[Determination of eight trace elements in kadsura coccinea by flame atomic absorption spectrophotometry]

In this paper, we used the flame atomic absorption spectrophotometry to determine the contents of Zn, Fe, Ca, Cu, K, Na, Mn, Mg in the kadsura coccinea. We assayed the determination conditions systematically. The SrCl2 was sued to eliminate coexisting elements. And we achieved the purpose that we can determine a lot of elements in the same liquor at the same time. It shows that this method is simple, convenient and accurate.

Perirenal lucency ("kidney sweat"): a new sign of renal failure

OBJECTIVE

This study describes a new sonographic finding in renal failure: perirenal lucency, which we call the "kidney sweat" sign.

MATERIALS AND METHODS

During 1 year at our institution, 502 renal sonograms were obtained. Sonography evaluated 330 patients with renal failure. All of the examinations were retrospectively analyzed.

RESULTS

An extracapsular hypoechoic rim was present in 47 (14%) of the 330 patients with renal failure. The finding, when present, was always bilateral. The hypoechoic rim was not present in the remaining 283 patients with renal failure. Forty (85%) of the 47 patients had kidneys that were hyperechoic compared with the liver. Twenty-eight (60%) of the 47 patients had kidneys that were hyperechoic compared with the spleen. In 15 (32%) of the 47 patients, the kidneys were small. Ascites was present in 11 (23%) of the 47 patients. Of the 283 patients with renal failure whose sonograms did not show the hypoechoic rim, 76 patients had normal sonographic findings. The remaining 207 patients with renal failure who did not show the kidney sweat sign had hydronephrosis, stones, cysts, echogenic kidneys, small kidneys, or ascites.

CONCLUSION

An extracapsular hypoechoic rim is found in patients with renal failure. We call this finding "kidney sweat." We believe, but cannot currently prove, that the kidney sweat sign represents edema. It is an additional sonographic finding in patients with renal failure.

Activation of caspase-3 in the retina of transgenic rats with the rhodopsin mutation s334ter during photoreceptor degeneration

The role of caspase-3 in photoreceptor degeneration was examined in a line of transgenic rats that carry a rhodopsin mutation S334ter. Photoreceptor degeneration in these animals is rapid. It is detected as early as postnatal day (PD) 8, and by PD 20, only one of the original 12 rows of nuclei remain in the outer nuclear layer. At PD 11 and 12, the number of photoreceptors dying per day reaches a peak of approximately 30% of the total photoreceptors in the retina. Coincident with this rapid degeneration is an increase in caspase-3-like activity as assessed by the cleavage of a fluorescent substrate N-acetyl-Asp-Glu-Val-Asp-aminomethylcoumarin and an increase in activated caspase-3 as determined by Western blot analysis for its 12 kDa subunit. Intraocular injection of an irreversible caspase-3 inhibitor N-benzyloxycarbonal-Asp(OMe)-Glu(OMe)-Val-Asp(Ome)-fluoromethyk etone partially protected photoreceptors from degeneration. These findings indicate that a caspase-3-dependent mechanism is operative in photoreceptor death in the transgenic rats under investigation.

Characterization of dendritic cells generated from peripheral blood of patients with malignant melanoma

Dendritic cells (DCs) are professional antigen presenting cells. Two x 10(7) peripheral blood mononuclear cells (PBMCs) from each of 6 melanoma patients and 4 normal donors were incubated in 6-well plates. The adherent cells were cultured in GM-CSF (800 U/ml) and IL-4 (1000 U/ml) for 10 days. Anti-CD80, anti-CD86, anti-HLA-DR, anti-HLA-class I monoclonal antibodies and supernatant from two melanoma cell lines were incubated with DCs before responder T cells were added in mixed lymphocyte reaction (MLR). The mean yields of DCs were 3.6 x 10(5) and 9.3 x 10(5) for donor and the melanoma patients respectively. MLR was inhibited by anti-CD80, anti-CD86, anti-HLA-DR, anti-HLA-Class I and supernatant of melanoma cultures. The characteristics of DCs generated from melanoma patients were comparable to those from donors. DC function was inhibited by soluble factors in melanoma cultures. Further studies are warranted to characterize these inhibitory factors.

Effects of vomeronasal organ removal on individual odor discrimination, sex-odor preference, and scent marking by female hamsters

Removal of the vomeronasal organ (VNX) did not eliminate the ability of female hamsters to discriminate between individual male's flank gland or urine odors in a habituation/discrimination task nor did it impair preference for male odors over female odors from a distance. Vomeronasal organ removal did reduce overall levels of investigation of flank gland odor in the habituation/discrimination task. Although VNX females did not show severe impairments in the frequency of either flank or vaginal marking in response to odors, they did show an abnormal pattern of marking. VNX females, unlike shams, did not flank mark more to female odors than to male odors, nor did they vaginal mark more to male odors than to female odors. Thus, the vomeronasal organ in female hamsters appears to be important for differences in scent marking toward male and female odors, but is not essential for discrimination of individual odors or for preferences for male over female odors.

Digital quantification of the enzyme-linked immunospot (ELISPOT)

Enzyme-linked immunospot (ELISPOT) is a sensitive technique for the detection of cytokines released by immune cells. The technique is well established and correlates closely with the enzyme-linked immunosorbent assay (ELISA) technique. Here, we introduce an integrated imaging-analysis system to quantitate the spots formed by the ELISPOT assay. The spots can be easily counted when the background is clear and the spots are few. However, when the number of spots increases to > 100, this task becomes challenging and time-consuming. To minimize time and standardize the counting procedure, we have used a digital camera linked to a computer system for reading the plates. In general, the computer is able to count more spots and has a smaller standard deviation when compared with the manual microscopic count. This integrated system is commercially available, and we believe that this method is objective, time-saving and consistent in routine ELISPOT assay counting, especially when numerous spots are present.

Alpha2-adrenergic agonists selectively activate extracellular signal-regulated kinases in Müller cells in vivo

PURPOSE

Alpha2-adrenergic agonists have specific and selective effects on the retina to induce expression of basic fibroblast growth factor and to protect photoreceptors. This work explores the signaling pathway that mediates these effects.

METHODS

Alpha2-adrenergic agonists xylazine and clonidine were administered systemically to male adult Sprague-Dawley rats. The activation state of extracellular signal-regulated kinases (ERKs) in the retina was assessed by immunoblot analysis, using antibodies that specifically recognize the dually phosphorylated forms of p44/p42 ERKs. Localization of phosphorylated ERKs was determined by immunocytochemistry.

