Fluorescent polyene aliphatics as spectroscopic and mechanistic probes for bacterial luciferase: evidence against carbonyl product from aldehyde as the primary excited species

The fluorescent alpha-parinaric acid (alpha-PAC) and beta-parinaric acid (beta-PAC) were converted to the corresponding aldehydes and alcohols all of which exhibited absorption and fluorescence properties closely resembling those of the parent acids. alpha-PAC and beta-PAC each binds to luciferase in competition with aldehyde. The hydrophobic nature of the aldehyde site was indicated by the enhanced fluorescence quantum yields of the bound alpha-PAC and beta-PAC. These two polyene acids and the beta-parinaryl alcohol were shown to stabilize the luciferase flavin-peroxide intermediate. alpha-Parinaraldehyde (alpha-PAD) and beta-parainaraldehyde (beta-PAD) were active substrates for Vibrio harveyi and Vibrio fischeri luciferases and, for the former enzyme, exhibited Km values similar to and quantum yields about 20-30% as those for decanal and dodecanal. For the V. harveyi luciferase with reduced FMN as a co-substrate, the alpha-PAD- or beta-PAD-initiated luminescence was indistinguishable from the normal emission obtained with octanal (lambda max 495 nm) showing no additional 430-nm component correlatable with emission from excited alpha-PAC or beta-PAC. In reactions using reduced 2-thioFMN for V. harveyi luciferase or reduced FMN for V. fischeri luciferase plus yellow fluorescent protein, the replacement of octanal by beta-PAD again resulted in no additional 430-nm emission. The lack of any emission correlatable with excited alpha-PAC, beta-PAC, or equivalent carbonyl product was not due to the quenching of the polyene moiety by chemical transformation, binding to luciferase, or a 100% energy transfer to the flavin 4a-hydroxide emitter.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of the Xenopus Hox 2.4 gene and identification of control elements in its intron

We report on the Xenopus homolog of the Hox 2.4 gene. This gene occupies the next to 5'-most position in the Xenopus Hox2 complex. Hox 2.4 RNA is first detected at the early neurula stage, reaching a peak at the early tailbud stage, and is localized in the middle and posterior portions of the embryos. Antibodies raised against a fusion protein show expression of Hox 2.4 protein in Xenopus embryos in a band located in the mid spinal cord. Thus, the protein is expressed in a narrower domain than that of Hox 2.4 mRNA. The Xenopus Hox 2.4 antibody cross-reacts readily with mouse embryonic tissue, where the protein is detected in migrating neural crest cells, the dorsal portion of the spinal cord, somites, lateral plate mesoderm, and in the forelimb bud. The Xenopus Hox 2.4 intron shares considerable sequence identity with the intron in the mouse homolog. A reporter gene containing an element from this intron which can bind homeodomain proteins is activated following microinjection into Xenopus embryos. The short distance between the end of the Hox 2.4 cDNA and the start site of the neighboring gene in the complex raises the possibility that this transcriptional element might be shared by two Hox genes.

Single injection of pentobarbital induces long-lasting effects on ANP synthesis and gene expression in the rat atria

To define the long-term effects of pentobarbital sodium on the plasma and atrial atrial natriuretic peptide (ANP) system, experiments were performed in female Sprague-Dawley rats. The plasma levels of immunoreactive (ir) ANP showed chronic as well as acute response to pentobarbital sodium administration. A single dose (30 mg/kg, i.p.) of pentobarbital sodium resulted in a suppression in the plasma levels of irANP up to 1 week of administration. The suppressive effect on plasma irANP concentrations was dose-dependent. Right but not left atrial contents of irANP increased by an administration of pentobarbital sodium up to 4 weeks. ANP mRNA contents of the atrial exposed to pentobarbital sodium began to increase after 2 days, reached to the peak after 2 weeks, and began to return to control values after 6 weeks. Surgical stress accentuated these patterns of plasma and atrial ANP responses to pentobarbital sodium treatment. The present data, therefore, suggest that even a single anesthetic dose of pentobarbital could elicit long-lasting profound changes in ANP system, i.e., changes in gene expression, synthesis and the secretion of ANP.

Presence and release of immunoreactive atrial natriuretic peptide in granulosa cells of the pig ovarian follicle

Atrial natriuretic peptide (ANP) has been reported to be locally synthesized in the ovary although its physiological roles are still unknown. To define the origin of ovarian ANP, we demonstrated the presence and release of immunoreactive (ir) ANP in pig granulosa cells and characterized its biochemical properties. Serial dilution curves made with the extracts of pig granulosa cells, their perfusates and follicular fluid were paralleled to the standard curve of ANP. The amount of irANP in the granulosa cell was 2 fg/cell. The total amount of irANP in granulosa cells significantly correlated with the levels of irANP in follicular fluid. Additionally, the total content of irANP in the follicle negatively correlated with the follicular size. On reverse phase HPLC, the major form of irANP in granulosa cells and follicular fluid was high molecular weight but that in perfusate was low molecular weight. In Northern blot analysis, ANP mRNA was detected in the pig granulosa cells. Immunohistochemistry showed ANP prohormone location in granulosa cells of rat ovary. These data strongly suggest that the granulosa cells synthesize and secrete ANP.

