The sensitivity of human melanoma heterotransplants to chemotherapeutic action]

There were revealed considerable individual differences in the sensitivity of human melanomas cultivated in diffusion chambers in the abdominal cavity of mice and the explants into the cheek pouches of Cricetus auratus W. to the combined action of three drugs: vincristin (or vinblastin), nitrosomethylurea, and dactinomycin. In comparing the results obtained in these two variants of investigations they proved to coincide in 3 of 5 cases. In 2 cases a negative result obtained in experimentas with Cricetus auratus W. corresponded to the positive result in experiments with diffuse chambers.     

Monosodium glutamate impairs the contraction of uterine visceral smooth muscle ex vivo of rat through augmentation of acetylcholine and nitric oxide signaling pathways

The aim of the study was to examine the toxic effects of Monosodium glutamate (MSG), an extensively used food additive, on the contraction of uterine visceral smooth muscle (UVSM) in rat and to elucidate the probable neurocrine mechanism involved in it. MSG produced significant potentiation of the force and inhibition of frequency of uterus recorded ex vivo in chronic MSG exposure and in single dose acute experiments. MSG also produced significant potentiation of force of acetylcholine induced contraction and no alterations in atropine induced contraction of uterus. Further, MSG produced significant increase in force and frequency of contraction of neostigmine incubated uterus. We have found significant potentiation of the post pause force of contraction of uterus when MSG was applied in adrenaline incubated uterus. MSG also produced significant decrease in frequency of contraction of sodium nitroprusside incubated uterus; increase in frequency of N-ω-Nitro-l-Arginine Methyl Ester incubated uterus and no significant changes in frequency of contraction of methylene blue incubated uterus. These results indicate that MSG potentiates the force of contraction of UVSM predominantly by augmenting the activity of cholinergic intrinsic efferents and inhibits the frequency of contraction probably by augmenting the activity of nitrergic efferents. In conclusion, MSG potentiates the force and inhibits the frequency of contraction of UVSM, and the MSG induced effect is probably mediated through the augmentation of acetylcholine and nitric oxide signaling pathways.     

Isolation, partial purification and pharmacodynamics of a slow contractile substance in the venom sac extract of the wasp Vespa cincta Fabr

The venom of V. cincta contains acetylcholine (ACh), histamine and 5-hydroxytryptamine (5-HT). Blockers of these agonists did not block completely the hypotensive and smooth muscle contractile activity of venom. On smooth muscle, there was a residual slow contraction. The active substance which produced this slow contraction was separated by solvent extraction, gel filtration and TLC. The purified material (which has been provisionally designated "Vecikinin") lowered cat, rat and guinea pig blood pressure, increased amplitude of cardiac contraction, and increased capillary permeability. Vecikinin contracted several smooth muscle preparations (rat uterus, rat ascending colon, guinea pig ileum, guinea pig colon and rat ileum), while relaxing rat duodenum. Its contractile activity was not lost on boiling, but acid or alkali-boiling reduced its contractile activity. It was inactivated on incubation with chymotrypsin and carboxypeptidase but not with trypsin, pepsin or leucine aminopeptidase. It is a peptide, appears to be of low molecular weight, and could be distinguished from substance P, angiotensin, bradykinin and hornet or wasp kinin.     

Effect of thyrotropin-releasing hormone on rat myometrium

The effect of TRH in vitro was observed on electromyograms and isometric tension changes in the uterine horn isolated from the rat. TRH induced transient prolongation of the duration of spike bursts in the electromyogram and an increased tension in contraction of diestrous uterine horns. No distinct response to TRH was elicited in preparations from rats during other estrous stages. TRH produced a contraction associated with a burst of spike potentials in the quiescent horn from the estrogen-primed ovariectomized rat. Priming with progesterone was not a prerequisite for responsiveness to TRH. In a medium with a high Ca concentration, diestrous uteri were quiescent but a transient contraction associated with a burst of spike potentials was induced by TRH. In a Ca-free medium, TRH failed to elicit any response in the diestrous uterus but acetylcholine induced a contraction without associated spike potentials. It appears that TRH stimulates Ca-influx into the uterine muscle in which responsiveness is dependent on estrogen priming.     

In vitro study of rat uterus after chronic formaldehyde exposure.

