Sodium channel mutations in paramyotonia congenita exhibit similar biophysical phenotypes in vitro

Mutations in the skeletal muscle voltage-gated Na+ channel alpha-subunit have been found in patients with two distinct hereditary disorders of sarcolemmal excitation: hyperkalemic periodic paralysis (HYPP) and paramyotonia congenita (PC). Six of these mutations have been functionally expressed in a heterologous cell line (tsA201 cells) using the recombinant human skeletal muscle Na+ channel alpha-subunit cDNA hSkM1. PC mutants from diverse locations in this subunit (T1313M, L1433R, R1448H, R1448C, A1156T) all exhibit a similar disturbance in channel inactivation characterized by reduced macroscopic rate, accelerated recovery, and altered voltage dependence. PC mutants had no significant abnormality in activation. In contrast, one HYPP mutation studied (T704M) has a normal inactivation rate but exhibits shifts in the midpoints of steady-state activation and inactivation along the voltage axis. These findings help to explain the phenotypic differences between HYPP and PC at the molecular and biophysical level and contribute to our understanding of Na+ channel structure and function.

Independent binding of peptide ligands to the SH2 and SH3 domains of Grb2

Grb2, composed entirely of SH2 and SH3 domains, serves as an adaptor protein in signaling from growth factor-activated tyrosine kinase receptors. It interacts via its SH2 domain with the autophosphorylated carboxyl-terminal tail of activated epidermal growth factor (EGF) receptor and via its SH3 domains with proline-rich sequences in the Ras guanine nucleotide releasing factor, Son of sevenless (Sos). Recruitment of the Grb2-Sos complex to the receptor upon its stimulation leads to Ras activation. A major question remains as to whether SH2-mediated binding of Grb2 to the activated receptor results in conformational changes that influence its SH3-mediated association with Sos, thereby affecting Sos activity. This question is addressed through studies of the binding to intact Grb2 of an EGF receptor-derived phosphotyrosine-containing peptide and a Sos-derived proline-rich peptide using isothermal titration calorimetry and surface plasmon resonance measurements. The phosphopeptide binds to Grb2 in a 1:1 complex, with a KD of 0.4 microns. The Sos proline-rich peptide binds to Grb2 in a 2:1 complex, with a KD of 22 microns. Saturation of the SH2 domain of Grb2 with the EGFR phosphopeptide was found not to affect its subsequent binding to the Sos peptide. Thus we detected no influence of SH2 binding upon SH3-mediated interactions, suggesting that the domains do not communicate, and that recruitment itself of Sos to the cell surface is sufficient for Ras signaling.

The germfree state prevents development of gut and joint inflammatory disease in HLA-B27 transgenic rats

A number of inflammatory disease states occur with greatly increased frequency in individuals inheriting the human major histocompatibility complex class I allele HLA-B27. In a minority of cases, namely those with B27-associated reactive arthritis, there is good evidence that the disease state is triggered by infection with an enteric or genitourinary bacterial pathogen. For the majority of B27-associated disease, no definite pathogenetic role for bacteria has been established. However, in these latter cases intestinal inflammation can often be demonstrated, and it sometimes occupies a major part of the clinical picture. Rats transgenic for B27 are known to develop a disorder resembling B27-associated human disease, with prominent intestinal, joint, skin, and male genital inflammatory lesions. We report here that B27 transgenic rats raised in a germfree environment do not develop inflammatory intestinal or peripheral joint disease, whereas the skin and genital inflammatory lesions are unaffected by the germfree state. These findings support the concept that gut and joint inflammation are pathogenetically closely related, and they provide direct evidence that the commensal gut flora play an important role in the pathogenesis of B27-associated gut and joint inflammation.

Modulation of endothelin-1 production by a pulmonary epithelial cell line. I. Regulation by glucocorticoids

Endothelin-1 (ET-1) is one of the most potent bronchoconstrictor agents yet described. Bronchial epithelial cells of asthmatic patients in vivo express preproET-1 and in vitro release high amounts of ET-1. Healthy and chronic bronchitic controls do not express preproET-1 or release ET-1. Interleukin-2 (IL-2) and other cytokines up-regulate the in vitro ET-1 release in guinea pig airway epithelial cells. We explored whether two glucocorticoids, dexamethasone (Dex) and triamcinolone acetonide (TA), inhibit the synthesis and release of ET-1 by A549 cells, a transformed human pulmonary epithelial cell line, since ET-1 may have a basic role in the pathogenesis of asthma. Cells were grown to confluence in RPMI 1640 plus 10% fetal bovine serum (FBS). Cells were then cultured for 3 days without serum to obtain ET-1 basal levels. The effects of 10% FBS, IL-2 (10 U/mL), Dex, TA or mifepristone, a steroid antagonist (1, 10 or 100 nM), were evaluated on ET-1 as measured by radioimmunoassay (RIA). ET-1 production increased from 57.6 +/- 5 pg/mg cell protein at 6 hr to 170 +/- 9 pg/mg cell protein at 72 hr in control cultures. Ten percent FBS increased ET-1 production from 58.7 +/- 9.6 to 399 +/- 14.5 pg/mg cell protein. IL-2 significantly increased ET-1 from 100.7 +/- 6.1 to 144 +/- 6.7 at 24 hr and from 170 +/- 9 to 207.7 +/- 24 at 72 hr. Dex and TA (10 and 100 nM) at 24-72 hr decreased ET-1 under basal conditions. Both drugs (only at 100 nM) decreased ET-1 production in 10% FBS- and IL-2-stimulated cells. Mifepristone (10 and 100 nM) reversed the decreased production of ET-1 induced by Dex (100 nM) at 24-72 hr. Northern blot analysis showed that Dex (100 nM) decreased the expression of ET-1 mRNA at 6 and 24 hr, but that mifepristone (100 nM) reversed this effect in cells cultured with Dex. In conclusion, Dex and TA down-regulate the synthesis and production of ET-1 by this human pulmonary epithelial cell line under basal or stimulated conditions, and these effects are reversed by mifepristone. These findings suggest a novel mechanism of glucocorticoid effect during the treatment of asthma.

