The P2Y purinergic receptor expressed by enteric neurones in guinea-pig intestine.

Electrophysiological recording methods provided evidence for presynaptic release of ATP from enteric neurones and postganglionic sympathetic fibres in the enteric nervous system (ENS) of guinea-pig intestine (J Physiol Lond 2003; 550: 493-504). The released ATP acted at postsynaptic P2Y(1) receptors to evoke slow synaptic excitation in neurones in the submucosal division of the ENS. Here, we report the cloning and characterization of the P2Y(1) receptor, which was found in the guinea-pig submucosal layer. A 1178 bp cDNA clone was isolated from guinea-pig submucosal RNA by reverse transcription polymerase chain reaction (RT-PCR). The cDNA contained an open-reading frame of 1119 bp, encoding a 373 amino acid polypeptide of the same length and with 95% identity to the human P2Y(1) receptor. Stable expression of the guinea-pig cDNA in human embryonic kidney (HEK)293 cells was accompanied by a marked increase in sensitivity for elevation of free intracellular calcium evoked by ATP or related nucleotides. The potency order for ATP and its analogues was: 2-methio-adenosine diphosphate > 2-methio-adenosine triphosphate > ADP > ATP-gamma-S > ATP. The selective P2Y(1) receptor antagonist, MRS2179, was a competitive antagonist for the receptor with a pA(2) value of 6.5. The results add to existing evidence for expression of a functional P2Y(1) purinergic receptor in neurones of the submucosal division of the ENS.

[Determination of dicofol residue in tea by wide-bore capillary gas chromatographic column].

Dicofol residue is harmful to health. More and more countries have established the limitation of dicofol in foods. This paper describes an efficient method of determination for the dicofol residue in tea. The dicofol was extracted from the tea sample with 20% acetone-hexane, cleaned up on a column of Florisil and acidic siliceous earth (sulfuric acid 0.3 mL/g) in series. Then the column was washed with 10 mL, 20% dichloromethane-hexane, the flow rate was 1 mL/min. At last dicofol was hydrolyzed with potassium hydroxide solution, forming p,p'-dichlorobenzophenone(DBP), which was separated from other ingredients through wide-bore capillary(LZ-II, 25 m x 0.53 mm i.d.) and determinated by gas chromatography with electron capture detector(ECD), using Aldrin as internal standard. When the mass ratio of dicofol was in the range of 0.05-3.0 mg/kg, the recoveries were 78%-104% and the limit of determination was 0.5 microgram/kg. This method is simple, sensitive and suitable for pesticide residue analysis. It can also be applied to the determination of dicofol residues in other plant samples such as vegetables, fruits and so on.

Control of pollen tube tip growth by a Rop GTPase-dependent pathway that leads to tip-localized calcium influx.

We have shown that Rop1At, a pollen-specific Rop GTPase that is a member of the Rho family of small GTP binding proteins, acts as a key molecular switch controlling tip growth in Arabidopsis pollen tubes. Pollen-specific expression of constitutively active rop1at mutants induced isotropic growth of pollen tubes. Overexpression of wild-type Arabidopsis Rop1At led to ectopic accumulation of Rop1At in the plasma membrane at the tip and caused depolarization of pollen tube growth, which was less severe than that induced by the constitutively active rop1at. These results indicate that both Rop1At signaling and polar localization are critical for controlling the site of tip growth. Dominant negative rop1at mutants or antisense rop1at RNA inhibited tube growth at 0.5 mM extracellular Ca(2+), but growth inhibition was reversed by higher extracellular Ca(2+). Injection of anti-Rop antibodies disrupted the tip-focused intracellular Ca(2+) gradient known to be crucial for tip growth. These studies provide strong evidence for a Rop GTPase-dependent tip growth pathway that couples the control of growth sites with the rate of tip growth through the regulation of tip-localized extracellular Ca(2+) influxes and formation of the tip-high intracellular Ca(2+) gradient in pollen tubes.

[Effect of diphenylhydantoin sodium in causing deformity and that of folic acid preparations for its prevention].

Pregnant rats were divided into four groups. The groups A, B and C were intraperitoneally injected with DPH during the 9 to 11 days of gestation in doses of 75 Mg/kg/day. The groups A and B were supplemented with a mixture of folic acid (FA) or with FA alone in the food fed during pregnancy. The results showed that DPH induced a significant decrease in the body weights and lengths of fetal rats (P less than 0.01), but induced an increase in the incidences of subcutaneous bleeding (P less than 0.05) as well as skeletal and internal malformation (P less than 0.05). The supplement of FA or a mixture of FA in the food fed during pregnancy exhibited partial preventive effects on DPH to induce teratogenicity. The effect of a mixture of FA was better than that with FA alone in reducing the incidences of internal abnormalities and agenesis of the bones of the distant phalanges and subcutaneous bleeding.

Reduction of the teratogenic effects of phenytoin by folic acid and a mixture of folic acid, vitamins, and amino acids: a preliminary trial.

Four groups of pregnant rats were used to study the effects of dietary supplements of folic acid (FA) alone or a mixture of FA, vitamins (Vit), and amino acids (AA) on the teratogenic effects of phenytoin (PHT). Groups A, B, and C received intraperitoneal (i.p.) injections of high-dose (75 mg/kg/day) phenytoin (PHT) between 9 and 11 days of gestation, while the controls, group D, rats received distilled water. The diet was modified in groups A and B. Group A received a mixture of FA, Vit, and AA, while group B received FA supplementation alone. Groups C and D received a regular diet. We found that PHT, when administered without dietary supplementation, resulted in a decrease in weight and length of the fetuses, an increased rate of subcutaneous (s.c.) bleeding, a retardation of ossification centers, and an increased number of malformations. Supplementation of the diet with FA alone or FA with Vit and AA resulted in statistically greater fetal weight and length, decreased subcutaneous bleeding, more ossification centers, and fewer malformations. The mixture of FA and Vit and AA was superior to FA alone in reducing the incidence of internal abnormalities, ossification abnormalities of the distant phalanxes, and s.c. bleeding.