To measure cholinergic, adrenergic and tryptaminergic receptor activity of formaldehyde (HCHO) in rat uterus, albino rats were treated with 5 and 10 mg/kg, ip HCHO for 30 days. Acetylcholine (ACh) in doses 1.33, 2 and 3 micrograms/ml produced mild to moderate contraction of isolated rat uterus in control group. HCHO had no effect on isolated rat uterus per se, however it reduced ACh and carbachol induced contraction and presence of adrenaline influences in respect of ACh and carbachol activity. Adrenaline per se had no effect in control preparations, but reduced carbachol induced contraction. Propranolol had no effect on rat uterus; but its presence in the bathing medium increased activity of adrenaline. 5-Hydroxytryptamine (5-HT) had no effect of its own on isolated rat uterus but its presence in the bathing medium enhanced contractions of carbachol and oxytocin.     

Compliance and smooth muscle reactivity of rainbow trout (Oncorhynchus mykiss) vessels in vitro

Systemic veins have a profound influence on cardiac output in mammals. Venoregulatory mechanisms have not been adequately studied in fish and their existence has been questioned. In the present study, two characteristics of vascular mechanics, compliance and agonist-induced tension development, were investigated in rainbow trout vessels in vitro. Rapid compliance in the anterior cardinal vein and efferent branchial artery was calculated from step-wise changes in the volume-pressure curve of isolated vessel segments. Agonist-induced tension development was examined in four veins; anterior and posterior cardinals, intestinal and duct of Cuvier. Venous compliance was not altered in response to epinephrine, norepinephrine or angiotensin II, while efferent branchial artery compliance was decreased by 10^-6 mol·l^-1 epinephrine and norepinephrine but not angiotensin II. The ratios of venous to arterial compliance in vessels from two rainbow trout strains were similar (21:1 and 32:1) and consistent with the ratio reported for mammalian viens (24:1). Trout veins contracted in response to agonists in both an, agonist- and vesselspecific manner. The greatest tension per vessel wet weight was produced in anterior cardinal vein. The response pattern of anterior cardinal vein and duct of Cuvier were similar; acetylcholine, arginine vasotocin, epinephrine and norepinephrine, and the thromboxane A₂ agonist, U-44,069, produced approximately identical contractions, whereas angiotensin II was virtually ineffective. Conversely, angiotensin II was more potent than epinephrine in posterior cardinal vein. In cumulative dose-response experiments, epinephrine was equipotent in anterior cardinal vein and duct of Cuvier, whereas the latter was less sensitive to acetylcholine. Both atrial natriuretic peptide and sodium nitroprusside relaxed precontracted veins. This is the first study to determine compliance in fish vessels and the contractile nature of different rainbow trout veins. These findings suggest that venous tone and therefore cardiac output in fish may be regulated by neural or humoral mechanisms.Abbreviations ACH acetylcholine - ACV anterior cardinal vein - ANG II salmon asn¹-val⁵ angiotensin II - ANP rat atrial natriuretic peptide - AVT arginine vasotocin - DNR Department of Natural Resources - DOC duct of Cuvier - EBA efferent branchial artery - EC₅ threshold dose producing 5% maximal contraction - EC₅₀ dose producing 50% maximal contraction - EPI epinephrine - HI K⁺ 80 mmol·l^-1 - KCl IV, intestinal vein - NEPI norepinephrine - PBS phosphate buffered saline - PCV posterior cardinal vein - SNP sodium nitroprusside - U-44,069 thromboxane A₂ agonist     

Agonist-induced tension determines vascular reactivity during anoxia and reoxygenation.

To determine the influence of pre-existing pharmacologically-induced tension on vascular reactivity during anoxia and reoxygenation, rat aortic rings were contracted with norepinephrine, epinephrine, endothelin or KCl to 1, 2 or 4 g of tension. The rings were then exposed to anoxia (95% N2) for 10 min followed by reoxygenation (95% O2). The degree of anoxia-mediated contraction varied with the magnitude of tension before anoxia and resembled the length-tension relationship in myocardial fibers. The optimal agonist-induced tension for maximal anoxic contraction was approximately 1 to 2 g. This relationship between tension and anoxic contraction was observed in all but KCl-contracted rings. The agonist- as well as KCl-contracted rings showed normal relaxant response to acetylcholine, suggesting that a decrease in endothelium-derived relaxing factor (EDRF) alone cannot be the basis of anoxic contraction and release of endothelium-derived constricting factors (EDCFs) may relate to anoxic contraction in agonist-preconstricted rings. The relationship between the magnitude of agonist-induced tension and the extent of anoxia-mediated contraction may relate to the ability of endothelium to release EDRF and EDCFs as well as to the degree of phosphorylation in vascular smooth muscle cells. The reoxygenation-mediated contraction was noted to progressively increase in all experiments regardless of the pharmacologic agent used. This increase in reoxygenation-mediated contraction correlated with pre-existing pharmacologic tension, and may relate to calcium influx and restoration of ATP and other mediators in the vascular tissues during reoxygenation.     

