Conformational study of a custom antibacterial peptide cecropin B1: implications of the lytic activity

Cecropin B1 (CB1) with two amphipathic alpha-helical segments is a derivative of the natural antibacterial peptide, cecropin B. The assays of cell lysis show that, compared with cecropin A (CA), CB1 has a similar ability to lyse bacteria with a higher potency (two- to six-fold higher) in killing cancer cells. The difference may be due to the fact that the peptides possess different structures and sequences. In this study, the solution structure of CB1 in 20% hexafluoroisopropanol was determined by two-dimensional nuclear magnetic resonance (NMR) spectroscopy. The (1)H NMR resonances were assigned. A total of 350 inter-proton distances were used to calculate the solution structure of CB1. The final ensemble structures were well converged, showing the minimum root mean square deviation. The results indicate that CB1 has two stretches of helices spanning from residues 3 to 22 and from residues 26 to 33, which are connected by a hinge section formed by Gly-23 and Pro-24. Lys-25 is partially incorporated in the hinge region. The bent angle between two helical segments located in two planes was between 100 and 110 degrees. With comparisons of the known NMR structure of CA and its activities on bacteria and cancer cells, the structure-function relationship of the peptides is discussed.

Perceptual differences between stroke patients with cerebral infarction and intracerebral hemorrhage

OBJECTIVE

To assess perceptual performances of patients with intracerebral hemorrhage (ICH) compared with those of ischemic patients early after stroke and to analyze the psychometric properties of three perceptual tests used in the study.

DESIGN

Cross-sectional study.

SETTING

A rehabilitation unit at a teaching hospital.

PATIENTS

Twenty-two stroke patients with ICH and 22 demographically matched stroke patients with infarction.

MAIN OUTCOME MEASURES

Loewenstein Occupational Therapy Cognitive Assessment (LOTCA), Rivermead Perceptual Assessment Battery (RPAB), and Motor-Free Visual Perception Test (MVPT).

RESULTS

Stroke patients with ICH had significantly more severe deficits on a task of thinking operations than did patients with infarction. A significant lateralized effect of stroke existed in the ICH group, with patients with right-hemisphere strokes scoring lower than patients with left-hemisphere strokes on the figure-ground discrimination subtest of the RPAB. A considerable overlap among the three instruments was found. Yet, the observed correlations between supposedly similar subtests from the tests proved to be moderate, indicating that to a certain extent these test measures tap different perceptual processes. Four factors were generated from a joint LOTCA-RPAB-MVPT factor analysis. They assessed different facets of perceptual functioning, including higher-level and lower-level perceptual skills, part/whole conceptual integration, and color perception. This factor pattern accounted for 75.5% of the variance.

CONCLUSIONS

Higher-level perceptual functions tend to be relatively susceptible to ICH stroke pathology early in the course of the disease. This information has important clinical implications in the early treatment planning for the stroke patients with ICH, such that specific compensatory strategies for these deficiencies should be devised to facilitate a successful rehabilitation. Knowledge regarding the influences of specific deficits on the performance of daily activities may also be useful to the patients' family.

A novel approach of intravenous electrocardiograph technique in correct position the long-term central venous catheter

Intravenous electrocardiograph (IVECG) can correctly positioning the catheter tip by enlarging p wave as it is moved toward right atrium, and it is a safe, reliable and accurate technique. To evaluate the efficacy of wire-conducted IVECG signal and IVECG signal from the port with sodium bicarbonate (NaHCO3) flushed catheter and to compare those with conventional anatomy landmark method was the propose of this study. This prospective study was carried out in 216 patients who suffered from malignant diseases. The correct position of the catheter tip among these groups was confirmed as follows. In group 1 (n = 80), the anatomy landmark method and portable chest radiograph recognized the correct position. In group 2 (n = 72), IVECG signal was conducted from guide wire to identify the tip position. In group 3 (n = 64), IVECG signal was conducted from the port with NaHCO3 (0.8 mEq/mL) flushed catheter to ascertain the tip position. The patient characteristics did not differ significantly among the groups. The duration of operation was significantly (P < 0.001) longer in group 1 than in group 2 and group 3 (45.4 +/- 9.3 minutes vs 35.7 +/- 8.0 minutes and 35.2 +/- 9.7 minutes, respectively). Catheter tip placement times were shorter in group 2 and group 3 than in group 1 (5.3 +/- 2.9 minutes and 6.4 +/- 3.0 minutes vs 16.7 +/- 5.7 minutes, respectively); there was a statistically significant difference between the group 1 and group 2 and group 3 (p < 0.001). Nonetheless, the duration of operation and catheter tip placement time was similar in group 2 and group 3. Early and late complications within the subsequent 3 months showed no significant difference among groups. We concluded that IVECG signal conducted from guide wire obtained a similar efficiency to that signal from the port with NaHCO3 flushed catheter on positioning the catheter tip of the venous Port-A-Cath system. It is recommended to use these methods to facilitate implanting long-term central venous devices.

