Effect on product formation in recombinant Saccharomyces cerevisiae strains expressing different levels of xylose metabolic genes

The XYL1 and XYL2 genes from Pichia stipitis encoding xylose reductase (XR) and xylilitol dehydrogenase (XDH), respectively, were transformed into Saccharomyces cerevisiae. These two genes were placed in different directions under the control of the alcohol dehydrogenase I (ADHI) and phosphoglycerate kinase (PGK) promoters and inserted into the E. coli-yeast shuttle plasmid YEp24. Different recombinant S. cerevisiae strains were constructed with different specific activities of XR and XDH. The highest XR or XDH activities were obtained when the expressed gene was controlled by the PGK promoter and located downstream after the ADHI promoter-gene-terminator sequence. The XR/XDH ratio (ratio of specific enzyme activities of XR and XDH) in these recombinant S. cerevisiae strains varied from 17.5 to 0.06. In order to enhance xylose utilization, in the XYL1, XYL2 containing S. cerevisiae strains, the native TKL1 gene encoding transketolase and the TALI gene encoding transaldolase were also overexpressed, which showed considerably good growth on the xylose plate. Fermentation of the recombinant S. cerevisiae strains containing XYL1, XYL2, TKL1, and TAL1 were studied with mixtures of glucose and xylose. The strain with XR/XDH ratio of 0.06 consumed 3.25 g/L xylose and formed no xylitol and less glycerol and acetic acid, but more ethanol compared with the strains with a higher XR/XDH ratio.

Site-specific d(GpG) intrastrand cross-links formed by dinuclear platinum complexes. Bending and NMR studies

The novel platinum drugs [{trans-PtCl(NH3)2}2H2N(CH2)nNH2]2+ (1,1/t,t) are currently undergoing preclinical development. The bifunctional DNA binding of these agents allows comparison with that of cisplatin [Farrell et al. (1995) Biochemistry, 34, 15480]. The major DNA lesion of cisplatin, the 1,2-d(GpG) intrastrand adduct, produces a rigid, directed bend 30-35 degrees into the major groove of DNA. We have now completed a structural analysis of the corresponding adduct formed with the dinuclear complexes. Gel retardation assays on 15-22 bp oligonucleotides containing a central d(TG*G*T) site show that the (Pt,Pt)-intrastrand adducts result in a flexible nondirectional bend. This bend is essentially independent of chain length (n = 2, 4, 6). Chemical reactivity assays indicated a hypersensitivity of the thymine 5' to the adduct and an enhanced sensitivity of the 3'-thymine to OsO4. 2D 1H NMR studies on a d(TG1G2T) adduct of [{trans-PtCl(NH3)2}2H2N(CH2)6NH2]2+ have delineated the structural features responsible for these observations. In contrast to the cisplatin adduct, which displays a 100% N-type sugar of the 5'-G and an anti base conformation of the platinated bases in both solid state and solution, the dinuclear adduct does not display the typical N-type sugar pucker. The base orientations are anti (5'-T), anti (G1), anti/syn (G2), and anti (3'-T) while the sugar conformations are N, S/N, N, and S, respectively. The 5'-T remains stacked with its guanine neighbor while the 3'-T becomes unstacked, a reverse of the situation observed for cis-DDP.

Charcot-Marie-Tooth disease type 1A: a family study with microsatellites

Charcot-Marie-Tooth (CMT) disease (also called Hereditary Motor and Sensory Neuropathy) is an inherited peripheral neuropathy with a prevalence rate of 1 in 2,500. Charcot-Marie-Tooth disease type 1A (CMT1A), the most common autosomal dominant form of the disease, is associated with a duplication of a segment of chromosome 17 (17p11.2). In this report we present a three-generation family with CMT1A where simple sequence repeats (di- or tri-nucleotide repeats, also called microsatellites) were used in conjunction with polymerase chain reaction (PCR) to identify the duplication. The presence of three alleles or the presence of two alleles with a dosage ratio of 1:2 for the markers D17S839 and D17S921 indicates the presence of the duplicated segment in affected family members, whereas two alleles with a ratio of 1:1 indicate absence of the duplication. Several markers outside the duplication region which have two alleles with a dosage ratio of 1:1 were used as controls. Seven CMT1A patients in this family carry the CMT1A duplication. One 12-year-old boy who has not exhibited any clinical symptoms does not have the CMT1A duplication. We believe that this is a simple, rapid, and effective method to identify the CMT1A duplication in most patients suspected of having CMT1A.

Phosphorylation of S1505 in the cardiac Na+ channel inactivation gate is required for modulation by protein kinase C

Inactivation of both brain and cardiac Na+ channels is modulated by activation of protein kinase C (PKC) but in different ways. Previous experiments had shown that phosphorylation of serine 1506 in the highly conserved loop connecting homologous domains III and IV (LIII/IV) of the brain Na+ channel alpha subunit is necessary for all effects of PKC. Here we examine the importance of the analogous serine for the different modulation of the rH1 cardiac Na+ channel. Serine 1505 of rH1 was mutated to alanine to prevent its phosphorylation, and the resulting mutant channel was expressed in 1610 cells. Electrophysiological properties of these mutant channels were indistinguishable from those of wild-type (WT) rH1 channels. Activation of PKC with 1-oleoyl-2-acetyl-sn-glycerol (OAG) reduced WT Na+ current by 49.3 +/- 4.2% (P < 0.01) but S1505A mutant current was reduced by only 8.5 +/- 5.4% (P = 0.29) when the holding potential was -94 mV. PKC activation also caused a -17-mV shift in the voltage dependence of steady-state inactivation of the WT channel which was abolished in the mutant. Thus, phosphorylation of serine 1505 is required for both the negative shift in the inactivation curve and the reduction in Na+ current by PKC. Phosphorylation of S1505/1506 has common and divergent effects in brain and cardiac Na+ channels. In both brain and cardiac Na+ channels, phosphorylation of this site by PKC is required for reduction of peak Na+ current. However, phosphorylation of S1506 in brain Na+ channels slows and destabilizes inactivation of the open channel. Phosphorylation of S1505 in cardiac, but not S1506 in brain, Na+ channels causes a negative shift in the inactivation curve, indicating that it stabilizes inactivation from closed states. Since LIII/IV containing S1505/S1506 is completely conserved, interaction of the phosphorylated serine with other regions of the channel must differ in the two channel types.

Molecular prenatal diagnosis of glycogen storage disease type Ia

Glycogen storage disease type Ia (GSD Ia, von Gierke disease) is an autosomal recessive inborn error of metabolism caused by the deficiency of D-glucose-6-phosphatase (G6Pase). Since this enzyme is expressed primarily in hepatocytes, couples at risk for GSD type Ia relied on fetal liver biopsy for prenatal diagnosis. The recent isolation of the G6Pase gene and identification of several disease-causing mutations have permitted molecular prenatal diagnosis using amniocytes or chorionic villi. Chorionic villus sampling (CVS) was performed in an Ashkenazi Jewish family in whom a previous child was homoallelic and both parents were heterozygous for the R83C mutation. Molecular analysis revealed that the fetus was not affected. The prenatal diagnosis was confirmed postnatally by biochemical and molecular studies. Thus, the molecular prenatal diagnosis of GSD type Ia can be safely and accurately made in the first trimester.

