First-pass effects of verapamil on the intestinal absorption and liver disposition of fexofenadine in the porcine model.

The aim of this study in pigs was to investigate the local pharmacokinetics of fexofenadine in the intestine and liver by using the pig as a model for drug transport in the entero-hepatobiliary system. A parallel group design included seven pigs (10-12 weeks, 22.2-29.5 kg) in three groups (G1, G2, G3), and a jejunal single-pass perfusion combined with sampling from the bile duct and the portal, hepatic, and superior caval veins was performed. Fexofenadine was perfused through the jejunal segment alone (G1: 120 mg/l, total dose 24 mg) or with two different verapamil doses (G2: 175 mg/l, total dose 35 mg; and G3: 1000 mg/l, total dose 200 mg). The animals were fully anesthetized and monitored throughout the experiment. Fexofenadine had a low liver extraction (E(H); mean +/- S.E.M.), and the given doses of verapamil did not affect the E(H) (0.13 +/- 0.04, 0.16 +/- 0.03, and 0.12 +/- 0.02 for G1, G2, and G3, respectively) or biliary clearance. The E(H) for verapamil and antipyrine agreed well with human in vivo data. Verapamil did not increase the intestinal absorption of fexofenadine, even though the jejunal permeability of fexofenadine, verapamil, and antipyrine showed a tendency to increase in G2. This combined perfusion and hepatobiliary sampling method showed that verapamil did not affect the transport of fexofenadine in the intestine or liver. In this model the E(H) values for both verapamil and antipyrine were similar to the corresponding values in vivo in humans.     

Muscle membrane polarisation after provocative tests, and after cooling: the normal CMAP changes to be expected.

OBJECTIVE: To know the range of changes of compound muscle action potentials (CMAPs) in the muscles innervated by the ulnar nerve after diverse provocative tests, 14 healthy patients were studied with the same protocol. METHODS: CMAPs were measured at rest, just after a short exercise test (SET), during short 5 and 10c/s repetitive nerve stimulation (RNS) trains, at approximately 32 and approximately 20 degrees C. RESULTS: At 32 degrees C, the SET induced a significant but transient enlargement of the CMAPs (amplitude increased by 8.3%, duration decreased by 9%) that was only partially reproduced by RNS trains, except for a significant shortening of the CMAPs at 10c/s. At 20 degrees C without exercise, CMAPs increased significantly by approximately 30% in amplitude, duration and area, and after the SET the inverse of what has been seen at 32 degrees C was observed (amplitude decreased by 1.7% and duration increased by 9%). RNS at 20 degrees C produced a marked interpatient heterogeneity except for a significant shortening of the CMAPs at 10c/s. In one pure autonomic failure patient, the infusion of norepinephrine induced potentiation of the responses at rest and a decrease in the expected changes after provocative tests. CONCLUSIONS: CMAP amplitude and duration are significantly modified just after the SET at 32 degrees C, at rest at 20 degrees C and after RNS at 10c/s but not at 5c/s. Although providing indirect evidence, these findings indicate that provocative tests make the muscle membrane hyperexcitable by the way of a direct influence on the electrical events and by an indirect local catecholamine spillover.     

Isolation and characterization of toxic fractions from Brucella abortus.

Two types of toxic fractions, protein-rich and carbohydrate-rich, were isolated from attenuated (strain 19) and virulent (strain 2308) Brucella abortus organisms. Polyacrylamide gel electrophoresis of the protein-rich fraction, in the presence and absence of sodium dodecyl sulfate, revealed qualitative and quantitative differences in the protein bands derived from the attenuated and virulent strains. Sodium dodecyl sulfate-gel electrophoresis indicated that the major differences between these protein fractions were in the molecular weight range from 14,000 to 40,000. Immunoelectrophoresis of these fractions from the attenuated and virulent strains revealed differences in the antigenic spectrum. Polypeptides in the carbohydrate-rich fraction could be visualized on polyacrylamide gels only when reacted with fluorescamine before electrophoresis. Immune sera did not precipitate the components of the carbohydrate-rich fraction. Intradermal injecttion of the protein and carbohydrate-rich fractions resulted in different types of skin lesions in guinea pigs, i.e., edematous/erythematous and necrotic lesions, respectively. Fractions derived from attenuated and virulent strains of B. abortus were equally toxic in the guinea pig skin test. The toxic activity of both types of fractions was susceptible to pronase and heat treatment.     

Vaccine-associated paralytic poliomyelitis in a patient with MHC class II deficiency.

Vaccine-associated paralytic poliomyelitis (VAPP) is a rare complication of oral polio vaccine. We describe a fatal case of VAPP in an 8-month-old boy with Major Histocompatibility Class II deficiency. The isolated poliovirus was a Sabin type 2-type 1 recombinant that showed 1.4% VP1 divergence from Sabin type 2.     

