Characterization of the antisecretory action of prostaglandin D2 in the rat colon

Previous studies have shown that prostaglandin D₂ (PGD₂) inhibits neuronally mediated secretion in the rat colon. This antisecretory action of PGD₂ was further characterized by the use of a prostaglandin D receptor blocker. Prostaglandin D₂ inhibited the neuronally mediated short-circuit current evoked by prostaglandin I₂, which represents Cl^- secretion. The concentration-response curve for the inhibition by PGD₂ was shifted to the right in the presence of the prostaglandin D receptor blocker, AH 6809. AH 6809 had no effect on the short-circuit current response induced by prostaglandin E₂ or iloprost, a stable prostaglandin I₂ analogue, suggesting an interaction of the blocker with receptors specific for PGD₂. A direct interaction of PGD₂ with enteric neurones was studied by determining its effect on acetylcholine release from enteric neurones preloaded with [³H]choline. Prostaglandin D₂ suppressed ³H release induced by electric field stimulation. It had, however, no effect on the release induced by depolarization with potassium. The results suggest that the inhibitory action of PGD₂ on enteric cholinergic neurones is mediated by prostaglandin D receptors.     

Sputum induction as a research tool for the study of human respiratory mucus

The study objectives were to compare in vitro transportability and physical properties of respiratory mucus, obtained invasively by direct collection (DC) right after endotracheal intubation and non-invasively by sputum induction with 3% hypertonic saline solution inhalation (SI) 24 h before the anesthesia. Twenty-two patients with no pulmonary disease scheduled for elective abdominal surgical procedures were studied. The parameters analyzed and the main results are as follows. (1) Transportability by cilia (MCT), SI was higher than DC (0.94+/-0.25 and 0.62+/-0.25; P<0.001). There was a significant correlation between the two methods and DC could be estimated by: DC=0.21+(0.44 SI) (r=0.44; P<0.001). (2) Transportability by cough (CC), SI was higher than DC (68.23+/-32.1 and 33.58+/-19.04 mm; P=0.002). (3) Contact angle (CA), SI was lower than DC (10+/-3 degrees and 22+/-14 degrees ; P=0.025). (4) Rheological properties (no significant difference obtained between SI and DC). These results indicated that SI changes mucus physical properties and transportability in non-expectorators.     

天然免疫模式识别途径:胞外识别与胞内识别

天然免疫系统通常籍模式识别受体识别病原体相关分子模式。取决于感染的性质,模式识别受体通过细胞外 或细胞内途径识别病原体,并传导相应的信号,激活宿主防御应答,消灭入侵病原体。     

Intracellular survival of persistent group A streptococci in cultured epithelial cells

Group A streptococcus (GAS) is the principle etiologic agent of bacterial pharyngotonsillitis and a wide range of other diseases. Failure to eradicate GAS from patients has been documented in 5-30% of patients with pharyngotonsillitis, in spite of the continued sensitivity of GAS to penicillin and other beta-lactams. It was recently proposed that eradication failure might be attributed to the ability of GAS to maintain an intracellular reservoir during antibiotic treatment. We have previously shown that strains derived from patients with bacterial eradication failure, despite antibiotic treatment (persistent strains), adhered to and were internalized by cultured epithelial cells more efficiently than strains that were successfully eradicated. Since, penicillin and other beta-lactams do not penetrate well into mammalian cells, intracellular survival of GAS is crucial in order to persist during prolonged antibiotic treatment. In this study, we compared the survival of GAS strains from cases of eradication failure and eradication success, using an epithelial cell culture model. We found that persistent strains show significantly increased intracellular survival, compared to the 'eradication success' strains. This finding supports the idea that an intracellular reservoir of GAS plays a role in the etiology of antibiotic eradication failure.     