RESULTS

Intramuscular injection of 6 mg/kg xylazine induced an increase in ERK phosphorylation in the retina within 30 minutes that lasted 3 hours. Xylazine induced ERK phosphorylation at 1 mg/kg and reached a maximum at 10 mg/kg. Injection of clonidine also induced ERK phosphorylation in the retina. Yohimbine, a specific alpha2-adrenergic antagonist, completely prevented the induction of ERK phosphorylation. Immunocytochemical studies showed that the increase in ERK phosphorylation occurred mainly in Müller cells. In the brain, xylazine injection resulted in a decrease in ERK phosphorylation.

CONCLUSIONS

Our results indicate that systemically administered alpha2-adrenergic agonists selectively activate ERKs in retinal Müller cells. The induced activation of ERKs in Müller cells is probably one of the early events that result in photoreceptor protection. These results also indicate that Müller cells are unique in response to alpha2-adrenergic agonists and imply a role for Müller cells in alpha2-adrenergic agonist-induced photoreceptor protection.

[Alpha1-adrenoceptor subtypes in rabbit penile corpus cavernosum]

OBJECTIVE

To study alpha(1)- adrenoceptor (alpha(1)- AR) subtypes with the functional role and the distribution of its subtypes in rabbit penile corpus cavernosum.

METHOD

The rabbit penile corpus cavernosum was studied by using functional experiment and radioligand binding assay.

RESULT

In the radioligand binding assay, the maximal binding capacity (Bmax of (125)IBE and alpha(1)-AR) decreased obviously after pretreatment with chloroethylclonidine (CEC), which were 746 +/- 236 fmol/mg protein and 214 +/- 71 fmol/mg protein, respectively. Alpha(1A)-, alpha(1D)-and alpha(1B)-AR took about 20%, 25% and 55%, respectively. In the functional experiments, the maximal contraction induced by norepinephrine (NE) was not decreased significantly after pretreatment with CEC. The pA(2) values of two alpha(1)-AR selective antagonists, 5-MU, BMY7378, for antagonizing NE-induced penile corpus cavernosum contraction had a high correlative association with the pK(I) values for cloned alpha(1A)-AR.

CONCLUSION

The functional alpha(1)-AR subtype is alpha(1A)-AR although there are three subtypes in the penile corpus cavernosum.

Expression of somatostatin receptor genes and acetylcholine receptor development in rat skeletal muscle during postnatal development

Our laboratory reported previously that somatostatin (SST) is transiently expressed in rat motoneurons during the first 14 days after birth. We investigated the possibility that the SST receptor (SSTR) is expressed in skeletal muscle. We found that two of the five subtypes of SSTR (SSTR3 and SSTR4) are expressed in skeletal muscle with a time course that correlates with the transient expression of SST in motoneurons. In addition, SSTR2A is expressed from birth to adulthood in skeletal muscle. Both SSTR2A and SSTR4 are also expressed in L6 cells, a skeletal muscle cell line. Somatostatin acting through its receptors has been shown to stimulate tyrosine phosphatase activity in a number of different tissues. We found that several proteins (50, 65, 90, 140, 180 and 200 kDa) exhibited a reduced degree of tyrosine phosphorylation following SST treatment. Inhibition of tyrosine phosphatase activity with sodium orthovanadate increased expression of the nicotinic acetyl-choline receptor (nAChR) epsilon subunit mRNA by three fold. Somatostatin reversed the elevated epsilon mRNA following orthovanadate treatment. These findings show that SSTR is expressed in skeletal muscle and that SST acting via the SSTR regulates tyrosine phosphorylation and expression of the epsilon subunit of the AChR in the rat skeletal muscle.

Angiotensin II induces diverse signal transduction pathways via both Gq and Gi proteins in liver epithelial cells

Angiotensin II stimulates a biphasic activation of Raf-1, MEK, and ERK in WB liver epithelial cells. The first peak of activity is rapid and transient and is followed by a sustained phase. Angiotensin II also causes a rapid activation of p21ras in these cells. Moreover, two Src family kinases (Fyn and Yes) were activated by angiotensin II in a time- and concentration-dependent manner. Microinjection of antibodies against Fyn and Yes blocked angiotensin II-induced DNA synthesis and c-Fos expression in WB cells, indicating an obligatory involvement of these tyrosine kinases in the activation of the ERK cascade by angiotensin II. Finally, substantial reduction of the angiotensin II-stimulated activation of Fyn, Raf-1, ERK, and expression of c-Fos by pertussis toxin pretreatment argues that G proteins of the Gi family as well as the Gq family are involved in angiotensin II-mediated mitogenic pathways in WB cells.

Ontogeny of insulin-like growth factors (IGF), IGF binding proteins, IGF receptors, and growth hormone receptor mRNA levels in porcine pancreas

We examined the ontogeny of mRNA levels of IGF-I and -II, IGF type 1 (IGFI-R) and type II receptors (IGFII-R), IGF binding protein-1 and -3 (IGFBP-1 and -3), GH receptor (GHR), and tissue concentrations of IGF and IGFBP in the pancreas of pigs. Tissues were collected from fetuses at 90 and 110 d of gestation and from pigs at 1, 21, 90 and 180 d of age. Northern blots were performed using total RNA hybridized with 32P-labeled cDNA probes (human IGF-I and human IGFI-R) and cRNA probes (rat IGF-II, human IGFII-R, human IGFBP-1, pig IGFBP-3, and pig GHR). There were two accelerated growth stages of the pancreas: the first one at 90 d of fetal life, which is characterized by cell hyperplasia (high ratio of DNA to body weight), and the second one at postnatal 90 d, which is attributed to cell hypertrophy (high ratios of pancreatic weight, RNA, and protein to DNA). The level of IGF-II mRNA and its tissue concentration were predominant during fetal life and low thereafter. The IGF-I mRNA level was high during fetal and early postnatal life and decreased thereafter. Messenger RNA levels of IGFI-R, IGFBP-3, and GHR and concentrations of IGFBP-1 and -2 were abundant during fetal and early postnatal life. In conclusion, IGF may be involved in various physiological periods of pancreatic development in pigs.

Alboaggregins A and B. Structure and interaction with human platelets

Viper venoms contain a variety of platelet binding proteins including those which bind to platelet GPIb/GPIX. Most of these proteins inhibit von Willebrand factor mediated platelet agglutination. Here we report the primary structures of unique members of this family, alboaggregins A and B, isolated from Trimeresurus albolabris, which have the ability to stimulate platelet agglutination and aggregation. Four chains of alboaggregin A and two chains of alboaggregin B share a high degree of homology and all cysteines in both alboaggregins are conserved. Both alboaggregins caused similar agglutination of fixed platelets. Alboaggregin A induced platelet aggregation and release reaction with EC50 = 10 and 30 nM, respectively, which is 20-fold lower than those for alboaggregin B. These observations suggest that the dimeric structure of alboaggregin B is sufficient to mediate its binding to GPIb and induce agglutination of platelets whereas aggregation and release reaction are significantly enhanced by tetrameric structure of alboaggregin A.