K(+)-aggravated myotonia: destabilization of the inactivated state of the human muscle Na+ channel by the V1589M mutation

1. Wild type (WT) and V1589M channels were expressed in human embryonic kidney (HEK293) cells for the study of the pathophysiology of the V1589M muscle Na+ channel mutation leading to K(+)-aggravated myotonia. 2. In comparison to WT, whole-cell recordings with V1589M channels showed an increased Na+ steady-state to peak current ratio (Iss/Ipeak) (3.15 +/- 0.70 vs. 0.87 +/- 0.10%, at -15 mV) and a significantly faster recovery from inactivation. The recovery time constants, tau r1 and tau r2, were decreased from 1.28 +/- 0.12 to 0.92 +/- 0.08 ms and from 4.74 +/- 0.94 to 2.66 +/- 0.51 ms for the WT and mutant channels, respectively. 3. Single-channel recordings with mutant channels showed higher probability of short isolated late openings (0.40 +/- 0.09 vs. 0.06 +/- 0.02, at -30 mV) and bursts of late openings (0.011 +/- 0.003 vs. 0.003 +/- 0.001, at -30 mV) compared to WT. 4. These results suggest that the mutation increases the probabilities for channel transitions from the inactivated to the closed and the opened states. 5. Increased extracellular concentrations of K+ had no effects on either V1589M or WT currents in HEK293 cells. The aggravation of myotonia seen in patients during increased serum K+ may arise from the associated membrane depolarization which favours the occurrence of late openings in the mutant channel.

[215 cases of diffuse pulmonary disease diagnosed with transbronchial lung biopsy via bronchofibroscope]

215 cases of diffuse pulmonary disease diagnosed with transbronchial lung biopsy (TBLB) via bronchofibroscope were reported. The incidence of successful biopsy was 96.7%. The total diagnostic rate was 80.5%. There were no other serious complications except for bloody or blood-streaking sputum, but the amount rarely exceeded 50 ml, and pneumothorax occurred occasionally. It was suggested that TBLB is an easy, safe and useful method for diagnosing diffuse pulmonary disease.

Characterization of a myeloperoxidase mRNA(+) acute lymphoblastic leukemia cell line (EU-1/ALL) established from a child with an apparent case of ALL

A myeloid-antigen-positive acute lymphoblastic leukemia (My+ALL) cell line (EU-1) was established from the bone marrow cells of a child with apparent ALL. By morphology, cytochemistry and fluorescent-antibody phenotyping, EU-1 cells appeared to be lymphoblastic (L1 morphology, TdT+, CD10+, CD19+). However, by a sensitive immunocytochemical assay, EU-1 cells additionally displayed several myeloid antigens (CD13, CD14, CD33) not detected by flow-cytometry. Furthermore, EU-1 cells were cytochemically and immunocytochemically negative for myeloperoxidase (MPO) but positive for MPO mRNA by Northern blot analysis. After incubation with dimethylsulfoxide (DMSO), myeloid cell surface antigens were detected on EU-1 cells by flow cytometry, and a marked decrease in MPO mRNA expression was observed. These results demonstrate that EU-1 is a unique ALL cell line representing a significant subset of pediatric ALL patients who also express myeloid antigens and have poor prognosis.

Cloning, sequencing, and expression in Escherichia coli of the gene encoding a 45-kilodalton protein, elongation factor Tu, from Chlamydia trachomatis serovar F

The gene encoding a 45-kDa protein (45K) of Chlamydia trachomatis serovar F was cloned, sequenced, and overexpressed in Escherichia coli. Alignment of the deduced peptide sequence with E. coli elongation factor Tu (EF-Tu) demonstrated 69% identity. The 45K was recognized by a Chlamydia genus-specific monoclonal antibody GP-45 and cross-reacted with a monospecific polyclonal antibody to E. coli EF-Tu. Purified recombinant 45K has the capability to bind GDP, and the binding was enhanced in the presence of E. coli elongation factor Ts (EF-Ts). The GDP binding was specifically inhibited by the monoclonal antibody GP-45. These data suggest that the 45K is a chlamydial EF-Tu, and it forms a functional complex with E. coli EF-Ts protein.

Sodium channel mutations in paramyotonia congenita uncouple inactivation from activation

Mutations in the adult human skeletal muscle Na+ channel alpha subunit cause the disease paramyotonia congenita. Two paramyotonia congenita mutations, R1448H and R1448C, substitute histidine and cysteine for arginine in the S4 segment of domain 4. These mutations, expressed in a cell line, have only small effects on the activation of Na+ currents, but mutant channels inactivate more slowly with less voltage dependence than wild-type channels and exhibit an enhanced rate of recovery from inactivation. Increase of extracellular pH made the rate of inactivation of R1448H similar to that of R1448C, suggesting that this residue has an extracellular location and that its charge is important for normal inactivation. Analysis of single-channel data reveals that mutant channels inactivate normally from closed states, but poorly from the open state. The data suggest a critical role for the S4 helix of domain 4 in coupling between activation and inactivation.

Nck associates with the SH2 domain-docking protein IRS-1 in insulin-stimulated cells

Nck, an oncogenic protein composed of one SH2 and three SH3 domains, is a common target for various cell surface receptors. Nck is thought to function as an adaptor protein to couple cell surface receptors to downstream effector molecules that regulate cellular responses induced by receptor activation. In this report, we show that Nck forms a stable complex in vivo with IRS-1 in insulin-stimulated cells. The interaction between IRS-1 and Nck is mediated by the binding of the SH2 domain of Nck to tyrosine-phosphorylated IRS-1. Although Nck associates with IRS-1, Nck phosphorylation is not affected by insulin stimulation. Furthermore, in vitro and in vivo studies show that the SH2 domains of Nck, GRB2, and p85 bind distinct phosphotyrosine residues in IRS-1. After insulin stimulation all three signaling molecules can be found complexed to a single IRS-1 molecule. These findings provide further evidence that, in response to insulin stimulation, IRS-1 acts as an SH2 docking protein that coordinates the regulation of various different signaling pathways activated by the insulin receptor.

