Adjuvant hepatic intra-arterial iodine-131-lipiodol following curative resection of hepatocellular carcinoma: a prospective randomized trial.

BACKGROUND: The purpose of the present study was to determine whether intrahepatic injection of (131)I-lipiodol (Lipiodol) is effective against recurrence of surgically resected hepatocellular carcinoma (HCC). METHODS: From June 2001 through March 2007, this nationwide multi-center prospective randomized controlled trial enrolled 103 patients 4-6 weeks after curative resection of HCC with complete recovery (52: Lipiodol, 51: Control). Follow-up was every 3 months for 1 year, then every 6 months. Primary and secondary endpoints were recurrence-free survival (RFS) and overall survival (OS), respectively, both of which were evaluated by the Kaplan-Meier technique and summarized by the hazard ratio (HR). The design was based on information obtained from a similar trial that had been conducted in Hong Kong. RESULTS: The Lipiodol group showed a small, and nonsignificant, improvement over control in RFS (HR = 0.75; 95 % confidence interval [95 % CI] 0.46-1.23; p = 0.25) and OS (HR = 0.88; 95 % CI 0.51-1.51; p = 0.64). Only two serious adverse events were reported, both with hypothyroidism caused by (131)I-lipiodol and hepatic artery dissection during angiography. CONCLUSIONS: The randomized trial provides insufficient evidence to recommend the routine use of (131)I-lipiodol in these patients.

A radioassay for aminoacylproline hydrolase (aminopeptidase P) activity.

A radioassay was developed in which aminoacylproline hydrolase acts on Arg-Pro-Pro-[3H]benzylamide to yield arginine plus Pro-Pro-[3H]benzylamide. By stopping the reaction with base (0.1 M NaOH), the radioactive product is deprotonated to an organophilic form and is separable from the hydrophilic substrate by extraction of the alkaline aqueous solution with an organic solvent. When scintillants are included in the organic solvent, the enzyme:substrate reaction, extraction and quantification of Pro-Pro-[3H]benzylamide can all be conducted using a single liquid scintillation vial. Thus, aminoacylproline hydrolase activity is measured in terms of the rate of release of Pro-Pro-[3H]benzylamide. The substrate is obtainable at greater than 20 Ci/mmol, which enables its use under conditions of first-order enzyme kinetics. Conditions of near-zero order kinetics are readily attained by adding unlabeled substrate (Km 0.7 microM). The substrate is highly reactive (a 1:2000 dilution of guinea pig plasma hydrolyzed greater than 10% of the substrate during a 10 min incubation at 37 degrees C) and specific in that it is not degraded by leucine aminopeptidase, aminopeptidase A or N, dipeptidyl peptidase IV nor prolyl endopeptidase. The assay was used to measure aminoacylproline hydrolase specific activities in tissues of rat and guinea pig. Activity was found in virtually all major tissues of both species, and some guinea pig tissues (e.g. kidney and plasma) were found to be notably rich sources of the enzyme.

Purification and characterization of guinea pig serum aminoacylproline hydrolase (aminopeptidase P).