Preconditioning with bright light evokes a protective response against light damage in the rat retina

Constant exposure to bright light induces photoreceptor degeneration and at the same time upregulates the expression of several neurotrophic factors in the retina. At issue is whether the induced neurotrophic factors protect photoreceptors. We used a preconditioning paradigm to show that animals preconditioned with bright light became resistant to subsequent light damage. The preconditioning consisted of a 12-48 hr preexposure, followed by a 48 hr "rest phase" of normal cyclic lighting. The greatest protection was achieved by a 12 hr preexposure. Preconditioning induces a prolonged increase in two endogenous neurotrophic factors: basic fibroblast growth factor (bFGF) and ciliary neurotrophic factor (CNTF). It also stimulates the phosphorylation of extracellular signal-regulated protein kinases (Erks) in both photoreceptors and Müller cells. These findings indicate that exposure to bright light initiates two opposing processes: a fast degenerative process that kills photoreceptors and a relatively slower process that leads to the protection of photoreceptors. The extent of light damage, therefore, depends on the interaction of the two processes. These results also suggest a role of endogenous bFGF and CNTF in photoreceptor protection and the importance of Erk activation in photoreceptor survival.

[The experimental study of the effect of insulin and danshen on culture of fibroblast in vitro]

To investigate the effect of Insulin and Danshen on anabolism and catabolism of collagen during the healing of wound, fibroblast which was cultured from human embryonic skin were divided into 3 groups: Insulin group, Danshen group and contral group. Each group was cultured for 2, 4 and 6 days, then the growth curve was established respectively.

RESULTS

1. The growth curve showed-insulin group > control group > Danshen group. 2. The rate of cell division in 3 groups was 19.6/1000, 2.5/1000, 3.77/1000 respectively. 3. The electron microscopic scanning showed that there was much of fibroid tissue surrounding the fibroblast cell in insulin group, but there was little fibroid tissue in Danshen group. The conclusion showed that insulin can accelerates proliferation of fibroblast and synthesis of collagen, but the effect of denshen was just on the contrary.

Inhibition of thrombin-stimulated cell proliferation by ceramide is not through inhibition of extracellular signal-regulated protein kinase

Activation of the thrombin receptor provides a strong mitogenic signal in CCL39 cells. Ceramide was found to inhibit thrombin-mediated mitogenesis in these cells while dihydroceramide had no effect. Many growth inhibitors exert their effect by inhibiting extracellular signal-regulated kinase (ERK) signaling pathway. However, neither ceramide nor dihydroceramide blocked the thrombin-induced activation of ERK. In contrast, both agents potentiated ERK activity. The expression of c-fos, c-jun and cyclin D1, which are downstream of ERK in the mitogenic pathway were stimulated by thrombin but this stimulation was not affected by ceramide or dihydroceramide. Therefore, the ceramide inhibition of thrombin-stimulated cell growth in CCL39 cells does not appear to be mediated by an effect on the activation of ERK. Furthermore, the data also suggest that the separate effects of ceramide on thrombin-stimulated cell growth and ERK activity are mediated by different mechanisms.

Ontogeny of epidermal growth factor (EGF), EGF receptor (EGFR) and basic fibroblast growth factor (bFGF) mRNA levels in pancreas, liver, kidney, and skeletal muscle of pig

Epidermal growth factor (EGF), EGF receptor (EGFR), and basic fibroblast growth factor (bFGF) messenger RNA (mRNA) levels were examined by Northern blot analysis in four tissues (pancreas, liver, kidney, and skeletal muscle) of pig from fetal 90 d to postnatal 180 d of age. The present study shows for the first time that EGF mRNA increased with advancing age in the kidney and skeletal muscle of pig. A high level of EGF mRNA was observed in the kidney compared with the liver and skeletal muscle. In the pancreas, high levels of EGF mRNA were found in fetuses and newborns and were low in older pigs. Pancreatic EGFR mRNA level parallelled its EGF mRNA, whereas in the kidney and skeletal muscle, patterns of EGFR mRNA were reversed to their EGF mRNA levels. In the liver, EGFR mRNA was abundant but EGF mRNA was undetected. In the pancreas and skeletal muscle, the highest levels of bFGF mRNA were found in fetuses of 90 d of age and then decreased with advancing age. In the liver and kidney, there were no major changes in bFGF mRNA levels during the examined developmental periods. These results show that EGF, EGFR, and bFGF mRNA levels are developmentally and tissue specifically regulated in pig. In the pancreas, mRNA levels of EGF, EGFR and bFGF were high in fetal and neonatal life and low thereafter. In the kidney and skeletal muscle, EGF mRNA increased with advancing age. EGF may play a role in muscle growth and maintenance in growing pigs during the later stage of development.

Regulation of gene expression for tyrosine hydroxylase in oxygen sensitive cells by hypoxia

Carotid body type I cells and the O2 sensitive pheochromocytoma (PC12) cells release dopamine during hypoxia. Reduced O2 tension causes inhibition of an outward rectifying the O2-sensitive potassium (K) channel in the O2-sensitive pheochromocytoma (PC12) cell line, which leads to membrane depolarization and increased intracellular free Ca2+. We found that removal of Ca2+ from the extracellular milieu, inhibition of voltage-dependent Ca2+ channels, and chelation of intracellular Ca2+ prevents full activation of the TH gene expression during hypoxia. These findings suggest that membrane depolarization and regulation of intracellular free Ca2+ are critical signal transduction events that regulate expression of the TH gene in PC12 cells during hypoxia. Gene expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in the biosynthesis of dopamine, is stimulated by reduced O2 tension in both type I cells and PC12 cells. The increase in TH gene expression in PC12 cells during hypoxia is due to increases in both the rate of transcription and mRNA stability. Analysis of reporter-gene constructs revealed that increased transcription of the TH gene during hypoxia is regulated by a region of the proximal promoter that extends from -284 to -150 bases, relative to the transcription start site. This region of the gene contains a number of cis-acting regulatory elements including AP1, AP2 and hypoxia-inducible factor (HIF-1). Competition assays revealed that hypoxia-induced binding occurs at both the AP1 and HIF-1 sites. Results from super-shift and shift Western assays showed that a heterodimer consisting of c-Fos and JunB binds to the AP1 site during hypoxia. Mutagenesis experiments revealed that the AP1 site is required for increased transcription of the TH gene during hypoxia. We also found that the genes that encode the c-Fos and JunB transcription factor proteins are regulated by reduced O2 tension.