Frog lymph heart synthesizes and stores immunoreactive atrial natriuretic peptide

The presence of immunoreactive atrial natriuretic peptide (irANP) and ANP gene expression in the frog lymph heart was examined by a radioimmunoassay (RIA) combined with HPLC and by Northern blot hybridization of total RNA. Serial dilution curve of the lymph heart extract was paralleled with the RIA standard curve. The lymph heart contained 153.32 +/- 35.80 pg of irANP/mg of wet tissue. The major form of irANP in the frog lymph heart was high molecular weight on reverse-phase and gel permeation high performance liquid chromatography as in the frog atria and ventricles. The frog lymph heart, as well as frog atria and ventricles, was shown to express mRNA coding for ANP. Dense core secretory granules similar to those observed in the mammalian atria were also found in the frog lymph heart. The presence of irANP and the expression of ANP gene in the frog lymph heart suggest that the lymph heart may participate in the regulation of homeostasis of lymph circulation and blood volume change through the synthesis and release of ANP.

Gastrulation in the mouse: The role of the homeobox gene goosecoid

Mouse goosecoid is a homeobox gene expressed briefly during early gastrulation. Its mRNA accumulates as a patch on the side of the epiblast at the site where the primitive streak is first formed. goosecoid-expressing cells are then found at the anterior end of the developing primitive streak, and finally in the anteriormost mesoderm at the tip of the early mouse gastrula, a region that gives rise to the head process. Treatment of early mouse embryos with activin results in goosecoid mRNA accumulation in the entire epiblast, suggesting that a localized signal induces goosecoid expression during development. Transplantation experiments indicate that the tip of the murine early gastrula is the equivalent of the organizer of the amphibian gastrula.

Right atrial predominance of atrial natriuretic peptide secretion in isolated perfused rat atria

In order to investigate the regulatory mechanism for the atrial release of atrial natriuretic peptide (ANP), a perfused rabbit atrial model was devised. In the present experiments, the effect of a reduction in atrial distension on the immunoreactive ANP (irANP) secretion was investigated and compared in the perfused right and left atria of rats. Elevations in right and left atrial pressure resulted in proportional increases in the volume of atrial distension-reduction which was larger in the right than in the left atria. The basal rate of irANP secretion was higher in the right than in the left atria. Increases in the volume of atrial distension-reduction resulted in proportional increases in irANP secretion in both atria. Increment in irANP secretion in response to a reduction in atrial distension was significantly higher in the right than in the left atria. Higher rate of irANP secretion in response to unit volume change was observed in the right atria. Increases in the volume of atrial distension-reduction resulted in accentuated irANP responses in the right atrium. IrANP content was significantly higher in the right than in the left atria. The results suggest that the right atrium is a predominant site in ANP secretion in rats.

Ovarian atrial natriuretic peptide during the rat estrous cycle

The changes in ovarian levels of immunoreactive atrial natriuretic peptide (irANP) and arginine vasopressin (irAVP) were observed during the estrous cycle of rat. We also demonstrated the synthesis of ovarian ANP. In adult 4-day cycling rats, ovarian level of irANP was found to be the highest on proestrus and was to be the lowest on diestrus. Ovarian irANP level inversely correlated with ovarian level of irAVP. On reverse-phase HPLC, two distinct peaks of ovarian irANP, high and low molecular weight forms, existed in the each stage of the estrous cycle. However, no significant changes in plasma and atrial concentrations of ANP were observed during the cycle. The rat ovary contained mRNA coding for ANP. These data showing the synchronized cyclic change of ovarian irANP and irAVP with the estrous cycle suggest that the ovary locally synthesizes ANP and ovarian ANP may play regulatory roles on the follicular fluid dynamics.

Molecular nature of Spemann's organizer: the role of the Xenopus homeobox gene goosecoid

This study analyzes the function of the homeobox gene goosecoid in Xenopus development. First, we find that goosecoid mRNA distribution closely mimics the expected localization of organizer tissue in normal embryos as well as in those treated with LiCl and UV light. Second, goosecoid mRNA accumulation is induced by activin, even in the absence of protein synthesis. It is not affected by bFGF and is repressed by retinoic acid. Lastly, microinjection of goosecoid mRNA into the ventral side of Xenopus embryos, where goosecoid is normally absent, leads to the formation of an additional complete body axis, including head structures and abundant notochordal tissue. The results suggest that the goosecoid homeodomain protein plays a central role in executing Spemann's organizer phenomenon.

Organizer-specific homeobox genes in Xenopus laevis embryos

The dorsal blastopore lip of the early Xenopus laevis gastrula can organize a complete secondary body axis when transplanted to another embryo. A search for potential gene regulatory components specifically expressed in the organizer was undertaken that resulted in the identification of four types of complementary DNAs from homeobox-containing genes that fulfill this criterion. The most abundant of these encodes a DNA-binding specificity similar to that of the Drosophila melanogaster anterior morphogen bicoid. The other three are also homologous to developmentally significant Drosophila genes. These four genes may participate in the regulation of the developmental potential of the organizer.