Calcium requirement of uterine contraction induced by PGE1: importance of intracellular calcium stores

The contraction of the rat uterus in response to PGE1 in high K+ medium and in Ca-free solution which contained EDTA has been investigated in order to examine whether excitation-contraction coupling involves the release of Ca from an intracellular store. In uterus maximally contracted by K+, cumulative concentrations of PGE1 (1.25 - 20 ng/ml) caused maintained concentration-dependent contraction. PGE1 induced sustained contraction of rat uterus in Ca-free medium after incubation with 3mM EDTA for 50 min. In these conditions the involvement of extracellular Ca is highly unlikely. The PGE1-induced contraction could be repeated without exposure to external Ca ions and with only slight reduction in magnitude. The PGE1 concentrations required to elicit uterine contraction in Ca-free solution were about 1000 times higher than the effective doses in KCl-depolarized uterus. In conclusion, the present investigation shows that Ca influx is not essential for PGE1-induced contraction of rat uterus, although extracellular Ca enhances it presumably by increasing the free Ca levels in the cytosol.     

Inhibition of hemostasis by a high affinity biogenic amine-binding protein from the saliva of a blood-feeding insect

The saliva of the blood-feeding insect Rhodnius prolixus contains numerous pharmacologically active substances. Included among these are a number of lipocalin proteins that bind various ligands important in hemostasis and inflammation. One such protein is a biogenic amine-binding protein (ABP) that binds serotonin, epinephrine, and norepinephrine. Based on amino acid alignments, it is most similar to the nitrophorin group of lipocalins found in the same insect species. Physiologically, this protein appears to act as both a vasodilator and platelet aggregation inhibitor. This protein inhibits smooth muscle contraction of the rat uterus in response to serotonin and of the rabbit aorta in response to norepinephrine. Platelet aggregation induced by a combination of low concentrations of ADP and either serotonin or epinephrine is inhibited because of the binding of serotonin and epinephrine. Potentiation of aggregation induced by low concentrations of collagen along with serotonin or epinephrine is also inhibited. Dissociation constants for biogenic amines were measured using isothermal titration calorimetry and the Hummel-Dreyer method of equilibrium gel filtration. In this manner, K(d) values of 102, 24, and 345 nm were found for serotonin, norepinephrine, and epinephrine, respectively. Molecular modeling of ABP suggests that ligand binding is mediated by interaction with the side chains of aromatic amino acids and charged residues that line the binding pocket.     

Propranolol prevents epinephrine from limiting insulin-stimulated muscle glucose uptake during contraction.

Beta-blockade results in rapid glucose clearance and premature fatigue during exercise. To investigate the cause of this increased glucose clearance, we studied the acute effects of propranolol on insulin-stimulated muscle glucose uptake during contraction in the presence of epinephrine with an isolated rat muscle preparation. Glucose uptake increased in both fast- (epitrochlearis) and slow-twitch (soleus) muscle during insulin or contraction stimulation. In the presence of 24 nM epinephrine, glucose uptake during contraction was completely suppressed when insulin was present. This suppression of glucose uptake by epinephrine was accompanied by a decrease in insulin receptor substrate (IRS)-1-phosphatidylinositol 3 (PI3)-kinase activity. Propranolol had no direct effect on insulin-stimulated glucose uptake during contraction. However, epinephrine was ineffective in attenuating insulin-stimulated glucose uptake during contraction in the presence of propranolol. This ineffectiveness of epinephrine to suppress insulin-stimulated glucose uptake during contraction occurred in conjunction with its inability to completely suppress IRS-1-PI3-kinase activity. Results of this study indicate that the effectiveness of epinephrine to inhibit insulin-stimulated glucose uptake during contraction is severely diminished in muscle exposed to propranolol. Thus the increase in glucose clearance and premature fatigue associated with beta-blockade could result from the inability of epinephrine to attenuate insulin-stimulated muscle glucose uptake.     

The synergism acetylcholine-eserine in the epinephrine induced ventricular automaticity

Heart ventricular strips of the rat in Krebs solution were used to test the synergism acetylcholine-eserine. Ventricular automaticity induced by epinephrine 1 10(-6) is inhibited by acetylcholine (a 50% reduction of the automatism is observed with acetylcholine 1,23 10(-8) while four different concentrations of eserine cause an evident potentiation of the effect of acetylcholine (with eserine a 10(-5) the ED50 of acetylcholine is 2,57 10(-14)). It is concluded that the synergism eserine-acetylcholine is a synergism with potentiation and the acetylcholine introduced in the Krebs solution interacts with receptors different from those activated by the acetylcholine which accumulates when cholinesterase is inhibited by eserine.     

