[Study on mitoxantrone albumin microspheres for liver targeting]

An optimum procedure was established for preparing mitoxantrone albumin microspheres (DHAQ-BSA-MS) with emulsion-heating solidification. The morphology, diameters, drug loading, release characteristics, stability and its distribution in vivo of the drug-loaded albumin microspheres were studied. The results showed that the surface was regular, the average diameter was 0.99 micron, mean surface diameter was 1.24 microns and mean volume diameter was 1.44 microns, apparent drug loading was 2.558 +/- 0.101 micrograms.mg-1 (n = 5), effective drug loading was 1.503% +/- 0.127% (n = 5), embedding ratio was 92.82% +/- 6.48% (n = 5), and the release characteristics were in accord with "biphase kinetics equation": 1 - Q = 0.6428e-0.2132t + 0.3988e-0.00150t (gamma 1 = -0.9951, gamma 2 = -0.9982); T1/2 alpha = 3.250 h, T1/2 beta = 461.7 h. The stability of the drug-loaded albumin microspheres was good after three months storage at room temperature. The results determined by HPLC showed that the drug accumulated about 77.6% +/- 1.38% of the dose in the liver 20 minutes after intravenous injection to mice. This indicates that DHAQ-BSA-MS showed remarkable targeting for liver, and it seems to have important value for increasing the antihepatoma effect and decreasing the toxicity of mitoxantrone.

[Construction of luciferase reporter plasmid which is under the control of dioxin-responsive enhancers]

To improve the bio-detection of dioxin-type chemicals, we constructed a plasmid containing reporter under the control of dioxin-responsive enhancer. After connected the enhancer from the plasmid pHAV with the MMTV promoter of the plasmid pCatM, the connected segment was linked with the luciferase vector. Then the recombinant plasmid was transfected to the HepG2 human hepatoma cell line, and the luciferase activity was induced by 2,3,7,8-TCDD. The result suggested that expression of the recombinant luciferase was controlled by the dioxin-responsive enhancer, and there were a linear relationship between the activity of luciferase and certain range of 2,3,7,8-TCDD concentration. It is promising that the transfected cell line could be used for rapid screen and semi quantitation of dioxin-type chemicals, and a standard and routine method for the detection of dioxin-type chemicals by this recombinant plasmid is being under way.

[Conjugation of mitoxantrone-loaded nanospheres and anti-C-erbB-2 monoclonal antibodies]

AIM

To improve the treatment efficacy of anti-tumor drug mitoxantrone, the conjugation of mitoxantrone-loaded nanospheres and anti-C-erbB-2 monoclonal antibodies were prepared.

METHODS

Mitoxantrone-loaded nanospheres were prepared with emulsion-heating solidification technique. A heterobifunctional reagent, N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP), was used as the crosslinker of mitoxantrone-loaded nanospheres and anti-C-erbB-2 monoclonal antibodies; pharmaceutical properties of immunonanocapsuls were studied; the conjugates of nanospheres and monoclonal antibodies was confirmed with immunological methods such as slide agglutination test, fluorescent immunossay and rosset formation test, fluorescent staining and scanning electron microscope.

RESULTS

Mitoxantrone-loaded nanospheres were spherical, with smooth surface and median diameter of 0.665 micron. When stored at 3-5, 20-25 and 37 degrees C, RH 75% for three months, the appearance, morphology, size distribution, drug loading and in vitro release characteristics showed no significant change and the stability was satisfactory. The size analysis demonstrated that there was no obvious increase in the particle size of nanoparticles after conjugation. Immunological tests indicate highly selective binding of antibody-targeted nanospheres to C-erbB-2-overexpressing cells SK-BR-3.

CONCLUSION

The conjugation of mitoxantrone-loaded nanospheres and anti-C-erbB-2 monoclonal antibodies can keep the activity of anti-C-erbB-2 and increase the therapeutic efficacy of anti-mammary cancer drugs.