Aminoacylproline hydrolase (EC 3.4.11.9) of guinea pig serum has been obtained as two apparently homogeneous isoforms. Dialyzed serum was chromatographed successively on Affi-gel blue, hydroxyapatite, DE-cellulose, phenyl-Sepharose, an affinity matrix for angiotensin converting enzyme and concanavalin-Sepharose. On the latter matrix, 68% of the enzyme activity was eluted with alpha-methyl mannoside at 10 and 100 mM, and 29% was eluted with alpha-methyl glucoside, 500 mM, at 56 degrees C. The two fractions ('biantennary' and 'high mannose' fractions, respectively) were concentrated and then chromatographed separately on Sephacryl S-200HR. Both fractions were eluted as expected for a globular protein of Mr 217,000. On SDS-PAGE, under reducing and non-reducing conditions, each of the concanavalin-Sepharose fractions was separated into two protein bands, Mr 89,000 and Mr 81,500. Each of the bands was found to be N-blocked when N-terminal amino acid sequencing was attempted. The reaction of the 'biantennary' fraction with the synthetic substrate Arg-Pro-Pro-[3H]benzylamide was characterized in part: Km 0.7 microM, kcat 124.6 min-1, kcat/Km 1.78.10(8) M-1 min-1. Hydrolysis of the substrate was strongly inhibited by bradykinin and those of its lower homologs that contain two adjacent proline residues. Cu2+ was strongly inhibitory. Co2+ at 30 microM activated the enzyme, as did Mn2+, Mg2+ and Ca2+ at higher concentrations. Sulfhydryl compounds, including captopril, inhibited the enzyme as did 1,10-phenanthroline. Iodoacetamide and N-ethylmaleimide had no effects, but 4-hydroxymercuribenzoate conferred a partial inhibition over a remarkably wide concentration range: 0.34-1400 microM. Amastatin and bestatin did not inhibit the enzyme. Aminoacylproline hydrolase of guinea pig serum appears to be a heterogeneous, glycosylated metallo-enzyme with a high affinity for bradykinin and related peptides in which the sequence Pro-Pro, Xaa-Pro-Pro or Xaa-Pro-Hyp is N-terminal.

Protective role of quercetin against cisplatin-induced hair cell damage in zebrafish embryos.

BACKGROUND AND OBJECTIVES: The aim of this study was to evaluate the protective effects of quercetin on cisplatin-induced hair cell damage in transgenic zebrafish embryos. MATERIALS AND METHODS: Five days postfertilization zebrafish embryos were exposed to 1 mM cisplatin and quercetin at 10, 50, 100, or 200 µM for 4 h. Hair cells within neuromasts of the supraorbital, otic, and occipital lateral lines were analyzed by fluorescent microscopy (n = 10). Survival of hair cells was calculated as the average number of hair cells in the control group that were not exposed to cisplatin. Ultrastructural changes were evaluated using scanning electron microscopy. RESULTS: Hair cell damage in neuromasts was decreased by co-treatment of quercetin and cisplatin (quercetin 100 µM: 8.6 ± 1.1 cells; 1 mM cisplatin only: 5.0 ± 0.5 cells; n = 10, p < 0.05); apoptosis of hair cells examined by special stain was also decreased by quercetin. The ultrastructure of hair cells within neuromasts was preserved in zebrafish by the combination of quercetin (100 µM) and cisplatin (1 mM). CONCLUSION: In conclusion, quercetin showed protective effects against cisplatin-induced toxicity in a zebrafish model. The results of this study suggest the possibility of a protective role of quercetin against cisplatin-induced apoptotic cell death in zebrafish.

Inhibition of endothelial-bound angiotensin converting enzyme, in vivo.

1. We determined apparent Ki constants of two inhibitors, captopril and CL242,817, for pulmonary endothelial-bound angiotensin converting enzyme (ACE) in anaesthetized rabbits. [3H]-benzoyl-Phe-Ala-Pro was used as the substrate. The apparent kinetic parameters Km and Amax (product of Vmax and microvascular plasma volume) were measured, as was the ratio (Amax/Km) (measured under first order reaction conditions) before and 30s after the i.v. administration of captopril 10 nmol kg-1 or CL242,817, 35 nmol kg-1. 2. Under mixed order reaction conditions, ([S] greater than or equal to Km), apparent Km values increased from 12.2 +/- 1.9 microM to 32.9 +/- 3.3 microM (P less than 0.05) in the captopril-treated rabbits and from 9.3 +/- 2.3 microM to 45.8 +/- 9.8 microM (P less than 0.05) in the CL242,817-treated rabbits, indicative of competitive inhibition. However, apparent Amax values decreased from 10.3 +/- 2.1 to 4.5 +/- 0.8 mumol min-1 (P less than 0.05) and 8.9 +/- 1.7 to 4.8 +/- 0.5 mumol min-1 (P less than 0.05), respectively. 3. Under first order reaction conditions ([S] much less than Km), the Amax/Km ratio decreased from 763 +/- 100 to 125 +/- 38 ml min-1 (P less than 0.05) and 1009 +/- 149 to 126 +/- 44 ml min-1 (P less than 0.05) in the captopril- and CL242,817-treated groups respectively. 4. When the single pass transpulmonary binding of 80pmol [3H]-RAC-X-65 (an ACE inhibitor) was measured in additional rabbits, a significant (P < 0.05) decrease in RAC-X-65 binding was observed 30s after captopril (80% decrease) or CL242,817 (85% decrease), a result expected for a loss of catalytically active enzyme mass due to tightly bound captopril or CL242,817. 5. These results indicate that, in vivo, both captopril and CL242,817 are competitive, tight binding inhibitors of lung ACE. Furthermore, they suggest means for evaluating the interaction of other potential ACE inhibitors with the pulmonary endothelial membrane-bound enzyme, in vivo, possibly in phase I clinical trials.

