Inhibitory effect of fluoride on the secretion of insulin

Summary The oral administration of sodium fluoride (NaF) (40 μmol/100 body weight [bw]) to fasting rats produced an immediate fall in insulin levels and the consequent increase in glycemia. These phenomena were observed with plasma fluoride concentrations 5–15 μM. Glycemia and insulin returned to normal levels within 4–5 hours, together with the washing out of fluoride from plasma and soft tissues. The insulin secretion of isolated Langerhans islets, perifused with solutions containing 5, 10, or 20 μM fluoride, was found to be significantly inhibited as a function of fluoride levels, both with basal and stimulatory concentrations of glucose. One hour after the intake of 60 mg of NaF, fasting human volunteers showed increased fluoride (5–15 μM) together with a significant fall of plasma insulin levels.     

Pharmacological characterization of the receptor mediating the adrenergic inhibition of responses to substance P in the cingulate cortex

The excitatory responses of neurones in the anterior cingulate cortex of the rat to iontophoretically applied substance P (SP) are reduced by noradrenaline (NA) applied iontophoretically or released from noradrenergic pathways. In order to determine the receptor involved in this inhibitory effect we have studied the effects of a number of receptor-specific adrenergic agonists and antagonists on responses of cingulate neurones to SP in rats anaesthetized with chloral hydrate. Low iontophoretic currents (0-15 nA) of NA, adrenaline and the beta-agonist, clenbuterol, all strongly reduced responses to SP. Isoprenaline was also effective but less consistently so, although problems were experienced with its iontophoretic release from micropipettes. The alpha 1-agonists, phenylephrine and methoxamine were also able to reduce responses to SP. However, this reduction required higher iontophoretic currents (15-60 nA) and was associated with depressant effects on baseline firing rate. The alpha 2-agonist clonidine was only weakly active at high currents and this too was associated with depression of baseline firing. Similar weak effects were noted with dopamine. The inhibitory effects of NA on SP responses were convincingly blocked or reversed by the beta-antagonist, practolol, but not by the alpha 1-antagonist, prazosin. The reduction of SP responses by phenylephrine was also blocked by practolol but unaffected by prazosin. Finally, reduction of SP excitations by activation of the coeruleocortical pathway was also blocked by practolol applied iontophoretically to the cortical cells. These results are consistent with the hypothesis that the effect of NA on SP responsiveness in the cingulate cortex is mediated by beta-adrenoreceptors.     

Effect of intraperitoneally injected fluoride on plasma calcium in suckling and adult rats

Summary Sodium fluoride 10, 20, or 40 mg/kg body weight was given intraperitoneally to rats (6–11 days old and 90–95 days old). Blood analyses showed an initial increase in plasma fluoride concentration. The subsequent decrease in fluoride was paralleled by a decrease in total plasma calcium. These plasma concentrations were normal at blood collection 4 days after fluoride injection. The baby rats differed from the older rats in that their initial plasma calcium was higher and that the drop in plasma calcium concentration was less pronounced than in the old rats. A diet low in calcium and phosphate enhanced the effects of fluoride on total plasma calcium. The data indicate that the effect of large doses of fluoride on lowering the plasma calcium level is modified by the calcium intake.     

扩散－电极法测定食品中氟

样品中氟在扩散盒中与硫酸作用生成氟化氢，经扩散吸附在扩散盒的碱膜上。碱膜用缓冲液溶解后，氟化物含量由氟离子选择电极测定。用本法对菜花、菠菜、大米、鱼片干四种样品以及玉米氟样品的氟进行了精密度和准确度试验。相对标准偏差在５％以内，回收率为９０％～１０３％，最小检测量为０．２４μｇ。该法可直接测定含氟量在０．５～１００ｍｇ／ｋｇ（干重）的食品。     

