beta-blocker therapy in patients after aortic valve replacement for aortic regurgitation

BACKGROUND

beta-blocker therapy for dilated or ischemic cardiomyopathy is now an accepted and effective treatment. However, little is known about its efficacy in patients with postoperative impaired left ventricular function. This retrospective study was designed to assess the effects of beta-blocker therapy in patients after aortic valve replacement (AVR) for aortic regurgitation (AR).

METHODS

A total of 59 patients who underwent AVR for chronic AR were assigned to four groups. Twelve patients were treated with both ACE inhibitors and beta-blockers, 12 patients with only ACE inhibitors, eight patients with only beta-blockers, and 27 patients without beta-blockers or ACE inhibitors. A postoperative echocardiographic study was performed one year after surgery.

RESULTS

The heart rate was significantly reduced in patients with beta-blockers despite the use of ACE inhibitors after surgery. Postoperative left ventricular volume was more significantly decreased in beta patients than in non-beta patients despite the use of ACE inhibitors. There were also significant reductions in left ventricular mass index in ACE+beta patients compared to ACE+non-beta patients. However, there were no significant differences in NYHA functional class and survival rate between beta patients and non-beta patients.

CONCLUSIONS

beta-blocker therapy may improve cardiac performance by reducing cardiac volume and mass in patients with impaired LV function after AVR for AR.

Treatment for abdominal aortic graft infection: irrigation with electrolyzed strong aqueous acid, in-situ grafting, and omentoplasty

We report on successful surgical treatment of consecutive three patients with infection of an abdominal aortic graft, Therapy involved a combination of removal of the infected graft, elaborate debridement, irrigation with electrolyzed strongly acidic aqueous solution (ESAAS), in-situ regrafting, and omentoplasty. The use of ESAAS is discussed.

Oral administration of the dopamine prodrug docarpamine shortens need for drip infusion of dopamine in patients with low cardiac output syndrome after cardiac surgery

BACKGROUND

Docarpamine (DOC) is a dopamine prodrug which can be orally administered. It has been found that oral docarpamine transforms into dopamine in vivo, and increases cardiac output and renal blood flow as effectively as intravenous dopamine.

METHODS

We reviewed the records of 26 patients who had developed low cardiac output syndrome (LOS) after cardiac surgery and received docarpamine during the early postoperative course. Five patients discontinued docarpamine within 2 days due to arrhythmia. There were 3 hospital deaths. The remaining 18 patients were divided into two groups according to the timing of docarpamine administration. In group A docarpamine was administered during and after weaning from intravenous catecholamines, in group B only on demand after weaning from intravenous catecholamines.

RESULTS

There were 12 patients in group A and 6 in group B, and the severity of LOS was relatively milder in group B than in group A. Stable hemodynamics and sufficient daily urinary output were maintained by oral administration of DOC in both groups just as well as by drip infusion of catecholamines.

CONCLUSION

Sinse continuous drip infusion of catecholamine commonly slows recovery in LOS patients, it is considered that switching from drip infusion of catecholamines to oral DOC administration is safe and useful for earlier recovery in LOS patients after cardiac surgery.

Combined cardiac surgery and total thyroidectomy: a case report

A 65-year-old woman with aortic stenosis, ischemic heart disease, and Graves' disease had complained of effort angina. She then suffered from liver dysfunction due to treatment with antithyroid drugs. One year after the start of radioiodine administration, she demonstrated unstable angina with palpitation and sweating. Laboratory studies revealed a recurrent hyperthyroid state, and a second coronary angiogram revealed progressive ischemic heart disease. Combined coronary artery bypass grafting, aortic valve replacement, and total thyroidectomy were performed. The postoperative course was uneventful without any problems associated with hyperthyroidism or hypothyroidism. Combined cardiac surgery and total thyroidectomy can be performed safely if the perioperative levels of thyroid hormone are maintained at euthyroid or hypothyroid levels.

