Dual effects of nicardipine: evidence from intracellular Ca2+ transients and twitch contractions observed in single myocytes obtained from rat heart

Mechanisms responsible for dual actions of nicardipine were examined using myocytes isolated from ventricular muscle of rat heart. About 60% of isolated rat myocytes showed positive force-frequency relationships. These cells had lower intracellular Ca2+ concentrations at rest. In the remaining cells that had higher resting Ca(2+)-concentrations, an increase in frequency of stimulation from 1 Hz to 2 Hz produced either no change or reduction in the amplitude of Ca2+ transients and twitch contractions. In 13 of 34 myocytes that showed positive force-frequency relationships, nicardipine enhanced the Ca2+ transient and produced sustained positive inotropic effects. In 11 of 20 cells that showed negative force-frequency relationships, nicardipine produced negative inotropic effects. Inhibition was partly reversed by an increase in extracellular CaCl2 concentration from 1.2 to 3.6 mM. In the remaining cells, nicardipine failed to either increase or decrease the amplitude of Ca2+ transient or twitch contraction. Bay K-8644 produced positive inotropic effects in most cells. These results indicate that nicardipine either enhances or inhibits Ca2+ transients and twitch contractions depending on the Ca2+ loading state of myocytes. The present results are consistent with the hypothesis that nicardipine stabilizes the state of Ca2+ channels, either in the inactivated state in cells that are well loaded with Ca2+, or in the activated state when the degree of Ca2+ loading is relatively low.

[Cloning and sequencing of the major surface antigen gene of Toxoplasma gondii]

According to the published gene sequence of the major surface antigen (P30), a pair of primers were designed and synthesized. At the 5' end of sense and anti-sense strand of the primers, EcoRI and BamHI sites were added, respectively. Using PCR, the coding sequences of P30 gene were amplified. The amplified gene fragments and plasmid pBV220 were digested with EcoRI and BamHI, and then ligated. The inserted gene fragment was sequenced by the chain termination method. The reading revealed that nucleotide sequence determined here was the same as the sequence published by Burg (1988), except one base was exchanged. The recombinant plasmid pBV220-P30 was constructed.

Stable expression of the rat GLP-I receptor in CHO cells: activation and binding characteristics utilizing GLP-I(7-36)-amide, oxyntomodulin, exendin-4, and exendin(9-39)

Glucagon-like peptide-I (GLP-I) is a potent insulinotropic peptide that mediates its actions at pancreatic B-cells via specific receptors. In the present study we stably expressed the rat B-cell GLP-I receptor in CHO cells and studied binding characteristics and receptor activation utilizing the naturally occurring receptor agonist GLP-I(7-36)-amide (GLP-I), the proglucagon-derived GLP-I-related peptide oxyntomodulin, the GLP-I receptor agonist exendin-4, and the specific antagonist exendin(9-39). The potencies to displace [125I]GLP-I from the receptor were GLP-I > exendin-4 > exendin(9-39) > oxyntomodulin, and to displace [125I]exendin-4 GLP-I = exendin-4 > exendin(9-39) > oxyntomodulin. cAMP production was stimulated equally by GLP-I and exendin-4. Oxyntomodulin was less potent to stimulate cAMP generation. Exendin(9-39) blocked the stimulatory action of GLP-I and exendin-4 on cAMP production, but not that of oxyntomodulin. This study shows that GLP-I and exendin-4 are potent agonists at the transfected rat B-cell GLP-I receptor whereas oxyntomodulin is only a weak GLP-I receptor agonist. Furthermore, exendin(9-39) is a potent GLP-I receptor antagonist. This peptide is a valuable tool to further study the physiological actions of GLP-I.

