Alginate, inorganic polyphosphate, GTP and ppGpp synthesis co-regulated in Pseudomonas aeruginosa: implications for stationary phase survival and synthesis of RNA/DNA precursors

The regulatory protein AlgR2 in Pseudomonas aeruginosa positively regulates nucleoside diphosphate kinase (Ndk) and succinyl-CoA synthetase, enzymes critical in nucleoside triphosphate (NTP) formation. AlgR2 positively regulates the production of alginate, GTP, ppGpp and inorganic polyphosphate (poly P). An algR2 mutant with low levels of these metabolites has them restored by introducing and overexpressing either the algR2 or the ndk gene into the algR2 mutant. Thus, Ndk is involved in the formation of these compounds and largely prevents the death of the algR2 mutant, which occurs early in the stationary phase. We demonstrate that the 12 kDa Ndk-pyruvate kinase (Pk) complex, previously shown to generate predominantly GTP instead of all the NTPs, has a low affinity for the deoxynucleoside diphosphates and cannot generate the dNTPs needed for DNA replication and cell division; this complex may thus be involved in regulating the levels of both NTPs and dNTPs that modulate cell division and survival in the stationary phase.

[Textual research on herb youba]

A textual research has been conducted to clarify the botanical origin of the herb Youba in ancient medicinal literatures. The name Youba in (Xin Xiu Ben Cao) published in the Tang dynasty and (Ben Cao Gang Mu) published in the Ming dynasty has been confirmed to be the immature tuber of Pinellia pedatisecta (without branches around the tuber), whereas the same name Youba in (Zhi Wu Ming Shi Tu Kao) published in the Qing dynasty refers to Arisaema yunnanense.

Genetic analysis of chloroplast c-type cytochrome assembly in Chlamydomonas reinhardtii: One chloroplast locus and at least four nuclear loci are required for heme attachment

Chloroplasts contain up to two c-type cytochromes, membrane-anchored cytochrome f and soluble cytochrome c6. To elucidate the post-translational events required for their assembly, acetate-requiring mutants of Chlamydomonas reinhardtii that have combined deficiencies in both plastid-encoded cytochrome f and nucleus-encoded cytochrome c6 have been identified and analyzed. For strains ct34 and ct59, where the phenotype displays uniparental inheritance, the mutations were localized to the chloroplast ccsA gene, which was shown previously to be required for heme attachment to chloroplast apocytochromes. The mutations in another eight strains were localized to the nuclear genome. Complementation tests of these strains plus three previously identified strains of the same phenotype (ac206, F18, and F2D8) indicate that the 11 ccs strains define four nuclear loci, CCS1-CCS4. We conclude that the products of the CCS1-CCS4 loci are not required for translocation or processing of the preproteins but, like CcsA, they are required for the heme attachment step during assembly of both holocytochrome f and holocytochrome c6. The ccsA gene is transcribed in each of the nuclear mutants, but its protein product is absent in ccs1 mutants, and it appears to be degradation susceptible in ccs3 and ccs4 strains. We suggest that Ccsl may be associated with CcsA in a multisubunit "holocytochrome c assembly complex," and we hypothesize that the products of the other CCS loci may correspond to other subunits.

Drosophila factor 2, an RNA polymerase II transcript release factor, has DNA-dependent ATPase activity

Drosophila factor 2 has been identified as a component of negative transcription elongation factor (N-TEF) that causes the release of RNA polymerase II transcripts in an ATP-dependent manner (Xie, Z. and Price D. H. (1996) J. Biol. Chem. 271, 11043-11046). We show here that the transcript release activity of factor 2 requires ATP or dATP and that adenosine 5'-O-(thiotriphosphate) (ATPgammaS), adenosine 5'-(beta,gamma-imino)triphosphate (AMP-PNP), or other NTPs do not support the activity. Factor 2 demonstrated a strong DNA-dependent ATPase activity that correlated with its transcript release activity. At 20 microg/ml DNA, the ATPase activity of factor 2 had an apparent Km(ATP) of 28 microM and an estimated Kcat of 140 min-1. Factor 2 caused the release of nascent transcripts associated with elongation complexes generated by RNA polymerase II on a dC-tailed template. Therefore, no other protein cofactors are required for the transcript release activity of factor 2. Using the dC-tailed template assay, it was found that renaturation of the template was required for factor 2 function.

[Purification and properties of inulinase from Kluyveromyces sp. Y-85]

The crude endocellular inulinase from Kluyveromyces sp. Y-85 was purified to two components, designated as EI and EII, using PEG6000-phosphate buffer extraction, (NH4)2SO4 fractionation, DEAE chromatography and gel filtration (Protein-PAK); The crude exocellular inulinase from this strain was purified to Eexo by means of PEG6000-phosphate buffer extraction, double DEAE-Sephace chromatography, Sephadex G-150 gel filtration. EI, EII and Eexo were demonstrated to be homogeneous by Waters 650E protein purification system. Their molecular weights are 42 kD, 65 kD and 57 kD, respectively. All the inulinases were glycoproteins containing a saccharide (from 25% to 35%) and belonged to the endo-inulinase. In addition, EI, EII, Eexo were optimally reactive at pH4.6, 4.5, 4.6 and at 52 degrees C, 52 degrees C, 55 degrees C, respectively. Ag+, Hg2+ and PCMB inhibited these enzymes' activity strongly. The products of raw inulin extracted from Helianthus tuberosus hydrolyzed by these three enzymes were fructose (86.5%) and glycose (13.5%).

Effects of transient coronary occlusion on the capillary network in the left ventricle of rat

The objective was to examine the changes in the capillary network in the left ventricle of rats subjected to transient occlusion of the left coronary artery followed by reperfusion (I-R). Eighteen Wistar rats were divided into three groups and all rats were anaesthetized with ethyl ether and artificially ventilated. The I-R 1 rats were subjected to a 3 min occlusion followed by reperfusion; the I-R 3 rats had three 3 min occlusions separated by 3 min of reperfusion; the Sham-operated rats underwent surgery but the coronary artery was not occluded. The thorax was closed at the end of the procedures and the rats were sacrificed for isolation of the hearts 30 d after treatment. Frozen sections of the left ventricles were cut and differential staining was used to classify the capillary portions. Five additional rats treated as the I-R 1 group were sacrificed at 120 min after reperfusion. Their left ventricles were used for immunohistochemical investigation of the early expression of bFGF and VEGF. By comparison with the Sham-operated rats, both I-R groups showed increases in the capillary density of total and venular capillary portions, an increased capillary : myocyte (C : M) ratio and a decrease in the capillary domain area in the three capillary portions. The changes in the I-R 1 group were significantly greater than those in the I-R 3 group, suggesting that the frequent experience of ischemic attack reduces the capacity of angiogenesis. In the rats sacrificed 120 min after the start of reperfusion, bFGF and VEGF were expressed on capillaries and in some myocytes. Punctate bFGF or VEGF staining was observed even 30 d after the transient ischemia. One 3 min occlusion of the left coronary artery followed by reperfusion produced changes in capillarity that would increase the oxygen supply to ventricular tissues. These effects may be attributed to the bFGF and VEGF expressed around capillaries. Repeated occlusions interspersed with a short period of reperfusion reduced the advantageous effects on capillarity.