Effect of weaning on epidermal growth factor and its receptor messenger RNA levels in various tissues of piglets

Weights of pancreas, liver, and stomach, and total DNA of pancreas and stomach mucosa per body weight were greater (P < 0.05) in weaned piglets than suckling ones at 30 d of age. There was no effect (P > 0.05) of weaning on epidermal growth factor (EGF) and EGF receptor (EGFR) messenger RNA levels in liver, stomach, duodenum, and skeletal muscle. Messenger RNAs of EGF in pancreas increased following weaning in piglets of 27 (P = 0.0001) and 30 (P = 0.004) d of age, indicating a possible involvement of EGF in pancreatic development during this period. Key words: Weaning, EGF, EGFR mRNA, Pig tissues

Chronic exposure of neonatal cardiac myocytes to hydrogen peroxide enhances the expression of catalase

The adaptive response of antioxidant enzymes to oxidative stress in the heart has not been investigated. Because H2O2 is considered to play a major role in reperfusion injury to the heart, this study was undertaken to examine if H2O2 alters the expression of these enzymes in the rat neonatal myocytes. H2O2 was continuously generated by the addition of glucose oxidase to the culture medium. Both the activity and the mRNA for catalase were increased following incubation of neonatal myocytes with non-toxic concentrations of glucose oxidase. The induction of mRNA preceded the enhancement of activity, and both remained elevated after 24 h incubation. Nuclear run-on assay indicated that the transcriptional rate for catalase mRNA was increased. The same treatment did not alter the activities for total superoxide dismutase and Se-glutathione peroxidase. The results suggest that H2O2-induced expression of catalase was in part due to transcriptional activation. It further implies that the induction of catalase may play an important role in protecting hearts from ischemic/reperfusion injury.

Development of GP-2 and five zymogens in the fetal and young pig: biochemical and immunocytochemical evidence of an atypical zymogen granule composition in the fetus

To uncover the mechanisms involved in the biogenesis of secretory granules, we studied development of the exocrine pancreas in the pig from the fetus up to the mature animal by following the enzyme activities and expression (Northern blot) of five zymogens and GP-2, the major protein of the granule membrane. Fetal pancreas mainly contained chymotrypsinogen and barely detectable amounts of amylase, trypsin, lipase, and elastase. GP-2 was not notably expressed before the Day 21 of life. Ultrastructural examination of the fetal tissue embedded in Epon with osmium postfixation or in Lowicryl at -20 degrees C without postfixation showed dense granules with an irregular shape but also showed that most granules had uncondensed contents, with the aspect of immature granules, or had a dense core surrounded by light material. With immunogold cytochemistry, the concentration of chymotrypsinogen was directly associated with the acquisition of electron density by the granule matrix. These observations suggest that fetal granules have a slower rhythm of zymogen condensation and an irregular shape that could be due to the particular composition of the matrix and the absence of GP-2. We conclude that, in the exocrine pancreas, secretory granules can be formed under various conditions, even with a matrix containing a ratio of components very different from that of the normal mature animal.

Partial inhibition of Na+/K+-ATPase by ouabain induces the Ca2+-dependent expressions of early-response genes in cardiac myocytes

Exposure of neonatal rat cardiac myocytes to ouabain concentrations that caused partial inhibition of Na+/K+-ATPase but no loss of viability, increased c-fos and c-jun mRNAs and the transcription factor AP-1. The increased mRNAs were proportional to the extent of inhibition of Na+/K+-ATPase and the resulting rise in steady state intracellular Ca2+ concentration. The rapid and sustained increase of c-fos mRNA was shown to be due to increased transcriptional rate. Induction of c-fos by ouabain was prevented when either extracellular or intracellular Ca2+ was lowered and was attenuated by pretreatment of myocytes with a phorbol ester under conditions known to down-regulate protein kinase C. Exposure to ouabain for 24-48 h also increased total transcriptional activity and protein content of myocytes. The findings suggest that the same signal responsible for the positive inotropic action of ouabain, i.e. net influx of Ca2+ caused by partial inhibition of Na+/K+-ATPase, also initiates the rapid protein kinase C-dependent inductions of the early-response genes, the subsequent regulations of other cardiac genes by the resulting transcription factors, and stimulation of myocyte growth. Whether these hitherto unrecognized effects of cardiac glycosides are obtained in the intact heart and their relevance to the therapeutic uses of these drugs remain to be determined.

Identification of the conserved coding sequences of three chitin synthase genes in Fonsecaea pedrosoi

Primers having designs based on highly conserved stretches in the deduced amino acid sequences of chitin synthase (CHS) genes were used in PCR reactions to amplify 600 bp and 366 bp products from the genomic DNA of three major causal agents of chromoblastomycosis. Cloning and sequencing of the PCR products of one of these fungi, Fonsecaea pedrosoi, identified three CHS sequences designated as FpCHS1, FpCHS2 and FpCHS3. FpCHS1 and FpCHS2 were homologous to regions of CHS1 and CHS2 of Saccharomyces cerevisiae, and their derived amino acid sequences fell into chitin synthase classes I and II, respectively. FpCHS3 was homologous to a region of the CAL1/CSD2 gene of S. cerevisiae, which codes for the chitin synthase three (Chs3) enzyme in that fungus. Phylogenetic trees constructed using the deduced amino acid sequences of PCR-amplified CHS products from many fungi clustered F. pedrosoi with other dematiaceous fungi, providing new molecular evidence for the genetic relatedness of these organisms. The identification of these CHS genes in F. pedrosoi will facilitate future studies of the functional roles of chitin synthases in the unique in vivo dimorphism exhibited by chromoblastomycotic fungi.

Regulation of ionic conductances and gene expression by hypoxia in an oxygen sensitive cell line

We have shown that the PC12 cell line is an excellent model system for investigations of the molecular and cellular processes involved in O2-chemosensitivity. We have identified an O2-sensitive K channel in this cell line that mediates membrane depolarization, an increase in intracellular free Ca2+, and dopamine release during hypoxia. We also presented evidence which shows that expression of the gene for tyrosine hydroxylase, the rate-limiting enzyme in dopamine biosynthesis, is stimulated by reduced O2 tension in PC12 and type I carotid body cells. In addition, we have successfully identified the DNA sequences and trans-acting protein factors that regulate transcription of the TH gene during hypoxia. The mechanisms by which a reduction in O2 tension is transduced into alter cell function including increased gene expression remain unknown. Unpublished results from our laboratory show that the increased TH gene expression during hypoxia does not require activation of the cAMP-PKA signal transduction pathway. We propose that the increase in intracellular free Ca2+ that occurs as a result of membrane depolarization might play an important role. Preliminary findings from our laboratory show that blockade of the voltage operated Ca2+ channel or chelation of intracellular Ca2+ prevent full activation of the TH gene during hypoxia.

