular process including: (1) most of these genes were associated with CD4+ T cells functions, particularly related to cellular developments; (2) Ras pathway genes as RANBP10, GMIP, RASGRP2 and ARL5 might be responsible for the abnormal development of CD4+ T cells of SLE; (3) HIG2, TCF7, KHSRP, WWP1, SMAD3, TLK2, AES, CCNI and PIM2 belong to Wnt/beta-catenin way, they could play roles in modulating proliferation and differentiation of T lymphocytes; (4) uncertain viral infections may initiate autoimmunity because high levels expression genes were detected in T4-1s such as TRIM22, IER2, ABCE1, DUT, G1P2, G1P3, HNRPUL1, EVER2, IFNAR1, TNFSF14, TMP21 and PVRL2; and (5) apoptosis relating genes as EIF3S8, SH3BGRL3, GPX4, TOSO, PFDN5, BIN1, XIAPAF1, TEGT and CUGBP2 may contribute to over uploading of selfantigens in SLE cells. Abnormalities findings of multiple genes expression involving with a variety of CD4+ T cells process might be meaningful to understanding the pathogenesis of SLE, and immature CD4+ T cells may be responsible for SLE.

[Study on anticardiolipin antibody in the patients with primary nephrotic syndrome]

Combination of the anticardiolipin antibody with the phospholipids on the surfaces of the endothelia and thrombocytes can damage the basic functions of cells. In this study, the anticardiolipin antibody was detected in 68 cases with primary nephrotic syndrome and 30 healthy persons. The positive rates were 32.35% and 3.33%, respectively. The hypercoagulability and glomerular impairment in the positive cases were more evident than those in the negative cases. In addition, the sensitivity to treatment in the positive cases was markedly decreased. These findings indicate that the anticardiolipin antibody may play an important role in pathophysiological processes of primary nephrotic syndrome.

Vesicular stomatitis virus G-pseudotyped lentivirus vectors mediate efficient apical transduction of polarized quiescent primary alveolar epithelial cells

We investigated the use of lentivirus vectors for gene transfer to quiescent alveolar epithelial cells. Primary rat alveolar epithelial cells (AEC) grown on plastic or as polarized monolayers on tissue culture-treated polycarbonate semipermeable supports were transduced with a replication-defective human immunodeficiency virus-based lentivirus vector pseudotyped with the vesicular stomatitis virus G (VSV-G) protein and encoding an enhanced green fluorescent protein reporter gene. Transduction efficiency, evaluated by confocal microscopy and quantified by fluorescence-activated cell sorting, was dependent on the dose of vector, ranging from 4% at a multiplicity of infection (MOI) of 0.1 to 99% at an MOI of 50 for AEC grown on plastic. At a comparable titer and MOI, transduction of these cells by a similarly pseudotyped murine leukemia virus vector was approximately 30-fold less than by the lentivirus vector. Importantly, comparison of lentivirus-mediated gene transfer from the apical or basolateral surface of confluent AEC monolayers (R(t) > 2 kOmega. cm(2); MOI = 10) revealed efficient transduction only when VSV-G-pseudotyped lentivirus was applied apically. Furthermore, treatment with EGTA to increase access to the basolateral surface did not increase transduction of apically applied virus, indicating that transduction was primarily via the apical membrane domain. In contrast, differentiated tracheal epithelial cells were transduced by apically applied lentivirus only in the presence of EGTA and at a much lower overall efficiency (approximately 15-fold) than was observed for AEC. Efficient transduction of AEC from the apical cell surface supports the feasibility of using VSV-G-pseudotyped lentivirus vectors for gene transfer to the alveolar epithelium and suggests that differences exist between upper and lower airways in the polarity of available receptors for the VSV-G protein.

Effects of paramyxoviral infection on airway epithelial cell Foxj1 expression, ciliogenesis, and mucociliary function

To elucidate molecular mechanisms underlying the association between respiratory viral infection and predisposition to subsequent bacterial infection, we used in vivo and in vitro models and human samples to characterize respiratory virus-induced changes in airway epithelial cell morphology, gene expression, and mucociliary function. Mouse paramyxoviral bronchitis resulted in airway epithelial cell infection and a distinct pattern of epithelial cell morphology changes and altered expression of the differentiation markers beta-tubulin-IV, Clara cell secretory protein, and Foxj1. Furthermore, changes in gene expression were recapitulated using an in vitro epithelial cell culture system and progressed independent of the host inflammatory response. Restoration of mature airway epithelium occurred in a pattern similar to epithelial cell differentiation and ciliogenesis in embryonic lung development characterized by sequential proliferation of undifferentiated cells, basal body production, Foxj1 expression, and beta-tubulin-IV expression. The effects of virus-induced alterations in morphology and gene expression on epithelial cell function were illustrated by decreased airway mucociliary velocity and impaired bacterial clearance. Similar changes in epithelial cell Foxj1 expression were also observed in human paramyxoviral respiratory infection. Taken together, these model systems of paramyxoviral respiratory infection mimic human pathology and identify epithelial cell Foxj1 expression as an early marker of epithelial cell differentiation, recovery, and function.

In vitro-inhibition of shear-induced platelet aggregation by verapamil

The purpose of the study was to investigate the effect of verapamil on shear induced platelet aggregation (SIPA). Blood of New Zealand rabbit was collected to prepare platelet-rich-plasma (PRP) by routine centrifugation. A cone-plate shear device was employed to generate shear stress. The verapamil-treated PRP or control PRP were sheared at 37 degrees C for 120 sec. SIPA was determined from counting of free platelet. The inhibition rates of SIPA by verapamil for five doses at three shear levels were calculated accordingly. The concentration of half inhibition (IC50) was 0.03, 0.07 and 0.09 mmol/l for 20, 40 and 52 dyn/cm2, respectively. The regression for IC50 of verapamil and shear stress follows the linear equation: IC50=-0.0071+0.0019tau (r=0.999,P=0.03). The results indicate that calcium antagonist may have the potential for inhibition of SIPA although the current IC50 for rabbit platelet is higher than that of human routine blood concentration of verapamil.

