Concentrative biliary secretion of ceftriaxone. Inhibition of lipid secretion and precipitation of calcium ceftriaxone in bile

The hepatic transport of ceftriaxone, a third-generation cephalosporin, was characterized in the rat and hamster; its effect on bile flow and bile acid-induced biliary lipid secretion was also measured. In anesthetized rats with biliary fistulae, the Tmax was about 5 mumol.min-1.kg-1, and in the hamster the Tmax was about 1 mumol.min-1.kg-1. The compound was not biotransformed. At high secretion rates, the concentration of cephalosporin in bile increased to 27 mmol/L, a concentration far exceeding the solubility product of its calcium salt [2 x 10(-6) (mol/L)2], which precipitated from bile. In the rat, ceftriaxone induced choleresis (22 microL/mumol ceftriaxone, the expected value for a dianionic compound). In the isolated perfused rat liver, ceftriaxone had a fractional hepatic extraction rate averaging 3%; the compound was concentratively secreted into bile, the bile-perfusate ratio ranging from 35-250. Ceftriaxone inhibited phospholipid and cholesterol secretion induced by endogenous or exogenous bile acids; the rate of inhibition was linearly proportional to the canalicular secretion rate of ceftriaxone. Hepatic transport of ceftriaxone had no influence on hepatic secretion of ursodeoxycholyltaurine. In contrast, the net hepatic transport of ursodeoxycholic acid, ursodeoxycholyltaurine, or cholyltaurine inhibited ceftriaxone transport in a dose-dependent manner. It is concluded that ceftriaxone and bile acids share a common mechanism for hepatic transport in the rat and also interact in the processes involved in biliary lipid secretion. Biliary secretion of unbiotransformed ceftriaxone occurs at high concentrations; secondary Ca2+ entry results in the formation of supersaturated canalicular bile and subsequent precipitation as a calcium salt in the biliary tract. These data explain the formation of biliary sludge that occurs in patients undergoing high-dose ceftriaxone therapy.

[Relationship between spinal PCP receptor on cardiovascular effect and noradrenergic system]

By using receptor blockade, HPLC, destroying catecholaminergic nerve terminals by 6-OHDA, autoradiography, and other techniques, the relationship between effects of the spinal PCP receptor on cardiovascular function and noradrenergic system was studied. The main results were as following. Hypotension and bradycardia induced by ith PCP were significantly antagonized by prazosin and yohimbine; the MHPG levels in spinal CSF were significantly increased during the ith PCP induced hypotension and bradycardia; pretreatment with 6-OHDA to destroy NA terminals in the spinal cord significantly decreased the ith PCP induced hypotension and bradycardia, and the density of PCP receptors in the spinal cord. The results suggest that there are PCP receptors on the NA terminals in the spinal cord, which promoted the release of NA and/or inhibited the reuptake of NA. This may be a possible mechanism underlying the influence of spinal PCP receptors on cardiovascular function.

[A lingulate valve formed from full layer of the jejunum in Roux-en-Y choledocho-jejunostomy and its effect against regurgitation of intestinal contents]

A lingulal valve formed from full layer of the jejunum designed to work against regurgitation of intestinal contents was reported. Animal experiment and the observation on fresh bodies documented that it could prevent regurgitation at the pressure of 2.94 kPa (300 mmH2O). The valve-plasty was added to Roux-en-Y choledocho (pancreatico)-jejunostomy in ten cases with satisfactory results. The procedure is not technically difficult, and long term follow-up found no severe complications.

[Mechanism of dynorphin inhibition on vasoconstriction in vitro]

Bioassay and HPLC detection were used to analyze the mechanism of inhibition of stimulation-induced vasoconstriction by dynorphin 1-13 (D1-13). Bioassay showed that D1-13 inhibited the contraction of rabbit ear artery and mesenteric artery induced by electrical field stimulation with IC50s of 8.5 +/- 1.2 x 10(-8) mol/L (n = 4) and 5.02 +/- 1.3 x 10(-7) mol/L (n = 5), respectively. D1-13 was ineffective in rabbit femoral artery at a concentration even larger than 10(-6) mol/L. D1-13 did not alter the basal tension of the blood vessel, nor the vasoconstriction induced by adding norepinephrine (NE) into the bath medium, and both constriction were markedly inhibited by phentolamine, an alpha-adrenoceptor blocker. With HPLC detection, the contents of NE in the bath medium were significantly reduced by D1-13 (5 x 10(-7) mol/L) from 340.56 +/- 73.13 pg/ml to 76.91 +/- 10.26 pg/ml as compared with control group (P less than 0.05). The effect could be completely reversed by naloxone at a concentration of 10(-6) mol/L (P less than 0.05). The results suggest that D1-13 reduces stimulation-induced vasoconstriction probably through a presynaptic inhibition of NE release from the nerve terminals.

