[Effect of ET-1 antisense oligodeoxynucleotide on the hemodynamics of normal and experimental hypertensive rats]

It was previously found that a phosphorothioated antisense oligodeoxynucleotide (ETASODN) significantly inhibits production of endothelin-1 (ET-1). The purpose of the present study was to determine whether intracerebroventricular injection of ETASODN targeted to prepro-ET-1 is capable of exerting the same preventing effect on the aorta narrowing of experimentally modeled hypertensive rats. Radioimmunoassay showed that ET-1 level in the brain stem of hypertensive rats was significantly elevated. In addition to down-regulating the ET-1 level, astisense could also reduce mean arterial pressure (MAP), heart rate and LVSP in model rats. The antisense also down-regulated the ET-1 level in hypothalamus and brain stem, reducing MAP in normal control rats. After treatment with the antisense, the value of delta MAP was markedly lowered in experimental hypertensive rats as compared to the control ones. Thus it appears that (1) ET-1 might play an important role in central cardiovascular regulation in rats and (2) antisense ETASODN might be used in treatment of hypertension via inhibiting ET-1 production.

Infrequent loss of heterozygosity of APC/MCC and DCC genes in gastric cancer showing DNA microsatellite instability

AIM

To investigate the role of DNA microsatellite instability (MSI) in gastric carcinogenesis by studying associations between MSI status, clinicopathological features, and loss of genetic loci.

METHODS

Six microsatellite loci and loss of heterozygosity at APC, DCC, and MCC were analysed by polymerase chain reaction based methods in 53 cases of advanced gastric cancer.

RESULTS

MSI was observed in 32.1% of gastric carcinomas (17/53) and 20% of foci of intestinal metaplasia (3/15). Seven gastric carcinomas (13.7%) were MSI-high (MSI-H) (three loci or more) and 10 (18.9%) were MSI-low (MSI-L) (one or two loci). The frequency of MSI-H was higher in intestinal (25.0%) than in diffuse carcinomas (3.7%) (p < 0.05). None of the MSI-H tumours showed loss of heterozygosity at APC, MCC, or DCC loci.

CONCLUSIONS

MSI may have an important and early role in a subset of gastric cancers, particularly the intestinal type. The MSI-H subset of gastric cancer has features in common with its colorectal counterpart, whereas MSI-L and microsatellite stable cancers appear to develop through the loss of heterozygosity pathway.

Loss of heterozygosity and loss of expression of the DCC gene in gastric cancer

AIM

To investigate the role of DCC gene inactivation in the development and progression of gastric cancer.

METHODS

Loss of heterozygosity and loss of expression of the DCC gene was studied in 51 surgical specimens of gastric cancer using detection based on polymerase chain reaction.

RESULTS

Loss of heterozygosity was found in 35.3% (18 of 51) of specimens and was detected more often in stage III and IV (50%) than in stage I and II cancers (14.3%) (p < 0.05). Occurrence of loss of heterozygosity was not correlated with histological type, tumour size, depth of invasion, or lymph node metastasis. Loss of expression was found in 49% of cases (25 of 51). Loss of expression was not significantly correlated with any clinicopathological variable.

CONCLUSIONS

Loss of heterozygosity and loss of expression of the DCC gene are often encountered in gastric cancer. Loss of heterozygosity of the DCC gene is a late event and associated with malignant progression.

Autonomous epicardial and endocardial boundary detection in echocardiographic short-axis images

An autonomous endocardial and epicardial boundary detection (ABD) method is reported. One hundred ten cycles from 55 clinical studies were selected retrospectively. Image sequences were digitized at 512 x 480 pixel resolution. The point-by-point boundary positions of the ABD and the areas enclosed were compared with positions and enclosed areas drawn by three independent observers. Correlation coefficients for epicardial end-diastolic (ED) and end-systolic (ES) areas, endocardial ED and ES areas, muscle area, and fractional area change were 0.970, 0.976, 0.951, 0.985, 0.887, and 0.878, respectively. Bland-Altman analysis showed negligible biases with standard deviations comparable to those of the observers. The mean difference between the ABD border and the consensus observer border positions in 64 directions falls within the mean range of interobserver border positions, suggesting that shape is also well defined by the ABD.