[cDNA cloning, sequence analysis of trehalose-6-phosphate synthase gene from Saccharomyces cerevisiae AS2.1416]

The trehalose-6-phosphate synthase gene tps1 was amplified from yeast S. cerevisiae AS2.1416 cDNA library by polymerase chain reaction. This 1.5 kb fragment was cloned into PstI and BamHI sites of pGEM-T easy vector and the sequence of the gene indicated the cloned tps1 gene contained 1485 nucleotides encoding for 495 amino acid and shared a sequence homology of 99.6% with that from S. cerevisiae S288C.

Determination of interactions between human thrombopoietin and its receptor MPL by yeast two-hybrid system and affinity biosensor

The binding of human thrombopoietin to the extracellular domain of its receptor MPL prompts a cascade transduction of intracellular signals, leading to the development of megakaryocyte precursors and the production of circulating platelets. We have used a yeast two-hybrid system to reveal, via in vivo interactions between different deletion constructs of MPL and thrombopoietin, that the extracellular subunit 1 of MPL is the ligand binding site and the N-terminal domain of thrombopoietin alone is sufficient for the binding. The extracellular portion of MPL was heterologously expressed in E. coli and its specific affinity with thrombopoietin was visualized in vitro by resonance mirror biosensor technique.

Carcinogenesis in the biliary system associated with APDJ

Anomalous pancreaticobiliary ductal junction (APDJ) is a rare congenital anomaly which is considered to be an etiological factor in the development of carcinoma of the biliary tract. It is generally accepted that pancreatic juice reflux into the biliary tract due to APDJ is one of the etiologies of biliary tract cancers. Refluxing pancreatic juice results in changes of bile and induces chronic inflammation and increased cellular proliferation, leading to epithelial hyperplasia, metaplasia, and carcinoma of the biliary tract. K-ras mutations are more prevalent in the carcinomas of biliary tract associated with APDJ compared with those without APDJ. There is no difference in the overexpression of p53 between biliary tract carcinomas associated with APDJ and those unassociated with APDJ. Further studies are needed to evaluate the role of cytokines and growth factors in carcinogenesis of the biliary system associated with APDJ.

Concomitant management of airway and its adjacent vascular pathology in addition to repair of congenital cardiac defects

Respiratory symptoms are often present in infants with congenital cardiac anomalies, but the intrinsic pathology of the airway itself or external compression by abnormal vessels is frequently undetected before cardiac repair. We collected 12 patients with airway pathology from July 1996 to October 1998; all had definite diagnosis of lesions of the airway and its adjacent vessels by preoperative ultrafast computed tomography. Four had intrinsic pathology (one retrotracheal diverticulum, three tracheal stenosis) as well as external compression. Among them, six had complete vascular ring, four partial rings and three had bronchial compression by aneurysmal dilatation of branch pulmonary arteries. Simultaneous airway repair (one diverticulectomy, three patch tracheoplasty) and external decompression were performed in ten cases under cardiopulmonary bypass, nine of ten had simultaneous cardiac repair; the other two were done before cardiac repair. All survived except three. We concluded that ultrafast computed tomography is indispensable for definite diagnosis of airway and adjacent cardiovascular pathology. Mere repair of congenital cardiac defects without rectification of the airway and its adjacent structures is incompatible with survival.

Effects of timing of diatrizoate (water-soluble contrast medium) administration on pancreatic microcirculatory derangement in cerulein pancreatitis in rats

OBJECTIVE

We investigated whether the timing of administration of contrast medium after onset of acute pancreatitis is critical in determining the magnitude of microcirculatory derangement.