[Characters of uncoupling protein and its relation with obesity]

Uncoupling proteins(UCP) are carrier proteins in mitochondria. In eukaryotic cells, ATP is generated by oxidative phosphorylation, an energetic coupling at mitochondria level. The oxidative reactions occurring in the respiratory chain generate an electrochemical proton gradient at both sides of the inner membrane of mitochondria. This gradient is used by the ATP synthase to phosphorylate ADP into ATP. The coupling of cell respiration with ADP phosphorylation is only partial in brown adipose tissue (BAT) mitochondria, where UCP causes a reentry of protons into the matrix and abolishes the electrochemical proton gradient. The liberated energy is then dissipated as heat and the synthesis of ATP is reduced. Recently, the cloning of new UCPs expressed in other tissues revealed the importance of this kind of regulation of respiratory control in metabolism and energy expenditure. The newly characterized UCPs are potential target drugs for obesity treatment, which could be favor of energy expenditure and diminish the metabolic efficiency.

Esters of 2-(1-hydroxyalkyl)-1,4-dihydroxy-9,10-anthraquinones with melphalan as multifunctional anticancer agents

Eight esters of 2-(1-hydroxyalkyl)-1,4-dihydroxy-9,10-anthraquinone with melphalan were prepared and tested for their antitumor activity (S-180) and cytotoxicity. 2-[1-[4-(p-Bis(2-chloroethyl)-aminophenyl)-butanoyloxy]methyl]-1,4-dihydroxy-9,10-anthraquinone and 2-[1-[4-(p-bis(2-chloroethyl)-aminophenyl)-butanoyloxy]ethyl]-1,4-dihydroxy-9,10-anthraquinone showed remarkable antitumor activity (T/C, 265 and 272%).

Expression of Fos immunoreactivity in some catecholaminergic brainstem neurons in rats following high-altitude exposure

This study examined the response of neurons of the cardiorespiratory centers, i.e., the nucleus tractus solitarius and the ventrolateral medulla as well as the area postrema in adult and postnatal rats subjected to high-altitude exposure at 4,000 m and 8,000 m. In adult control rats, sporadic Fos-positive neurons were detected in the above-mentioned areas. On exposure to 4,000 m altitude, the number of Fos-positive neurons was noticeably increased. At 8,000 m, the incidence of labeled cells was markedly increased, with many of them doubly labeled for tyrosine hydroxylase. In postnatal rats, Fos expression was not detected in these areas in either control rats or rats exposed to 4,000 m altitude. Fos-positive cells, however, were observed in the these areas in postnatal rats exposed to 8,000 m. In the latter, tyrosine hydroxylase labeling was observed in some Fos-positive cells in the nucleus tractus solitarius and ventrolateral medulla. In rats killed at 24 hr after exposure to high altitude, Fos expression in both the adult and the postnatal rats was comparable to that in their corresponding control rats. Present results suggest that Fos expression in various brainstem areas was induced by reduced oxygen tension in the ambient air at high altitude. Double labeling of some Fos-positive neurons with tyrosine hydroxylase indicates an increased sympathetic activation, which may be involved in the mediation of cardiorespiratory responses to hypoxia. This, however, was less evident in the postnatal animals. It is possible that the peripheral chemoreceptors or the regulation of autonomic functions is not fully developed in this age group.

Ultrastructure and function of the amoeboid microglial cells in the periventricular white matter in postnatal rat brain following a hypoxic exposure

The ameboid microglial cells (AMC), located in the periventricular white matter, were examined ultrastucturally in neonatal rats following a hypoxic exposure. For 10 min to 1 day, following the hypoxic exposure, a large number of glial cells with nuclear chromatin condensation, undergoing degeneration, were observed in the white matter. Such cells were often being phagocytosed by the AMC. At 3-7 days after the hypoxic exposure, the cytoplasm of many AMC contained a number of phagosomes whereas at 14-28 days a large amount of lipid accumulation was observed in them. AMC were labeled intensely with horseradish peroxidase (HRP) administered intraperitoneally following the hypoxic exposure. The phagocytosis of degenerating cells by the AMC and uptake of HRP by them indicates that these cells efficiently remove the degenerating cells/debris from the neonatal white matter following hypoxia in an attempt to protect it from any harmful substances that may be secreted by the degenerating cells or from serum derived substances that may enter the brain through blood circulation.

Physical mapping of male fertility and meiotic drive quantitative trait loci in the mouse t complex using chromosome deficiencies

The t complex spans 20 cM of the proximal region of mouse chromosome 17. A variant form, the t haplotype (t), exists at significant frequencies in wild mouse populations and is characterized by the presence of inversions that suppress recombination with wild-type (+) chromosomes. Transmission ratio distortion and sterility are associated with t and affect males only. It is hypothesized that these phenomena are caused by trans-acting distorter/sterility factors that interact with a responder locus (Tcr(t)) and that the distorter and sterility factors are the same because homozygosity of the distorters causes male sterility. One factor, Tcd1, was previously shown to be amorphic using a chromosome deletion. To overcome limitations imposed by recombination suppression, we used a series of deletions within the t complex in trans to t chromosomes to characterize the Tcd1 region. We find that the distorter activity of Tcd1 is distinct from a linked sterility factor, originally called tcs1. YACs mapped with respect to deletion breakpoints localize tcs1 to a 1.1-Mb interval flanked by D17Aus9 and Tctex1. We present evidence for the existence of multiple proximal t complex regions that exhibit distorter activity. These studies demonstrate the utility of chromosome deletions for complex trait analysis.

Expression of induced nitric oxide synthase in amoeboid microglia in postnatal rats following an exposure to hypoxia

The present study showed the expression of induced nitric oxide synthase (iNOS) immunoreactivity in amoeboid microglia following an exposure to transient hypoxia in postnatal rats. iNOS immunoreactivity was expressed mainly in the amoeboid microglia in corpus callosum and subependymal regions of the ventricles within 3 h after hypoxia. The expression declined after 5 h, and became undetectable after 15 h and in longer surviving rats. The immunoreactivity of these cells with OX-42, which is a marker for microglia cells and detects complement type three receptors (CR3), was comparable in the rats exposed to hypoxia and the control rats. Immunoglobulin G (IgG) immunoreactivity was observed in the amoeboid microglia up to 3 h after hypoxia but it was undetectable in longer surviving rats and in the control rats. The iNOS expression in the amoeboid mircoglial cells may be related to the host defense and maintenance of structural integrity of the highly vulnerable periventricular white matter after hypoxia. The immunostaining of amoeboid microglial cells with IgG following hypoxia indicates leakage of plasma immunoglobulin from the blood vessels and its removal by the amoeboid microglial cells.