[Study of estrogen receptors in hepatocellular carcinoma and its response to anti-estrogen therapy]

OBJECTIVE

To study the usefulness of anti-estrogen therapy for moderately and advanced hepatocellular carcinoma (HCC).

METHODS

Estrogen receptors (ER) were examined in 51 cases of HCC by immunohistochemical staining of needle aspiration biopsy HCC specimens. The cases studied were randomly divided into two groups: the control group (N = 25) and the anti-estrogen treated group (N = 26). Patients in the control group were given matelin and immune RNA while those in the anti-estrogen treated group were given Tamoxifen in addition. A 50% reduction of serum AFP level and a 50% decrease in tumor size were considered therapeutically effective.

RESULTS

In the control group, the response rate as judged by AFP level (RR-AFP) and by tumor size (RR-TS) in the ER+ patients was 42.9% (3 of 7 cases) and 14.3% (1 of 7 cases), respectively, while the 2 RRs in the ER- patients were lower but the difference was statistically insignificant. In contrast, in the Tamoxifen-treated group, RR-AFP was 83.3% (5 of 6 cases) and RR-TS was 50.0% (3 of 6 cases). The difference in RRs of ER+ patients in the 2 groups was statistically significant. No complete remission was observed.

CONCLUSION

Endocrinotherapy may be of value in the treatment of ER+ HCC.

Differential regulation of Na/K-ATPase alpha-subunit isoform gene expressions in cardiac myocytes by ouabain and other hypertrophic stimuli

We showed before that partial inhibition of Na/K-ATPase by non-toxic concentrations of ouabain caused hypertrophic growth of neonatal rat cardiac myocytes, and induced several early- and late-response genes that are markers of cardiac hypertrophy. The aim of this study was to determine if the genes of the alpha-subunit isoforms of Na/K-ATPase were among those regulated by ouabain; and if so, to begin the characterization of the pathways regulating these genes. When neonatal myocytes, expressing alpha1- and alpha3-isoform messages, were exposed to 5-100 micro M ouabain, alpha1 mRNA was not affected, but alpha3 mRNA was decreased in a dose- and time-dependent manner. Ouabain-induced down-regulation of alpha3 mRNA was accompanied by a decrease in alpha3-protein content in these myocytes. There was a significant correlation between ouabain effects on alpha3-repression and skeletal alpha-actin induction; also, ouabain's transcriptional effects on both genes were antagonised by retinoic acid. These findings suggested the association of alpha3 repression with ouabain-induced hypertrophy. Phenylephrine and a phorbol ester, two hypertrophic stimuli that do not inhibit Na/K-ATPase, also down-regulated alpha3 mRNA without affecting alpha1 mRNA, suggesting that alpha3-repression is a common feature of the hypertrophic phenotype in these myocytes. Ouabain-induced repression of alpha3 required the influx of extracellular Ca2+, and was antagonized by inhibitors of protein kinase C, Ca2+-calmodulin kinase, and mitogen-activated protein kinase but not by inhibition of protein kinase A. These data, and prior findings on the mechanisms of hypertrophic effects of phenylephrine and phorbol esters, suggest that transcriptional repression of alpha3 by ouabain and other hypertrophic stimuli involves a common step regulated by a mitogen-activated protein kinase.

Effects of the beta 2-adrenergic agonist clenbuterol on capillary geometry in cardiac and skeletal muscles in young and middle-aged rats

The effects of 10 day clenbuterol administration on cardiac and skeletal muscle capillarities were studied, particularly in terms of the distribution of arteriolar and venular capillaries and their capillary density, in young (10-week-old) and middle-aged (37-week-old) male Wistar rats. Rats of the treated groups were fed a diet containing 2 mg kg-1 clenbuterol hydrochloride. In both young and middle aged rats, clenbuterol treatment increased the body wt and the weights of the heart and hindlimb muscles. The mean fibre cross-sectional area was significantly increased after the treatment in the left ventricle, soleus, plantaris and both deep and superficial portions of gastrocnemius (P < 0.01). In the left ventricle, the total capillary density and the density of venular capillaries were decreased after the treatment in both young (9 and 13%, respectively) and middle-aged rats (10 and 11%, respectively). A decrease in total capillary density was also observed in all skeletal muscles examined. In both young and middle-aged rats, the capillary-to-fibre (C:F) ratio and the proportion of each capillary did not change after the treatment in both the left ventricle and skeletal muscles. Clenbuterol significantly decreased the activity of succinate dehydrogenase in all skeletal muscles examined (P < 0.01). These results suggest that clenbuterol increased the diffusion distance for oxygen in the left ventricle and skeletal muscles. These changes may reduce the oxygen supply to tissues and increase muscle fatigability.

[Effect of hypoxia on maximal myocardial blood flow in right ventricle]

In order to study the changes of coronary reserve capacity, the effects of hypoxia on hemodynamics and maximal myocardial blood flow in right ventricle were observed. Rats wre divided into 3 groups:normoxic group (control), acute hypoxic group and chronic hypoxic group. Maxmimal myocardial blood flow in the right ventricle was measured with 99 m Tc radiolabelled from RBC during adenosine infusion. The results showed that cardiac output, PaO2 and oxygen delivery were decreased during acute hypoxia, but myocardial blood flow in right ventricle was increased, as compared with the control group. There were no significant change of maximal myocardial blood flow in the right ventricle in acute hypoxic rats. Hematocrit and blood viscosity at different shear rate and RV weight index were augmented, whereas oxygen delivery and myocardial blood flow became normal during chronic hypoxia. Maximal blood flow in RV was significantly decreased whereas arterial wall thickness and collagen in arterial adventitia were increased in chronic hypoxic rats. The above results suggest that the decreased coronary reserve might beresulted from the increasedblood viscosity, arterial wall thickness and collagen in arterial adventitia and right ventricular hypertrophy.