METHODS

An acute pancreatitis model in male Sprague-Dawley rats (225-275 g) was established by continuous infusion of cerulein (15 mg/kg per hour). The mean arterial pressure was monitored continuously by means of a femoral artery catheter. Diatrizoate (Hypaque-76), a water-soluble contrast medium, was delivered through a femoral vein catheter at doses corresponding to those given to humans, either 1, 2, or 3 hours after pancreatitis induction. In vivo microscopy and laser-Doppler flowmetry were used to investigate microcirculatory derangement. The water contents of the pancreas and lung, the malondialdehyde levels of the pancreas, and the trypsinogen activation peptide levels in the serum were measured at the end of the experiment (8 hours after infusion of cerulein).

RESULTS

Early administration of contrast medium (1 hour after pancreatitis induction) resulted in significantly greater changes in microcirculation and mean arterial pressure than did late administration (2 or 3 hours after pancreatitis induction). Rats given contrast medium 1 hour after induction also had highest pancreas and lung water contents, the highest pancreas malondialdehyde levels, and the highest serum trypsinogen activation peptide levels.

CONCLUSION

These results show that a water soluble contrast medium that is often used for computed tomographic imaging of the pancreas can adversely affect the pancreatic microcirculatory parameters, such as tissue perfusion and leukocyte sticking, and hemodynamics in a cerulein-induced model of acute pancreatitis. Early administration seems to cause more severe derangement of the pancreatic microcirculation.

AZU-1: a candidate breast tumor suppressor and biomarker for tumor progression

To identify genes misregulated in the final stages of breast carcinogenesis, we performed differential display to compare the gene expression patterns of the human tumorigenic mammary epithelial cells, HMT-3522-T4-2, with those of their immediate premalignant progenitors, HMT-3522-S2. We identified a novel gene, called anti-zuai-1 (AZU-1), that was abundantly expressed in non- and premalignant cells and tissues but was appreciably reduced in breast tumor cell types and in primary tumors. The AZU-1 gene encodes an acidic 571-amino-acid protein containing at least two structurally distinct domains with potential protein-binding functions: an N-terminal serine and proline-rich domain with a predicted immunoglobulin-like fold and a C-terminal coiled-coil domain. In HMT-3522 cells, the bulk of AZU-1 protein resided in a detergent-extractable cytoplasmic pool and was present at much lower levels in tumorigenic T4-2 cells than in their nonmalignant counterparts. Reversion of the tumorigenic phenotype of T4-2 cells, by means described previously, was accompanied by the up-regulation of AZU-1. In addition, reexpression of AZU-1 in T4-2 cells, using viral vectors, was sufficient to reduce their malignant phenotype substantially, both in culture and in vivo. These results indicate that AZU-1 is a candidate breast tumor suppressor that may exert its effects by promoting correct tissue morphogenesis.

Malignancy in choledochal cysts

BACKGROUND/AIMS

Malignancy in choledochal cysts is a rare condition. This study presents our experience with this condition, with emphasis on the clinical presentation, management and outcome.

METHODOLOGY

Subjects included 80 adults with choledochal cysts treated from January 1979 to December 1995. Of these patients, 8 were found to have malignancy in the cyst and formed the basis of this study.

RESULTS

Four patients had synchronous and 4 had metachronous carcinoma lesions arising in the choledochal cyst. The clinical presentation was: biliary tract infection in 5 patients, gastric outlet obstruction in 2 and right upper quadrant pain and body weight loss in 1. Operations for bile duct malignancy included total excision in 2 patients, choledochotomy with T-tube drainage in 2 patients, gastrojejunostomy in 2 patients, percutaneous transhepatic biliary drainage and gastrojejunostomy in 1 patient and metastatic lymph node biopsy only in 1. One patient died due to septic shock within 30 days of the operation (operative mortality). Postoperative survival time ranged from 4-13 months with a mean of 6.2 months.

CONCLUSIONS

The frequency of malignancy in the choledochal cysts was 10% in the present series. Malignancy in the choledochal cyst should be highly suspected in patients with cholangitis symptoms, body weight loss and anemia. Prognosis in this disease entity is poor.

Selective inhibition of inducible nitric oxide in ischemia-reperfusion of rat small intestine

PURPOSE

We investigated the role of constitutive and inducible nitric oxide (NO) synthases in intestinal ischemia-reperfusion (I/R) injury by observing the alterations in hemodynamics and intestinal microcirculation in response to I/R in rats, with or without inhibitors of NO synthases.