Random effects models in latent class analysis for evaluating accuracy of diagnostic tests

When the results of a reference (or gold standard) test are missing or not error-free, the accuracy of diagnostic tests is often assessed through latent class models with two latent classes, representing diseased or nondiseased status. Such models, however, require that conditional on the true disease status, the tests are statistically independent, an assumption often violated in practice. Consequently, the model generally fits the data poorly. In this paper, we develop a general latent class model with random effects to model the conditional dependence among multiple diagnostic tests (or readers). We also develop a graphical method for checking whether or not the conditional dependence is of concern and for identifying the pattern of the correlation. Using the random-effects model and the graphical method, a simple adequate model that is easy to interpret can be obtained. The methods are illustrated with three examples from the biometric literature. The proposed methodology is also applicable when the true disease status is indeed known and conditional dependence could well be present.

Molecular determinants of high affinity binding of alpha-scorpion toxin and sea anemone toxin in the S3-S4 extracellular loop in domain IV of the Na+ channel alpha subunit

alpha-Scorpion toxins and sea anemone toxins bind to a common extracellular site on the Na+ channel and inhibit fast inactivation. Basic amino acids of the toxins and domains I and IV of the Na+ channel alpha subunit have been previously implicated in toxin binding. To identify acidic residues required for toxin binding, extracellular acidic amino acids in domains I and IV of the type IIa Na+ channel alpha subunit were converted to neutral or basic amino acids using site-directed mutagenesis, and altered channels were transiently expressed in tsA-201 cells and tested for 125I-alpha-scorpion toxin binding. Conversion of Glu1613 at the extracellular end of transmembrane segment IVS3 to Arg or His blocked measurable alpha-scorpion toxin binding, but did not affect the level of expression or saxitoxin binding affinity. Conversion of individual residues in the IVS3-S4 extracellular loop to differently charged residues or to Ala identified seven additional residues whose mutation caused significant effects on binding of alpha-scorpion toxin or sea anemone toxin. Moreover, chimeric Na+ channels in which amino acid residues at the extracellular end of segment IVS3 of the alpha subunit of cardiac Na+ channels were substituted into the type IIa channel sequence had reduced affinity for alpha-scorpion toxin characteristic of cardiac Na+ channels. Electrophysiological analysis showed that E1613R has 62- and 82-fold lower affinities for alpha-scorpion and sea anemone toxins, respectively. Dissociation of alpha-scorpion toxin is substantially accelerated at all potentials compared to wild-type channels. alpha-Scorpion toxin binding to wild type and E1613R had similar voltage dependence, which was slightly more positive and steeper than the voltage dependence of steady-state inactivation. These results indicate that nonidentical amino acids of the IVS3-S4 loop participate in alpha-scorpion toxin and sea anemone toxin binding to overlapping sites and that neighboring amino acid residues in the IVS3 segment contribute to the difference in alpha-scorpion toxin binding affinity between cardiac and neuronal Na+ channels. The results also support the hypothesis that this region of the Na+ channel is important for coupling channel activation to fast inactivation.

A circular dichroism study of ethidium bromide binding to Z-DNA induced by dinuclear platinum complexes

Dinuclear bis(platinum) complexes have been shown previously to induce the B-->Z transition in synthetic DNAs (Nucleic Acids Res. 7, 1697-1703, J. Inorganic Biochem. 54, 207-220). In this paper, the reversibility of the Z conformation back to the B form was assessed by treatment of the induced Z form in poly(dG-dC).poly(dG-dC) with ethidium bromide (Etd). Z-DNA induced by the tetra-amine cations [{Pt(NH3)3}2(H2N(CH2)nNH2)]4+, which are capable of only electrostatic interactions with the polynucleotide, was readily reversible. The spectroscopic data mirrored that of ethidium bromide/poly(dG-dC).poly(dG-dC) in the presence of 4.4 M NaCl. In contrast, Z-DNA induced by the bifunctional complexes [{trans-PtCl(NH3)2}2(H2N(CH2)nNH2)]2+ did not produce spectra typical of Etd intercalation and reversal to B-form DNA. The original Z-form CD spectra of DNA treated with the bifunctional complexes could be reobtained following removal of Etd by extensive dialysis. The bifunctional complexes are very effective interstrand cross-linking agents. The data suggest that interstrand cross-linking by dinuclear complexes can stabilize or "lock" the Z-conformation prohibiting its reversal to the B-form. The implications for the biological activity of the dinuclear complexes are briefly discussed.

Platelet I1-imidazoline binding sites are decreased by two dissimilar antidepressant agents in depressed patients

Previous studies have indicated that there may be a dysregulation of alpha 2-adrenoceptors and imidazoline receptors in depression. This study compares the effects of chronic antidepressant treatment with a serotonin reuptake inhibitor (fluoxetine) versus a noradrenaline reuptake inhibitor (desipramine) on the binding parameters of the platelet imidazoline binding site (subtype I1) and of the platelet alpha 2-adrenoceptor in depressed patients. After 6 weeks of treatment with either antidepressant, platelet I1 binding sites became normalized (i.e. downregulated). A negative correlation was obtained between plasma epinephrine concentrations and platelet alpha 2-adrenoceptor Bmax values within the samples, but no correlation was obtained between any plasma catecholamine and a platelet I1 binding parameter. An additional finding was the increased affinity of alpha 2-adrenoceptors for p125I-clonidine in untreated depressed patients compared to healthy subjects. Because of the density of platelet I1 binding sites was downregulated by both of the antidepressants, we postulate that a decrease in platelet I1 binding site density may be related to an improved state from depression that these antidepressants produce.

A SAS macro for stepwise correlated binary regression

Several regression methods have been proposed for the analysis of correlated binary data, but none deals with the selection of covariates when there exist a large number of potentially relevant covariates. We present a SAS macro based on a stepwise selection procedure for the analysis of correlated binary data. Using regression methods based on generalized estimating equations originally proposed by Liang and Zeger and extended by Prentice, we describe a score test for forward selection, a Wald's test for backward elimination, and a test for model adequacy based on generalized scores. The methodology and the accompanying computer macro program written in SAS IML are illustrated with data from a prospective study of functional decline in the activities of daily living in a group of elderly patients.

