24-Hour Carotid Stent Patency and Outcomes After Endovascular Therapy: A Multicenter Study

BACKGROUND

Management of extracranial internal carotid artery steno-occlusive lesion during endovascular therapy remains debated. Stent occlusion within 24 hours of endovascular therapy is a frequent event after acute carotid artery stenting, and we currently lack large population results. We investigated the incidence, predictors, and clinical impact of stent occlusion after acute carotid artery stenting in current clinical practice.

METHODS

Patients treated by endovascular therapy with acute carotid artery stenting between 2015 and 2019 in 5 large-volume endovascular-capable centers were retrospectively analyzed. Patients were separated in 2 groups according to the stent patency at 24 hours after carotid artery stenting. We compared baseline characteristics, treatment modalities, and clinical outcome depending on 24-hour stent patency. Primary end point was favorable outcome, defined as a modified Rankin Scale score 0-2 at 3 months.

RESULTS

A stent occlusion was observed in 47/225 patients (20.9%). Patients with stent patency had a lower baseline National Institutes of Health Stroke Scale (median [interquartile range]: 13 [7-17] versus 18 [12-21]) and had more often stroke of atherothrombotic origin (77.0% versus 53.2%). A higher stent patency rate was found for patients treated with P2Y₁₂ antagonists at the acute phase (odds ratio [OR]' 2.95 [95% CI' 1.10-7.91]; P=0.026) and treated with angioplasty (OR' 2.42 [95% CI' 1.24-4.67]; P=0.008). A better intracranial angiographic reperfusion was observed in patients with 24-hour stent patency compared with patients without stent patency (OR' 8.38 [95% CI' 3.07-22.78]; P<0.001). Patients with a stent patency at 24 hours had a higher chance of favorable outcome (OR' 3.29 [95% CI, 1.66-6.52]; P<0.001) and a lower risk of death (OR' 0.32 [95% CI, 0.13-0.76]; P=0.009).

CONCLUSIONS

One out of 5 patients treated with carotid artery stenting during endovascular therapy presented a stent occlusion within 24 hours. This event was associated with worse functional outcome. Stroke etiology, P2Y₁₂ antagonist administration, quality of intracranial reperfusion, and angioplasty were associated with 24-hour stent patency.

Profiling of drugs and environmental chemicals for functional impairment of neural crest migration in a novel stem cell-based test battery

Developmental toxicity in vitro assays have hitherto been established as stand-alone systems, based on a limited number of toxicants. Within the embryonic stem cell-based novel alternative tests project, we developed a test battery framework that allows inclusion of any developmental toxicity assay and that explores the responses of such test systems to a wide range of drug-like compounds. We selected 28 compounds, including several biologics (e.g., erythropoietin), classical pharmaceuticals (e.g., roflumilast) and also six environmental toxicants. The chemical, toxicological and clinical data of this screen library were compiled. In order to determine a non-cytotoxic concentration range, cytotoxicity data were obtained for all compounds from HEK293 cells and from murine embryonic stem cells. Moreover, an estimate of relevant exposures was provided by literature data mining. To evaluate feasibility of the suggested test framework, we selected a well-characterized assay that evaluates ‘migration inhibition of neural crest cells.’ Screening at the highest non-cytotoxic concentration resulted in 11 hits (e.g., geldanamycin, abiraterone, gefitinib, chlorpromazine, cyproconazole, arsenite). These were confirmed in concentration–response studies. Subsequent pharmacokinetic modeling indicated that triadimefon exerted its effects at concentrations relevant to the in vivo situation, and also interferon-β and polybrominated diphenyl ether showed effects within the same order of magnitude of concentrations that may be reached in humans. In conclusion, the test battery framework can identify compounds that disturb processes relevant for human development and therefore may represent developmental toxicants. The open structure of the strategy allows rich information to be generated on both the underlying library, and on any contributing assay.

Embryonic stem cell-based screen for small molecules: cluster analysis reveals four response patterns in developing neural cells

Neural differentiation of embryonic stem cells (ESC) is considered a promising model to perform in vitro testing for neuroactive and neurotoxic compounds. We studied the potential of a dual reporter murine ESC line to identify bioactive and/or toxic compounds. This line expressed firefly luciferase under the control of the neural cell-specific tubulin alpha promoter (TUBA1A), and renilla luciferase under the control of the ubiquitous translation elongation factor 1-alpha-1 (EEF1A1) promoter. During neural differentiation, TUBA1A activity increased, while EEF1A1 activity decreased. We first validated our test system using the known neurotoxin methyl mercury. This compound altered expression of both reporter genes, with ESC-derived neural precursors being affected at markedly lower concentrations than undifferentiated ESCs. Analysis of a library of 1040 bioactive compounds picked up 127 compounds with altered EEF1A1 and/or TUBA1A promoter activity, which were classified in 4 clusters. Cluster 1 (low EEF1A1 and TUBA1A) was the largest cluster, containing many cytostatic drugs, as well as known neurodevelopmental toxicants, psychotropic drugs and endocrine disruptors. Cluster 2 (high EEF1A1, stable TUBA1A) was limited to three sulfonamides. Cluster 3 (high EEF1A1 and TUBA1A) was small, but markedly enriched in neuroactive and neurotoxic compounds. Cluster 4 (stable EEF1A1, high TUBA1A) was heterogeneous, containing endocrine disruptors, neurotoxic and cytostatic drugs. The dual reporter gene assay described here might be a useful addition to in vitro drug testing panels. Our two-dimensional testing strategy provides information on complex response patterns, which could not be achieved by a single marker approach.