Suitable fixation condition for rat liver using microwave irradiation and its application to the immunohistochemistry of glutamate dehydrogenase

The rat liver was fixed with microwave (MW) fixation technique using a domestic microwave oven and glutamate dehydrogenase (GDH) was immunostained in the liver. The structure of liver was well preserved and formation of artificial vacuoles was hardly recognizable in the cytoplasm of liver cells when 2% paraformaldehyde containing 10% glucose and 0.025% CaCl2 was employed for a fixative and continuous MW irradiation was carried out for 30 sec. Granulated immunoreaction products of GDH were present in the cytoplasm of the liver cells and Kupffer cells. The intensity of the reaction was almost homogeneous among the cells. On the other hand, when the tissue was fixed with immersion fixation method, a diffuse reaction was seen in the cytoplasm of liver cells and intensity of the immunostaining was heterogeneous among the cells; the liver cells in zone 2 showed weaker reaction than those in zone 1 and 3. Immunoelectron microscopy revealed that GDH was located in the mitochondrial matrix along the inner membrane including crystal membrane.

Two signaling molecules share a phosphotyrosine-containing binding site in the platelet-derived growth factor receptor

Autophosphorylation sites of growth factor receptors with tyrosine kinase activity function as specific binding sites for Src homology 2 (SH2) domains of signaling molecules. This interaction appears to be a crucial step in a mechanism by which receptor tyrosine kinases relay signals to downstream signaling pathways. Nck is a widely expressed protein consisting exclusively of SH2 and SH3 domains, the overexpression of which causes cell transformation. It has been shown that various growth factors stimulate the phosphorylation of Nck and its association with autophosphorylated growth factor receptors. A panel of platelet-derived growth factor (PDGF) receptor mutations at tyrosine residues has been used to identify the Nck binding site. Here we show that mutation at Tyr-751 of the PDGF beta-receptor eliminates Nck binding both in vitro and in living cells. Moreover, the Y751F PDGF receptor mutant failed to mediate PDGF-stimulated phosphorylation of Nck in intact cells. A phosphorylated Tyr-751 is also required for binding of phosphatidylinositol-3 kinase to the PDGF receptor. Hence, the SH2 domains of p85 and Nck share a binding site in the PDGF receptor. Competition experiments with different phosphopeptides derived from the PDGF receptor suggest that binding of Nck and p85 is influenced by different residues around Tyr-751. Thus, a single tyrosine autophosphorylation site is able to link the PDGF receptor to two distinct SH2 domain-containing signaling molecules.

Leukocyte response integrin and integrin-associated protein act as a signal transduction unit in generation of a phagocyte respiratory burst

The leukocyte response integrin (LRI) is a phagocyte integrin which recognizes the basement membrane protein entactin and the synthetic peptide Lys-Gly-Ala-Gly-Asp-Val (KGAGDV). The function of LRI is intimately associated with that of a distinct membrane protein, integrin-associated protein (IAP), as antibodies which recognizes IAP can inhibit all known functions of LRI. When adherent to surface, the LRI ligands entactin and KGAGDV activate the respiratory burst in polymorphonuclear leukocytes (PMN) and monocytes, as do monoclonal antibodies (mAb) directed at either LRI or IAP. When added in solution, peptides and antibodies specific for LRI, and some, but not all, anti-IAP antibodies, can inhibit the respiratory burst activated by any of these surface-adherent ligands. Only monoclonal anti-IAP antibodies which can inhibit LRI function when added in solution are competent to activate the respiratory burst when adherent to a surface. KGAGDV peptide and anti-LRI added in solution can inhibit anti-IAP-stimulated respiratory burst. The LRI-IAP-initiated respiratory burst is independent of CD18, as judged by: (a) blockade of inhibition by anti-CD18 mAb with the protein kinase A inhibitor HA1004; (b) enhanced sensitivity of CD18-dependent respiratory burst compared with LRI/IAP-dependent respiratory burst to the tyrosine kinase inhibitors genestein and herbimicin; and (c) generation of a respiratory burst in response to KGAGDV, anti-LRI, and anti-IAP coated surfaces in PMN from a patient with LAD. Despite its apparent CD18 independence, LRI/IAP-initiated respiratory burst requires a solid phase ligand and is sensitive to cytochalasin B. These data suggest a model in which LRI and IAP act together as a single signal transduction unit to activate the phagocyte respiratory burst, in a manner that requires CD18-independent cell adhesion.

Real-time measurements of kinetics of EGF binding to soluble EGF receptor monomers and dimers support the dimerization model for receptor activation

We have tested one aspect of the allosteric dimerization model for the activation of EGF receptor (EGFR) by EGF: whether EGF binding favors dimerization of the receptor. For this to be true, EGF molecules must bind with higher affinity to dimeric receptors than to monomeric receptors. We have tested this directly in a defined system using the soluble, extracellular ligand binding domain of EGFR monomers (sEGFR) and sEGFR dimers stabilized by treatment with a covalent cross-linking agent. We describe real-time kinetic measurements of EGF binding to receptor monomers and dimers employing the method of total internal reflection (surface plasmon resonance). Our data show that sEGFR dimers bound EGF with 30-40-fold higher affinity [KD = (2-3) x 10(-8) M] than did sEGFR monomers. The enhanced binding affinity of sEGFR dimers resulted mainly from a reduced off-rate with k(off) = 0.001 s-1 for sEGFR dimers as compared to k(off) = 0.06 s-1 for sEGFR monomers. These measurements indicate that dimerization of sEGFR increases its affinity for EGF by prolonging the amount of time that EGF remains bound to the receptor. This provides evidence that EGF binding stabilizes receptor dimerization and provides further support for the allosteric dimerization model as a mechanism for ligand induced receptor activation.

