In vivo characteristics of low molecular weight copoly (D,L-lactic acid) formulations with controlled release of LH-RH agonist.

Amorphous and crystalline copolymers with a relatively low molecular weight of 1800 were synthesized by direct copolycondensation of D-lactic acid and L-lactic acid in the absence of a catalyst, to evaluate their in vivo capabilities as biodegradable carriers for drug delivery systems. A luteinizing hormone-releasing hormone agonist, des-Gly10-(D-Leu6)-LH-RH ethylamide, was incorporated in a fine cylindrical copolymer formulation, under melt-pressing technique, a mild heat-pressure condition. This formulation was implanted subcutaneously in the back of male rats. The rate of in vivo degradation of amorphous copolymer was much faster than that of crystalline copolymer. Contrary to this tendency, the in vivo release of the drug from this amorphous formulation was held constant over a longer period, compared with the crystalline formulation. This can be closely related to the difference in dispersion of the drug in the formulation.

In vivo characteristics of low molecular weight copolymers composed of L-lactic acid and various DL-hydroxy acids as biodegradable carriers for drug delivery systems.

Low molecular weight and amorphous copolyesters composed of 70 mol% L-lactic acid and 30 mol% DL-hydroxy acids such as DL-lactic acid, DL-alpha-hydroxy-n-butyric acid, DL-alpha-hydroxyisovaleric acid and DL-alpha-hydroxyisocaproic acid were synthesized by direct copolycondensation in the absence of catalysts, to evaluate their in vivo capabilities as biodegradable carriers for drug delivery systems. For this purpose, the copolyester was moulded into a small cylindrical specimen under melt-pressing technique and implanted subcutaneously in the back of male adult rats. The in vivo degradation pattern can be subdivided into three types: the formations of parabolic type (L-LA/DL-HBA copolymer), linear type (L-LA/DL-LA copolymer) and S type (L-LA/DL-HIVA and L-LA/DL-HICA copolymers). A luteinizing hormone-releasing hormone agonist, des-Gly10-(D-Leu6)-LH-RH ethylamide monoacetate (LH-RH agonist), was incorporated into the small cylinders of copolyester formulations, of which the strongest pharmacological influence was observed in a copoly(L-LA/DL-HICA) formulation system, resulting in the maintenance of effective pharmacological influence throughout an experimental period of 15 wk, at which the in vivo release rate of LH-RH agonist was held constant at approximately 45 micrograms/d.

In vivo characteristics of high molecular weight copoly(L-lactide/glycolide) with S-type degradation pattern for application in drug delivery systems.

Amorphous copoly(L-lactide)/glycolide, 70/30 mol%) with weight average molecular weights of 16,900-41,300 were synthesized by ring-opening polymerization in the presence of catalysts using a molecular weight moderator lauryl alcohol. The in vivo degradation profiles of the copolyesters, which were evaluated by implanting them subcutaneously in the back of rats, showed a typical S-type degradation pattern. A luteinizing hormone-releasing hormone agonist (LH-RH agonist), des-Gly10-[Leu6]-LH-RH ethylamide monoacetate, was incorporated into the small cylinders of copoly (L-lactide/glycolide) with a weight average molecular weight of 24,000. The cumulative amount of drug released in vivo from the cylinders showed an S-type profile in analogy with the in vivo degradation pattern. This was demonstrated from data such as serum drug level and pharmacological influence on rat prostates.

Controlled release of cisplatin incorporated into biodegradable poly-d, l-lactic acid.

Using a melt-pressing technique, we produced a small solid cylinder containing cisplatin (CDDP) embedded in poly-d, l-lactic acid (CDDP-PLA). The in vitro release of CDDP from the polymer was examined in an immersion system. CDDP was released continuously for more than four weeks with no initial burst. Drug distribution for CDDP-PLA was compared with CDDP solution (CDDP-SOL) by subcutaneous administration into the back of rats. In the CDDP-PLA group, a high concentration of CDDP was maintained in the subcutaneous tissues near the implants for 20 days. However, in the CDDP-SOL group, the concentration of CDDP was low by 10 days after drug administration. CDDP-PLA may become a useful tool in locoregional chemotherapy as a solid type of drug delivery system with longlasting release.

[A basic study on usefulness of bleomycin incorporated in poly DL-lactic acid].

