Ratio of triglycerides to HDL cholesterol is an indicator of LDL particle size in patients with type 2 diabetes and normal HDL cholesterol levels

OBJECTIVE

In patients with type 2 diabetes, a normal HDL cholesterol level does not rule out that LDL particles may be small. Although techniques for analyzing LDL subfractions are not likely to be used in clinical practice, a prediction of LDL size based on a regular lipid profile may be useful for assessment of cardiovascular risk.

RESEARCH DESIGN AND METHODS

Sixty patients with type 2 diabetes with acceptable glycemic control and an HDL cholesterol level > or = 1 mmol/l were recruited after cessation of lipid-altering treatments. LDL size was determined by 2-20% PAGE; patients having small LDL (n = 30) were compared with those having intermediate or large LDL (n = 30).

RESULTS

Clinical characteristics, pharmacological therapies, lifestyle, and prevalence of diabetes-related complications were similar in both patient groups. LDL size correlated negatively with plasma triglycerides (TGs) (R2 = 0.52) and positively with HDL cholesterol (R2 = 0.14). However, an inverse correlation between the TG-to-HDL cholesterol molar ratio and LDL size was even stronger (R2 = 0.59). The ratio was > 1.33 in 90% of the patients with small LDL particles (95% CI 79.3-100) and 16.5% of those with larger LDL particles. A cutoff point of 1.33 for the TG-to-HDL cholesterol ratio distinguishes between patients having small LDL values better than TG cutoff of 1.70 and 1.45 mmol/l.

CONCLUSIONS

The TG-to-HDL cholesterol ratio may be related to the processes involved in LDL size pathophysiology and relevant with regard to the risk of clinical vascular disease. It may be suitable for the selection of patients needing an earlier and aggressive treatment of lipid abnormalities.

N-arginine dibasic convertase, a metalloendopeptidase as a prototype of a class of processing enzymes

N-Arg dibasic convertase is a metalloendopeptidase from rat brain cortex and testis that cleaves peptide substrates on the N terminus of Arg residues in dibasic stretches. By using both an oligonucleotide and antibodies to screen a rat testis cDNA library, a full-length cDNA was isolated. The sequence contains an open reading frame of 1161 codons corresponding to a protein of 133 kDa that exhibits 35% and 48% similarity with Escherichia coli protease III (pitrilysin, EC 3.4.99.44) and rat or human insulinase (EC 3.4.99.45), respectively. Moreover, the presence of the HXXEH amino acid signature (XX = FL) clearly classifies N-Arg dibasic convertase as a member of the pitrilysin family of zinc-metalloendopeptidases. In addition, a Cys residue that may be responsible for the thiol sensitivity of the insulinase and N-Arg dibasic convertase was proposed. The protein sequence contains a distinctive additional feature consisting of a stretch of 71 acidic amino acids. We hypothesize that this metalloendopeptidase may be a member of a distinct class of processing enzymes.

Temporin-SHf, a new type of phe-rich and hydrophobic ultrashort antimicrobial peptide

Because issues of cost and bioavailability have hampered the development of gene-encoded antimicrobial peptides to combat infectious diseases, short linear peptides with high microbial cell selectivity have been recently considered as antibiotic substitutes. A new type of short antimicrobial peptide, designated temporin-SHf, was isolated and cloned from the skin of the frog Pelophylax saharica. Temporin-SHf has a highly hydrophobic sequence (FFFLSRIFa) and possesses the highest percentage of Phe residues of any known peptide or protein. Moreover, it is the smallest natural linear antimicrobial peptide found to date, with only eight residues. Despite its small size and hydrophobicity, temporin-SHf has broad-spectrum microbicidal activity against Gram-positive and Gram-negative bacteria and yeasts, with no hemolytic activity. CD and NMR spectroscopy combined with restrained molecular dynamics calculations showed that the peptide adopts a well defined non-amphipathic alpha-helical structure from residue 3 to 8, when bound to zwitterionic dodecyl phosphocholine or anionic SDS micelles. Relaxation enhancement caused by paramagnetic probes showed that the peptide adopts nearly parallel orientations to the micelle surface and that the helical structure is stabilized by a compact hydrophobic core on one face that penetrates into the micelle interior. Differential scanning calorimetry on multilamellar vesicles combined with membrane permeabilization assays on bacterial cells indicated that temporin-SHf disrupts the acyl chain packing of anionic lipid bilayers, thereby triggering local cracks and microbial membrane disintegration through a detergent-like effect probably via the carpet mechanism. The short length, compositional simplicity, and broad-spectrum activity of temporin-SHf make it an attractive candidate to develop new antibiotic agents.