Gradient fields and homeobox genes

We review here old experiments that defined the existence of morphogenetic gradient fields in vertebrate embryos. The rather abstract idea of cell fields of organ-forming potential has become less popular among modern developmental and molecular biologists. Results obtained with antibodies directed against homeodomain proteins suggest that gradient fields may indeed be visualized at the level of individual regulatory molecules in vertebrate embryos.

Role of membrane sulfhydryl groups in stimulation of renin secretion by sulfhydryl reagents

The present study was designed to address the reactivity and accessibility of the particular class of sulfhydryl groups involved in the regulatory process of renin secretion. Both mercurial (such as P-chloromercuriphenyl sulfonate [PCMPS] and non-mercurial sulfhydryl reagents (for example, 6,6-dithiodinicotinic acid [DTDN]), which very slowly penetrate the cell membrane of intact cells, stimulated renin secretion. The membrane permeant sulfhydryl reagent N-ethylmaleimide had no effect on renin secretion but its membrane impermeant derivative, stilbene maleimide, strongly stimulated secretion. Furthermore, disulfide reducing agents such as dithiothreitol (DTT) had no effect on renin secretion at low concentrations, but strongly inhibited it at high concentrations. Several reagents which are known to primarily deplete cellular reduced glutathione were without effect on renin secretion. The stimulation of renin secretion by PCMPS was rapid in onset, and prevented and reversed by DTT and L-cysteine. Furthermore, the maximal stimulatory effect of PCMPS was not additive to that by diuretics with sulfhydryl reactivity (such as, ethacrynic acid and mersalyl). The stimulatory effect of PCMPS was not affected by diuretics which lack sulfhydryl reactivity (such as, bumetanide and furosemide). These results suggest that sulfhydryl reagents of both with and without diuretic activity stimulate renin secretion by reacting with specific class of sulfhydryl groups which are readily accessible from the extracellular compartment. In addition, these results provide further support the possibility that a sulfhydryl-disulfide interchange in the membrane may play a regulatory role in the renin secretory process.

Overexpression of a homeodomain protein confers axis-forming activity to uncommitted Xenopus embryonic cells

The anteroposterior character of mesoderm induced by a peptide growth factor (XTC-MIF) was tested by transplantation into host Xenopus gastrulae. Both retinoic acid and a homeodomain protein were able to override the anteriorizing effect of the growth factor. Microinjection of a posteriorly expressed homeobox mRNA can respecify anteroposterior identity, transforming head mesoderm into tail-inducing mesoderm. Unexpectedly, overexpression of XIHbox 6 protein in the transplanted cells, without addition of growth factors, caused the formation of tail-like structures. The cells overexpressing XIHbox 6 were able to recruit cells from the host into the secondary axis. The results suggest that vertebrate homeodomain proteins are part of the biochemical pathway leading to the generation of the body axis.

Atrial pressure, distension, and pacing frequency in ANP secretion in isolated perfused rabbit atria

It has been suggested in this laboratory that the principal stimulus for the secretion of atrial natriuretic peptide (ANP) is the reduction of atrial distension and that the secretion of ANP is dependent on both atrial reduction volume and reduction frequency. To investigate the relationship among the changes in atrial pressure, distension, pacing frequency, and ANP secretion, we performed a series of experiments in the isolated perfused rabbit atria. Increase in atrial pressure without changes in transmural pressure and thus without volume changes did not raise immunoreactive ANP (irANP) secretion. Atrial distension without changes in intracavitary atrial pressure increased irANP secretion with the reduction. Electrical stimulation with atrial distension resulted in an increase in irANP secretion in proportion to pacing frequency. Incremental response of irANP secretion to electrical stimulation was accentuated by increasing atrial distension. Neither atrial pacing without distension nor distension without pacing raised irANP secretion. These results suggest that the direct and principal stimulus for irANP secretion in response to atrial pacing and distension is the length shortening of atrial myocytes and that the incremental response of irANP secretion to increasing pacing frequency is the result of an increase in frequency of the length shortening of atrial myocytes.

Identification of immunoreactive atrial natriuretic peptide in bulbus arteriosus of freshwater teleostean fish

1. The presence and partial characterization of immunoreactive atrial natriuretic peptide (ir-ANP) in the bulbus arteriosus were investigated using high performance liquid chromatography (HPLC) and radioimmunoassay (RIA) in several freshwater teleostean fish (catfish, silver crusian carp, snakehead, and rice eel). 2. The level of ir-ANP in the bulbus arteriosus was comparable with that in the atria at about 5-15 pg/mg, 6-13 pg/mg wet wt, respectively, but was 2-4-fold higher than that in the ventricles in all species observed. 3. The HPLC profile of ir-ANP showed two main peaks corresponding to low and high mol. wt rat ANPs. 4. Our results provide evidence for the presence of ir-ANP with high as well as low mol. wts in the bulbus arteriosus of freshwater teleostean fish.