Bioconcentration of cadmium in water hyacinth (Eichhornia crassipes) in relation to thiol group content

To study the bioconcentration of cadmium in water hyacinth, the plants were exposed to water containing 2 microg Cd2+/ml for extended periods of time. Three strains from several exposures during a 30-day period were sampled for the analyses of cadmium and thiol group. The data showed that the plant concentrates cadmium mainly in the roots and that the cadmium uptake is proportional to the increase of the thiol group content. The latter suggests the possibility of using the thiol group content to assess the bioconcentration of heavy metal ions in water hyacinth and as a general parameter for monitoring the heavy metal pollution of water. A simple two-compartmental model was used to simulate the kinetics of cadmium uptake. The calculated bioconcentration factor matches the one derived directly from experimental data, indicating the adequacy of the model.

Detection of the human glucagon-like peptide 1(7-36) amide receptor on insulinoma-derived cell membranes

125I-glucagon-like peptide 1(7-36)amide was covalently cross-linked to a specific binding protein in human insulinoma cell membranes. A single radiolabeled band at M(r) 63,000 was identified by SDS-PAGE after solubilization of the ligand-binding protein complex. The molecular weight of this apparent GLP-1 receptor in human endocrine pancreatic tissue was of identical size as the GLP-1 receptor on rat insulinoma-derived RINm5F cell membranes. The radiolabeled band was undetectable when 1 microM of unlabeled GLP-1(7-36)amide or of the GLP-1 antagonist exendin(9-39)amide was included in the binding assay. Utilizing isolated poly-A+ RNA from the human insulinoma and a 1,500 bp Eco-RI fragment of the cDNA coding for the rat GLP-1(7-36)amide receptor for Northern blot analysis, a main hybridization signal at about 7 kb was found by Northern blotting. Our data provide the first direct evidence of the existence of GLP-1 receptors in human endocrine pancreatic tissue.

Introgression of Elymus trachycaulus chromatin into common wheat

A number of wheat-Elymus trachycaulus (2n = 4x = 28, genomically StStHtHt) chromosome addition, substitution, and translocation lines were isolated from the derivatives of an E. trachycaulus x wheat hybrid. Eighteen out of a total of 28 chromosome arms of E. trachycaulus were recovered in the addition lines. The genomic affinity of individual E. trachycaulus chromosomes was analysed by comparative chromosome banding and in situ hybridization using genome-specific repetitive DNA sequences as probes. The homoeology of the E. trachycaulus chromosomes added to wheat was determined by storage protein, isozyme, and restriction fragment length polymorphism analysis. Alloplasmic wheat-E. trachycaulus chromosome additions were isolated which only involved chromosome 1Ht and 1St that carry fertility restoration gene Rf-Ht1 and Rf-St1, respectively. Based on the results of production and characterization of a wheat-E. trachycaulus 5Ht(5B) substitution line, it is likely that some wheat chromosomes can be well compensated genetically by E. trachycaulus chromosomes. Several spontaneous wheat-E. trachycaulus chromosome translocation lines were detected. All the translocation lines involved either 1Ht or 1St. To estimate the potential of recombination between wheat and E. trachycaulus chromosomes, a backcross population derived from a plant which was double monosomic for chromosomes 7A and 7AL.7AS-1StS and a ph1b gene was developed. The plants from this population were analysed for 1St-specific genetic markers and no recombinant was recovered.

Different species-specific chromosome translocations in Triticum timopheevii and T. turgidum support the diphyletic origin of polyploid wheats

Triticum timopheevii ssp. timopheevii and T. timopheevii ssp. araraticum were analysed by sequential N-banding and genomic in situ hybridization. Three chromosomes, 6At, 1G and 4G, were involved in At-G intergenomic translocations in all six lines analysed. These chromosomes may be derived from a cyclic translocation that is species-specific to T. timopheevii. In contrast, Triticum turgidum has a species-specific cyclic translocation involving chromosomes 4A, 5A and 7B. The discovery of different species-specific chromosome translocations supports the diphyletic hypothesis of the evolution of tetraploid wheats. The results from genomic blocking analysis also revealed that the chromosomes of Aegilops speltoides are closer to the G genome than the B genome chromosomes. The possible role of species-specific translocations in the evolution of wheat is discussed.