Platelet I1-imidazoline binding sites are elevated in depression but not generalized anxiety disorder

Depressed patients have been reported to have a higher than normal density of platelet binding sites for 3H-clonidine, an alpha 2-adrenoceptor agonist. Paradoxically, other studies using 3H-alpha 2, antagonists have found no differences from controls. Because 3H-clonidine interacts with platelet alpha 2-adrenoceptors to form G-protein complexes, whereas 3H-alpha 2-antagonists bind with uncoupled receptors, an elevation in G-protein coupling might explain this paradox. Another possibility is that depression might be associated with increased non-adrenergic I1-imidazoline binding sites, which are also clonidine sensitive. To distinguish these possibilities, we utilized p125I-clonidine to measure density (Bmax) and affinity (KD) of platelet G-protein coupled alpha 2-adrenoceptors as well as platelet I1 binding sites, and compared diagnostic groups of major depressive disorder (MDD), generalized anxiety disorder (GAD) and healthy subjects. Specific inhibition of binding by norepinephrine (NE = 10 microM) was used to selectively quantify alpha 2-adrenoceptors, whereas inhibition by 10 microM moxonidine (a > 100-fold selective I1 ligand) quantified I1 binding sites under a NE mask. I1 sites were found to be markedly elevated by, on average, +136% in MDD patients (p = .0007), whereas there was only a marginal increase in alpha 2-adrenoceptor Bmax values in MDD patients (p = .08; GAD and healthy subjects did not differ). Treatment of MDD patients for 6-8 weeks with desipramine downregulated I1 sites as well as alpha 2-adrenoceptors. Positive correlations were also noted for both sites: (a) between Bmax values and the severity of depression (using the Hamilton Depression Rating Scale); and (b) between end-of-treatment plasma desipramine concentrations and the extent of downregulation in Bmax values when subject groups were pooled. None of the binding parameters was associated with plasma catecholamine concentrations. The results suggest that an increased density of platelet I1 binding sites may partially explain the utility of radiolabeled clonidine as a potential biological marker for depressive illness, although an additional increase in G-protein coupling cannot be excluded.

Molecular prenatal diagnosis of glycogen storage disease type Ia

Glycogen storage disease type Ia (GSD Ia, von Gierke disease) is an autosomal recessive inborn error of metabolism caused by the deficiency of D-glucose-6-phosphatase (G6Pase). Since this enzyme is expressed primarily in hepatocytes, couples at risk for GSD type Ia relied on fetal liver biopsy for prenatal diagnosis. The recent isolation of the G6Pase gene and identification of several disease-causing mutations have permitted molecular prenatal diagnosis using amniocytes or chorionic villi. Chorionic villus sampling (CVS) was performed in an Ashkenazi Jewish family in whom a previous child was homoallelic and both parents were heterozygous for the R83C mutation. Molecular analysis revealed that the fetus was not affected. The prenatal diagnosis was confirmed postnatally by biochemical and molecular studies. Thus, the molecular prenatal diagnosis of GSD type Ia can be safely and accurately made in the first trimester.

Adaptive motor unit action potential clustering using shape and temporal information

An adaptive algorithm is described that groups motor unit action potentials (MUAPs), detected in a composite EMG signal during signal decomposition, and creates partial motor unit action potential trains (MUAPTs). Data-driven MUAP shape and motor unit firing-pattern based criteria are used to form the clusters. An algorithm for estimating MUAPT temporal parameters, which provides accurate estimates even for partially defined trains, is used to obtain firing-pattern information. No a priori knowledge is required regarding the number of clusters or the distribution of their template shapes. The clustering algorithm when applied to real concentric-needle detected MUAP data provides accurate and useful clustering results. Compared to a classical leader-based algorithm, it provides more robust performance, is better able to estimate the true number of motor units represented in a set of detected MUAPs, and obtains more complete and accurate MUAPTs.

Robust method for estimating motor unit firing-pattern statistics

An error-filtered estimation (EFE) algorithm for estimating the mean and standard deviation of a set of time intervals between consecutive motor unit firing times (inter-pulse intervals (IPIs)) is described. As the input IPI data are filtered and only valid IPIs are used to estimate mean and standard deviation values, the EFE algorithm provides accurate estimates even when the data defining the train of motor unit firing times are only partially complete or have several erroneous firing times. The algorithm has been evaluated using both simulated and real motor unit firing time data, and has been found to provide accurate and unbiased mean and standard deviation estimates, even when up to 70% of the IPI data are incorrect.

Molecular determinants of drug access to the receptor site for antiarrhythmic drugs in the cardiac Na+ channel

The clinical efficacy of local anesthetic and antiarrhythmic drugs is due to their voltage- and frequency-dependent block of Na+ channels. Quaternary local anesthetic analogs such as QX-314, which are permanently charged and membrane-impermeant, effectively block cardiac Na+ channels when applied from either side of the membrane but block neuronal Na+ channels only from the intracellular side. This difference in extracellular access to QX-314 is retained when rat brain rIIA Na+ channel alpha subunits and rat heart rH1 Na+ channel alpha subunits are expressed transiently in tsA-201 cells. Amino acid residues in transmembrane segment S6 of homologous domain IV (IVS6) of Na+ channel alpha subunits have important effects on block by local anesthetic drugs. Although five amino acid residues in IVS6 differ between brain rIIA and cardiac rH1, exchange of these amino acid residues by site-directed mutagenesis showed that only conversion of Thr-1755 in rH1 to Val as in rIIA was sufficient to reduce the rate and extent of block by extracellular QX-314 and slow the escape of drug from closed channels after use-dependent block. Tetrodotoxin also reduced the rate of block by extracellular QX-314 and slowed escape of bound QX-314 via the extracellular pathway in rH1, indicating that QX-314 must move through the pore to escape. QX-314 binding was inhibited by mutation of Phe-1762 in the local anesthetic receptor site of rH1 to Ala whether the drug was applied extracellularly or intracellularly. Thus, QX-314 binds to a single site in the rH1 Na+ channel alpha subunit that contains Phe-1762, whether it is applied from the extracellular or intracellular side of the membrane. Access to that site from the extracellular side of the pore is determined by the amino acid at position 1755 in the rH1 cardiac Na+ channel.

Effects of geometric isomerism and ligand substitution in bifunctional dinuclear platinum complexes on binding properties and conformational changes in DNA

The DNA binding profile of a series of dinuclear platinum complexes [{trans-PtCl-(L)2}2H2N(CH2)nNH2]2+ (L = NH3 or py; 1,1/t,t/NH3 and 1,1/t,t/py, respectively) and [{cis-PtCl-(NH3)2H2N(CH2)nNH2]2+ (1,1/c,c/NH3) was examined to compare the effects of geometrical isomerism and the presence of ligands other than NH3 in the coordination sphere. Steric effects, because of the geometry of the leaving groups cis to the diamine bridge or the presence of planar pyridine ligands, result in diminished binding to calf thymus DNA for these isomers. In contrast, the pyridine derivative shows a distinct binding preference for poly(dG-dC).poly(dG-dC) in comparison to both NH3 isomers. Both NH3 complexes induced the B-->Z transition in poly(dG-dC).poly(dG-dC), but the presence of a pyridine ligand stabilized the B conformation. The bifunctional binding of the NH3 isomers results in unwinding of supercoiled pUC19 plasmid DNA equivalent to cis-DDP, while the unwinding of the pyridine derivative is approximately twice that of the mononuclear trans-[PtCl2(py)2]. DNA-DNA interstrand cross-linking is very efficient for all three agents, but sequencing studies indicated that only the 1,1/t,t/NH3 derivative is capable of forming a (Pt,Pt) intrastrand cross-link to the adjacent guanines of a d(GpG) sequence. The effects on DNA caused by bifunctional binding of dinuclear complexes are compared with those from the mononuclear [PtCl2(NH3)2] isomers. The results are discussed with respect to the antitumor activity of the dinuclear series.