[3H]benzylpempidine, a new radioligand for probing a putative channel site on nicotinic cholinergic receptors

A study was undertaken to assess the receptor binding characteristics of [3H]4-benzylpempidine to an allosteric site on calf brain membranes associated with nicotinic cholinergic receptors and to compare the binding affinity of novel arylpempidine analogs with their ability to antagonize the behavioral effects of nicotine in mice. Scatchard analysis of the binding yielded a K(d) of 20 nM and a B(max) of 330 fmols/mg membrane protein. [3H]4-benzylpempidine appears to be a more satisfactory ligand than [3H]mecamylamine, since it possessed a 50-fold greater affinity and its binding was far less sensitive to inorganic ions and Tris. Among the arylpempidine analogs 4-m-chlorobenzylidenepempidine and 4-benzylidenepempidine had the lowest K(i) values (1.4 nM and 5.0 nM, respectively) and were the most potent in antagonizing nicotine-induced seizures in mice. Although the K(i) values for pempidine and mecamylamine were 1-2 orders of magnitude greater than any of the arylpempidines, the dose required to antagonize nicotine-induced seizures in mice was comparable to the arylpempidines. One explanation for this apparent discrepancy in the correlation of binding affinity and nicotine antagonism is the lower brain penetration of arylpempidines compared to mecamylamine, following their systemic administration to mice.

Molecular and functional identification of m1 muscarinic acetylcholine receptors in rat ventricular myocytes

The expression of muscarinic acetylcholine receptor (mAChR) subtypes in freshly isolated adult rat ventricular myocytes was investigated by reverse transcription of cellular mRNA followed by amplification of cDNA using the polymerase chain reaction (PCR). After reverse-transcriptase PCR, bands were obtained corresponding to the expected sizes for the m1 and m2 but not for the m3 to m5 mAChRs. The identity of the m1 and m2 bands was confirmed by single-cell PCR, restriction digest mapping, and Southern blot analysis. The presence of m1 and m2, but not m3, mAChR protein in these cells was shown by indirect immunofluorescence studies using subtype-specific antibodies. It was further investigated whether the identified m1 mAChR was responsible for the stimulatory effects on Ca2+ transients by high concentrations of carbachol ( > 10 mumol/L) known to occur in these cells. In pertussis toxin-treated ventricular myocytes electrically stimulated at 1 Hz, carbachol (300 mumol/L) increased the basal Ca2+ level from 96 +/- 7 to 118 +/- 8 nmol/L and the peak Ca2+ transient level from 519 +/- 32 to 640 +/- 36 nmol/L (mean +/- SEM P < .05 for both, n = 8). These effects of carbachol on Ca2+ transients were antagonized by 10 nmol/L pirenzepine, an m1 mAChR-selective antagonist. In contrast, the m2 mAChR-selective antagonist methoctramine (up to 100 nmol/L) did not inhibit the response. These results are the first to use single-cell PCR to probe cardiomyocyte-specific gene expression and indicate that m1 mAChRs are expressed on adult rat ventricular myocytes in addition to m2 mAChRs. The results further suggest that m1 mAChRs mediate the stimulatory responses on Ca2+ transients to high concentrations of cholinergic agonists seen in these cells.

Expression and characterization of the rat alpha 4 beta 2 neuronal nicotinic cholinergic receptor in baculovirus-infected insect cells