Poly DL-lactic acid (PLA) is one of the biodegradable polymers. Bleomycin (BLM) incorporated into small cylinders of PLA blends was prepared as a new dosage (BLM-PLA). When BLM-PLA was preserved in saline, the dissolution rate of BLM from BLM-PLA was 49.2% after 7 days, 85.2% after 14 days and 99.7% after 21 days, respectively. BLM-PLA was implanted subcutaneously into the back of 36 rats. On days 3, 7, 14, 21, 28 and 35, the connective tissues near the implants, lymph node, lung, liver and kidney were removed and BLM activity was measured. The BLM concentration was maintained at a high level in the connective tissues until 14 days, and in the lymph node between 21 and 28 days. On the other hand, the BLM level was low in the lung, liver and kidney. Consequently, it was suggested that PLA is useful as a carrier for drug delivery system and that administration of BLM-PLA is an effective anti-cancer modality, especially in local chemotherapy.

[Drug distribution and antitumor effect of bleomycin incorporated in poly DL-lactic acid in rats].

Two bleomycin (BLM)-containing agents (BLM-PLA, BLM-SOL) were prepared, and the drug distribution and antitumor effect were studied. BLM-PLA is an agent in which BLM is incorporated into biodegradable low-molecular-weight polylactic acid, and BLM-SOL is an aqueous solution of BLM. BLM-PLA or BLM-SOL was subcutaneously administered in the back of rats. When BLM-PLA was implanted, high BLM activity of the connective tissues near the implants was maintained for 2 weeks. On the other hand, BLM activity was very low when BLM-SOL was administered. The effects of BLM-PLA, BLM-SOL and nontreatment on tumor growth and survival time were compared using subcutaneous tumor of Yoshida sarcoma in 21 rats each. The survivors and mean survival time in BLM-PLA group, BLM-SOL group and nontreatment group was 14 and 44.6 days, 5 and 23.7 days, and 0 and 11.3 days, respectively. BLM-PLA was superior to BLM-SOL in both drug distribution and antitumor effect, and consequently BLM-PLA could be a useful tool in loco-regional chemotherapy.

5-Hydroxytryptamine induces phospholipase C-mediated hydrolysis of phosphoinositides through 5-hydroxytryptamine-2 receptors in cultured fetal mouse ventricular myocytes.

5-Hydroxytryptamine (5-HT) stimulates the rate and force of cardiac contraction. However, the molecular mechanisms of 5-HT actions on the heart are unknown. We examined effects of 5-HT on phospholipase C-mediated hydrolysis of phosphoinositides and its regulation in cultured fetal mouse ventricular myocytes labeled with [3H]inositol. Accumulation of inositol monophosphate, inositol bisphosphate, and inositol trisphosphate was assessed after stimulation with 5-HT, catecholamines, and AlF4-. Inositol bisphosphate and trisphosphate reached a peak at 15 minutes by 5-HT stimulation and at 30 minutes by AlF4- stimulation. Inositol monophosphate accumulated linearly for at least 30 minutes in the presence of LiCl. The 5-HT effect was dose dependent, and the threshold concentration was 0.1 microM with the half-maximum effective concentration of 1 microM. Ketanserin in nanomolar concentrations inhibited the phospholipase C reaction by 100 microM 5-HT with the half-maximum inhibitory concentration of 0.5 nM. Pertussis toxin (100-1,000 ng/ml) did not influence the phospholipase C reaction by 5-HT, but it partially inhibited the reaction by AlF4-. Protein kinase C-activating phorbol esters like 12-O-tetradecanoylphorbol 13-acetate (TPA) and phorbol 12,13-dibutyrate, but not 4 alpha-phorbol 12,13-didecanoate, which is inactive for protein kinase C, completely inhibited the reaction by 5-HT; TPA showed 30% inhibition on the reaction by AlF4-. The magnitude of accumulated inositol phosphates by AlF4- was at least several times greater than that by 5-HT. Norepinephrine- and epinephrine-stimulated phospholipase C reactions were completely abolished by prazosin. These results suggest that 5-HT directly stimulates phospholipase C-mediated hydrolysis of phosphoinositides through 5-hydroxytryptamine-2 (5-HT2) receptors in the ventricular myocytes and that this reaction is negatively regulated by protein kinase C. 5-HT2 receptors may be coupled to phospholipase C via a pertussis toxin-insensitive GTP-binding protein in the myocytes.

[The effect of aging on respiratory muscle function].

To elucidate the effect of aging on respiratory muscle function, the authors performed respiratory muscle function tests in 116 normal subjects. Respiratory muscle function was evaluated with maximal expiratory mouth pressure at the TLC level (PEmax) and maximal inspiratory mouth pressure at the RV level (PImax). PEmax and PImax in both sexes showed significant correlations with age. PEmax in males was significantly higher than that in females (123.6 +/- 29.7 cmH2O and 79.0 +/- 21.1 cmH2O, p less than 0.01, respectively). PImax in males was also significantly higher than that in females (98.4 +/- 26.0 cmH2O and 71.9 +/- 26.4 cmH2O, p less than 0.01, respectively). PEmax correlated significantly with TLC, and PImax showed a significant inverse correlation with RV/TLC. Furthermore, there was a significant inverse correlation between RV/TLC and age. Our data suggest that inspiratory muscle weakness in aging may be responsible for the increase in RV/TLC.