Interaction between permeation and gating in a putative pore domain mutant in the cystic fibrosis transmembrane conductance regulator

The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel with distinctive kinetics. At the whole-cell level, CFTR currents in response to voltage steps are time independent for wild type and for the many mutants reported so far. Single channels open for periods lasting up to tens of seconds; the openings are interrupted by brief closures at hyperpolarized, but not depolarized, potentials. Here we report a serine-to-phenylalanine mutation (S1118F) in the 11th transmembrane domain that confers voltage-dependent, single-exponential current relaxations and moderate inward rectification of the macroscopic currents upon expression in Xenopus oocytes. At steady state, the S1118F-CFTR single-channel conductance rectifies, corresponding to the whole-cell rectification. In addition, the open-channel burst duration is decreased 10-fold compared with wild-type channels. S1118F-CFTR currents are blocked in a voltage-dependent manner by diphenylamine-2-carboxylate (DPC); the affinity of S1118F-CFTR for DPC is similar to that of the wild-type channel, but blockade exhibits moderately reduced voltage dependence. Selectivity of the channel to a range of anions is also affected by this mutation. Furthermore, the permeation properties change during the relaxations, which suggests that there is an interaction between gating and permeation in this mutant. The existence of a mutation that confers voltage dependence upon CFTR currents and that changes kinetics and permeation properties of the channel suggests a functional role for the 11th transmembrane domain in the pore in the wild-type channel.

Direct comparison of NPPB and DPC as probes of CFTR expressed in Xenopus oocytes

Blockers of CFTR with well-characterized kinetics and mechanism of action will be useful as probes of pore structure. We have studied the mechanism of block of CFTR by the arylaminobenzoates NPPB and DPC. Block of macroscopic currents by NPPB and DPC exhibited similar voltage-dependence, suggestive of an overlapping binding region. Kinetic analysis of single-channel currents in the presence of NPPB indicate drug-induced closed time constants averaging 2.2 msec at -100 mV. The affinity for NPPB calculated from single-channel block, K(D) = 35 microm, exceeds that for other arylaminobenzoates studied thus far. These drugs do not affect the rate of activation of wild-type (WT) channels expressed in oocytes, consistent with a simple mechanism of block by pore occlusion, and appear to have a single binding site in the pore. Block by NPPB and DPC were affected by pore-domain mutations in different ways. In contrast to its effects on block by DPC, mutation T1134F-CFTR decreased the affinity and reduced the voltage-dependence for block by NPPB. We also show that the alteration of macroscopic block by NPPB and DPC upon changes in bath pH is due to both direct effects (i.e., alteration of voltage-dependence) and indirect effects (alteration of cytoplasmic drug loading). These results indicate that both NPPB and DPC block CFTR by entering the pore from the cytoplasmic side and that the structural requirements for binding are not the same, although the binding regions within the pore are similar. The two drugs may be useful as probes for overlapping regions in the pore.

Study on the direct electron transfer process of superoxide dismutase

The electron transfer process of biological important species, superoxide dismutase (SOD), was studied using cyclic voltammetric method at different conditions. The rate of electron transfer process of SOD at conventional bare gold electrode was very low. Different methods were used to enhance the rate of this process. Gold microdisk electrode and gold minigrid electrode were used to replace the used conventional size gold electrode and the electron transfer rate was enhanced obviously. Different promoters, such as bis(4-pyridyl)disulfide, histidine and arginine, were used to promote the electron transfer process also. Promising results were observed with the help of those promoters. The rate enhancement through the participation of amino acids might be more interesting for the exploration of the real process of SOD-related reaction inside the human body.

[Study on the mitoxantrone ethylcellulose microspheres for liver artery embolization]

In this paper, orthogonal test was used to optimize the preparation conditions and technique of mitoxantrone ethylcellulose microspheres (DHAQ-EC-MS) for liver embolization. The dynamic osmosis method was used to study the drug release characteristics of DHAQ-EC-MS. DHAQ-EC-MS suspension for clinical liver artery embolization was prepared. The result showed that the DHAQ-EC-MS is regular in its morphology with a mean diameter of 110.24 +/- 38.19 microns. The drug loading was 12.5% and embedding ratio was 55.6%. The release characteristics was in accord with single exponential model. The drug release equation is lg(Yinfinity - Y) = -0.116t - 1.198 x 10(-3) (gamma = 0.9992, t50 = 2.6 h). The DHAQ-EC-MS was shown to be physically and chemically stable and its suspension is suitable for clinical use. Experiments in dogs indicate that drug concentration of DHAQ-EC-MS in hepatic vein blood was higher than DHAQ solution, and the MRT0-72 was 2.45 times higher than DHAQ solution.