Differential activation of Xenopus homeo box genes by mesoderm-inducing growth factors and retinoic acid

What is the nature of positional information during embryogenesis? By using Xenopus homeo box genes as anteroposterior (A-P) markers, we confirm the findings of others that mesoderm-inducing growth factors and retinoic acid (RA) can provide positional information along the axis of the body. Xenopus tissue culture-mesoderm-inducing factor (XTC-MIF) selectively activates an anteriorly expressed homeo box gene (XlHbox 1), while basic fibroblast growth factor (bFGF) activates selectively a posteriorly expressed homeo box gene (XlHbox 6). RA activates expression of the posterior gene XlHbox 6, but not of XlHbox 1. This activation, however, requires exposure to growth factors. The data suggest that growth factors and RA may cooperate with each other to provide positional information in vertebrates.

Sequential mechanism of atrial natriuretic peptide secretion in isolated perfused rabbit atria

It is well known that the secretion of atrial natriuretic peptide (ANP) is dependent on the atrial stretch. It has been claimed in this laboratory that the secretion of ANP occurs with a reduction in atrial distension. It was shown in the present experiment that the secretion of immunoreactive (ir) ANP occurs coincidently with a translocation of extracellular space marker (3-H)-inulin in the isolated perfused rabbit atria. Translocation of extracellular space fluid was observed with a reduction in atrial distension. The secretion of irANP into the atrial lumen occurs less than 15 sec of the reduction in atrial distension. It is therefore suggested that the incremental response of irANP secretion to the reduction in atrial distension is a sequential mechanism of ANP secretion, in which first is the release of ANP from the atrial myocytes into the extracellular space and then second is the translocation of ANP with extracellular space fluid into the atrial lumen with a reduction in atrial distension.

Elicitation of an oxidase activity in bacterial luciferase by site-directed mutation of a noncatalytic residue

Flavin-dependent external monooxygenases and oxidases could catalyze the same flavin oxidation reaction involving distinct mechanisms. To gain insights into enzyme structure-function relationship, site-directed mutagenesis was carried out for Vibrio harveyi luciferase, a monooxygenase. The substitution of the alpha subunit cysteine 106 by alanine shows unambiguously that the alphaCys106 is not essential to catalysis. The corresponding substitution by valine resulted in a substantial reduction of the bioluminescence activity correlatable with the induction of a new flavin oxidation activity typical for oxidases. These findings indicate that mutation of a single noncatalytic residue at the active center of a flavoenzyme could transform one enzyme type to another, thus highlighting the subtlety of enzyme active site structure in relation to catalysis and the versatility of enzyme evolution.

A time-dependent bacterial bioluminescence emission spectrum in an in vitro single turnover system: energy transfer alone cannot account for the yellow emission of Vibrio fischeri Y-1

Yellow fluorescent protein (YFP), which has a bound FMN, was isolated from the marine bacterium Vibrio fischeri strain Y-1b. Its presence in a luciferase [alkanal monooxygenase (FMN-linked); alkanal, reduced-FMN:oxygen oxidoreductase (1-hydroxylating, luminescing), EC 1.14.14.3] reaction mixture causes a striking color change, and an increase in bioluminescence intensity, as well as a faster rate of intensity decay, so that the quantum yield is not changed. The emission spectrum shows two distinct color bands, one at 490 nm attributed to the unaltered emission of the luciferase system, the other peaking in the yellow around 540 nm due to YFP emission. The kinetics of the two color bands differ, so the spectrum changes with time. The yellow emission reaches its initial maximum intensity later than the blue, and then both blue and yellow emissions decay exponentially with nearly the same pseudo-first-order rate constants, linearly dependent on [YFP] (from 0.01 sec-1 with no YFP to a maximum of approximately 0.1 sec-1 at 4 degrees C) but exhibiting a saturation behavior. The data can be interpreted by assuming the interaction of YFP with the peroxyhemiacetal intermediate in the luciferase reaction to form an unstable new complex whose breakdown gives the yellow emitter in its excited state. This simple model fits well the data at [YFP] less than 15 microM. The results indicate that a single primary excited state cannot be responsible for the blue and the yellow emissions.

Presence of immunoreactive atrial natriuretic peptides in pericardial fluid of human subjects with congenital heart diseases

The epicardial release of immunoreactive atrial natriuretic peptides (ir-ANPs) in inside-out perfused rabbit atria has been reported. In order to determine the presence of ir-ANPs in pericardial fluid and to evaluate their biochemical characteristics, we measured the concentration of ir-ANPs in pericardial fluid obtained from the patients with congenital heart diseases during open heart surgery. Serial dilution curves made with the extrats of pericardial fluid using Sep-Pak C18 cartridges were parallel with standard curve. The concentration of ir-ANPs in pericardial fluid was significantly lower than the corresponding plasma concentration. On gel permeation and reverse-phase high performance liquid chromatography, the ir-ANPs in pericardial fluid, plasma and atrial appendage showed both high and low molecular weights. The major peak of ir-ANPs in plasma was observed at the corresponding fraction to the alpha-human ANP and considerable amount of high molecular weight form of ir-ANPs was observed in pericardial fluid. However, the major peak of ir-ANPs in atrial appendage was observed at the corresponding fraction to the rat pro-ANP. The data suggest that ir-ANPs exist both high and low molecular weight forms in pericardial fluid.