Induction of an adaptive response to dominant lethality and to chromosome damage of mouse germ cells by low dose radiation

In the present paper, dominant lethal mutations, chromosome aberrations in spermatocytes and reciprocal translocations in stem spermatogonia were analyzed after whole body exposure of mice to X-radiation. Results both from chromosome aberrations in spermatocytes and for reciprocal translocations in spermatogonia showed that pre-exposure to low doses up to 200 mGy could induce a significant dose-dependent reduction in adapted mice compared to the non-adapted mice; the lower the adaptive dose, the greater the reduction. For dominant lethal mutations, it was found that spermatogonia (both stem cells and differentiated cells) and spermatocytes adapted to 50 mGy X-rays could show an adaptive response, but spermatids and spermatozoa could not.

[Identification of the metabolites of T-018 in the urine in female rats]

In order to identify the metabolites of T-018 (alpha-iso-butyl-p-hydroxybenzyl alcohol) in vivo, T-018 labelled with deuterium and unlabelled T-018 were administered intragastrically to two female rats. Based on the results measured by gas chromatograph mass spectrometry (GC/MS), T-018 and its four metabolites were found in the urinary extracts of the rats.

A 'zebra' chromosome arising from multiple translocations involving non-homologous chromosomes

An alloplasmic wheat line carrying a 'zebra' chromosome z5A was isolated from the derivatives of an Elymus trachycaulus x Triticum aestivum cv Chinese Spring hybrid. Chromosome z5A was named zebra because of its striped genomic in situ hybridization pattern. z5A consists of four chromosome segments derived from E. trachycaulus and four chromosome segments, including the centromere, from wheat. The short arm of z5A paired with the telocentric chromosome 1H(t)S of E. trachycaulus and the long arm with the long arm of normal 5A. z5A also carried several genetic markers derived from 1H(t)S. Chromosome 1H(t) was the only E. trachycaulus chromosome found in the sib plants of a previous generation from which z5A was derived. Monosomic 5A and telocentric chromosome 5AL were also found in most of the sib plants. The zebra chromosome most probably originated from spontaneous multiple translocations between chromosomes 5A and 1H(t)S or 5A and 1H(t).

Modulated excitation of singly ligated carboxyhemoglobin

We have extended the method of modulated excitation, a small perturbation kinetic method, to study ligand binding and conformational change of hemoglobin tetramers with a single ligand bound. To restrict the excitation to the first ligand, only 1% of the hemes have bound CO, and the remainder are kept unliganded. A detailed theory is presented which agrees well with the experimental observations. This method of observing ligand recombination also provides a novel and simple method for determination of hemoglobin concentration. Additional relaxation processes are also observed. By fitting independently determined spectra to the spectra associated with the relaxations, these processes are assigned as thermal excitation and thermally driven protonation/deprotonation reactions. These added relaxations arise from the deoxy-Hb portion of the samples, and demonstrate that modulated excitation can be used effectively for temperature perturbation in the absence of photodissociation. The spectra observed are not well described by the spectra of allosteric change, however, and we conclude that there is no significant mixing of quaternary states at the first ligation step. In an appendix we present a derivation of the particular features seen in thermally modulated protonation reactions.

[Capillary blood viscosimeter of the microcomputer]

On the basis of specific property of non-Newtonian fluid (blood) we have worked out the formula of capillary blood viscosimeter:sheat stress tau alpha = alpha rho gh/2L shear rate f (tau alpha) = 1/pi alpha 3 [3q + h(dq/dh)] and designed and produced the prototype. Repetition experiments have indicated that the property of the instrument is stable, and a comparison of the prototype with the cone and plate viscosimeter has demonstrated the reliability of the measurements.