Methodological study of cell separation with domestic immunomagnetic beads

To establish the method of cell separation with domestic immuomagnetic beads, three methods were investigated. Direct method, SPA method and Biotin-Avidin method were applied to separate cell strain Hut-78 and CD4 positive cells. Separation rate of strain Hut-78 was more than 90% in direct method. Detachment rate with papain was over 95%. Cell activity was well retained. SPA method and Biotin-Avidin methods were also effective, but the direct method was superior to the other two techniques. Before separated by the direct method, CD4 positive cells constituted 46.4% +/- 6.4% of mononuclear cells (MNC), but in eliminated suspension there was only 6.2% +/- 2.3% CD4 positive cells left. In the separated part, 80.6% +/- 7.2% of the cells combined with the beads. It is concluded that the direct method in separating cells had high sensitivity and specificity.

Separation of CD34 positive cells and determination of surface homing antigen

To study the differences in homing potential between bone marrow cells and umbilical blood cells, CD34 positive cells were obtained from bone marrow (BM) and umbilical blood (UB) by the direct cell separation with domestic immunomagnetic beads. The expression of the two adhesion molecules CD11a/CD18 and CD44 were examined. After separation, CD34 positive cells accounted for 51%-82% of the harvested cells and dye-resistance rate was 82%-88%. The expression of CD11a/CD18 and CD44 on the surfaces of UB cells was 49.6% +/- 10.2% and 37.7% +/- 10.3% respectively. On BM cells they were 50.2% +/- 6.2% and 34% +/- 13.3% respectively. There were no significant differences in the expression of these two molecules. It was concluded that the cell separation method with domestic immunomagnetic beads was effective and the stem cells from UB could serve as an alternative source for transplantation.

[Genetic complementation group analysis of xeroderma pigmentosum patients in China]

OBJECTIVE

To establish skin fibroblast cell strains derived from Chinese xeroderma pigmentosum(XP) patients and to analyze the genetic complementation group and distribution.

METHODS

From four XP patients, skin fibroblast cell strains were derived and used for the complementation group analysis by autoradiography and cell-fusion technique.

RESULTS

Of the four XP patients from apparently independent families, three were assigned to group C, and one belonged to group E. This is the first report on XP-E patient in China.

CONCLUSION

Based on the data from the previous 7 cases and the present 4 cases, the distribution of complementation group in Chinese XP patients known at present is: nine XP-C, one XP-F and one XP-E. Although the number of cases is still limited, XP-C appears to be more frequent in China. This forms a marked contrast to Japanese XP patients, who are dominated by XP-A with infrequent presence of XP-C.

[The significance of pattern electroretinogram in detecting retinal function in primary open angle glaucoma]

OBJECTIVE

To evaluate the clinical significance of pattern electroretinogram (PERG) in primary open angle glaucoma (POAG).

METHOD

Thirty-six patients (59 eyes) with POAG and 32 persons (59 eyes) as age-matched normal controls were tested by PERG.

RESULTS

The changes of PERG in POAG included reduction of amplitudes of P(1), N(2), P(1) + N(2) and N(2)/P(1). Using the criteria of AN(2) + AP(1) < 2.7 and AN(2)/AP(1) < 0.7 (A = amplitude), the positive rate was 90% in 59 eyes with POAG, and no eye from the normal control group was considered as abnormal. The amplitudes of PERG had already been abnormal before the early visual field loss occurred in POAG eyes. The amplitudes of P(1) and N(2) waves decreased with the enlargement of visual field defect, were positively correlated to the patient's visual acuity and negatively correlated to the cup/disc ratio of optic nerve papilla, and linear regression equations between them were respectively established.

CONCLUSION

PERG is an useful method in detecting the retinal functions in POAG.

Recombinant fusion protein and DNA vaccines against foot and mouth disease virus infection in guinea pig and swine

In this study, we provide evidence that a recombinant fusion protein containing beta-galactosidase and a tandem repeat peptide of immunogenic dominant epitope of foot-and-mouth disease virus (FMDV) VP1 protein elicits high levels of neutralizing antibody and protects both guinea pigs and swine against infection. Vaccination with this fusion protein induced a FMDV-specific proliferative T-cell response and a neutralizing antibody response. The immunized guinea pigs and swine were protected against FMD type O virus infection. Two DNA plasmids expressing genes of foot-and-mouth disease were constructed. Both plasmids pBO1 and pCO1 contain a signal sequence of the swine immunoglobulin G (IgG) gene and fusion protein gene of pXZ84. The signal sequence and fusion protein gene were under the control of a metallothionein promoter in the case of the pBO1 plasmid and under the control of a cytomegalovirus immediate early promoter in the case of pCO1 plasmid. When pBO1 and pCO1 were inoculated intramuscularly into guinea pigs, both plasmids elicited a neutralizing antibody response and spleen cell proliferation increased following stimulation with FMDV antigen, but animals were not protected from viral challenge.

Shared and unique determinants of the erythropoietin (EPO) receptor are important for binding EPO and EPO mimetic peptide

We have shown previously that Phe93 in the extracellular domain of the erythropoietin (EPO) receptor (EPOR) is crucial for binding EPO. Substitution of Phe93 with alanine resulted in a dramatic decrease in EPO binding to the Escherichia coli-expressed extracellular domain of the EPOR (EPO-binding protein or EBP) and no detectable binding to full-length mutant receptor expressed in COS cells. Remarkably, Phe93 forms extensive contacts with a peptide ligand in the crystal structure of the EBP bound to an EPO-mimetic peptide (EMP1), suggesting that Phe93 is also important for EMP1 binding. We used alanine substitution of EBP residues that contact EMP1 in the crystal structure to investigate the function of these residues in both EMP1 and EPO binding. The three largest hydrophobic contacts at Phe93, Met150, and Phe205 and a hydrogen bonding interaction at Thr151 were examined. Our results indicate that Phe93 and Phe205 are important for both EPO and EMP1 binding, Met150 is not important for EPO binding but is critical for EMP1 binding, and Thr151 is not important for binding either ligand. Thus, Phe93 and Phe205 are important binding determinants for both EPO and EMP1, even though these ligands share no sequence or structural homology, suggesting that these residues may represent a minimum epitope on the EPOR for productive ligand binding.