Controlled release of poly-D,L-lactic acid containing bleomycin.

By use of four types of in vivo degradable polylactic acid (PLA), i.e. PLA with an average molecular weight of 1500 (1500DL), 2200 (2200DL), 2800 (2800DL) and 3500 (3500DL), preparations of bleomycin (BLM)-containing solid forms (polymers) were tested. The in vitro release of BLM from the polymers was also examined in an immersion system. By the melt-pressing technique, five types of BLM (2.5 mg) containing solid forms, i.e. 1500DL polymer, 2200DL polymer, 2800DL polymer, 3500DL polymer and 1500DL + 3500DL (a mixture of 1500DL and 3500DL) polymer were prepared. In all five types of polymers, cumulative BLM release was controlled to less than 5% by the third day and no initial burst of the release was observed. BLM release from the polymer continued for 3 weeks at the shortest and 6 weeks at the longest. Various polymers containing BLM could be useful for the site of drug administration or anti-cancer release pattern.

Preparation and microstructure analysis of chitosan/hydroxyapatite nanocomposites.

Chitosan/hydroxyapatite (HAp) composites with a homogeneous nanostructure have been prepared by a co-precipitation method. According to TEM observations, HAp crystallites in the composites formed elliptic aggregations 230 nm in length and 50 nm in width. The typical length of the aggregations corresponded approximately to that of a chitosan molecule. The size of the constituent HAp crystallites was found to be predominantly 30 nm in length and 10 nm in width, and the c-axes were well aligned in parallel with the chitosan molecules in the respective aggregations. The growth of the HAp crystallites is considered to occur at nucleation sites, most probably forming the complexes with amino groups on chitosan with calcium ions. The compact composites obtained have been found to be mechanically flexible, and this flexibility has been improved further by heating at 120 degrees C for 20 min in an autoclave with saturated steam pressure.

In vivo activity of bleomycin incorporated with biodegradable poly-d,l-lactic acid and implanted in the mediastinum of dogs.

The possible usefulness of bleomycin incorporated with biodegradable poly-d, l-lactic acid (BLM-PLA) for targeting chemotherapy for esophageal cancer was studied in vivo. Local levels of BLM after administration were compared with those after injection of BLM-SOL, an aqueous solution of BLM. BLM-PLA or BLM-SOL was administered into the upper mediastinum under a right thoracotomy in 36 mongrel dogs. On days 10, 20, and 30 after administration, connective tissues, lymph nodes, lung, liver, kidney, and spleen were removed, and BLM activity was measured. High activity of BLM was detected for 30 days after BLM-PLA administration in both the connective tissues and the lymph nodes, compared with BLM-SOL administration. BLM activity was low in the other organs after BLM-PLA administration. BLM in the blood was significantly lower after administration of BLM-PLA than BLM-SOL. The results indicate that BLM-PLA may become a useful tool in targeting chemotherapy for esophageal cancer.

Evaluation of new pasty-type implantable devices consisting of poly(epsilon-caprolactone/delta-valerolactone) and Estracyt or estramustine.

Biodegradable pasty-type copolyesters with a relatively low molecular weight of 4500 were synthesized by direct copolycondensation of epsilon-caprolactone (CL) and delta-valerolactone (VL) in the absence of catalysts to evaluate in vivo capabilities of the polymer for implantable controlled release devices in drug delivery systems. The devices in cylindrical shape were prepared by the melt-pressing technique using pasty-type copoly(CL/VL) with 53 mol% CL unit, in which Estracyt and estramustine were used as a water soluble and insoluble drug, respectively. The degradation and drug release in vivo of the devices were examined by subcutaneous implantation in the backs of male rats. The degradation of the device was remarkably accelerated by the presence of hydrophilic Estracyt, and was slightly suppressed by hydrohobic estramustine. The estramustine release profile roughly corresponded to the polymer degradation one. It was found that the degradation of the polymer in the device was affected by hydrophilicity of the drug. A reasonable release of estramustine from the device was kept for a period of more than 20 weeks. Furthermore, the release of the drugs in vivo was able to lead to an atrophy of accessory sex organs such as ventral prostates (VP) and right-side seminal vesicle (SV), resulting in pharmacological influence.

[Pulsed Doppler echocardiographic findings in 117 professional cyclists].