大鼠前庭神经核群向腰髓投射特征——BDA法逆行研究

目的　研究大鼠前庭神经核群向脊髓的投射纤维特征。方法　在 7例SD大鼠采用结合生物素的葡聚糖胺(BDA)逆行法观察大鼠前庭核群向脊髓的投射。结果　除前庭神经上核 (SVN)外的其余各前庭核均有向大鼠腰髓的投射 ,单侧注射的实验动物中 ,前庭神经内侧核 (MVN)、外侧核 (LVN)和降核 (DVN)的标记神经元可见于双侧 ,其中MVN和LVN的标记神经元以注射同侧占优势 ,而DVN标记神经元两侧数量基本一致。结论　大鼠前庭脊髓尾侧束发出纤维投向脊髓腰段     

BicD-dependent localization processes: from Drosophilia development to human cell biology

Many eukaryotic cells depend on proper cell polarization for their development and physiological function. The establishment of these polarities often involve the subcellular localization of a specific subset of proteins, RNAs and organelles. In Drosophila, the microtubule-dependent BicD (BicaudalD) localization machinery is involved in the proper localization of mRNA during oogenesis and embryogenesis and the proper positioning of the oocyte and photoreceptor nuclei. BicD acts together with the minus-end directed motor dynein as well as Egl and Lis-1. The finding that the mammalian homologs of BicD function in retrograde Golgi-to-ER transport has supported the view that BicD may be part of a repeatedly used and evolutionary conserved localization machinery. In this review we focus on the various processes in which BicD is involved during Drosophilian development and in mammals. In addition, we evaluate the interactions between BicD, the dynein localization machinery and associated factors.     

Coupling between proximal tubular transport processes

Summary The rate of active transport by the proximal renal tubule of amino acid (l-histidine), sugar (-methyl-d-glycoside), H⁺ ions (glycodiazine), phosphate and para-aminohippurate was evaluated by measuring the zero net flux concentration difference (c) of these substances. In the case of calcium the electrochemical potential differencec +zFc_i /RT) was the criterion employed. The rate of isotonic Na⁺-absorption (J_Na) was measured with the shrinking droplet method. The effect of ouabain on the transport of these substances was tested in the golden hamster and the effect of SITS (4-acetamido-4isothiocyanatostilbene 2,2-disulfonic acid) was observed in rats.Ouabain (1 mM) applied peritubularly incompletely inhibited J_Na (80%), but in combination with acetazolamide (0.2 mM) the inhibition was almost complete (93%). In addition, ouabain inhibited the sodium coupled (secondary active) transport processes ofl-histidine, -methyl-d-glycoside, calcium and phosphate by more than 75%. It did not affect H⁺ (glycodiazine) transport and PAH transport was only slightly affected.When SITS (1 mM) was applied from both sides of the cell it inhibited H⁺ (glycodiazine) transport by 72% and reduced J_Na by 38% when given from only the peritubular cell side. SITS (1 mM), however, had no significant affect on H⁺ secretion and sodium reabsorption if it was applied from only the luminal side. Furthermore it had no affect on the other transport processes tested, regardless of the cell side to which it was applied.When the HCO ₃ ^– buffer or physically related buffers were omitted from the perfusate the absorption of Na⁺ was reduced by 66%, phosphate by 44%, andl-histidine by 15%. All the other transport processes tested were not significantly affected.The data are consistent with the hypothesis that the active transport processes of histidine, -methyl-d-glycoside and phosphate, which are located in the brush border, are driven by a sodium gradient which is abolished by ouabain. This may also apply to the Na⁺-Ca²⁺ countertransport located at the contraluminal cell side. The residual Na⁺ transport remaining in the presence of ouabain is likely to be passively driven by the continuing H⁺ transport which probably is driven directly by ATP. SITS seems to inhibit the exit step of HCO ₃ ^– from the cell and secondary to that, the luminal H⁺-Na⁺ exchange and consequently the Na⁺ reabsorption. In the absence of HCO ₃ ^– buffer in the perfusates the luminal H⁺-Na⁺ exchange seems to be affected and the pattern of inhibition of the other transport processes is almost the same as with SITS. The different effects onP _i reabsorption observed under these conditions might be explained by possible variations in intracellular pH.     