Expression of myeloperoxidase mRNA by leukemic cells from childhood acute lymphoblastic leukemia

The frequency of acute lymphoblastic leukemia (ALL) expressing the myeloperoxidase (MPO) gene and other myeloid-associated characteristics was determined in 26 (20 B-lineage, six T-lineage) children at diagnosis. All cases were diagnosed as ALL by standard morphological and cytochemical criteria. In the 26 cases, leukemic blast cells from four B-lineage and two T-lineage ALL patients were simultaneously expressing myeloid-associated antigens. By Northern blot analysis, MPO mRNA was detected in leukemic cells from five out of six cases expressing both lymphoid and myeloid antigens, and from four out of 16 B-lineage and one out of four T-lineage ALL without myeloid antigens. There was no detectable MPO protein or enzymatic activity in the leukemic cells of these cases as examined by immunocytochemistry and cytochemistry. MPO mRNA expression in ALL cells was significantly associated with age < 1 year: leukemic blast cells from all five infant ALL patients expressed MPO mRNA, compared to five out of 21 ALL patients > 1 year of age whose leukemic cells were MPO mRNA(+) (p < 0.01). These results suggest that MPO gene transcription in the absence of translation may characterize a recently described subset of pediatric ALL patients who also express myeloid markers, and may serve as a useful marker for this entity.

Pentoxifylline restores cardiac output and tissue perfusion after trauma-hemorrhage and decreases susceptibility to sepsis

BACKGROUND

Although pentoxifylline produces various beneficial effects in a preheparinized model of hemorrhagic shock, it was unknown whether this agent restores the depressed cardiac output (CO) and tissue perfusion in a nonheparinized model of trauma-hemorrhage and resuscitation and, if so, whether it decreases the susceptibility to sepsis after hemorrhage.

METHODS

After laparotomy (i.e., induction of trauma), rats were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximum shed blood volume was returned in the form of Ringer's lactate. The animals were then resuscitated with Ringer's lactate, four times the volume of shed blood. Pentoxifylline (50 mg/kg body weight) or normal saline solution was infused intravenously more than 95 minutes during and after resuscitation. At 1.5 and 4 hours after resuscitation, CO, tissue perfusion, and plasma liver enzyme levels were determined. Sepsis was induced by cecal ligation and puncture at 20 hours after hemorrhage, and the necrotic cecum was excised 10 hours thereafter.

RESULTS

CO and tissue perfusion in the liver, kidney, spleen, and small intestine decreased significantly after hemorrhage and resuscitation. Pentoxifylline treatment, however, restored the depressed CO and tissue perfusion. The elevated liver enzyme levels were also significantly reduced by pentoxifylline treatment. Moreover, pentoxifylline prevented the increased mortality of posthemorrhaged rats subjected to sepsis.

CONCLUSIONS

Because pentoxifylline restored the depressed CO and tissue perfusion and decreased the susceptibility to sepsis, this agent appears to be a useful adjunct to crystalloid resuscitation after trauma and hemorrhage, even in the absence of blood resuscitation.

Synthesis of phosphotyrosine-containing peptides by the solid-phase method. A re-examination of the use of Boc-Tyr(PO3Bzl2)-OH

A practical and convenient procedure for making phosphotyrosine-containing peptides by the solid-phase method was developed. Phosphotyrosine was incorporated via Boc-Tyr(PO3Bzl2)-OH. The completed peptide was cleaved from the solid support by treatment with 1 M TMSBr-thioanisole-TFA. By gel-phase 31P-NMR spectroscopy we found that one of the benzyl protecting groups on phosphate was completely removed by two consecutive runs of Boc deprotection with 50% TFA-DCM. However, the other benzyl group remained intact throughout the synthesis (35 cycles).

Cloning and expression of a rat cytochrome P-450 11 beta-hydroxylase/aldosterone synthase (CYP11B2) cDNA variant

A variant cytochrome P450 11 beta-hydroxylase/aldosterone synthase cDNA (CYP11B2) clone, pALDO-4, was isolated and sequenced from a rat zona glomerulosa cDNA library. This clone contains a 1521 bp open reading frame coding for a 506 amino acid residue protein which has a 30 amino acid extension peptide which is 6 residues longer than that reported by others. Seven nucleotide mutations in the coding region of the mature protein were found in comparison to the reported cDNAs. These mutations resulted in three amino acid changes in the mature protein which were identical to those present in the cytochrome P-450 11 beta-hydroxylase (CYP11B1). Two nucleotide substitutions and two nucleotide insertions were also identified in the 3'-noncoding region. The expression product of this cDNA transfected into COS7 cells converted DOC to aldosterone, corticosterone and 18-hydroxycorticosterone less efficiently than the plasmid containing the cDNA with normal 24 amino acid extension peptide.

Potentiation of triamcinolone-induced cleft palate in mice by maternal high dietary fat

This study investigated whether the current range in dietary fat levels, which has arisen partly in response to some major health concerns, would affect frequency of congenital anomalies if continued into the period of early pregnancy. The effect of 5.6%, or 48% of calories from fat in the maternal diet, was tested on pregnant strain CD-1 mice injected with triamcinolone in doses of 0.01 mg, 0.02 mg, 0.04 mg, or 0.06 mg per day on days 11 through 14 of gestation. Frequency of cleft palate increased with increasing doses of triamcinolone, with clefts of the palate being rare at the two lower doses. No clefts appeared without triamcinolone on either diet. In combination with triamcinolone treatment, 226 fetuses exposed to a maternal low fat diet had normal palates and 86 had cleft palates. With exposure to high fat, 186 fetuses had normal palates and 101 had cleft palates, which was a significant increase in clefting (p < 0.05). Also, the latter group showed a greater degree of retardation in palate development (p < 0.05). Thus both a greater frequency and a more severe form of clefting support the conclusion that high dietary fat potentiated the cleft palate-producing effects of triamcinolone in mice.

Tumor necrosis factor-alpha produces hepatocellular dysfunction despite normal cardiac output and hepatic microcirculation

Although plasma levels of tumor necrosis factor (TNF) are elevated and hepatocellular dysfunction occurs even in the early hyperdynamic stage of sepsis, the precise mechanism responsible for this dysfunction remains unknown. Although TNF at high doses produces circulatory failure, it is not known whether the dose of TNF that does not adversely affect hemodynamics alters hepatocellular function. To study this, recombinant murine TNF-alpha was infused intravenously (0.05 or 0.25 mg/kg) over 30 min in normal rats. At 1 and 4 h after infusion of TNF-alpha or an equivalent volume of saline, hepatocellular function [i.e., maximum velocity (Vmax) and Michaelis constant (Km)] was assessed using in vivo indocyanine green clearance without blood sampling. Additional parameters measured were as follows: cardiac output by dye dilution, hepatic microcirculation by laser Doppler flowmetry and colloidal carbon infusion, plasma TNF and interleukin-6 (IL-6) by cytokine-dependent cellular assays, and plasma glucose enzymatically. The results indicate that although infusion of 0.05 mg/kg TNF-alpha did not affect Vmax and Km, its infusion at 0.25 mg/kg produced a significant depression of hepatocellular function and markedly increased the synthesis and/or release of IL-6. TNF-alpha-induced hepatocellular dysfunction was not associated with any significant changes in hepatic microcirculation, plasma glucose, cardiac output, and other measured hemodynamic parameters. Thus hepatocellular dysfunction observed after TNF infusion may be due to the direct effect of this cytokine alone or in combination with IL-6.