To investigate the effect of long-term athletic training on the heart, pulsed Doppler echocardiography was performed in 117 male professional cyclists (Group C: 20-59 years of age), and 40 age- and sex-matched untrained normal controls (Group N). According to age, the subjects in each group were categorized in two subgroups: 74 cyclists (Group CI), 20-39 years of age and 43 cyclists (Group CII), 40-59 years of age; 24 control subjects (Group NI), 20-39 years of age and 16 control subjects (Group NII), 40-59 years of age. The average durations as professional cyclists were eight years in Group CI and 29 years in Group CII. The ratios of pre-ejection period to ejection time (LV-PEP/ET, RV-PEP/ET) as obtained from Doppler flow velocity patterns of the left and right ventricles (LV, RV) were used as parameters of systolic function. The peak flow velocities during rapid filling (LV-R, RV-R) and atrial systole (LV-A, RV-A), and the ratio of A to R (LV-A/R, RV-A/R) were used as parameters of diastolic filling dynamics. The parameters of systolic function of both ventricles and those of diastolic filling dynamics of the RV did not differ between Group C and Group N, Group CI and Group NI, and Group CII and Group NII. Study of the diastolic filling dynamics of the LV disclosed that Group C had a significantly higher LV-A/R (p less than 0.05) than did Group N; therefore, no significant differences between Group CI and Group NI, and Group CII had a significantly lower LV-R (p less than 0.005) and a higher LV-A/R (p less than 0.005) than did Group NII. Twenty-four hour ambulatory ECG monitoring was performed for 49 cyclists. Thirty cyclists aged 20-39 years were categorized in two groups according to their LV-A/R values: eight cyclists (Group A) with the LV-A/R greater than the mean + SD value (0.69) in Group NI and 22 cyclists (Group B) with the LV-A/R lower than or equal to 0.69. Nineteen cyclists aged 40-59 years were separated into two groups according to the LV-A/R value: 11 cyclists (Group A) with the LV-A/R values greater than the mean + SD value (0.89) in Group NII, and eight cyclists (Group B) with the LV-A/R equal to or less than 0.89.(ABSTRACT TRUNCATED AT 400 WORDS)

Gastroesophageal reflux after endoscopic injection sclerotherapy.

The effect of sclerotherapy of esophageal varices on the gastroesophageal reflux was studied. Gastroesophageal reflux was monitored by a 24-h pH-monitoring catheter introduced into the distal esophagus. The results of pH monitoring of 16 patients who underwent sclerotherapy were compared with those of 21 patients with untreated varices. Seven of the 16 treated patients showed high occurrence rates of gastroesophageal reflux comparable to those observed in cases with severe reflux esophagitis. In the untreated group, only one patient showed pathological reflux (there was a significant difference between treated and untreated groups; p less than 0.01). When the level of reflux was compared with factors that might influence sclerotherapy-induced gastroesophageal reflux, there was a positive correlation between the magnitude of reflux and amount of sclerosant injected paravariceally in the submucosal tissue (p less than 0.05). The results indicate that the paravariceal injection of sclerosant for the treatment of esophageal varix may cause pathological gastroesophageal reflux after sclerotherapy is completed.

A new biodegradable copolymer of glycolic acid and lactones with relatively low molecular weight prepared by direct copolycondensation in the absence of catalysts.

Relatively low-molecular-weight copolyesters of glycolic acid (GA) with lactones such as gamma-butyrolactone (BL), delta-valerolactone (VL), and epsilon-caprolactone (CL) were synthesized by copolycondensation without catalysts. The resulting copolyesters are intended as carriers for drug delivery systems. Copolyesters with approximately 85 mol% GA (number-average molecular weight (Mn): 2900 +/- 100) are crystalline and solid and show a parabolic-type in vivo degradation pattern. The in vivo degradation of amorphous-pasty poly (GA/CL) (approximately 50/50 mol%) changed from parabolic-type to linear-type to S-type pattern as their molecular weight increased. A luteinizing hormone-releasing hormone agonist, [D-Leu6, des-Gly10]-LHRH ethylamide monoacetate (LHRH agonist), was incorporated into small cylinders with these copolyesters. An initial burst of LHRH agonist was observed for cylinders prepared with parabolic-type degrading copolyesters, in contrast to a marked delay in LHRH agonist release for cylinders prepared with S-type degrading copolyesters. The resulting daily dose of drug was maintained an approximately constant, though decreasing stepwise with time. For example, the daily amount of LHRH agonist released in vivo from a cylinder prepared with poly(GA/CL) (50/50 mol%; Mn = 4500) was 61 +/- 39 micrograms/day throughout an experimental period of 10 weeks with a corresponding pharmacological effect on the rat prostate.