Clonal growth of human acute leukemia cells in serum-free methylcellulose medium

The clonal growth of human acute leukemia cell line (K562) and acute myeloid leukemia cells in the serum-free culture (SFC) was studied in order to establish a SFC system which could replace the effects of serum by using semi-solid methylcellulose culture technique. Our results showed that the clonal growth of K562 cells in semi-solid culture was dependent on exogenous serum. The K562 could be grown in SFC supplemented with 4 major replacing substances. The multifactor and multilevel orthogonal experiment demonstrated that the colony formation was statistically influenced by the 4 replacing substances at various concentrations (P < 0.01). Among them, bovine serum albumin had greatest effect on clonal growth of K562 cells with the optimal concentration being 15 mg/L, followed by transferring, cholesterol and insulin with their optimal concentrations being of 150 mg/L, 7.8 mg/L and 7.0 mg/L respectively. SFC system was formed with the 4 substances at their optimal concentrations. Colony formation of the blast cells in 10 patients with acute myeloid leukemia was observed in this SFC system. There was a heterogeneity of acute myeloid leukemia cells among the 10 patients in response to the growth substances. In SFC system, there was a linear relationship between the number of the clonal formation and the count of the added cells, indicating the colony growth of the cells. Primary acute leukemia cells maintained in SFC system in 10 cases could completely form clones. The colony formation number in some cases in SFC system was more than that of the serum-containing culture. The SFC system could partially replace the serum for study of the clonal formation of human leukemia cells.

Multidrug resistance P-glycoprotein function of bone marrow hematopoietic cells and the reversal agent effect

The multidrug resistance P-glycoprotein (P-gp) expression and function in hematopoietic stem/progenitor cells were studied to investigate whether the inhibition of hematopoietic cell P-gp function by multidrug resistance reversal agent increases the cytotoxicity of chemotherapy drugs on the hematopoietic cells. The expression of P-gp on the surface of CD34+ cells from healthy human marrow was examined by flow cytometry. The multidrug resistance reversal agent MS-209 was used to measure the effects of MS-209 on the Rhodamin-123 uptaking of CD34+ hematopoietic cells. By using methylcellulose semi-solid culture, normal human granulocyte-macrophage clonal formation unit (CFU-GM) was cultured. The changes in CFU-GM inhibitory rate caused by daunorubicin were determined in the presence or absence of MS-209. The results showed that the P-gp expression rate of bone marrow CD34+ cells was 13.3%. MS-209 obviously increased the Rhodamin-123 uptake of CD34+ positive cells. The mean inhibitory rate of daunorubicin for CFU-GM was 29.6%, but it was increased to 43.3% in the presence of MS-209 with the difference being significant (P < 0.05). It was concluded that hematopoietic cells expressed P-gp protein and possessed active function. MS-209 could inhibit the membrane efflux pump and increase the cytotoxicity of chemotherapy drugs to the clonal growth of hematopoetic stem cells, suggesting the side effects of these drugs on the hematopoietic system should be taken into consideration in the clinical use.

Measurement of the activation of IL-2 on bone marrow by flow cytometry

The changes of cell surface markers before and after activation by IL-2 were detected by flow cytometry (FCM) to establish a more convenient and precise criterion for the judgment of the activation of bone marrow. By using the measurement of the release of lactate dehydrogenase (LDH) the cytotoxicity of mononuclear cells (MNCs) from bone marrow, activated or inactivated, on tumor cell line K562 was evaluated, and at the same time the changes of surface markers on MNCs before and after activation were examined by using FCM. The results showed that the cytotoxicity of MNCs from bone marrow activated by IL-2 on tumor cell line K562 was increased obviously and the number of CD25+ and CD70+ positive cells in bone marrow MNCs was higher than before activation. The enhanced cytotoxicity of MNCs on tumor cell line K562 was synchronous with the increase of the number of CD25+ and CD70+ positive cells in 48 to 72 h. It is more direct, simple and precise to demonstrate the activation of IL-2 on bone marrow by detecting the changes of the amount of the CD25+ and CD70+ positive cells in bone marrow by FCM.

An antagonist peptide-EPO receptor complex suggests that receptor dimerization is not sufficient for activation

Dimerization of the erythropoietin (EPO) receptor (EPOR), in the presence of either natural (EPO) or synthetic (EPO-mimetic peptides, EMPs) ligands is the principal extracellular event that leads to receptor activation. The crystal structure of the extracellular domain of EPOR bound to an inactive (antagonist) peptide at 2.7 A resolution has unexpectedly revealed that dimerization still occurs, but the orientation between receptor molecules is altered relative to active (agonist) peptide complexes. Comparison of the biological properties of agonist and antagonist EMPs with EPO suggests that the extracellular domain orientation is tightly coupled to the cytoplasmic signaling events and, hence, provides valuable new insights into the design of synthetic ligands for EPOR and other cytokine receptors.

Deletion mapping of the head tilt (het) gene in mice: a vestibular mutation causing specific absence of otoliths

Head tilt (het) is a recessive mutation in mice causing vestibular dysfunction. Homozygotes display abnormal responses to position change and linear acceleration and cannot swim. However, they are not deaf. het was mapped to the proximal region of mouse chromosome 17, near the T locus. Here we report anatomical characterization of het mutants and high resolution mapping using a set of chromosome deletions. The defect in het mutants is limited to the utricle and saccule of the inner ear, which completely lack otoliths. The unique specificity of the het mutation provides an opportunity to better understand the development of the vestibular system. Complementation analyses with a collection of embryonic stem (ES)- and germ cell-induced deletions localized het to an interval near the centromere of chromosome 17 that was indivisible by recombination mapping. This approach demonstrates the utility of chromosome deletions as reagents for mapping and characterizing mutations, particularly in situations where recombinational mapping is inadequate.

Absence of cytokine receptor-dependent specificity in red blood cell differentiation in vivo

Erythropoietin (EPO) is required for red blood cell development, but whether EPO-specific signals directly instruct erythroid differentiation is unknown. We used a dominant system in which constitutively active variants of the EPO receptor were introduced into erythroid progenitors in mice. Chimeric receptors were constructed by replacing the cytoplasmic tail of constitutively active variants of the EPO receptor with tails of diverse cytokine receptors. Receptors linked to granulocyte or platelet production supported complete erythroid development in vitro and in vivo, as did the growth hormone receptor, a nonhematopoietic receptor. Therefore, EPOR-specific signals are not required for terminal differentiation of erythrocytes. Furthermore, we found that cellular context can influence cytokine receptor signaling.