Aminopeptidase B from the rat testis is a bifunctional enzyme structurally related to leukotriene-A4 hydrolase

An aminopeptidase B (Ap-B) was previously purified to homogeneity from rat testis extracts and characterized. In the present work, by using oligonucleotides selected on the basis of partial amino acid microsequences of pure Ap-B and PCR techniques, the nucleotide sequence of a 2.2-kb cDNA was obtained. The deduced amino acid sequence corresponds to a 648-residue protein (72.3 kDa) containing the canonical "HEXXHX18E" signature, which allowed its classification as a member of the M1 family of metallopeptidases. It exhibits 33% identity and 48% similarity with leukotriene-A4 hydrolase, a relation further supported by the capacity of Ap-B to hydrolyze leukotriene A4. Both enzymes also were closely related to a partially sequenced protein from Dictyostelium discoideum, which might constitute the putative common ancestor of either aminopeptidase or epoxide hydrolase, or both. Ap-B and its mRNA were detected in the germ line and in the Sertoli and peritubular cells of the seminiferous tubules. Because the enzyme was found in the medium conditioned by spermatocytes and spermatids and in the acrosome during spermatozoa formation, together these observations suggested an involvement of this exometallopeptidase in the secretory pathway. It is concluded that this ubiquitous enzyme may be involved in multiple processing mechanisms.

Aminopeptidase-B in the rat testes: isolation, functional properties and cellular localization in the seminiferous tubules

An aminopeptidase of the B-type, with an apparent M(r) 72,000 and pI = 4.9, was isolated from rat testes and characterized. The enzyme was able to remove only Arg and/or Lys residues from L-amino acid beta-naphthylamide derivatives and from the N-terminus of several peptides. No cleavage occurred in the case of Arg-Pro bonds as found in bradykinin and substance P. The enzyme was sensitive to cysteinyl reagents and to aminopeptidase inhibitors, such as bestatin, amastatin and arphamenines A and B. The aminopeptidase activity, tested with L-Arg beta-naphthylamide and with Arg0-Met-enkephalin as substrates, was inhibited by o-phenanthroline, and restored by Zn2+ suggesting its metallopeptidase character. The partial characterization of an aminopeptidase-B activity in rat brain cortex identified a protein which is biochemically and immunologically related to the testis enzyme. By immunohistochemistry, the aminopeptidase-B was found to be particularly abundant in the seminiferous tubules at late stages of spermatogenesis and was clearly detected in a restricted area of elongated spermatids. Remarkably, the enzyme was observed to concentrate massively in the residual bodies. Since this aminopeptidase-B was able in vitro to trim out N-terminal Arg and/or Lys residues from peptides mimicking processing intermediates, it is proposed that this enzyme may be involved in propeptide and proprotein processing mechanisms in the course of spermatid differentiation.

Secretory vesicle aminopeptidase B related to neuropeptide processing: molecular identification and subcellular localization to enkephalin- and NPY-containing chromaffin granules

Biosynthesis of peptide hormones and neurotransmittters involves proteolysis of proprotein precursors by secretory vesicle cathepsin L. Cathepsin L generates peptide intermediates with basic residues at their NH(2)-termini, indicating that Arg/Lys aminopeptidase is needed to generate the smaller biologically active peptide. Therefore, this study identified the Arg/Lys aminopeptidase that is present in secretory vesicles of adrenal medulla and neuroendocrine tissues, achieved by molecular cloning and localization in 'model' neuropeptide-containing secretory vesicles (bovine). Molecular cloning of the bovine aminopeptidase B (AP-B) cDNA defined its primary sequence that allowed selection of antisera for immunolocalization studies. AP-B was present in secretory vesicles that contain cathepsin L with the neuropeptides enkephalin and neuropeptide Y. The AP-B in several neuroendocrine tissues was detected by western blots. Recombinant bovine AP-B showed preference for Arg-methylcoumarinamide substrate. AP-B was inhibited by arphamenine, an inhibitor of aminopeptidases. Bovine AP-B showed similar activities for Arg-(Met)enkephalin (ME) and Lys-ME neuropeptide substrates to generate ME, while rat AP-B preferred Arg-ME. Furthermore, AP-B possesses an acidic pH optimum of 5.5-6.5 that is similar to the internal pH of secretory vesicles. The significant finding of the secretory vesicle localization of AP-B with neuropeptides and cathepsin L suggests a role for this exopeptidase in the biosynthesis of neuropeptides.