Characterization of acetate uptake by the colonic epithelial cells of the rat

The characteristics of acetate uptake by colonic epithelial cells of the rat were studied. Clear saturation kinetics of acetate uptake were not observed in these experiments at either 0° C or 30° C. A decrease in the pH of the medium markedly increased the acetate uptake. The activation energy for acetete uptake derived from an Arrhenius plot was about 6.1 kcal/mole. Among the inhibitors tested, no effective inhibition of acetate uptake at 0° C was observer. Metabolic inhibitors severely inhibited transport at 30° C. Inhibition of acetate uptake by other short chain fatty acids, which was non-competitive, was observed. The finding that efflux from the cells was stimulated in the presence of compounds such as pyruvate and bicarbonate supported the notion of a close interrelationship between weak electrolyte transports in vivo. Although the H⁺ gradient across the cell membrane is suggested to be one of the factors determining the uptake rate, it seems difficult to explain all the results in this way.     

Transport of Ca2+ ions in the mitochondria of Ehrlich's ascites tumor cells

The pattern of Ca²⁺ accumulation by tumor mitochondria (MC) was investigated under various experimental conditions. In the absence of penetrating anions tumor MC were shown to take up Ca²⁺ in only one fifth the amount taken up by liver MC. In the presence of acetate this difference was greater still. Inorganic phosphate (P_in) abolished the observed defects of Ca²⁺ transport and increased the Ca²⁺ capacity of the tumor MC considerably. By contrast with liver MC, P_in also had a stabilizing effect on membrane permeability of the tumor MC; this may be the cause of the increasee Ca²⁺ capacity of these MC.Department of Bioenergetics, Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oka. (Presented by Academician of the Academy of Medical Sciences of the USSR S. E. Severin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 8, pp. 202–205, August, 1977.     

Intracellular Ca2+ concentrations are not elevated in resting cultured muscle from Duchenne (DMD) patients and in MDX mouse muscle fibres

The free intracellular calcium concentration, [Ca²⁺]_i, was studied in single myotubes using the fluorescent Ca²⁺ indicator fura-2. Myotubes cultured from satellite cells of small muscle specimens from Duchenne muscular dystrophy (DMD) patients were compared with human control myotubes and with myotubes cultured from MDX and control mouse muscle satellite cells. The resting [Ca²⁺]_i levels in DMD and control myotubes were not significantly different, i. e. 104 ±26 nM (mean ± SD, n=190 cells from eight DMD patients) compared with 97±25 nM (175/seven controls) and were not significantly lower than the corresponding murine values (154±33 nM, n=135 MDX myotubes; 159±34 nM, n=135 controls). All myotubes reacted to 10 M acetylcholine or 40 mM KCl with fast transient increases of [Ca²⁺]_i. After application of a hyposmotic (130 mOsm) solution, [Ca²⁺]_i was increased 1.5- to 3-fold within 2–3 min, the DMD myotubes tending to stronger reactions (significantly higher [Ca²⁺]_i in 2 out of 6 cases). The response was usually transient, [Ca²⁺]_i decreasing to the initial level within 10 min. Gadolinium (50 M) reduced the response by 50%–70%, indicating that the osmotic shock increased Ca²⁺ influx. During exposure to high (15 mM) [Ca²⁺]e, [Ca²⁺]_i of DMD and control cells was 1.5- to 2-fold higher. Adult muscle fibres from MDX mice and controls showed identical Ca²⁺ resting levels (n=45 fibres from three mice in each case), but did not respond to decreased external osmolarity with a change in [Ca²⁺]_i. The results indicate that lack of dystrophin in muscle fibres does not necessarily lead to increased [Ca²⁺]_i. It is suggested that increased [Ca²⁺]_i is probably a secondary consequence of fibre damage.