METHODS

Adult male Sprague-Dawley rats (n = 9/group) received a standard I/R procedure alone: I/R plus intravenous administration of aminoguanidine (an inhibitor of inducible NO synthase); I/R plus L-NAME (NG-nitro-L-arginine methyl ester, an inhibitor of constitutive and inducible NO synthase); IR + L-Arg (L-arginine, an NO precursor); or a sham operation plus the vehicle. The I/R procedure was performed by clamping the perfusion vessels of a segment of the terminal ileum, and medication was administered intravenously before and after intestinal ischemia. The intestinal perfusion and leukocyte-endothelial interactions were evaluated with in vivo microscopy and laser Doppler flowmetry. Surface expression of CD11b (an adhesion molecule) of circulating granulocytes was measured with flow cytometry.

RESULTS

Intestinal I/R produced circulatory alterations, intestinal microcirculatory derangement, energy depletion, and lipid peroxidation. Aminoguanidine significantly attenuated the reperfusion-related depression of mean arterial pressure (MAP), the decrease in intestinal perfusion index, the decrease in tissue ATP preservation, the increase in tissue malondialdehyde (MDA) level, and the expression of CD11b of circulating granulocytes. Administration of L-NAME had only minor and transient effects on reperfusion-related changes of MAP, intestinal flux, numbers of adherent leukocytes, and CD11b expression, but had some protective effects on tissue MDA and adenosine triphosphate levels and flow velocity. L-Arg further decreased the MAP but did not affect reperfusion-related variables.

CONCLUSIONS

Our results show that the selective inhibition of inducible NO synthase by aminoguanidine attenuates the hemodynamic and microcirculatory derangement that results from intestinal I/R.

Arcobacter butzleri bacteremia in a patient with liver cirrhosis

Invasive Arcobacter butzleri infection in humans has been rarely described. We report a 60-year-old man with liver cirrhosis who presented with high fever and esophageal variceal bleeding. Two aerobic blood cultures grew Campylobacter-like organisms. The biochemical reactions of the isolate were inconclusive, while sequence analysis of the 16S rRNA gene definitively identified the organism as A. butzleri. The patient's bleeding stopped after endoscopic sclerosing therapy. Although the organism appeared to be resistant to cephalosporins on the basis of the minimum inhibitory concentrations determined with the E test, the fever resolved with parenteral cefuroxime. Whether the clinical improvement was related to cephalosporin therapy or to the self-limited nature of Arcobacter bacteremia is not known.

A reusable and specific protein A-coated piezoelectric biosensor for flow injection immunoassay

A hydrophilic matrix of periodate-oxidized dextran was used as a double-sided linker to covalently immobilize Staphylococcus aureus protein A (SpA) molecules onto a poly-L-lysine-modified piezoelectric crystal surface to improve their stability, activity, and binding specificity with human immunoglobulin G (IgG) in flow injection assays. The prepared sensing crystals displayed best sensitivity and reusability at a flow rate of 140 microL/min. A human IgG concentration as low as 0.3 nM can be detected by this system. Up to 19 successive assay repetitions were achieved without significant loss of sensitivity using the same crystal. The analysis of adsorption kinetics indicates that such a preparation can greatly increase the amount of available active human IgG binding sites on immobilized SpA. Hardly any response arising from unspecific binding was detected. In addition, the sensing crystal prepared by this method was found to retain activity better than one prepared via direct deposition when stored in either wet or dry states. Finally, the prepared SpA-coated crystals were applied to the affinity immobilization of polyclonal goat anti-Schistosoma japonicum glutathione-S-transferase (GST) and were able to subsequently detect GST and its genetically engineered mutant either in a purified form or in the crude cell lysate.

Use of alternative therapy among pediatric oncology patients in Taiwan

Both alternative medicine and western medicine have been commonly used to treat pediatric cancer patients in Taiwan. Each has its own intrinsic strengths and weaknesses and they can be complementary. Little is known about medical help-seeking behaviors of parents of pediatric cancer patients, especially those related to alternative therapies. This study investigated the extent and parental expectations on use of alternative therapies. All primary caregivers of 63 eligible patients were interviewed. Use of alternative therapies, regardless of education level or social status of their families, is prevalent (n = 46, 73%) in Taiwan. Commonly used alternative therapies included, in order of popularity, formulated functional food (n = 22, 48%), temple worship/shamanism (n = 19, 40%), traditional Chinese medicine (n = 9, 20%), secret recipes/herbs (n = 13, 28%), and diet supplements (n = 9, 19%). Such practices generally occur without medical guidance from oncologists, largely because of poor interactions between parents and oncologists. Future efforts should be made to encourage both parents and oncologists to discuss this issue. Nurses may serve as mediators by developing mutual trust and a sharing relationship between these groups.