Serine Protease Inhibitors in Ticks: An Overview of Their Role in Tick Biology and Tick-Borne Pathogen Transmission

New tick and tick-borne pathogen control approaches that are both environmentally sustainable and which provide broad protection are urgently needed. Their development, however, will rely on a greater understanding of tick biology, tick-pathogen, and tick-host interactions. The recent advances in new generation technologies to study genomes, transcriptomes, and proteomes has resulted in a plethora of tick biomacromolecular studies. Among these, many enzyme inhibitors have been described, notably serine protease inhibitors (SPIs), whose importance in various tick biological processes is only just beginning to be fully appreciated. Among the multiple active substances secreted during tick feeding, SPIs have been shown to be directly involved in regulation of inflammation, blood clotting, wound healing, vasoconstriction and the modulation of host defense mechanisms. In light of these activities, several SPIs were examined and were experimentally confirmed to facilitate tick pathogen transmission. In addition, to prevent coagulation of the ingested blood meal within the tick alimentary canal, SPIs are also involved in blood digestion and nutrient extraction from the meal. The presence of SPIs in tick hemocytes and their involvement in tick innate immune defenses have also been demonstrated, as well as their implication in hemolymph coagulation and egg development. Considering the involvement of SPIs in multiple crucial aspects of tick-host-pathogen interactions, as well as in various aspects of the tick parasitic lifestyle, these molecules represent highly suitable and attractive targets for the development of effective tick control strategies. Here we review the current knowledge regarding this class of inhibitors in tick biology and tick-borne pathogen transmission, and their potential as targets for future tick control trials.

Molecular epidemiology of an outbreak of multiresistant Klebsiella pneumoniae in a Tunisian neonatal ward

During the first quarter of 1996, a major outbreak of clinical infection caused by multiresistant Klebsiella pneumoniae (MRKP) occurred in the neonatal ward of the 'Maternité Wassila Bourguiba' in Tunis, Tunisia. In total, 32 isolates of MRKP, comprising 23 clinical isolates and nine surveillance isolates, were recovered during this period and analysed for epidemiological relatedness. The isolates were compared with 17 other isolates of MRKP that were recovered during 1995. Macrorestriction profiles of total genomic DNA following XbaI restriction endonuclease digestion were analysed by PFGE; this typing classified 56% of the 32 isolates recovered in 1996 into two major clusters. Cluster A included ten isolates from 1996 and three isolates recovered in 1995, whereas cluster B included eight isolates from the outbreak of 1996. The remaining isolates were genetically unrelated to those of clusters A and B; they constituted sporadic strains. The two major clusters were also evident using other molecular typing methods, such as random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus (ERIC)-PCR, where isolates of clusters A and B could be identified on the basis of their discriminative patterns. This investigation showed the predominance of two epidemic strains, and illustrated the ease with which MRKP strains can disseminate and persist within a single ward.

Gene organization in the UL region and inverted repeats of the canine herpesvirus genome

Restriction mapping and the determination of scattered nucleotide sequences have permitted a description of the global structure and evolutionary affinities of the canine herpesvirus (CHV) genome. The global structure closely resembles that of the totally sequenced genomes of varicella-zoster virus and equine herpesvirus 1 (EHV-1) in having a 37 bp inverted repeat flanking a long unique region (UL) of approximately 100,000 bp, and a 10,100-10,700 bp inverted repeat flanking a short unique region (U8) of roughly 7,400-8,600 bp. On the basis of the sequences obtained, 35 homologues to previously identified herpesvirus gene products were found in UL and the major inverted repeat, and the level of the similarities indicated that CHV belongs to the genus Varicellovirus. Within the genus, CHV appears to be most closely related to EHV-1, pseudorabies virus and feline herpesvirus. Surprisingly, genes for both subunits of the viral ribonucleotide reductase were found to be missing from their equivalent place in other herpesvirus genomes. Either they have been translocated to another position in the CHV genome or, we think more likely, they have been lost.

Antibacterial and leishmanicidal activities of temporin-SHd, a 17-residue long membrane-damaging peptide