Genetic transformation of the pathogenic fungus Wangiella dermatitidis

Genetic transformation of Wangiella dermatitidis was studied using three plasmid vectors (pAN7-1, pWU44, and pKK5) and both electroporation and polyethyleneglycol-mediated methods. pAN7-1 contains the E. coli hygromycin B (HmB) phosphotransferase (hph) gene. Expression of the hph gene confers resistance to antibiotic HmB. Selection for resistance, indicative of transformation, resulted in 10 203 HmB-resistant colonies/micrograms pAN7-1 on medium containing 100 micrograms HmB/ml. Strains of W. dermatitidis used in this study have innate sensitivity to HmB at a critical inhibitory concentration of 20-40 micrograms/ml. Vectors pWU44 and pKK5 contain a URA5 gene from Podospora anserina. A ura5 auxotroph of W. dermatitidis was transformed to prototrophy with pWU44 or pKK5 by complementation. Transformation frequencies for these two plasmids were between 17-50 transformants/micrograms vector DNA. Southern blotting analysis and polymerase chain reaction detection of DNA from putative transformants confirmed transformation.

Binding sites of monoclonal antibodies and dihydropyridine receptor alpha 1 subunit cytoplasmic II-III loop on skeletal muscle triadin fusion peptides

Triadin binds to the dihydropyridine receptor (DHPr) and the junction foot protein (JFP) in Western blot protein overlay experiments. Fusion peptides were synthesized using an expression system, pGSTag, which includes a protein kinase A phosphorylation site. Expressed peptides are DHPr664-799 encoding rabbit skeletal DHPr alpha1 subunit amino acids 664-799, triadin 1 (1-49), triadin 2 (68-389), triadin 2' (110-389), triadin 2a (68-278), triadin 2a1 (67-163), triadin 2a2 (165-240), triadin 2b (242-389), triadin 2b1 (242-299), triadin 3 (370-706), triadin 3a (370-562), triadin 3b (551-706), triadin 3b1 (551-672), and triadin 3b2 (673-706) (the numbers in parentheses correspond to the amino acid sequence of triadin). The triadin monoclonal antibodies, GE4.90 and AE8.91, bind to intact triadic vesicles as well as to vesicle fragments prepared after treatment with Triton X-100, indicating that they have cytoplasmic epitopes. MAb AE8.91 binds to triadin 2, 2', 2a, and 2a1, while mAb GE4.90 binds to triadin 3, 3b, and 3b2 indicating that residues 110-163 and the C-terminal 34 amino acids contain cytoplasmic domains. Radiolabeled DHPr664-799 binds to triadin in intact vesicles under nonreducing and reducing conditions. It binds to triadin fusion peptides, triadin 2, 2a, 3, 3b, and 3b1, but no to triadin 1 or triadin 3b2. The binding to triadin 2a is the most prominent. Direct binding between DHPr-644-799 and JFP was not seen. These experimental findings indicate that triadin contains an extensive cytoplasmic domain that binds to the domain of DHPr which is considered critical for signal transmission during skeletal muscle excitation-contraction sampling.

Interaction of echicetin with a high affinity thrombin binding site on platelet glycoprotein GPIb

Echicetin, a protein isolated from Echis carinatus snake venom, inhibited platelet aggregation and secretion induced by low concentrations of thrombin ( < 0.2 U/ml), by binding to platelet glycoprotein Ib (GPIb). The inhibition was not observed when the platelets were stimulated with higher concentrations of thrombin ( > 0.2 U/ml). Echicetin competed with thrombin for binding to the high affinity site on GPIb. Thrombin also inhibited 50% of the binding of 125I-echicetin to the platelets.

The receptor DEC-205 expressed by dendritic cells and thymic epithelial cells is involved in antigen processing

Dendritic cells and thymic epithelial cells perform important immunoregulatory functions by presenting antigens in the form of peptides bound to cell-surface major histocompatibility complex (MHC) molecules to T cells. Whereas B cells are known to present specific antigens efficiently through their surface immunoglobins, a comparable mechanism for the capture and efficient presentation of diverse antigens by dendritic cells and thymic epithelial cells has not previously been described. We show here that their antigen-presentation function is associated with the high-level expression of DEC-205, an integral membrane protein homologous to the macrophage mannose receptor and related receptors which are able to bind carbohydrates and mediate endocytosis. DEC-205 is rapidly taken up by means of coated pits and vesicles, and is delivered to a multivesicular endosomal compartment that resembles the MHC class II-containing vesicles implicated in antigen presentation. Rabbit antibodies that bind DEC-205 are presented to reactive T-cell hybridomas 100-fold more efficiently than rabbit antibodies that do not bind DEC-205. Thus DEC-205 is a novel endocytic receptor that can be used by dendritic cells and thymic epithelial cells to direct captured antigens from the extracellular space to a specialized antigen-processing compartment.

Use of the polymerase chain reaction to identify coding sequences for chitin synthase isozymes in Phialophora verrucosa

Based on conserved amino-acid regions predicted for the chitin synthases (Chs) of Saccharomyces cerevisiae, two different primer sets were synthesized and used in polymerase chain reactions (PCRs) to amplify 614-bp and 366-bp sequences from genomic DNA of the zoopathogenic fungus Phialophora verrucosa. DNA-sequencing and Southern-blotting analyses of the 614-bp DNA amplification products suggested that portions of two distinct P. verrucosa chitin synthase genes (PvCHS1, PvCHS2), coding for two different zymogenic-type PvChs isozymes, had been identified. The deduced amino-acid sequence of each fell into different Chs classes, namely class I and class II. In addition, the 366-bp DNA segment was shown to code for a conserved region having homology with the CSD2/CAL1 gene of S. cerevisiae, which encodes a nonzymogenic-type enzyme, Chs3, in that fungus. The amino-acid sequence derived from PvCHS3 exhibits 88.2% similarity and 78.4% identity to the same amino-acid region of the S. cerevisiae enzyme. These results provide a critical first step toward investigating the molecular and pathogenic importance of CHS gene regulation in this fungus and for exploring steps leading to Chs function as potential targets for the design of new therapeutic agents.