Functional expression of a rapidly inactivating neuronal calcium channel

Diverse types of calcium channels in vertebrate neurons are important in linking electrical activity to transmitter release, gene expression and modulation of membrane excitability. Four classes of Ca2+ channels (T, N, L and P-type) have been distinguished on the basis of their electrophysiological and pharmacological properties. Most of the recently cloned Ca2+ channels fit within this functional classification. But one major branch of the Ca2+ channel gene family, including BII (ref. 15) and doe-1 (ref. 16), has not been functionally characterized. We report here the expression of doe-1 and show that it is a high-voltage-activated (HVA) Ca2+ channel that inactivates more rapidly than previously expressed calcium channels. Unlike L-type or P-type channels, doe-1 is not blocked by dihydropyridine antagonists or the peptide toxin omega-Aga-IVA, respectively. In contrast to a previously cloned N-type channel, doe-1 block by omega-CTx-GVIA requires micromolar toxin and is readily reversible. Unlike most HVA channels, doe-1 also shows unusual sensitivity to block by Ni2+. Thus, doe-1 is an HVA Ca2+ channel with novel functional properties. We have identified a Ca2+ channel current in rat cerebellar granule neurons that resembles doe-1 in many kinetic and pharmacological features.

Alterations in circulating blood volume during polymicrobial sepsis

Although a great deal is known concerning the pathophysiology of sepsis, it is not clear whether circulating blood volume (CBV) is altered under such conditions. To study, this, rats were subjected to sepsis by cecal ligation and puncture (CLP). Immediately after CLP or sham operation, the animals received 3 ml/100 g body weight normal saline subcutaneously. CBV was determined by using in vivo indocyanine green (ICG) clearance at 2, 5, 10, or 20 hr after CLP or sham operation. This technique does not require any blood sampling. Serum glutamic pyruvic transaminase (SGPT) and glutamic oxaloacetic transaminase (SGOT) were assayed enzymatically as indicators of hepatocyte damage. Hepatic microcirculation was assessed at a selected time point (10 hr post-CLP) by using laser Doppler flowmetry and colloidal carbon infusion techniques. The results indicate that CBV, as determined by ICG clearance, remained unchanged up to 10 hr following the onset of sepsis (i.e., early sepsis) but decreased significantly at 20 hr after CLP (late sepsis). However, systemic hematocrit increased significantly at 5, 10, and 20 hr after CLP, indicating that plasma volume decreased at those time points. This suggests that there may be limitations in accurately assessing CBV at 5 and 10 hr after CLP, i.e., during the hyperdynamic circulatory state of sepsis, using the ICG clearance method. Moreover, SGPT and SGOT levels increased significantly at 10 hr, and the levels increased further at 20 hr post-CLP. In contrast, microvascular blood flow and carbon-perfused areas in the liver were significantly increased at 10 hr post-CLP.

The SH2/SH3 domain-containing protein GRB2 interacts with tyrosine-phosphorylated IRS1 and Shc: implications for insulin control of ras signalling

GRB2, a small protein comprising one SH2 domain and two SH3 domains, represents the human homologue of the Caenorhabditis elegans protein, sem-5. Both GRB2 and sem-5 have been implicated in a highly conserved mechanism that regulates p21ras signalling by receptor tyrosine kinases. In this report we show that in response to insulin, GRB2 forms a stable complex with two tyrosine-phosphorylated proteins. One protein is the major insulin receptor substrate IRS-1 and the second is the SH2 domain-containing oncogenic protein, Shc. The interactions between GRB2 and these two proteins require ligand activation of the insulin receptor and are mediated by the binding of the SH2 domain of GRB2 to phosphotyrosines on both IRS-1 and Shc. Although GRB2 associates with IRS-1 and Shc, it is not tyrosine-phosphorylated after insulin stimulation, implying that GRB2 is not a substrate for the insulin receptor. Furthermore, we have identified a short sequence motif (YV/IN) present in IRS-1, EGFR and Shc, which specifically binds the SH2 domain of GRB2 with high affinity. Interestingly, both GRB2 and phosphatidylinositol-3 (PI-3) kinase can simultaneously bind distinct tyrosine phosphorylated regions on the same IRS-1 molecule, suggesting a mechanism whereby IRS-1 could provide the core for a large signalling complex. We propose a model whereby insulin stimulation leads to formation of multiple protein--protein interactions between GRB2 and the two targets IRS-1 and Shc. These interactions may play a crucial role in activation of p21ras and the control of downstream effector molecules.

Molecular diversity of Ca2+ channel alpha 1 subunits from the marine ray Discopyge ommata

In many neurons, transmitter release from presynaptic terminals is triggered by Ca2+ entry via dihydropyridine-insensitive Ca2+ channels. We have looked for cDNAs for such channels in the nervous system of the marine ray Discopyge ommata. One cDNA (doe-2) is similar to dihydropyridine-sensitive L-type channels, and two cDNAs (doe-1 and doe-4) are similar to the subfamily of dihydropyridine-insensitive non-L-type channels. doe-4, which encodes a protein of 2326 aa, most closely resembles a previously cloned N-type channel. doe-1, which encodes a protein of 2223 aa, is a member of a separate branch of the non-L-type channels. Northern blot analysis reveals that doe-1 is abundant in the forebrain. doe-4 is more plentiful in the electric lobe and, therefore, may control neurotransmitter release in motor nerve terminals. These results show that the familial pattern of Ca(2+)-channel genes has been preserved from a stage in evolution before the divergence of higher and lower vertebrates > 400 million years ago. The cloning of these channels may be a useful starting point for elucidating the role of the Ca2+ channels in excitation-secretion coupling in nerve terminals.