Temporins are a family of short antimicrobial peptides (8-17 residues) that mostly show potent activity against Gram-positive bacteria. Herein, we demonstrate that temporin-SHd, a 17-residue peptide with a net charge of +2 (FLPAALAGIGGILGKLF(amide)), expressed a broad spectrum of antimicrobial activity. This peptide displayed potent antibacterial activities against Gram-negative and Gram-positive bacteria, including multi-drug resistant Staphylococcus aureus strains, as well as antiparasitic activity against promastigote and the intracellular stage (amastigote) of Leishmania infantum, at concentration not toxic for the macrophages. Temporin-SHd that is structured in a non-amphipathic α-helix in anionic membrane-mimetic environments, strongly and selectively perturbs anionic bilayer membranes by interacting with the polar head groups and acyl region of the phospholipids, with formation of regions of two coexisting phases: one phase rich in peptide and the other lipid-rich. The disruption of lipid packing within the bilayer may lead to the formation of transient pores and membrane permeation/disruption once a threshold peptide accumulation is reached. To our knowledge, Temporin-SHd represents the first known 17-residue long temporin expressing such broad spectrum of antimicrobial activity including members of the trypanosomatidae family. Additionally, since only a few shorter members (13 residues) of the temporin family are known to display antileishmanial activity (temporins-TA, -TB and -SHa), SHd is an interesting tool to analyze the antiparasitic mechanism of action of temporins.

Aminopeptidase B (EC 3.4.11.6)

Aminopeptidase B (EC 3.4.11.6) is a Zn(2+)-dependent exopeptidase which selectively removes arginine and/or lysine residues from the NH2-terminus of several peptide substrates including Arg0-Leu-enkephalin, Arg0-Met-enkephalin and Arg-1-Lys0-somatostatin-14. Analysis of its primary structure showed that aminopeptidase-B is structurally related to leukotriene A4 hydrolase, an important enzyme of the arachidonic acid pathway. This structural relationship is further supported by the capacity of aminopeptidase-B to hydrolyse leukotriene A4. Aminopeptidase-B is widely distributed in a number of tissues, including endocrine and non-endocrine cells. Moreover, in rat PC12 pheochromocytoma cells, the enzyme is secreted and associated with the external face of the plasma membrane. Together these data strongly argue in favour of a role of this bi-functional enzyme in the final stages of precursor processing mechanisms occurring either in the secretory pathway, at the plasma membrane, or at both locations.

Cathepsin L plays a major role in cholecystokinin production in mouse brain cortex and in pituitary AtT-20 cells: protease gene knockout and inhibitor studies

Cholecystokinin (CCK) is a peptide neurotransmitter whose production requires proteolytic processing of the proCCK precursor to generate active CCK8 neuropeptide in brain. This study demonstrates the significant role of the cysteine protease cathepsin L for CCK8 production. In cathepsin L knockout (KO) mice, CCK8 levels were substantially reduced in brain cortex by an average of 75%. To evaluate the role of cathepsin L in producing CCK in the regulated secretory pathway of neuroendocrine cells, pituitary AtT-20 cells that stably produce CCK were treated with the specific cathepsin L inhibitor, CLIK-148. CLIK-148 inhibitor treatment resulted in decreased amounts of CCK secreted from the regulated secretory pathway of AtT-20 cells. CLIK-148 also reduced cellular levels of CCK9 (Arg-CCK8), consistent with CCK9 as an intermediate product of cathepsin L, shown by the decreased ratio of CCK9/CCK8. The decreased CCK9/CCK8 ratio also suggests a shift in the production to CCK8 over CCK9 during inhibition of cathepsin L. During reduction of the PC1/3 processing enzyme by siRNA, the ratio of CCK9/CCK8 was increased, suggesting a shift to the cathepsin L pathway for the production of CCK9. The changes in ratios of CCK9 compared to CCK8 are consistent with dual roles of the cathepsin L protease pathway that includes aminopeptidase B to remove NH2-terminal Arg or Lys, and the PC1/3 protease pathway. These results suggest that cathepsin L functions as a major protease responsible for CCK8 production in mouse brain cortex, and participates with PC1/3 for CCK8 production in pituitary cells.

Glucose transporter Glut3 is targeted to secretory vesicles in neurons and PC12 cells

In rat brain and cultured neuroendocrine PC12 cells, Glut3 is localized at the cell surface and, also, in a distinct population of homogenous synaptic-like vesicles. Glut3-containing vesicles co-purify with "classical" synaptic vesicles, but can be separated from the latter by sucrose gradient centrifugation. Unlike classical synaptic vesicles, Glut3-containing vesicles possess a high level of aminopeptidase activity, which has been identified as aminopeptidase B. This enzyme has recently been shown to be a marker of the secretory pathway in PC12 cells (Balogh, A., Cadel, S., Foulon, T., Picart, R., Der Garabedian, A., Rousselet, A., Tougard, C., and Cohen, P. (1998) J. Cell Sci. 111, 161-169). We, therefore, conclude that Glut3 is targeted to secretory vesicles in both neurons and PC12 cells.