The effect of pH on the structure, binding and model membrane lysis by cecropin B and analogs

Cecropins are a group of anti-bacterial, cationic peptides that have an amphipathic N-terminal segment, and a largely hydrophobic C-terminal segment and normally form a helix-hinge-helix structure. In this study, the ability of cecropin B (CB) and two analogs to lyse phospholipid bilayers, which have two levels of anionic content, has been examined by dye-leakage measurements over the pH range 2. 0-12.0. The two analogs differ from the natural peptide by having either two amphipathic segments (CB1) or two hydrophobic segments (CB3). All these peptides (except CB3 on low anionic content bilayers where it is not active) have maximal lytic activity on both types of bilayers at high pH. However, the pattern of secondary structure formation on these bilayers by the peptides, as measured by circular dichroism (CD), and the pattern of their ability to bind lipid monolayers, as measured using a biosensor, do not directly correlate with the pattern of their lytic ability. CB and CB1 with low anionic content bilayers have secondary structures as measured by CD with a similar pattern to membrane lysis, but binding is maximal near neutral, not high, pH. CB3 has some secondary structures on low anionic content bilayers at low pH and this becomes maximal over the basic range, but CB3 neither binds to nor lyses with these lipid layers. On high anionic content lipid layers, all peptides show high levels of secondary structures over most of the pH range and maximal binding at neutral pH (except for CB3, which does not bind). All three peptides lyse with high anionic content bilayers, but show no activity at neutral pH and reach maximal activity at very high pH. This work shows that pH is a major factor in the capability of antibacterial peptides to lyse with liposomes and that secondary structure and binding ability may not be the main determinants.

The skill components of a therapeutic chopsticks task and their relationship with hand function tests

Chopsticks are the primary tools used for eating and the physical movements of control are familiar to Chinese people. Chopsticks are easy to obtain in most rehabilitative settings. Occupational therapists often guide patients to practice miscellaneous chopsticks tasks to increase hand function in any case. The objective of this study was to investigate the skill components of the therapeutic chopsticks task and their relationship with hand function tests, and to identify clinical value. Eighty normal subjects (41 males and 39 females) whose age ranged from 17 to 26 years old participated in this study. Five standard hand function tests including three dexterity tests [Minnesota Rate of Manipulation Test (MRMT), Purdue Pegboard Test, and O'Connor Tweezer Dexterity Test (OTDT)], and two strength tests (Jamar Handgrip Test, and Pinchometer Test) were chosen to measure the dexterity and strength of hands. Additionally, the Test of Chopsticks Manipulation (TCM) was designed and used to assess the chopsticks manipulation skills. Subjects were tested with all the hand function tests and TCM in a random sequence. Results of six tests were obtained for each subject. Factor analysis showed that the skill components of TCM should be categorized into the "dexterity" component. In addition, a significant relationship (p < 0.05) was only seen between TCM and OTDT, there was no significant correlation between TCM and the other hand function tests. Findings in this study are valuable in setting the rehabilitation programs for patients with dexterity problems.

Aminoguanidine attenuates hemodynamic and microcirculatory derangement in rat intestinal ischemia and reperfusion

BACKGROUND

Nitric oxide (NO) participates in the regulation of hemodynamic and microcirculatory changes in intestinal ischemia and reperfusion (I/R). However, the nature of the involvement of an inducible NO release has been controversial. This study evaluates the impact of an inducible NO synthase inhibitor, aminoguanidine, used as a treatment in a rat intestinal I/R model.

METHODS

We investigated the hemodynamics by measuring the mean arterial pressure (MAP), and the microcirculatory responses of the intestine and liver to systemically administered aminoguanidine by use of laser-Doppler flowmetry (LDF), in vivo microscopy, and flow cytometry.

