Functional roles of the N-terminal amino acid residues in the Mn(II)-L-malate binding and subunit interactions of pigeon liver malic enzyme

Pigeon liver malic enzyme has an N-terminal amino acid sequence of Met-Lys-Lys-Gly-Tyr-Glu-. In this work, various mutants of the enzyme with individual or combinational deletion (delta) or substitution at these amino acids were constructed and functionally expressed in Escherichia coli cells. A major protein band corresponding to an Mr of approximately 65000 was observed for all recombinant enzymes in sodium dodecyl sulfate polyacrylamide gel electrophoresis. However, when examining by polyacrylamide gel electrophoresis under native conditions, the recombinant enzymes were found to possess a tetrameric structure with Mr approximately 260000 or a mixture of tetramers and dimers with the exception of delta(K2K3G4) and delta(1-16) mutants, which existed exclusively as dimers at the protein concentration we employed. K3A and K3E also dissociated substantially. K(2,3)A was a tetramer but K(2,3)E essentially existed as dimers. All tetramers and dimers were enzymatically active in the gels. All mutants displayed a similar apparent Km value for NADP+. The apparent Km for L-malate and Mn(II), on the other hand, was increased by 4-27-fold for the delta(K2/K3) and the delta(1-16) mutants. The small binding affinity of delta(K2/K3) with Mn(II)-L-malate was specific. With additional deletion at positions 3 and/or 4, the delta(K2K3), delta(K2G4/K3G4) or delta(K2K3G4) mutants exhibited similar kinetic properties for the wild type. The lysine residues at the positions 2 or 3 seem to be crucial for the correct active site conformation. The results indicate that the N-terminus of malic enzyme is located at the Mn(II)-L-malate binding domain of the active center and is also near the subunit's interface. These results were interpreted with our asymmetric double-dimer model for the enzyme in which the N-terminus was involved in the head-to-tail monomer-monomer interactions but not the dimer-dimer interactions.

[Clinical report of 60 cases of diabetic cardio-vascular autonomous neuropathy by stasis removing treatment of combined traditional and Western medicine]

OBJECTIVE

To study the treatment of diabetic cardio-vascular autonomous neuropathy (DCVAN) by TCM-WM following the principle of promoting blood circulation to remove blood stasis.

METHODS

Sixty patients with DCVAN were randomly divided into two groups, the treatment group (30 patients) were treated with combined TCM-WM therapy. Based on the control of blood sugar by WM effectively, then use TCM-Tangxinshen ([symbol: see text], TXS) with the function of supplementing the Qi and nourishing Yin, promoting blood circulation to remove blood stasis. Thirty cases of the control group were treated with WM alone. The course of treatment was three months.

RESULTS

The total effective rate of the treatment group and the control group was 77.3% and 33.4% respectively, which were significantly different statistically (P < 0.005).

CONCLUSION

The therapeutic effect of TCM-WM was better than that of WM.

Intestinal obstruction after laparoscopic herniorrhaphy

Laparoscopic herniorrhaphy is still a controversial procedure. Two cases of intestinal obstruction after laparoscopic herniorrhaphy are reported. The clinical features, possible mechanisms, managements, and outcomes were analyzed. The results showed that preexisting mesenteric defect, fibrin depositions, and longer operation time were predisposing factors for post-laparoscopic herniorrhaphy intestinal obstruction. These findings suggest that cleansing of fibrin deposition and shorter operation times may be important to avoid postoperative intestinal obstruction.

Bezoar manifested with digestive and biliary obstruction

BACKGROUND/AIMS

Gastrointestinal obstructions caused by bezoars are uncommon but are encountered with increasing frequency in general surgery.

METHODOLOGY

We made a retrospective review of 30 cases treated in the National Cheng Kung University hospital between July 1988 and December 1994.

RESULTS

Fourteen patients had either prior gastric surgery (9) or peptic ulcer disease (5) and were categorized as group I. The remaining 16 patients without above conditions were categorized as group II; and seven of them had history of ingestion of Pho Pu Zi (Cordia dichotoma Frost. f.), three had food bolus ingestion, two had diverticulum, two had adhesion and the remaining two had no significant features. Two patients, who received endoscopic removal of gastric bezoar and subsequently developed bowel obstruction, needed operation. Sixteen of 30 who underwent operation within 24 hours after arrival, recuperated uneventfully and most were discharged within a week. Eleven patients who received operation after 24 hours resulted in prolonged hospitalization in 9 and death in two. Re-operation was performed in one case for the recurrence of obstruction by the residual bezoar.

CONCLUSION

Dietary factors (Pho Pu Zi or bolus ingestion), and gastrointestinal (GI) anatomical lesion (diverticulum or adhesion) are the profound etiologies for formation of bezoars in cases without previous gastric surgery. On the other hand, gastric factors (previous ulcer surgery or peptic ulcer) play a major role even after ingestion of nonspecific high fiber diet. Early diagnosis, surgical intervention without delay and thorough exploration of the entire GI tract are essential for good postoperative results.

Prenatal molecular diagnosis of RET proto-oncogene mutation in multiple endocrine neoplasia type 2A

We report a case of multiple endocrine neoplasia type 2A (MEN 2A) diagnosed prenatally at 16 weeks gestation. The 35-year-old mother is a MEN 2A patient. She had had three prior pregnancies: one resulted in a stillbirth; one produced a genetically unaffected boy; and the third was terminated in the first trimester owing to a diagnosis of blighted ovum. Autopsy did not reveal the cause of death of the stillborn infant, who was also found to be affected with MEN 2A by molecular study of paraffin-embedded tissue. Because of poor obstetric history and the patient's age, amniocentesis for cytogenetic and molecular studies was performed at 16 weeks' gestation during the pregnancy under discussion. As with other affected members in the mother's family, the missense mutation of TGC to TTC at codon 634 of the RET proto-oncogene was found in amniotic fluid cells. Analysis of DNA extracted from the lymphocytes of the infant's blood at birth confirmed the diagnosis. To our knowledge, this is the first report of prenatal diagnosis of MEN 2A.

Implications of serum basic fibroblast growth factor levels in chronic liver diseases and hepatocellular carcinoma

Angiogenesis occurs in response to tissue damage, and is of vital importance for tumor growth and metastasis. Basic fibroblast growth factor (bFGF), a well-known angiogenic factor, has been suggested to be a useful diagnostic marker in certain hypervascular tumors. However, the relevance of its detection has not been well evaluated in patients with hepatocellular carcinoma (HCC) and benign chronic liver diseases. In the current study, immunoassay of bFGF was performed on serum samples from 39 patients with HCC, 21 with liver cirrhosis, 22 with chronic hepatitis and 40 normal subjects. The serum bFGF level was significantly increased in patients with liver cirrhosis and HCC when compared with those with chronic hepatitis or normal subjects (all p-values < 0.001). However, no difference was observed between the groups with liver cirrhosis and HCC (p > 0.05). If we set 9.6 pg/ml (mean + 3 standard deviations of bFGF in the control group) as the upper limit of normal serum level of bFGF, elevated bFGF concentrations were noted in 9.1%, 42.9% and 51.3% of patients with chronic hepatitis, liver cirrhosis and HCC respectively. In non-cancer patients, the coexistence of acute illness (p = 0.000) was an independent factor related to the elevation of serum bFGF. On the other hand, a multivariate analysis demonstrated that both advanced stage of cancer (p = 0.026) and coexistence of acute illness (p = 0.000) influence the serum level of bFGF in patients with HCC. We conclude that serum bFGF levels are significantly higher in patients with HCC and are positively correlated with advanced tumor stage. Nevertheless, elevation of serum bFGF may also be observed in a significant number of patients with liver cirrhosis. Therefore, measurement of serum bFGF alone cannot be satisfactory as a tumor marker for diagnosis of HCC. In addition, it is important to point out that coexistence of acute illness may be a crucial confounding factor in the diagnosis or monitoring of any cancer by the estimation of serum bFGF.

