[Observation on effect of chongcao shenkang capsules in preventing and treating acute renal failure in cases of hemorrhagic fever with renal syndrome]

OBJECTIVE

To observe the effect of Chongcao shenkang capsules in preventing and treating acute renal failure in cases of hemorrhagic fever with renal syndrome (HFRS).

METHODS

150 cases of HFRS were randomly divided into two groups: the treatment group and the control group. The former contained 76 cases and the latter the 74 cases. All cases in both groups were given a combined therapy mainly composed of balanced salt solution and ribavirin, cases in treatment group additionally accepted Chongcao shenkang capsules 2.7 grams tid, till the end of polyuric phase.

RESULTS

The results showed that in the treatment group the occurrence rate of cases with oliguric phase was 13.0% (4/46) and the oliguric and polyuric periods were 2.7 +/- 1.6 days and 6.8 +/- 2.9 days respectively while those in the control group were 31.1% (4/45), 4.3 +/- 2.1 dnys and 8.2 +/- 3.4 days respectively (P < 0.01 or P < 0.05). The urinary protein of the treatment group disappeared within 5.1 +/- 2.3 days and their serum creatinine restored within 10.9 +/- 6.2 days, but the urinary protein disappearing and the serum creatinine restoring periods of the control group were 6.8 +/- 2.7 days and 13.7 +/- 7.4 days respectively (P < 0.01 or P < 0.05). The serum and urine beta 2-microglobulin levels of the treatment group were remarkably lower than those of the control group on the fifth and tenth days after treatment (P < 0.01 or P < 0.05). Compared with those of the control group of 33.8% (25/74) and 87.8% (65/74), the occurrence rate of severe complications and curative rate of the treatment group were 18.4% (14/76) and 94.7% (72/76) respectively (the former P < 0.05, but the latter P > 0.05).

CONCLUSION

It was concluded that Chongcao shenkang capsules is capable of reducing the occurrence rate of acute renal failure in HFRS patients, shortening the duration of acute renal failure, decreasing their needs for dialysis, lessening their complications and increasing their curative rate. Its administration is safe and convenient and therefore it is worthy to be popularized.

RAGE mediates a novel proinflammatory axis: a central cell surface receptor for S100/calgranulin polypeptides

S100/calgranulin polypeptides are present at sites of inflammation, likely released by inflammatory cells targeted to such loci by a range of environmental cues. We report here that receptor for AGE (RAGE) is a central cell surface receptor for EN-RAGE (extracellular newly identified RAGE-binding protein) and related members of the S100/calgranulin superfamily. Interaction of EN-RAGEs with cellular RAGE on endothelium, mononuclear phagocytes, and lymphocytes triggers cellular activation, with generation of key proinflammatory mediators. Blockade of EN-RAGE/RAGE quenches delayed-type hypersensitivity and inflammatory colitis in murine models by arresting activation of central signaling pathways and expression of inflammatory gene mediators. These data highlight a novel paradigm in inflammation and identify roles for EN-RAGEs and RAGE in chronic cellular activation and tissue injury.

Administration of interleukin-12 exerts a therapeutic instead of a long-term preventive effect on mite Der p I allergen-induced animal model of airway inflammation

Interleukin-12 (IL-12) is a key cytokine, which promotes T helper type 1 (Th1) cell-mediated immunity and inhibits Th2-type responses. It has been previously shown that IL-12 administration during active immunization following a single allergen exposure can prevent antigen-induced increases in immunoglobulin E (IgE) formation, Th2 cytokine production and bronchoalveolar lavage (BAL) eosinophils in a murine model of allergic airway inflammation. Thus, these studies have now been extended and two IL-12 treatment protocols on this murine model were evaluated. Administration of IL-12 during the active immunization strikingly increased Der p I-specific serum IgG2a and transiently decreased the levels of IgG1 and IgE antibodies following multiple allergen challenges. Such early treatment of IL-12 down-regulated IL-5 production and modestly up-regulated interferon-gamma production but did not effect BAL eosinophilia. These results suggest that repeated exposure to antigen and IL-12 is necessary to maintain a persistent Th1-recall response. Furthermore, administration of IL-12 to actively immunized mice, in which Th2-associated responses were established, had a significant effect on IgG2a synthesis and a modest effect on IgE levels, also down-regulation of IL-5 production, and markedly increased interferon-gamma production and abolished recruitment of eosinophils. Therefore, these data indicate that IL-12 can inhibit antigen-induced eosinophil infiltration into airways, despite the existence of a Th2-associated response. Taken together, these studies suggest that IL-12 may be useful as an immunotherapeutic agent in the treatment of such pulmonary allergic disorders as bronchial asthma.

Glucocorticoid resistance caused by reduced expression of the glucocorticoid receptor in cells from human vascular lesions

Mechanisms that control the balance between cell proliferation and death are important in the development of vascular lesions. Rat primary smooth muscle cells were 80% inhibited by low microgram doses of hydrocortisone (HC) and 50% inhibited by nanogram concentrations of transforming growth factor-beta1 (TGF-beta1), although some lines acquired resistance in late passage. However, comparable doses of HC, or TGF-beta1, failed to inhibit most human lesion-derived cell (LDC) lines. In sensitive LDC, HC (10 microg/mL) inhibited proliferation by up to 50%, with obvious apoptosis in some lines, and TGF-beta1 inhibited proliferation by more than 90%. Collagen production, as measured by [3H]proline incorporation or RIA for type III pro-collagen, was either unaffected or increased in the LDCs by HC. These divergent responses between LDC lines were partially explained by the absence of the glucocorticoid receptor (GR) and heat shock protein 90 mRNA in 10 of 12 LDC lines, but the presence of the mineralocorticoid receptor and 11beta-hydroxysteroid dehydrogenase type II. Western blot analysis confirmed the absence of the GR protein in cells lacking GR mRNA. Immunohistochemistry of human carotid lesions showed high levels of GR in the tunica media, but large areas lacking GR in the fibrous lesion. Considering the absence of the GR in most lines, the effects of HC may be elicited through the mineralocorticoid receptor. Functional resistance to the antiproliferative and antifibrotic effects of HC may contribute to excessive wound repair in atherosclerosis and restenosis.

BLNK required for coupling Syk to PLC gamma 2 and Rac1-JNK in B cells

Signaling through the B cell receptor (BCR) is essential for B cell function and development. Despite the key role of Syk in BCR signaling, little is known about the mechanism by which Syk transmits downstream effectors. BLNK (B cell LiNKer protein), a substrate for Syk, is now shown to be essential in activating phospholipase C (PLC)gamma 2 and JNK. The BCR-induced PLC gamma 2 activation, but not the JNK activation, was restored by introduction of PLC gamma 2 membrane-associated form into BLNK-deficient B cells. As JNK activation requires both Rac1 and PLC gamma 2, our results suggest that BLNK regulates the Rac1-JNK pathway, in addition to modulating PLC gamma 2 localization.