RESULTS

During the 30-min ischemia of the selected 20-cm ileal segment, no MAP change was noted. At reperfusion, a marked decrease of MAP was noted and the lowest levels were noted 3 hours after reperfusion (67 +/- 4% vs. 99 +/- 5% in sham-operated control animals). A marked decrease in liver perfusion as measured by LDF was noted 1 hour after reperfusion and remained low at 5 hours (72 +/- 4% vs. 97 +/- 3% in sham-operated control animals). A marked decrease in intestine perfusion was noted by using LDF 1 hour after reperfusion and remained low at 5 hours (43 +/- 3% vs. 92 +/- 4% in sham-operated control animals). The flow velocity of the postcapillary venules of the intestine was markedly decreased (1.01 +/- 0.62 vs. 2.67 +/- 0.34 mm/s in sham-operated control animals) at 5 hours after reperfusion. The flow velocity of the postsinusoidal venules of the liver was also markedly decreased (1.01 +/- 0.62% vs. 2.67 +/- 0.34% in sham-operated control animals). Leukocyte-endothelial interaction (adhesion) was increased in the postcapillary venules of the intestine (54 +/- 12 vs. 6 +/- 4/microm2 in sham-operated control animals) and in the postsinusoidal venules of the liver (32 +/- 8 vs. 2 +/- 2/microm2 in sham-operated control animals). Concomitantly, the granulocyte count was increased (9.1 +/- 0.6 vs. 2.1 +/- 0.3% of total circulating leukocytes in sham-operated control animals), with an increase of CD 11b expression. Aminoguanidine administration (1 mg/kg) 0.5 hour before ischemia and 1 hour after reperfusion significantly increased MAP, increased intestine and liver perfusion, decreased adhesion, and decreased circulating granulocytes and CD 11b expression.

CONCLUSION

Inhibition of an inducible NO release by aminoguanidine in intestinal I/R can attenuate hemodynamic and microcirculatory derangement.

Neutrophil elastase inhibitor (ONO-5046) attenuates reperfusion-induced hepatic microcirculatory derangement, energy depletion and lipid peroxidation in rats

Microcirculatory derangement, energy depletion, and lipid peroxidation are associated with the development of ischemia-reperfusion injury in the liver. This study investigated the effects of a neutrophil elastase inhibitor (ONO-5046) on hepatic ischemia-reperfusion injury. Adult, male Sprague-Dawley rats were divided into four treatment groups: 1) sham-operated control (laparotomy only, no ischemia) and saline injection (1 mL/kg), n = 6; 2) ischemia control (1-h ischemia, 2-h reperfusion) and saline injection (1 mL/kg), n = 6; 3) intravenous injection with ONO-5046 at a dose of 1 mg/kg 5 min before ischemia and immediately after reperfusion plus 1-h ischemia and 2-h reperfusion, n = 6; and 4) intravenous injection with ONO-5046 at a dose of 10 mg/kg 5 min before ischemia and immediately after reperfusion plus 1-h ischemia and 2-h reperfusion, n = 6. A laser-Doppler flowmeter and in vivo microscopy were used to investigate hepatic microcirculation. Tissue malondialdehyde (MDA) and adenosine triphosphate (ATP) levels were determined at the end of the experiment.

RESULTS

Compared with ischemia alone, ONO-5046 significantly reduced the extent of microcirculatory and hemodynamic derangement after ischemia-reperfusion. ONO-5046 at both doses significantly attenuated decreases in mean arterial pressure. ONO-5046 lessened adherent leukocyte count and improved flow velocity in the sinusoids and postsinusoidal venules. ONO-5046 at the dose of 10m/kg reduced MDA (1.97 +/- 0.54 micromol/g protein vs. 3.58 +/- 1.21 micromol/g protein in the ischemia and reperfusion group) and increased ATP levels (2.62 +/- 0.19 micromol/g wet wt vs. 0.57 +/- 0.37 pmol/g wet wt in the ischemia and reperfusion group), whereas ONO-5046 at a smaller dose (1 mg/kg) had lesser but significant effects on MDA and ATP alterations. This study demonstrates that treatment with ONO-5046, a neutrophil elastase inhibitor, can ameliorate ischemia-reperfusion injury of the rat liver.

Membrane lysis by the antibacterial peptides cecropins B1 and B3: A spin-label electron spin resonance study on phospholipid bilayers