Segment-specific branching patterns of single vestibulospinal tract axons arising from the lateral vestibular nucleus in the cat: A PHA-L tracing study

The purpose of the present study was to detail the spinal cord (SC) trajectories and arborization patterns of vestibulospinal axons descending from the lateral vestibular nucleus (LVN). An anterograde neural tracer, Phaseolus vulgaris-leucoagglutinin (PHA-L), was focally injected into the right-side LVN in 8 cats. Their subsequent survival times varied from 4 days to 12 weeks. The labeled axons were found mainly in the brainstem after 4-5 days and in successively more caudal spinal segments after longer survival times: i.e., in C1-T2 after 2-3 weeks, in C3-T11 after 6-7 weeks, and in T7-S1 after 10-12 weeks. The trajectories of 28 single, thick (diameter >/=2.4 microm) lateral vestibulospinal tract (LVST) axons were traced from serial transverse sections of the SC from C1-8 (n = 10), T1-9 (n = 11), and T11-L7 (n = 7). In the cervical segments, the LVST axons gave off collateral fibers, which terminated mainly in Rexed's laminae VII-VIII. The terminal-field patterns of these collaterals differed from one stem axon to another. In the thoracic segments, the terminal-field patterns from a given LVST axon were similar at each segmental level, i.e., a few main branches with or without short side branches. At the L3-5 midlumbar level, the collaterals usually arborized more extensively, such that their terminal fields occupied a much greater region of laminae VII-VIII. In contrast, at the L6-7 lower lumbar level, collaterals arising from thin axons (diameter <1.0 microm) tended to innervate, with even more extensive arborization, the medial part of the lamina VIII. These results revealed common and segment-specific collateral distribution patterns of LVST axons along the full extent of the spinal neuraxis.

Tumor angiogenesis, apoptosis, and p53 oncogene in stage I lung adenocarcinoma

The purpose of this study was to clarify which factors are important as predictors not only of patient survival but also of hematogenic metastasis in 15 patients with stage I lung adenocarcinoma who underwent curative operation. The relationship between tumor angiogenesis, apoptosis, and p53 oncogene was also studied. A total of 15 patients were divided into two groups: surviving group (n = 7) and nonsurviving (metastasis) group (n = 8). We studied the medical charts, operative records, pathologic reports, and tumor specimens taken at surgical resection. We measured the apoptotic index using the ApopTag kit and the intratumoral microvessel count using an anti-CD34 monoclonal antibody. In addition, immunohistochemical staining for the expression of p53 was conducted simultaneously. The clinicopathological characteristics, including age, sex, tumor size (pT), and histological differentiation, were not significantly different between the surviving and the nonsurviving group. The microvessel count was significantly higher in nonsurviving group than in the surviving group. The apoptotic index and the expression of p53 was not significantly different between the two groups. An inverse correlation between the apoptotic index and microvessel count, and a positive correlation between the expression of p53 and microvessel count, were observed. Angiogenesis may be an important prognostic factor in patients with stage I lung adenocarcinoma.

Distance between mitral anulus and papillary muscles: anatomic study in normal human hearts

BACKGROUND

Preservation of the annulo-papillary muscle continuity in mitral valve replacement is important. Even in patients who require excision of the mitral apparatus, the continuity can be restored. However, there is no guide to the proper length for the resuspension.

METHODS

In 57 normal cadaveric hearts, the distance from the tip of the papillary muscle to its corresponding mitral anulus was directly measured.

RESULTS

The distance from the tip of the anterolateral papillary muscle to the left trigone (10-o'clock position: D10) and to the point between the anterior and the middle scallops of the mural leaflet (8-o'clock position: D8) was 23.5 +/- 3.7 mm and 23.2 +/- 3.6 mm, respectively. The distance from the tip of the posteromedial papillary muscle to the right trigone (2-o'clock position: D2) and to the point between the middle and the posterior scallops of the mural leaflet (4-o'clock position: D4) was 23.5 +/- 4.0 mm and 23.5 +/- 3.9 mm, respectively. There was no statistically significant difference among the 4 distances (P =.96). Each distance was significantly longer than the corresponding chordae tendineae (D10 vs the anterior main chorda: 17.2 +/- 3.9 mm, D8 vs the anterior cleft chorda: 14.5 +/- 3.2 mm, D2 vs the posterior main chorda: 17.9 +/- 4.3 mm, and D4 vs the posterior cleft chorda: 14.9 +/- 3.2 mm, respectively; P =.0001). The mean distance had a significant correlation with the mitral annular diameter (r = 0.31, P =.019).

CONCLUSIONS

In normal hearts, the annulo-papillary muscle distances of the mitral apparatus are similar in 2-, 4-, 8-, and 10-o'clock positions and correlate with the mitral annular diameter.