Expression of vascular endothelial growth factor in normal liver and hepatocellular carcinoma: an immunohistochemical study

Angiogenesis is of vital importance during the development and progression of solid tumors. To examine the role of vascular endothelial growth factor (VEGF) in hepatocarcinogenesis, we evaluated the expression of peptide in normal human liver (n = 6) and in 36 cases of hepatocellular carcinoma (HCC). Immunoreactivity for VEGF was present in the extracellular matrix of the portal tracts in the normal and nontumor part of liver, but not in hepatocytes and bile duct epithelium. For HCC, variable amounts of VEGF were expressed in 13 cases (36.1%) of tumor cells. Using a logistic regression model, expression of VEGF was significantly associated with a higher proliferative index (P = .01) and sonographic portal vein thrombosis (P = .05). However, VEGF expression did not correlate with a biochemical liver profile, alpha-fetoprotein levels, histological grading, gender, or clinical stage of cirrhosis (P > 0.1, respectively). Log-rank test showed that evaluation of VEGF did not provide more prognostic information (P > .5) than that from tumor volume and portal vein thrombosis (P < .01, respectively). In addition, VEGF was always present in the fibrovascular stroma or pericellular matrix of HCC, although no strong relationship was observed with the expression of VEGF in tumor cells (P > .5). Our data suggested that expression of VEGF may characterize a progression toward higher proliferation in hepatocarcinogenesis in vivo. The relevance of VEGF existing in the extracellular matrix of the normal liver and HCC remains to be clarified.

High dose chemotherapy with peripheral blood stem cells transplantation in patients with relapsed or refractory lymphomas preliminary reports

High dose chemotherapy with peripheral blood stem cells transplantation (PBSCT) has been used worldwide in the treatment of patients with various hematological malignancies and other solid tumors. It has just come into use as a salvage therapy in various malignancies in Taiwan in recent years. We report eight cases with relapsed or refractory lymphoma treated with high dose chemotherapy and PBSCT. Our results showed all cases but one achieved complete remission. The mean days of white cell recovery were 10 days to > 500/microliter (ranges, 8-16 days) and 12 days to > 1,000/microliter (ranges, 9-19 days). The mean days to platelet transfusion independent, i.e. platelet > 20,000/microliters, was 14 days. No specific side effect was noted except death in one case on D+9 during cytopenia state. Four patients relapsed and died during the follow-up after PBSCT. From our preliminary results we suggest that high dose chemotherapy with PBSCT could be used as a salvage therapy in patients with relapsed or refractory lymphomas with favorable and sustained hematological recovery. Most cases were tolerable with myeloablative chemotherapy and re-achieved remission, however, remission duration was still short and relapse remained the main problem to be overcome. The long term effects of high dose chemotherapy with PBSCT still need further study.

Cardiac and glycemic benefits of troglitazone treatment in NIDDM. The Troglitazone Study Group

Troglitazone is a thiazolidinedione under development for the treatment of NIDDM and potentially other insulin-resistant disease states. Treatment with troglitazone is associated with an improvement in hyperglycemia, hyperinsulinemia, and insulin-mediated glucose disposal. No significant side effects have been observed in humans. Because of reported cardiac changes in animals treated with drugs of this class, this multicenter 48-week study was conducted to evaluate whether NIDDM patients treated with troglitazone develop any cardiac mass increase or functional impairment. A total of 154 NIDDM patients were randomized to receive troglitazone 800 mg q.d. or glyburide titrated to achieve glycemic control (< or =20 mg b.i.d. or q.d.). Two-dimensional echocardiography and pulsed Doppler were used to measure left ventricular mass index (LVMI), cardiac index (CI), and stroke volume index (SVI). All echocardiograms were performed at each center (baseline, 12, 24, 36, and 48 weeks), recorded on videotape, and forwarded to a blinded central echocardiographic interpreter for analysis. The results showed that LVMI of patients treated with troglitazone was not statistically or clinically different from baseline after 24 or 48 weeks. Statistically significant increases in SVI and CI and a statistically significant decrease in diastolic pressure and estimated peripheral resistance were observed in troglitazone-treated patients. These results were not sex-specific. Glycemic benefits of troglitazone treatment were observed as evidenced by long-term improvement of HbA1c and C-peptide levels. Furthermore, triglycerides were significantly lower, and HDL was significantly higher at weeks 24 and 48. In conclusion, NIDDM patients treated with troglitazone do not show any cardiac mass increase or cardiac function impairment. Conversely, patients on troglitazone benefited from enhanced cardiac output and stroke volume, possibly as a result of decreased peripheral resistance. Treatment with troglitazone appears to have a favorable impact on known cardiovascular risk factors and could potentially lower cardiovascular morbidity in NIDDM patients.

Comparison of intravenous granisetron with metoclopramide plus dexamethasone in the prevention of nausea and vomiting associated with emetogenic cytotoxic chemotherapy

Fifty-one patients who received their first course of chemotherapy were studied to compare the respective efficacy and safety of granisetron and metoclopramide plus dexamethasone in the prevention of nausea and vomiting induced by emetogenic cytotoxic drugs. The results showed the response rate of antiemesis in the first 24 hours was higher in the metoclopramide plus dexamethasone group than in the granisetron group: 95% vs 84%. For the next six days of the study period, the response rate of the granisetron group was shown to be more effective than that of metoclopramide plus dexamethasone group: 77% vs 60%. Furthermore, the granisetron seemed to display enhanced tolerability with less drug-related side effects and no extrapyramidal effects which appeared in 2 cases of the metoclopramide plus dexamethasone group. In conclusion, a single dose of granisetron can be as effective as the gold standard of metoclopramide plus dexamethasone regimen in preventing and treating acute nausea and vomiting. For preventing delayed nausea and vomiting, granisetron is shown to be more effective than metoclopramide plus dexamethasone.

Familial hyperparathyroidism without multiple endocrine neoplasia

Hyperparathyroidism occurs sporadically, in association with multiple endocrine neoplasia (MEN) types I and II, or rarely as familial hyperparathyroidism (FHPT) without other manifestations. We analyzed our experience in 16 FHPT patients from 14 families treated between 1934 and 1991 and reviewed 51 other FHPT patients reported in the literature to determine the clinical course of these patients. Among our 16 patients, 7 (44%) had a serum calcium level >/= 3.75 mmol/L, 5 (31%) presented with hypercalcemic crisis, 3 (19%) had osteitis fibrosa cystica, 5 (31%) had nephrolithiasis, 1 had pancreatitis, 12 (75%) had multiple abnormal parathyroid glands, 3 (19%) had supernumerary glands, and 7 (44%) required reoperation for persistent (n = 4) or recurrent (n = 3) hyperparathyroidism. Three patients (19%) also had papillary thyroid cancer, and 7 (44%) had other coexistent thyroid disorders. Among 51 patients with FHPT reported in the literature, 23 (45%) had serum calcium >/= 3.75 mmol/L, and 23 (45%) had multiple abnormal parathyroid glands; 10 (20%) had recurrent hyperparathyroidism. FHPT without other endocrinopathies is a distinct entity. Patients with FHPT have multiple abnormal parathyroid glands and are prone to both recurrent and persistent hyperparathyroidism. They frequently present with profound hypercalcemia or hypercalcemic crisis, in contrast to patients with MEN-associated hyperparathyroidism or sporadic hyperparathyroidism.