Increased brain damage after ischaemic stroke in mice lacking the chemokine receptor CCR5

BACKGROUND AND PURPOSE

The chemokine receptor CCR5 is well known for its function in immune cells; however, it is also expressed in the brain, where its specific role remains to be elucidated. Because genetic factors may influence the risk of developing cerebral ischaemia or affect its clinical outcome, we have analysed the role of CCR5 in experimental stroke.

EXPERIMENTAL APPROACH

Permanent cerebral ischaemia was performed by occlusion of the middle cerebral artery in wild-type and CCR5-deficient mice. Locomotor behaviour, infarct size and histochemical alterations were analysed at different time points after occlusion.

KEY RESULTS

The cerebral vasculature was comparable in wild-type and CCR5-deficient mice. However, the size of the infarct and the motor deficits after occlusion were markedly increased in CCR5-deficient mice as compared with wild type. No differences between wild-type and CCR5-deficient mice were elicited by occlusion with respect to the morphology and abundance of astrocytes and microglia. Seven days after occlusion the majority of CCR5-deficient mice displayed neutrophil invasion in the infarct region, which was not observed in wild type. As compared with wild type, the infarct regions of CCR5-deficient mice were characterized by increased neuronal death.

CONCLUSIONS AND IMPLICATIONS

Lack of CCR5 increased the severity of brain injury following occlusion of the middle cerebral artery. This is of particular interest with respect to the relatively frequent occurrence of CCR5 deficiency in the human population (1-2% of the Caucasian population) and the advent of CCR5 inhibitors as novel drugs.

Immunohistochemical localisation of intravitreally injected bevacizumab in the anterior chamber angle, iris and ciliary body of the primate eye

AIMS

To locate bevacizumab in the tissues related to neovascularisation in the anterior segment within 1-14 days after intravitreal injection in the primate eye.

METHODS

Four cynomolgus monkeys received an intravitreal injection of 1.25 mg bevacizumab. Control eyes remained untreated. The eyes were enucleated on day 1, 4 and 14 for immunohistochemistry, using donkey anti-human Cy3-IgG.

RESULTS

Immunoreactivity for bevacizumab was found in the blood vessels walls of the iris, anterior chamber angle and ciliary body. In the iris and chamber angle, immunoreactivity was most prominent on day 1 after injection and diminished until day 14. In the ciliary body, staining was most intense on day 4 and remained prominent until day 14. Immunoreactivity was also present in certain vessel lumens, especially in the ciliary body and the iris on day 4 and 14.

CONCLUSION

Bevacizumab penetrates quickly into the iris, anterior chamber angle and ciliary body after intravitreal injection in the primate eye and accumulates particularly in blood-vessel walls. The highest concentration of bevacizumab in these tissues is present on day 1-4, the iris and anterior chamber angle being penetrated slightly earlier than the ciliary body. Our findings support the clinically observed rapid effect in the treatment of iris neovascularisation.

Activation of NF-kappaB by Akt upregulates Snail expression and induces epithelium mesenchyme transition

Carcinoma progression is associated with the loss of epithelial features, and the acquisition of mesenchymal characteristics and invasive properties by tumour cells. The loss of cell-cell contacts may be the first step of the epithelium mesenchyme transition (EMT) and involves the functional inactivation of the cell-cell adhesion molecule E-cadherin. Repression of E-cadherin expression by the transcription factor Snail is a central event during the loss of epithelial phenotype. Akt kinase activation is frequent in human carcinomas, and Akt regulates various cellular mechanisms including EMT. Here, we show that Snail activation and consequent repression of E-cadherin may depend on AKT-mediated nuclear factor-kappaB (NF-kappaB) activation, and that NF-kappaB induces Snail expression. Expression of the NF-kappaB subunit p65 is sufficient for EMT induction, validating this signalling module during EMT. NF-kappaB pathway activation is associated with tumour progression and metastasis of several human tumour types; E-cadherin acts as a metastasis suppressor protein. Thus, this signalling and transcriptional network linking AKT, NF-kappaB, Snail and E-cadherin during EMT is a potential target for antimetastatic therapeutics.