Interference with function of a homeobox gene in Xenopus embryos produces malformations of the anterior spinal cord

XIHbox 1 is expressed in a narrow band across the cervical region of Xenopus embryos. The gene produces two related proteins: "long" and "short" XIHbox 1 homeodomain proteins. Injection of antibodies to the long XIHbox 1 protein into 1-cell embryos caused a phenotype in which the anterior spinal cord was morphologically transformed into a hindbrain-like structure. This alteration was restricted to the region normally expressing long XIHbox 1 protein. Injection of long protein mRNA disrupted segmentation and tissue organization without inhibiting cell proliferation. Injection of short protein mRNA into 1-cell embryos produced spinal cord malformations similar, but not identical, to those caused by the antibodies, suggesting antagonistic roles for long and short XIHbox 1 proteins. We immunostained tadpoles carrying extended hindbrains for N-CAM and consistently found defective organization of spinal nerves over the affected region.

Growth and luminescence of the bacterium Xenorhabdus luminescens from a human wound

Xenorhabdus luminescens, a newly isolated luminous bacterium collected from a human wound, was characterized. The effects of ionic strength, temperature, oxygen, and iron on growth and development of the bioluminescent system were studied. The bacteria grew and emitted light best at 33 degrees C in a medium with low salt, and the medium after growth of cells to a high density was found to have antibiotic activity. The emission spectrum peaked at 482 nm in vivo and at 490 nm in vitro. Both growth and the development of luminescence in X. luminescens required oxygen and iron. The isolated luciferase itself exhibited a temperature optimum at about 40 degrees C; after purification by affinity chromatography, it showed two bands (52 and 41 kilodaltons) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicative of an alpha and beta subunit structure. Reduced flavin mononucleotide (Km of 1.4 microM) and tetradecanal (Km of 2.1 microM) were the best substrates for the luciferase, and the first-order decay constant under these conditions at 37 degrees C was 0.79 s-1.

Reduction volume dependence of immunoreactive atrial natriuretic peptide secretion in isolated perfused rabbit atria

A new technique to permit gradual changes in atrial distension has been developed in an isolated perfused rabbit atrium preparation. Graded volume reduction in the atrium was induced by changing the elevation of the outflow catheter tip. Pressure reduction from 6 cm H2O atrial distension resulted in a decrease in atrial distension volume. Atrial distension by 6 cmH2O did not change the release of immunoreactive atrial natriuretic peptide (irANP). The graded reduction in atrial distension from 0.11 +/- 0.03 (1.5 cm H2O) to 1.36 +/- 0.19 microliters/mg wet weight (6.0 cm H2O) resulted in 1.7 (6.76 +/- 2.05 versus 3.83 +/- 1.18 pg/mg per min, n = 9, P less than 0.025) to 40.1-fold (77.66 +/- 17.82 versus 3.0 +/- 1.14 pg/mg per min, n = 11, P less than 0.025) increases in irANP release. IrANP release in response to the reduction of atrial distension was volume dependent. The relation of percentage increase in irANP release with the percentage reduction of atrial distension was exponential. The data suggest that the atrial muscle shortening, but not stretch per se, may be a potent direct stimulus for the regulation of irANP secretion.

Phylogenetic study on the immunoreactive atrial natriuretic peptide in the heart

Using two antisera against atriopeptin III (AP III) which had different characteristics in cross-reactivities with atrial natriuretic peptide (ANP) analogs, we have measured an immunoreactive ANP (ir-ANP) in the heart extracts of several species. ir-ANP in atrial extracts showed both high and low molecular weights. Serial dilutions of atrial extracts from chickens, turtles, frogs, and fish yielded competition curves which were parallel to the standard curve of AP III with antiserum No. 4. In comparison with two serial dilution curves of atrial extracts made using two antisera, No. 4 and No. 9, we suggest that the amino acid at position 12 of ir-ANP in the atrial extracts of chicken, turtle, frog, and fish is not isoleucine but is some other amino acid.

Stimulation of renin secretion by non-diuretic sulfhydryl reagents

Organomercurial diuretics stimulate renin secretion although the underlying cellular mechanisms remain undefined. Since organomercurials are also known to react with sulfhydryl groups, the present studies determined the effects of sulfhydryl reagents on renin secretion. The effects of the non-diuretic mercurial agent, parachloromercuriphenyl-sulfonate (PCMPS), as well as that of other sulfhydryl reagents, N-ethylmaleimide (NEM), N-phenylmaleimide (NPM) and monobromotrimethylammoniobimane (qBBR), on renin secretion were determined in rabbit renal cortical slices. All four reagents stimulated renin secretion. NEM, which has a high membrane permeability, stimulated secretion to a relatively small extent and its effects were not apparent for at least one hour. Conversely, PCMPS, which is much less permanent than NEM, produced the largest stimulation and these effects were apparent within one hour. The stimulation of secretion by sulfhydryl reagents was independent of the concentration of Ca2+, Na+, and K+ in the incubation media, suggesting that the stimulation is not secondary to alterations of intracellular ion concentrations. These results raise the possibility of direct involvement of sulfhydryl groups of particular membrane protein(s) of the juxtaglomerular (JG) cells in some steps leading to renin secretion, and raise the possibility that sulfhydryl reactivity might in part account for the stimulatory effects of organomercurial and other diuretics.