Effect of thyroid hormone on urinary excretion of epidermal growth factor

Thyroid hormones were demonstrated to upregulate the synthesis of epidermal growth factor (EGF) mRNA and proEGF in the kidneys in vivo. This prospective study was performed to examine the extent of the hypothyroid state in modulating EGF excretion in the urine (U-EGF; n = 23). Patients with thyroid cancer were serially followed up from the euthyroid status, which was retained by thyroxine supplement after thyroidectomy, to the hypothyroidism in preparing for 131I whole body scanning. Paired thyroid function panel, including triiodothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), and U-EGF levels were measured on a weekly basis. Logarithmically transformed values of U-EGF were inversely correlated with TSH serum levels (p = 0.0000), but positively associated with T4 levels (p = 0.0005). No apparent correlation was observed with the T3 serum content, age and gender of the patients (p > 0.1, respectively). If the interval of measurement was taken into consideration, serum TSH was the most significant factor in association with U-EGF (p = 0.0003). Our data indicate that excretion of EGF in human urine depends substantially upon thyroid hormone support.

A prospective randomised study of laparoscopic v. open cholecystectomy in aged patients with cholecystolithiasis

Between August 1992 and July 1993, 27 patients aged 70 years of older with cholelithiasis were prospectively randomised into 2 groups. Fifteen patients underwent laparoscopic cholecystectomy and 12 patients underwent open cholecystectomy. Shorter operation time (93.3 +/- 25.3 minutes v. 176.3 +/- 26.1 minutes, P < 0.00001), fewer postoperative analgesic requirements (0.53 +/- 0.52 days v. 2.00 +/- 0.74 days, P < 0.00001), shorter postoperative hospital stay (3.93 +/- 1.71 days v. 7.92 +/- 0.79 days, P < 0.00001) and better cosmesis were found in the laparoscopic cholecystectomy group. The above data suggest that laparoscopic cholecystectomy is the treatment of choice for cholecystolithiasis in elderly patients.

Surgical resection of primary hepatocellular carcinoma extending to adjacent organ(s)

Primary hepatocellular carcinoma (HCC) extending to the adjacent organ(s) is sometimes encountered in patients with large, peripherally located tumours. Over a 4-year period, a total of 151 patients received curative resection of HCC at the Surgical Department of Veterans General Hospital-Taipei, Taiwan. Of these patients, 21 underwent hepatic resection combined with en-bloc resection of the adjacent organ(s) because tumour extension was found during operation. Subsequent histological examination of the resected specimens found evidence of HCC invasion into the resected adjacent organ(s) in only nine patients (group I), and the remaining 12 patients showed no evidence of extrahepatic HCC invasion (group II). Twenty-seven HCC patients with clinico-pathologically matched tumours but without extrahepatic extension were selected as controls (group III). One patient in group I died of hepatic failure after the operation. The morbidity rate was 48% in group I and group II patients, and 30% in group III patients. The difference was not statistically significant. On evaluating the clinico-pathological factors, including DNA ploidy status of the tumours, there were no significant differences between tumours with and without extrahepatic invasion. Patients with locally invasive HCC (group I) had disease-free and overall survival rates comparable with those of the patients without local tumour invasion (group II and III). We conclude that HCC with invasion to the adjacent organ(s) does not seem to be directly related to the 'aggressiveness' of the tumour, and extrahepatic infiltration of the tumour does not preclude a chance of cure. Our results underscore the need for en-bloc resection as treatment of choice for these patients.

ACAT inhibitors derived from hetero-Diels-Alder cycloadducts of thioaldehydes

Acyl-CoA:cholesterol acyltransferase (ACAT) is the enzyme largely responsible for intracellular cholesterol esterification. A systemic inhibitor of ACAT is believed to be able to slow or even reverse the atherosclerotic process. Towards that goal, a series of cyclic sulfides, derived from the hetero-Diels-Alder reaction of thioaldehydes with 1,3-dienes, and bearing carboxamide substituents, were prepared and evaluated for in vitro (in several tissues and species) and ex vivo ACAT inhibition. Minor changes in subsequent structure were found to have a significant effect in optimization of the biological activity of this series of compounds.

Involvement of Phe19 in the Mn(2+)-L-malate binding and the subunit interactions of pigeon liver malic enzyme

A triple mutant, F19S/N250S/L353Q, of pigeon liver malic enzyme was found to have no detectable enzymatic activity [Chou, W.-Y., Huang, S.-M., & Chang, G.-G. (1994) Arch. Biochem. Biophys. 310, 158-166]. In the present study, point mutants at these positions (F19S, N250S, and L353Q) were prepared by site-directed mutagenesis. Both N250S and L353Q have kinetic properties similar to those of the wild-type. On the other hand, the K(m)(app) values for both Mn2+ and L-malate of F19S were increased by approximately 10-fold, while the kcat value was decreased by 5-fold, which results in a decrease of the apparent catalytic efficiency (kcat/K(mNADP)K(mMal)K(mMn) by approximately 300-fold. These results clearly indicate that the F19S mutation is mainly responsible for the undetectable enzyme activity of the triple mutant. Three more Phe19 mutants (F19Y, F19G, and F19A) were then prepared. There is a direct correlation between the size of the substitutes and the affinities for Mn2+ and L-malate. The kinetic parameters for F19Y were similar to those for wild-type. Both F19A and F19G reveal a 5-fold decrease of kcat values. Two K(dMn) values for the high- and low-affinity sites, respectively, were detectable for the wild-type. On the contrary, only one K(dMn) value was detected for the F19 mutants, which was increased in the order of F19G > F19A > F19S > F19Y, with F19G being the most affected mutant. The K(mMal) values of F19G and F19A were increased 100- and 6-fold, respectively. The catalytic efficiency (kcat/K(mNADP)K(dMal)K(dMn)) of F19G was decreased to only 0.01% of that of the wild-type. The above results clearly indicate that the hydrophobic aromatic ring at position 19 plays a critical role in L-malate and Mn2+ binding. Furthermore, all mutants that have a small residue at position 19 exist as monomers. Therefore, Phe19 may locate in or near the regions for Mn(2+)-L-malate binding as well as for the subunit contact. These results are compatible with the asymmetric model for the quaternary structure of malic enzyme we proposed previously [Chang, G.-G., Huang, T.-M., Huang, S.-M., & Chou, W.-Y. (1994) Eur. J. Biochem. 225, 1021-1027]. The possible roles of the N-terminus of malic enzyme were also addressed.

Transverse abdominis musculo-peritoneal (TRAMP) flap for the repair of large duodenal defects

Definitive surgical management of major acute injuries to the second and third portions of the duodenum has been enigmatic. Sometimes, the defect is so large that it is unwise to do primary repair, and resection at this critical portion of the intestinal tract is technically hazardous or impossible. A serosal or mucosal patch technique has been used to repair this kind of duodenal defect with encouraging results. Since the use of this technique has proved effective, such a defect was not necessarily treated with the more complicated pancreaticoduodenectomy and was managed with less morbidity and mortality. But these techniques are still controversial. So, we tried a pedicle flap, called the transverse abdominis musculo-peritoneal (TRAMP) flap, for repair of large duodenal defect. We have used this flap in 25 rabbits, and the specimens were followed up to a period of 3 months. The flap showed satisfactory results and is presented as another option for repair of large duodenal defects.

An alternative approach of choledocholithotomy via laparoscopic choledochotomy

OBJECTIVE

To evaluate the safety and feasibility of laparoscopic choledocholithotomy via choledochotomy for the treatment of choledocholithiasis.