Interaction between alpha and beta adrenergic receptors and cholinergic receptors in isolated perfused rat heart: effects on cAMP-protein kinase and phosphorylase

The ability of acetylcholine to antagonize catecholamine-induced activation of myocardial cyclic AMP dependent protein kinase and glycogen phosphorylase activity was assessed using isolated perfused rat hearts. Perfused hearts were treated with either saline, epinephrine, epinephrine plus phentolamine or isoproterenol. After 1 minute of infusion of the indicated drug a second infusion containing acetylcholine was started. After an additional minute hearts were frozen and analyzed for cyclic nucleotide content and enzyme activity. In the presence of the alpha receptor blocking agent, phentolamine, epinephrine is a more effective activator of protein kinase than in its absence. Under these conditions the antagonistic action of acetylcholine on protein kinase activation is more pronounced. In the presence of epinephrine plus phentolamine or in the presence of isoproterenol the antagonistic action of acetylcholine on phosphorylase activity can be accounted for by a reduction in cyclic AMP-protein kinase. This same action of acetylcholine on epinephrine-stimulated phosphorylase in the aabsence of phentolamine, however, cannot be totally accounted for by a reduction in cyclic AMP content or in protein kinase activity.     

Presynaptic alpha-adrenoceptor mediated inhibition of the neurogenic cholinergic contraction in the isolated intestinal bulb of the carp (Cyprinus carpio)

The effects of norepinephrine, epinephrine and clonidine on neurogenic cholinergic contraction were examined in the presence of a beta-adrenoceptor blocking agent, carteolol (5 X 10(-6) M), in the isolated intestinal bulb of the carp. Norepinephrine, epinephrine (10(-9)-10(-6) M) and clonidine (10(-8)-10(-5) M) inhibited the contraction induced by low frequency (2 or 5 Hz) transmural stimulation (TMS) without inhibiting the contraction induced by acetylcholine (ACh, 6 X 10(-8)-4 X 10(-7) M). Methoxamine (10(-4) M) and phenylephrine (10(-4) M) showed no such inhibitory effect on the TMS-induced contraction. The inhibitory effects of catecholamines and clonidine were decreased by phentolamine (5.4 X 10(-6) M) and yohimbine (10(-7)-10(-6) M) but not by prazosin (7 X 10(-7)-10(-6) M). Nicotine (10(-6)-10(-4) M) and serotonin (3 X 10(-8)-3 X 10(-6) M) caused contraction of the intestinal bulb indirectly by releasing endogenous ACh. This contraction was inhibited by norepinephrine, epinephrine and clonidine in a concentration-dependent manner. The present results suggest that catecholamines and clonidine inhibit cholinergic transmission via the activation of a presynaptic alpha-adrenoceptor (presumably of alpha-2 type) located on the cholinergic nerve terminals innervating the smooth muscle of the intestinal bulb of the carp.     

Studies on sex chromosomes of four hamster species: Cricetus cricetus, Cricetulus griseus, Mesocricetus auratus, and Phodopus sungorus.

In this paper, we present an analysis of the sex chromosomes of four hamster species after application of different staining techniques. The mitotic X chromosomes show a striking similarity in G-banding pattern but rather great differences in their C-banding patterns. A presumably homologous euchromatic segment that exhibits two distinct G-bands appears in the X chromosome of each species. The Y chromosome of Cricetus cricetus is in contrast to those of the other species, because it reveals a relatively well-differentiated G- and C-banding pattern. In meiotic metaphase I, interstitial chiasmata can be found in the sex bivalents of Cricetus cricetus and Cricetulus griseus, whereas the gonosomes of Mesocricetus auratus and Phodopus sungorus sungorus are terminally associated. The regions that are involved in pairing or association are always heterochromatic.     

Effect of aflatoxin B1 in vitro and in vivo]

The direct and transplacental action of aflatoxin B1 was studied on organic cultures of the embryonic pulmonary tissue of mice of the A line, BD-IX rats and golden hamsters (Cricetus auratus W.). Its toxic action on the cultures and the absence of any blastomogenic effect was demonstrated. In experiments on mice the transplacental penetration of aflatoxin B1 led to an increase in the incidence of the breast tumours in the progeny.     