Modulation of cardiac Na+ channel expression in Xenopus oocytes by beta 1 subunits

Voltage-gated Na+ channels consist of a large alpha subunit of 260 kDa associated with beta 1 and/or beta 2 subunits of 36 and 33 kDa, respectively. alpha subunits of rat cardiac Na+ channels (rH1) are functional when expressed alone in Xenopus oocytes or mammalian cells. beta 1 subunits are present in the heart, and localization of beta 1 subunit mRNA by in situ hybridization shows expression in the perinuclear cytoplasm of cardiac myocytes. Coexpression of beta 1 subunits with rH1 alpha subunits in Xenopus oocytes increases Na+ currents up to 6-fold in a concentration-dependent manner. However, no effects of beta 1 subunit coexpression on the kinetics or voltage dependence of the rH1 Na+ current were detected. Increased expression of Na+ currents is not observed when an equivalent mRNA encoding a nonfunctional mutant beta 1 subunit is coexpressed. Our results show that beta 1 subunits are expressed in cardiac muscle cells and that they interact with alpha subunits to increase the expression of cardiac Na+ channels in Xenopus oocytes, suggesting that beta 1 subunits are important determinants of the level of excitability of cardiac myocytes in vivo.

Proton nuclear magnetic resonance studies on huwentoxin-I from the venom of the spider Selenocosmia huwena: 1. Sequence-specific 1H-NMR assignments

The complete sequence-specific assignments of resonances in the 1H-NMR spectrum of huwentoxin-I from the Chinese bird spider, Selencocosmia huwena, is described. A combination of two-dimensional NMR experiments including 2D-COSY, 2D-NOESY, and 2D-TOCSY has been employed on samples of the toxin dissolved in D2O and in H2O for assignment purposes. Protons belonging to spin systems for each of the 33 amino acids were identified. The sequence-specific assignments were facilitated by the identification of d alpha N connectivities on the fingerprint regions of the COSY and NOESY spectra and were supported by the identification of dNN and d alpha N connectivities in the TOCSY and NOESY spectra. These studies provide a basis for the determination of the solution-phase conformation of this toxin.

Interrater reliability of the multiple sleep latency test

The purpose of this study was to evaluate interrater reliability in the interpretation of the multiple sleep latency test (MSLT). We prospectively analyzed MSLTs performed on 21 patients with excessive daytime sleepiness. MSLTs were recorded on Grass Model 78 polygraphs with EEG, electro-oculogram, and chin EMG. Each test was performed simultaneously at paper speeds of 10 and 30 mm/sec and was scored blindly by 3 readers using standard criteria. For the quantitative variable (sleep latency), a LISREL model was used. For the binary variable (REM present or not), a kappa coefficient was used. Interrater reliability of sleep latency was 0.850 at speed 10, and 0.884 at speed 30. There was no significant difference between speed 10 and 30. Interrater reliability for the presence or absence of REM was 0.515-0.563 at speed 10, and 0.447-0.525 at speed 30. On the MSLT, the estimation of sleep latency showed excellent consistency between different readers. The determination of the presence or absence of REM only showed fair to good agreement among observers. There was no significant difference between a paper speed of 10 vs. 30 mm/sec.

Latent variable models for clustered ordinal data

Existing methods for the analysis of clustered, ordinal data are inappropriate for certain applications. We propose latent variable models for clustered ordinal data which are derived as natural extensions of latent variable models for clustered binary data (Qu, Williams, Beck, and Medendorp, 1992. Biometrics 48, 1095-1102). These models can be applied to repeated measures data, familial data, longitudinal data, and data with both cluster specific and occasion specific covariates with a wide range of correlation structures.

Research of the exploitation of human resources in blind prevention and primary eye care

PURPOSE

This research studied how to establish a relatively advanced blindness prevention and eye care cause in economically underdeveloped countryside.

METHODS

Ophthalmic vocational schools and professional lectures were held to train "practical type" primary eye care workers for the countryside. Further study in high-level (above provincial) hospitals was taken to train blindness prevention & eye care backbones and leaders.

RESULTS

In 1986, the ratio of the number of the eye care workers of all levels to the number of the whole population in the prefecture was 1:26,000. In 1992, it rose to 1:17,000. An eye care network of 222 stations had been established in the countryside. Ten in the 13 county hospitals had a seperated ophthalmology department, in which 3 were awarded "National advanced blindness prevention County". Twenty one hospitals were appointed as the Unit of Surgical Vision-Rehabilitation of Cataract. Blindness prevention and eye care covered 1,000,000 population (eye care available within 5 kilometers), 23.5% of the whole population.

CONCLUSIONS

In a demographically large but economically underdeveloped countryside area, the key to wide-range blindness prevention and eye care is to exploit human resources effectively. We should train "Practical type" primary eye care workers, and have a number of department leaders who are authoritive, influential in this field and ready to sacrifice to this cause.

Chemical reactivity and DNA sequence specificity of formally monofunctional and bifunctional bis(platinum) complexes

The synthesis of the formally monofunctional bis(platinum) complex [(Pt(NH3)3)mu-H2N(CH2)4NH2-(trans-PtCl(NH3)2)]3+ (1,0/t) is reported. The interactions of this species and the formally bifunctional bis(platinum) complex [(trans-PtCl(NH3)2)2H2N(CH2)4NH2]Cl2(1,1/t,t) with DNA were investigated. Comparison was made with the monomeric [PtCl(dien)]Cl, (Pt(DIEN)), and cis-[PtCl2(NH3)2], (cis-DDP). The initial rates of reaction with small self-complementary oligonucleotides 5'-ATATATN4ATATAT-3' (N4 = GCGC and N4 = GGCC) were calculated. For all compounds, the GGCC oligonucleotide reacted faster than the GCGC counterpart. The order of reactivity of the platinum compounds for the GCGC oligonucleotide was 1,1/t,t > 1,0/t > Pt(DIEN) > cis-DDP. The reaction of 1,0/t and 1,1/t,t with poly(dG-dC).poly(dG-dC) was also investigated using circular dichroism (CD) spectroscopy where both compounds were shown to induce a B-->Z conformational change.