DESIGN

A prospective series of 1332 consecutive patients who underwent laparoscopic cholecystectomies, with a mean follow-up of 21.2 months.

SETTING

University-affiliated referral center.

PATIENTS

Forty-three patients (3%) with documented common bile duct stones from January 1991 to February 1995.

INTERVENTIONS

Laparoscopic choledocholithotomy with choledochotomy and T tube drainage were performed in 40 patients. Postoperative endoscopic sphincterotomy after laparoscopic cholecystectomy was performed in three patients.

MAIN OUTCOME MEASURES

Documented removal of common bile duct stones and procedure-related complications.

RESULTS

Laparoscopic choledocholithotomy via choledochotomy was successful in 35 (88%) of 40 patients in whom this procedure was attempted. The mean (+/- SD) operation time was 191.3 +/- 75.4 minutes, and the mean (+/- SD) length of postoperative stay was 10.4 +/- 2.7 days. Seven complications (18%) were recorded, including three major complications (8%) and two retained stones (5%).

CONCLUSIONS

Laparoscopic choledocholithotomy via choledochotomy can be performed safely, without increasing the morbidity rate as compared with that of open choledocholithotomy. Thus, some of the advantages of minimally invasive surgery are preserved.

Nonidentity of the cDNA sequence of human breast cancer cell malic enzyme to that from the normal human cell

A cDNA coding for human breast cancer cell cytosolic NADP(+)-dependent malic enzyme was obtained. This cDNA is composed of a length of 2084 base pairs, with 1698 base pairs coding for 565 amino acid residues and a length of 386 base pairs representing a 3'-noncoding region. Comparing this nucleotide sequence with that from the normal human tissue [Loeber, G., Dworkin, M. B., Infante, A., and Ahorn, H. (1994), FEBS Lett. 344, 181-186] reveals that three nucleotides in the open reading frame and the length of 3'-noncoding region of the cDNA are different. One of the changes results in a substitution of serine at position 438 for proline, which, however, may not cause significant changes in the predicted secondary structure. A partial cDNA lacking the first 84 nucleotides in the open reading frame was successfully cloned and expressed functionally in Escherichia coli cells. Its Km value for L-malate (1.21 +/- 0.11 mM) is four times higher than that for the natural human breast cancer cell malic enzyme (0.29 +/- 0.04 mM) but similar to that for the full-length recombinant enzyme (1.06 +/- 0.07 mM). The Km values for Mn2+ and NADP+ (0.26 +/- 0.03 and 0.97 +/- 0.4 microM, respectively) are similar to those for the natural enzyme (0.12 +/- 0.02 and 1.9 +/- 0.3 microM, respectively) or the recombinant wild-type enzyme (0.56 +/- 0.04 and 0.44 +/- 0.02 microM, respectively). A recombinant pigeon liver malic enzyme without the first 13 amino acid residues was used for comparison. The Km values for L-malate and Mn2+ of the truncated enzyme (11.2 +/- 0.9 mM and 61.2 +/- 4.6 microM, respectively) are over 40 times larger than those for the natural pigeon liver malic enzyme (0.21 +/- 0.02 mM and 1.06 +/- 0.08 microM, respectively) or the recombinant wild-type enzyme (0.25 +/- 0.01 mM and 1.48 +/- 0.05 microM, respectively). We suggest that the N-terminus of malic enzyme may be required for the substrate binding during the catalytic cycle.

Overexpression of a Rrp1 transgene reduces the somatic mutation and recombination frequency induced by oxidative DNA damage in Drosophila melanogaster

Recombination repair protein 1 (Rrp1) includes a C-terminal region homologous to several DNA repair proteins, including Escherichia coli exonuclease III and human APE, that repair oxidative and alkylation damage to DNA. The nuclease activities of Rrp1 include apurinic/apyrimidinic endonuclease, 3'-phosphodiesterase, 3'-phosphatase, and 3'-exonuclease. As shown previously, the C-terminal nuclease region of Rrp1 is sufficient to repair oxidative- and alkylation-induced DNA damage in repair-deficient E. coli mutants. DNA strand-transfer and single-stranded DNA renaturation activities are associated with the unique N-terminal region of Rrp1, which suggests possible additional functions that include recombinational repair or homologous recombination. By using the Drosophila w/w+ mosaic eye system, which detects loss of heterozygosity as changes in eye pigmentation, somatic mutation and recombination frequencies were determined in transgenic flies overexpressing wild-type Rrp1 protein from a heat-shock-inducible transgene. A large decrease in mosaic clone frequency is observed when Rrp1 overexpression precedes treatment with gamma-rays, bleomycin, or paraquat. In contrast, Rrp1 overexpression does not alter the spot frequency after treatment with the alkylating agents methyl methanesulfonate or methyl nitrosourea. A reduction in mosaic clone frequency depends on the expression of the Rrp1 transgene and on the nature of the induced DNA damage. These data suggest a lesion-specific involvement of Rrp1 in the repair of oxidative DNA damage.

Pharmacokinetics and metabolism of EXP921, a novel cognitive enhancer, in rats

EXP921, 5,5-bis(4-pyridinylmethyl)-5H-cyclopenta[2,1-b:3,4-b']-dipyridine, was a potential drug candidate for the improvement of cognitive performance in patients with Alzheimer's-type dementia. It has been shown to improve cognitive performance in rodent and primate models of learning and memory. To characterize the disposition of EXP921, the pharmacokinetics and metabolism of this compound were studied in rats after oral and intravenous administrations. EXP921 exhibited good bioavailability, 43% at 3 mg/kg and 61% at 10 mg/kg and was rapidly eliminated with a terminal half-life ranging from 1.28 to 2.29 hr after oral doses. Absorption from oral doses was rapid, as peak plasma levels were reached within 1 hr. A major metabolite was identified in plasma as the pyridinyl mono-N-oxide of EXP921. This metabolite (EXP696) was rapidly formed, and significant levels were detected in rat plasma after oral or intravenous administration. Its terminal half-life was slightly longer than that of EXP921. EXP696 was found to be reduced back to EXP921, demonstrating that the N-oxidation at the pyridyl ring is reversible. The interconversion favored the oxidation of EXP921 to EXP696. Two additional metabolites were identified in rat plasma at doses higher than or equal to 30 mg/kg. They result from despicolylation, followed by hydroxylation in the cyclopentane ring.

Effects of structural modifications on the intestinal permeability of angiotensin II receptor antagonists and the correlation of in vitro, in situ, and in vivo absorption

PURPOSE

The effects of structural modifications on the membrane permeability of angiotensin II (Ang II) receptor antagonists and the usefulness of in vitro and in situ intestinal absorption models in predicting in vivo absorption or bioavailability were investigated.

METHODS

Intestinal permeability was determined in vitro using Caco-2 cell monolayers and in situ using a perfused rat intestine method. Several physicochemical parameters were either measured or computed, and correlated with intestinal permeation.

RESULTS

Permeation coefficients (Pa) across Caco-2 cell monolayers correlated well with both in situ absorption rate constants (ka) and in vivo bioavailability or % absorption. For these Ang II antagonists, Pa values larger than 3 x 10(-6) cm sec-1 and in situ ka values of 2 x 10(-4) min-1 cm-1 or above were associated with good in vivo absorption. Structural modifications at the R5 position, where a COOH group was substituted with either a CHO or CH2OH group, enhanced the permeability of the Ang II receptor antagonists up to 100-fold. There were good correlations between permeability and log P(octanol/buffer), log PHPLC, charge, solvation/desolvation energy and assigned hydrogen bonding potential.