[The development of an computerized analysis system for the women pelvic cavity impedance rheogram]

This article introduces the components and functions of an computered analysis system for the women pelvic cavity impedance rheogram. It can sample the pelvic cavity impedance rheogram signal of the body double-side and the reference ECG signal. With help of manual intervence, it also can automatically recognize characteristic points of the pelvic cavity impedance rheogram and measure the parameters. It can correct the recognized characteristic points simultaneously and print the pelvic cavity impedance rheogram of the body double-side and 15 characteristic data parameters. After clinical applying, the analysis results of mors 100 patients make clear that: this system has remarkably clinical significance for diagnosis of the women pelvic cavity extravasated blood and evaluation of treating effect, so it has much better clinical applied expectation.

Cyclic AMP-independent activation of neutrophil-like HL-60 cells by prostaglandin E2

The role of cAMP in mediating prostaglandin E2 (PGE2)-stimulated aggregation of neutrophil-like HL-60 cells has been investigated. Although the EP2 receptors appear to couple to Gs-proteins, PGE2 stimulated HL-60 cell aggregation appears to be a cAMP-independent process. This response to PGE2 in independent of calcium and tyrosine kinase activity, appears to involve activation of phosphatidylinositol 3-kinase which is negatively regulated by phosphatidic acid generated from phospholipase D activity, and is partially dependent on protein kinase C activity. In contrast, although the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) produces a similar aggregation response to PGE2, FMLP uses a distinct intracellular signalling pathway. The aggregation response to FMLP involves activation of Gi-proteins, is partially dependent on extracellular calcium, is negatively regulated by protein kinase C, and is independent of phosphatidylinositol 3-kinase, phospholipase D and tyrosine kinase activity. The possibility exists that EP2 receptor activation leads to Gs-dependent, but cAMP-independent, stimulation of phosphatidylinositol 3-kinase activity in HL-60 cells.

Association between IgE antibody against soluble egg antigen and resistance to reinfection with Schistosoma japonicum

There is evidence that immunoglobulin (Ig) E antibody may be a critical component of protective immunity against Schistosoma mansoni and S. haematobium reinfection. In the present study, 555 individuals aged 3-67 years infected with S.japonicum received praziquantel treatment before the transmission season commenced; 45 d later, blood samples from 265 individuals who had no S. japonicum egg in their stool were examined by enzyme-linked immunosorbent assay for specific isotypic antibodies. Single, non-conditional logistic regression analysis showed that exposure intensity, age, soluble egg antigen (SEA)-IgE, SEA-IgM and soluble adult worm antigen-IgG4 were relevant to reinfection; multiple, non-conditional logistic regression analysis showed that exposure intensity was still a significant factor for reinfection while the SEA-IgE antibody level was associated with resistance to reinfection with S. japonicum, with a protective index of 2.00. It is suggested that this population in an area endemic for schistosomiasis japonica exhibits acquired immunity.

Enzymatic properties of human Na,K-ATPase alpha1beta3 isozyme

Recent results of a wide-scale human cDNA sequencing project have identified a cDNA which encodes a hitherto unknown human protein sequence exhibiting structural similarities with beta-subunits of the Na,K- and H,K-ATPase family and with the amphibian Na,KATPase beta3-subunit, in particular. In this study the ability of the putative human beta3-subunit to assemble with the human alpha1-subunit in functionally active Na,KATPase was examined using the baculovirus expression system. The recombinant baculovirus simultaneously expressing both alpha1 and beta3 human proteins was produced using the dual-promoter transfer vector p2Bac. The expression of both human proteins in baculovirus-infected Sf-9 cell membranes detected with specific antibodies resulted in the formation of a catalytically competent alpha1beta3 ATPase complex. Characterization of the recombinant ATPase complex involved the analysis of Na+, K+, and ATP dependencies of enzyme activity and its sensitivity toward ouabain. Preparations of HeLa cell membranes containing alpha1beta1 isozyme of human Na,K-ATPase were used as control. The data obtained clearly demonstrated that alpha1beta3 ATPase exhibits enzymatic properties which are characteristic of Na, K-ATPase. The recombinant alpha1beta3 isozyme displayed significantly lower sensitivity to ouabain than native alpha1beta1. These findings indicate that the hitherto unknown alpha1beta3 isozyme of human Na,K-ATPase is likely to exist in vivo, thus suggesting further expansion of human Na,K-ATPase isozyme diversity. The present studies are the first in which heterologous expression has been used for the characterization of an isozyme of human Na, K-ATPase.

BAG-1 modulates the chaperone activity of Hsp70/Hsc70

The 70 kDa heat shock family of molecular chaperones is essential to a variety of cellular processes, yet it is unclear how these proteins are regulated in vivo. We present evidence that the protein BAG-1 is a potential modulator of the molecular chaperones, Hsp70 and Hsc70. BAG-1 binds to the ATPase domain of Hsp70 and Hsc70, without requirement for their carboxy-terminal peptide-binding domain, and can be co-immunoprecipitated with Hsp/Hsc70 from cell lysates. Purified BAG-1 and Hsp/Hsc70 efficiently form heteromeric complexes in vitro. BAG-1 inhibits Hsp/Hsc70-mediated in vitro refolding of an unfolded protein substrate, whereas BAG-1 mutants that fail to bind Hsp/Hsc70 do not affect chaperone activity. The binding of BAG-1 to one of its known cellular targets, Bcl-2, in cell lysates was found to be dependent on ATP, consistent with the possible involvement of Hsp/Hsc70 in complex formation. Overexpression of BAG-1 also protected certain cell lines from heat shock-induced cell death. The identification of Hsp/Hsc70 as a partner protein for BAG-1 may explain the diverse interactions observed between BAG-1 and several other proteins, including Raf-1, steroid hormone receptors and certain tyrosine kinase growth factor receptors. The inhibitory effects of BAG-1 on Hsp/Hsc70 chaperone activity suggest that BAG-1 represents a novel type of chaperone regulatory proteins and thus suggest a link between cell signaling, cell death and the stress response.