Conversion of a dorsal-dependent silencer into an enhancer: evidence for dorsal corepressors

In Drosophila, the dorsal (dl) morphogen gradient initiates the differentiation of the embryonic mesoderm and neuroectoderm by activating the expression of regulatory genes (e.g. twist and snail) in a concentration-dependent manner. dl also functions as a repressor that establishes the dorsal epidermis and amnioserosa by restricting regulatory genes such as dpp and zen to dorsal regions of the embryo. The ability of dl to function as both an activator and repressor distinguishes it from the bicoid morphogen, which appears to function solely as an activator. In an effort to determine how dl functions as a repressor we have performed a detailed characterization of a zen silencer element, called the VRE, which mediates ventral repression in response to the dl gradient. A minimal 110 bp VRE sequence is identified, which is able to silence the ventral expression of a heterologous promoter. This sequence contains two dl binding sites as well as binding sites for additional nuclear factors present in early embryos. Mutations in the latter binding sites convert the minimal VRE into an enhancer, which mediates transcriptional activation in ventral regions in response to dl. These results suggest that dl is intrinsically an activator, but is converted into a potent silencer when it interacts with neighboring corepressors.

Regulation of glutamic acid decarboxylase diabetes autoantigen expression in highly purified isolated islets from Macaca nemestrina

Macaca nemestrina, which may have larger and more numerous pancreatic islets than other species, was used for large scale islet isolation by ductal collagenase perfusion and Ficoll gradient centrifugation. The average yield was 51,000 islet equivalents per pancreas, or 8,750 islets equivalents per g. The average purity was 91%, often exceeding 95%. These are the highest reported size, purity, and yield per g of any nonautomated primate islet series. Perifusion with glucose, arginine, and isobutylmethylxanthine showed appropriate biphasic insulin secretion. Unlike that in the rat, human islet glutamic acid decarboxylase (GAD) isoform expression is restricted. However, glycemic regulation of GAD expression has been shown only in rats. We, therefore, tested hypotheses that M. nemestrina islets also have restricted GAD expression, that GAD expression in primates is stimulated by glucose, and that this stimulation remains restricted to the 64,000 mol wt (GAD65) isoform. Immunoprecipitation of labeled islet extracts showed that GAD65 expression increased 16.7 +/- 0.6-fold during high glucose in vitro culture. After controlling for observed increases in protein synthesis, specific glucose stimulation was still 4.2 +/- 0.2-fold. Specific antisera revealed no GAD67 expression under basal conditions, and isoform restriction was maintained during stimulation. Increased GAD65 synthesis thus accounts for glucose stimulation of 64K expression. These time- and concentration-dependent effects of glucose suggest that hyperglycemia increases autoantigenicity and may accelerate beta-cell destruction in primates, supporting a role for beta-cell rest in insulin-dependent diabetes mellitus prevention.

[The turnover of three amino acids in the plasma of chronic renal failure patients]

In this study, three amino acids (Ala, Leu and Phe) labelled with stable isotopes were administered to a group of CRF patients and of normal controls, respectively. Based on the measurement of gas chromatography and mass spectrometry, a series of kinetic parameters of amino acid metabolism were calculated and the differences between the two groups were compared.

Allosteric kinetics and equilibria of triligated, cross-linked hemoglobin

Using modulated excitation, we have measured the forward and reverse rates of the allosteric transition between relaxed (R) and tense (T) quaternary structures for triply ligated hemoglobin (Hb), cross-linked between the alpha chains at Lys 99. Oxygen, carbon monoxide, and water were used as ligands and were studied in phosphate and low Cl- bis-Tris buffers at neutral pH. Since the cross-link prohibits disproportionation, triply ligated aquomet Hb species with ferrous beta chains were specifically isolated by isoelectric focusing. Modulated excitation provides rate pairs and therefore gives equilibrium constants between quaternary structures. To coordinate with that information, oxygen binding curves of fully ferrous and tri-aquomet Hb were also measured. L3, the equilibrium constant between three liganded R and T structures, is determined by modulated excitation to be of order unity for O2 or CO (1.1 to 1.5 for 3O2 and 0.7 for 3CO bound), while with three aquomet subunits it is much greater (> or = 23). R-->T conversion rates are similar to those found for HbA, with weak sensitivity to changes in L3. The L3 values from HbXL O2 were used to obtain a unique allosteric decomposition of the ferrous O2 binding curve in terms of KT, KR, and L3. From these values and the O2 binding curve of tri-aquomet HbXL, L3 was calculated to be 2.7 for the tri-aquomet derivative. Consistency in L3 values between equilibrium and modulated excitation data for tri-aquomet-HbXL can be achieved if the equilibrium constant for O2 binding to the alpha chains is six times lower than that for binding to the beta chains in the R state, while the cooperative properties remain homogeneous. The results are in quantitative agreement with other studies, and suggest that the principal effect of the cross-link is to decrease the R state and T state affinity of the alpha subunits with almost no change in the affinity of the beta subunits, leaving the allosteric parameters L and c unchanged.