Cardiac angiotensin-converting enzyme activity in myocardial infarction

The cardiac renin-angiotensin system is regarded as an important modulator in the infarct heart. Little is known about their presence and regulation in human hearts. We measured angiotensin-converting enzyme (ACE) and renin activities at the aortic root and anterior interventricular vein (AIV) in 51 patients with previous myocardial infarction (MI): anterior wall MI in 31 and inferior wall MI in 20 and 33 control subjects. In the anterior wall MI group, the serum ACE activity was increased significantly in the AIV than in the aortic root (16.2 +/- 5.3 vs 15.3 +/- 5.0 nmol/min/ml, p <0.001), whereas the activity was not different between the aortic root and AIV in the control (14.4 +/- 3.7 vs 14.4 +/- 3.7 nmol/min/ ml) and in the inferior wall MI (16.5 +/- 4.8 vs. 17.0 +/-5.2 nmol/min/ml) groups. On the other hand, there was no significant difference in plasma renin activity between the AIV and aortic root in the 3 groups (control group, 1.0 +/- 0.5 vs 1.0 +/- 0.5 pg/ml/hour; anterior wall MI group, 1.3 +/- 0.8 vs 1.3 +/- 0.8 pg/ml/hour; inferior wall MI group, 1.2 +/- 0.7 vs 1.3 +/- 0.8 pg/ml/ hour). The difference in serum ACE activity between the AIV and aortic root had a significant positive linear correlation with pulmonary capillary wedge pressure (r = 0.606, p <0.001), and had a significant negative linear correlation with left ventricular ejection fraction (r = -0.620, p <0.001) in the anterior wall MI group. Serum ACE activity from the infarct region of the left ventricle was augmented in patients with MI, and the activity was increased in proportion to the severity of left ventricular dysfunction.

Aortic valve replacement for aortic regurgitation in a patient with primary antiphospholipid syndrome

A 42-year-old woman with the diagnosis of aortic regurgitation was admitted to hospital for surgical treatment. Ten years ago, primary antiphospholipid syndrome had been diagnosed, and she had a history of recurrent spontaneous abortions and deep vein thrombosis. She was suffering from moderate exertional dyspnea and chest pain. Catheter investigation revealed progressive dilatation of the left ventricle and a deterioration of the ejection fraction. The aortic valve was excised and replaced with a mechanical valve. A specimen of the aortic valve showed localized thickening and shrinkage of the midportion and base of each cusp, with vegetation on the surface. These localized, specific findings suggest that another mechanism may be involved in the cardiac valve pathology in patients with primary antiphospholipid syndrome. No hemostatic or thromboembolic problems were encountered after the surgery, and her postoperative course was uneventful.

Effect of charcoal hemoperfusion on clearance of cibenzoline succinate (cifenline) poisoning

BACKGROUND

Management of cibenzoline succinate (cifenline) poisoning by symptomatic treatment is recommended because it has been reported cibenzoline succinate is not effectively removed by hemodialysis. The use of charcoal hemoperfusion for patients with cibenzoline succinate poisoning has not been reported previously.

CASE REPORT

An 80-year-old woman with permanent right ventricular pacing was admitted to our hospital with general fatigue and clouding of consciousness. She had been receiving cibenzoline succinate for 1 month. The patient was clearly in shock on admission. Electrocardiogram showed a prolonged QRS and QTc interval and pacing failure. Hemodynamic failure, electrocardiographic abnormalities including pacing failure, and liver and renal dysfunction were compatible with cibenzoline succinate poisoning. Symptomatic treatment was provided. On day 4, charcoal hemoperfusion was initiated because of the development of hypoglycemia accompanied by liver and renal dysfunction. After charcoal hemoperfusion, the hypoglycemia, liver and renal dysfunction, prolonged QRS and QTc interval, and pacing threshold resolved. She was discharged on digoxin. We present a case of cibenzoline succinate poisoning treated with charcoal hemoperfusion which resulted in a rapid reduction of cibenzoline plasma concentrations with a significant clinical improvement.