Modulation of cardiac Na+ channels expressed in a mammalian cell line and in ventricular myocytes by protein kinase C

Cardiac rH1 Na+ channel alpha subunits were expressed in cells of the Chinese hamster lung 1610 cell line by transfection, and a stable cell line expressing cardiac Na+ channels (SNa-rH1) was isolated. Mean Na+ currents of 2.2 +/- 1.0 nA were recorded, which corresponds to a cell surface density of approximately 1-2 channels active at the peak of the Na+ current per micron2. The expressed cardiac Na+ current was tetrodotoxin resistant (Kd = 1.8 microM) and had voltage-dependent properties similar to those of the Na+ current in neonatal ventricular myocytes. Activation of protein kinase C by 1-oleoyl-2-acetyl-sn-glycerol (OAG) (10 microM) decreased this current approximately 33% at a holding potential of -114 mV and 56% at -94 mV. This reduction in peak current was caused in part by an 8- to 14-mV shift of steady-state inactivation in the hyperpolarized direction. Na+ channel activation was unchanged. Effects of OAG in SNa-rH1 cells and in neonatal rat cardiac myocytes were similar, except that the time course of inactivation was slowed either transiently or persistently when protein kinase C was activated in myocytes bathed in low-Ca2+ (1 microM) or Ca(2+)-free solution but was unaffected in SNa-rH1 cells. The effects of OAG on cardiac Na+ current were blocked in cells that had been previously microinjected with a peptide inhibitor of protein kinase C but not with a peptide inhibitor of cAMP-dependent protein kinase, indicating that protein kinase C is responsible for the effect of OAG. Single-channel recordings from SNa-rH1 cells showed that the probability of channel opening was reduced by OAG, but the conductance was unaffected. OAG did not induce the late Na+ channel openings observed with PKC modulation of neuronal and skeletal muscle Na+ channels. Thus, the substantial reduction in Na+ current at normal diastolic depolarizations with 10 microM OAG is due to failure of channel opening in response to depolarization. Such Na+ current reductions may have profound effects on cardiac cell excitability.

Homodinuclear (Pt,Pt) and heterodinuclear (Ru,Pt) metal compounds as DNA-protein cross-linking agents: potential suicide DNA lesions

Homodinuclear (Pt,Pt) and heterodinuclear (Ru,Pt) metal compounds having the generalized formula M(a)NH2(CH)4NH2M(b) are shown to form specific DNA lesions which can efficiently cross-link proteins to DNA. In this study, the homodinuclear case is represented by M(a) = M(b) = [cis-Pt(Cl2)-(NH3)] and the heterodinuclear case is represented by M(a) = [cis-RuCl2(DMSO)3] and M(b) = [cis-PtCl2(NH3)]. Native and denaturing polyacrylamide gel electrophoresis was used to show the formation of ternary coordination complexes between the metal-treated 49-bp DNA fragment and the Escherichia coli UvrA and UvrB DNA repair proteins. Treatment with proteinase K results in loss of the DNA-protein cross-links. DNA-protein cross-links formed between UvrA and DNA previously modified with the dinuclear metal compounds are reversible with the reducing agent beta-mercaptoethanol. The DNA lesion responsible for efficient DNA-protein cross-linking is most probably a DNA-DNA interstrand cross-link in which each metal atom is coordinated with one strand of the DNA helix. The formation of DNA repair protein associated DNA cross-links, potential "suicide adducts", suggests a novel action mechanism for these anticancer compounds. In addition, these dinuclear metal compounds should be very useful agents for the investigation of a wide range of protein-DNA interactions.

Modulation of L-type Ca2+ current by extracellular ATP in ferret isolated right ventricular myocytes

1. The effects of extracellular adenosine triphosphate (ATP) on the basal L-type Ca2+ current (ICa) were investigated in ferret isolated right ventricular myocytes using the gigaohm seal voltage clamp in the whole-cell and cell-attached configurations. 2. Micromolar levels of extracellular ATP reversibly inhibited ICa in a concentration-dependent manner, without any significant changes in the voltage dependence of either the peak ICa I-V relationship or steady-state activation curve. 3. In contrast, micromolar levels of extracellular ATP did significantly alter the inactivation characteristics of ICa. Ten micromolar ATP: (i) increased the degree of steady-state inactivation of ICa; (ii) altered the time constants of ICa inactivation at 0 mV; and (iii) decreased the time constant of ICa recovery from inactivation at -70 mV. 4. The inhibitory effect of ATP on ICa was not blocked by atropine, a muscarinic cholinergic receptor antagonist, or CPDPX (8-cyclopentyl-3,4-dipropylxanthine), an A1 adenosine receptor antagonist. In contrast, the inhibitory effect of 10 microM ATP could be nearly completely antagonized by 100 microM suramin, a purinergic P2 receptor antagonist. 5. The potency order of ATP analogues in inhibiting ICa was 2-methyl-thio-ATP > ATP > alpha,beta-methylene-ATP, indicating involvement of a P2Y-type ATP receptor. 6. Pretreatment of cells with pertussis toxin (PTX) did not prevent the ATP-induced decrease in ICa. However, (i) ATP produced an irreversible decrease of ICa in the presence of intracellular GTP gamma S, and (ii) the inhibitory effect was significantly attenuated in the presence of intracellular GDP beta S, indicating the involvement of a PTX-insensitive G protein in the P2Y receptor-coupling process. 7. Neither (i) replacing extracellular Ca2+ with 1 mM Ba2+, nor (ii) intracellular perfusion of 10 mM BAPTA for at least 30 min attenuated the inhibitory effect of ATP on the current through Ca2+ channels, suggesting that the inhibitory effect was not obligatorily dependent upon influx of Ca2+ or changes in [Ca2+]i. 8. Ensemble-average current behaviour constructed from cell-attached patch recordings of single L-type Ca2+ channels (110 mM BaCl2) demonstrated that when 10 microM ATP was added to the superfusate on the outside of the patch electrode the inhibition of ICa was still observed, providing evidence for the involvement of intracellular diffusible second messenger(s).(ABSTRACT TRUNCATED AT 400 WORDS)

Modulation of basal L-type Ca2+ current by adenosine in ferret isolated right ventricular myocytes

1. The whole-cell configuration of the gigaohm seal voltage clamp and an internal perfusion technique were used to study the effects of adenosine on the basal L-type Ca2+ current (ICa) in enzymatically isolated right ventricular myocytes of ferrets. Basal L-type ICa was isolated by using a Na(+)- and K(+)-free saline (replacement by N-methyl-D-glucamine+, Cs+ and TEA+, respectively). All experiments were conducted at room temperature (22-24 degrees C). 2. Basal ICa was markedly reduced during exposure to adenosine in a concentration-dependent manner with a half-inhibitory concentration (IC50) of 0.3 microM and maximum inhibition of 35%. This effect was completely abolished by 50 nM 8-cyclopentyl-1,3-dipropylxanthine (CPDPX), a specific A1 adenosine receptor antagonist with an inhibition constant, Ki = 0.48 nM. Inhibition was also observed in the presence of 1 microM atropine. 3. Adenosine decreased basal ICa by decreasing the peak amplitude of ICa without significantly altering (i) the voltage dependence of the current-voltage relationship, (ii) the apparent reversal potential, (iii) the voltage dependence of steady-state activation and inactivation, (iv) the kinetics of inactivation at 0 mV, and (v) the kinetics of recovery from inactivation at -70 mV. 4. Pretreatment of cells with 0.4 microns/ml pertussis toxin (PTX) for 4 h at 37 degrees C produced greater than 90% ADP ribosylation of PTX-sensitive G proteins. PTX pretreatment significantly attenuated the adenosine-mediated decrease in ICa (35% in control; 4.6% after PTX pretreatment). 5. The peptide inhibitor (PKI) of cyclic AMP-dependent protein kinase A at a concentration of 2 microM neither inhibited basal ICa nor attenuated the effects of adenosine on basal ICa. However, PKI decreased the stimulatory effects of 100 microM cAMP on ICa. 6. Increasing intracellular cAMP to a supra-saturable level by using 10 mM cAMP and 100 microM papaverine did not prevent adenosine from inhibiting ICa. 7. Consistent with the reduction of basal ICa, adenosine produced an inhibitory effect on the action potential under basal conditions, i.e. hyperpolarization of the plateau phase and marked shortening of action potential duration. These effects were concentration dependent. 8. These results demonstrate a reduction of the basal L-type ICa by adenosine in ferret ventricular myocardium. This reduction is not mediated by modification of voltage-dependent properties of macroscopic ICa. The shortening of action potentials may be explained in part by the reduction in ICa.(ABSTRACT TRUNCATED AT 400 WORDS)

