Inclusion of albumin in the perfusate has been previously shown to be detrimental to liver function, but its effect on hepatic vascular reactivity remains unknown. The aim of this study was to determine the effects of albumin on hepatic arterial vascular reactivity and liver viability in the isolated dual-perfused rat liver. A total of 12 rat livers were perfused with Krebs-Bülbring buffer without (Group 1) and with (Group 2) addition of 1% bovine serum albumin (BSA) through the hepatic artery and portal vein for up to 5 h. Hepatic arterial responses to acetylcholine and sodium nitroprusside were studied at 30-min intervals. Liver viability was assessed by bile volume production, release of aspartate serine aminotransferase (AST) and lactic acid dehydrogenase (LDH), and histological examination. Hepatic arterial responses to acetylcholine were significantly attenuated in Group 2. No significant differences in sodium nitroprusside responses were noted. However, bile volume production in Group 2 was significantly decreased compared to Group 1. Effluent AST and LDH release increased significantly in Group 1 but not in Group 2. Histological results showed that sinusoidal endothelial cells and hepatocytes were well preserved without significant deterioration in either group, although there was a marked decrease in vasodilatation to acetylcholine in Group 2. This data suggested that the presence of albumin in the perfusate did not improve retention of smooth muscle reactivity and reduced endothelium-dependent vasodilatation and bile volume production during perfusion. However, improved liver parenchymal cell function was observed.

Acetylcholine↗

PubMedDate not supplied

Simultaneous determination of mepivacaine, tetracaine, and p-butylaminobenzoic acid by high-performance liquid chromatography.

INTRODUCTION: The purpose of the present study was to develop a simple method for the simultaneous determination of mepivacaine, tetracaine, and p-butylaminobenzoic acid (BABA) in human plasma using high-performance liquid chromatography (HPLC) with a multiwavelength detector. METHODS: Human blood samples containing heparin, as an anticoagulant, and physostigmine (100 microg/ml), as an anticholinesterase, or human plasma containing physostigmine were spiked with various concentrations of mepivacaine, tetracaine and, in some cases, BABA. Blood samples were centrifuged and plasma was deproteinized with trifluoroacetic acid (TFA; 7%). After centrifugation, the pH was adjusted to 4.5 and an aliquot of 20, 50 or 100 microl was injected into the HPLC apparatus. The detection was done simultaneously at wavelengths of 214 and 300 nm. Analytical chromatography was done on a Waters microBondapak C(18) reverse-phase column (3.9 x 300 mm; particle size 10 microm) with a 30-min increasing linear gradient of 20-40% acetonitrile+0.05% TFA in H(2)O+0.05% TFA at a flow rate of 1 ml/min. The Waters HPLC system included two pumps, an automatic injector, a column oven, and a M490 multiwavelength detector. Quantification was done using integration of peak areas with peaks of authentic mepivacaine, tetracaine, and BABA standards. RESULTS: Calibration curves for standards of mepivacaine, tetracaine, and BABA were linear in the concentration ranges from 0.1 to 100 microg/ml, and the correlation coefficients exceeded.99 for all compounds. The lower limits of detection were 100 ng/ml for mepivacaine and 50 ng/ml for tetracaine and BABA. The yields for mepivacaine, tetracaine, and BABA were 91+/-2.1%, 82+/-3.3%, and 88+/-2.0% (mean+/-S.E.M., n=6), respectively. Degradation of tetracaine by human plasma at 37 degrees C was inhibited by physostigmine. DISCUSSION: The method is sensitive enough to allow blood concentration determinations of mepivacaine and tetracaine or its metabolite, BABA, following local anesthesia induced by these two drugs, especially when their toxic effect may be present. This method also may be useful in forensic medicine for determination of the cause of death after local anesthesia with mepivacaine and/or tetracaine.

4-Aminobenzoic Acid↗

PubMedDate not supplied

A simple and accurate mathematical method for calculation of the EC50.

A simple, accurate, and speedy noncomputational technique for the calculation of the EC50 or any other concentration-related parameter of concentration-effect curves is presented. It avoids the necessity for graph construction or computational curve-fitting programs and allows accurate calculation of the EC50, where the value falls between two known concentrations The technique has been applied to a concentration-response curve constructed to hepatic arterial (HA) vasoconstrictor responses to HA injections of noradrenaline in an isolated dual-perfused rat liver preparation. EC50 values calculated by the new technique were compared to those calculated by conventional, established, noncomputational techniques. The new technique is faster, more accurate, and simpler to perform than other established noncomputational techniques used for the calculation of the EC50 and can be widely applied to many other pharmacological investigations.

Animals↗

PubMedDate not supplied

Metabolite concentrations in human term placentae and their changes due to delayed collection after delivery.

The present study was designed to quantify the major cellular metabolites in human placentae and their changes due to the confounding effect of time and subsequent hypoxia during sample collection using magnetic resonance spectroscopy ((1)H-and (31)P-MRS). The absolute placental concentrations of lactate, glucose, major amino acids and cellular volume/osmo-regulators, glutathione, high-energy phosphates, fatty acids, phospholipids, triglycerols, and cholesterol are reported. There were no spatial differences in metabolism or protein expression throughout the placenta. The most significant temporal changes, due to the collection time (from 1 to 25 min after delivery), were increased concentrations of lactate (r=0.996, statistically significant P< 0.01 after 11 min) and decreased concentration of glucose and ATP (r=-0.963 and -0.97, respectively, P< 0.01 after 11 min). The placental samples from the later collection groups (16-24 min) had also significantly lower level of NAD(+) (r=-0.95, P< 0.01). Only the latest collection group (21-24 min) had increased lipid peroxidation and changes in lipid metabolites (P< 0.01). We conclude that the optimal window for collecting placental tissue without incurring metabolic artifacts due to hypoxic conditions is within 9 min of placental delivery.

Adult↗

PubMedDate not supplied

The effect of chilli ingestion on gastrointestinal mucosal proliferation and azoxymethane-induced cancer in the rat.

Of the three main races of Singapore, Malays and Indians are less susceptible to gastric and colorectal carcinoma and peptic ulcer when compared with Chinese. Racial differences in dietary habits include a smaller amount of chilli consumed by the Chinese when compared with the other two races. Chilli may be expected to accelerate gastrointestinal transit and hence to inhibit colonic carcinogenesis, while its active ingredient capsaicin protects against experimental gastric mucosal injury. The effect of chilli consumption was studied in relation to: (i) gastrointestinal crypt cell production rate and nucleic acid content as indices of mucosal proliferation, which is related to the risk of development of gastrointestinal cancer and peptic ulcer; and (ii) azoxymethane-induced intestinal cancer. Sprague-Dawley rats (n = 102) received either standard powdered chow or chow supplemented with 100 or 200 mg of chilli powder daily for 1, 18 or 24 weeks. Gastric, small-bowel and colonic crypt cell production rates were studied at all three time periods, while mucosal DNA, RNA and protein contents were measured at 1 and 24 weeks. While crypt cell production rates were unaffected by chilli ingestion, mucosal contents of nucleic acid and protein were mostly increased in chilli-fed animals compared to controls, especially in the colon at 24 weeks. A further 99 rats received subcutaneous injections of either azoxymethane 15 mg/kg/week x 6 or sterile water and were randomized to the same three dietary groups for 26 weeks. The number, size and location of benign and malignant duodenal and colonic tumours were unaffected by chilli intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