Effects of methylguanidine on sodium and organic ion transport

We studied the acute effect of methylguanidine (MG), a suspected uremic toxin that accumulates in renal failure, on p-aminohippurate (PAH) and tetraethylammonium (TEA) uptake in rabbit kidney slices, on Na+,K+ ATPase activity in the microsomal fraction of rabbit kidneys, and on transepithelial active Na transport across toad skin. MG at concentrations ranging from 0.05 (similar to that reported in uremic patients) to 1.0 mM does not affect the organic anion (PAH) uptake, although it exhibits a concentration-dependent inhibition of organic cation (TEA) uptake. MG at concentrations from 0.05 to 5 mM had no effect on kidney Na+,K+ ATPase activity or on active transepithelial Na transport across toad skins when applied to the outside bathing solution; however, MG (greater than 1 mM) stimulated Na transport when applied to the inside bathing solution. These results are not consistent with the hypothesis that MG is a potential uremic toxin that causes the natriuresis and other toxic effects. However, long-term toxic effects of MG on the kidney were not assessed in the present study.

Evidence that M3 muscarinic receptors in rat parotid gland couple to two second messenger systems

The binding affinities of muscarinic antagonists were compared with their abilities to block carbachol (CCh)-mediated stimulation of Ca2+ mobilization and inhibition of isoproterenol-elicited adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in rat parotid cells. The binding of [3H]quinuclidinyl benzilate (QNB) to membranes was inhibited by antagonists with the following potencies (dissociation constant, nM): atropine (1.1) approximately 4-diphenylacetoxy-N-methylpiperidine methbromide (4-DAMP) (1.6) much greater than pirenzepine (136) greater than 11-[[2-[(diethylamino)methyl-1-piperidinyl]-acetyl]acetyl]-5,11- dihydro-6H-pyrido[2,3-b][1,4]-benzodiazepine-6-one (AF-DX 116) (5,293). AF-DX 116 blocked Ca2+ mobilization and inhibition of cAMP accumulation with low affinities [inhibitory concentration at 50% (IC50) = 3150 and 6,528 nM, respectively], whereas 4-DAMP blocked these responses with considerably higher affinities (IC50 = 4.3 and 11.4 nM, respectively). Schild plots of 4-DAMP and AF-DX 116 antagonism of CCh-stimulated inositol trisphosphate accumulation showed inhibitor constant (Ki) values of 0.85 and 1,585 nM, respectively, whereas Schild plots of 4-DAMP, AF-DX 116, and methoctramine antagonism of CCh-induced inhibition of cAMP accumulation showed Ki values of 1.3, 1,585, and 2,754 nM, respectively. Preincubation of cells with 0.1 mM 3-isobutyl-1-methylxanthine did not prevent the capacity of CCh to inhibit cAMP accumulation. Pertussis toxin blocked the CCh-elicited and Gi-mediated inhibition of cAMP formation. Northern blot analysis showed the presence of mRNA for the M3, but not for the M2, subtype in parotid gland. An immunochemical procedure using m1-m5 specific antibodies was performed in parotid membranes and showed that the m3 receptor accounts for 93% of precipitable receptors. These data suggest that M3 receptors in the rat parotid are coupled to both the stimulation of Ca2+ mobilization and the inhibition of cAMP accumulation.

Epidermal growth factor elevates intracellular pH in chicken granulosa cells by activating protein kinase C

Previous studies from our laboratory have demonstrated that epidermal growth factor (EGF), induces intracellular alkalinization in chicken granulosa cells by activating a sodium-dependent and amiloride-sensitive Na+/H+ antiporter. In the present investigation we have examined the possible involvement of protein kinase C (PKC) in the regulation of intracellular pH (pHi) by EGF in chicken granulosa cells. Intracellular pH in granulosa cells obtained from the two largest preovulatory follicles was determined spectrofluorometrically using the dye 2',7'-bis-(carboxyethyl)-5(6)-carboxyfluorescein. The resting pHi was 6.81 +/- 0.01 (n = 30) when the extracellular pH and sodium concentration were 7.3 and 144 mM, respectively. 12-O-Tetradecanoyl-phorbol-13-acetate (TPA; 50-400 ng/ml) and 1-oleoyl-2-acetylglycerol (OAG; 1-75 micrograms/ml) mimicked the actions of EGF by inducing a concentration-dependent increase in pHi which reached a maximum of 0.25-0.30 pH units. 4 alpha-Phorbol 12,13-didecanoate, a phorbol ester with no tumor promoting activity had no effect on pHi. Cytosolic alkalinization was observed within 10 min of the addition of each agent and increased over the 60-min observation period. Like EGF-induced cytosolic alkalinization, the increases in pHi in response to TPA or OAG were dependent on the presence of sodium concentration and were inhibited by amiloride, an inhibitor of the Na+/H+ antiporter. The effects of EGF, TPA, and OAG were attenuated by the PKC inhibitors 5-isoquinolinylsulfonyl-2-methyl piperazine and trifluoperazine. Down-regulation of granulosa cell PKC by pretreatment with TPA (200 ng/ml) for 2.5 h inhibited EGF-, TPA-, and OAG-induced cytosolic alkalinization. The effects of maximally stimulatory concentrations of EGF and TPA on cytosolic alkalinization were not additive. The increases in pHi induced by TPA and OAG, but not by EGF, were dependent on the presence of extracellular Ca++. These studies suggest that the EGF-induced intracellular alkalinization in chicken granulosa cells involves a PKC-mediated activation of the Na+/H+ antiporter.