CONCLUSIONS

The correlations obtained in this study indicate that both the Caco-2 cell model and the in situ perfused rat intestine could be used to predict intestinal absorption in vivo. Structural modifications of the Ang II antagonists had a significant impact on the intestinal permeability. Charge, solvation energy, and hydrogen bonding are predominant determinants of intestinal permeability and oral bioavailability of these compounds.

Determination of XR510, a balanced angiotensin II receptor antagonist, in dog and rat plasma by combined liquid-liquid/solid-phase extraction and high-performance liquid chromatography

A sensitive and selective high-performance liquid chromatographic method for the determination of XR510 (I), a new non-peptide angiotensin II (AII) receptor antagonist with balanced affinity for AT1 and AT2 receptor subtypes is described. I and the internal standard, XR513, were extracted from acidified plasma by combined liquid-liquid/solid-phase extraction and chromatographed on a phenyl column with ultraviolet absorbance detection at a wavelength of 272 nm. The mobile phase consisted of a mixture of acetonitrile and sodium phosphate buffer. For both rat and dog plasma, the limit of quantitation was 5 ng/ml. This method has been validated and successfully utilized to investigate the disposition of I.

Pharmacology and pharmacokinetics of a novel nonpeptide angiotensin II receptor antagonist--DMP 811

DMP 811 exhibited high binding affinity for the angiotensin II subtype receptor AT1 in rat adrenal tissues with an IC50 of 6 nM, but not for the subtype receptor AT2. In the isolated rabbit aorta, DMP 811 inhibited the contractile response to angiotensin II selectively and noncompetitively with a KB value of 0.1 nM. In conscious renal hypertensive rats, DMP 811 decreased blood pressure with i.v. and p.o. ED30s of 0.005 and 0.03 mg/kg, respectively (p.o. ED30 for losartan = 0.59 mg/kg). In conscious furosemide-treated dogs, DMP 811 given either at 0.3 or 1 mg/kg p.o. decreased blood pressure. DMP 811 has oral bioavailabilities of 7 and 29% in rats and dogs, respectively, after a solution dose and 8 and 13%, respectively, after a suspension or capsule dosing. Our study indicates that DMP 811 is a selective and insurmountable AT1 receptor antagonist and is a 20-fold more potent orally-active antihypertensive agent than losartan.

Application of ABO genotyping using polymerase chain reaction method to assess engraftment in bone marrow transplantation--a case report

We described a case of acute promyelocytic leukemia with O blood type who received bone marrow transplantation during a second remission from his HLA identical, B blood type sibling. Using PCR genotyping of the ABO group and analysis of the variable number of tandem repeats of the D1S80 locus, we could quickly document the successful early engraftment in this patient. We emphasize that the use of PCR ABO genotyping is a quick and valuable method which could be applied to assess the engraftment and its follow up in those transplant cases with donors of mismatched blood groups.

Effects of phosphodiesterase inhibitors on spontaneous electrical activity (slow waves) in the guinea-pig gastric muscle

1. The effects of the phosphodiesterase inhibitors caffeine, theophylline, isobutylmethylxanthine (IBMX) and rolipram on spontaneous electrical activity (slow waves) were studied in the circular muscle of the guinea-pig gastric antrum. 2. All the inhibitors reduced slow wave frequency without changing the membrane potential and the slow wave configuration, but at higher concentrations they blocked the slow waves and caused membrane hyperpolarization. In the presence of the inhibitors a low level of irregular electrical activity could be observed in many preparations. 3. Isoprenaline, forskolin, dibutyryl cAMP and 8-bromo-cAMP all produced effects essentially similar to those of phosphodiesterase inhibitors. K+ (12 mM) and removal of K+ both depolarized the membrane and these were not affected by IBMX (1-3 microM). A decrease in frequency caused by IBMX was also not significantly affected by 12 mM K+ or K+ removal and only partially antagonized by TEA or 4-aminopyridine. 4. These results suggest that an increase in intracellular cAMP inhibits pacemaker activity of slow waves. An increase in K+ conductance does not seem to be a major factor in this inhibition. Slow waves appear to be a compound electrical activity in a group of muscle cells and are likely to be disintegrated by xanthine derivatives.

Significance of c-erbB-2 expression in normal and neoplastic epithelium of biliary tract

There were few, but conflicting, reports dealing with the clinical significance of c-erbB-2 in biliary tract cancer. We evaluated the expression of c-erbB-2 in normal epithelium of bile ducts (n = 46), gallbladder cancer (n = 11), carcinoma of the ampulla of Vater (n = 18), and intrahepatic cholangiocarcinoma (CC) (n = 18). c-erbB-2 protein is present in 63% (29/46) of surface epithelium in large and septal bile ducts, but not in peripheral small ducts. Overexpression of the gene product was found in 27.8% (5/18) of intrahepatic CC, 27.8% (5/18) of carcinoma of the ampulla of Vater, and 63.6% (7/11) of gallbladder cancer. But, there was no c-erbB-2 overexpression in the hyperplasia or atypical hyperplastic bile duct epithelium (p = 0.002). In terms of prognostic implication, expression of c-erbB-2 did not correlate to the histopathological grade (p = 0.60) and tumor stage (p = 0.63). The results indicate that c-erbB-2 protein may play some roles in physiology of normal bile ducts. Overexpression of the gene product occurs in one forth to about two thirds of carcinoma of biliary tract, and may be used as phenotypic marker for neoplastic transformation. However, the gene product may not be important in the aggressive behavior of tumor.

Sustained contraction produced by caffeine after ryanodine treatment in the circular muscle of the guinea-pig gastric antrum and rabbit portal vein

1. Caffeine inhibited spontaneous mechanical activity at 0.3-1 mM, but produced a tonic contraction at concentrations higher than 3 mM in the circular muscle of the guinea-pig gastric antrum. In the circular muscle of the rabbit portal vein, caffeine at concentrations higher than 1 mM produced an early phasic contraction followed by a small tonic component. The caffeine-induced contraction was abolished by removal of the external Ca2+ more rapidly in the gastric antrum than the portal vein. 2. When the preparations were pretreated with ryanodine (1 microM) a sustained contraction developed on wash-out of caffeine (10 mM) both in the gastric antrum and portal vein. This contraction was not affected by nicardipine (3 microM) or verapamil (3 microM), but was readily abolished by removal of the external Ca2+ or by addition of cobalt (1 mM). Spontaneous electrical activity, the slow wave, in gastric muscles was blocked in the presence of 10 mM caffeine, but reappeared during the sustained contraction. 3. Both the contractions induced directly by caffeine and those produced following caffeine wash-out after ryanodine treatment were accompanied by a maintained increase in intracellular Ca2+ concentration measured with fura-2. 4. The presence or absence of Ca2+ during the application of ryanodine did not affect the ability of caffeine to initiate sustained contractions, provided Ca2+ was present during the exposure to caffeine. 5. It is concluded that caffeine can induce a sustained contraction after ryanodine treatment both in the guinea-pig gastric antrum and rabbit portal vein, by activating a Ca2+ influx pathway insensitive to organic Ca2+ channel blockers. No clear evidence was obtained for involvement of the Ca2+ influx pathway activated through depletion of intracellular Ca2+ stores. A hypothesis is proposed that the plasma membrane of these preparations is similar to the sarcoplasmic reticulum membrane in that Ca2+permeability can be increased almost irreversibly by a combination of caffeine and ryanodine in the presence of the external Ca2+.