Difficulties in obtaining monoclonal antibodies to subsets of human leukocytes, using neonatal tolerance induction in mice

Many antigens are shared between different types of human leukocytes. In an effort to obtain new lineage-specific monoclonal antibodies, particularly antibodies to dendritic cells, we attempted to tolerize newborn mice to one type of leukocyte and then immunize the adults with another. We found that T cells, either unstimulated T cells or T blasts, were more effective at inducing neonatal tolerance than non-T cells or B cell lines. However, the tolerance that was achieved was not restricted to T cells, since we could not elicit from the tolerized mice a specific antibody response to a B cell line or to blood dendritic cells. Here we describe several efforts, all unsuccessful, to achieve cell specific immune responses in tolerant mice. The parameters we considered included the type of cell used to tolerize neonatal mice, the regimen of injections for inducing tolerance or eliciting immunity, and the use of several different adjuvants.

Isolation, characterization and amino acid sequence of echicetin beta subunit, a specific inhibitor of von Willebrand factor and thrombin interaction with glycoprotein Ib

Echicetin is a dimeric protein isolated from the venom of Echis carinatus that is a potent inhibitor of von Willebrand Factor and thrombin binding to glycoprotein Ib. Here, we report isolation and amino acid sequence of the beta subunit of echicetin that contains 123 amino acids, including 7 cysteines, and shows similarity with amino acid sequences of botrocetin and Factor IXa/Xa binding protein. We provide evidence that biological activity of echicetin which resides in this beta subunit is relatively resistant to reduction of the molecule.

Structural diversity of triadin in skeletal muscle and evidence of its existence in heart

Triadin has been characterized as an abundant protein co-localized with the calcium release channel on the terminal cisternae of the sarcoplasmic reticulum of the skeletal muscle. Its localization to terminal cisternae of the sarcoplasmic reticulum and functional studies suggest that it has an important role in excitation-contraction coupling. In this study we identify three triadin isoforms in rabbit skeletal muscle and by Northern blot analysis demonstrate that triadin also exists in the heart.

Human blood contains two subsets of dendritic cells, one immunologically mature and the other immature

Two subsets of dendritic cells, differing in T-cell stimulatory function, have been purified directly from human blood. Both subsets are positive for major histocompatibility complex (MHC) class II expression and negative for lineage-specific antigens (e.g. CD3, CD14, CD16, CD19 negative), but are separated by exploiting differences in expression of the beta 2-integrin, CD11c. The CD11c-negative subset is functionally immature, requiring monocyte-derived cytokines to develop into typical dendritic cells. The CD11c-positive subset has potent T-cell stimulating activity and expresses the activation antigen CD45RO, unlike its immature counterpart. However, these mature cells only develop typical dendritic morphology and high levels of MHC proteins and adhesins after a period of culture independent of exogenous cytokines. Although the freshly isolated mature dendritic cells resemble monocytes in cytospin preparations, the former lack CD14 and have a much stronger primary T-cell stimulatory capacity. We hypothesize that the CD11c-negative immature cells are marrow-derived precursors to tissue dendritic cells, such as epidermal Langerhans' cells, while the CD11c-positive cells are derived from tissues where they have been activated by antigen, and are en route to the spleen or lymph nodes to stimulate T-cell responses there.

Multicentric evaluation of a new PT reagent based on recombinant human tissue factor and synthetic phospholipids

A new PT reagent based on recombinant human tissue factor and synthetic phospholipids (phosphatidyl choline and phosphatidyl serine) with defined fatty acid side chains was calibrated against BCT/253 and CRM 149R. A small but consistent bias in the International Sensitivity Index (ISI) value was obtained using either the human or rabbit brain reference material. ISI values were around 1.0 or slightly lower depending on the respective instrument. Mixing studies with factor deficient plasmas showed a high factor sensitivity especially for factor VII as compared to commercial rabbit brain or human placenta thromboplastin. In an international field trial the reagent was tested using fully or semi automated Electra coagulometers in 4 different laboratories. Results with normal samples were in excellent agreement among the different laboratories. Mean values were 10.9, 10.9, 11.0, 11.2 s with a range of 9.5 to 12.5 s. Results of males and females were not different. In patients with liver disease very similar PT activities were found as compared to sensitive rabbit brain or human placental thromboplastins. In normals and patients with oral anticoagulation INR values correlated very well against BCT (r = 0.98, regression line y = -0.07 + 0.9 x). The distribution of samples was linear over the whole range. In the comparison against sensitive rabbit brain thromboplastin or human placental thromboplastin similar correlations were found. In a few cases higher INR values were observed for the recombinant reagent especially in patients with intensive treatment. Factor assays in those patients showed at least the strong reduction of one vitamin K-dependent coagulation factor.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pathology of muscle contracture caused by injection and activity of phosphochesterase and insulin receptor]

The animal model of muscle contracture caused by injection was set up in the experiment. We used the model for excessive healing studies and researched the changes in its pathology, and activity of phosphochesterase and insulin receptor in this model. The experimental results revealed that the pathologic changes belonged to excessive proliferation of connective tissue (excessive healing). When occurred muscle degeneration, infiltration of inflammatory cells, proliferation of fibroblasts and descending of collagen fibers, the activity level phosphochesterase and insulin receptor became higher. The excessive healing occurrence may have something to do with the changes of phosphochesterase and insulin receptor.

Dendritic cells freshly isolated from human blood express CD4 and mature into typical immunostimulatory dendritic cells after culture in monocyte-conditioned medium

A procedure has been developed to isolate dendritic cells to a high degree of purity from fresh blood. Prior enrichment methods have relied upon an initial 1-2-d culture period. Purified fresh isolates lack the characteristic morphology, phenotype, and immunostimulatory function of dendritic cells. The purified cells have the appearance of medium sized lymphocytes and express substantial levels of CD4, but lack the T cell molecules CD3, CD8, and T cell receptor. When placed in culture, the cells mature in a manner resembling the previously described, cytokine-dependent maturation of epidermal dendritic cells (Langerhans cells). The cells enlarge and exhibit many cell processes, express much higher levels of major histocompatibility complex class II and a panel of accessory molecules for T cell activation, and become potent stimulators of the mixed leukocyte reaction. Among the many changes during this maturation process are a fall in CD4 and the appearance of high levels of B7/BB1, the costimulator for enhanced interleukin 2 production in T cells. These changes are not associated with cell proliferation, but are dependent upon the addition of monocyte-conditioned medium. We suggest that the freshly isolated CD4-positive blood dendritic cells are recent migrants from the bone marrow, and that subsequent maturation of the lineage occurs in tissues in situ upon appropriate exposure to cytokines.