Baculovirus expression systems have been developed to generate 1) a neuronal nicotinic cholinergic receptor comprising both the alpha 4 and beta 2 subunits and 2) the alpha 4 and beta 2 subunits individually. The presence of the alpha 4 and beta 2 genes in the various baculovirus-infected Sf9 cells was confirmed following polymerase chain reaction (PCR) of the extracted viral DNAs, gel electrophoresis, and double strand sequencing. Autofluorography, following sodium dodecyl sulfate-polyacrylamide gel electrophoresis of infected cell lysates radiolabeled with 35S-methionine and immunoprecipated with mAb 270 (specific for the beta 2 subunit), revealed the presence of characteristic 52-kD bands in beta 2- and alpha 4 beta 2 recombinant viral-infected cells, but not in control cells or cells infected with wild-type virus or recombinant virus containing alpha 4 alone. The 52-kD protein, which is specific for mAb 270, is known to be the beta 2 subunit of neuronal nAChRs. Specific [3H]methylcarbamylcholine binding was observed in cells infected with both alpha 4 or beta 2 but not with the alpha 4 or beta 2 genes alone. Scatchard analysis revealed a Bmax = 5.50 pmol/mg and a Kd = 1 nM. The degree of [3H]methylcarbamylcholine binding/mg membrane protein was 180-fold greater than that found in rat brain. The study demonstrates that the major neuronal nAChR, which comprises alpha 4 and beta 2 subunits and is present in very low abundance in mammalian brain, can be prepared by a baculovirus expression system in sufficient quantities for chemical and crystallographic structural analysis.

[Binding of [3H] dihydroetorphine to opioid receptors in rat brain membrane]

AIM

To study the binding characteristics of dihydroetorphine (DHE) to opioid receptors.

METHODS

The binding of [3H] DHE to rat brain membrane opioid receptors was observed by radioligand binding study.

RESULTS

Saturation study showed the binding of [3H] DHE to rat brain membrane presented a single high-affinity class of binding sites with Kd = 0.19 nmol.L-1 and Bmax = 115 pmol/g protein. Kinetics study showed the association rate of [3H] DHE to opioid receptor was very rapid and dissociation very slow. NaCl 100 mmol.L-1 + guanosine triphosphate (GTP) 50 mumol.L-1 inhibited the binding of [3H] DHE and made Kd increase to 7.87 nmol.L-1, without effect on Bmax. Competitive inhibition of agonists and antagonists indicated that the affinity of [3H]DHE to mu opioid receptor was higher than to delta and kappa opioid receptors.

CONCLUSION

DHE is a selective agonist of mu opioid receptors.

Power distribution in two-dimensional optical network channels

The power distribution in two-dimensional optical network channels is analyzed. The maximum number of allowable channels as determined by the characteristics of optical detector is identified, in particular, for neural-network and wavelet-transform applications.

3,3',4,4'-tetrachloroazobenzene absorption, disposition, and metabolism in male Fischer 344 rats

3,3',4,4'-Tetrachloroazobenzene (TCAB) is a contaminant generated during the synthesis of 3,4-dichloroaniline and 3,4-dichloroaniline-derived pesticides. TCAB is isosteric to 2,3,7,8-tetrachlorodibenzo-p-dioxin and has been shown to bind to the Ah receptor. Following oral administration of [14C]TCAB (3.2 and 32 mg/kg), 39-45% of the dosed radioactivity was excreted into the urine and 53-56% was recovered in the feces within 48 hr. Less than 6% of the dosed radioactivity remained in the tissues examined at 96 hr. After intravenous administration (3.2 mg/kg), 33% of the dose was excreted in the bile during 6 hr. TCAB metabolites in urine were identified using LC/MS. The major metabolites were sulfate ester conjugates of hydroxylated mono- or dichloroaniline derivatives. Some of these metabolites were also acetylated. After intravenous administration, the disappearance of [14C]TCAB from blood was monitored, and the pharmacokinetic profile was consistent with a two-compartment model. Pharmacokinetic parameters reveal that the compound is readily cleared from the blood with a t1/2 of 4.0 hr, clearance of 12.3 ml/min.kg, and an apparent volume of distribution of 4.3 liters/kg. The absolute oral bioavailability was determined to be 30%. The extensive azo reduction of TCAB decreases its systemic absorption after oral administration and thereby limits the amount of parent compound available to interact with the Ah receptor and decreases the Ah receptor-mediated toxicity.