Aminopeptidase B: a processing enzyme secreted and associated with the plasma membrane of rat pheochromocytoma (PC12) cells

Aminopeptidase B (Ap-B) is a Zn2+-dependent exopeptidase which selectively removes Arg and/or Lys residues from the N terminus of several peptide substrates. Isolated and characterized from rat testes, this ubiquitous enzyme may participate in the final stages of precursor processing mechanisms. To test this hypothesis, we have investigated the secretion and subcellular localization of this enzyme in a rat cell line of pheochromocytoma (PC12 cells). By using a combination of biochemical and immunocytochemical methods, the following observations were made: (i) the level of aminopeptidase B detectable in the cell culture medium increased with time; (ii) 8-bromo-adenosine 3′-5′-cyclic monophosphate and the Ca2+ ionophore A23187 both stimulated enzyme liberation in the culture medium; (iii) brefeldin A, an inhibitor of vesicular transport from the endoplasmic reticulum to the Golgi apparatus, decreased enzyme secretion in a time-dependent manner; (iv) whereas nocodazole, a microtubule depolymerizing agent, inhibited enzyme secretion, cytochalasin D, a microfilament disruption agent, had no effect on released aminopeptidase B level; (v) immunofluorescence demonstrated the presence of aminopeptidase B in the Golgi apparatus; (vi) immunofluorescence, electron microscopy and tests of enzyme activity on intact cells showed an association of the peptidase with the external face of the plasma membrane. Together these data strongly argued in favour of the enzyme secretion by PC12 cells. It is concluded that aminopeptidase B may participate in processing events occurring either during its intracellular transport along the secretory pathway or at the plasma membrane level, or both.

Miniglucagon (MG)-generating endopeptidase, which processes glucagon into MG, is composed of N-arginine dibasic convertase and aminopeptidase B

Miniglucagon (MG), the C-terminal glucagon fragment, processed from glucagon by the MG-generating endopeptidase (MGE) at the Arg17-Arg18 dibasic site, displays biological effects opposite to that of the mother-hormone. This secondary processing occurs in the glucagon- and MG-producing alpha-cells of the islets of Langerhans and from circulating glucagon. We first characterized the enzymatic activities of MGE in culture media from glucagon and MG-secreting alphaTC1.6 cells as made of a metalloendoprotease and an aminopeptidase. We observed that glucagon is a substrate for N-arginine dibasic convertase (NRDc), a metalloendoprotease, and that aminopeptidase B cleaves in vitro the intermediate cleavage products sequentially, releasing mature MG. Furthermore, immunodepletion of either enzyme resulted in the disappearance of the majority of MGE activity from the culture medium. We found RNAs and proteins corresponding to both enzymes in different cell lines containing a MGE activity (mouse alphaTC1.6 cells, rat hepatic FaO, and rat pituitary GH4C1). Using confocal microscopy, we observed a granular immunostaining of both enzymes in the alphaTC1.6 and native rat alpha-cells from islets of Langerhans. By immunogold electron microscopy, both enzymes were found in the mature secretory granules of alpha-cells, close to their substrate (glucagon) and their product (MG). Finally, we found NRDc only in the fractions from perfused pancreas that contain glucagon and MG after stimulation by hypoglycemia. We conclude that MGE is composed of NRDc and aminopeptidase B acting sequentially, providing a molecular basis for this uncommon regulatory process, which should be now addressed in both physiological and pathophysiological situations.

Effect of an acute zinc depletion on rat lipoprotein distribution and peroxidation

The aim of this study was to determine the extent to which zinc depletion leads to lipoprotein modifications by measuring both lipoprotein-fraction distribution and peroxidation in zinc-depleted rats. The animals were divided into three groups and fed for 8 wk a zinc-adequate diet (100 ppm) ad libitum (AL), a zinc-deficient diet (0.2 ppm) ad libitum (ZD), or a zinc-adequate diet according to the pair feeding method (PF). Trace-element status, tissular lipids, and lipoprotein-fraction study were performed. The MDA production by the lipoprotein fraction was measured before and after induced peroxidation. Cholesterol and phospholipids were increased in ZD rats. An important increase of VLDL and IDL was observed and a significant enhanced production of MDA by the LDL was related to zinc deficiency. From this observation, we may conclude that LDL fractions of ZD rats are more susceptible to induced oxidative damage. These results suggest that in zinc deficiency, the lipoprotein fragility is an aggravating factor of peroxidation and the dyslipoproteinemia may lead to an atherogenic risk.