[Histological study on the using of autogenous costal perichondrium graft to repair the cartilage of condylar process of mandible]

In order to observe the histological changes of the autogenous perichondrium graft from rib in the repair of injured articular cartilage of the condylar process of mandible, 50 rabbits were used, in which 15 were served as control. The articular cartilage with its subchondral bone were resected and an autogenous graft of costal perichondrium was sutured onto the raw surface of the condylar process, and in the controls, only the articular portion of the condylar process was resected without the application of autogenous costal perichondrium graft. The morphological changes of the newly formed cartilage during the process of its development were investigated by hiostological and autoradiog aphic techniques. The result revealed that 10 days after operation, the graft had increased in thickness and was richly populated form the proliferation of mesenchyme-like cells. Twenty to thirty days later, the chondrocytes were matured and the newly formed cartilage had covered the bony surface of mandibular condyle. At 60 days, the newly formed cartilagenous joint surface became glossy, and the morphology and arrangement of cells tended to be regular simulating the morphology of normal articular cartilage. From the experiment, it could be concluded that (1) The autogenous perichondrium graft placed on the condylar surface of mandible could form new articular cartilage which was similar in tissue morphology to the normal condylar cartilage. (2) The process of development of newly formed cartilage was similar to that of the normal cartilage. (3) The motion and loading on the joint could promote the formation of new cartilage and undergo biological reformation, gradually resulting in normal joint morphology. On this basis, the clinical application of autogenous perichondrium graft to repair injured cartilage of the condylar process of the mandible was feasible.

Amplification of avian reovirus RNA using the reverse transcriptase-polymerase chain reaction

A reverse transcriptase-polymerase chain reaction method was developed for the detection of avian reovirus. The origin of primers was from the S1 gene of the avian reovirus genome. A reovirus-specific 532-base pair cDNA product was amplified by these primers from six reference strains and 23 field isolates of avian reoviruses, but not from seven different avian pathogenic viruses and bacteria. As little as 1 pg of avian reovirus RNA was detected using gel electrophoresis and Southern blot hybridization.

[Identification of herba hedyotis diffusae and its confused material Herba Hedyotis pinifoliae]

This article has reported the results of the study on the outer properties, inter organization and TLC of Herba Hedyotis Diffuse and its confused material Herba Hedyotis Pinifoliae. The results show the two have obvious distinction and can not be confusediy used.

Remodeling of capillary network in left ventricular subendocardial tissues induced by intravenous vasopressin administration

OBJECTIVE

The question of whether the coronary vasospasm induced by intravenous administration of vasopressin produces any remodeling of the capillary network in the left ventricle was investigated. To this end, cardiac tissues obtained from vasopressin-injected rats were stained to allow capillary counting and for basic fibroblast growth factor (bFGF).

METHODS

Nine male Donryu rats were divided into three groups that received, respectively, 0.25 ml of saline containing 0, 0.5, or 1.0 U/kg vasopressin injected into the tail vein once daily for 4 days. Rats were killed 30 days after the last injection. Two additional rats each received a single intravenous injection of 1.0 U/kg vasopressin and were killed 24 hours later. The left ventricles were removed and 16- or 10-micron frozen sections were cut for differential staining and distribution of bFGF, respectively. Differential staining was used to classify the capillary portions, and bFGF was identified by immunohistological staining.

RESULTS

Compared with the control group, total capillary density was increased in both vasopressin-treated groups, capillary to myocyte ratio was increased, and the capillary domain areas decreased in the three capillary portions. Arteriolar and intermediate capillary portions increased, while the venular capillary portion decreased. In rats killed 24 hours after vasopressin injection, a considerable amount of bFGF could be demonstrated immunohistochemically in the ventricular tissues, and the punctate distribution of bFGF was still found in rats killed 30 days after treatment.

CONCLUSIONS

A remodeling of capillary network which would increase the oxygen transport capacity to cardiac tissues was produced in left ventricular tissues by intravenous injection of vasopressin. bFGF located around capillaries and in the interstitial space may have been involved in the capillary remodeling.

Isotypic antibody responses of a population in an endemic area of schistosomiasis japonica and their epidemiologic significance

The present study was designed to explore if there exists a correlation between predominant isotype-defined antibody levels and reinfection in low age groups of the population in an endemic area of schistosomiasis japonica in China. One hundred and thirty-eight individuals aged 3-25 years old were selected for serological investigations including the levels of IgG, IgG4, IgM and IgE, detected by ELISA with soluble egg antigen and soluble adult worm antigen. Results show that age is a determinant for SEA-specific IgG, IgG4, and IgE, and SWA-specific IgG and IgG4 antibody levels, which increased with age, and that SEA- and SWA- specific IgG4 antibody levels are risk factors of reinfection, ie, the risk of reinfection occurrence of the population with high level of SEA or SWA-specific IgG4 is 2.83 or 2.40 times, respectively, that with low level of SEA or SWA-specific IgG4, suggesting that in the endemic area of schistosomiasis japonica, there exists a possibility that in the population aged 3-25 years, SEA and SWA-specific IgG4 antibodies mediate a blocking immunity response.

A clinical study on the effect of reinforcement of kidney on senile brain functions

In this study, Wu Zi Yan Zong ([symbol: see text] WZYZ) fluid was used as the main recipe for reinforcement of the kidney. Six weeks after the therapy, the abilities of instantaneous memory and the memory of the segments of logical story were elevated, the time of upright standing with one leg and closure of the eye was prolonged, and the hand tremor and degree of kidney deficiency were improved, but the memory width (memory in sequence and in reverse sequence of a figure) showed no significant difference in comparison with that before treatment.

Channel formation by antiapoptotic protein Bcl-2

Bcl-2 is the prototypical member of a large family of apoptosis-regulating proteins, consisting of blockers and promoters of cell death. The three-dimensional structure of a Bcl-2 homologue, Bcl-XL, suggests striking similarity to the pore-forming domains of diphtheria toxin and the bacterial colicins, prompting exploration of whether Bcl-2 is capable of forming pores in lipid membranes. Using chloride efflux from KCl-loaded unilamellar lipid vesicles as an assay, purified recombinant Bcl-2 protein exhibited pore-forming activity with properties similar to those of the bacterial toxins, diphtheria toxin, and colicins, i.e., dependence on low pH and acidic lipid membranes. In contrast, a mutant of Bcl-2 lacking the two core hydrophobic alpha-helices (helices 5 and 6), predicted to be required for membrane insertion and channel formation, produced only nonspecific effects. In planar lipid bilayers, where detection of single channels is possible, Bcl-2 formed discrete ion-conducting, cation-selective channels, whereas the Bcl-2 (Deltah5, 6) mutant did not. The most frequent conductance observed (18 +/- 2 pS in 0.5 M KCl at pH 7.4) is consistent with a four-helix bundle structure arising from Bcl-2 dimers. However, larger channel conductances (41 +/- 2 pS and 90 +/- 10 pS) also were detected with progressively lower occurrence, implying the step-wise formation of larger oligomers of Bcl-2 in membranes. These findings thus provide biophysical evidence that Bcl-2 forms channels in lipid membranes, suggesting a novel function for this antiapoptotic protein.