[Therapeutic effect of recombinant interferon alpha-2b on hemorrhagic fever with renal syndrome]

To study the therapeutic effect of recombinant interferon alpha-2b(rIFN alpha-2b) on cases of hemorrhagic fever with renal syndrome(HFRS) in early stage, 146 cases of HFRS in feverish stage and within five days of onset were randomly divided into two groups: the treatment and the control, each group included 73 cases. The control group was given the traditional combined therapy with a predominance of balanced solution, the treatment group was given rIFN alpha-2b 1 x 10(6)U per day, i.m., for three days. The treatment group showed much better effects in improving the viremia, the clinical conditions, skipping phases, restoring kidney function and platelet account, decreasing complications than the control group (P < 0.05). All the patients of the treatment group recovered, and four patients of the control group died, accounting for 5.47%. No side-effect resulting from rIFN alpha-2b was found. Administration of rIFN alpha-2b to patients with HFRS within five days of onset could lighten the organ lesions, shorten the course of disease and raise the curative rate.

[Sensitivity of cationic polymer Eudragit RL to electrolytes and its effect on drug release from Eudragit RL matrix]

The swelling behavior of acrylic polymer Eudragit RL in different concentration and species of electrolyte aqueous media, and the effect of media and polymer swelling on drug release from Eudragit RL matrix system were investigated with nifedipine, chlorpheniramine maleate and indomethacin as model drugs. It was found that Eudragit RL was sensitive to the electrolytes in aqueous media. The swelling of Eudragit RL decreased with increasing electrolyte concentration and was significantly affected by the electrolyte species. The swelling behavior was reversible. The release of 3 drugs from Eudragit RL matrix was remarkably affected by the electrolytes in the media. The rates of release of nifedipine and chlorpheniramine maleate from the polymer matrices were controlled by the polymer swelling behavior, and the rate of release correlated well with the swelling behavior. However, the rates of release of indomethacin from the Eudragit RL matrix were controlled not only by the polymer swelling but also by the drug displacement by the medium anion, which was attributed to the presence of an interaction between indomethacin and Eudragit RL.

BLNK: a central linker protein in B cell activation

Linker or adapter proteins provide mechanisms by which receptors can amplify and regulate downstream effector proteins. We describe here the identification of a novel B cell linker protein, termed BLNK, that interfaces the B cell receptor-associated Syk tyrosine kinase with PLCgamma, the Vav guanine nucleotide exchange factor, and the Grb2 and Nck adapter proteins. Tyrosine phosphorylation of BLNK by Syk provides docking sites for these SH2-containing effector molecules that, in turn, permits the phosphorylation and/or activation of their respective signaling pathways. Hence, BLNK represents a central linker protein that bridges the B cell receptor-associated kinases with a multitude of signaling pathways and may regulate the biologic outcomes of B cell function and development.

Modification of the clinical course of intestinal microsporidiosis in acquired immunodeficiency syndrome patients by immune status and anti-human immunodeficiency virus therapy

The clinical course of 37 Enterocytozoon bieneusi-infected acquired immunodeficiency syndrome patients with diarrhea was studied. Parasite clearance was seen in 15 patients (40.5%). Clearance of E. bieneusi resulted in a 25-100% reduction in episodes of diarrhea, suggesting that microsporidia are true pathogens. Univariate and multivariate proportional hazards analyses revealed that peripheral blood CD4 cell counts > or = 100/mm3, the use of two or more antiretroviral medications, and use of a protease inhibitor were statistically associated with decreased time to clearance of E. bieneusi. Specific anti-microsporidial therapy (albendazole) was not associated with parasite eradication. Factors related to immunocompetence and human immunodeficiency virus suppression appeared to be important in the clearance of E. bieneusi.

[Development of gas-liquid exchanger for complex retina pare operation]

A gas-liquid exchanger apparatus was developed for the complex operation of the retinal detachment. The bacteria-free gas can be obtained by using this apparatus. The pressure of the gas is successively adjustable, from 0 to 100 mmHg. The apparatus is very suitable for exchanging gas for liquid in the retinal surgery and raises the effect of the operation.

Identification of two tyrosine phosphoproteins, pp70 and pp68, which interact with phospholipase Cgamma, Grb2, and Vav after B cell antigen receptor activation

Tyrosine phosphorylation of cellular proteins mediates the assembly and localization of effector proteins through interactions facilitated by modular Src homology 2 (SH2) and phosphotyrosine binding domains. We describe here two tyrosine-phosphorylated proteins with Mr values of 70,000 and 68,000 that interact with Grb2, phospholipase C (PLCgamma1 and PLCgamma2), and Vav after B cell receptor cross-linking. The interaction of pp70 and pp68 with PLC and Vav is mediated by the carboxyl-terminal SH2 domain of PLC and the SH2 domain of Vav. In contrast, the interaction of pp70 and pp68 with Grb2 requires cooperative binding of the SH2 and SH3 domains of Grb2. Western blot analysis demonstrated that neither pp70 nor pp68 represented the recently described linker protein SLP-76, which binds Grb2, PLC, and Vav in T cells after T cell receptor activation. Moreover, SLP-76 protein was not detected in a number of B cell lines or in normal mouse B cells. Hence, we propose that pp70 and pp68 likely represent B cell homologs of SLP-76 which facilitate and coordinate B cell activation.

[A research on the determination of trace secondary amines by reversed-phase high performance liquid chromatography with electrochemical detection]

A new sensitive method for determination of ultratrace secondary amines has been described. It is the first time to use dansyl chloride as electrochemical derivatization reagent for secondary amines. The optimum experimental conditions have been established. At first, trace secondary amines were derivatised with dansyl chloride at 40 degrees C for 30 minutes, then the mixture was injected and separated on a Perkin-Elmer/HS-3 C18 (83 mm x 4.6 mm i.d. 3 microm) column with methanol aqueous solution (70/30, pH 3.3) which contained 20 mmol/L potassium biphthalate buffer as mobile phase and detected with electrochemical detection at E = +1.1 V (Ag/AgCl). The calibration curves were linear in the range of 0.225-54 pg for dimethylamine; 1.1-264 pg for diethylamine, 0.43-102 pg for piperidine. The detection limits were 0.024, 0.60, 0.090 pg respectively and the coefficients of variation were less than 3.5% (n = 7).