Morphology of single pontine reticulospinal axons in the lumbar enlargement of the cat: a study using the anterograde tracer PHA-L

The fine morphology of single pontine reticulospinal axons in the lumbar enlargement was investigated by using an anterograde Phaseolus vulgaris-leucoagglutinin (PHA-L) tracing technique. Localized injections of PHA-L were made into the nuclei reticularis pontis oralis and caudalis in four cats. Following survival periods of 8-9 weeks, PHA-L-labeled axons were found throughout the lumbar enlargement from segments L4 to S2, in which the diameter of labeled axons was 0.6-2.5 microns. From serial transverse sections (50 microns), trajectories of 21 single pontine reticulospinal axons were traced in continuity over distances of 18.9-36.3 mm, corresponding to three to six segments, respectively. All the identified axons gave off multiple (two to nine) axon collaterals along their courses, with mean intercollateral distances of approximately 5-6 mm. Detailed reconstruction of the collateral arborization in the lumbar enlargement showed a high degree of similarity to that of single axons in the cervical enlargement previously reported (Matsuyama et al. [1997] J. Comp. Neurol. 377:234-250). First, axon collaterals arising from a majority (n = 18) of identified axons innervated the gray matter unilaterally, ipsilateral to the parent axons, whereas those from the remaining three axons innervated the gray matter bilaterally. Second, collateral projections terminated mainly in laminae VIII and VII, with the arborization field confined to a narrow rostrocaudal extent (< 1 mm). Third, the termination fields of axon collaterals arising from a given reticulospinal axon were similar at each segmental level and differed from one stem axon to another. These results suggest that the long descending pontine reticulospinal pathway is composed of different types of axons that may innervate the cervical and lumbar enlargements in continuity in a similar manner.

[Kinetic analysis of therapeutic doses of beta-blockers for angina pectoris based on receptor occupancy theory--relationship between beta 1-receptor occupancy or vasodilative action and dose]

Beta-adrenoceptor blocking agents (beta-blockers) have been widely used for the treatment of angina pectoris. The average/standard therapeutic doses vary widely among beta-blockers with the maximum of about a 120-fold difference. In order to clarify the mechanism of this difference, we analyzed retrospectively the pharmacological effects of beta-blockers in consideration of the beta 1-receptor binding affinity and the vasodilative activity on the basis of pharmacokinetics and the receptor occupancy theory. The analysis was performed on eight beta-blockers without a vasodilative effect and on four beta-blockers with a vasodilative effect. The beta 1-receptor occupancies at the steady-state condition after oral administration of standard doses were calculated by the use of the data on the concentration of unbound agents in plasma and on the dissociation constant of receptors. The estimated receptor occupancies were 87 +/- 6% or 88 +/- 10% for the beta-blockers with or without a vasodilative effect, respectively, and a significant difference was not observed between these groups. These results suggest that the beta 1-receptor occupancies may be a principal indicator for the therapeutic effects for angina pectoris regardless of their vasodilative effects.

Stimulation of a restricted region in the midline cerebellar white matter evokes coordinated quadrupedal locomotion in the decerebrate cat

In the reflexively standing acute decerebrate cat, we have previously shown that pulse train microstimulation of the hook bundle of Russel in the midline of the cerebellar white matter, through which crossed fastigiofugal fibers decussate, augments the postural tone of neck, trunk, fore-, and hindlimb extensor muscles. In the present study we examined the possible role of such stimulation in evoking locomotion as the animal is supported by a rubber hammock with its feet contacting the moving surface of a treadmill. We were able to provoke well-coordinated, bilaterally symmetrical, fore- and hindlimb movements, whose cycle time and pattern were controlled by appropriate changes in stimulus intensity and treadmill speed. We carefully and systematically mapped this cerebellar locomotor region (CLR) through repeated dorsoventral penetrations with a glass-coated tungsten microelectrode in a single animal and between animals. We found that the optimal locus for evoking locomotion was centered on the midline, at Horsley-Clarke coordinates H0 and P7.0, and extended over a rostrocaudal and dorsolateral range of approximately 0.5 mm. The lowest effective stimulus intensity at the optimal site was in the range of 5-8 microA. Along penetration tracks to left or right of the midline, effective stimulus intensity increased and evoked locomotor patterns were no longer symmetrical, but rather shifted toward the contralateral limbs. In the same animals, controlled locomotion was evoked by stimulating the mesencephalic locomotor region (MLR). With concomitant stimulation of the optimal sites in the CLR and the MLR, each at subthreshold strength, locomotor movements identical to those seen with suprathreshold stimulation of each site alone were evoked. With concomitant stimulation at suprathreshold strength for each site, locomotion became vigorous, with a shortened cycle time. After making ablative lesions at either the CLR or MLR (unilateral or bilateral), controlled locomotion was still evoked at the prior stimulus strength by stimulating the remaining site. Together, these results demonstrate that selective stimulation of the hook bundle of Russel in the midsagittal plane of the cerebellar white matter evokes "controlled" locomotion identical to that evoked by stimulating the MLR. We have shown that the fastigial nucleus is one of the supraspinal locomotion inducing sites and that it can independently and simultaneously trigger brain stem and spinal locomotor subprograms formerly believed to be the domain of various brain stem regions including the MLR and the subthalamic locomotor region.