[Blocking effects of dimethoate on acetylcholine receptor channels]

The patch-clamp technique was used to study the inhibitory effect of dimethoate, an organophosphrous pesticide, on the membrane of embryoinc Xenopus musle cells in culture. Using whole-cell clamp and cell-attached clamp, we found that the direct inhibitory effects of dimethoate was evidenced on both miniature end-plate currents (MEPC) and single channel currents. Dimethoate increased the amplitude and frequency of MEPC at a lower concentration (21.6 mumol/L) while both decreased at a higher concentration (237 mumol/L). The dimethoate at a concentration of 146 mumol/L shortened the opening time and decreased the opening probability of the single channel. The results show that dimethoate is an AChR channel blocker.

Augmentation of ouabain sensitivity of rat liver Na/K-ATPase by in vivo adenovirus-mediated expression of the Na/K-ATPase alpha2 subunit

These are the first experiments to study the effect of in vivo expression of the Na/K-ATPase alpha2 subunit which serves as a receptor for cardiac glycosides. The alpha2 subunit is not normally expressed in rat liver, so hepatocytes which lack endogenous alpha2 protein are a logical first target to study the effects of alpha2 expression on membrane Na/K-ATPase activity. At 3 days after alpha2 adenovirus vector infusion, Wistar rat livers contained alpha2 DNA, alpha2 mRNA, and alpha2 protein. Rat liver membrane ouabain binding activity and the sensitivity of Na/K-ATPase activity to ouabain significantly increased. Total membrane Na/K-ATPase was regulated at a constant level while expressed alpha2 activity represented 10% of the total active Na/K-ATPase sites in alpha2 transduced rat liver. These studies are the first to establish a paradigm in which an endogenous drug receptor is expressed to alter cellular pharmacologic sensitivity.

Isolation and characterization of the human nucleophosmin/B23 (NPM) gene: identification of the YY1 binding site at the 5' enhancer region

NPM (nucleophosmin/B23) is a major nucleolar protein which is 20 times more abundant in tumor or proliferating cells than in normal resting cells. Recently, it was found that NPM gene is located at the breakpoints of the t(2:5), t(3:5) and t(5:17) chromosome translocation. To understand the human NPM gene's structure and regulation, four genomic clones were isolated from the human chromosome 5 library and their DNA sequences analyzed. The human NPM gene has 12 exons of sizes ranging from 58 to 358 bp. The chromosome breakpoint for t(2:5) and t(5:17) translocation is within intron 4 and the breakpoint for t(3:5) translocation is within intron 6. The initiation site is located 96 bp upstream from the ATG site. A typical TATA box (at -25 nt) and a GC box (at -65 nt) were identified in the promoter region. We identified two gel-shift bands (A and B) with DNA fragment E (-741/-250 nt) by EMSA. A DNA footprint was observed at (-371/-344 nt) with the nuclear extract. A double stranded DNA with the footprint sequence (-371/-344 nt) competed the formation of gel-shift bands A and B in EMSA suggesting that proteins A and B bind to the footprint region. We confirmed that protein A is transcription factor YY1. These results suggest that YY1 may play a role in NPM gene expression. This is the first report on human NPM gene structure and sequence.

Cloning of the human phospholipase C-gamma1 promoter and identification of a DR6-type vitamin D-responsive element

The 5'-flanking region of the human phospholipase C-gamma1 gene was isolated from a human P1 genomic DNA library. The S1-nuclease mapping and primer extension analysis revealed that there is a single transcriptional start site located at 135 bases upstream from the translation start codon in the human phospholipase C-gamma1 gene. DNA sequence analysis showed that the sequence around the transcriptional start site is very GC-rich and has no TATA box. The fragment +135 to -877 in the 5'-flanking region of the human phospholipase C-gamma1 gene was subcloned into a luciferase reporter vector. The chimeric gene produced a high level of luciferase activity and responded to 1,25-(OH)2D3 in transiently transfected human keratinocytes. Deletion and mutation studies of the fragment +135 to -877 demonstrated a vitamin D-responsive element that contains a motif arranged as two direct repeats separated by 6 bases (DR6), AGGTCAgaccacTGGACA, located between -786 and -803 base pairs. Incubation of the oligonucleotide containing the DR6 with keratinocyte nuclear extracts produced a specific protein-DNA complex that shifted to a higher molecular weight form upon the addition of an antibody specific to the 1,25-(OH)2D3 receptor. Therefore, the 5'-flanking region of the human phospholipase C-gamma1 gene confers promoter activity and contains a DR6-type vitamin D-responsive element that mediates, at least in part, the enhanced expression of this gene in human keratinocytes by 1, 25-(OH)2D3.

Infiltration of eosinophils into the asthmatic airways caused by interleukin 5

Interleukin (IL)-5 is thought to play an important role in asthmatic bronchial mucosal inflammation and is a potential therapeutic target. To investigate the effect of IL-5 on the infiltration of eosinophils in airway in vivo, we compared eosinophil counts and their activation status in airways without and after the topical instillation of recombinant human IL-5. Eight subjects with mild atopic asthma underwent initial bronchoscopy during which control bronchoalveolar lavage (BAL) fluid as well as bronchial mucosa were obtained, and at the same time, normal saline and IL-5 were administered to two sublobar segments separately. The second bronchoscopy were carried out and samples from challenged sites were taken 24 h later. It was found that the total eosinophils (BMK-13+ cells) and the activated eosinophils (EG2+ cells) in bronchial mucosa, the eosinophil numbers in BAL fluid, as well as eosinophil cationic protein (ECP) in BAL fluid from saline-challenged segments were not different from those in unchallenged segments. However, a significant eosinophilia was observed in bronchial mucosa and BAL fluid from IL-5-challenged sites. Eosinophil activation, as assessed by secretion of ECP, was also increased significantly in bronchial mucosa and BAL fluid. The results strongly suggested that IL-5 is capable of inducing eosinophil infiltration into the asthmatic airways, as well as the activation of infiltrating eosinophils.

