Structure, expression, and chromosomal localization of the type I human vasoactive intestinal peptide receptor gene

Vasoactive intestinal peptide (VIP) and other members of the pituitary adenylyl cyclase-activating peptide (PACAP) and secretin neuroendocrine peptide family are recognized with specificity by related G protein-coupled receptors. We report here the cloning, characterization, and chromosomal location of the gene encoding the human type I VIP receptor (HVR1), also termed the type II PACAP receptor. The gene spans approximately 22 kb and is composed of 13 exons ranging from 42 to 1400 bp and 12 introns ranging from 0.3 to 6.1 kb. Primer extension analysis with poly(A)+ RNA from human HT29 colonic adenocarcinoma cells indicated that the transcription initiation site is located at position -110 upstream of the first nucleotide (+1) of the translation start codon, and 75 nt downstream of a consensus CCAAT-box motif. The G+C-rich 5' flanking region contains potential binding sites for several nuclear factors, including Sp1, AP2, ATF, interferon regulatory factor 1, NF-IL6, acute-phase response factor, and NF-kappa B. The HVR1 gene is expressed selectively in human tissues with a relative prevalence of lung > prostate > peripheral blood leukocytes, liver, brain, small intestine > colon, heart, spleen > placenta, kidney, thymus, testis. Fluorescence in situ hybridization localized the HVR1 gene to the short arm of human chromosome 3 (3p22), in a region associated with small-cell lung cancer.

Mechanisms of cell transformation in the embryonic heart

The process of cell transformation in the heart is a complex one. By use of the invasion bioassay, we have been able to identify several critical components of the cell transformation process in the heart. TGF beta 3 can be visualized as a switch in the environment that contributes to the initial process of cell transformation. Our data show that it is a critical switch in the transformation process. Even so, it is apparently only one of the factors involved. Others may include other TGF beta family members, the ES antigens described by Markwald and co-workers and additional unknown substances. Observing the sensitivity of the process to pertussis toxin, there is likely to be a G-protein-linked receptor involved, yet we have not identified a known ligand for this type of receptor. Clearly, there are several different signal transduction processes involved. The existence of multiple pathways is consistent with the idea that the target endothelial cells receive a variety of environmental imputs, the sum of which will produce cell transformation at the correct time and place. Adjacent endothelial cells of the ventricle that do not undergo cell transformation are apparently refractory to one or more of the stimuli. Figure 4 depicts a summary diagram of this invasion process with localization of most of the molecules mentioned in this narrative. As hypothesized here, elements of the transformation process may recapitulate aspects of gastrulation. Since some conservation of mechanism is expected in cells, it is not surprising that cells undergoing phenotypic change might reutilize mechanisms used previously to produce mesenchyme from the blastodisk. Though we have preliminary data to suggest this point, confirmation of the hypothesis by perturbation of genes such as brachyury, msx-1, etc. will be required to establish this point. The advantage of this hypothesis is that it provides, from the work of others in the area of gastrulation, a ready source of molecules and mechanisms that can be tested in the transforming heart. Whereas, perturbation of such mechanisms at gastrulation may be lethal to the embryo, such molecules and mechanisms may be responsible for the high incidence of birth defects in the heart.

Cloning and functional expression of a human neuroendocrine vasoactive intestinal peptide receptor

Vasoactive intestinal peptide (VIP) is a potent mediator of gastrointestinal, nervous, pulmonary, vascular and immune functions. A cDNA was obtained from human HT29 intestinal epithelial cells and found to encode a 457 amino acid, 52 kDa VIP receptor. Transfection of the cDNA into COS-7 cells and 293 cells resulted in expression of specific saturable binding of VIP with a Kd of 0.8 nM, and induction of increases in intracellular cAMP by VIP with an EC50 of 1 nM. The human VIP receptor is homologous to other G protein-coupled receptors of the secretin-parathyroid hormone receptor family. A 2.8 kb transcript was detected in human lung, HT29 cells and Raji B-lymphoblasts with weaker expression in human brain, heart, kidney, liver and placenta.