Barrier effects of hyperosmolar signaling in microvascular endothelium of rat lung

We determined the effects of hyperosmolarity on lung microvascular barrier properties by means of the split-drop technique in single venular capillaries of the isolated, blood-perfused rat lung. Using isosmolar and hyperosmolar test solutions (colloid osmotic pressure = 21 cm H2O), we quantified transcapillary flux at a fixed absorptive capillary pressure, and the capillary hydraulic conductivity (Lp). Loss of barrier function was indicated in flux reversal from isosmolar absorption to hyperosmolar filtration (P < 0. 01), and by hyperosmolarity-induced Lp increase (P < 0.01). Barrier recovery after a 1-min hyperosmolar exposure was delayed > 25 min. The flux reversal was blocked by the tyrosine kinase inhibitors genistein and MDC (P < 0.01). Genistein also inhibited the Lp increase (P < 0.01). Immunoblots of hyperosmolarity-exposed, cultured rat lung microvascular endothelial cells (RLMEC) and of endothelial cells freshly harvested from lungs given hyperosmolar infusions indicated a genistein-inhibitable enhancement of protein tyrosine phosphorylation. Immunoprecipitation studies indicated tyrosine phosphorylation of the mitogen activated protein kinases (MAPK) ERK1 and ERK2 and the adaptor protein Shc in lysates of RLMEC exposed to hyperosmolar conditions. We conclude that in lung venular capillaries hyperosmolarity deteriorates barrier properties, possibly by inducing tyrosine phosphorylation of endothelial proteins.

Cerebral malacia caused by Takayasu's arteritis--a case report

This paper reports an unusual autopsy case, a 27-year-old man, who died from severe cerebral malacia. It is well known to our legal medical workers that cerebral malacia could be caused by injury and/ or disease. By coincidence, the deceased was subjected to head injury nine months prior to death, so differential diagnosis of cerebral malacia is very important in this case. His cerebral malacia was finally confirmed to be caused by Takayasu's arteritis not by his head injury by means of autopsy and pathological examination.

Viscous fluid expulsion in the evaluation of the constipated patient

PURPOSE

The aim of this study was to evaluate a viscous fluid expulsion test as a method for quantifying rectal outlet obstruction.

METHODS

We examined the ability of 30 severely constipated patients and 40 healthy control subjects to expel a viscous fluid simulating feces.

RESULTS

Constipated patients with defecographic rectal retention expelled a significant lower viscous fluid volume compared with controls (P < 0.0001). Considering the viscous fluid expulsion test to be positive if the patient expelled less than 160 ml of fluid (lower 95 percent confidence value in healthy controls) and using the presence of defecographic rectal outlet obstruction as a reference, the predictive value of a negative viscous fluid expulsion test was 100 percent, the predictive value of a positive test was 67 percent, and sensitivity and specificity was 100 percent and 82 percent, respectively. The viscous fluid test identified symptomatic outlet obstruction in almost twice as many patients as did defecography. Some patients, however are-despite their obstructive symptoms-able to evacuate their rectum when examined in the laboratory.

CONCLUSION

The viscous fluid expulsion test is a simple, reproducible, nonionizing, and low-cost method of quantifying rectal outlet obstruction. A positive test result should lead to a defecography, whereas a negative test result renders defecography dispensable and spares the patient from pelvic radiation.

The HypB protein from Bradyrhizobium japonicum can store nickel and is required for the nickel-dependent transcriptional regulation of hydrogenase

The HypB protein from Bradyrhizobium japonicum is a metal-binding GTPase required for hydrogenase expression. In-frame mutagenesis of hypB resulted in strains that were partially or completely deficient in hydrogenase expression, depending on the degree of disruption of the gene. Complete deletion of the gene yielded a strain (JH delta Eg) which lacked hydrogenase activity under all conditions tested, including the situation as bacteroids from soybean nodules. Mutant strain JH delta 23H lacking only the N-terminal histidine-rich region (38 amino acids deleted, 23 of which are His residues) expressed partial hydrogenase activity. The activity of strain JH delta 23H was low in comparison to the wild type in 10-50 nM nickel levels, but could be cured to nearly wild-type levels by including 50 microM nickel during the derepression incubation. Studies on strains harbouring the hup promoter-lacZ fusion plasmid showed that the complete deletion of hypB nearly abolished hup promoter activity, whereas the histidine deletion mutant had 60% of the wild-type promoter activity in 50 microM NiCl2. Further evidence that HypB is required for hup promoter-binding activity was obtained from gel-shift assays. HypB could not be detected by immunoblotting when the cells were cultured heterotrophically, but when there was a switch to microaerobic conditions (1% partial pressure O2, 10% partial pressure H2) HypB was detected, and its expression preceded hydrogenase synthesis by 3-6 h. 63Ni accumulation by whole cells showed that both of the mutant strains accumulate less nickel than the wild-type strain at all time points tested during the derepression incubation. Wild-type cultures that received nickel during the HypB expression-specific period and were then washed and derepressed for hydrogenase without nickel had activities comparable to those cells that were derepressed for hydrogenase with nickel for the entire time period. In contrast to the wild type, strain JH delta 23H cultures supplied with nickel only during the HypB expression period achieved hydrogenase activities that were 30% of those cultures supplied with nickel for the entire hydrogenase derepression period. These results indicate that the loss of the metal-binding area of HypB causes a decrease in the ability of the cells to sequester and store nickel for later use in one or more hydrogenase expression steps.

[Determination of stability constants of metal complexes by on-column derivatization reversed phase high performance liquid chromatography]

The stability constant of metal complexes is an important chemical parameter. There are many methods for its determination, but few analyst has calculated it with high performance liquid chromatography (HPLC). In the present paper a new model for determining the stability constant of metal complexes with on-column derivatization reversed phase HPLC has been proposed where complexation forming reactions are taking place in the mobile phase. Based on the retention mechanism of neutral complexes, the equation for calculation is deduced. It has been applied to some cations (Hg2+, Pb2+, Ni2+, Cu2+, Ag+, Hg+)-DDTC complexes. The results are in agreement with those given in the literature. Then, a simple, practical and rapid graphic method is studied for monovalent metal complexes. The stability constants can be obtained simply as the quotient of the line slope and the axis intercept of the linear dependence. The relations derived in this paper may be used not only for calculating the stability constants from chromatographic measurements but also for optimizing the process of separation based on the values of the stability constants available in literature.

Recognition of unique carboxyl-terminal motifs by distinct PDZ domains

The oriented peptide library technique was used to investigate the peptide-binding specificities of nine PDZ domains. Each PDZ domain selected peptides with hydrophobic residues at the carboxyl terminus. Individual PDZ domains selected unique optimal motifs defined primarily by the carboxyl terminal three to seven residues of the peptides. One family of PDZ domains, including those of the Discs Large protein, selected peptides with the consensus motif Glu-(Ser/Thr)-Xxx-(Val/Ile) (where Xxx represents any amino acid) at the carboxyl terminus. In contrast, another family of PDZ domains, including those of LIN-2, p55, and Tiam-1, selected peptides with hydrophobic or aromatic side chains at the carboxyl terminal three residues. On the basis of crystal structures of the PSD-95-3 PDZ domain, the specificities observed with the peptide library can be rationalized.