Induction of AP-1 activity associated with c-Jun and JunB is required for mitogenesis induced by insulin and vanadate in SV40-transformed 3T3T cells

Insulin and vanadate function as complete mitogens for SV40-transformed murine 3T3T (CSV3-1) cells but not for nontransformed 3T3T cells. Mitogenesis induced by insulin and vanadate in CSV3-1 cells is associated with the induction of the expression of protooncogenes c-jun and junB, two major AP-1 transcription factor components. We now report that both insulin and vanadate induce a significant increase in AP-1 DNA binding activity in CSV3-1 cells but not in 3T3T cells. Gel supershift assays and Western blot analysis using specific antibodies demonstrate that the increased AP-1 binding activity induced by insulin and vanadate in CSV3-1 cells is primarily contributed by an increase in the expression of c-Jun and JunB protein levels. Furthermore, treatment of CSV3-1 cells with antisense oligodeoxyribonucleotides to c-jun or to junB blocks insulin- and vanadate-induced mitogenesis whereas antisense junD oligomers have no inhibitory effects. These results therefore demonstrate that the induction of AP-1 binding activity associated with c-Jun and JunB is required for insulin- and vandate-induced mitogenesis in SV40-transformed murine 3T3T cells. Additional data presented in this paper show that JunD/AP-1 binding activity, which is thought to play a negative role in regulating cell proliferation, is also slightly induced following insulin and vanadate stimulation in CSV3-1 cells. Nevertheless, the ratio of proliferation promoting c-Jun/AP-1 and JunB/AP-1 binding activities to proliferation inhibiting JunD/AP-1 binding activity is significantly increased following insulin and vanadate stimulation. These results therefore support the concept that modulation of the balance of positive Jun/AP-1 and negative Jun/AP-1 activities is important in regulating cell proliferation.

The capillarity of left ventricular tissue of rats subjected to coronary artery occlusion

OBJECTIVE

The effects of chronic coronary occlusion on the capillarity of left ventricular tissue in rat heart.

METHODS

The heart was exposed through a left-sided thoracotomy in ethylether-anesthetized and ventilated rats. The left coronary artery was occluded with a thin suture and the thorax was closed. Thirty days after the surgery the heart was removed and cross-sections were made for morphometric analyses.

RESULTS

The cross-sectional area of cardiomyocytes increased markedly in the subepi- and subendocardia with a concomitant increase in the capillary to myocyte ratio. The total capillary density increased in the non-ischemic zone. The balance between the increase in capillary density and myocyte hypertrophy was assessed from the capillary domain area (CDA). CDAs were significantly smaller for the venular capillary portion in the subendocardial non-ischemic zone. However, CDAs in the transition zone around the necrosis were significantly increased in the venular capillary portion in the subendocardium and in all capillary portions in the subepicardium compared with those in the non-ischemic zone. Immunohistological staining for basic fibroblast growth factor (bFGF) revealed punctate bFGF distribution in both the non-ischemic and transition zones of ventricular tissues 30 days after occlusion, suggesting a persistent stimulation for capillary angiogenesis.

CONCLUSION

The remodelling of the capillary bed is not uniform throughout the cardiac tissue in coronary-occluded rat hearts. CDAs decreased in the non-ischemic zone but increased in the transition zone. The rate of capillary angiogenesis failed to parallel the development of hypertrophy in the transition zone over 30 days, as could be seen from the significant reduction in the percentage of venular capillary portions.

Five-Coordinate Hydrogen: Neutron Diffraction Analysis of the Hydrido Cluster Complex

Pentacoordinate hydrogen atoms were identified by single-crystal neutron diffraction analysis of [N(CH3)4]3[H2Rh13(CO)24]. The hydrogen atoms are located in square pyramidal cavities of the Rh13 cluster, in positions almost coplanar with the Rh4 faces on the surface of the cluster. They are slightly displaced inward, toward the central rhodium atom of the cluster, with average H-Rh(central) and H-Rh(surface) distances of 1.84(2) and 1.97(2) angstroms, respectively. This result shows that hydrogen, which normally forms only one bond, can be attached to five other atoms simultaneously in a large metal cluster.

[Inhibition of voltage-dependent K+ currents in rat C6 glioma cells by haloperidol and R(-)-NPA]

In this study, the inhibitory effects of R(-)-NPA (R(-)-Propylnorapomorphine) and haloperidol on voltage-dependent K+ currents in rat C6 glioma cells (C6 cells) were observed by means of the whole-cell patch-clamp recording technique. The mechanisms of the effects were also analyzed. The main results were as follows: (1) Both R(-)-NPA and haloperidol could inhibit K+ currents dose-dependently and reversibly in C6 cells. (2) R(-)-NPA and haloperidol inhibited mainly the slow component of the K+ currents. (3) These inhibitory responses were not mediated by dopamine receptors or dependent on G-proteins and intracellular calcium. It was suggested that they refer to some direct action on K+ channels.

[Voltage-dependent potassium currents in rat C6 glioma cells]

In the present study, the properties of voltage-dependent K- currents in cultured rat C6 glioma cells were investigated with the whole cell patch-clamp recording technique. A total of 97 cells were recorded. The mean value of the membrane potential was -47.5 +/- 9.4 mV. Seven percent of the recorded C6 glioma cells did not show any outward potassium currents. The rest had outward K+ currents which could be activated at -36.5 +/- 5.9 mV from a holding potential of -70 mV. Ananalysis of tail currents, showed the mean value of the reversal potential was -84.6 +/- 4.1 mV, close to the K+ equilibrium potential. The K+ currents of 60% of the recorded C6 cells consisted of both a fast and a slow component, while those of the 33% only with a slow component.

Ouabain-induced hypertrophy in cultured cardiac myocytes is accompanied by changes in expression of several late response genes

Partial inhibition of cardiac Na/K-ATPase by digitalis drugs such as ouabain is the initial event leading to positive inotropy in the heart. We showed recently that exposure of rat cardiac myocytes to ouabain concentrations that produce positive inotropy, but no overt toxicity, caused inductions of some early response genes and hypertrophy of these myocytes. The aim of this work was to determine if ouabain also affects the expressions of certain late response genes that are regulated by other hypertrophic stimuli. Non-toxic concentrations of ouabain (5-100 microM) increased mRNAs of skeletal alpha-actin, atrial natriuretic factor, myosin light chain 2, and transforming growth factor beta: indicating that ouabain's effects on these marker genes are similar to those of hypertrophic stimuli that mimic the effects of pressure overload. Expression of skeletal alpha-actin was more sensitive to ouabain than that of atrial natriuretic factor, suggesting significant differences in the ouabain-specific pathways of the induction of these fetal genes. The effects of ouabain on skeletal alpha-actin gene were transcriptional, and required an increase in net influx of extracellular Ca2+. Protein kinase C and Ca(2+)-calmodulin kinases, but not protein kinase A, were involved in the signal pathways leading to the induction of skeletal alpha-actin gene. These data and our prior findings indicate that an increase in net influx of Ca2+ through partial inhibition of Na/K-ATPase initiates protein kinase-dependent pathways resulting in alterations in cardiac growth and expressions of both early and late response genes.