Coronary artery bypass grafting in a case with severe aortic atheromatosis associated with abdominal aortic aneurysm

A 69-year-old man with coronary artery disease associated with abdominal aortic aneurysm underwent a one-stage operation utilizing a low-flow cardiopulmonary bypass. Ordinary cardiopulmonary bypass was abandoned as a result of severe atheromatous finding in the entire aorta. However, coronary artery bypass grafting without cardiopulmonary bypass was hazardous as a result of heart enlargement and deteriorating function. Therefore, the abdominal aortic aneurysm was first replaced with a bifurcated graft. Coronary artery bypass grafting with two arterial grafts was then performed successfully on the beating heart with the support of a low-flow cardiopulmonary bypass connected to the bifurcated graft.

Effect of vitamin E in gastric mucosal injury induced by ischaemia-reperfusion in nitric oxide-depleted rats

BACKGROUND

Neutrophil infiltration and lipid peroxide accumulation are involved in reperfusion-induced gastric mucosal injury in nitric oxide-depleted rats.

AIM

To assess the effect of vitamin E on this injury.

METHODS

After ischaemia-reperfusion, the total area of erosions, lipid peroxide contents in gastric mucosa, and gastric neutrophil accumulation were compared between nitric oxide-depleted rats with deficient, normal, and increased vitamin E intake over 8 weeks. Thiobarbituric acid-reactive substances and tissue-associated myeloperoxidase activity were measured in gastric mucosa as indices of lipid peroxidation and neutrophil infiltration.

RESULTS

The total area of erosions was significantly increased in the vitamin E-deficient group compared with the sufficient-intake and vitamin-supplemented groups. Both thiobarbituric acid-reactive substances and myeloperoxidase activity also were significantly increased in the vitamin E-deficient group compared with others. The total area of erosions closely paralleled the increases in both thiobarbituric acid-reactive substances and myeloperoxidase activity.

CONCLUSION

These results indicate that the inhibition of lipid peroxidation and interference with neutrophil infiltration by vitamin E may be responsible for its cytoprotective effect in ischaemia-reperfusion.

[Valve replacement in children]

Between May 1979 and September 1998, 202 children underwent surgical treatment for valvular heart disease. Of these 23, who ranged in age from 25 days to 15 years, underwent valve replacement, including 1 reoperation. The valve replacement consisted of the aortic valve in 5 patients, the mitral valve in 3, the tricuspid valves in 9, including 5 systemic atrioventricular valves for atrioventricular discordance, the pulmonary valve in 6, 5 bioprostheses and 18 mechanical prostheses. There were 4 operative deaths, 1 hospital death and 3 late deaths. At the 10-years follow-up, the actual survival rate was 67.8%, the event free rate was 76.1% and the freedom from reoperation rate was 86.2%. Valve re-replacement was performed in only 1 patient due to a thrombosed tricuspid valve. These results suggest that there is a small risk of major complications and reoperation in children who undergo valve replacement, whether a bioprosthetic valve or a mechanical valve. The long-term results of younger patients should be followed more closely according to their growth.

Hypokalemia with syncope caused by habitual drinking of oolong tea

A 61-year-old woman developed hypokalemia, atrioventricular block and ventricular tachycardia with syncope after habitual drinking 2 to 3 liters of oolong tea per day. She had been suffering from rheumatoid arthritis and Sjögren's syndrome and her serum albumin was decreased (2.9 g/dl). Oolong tea contains caffeine at approximately 20 mg/dl. Great quantities of caffeine can induce hypokalemia. The serum protein binding caffeine is albumin. Accordingly, in patients with hypoalbuminemia, caffeine is apt to induce hypokalemia. This case suggested that great quantities of oolong tea, one of the so-called "healthy" drinks, result in serious symptoms for patients with hypoalbuminemia.