Dihydroetorphine is a mu-receptor-selective ligand

The selectivity to opioid receptors of dihydroetorphine, a potent analgesic with only mild physical dependence, was investigated using radioligand binding assay and its analgesic activity in mice determined. The relative affinity ratio of dihydroetorphine to mu-, delta- and kappa- opioid receptors was 333:1:1. The analgesic effect of intracerebro-ventricular injection in mice could be antagonized by the mu-antagonist beta-funaltrexamine but could not be antagonized by delta- and kappa-selective antagonists naltrindole and norbinaltorphimine. We conclude that dihydroetorphine is a selective ligand for the mu-opioid receptor.

Effects of 3,4-dihydroxyacetophenone (3,4-DHAP) on hypoxic pulmonary and systemic vascular response in dogs

The effects of 3,4-DHAP on hypoxic pulmonary and systemic vascular responses were studied in anaesthetized dogs. The percentage change in pulmonary vascular resistance (delta PVR %) and that in systemic vascular resistance (delta SVR %) induced by 5 min hypoxia decreased significantly. 3,4-DHAP in doses of 1 mg/kg, 3 mg/kg, and 10 mg/kg i.v. caused a decrease in delta PVR% from the control value of 47.27 +/- 22.27% to 24.62 +/- 21.76%, 18.15 +/- 18.73%, and 24.10 +/- 19.76% respectively, and a decrease in delta SVR % from the control value of 12.91 +/- 7.39 % to -0.34 +/- 12.70%, -2.11 +/- 12.76%, and -2.37 +/- 15.52 % respectively. The results showed that 3,4-DHAP could decrease the hypoxic responses of pulmonary and systemic blood vessels. But it did not change delta PVR % or delta SVR % in dose of 30 mg/kg, neither did it influence the heart rate, cardiac output or cerebral blood flow during hypoxia in all the doses used.

Both hypoxic endothelial cell conditioned medium and hypoxia elevate intracellular free calcium in pulmonary artery smooth muscle cells

By using Ca(2+)-sensitive fluorescent probe, Fura- 2, the effects of endothelial cell-conditioned medium and hypoxia on intracellular free calcium ([Ca2+]i) in cultured pulmonary artery smooth muscle cell (PASMC) were studied. Normoxic porcine pulmonary artery endothelial cell-conditioned medium (NPAECCM) obviously elevated [Ca2+]i in PASMC, whereas the hypoxic porcine pulmonary artery endothelial cell conditioned medium (HPAECCM) significantly elevated [Ca2+]i in PASMC much more than NPAECCM. Both the effects of NPAECCM and HPAECCM were dependent on the cultured endothelial cell extracellular calcium concentrations, ranged from 1.8 mmol/L to 2.4 mmol/L. Meanwhile, hypoxia directly increased, which was partially inhibited by verapamil, [Ca2+]i in PASMC through Ca2+ influx pathway. The data suggest that the augmented regulation of endothelial cell on PASMC via Ca2+ second messenger system and the hypoxia-induced Ca2+ influx into PASMC, particularly the former, may be components of mechanisms underlying hypoxic pulmonary vasoconstriction and chronic pulmonary hypertension.

Effects of 3,4-dihydroxyacetophenone on hypoxic vasoconstriction in isolated pulmonary and basilar arterial rings

The effects of 3,4-DHAP on hypoxic vasoconstriction response in pulmonary (PA) and basilar arterial (BA) rings of rabbits and their mechanism were compared in vitro. 3,4-DHAP in different concentration (2.64 x 10(-4), 7.92 x 10(-4), 2.376 x 10(-3) mol/L) decreased the basal tone of PA rings by 32.39 +/- 9.4 mg, 68.96 +/- 26.54 mg and 145.60 +/- 58.07 mg respectively, while the tension of the BA rings was decreased by 13.80 +/- 5.08 mg, 17.18 +/- 3.36 mg and 25.00 +/- 4.02 mg respectively. In PA rings it also decreased the percentage increase in tension induced by hypoxia (TIH%) from the control value 48.82 +/- 5.75% to 10.02 +/- 3.62%, 2.14 +/- 0.96%, and 0.00% respectively, while in BA rings from 27.27 +/- 5.78% to 11.23 +/- 2.71%, 7.49 +/- 1.62%, and 1.45 +/- 1.13% respectively. The effects of 3, 4-DHAP on TIH% were partially blocked by indomethacin 10 M and L-NAME 10 M. The results showed that 3, 4-DHAP can decrease the hypoxic pulmonary and basilar vasoconstriction in vitro, which can be partially inhibited by cyclooxygenase inhibitor and NO/EDRF inhibitor.