JunD phosphorylation, and expression of AP-1 DNA binding activity modulated by serum growth factors in quiescent murine 3T3T cells

JunD has been implicated as a negative regulator of cell proliferation. If and how JunD is regulated by growth factors however has not been well investigated. We now report that in quiescent murine 3T3T cells, JunD is present in a hypophosphorylated form, but that when quiescent cells are stimulated to proliferate with serum, JunD undergoes a transient increase in its phosphorylation that occurs within 10 min and persists for up to 4 h. The increase in JunD phosphorylation correlates with the induction of cell proliferation since only those growth factors that promote cell proliferation can induce JunD phosphorylation. Treatment of quiescent 3T3T cells with serum also induces significant decreases in JunD/AP-1 DNA binding activity within 2 h and in JunD expression after 8-48h. However, both hypophosphorylated and hyperphosphorylated forms of JunD can bind AP-1 DNA. These results suggest that serum growth factors can modulate JunD characteristics in a variety of apparently independent ways to overcome its negative regulatory effect in controlling cell proliferation. These include induction of a transient increase in JunD phosphorylation, repression of JunD AP-1 DNA binding activity and downregulation of JunD expression.

Regulation of rat Na+/Pi cotransporter-1 gene expression: the roles of glucose and insulin

Cytosolic inorganic phosphate (P(i)) is important for glucose metabolism. It plays a role in homeostatic regulation of glucose by insulin and glucagon. Recently, we isolated two cDNA clones for rat Na+/P(i) cotransporter-1 (rNaPi-1) and demonstrated that they are expressed primarily in the rat liver and kidney. We now report that the expression of rNaPi-1 in these tissues is regulated by fasting and streptozotocin-induced diabetes. Using rat hepatocytes in primary culture, we also demonstrate that glucose and insulin upregulate rNaPi-1 expression, whereas glucagon and elevated intracellular adenosine 3',5'-cyclic monophosphate levels downregulate its expression. Because 2-deoxyglucose exhibits no effect on rNaPi-1 gene expression, we suggest that some metabolite accumulated during glucose metabolism may be responsible for the effects of glucose and insulin on rNaPi-1 gene expression. Our data also reveal that other known Na+/P(i) cotransporter genes, NaPi-2 and Ram-1 (a receptor for amphotropic murine retrovirus), are not regulated by insulin and glucose. It is therefore proposed that various subtypes of Na+/P(i) cotransporters are differentially regulated and that each subtype may be involved in a specific cellular function, rNaPi-1 may be responsible for Pi uptake by liver and kidney for glucose metabolism, whereas NaPi-2 may play a key role in P(i) reabsorption in the kidney.

Differentiation modulates the balance of positive and negative Jun/AP-1 DNA binding activities to regulate cellular proliferative potential: different effects in nontransformed and transformed cells

Differentiation of 3T3T cells into adipocytes results in the progressive repression of growth factor responsiveness. This is associated with the transcriptional repression of the inducibility of c-jun and junB expression by serum. In contrast, differentiation of SV-40 large T antigen-transformed 3T3T cells (CSV3-1) does not repress growth factor responsiveness nor c-jun or junB inducibility even though CSV3-1 cells can differentiate into adipocytes. To better explain these observations, we have studied compositional changes in AP-1 DNA binding activity attributed to c-Jun, JunB, and JunD during the differentiation process in 3T3T and CSV3-1 cells. The results show that in nontransformed 3T3T cells, differentiation represses AP-1 DNA binding activity via a proportionate downregulation of c-Jun, JunB, and JunD. In contrast, in CSV3-1 cells, AP-1 DNA binding activity increases twofold during differentiation, which is accounted for by an increase in JunD with no change in c-Jun and JunB. If c-Jun and JunB serve as positive regulators and JunD serves as a negative regulator for cell proliferation as suggested by previous studies, the repression of JunD expression in differentiating CSV3-1 cells should be mitogenic because decreasing JunD/AP-1 DNA binding activity would allow c-Jun/AP-1 and JunB/AP-1 DNA binding activities to be dominant. The results confirm this prediction showing that antisense junD oligodeoxyribonucleotides are mitogenic for differentiating CSV3-1 cells whereas antisense c-jun and junB inhibit mitogenesis. These data support the conclusion that differentiation can regulate cellular proliferative potential by modulating the balance of positive and negative Jun/AP-1 DNA binding activities in distinct ways in nontransformed and transformed cells.

Control of RNA polymerase II elongation potential by a novel carboxyl-terminal domain kinase

The entry of RNA polymerase II into a productive mode of elongation is controlled, in part, by the postinitiation activity of positive transcription elongation factor b (P-TEFb) (Marshall, N. F., and Price, D. H. (1995) J. Biol. Chem. 270, 12335-12338). We report here that removal of the carboxyl-terminal domain (CTD) of the large subunit of RNA polymerase II abolishes productive elongation. Correspondingly, we found that P-TEFb can phosphorylate the CTD of pure RNA polymerase II. Furthermore, P-TEFb can phosphorylate the CTD of RNA polymerase II when the polymerase is in an early elongation complex. Both the function and kinase activity of P-TEFb are blocked by the drugs 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) and H-8. P-TEFb is distinct from transcription factor IIH (TFIIH) because the two factors have no subunits in common, P-TEFb is more sensitive to DRB than is TFIIH, and most importantly, TFIIH cannot substitute functionally for P-TEFb. We propose that phosphorylation of the CTD by P-TEFb controls the transition from abortive into productive elongation mode.