Cocapping of the leukoadhesin molecules complement receptor type 3 and lymphocyte function-associated antigen-1 with Fc gamma receptor III on human neutrophils. Possible role of lectin-like interactions

We have tested the possible physical interactions between the iC3b receptor (CR3), lymphocyte function-associated Ag-1, and class III Fc gamma receptor (Fc gamma RIII) at neutrophil surfaces. Cells were labeled using fluorochrome-conjugated Fab or F(ab')2 fragments of antireceptor mAb. Labeled receptors were capped using second-step F(ab')2 fragments of goat anti-mouse Fab antiserum. After 20 min at 37 degrees C, 68% of the cells capped the anti-CR3 plus second-step complex. Capping was time, temperature, and cytochalasin B sensitive. When capped cells were probed with Fab' or F(ab')2 fragments of anti-Fc gamma RIII labeled with a distinct fluorochrome, 41% of the cells cocapped Fc gamma RIII. Indistinguishable results were obtained when potential antibody combining sites within caps were blocked with a large excess of Fab or F(ab')2 fragments. When Fc gamma RIII was capped, 49% of the cells cocapped CR3. Similarly, LFA-1 cocapped with both CR3 and Fc gamma RIII. Importantly, other membrane components including HLA class I, Mo5, CD13, CR type 1, and IL-8 receptors and N-4-nitrobenzo-2-oxa-1, 3-diszole L-alpha-dimyristoyl phosphatidylethanolamine did not cocap with CR3. However, the positive control Con A did cocap with CR3 and Fc gamma RIII. We next evaluated the effect of saccharides on CR3-Fc gamma RIII cocapping and found that 0.15 M N-acetyl-D-glucosamine (NADG), alpha-methyl-D-mannoside, and D-mannose significantly inhibited cocapping by 70, 58, and 48%, respectively. No inhibition was obtained using glucose, galactose, N-acetyl-neuraminic acid, fucose, sorbitol, fructose, or sucrose. Similarly, Fc gamma RIII-lymphocyte function-associated-1 cocapping was inhibited by NADG. However, the cocapping of CR3 with lymphocyte function-associated-1 or Con A were not affected by 0.15 M NADG, which suggests that NADG inhibition of leukoadhesin-Fc gamma RIII cocapping is not due to a general effect of NADG on capping. Inasmuch as Fc gamma RIII is a glycophospholipid-linked membrane protein, we speculate that it interacts with CR3 and/or lymphocyte function-associated-1 via lectin-like interactions.

Cocapping of the leukoadhesin molecules complement receptor type 3 and lymphocyte function-associated antigen-1 with Fc gamma receptor III on human neutrophils. Possible role of lectin-like interactions

We have tested the possible physical interactions between the iC3b receptor (CR3), lymphocyte function-associated Ag-1, and class III Fc gamma receptor (Fc gamma RIII) at neutrophil surfaces. Cells were labeled using fluorochrome-conjugated Fab or F(ab')2 fragments of antireceptor mAb. Labeled receptors were capped using second-step F(ab')2 fragments of goat anti-mouse Fab antiserum. After 20 min at 37 degrees C, 68% of the cells capped the anti-CR3 plus second-step complex. Capping was time, temperature, and cytochalasin B sensitive. When capped cells were probed with Fab' or F(ab')2 fragments of anti-Fc gamma RIII labeled with a distinct fluorochrome, 41% of the cells cocapped Fc gamma RIII. Indistinguishable results were obtained when potential antibody combining sites within caps were blocked with a large excess of Fab or F(ab')2 fragments. When Fc gamma RIII was capped, 49% of the cells cocapped CR3. Similarly, LFA-1 cocapped with both CR3 and Fc gamma RIII. Importantly, other membrane components including HLA class I, Mo5, CD13, CR type 1, and IL-8 receptors and N-4-nitrobenzo-2-oxa-1, 3-diszole L-alpha-dimyristoyl phosphatidylethanolamine did not cocap with CR3. However, the positive control Con A did cocap with CR3 and Fc gamma RIII. We next evaluated the effect of saccharides on CR3-Fc gamma RIII cocapping and found that 0.15 M N-acetyl-D-glucosamine (NADG), alpha-methyl-D-mannoside, and D-mannose significantly inhibited cocapping by 70, 58, and 48%, respectively. No inhibition was obtained using glucose, galactose, N-acetyl-neuraminic acid, fucose, sorbitol, fructose, or sucrose. Similarly, Fc gamma RIII-lymphocyte function-associated-1 cocapping was inhibited by NADG. However, the cocapping of CR3 with lymphocyte function-associated-1 or Con A were not affected by 0.15 M NADG, which suggests that NADG inhibition of leukoadhesin-Fc gamma RIII cocapping is not due to a general effect of NADG on capping. Inasmuch as Fc gamma RIII is a glycophospholipid-linked membrane protein, we speculate that it interacts with CR3 and/or lymphocyte function-associated-1 via lectin-like interactions.

SH2 domains exhibit high-affinity binding to tyrosine-phosphorylated peptides yet also exhibit rapid dissociation and exchange

src homology 2 (SH2) domains of intracellular signaling molecules such as phospholipase C-gamma and phosphatidylinositol 3'-kinase-associated protein p85 represent recognition motifs for specific phosphotyrosine-containing regions on activated growth factor receptors. The binding of SH2 domains to activated growth factor receptors controls the interaction with signaling molecules and the regulation of their activities. In this report, we describe the kinetic parameters and binding affinities of SH2 domains of p85 toward short phosphotyrosine-containing peptides with the amino acid sequence motif YMXM, derived from a major insulin receptor substrate, IRS-1, by using real time biospecific interaction analysis (BIAcore). Associations were specific and of very high affinity, with dissociation constants of 0.3 to 3 nM, between phosphopeptides and the two separate SH2 domains contained within p85. Nonphosphorylated peptides showed no measurable binding, and the interactions were specific for the primary sequence very close to the phosphotyrosine residue. Moreover, the interactions between phosphopeptides and SH2 domains of other signaling molecules were of much lower affinity. Interestingly, the binding of the SH2 domains to the tyrosine-phosphorylated peptides was of high affinity as a result of a very high on rate, of 3 x 10(7) to 40 x 10(7)/M/s; at the same time, the rate of dissociation, of 0.11 to 0.19/s, was rapid, allowing for rapid exchange of associating proteins with the tyrosine phosphorylation sites.