Heteromerization of the gammac chain with the interleukin-9 receptor alpha subunit leads to STAT activation and prevention of apoptosis

Interleukin-9 (IL-9) is a cytokine with pleiotropic effects on mast cell and T cell lines. It exerts its effects through the IL-9R complex consisting of IL-9Ralpha and the common gammac subunit. Here we report functional evidence for receptor heteromerization for efficient signal transduction, and we define minimal requirements in the two receptor subunits for IL-9R function. Tyrosine 336 of the IL-9Ralpha and the membrane-proximal segment of gammac are both crucial for signaling. The activated IL-9R complex employs the Janus kinases JAK1 and JAK3 for subsequent activation of the signal transducer and activator transcription (STAT) factors STAT-1, STAT-3, and STAT-5. This process is independent of Tyk2. We demonstrate further that the activated STAT complexes consist of STAT-1 and STAT-5 homodimers and STAT-1-STAT-3 heterodimers. Finally, we show that IL-9R signaling in a T cell line does not result in detectable mitogen-activated protein kinase activation and leads to unsustained proliferation. Nonetheless, these T cells are efficiently protected from dexamethasone-induced apoptosis. These results further define the molecular architecture of the IL-9R and its specific connections to various biologic responses.

Sensitization of acnu killing effects on HeLa S3 cells by MGMT antisense RNA transfection

O6-methylguanine-DNA-methyltransferase (MGMT) plays a very important role in the cellular resistance to nitrosoureas drugs. Inhibition of MGMT might be a useful approach in tumor chemotherapy. In this study, the depletion of MGMT activity by retroviral-mediated antisense RNA transfection were reported. Three retroviral vectors expressing MGMT antisense RNA were constructed and transfected into HeLa S3 cells. The difference of MGMT mRNA, MGMT activity as well as cellular resistance to ACNU before and after transfection were observed. It was found that antisense RNA targeting 5' region and whole length of MGMT mRNA could partially deplete MGMT activity and enhance killing effects of ACNU. However, 3' region antisense RNA had no effect on MGMT modulation.

Utility of C57BL/6J x 129/SvJae embryonic stem cells for generating chromosomal deletions: tolerance to gamma radiation and microsatellite polymorphism

We have previously reported a method for making nested deletion complexes in mice by irradiation of ES cells. The key to this technology is that F1 hybrid ES cells (called v17.2) of the genotype (BALB/cTa x 129/SvJae) retain germline colonizing ability after exposure to levels of ionizing radiation that induce chromosomal deletions. In an effort to identify other genotypes of ES cells that are suitable for this technology, the radiation sensitivity of the cell line v6.4, which is of the genotype (C57BL/6J x 129/SvJae), was investigated. After treatment with a range of radiation exposures, the developmental potential of these cells was assayed by injecting them into blastocysts to generate chimeric mice. These experiments showed that while cell lethality increased as the level of radiation increased, the surviving ES cells retained full totipotency at all exposure levels, up to 400 Rads. Because polymorphism between parental microsatellite alleles in the F1 hybrid ES cells is important for ascertaining the sizes of induced deletions, the 129/SvJ and 129/SvJae allele sizes of 48 microsatellite loci on chromosome (Chr) 17 were determined. This revealed a higher level of polymorphism between 129 and C57BL/6J on Chr 17. The radiation tolerance, high polymorphism between parental strains, and presence of the widely used C57BL/6J strain component make v6.4 ES cells an attractive cell line for generating radiation-induced chromosomal deletions.

Redundant and selective roles for erythropoietin receptor tyrosines in erythropoiesis in vivo

Cytokine receptors have been shown in cell culture systems to use phosphotyrosine residues as docking sites for certain signal transduction intermediates. Studies using various cellular backgrounds have yielded conflicting information about the importance of such residues. The present studies were undertaken to determine whether or not tyrosine residues within the erythropoietin receptor (EPOR) are essential for biologic activity during hematopoiesis in vivo. A variant of the EPOR was constructed that contains both a substitution (R129C) causing constitutive receptor activation as well as replacement of all eight cytoplasmic tyrosines by phenylalanines (cEPORYF). A comparison between animals exposed to recombinant retroviruses expressing cEPOR and cEPORYF showed that efficient red blood cell (RBC) development in vivo is dependent on the pressence of tyrosine residues in the cytoplasmic domain of the EPOR. In addition, an inefficient EPOR tyrosine independent pathway supporting RBC development was detected. Tyrosine add-back mutants showed that multiple individual tyrosines have the capacity to restore full erythropoietic potential to the EPOR as determined in whole animals. The analysis of primary erythroid progenitors transduced with the various cEPOR tyrosine mutants and tyrosine add-backs showed that only tyrosine 343 (Y1) and tyrosine 479 (Y8) were capable of supporting immature burst-forming unit-erythroid progenitor development. Thus, this receptor is characterized by striking functional redundancy of tyrosines in a biologically relevant context. However, selective tyrosine residues may be uniquely important for early signals supporting erythroid development.

Assignment of three Chinese xeroderma pigmentosum patients to complementation group C and one to group E

Four Chinese patients with xeroderma pigmentosum (XP), who had different degrees of skin symptoms, were tested for their genetic complementation groups. Skin fibroblasts obtained from the patients were used for complementation analysis done by a cell-fusion technique. Three of the patients belonged to group C and one, who had the mildest cutaneous manifestations, to group E. This is the first report of a group E XP patient in China. Our present findings together with previous reports suggest that group C XP is more common in China, similar to the distribution among Caucasian XP patients but markedly different from the Japanese distribution.

[Determination and significance of catecholamines in aqueous humor, plasma and 24 hour urine of patients with acute angle-closure glaucoma]

OBJECTIVE

To study the functional state of ocular and systemic sympathetic nervous system and the effects of its related neurohumoral factor, catecholamines (CA), on intraocular pressure (IOP) in patients with acute angle-closure glaucoma (AACG).

METHODS

The levels of CA in the aqueous humor, plasma and the total amount of CA in 24 hour urine of cases with AACG during attack stage were determined with fluorometry, and the results were compared to that of patients with senile cataract and normal adults.

RESULTS

The CA levels within aqueous humor and plasma and in 24 hour urine of the patients with AACG during attack stage were elevated obviously as compared with that of the control subjects (P < 0.001), and positively correlated with the level of IOP.