Three-dimensional modeling and molecular evolution of Matrix Cell Adhesion Molecule #2: MAT-CAM 2

Our research group has recently reported the partial amino acid sequence of an aortic adventitial collagen-associated fibrillar protein, which may be the target of an autoimmune response in patients with abdommal aortic aneurysms (AAA). Its apparent molecular weight is approximately 40 kDa, so we have named it aneurysm-associated antigenic protein-40 kDa (AAAP-40). It has similarities to microfibril-associated glycoprotein-36 kDa (MAGP-36), which was reported by Kobayashi et al. to have a tissue distribution limited to the aorta in pig; unlike other microfibrillar proteins which appear to distribute ubiquitously throughout the body with elastin. Accordingly, if AAAP-40 is the human homolog of MAGP-36, it would explain how an autoimmune reaction against this protein might have consequences more or less limited to the aorta and its branches.

Ca2+ waves in lung capillary endothelium

Although cytosolic Ca2+ importantly regulates organ function, lung microvascular [Ca2+]i regulation remains poorly understood because of the lack of direct in situ quantification. In the present study, we report the first endothelial [Ca2+]i quantification by the fura 2 method in microscopically imaged venular capillaries of the isolated blood-perfused rat lung. Sequential images indicated the presence of intercellular Ca2+ waves that spontaneously originated from pacemaker endothelial cells and then spread for short distances along the capillary wall, inducing synchronous endothelial [Ca2+]i oscillations. Fast Fourier analyses of the oscillations revealed a dominant wave component with an amplitude of 37 nmol/L, frequency of 0.4 min-1, and velocity of 5 microns/s. The intracellular Ca2+ wave was unaffected by blood flow stoppage or by infusions of Ca(2+)-containing or Ca(2+)-free dextran. Inhibition of the wave by thapsigargin in Ca(2+)-free dextran and by the gap junction uncoupler, heptanol, indicated that it was generated by endosomal Ca2+ release in the pacemaker cell and was propagated by gap junctional communication. In the presence of histamine, enhancement of the wave accounted for a significant component of the coordinated [Ca2+]i increase in the capillary segment. No intercellular Ca2+ waves were evident in adjoining alveolar epithelial cells. Our findings indicate a novel mechanism of [Ca2+]i regulation in the lung capillary under both resting and stimulated conditions. Pacemaker-induced Ca2+ waves, generated intracellularly by unknown initiating mechanisms, communicated to adjoining cells to determine [Ca2+]i profiles in short interbranch segments of capillary walls.

Phosphorylation of SLP-76 by the ZAP-70 protein-tyrosine kinase is required for T-cell receptor function

Two families of tyrosine kinases, the Src and Syk families, are required for T-cell receptor activation. While the Src kinases are responsible for phosphorylation of receptor-encoded signaling motifs and for up-regulation of ZAP-70 activity, the downstream substrates of ZAP-70 are unknown. Evidence is presented herein that the Src homology 2 (SH2) domain-containing leukocyte protein of 76 kDa (SLP-76) is a substrate of ZAP-70. Phosphorylation of SLP-76 is diminished in T cells that express a catalytically inactive ZAP-70. Moreover, SLP-76 is preferentially phosphorylated by ZAP-70 in vitro and in heterologous cellular systems. In T cells, overexpression of wild-type SLP-76 results in a hyperactive receptor, while expression of a SLP-76 molecule that is unable to be tyrosine-phosphorylated attenuates receptor function. In addition, the SH2 domain of SLP-76 is required for T-cell receptor function, although its role is independent of the ability of SLP-76 to undergo tyrosine phosphorylation. As SLP-76 interacts with both Grb2 and phospholipase C-gamma1, these data indicate that phosphorylation of SLP-76 by ZAP-70 provides an important functional link between the T-cell receptor and activation of ras and calcium pathways.

Hydrogen uptake hydrogenase in Helicobacter pylori

The peptic ulcer-causing bacterium Helicobacter pylori was found to contain an H2-uptake hydrogenase activity coupled to whole cell (aerobic) respiration. The activity was localized to membranes which functioned in the H2-oxidizing direction with a variety of artificial and physiological electron acceptors of positive redox potential. Immunoblotting of H. pylori membrane components with anti (B. japonicum) hydrogenase large and small subunit-specific antisera identified H. pylori hydrogenase peptides of approximately 65 and 26 kDa respectively, and H. pylori genomic DNA fragments hybridizing to the (B. japonicum) hydrogenase structural genes were identified. The membrane-bound activity was subject to anaerobic activation, like many NiFe hydrogenases. Difference absorption spectral studies revealed absorption peaks characteristic of b and c-type cytochromes, as well as of a bd-type terminal oxidase in the H. pylori H2-oxidizing membrane-associated respiratory chain.

Different properties of the atrial G protein-gated K+ channels activated by extracellular ATP and adenosine

Extracellular ATP (ATPo) and adenosine activate G protein-gated inwardly rectifying K+ currents in atrial cells. Earlier studies have suggested that the two agonists may use separate pathways to activate the K+ current. Therefore, we examined whether the K+ channels activated by the two agonists have different properties under identical ionic conditions. In cell-attached patches, K+ channels activated by 100 microM ATP in the pipette had a single-channel conductance and mean open time of 32.0 +/- 0.2 pS and 0.5 +/- 0.1 ms, respectively, compared with 31.3 +/- 0.3 pS and 0.9 +/- 0.1 ms for the K+ channels activated by adenosine (140 mM KCl). With ATPo as the agonist, the K+ channel activity in cell-attached patches was approximately threefold lower than that in inside-out patches with 100 microM GTP in the bath. Applying ATP to the cytoplasmic side of the membrane (ATPi) produced a biphasic concentration-dependent effect on channel activity: an increase at low [mean affinity constant (K0.5) = 190 microM] and a decrease at high (K0.5 = 1.3 mM) concentrations. In contrast, with adenosine as the agonist, K+ channel activity in cell-attached patches was approximately fourfold greater than that in inside-out patches with 100 microM GTP in the bath. In inside-out patches, ATPi only augmented the K+ channel activity (K0.5 = 32 microM). These results show that although both ATPo and adenosine activate kinetically similar K+ channels in atrial cells, the channels are regulated differently by intracellular nucleotides.