In-line measurement of pulmonary metabolic function in the anesthetized rabbit.

Quantitative assessment of lung metabolic function is thought to provide biochemical information reflecting integrity of the pulmonary microcirculation. Although multiple indicator-dilution techniques are useful in such pharmacokinetic studies, the need for fractionation and subsequent processing of blood samples greatly prolongs data generation. Accordingly, we designed and tested an in-line system which rapidly can quantify single-pass disposition of photon-emitting substances in the pulmonary circulation of intact animals. The nuclear detection system consisted of a phoswich scintillation probe optically coupled to a photomultiplier tube. Pulses were discriminated for height and shape and counts recorded in a counter-timer, the output of which was interfaced with a personal computer. A mixture of an intravascular reference substance (99mTc-sulfur colloid) and an inhibitor of angiotensin-converting enzyme, N-[1(S)-carboxy-(4-OH-3-[125I]-phenyl) ethyl]-L-alanyl-L-proline (125I-CPAP), was injected as a bolus in the right heart of anesthetized ventilated rabbits and arterial blood was diverted through a flow-cell cuvette directly apposed to the phoswich detector. Single-pass extraction of 125I-CPAP was 39 +/- 3% (mean +/- SE; n = 20) and was depressed in a dose-dependent fashion by the addition of unlabeled CPAP (1-10 micrograms/kg) to the injection. These data indicate that we can now quantify, in the intact animal, saturable binding of an inhibitor to angiotensin-converting enzyme expressed on the surface of the pulmonary microvascular endothelium. Furthermore, such data can be obtained rapidly.

Carboxyalkyl peptide inhibitors of kininase II: chiral synthesis.

Heretofore, carboxyalkyl peptide inhibitors of kininase II (e.g. N-[1-carboxy-3-phenylpropyl]-Ala-Pro, "enalaprilic acid") have been synthesized by means that yield racemic product. Typically, the secondary amine bond is formed by reacting an amino acid or dipeptide with a 2-keto carboxylic acid ester or imide. The group providing the 2-keto function must be used in excess, and the desired S,S,S isomer must be obtained by resolution procedures. We have developed a procedure whereby enalaprilic acid, RAC-X-64 and related compounds are synthesized stereospecifically and in relatively high yields.

Slow tight binding inhibitors of angiotensin converting enzyme.

We have found that apparent Ki values of some, but not all, carboxyalkyl-dipeptide inhibitors of angiotensin converting enzyme decrease as a function of incubation time. The most potent of the ACE inhibitors tested so far is RAC-X-65 (N-[1(S)-carboxy-3-carboxanilidiopropyl]-L-Ala-L-Pro). When RAC-X-65 is not preincubated with human serum ACE (2.4 X 10(-11) M), the apparent Ki value is 4.4 X 10(-10) M. Preincubation of RAC-X-65 with ACE for 15 min before addition of substrate yields an apparent Ki of 4.1 X 10(-11) M. a 90 min preincubation of the inhibitor with ACE yields an apparent Ki of 1.2 X 10(-11) M, i.e., the reaction of the inhibitor with enzyme is virtually stoichiometric. The enzyme:inhibitor complex is poorly separated by molecular sieve chromatography or by dilution. That such tightly bound complexes are formed in vivo is suggested by the following results: The intravenous ED50 (anesthetized rats) of RAC-X-65 is 9.43 nmol/kg, and the time for half recovery (t1/2) of responsiveness to i.v. angiotensin I, 120 ng/kg, following a cumulative dose of 240 nmol/kg of the inhibitor is 165 min. For comparison, the i.v. ED50 of captopril is 105 nmol/kg, and its t1/2 following a cumulative dose of 240 nmol/kg is 16 min. Implied is the possibility that slow tight binding inhibitors of ACE may be used in a 1 pill per day regimen for the treatment of hypertension.