CONCLUSION

During attack stage of AACG, the ocular sympathetic nervous system is highly excited and a large amount of CA is released into the aqueous humor, in the meantime the systemic sympathetic nervous system is also excited and CA is released into the blood circulation, which may play a certain role in the regulation of IOP. Possibly, CA is an important supplemental factor within the attack stage of AACG.

Beta-adrenoceptor-coupled Gs protein facilitates the activation of cAMP-dependent cardiac Cl- current

Here a comparison is made between adenosine 3',5'-cyclic monophosphate (cAMP)-activated Cl- current (ICl) density and activation time course in response to beta-adrenoceptor stimulation with isoproterenol and adenylyl cyclase activation with forskolin. Saturating concentrations of isoproterenol and forskolin failed to activate an ICl in guinea pig atrial as well as in rat and frog ventricular cardiomyocytes. In guinea pig ventricular cardiomyocytes, step application of 1 microM isoproterenol induced an ICl of -0.89 +/- 0.32 pA/pF (holding potential -40 mV, temperature 22 +/- 1 degrees C). ICl activation started after 3 +/- 1 s, was complete within 44 +/- 9 s, and was abolished after cell dialysis with the Rp diastereomer of adenosine 3',5'-cyclic monophosphothioate. Stimulation with increasing concentrations of forskolin (0.01-10 microM) increased ICl density and accelerated ICl activation. With 1 microM forskolin, ICl density was maximal (-0.57 +/- 0.30 pA/pF) but significantly smaller than that achieved with 1 microM isoproterenol. Although ICl density could not be further augmented by forskolin > 1 microM, current activation (latency 28 +/- 8 s, full activation after 112 +/- 8 s with 1 microM forskolin) was further accelerated by 3 and 10 microM forskolin. However, ICl activation with 10 microM forskolin was still slower than that with 1 microM isoproterenol. A low isoproterenol concentration (1 nM), which did not activate ICl by itself, accelerated the 1 microM forskolin-induced activation of ICl by 35%; this speeding up was abolished after cell dialysis with guanosine 5'-O-(2-thiodiphosphate). ICl deactivation after the washout of 1 microM forskolin or 1 microM isoproterenol followed a similar time course. After stimulation with 10 microM forskolin or 1 microM forskolin + 1 microM isoproterenol, but not with 1 microM forskolin + 1 nM isoproterenol, the decay of ICl was significantly delayed. These results indicate that both cAMP-dependent and cAMP-independent G protein pathways contribute to the regulation of guinea pig ventricular ICl.

Generation of radiation-induced deletion complexes in the mouse genome using embryonic stem cells

As the genetic and physical mapping stage of the Human Genome Project nears completion, the focus is shifting toward the development of technologies for high-throughput analysis of gene function. Whereas DNA sequencing will enable the assignment of presumed function to a large number of genes in mice and humans, it is clear that the great majority of genes will have to be evaluated in vivo to accurately assess their role in a complex organism. While gene targeting in mouse embryonic stem (ES) cells is the current method of choice for the characterization of gene function in mice, it remains relatively labor intensive and lacks the throughput required for analysis of genome function on a large scale. Alternative methods of efficient mutagenesis will clearly be required for this task. Chromosomal deletions are powerful tools in the genetic analysis of complex genomes, enabling the systematic identification and localization of functional units along defined chromosomal regions. Not only are deletions useful for the identification of genetic functions, but they serve as mapping reagents for existing mutations or traits. While their use has been an essential tool in Drosophila genetics, classical mutagenesis in mice has been logistically impractical for generating deletions. We have previously described an efficient method for generating radiation-induced deletion complexes at defined regions in the genome using ES cells. In this article, we detail the methodological aspects of this technology and describe the applications of chromosomal deletions for characterizing gene function in ways that make optimal use of the information generated by the first stage of the Genome Project.

Membrane currents underlying the modified electrical activity of guinea-pig ventricular myocytes exposed to hyperosmotic solution

1. Guinea-pig ventricular myocytes were superfused with hyperosmotic (sucrose) Tyrode solution (1.2-2.8 times (T) normal osmolality) for up to 40 min. Action potentials were recorded with microelectrodes, and membrane currents with the perforated- or ruptured-patch technique. 2. Hyperosmotic treatment for 20 min shrunk cell volume and hyperpolarized the membrane. Moderate (1.2-1.5 T) treatment caused biphasic changes in action potential configuration (rapid minor shortening quickly followed by lengthening to a stable 110% control duration). Severe (2.2-2.8 T) treatment caused triphasic changes (marked early shortening, strong rebound lengthening and subsequent pronounced shortening). At peak lengthening (6-10 min) action potentials (165% control duration) had a hump near -30 mV and slowed terminal repolarization. 3. In accordance with previous studies, hyperosmotic solution inhibited the delayed rectifier K+ current, and enhanced the outward Na(+)-Ca2+ exchange current (INaCa) at plateau potentials. A novel finding was that hyperosmolality reduced the amplitude of L-type Ca2+ current (ICa,L) and slowed its rate of inactivation. Experiments on myocytes loaded with indo-1 suggest that the reduction in ICa,L is due to a rapid elevation of [Ca2+]i. 4. When impaled myocytes were preloaded with EGTA, severe hyperosmotic treatment induced a rapid monotonic shortening of the action potential to a stable 20% of control duration. Addition of external K+ quickly nulled the hyperpolarization and slowly lengthened the action potential. 5. The results suggest that modified electrical activity in osmotically shrunken myocytes is primarily caused by increases in [K+]i, [Na+]i and [Ca2+]i: (i) elevated [K+]i hyperpolarizes the membrane (which may contribute to increased [Na+]i); (ii) elevated [Na+.]i shortens all phases of the action potential (increased outward-directed INaCa); and (iii) elevated [Ca2+]i has antagonistic plateau shortening (inhibition of inward ICa,L) and plateau lengthening (reduced outward INaCa) influences, as well as a strong subplateau lengthening effect (enhanced inward INaCa).

[Determination of fumaric acid in Sarcandra glabra (Thunb.) Nakai by HPLC]

A method for the determination of fumaric acid in Sarcandra glabra is reported. After the sample was pretreated with an anion exchange resin column, fumaric acid was determined on a Spherisorb C18 column, with methanol-0.02 mol/L monobasic potassium (20:80, pH2.5) as the mobile phase and detected at 210 nm. The method is simple and accurate.