Calcium requirement of uterine contraction induced by PGE1: Importance of intracellular calcium stores

The contraction of the rat uterus in response to PGE₁ in high K⁺ medium and in Ca-free solution which contained EDTA has been investigated in order to examine whether excitation-contraction coupling involves the release of Ca from an intracellular store.In uterus maximally contracted by K⁺, cumulative concentrations of PGE₁ (1.25 – 20 ng/ml) caused maintained concentration-dependent contraction. PGE₁ induced sustained contraction of rat uterus in Ca-free medium after incubation with 3mM EDTA for 50 min. In these conditions the involvement of extracellular Ca is highly unlikely. The PGE₁-induced contraction could be repeated without exposure to external Ca ions and with only slight reduction in magnitude. The PGE₁ concentrations required to elicit uterine contraction in Ca-free solution were about 1000 times higher than the effective doses in KCl-depolarized uterus.In conclusion, the present investigation shows that Ca influx is not essential for PGE₁-induced contraction of rat uterus, although extracellular Ca enhances it presumably by increasing the free Ca levels in the cytosol.     

元胡止痛胶囊的含药血清对痛经模型动物的影响

目的采用血清药理学实验方法 ,观察元胡止痛胶囊的含药血清对痛经模型动物的影响。方法缩宫素诱发大鼠痛经模型和前列腺素E诱发小鼠痛经模型法,对大鼠离体子宫收缩活动的影响。结果元胡止痛胶囊的含药血清能减少缩宫素所致大鼠扭体反应次数和前列腺素E1所致小鼠扭体反应次数,并能拮抗缩宫素对大鼠离体子宫的收缩作用。结论元胡止痛胶囊的含药血清对痛经模型动物有镇痛作用,并对大鼠离体子宫收缩有解痉作用。     

Spasmolytic effect of histamine in the isolated intestine of the hamster (Cricetus auratus)]

A comparative study of the effects produced by histamine on 15 different sections of the small intestine of hamsters (Cricetus auratus) from the stomach to the ileocecal valve was performed to find a substitute for that of guinea pigs and to ascertain which of the sections was the most sensitive. Changes in tone, amplitude and frequency of contractions with respect to control (spontaneous motility, were significant (P less than 0.01); the variance analysis showed no significant variations in the sensitivity or the motility of the different sections.     

Peripheral receptor populations involved in the regulation of gastrointestinal motility and the pharmacological actions of metoclopramide-like drugs

This minireview is concerned with a re-examination of the locus of action and the possible peripheral mechanisms involved in the gastrointestinal (GI) stimulant effects of metoclopramide. Such a re-evaluation is opportune given the increasing use of this drug in the therapy of certain GI tract disorders. To provide an orientation on this subject the location in the GI tract and function of several relevant receptor types have been reviewed. In the past metoclopramide has been reported to enhance contractions of a variety of GI preparations to electrical stimulation, acetylcholine, carbachol and ganglion stimulants, to inhibit responses to alpha 2-adrenoreceptor agonists and 5-hydroxytryptamine, as well as blocking those to dopamine. Also in such preparations metoclopramide facilitates the release of acetylcholine to transmural stimulation. One important question is whether this effect is mediated via a specific prejunctional receptor. In this respect 2 suggestions have been made. Firstly that the drug may act as a preferential, prejunctional muscarinic antagonist thus inhibiting the negative feedback inhibition of acetylcholine release and secondly that metoclopramide may be a prejunctional agonist (partial) at 5-hydroxy-tryptamine receptors. Although the latter possibility appears most tenable at present, the involvement of a specific receptor remains to be confirmed. The important finding that dopamine receptors are probably not involved in the local stimulant effects of metoclopramide has important implications for future research orientated towards the discovery of a new generation of GI drugs lacking the side effects associated with central dopamine receptor blockade. Several compounds (cinitapride, BRL 20627A and cisapride) are now in the early stages of clinical evaluation.     

Effects of acetylcholine and nitroprusside on cGMP-dependent protein kinase in the perfused rat heart

The effects of acetylcholine and sodium nitroprusside on the activity of cGMP-dependent protein kinase were studied in the perfused rat heart. Acetylcholine produced a dose-dependent increase in cGMP levels and cGMP-dependent protein kinase activity, and reduced the force of contraction. Both acetylcholine and sodium nitroprusside produced rapid increases in cardiac cGMP, with nitroprusside being the more potent agent. Only acetylcholine, however, raised the activity ratio of the cGMP-dependent protein kinase and decreased the force of contraction. Whereas acetylcholine and nitroprusside were slightly additive in their effects on total cGMP levels, the increase in the activity ratio of the cGMP-dependent protein kinase and the decrease in the force of contraction produced by acetylcholine were unchanged by nitroprusside. The results suggest that the cGMP produced by acetylcholine, but not nitroprusside, was coupled to protein kinase activation in this tissue.