Ligation of endothelial alpha v beta 3 integrin increases capillary hydraulic conductivity of rat lung

Complement-mediated pulmonary edema results from increases in lung capillary hydraulic conductivity (Lp), possibly by receptor-mediated mechanisms. We considered the Lp effects of vitronectin and the vitronectin-containing complement complex SC5b-9, which ligate the integrin alpha v beta 3. Vitronectin, SC5b-9, and SC5b-9-enriched zymosan-activated serum all rapidly increased Lp, as determined by the split-drop technique in single lung capillaries of rat lung. The Lp increases were inhibited by a monospecific (LM609) and a polyclonal (R838) antibody against the alpha v beta 3 integrin but not by an irrelevant monoclonal antibody isotype matched with LM609, by a monoclonal antibody against the alpha v beta 5 integrin, or by preimmune rabbit serum. Vitronectin monomers failed to increase Lp. The tyrosine kinase blockers genistein and methyl 2,5-dihydroxycinnamate caused significant concentration-dependent inhibitions of Lp increases due to vitronectin and zymosan-activated serum. By contrast, the protein kinase C blocker calphostin C had no major effect. We conclude that (1) multivalent ligation of the luminally located alpha v beta 3 integrin of lung capillary endothelium increases transcapillary liquid flux, and (2) the dominant signal transduction pathway for this effect occurs through tyrosine kinase activation.

Effects of TNF alone or in combination with chemotherapeutic agents on human ovarian cancers in vitro and in nude mice

Using the tetrazolium (MTT) assay, we examined the cytotoxicities of recombinant human tumor necrosis factor (rhTNF) and five chemotherapeutic agents, namely CTX, 5-FU, VCR, DDP and KSM, on human ovarian cancer cell lines OVCAR3 and CAOV3. The results showed that the cytotoxicities of rhTNF at concentrations of 50-50,000 U/ml on OVCAR3 cell line and CAOV3 cell line exposed to rhTNF for 24 hours were from 14.2% +/- 6.8% to 67.2% +/- 3.0% and from 8.2% +/- 4.3% to 60.9% +/- 1.3%, respectively. The cytotoxicities of all five chemotherapeutic agents tested on the two cell lines were much lower than that of rhTNF. We also studied the combined antitumor potential of rhTNF with the five chemotherapeutic agents and the results showed that there were various degrees of synergism in cytotoxicities of rhTNF in combination with DDP or KSM on the two cell lines. Based on experiments in vitro, the in vivo antitumor activities of rhTNF, both alone and in combination with KSM, were examined in OVCAR3 cancer transplanted in nude mice. The results showed a considerable antitumor effect of rhTNF when it was used alone and a marked synergistic effect when it was used in combination with KSM on the xenograft tumors.

Soluble ligands of the alpha v beta 3 integrin mediate enhanced tyrosine phosphorylation of multiple proteins in adherent bovine pulmonary artery endothelial cells

Binding of substrate-bound extracellular matrix proteins to cell surface integrins results in a variety of cellular responses including adhesion, cytoskeletal reorganization, and gene expression. We have previously shown that addition of soluble SC5b-9, the complement-vitronectin complex, resulted in an RGD-dependent increase in lung venular hydraulic conductivity (Ishikawa, S., Tsukada, H., and Bhattacharya, J. (1993) J. Clin. Invest. 91, 103-109). To identify specific integrin(s) and signal transduction pathways that are responsive to soluble vitronectin-containing ligands, we exposed confluent bovine pulmonary artery cells to purified soluble human mono- or multimeric vitronectin, or SC5b-9, and determined the extent of endothelial cell protein tyrosine phosphorylation. Monomeric vitronectin (Vn) did not induce enhanced protein tyrosine phosphorylation. However, multimeric Vn and SC5b-9 elicited time- and concentration-dependent increases in tyrosine phosphorylation of numerous proteins. Antiserum against vitronectin, RGD peptides, and monoclonal and polyclonal antibodies against the alpha v beta 3 integrin blocked the vitronectin- or SC5b-9-induced enhanced accumulation of tyrosine phosphoproteins, while antibodies against beta 1 integrins and the alpha v beta 5 integrin did not. Clustering of the alpha v beta 3 integrin using monoclonal antibody LM609 caused a pattern of enhanced tyrosine phosphorylation similar to that caused by multimeric Vn and SC5b-9, suggesting that aggregation of alpha v beta 3 was critical for signaling. Among the proteins that underwent enhanced tyrosine phosphorylation in response to vitronectin were the cytoskeletal proteins paxillin, cortactin, and ezrin, as well as the SH2 domain-containing protein Shc, and p125FAK. We conclude that ligation of the alpha v beta 3 integrin by soluble ligands promotes enhanced phosphorylation of several proteins implicated in tyrosine kinase signaling and suggest that this pathway may be important in inflammatory states which are accompanied by accumulation of SC5b-9.

HypB protein of Bradyrhizobium japonicum is a metal-binding GTPase capable of binding 18 divalent nickel ions per dimer

Bradyrhizobium japonicum hypB encodes a protein containing an extremely histidine-rich region (24 histidine residues within a 39-amino-acid stretch) and guanine nucleotide-binding domains. The product of the hypB gene was overexpressed in Escherichia coli and purified by Ni(2+)-charged metal chelate affinity chromatography (MCAC) in a single step. In SDS/PAGE, HypB migrated at 38 kDa--slightly larger than the calculated molecular mass (32.8 kDa). Purified HypB has GTPase activity with a kcat of 0.18 min-1 and a Km for GTP of 7 microM, and it has dGTPase activity as well. HypB exists as a dimer of molecular mass 78 kDa in native solution as determined by fast protein liquid chromatography on Superose 12. It binds 9.0 +/- 0.14 divalent nickel ions per monomer (18 Ni2+ per dimer) with a Kd of 2.3 microM; it also binds Zn2+, Cu2+, Co2+, Cd2+, and Mn2+. In-frame deletion of the histidine-rich region (deletion of 38 amino acids including 23 histidine residues) resulted in a truncated HypB that did not bind to the MCAC column, whereas in-frame deletion of 14 amino acids including 8 histidine residues within HypB resulted in a truncated HypB that still bound to the column. The results indicate that the histidine residues within the histidine-rich region of HypB are involved in metal binding.

A study of immunoactivity of retinal S-antigen in retinoblastoma

PURPOSES

To study retinal S-antigen expression in human retinoblastoma and assess if there is a correlation between S-antigen immunoactivity and degree of retinoblastoma cell differentiations.

METHODS

Ten cases of Chinese retinoblastoma parafin-embedded tissues were applied for this study. A strain of monoclonal antibody,MabA9C6, which defines an epitope in S-antigen retained in fixed-tissue sections, was used to study S-antigen expression in 10 cases of retinoblastomas. S-antigen was localized by the biotinavidin indirect immunoperoxidase technique and purified MabA9C6 ascites fluid was used with 1:100 dilution. The whole procedure could be finished within a few hours.