A nucleotide sequence involved in replicative transformation of a filamentous fungus

Replicative plasmids generated through in-vivo recombination have been identified among transformants of the fungus Pleurotus ostreatus. In addition to sequences from a standard selection vector (pAN7-1), these recombinant plasmids contain recombined sequences of chromosomal origin conferring replicative potential upon the vector. One such recombined sequence, an 1148-bp insert into plasmid pP01, has been characterized. This sequence has been analyzed for secondary structural features as well as for consensus sites affiliated with origins of replication (ori) in other eukaryotic systems. The 1148-bp insert lacks an ORF and does not contain an acceptable match to the commonly identified 11-bp ars consensus sequence (A/TTTTATA/GTTTA/T) for autonomous replication in the yeast Saccharomyces cerevisiae. The analysis, however, revealed a cluster of three hairpin-loop-forming subsequences with individual delta G25 degrees C free energy values of -7.6, -6.4 and -5.2 kcal mol-1. Also found were two 7-bp analogues to centromere-affiliated sequences recognized in other fungi, as well as several putative gyrase recognition sites comparable to the 9-bp S. cerevisiae/E. coli gyrase-binding consensus sequence. Sequences comparable to the ori of the yeast 2-microns plasmid or to various sequences associated with ori of yeast/fungal mitochondrial DNAs (mtDNA) were not present in the 1148-bp insert. Replication of pP01 appears rather to involve a replication of chromosomal derivation devoid of an ars-type consensus.

Echicetin: a snake venom protein that inhibits binding of von Willebrand factor and alboaggregins to platelet glycoprotein Ib

Echicetin, a new protein isolated from Echis carinatus venom by reverse phase and ion exchange chromatography specifically inhibited agglutination of fixed platelets induced by several platelet glycoprotein Ib (GPIb) agonists, such as bovine von Willebrand factor (vWF), alboaggregins, and human vWF in the presence of botrocetin. Unlike alboaggregins, echicetin bound to GPIb but did not induce agglutination of washed or fixed platelets. In contrast to disintegrins, it did not block adenosine 5'-diphosphate (ADP)-induced platelet aggregation in the presence of fibrinogen. The apparent molecular weight of echicetin measured on sodium dodecyl sulfate (SDS) gel electrophoresis was 26 Kd under nonreducing conditions. On reduction, echicetin showed 16 and 14-Kd subunits suggesting that the molecule is a dimer. Reduced echicetin retained its binding activity and its inhibitory effect on the agglutination of fixed platelets induced by bovine vWF. 125I-echicetin bound to fixed platelets with high affinity (kd = 30 +/- 1.8 nmol/L) at 45,000 +/- 2,400 binding sites per platelet. The binding was selectively inhibited by a monoclonal antibody to the 45-Kd N-terminal domain of platelet GPIb, but not by monoclonal antibodies to other regions on GPIb. Binding of 125I-bovine vWF to fixed platelets was strongly inhibited by echicetin. In contrast, bovine vWF showed a much weaker inhibitory activity on binding of 125I-echicetin to platelets. The half life of echicetin in blood was approximately 170 minutes with no detectable degradation. Echicetin significantly prolonged the bleeding time of mice, suggesting that it may inhibit vWF binding to GPIb in vivo as well as in vitro.

Transient expression of the Epstein-Barr virus LMP1 gene in B-cell chronic lymphocytic leukemia cells, T cells, and hematopoietic cell lines: cell-type-independent-induction of CD23, CD21, and ICAM-1

The Epstein-Barr virus (EBV) genome has recently been detected in various non-B cell neoplasms, including various T-cell leukemias and in Reed-Sternberg cells of Hodgkin's disease, but the contribution of EBV genes to the transformed phenotype remains unclear. We have investigated the possible effect which the EBV genes LMP1 and EBNA2, of which the expression has been reported in non-B cell neoplasms, may have on a variety of cell types. The LMP1 and EBNA2 genes were transiently expressed from heterologous promoters in two human T-cell lines (HPB-ALL and Jurkat), two human cell lines of the myeloid lineage (K562 and U937), one type I Burkitt's lymphoma cell line (Rael) and in human primary T cells and B-cell chronic lymphocytic leukemia cells. The cell surface expression of CD23, CD21, ICAM-1 and LFA-1 was monitored on transfected cells. In the cell lines, except U937, the surface antigens CD21 and ICAM-1 were upregulated in a dose-dependent and transient manner by the transient expression of LMP1, and EBNA2 slightly enhanced the effects of LMP1 on CD23 and CD21 upregulation. LMP1 also induced increased CD21, ICAM-1 and LFA-1 surface expression on transfected primary T-cells, and CD21 and ICAM-1 in four of five B-cell chronic lymphocytic leukemias tested. Finally, LMP1 transient expression caused increased cell size of the primary T cells and responding B-cell chronic lymphocytic leukemia cells. Our results strongly suggest that LMP1 can trigger specific responses in a variety of white cell types and thus is probably contributing to the phenotype of EBV-positive tumor cells not only in the B-cell lineage.

Transient expression of the Epstein-Barr virus LMP1 gene in human primary B cells induces cellular activation and DNA synthesis

The Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) and Epstein-Barr virus nuclear antigen 2 (EBNA2) are expressed in EBV-immortalized human B cells. It has previously been shown that transfection of the LMP1 and EBNA2 genes into Burkitt's lymphoma cell lines results in the up-regulation of CD23, CD21, ICAM-1 and LFA-1 cell-surface proteins. In the present study, the effects of transient expression of the LMP1 and EBNA2 genes were studied in normal primary human B cells pretreated with UV-inactivated EBV particles. To identify and purify cells which express the transfected DNA we used a gene encoding a surface molecule, CD2, as a co-transfection marker. We show that transient expression of the LMP1 gene, from heterologous promoters, is sufficient to induce cellular enlargement and up-regulation of surface expression of the activation markers CD23, CD21, ICAM-1 and LFA-1 in primary B cells. Most importantly, we show that transient expression of the LMP1 gene is sufficient to induce DNA synthesis in human primary B cells. Transient EBNA2 expression enhanced the effect of transient LMP1 expression on CD21 and CD23 cell-surface expression but, under our experimental conditions, inhibited the induction of DNA synthesis by LMP1. We conclude that activation of primary B cells with inactivated EBV particles, followed by transient expression of only two viral genes, EBNA2 and LMP1, is sufficient to reconstitute some of the early events of B-cell immortalization by EBV.