Responses of the bovine mammary artery to angiotensins

The main objective of our study was to determine whether angiotensins cause vasoconstriction of mammary arterial segments in vitro. Once this action was established, its specificity was determined. Mammary arterial sections were obtained from lactating cattle at slaughter. Vessel sections were placed in a gravity-fed, closed, perfusion apparatus, and flow was measured by a transit-time flow sensor mounted in-line. Treatments were administered by injection into a leurlock port located proximal to the sensor. Angiotensins I, II, and III induced a dose-dependent vasoconstriction of arterial segments at concentrations of 5 x 10(-10) to 5 x 10(-6) M. Angiotensin II receptor antagonists, Saralisin and (Sarl, Thr8)-angiotensin II (5 x 10(-8) M)), inhibited vasoconstriction induced by angiotensins I, II, and III. The angiotensin-converting enzyme inhibitor, Captopril (5 x 10(-8) M), inhibited angiotensin I vasoconstriction, thereby showing that the vasoconstriction by angiotensin I was mediated through its conversion to angiotensin II. These data demonstrated that the mammary artery of lactating cows is responsive to the angiotensin family. Furthermore, mammary arteries contain angiotensin-converting enzyme and specific receptors for angiotensin II. This system may be important in the normal physiological regulation of mammary gland blood flow of lactating cows.

[The metabolism of TMPz in vivo]

The metabolism of tetramethylpyrazine (TMPz) in rats was investigated. Deuterated TMPz and unlabelled TMPz were administered by intragastric perfusion to two rats, respectively. Extracts from urine samples were analyzed within 24h by gas chromatography/mass spectrometry (GC/MS). By applying the ion cluster technique, TMPz and its three metabolites were identified.

Radiation-induced nonhomoeologous wheat-Agropyron intermedium chromosomal translocations conferring resistance to leaf rust

The Agropyron intermedium chromosome 7Ai #2 is the source of the leaf rust resistance gene Lr38 which was transferred to wheat by irradiation. The chromosomal constitutions of eight radiation-induced rust-resistant wheat-Agropyron intermedium derivatives were analyzed by C-banding and genomic in-situ hybridization (GISH). Five lines were identified as wheat Ag. intermedium chromosome translocation lines with the translocation chromosomes T2AS·2AL-7Ai#2L, T5AL · 5AS-7Ai # 2L, T1DS · 1DL-7Ai # 2L, T3DL · 3DS-7Ai#2L, and T6DS · 6DL-7Ai#2L. The sizes of the 7Ai#2L segments in mitotic metaphases of these translocations are 2.42 μm, 4.20 μm, 2.55 μm, 2.78 μm, and 4.19 μm, respectively. One line was identified as a wheat-Ag. intermedium chromosome addition line. The added Ag. intermedium chromosome in this line is different from 7Ai # 2. This line has resistance to leaf rust and stem rust. Based on the rust reactions, and the C-banding and GISH results, the remaining two lines do not contain any Ag. intermedium-derived chromatin.

Binding affinities and cooperative interactions with bHLH activators delimit threshold responses to the dorsal gradient morphogen

The dorsal (dl) morphogen gradient initiates the formation of the mesoderm, neuroectoderm, and dorsal ectoderm by setting different limits of regulatory gene expression along the dorsoventral axis of the early Drosophila embryo. In this paper, we show that low affinity dl-binding sites restrict target gene expression to the ventralmost regions (presumptive mesoderm), where there are peak levels of dl, while high affinity sites permit expression in ventrolateral regions (mesoderm and mesectoderm) containing intermediate levels of the morphogen. Activation by low levels of dl in lateral regions (the presumptive neuroectoderm) depends on cooperative DNA binding interactions between dl and bHLH proteins. The snail repressor blocks this interaction and restricts expression to the neuroectoderm. We discuss how enhancers serve as templates to bring weakly interacting regulatory factors into close proximity so that they can function combinatorially to activate and repress transcription.