RESULTS

The S-antigen immunoactivity was observed in different patterns: the "normal" photoreceptor elements incorporated in 3 cases of growing tumors; 3 of 4 Fleurettes and E-W rosettes; and scattered tumor cells in 50% of the cases.

CONCLUSIONS

The result suggests that the expression of S-antigen in retinoblastoma may be used to assess the degree of tumor differentiation as another tumor marker in retinoblastoma.

Structure and function of the mouse insulin-like growth factor binding protein 5 gene promoter

The actions of insulin-like growth factors I and II (IGF-I and -II) are modulated by interactions with one or more of a family of secreted IGF binding proteins (IGFBPs). IGFBP-5, the most conserved of the six known IGFBPs, is a 252-amino-acid protein that has been shown both to potentiate and inhibit IGF action. In previous studies, we have cloned and characterized the mouse IGFBP-5 gene and demonstrated that it is expressed in a hierarchical pattern in different adult mouse tissues and during rodent embryonic development. In this report, we describe the initial analysis of the IGFBP-5 gene promoter. By transient gene transfer studies, we show the orientation-specific activity of DNA fragments containing from 31 to 4,100 bp from the 5'-flanking region of the mouse IGFBP-5 gene in directing expression of the heterologous reporter gene luciferase in Hep G2 cells. DNA fragments with only 156 bp of 5'-flanking sequence mediated over 60% of maximal promoter activity, and a segment containing the TATA box and the first 120 bp of exon 1 still conferred some promoter function. Within the highly active 156-bp region, we identified a 37-bp segment from -70 to -34 that exhibited specific binding in DNase I footprinting and gel-mobility shift experiments with Hep G2 nuclear protein extracts. The footprinted region, which is almost completely conserved in the rat and human IGFBP-5 genes, was responsible for at least 70% of the activity of the intact promoter, as evidenced by the deleterious consequences of small internal deletions within this sequence on promoter function.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequences and characterization of hupU and hupV genes of Bradyrhizobium japonicum encoding a possible nickel-sensing complex involved in hydrogenase expression

A 2.7-kb DNA fragment of Bradyrhizobium japonicum previously shown to be involved in hydrogenase expression has been sequenced. The area is located just upstream of the hupSLCDF operon and was found to contain two open reading frames, designated hupU and hupV; these encode proteins of 35.4 and 51.8 kDa, respectively. These proteins are homologous to Rhodobacter capsulatus HupU, a possible repressor of hydrogenase expression in that organism. B. japonicum HupU is 54% identical to the N terminus of R. capsulatus HupU, and HupV is 50% identical to the C terminus of R. capsulatus HupU. HupU and HupV also show homology to the [Ni-Fe] hydrogenase small and large subunits, respectively. Notably, HupV contains the probable nickel-binding sites RxCGxC and DPCxxCxxH, which are located in the N- and C-terminal portions, respectively, of the large subunit of hydrogenases. Hydrogenase activity assays, immunological assays for hydrogenase subunits, and beta-galactosidase assays on mutant strain JHCS2 (lacking a portion of HupV) were all indicative that HupV is necessary for transcriptional activation of hydrogenase. A physiological role as a possible nickel- or other environmental (i.e., oxygen or hydrogen)-sensing complex is proposed for HupU and HupV.

The FeSII protein of Azotobacter vinelandii is not essential for aerobic nitrogen fixation, but confers significant protection to oxygen-mediated inactivation of nitrogenase in vitro and in vivo

The FeSII protein of Azotobacter vinelandii has been proposed to mediate the 'conformational protection' of the molybdenum-dependent nitrogenase components against oxygen inactivation. We have cloned and characterized the structural gene for the FeSII protein (the fesII locus). Hybridization studies did not reveal the presence of fesII-like genes in a number of diverse species of well-studied nitrogen-fixing bacteria, with the exception of Azotobacter chroococcum. The fesII locus is transcriptionally expressed during both nitrogen fixing and non-nitrogen fixing conditions, although the level of its message is upregulated by approximately 2.5-fold during nitrogen fixation. The promoter region was identified by primer extension analysis, and is similar to other sigma 70-type promoters. Mutants devoid of the FeSII protein were constructed. These mutants possessed growth characteristics on a variety of carbon substrates during non-diazotrophic as well as diazotrophic growth that were essentially indistinguishable from the wild-type strain. Nevertheless, the nitrogenase activity in cell-free extracts is significantly more sensitive to irreversible oxygen inactivation in the mutants as compared with the wild type. When treated with 250 mM NaCl (a condition known to dissociate FeSII from nitrogenase components), the wild-type and mutant extracts were equally hypersensitive to oxygen inactivation. Upon energy starvation, conditions in which 'respiratory protection' is inoperable, the MoFe and Fe proteins of nitrogenase are degraded much more rapidly in vivo in the deletion mutants, compared to the wild type. Strains relying on either the vanadium or the 'iron-only' alternative nitrogenases exhibited similar growth rates irrespective of the presence or absence of the FeSII protein, and the in vitro inactivation of the vanadium nitrogenase components was not affected by the lack of the FeSII protein. All in all, these results are consistent with a model whereby 'respiratory protection' is the major physiological mechanism responsible for the protection of all three nitrogenases during energy-supplemented growth. Upon energy starvation, however, 'conformational protection', mediated by the FeSII protein is capable of temporarily protecting the conventional molybdenum nitrogenase components from inactivation and subsequent degradation.

Cloning and sequence of the Xenopus laevis homologue of the midkine cDNA

The Xenopus laevis (Xl) homologue of the midkine-encoding gene (MK) has been isolated and sequenced from a X. laevis cDNA library made from the head region of stage-22 embryo. The nucleotide and deduced amino-acid sequences show a high degree of conservation with the avian and mammalian MK and pleiotrophin (PTN) genes and gene products. Highly conserved domains may indicate important regions for the function of the MK and PTN proteins.

Organization of the hydrogenase gene cluster from Bradyrhizobium japonicum: sequences and analysis of five more hydrogenase-related genes

Previously, the deletion of a 2.9-kb chromosomal EcoRI fragment of DNA located 2.2 kb downstream from the end of the Bradyrhizobium japonicum hydrogenase structural genes caused lack of normal-sized hydrogenase (Hup) subunits and complete loss of Hup activity. It was suggested that this region encodes one or more genes required for Hup processing. Sequencing of a 3322-bp XcmI fragment of DNA covering this 2.9-kb EcoRI fragment within the hup gene cluster revealed the presence of five open reading frames (ORFs) designated hupG, hupH, hupI, hupJ and hupK, encoding polypeptides with calculated molecular masses of 15.8, 30.7, 7.6, 18.1 and 38 kDa, respectively. Based on deduced amino acid (aa) sequences, all five products of the hupGHIJK genes showed significant homology with other genes' products in several H2-utilizing bacteria. Of particular interest are HupG and HupI. HupG showed 70% similarity (28% identity) to the HyaE of the Escherichia coli hydrogenase-1 operon which was demonstrated to be involved in the processing of hydrogenase-1. HupI showed strong identity to rubredoxin and rubredoxin-like proteins from many other bacteria. The latter proteins contain two 'C-X-X-C' motifs, which may serve as iron ligands for non-heme iron proteins involved as intermediate electron carriers or in the assembly process for Fe-S (or NiFe-S) clusters.