Restoration of phosphorylation capacity to the dormant half of the alpha-subunits of Na+, K(+)-ATPase

Purified kidney Na+, K(+)-ATPase whose alpha-subunit is cleaved by chymotrypsin at Leu266-Ala267, loses ATPase activity but forms the phosphoenzyme intermediate (EP) from ATP. When EP formation was correlated with extent of alpha-cleavage in the course of proteolysis, total EP increased with time before it declined. The magnitude of this rise indicated doubling of the number of phosphorylation sites after cleavage. Together with previous findings, these data establish that half of the alpha-subunits of oligomeric membrane-bound enzyme are dormant and that interaction of the N-terminal domain of alpha-subunit with its phosphorylation domain causes this half-site reactivity. Evidently, disruption of this interaction by proteolysis abolishes overall activity while it opens access to phosphorylation sites of all alpha-subunits.

Comparative study on the mechanism of formation of pulse manifestations in coronary heart disease and hematopathic patients

Most patients suffering from coronary heart disease have string--like pulse due mainly to disorder of cardiac function, lowered arterial compliance and increased total peripheral resistance. The common type of pulse in hematopathy patients is rapid, thready, string--like and slippery, due mainly to increased compensatory pumping action of heart, shortening of ejection time of left ventricle, relatively better vessel compliance and blood rheology as well as low total peripheral resistance.

Similarities and differences between the properties of native and recombinant Na+/K+-ATPases

Progress of mutagenesis studies on the relation of the structure of Na+/K+-ATPase to its reaction mechanism has been impeded by the paucity of information on the properties of small amounts of impure recombinant enzyme obtained in the currently available expression systems, and the uncertainty of whether expression in a new environment alters the various catalytic activities of this membrane enzyme. Hence, our aim was to make a detailed comparison of the properties of the extensively studied canine kidney Na+/K+-ATPase with those of its alpha1,beta1 subunits expressed in the baculovirus-infected Sf-9 cells. The active fraction of the recombinant enzyme, containing 10-20% of the expressed a subunits, was found to have normal molar activity, all the partial reactions, and the ability to catalyze ATP-dependent Na+/K+ exchange after reconstitution into proteoliposomes. Comparison of steady-state kinetics of the hydrolytic activities of recombinant and native enzymes showed that (a) ATP and Na+ plots of Na+-ATPase were the same in the two preparations; (b) apparent K+ affinity of K+-phosphatase of recombinant enzyme was lower than that of kidney enzyme; and (c) for Na+/K+- ATPase activity, apparent K+ affinity of recombinant enzyme was lower, and its apparent Na+ and ATP affinities were higher than those of kidney enzyme. The two enzymes had similar ADP- and K+-sensitive phosphointermediates, identical affinities for ouabain, and similar ligand sensitivities of dissociation rates of ouabain-enzyme complexes. Evidently, the recombinant enzyme has reduced affinity at cytoplasmic K+ sites, but no changes at multiple Na+, ATP, and ouabain binding sites. Likely causes of this selective change include altered glycosylation state of beta and interactions among active and inactive recombinant enzymes. The present results provide the necessary database for the appropriate use of an expression system in structure-function studies on canine alpha1,beta1 isoform of Na+/K+-ATPase, and indicate the need for similar studies on recombinant Na+/K+-ATPases obtained in other expression systems.

Purification of an RNA polymerase II transcript release factor from Drosophila

Factor 2 was previously identified in Drosophila Kc cell nuclear extract (KcN) as an activity suppressing the appearance of long transcripts (Price, D. H., Sluder, A. E., and Greenleaf, A. L. (1987) J. Biol. Chem. 262, 3244-3255). A 154-kDa protein with factor 2 activity was purified to apparent homogeneity from KcN. An immobilized template assay indicated that factor 2 caused the release of transcripts by RNA polymerase II in an ATP-dependent manner. Some early elongation complexes were resistant to factor 2 action but became sensitive after treatment with 1 M KCl. In the absence of factor 2, transcription complexes still exhibited a low degree of processivity suggesting that factor 2 was only partially responsible for abortive elongation.

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

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

The plastid-encoded ccsA gene is required for heme attachment to chloroplast c-type cytochromes

A chloroplast gene, ycf5, which displays limited sequence identity to bacterial genes (ccl1/cycK) required for the biogenesis of c-type cytochromes, was tested for its function in chloroplast cytochrome biogenesis in Chlamydomonas reinhardtii. Targeted inactivation of the ycf5 gene results in a non-photosynthetic phenotype attributable to the absence of c-type cytochromes. The cloned ycf5 gene also complements the phototrophic growth deficiency in strain B6 of C. reinhardtii. B6 is unable to synthesize functional forms of cytochromes f and c6 owing to a chloroplast genome mutation that prevents heme attachment. The selected (phototrophic growth) as well as the unselected (holocytochrome c6 accumulation) phenotypes were restored in complemented strains. The complementing gene, renamed ccsA (for c-type cytochrome synthesis), is expressed in wild-type and B6 cells but is non-functional in B6 owing to an early frameshift mutation. Antibodies raised against the ccsA gene product recognize a 29-kDa protein in C. reinhardtii. The 29-kDa protein is absent in strain B6 but is restored in a spontaneous revertant (B6R) isolated from a culture of B6. Sequence analysis of the ccsA gene in strain B6R indicates that it is a true revertant. We conclude that the ccsA gene is expressed and that it encodes a protein required for heme attachment to c-type cytochromes.

Activation of Na+/K(+)-ATPase by fatty acids, acylglycerols, and related amphiphiles: structure-activity relationship

A number of fatty acids and derivatives have been shown to activate Na+/K(+)-ATPase when ATP is suboptimal. To explore the relation of the structures of these amphiphiles to enzyme activation, the effects of varying amphiphile concentrations on the activity of the highly purified kidney Na+/K(+)-ATPase at 50 microM ATP were determined. Among fatty acids, efficacy (maximal level of activation) and potency were found to be dependent, in different ways, on chain length and unsaturation. Compared to fatty acids, the corresponding alcohols had lower efficacies. Methyl esters of fatty acids inhibited, but CoA esters and monoacyl esters of glycerol activated the enzyme. Relation between chain length and potency among CoA esters and monoacylglycerols was the same as that observed with acids. Diacylglycerols did not activate, but they antagonized the effects of the activator amphiphiles. The substantial specificities of the amphiphile effects support the hypothesis that these ligands bind to a distinct amphipathic peptide segment of the intracellular central loop of the alpha-subunit to regulate ATP binding to the enzyme. The findings also suggest that direct effects of the changing intracellular levels of fatty acids and derivatives on Na+/K(+)-ATPase should be considered as a possible mechanism for the regulation of its function in the intact cell.