Prostaglandin E2 increases 7-pS Cl- channel density in the apical membrane of A6 distal nephron cells

In A6 distal nephron cells, short-circuit current (Isc) was increased by basolateral exposure to prostaglandin E2 (PGE2; peak response at 1 microM). The effect was only partially abolished by either apical amiloride, an Na+ channel blocker, or 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), a Cl- channel blocker. In apical cell-attached patches, we observed a 7-pS Cl- channel with a linear current-voltage relationship, a reversal potential near resting membrane potential, and open probability > 0.5. The channel was blocked by diphenylamine-2-carboxylate, glibenclamide, and NPPB but not by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. The frequency of observed Cl- channel activity increased 7-fold with 10-min exposure to PGE2 and 3.7-fold with longer (10-50 min) exposure to PGE2. The PGE2-induced increase in Cl- channel activity was due primarily to an increase in the number of functional channels. The following conclusions were made: 1) activation of apical, 7-pS Cl- channels in A6 cells accounts for the PGE2-induced increase in the amiloride-insensitive Isc, and 2) 7-pS Cl- channel activation was mediated via an increase in channel density without substantial effects on channel kinetics.

[Study on the geographic distribution and serological typing of HFRS in Hebei Province]

Surveillance on the HFRS had been carried out during the period of 1986-1993. Rodent density ranged from 4.6%-12.2% with R.norvegicus exceeding 60% in all kinds of rodents. HV antigen carrier rate of R.norvegicus was 1.3%-7.5%, much higher than that among other rodents. A significantly positive correlation had been observed between the HFRS morbidity and the R.norvegicus density. Of 129 specimens from HFRS patients, 89% belonged to the type of SEOV. In the eastern and centre Parts of Hebei plain, HTNV occupied 1.6%. A total number of 9,609 HFRS patients had been identified during the period of 1980-1993. The plain area in Hebei province was recognized as the major epidemic area. The key measure for decreasing the HFRS morbidity was deratizationin in the residential area in January and February and immunization with HFRS inactivated vaccine.

[Study on pharmacokinetics of mitoxantrone polycyanoacrylate nanoparticles freeze-dried injection by HPLC column switching technique]

The drug concentration--time curves of mitoxantrone polycyanoacrylate nanoparticles freeze-dried injection (DHAQ-PBCA-NP-FDIn) and mitoxantrone solution injection (DHAQ-SIn) in rabbit blood were determined by HPLC column switching technique, and the difference between the DHAQ-PBCA-NP-FDIn and DHAQ-SIn in vivo was observed. The pharmacokinetic parameters of DHAQ-PBCA-NP-FDIn and DHAQ-SIn were presented by statistical moment. The results showed that the MRT and T1/2 of DHAQ-PBCA-NP-FDIn were 2.15 times longer than that of DHAQ-SIn, and the Vss was 4.81 times bigger than that of DHAQ-SIn. This indicates that DHAQ-PBCA-NP-FDIn has targeting and prolonging effect on the action in vivo.

[Comparison of concentration of piroxicam in blood and local site after two routes of administration]

The systematic and local concentrations of piroxicam after oral and transdermal administration were determined and compared. Mice were randomly grouped, and oral suspensions (0.72 mg.ml-1) or transdermal gels 1 mg.ml-1 were given. Systematic concentration (Cs) and local concentration (C1) of the drug in each mouse were determined by HPLC method. After transdermal administration of 0.25 mg of piroxicam gels Cmax(s) = 8.06 micrograms.ml-1 and AUC(s)0-24(s) = 58.36 micrograms.h.ml-1 were obtained, whereas after oral administration of 0.026 mg.10 g-1 body weight of piroxicam suspensions Cmax(s) was 36.82 micrograms.ml-1 and AUC(s)0-24 was 155.59 micrograms.h.ml-1. The C1/Cs ratio (0.01) through oral route was far lower than the C1/Cs ratio (0.13) through transdermal route. The area under local concentration-time curve (15.85 micrograms.h.ml-1) calculated from transdermal administration was much higher than that from oral administration (1.93 micrograms.h.ml-1). So, it seems to be unreasonable that only serum concentration is taken as a criterion for bioavailability test of piroxicam for local dosage forms, the local drug concentration should also be investigated and evaluated.