Radiolabelled substrates for angiotensin converting enzyme.

Six [3H]benzoyl-tripeptides were prepared and tested as substrates for angiotensin converting enzyme. Each was prepared first as its [4-iodo]-benzoyl-analog, and an atom of 3H per molecule was introduced by catalytic dehalogenation in 3H2-gas. Kinetic parameters were measured at 37 degrees C using as buffer 0.05 M Hepes, pH 8.0 containing 0.1 M NaCl and 0.6 M Na2SO4. When the substrates were used at concentrations far below their respective Km values, fractional rates of substrate utilization per unit time for constant enzyme concentration were direct function of respective second order rate constants (Kc/Km). Although absolute values of Kc/Km differed for human enzyme as opposed to rabbit enzyme, relative values of Kc/Km were virtually identical. Similarly, relative rates of substrates utilization during passage through lungs of anesthetized rats were similar to relative values of Kc/Km measured in vitro. Thus, there is now a range of ACE substrates usable, in vitro and in vivo, under conditions of first order enzyme kinetics, conditions under which values of V/Km and Ki can be measured directly.

Prevalence of Helicobacter pylori in gastric cancer in a South-East Asian population by 14C-urea breath test.

BACKGROUND: Helicobacter pylori is believed to play an important role in the aetiology of gastric cancer. There is a great variability in seropositivity and histological frequency of H. pylori in gastric cancer. The present prospective study investigates the prevalence of H. pylori infection in gastric cancer patients using 14C-urea breath testing. METHODS: Patients with endoscopic biopsy-proven gastric cancer were fasted for 6 h prior to ingesting 18.5 x 104 Bq of 14C-urea cocktail orally. Breath samples were collected after 20 min by asking them to blow into a hyamine solution and measurements were read in a scintillation counter. RESULTS: Fifty out of 51 patients (98%) with gastric cancer were positive on the 14C-urea breath test compared to 29 patients (61%) who were positive on histology. There was no association between sex, age or tumour site, stage, differentiation, Lauren type and H. pylori status. The test was negative in one patient with cardial tumour in which histology of the resected specimen was also negative for the bacteria. CONCLUSIONS: Active H. pylori infection is highly prevalent in gastric cancer in a South-East Asian population. The 14C-urea breath test is a highly sensitive method for detecting the presence of H. pylori even in gastric adenocarcinoma irrespective of the stage.

Computed tomographic appearance of colorectal hepatic metastases.

INTRODUCTION: This article reviews the various computed tomography (CT) appearances of hepatic metastases from colorectal primaries and assesses the frequency of occurrence of the various patterns. MATERIALS AND METHODS: This is a retrospective study of the CT appearances of histologically proven colorectal hepatic metastases in a group of 52 patients who had undergone surgical hepatic resection between January 1994 and December 2001. A total of 74 hepatic metastatic lesions were reviewed. All lesions were examined in the portal venous phase. RESULTS: A discernible rim was seen in 54 lesions (73%). Thick rim was present in 36 lesions (48.6%) and thin rim in 18 lesions (24.3%). Enhancement of the rim was present in 62 cases (83.8%). Increased central attenuation was seen in 38 lesions (51.4%). Of these, the centre was heterogeneous in 76.3% and scar-like in 23.7%. A non-enhancing rim was seen in 12 lesions (16.2%) which appeared as lesions with "bevelled edge". Thick enhancing rim with non-enhancing centre was the most common combination in 15 lesions (20.3%). CONCLUSION: An enhancing rim could be seen in 83.8% of lesions. Increased central attenuation was present in 51.4% of the lesions. Familiarity with the various CT appearances may facilitate identification and diagnosis of colorectal liver metastases.

