A suprachoroidal electrical retinal stimulator design for long-term animal experiments and in vivo assessment of its feasibility and biocompatibility in rabbits.

This article reports on a retinal stimulation system for long-term use in animal electrical stimulation experiments. The presented system consisted of an implantable stimulator which provided continuous electrical stimulation, and an external component which provided preset stimulation patterns and power to the implanted stimulator via a paired radio frequency (RF) coil. A rechargeable internal battery and a parameter memory component were introduced to the implanted retinal stimulator. As a result, the external component was not necessary during the stimulation mode. The inductive coil pair was used to pass the parameter data and to recharge the battery. A switch circuit was used to separate the stimulation mode from the battery recharging mode. The implantable stimulator was implemented with IC chips and the electronics, except for the stimulation electrodes, were hermetically packaged in a biocompatible metal case. A polyimide-based gold electrode array was used. Surgical implantation into rabbits was performed to verify the functionality and safety of this newly designed system. The electrodes were implanted in the suprachoroidal space. Evoked cortical potentials were recorded during electrical stimulation of the retina. Long-term follow-up using OCT showed no chorioretinal abnormality after implantation of the electrodes.

HPLC determination of captopril in human plasma and its pharmacokinetic study.

A simple and sensitive reversed-phase liquid chromatographic method has been developed and validated for the analysis of captopril in human plasma and the study of the pharmacokinetics of the drug in human body. Captopril was stabilized by forming an adduct with p-bromophenacyl bromide. The adduct formed and 4-chloro-2-nitroaniline (internal standard) were extracted with ethyl acetate:benzene (1:1), and then measured by HPLC using a Spherisorb C18 column as stationary phase and a water:acetonitrile:acetic acid mixture (44:55:0.2, v/v/v) as mobile phase. Captopril was quantified by absorbance at 258 nm. The method proved to be linear in the clinical range of 5-500 ng/mL. The lower limit of detection of captopril in plasma was 2 ng/mL. Intra-day and inter-day coefficients of variation of assay for captopril in plasma were 5.8%-8.5% (n = 7) and 8.0%-9.5% (n = 5), respectively. The recoveries of captopril were 90%-98% for plasma. The data obtained was fitted with 3P87 program on computer to study the pharmacokinetics. The results showed that the disposition of captopril was conformed to a two-compartment open model with Tmax = 0.56 h, Cmax = 266.5 ng/mL and AUC(zero)-infinity = 380.3 ng.h/mL. The method has been used to determine captopril in plasma samples from ten volunteers and provided data on the pharmacokinetics of the drug. The results inferred that captopril is absorbed rapidly and had a relatively short half-life time in healthy individuals.

Circulatory effects of anisodamine on cardiopulmonary bypass.

Anisodamine, a new M-cholinergic blocker discovered in China, was employed in experimental dogs on cardiopulmonary bypass (CPB) with a view to observing its hypotensive activities. Before bypass an intravenous bolus injection of anisodamine 5 mg/kg caused a transient fall of about 20 mmHg in arterial blood pressure for 10 to 15 minutes, with an increase of about 10 mmHg in pulse pressure, indicating lowering afterload. During bypass, a continuous intravenous drip of anisodamine brought about 27 to 37 mmHg fall in perfusion pressure (compared with the control group) while the perfusion flow rate was kept constant. Beneficial effects of anisodamine were manifested, post-bypass, by enhancement of cardiac output, lack of elevation of pulmonary arterial pressure, a speedy recovery of the ST segment to normal, and a decrease of the rate-pressure product, as results of circulatory improvement and myocardial protection.

The effects of dauricine and verapamil as calcium channel blockers on the plasma concentration of 6-keto-prostaglandin F1 alpha and thromboxane B2 during cardiopulmonary bypass.

Three groups of ten dogs underwent 80 minutes cardiopulmonary bypass. Two of the three groups were administered dauricine, as a new calcium channel blocker, and verapamil, as a generally recognized calcium channel blocker, respectively, from 15 minutes pre-bypass to the end of the bypass procedure (a period of 95 minutes). By means of radioimmunoassay plasma 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TxB2) as the stable metabolites of prostacyclin and thromboxane A2 were surveyed. During the aortic clamping the hemodynamic changes were recorded. The dauricine and verapamil groups showed markedly inhibited generation of excessive 6-keto-PGF1 and TxB2, a narrowed ratio of TxB2 to 6-keto-PGF1 alpha, as well as a reduced total systemic peripheral resistance within the perfusion period. These results suggest that dauricine and verapamil have a salutary effect in extracorporeal circulation. The possible mechanisms are discussed.

The induction of cytotoxic T-lymphocyte precursor cells by recombinant vaccinia virus expressing human papillomavirus type 16 L1.

Expression of the major coat protein L1 of human papillomavirus type 16 by recombinant vaccinia viruses using a vaccinia late promoter and their use in generating antibodies have already been reported (Zhou et al., 1990). We have now constructed recombinant vaccinia viruses (VVs) which express the L1 protein from an early promoter with the intention of inducing cell-mediated immunity. This necessitated the removal of sequence motifs (TTTTTNT) from the L1 gene which would otherwise have caused transcription termination when expressed from a vaccinia virus early promoter. The nucleotide sequence was mutated to retain the correct amino acid sequence of the L1 protein. Full-length mRNA and L1 protein were generated in cells infected with the recombinant virus containing the mutant sequence, whereas the wild-type sequence generated only truncated mRNA and no detectable protein. Mice were immunized with VV expressing L1 from the mutant sequence and from the wild-type sequence in constructs with either early or late vaccinia virus promoters. Only the early promoter constructs were effective in priming cytotoxic T lymphocytes (CTL). Moreover the mutant sequence was significantly more effective than the wild-type sequence. The same L1 sequences, expressed from a vaccinia virus late promoter or coexpressed with MHC Class I molecules also expressed from a late promoter, produced high levels of L1 protein in both cases but nevertheless failed to elicit CTL activity. This is the first report of an HPV-specific CTL response and we have reaffirmed the importance of choosing the correct promoter and sequence expressed when using recombinant vaccinia viruses to induce cytotoxic T lymphocytes. These data are relevant for the design of vaccines to generate cell-mediated immunity against human papillomavirus infection.