[Study on mitoxantrone polycyanoacrylate nanospheres]

The mitoxantrone polybutylcyanoacrylate nanosparticles (DHAQ-PBCA-NP) were prepared by emulsion polymerization method. The surface charge, drug loading, morphology, size and size distribution, release characteristics in vitro, stability and distribution in animals of DHAQ-PBCA-NP were studied. The results showed that the mean size was d(av) = 55.23 nm, drug loading was 46.77%, embedding ratio was 84.89%. The surface carried negative charge and the release characteristics in vitro was in accord with two phases kinetics law. The colloidal solution of DHAQ-PBCA-NP can undergo boiling for 30 min sterilization. The radioactivity concentrated mainly in liver after iv 3H-DHAQ-PBCA-NP. The radioactivity in liver tumor was higher than that in the liver tissue. DHAQ-PBCA-NP was observed in parenchymal cell 15 min after iv DHAQ-PBCA-NS. This preparation seems to have important value for increasing the anti-liver tumor effect and decreasing the toxicity of DHAQ.

The entry of gossypol across the blood-testis barrier in rats

This paper presents the experimental data about how different formulations of gossypol enter the blood-testis barrier following intravenous administration in acute experiments on rats. It was found that gossypol encapsulated by liposomes crossed the blood-testis barrier more readily than free gossypol, without affecting its pharmacokinetic pattern in the circulating blood, suggesting that liposomes may be useful as drug carriers and may facilitate the entry of encapsulated gossypol into the seminiferous tubule from the blood.

Effects of spontaneously hypertensive rat plasma on blood pressure and tail artery calcium uptake in normotensive rats

Previous studies have described the presence of humoral hypertensive factors in spontaneously hypertensive rats (SHR). Other studies have described factors that increase calcium uptake in vascular tissue. In this study, we attempted to confirm, and thereby correlate, the presence of both types of factors in SHR plasma. Intravenous infusion or bolus administration of dialyzed SHR plasma consistently induced an increase in blood pressure in normotensive rats. This hypertensive response was somewhat delayed, with peak blood pressures occurring 45 minutes after bolus administration and 90 minutes after infusion of SHR plasma. Spontaneously hypertensive rat plasma also increased 45Ca uptake in isolated normotensive rat tail arteries in a dose-dependent manner, with a time course similar to that for the hypertensive response to bolus administration. These findings suggest, therefore, that a substance exists in SHR plasma that can increase intracellular calcium in vascular tissues and thereby increase blood pressure.

The correlation between the gossypol contents in blood plasma, rete testis fluid, and cauda epididymal fluid following chronic treatment with gossypol in rats

Concentrations of gossypol in blood plasma, rete testis fluid, and fluid from the caudia epididymidis were measured simultaneously by high performance liquid chromatography in rats treated with gossypol (15 mg/kg daily for 3 weeks). Antispermatogenic effects were demonstrated by loss of sperm motility in the cauda epididymidis and structural changes in the testis. It was found in these treated rats that concentrations of gossypol were lower in rete testis fluid compared with blood plasma but increased significantly in fluid from the cauda epididymidis. The results indicate a restriction of the blood-testis barrier to gossypol and its local concentration in the epididymis after fluid resorption.

The biphasic effects of some opiates and opioid peptides on the rat vas deferens

It has been found that the effects of opiates and opioid peptides on RVD are of two types. Compounds of the first type such as Etor, Eton, fentanyl and prodine derivatives, Met- and Leu-Enk and DADL are biphasic in nature. At lower concentrations (10(-8)-10(-5) M) they have inhibitory effects and at higher concentrations (10(-5)-10(-4) M) they are excitatory. Compounds of the second type, such as Mor, benzomorphan derivates, Cyc and SKF and the antagonist Nx have virtually no or only weakly inhibitory effects but may antagonize the inhibitory effect produced by the first group of compounds at lower concentrations. MC belongs to the second type, but it cannot antagonize the inhibitory effect of beta-End. The results are discussed in terms of multiple receptors, the high and low affinity binding sites, and the interrelationship between receptors.

The effect of gossypol on ATPase activity of the kidney

The results of the present study have shown no change in the activity of ATPase of the renal cortex of rats administered gossypol for half a year. The Na+, K+-ATPase activity of the cellular membrane of renal cortex of guinea pigs fed with gossypol for 5 or 9 weeks is significantly altered. It seems possible to diminish or to delay the inhibition by allowing the guinea pigs a potassium-rich diet ad libitum. In vitro, gossypol inhibits significantly the activity of ATPase of the brain and the kidney of rats and guinea pigs uncompetitively. However, the inhibition of the ATPase of human fetus kidney is of a mixed type.