Vertebrate homeodomain proteins: families of region-specific transcription factors

Vertebrate homeodomain proteins are transcription factors whose genes can be isolated via a conserved DNA-binding domain called the homeobox. We review recent studies suggesting that one function of these genes is the early subdivision of the embryo along the antero-posterior axis into 'fields' of cells with different developmental potential.

Duplicated homeobox genes in Xenopus

Multiple kinds of clones and restriction fragment polymorphisms are frequently encountered when analyzing genes of the tetraploid frog Xenopus laevis. Two types of cDNA clone have been isolated for homeobox gene 2. Analysis of their corresponding genomic clones confirmed the existence of clearly distinct restriction maps; in addition the nearby presence of two additional homeoboxes suggests that this region is homologous to the Hox 2 gene complex of mammals. We asked whether the genetic polymorphism in Xenopus results from increased allelic differences due to tetraploidy or from having duplicated Hox 2 complexes. Using X. laevis/Xenopus borealis interspecies hybrids we show that the two types of X. laevis homeobox gene 2 transcripts result from two different genetic loci. They cannot represent alleles of the same gene because they do not segregate independently in the F1 hybrid progeny. Most other X. laevis homeobox genes studied so far are also found in two versions. Thus X. laevis seems to have two homeobox genes, both of which are expressed, for each one present in mammals or other vertebrates.

Presence of immunoreactive atrial natriuretic peptide in follicular fluid, ovary and ovarian perfusates

Immunoreactive atrial natriuretic peptide (ir-ANP) was measured in the follicular fluid of pig ovarian follicle, and rabbit ovarian homogenates and perfusates using a specific radioimmunoassay (RIA). Serial dilution curves made with the extracts of follicular fluid, ovarian homogenates and perfusates using SepPak C18 cartridges were parallel with the RIA standard curve. On gel filtration chromatography and reverse phase HPLC, all extracted materials showed high and low molecular weight forms of ir-ANP. The amount of ir-ANP in rabbit ovary was 40.70 +/- 0.39 pg/mg and that in follicular fluid of pig ovarian follicle was 18.88 +/- 2.49 pg/ml.

Plasma concentration of atrial natriuretic peptide in different phases of Korean hemorrhagic fever

Korean hemorrhagic fever (KHF) is an epidemic viral disease characterized by high fever, hemorrhagic tendency and renal failure, and by hemorrhages of right atrium and renal medulla as well as necrosis of anterior hypophysis. Plasma immunoreactive atrial natriuretic peptide (irANP) levels of 15 patients in the oliguric phase was 94.8 +/- 8.4 pg/ml (mean +/- SEM), 80% higher than of the normal control group (53.0 +/- 4.7 pg/ml; n = 28). In the diuretic phase it declined to 63.7 +/- 5.3 pg/ml (n = 26). Plasma renin activity (PRA) in the oliguric phase was 19.0 +/- 1.3 ng AI/ml/h, and in the diuretic phase 5.3 +/- 0.9 ng AI/ml/h, significantly higher than the control value (2.5 +/- 0.1 ng AI/ml/h). Elevations of irANP and PRA were not correlated in each group. Also systemic blood pressure as well as heart beats were significantly increased in the oliguric phase. These findings suggest that the increased irANP may have resulted from increased circulatory volume and that the ANP secretory process may not be affected by the disease.

Characteristics of distension-induced release of immunoreactive atrial natriuretic peptide in isolated perfused rabbit atria

Atrial pressure- or distension-induced release of atrial natriuretic peptide (ANP) has been considered as an important regulatory mechanism of ANP release in cardiac atria. A new technique to permit graded continuous atrial distension has been developed in an isolated perfused single rabbit atrium. Graded atrial distension was induced by changing the elevation of the outflow catheter tip. Intra-atrial volume expansion resulted in an increase in immunoreactive ANP release. The graded increase in atrial distension from 43.9 +/- 10.2 to 207.7 +/- 29.1 microliter resulted in 6.2-27.1-fold increases in volume-dependent immunoreactive ANP release. A rise in immunoreactive ANP release induced by increasing atrial distension did not occur in the state of atrial distension but occurred only after return to the reduced distension. However, in the case of atrial distension with pacing, an increase in immunoreactive ANP release was observed during atrial distension with pacing and after return to the basal level. The present study shows that the new technique is applicable to the study of the 'stretch-secretion coupling' mechanism of ANP release in vitro, and that the more important factor involved in the release of immunoreactive ANP induced by atrial distension may be the atrial reduction to basal level after distension rather than the stretch itself.

Differential utilization of the same reading frame in a Xenopus homeobox gene encodes two related proteins sharing the same DNA-binding specificity

Xenopus XlHbox 1 produces two transcripts during early development. One encodes a long open reading frame (ORF) and the other a short ORF sharing the same homeodomain, but differing by an 82 amino acid domain at the amino terminus. The long protein amino terminus is conserved with many other homeodomain proteins, and its absence from the short protein could have functional consequences. Some viral genes also utilize a single ORF to encode transcription factors of antagonistic functions. The overall organization of the homologous genes in frog and man is similar, supporting the notion that both transcripts are of functional significance. Studies on XlHbox 1 function show that the region common to the long and short proteins has a sequence-specific DNA-binding activity, and that microinjection of specific antibodies into embryos results in the loss of structures derived from cells normally expressing XlHbox 1.