Early and mid-term outcomes of cardiac and thoracic aortic surgery in over-75-year-olds with postoperative quality of life assessment

The early and mid-term outcomes of cardiac and thoracic aortic surgery were reviewed in seventy-two consecutive patients aged 75 years and older, together with assessment of postoperative quality of life. Twenty-six patients had ischemic heart disease, twenty had valvular heart disease, one had congenital heart disease, and twenty-five had thoracic aortic aneurysm. Twenty-five (34.7%) required an emergency operation. There were 6 early deaths (8.3%) and 11 late deaths (17.2%), of which the emergency cases had higher mortality of 5 early deaths (20.0%) and 3 late deaths (15.0%). In particular, most cases with a ruptured thoracic aortic aneurysm died eventually from various complications including neurological dysfunction. The others with a non-ruptured aneurysm also had atherosclerotic aortic or arterial lesions which caused a lethal cerebrovascular accident or ischemic heart disease. The quality of life of 51 of 53 survivors was assessed using the Rosser and Watts index being based on disability and distress scores. The response was satisfactory--the disability score was 2.6 +/- 1.9 and the distress score was 1.4 +/- 0.4. The patients with a thoracic aortic aneurysm had worse quality of life scores than those of the ischemic heart disease or valvular heart disease patient-groups because of various perioperative complications. Our experiences demonstrate that the results including the postoperative quality of life following cardiac and aortic surgery in the elderly is satisfactory except for emergency cases. The results would prompt us to operate, if possible, electively in their stable conditions, even on elderly over-75-year-olds.

Single-stage surgery for distal aortic arch aneurysm and infrarenal abdominal aortic aneurysm through anterolateral approach

A 58-year-old man with a distal aortic arch aneurysm (DAA) associated with an infrarenal abdominal aortic aneurysm (AAA) successfully underwent a single-stage replacement of the aneurysms. A left anterolateral thoracotomy was used for replacement of the DAA, which was performed using profound hypothermic circulatory arrest and continuous retrograde cerebral perfusion. An extraperitoneal approach in conjunction with a lateral abdominal incision was employed for replacement of the AAA. The combination of an anterolateral thoracotomy and a lateral abdominal incision is useful in combined surgery for DAA and AAA.

Cerebellar-induced locomotion: reticulospinal control of spinal rhythm generating mechanism in cats

In a decerebrate cat (locomotor preparation), stimulation of a restricted region along the midline cerebellar white matter has been found to evoke generalized augmentation of postural muscle tone on a stationary surface (Asanome et al. 1998. Neurosci. Res. 30: 257-269) and "controlled" locomotion on the surface of a moving treadmill. Characteristics of cerebellar-evoked locomotion were similar to those of mesencephalic locomotor region-evoked "controlled" locomotion on the same animal. Microinjection of a neural tracer (CTb-HRP) into the lesioned stimulus site of the cerebellar white matter resulted in both retrograde labelling of cells in the fastigial nuclei, bilaterally, and anterograde labeling of fibers descending to the brain stem. These results indicated that the effective cerebellar stimulus site (cerebellar locomotor region) corresponded to the midline region of the hook bundle of Russell (Rasmussen, A. T., 1933. J. Comp. Neurol. 57: 165-197), through which crossed fastigioreticular, fastigiovestibular, and fastigiospinal fibers pass. In this study, contribution of reticulospinal systems to the control of cerebellar-evoked locomotion was extensively studied. By stimulating the cerebellar locomotor region and the MLR in the same animal, a majority of antidromically identified pontomedullary reticulospinal cells were synaptically activated. The results of the present study demonstrated that fastigial cells with crossed fastigioreticular fibers and reticulospinal fibers play a crucial role in the control of posture and locomotion in the locomotor preparation.

Microencapsulation of hepatitis B core antigen for vaccine preparation

PURPOSE

To prepare poly(lactide-co-glycolide)(PLGA) microspheres containing recombinant hepatitis B core antigen (HBcAg; Mw = 3,600,000) by a w/o/w emulsion/solvent evaporation method and evaluate the possibility of this system as a potent long-acting carrier for hepatitis B core antigen in mice.