Evidence for the covalent binding of aflatoxin B1-dichloride to cytosine in DNA

In vitro studies of the effect of aflatoxin B1-dichloride (AFB1-Cl2) on the template function for RNA synthesis of several single- and double-stranded synthetic DNAs containing cytosine and/or hypoxanthine bases are reported. The results indicate: (i) AFB1-Cl2 strongly inhibits the template function of the single-stranded homopolymer polydC and has no effect on polydI, (ii) the inhibition is stronger when cytosine is in the double-stranded alternating copolymer poly[d(I-C)], and (iii) polydI directed RNA synthesis can be inhibited if it is in the double-stranded homopolymer polydI.polydC, although the template function of the polydC strand is still inhibited to a greater extent. The evidence that the selective inhibition of the DNA template function is a direct reflection of the binding specificities of AFB1-Cl2 is provided by the binding studies of [3H]AFB1-Cl2 to these DNAs. The binding of AFB1-Cl2 to polydC is substantiated by the dose-response template inhibition and by the dose-response template binding studies. Additionally, these results show that AFB1 per se has neither inhibitory nor binding activity. Auto radiography of [alpha-32P]GTP labeled RNAs suggests that the mechanism of inhibition of polydC template function by AFB1-Cl2 is mainly due to the inhibition of the elongation of RNA synthesis. Spectrum measurement of the products of enzyme digestion of the AFB1-Cl2 modified polydC reveals that the deoxycytidine fraction gives a typical cytosine absorption peak at 275 nm followed by a broad peak between 300 and 400 nm with a maximum at 390 nm. High performance liquid chromatography confirms the existence of a cytosine-AFB1 adduct which absorbs strongly in the regions between 250 and 400 nm with peaks identifiable at 260, 350 and 390 nm. These results strongly suggest that AFB1 in the activated form of AFB1-Cl2 is able to covalently bind to cytosine in DNA.

Applications of preparative high-performance liquid chromatography to the separation and purification of peptides and proteins

The basic differences between the problems encountered in the development of the analytical and preparative applications of high-performance liquid chromatography are analyzed and the principles of optimization of a preparative separation outlined. The application of these principles to the purification of peptides and proteins are discussed with emphasis on the specific problems raised by the separation of high-molecular-mass compounds. The relative advantages and inconveniences of displacement and overloaded elution are presented. The applications of the various retention modes of liquid chromatography (ion exchange, reversed-phase adsorption, hydrophobic interactions, size exclusion and bioaffinity) to the separation of various peptide and protein mixtures and/or to the extraction and purification of some of these compounds are reviewed. Separation performance reported in the literature are summarized in table form.

An electroneurographic assessment of subclinical lead neurotoxicity

While heavy exposure to inorganic lead is capable of inducing symptomatic neuropathy in man, the subclinical neuropathy due to low levels of occupational lead exposure remains to be proved. The reported results of electroneurographic studies on lead workers, however, have been controversial. In this study, 40 lead smeltery workers and 50 non-exposed referents were investigated. The air concentrations of lead at worksites were 0.25 to 42.5 mg/m3. The geometric means of PbB, PbU and delta-ALAU in lead exposed group were 40.03 micrograms/dl, 71 micrograms/l and 4.68 mg/l respectively, which were significantly higher (P less than 0.001) than those (7.01 micrograms/dl, 6.0 micrograms/l and 1.81 mg/l respectively) in the reference group. There were no clinical symptoms or signs of nerve damage in either group. Alcoholism and diabetes were excluded in both groups. Nerve conduction velocity was measured by a DISA 1500 electromyograph in both groups. Eleven electroneurographic parameters, including motor nerve conduction velocity (MCV) and distal latency (DML) of median, ulnar and peroneal nerves as well as sensory nerve conduction velocity (SCV) and distal latency (DSL) of median, ulnar and sural nerves, showed statistically significant differences between the two groups. However, the results of electroneurographic measurements of each individual in the lead-exposed group were all within the normal range. There was no correlation between the blood-lead levels and the neurophysiological measurements except for the median MCV. No correlation was seen between the median MCV and the exposure duration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption isotherms on high-performance liquid chromatographic sorbents. I. Peptides and nucleic acid constituents on octadecyl-silica

A miniaturized chromatographic system with short, narrow-bone columns was used for the measurement of adsorption isotherms of peptides and of nucleic acid constituents on octadecyl-silica by frontal chromatography. The range of mobile phase composition was similar to that used in elution chromatography of the substances investigated. Adsorption isotherms were measured under different experimental conditions as far as the mobile phase pH and composition as well as the column temperature are concerned. Most isotherms were concave down, and the data were fitted to both the Langmuir and Jovanović models, the former yielding a somewhat better fit. Under certain conditions, sigmoidal isotherms were also observed and this behavior was attributed to solvent-mediated conformational changes and molecular stacking. The results shed light on the adsorption behavior of the substances under investigation on octadecyl-silica, the most commonly employed sorbent in reversed-phase chromatography, over a wide range of concentrations. This is of interest in preparative and process-scale chromatography.