MDR1 gene expression in acute myeloid leukemia: clinical correlation

Acute myeloid leukemia (AML) has a poor long-term prognosis, with a disease-free survival rate of only 20%. Drug resistance remains the major obstacle in this disease, although relatively little data are available on the correlation of multi-drug resistance (MDR) and clinical outcome. We examined 28 bone marrow samples from 24 patients with AML. The MDR1 RNA levels were determined by slot blot analysis. The incidence of positive expression of MDR1 mRNA in patients was 64.7% in samples from newly-diagnosed patients and 85.7% in relapse samples. The overall complete remission rate was 45%. However, the complete remission rate was lower for patients in the MDR1 RNA positive group than in the negative group. In three cases, the MDR1 RNA expression steadily rose during the period of disease progression and after several courses of chemotherapy. We suggest that a high frequency of MDR1 gene expression in patients with AML and higher MDR1 RNA levels are associated with a lower incidence of complete remission as well as a shorter disease-free time. The expression of MDR1 is a poor prognostic factor for AML treatment and it may play an important role in resistance to chemotherapy.

Characterization of the nuclease activity of Drosophila Rrp1 on phosphoglycolate- and phosphate-modified DNA 3'-termini

Drosophila Rrp1 includes a carboxy-terminal region homologous to Escherichia coli exonuclease III which is sufficient to repair both oxidative and alkylation damage to DNA. An apurinic/apyrimidinic endonuclease activity intrinsic to Rrp1 was characterized previously. In this work, the 3'-phosphodiesterase and 3'-phosphatase activities of Rrp1 are demonstrated and characterized. Phosphoglycolate- and phosphate-modified DNA 3'-termini are formed by oxygen radical induced DNA cleavage. To demonstrate the 3'-phosphodiesterase activity of Rrp1, a 3'-phosphoglycolate-terminated oligonucleotide substrate was generated by site-specific cleavage of a unique GpC dinucleotide by iron(II) bleomycin. Removal of the terminal phosphoglycolate is detected by mobility shift on a DNA sequencing gel. Rrp1 cleaves the phosphoglycolate and releases a product with a 3'-hydroxyl terminus. Phosphoglycolate is removed more readily than the 3'-terminal dGMP residue. Rrp1 phosphodiesterase activity is not inhibited by 120 mM NaCl, while the 3'-exonuclease is reduced 25-fold. Using a 3'-phosphate-terminated oligonucleotide, the phosphatase activity of Rrp1 is at least 25-fold lower than its phosphodiesterase or apurinic endonuclease, and 56-fold lower than exonuclease III activity on the identical substrate. Rrp1 3'-phosphatase is reduced 25-fold by 80 mM NaCl. These results were confirmed using an assay that measures the ability of Rrp1 to stimulate DNA synthesis on circular DNA substrates nicked by various DNA damage treatments. In that assay, Rrp1 poorly repairs 3'-phosphate-terminated nicks introduced by micrococcal nuclease. The significance of these enzymatic properties for the biological of Rrp1 is discussed.

Single amino acid changes alter the repair specificity of Drosophila Rrp1. Isolation of mutants deficient in repair of oxidative DNA damage

Drosophila Rrp1 has several tightly associated enzymatic activities, including double-strand DNA 3'-exonuclease, apurinic/apyrimidinic endonuclease, 3'-phosphatase, and 3'-phosphodiesterase. The carboxyl-terminal third of Rrp1, homologous to Escherichia coli exonuclease III, is sufficient to repair oxidative and alkylation-induced DNA damage in vivo. Using a screen for partial complementation of repair-deficient E. coli, we isolated three mutants of the nuclease domain of Rrp1: T462A, K463Q, and L484P, that protect against methyl methanesulfonate (MMS)-induced but not t-BuO2H-induced DNA damage. Thr-462 and Lys-463 are highly conserved residues found in a cluster of 5 conserved amino acids (LQETK), while Leu-484 is poorly conserved. Gln-460 Glu-461, Thr-462, and Lys-463 and Leu-484 were altered by site-directed mutagenesis using a plasmid including the entire Rrp1 gene and mutant proteins were purified. Mutants of the three residues Glu-461, Thr-462, and Lys-463 demonstrate 8-200-fold lower phosphodiesterase specific activity than wild-type Rrp1. E461A has a 30-fold reduction in AP endonuclease and is MMS-sensitive, but all other mutants have near-normal AP endonuclease and are MMS-resistant. Glu-461 appears to be essential for the nuclease function for Rrp1. Lys-463 and, to a lesser extent, Thr-462 influence the substrate specificity of the Rrp1 nuclease.

[Rhinocerebral mucormycosis in a case of malignant lymphoma]

Mucormycosis, an uncommon opportunistic fungal infection, usually occurs in immunocompromised patients. It is rapidly progressive and almost always fatal. Patients with lymphoma are susceptible to pulmonary or disseminated mucormycosis, whereas rhinocerebral mucormycosis in such patients, as far as we know, is rarely reported. We present a patient with malignant lymphoma who exhibited such an acute rhinocerebral infection after chemotherapy which manifested initially as a stuffy nose and intractable headache. Then ptosis, proptosis, chemosis and multiple cranial nerve palsies appeared. Eschar was found in the nasal cavity. Direct KOH smear and tissue biopsy revealed mucormycotic infection. He survived because of early diagnosis and prompt treatment.

Dissociation of pigeon-liver malic enzyme in reverse micelles

Pigeon-liver malic enzyme has a tendency to aggregate at a large concentration of protein. The larger aggregates (hexamer and octamer) were demonstrated to be enzymically active with specific activity similar to that of the tetramer. When the enzyme was embedded in a reverse micellar system prepared by dissolving the surfactant sodium bis(2-ethylhexyl)-sulfosuccinate (AOT) in isooctane, the tetrameric enzyme dissociated into monomers. The dissociated monomers were also enzymically active but with diminished specific activity relative to the activity in aqueous media. The decreased enzyme activity in reverse micelles was due to interactions of surfactant with the enzyme molecules, suggesting that the cytosolic malic enzyme is located near the plasma membrane. When the dissociation was monitored by altering the degree of hydration of the system (represented by the ratio [H2O]/[AOT]), the detergent and organic solvent slightly affected KTD, the dissociation constant of tetramer to dimers (T <--> 2 D), but increased KDM, the dissociation constant of dimer to monomers (D <--> 2 M), by 1-2 orders of magnitude; this change caused a 2-3 orders of magnitude increase in the overall dissociation constant KTM (T <--> 4 M). The dissociation of the tetrameric malic enzyme to monomers was favored by approximately 16 kJ/mol in AOT/isooctane reverse micelles versus aqueous media. We propose water-shell and induced-fit models for the enzyme in AOT/isooctane reverse micelles at large and small [H2O]/[AOT] ratios to explain this data, respectively. The asymmetric quaternary structure of the enzyme [Lee, H. J. & Chang, G. G. (1990) FEBS Lett. 277, 175-179] was re-evaluated in terms of the subunit interactions and various interconvertible enzyme forms.

Successful resection of a minute icteric hepatocellular carcinoma--case report

A 38-year-old male was admitted to our department with jaundice. Imaging studies including ultrasonography, ERCP, PTC and computed tomography (CT) revealed a hilar lesion. Right hepatic lobectomy, caudate lobectomy, excision of CBD and restoration of biloenteric continuity was performed. Pathological examination showed an icteric hepatoma (1.2 x 0.8 x 0.8 cm in size) originating in the caudate lobe. The tumor thrombus occupied the common hepatic duct and the right intrahepatic duct. The postoperative course was fairly unremarkable, and the patient has remained in good health for four years after surgery without any sign of recurrence.