Isolation and characterization of mannose 6-phosphate/insulin-like growth factor II receptor from bovine serum

A convenient means was devised for the purification of milligram quantities of a soluble form of the mannose 6-phosphate/insulin-like growth factor II receptor (Man-6-P/IGF II receptor). The receptor was purified to near homogeneity from bovine serum by affinity chromatography on agarose-pentamannosephosphate in the absence of detergent. Approximately 2.5 mg of receptor were obtained from 500 ml of fetal calf serum. The concentration of receptor in serum decreased sharply with development. Fetal calf serum Man-6-P/IGF II receptor was immunologically similar to detergent-solubilized, membrane-bound Man-6-P/IGF II receptor from bovine liver. N-Terminal sequence analysis revealed that the purified serum receptor, but not the solubilized, membrane-associated receptor, contains stoichiometric amounts of bound IGF II. The results of sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel chromatography studies suggest that the fetal calf serum receptor (in contrast to the solubilized, membrane-bound bovine testis receptor) does not aggregate. The affinity of the fetal calf serum receptor for bovine testis beta-galactosidase approximated one-half that observed for solubilized, membrane-bound bovine testis receptor.

Electroencephalography, magnetic resonance imaging and pathology in patients treated surgically for temporal lobe epilepsy

In a consecutive series of 40 patients selected by EEG studies for surgical treatment of temporal lobe seizures, magnetic resonance imaging showed structural lesions in 25% and signal abnormalities, usually in the mesial temporal region, in another 35%. Pathological changes included structural lesions in over 30% of patients and sclerosis of the amygdala in almost half of the series. These findings further substantiate the implication of the amygdala in the pathogenesis of temporal lobe seizures with automatism and amnesia.

Development of an antiserum against m3 muscarinic receptors: distribution of m3 receptors in rat tissues and clonal cell lines

A synthetic oligopeptide (QCDKRKRRKQQYQQRQSV) corresponding to a carboxyl-terminal sequence of the rat m3 receptor (amino acids 561-578) was coupled to carrier proteins and used to generate a polyclonal antiserum. This serum selectively immunoprecipitates at least 90% of the m3 receptors expressed by A9 cells transfected with the cDNA encoding the m3 muscarinic receptor but does not precipitate receptors from cells transfected with cDNA encoding m1, m2, m4, or m5 receptors. Using this m3 antiserum, the density of m3 receptors in various regions of rat brain was quantified. Areas expressing the highest density of m3 receptors are the cortex, hippocampus, striatum, and olfactory tubercle, with 232 fmol/mg, 197 fmol/mg, 140 fmol/mg, and 130 fmol/mg, respectively. Hindbrain regions (i.e., cerebellum, thalamus/hypothalamus, and pons/medulla) expressed fewer m3 receptors, both as a percentage of total muscarinic receptors (5-6%) and in terms of absolute receptor density (12-70 fmol/mg). A panel of subtype-selective antisera (m1, m2, and m3) was used to determine receptor distribution in several peripheral tissues of the rat (lung, ileum, and bladder). The m2 receptor subtype constitutes the majority of total receptors in the bladder (86%), lung (91%), and ileum (69%). The m3 receptor was found at lower densities in these tissues (5-11%), whereas the m1 receptor is present in highest amounts in the ileum (17%). Human clonal cell lines, in which regulation of muscarinic receptors has been commonly studied, were also examined. The SK-N-SH neuroblastoma line, which has been reported to express M3 receptors, on the basis of pharmacology and molecular size, was found to express a mixture of subtypes (m1 = 31%, m2 = 21%, m3 = 43%). Interestingly, SH-SY-5Y and SH-IN cells, both derived from SK-N-SH cells, exhibit predominantly m3 receptors (74% for SH-SY-5Y; 58% for SH-IN), with lower levels of m1 and m2 receptors (5% and 8% for SH-SY-5Y; 4% and 23% for SH-IN, respectively.) Another commonly studied cell line, 132-1-N1 astrocytoma cells, reportedly expressing M3 receptors, based upon mRNA measurements and second messenger linkage, also expresses a predominance of m3 receptors (91% of total). This m3-selective antiserum should prove useful not only for localizing and quantifying m3 muscarinic receptors but also for examining mechanisms involved in the regulation of receptor expression in human tissues or animal models of disease, as well as in cell culture.