Cloning, expression, and occurrence of the Brucella Cu-Zn superoxide dismutase.

Recently, the complete amino acid sequence of a protein expressed in Escherichia coli from cloned Brucella abortus DNA was reported. On the basis of amino acid homology, this protein was identified as a copper-zinc superoxide dismutase (Cu-Zn SOD) (B. L. Beck, L. B. Tabatabai, and J. E. Mayfield, Biochemistry 29:372-376, 1990). We demonstrate in this paper that the sequenced protein is the same as the previously studied salt-extractable protein BCSP20. The plasmid-encoded protein expressed from recombinant E. coli is identical to the Brucella-derived BCSP20 in molecular mass, N-terminal amino acid sequence, and cross-reactivity with homologous and heterologous rabbit sera against either the recombinant gene product or the Brucella-derived protein. A survey of the expression of the Cu-Zn SOD protein in Brucella biovars representing all species was done by Western blotting (immunoblotting) using antisera raised against the recombinant E. coli-derived protein. With the exception of B. neotomae and B. suis biovar 2, the Cu-Zn SOD protein was detectable in all Brucella species and biovars tested, including eight biovars of B. abortus.     

Demonstration of A-currents in pancreatic islet cells

Voltage-activated K⁺ currents resistant to TEA but blockable by 4-AP were recorded from mouse pancreatic islet cells. These currents first become observable during depolarizations to voltages more positive than –40 mV, reaching a peak amplitude of 120±34 pA at +6 mV (n=4), display rapid turn on (=3.3±1.1 ms at +6 mV) and inactivate completely within 250 ms (=65±5 at +6 mV). The current is subject to steady-state inactivation. The midpoint (V _h) of the inactivation curve (h) was observed at –72±2 mV. The properties of this current resemble those reported for the A-current in neurons.     

Oral immunization of mice with attenuated Salmonella typhimurium containing a recombinant plasmid which codes for production of a 31-kilodalton protein of Brucella abortus.

Salmonella typhimurium chi 4064, an attenuated delta cya delta crp mutant of S. typhimurium SR-11, was used as a carrier for the plasmid pBA31-R7. This plasmid codes for the expression of a 31-kilodalton (kDa) protein from Brucella abortus (BCSP31). Recombinant S. typhimurium chi 4064(pBA31-R7) expressed BCSP31 in vitro as shown by Western blot (immunoblot) analysis. The plasmid was stable in vitro and in vivo and did not affect the ability of the mutant to invade and colonize the small intestine, mesenteric lymph nodes, liver, or spleen of BALB/cByJ mice. Animals orally immunized with S. typhimurium chi 4064(pBA31-R7) developed serum and intestinal antibody responses to the B. abortus 31-kDa protein and to salmonella endotoxin as measured by enzyme-linked immunosorbent assay. Mice orally immunized with S. typhimurium chi 4064pBA31-R7 did not develop a delayed-type hypersensitivity following a footpad injection with recombinant BCSP31. Antigen-specific blastogenic data also support these in vivo results. All data indicate that this route of antigen delivery is effective for stimulating antibody-mediated immunity but that the B. abortus 31-kDa protein is a poor immunogen for inducing a cell-mediated immune response in BALB/cByJ mice.     

Perchlorate stimulates insulin secretion by shifting the gating of L-type Ca2+ currents in mouse pancreatic B-cells towards negative potentials

The effects of the chaotrophic anion perchlorate (ClO4-) on glucose-induced electrical activity, exocytosis and ion channel activity in mouse pancreatic B-cells were investigated by patch-clamp recordings and capacitance measurements. ClO4- stimulated glucose-induced electrical activity and increased the action potential frequency by 70% whilst not affecting the membrane potential when applied in the presence of a subthreshold concentration of the sugar. ClO4- did not influence ATP-dependent K (KATP) channel activity and voltage-gated delayed K+ current. Similarly, ClO4- had no effect on Ca2+-dependent exocytosis. The stimulation of electrical activity and insulin secretion was instead attributable to an enhancement of the whole-cell Ca2+ current. This effect was particularly pronounced at voltages around the threshold for action potential initiation and a doubling of the current amplitude was observed at -30 mV. This was due to a 7-mV shift in the gating of the Ca2+ current towards negative voltages. The action of ClO4- was more pronounced when added in the presence of 0.1 mM BAY K8644, whereas no stimulation was observed when applied at a maximal concentration of the agonist (1 mM). Single-channel recordings revealed that the effect of ClO4- on whole-cell currents was principally due to a 60% increase in the mean duration of the long openings and the number of active channels. We propose that ClO4- stimulates insulin secretion and electrical activity by exerting a BAY K8644-like action on Ca2+ channel gating.