In vitro tracheal mechanics by nuclear magnetic resonance imaging

Images of rabbit tracheal cross sections were obtained at a series of transmural pressures ranging from 22 to -95 cmH2O by use of a nuclear magnetic resonance imaging microscope. The excised, washed tracheas were immersed in a solution of phosphate-buffered saline made up in deuterium oxide (D2O, pH 7.3). The images are maps of proton density in the image slice (2.5 mm thick). All but one series of images showed a collapse process in which the trachealis muscle invaginated asymmetrically, i.e., the muscle appeared to favor one side of the cartilage ring system more than the other. The connecting tissue between the cartilage rings appeared to be more compliant than the rings themselves, thus suggesting that the tracheal lumen became corrugated at negative pressures. In the plane of a cartilage ring, the lumen appeared to remain patent at pressures as low as -95 cmH2O. However, between rings, where the tracheal wall was more compliant, the lumen appeared to be totally occluded at -53 cmH2O. Lumen areas in both the plane of the cartilage rings and in a plane between rings were measured from each series of printed images for six tracheas. These measurements, when normalized, averaged, and plotted against transmural pressure gave asymptotic logarithmic compliances (n1 in the model of Lambert et al., J. Appl. Physiol. 52: 44-56, 1982) of 1.2 +/- 0.4 and 20 +/- 7 for the interring and ring regions, respectively. These values are greater than the critical value of 0.5 (J. Appl. Physiol. 62: 2426-2435, 1987) and are thus consistent with wave speed flow limitation being possible anywhere in the trachea during forced expiration.

Restriction endonuclease activity induced by NC-1A virus infection of a Chlorella-like green alga

A type II restriction endonuclease, CviBI, was isolated from a eukaryotic, Chlorella-like green alga infected with the dsDNA containing virus NC-1A. The enzyme recognizes the sequence GANTC and cleaves DNA between the G and A. Methylation of deoxyadenosine in the GANTC sequence probably inhibits enzyme activity. In vitro CviBI cleaves host nuclear DNA but not viral DNA. A survey of 18 other viruses which infect the same Chlorella sp. revealed that infection with 5 of these viruses also induced a restriction endonuclease which cleaves DNA into the same size fragments as CviBI.

Electrophysiological studies on the termination sites of double projection spinal dorsal horn neurons in the cat

Some projection neurons in laminae III, IV and V of the feline lumbar dorsal horn have been found to be antidromically driven from stimulation of both the ipsilateral cervical dorsal and dorsolateral funiculi that are well-dissected and insulated from one another. No detectable responses can be evoked from these neurons when stimulation is applied to sites rostral to the lateral cervical nucleus and the dorsal column nuclei, suggesting that the dorsal and dorsolateral funicular branches of these neuron's axons terminate in the lateral cervical nucleus and the dorsal column nuclei, respectively. The results indicate that these neurons are an intersection set of the spinal cervical tract (SCT) and dorsal column postsynaptic (DCPS) neurons and have been thus named spinal cervical tract-dorsal column postsynaptic (SCT-DCPS) neurons.

Roles of opioid peptides of PAG in analogous electro-acupuncture inhibition of experimental arrhythmia: analyzed by specific antisera microinjection

Using specific antisera microinjected into periaqueductal grey (PAG), we further studied the mechanism of the analogous electroacupuncture, deep peroneal nerve stimulation (DPNS), inhibition on the experimental arrhythmia, hypothalamic stimulation-induced ventricular extrasystoles (HVE). Neither normal serum nor anti-leu-enkephalin antiserum interfered with DPNS inhibition; anti-dynorphin A (1-8) tended to attenuate the inhibition; and anti-beta-endorphin antiserum blocked it. The results provided further evidence for the hypothesis that beta-endorphin in PAG plays an important role in the neural circuit of DPNS inhibition on HVE.

Inhibitory effect of analogous electro-acupuncture on experimental arrhythmia

Rabbits were used to study the inhibitory effect of analogous electro-acupuncture on the experimental arrhythmias, i.e. hypothalamic stimulation-induced ventricular extrasystole (HVE). The result revealed that HVE, which was due to an increased cardiac sympathetic activity, could be inhibited by deep peroneal nerve stimulation with an electrical current of low frequency and low intensity. Such effect is related to endogenous opioid peptides and serotonin in the arcuatus area, the periaqueductal gray and and the medial medulla. The acupuncture correction of arrhythmias may have the same mechanism.

Structural proteins and lipids in a virus, PBCV-1, which replicates in a Chlorella-like alga

PBCV-1, a large dsDNA-containing virus which replicates in a Chlorella-like green alga, is composed of approximately 64% protein, 25% DNA, and 5-10% lipid on a weight basis. Polyacrylamide gel electrophoresis of the dissociated virus particle resolves 50 to 60 proteins which range in apparent molecular weight from 10,000 to 135,000. Two of these proteins are glycoproteins and at least four are located on the viral surface. The major lipids are phosphatidyl choline, phosphatidyl ethanolamine, and an unidentified component. The effect of organic solvents, surfactants, and chelating and reducing agents on viral infectivity and ultrastructure are reported. Inhibitor studies established that PBCV-1 protein synthesis occurs on cytoplasmic ribosomes.