Expression of two different forms of fibroblast growth factor receptor 1 in different mouse tissues and cell lines

The fibroblast growth factor receptors (FGFRs) form a multigene family of at least four members, all having extracellular regions consisting of either two or three immunoglobin-like (Ig-like) domains. By RNase protection analysis we have analyzed the expression of FGFR-1 mRNA in various tissues and cell lines and demonstrated that all of the cell lines studied expressed at least two different forms of the FGFR-1 at similar levels. Although muscle and heart express forms having either two [FGFR-1 short (FGFR-1S)] or three [FGFR-1 long (FGFR-1L)] Ig-like domains, the developing brain and adult brain express only mRNA encoding the longer form. The two forms of the receptor were characterized further by stably introducing expression vectors expressing them into Rat-2 fibroblasts and FDC-P1 myeloid cells. Treatment of the transfected Rat-2 cells with acidic FGF (aFGF) or basic FGF (bFGF) resulted in focus formation. The transformed phenotype was observed even without addition of ligand after growth in culture for greater than 2 months. Cross-linking of 125I-labeled bFGF (125I-bFGF) to Rat-2 cells expressing either FGFR-1L or FGFR-1S yielded two similar complexes of 150 and 110 kDa. Although Rat-2 cells expressing FGFR-1L yielded similar complexes with 125I-labeled aFGF (125I-aFGF), only the 150-kDa complex was formed with cells expressing FGFR-1S. The 150-kDa complex was also observed when 125I-aFGF or 125I-bFGF was cross-linked to FDC-P1 cells expressing FGFR-1L. Significantly, these complexes were only observed when heparin was present in the cross-linking reaction. FDC-P1 cells expressing FGFR-1 bound aFGF and bFGF with high affinity but only in the presence of heparin. The factor dependence of these cells could be switched from interleukin 3 to FGF in the presence of heparin.

[Effects of phencyclidine on rabbit basilar artery in vitro and rabbit cerebral blood flow in vivo]

The effect of phencyclidine [1-(1-phenylcyclohexyl)piperidine, PCP] on rabbit basilar arteries was studied with an in vitro model of ring segment arteries. PCP 0.05-500 mumol.L-1 caused vasoconstriction of basilar arteries in a concentration-dependent manner. Its maximal effect (Emax) was 94 +/- 21 mg and the concentration causing half maximal effect (EC50) was 25 +/- 18 mumol.L-1. PCP 0.01-10 mumol.L-1 also concentration-dependently augmented the vasoconstriction induced by electric stimulation in rabbit basilar arteries. Its Emax was 91 +/- 18 mg and EC50 was 0.27 +/- 0.17 mumol.L-1. The effects of PCP on mean arterial blood pressure (MABP) and heart rate (HR) of rabbits were observed. PCP iv 4 mg.kg-1 reduced MABP from 14.3 +/- 0.8 to 12.2 +/- 1.0 kPa and HR from 300 +/- 0 to 278 +/- 5 bpm in 5 min. Using the technique of radionuclide imaging in rabbit brain in vivo, we studied the effect of PCP on cerebral blood flow. After iv PCP 4 mg.kg-1, the tp of radiocerebrogram was increased from 4.5 +/- 1.1 to 6.1 +/- 1.0 s, the tg of radiocerebrogram was increased from 11.7 +/- 0.6 to 18.2 +/- 3.3 s and the rate of clearance was decreased. After iv PCP 2 mg.kg-1, only tg increased from 12.6 +/- 2.1 to 15.9 +/- 0.6 s. Hence PCP increased the transit time of nondiffusible indicators (99mTc) through the cerebral circulation. These results suggest that PCP causes constriction of basilar artery and slows down the cerebral blood flow.