An experimental model for study of Candida survival and transmission in human volunteers

In order to determine the potential for cross-transmission of Candida spp. between health-care workers and patients, the survival of clinical isolates of five species of Candida on the palms of human volunteers was tested. One hundred microliters of a McFarland 1.0 density suspension (5 x 10(5) cfu) from an overnight culture of Candida albicans, Candida krusei, Candida parapsilosis, Candida tropicalis and Candida glabrata was used as inoculum. The degree of hydrophobicity of the different Candida species was also tested and did not influence the survival. The half-lives were brief, being 9.5, 12.4, 7.4, 12.8, 9.6 min for Candida albicans, Candida krusei, Candida glabrata, Candida parapsilosis, and Candida tropicalis, respectively, but at 45 min 2.6 x 10(3) to 3 x 10(4) organisms remained on the hands. Survival of Candida albicans for as long as 24 h on inanimate surfaces was observed. Transmission from one hand to a second hand occurred in 69% of the experiments and from the first to a third hand in 38%. Transmission to and from inanimate surfaces was successful in most of the experiments (90%). This experimental model aids in the biological study of Candida spp. and suggests some of the potential mechanisms of transmission.

The immunocytochemical demonstration of a relative lack of nerve fibres in the atrioventricular node and bundle of His in the sudden infant death syndrome (SIDS)

Whilst examining the variation with age of the nerve fibre content of the cardiac conduction system (CCS), using an immunocytochemical approach, it became evident that in two sudden infant death syndrome (SIDS) cases there was a selective lack of S100 positive nerve fibres in the atrioventricular (AV) node and His bundle. In the present study therefore, the examination of CCS with S100 was extended to a further five SIDS cases and three cases of sudden explained death. Also, in addition to S100--which selectively marks Schwann cells associated with both myelinated and non-myelinated nerves--PGP 9.5 (protein gene product) was used to reveal the presence of nerve axonal elements associated with the CCS. The results showed a uniform presence of S100 and PGP 9.5 positive nerve fibres in the sinoatrial (SA) node, the AV node and His bundle tissue of all three control cases. In contrast, five out of seven SIDS cases showed a uniform lack of staining with these markers in the AV node and His bundle tissue, whilst in the two remaining cases it was present in greatly diminished amounts. Staining in the SA node, although present in all seven cases, was reduced when compared with the control cases. This is the first time the CCS of SIDS cases has been studied with immunocytochemical markers of nerve elements. The overall results taken in conjunction with the epidemiology of SIDS suggest that the lack of AV node and His bundle innervation most probably reflects a delay in the development or maturation of the nerve elements of the CCS, similar to that noted for other parts of the central and peripheral nervous systems in SIDS.

Bacterial genes involved in incorporation of nickel into a hydrogenase enzyme

Nickel is an essential component of all H2-uptake hydrogenases. A fragment of DNA that complements a H2-uptake-deficient but nickel-cured mutant strain (JHK7) of Bradyrhizobium japonicum was isolated and sequenced. This 4.5-kb DNA fragment contains four open reading frames designated as ORF1, hupN, hupO, and hupP, which encode polypeptides with predicted masses of 17, 40, 19, and 63.5 kDa, respectively. The last three open reading frames (hupNOP) are most likely organized as an operon with a putative sigma 54-type promoter. Based on its hydropathy profile, HupN is predicted to be a transmembrane protein. It has 56% identity to the previously described HoxN (high-affinity nickel transport protein) of Alcaligenes eutrophus. A subclone (pJF23) containing the hupNOP genes excluding ORF1 completely complemented (in trans) strain JHK7 for hydrogenase activity in low nickel conditions. pJF26 containing only a functional hupN complemented the hydrogenase activity of mutant strain JHK7 to 30-55% of the wild-type level. Mutant strain JHK70, with a chromosomal deletion in hupP but with an intact hupNO, showed greater activities than pJF26-complemented JHK7 but still had lower activities than the wild type at all nickel levels tested. pJF25, containing the entire hupO and hupP, but without hupN (a portion of hupN was deleted), did not complement hydrogenase activity of mutant strain JHK7. The results suggest that the products of the hupNOP operon are all involved in nickel incorporation/metabolism into the hydrogenase apoprotein. Based on (previous) nickel transport studies of strain JHK7, the hupNOP genes appear not to be involved in nickel transport by whole cells. The deleterious effects on hydrogenase expression are most pronounced by lack of the HupN product.

Sequence and characterization of three genes within the hydrogenase gene cluster of Bradyrhizobium japonicum

A 2.0-kb DNA fragment downstream from the hydrogenase-encoding structural genes within the hydrogenase gene cluster of Bradyrhizobium japonicum was sequenced. Analysis of the nucleotide (nt) sequence revealed three open reading frames (ORFs), designated hupC, hupD and hupF, which encode polypeptides of 28, 21 and 10.7 kDa, respectively. Based on analysis of the nt sequence and physiological studies, hupSL (hydrogenase structural genes) and hupCDF are organized as a single transcriptional unit. Plasmid pRY12 carrying hupSL genes did not complement (restore) hydrogenase activity of the hupSL deletion mutant strain (JHCS2), whereas the activity of the mutant was considerably restored by pLD22 harboring the entire hydrogenase operon (hupSLCDF genes). Western blots revealed a very low level of hydrogenase protein in JHCS2 containing pRY12. The results suggest that the products of the hupCDF genes may be involved in either stabilizing the hydrogenase peptides (i.e., from degradation) or in post-translational regulation of hydrogenase production. The products of hupC and hupD were successfully expressed in Escherichia coli by a phage T7 promoter system, although the apparent sizes of the gene products were slightly larger than those calculated from the deduced amino-acid sequences.