METHODS

Various additives had been incorporated in the internal aqueous phase during the process of microencapsulating HBcAg, HBcAg antigenicity in the medium extracted from the prepared microspheres were measured by ELISA. Shape confirmation of the HBcAg antigen was performed by a sucrose gradient velocity centrifugal technique. For in vivo study, prepared microspheres were administered subcutaneously to Balb/C mice, and the serum IgG level was determined by ELISA.

RESULTS

The inactivation of HBcAg by methylene chloride was dramatically reduced by the addition of gelatin (4-8% (w/v)) to the internal aqueous phase during the preparation. Further improvement of the loading efficiency to almost 61% resulted with cooling (4 degrees C). The prepared microspheres (4.27 microm+/-1.23 microm) containing 0.15% HBcAg displayed burst release (50-60% within 2 days). In subcutaneous inoculation, the adjuvant effect of PLGA microspheres was almost the same as that of the complete Freund's adjuvant. Whereas oral inoculation using the microspheres was not effective.

CONCLUSIONS

The pH of the added gelatin seemed to be the key to the stabilization of HBcAg from various stability tests and CD spectrum study. Finally, the possibility of using this system as a potent long-acting hepatitis B vaccine was demonstrated.

Involvement of lipid peroxidation in free fatty acid-induced isolated rat pancreatic acinar cell injury

It was reported that free fatty acids degraded from triglycerides by lipase may play a major role in acute necrotizing or hyperlipidemia-induced pancreatitis. We hypothesized that this injury may be related to the peroxidation of cell membrane phospholipids and tested this hypothesis using isolated pancreatic acini. Pancreatic acini were prepared from male Sprague-Dawley rats by collagenase digestion. Linoleic acid was added (0.1-1.0 mM) to the acinar cell suspension to induce cell injury. Acinar cell damage was measured by lactate dehydrogenase release and by trypan blue exclusion. Phosphatidylcholine hydroperoxide and alpha-tocopherol in the acinar cells were measured. Protective effects of alpha-tocopherol (0.5, 5.0 mM) against this type of cell injury were also evaluated. When isolated acinar cells were treated with linoleic acid, a significant decrease in viability was observed in a time- and dose-dependent manner. In addition, the levels of phosphatidylcholine hydroperoxide after treatment of 0.5 mM of linoleic acid were increased and levels of alpha-tocopherol were decreased significantly. alpha-Tocopherol significantly ameliorated both cellular injury (p < 0.01) and increases in phosphatidylcholine hydroperoxide (p < 0.01). These data suggest that lipid peroxidation of the cellular membrane is an important component of the pancreatic cell injury mediated by free fatty acids.

Preparation and characterization of enteric microspheres containing bovine insulin by a w/o/w emulsion solvent evaporation method

The objective of this study was to produce enteric microspheres containing bovine insulin as a model drug using a water-in-oil-in-water (w/o/w) emulsion solvent evaporation method, and the preparative conditions were optimized. When hydroxypropylmethylcellulose acetate succinate (AS-HG type; high content of succinyl group) was employed as an enteric wall material, optimized microspheres showed almost 90% of the loading efficiency of insulin and 30.8 microns of mean volume diameter. The mixture of methylene chloride and acetone (4:1) as an oleaginous phase, 400 microliters of bovine insulin solution (dissolved in 30% of acetic acid) as an internal aqueous phase, and 1.0% of polyvinylalcohol dissolved in pH 3.0 citrate buffer as an external aqueous phase, were employed in the experiment. In relation to other enteric cellulose derivatives (AS-MG type, AS-LG type; medium and low content of succinyl group, respectively), the microencapsulation using a simultaneous preparation method also resulted in quite high loading efficiencies, whereas the choice of poly(methyl methacrylate) as a wall material caused aggregation or flocculation in the preparative process of every batch. The AS-HG microspheres showed very fast release profile in pH 6.8 buffer, but no released fraction was observed in pH 1.2 buffer. This phenomenon suggested enteric characteristics of prepared microspheres. Finally AS-HG microspheres containing 4% lauric acid and 9% insulin were prepared, suspended in 0.1% of carboxymethyl cellulose solution, and administered to the rat rectum (corresponding to 50 I.U./kg insulin). The plasma glucose level reached minimum level at 0.5 h after administration then gradually rose to normal.