Low incidence of penetrating trauma in a high-volume tertiary center: 10-year mortality review.

BACKGROUND: Trauma morbidity and mortality outcome is better in high-volume trauma centers. However, there are few publications investigating the experience of high-volume centers with high non-trauma emergency load but seeing a relatively low incidence of trauma. The objective of this study is to review the presentation and outcomes for the low volume of patients presenting with penetrating injuries in a high-volume hospital. METHODS: Data were extracted from the Singapore General Hospital database between 1998 and 2007. There were 1,233 patients who sustained penetrating injuries and were brought to the hospital during the 10-year period. Of these, only 78 patients had injury severity score (ISS) values of 16 or more. In the same period, there were 1,270 patients with ISS > 15 who were admitted with blunt injury. SPSS 10.1 was used to conduct univariate and multivariate analyses to elucidate risk factors for mortality. RESULTS: Age, ISS, and trauma injury severity score (TRISS) were significant predictors of mortality. Gender and type of injury were not predictive of mortality. Mortality outcomes were independently predicted by age, TRISS, and ISS. The most common site of injury was the chest, followed closely by the head and neck. The abdomen/pelvis was the third most common site of injury. There was no significant difference in anatomical site injury pattern between the survivors and non-survivors. For both groups, chest injuries and head and neck injuries dominated, with maximal abdominal/pelvic injuries a distant third. CONCLUSION: With a trauma system in place, high-volume centers with a low volume of penetrating injury patients can still manage uncommon injuries without jeopardizing patient care.

Comparing the efficacy of sunitinib with sorafenib in xenograft models of human hepatocellular carcinoma: mechanistic explanation.

Hepatocellular carcinoma (HCC) is the fifth most common and third deadliest malignancy. Sorafenib has demonstrated 44% survival advantage over placebo and has emerged as a standard of care in advanced HCC. The therapeutic effects of sorafenib are however transient and hence additional treatment options are warranted. In this study, we aimed to compare the efficacy of sunitinib relative to sorafenib, two potent inhibitors of protein tyrosine kinases involved in tumor growth, metastasis, or angiogenesis. We reported that sorafenib and sunitinib suppressed tumor growth, angiogenesis, cell proliferation, and induced apoptosis in both orthotopic and ectopic models of HCC. However, the antitumor effect of 50 mg/kg sorafenib was greater than that of 40 mg/kg sunitinib. Sorafenib inhibited p-eIF4E Ser209, p-p38 Thr180/Tyr182 and reduced survivin expression. This was not seen with sunitinib. In addition, the antitumor and apoptotic effects of sorafenib, which are associated with upregulation of fast migrating Bim and ASK1 and downregulation of survivin, were greater than that of sunitinib. These observations explained in part the apparent superior anti-tumor activity of sorafenib compared to sunitinib. In conclusion, sunitinib demonstrated an inferior anti-tumor activity compared to sorafenib in ectopic and orthotopic models of human HCC. It remains to be seen whether such observations would be recapitulated in humans.

Sunitinib (SUTENT, SU11248) suppresses tumor growth and induces apoptosis in xenograft models of human hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the fifth most common and third deadliest primary neoplasm. Since HCC is a particularly vascular solid tumor, we determined the antitumor and antiangiogenic activities of sunitinib malate, a potent inhibitor of two receptors involved in angiogenesis - vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR). In the present study, we reported that treatment of HepG2 and SK-Hep-1 cells with sunitinib led to growth inhibition and apoptosis in a dose-dependent fashion. Sunitinib inhibited phosphorylation of VEGFR-2 at Tyr951 and PDGFR-beta at Tyr1021 both in vitro and in vivo. Sunitinib also suppressed tumor growth of five patient-derived xenografts. Sunitinib-induced tumor growth inhibition was associated with increased apoptosis, reduced microvessel density and inhibition of cell proliferation. This study provides a strong rationale for further clinical investigation of sunitinib in patients with hepatocellular carcinoma.

Controlled localized buckling responses of orthodontic arch wires.