A Kaposi's sarcoma-associated herpesvirus-encoded cytokine homolog (vIL-6) activates signaling through the shared gp130 receptor subunit

The present studies analyzed the biologic activity of a gene product (vIL-6) encoded by the recently discovered Kaposi's sarcoma-associated herpesvirus (KSHV) bearing 24.8% amino acid identity with human interleukin-6 (huIL-6). Based on this similarity, we hypothesized that this viral homolog might trigger the JAK/STAT pathway, which typically is engaged by IL-6 and other cytokines. Activation of receptor-associated Janus tyrosine kinases (JAKs) results in the subsequent phosphorylation of signal transducers and activators of transcription (STATs) leading to nuclear entry and transcriptional regulation of target genes. Treatment of HepG2 cells with culture medium containing recombinant KSHV-encoded vIL-6 led to rapid induction of JAK1 phosphorylation and a nuclear DNA-binding activity found to contain STAT1 and STAT3. An antibody to the IL-6 receptor (IL-6R) alpha subunit effectively neutralized the response to huIL-6 but failed to block STAT activation by vIL-6. In contrast, an antibody reactive with the gp130 subunit of IL-6R abrogated signaling of both responses. Moreover, a transfected cell line expressing human gp130 without IL-6Ralpha exhibited a robust response to vIL-6 but not to huIL-6. These results demonstrate that KSHV encodes a cytokine that activates specific JAK/STAT signaling via interactions with the gp130 signal transducing subunit independently of the IL-6Ralpha chain. This activity may have an impact on gp130-mediated signaling in response to native cytokines and thereby influence disease pathogenesis upon KSHV infection.

[Determination of docosyl ferulate in extract of Pygeum africanton Hook. by high performance liquid chromatography (HPLC)]

This paper reports a method for the determination of docosyl ferulate in the extract of bark of pygeum africanum Hook. by HPLC. After the sample was pretreated, the docosyl ferulate was well separated and determined on a Spherisorb C18 column (250 x 4.6mm, 5microm) using a mobile phase of methanol with a flow rate of 1mL/min. The column temperature was selected at 40 degrees C to avoid tailing of peak. UV detection was performed at 326nm. In order to confirm the docosyl ferulate separated from sample, the peak apex at 10.4 minute was scanned from 195nm to 360nm by photodiode array detector. Its spectrum showed the maxium absorption peak at 240nm and 326nm corresponding with the spectrum of docosyl ferulate. The linear correlation was observed from the 10mg/L to 100mg/L of docosyl ferulate (r = 0.9995). The average recovery was 98.4% +/- 1.98%. Three batches of sample were determined.

Chromosomal deletion complexes in mice by radiation of embryonic stem cells

Chromosomal deletions ("deficiencies') are powerful tools in the genetic analysis of complex genomes. They have been exploited extensively in Drosophila melanogaster, an organism in which deficiencies can be efficiently induced and selected. Spontaneous deletions in humans have facilitated the dissection of phenotypes in contiguous gene syndromes and led to the positional cloning of critical genes. In mice, deletion complexes created by whole animal irradiation experiments have enabled a systematic characterization of functional units along defined chromosomal regions. However, classical mutagenesis in mice is logistically impractical for generating deletion sets on a genome-wide scale. Here, we report a high-throughput method for generating radiation-induced deletion complexes at defined regions in the genome using ES cells. Dozens of deletions of up to several centiMorgans, encompassing a specific locus, can be created in a single experiment and transmitted through the germline. The ability to rapidly create deletion complexes along chromosomes will facilitate systematic functional analyses of the mammalian genome.

Modulation of L-type Ca2+ current by fast and slow Ca2+ buffering in guinea pig ventricular cardiomyocytes

Free Ca2+ near Ca2+ channel pores is expected to be lower in cardiomyocytes dialyzed with bis-(o-amino-phenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA) than with ethyleneglycol-bis-(beta-aminoethyl)-N,N,N',N'-tetraacetic acid (EGTA) because BAPTA chelates incoming Ca2+ more rapidly. The consequences of intracellular Ca2+ buffering by BAPTA (0.2-60 mM) and by EGTA (0.2-67 mM) on whole-cell L-type Ca2+ current (ICa,L) were investigated in voltage-clamped guinea pig ventricular cardiomyocytes; bulk cytoplasmic free Ca2+ (Cac2+) was monitored using the fluorescent Ca2+ indicator indo-1. ICa,L was augmented by approximately 12-fold when BAPTA in the cell dialysate was increased from 0.2 to 50 mM (half-maximal stimulation at 31 mM), whereas elevating internal EGTA from 0.2 to 67 mM increased ICa,L only by approximately 2-fold. Cac2+ was < 20 nM with internal BAPTA or EGTA > or = 20 mM. While EGTA up to 67 mM had only an insignificant inhibitory effect on the stimulation of ICa,L by 3 microM forskolin, ICa,L in 50 mM BAPTA-dialyzed myocytes was insensitive to forskolin-induced elevation of adenosine 3',5'-cyclic monophosphate (cAMP); conversely, ICa,L in cAMP-loaded cells was unresponsive to BAPTA dialysis. Cell dialysis with BAPTA, but not with EGTA, accelerated the slow component of ICa,L inactivation (tau S) without affecting its fast component (tau F), resembling the effects of cAMP-dependent phosphorylation. BAPTA-stimulated ICa,L was inhibited by acetylcholine and by the cAMP-dependent protein kinase (PKA) blocker H-89. These results suggest that BAPTA-induced lowering of peri-channel Ca2+ stimulates cAMP synthesis and channel phosphorylation by disinhibiting Ca(2+)-sensitive adenylyl cyclase.

Nickellike soft-x-ray lasing at the wavelengths between 14 and 7.9 nm

We report what we believe is the first observation of clear soft-x-ray lasing in Ni-like Ag, Te, La, Ce, and Pr and also in Nd covering the spectral range 14.3-7.9 nm. A curved slab target was irradiated with quadruple 1.053-microm laser pulses. The pulse-to-pulse separation for the first three pulses was 400 ps, and that between the third and the fourth pulses was 1.6 ns. The pulse duration and irradiance on the target were 100 ps and ~7 x 10(13) W/cm(2), respectively. For all the targets the most intense lasing was observed at the fourth pump pulse.