Protein kinase C: a novel target for inhibiting gastric cancer cell invasion

BACKGROUND

Gastric adenocarcinoma is a common neoplasm worldwide. Patients with completely resected disease often have locoregional recurrence, and adjuvant chemotherapy has failed to reduce the common occurrence of metastases. Protein kinase C (PKC) is thought to be important in tumor cell invasion, but its relationship to gastric cancer cell invasion, and thus metastases, remains unexplored. We recently identified and established invasive and noninvasive human gastric adenocarcinoma cell lines, which can now be used to test agents for inhibition of tumor cell invasion by inhibition of PKC activity.

PURPOSE

The objectives were (a) to test threo-dihydrosphingosine (SPC100221), a specific inhibitor of PKC at its regulatory site, and staurosporine, a potent but nonspecific inhibitor of PKC at its catalytic site, for their effects on gastric cancer cell invasion in vitro and (b) to determine whether the expression of PKC isoforms can distinguish invasive from noninvasive gastric cancer cells.

METHODS

Gastric cancer cell invasion through Matrigel-coated Nuclepore filters in the Boyden chamber assay was analyzed in the presence of graded concentrations of SPC100221 and staurosporine. The invasive SK-GT-1 and SK-GT-5 cell lines and the noninvasive SK-GT-2 and SK-GT-4 cell lines were used. PKC isoform expression was determined by reverse transcription of messenger RNAs to complementary DNA and subsequent amplification by the polymerase chain reaction.

RESULTS

The effects of staurosporine and SPC100221 on tumor cell invasion were tested at drug concentrations that did not inhibit cell proliferation, as evidenced by [3H]thymidine uptake. Staurosporine and SPC100221 at subtoxic doses inhibited human gastric cancer cell invasion by 50% at 5 x 10(-9) M and 2 x 10(-7) M, respectively. The expression of PKC beta was observed in the invasive but not the noninvasive gastric cancer cells. Both types of cells, however, expressed the PKC alpha and PKC gamma isoforms.

CONCLUSIONS

Gastric cancer cell invasion can be inhibited by PKC inhibitors, and expression of PKC beta may be a marker of invasiveness in gastric cancer.

IMPLICATIONS

PKC appears to represent a new target for inhibition of gastric cancer cell invasion, and SPC100221, in view of its PKC specificity, may provide a model for future drug development in this area. Moreover, PKC beta may have a fundamental role in the development of invasive potential in gastric cancer.

Molecular cytogenetic analysis of Agropyron elongatum chromatin in wheat germplasm specifying resistance to wheat streak mosaic virus

Three lines derived from wheat (6x) x Agropyron elongatum (10x) that are resistant to wheat streak mosaic virus (WSMV) were analyzed by chromosome pairing, banding, and in situ hybridization. Line CI15321 was identified as a disomic substitution line where wheat chromosome 1D is replaced by Ag. elongatum chromosome 1Ae-1. Line 87-94-1 is a wheat-Ag. elongatum ditelosomic addition 1Ae-1L. Line CI15322 contains an Ag. elongatum chromosome, 1Ae-2, that substitutes for chromosome 1D. The short arm of 1Ae-2 paired with the short arm of 1Ae-1 at metaphase I (MI) in 82% of the pollen mother cells (PMCs). However, the long arms of these two chromosomes did not pair with each other. In CI15322, the long arm of chromosome 4D has an Agropyron chromosome segment which was derived from the distal part of 1Ae-1L. This translocation chromosome is designated as T4DS·4DL-1L. T4DS·4DL-1Ae-1L has a 0.73 μm distal part of the long arm of 4D replaced by a 1.31 μm distal segment from 1Ae-1L. The major WSMV resistance gene(s) in these lines is located on the distal part of 1Ae-1L.