Custom antibacterial peptides, cecropins B1 (CB1) and B3 (CB3), were synthesized. These peptides have particular sequence characteristics, with CB1 having two amphipathic alpha-helical segments and CB3 having two hydrophobic alpha-helical segments. These differences were exploited for a study of their efficacy in breaking up liposomes, which had different combinations of phosphatidic acid (PA) and phosphatidylcholine (PC), and a study of their lipid binding ability. Binding and nonbinding lysis actions of CB1 and CB3 on liposomes were examined further by electron spin resonance (ESR). The spin-labeled lipids 5'SL-PC, 7'SL-PC, 10'SL-PC, 12'SL-PC, and 16'SL-PC were used as probes. The ESR spectra revealed larger outer hyperfine splittings (2A(max)) for CB1 when the interactions of CB1 and CB3 with liposomes were compared. These observations indicate a larger restriction of the motion of the spin-labeled chains in the presence of CB1. Plots of the effective order parameter at the various probe positions (chain flexibility gradient) versus the peptide-lipid ratio further suggested that the lysis action of CB1 is related to its capacity to bind to the lipid bilayers. In contrast, there is no evidence of binding for CB3. To augment these findings, four spin-labeled peptides, C8SL-CB1, C32SL-CB1, C5SL-CB3, and C30SL-CB3, were also examined for their binding to and their state of aggregation within the lipid bilayers. Association isotherms of the peptides were measured for liposomes containing two molar fractions of PA (0.25 and 0.75). The membrane binding of the CB1 peptides exhibited a cooperative behavior, whereas the association isotherm of CB3 revealed binding to the lipid only for beta = 0.75 liposomes. To further identify the location of CB1 in the lipid bilayers, measurements of the collision rate with chromium oxalate in solution were conducted. Results from ESR power saturation measurements suggested that the NH(2)-terminal alpha-helix of CB1 is located on the surface of the lipid bilayers, whereas the COOH-terminal alpha-helix of CB1 is embedded below the surface of the lipid bilayers. These conclusions were further supported by the observed relationship between the partition distribution of peptides bound to liposomes at different PA/PC ratios and the amounts of free peptides. Based on the above observations, possible mechanisms of the bilayer lysis induced by CB1 and CB3 on liposomes of different composition are discussed.

[RAPD method for the identification of intergeneric asymmetric somatic hybrid plants of wheat]

Randomly amplified polymorphic DNA (RAPD) method was used to identify the hybrid nature of three kinds of intergeneric asymmetric somatic hybrid plants of wheat: wheat (Triticum aestivum) + Haynaldia villosa, Wheat + Leymus chinensis and wheat + Agropyron elongatum. It was shown from the electrophoresis profiles that the genome of somatic hybrid plants contained specific section genome of both parents after DNA amplification with arbitrary primers. A specific RAPD product (DNA fragment of 0.77 kbp) of A. elongatum generated with primer OPJ-12 was isolated, purified, labeled and used as a probe. Southern blot from OPJ-12 primer-generated specific section genome of the hybrid (T. aestivum + A. elongatum) hybridized to this probe (0.77 kbp) proved that they are homologous in nature. This paper also discussed the advantage of RAPD method in identification of hybrid plants, especially asymmetric somatic hybrids.

Spinal nitric oxide participates in the control of the blood pressure during graded hemorrhage in the conscious rat

We sought to evaluate the role of spinal nitric oxide (NO) in the control of blood pressure in the conscious animal and determine its possible participation in the progression of hemorrhagic shock. Adult, male Sprague-Dawley rats were chronically prepared with intrathecal, intravenous, and intra-arterial catheters. We first investigated the role of spinal NO on blood pressure control by intrathecal administration of N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME) at 0.37 micromol, 0.74 micromol. or 1.48 micromol. A dose-related increase in blood pressure was observed. We next pretreated animals with intrathecal or intravenous L-NAME at 0.37 micromol and induced the animal to shock by graded hemorrhage. Animals that received vehicle control or intravenous L-NAME had a decrease in blood pressure after 12% of the total circulatory blood volume (TBV) had been removed and developed severe hypotension after 24% TBV was bled. On the other hand, intrathecal pretreatment of L-NAME significantly attenuated the decrease in blood pressure. The blood pressure was maintained until 40% TBV had been withdrawn. We concluded that inhibition of NO synthase, in the spinal cord, increased blood pressure in a dose-dependent manner, and hemorrhagic shock induced by graded hemorrhage may involve an upregulation mechanism of spinal NO synthase in producing severe hypotension in conscious rats.