The orthodontic arch wire is often activated locally, in transverse bending and/or longitudinal torsion, to engage an individual malaligned tooth. Arch wires with substantial flexibilities and elastic ranges in bending are available. Several clinical reports of distal displacements of molars with appliances activated by locally buckling the arch wire have appeared in the recent published literature. This article contains an explanation of buckling or "column" action and the postbuckling response of a wire, and a report of the results of a controlled, in-vitro study of a sample of 256 wire segments subjected to activation-deactivation, buckling-postbuckling-unbuckling cycles. Continuous force-displacement diagrams were obtained from mechanical tests run at oral temperature. Four orthodontics-relevant, mechanical characteristics were quantified from each diagram, and each specimen was subjected to posttest evaluation for inelastic behavior. Although the deformation of the buckled wire is, in fact, bending, the force-displacement diagrams obtained differed substantially from their familiar counterparts generated in transverse bending. Judging from the force magnitudes induced as the deactivation half-cycles commenced as well as the deactivation rates, not all of the 8 wires seem to be clinically suitable for activation initiated by buckling. Magnitudes of springback were substantial from activations as large as 6 mm, and only 2 of the 8 wires exhibited full deactivations less than 80% of their activating displacements. This relatively new mode of arch wire activation that enables delivery to the dentition of mesiodistal pushing forces has substantial potential for clinical application from several biomechanical standpoints.

Characterization of rat pulmonary vascular aminopeptidase P in vivo: role in the inactivation of bradykinin.

The nonapeptide bradykinin (BK) is hydrolyzed at multiple sites during a single passage through the rat pulmonary vascular bed. Hydrolysis of one bond, Arg1-Pro2, appears to be catalyzed by an aminoacylproline hydrolase called aminopeptidase P (AmP). To help clarify its role in BK degradation, we have characterized rat pulmonary AmP in vivo in terms of its ability to react with intravascular substrates, its saturability and its contributions to the inactivation of circulating BK. By using indicator dilution methodology, hydrolysis of tracer doses of the AmP substrate Arg-Pro-Pro-[3H]benzylamide ([3H]APPB) during a single transit through the pulmonary vascular bed was measured. Transpulmonary hydrolysis of [3H]APPB obeyed first-order enzyme kinetics and was inhibited by carrier substrate (APPB) and two alternative AmP substrates, BK and des-Arg9-BK. APPB, des-Arg9-BK and des-Arg1-BK, all capable of binding to AmP in vitro, potentiated hypotensive effects of BK injected i.v. A saturating dose of APPB, 2 mumol/kg, in coinjections with BK, potentiated effects of i.v. BK by about 4-fold when pulmonary angiotensin converting enzyme (ACE) was active or inhibited completely. Complete inhibition of ACE potentiated blood pressure effects of i.v. BK by 40- to 120-fold. When both AmP and ACE were inhibited, the effects of i.v. BK were potentiated by up to 800-fold, and the hypotensive effects of BK injected i.v. on systemic mean arterial blood pressure were equivalent to effects of BK injected into the ascending aorta (i.a.); the BK i.v. and i.a. log dose-response curves were virtually superimposable.(ABSTRACT TRUNCATED AT 250 WORDS)

The modified dipeptide, enalapril, an angiotensin-converting enzyme inhibitor, is transported by the rat liver organic anion transport protein.

Oatp1, the organic anion transport polypeptide, is an integral membrane protein cloned from rat liver that mediates the uptake of various organic anions such as bromosulfophthalein (BSP) and taurocholate (TCA). Recent studies by others revealed that the thrombin inhibitor, CRC 220, a modified dipeptide, was transported by oatp1. The present study was designed to examine whether another modified peptide, enalapril, an angiotensin-converting enzyme inhibitor, was also a substrate. Transport was studied with enalapril (1 to 800 micromol/L, with [3H]enalapril) in a HeLa cell line stably transfected with oatp1-cDNA under the regulation of a Zn2+-inducible promoter. Noninduced transfected cells (without zinc) that did not express oatp1 failed to take up enalapril. In contrast, cells expressing oatp1 transported enalapril, estrone sulfate (E1S), taurolithocholic acid sulfate (TLCAS), and the glutathione conjugate of BSP (BSPGSH). Uptake of enalapril by oatp1 at 37 degreesC was substantially higher than that at 4 degreesC. The rate at 37 degreesC (uptake rates for induced - noninduced, transfected cells) was linear over 5 minutes and was concentration-dependent, characterized by a Km of 214 +/- 67 micromol/L and a Vmax of 0.51 +/- 0.15 nmol/min/mg protein. Enalapril uptake was inhibited competitively by BSP (at 1, 5, 10, and 50 micromol/L) and TCA (at 5, 25, and 100 micromol/L) with inhibition constants (Ki) of 2 and 32 micromol/L, respectively. The metabolite enalaprilat was, however, not transported by oatp1. That oatp1 is not a general transporter of anionic compounds was further shown by the lack of transport of harmol sulfate, benzoate, and hippurate. These observations attest to the role of oatp1 as a specific transporter for at least two classes of pharmacologically important peptides.