A pharmacokinetic evaluation of HIV protease inhibitors, cyclic ureas, in rats and dogs

The pharmacokinetics of a series of novel cyclic, non-peptide inhibitors of HIV protease were studied in rats or dogs after intravenous and oral administration. Six symmetrically substituted cyclic urea compounds (XK234, XM311, XM320, XM321, XM323, and XM412), which effectively inhibited HIV virus replication, with IC90 values of 0.03-1.0 microM (0.017-0.76 microgram mL-1), were evaluated. Plasma concentrations were measured in rats and dogs using specific and sensitive HPLC methods. In rats, the maximum plasma concentrations of 0.21-1.88 micrograms mL-1 were detected within 1 h of oral administration of 10 mg kg-1 of the compounds. The elimination half-lives ranged from 1.25 to 3.3 h in rats and the absolute oral bioavailability ranged from 18 to 100%. In dogs, the maximum plasma concentration and absolute oral bioavailability were 4.37 micrograms mL-1 and 48%, 1.07 micrograms mL-1 and 16%, and 1.48 mg ML-1 and 38% for XK234, XM311, and XM323, respectively. The data demonstrated that the maximum plasma concentrations of these cyclic ureas were several times higher than the IC90 for inhibition of viral replication after single doses of 10 mg kg-1 in rats and dogs. With this combination of high potency against virus replication and good oral bioavailability, these cyclic ureas represent a new class of compounds that are suitable for development as therapeutic agents for the treatment of HIV-associated diseases.

Pharmacokinetics of HIV protease inhibitor DMP 323 in rats and dogs

DMP 323 is a symmetrically substituted cyclic urea compound with demonstrated activity against human immunodeficiency virus (HIV) in vitro. DMP 323 has been measured in rat and dog plasma via liquid-liquid extraction and HPLC. The limit of quantitation is 10 ng/ml using 0.5 ml plasma. Following an intravenous dose of 5 mg/kg to rats, DMP 323 exhibited an apparent volume of distribution at steady-state of 6.36 liters/kg and clearance of 7.12 liters/hr/kg. The same dose administered intravenously to dogs resulted in apparent volume of distribution at steady-state and clearance values of 2.28 liters/kg and 1.48 liters/hr/kg, respectively. Elimination half-lives were 0.95 hr in rats and 1.80 hr in dogs. DMP 323 was rapidly absorbed from oral solution doses in rats (3, 5, and 10 mg/kg) and dogs (5 and 10 mg/kg), achieving maximum plasma concentrations in 1 hr or less in both species. Absolute bioavailability of DMP 323 from oral doses ranged from 15 to 27% in rats and from 37 to 38% in dogs. Pharmacokinetics were unchanged in rats and dogs over 8-day t.i.d. and 5-day b.i.d. multiple oral dose regimens, respectively. Oral doses administered to fed animals resulted in lower plasma concentrations of DMP 323 than the same doses administered to fasted animals. Because of its in vitro high potency and acceptable pharmacokinetics, DMP 323 seems to be a worthy candidate for further study in the effort to develop an inhibitor of HIV protease for use in the therapy of AIDS.

Determination of DMP 728, a IIb/IIIa receptor antagonist, in rat and dog plasma by high-performance liquid chromatography with fluorimetric detection

A specific and sensitive HPLC assay for the determination of DMP 728 in dog and rat plasma has been developed. The method involves solid-phase extraction of DMP 728 and the internal standard from plasma using a C2 column. The extracted compounds are derivatized with benzoin under alkaline conditions. Using a mixture of acetonitrile and 0.1 M potassium phosphate buffer (25:75, v/v, pH 7.4) as mobile phase, the derivatized products are separated on a Regis semipermeable surface C8 column and monitored fluorometrically using 325 nm and 425 nm as excitation and emission wavelengths, respectively. The assay is linear from 2.5 to 1000 ng/ml in dog plasma and from 5 to 1000 ng/ml in rat plasma. The limit of quantitation is 2.5 ng/ml using 0.5 ml of dog plasma and 5 ng/ml using 0.5 ml of rat plasma. The assay has been used in pharmacokinetic studies of DMP 728 in dogs and rats.

Affinity cleavage at the putative metal-binding site of pigeon liver malic enzyme by the Fe(2+)-ascorbate system

Pigeon liver malic enzyme was rapidly inactivated by micromolar concentrations of ferrous sulfate in the presence of ascorbate at neutral pH and 0 or 25 degrees C. Omitting the ascorbate or replacing the ferrous ion with manganese ion did not lead to any inactivation. Manganese, magnesium, zinc, cobalt, or calcium ion at 200 molar excess over ferrous ion offered complete protection of the enzyme from Fe(2+)-induced inactivation. Ni2+ provided partial protection, while Ba2+ or imidazole was ineffective in protection. Addition of 4 mM Mn2+ or 5 mM EDTA into a partially modified enzyme stopped further inactivation of the enzyme. Inclusion of substrates (L-malate or NADP+, singly or in combination) in the incubation mixture did not affect the inactivation rate. The enzyme inactivation was demonstrated to be followed by protein cleavage. Native pigeon liver malic enzyme had a subunit M(r) of 65,000. The inactivated enzyme with residual activity of only 0.3% was cleaved into two fragments with M(r) of 31,000 and 34,000, respectively. The cleavage site was identified as the peptide bond between Asp258 and Ile259. Native pigeon liver malic enzyme was blocked at the N-terminus. Cleavage at the putative metal-binding site exposed a new N-terminus, which was identified to be at the 34-kDa fragment containing the C-terminal half of original sequence 259-557. Our results indicated that Fe2+ catalyzed a specific oxidation of pigeon liver malic enzyme at Asp258 and/or some other essential amino acid residues that caused enzyme inactivation. The modified enzyme was then affinity cleaved at the Mn(2+)-binding site.

Hyperammonemic encephalopathy due to essential amino acid hyperalimentation

Hyperammonemic encephalopathy has occasionally been reported in uremic patients receiving hyperalimentation with essential amino acid (EAA) as a source of nitrogen as one of the remaining treatment options when the enteric routes were prohibited. We encountered this complication in a patient with normal renal function. A rat animal model was designed to elucidate the mechanism of hyperammonemia resulting from hyperalimentation with EAA as a source of nitrogen. Sixty-four male Long-Evan rats were divided into eight groups receiving feeds ad libitum or different formula of hyperalimentation. Hyperammonemia was found in every rat given hyperalimentation with EAA as the only nitrogen source. Using the Tukey honestly significant difference test, the results were significantly higher (p < 0.001) than that of the control group which were given feeds ad libitum and those groups given hyperalimentation for the same number of days but with mixed amino acid (MAA) as the nitrogen source. Adding arginine to EAA for a further four days after initial administration of EAA hyperalimentation for three days only slightly lowered the mean serum ammonia level. When compared to that of the three-day EAA hyperalimentation group, the difference was not statistically significant. Adding arginine, citrulline, and ornithine to EAA for a further four days significantly lowered the mean serum ammonia level. When we changed EAA hyperalimentation to MAA hyperalimentation for a further four days, the mean serum ammonia level decreased dramatically to nearly normal. Hyperalimentation using EAA as the exclusive source of nitrogen resulted in hyperammonemia. A deficiency of arginine or other amino acids of the urea cycle failed to account completely for the hyperammonemia observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning and expression of pigeon liver cytosolic NADP(+)-dependent malic enzyme cDNA and some of its abortive mutants