Affinity purification of Schistosoma japonicum glutathione-S-transferase and its site-directed mutants with glutathione affinity chromatography and immobilized metal affinity chromatography

A C-terminally polyhistidine-tagged protein of Schistosoma japonicum glutathione-S-transferase, named as SjGST/His, and its Cys85-->Ser, Cys138-->Ser, and Cys178-->Ser site-directed mutants were prepared and highly expressed in Escherichia coli. Both immobilized metal affinity chromatography (IMAC) and glutathione (GSH) affinity chromatography were used to purify these four enzymes. All of them were purified with equal efficiency by Ni2+-chelated nitrilotriacetic acid agarose gel, but not by GSH Sepharose 4B gel. The protein amounts of wild-type and Cys85-->Ser enzymes purified by the latter gel were three to seven-fold greater than those of the other two enzymes purified by the same gel, while their specific activities were two-fold lower, presumably because of the occurrence of noncovalent aggregation. Both purification methods yielded highly pure enzymes, while there were minor amounts of inter- and intra-disulfide forms in the IMAC purified enzymes except for the Cys85-->Ser mutant. Addition of dithiothreitol to GSH-affinity purified enzymes shifted all of their mass spectra of matrix-assisted laser desorption/ionization-time of flight mass spectrometry toward low molecular-mass regions, while addition of GSH to IMAC purified enzymes shifted the spectra toward high molecular-mass regions. The shift values of wild-type enzyme were larger than those of the three mutants, indicating that the Cys85, Cys138, and Cys178 residues were S-thiolated by GSH during the GSH-affinity purification. This result was confirmed by isoelectric focusing. These findings suggest that IMAC is more efficient than the conventional GSH-affinity system for the purification of SjGST/His enzyme, especially for its mutants and fusion proteins.

Intrahepatic cholangiocarcinoma in Taiwan

We report our experience of the surgical treatment of intrahepatic cholangiocarcinoma (ICC) in Taiwanese patients. A total of 162 patients with histologically proven ICC were treated of whom 106 (65. 4%) had associated hepatolithiasis. Patients with hepatolithiasis were in earlier stages than those without hepatolithiasis. Two-thirds of the patients with hepatolithiasis presented with acute cholangitis, and two-thirds of those without hepatolithiasis presented with hepatomegaly. The rate of hepatic resection was 29.6% (48 of 162), and these rates were 31.1% and 26.8% for the patients with and without hepatolithiasis, respectively. Ninety-three percent of the patients with hepatolithiasis underwent common bile duct exploration, compared with 18% of those without hepatolithiasis. The surgical mortality rates were 3.7% (6/162), for all patients, and 3. 8% and 3.6% for patients with and without hepatolithiasis, respectively. The morbidity rate was much higher in the patients with hepatolithiasis (37.7% vs 16.1%). The 1-, 3-, and 5-year survival rates were 35.5%, 20.5%, and 16.5% in the patients with hepatolithiasis and 27.2%, 8.8%, and 7.8% in those without hepatolithiasis. Concomitant hepatolithiasis prevented precise diagnosis preoperatively and precipitated biliary sepsis, which affected resectability and increased postoperative morbidity. Hepatolithiasis per se did not influence long-term survival.

Secondary structure formation is the earliest structural event in the refolding of an all beta-sheet protein

The refolding kinetics of cobrotoxin (CBTX), a small-molecular-weight ( approximately 7 kDa) all beta-sheet protein, has been monitored using a variety of biophysical techniques. The secondary structure formation and hydrophobic collapse occur as distinct events during the refolding of the protein. Complete secondary structure formation occurs prior to the clustering of the hydrophobic residues. The late stage(s) of the refolding pathway of CBTX is characterized by change(s) in the local environment and optical asymmetry of the indole ring of the sole tryptophan residue. The results obtained in the present study, to our knowledge, represent the first unambiguous experimental support for the framework model of protein folding.

[Induction of programmed cell death by menadione in suspension culture of carrot cells]

Menadione (VK3), a quinone that undergoes redox cycles leading to the formation of superoxide radicals, was found to induce cell death in suspension culture of carrot cells. The effect of menadione was in a dose-dependent manner. 100-800 mumol/L menadione caused 10-33 percent cell death. When concentration of menadione reached 1 mmol/L, 100 percent of cell death was observed. DNA cleavage, a hallmark of apoptosis was further studied. DNA ladders were observed in cells treated with 600 and 800 mumol/L menadione but not with lower concentration treatments where only very low percentage of cell death was found. There was no DNA ladders in the cells treated with 1 mmol/L menadion indicating that necrosis may occur. In situ detection of nuclear DNA fragmentation by TUNEL reaction revealed fragmented nuclear DNA in cells treated with 100-800 mumol/L menadion but not in cells treated with 1 mmol/L menadione.