The diversity of beetle assemblages in different habitat types in Sabah, Malaysia.

The diversity of beetle assemblages in different habitat types (primary forest, logged forest, acacia plantation and oil palm plantation) in Sabah, Malaysia was investigated using three different methods based on habitat levels (Winkler sampling, flight-interception-trapping and mist-blowing). The overall diversity was extremely high, with 1711 species recorded from only 8028 individuals and 81 families (115 family and subfamily groups). Different degrees of environmental changes had varying effects on the beetle species richness and abundance, with oil palm plantation assemblage being most severely affected, followed by acacia plantation and then logged forest. A few species became numerically dominant in the oil palm plantation. In terms of beetle species composition, the acacia fauna showed much similarity with the logged forest fauna, and the oil palm fauna was very different from the rest. The effects of environmental variables (number of plant species, sapling and tree densities, amount of leaf litter, ground cover, canopy cover, soil pH and compaction) on the beetle assemblage were also investigated. Leaf litter correlated with species richness, abundance and composition of subterranean beetles. Plant species richness, tree and sapling densities correlated with species richness, abundance and composition of understorey beetles while ground cover correlated only with the species richness and abundance of these beetles. Canopy cover correlated only with arboreal beetles. In trophic structure, predators represented more than 40% of the species and individuals. Environmental changes affected the trophic structure with proportionally more herbivores (abundance) but fewer predators (species richness and abundance) in the oil palm plantation. Biodiversity, conservation and practical aspects of pest management were also highlighted in this study.

A radiochemical assay for aminopeptidase N.

We developed an assay for aminopeptidase N (AmN) in which substrate, Arg-Phe-[3H]anilide (24.9 Ci/mmol), can be used at concentrations (1-200 nM) well below Km (12 microM) and at or below enzyme concentration ([E]). Such reaction conditions simulate those in vivo where peptide hormones in picomolar concentrations (<< Km) are degraded by nano- or micromolar concentrations of enzyme. The Arg-Phe-[3H]anilide:AmN reaction obeyed first-order enzyme kinetics when human serum, human seminal plasma, guinea pig serum, or homogeneous porcine kidney AmN was used as enzyme source and substrate was within the concentration range of 1-200 nM. For porcine AmN, kcat/Km was 1.47 x 10(9) M-1 min-1, kcat 17,640 min-1. Human serum AmN was in a concentration (about 4.6 nM) in great excess over those reported for substrates such as angiotensin III. Several advantages accrue under conditions of first-order enzyme kinetics: (1) Vmax/Km is measured directly. (2) When kcat/Km is known, [E] can be computed in mol/liter. (3) IC50 values for alternative substrates can be taken as Km values. (4) IC50 values for inhibitors are Ki values when Ki >> [E]. Arg-Phe-[3H]anilide can be used to measure AmN activity in the presence of chromophores and fluorophores that interfere with photometric and fluorometric assays. We have confirmed that alleged substrates such as angiotensin III and Met-Lys- and Lys-bradykinin are bound by AmN with high affinities (Km values, 5.7, 9.1, and 14.3 microM). Bovine pulmonary artery endothelial cell cultures were found to possess AmN-like activity.(ABSTRACT TRUNCATED AT 250 WORDS)