Epidermal growth factor elevates intracellular pH in chicken granulosa cells

Many bioregulators, such as epidermal growth factor (EGF), induce intracellular alkalinization by activating a membrane bound Na+/H+ antiporter. The present studies were designed to examine the influence of EGF on intracellular pH (pHi) in chicken granulosa cells. pHi in granulosa cells from the two largest preovulatory follicles of hens was determined spectrofluorometrically using the dye 2',7'-bis(carboxyethyl-5(6)-carboxyfluorescein. The resting pHi was 6.81 +/- 0.006 (n = 30) when the extracellular pH and sodium concentration (Na+o) were 7.3 and 144 mM, respectively. EGF (5-100 ng/ml) induced a concentration-dependent increase in pHi, which reached a maximum of 0.217 +/- 0.009 pH units at a concentration of 100 ng/ml EGF. Cytosolic alkalinization was observed within 10 min of the addition of EGF and lasted over the 60 min observation period. The increase in pHi was dependent upon the presence of Na+o, since the EGF effect was attenuated when Na+o was substituted with equimolar concentrations of nonpermeant choline chloride. The EGF-induced pHi change was also inhibited by amiloride, dimethyl amiloride, and ethylisopropyl amiloride, inhibitors of the Na+/H+ antiporter. The alkalinization effect of EGF was mimicked by transforming growth factor-alpha but not by insulin, insulin-like growth factor-I, or transforming growth factor-beta. These studies suggest for the first time that intracellular alkalinization resulting from activation of the Na+/H+ antiporter may be a part of the transmembrane signaling pathway in the action of EGF on chicken granulosa cells.

Distribution of m2 muscarinic receptors in rat brain using antisera selective for m2 receptors

The DNA fragment encoding the third intracellular loop of rat m2 muscarinic receptor was fused to the gene for staphylococcal Protein A. The resultant fusion protein, expressed in bacteria, was purified via IgG affinity chromatography and used as an antigen to raise a polyclonal antiserum. Chinese hamster ovary cells transfected with cDNA coding for a single muscarinic receptor subtype were used as tissue sources to screen antisera. The antiserum was shown to immunoprecipitate quantitatively (greater than 90%) m2 receptors but not to precipitate m1, m3, m4, or m5 receptors. Additionally, immunoprecipitation by m2 antiserum could be inhibited by protein containing the third intracellular loop of the m2 receptor. This selective m2 antiserum was then used to study the distribution and density of m2 receptors in rat brain and heart. In agreement with previous studies, m2 receptors were found to be abundant in heart and comprise at least 92% of the total muscarinic receptor density. Hindbrain, brain stem, and midbrain regions such as cerebellum (75%), pons/medulla (70%), and thalamus/hypothalamus (43%) are also enriched in m2 receptors. In contrast, forebrain regions contain markedly lower percentages of m2 receptors, with cortex expressing 20%, hippocampus 19%, striatum 12%, and olfactory tubercle 20% of the total receptor density. Although the density of m2 receptors expressed as a percentage of total varied considerably from brain region to brain region, the absolute density of these receptors appeared relatively uniform throughout the brain. This study demonstrates that a gene fusion system can be used for efficient antibody production. The use of similar fusion protein antisera directed against other subtypes of muscarinic receptors should prove useful in future studies on regulation, function, and structure of muscarinic receptors.

Synthesis of (+/-)-N-2-methylpropyl-N-1'-methylacetonyl-nitrosamine

N-2-methylpropyl-N-1-methylacetonyl-nitrosamine (NMAMPA), first isolated from moldy and normal foods, was synthesized by chemical means. The structure and molecular weight of the synthetic NMAMPA were elucidated by spectrometry. A combination of spectral and chromatographic data indicated that the synthetic NMAMPA is identical to that obtained naturally. Synthetic NMAMPA is a racemic modification, and a carcinogen which can induce esophageal and forestomach cancer in rats.

[Experimental research of the effect of polysaccharides in semen Ziziphis Spinosae and Ziziphis Spinosae on enhancing the immune function of mice injured by radiation]

This article surveys the pharmacological effect of the polysaccharides in Semen Ziziphis Spinosae and Ziziphis Spinosae. The result shows that oral administration of this polysaccharide (0.1g/kg/d) can strengthen the immune function of cells nd body fluids and to a certain extent protect mice from radioactive injuries.