Polymerase chain reaction--amplification of the coding sequence of the type X collagen gene from genomic DNA and identification of a polymorphism that changes Gly to Arg at position 545 by single-strand conformation polymorphism analysis

Type X collagen is a specific product of hypertrophic growth plate chondrocytes and it has been suggested that mutations in the corresponding gene (COL1OA1) may be responsible for certain heritable disorders affecting growth plate cartilage such as the epiphyseal dysplasias. We have amplified the coding region of COL1OA1 employing polymerase chain reaction (PCR) of genomic DNA. Single-strand conformation polymorphism (SSCP) analysis of PCR products followed by direct sequencing identified a G to C transition that results in a Gly to Arg substitution at position 545 of the polypeptide chain. The sequence variation was confirmed by restriction enzyme analysis with BsaJ 1. Analysis of a family with multiple epiphyseal dysplasia ruled out this sequence change as a cause of the disease. This is the first report showing application of SSCP for detection of a sequence variant in COL1OA1.

Recovery of recombinant plasmids from Pleurotus ostreatus transformants

A transformation system employing selectable resistance to hygromycin B has been developed for the mushroom-forming fungus, Pleurotus ostreatus. Vector pAN7-1, a commonly used non-replicative vector for integrative transformation in fungi, yielded 5-46 resistant colonies per micrograms of DNA per 10(7) viable protoplasts. Southern blot analysis of certain transformants revealed unexpected replicative plasmids containing pAN7-1 sequences, but modified for size, methylation and restriction enzyme pattern when compared to the initial transforming vector. Two such replicative derivatives of pAN7-1 have been rescued from P. ostreatus by cloning into Escherichia coli. Rescued plasmids have been used to probe DNA from untransformed P. ostreatus in an effort to identify fungal sequences that recombined in vivo with pAN7-1 to form replicative plasmids. Such replicative sequences have been localized in high molecular weight (chromosomal) DNA of wild-type P. ostreatus. Transformation has been obtained for P. ostreatus using a rescued plasmid, thereby confirming the role of this recombinant plasmid as a shuttle vector.

Characterization of three alboaggregins purified from Trimeresurus albolabris venom

Alboaggregins (AL-A, AL-B, AL-C) isolated from Trimeresurus albolabris snake venom represent a new family of proteins which bind to platelet glycoprotein Ib (GPIb). These alboaggregins were purified to homogeneity with ion exchange HPLC (Mono-Q column) and hydrophobic HPLC (TSK Phenyl-5PW column). On SDS-polyacrylamide gel electrophoresis, apparent molecular weights of AL-A, AL-B and AL-C were 52 kDa, 26 kDa, and 121 kDa respectively, under nonreducing conditions. Upon reduction, each alboaggregin showed two types of chains with apparent molecular weights in the range of 15-20 kDa. All three alboaggregins agglutinated formalin-fixed platelets. Agglutination activities and binding of labeled alboaggregins to GPIb were specifically inhibited by the monoclonal antibody AK2 which is directed against the 45 kDa N-terminal region on GPIb, but not by monoclonal antibodies against other epitopes on GPIb. 125I-alboaggregin binding to platelets was not altered by the presence of thrombin. Alboaggregins did not bind to GPIIb/IIIa. Alboaggregins were competitive inhibitors for 125I-bovine vWF binding to platelets. Mutual competition studies between AL-A, AL-B and AL-C for the binding of labeled bovine vWF and AL-B to platelets demonstrated that AL-B and AL-C had a significantly higher affinity than AL-A.

Alboaggregin-B: a new platelet agonist that binds to platelet membrane glycoprotein Ib

A new protein, called alboaggregin-B (AL-B), has been isolated from Trimeresurus albolabris venom by ion-exchange chromatography. It agglutinated platelets without the need for Ca2+ or any other cofactor. The purified protein showed an apparent molecular mass on SDS-PAGE and gel filtration of about 23 kDa under nonreducing conditions. Ristocetin did not alter the binding of AL-B to platelets or affect AL-B-induced platelet agglutination. Agglutinating activity was not dependent on either proteolytic or lectin-like activity in AL-B. Binding analysis showed that AL-B bound to platelets with high affinity (Kd = 13.6 +/- 9.3 nM) at approximately 30,800 +/- 14,300 binding sites per platelet. AL-B inhibited the binding of labeled bovine von Willebrand factor (vWF) to platelets. Monoclonal antibodies against the 45-kDa N-terminal domain of platelet glycoprotein Ib inhibited the binding both of AL-B and of bovine vWF to platelets, and also inhibited platelet agglutination induced by AL-B and bovine vWF. Specific removal of the N-terminal domain of GPIb by treatment of the platelets with elastase or Serratia marcescens protease reduced the binding of labeled AL-B and bovine vWF to platelets and blocked platelet agglutination caused by both agonists. Monoclonal antibodies to glycoprotein IIb/IIIa, to bovine vWF, and to bovine serum albumin did not show any effect on the binding of AL-B to platelets. Our results indicate that the binding domain for AL-B on platelet GPIb is close to or identical with the one for vWF. This new protein may be a very useful tool for studying the interaction between platelets and vWF.

Identification of cysteine residues in lamb kidney (Na,K)-ATPase essential for ouabain binding

N-(1-Pyrene)maleimide is a hydrophobic, sulfhydryl-directed, chemical modification probe which, at a low concentration, inhibits the capacity of lamb kidney sodium- and potassium-activated adenosine triphosphatase [Na,K)-ATPase; EC 3.6.1.3) to bind ouabain. This inhibition is partially blocked by preincubation of the enzyme with ouabagenin, an aglycone derivative which can be used as a reversible protecting ligand for the ouabain binding site. The kinetics of inhibition are not first order, suggesting that there may be more than one site of labeling which is responsible for the inhibition of ouabain binding. Although earlier work (Kirley, T. L., Lane, L. K., and Wallick, E. T. (1986) J. Biol. Chem. 261, 4525-4528) indicates that the inhibition is accompanied by a loss in the number of binding sites rather than a decrease in affinity of the sites for the ligand, other data (Scheiner-Bobis, G., Zimmerman, M., Kirch, V., and Schoner, W. (1987) Eur. J. Biochem. 165, 653-656) indicates that there is no cysteine residue located extracellularly in the ouabain binding site. By sequence analysis of alpha subunit peptides labeled by N-(1-pyrene)maleimide in the absence but not in the presence of protecting ligand, it is demonstrated in this work that there are two major sites of labeling protected by the binding of ouabagenin, Cys-367 and Cys-656. Both of these sites are located in the large cytoplasmic domain of the alpha subunit, one close to the phosphorylation site (Asp-369), and the other implicated in the binding of ATP (Cys-656). Therefore, it appears from this data that the inhibition of ouabain binding by N-(1-pyrene)maleimide is not due to modification of a site in the binding pocket for cardiac glycosides, but rather to an allosteric effect, since cardiac glycoside binding is known to be dependent on the phosphorylation state of the enzyme. The dependence of inhibition on the presence of sodium, potassium, and ATP also is consistent with this interpretation. The work reported here thus explains the apparent paradox posed by the earlier data.