Lipoperoxidative damage in experimental rabbits with atherosclerosis

The extent of lipoperoxidation in experimental rabbits with atherosclerosis was determined dynamically during the experimental period of 65 days. Lipoperoxide (LPO) levels and selenium-dependent glutathions peroxidase (SeGSHPx) activities in liver, aorta, heart muscle, plasma erythrocyte (RBC) and platelet were examined on the 65th day. The results showed that the potential anti-lipoperoxidation in the atherosclerotic rabbits was decreased significantly, and the tissues were suffered from lipoperoxidative damage. It seems that there is a close relationship between lipoperoxidative damage and the development of atherosclerosis.

Transient activation of a distinct serine protein kinase is responsible for 27-kDa heat shock protein phosphorylation in mitogen-stimulated and heat-shocked cells

We have investigated the phosphorylation of HSP27, a 27-kDa heat shock protein which is involved in cellular thermoresistance and is also an early target of phosphorylation during heat shock and cell stimulation by a variety of growth and differentiation factors. HSP27 is transiently phosphorylated after shifting Chinese hamster cells from their normal temperature of 37 to 44 degrees C. The phosphorylation correlated in time with the transient activation of specific HSP27 protein kinase activities. HSP27 kinase was also induced to maximal levels within 5-15 min following stimulation of quiescent cells with heat shock, serum, thrombin, or basic fibroblast growth factor. Extracts from quiescent cells stimulated by heat shock or serum were analyzed after sequential chromatography on cation exchange and hydroxylapatite columns. In both cases, a single and identical peak of HSP27 kinase activity was obtained, suggesting that the same protein kinase was induced. The HSP27 kinase efficiently phosphorylated recombinant Chinese hamster HSP27 or the synthetic peptide RALNRQLSSGV containing the major in vivo phosphorylation site of rodent HSP27. The kinase was inactive toward the ribosomal S6 protein, the peptide RALSSLRA from S6 protein, or the mutant HSP27 proteins with in vivo phosphorylation sites altered to glycine. The partially purified HSP27 kinase had no kinase C, kinase A, or S6 kinase activities; conversely, HSP27 was not a good substrate for these kinases. HSP27 kinase was rapidly inactivated in the presence of acid phosphatase, suggesting that its activity was regulated by phosphorylation. It is suggested that this heat shock- and serum-induced HSP27 kinase is a novel serine kinase which is linked to a major signal transduction cascade.

Evaluation of 90:10 poly(D,L-lactide-co-glycolide) microspheres containing norethisterone: drug release and biodegradation

Poly(D,L-lactide-co-glycolide) (PLG, 90:10) microspheres containing 20% norethisterone (NET) were prepared by solvent evaporation method. Microspheres in the size ranges of 65 to 100 microns were sterilized by irradiation and used for further study. In vitro release showed fairly constant release of NET from the above microspheres over more than 90 days. However, in vivo drug release determined by residual NET analysis after i.m. injection in rats indicated a faster release rate. About 95% of NET was released in a period of 45 days. At the dose of 80 mg of microspheres, vaginal estrus cycles were inhibited for 45 days compared to 27 days for the same dose of NET crystals in rats. Biodegradation of the microspheres was tested by direct measurement of molecular weight losses and SEM observation of morphological changes of the microspheres, which showed continuous erosion in the internal matrix of microspheres with the decrease of molecular weight of PLG until total collapse of microspheres, and biodegradation was faster in rats than in human serum at 37 degrees C in vitro. Total degradation of 90:10 PLG microspheres was less than 7 months in rats and more than 9 months in vitro.

The effect of recombinant GM-CSF and G-CSF on the bone marrow cells of children with acute lymphoblastic leukemia

Colony stimulating factors (CSFs) are glycoprotein hormones that regulate growth and differentiation of hematopoietic progenitor cells. Their use to stimulate granulocyte precursors during periods of neutropenia in patients with acute myeloid leukemia (AML) is limited by their concomitant stimulation of the proliferation of myeloblasts. The effects of these agents on leukemic lymphoblasts is not entirely known. We have investigated the in vitro effects of granulocyte-CSF (G-CSF) and granulocyte/macrophage-CSF (GM-CSF) on leukemic cells from children with acute lymphoblastic leukemia (ALL). DNA synthesis of bone marrow cells from 22 children with ALL, either at diagnosis or in relapse, was examined with and without CSFs. Proliferative potential was also tested in a clonogenic assay with 13 bone marrow specimens. These factors did not stimulate the growth of ALL cells in either assay. Our results indicate that G-CSF and GM-CSF should be able to stimulate granulocyte proliferation without enhancing leukemic proliferation during periods of neutropenia in children with ALL.

[The effect of 211At labelled monoclonal antibody against gastric cancer on DNA, RNA and protein synthesis in gastric cancer cell]

By means of nuclide precursor incorporation, the effects of 211At labelled monoclonal antibody against gastric cancer (211At-3H11McAb) on DNA, RNA and protein synthesis in gastric cancer cell were studied. The results show that 211At-3H11McAb and Na211At-3 inhibit 3H-TdR, 3H-UR and 3H-Leu incorporation, especially 3H-UR incorporation, into gastric cancer cell at 3.7 x 10(4)Bq and 1.85 x 10(5)Bq; the inhibiting rates depend on concentration. The DNA biosynthesis in gastric cancer cell gradually recover after the drug is removed, suggesting that the drug should exert an inhibiting action on DNA biosynthesis in tumor cell through interference of DNA metabolism.