NRD convertase: a putative processing endoprotease associated with the axoneme and the manchette in late spermatids

N-arginine dibasic convertase is a novel metalloendopeptidase which selectively cleaves at the N terminus of arginine residues in paired basic amino acids. Although present in brain and several other tissues, NRD convertase is particularly abundant in testis, where its expression appeared to be restricted to germ cells. Low levels of both mRNA and its corresponding protein were detected early in spermatogenesis. However, a marked accumulation of the protein was observed during late steps (14 to 19) of spermiogenesis. By electron microscopy, the NRD convertase immunoreactivity was localized in the cytoplasm of elongating and elongated spermatids, with a noticeable concentration at the level of two microtubular structures, i.e. the manchette and the axoneme. These observations strongly support the hypothesis that NRD convertase is involved in processing events potentially associated with the morphological transformations occurring during spermiogenesis.

Effects of fish oil fatty acids on plasma lipids and lipoproteins and oxidant-antioxidant imbalance in healthy subjects

The purpose of this study was to investigate the effect of eicosapentaenoic and docosahexaenoic acids on plasma lipids and lipoproteins, lipid peroxidation and antioxidant status in healthy humans. A total of 19 healthy volunteers consumed 6 g/day Maxepa fish oil for 3 weeks (1.8 g n-3 fatty acids/day). At baseline and at day 21, we evaluated plasma lipoproteins, plasma and low-density lipoprotein fatty acids, lipid peroxidation markers (malondialdehyde concentration, low-density lipoprotein peroxidation in vitro), and the content of a number of antioxidants (reduced and oxidized glutathione in whole blood, plasma and erythrocyte glutathione peroxidases, plasma vitamin E and beta carotene). Plasma concentrations of total cholesterol, triglycerides, phospholipids, low-density lipoprotein cholesterol and low-density lipoprotein size did not differ significantly after 3 weeks of supplementation. Adding the fish oil to the diet increased the concentration of n-3 very-long-chain polyunsaturated fatty acids and decreased the concentration of n-6 fatty acid and oleic acid in plasma and low-density lipoprotein. Eicosapentaenoic and docosahexaenoic acid supplementation caused elevated values of the high-density lipoprotein cholesterol due to an increment of the high-density lipoprotein 2 fraction and reduced low-density lipoprotein peroxidation rate in vitro. However, we observed an imbalance between oxidizable substrates and antioxidants with an increased lipid peroxidation, whereas the content of reduced glutathione and beta carotene decreased without any variation in vitamin E. Association of antioxidants with n-3 PUFA could prevent lipid peroxidation and enhance the antiatherogenic effects of n-3 polyunsaturated fatty acids.

Involvement of SHV-12 and SHV-2a encoding plasmids in outbreaks of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in a Tunisian neonatal ward

Previous genotypic investigations of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae recovered in a Tunisian neonatal ward revealed the spread of two epidemic strains and a high number of genetically unrelated isolates. The aim of the present study was to determine the role of the dissemination of self-transferrable plasmids harboring bla genes in the outbreaks experienced by the ward. The 49 previously identified clinical isolates of ESBL-producing K. pneumoniae were examined for relationships between their enzymes and plasmids. Analysis of crude extracts by isoelectric focusing showed four beta-lactamase-activities at pI 8.2, 7.6, 6, and 5.4. Clinical isolates contained large plasmids that could be transferred by conjugation and transformation conferring resistance to expanded-spectrum cephalosporins. DNA amplification and sequencing were performed to confirm the identities of transferred beta-lactamases. Nucleotide sequence analysis of SHV-specific PCR products from six isolates identified two bla(SHV) genes corresponding to SHV derived ESBLs, SHV-12 and SHV-2a. PstI digestion of plasmid DNA from transformants revealed six restriction patterns. The occurrence of the prevalent plasmid pattern in both epidemic strains and unrelated isolates indicated that diffusion and endemic persistence of the bla(SHV-ESBL) genes in the ward were due to concomitant spread of epidemic strains and plasmid dissemination among unrelated strains.

Effects of two low-dose oral contraceptives containing ethinylestradiol and either desogestrel or levonorgestrel on serum lipids and lipoproteins with particular regard to LDL size

This study was designed to determine the effects of two low-dose oral contraceptives, most frequently given in our area, monophasic desogestrel/ethinylestradiol (DG/EE) and triphasic levonorgestrel/ethinylestradiol (LNG/EE), on lipoprotein parameters, especially LDL particle size and HDL subclass distribution (determined by lipid-stained 2%-20% polyacrylamide gradient gel electrophoresis) in 37 healthy normolipidemic women aged 19 to 27 years. Lipid and lipoprotein parameters were measured before the start of treatment and in the third month of oral contraceptive use. Results reflected the estrogen-progestin balance. As compared with baseline values, with both formulations, plasma total cholesterol, phospholipids, and HDL3 cholesterol increased, and LDL-predominant peak size decreased, with a translation of LDL pattern A towards pattern I. With DG/EE, plasma triglycerides, apolipoproteins AI and B increased. With LNG/EE, LDL cholesterol increased, and HDL2 cholesterol decreased. All these modifications were moderate, within threshold limits. Estrogen-dominant monophasic DG/EE appears to be more favorable than progestin-dominant triphasic LNG/EE, since the reduction in LDL-predominant peak size is not associated with an increase in LDL cholesterol or with a decrease in HDL2 cholesterol.