Omeprazole potentiates atracurium and succinylcholine paralysis in vivo in rats

We examined the effect of proton pump inhibitor omeprazole on neuromuscular paralysis induced with either nondepolarizing or depolarizing neuromuscular blocking drugs in anesthetized and mechanically ventilated rats. Neuromuscular paralysis, as judged by tibialis anterior muscle twitch tension in response to sciatic nerve stimulation, was maintained at about 50% with intravenous (i.v.) bolus and infusion regimens of either atracurium or succinylcholine. Omeprazole, 0.5, 1, and 10 mg/kg i.v., was then administered at 10-min intervals while the infusion of the neuromuscular blocker was continued. Omeprazole at all three doses increased the steady-state neuromuscular paralysis produced with either atracurium (pre-omeprazole versus final post-omeprazole paralysis; mean +/- SE, n = 6, 53.0% +/- 2.3% vs 80.0% +/- 5.3%) or succinylcholine (50.8% +/- 1.5% vs 86.4% +/- 5.1%). Omeprazole, 0.5, 1.0, and 10 mg/kg i.v., given directly and without any neuromuscular blocker, produced approximately 5% depression of the muscle twitch response. Omeprazole, i.v. at human therapeutic doses, alters neuromuscular function and enhances the action of both atracurium and succinylcholine in vivo in rats.

Nucleotide sequences of two hydrogenase-related genes (hypA and hypB) from Bradyrhizobium japonicum, one of which (hypB) encodes an extremely histidine-rich region and guanine nucleotide-binding domains

Sequencing of a 1359-bp (NruI-AccI) DNA fragment located approximately 5.2 kb downstream from the end of the hydrogenase structural genes of Bradyrhizobium japonicum revealed two open reading frames designated hypA and hypB, encoding polypeptides with predicted molecular masses of 12.3 and 32.8 kDa, respectively. Both hypA and hypB showed strong homology with other genes in hydrogenase-containing bacteria. Two 'C-X-X-C' motifs were contained in the deduced amino acid sequence of hypA, a motif that is present in all known products homologous to HypA. The deduced product of hypB contains an area remarkably rich in histidine residues at the N-terminus (24 histidines within a 39 amino acid stretch). The deduced HypB also contains GTP-binding domains. We postulate that the product of hypB is involved in nickel binding and accumulation, and may utilize energy (GTP) to mobilize nickel for its subsequent incorporation into hydrogenase.

A ribosomal frameshifting error during translation of the argI mRNA of Escherichia coli

Using fusions between the Escherichia coli genes argI and lacZ, it has been demonstrated that ribosomal frameshifting occurs at a frequency of between 3% and 16% within the argI mRNA, soon after the initiation codon. The frameshift involves a phenylalanyl-tRNA shifting into the +1 frame at the sequence UUU-U/C. The shift does not occur if the in-frame phenylalanine codon UUU is replaced by UUC. The level of frameshifting is higher in dense cultures and is not dependent on phenylalanine starvation. In the wild-type argI gene this frameshifting event would be an error, leading to a truncated, non-functional protein. Therefore, it is unlike the numerous examples of required frameshifting events that have been described in other genes.

Activation of a nonselective cation channel by swelling in atrial cells

Cell swelling has been shown to increase the permeability of the plasma membrane to ions such as K+, Na+, Ca2+ or Cl- in many types of cells. In cardiac cells, swelling has been reported to increase Cl- conductance, but whether cation-selective currents are activated by swelling is not known. Low Cl- or Cl(-)-free solutions were used to study the presence of such currents. Lowering the osmolarity of the extracellular medium from 299 to 219 mOsm resulted in cell swelling and concurrent activation of a cation-selective whole-cell current. When cell-attached patches were formed on swollen cells, opening of bursting single channel currents were observed in 18% of the patches studied. Ion substitution experiments indicated that the channel discriminated poorly among monovalent cations, and was impermeable to Cl-. The channel was permeable to Ca2+. In symmetrical 140 mM K+, the current-voltage relation was linear with a single channel conductance of 36 +/- 3 pS. Depolarization increased channel open probability. Interestingly, depending on the membrane patch studied, application of negative pressure to the pipette caused either an increase or a decrease in the open probability of the channel already activated by swelling. Thus, the sensitivity to tension of the swelling-activated channel was different from those of previously reported stretch-activated channels. These findings suggest that nonselective cation channels exist in rat atrial cells and may be involved in swelling-induced changes in cell function.

Monoclonal antibodies for structure-function studies of (R)-3-hydroxybutyrate dehydrogenase, a lipid-dependent membrane-bound enzyme

Monoclonal antibodies (mAbs) have been used to study structure-function relationships of (R)-3-hydroxybutyrate dehydrogenase (BDH) (EC 1.1.1.30), a lipid-requiring mitochondrial membrane enzyme with an absolute and specific requirement for phosphatidylcholine (PC) for enzymic activity. The purified enzyme (apoBDH, devoid of phospholipid and thereby inactive) can be re-activated with preformed phospholipid vesicles containing PC or by short-chain soluble PC. Five of six mAbs cross-react with BDH from bovine heart and rat liver, including two mAbs to conformational epitopes. One mAb was found to be specific for the C-terminal sequence of BDH and served to: (1) map endopeptidase cleavage and epitope sites on BDH; and (2) demonstrate that the C-terminus is essential for the activity of BDH. Carboxypeptidase cleavage of only a few (< or = 14) C-terminal amino acids from apoBDH (as detected by the loss of C-terminal epitope for mAb 3-10A) prevents activation by either bilayer or soluble PC. Further, for BDH in bilayers containing PC, the C-terminus is protected from carboxy-peptidase cleavage, whereas in bilayers devoid of PC the C-terminus is cleaved, and subsequent activation by PC is precluded. We conclude that: (1) the C-terminus of BDH is essential for enzymic activity, consistent with the prediction, from primary sequence analysis, that the PC-binding site is in the C-terminal domain of BDH; and (2) the allosteric activation of BDH by PC in bilayers protects the C-terminus from carboxypeptidase cleavage, indicative of a PC-induced conformational change in the enzyme.

Rapid and efficient selection of recombinant site-directed mutants of Bradyrhizobium japonicum by colony hybridization

Due to the high incidence of spontaneous antibiotic resistance and slow growth of Bradyrhizobium japonicum strains, screening for site-directed mutants is cumbersome and time-consuming. A rapid method for selection of recombinant site-directed mutants of B. japonicum was developed. A kanamycin (Km) and a spectinomycin (Sp) cassette were each used to replace DNA fragments in the chromosome by homologous recombination. The primary new features of this method involve a simple plate selection for the antibiotic (Km or Sp) resistant mutants, then colony streaking, and lysis for DNA hybridization on a nitrocellulose filter enabling direct identification of the recombinant site-directed mutants. This method has permitted us to quickly and easily identify a large number of positive recombinant mutants from a large number of individual colonies. The procedure eliminates the need to first isolate genomic DNA from each mutant for Southern hybridization. All of the tested site-directed mutants from this method were confirmed to exhibit the expected mutant phenotype.