[Studies of pickled vegetables and cause of esophageal cancer in Linxian. II. Determination of nitrosamines and their precursors]

Pickled vegetables are daily food consumed in the high-risk areas for esophageal cancer in China. We analyzed the nitrosamine content of Linxian pickles by GC/TEA and found that trace amounts of six nitrosamines (NDMA, NDEA, NMBA, NMAMBA, NDPA, NPYR) were present, with the highest concentrations being NDMA and NDEA (1.7 and 1.9 micrograms/kg wet weight respectively). The average level of nitrosamine precursors, such as nitrate (111.22 mg/L), nitrite (0.152 mg/L) and secondary amines (4.223 mg/L), in pickled vegetables were determined, and their pH values ranged from 3 to 5.

[A study on the male DNA special restricted fragment of bovine]

Bkm, which is related to sexes, is a satellite DNA of the female snake. After the genomic DNA of bovine was digested by Pst I, it was hybridized with Bkm sequence probe (p184) and subcloned in the vector pUC19. Recombinants were identified by the colony in situ and Southern blot hybridization. When we determined genomic DNA of bovine using the male DNA fragment, it was observed that the pattern of hybridization was different because of different sexes. The results showed that we could identify the sex of bovine by Southern blot hybridization with recombinants of male DNA special restricted fragment of bovine origin.

[Endoscopic retrograde cholangiopancreatography in children]

Endoscopic retrograde cholangiopancreatography (ERCP) was performed less in children than in adults. Twenty-seven children, aged from 56 days to 14 years (average 6 years), received ERCP from August 1989 to December 1990. The cannulation into the papilla of Vater was successful in 24 children (88.9%) and their pancreaticobiliary ductal system was visualized clearly. Congenital biliary dilatation (CBD) was diagnosed in 16 patients and other biliary disorders in 8 patients. The APBD was confirmed in almost all CBD patients, showing a close etiological relation. It was concluded that ERCP is helpful to diagnose and differentiate pediatric biliary diseases and to study the etiology and pathophysiology of CBD.

Role of the sympathetic nervous system in the onset of hypertension in the rat: the effect of 6-OH-dopamine

1. The effect of chemical sympathectomy with 6-OH-dopamine (6-OHDA) on the onset of adrenocorticotrophin (ACTH)-induced hypertension was examined in Sprague-Dawley rats (n = 23). 2. 6-OHDA injection produced a fall in systolic blood pressure (SBP) from 100 +/- 5 mmHg control to 74 +/- 4 mmHg post-6-OHDA Treatment Day 1 (P less than 0.001), but did not alter food or water intake, urine volume or electrolyte excretion. 3. Compared with sham injection, ACTH-treated rats showed an increase in blood pressure (sham: 98 +/- 7 mmHg; ACTH: 123 +/- 9 mmHg on Treatment Day 10; P less than 0.01), loss of bodyweight, and increases in water intake and urine volume. 4. The magnitude of the blood pressure rise on ACTH was greater in 6-OHDA-treated rats than in intact control rats. Metabolic changes were similar. 5. Chemical sympathectomy with 6-OHDA did not delay or block the onset of ACTH hypertension in the rat.

[An investigation on the resources of medicinal fungi in Sichuan]

This paper reports the classification, distributional traits, new distribution, specific species of medicinal fungi, as well as the status of anticancer medications and edible and medicinal fungi in Sichuan. Rational suggestions have been made with regard to the cultivation, development and utilization of those important species with proven curative effect.

[A study on components and compound prescription of huangqin decoction]

The results obtained from the pharmacological experiments have preliminarily demonstrated that the compound prescription is better than its individual component drug in the range and potency of pharmacological activities. In the prescription Radix Scutellariae plays a principal role in pharmacological effects. Radix Scutellariae and Radix Paeoniae Alba can potentiate each other. Radix Glycyrrhizae and Fructus Jujubae in the compound prescription also exhibit biological activities to some extent. The relieving effect of the prescription for spasm and pain may result from the synergistic interaction between Radix Paeoniae Alba and Radix Glycyrrhiza, and the heat clearing and diarrhea stopping action is due to the biological activity of Radix Scutellariae.

The chemiluminescence of amides and monoacyl hydrazides based on firefly dehydroluciferin

Monoacyl hydrazides based on 5-methyldehydroluciferin and simpler analogs have been synthesized; they proved to be chemiluminescent on treatment with a strong base in DMSO in the presence of oxygen. The light emitters in these cases appear to be the corresponding carboxylate ions; a pathway involving an oxidative decarboxylation was eliminated as a possibility by consideration of the fluorescence wavelengths of the corresponding oxyluciferins. A reaction mechanism for the luminescence involving the possible intermediacy of an azadioxetane is proposed. The corresponding amides were also synthesized; they proved to be equally chemiluminescent to the hydrazides in the dehydroluciferin series.