Structure-Activity Relationship-based Optimization of Small Temporin-SHf Analogs with Potent Antibacterial Activity

Short antimicrobial peptides represent attractive compounds for the development of new antibiotic agents. Previously, we identified an ultrashort hydrophobic and phenylalanine-rich peptide, called temporin-SHf, representing the smallest natural amphibian antimicrobial peptide known to date. Here, we report on the first structure-activity relationship study of this peptide. A series of temporin-SHf derivatives containing insertion of a basic arginine residue as well as residues containing neutral hydrophilic (serine and α-hydroxymethylserine) and hydrophobic (α-methyl phenylalanine and p-(t)butyl phenylalanine) groups were designed to improve the antimicrobial activity, and their α-helical structure was investigated by circular dichroism and nuclear magnetic resonance spectroscopy. Three compounds were found to display higher antimicrobial activity with the ability to disrupt (permeabilization/depolarization) the bacterial membrane while retaining the nontoxic character of the parent peptide toward rat erythrocytes and human cells (THP-1 derived macrophages and HEK-293). Antimicrobial assays were carried out to explore the influence of serum and physiological salt concentration on peptide activity. Analogs containing d-amino acid residues were also tested. Our study revealed that [p-(t)BuF(2), R(5)]SHf is an attractive ultrashort candidate that is highly potent (bactericidal) against Gram-positive bacteria (including multidrug resistant S. aureus) and against a wider range of clinically interesting Gram-negative bacteria than temporin-SHf, and also active at physiological salt concentrations and in 30% serum.

Plasma fatty acid status in Moroccan children: increased lipid peroxidation and impaired polyunsaturated fatty acid metabolism in protein-calorie malnutrition

In previous studies on plasma fatty acid and antioxidant status in 29 malnourished Moroccan children (12 with mild protein-calorie malnutrition, 17 with severe protein-calorie malnutrition) compared to 15 healthy control children from the same area, we pointed out that these populations were heterogeneous in terms of their essential fatty acid and antioxidant status. The aim of the present study was to classify the children using the Waterlow classification and their essential fatty acid status. The discrepancies in lipid parameters, nutritional and inflammatory markers, blood oxidative indexes, antioxidant micronutrients or trace elements (selenium, zinc, vitamin E) related to polyunsaturated fatty acids were checked in these populations. Eight of the control subjects and nine of the severe protein-calorie malnutrition children were essential fatty acid-deficient, compared to only one of the mild protein-calorie malnutrition group. Examination of the essential fatty acid-sufficient subjects with mild protein-calorie malnutrition, compared to the essential fatty acid-sufficient control subjects, showed only a decrease in Z scores and a non-significant decrease in selenium and vitamin E. In severely malnourished children, albumin, cholesterol and low density lipoprotein (LDL) cholesterol, plasma selenium, vitamin E and zinc were low, whereas inflammatory proteins and triglycerides were high. These features worsened with essential fatty acid deficiency. In all protein-calorie malnutrition subjects, there was oxidative stress (increase in thiobarbituric-acid reactants, imbalance between plasma polyunsaturated fatty acid, vitamin E and selenium levels), even in the absence of essential fatty acid deficiency. Monounsaturated fatty acids, oleic acid/stearic acid (C18:1 n-9/C18:0) delta9 desaturase and n-3 and n-6 elongase activity indexes increased. The C18:1/C18:0 delta9 desaturase activity index was negatively correlated to Z scores (r = -0.44, P< 0.01 for Z score weight, r = -0.39, P < 0.01 for Z score height), albumin (r = -0.82, P < 0.01) and zinc (r = -0.51, P< 0.01) levels. In essential fatty acid-deficient, severe protein-calorie malnutrition subjects, delta6 desaturase activity was impaired, and there was a non-significant decrease in arachidonic acid. Essential fatty acid deficiency is a type of malnutrition, and is associated with an aggravation of all parameters in severe protein-calorie malnutrition. The increase in the C18:1/C18:0 delta9 desaturase activity and enhanced lipid peroxidation without any essential fatty acid deficiency could be early markers of protein-calorie malnutrition.