Adsorption isotherms on high-performance liquid chromatographic sorbents. II. Proteins on cation exchangers with silica support

Adsorption isotherms of proteins were measured by frontal chromatography in a miniaturized chromatographic system with short, narrow-bore columns. The adsorbents were microparticulate, macroporous siliceous cation exchangers, used in the high-performance liquid chromatography of proteins, and the range of mobile phase compositions was similar to that used in elution chromatography for their separation. Adsorption of protein on the wetted stainless-steel parts of the system was reduced by coating the metal surface with a hydrophilic polymer layer. The adsorption isotherms of proteins were concave down and, in most cases, well represented by the Langmuir model. However, the data could also be fitted with reasonable accuracy to the isotherm equation by Jovanović. Although the siliceous cation exchangers were of different provenance, the isotherms of the proteins were similar. Isotherms measured by the shake-flask method were found to be identical with those obtained by frontal chromatography.

High-performance liquid chromatography of substituted p-benzoquinones and p-hydroquinones. II. Retention behavior, quantitative structure-retention relationships and octanol-water partition coefficients

The retention behavior of methoxy-substituted p-benzoquinones and the corresponding hydroquinones in reversed-phase chromatography was examined on octylsilica and two octadecylsilica stationary phases and with five hydroorganic mobile phases containing acetonitrile, methanol or tetrahydrofuran and additionally in most cases (NH3OH)3PO4 used as a reducing and buffering agent. The retention order of benzoquinones and hydroquinones was the same on each stationary phase with either methanol or acetonitrile as the organic modifier. On the other hand, minor differences in the retention order were observed with the various stationary phases. In all cases, satisfactory quantitative structure-retention relationships (QSRRs) were found and the data suggest that the differences in the retention behaviour of octadecylsilicas used in this study are silanophilic interactions which, together with solvophobic interaction contribute to the retention of these eluites. Further analysis showed that QSRRs of sterically crowded molecules must take into account reduced surface area available for binding. The retention data obtained with use of aqueous tetrahydrofuran as mobile phase failed to give rise to satisfactory QSRRs. This was attributed to selective solvation of eluite by tetrahydrofuran and/or nearly equipotent binding of eluite and tetrahydrofuran to stationary phase.

High-performance liquid chromatography of substituted p-benzoquinones and p-hydroquinones. I. Interplay of on-column redox reaction and the chromatographic retention process

Chromatograms exhibiting unusual elution profiles were obtained in the reversed-phase chromatography of methoxy-substituted hydroquinones with hydro-organic mobile phases. The dependence of the elution profiles on the flow-rate and the mass of injected sample indicated that peaks were caused by the interplay of the chromatographic retention process and the concomitant oxidation of hydroquinones in the chromatographic column. The reaction was first investigated in free solution and the first-order rate constants and equilibrium constants were estimated for the oxidation of 2-methoxy-, 2,5-dimethoxy-, 2,6-dimethoxy-, 2,3,5-trimethoxy- and 2,3,5,6-tetramethoxyhydroquinones. The effect of Fe3+ and Cu2+ on the oxidation of 2,6-dimethoxyhydroquinone was also examined and it was found that Fe3+ caused a ten-fold increase in the reaction rate. The oxidation of 2-methoxy- and 2,6-dimethoxyhydroquinones in the chromatographic column showed first-order and zerothorder kinetic behavior at low and high sample loads, respectively. Such change in reaction order is typical for heterogeneous reactions that follow Langmuir-Hinshelwood kinetics and suggests the existence of catalytically active sites on the silica. Upon purging the columns with EDTA, on-column oxidation of the hydroquinones was attenuated so that no reaction zones appeared on the chromatogram. Subsequent loading of the column with Fe3+, however, gave rise to broad reaction zones and possibly to total conversion of the hydroquinones to benzoquinones in the column. In all cases investigated the rate of oxidation was much higher in the column than in free solution. On the basis of the results obtained here, heavy mental-catalyzed reaction at the stationary phase surface is proposed to be the dominant mechanism for the oxidation reaction examined here.