Delayed desensitization of alpha 2-adrenoceptor-mediated platelet aggregation in depressed patients

After prolonged exposure to epinephrine, platelets are observed to desensitize alpha 2-adrenoceptor-mediated aggregation responses in vitro. Herein, this phenomenon was studied as a possible in vitro model for alpha 2-adrenoceptor dysregulation in depression. Platelet-rich plasmas obtained from 22 unipolar depressed patients and 25 healthy subjects were preincubated with 20 mumol/L of epinephrine for various lengths of time prior to stirring. By comparing the subsequent extents of aggregation, we observed significantly less desensitization at 4, 20, 30, or 60 minutes postepinephrine exposure (p < or = .05) in depressed patients as compared to healthy controls. This blunted desensitization appeared to be due to a delayed onset of desensitization during the first 0.5 to 2 minutes after epinephrine exposure, since thereafter, the monoexponential desensitization rate did not differ in depressed patients, but the extent of desensitization remained less as compared to healthy subjects. The extent of desensitization was correlated (r = -0.48, p = .02) with the density (Bmax) of the alpha 2-adrenoceptor high-affinity state, as detected in undesensitized platelet membranes by p125I-clonidine binding. An elevation was also observed in the density of nonadrenergic p125I-clonidine-binding sites (putative imidazoline I1 sites) in platelet membranes from depressed patients compared to healthy control subjects. Following treatment with desipramines, the patients (n = 15) displayed more normal (nonblunted) extents of desensitization of aggregation, and the Bmax values for the putative I1 sites were at the levels of healthy controls. If similar aberrations exist in neurons of depressed patients, this may explain a dysregulation of the noradrenergic system believed to underlie depression.

The calcium-independent transient outward potassium current in isolated ferret right ventricular myocytes. II. Closed state reverse use-dependent block by 4-aminopyridine

Block of the calcium-independent transient outward K+ current, I(to), by 4-aminopyridine (4-AP) was studied in ferret right ventricular myocytes using the whole cell patch clamp technique. 4-AP reduces I(to) through a closed state blocking mechanism displaying "reverse use-dependent" behavior that was inferred from: (a) development of tonic block at hyperpolarized potentials; (b) inhibition of development of tonic block at depolarized potentials; (c) appearance of "crossover phenomena" in which the peak current is delayed in the presence of 4-AP at depolarized potentials; (d) relief of block at depolarized potentials which is concentration dependent and parallels steady-state inactivation for low 4-AP concentrations (V1/2 approximately -10 mV in 0.1 mM 4-AP) and steady-state activation at higher concentrations (V1/2 = +7 mV in 1 mM 4-AP, +15 mV in 10 mM 4-AP); and (e) reassociation of 4-AP at hyperpolarized potentials. No evidence for interaction of 4-AP with either the open or inactivated state of the I(to) channel was obtained from measurements of kinetics of recovery and deactivation in the presence of 0.5-1.0 mM 4-AP. At hyperpolarized potentials (-30 to -90 mV) 10 mM 4-AP associates slowly (time constants ranging from approximately 800 to 1,300 ms) with the closed states of the channel (apparent Kd approximately 0.2 mM). From -90 to -20 mV the affinity of the I(to) channel for 4-AP appears to be voltage insensitive; however, at depolarized potentials (+20 to +100 mV) 4-AP dissociates with time constants ranging from approximately 350 to 150 ms. Consequently, the properties of 4-AP binding to the I(to) channel undergo a transition in the range of potentials over which channel activation and inactivation occurs (-30 to +20 mV). We propose a closed state model of I(to) channel gating and 4-AP binding kinetics, in which 4-AP binds to three closed states. In this model 4-AP has a progressively lower affinity as the channel approaches the open state, but has no intrinsic voltage dependence of binding.

The calcium-independent transient outward potassium current in isolated ferret right ventricular myocytes. I. Basic characterization and kinetic analysis

Enzymatically isolated myocytes from ferret right ventricles (12-16 wk, male) were studied using the whole cell patch clamp technique. The macroscopic properties of a transient outward K+ current I(to) were quantified. I(to) is selective for K+, with a PNa/PK of 0.082. Activation of I(to) is a voltage-dependent process, with both activation and inactivation being independent of Na+ or Ca2+ influx. Steady-state inactivation is well described by a single Boltzmann relationship (V1/2 = -13.5 mV; k = 5.6 mV). Substantial inactivation can occur during a subthreshold depolarization without any measurable macroscopic current. Both development of and recovery from inactivation are well described by single exponential processes. Ensemble averages of single I(to) channel currents recorded in cell-attached patches reproduce macroscopic I(to) and indicate that inactivation is complete at depolarized potentials. The overall inactivation/recovery time constant curve has a bell-shaped potential dependence that peaks between -10 and -20 mV, with time constants (22 degrees C) ranging from 23 ms (-90 mV) to 304 ms (-10 mV). Steady-state activation displays a sigmoidal dependence on membrane potential, with a net aggregate half-activation potential of +22.5 mV. Activation kinetics (0 to +70 mV, 22 degrees C) are rapid, with I(to) peaking in approximately 5-15 ms at +50 mV. Experiments conducted at reduced temperatures (12 degrees C) demonstrate that activation occurs with a time delay. A nonlinear least-squares analysis indicates that three closed kinetic states are necessary and sufficient to model activation. Derived time constants of activation (22 degrees C) ranged from 10 ms (+10 mV) to 2 ms (+70 mV). Within the framework of Hodgkin-Huxley formalism, Ito gating can be described using an a3i formulation.

Effects of extracellular ATP on ICa, [Ca2+]i, and contraction in isolated ferret ventricular myocytes

The effects of extracellular ATP on the voltage-activated "L-type" Ca current (ICa), action potential, resting and transient intracellular Ca2+ levels, and cell contraction were examined in enzymatically isolated myocytes from the right ventricles of ferrets. With the use of the whole cell patch-clamp technique, extracellular ATP (10(-7) to 10(-3) M) inhibited ICa in a time- and concentration-dependent manner. ATP decreased the peak amplitude of ICa without altering the residual current at the end of 500-ms clamp steps. The concentration-response relationship for ATP inhibition of ICa was well described by a conventional Michaelis-Menten relationship with a half-maximal inhibitory concentration of 1 microM and a maximal effect of 50%. Consistent with its inhibitory effect on ICa, ATP hyperpolarized the plateau phase and shortened the action potential duration. In fura-2-loaded myocytes, extracellular ATP did not change the resting myoplasmic Ca2+ levels; however, when current was elicited under voltage-clamp conditions, ATP both decreased the myoplasmic intracellular Ca2+ transient and inhibited the degree of cell shortening. Our results suggest that ATP could be a genuine and potent extracellular modulator of cardiac function in ferret ventricular myocardium.