Characterization of the cytoplasmic filament protein gene (cfpA) of Treponema pallidum subsp. pallidum

Treponema pallidum and other members of the genera Treponema, Spirochaeta, and Leptonema contain multiple cytoplasmic filaments that run the length of the organism just underneath the cytoplasmic membrane. These cytoplasmic filaments have a ribbon-like profile and consist of a major cytoplasmic filament protein subunit (CfpA, formerly called TpN83) with a relative molecular weight of approximately 80,000. Degenerate DNA primers based on N-terminal and CNBr cleavage fragment amino acid sequences of T. pallidum subsp. pallidum (Nichols) CfpA were utilized to amplify a fragment of the encoding gene (cfpA). A 6.8-kb EcoRI fragment containing all but the 5' end of cfpA was identified by hybridization with the resulting PCR product and cloned into Lambda ZAP II. The 5' region was obtained by inverse PCR, and the complete gene sequence was determined. The cfpA sequence contained a 2,034-nucleotide coding region, a putative promoter with consensus sequences (5'-TTTACA-3' for -35 and 5'-TACAAT-3' for -10) similar to the sigma70 recognition sequence of Escherichia coli and other organisms, and a putative ribosome-binding site (5'-AGGAG-3'). The deduced amino acid sequence of CfpA indicated a protein of 678 residues with a calculated molecular mass of 78.5 kDa and an estimated pI of 6.15. No significant homology to known proteins or structural motifs was found among known prokaryotic or eukaryotic sequences. Expression of a LacZ-CfpA fusion protein in E. coli was detrimental to survival and growth of the host strain and resulted in the formation of short, irregular filaments suggestive of partial self-assembly of CfpA. The cytoplasmic filaments of T. pallidum and other spirochetes appear to represent a unique form of prokaryotic intracytoplasmic inclusions.

Construction of eukaryotic expression vector pBlacz and its expression both in vitro and in vivo

A novel eukaryotic expression vector pBlacZ was constructed, which was transfected into the cell lines of NIH/3T3, COS-1, CHO and the primary culture of murine dermatic fibroblasts in vitro, and also into the murine subcutaneous layer and skeletal muscles of rats in vivo. It was detected that the gene expression vector could encode the E. Coli beta-galactosidase effectively in all these histocytes. The results suggested that pBlacZ, as a novel expression vector, might have certain value of application.

Two isoxazolidines

The crystal structures of trans-phenyl-1,6-dioxa-2-azaspiro[4,4]non- 3-yl ketone, C19H19NO3, and (3 alpha,3a alpha,6a alpha)-hexahydro-2-phenylfuro[3,2-d]isoxazol-3-yl phenyl ketone, C18H17NO3, are reported. In both compounds, the isoxazolidine rings adopt envelope conformations in which the O atom is bent out of the approximate plane of the other four ring atoms. Modest to negligible endo selectivities were confirmed in 1,3-dipolar cycloadditions of benzoylmethyleneaniline N-oxide with enol ethers.

Trypsin and forskolin decrease the sensitivity of L-type calcium current to inhibition by cytoplasmic free calcium in guinea pig heart muscle cells

A key feature of trypsin action on ionic membrane currents including L-type Ca2+ current (ICa) is the removal of inactivation upon intracellular application. Here we report that trypsin also occludes the resting cytoplasmic free Ca2+ ([Ca2+]i)-induced inhibition of peak ICa in isolated guinea pig ventricular cardiomyocytes, using the whole-cell patch clamp in combination with the Fura-2 ratio-fluorescence technique. The effectiveness of trypsin to guard ICa against [Ca2+]i-induced inhibition was compared with that of forskolin, as cAMP-dependent phosphorylation had been suggested to confer protection against [Ca2+]i-induced inactivation. Intracellular dialysis of trypsin (1 mg/ml) augmented ICa by 7.2-fold, significantly larger than the threefold increase induced by forskolin (3 microM). Forskolin application after trypsin dialysis did not further enhance ICa. An increase in [Ca2+]i from resting levels (varied by 0.2, 10, and 40 mM EGTA dialysis) to submicromolar concentrations after replacement of external Na+ (Na(o)+) with tetraethylammonium (TEA+) resulted in monotonic inhibition of control ICa, elicited from a holding potential of -40 mV at 22 degrees C. AFter trypsin dialysis, however, ICa became less sensitive to submicromolar [Ca2+]i; the [Ca2+]i of half-maximal inhibition (K0.5, normally around 60 nM) increased by approximately 20-fold. Forskolin also increased the K0.5 by approximately threefold. These and accompanying kinetic data on ICa decay are compatible with a model in which it is assumed that Ca2+ channels can exist in two modes (a high open probability "willing" and a low open probability "reluctant" mode) that are in equilibrium with one another. An increase in [Ca2+]i places a larger fraction of channels in the reluctant mode. This interconversion is hindered by cAMP-dependent phosphorylation and becomes nearly impossible after tryptic digestion.

Physical map of the genome of Treponema pallidum subsp. pallidum (Nichols)

A physical map of the chromosome of Treponema pallidum subsp. pallidum (Nichols), the causative agent of syphilis, was constructed from restriction fragments produced by NotI, SfiI, and SrfI. These rare-cutting restriction endonucleases cleaved the T. pallidum genome into 16, 8, and 15 fragments, respectively. Summation of the physical lengths of the fragments indicates that the chromosome of T. pallidum subsp. pallidum is approximately 1,030 to 1,080 kbp in size. The physical map was constructed by hybridizing a variety of probes to Southern blots of single and double digests of T. pallidum genomic DNA separated by contour-clamped homogeneous electric field electrophoresis. Probes included cosmid clones constructed from T. pallidum subsp. pallidum genomic DNA, restriction fragments excised from gels, and selected genes. Physical mapping confirmed that the chromosome of T. pallidum subsp. pallidum is circular, as the SfiI and SrfI maps formed complete circles. A total of 13 genes, including those encoding five membrane lipoproteins (tpn47, tpn41, tpn29-35, tpn17, and tpn15), a putative outer membrane porin (tpn50), the flagellar sheath and hook proteins (flaA and flgE), the cytoplasmic filament protein (cfpA), 16S rRNA (rrnA), a major sigma factor (rpoD), and a homolog of cysteinyl-tRNA synthetase (cysS), have been localized in the physical map as a first step toward studying the genetic organization of this noncultivable pathogen.