A full-length 1927-base-pair cDNA of pigeon liver malic enzyme was obtained by utilizing the screening of the cDNA library and polymerase chain reaction techniques. The cDNA contained one open reading frame coding for 557 amino acid residues, flanked by 86 and 167 nucleotides at the 5' and 3' termini, respectively, and was successfully cloned and expressed in Escherichia coli cells. Functionally active recombinant malic enzyme was purified from the cells. This recombinant enzyme has a Km value for L-malate of 160 +/- 30 microM, which is almost identical to that for the natural enzyme (150 +/- 17 microM). The Km value for Mn2+ (4.2 +/- 0.3 microM) is higher than that for the natural pigeon malic enzyme (1.4 +/- 0.2 microM), while the Km value for NADP+ (3.8 +/- 0.3 microM) is lower than that for the natural enzyme (10.8 +/- 0.1 microM). The catalytic constant (kcat) for the recombinant enzyme is decreased by 3.6-fold, but the substrate inhibition constant for L-malate is increased by about 40-fold. Change in the quaternary structure of the recombinant enzyme was revealed in the pH perturbation examination. A truncated pigeon liver malic enzyme, lacking the first 13 amino acid residues, and a recombinant protein, mutated at F19S, N250S, and L353Q, showed no enzymatic activity. Both abortive recombinant mutant proteins were still able to bind with 2',5'-ADP agarose; however, the fluorescence emission spectrum of the protein bound NADPH did not show a blue shift as the natural enzyme. In accordance with these observations, we suggest that the adenosine 2',5'-bisphosphate binding domain of the NADP+ binding site in the beta alpha beta motif may still be retained in these mutant proteins. However, the local hydrophobic environment for the binding of the nicotinamide moiety of the coenzyme molecule may be altered. Therefore, the lack of catalytic activity of the mutant proteins could be attributed to an improper orientation of the bound NADP+.

Comparison of aged and young adult patients with cholelithiasis: a prospective controlled study

BACKGROUND

Surgical operations for gallstones are associated with increased perioperative mortality in the elderly. The presence of pre-existing cardiovascular disease and acute cholangitis might be the cause as found in the literature.

METHODS

From August 1989 to December 1990, twenty-nine patients (Age > or = 70 years) with cholelithiasis undergoing biliary surgery in Veterans General Hospital-Taipei were collected as experimental group. Twenty-nine patients from 62 patients (Age < or = 50 years) with cholelithiasis were selected as control group. The basic data, symptomatology, blood biochemistry, peri-operative complications, mortality and gallstone compositions were analyzed and compared between both groups.

RESULTS

There was a higher male to female ratio (4.8:1) in the aged group. Aged patients had higher incidence of common bile duct stone (11/29 versus 3/29, P < 0.025), while young adult patients had higher incidence of intrahepatic stone (1/29 versus 10/29, P < 0.05). The perioperative morbidity and mortality was higher in the aged group (37.9% and 3.4%) as compared with the young age group (3.4% and 0%, P < 0.005).

CONCLUSIONS

Aged cholelithiatic patients were associated with male preponderance, more common bile duct stones, higher perioperative morbidity and mortality, as compared with the young adult cholelithiatic patients.

Pharmacokinetics and bioavailability of bemoradan, a long-acting inodilator in healthy males

Bemoradan is a potent, long-acting orally active inodilator. The pharmacokinetics and bioavailability of bemoradan were studied in twelve normal males following oral administration of single, ascending doses of the bemoradan HCL salt in capsules. Plasma and urine levels of bemoradan were determined by HPLC (detection limits: approximately 0.5 ng/ml for plasma and 5 ng/ml for urine). Bemoradan was rapidly absorbed from the capsule formulation at all doses (Cmax occurred at 2.1-2.4 hours). Bemoradan was slowly eliminated from the body (harmonic mean t1/2 16-23 hours). There was a dose-proportional increase in the AUC (0-48) values of bemoradan in humans following the administration of 0.5, 1, 1.5 and 2 mg of bemoradan. The AUC (0-48) values increased to 2.3, 3.4 and 4.0 times when the dose was increased to 2, 3 and 4 times. Urinary excretion of unchanged bemoradan accounted for approximately 5-12% of the dose. Results from this study and previous studies in rats and dogs indicate that bemoradan is well and rapidly absorbed after oral dosing, has linear pharmacokinetics and long elimination half-lives across species.

The pharmacokinetics and metabolism of DuP 532, a non-peptide angiotensin II receptor antagonist, in rats and dogs

DuP 532, 2-propyl-4-pentafluoroethyl-1-([2'-(1H-tetrazol-5-yl)biph eny l-4-]methyl) imidazole-5-carboxylic acid, is an orally active, non-peptide angiotensin II (AII) receptor antagonist. DuP 532 is more potent and longer acting than losartan, another AII receptor antagonist currently undergoing phase III clinical trials. The pharmacokinetics and the effect of the salt form on the bioavailability of DuP 532 were determined in rats and dogs. In rats, the absolute oral bioavailability and half-life averaged 8.0% and 3.5 h, respectively, after the sodium bicarbonate solution and 7.6% and 3.6 h, respectively, after the methyl cellulose suspension. In dogs, the absolute oral bioavailability averaged 13.4% after the sodium bicarbonate solution and 11.9% after hard gelatin capsules containing the neat powder. The data demonstrated that there were no differences in bioavailability between the free acid and the sodium salt of DuP 532 after oral administration to rats and dogs. The in vitro metabolism of 14C-DuP 532 was evaluated with rat, dog, and human liver microsomes. HPLC analyses with UV and radiochemical flow detection showed that recovery of DuP 532 was greater than 99%, suggesting that there was little if any metabolism by liver microsomal enzymes. Therefore, the low oral bioavailability in rats was probably due to poor absorption of DuP 532 from the GI tract rather than extensive metabolism.

Bile duct injury and bile leakage in laparoscopic cholecystectomy

Between January 1991 and July 1992, 350 laparoscopic cholecystectomies were performed. There were six biliary complications (1.7 per cent): common bile duct (CBD) injury (one patient), delayed CBD necrosis (one), immediate postoperative bile leakage (one) and delayed bile leakage (three). All six patients required laparotomy. Primary repair with long-arm T tube splinting for 3 months was performed for the CBD injury. Religation of the cystic duct was carried out after immediate postoperative bile leakage. Laparotomy with T tube choledochostomy only was performed in the three patients with delayed bile leakage, and hepatojejunostomy Roux-en-Y was undertaken for CBD necrosis. The patient with primary repair of the CBD injury required choledochojejunostomy Roux-en-Y 18 months later for stenosis. Episodes of intermittent cholangitis occurred in the patient with CBD necrosis. The outcome for the four patients with bile leakage was good. There were no deaths.

High-performance liquid chromatographic determination of a potent AII receptor antagonist (DMP 811) in plasma

An HPLC assay for DMP 811, 4-ethyl-2-propyl-1-[(2'-(1H-tetrazol-5-yl)biphenyl-4-yl)methyl]imi dazole-5- carboxylic acid (I) in rat and dog plasma has been developed. Compound I was isolated from plasma using a liquid-liquid back extraction procedure. The extraction recovery was greater than 81%. Separation of I from endogenous components in plasma was achieved on an E. Merck C8 column using a mobile phase of 0.05 M ammonium acetate, brought to pH 3.75 with acetic acid, and acetonitrile (78:22, v/v). The eluent was monitored by fluorescence with excitation and emission set at 235 and 370 nm, respectively. The assay was linear from 2 to 2000 ng/ml. Inter- and intra-day coefficients of variation for the rat-plasma assay ranged from 0.9 to 5.2% (5-2000 ng/ml) and 2.7 to 16.5% (2-2000 ng/ml), respectively. The respective coefficients of variation for the dog-plasma assay were 1.9 to 5.6% and 1.2 to 14.0%. The percent differences from the accuracy results were 12% or less. Using 0.5 ml of plasma for extraction, the minimum quantifiable limit was 2 ng/ml. This method has been used to quantify plasma levels of I in rats or dogs following 3-10 mg/kg i.v. or p.o. doses.