Effect of increasing biliary tract pressure on house rabbit blood dynamics in acute cholangitis of severe type

In this study 12 Japanese long ear rabbits were used as models of acute cholangitis of severe type (ACST), and also an increasing pressure apparatus of self-made caecus to form high pressure of the biliary tract. The animals were observed for changes in blood dynamics in an attempt to explore the effect and relation of high pressure of biliary tract and infective element in pathogenesis of ACST. It was found that when the biliary pressure was increased within 120 min in the 20 kPa group, the blood endotoxin level showed no obvious increment (P > 0.05), but the decreased range of average MAP (mean artery pressure) was over 4 kPa, and the cardiac output also decreased evidently (P < 0.05), and that when the biliary pressure was decreased, MAP and cardiac output were restored to normal gradually. Of these animals 3 didn't restore their normal condition when the blood pressure decreased to zero and died finally. Meanwhile the electric discharge frequency of the right greater splanchnic nerves increased (P < 0.05), but when pressure was reduced, the frequency slowed down. From the above findings, the authors came to the conclusion that the rapid increase of the biliary tract pressure is the important factor leading to a decrease in blood pressure of ACST, and even bringing about irreversible shock, which is involved in the activity of splanchnic nerves.

Differences in ligand binding and phosphoinositide turnover between M1 muscarinic receptor gene transfected cells and mouse and rat brain membranes

The present study describes some unexpected receptor mediated effects of N-methylcarbamylcholine on mouse M1 muscarinic receptor gene transfected cell line (M1Y1) that were not evident from biochemical studies with mouse and rat brain tissue where N-methylcarbamylcholine exhibited only nicotinic properties. Although N-methylcarbamycholine was devoid of muscarinic properties in mouse and rat brain preparations, as determined by phosphoinositide turnover and inhibition of [3H]QNB binding, it exhibited significant muscarinic characteristics in the transfected M1Y1 cell line. At a concentration of 10(-6) M or greater, N-methylcarbamycholine caused a transient increase in intracellular Ca2+ of 50 s duration that was reversible by atropine or pirezepine. The Ca(2+)-transient was not elicited by other nicotinic agents such as nicotine and N,N-dimethylcarbamylcholine, a close analogue of N-methylcarbamylcholine, with comparable affinity for nicotinic receptors and devoid of muscarinic activity. N-Methylcarbamylcholine also stimulated phosphoinositide turnover in M1Y1 cells with an estimated EC50 value 10 times greater than that of carbachol, and the effect was blocked by atropine. Both carbachol and N-methylcarbamycholine inhibited [3H]QNB binding in a concentration-dependent manner; however, the IC50 for carbachol was over two orders of magnitude greater than that observed in mouse and rat brain membranes. In considering possible explanations for the differential characteristics of N-methylcarbamylcholine in mouse and rat brain as compared to the transfected M1Y1 cells, it was concluded that the difference may be attributable to differences in the receptor-transduction coupling efficiency and the microenvironment of the muscarinic receptors.

Changes in cardiovascular activity during an increase in biliary tract pressure in rabbits

In order to study the mechanism of decreased blood pressure caused by an acute increase in biliary tract pressure, we observed house rabbit model of self-made caecus for changes in cardiovascular function when biliary tract pressure was increased. It was found that both the blood pressure and cardiac output evidently decreased (P < 0.05) parallelly, and the systolic pressure decreased more markedly than diastolic pressure. At the same time there was fluctuation in heart rate and in central venous pressure; but there was no significant difference between them (P > 0.05), suggesting that in the absence of infective agents, the increased biliary tract pressure can bring about a decrease in cardiac output, which is an important factor contributing to an early blood pressure decrease in acute cholangitis of severe type (ACST).