Model Features of a Cardiac lontophoretic Drug Delivery Implant

Pharmaceutical Research -     

3种氟素制剂氟离子进入离体乳牙釉质内含量的比较研究

目的：比较3种氟素制剂对离体乳牙釉质氟含量的影响。方法：24个乳前牙随机分为3组，各牙冠唇舌向均分为两半，分别开窗，酸蚀，随机将其中1个作为实验区分配给1种氟素制剂处理，另1个作对照。1、2、3组实验区分别用10％（NH4）2MoO2F4溶液、38％Ag(NH3)2F溶液和APF－LaCl3溶液联用处理3min，对照区去离子水处理。将经处理的标本各置入4ml 0.1mol/L乳酸中，48h后终止1、2组试验，第3组持续至144h。用氟离子电极法测定各管溶液内氟离子浓度，统计分析。结果：3种氟素制剂处理后，离体乳牙釉质中均有氟摄入；釉质氟增量以APF－LaCl3溶液联用组最多，38％Ag(NH3)2F溶液组次之，10％（NH4）2MoO2F4溶液组最少。结论：3种氟素制剂均可增加离体乳牙釉质内氟含量，其中APF－LaCl3溶液联用作用最强，10％（NH4）2MoO2F4溶液最弱。     

Mechanism of toxic action of fluoride in dental fluorosis: whether trimeric G proteins participate in the disturbance of intracellular transport of secretory ameloblast exposed to fluoride

In enamel fluorosis model rats treated with sodium fluoride, secretory ameloblasts of incisor tooth germs exhibited disruption of intracellular trafficking. We examined whether heterotrimeric G proteins participated in the disruption of vesicular trafficking of the secretory ameloblast exposed to fluoride, using immunoblotting and pertussis toxin (IAP)-induced adenosyl diphosphate (ADP)-ribosylation for membrane fractions of the cell. Immunoblotting of crude membranes, post supernatants of the ameloblast, with anti-G_i3/o and anti-G_s antibodies showed that G_i3 or G_o proteins existed in the secretory ameloblast, but G_s protein did not. Immunoblotting of the subcellular membrane fractions indicated that the G_i3 or G_o proteins were located in the Golgi membrane, but were not in the rough endoplasmic reticulum (rER) membrane. Autoradiograph of IAP-induced ADP-ribosylation, however, showed the existence of IAP-sensitive G proteins both in rER and Golgi membranes. Fluoride treatment decreased the G proteins bound to both membranes. These findings indicate that different G proteins, both of which are IAP-sensitive, are present in the rER and Golgi apparatus, and suggest that these G proteins participate in the disturbance of intracellular transport of the secretory ameloblast exposed to fluoride. Received: 24 June 1998 / Accepted: 8 September 1998     

Cholecystokinin Excites Neostriatal Neurons in Rats via CCKA or CCKB Receptors

The effect of iontophoretically applied cholecystokinin (CCK) on neurons of the neostriatum was studied in rats anaesthetized with urethane. The most frequently observed effect of the sulphated octapeptide (CCK-8S) on striatal neurons was excitation. Spontaneously active neurons responded more often to CCK-8S than quiescent cells. Silent, primarily non-responsive neurons could often be stimulated with CCK-8S using glutamate to induce an ongoing discharge. Thus, 45.8% of the 177 neurons studied changed their discharge rate by more than 30%. Certain CCK receptor antagonists could prevent the effect of CCK-8S, fully or at least partly, in the majority of CCK-responsive neurons. The data suggest that cholecystokinin modulates the firing of active neostriatal neurons via the CCKA or the CCKB receptor type. Furthermore, we compared neuronal responses to glutamate with those recorded during concomitant administration of CCK-8S in order to study the interaction of both transmitters, which may be colocalized in striatal afferents. CCK-8S mainly enhanced the excitatory effect of glutamate on striatal neurons, but in several neurons the response to glutamate was reduced. The CCKB receptor antagonist could prevent CCK-8S from increasing the glutamate-induced activation.     

拮氟锐对大鼠肠道氟吸收及微量元素的影响

拮氟锐是由硼、微量元素和中药制成的抗氟药物。本文应用肠道原位灌流技术。观察了拮氟锐对大鼠肠道氟吸收的干预作用及微量元素的影响。结果透明：拮氟锐可促进肠道ＢＦ４的形成，使氟吸收量减少，血氟降低。同时，拮氟锐可拮抗氟所致的微量元素的降低。与硼锌组比较，拮氟锐的抗氟作用效果更明显。