Differential alterations in microvascular perfusion in various organs during early and late sepsis

Although cellular dysfunction occurs very early in sepsis, it remains controversial whether this is solely due to a decrease in tissue perfusion. Recent studies have indicated that while active hepatocellular function was depressed, hepatic surface microvascular blood flow (MBF) increased in early sepsis but decreased in late sepsis as produced by cecal ligation and puncture (CLP). However, it is not known whether microvascular hyperperfusion in early sepsis and microvascular hypoperfusion in late sepsis are common events in other organs under such conditions. To study this, rats were subjected to sepsis by CLP, after which these and the corresponding shams received 3 ml/100 g body wt normal saline. Microvascular perfusion and MBF in various tissues were assessed by colloidal carbon infusion and laser-Doppler flowmetry, respectively, at 5 h (i.e., early sepsis) or 20 h (late sepsis) after CLP or sham operation. Carbon-perfused areas were quantitated by an Optomax image analyzer. The results indicate that the carbon-perfused areas and MBF in the liver, renal cortex, spleen, and small intestinal serosa (only MBF) increased significantly 5 h after CLP. In late sepsis, however, the carbon-perfused areas and MBF were found to be significantly decreased. A highly linear relationship was observed between the changes of carbon-perfused areas and MBF during sepsis in the tested organs. Thus the microvascular responses in the fluid-resuscitated sepsis model are characterized by hyperperfusion in the early stage and hypoperfusion in the late stage of sepsis in the tested tissues. The cellular dysfunctions observed during the early stage of sepsis are, therefore, not due to any reduction in tissue perfusion.

Protective effects of preheparinization on the microvasculature during and after hemorrhagic shock

Despite the fact that trauma patients are not heparinized at the time of injury, most models of hemorrhagic shock involve heparinization before the initiation of hemorrhage. To determine whether preheparinization has any effects on the microvasculature of organs during or after hemorrhage, rats (with and without preheparinization) were bled to a mean arterial blood pressure (BP) of 40 mm Hg. In two groups, this pressure was maintained by withdrawing additional blood until BP could no longer be maintained at 40 mm Hg (maximal bleedout, MB). In another two groups, the BP was maintained at 40 mm Hg until 40% of the MB volume was returned in the form of lactated Ringer's solution. The rats were then resuscitated with four times the volume of MB with lactated Ringer's. At MB or immediately after resuscitation, colloidal carbon black was rapidly infused and the liver, kidney, and spleen were excised, fixed, and sectioned. In additional animals, blood samples for platelet counts and total body fibrinogen estimates were taken before hemorrhage and at MB or at the end of resuscitation. The results indicate that at MB, microvascular patency in the kidney and liver was significantly depressed in the nonheparinized rats but not depressed in the preheparinized rats. This protective effect of heparin is not directly attributable to its anticoagulant properties, since there were no differences in the consumption of platelets or fibrinogen between the nonheparinized and preheparinized groups. Although the microvascular patency improved with resuscitation in the nonheparinized group, the glomeruli counts and perfusion of the spleen remained significantly lower than in the preheparinized group.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP-MgCl2 restores renal microcirculation following trauma and severe hemorrhage

Although ATP-MgCl2 enhances the recovery of renal function after ischemia and reperfusion, it is not known whether this agent has any beneficial effects on renal microcirculation and function in a nonheparinized model of trauma and severe hemorrhage. To study this, a midline laparotomy was performed (i.e., trauma induced) and the rats were bled to and maintained at a mean arterial pressure of 40 mmHg (1 mmHg = 133.32 Pa) until 40% of the maximum shed blood volume was returned in the form of Ringer's lactate (RL) solution. Animals were then resuscitated with 4 times the volume of the shed blood in the form of RL. ATP-MgCl2, 50 mumol/kg body weight, or an equivalent volume of saline, was infused intravenously during and following resuscitation. Renal microcirculation was examined by using colloidal carbon infusion and laser Doppler flow-metry. Glomerular filtration rate (GFR) was assessed with [3H]inulin clearance and cardiac output (CO) was determined by dye dilution technique. The results indicate that the depressed renal microcirculation following hemorrhage and resuscitation was restored by ATP-MgCl2 treatment. GFR was significantly higher in ATP-MgCl2-treated than saline-treated rats. ATP-MgCl2 also increased urine output, restored the decreased CO, and prevented the occurrence of renal edema after hemorrhage and resuscitation. Thus, ATP-MgCl2 appears to be a useful adjunct to crystalloid resuscitation following trauma and severe hemorrhagic shock even in the absence of blood resuscitation.

Human HSP27 is phosphorylated at serines 78 and 82 by heat shock and mitogen-activated kinases that recognize the same amino acid motif as S6 kinase II

The intracellular concentration of the 27-kDa mammalian heat shock protein, HSP27, increases several-fold after heat and other metabolic stresses and is closely associated with the acquisition of thermotolerance. Posttranslational modifications may also affect the function of HSP27. Heat shock of HeLa cell cultures, or treatment with arsenite, phorbol ester, or tumor necrosis factor, caused a rapid phosphorylation of preexisting HSP27 and the appearance of three phosphorylated isoforms, HSP27 B, C, and D. Digestion with trypsin and fractionation of the peptides by reverse phase high performance liquid chromatography revealed three 32P-labeled phosphopeptides. Microsequence analysis identified peak I as Ala76-Leu77-Ser78-Arg79 and peak II as Gln80-Leu81-Ser82-Ser83-Gly84-Val85- Ser86-Glu87-Ile88-Arg89; peak III contained the undigested peptide pair Ala76-Arg89. Ser82 was the major site and Ser78 the minor site of phosphorylation. Mutant proteins with Ser78 or Ser82 altered to glycine or Ser78-Ser82 double mutants were phosphorylated to reduced extents in vivo after heat or arsenite treatment. Ser78 and Ser82 (and Ser15) occur in the sequence motif RXXS, which is recognized by ribosomal protein S6 kinase II. Mitogenic stimulation of serum-deprived, Go-arrested Chinese hamster cells with serum, thrombin, or fibroblast growth factor also stimulated phosphorylation of HSP27 Ser78 and Ser82, and mitogenic stimulation and heat shock activated protein kinase activities that phosphorylated HSP27 and protein S6 in vitro. These results suggest that HSP27 may exert phosphorylation-activated functions linked with growth signaling pathways in unstressed cells. A homeostatic function at this level could protect cells from adverse effects of signal transduction systems which may be activated inappropriately during stress.