Epicardial release of immunoreactive atrial natriuretic peptides in inside-out perfused rabbit atria

An easy and convenient isolated atrial perfusion technique was developed. The effect of stretch of the atrial subpericardial myocytes was investigated in the inside-out perfused rabbit atria. Graded distension of the inverted atria was induced by changing the elevation of the atrial catheter tip. Intra-luminal volume expansion resulted in an increase in release of immunoreactive atrial natriuretic peptides (irANPs). The response was volume, or pressure dependent. Distension-induced release of irANPs occurred at the reduction of the distension. IrANPs in epicardial perfusate showed both high and low molecular weights. The major peak of irANP was observed at the corresponding fraction to the rat ANP-(1-28) in the Sephadex G-50 gel chromatography. The data suggest that the epicardial release of irANP is stretch-induced response and that the release may be involved in the regulation of cardiac function.

A Xenopus laevis gene encodes both homeobox-containing and homeobox-less transcripts

A cDNA clone (p52) that contains all the protein-coding region from the maternally expressed XlHbox 2 locus of the frog Xenopus laevis has been isolated and sequenced. A probe containing the exon preceding the homeobox detected transcripts which arise from a splicing event in which the homeobox-containing exon is replaced by another exon lying 5' to it in the genome. Both the homeobox-containing and homeobox-less splicing event occur in the same tissues, with the homeobox-less RNA representing the minority of mRNA from this gene. There may therefore be a function for two types of transcript, and hence protein, from this locus. This phenomenon may not be exclusive to the XlHbox 2 gene of Xenopus, but might occur more generally in other homeobox-containing genes. The protein deduced from the homeobox-containing cDNA is significantly similar to the yeast mating type factor a1 (MAT-a1) gene product. In addition to the previously described homology of the homeodomains, the amino-terminal domains of XlHbox 2 and MAT-a1 are similar to each other; thus essentially all of the MAT-a1 protein corresponds to some part of the XlHbox 2 protein. In the case of XlHbox 2, the protein coded for by the homeoboxless mRNA would contain all of the non-homeobox homology to yeast MAT-a1.

Circannual changes in renin concentration, plasma electrolytes, and osmolality in the freshwater turtle

Seasonal changes in heart rate, blood pressure, plasma and renal renin concentrations, plasma electrolyte concentrations, and osmolality were studied in freshwater turtles (Amyda japonica) exposed to the natural environment. Seasonal changes in heart rate and blood pressure showed a marked increase in summer and a decrease in winter, which correlated directly with that of an environmental temperature. Two peaks in plasma renin concentration were observed in November and May and correlated with the preparation for hibernation and arousal periods. Renal renin content exhibited a marked seasonal variation characterized mainly by an increase in summer, fall, and winter and a decrease in spring. Plasma sodium concentration and osmolality were the highest in summer, the lowest in winter, and intermediate during spring and fall. A change in plasma osmolality correlated closely with that of temperature. However, no marked seasonal variations in the concentrations of plasma potassium, chloride, and calcium were observed. On the basis of these data, we suggest that a circannual rhythm of renin concentration may be related to hibernation. We also suggest that seasonal changes in sodium concentration and osmolality relate closely to environmental temperature, although the mechanisms are not clear.

Renal and renin effects of sodium thiopental in rabbits

Unilateral renal arterial infusion of sodium thiopental on renal function and renin secretion were investigated in unanesthetized rabbits. Sodium thiopental infusion in doses of less than 0.3 mg/kg/min into unilateral renal artery caused dose-dependent increases in urine flow, urinary excretion of electrolytes, fractional excretion of sodium and free water clearance with no changes in systemic blood pressure and clearance of p-aminohippuric acid (renal blood flow). An anesthetic dose of sodium thiopental administered intravenously caused decreases in systemic blood pressure, renal hemodynamics, urine flow and free water clearance during the early period of anesthesia followed by increases in urinary excretion of sodium and fractional excretion of sodium. Unilateral renal arterial infusion of sodium thiopental decreased the renin secretion rate and plasma norepinephrine concentration in renal vein, whereas an anesthetic dose of sodium thiopental administered intravenously increased the renin secretion rate. These observations suggest that the diuretic, natriuretic and renin suppressive effects of sodium thiopental may be due to an inhibition of intrarenal sympathetic nervous system or due to a direct tubular action.

Characterization of angiotensin I-converting enzyme activity in the freshwater turtle, Amyda japonica

1. Angiotensin I-Converting Enzyme (ACE) activity has been characterized in the freshwater turtle, Amyda japonica. 2. Peak activity of ACE in plasma from the freshwater turtle was shown at pH 9.0, which was more alkaline compared to that of mammals. 3. Chloride requirements for the optimal ACE activity were different from species. 4. ACE inhibitors, EDTA, teprotide (SQ 20,881), Captopril (SQ 14,225) showed dose-dependent inhibitions of ACE activity in plasma from the freshwater turtle as well as mammals. 5. ACE activity was found in several different tissues with a different activity showing the highest activity in kidney homogenate from the freshwater turtle, Amyda japonica.