Temporin-SHa peptides grafted on gold surfaces display antibacterial activity

Development of resistant bacteria onto biomaterials is a major problem leading to nosocomial infections. Antimicrobial peptides are good candidates for the generation of antimicrobial surfaces because of their broad-spectrum activity and their original mechanism of action (i.e. rapid lysis of the bacterial membrane) making them less susceptible to the development of bacterial resistance. In this study, we report on the covalent immobilisation of temporin-SHa on a gold surface modified by a thiolated self-assembled monolayer. Temporin-SHa (FLSGIVGMLGKLF amide) is a small hydrophobic and low cationic antimicrobial peptide with potent and very broad-spectrum activity against Gram-positive and Gram-negative bacteria, yeasts and parasites. We have analysed the influence of the binding mode of temporin-SHa on the antibacterial efficiency by using a covalent binding either via the peptide NH2 groups (random grafting of α- and ε-NH2 to the surface) or via its C-terminal end (oriented grafting using the analogue temporin-SHa-COOH). The surface functionalization was characterised by IR spectroscopy (polarisation modulation reflection absorption IR spectroscopy) while antibacterial activity against Listeria ivanovii was assessed by microscopy techniques, such as atomic force microscopy and scanning electron microscopy equipped with a field emission gun. Our results revealed that temporin-SHa retains its antimicrobial activity after covalent grafting. A higher amount of bound temporin-SHa is observed for the C-terminally oriented grafting compared with the random grafting (NH2 groups). Temporin-SHa therefore represents an attractive candidate as antimicrobial coating agent.

Expression and purification of rat recombinant aminopeptidase B secreted from baculovirus-infected insect cells

Aminopeptidase B (Ap-B) is a ubiquitous enzyme and its physiological function still remains an open question. This Zn2+ -exopeptidase catalyzes the amino-terminal cleavage of basic residues of peptide or protein substrates, indicating a role in precursor processing. In addition, the enzyme exhibits a residual capacity to hydrolyze leukotriene A4 (LTA4) into the pro-inflammatory lipid mediator leukotriene B4 (LTB4) in vitro. This potential bi-functional nature of Ap-B is supported by a close structural relationship with LTA4 hydrolase, which hydrolyzes LTA4 into LTB4, in vivo, and exhibits an aminopeptidase activity, in vitro. Structural studies are necessary for the detailed understanding of the bi-functional enzymatic mechanism of Ap-B. In this study, we report cDNA cloning, baculovirus expression, and purification of the rat Ap-B (rAp-B). The Ap-B cDNA was constructed from extracted rat testes total RNA and introduced into the pBAC1 baculovirus transfer vector to generate recombinant baculoviruses. rAp-B expression, with or without COOH-hexahistidine tag, was tested in two different insect cell hosts (Sf9 and H5). The enzyme is secreted into the insect cell culture medium, which allowed a rapid purification of the protein. The His-tagged rAp-B was purified using metal affinity resin while the native recombinant rAp-B was partially purified using a single step DEAE Trisacryl ion exchange column. Although the recombinant rAp-B exhibits biochemical properties equivalent to those of the rat testes purified protein, the presence of the histidine-tag seems to partially inhibit the exopeptidase activity. However, this report shows that baculovirus-infected cells are a useful system to produce rat Ap-B for use in studying enzymatic mechanisms in vitro and 3D structure.

Rapid detection of pseudorabies virus genomic sequences in biological samples from infected pigs using polymerase chain reaction DNA amplification

The presence of the pseudorabies virus (PRV) genome in infected hosts has previously been studied by standard hybridization techniques, which showed the viral genome to be present at very low levels in infected tissues. The recently introduced polymerase chain reaction (PCR) procedure provides an alternative and rapid means of amplifying small quantities of specific DNA sequences. We applied this technique to a study of pigs infected by PRV. The sequence selected for amplification consisted of 222 base pairs lying in the gene coding for the glycoprotein gp50. We used a pair of 20-mer oligonucleotides flanking this sequence as primer and a cloned Stu-Nde fragment containing the sequence as target DNA. To avoid the tedious DNA extraction procedure we performed PCR directly on disrupted cells and detected specific amplification after 25 cycles of PCR with the thermostable Taq DNA polymerase. Amplified products were detected by gel electrophoresis directly. Nasal samples from experimentally and naturally infected pigs were tested by this PCR technique. When compared with tissue culture and serological tests, detection by gel electrophoresis of PCR amplified fragments provided excellent specificity and sensitivity. We concluded that PCR amplification will be a valuable tool for rapid diagnosis of PRV infection in pigs, taking less than 1 h to complete.