Neuromodulation of calcium current by extracellular ATP in isolated ventricular myocytes

The effects of extracellular ATP on the L-tpe Ca2+ current (ICa), action potential, and resting and intracellular Ca2+ levels were examined in enzymatically isolated myocytes from the right ventricles of ferrets. Extracellular ATP decreased the peak amplitude of ICa in a time- and concentration-dependent manner. The concentration-response relationship for ATP inhibition of ICa was well described by a conventional Michaelis-Menten relationship with a half maximal inhibitory concentration of 1 microM and a maximal effect of 50%. Extracellular ATP did not change the resting myoplasmic Ca2+ levels; however, it did decrease the Ca2+ transient. The effects of extracellular ATP were mediated independently of adenosine A1 receptors and a pertussis-toxin sensitive G protein. Pharmacological characterization of receptor subtype using ATP analogs was consistent with ATP binding to a P2Y type receptor.

3D MRI of the cervical spine: low flip angle FISP vs. Gd-DTPA TurboFLASH in degenerative disk disease

The authors undertook this study to compare bright and dark CSF three-dimensional (3D) gradient-echo (GE) MR techniques to answer the following questions: Could a single Gd-DTPA enhanced T1-weighted GE volume sequence (with multiplanar reformats) be diagnostically equivalent for degenerative cervical disk disease to a standard sequence consisting of sagittal T1-weighted spin echo and axial low flip angle volume GE images (with reformatted images)? Does performing oblique coronal reformats perpendicular to the course of exiting cervical nerve roots improve diagnostic confidence over axial images alone? Thirty-one consecutive patients received a "routine" MR examination consisting of a sagittal T1-weighted spin echo and axial low flip angle volume sequence (FISP) [(35/7/5), 64 slices, 2 mm slice thickness, 192 x 256 matrix, 7.2 min]. Each patient was then given 0.1 mmol/kg Gd-DTPA intravenously, and reimaged with a T1-weighted volume GE sequence [(13/6/12), acquired as 128-1.2 mm coronal partitions, 192 x 256 matrix, 5.5 min]. Sequences were reconstructed on the standard diagnostic console in 1 mm increments. Sets of examinations (routine vs T1-weighted volume) were independently interpreted by three neuroradiologists for location, type, and severity of extradural degenerative disease. There was no strong or consistent trend for increased detection of disease by one imaging sequence over the other. For lateral disk disease, only 3% of the observations were in discordance. For disk disease, there was close agreement in the severity scores. All readers indicated that additional information was provided by the reformatted images more frequently with TurboFLASH (fast low angle shot) than with FISP. All readers indicated that increased confidence was provided by the reformatted images more frequently with TurboFLASH than with FISP. A single 3D contrast-enhanced TurboFLASH sequence is diagnostically equivalent to a set of two-dimensional T1-weighted sagittal spin echo and 3D axial low flip angle sequences for assessing the location and degree of cervical extradural degenerative disease. A screening examination of the cervical spine could be performed with a single contrast-enhanced 5.2 min study, and then relying on computer postprocessing to provide additional imaging planes.

Protein kinase C mediated activation and phosphorylation of Ca(2+)-pump in cardiac sarcolemma

The effects of purified protein kinase C (PKC) on the Ca(2+)-pumping ATPase of cardiac sarcolemma were investigated. The addition of PKC to sarcolemmal vesicles resulted in a significant increase in ATP-dependent Ca2+ uptake, by increasing the calcium affinity by 2.8-fold (Km 0.14 vs. 0.4 microM for control) and by increasing Vmax from 5 to 6.8 nmol.mg protein-1.min-1. The addition of PKC also stimulated Ca2+ ATPase activity in sarcolemmal preparations. This activity was increased further upon the addition of calmodulin. These results suggest that PKC stimulates Ca2+ ATPase through a kinase-directed phosphorylation. The addition of PKC to a purified preparation of Ca2+ ATPase in the presence of [gamma-32P]ATP resulted in a 100% increase in phosphorylation that was dependent on the presence of Ca2+, phosphatidylserine, and phorbol 12,13-dibutyrate. These results demonstrate that the Ca2+ ATPase of canine cardiac muscle can be phosphorylated by PKC in vitro, resulting in increased affinity of the Ca2+ ATPase for Ca2+ and increase in the Ca2+ pump pumping rate. The results suggest that the Ca(2+)-pumping ATPase in heart tissue can be stimulated by PKC, thereby regulating the intracellular Ca2+ levels in whole heart.

B----Z DNA conformational changes induced by a family of dinuclear bis(platinum) complexes

The reactions of bis(platinum) complexes of general formula [(PtClm(NH3)3-m)2(NH2(CH2)nNH2)]2(2-m)+ were studied with poly(dG-dC).poly(dG-dC), poly(dG-m5dC).poly(dG-m5dC) and poly(dG).poly(dC). When m = 0 (Complexes II, n = 2,4) the complexes are saturated 4+ cations capable only of electrostatic interactions with the polynucleotide. Where m = 1 the complexes contain two monodentate platinum coordination spheres with the chloride trans to the diamine bridge (Complexes I, n = 2,4, 1,1/t,t). Complexes I give CD spectra characteristic of a 'Z-like' conformation upon reaction with poly(dG-dC).poly(dG-dC) and poly(dG-m5dC).poly(dG-m5dC) but not poly(dG).poly(dC). The B----Z transition appears independent of interplatinum diamine chain length. As little as 1 bis(platinum) complex per 25-30 base pairs is sufficient to observe the Z-like spectrum. Covalent binding is however not a prerequisite for Z-DNA formation because the polyvalent cations II are also very effective in inducing the B----Z transition in either poly(dG-dC).poly(dG-dC) or poly (dG-m5dC).poly(dG-m5dC). In these cases, the concentrations of II required are significantly lower than analogous monomeric agents such as [Co(NH3)6]3+. The possible biological consequences of the Z-DNA induction by bis(platinum) complexes are discussed.

Additional ecological evidence: lipids and breast cancer mortality among women aged 55 and over in China

That dietary fat increases breast cancer risk has been strongly supported by international data collected among developed countries during the past few decades. Population aggregates with elevated lipid intake have tended to report elevated breast cancer incidence and mortality. This study is an ecological analysis of the association of various indicators of lipid intake with breast cancer mortality in 65 county-wide population aggregates in the People's Republic of China. Although the result is consistent with a positive association between lipid intake and breast cancer risk, the observed association is weaker than the association previously observed. This finding provides only modest support for the possibility of a diet-breast cancer link.