Unilateral renal arterial infusion and renal vein catheterization in rabbits. Study of renal function and renin release

This study evaluates the direct effects of verapamil and furosemide infused into the unilateral renal artery on renal function and the renin secretion rate in renal vein-catheterized rabbits. Catheterization did not alter the renal function parameters of the kidney. Verapamil and furosemide increased renal blood flow, urine flow, and urinary sodium, potassium and chloride excretions confined to the infused kidney. Verapamil increased the glomerular filtration rate and free water clearance. The renin secretion rate was increased by furosemide but not by verapamil. The present study shows that the technique is applicable to renal function studies in which unilateral renal arterial infusion of the agents studied is required. The contralateral kidney can be a reliable control for the infused kidney. It also provides a useful technique for the study of renin release in rabbits.

The gene encoding the large subunit of human RNA polymerase II is located on the short arm of chromosome 17

We have used chromosomal in situ hybridization and Southern blot analysis of DNA from somatic cell hybrids to determine the chromosomal localization of the subgenomic DNA fragment that encodes part of the large subunit of human RNA polymerase II. The results of our analysis demonstrate localization of the human RNA polymerase II large subunit gene to the short arm of chromosome 17.

The gene encoding the large subunit of human RNA polymerase II

As a first step to approach the structural and functional analysis of DNA-dependent RNA polymerase II (EC 2.7.7.8), we have isolated genomic sequences for the large subunit of the human enzyme. The sequences homologous to Drosophila RNA polymerase II large subunit sequences are present in the genome as single copy genes, when assayed at high stringency. The polypeptide information is encoded in a mRNA of 7.35 kilobases, as determined by Northern blot analysis. In vitro translation reveals a polypeptide of 220 kDa, similar in electrophoretic mobility to the largest subunit of the enzyme. A fusion-polypeptide synthesized in bacteria contains a region that cross-reacts with anti-RNA polymerase II antiserum. Antiserum directed against the purified fusion protein reacts with the large subunit of RNA polymerase II, whether in the intact IIA (220 kDa) or in the degraded IIB (180 kDa) forms. Moreover, the antifusion protein antibody inhibits not only the purified calf thymus RNA polymerase II activity but also specific RNA polymerase II transcription in a HeLa cell extract. Thus, the DNA fragment isolated contains structural and functional domains of the human RNA polymerase II large subunit.

Temperature-induced conversion of the renal adrenoreceptor: modulating renin release

The release of renin from dog cortical kidney slice preparations incubated in a physiological salt solution can be modulated by alpha- and beta-adrenergic drugs. When given to slices maintained at 37 degrees C, the beta-agonists isoproterenol (ISP) and norepinephrine stimulated renin release from the slices. When the slices were maintained at 20 degrees C, the beta-agonists had no effect on renin release. However, the alpha-agonist phenylephrine inhibited renin release from the slices incubated at 20 degrees C in a dose-dependent manner, whereas its effect on slices incubated at 37 degrees C was less pronounced. The change in response of the slices from beta dominant at 37 degrees C to alpha dominant at 20 degrees C appeared to be a receptor phenomenon. When the cortical slices were incubated with the irreversible alpha-antagonist phenoxybenzamine (POB) at 20 degrees C for 1 h, they were unable to respond to ISP when returned to 37 degrees C. However, POB had no effect on the response of slices to ISP when given at 37 degrees C. It appears that with a decrease in temperature the renal beta-receptors demonstrate properties normally associated with alpha-receptors, namely the potential to be blocked by POB. This may be due to an interconversion of the renal alpha- and beta-adrenoceptors.

Renin inactivation during in vitro experiments

Experiments were designed to clarify the factors affecting renin released during in vitro experiments. Kidneys from rat, dog, and pig were used. Experiments were done in which the gas phase was either bubbled through the incubation medium or layered above it. Renin released into the incubation medium disappeared very rapidly when gas was bubbled through the medium. The decline was similar in mediums bubbled with oxygen-CO2 (95%--5%) or nitrogen-CO2 (95%--5%). The half-life of renin activity in the bubbled medium was approximately 15 min in both cases. However, in experiments in which nonbubbled medium was used throughout, renin released into the incubation medium did not disappear after removal of slices. These data are interpreted to mean that the renin released into the incubation medium is inactivated at the air-water interface.

Renin secretion as a function of renal renin content in dogs

The in vivo and in vitro rates of renin secretion were measured in kidneys from five groups of dogs in which renal perfusion pressure, salt diet, and neural input were varied to cause large changes in renin secretion rates and renal renin content. It was found that both the in vivo and in vitro secretory rates were proportional to the renal renin content. However, in vitro secretion rates were dependent on content up to 100 ng angiotensin I/mg tissue per h. At higher renin contents no increment in in vitro secretion rate was seen. In vivo secretion rate did not appear to reach a maximum until renal renin content was above 250 ng AI/mg tissue per h. The data are interpreted to support the hypothesis that there exist at least two pools of renin. One releases renin at a fractional rate of about 1.5% of the total content per hour. The other releases renin at a rate dependent on the magnitude of the stimuli acting on the kidneys. It is also suggested that the rate of renin synthesis may be a determinant of the basla rate of renin secretion.