Endogenous substrates of rat heart protein kinase C type I, II, and III isozymic forms in cardiac sarcolemma

The endogenous substrate proteins of rat cardiac protein kinase C type I, II, and III isozymic forms were studied in rat cardiac sarcolemma. The 19-, 21-, 29-, 35-, and 95-kDa proteins were phosphorylated by both types II and III, but not type I. The extent of phosphorylation by individual protein kinase C isozymic forms was additive and equal to the extent of phosphorylation observed when a mixture of isozymic forms was employed. The extent of phosphorylation of the 21-kDa protein by type III was much higher than that by type II. These results suggest that the protein kinase C isozymes have preferences for specific endogenous substrate proteins. The phosphorylation of these endogenous substrate proteins by protein kinase C isozymes probably plays a role in cardiac cell functions.

Rapid automated quantitation of isoleucine, leucine, tyrosine and phenylalanine from dried blood filter paper specimens

Isothermal and isocratic HPLC chromatography for rapid quantitation of isoleucine and leucine (merged peak), tyrosine and phenylalanine from a single dried blood filter paper specimen (1/8" dot blot) is described. The net chromatography time of the relevant peaks is less than 3 min. The results can be used to screen for PKU, MSUD, and tyrosinemia in one single assay. The advantage for early determination of PKU by simultaneous quantitation of both phenylalanine and tyrosine with the determination of their ratio is discussed. Using a dual column system this procedure might be suitable for large-scale newborn screening.

Carbachol-stimulated phosphorylation of a 170-kDa endogenous protein in avian salt gland cells

The effect of cholinergic stimulation of cellular protein phosphorylation was studied using an intact cell preparation isolated from the avian salt gland. Isolated cells were allowed to incorporate 32Pi into the cellular ATP pool and then challenged with compounds known to induce ion secretion in this tissue. Addition of carbachol resulted in a time- and concentration-dependent (EC50 = 500 nM) increase in 32Pi content of a 170-kDa protein (pp170). The stimulated phosphorylation could be blocked by the inclusion of atropine (100 microM). Subcellular fractionation studies localized pp170 to the plasma membrane fraction of the tissue. The integral nature of this protein was demonstrated by detergent-solubilization experiments with Triton X-100. The possibility that carbachol stimulates phosphorylation of pp170 via activation of protein kinase C (PKC) was investigated. Incubating salt gland cells with 4 beta-phorbol 12-myristate 13-acetate (PMA; 1 microM) or carbachol (100 microM) resulted in a translocation of soluble PKC from the cytosol to a plasma membrane fraction. Addition of either PMA (1 microM) or ionomycin (1 microM) alone did not enhance phosphorylation of pp170. A 4.5-fold increase in the phosphorylation state of pp170 was only observed when PMA and ionomycin were added concurrently. Preincubation of salt gland cells with PKC inhibitors H-7 (50 microM) or staurosporine (10 microM) inhibited the carbachol-stimulated phosphorylation of pp170. These findings suggest that carbachol mediates its secretomimetic effects via activation of PKC and that pp170 may represent a novel integral membrane PKC substrate protein.

Purification and characterization of protein kinase C isozymes from rat heart

A calcium-sensitive, phospholipid-dependent protein kinase (protein kinase C) and its three isozymes were purified from rat heart cytosolic fractions utilizing a rapid purification method. The purified protein kinase C enzyme showed a single polypeptide band of 80 KDa on SDS-polyacrylamide gel electrophoresis, and was totally dependent on the presence of Ca2+ and phospholipid for activity. Diacylglycerol was also found to stimulate enzymatic activity. Autophosphorylation of the purified PKC showed an 80 KDa polypeptide. The identity of the purified protein was also verified with monoclonal antibodies specific for PKC. Further fractionation of the purified PKC on a hydroxylapatite column yielded three distinct peaks of enzyme activity, corresponding to type I, II and III based on similar chromatographic behaviour as the rat brain enzyme. All three forms were entirely Ca2+ and phosphatidylserine dependent. Type II was found to be the most abundant. Type I was found to be highly unstable. PKC activity studies demonstrate that types II and III isozymic forms are different with respect to their sensitivity to Ca2+.

Comparison of chemical reactivity, cytotoxicity, interstrand cross-linking and DNA sequence specificity of bis(platinum) complexes containing monodentate or bidentate coordination spheres with their monomeric analogues

The properties of a new bis(platinum) complex containing two monodentate coordination spheres, [(trans-PtCl(NH3)2)2H2N(CH2)4NH2]Cl2 (1,1/t,t), are reported. Comparison is made with respect to chemical reactivity, in vitro biological activity in murine and tumor cells, DNA conformational changes, cross-linking efficiency, and sequence specificity between this complex and the previously reported complex containing two bidentate platinum atoms, [(Pt(mal)(NH3))2H2N(CH2)4NH2] (2,2/c,c), as well as with their respective monomeric analogues, [PtCl(dien)]Cl and cis-[PtCl2(NH3)2](cis-DDP). While both bis(platinum) complexes are active against cis-DDP-resistant cells, the monodentate bis(platinum) complex (1,1/t,t) has a lower resistance factor than the complex with bidentate coordination spheres (2,2/c,c). More importantly, this property is repeated in a human ovarian carcinoma cell line. DNA-binding studies show that DNA interstrand cross-linking is more efficient for the 1,1/t,t complex. DNA sequencing studies employing the exonuclease activity of T4-polymerase demonstrate that there are a variety of binding sites; some are common to all complexes and some common to both bis(platinum) complexes, while the monodentate 1,1/t,t species also reacts at unique sites, not attacked by any of the other complexes studied. The circular dichroism of CT DNA modified by the 1,1/t,t complex is also unique and is not seen for any of the other agents.

Cytotoxicity and antitumor activity of bis(platinum) complexes. A novel class of platinum complexes active in cell lines resistant to both cisplatin and 1,2-diaminocyclohexane complexes

The in vitro cytotoxicity and in vivo antitumor activity of bis(platinum) complexes of general formula [(PtX2-(L))2H2N(CH2)nNH2] (L = NH3, X = Cl or X2 = malonato or where L = py, X = Cl) is reported. Chloride complexes [(PtCl2(NH3]2H2N(CH2)nNH2] may exist as three possible isomers: those containing both coordination units in the cis configuration (2,2/c,c), both coordination units in the trans configuration (2,2/t,t), and the mixed cis,trans species (2,2/c,t), whose synthesis is reported here. The preparation of further complexes with sterically hindered diamine backbones, such as 2,5-dimethyl-2,5-hexanediamine, is exemplified. The biological activity of all complexes were compared. The 2,2/c,c complexes are particularly active in tissue culture in cells resistant both to cisplatin and its 1,2-diaminocyclohexane (dach) analogue. The inhibition of DNA synthesis in L1210/0 cells by the 2,2/c,c complexes is equivalent to that of cisplatin. The presence of at least one cis-[Pt(amine)2] unit appears necessary for activity in cell lines sensitive to cisplatin.