ST6GalNAc I expression in MDA-MB-231 breast cancer cells greatly modifies their O-glycosylation pattern and enhances their tumourigenicity

Sialyl-Tn is a carbohydrate antigen overexpressed in several epithelial cancers, including breast cancer, and usually associated with poor prognosis. Sialyl-Tn is synthesized by a CMP-Neu5Ac:GalNAcalpha2,6-sialyltransferase: CMP-Neu5Ac: R-GalNAcalpha1-O-Ser/Thr alpha2,6-sialyltransferase (EC 2.4.99.3) (ST6GalNAc I), which transfers a sialic acid residue in alpha2,6-linkage to the GalNAcalpha1-O-Ser/Thr structure. However, established breast cancer cell lines express neither ST6GalNAc I nor sialyl-Tn. We have previously shown that stable transfection of MDA-MB-231, a human breast cancer cell line, with ST6GalNAc I cDNA induces sialyl-Tn antigen (STn) expression. We report here the modifications of the O-glycosylation pattern of a MUC1-related recombinant protein secreted by MDA-MB-231 sialyl-Tn positive cells. We also show that sialyl-Tn expression and concomitant changes in the overall O-glycan profiles induce a decrease of adhesion and an increase of migration of MDA-MB-231. Moreover, STn positive clones exhibit an increased tumour growth in severe combined immunodeficiency (SCID) mice. These observations suggest that modification of the O-glycosylation pattern induced by ST6GalNAc I expression are sufficient to enhance the tumourigenicity of MDA-MB-231 breast cancer cells.

Inhibitory effect of probiotic Escherichia coli strain Nissle 1917 on adhesion to and invasion of intestinal epithelial cells by adherent-invasive E. coli strains isolated from patients with Crohn's disease

BACKGROUND

Pathogenic adherent-invasive Escherichia coli have been isolated from ileal lesions of Crohn's disease.

AIM

: To investigate the non-pathogenic E. coli strain Nissle 1917 (Mutaflor) as possible maintenance therapy in inflammatory bowel disease by testing its ability to prevent adherent-invasive E. coli strains from adhering to and invading human intestinal epithelial cells in vitro.

METHODS

Bacterial adhesion to and invasion of intestinal epithelial cells (Intestine-407) were assessed by counting the colony-forming units. The inhibitory effect of E. coli Nissle 1917 was determined after co-incubation with adherent-invasive E. coli strains or after pre-incubation of the intestinal epithelial cells with this probiotic strain prior to infection with adherent-invasive E. coli strains.

RESULTS

Strain Nissle 1917 exhibited dose- and time-dependent adherence to intestinal epithelial cells and inhibited the adhesion and invasion of various adherent-invasive E. coli strains. In co-infection experiments, the inhibitory effect on adherent-invasive E. coli adhesion reached 78-99.9%. Pre-incubation of intestinal epithelial cells with strain Nissle 1917 reduced adherent-invasive E. coli adhesion by 97.2-99.9%. The inhibitory effect on adherent-invasive E. coli invasion paralleled that on adhesion.

CONCLUSION

As strong and significant inhibitory effects on adherent-invasive E. coli adhesion and invasion were observed in co-infection and pre-infection experiments, E. coli Nissle 1917 could be efficient for preventive or curative probiotic therapy in patients with Crohn's disease.

Expression of thymidine kinase driven by an endothelial-specific promoter inhibits tumor growth of Lewis lung carcinoma cells in transgenic mice

The possibility of inhibiting tumor growth by limiting angiogenesis has raised considerable interest. In this study, we examined the feasibility of inhibiting tumor growth by targeting a suicide gene in the endothelium. Toxicity must be directed solely to angiogenic cells. Therefore, we used the herpes simplex virus-thymidine kinase (TK) gene, in combination with the prodrug ganciclovir (GCV), which affects replicative cells. To test this strategy, we produced transgenic mice carrying the TK gene driven by the vascular endothelial (VE)-cadherin promoter. Lewis lung carcinoma cells were injected subcutaneously to establish tumors and to test the effect of GCV on tumor growth. In two independent transgenic lines, GCV treatment (75 mg/kg/day) resulted in a 66-71% reduction of tumor volume at day 20 postimplantation compared to wild-type mice (650 and 550 versus 1930 mm(3), P<0.02 and 0.01, respectively), whereas no significant difference was observed when vehicle alone was injected. Tumor growth inhibition was accompanied by a marked reduction in tumor vascular density (151 versus 276 vessels/mm(2), P<0.05) and an increase in tumor cell death, suggesting that tumor growth inhibition was caused by a reduction in tumor angiogenesis. Our data support the potential utility of endothelial targeting of suicide genes in cancer therapy.

Expression of sialyl-Tn antigen in breast cancer cells transfected with the human CMP-Neu5Ac: GalNAc alpha2,6-sialyltransferase (ST6GalNac I) cDNA

Sialyl-Tn antigen (STn) is a cancer associated carbohydrate antigen over-expressed in several cancers including breast cancer, and currently associated with more aggressive diseases and poor prognosis. However, the commonly used breast cancer cell lines (MDA-MB-231, T47-D and MCF7) do not express STn antigen. The key step in the biosynthesis of STn is the transfer of a sialic acid residue in alpha2,6-linkage to GalNAc alpha-O-Ser/Thr. This reaction is mainly catalyzed by a CMP-Neu5Ac GalNAc alpha2,6-sialyltransferase: ST6GalNAc I. In order to generate STn-positive breast cancer cells, we have cloned a cDNA encoding the full-length human ST6GalNAc I from HT-29-MTX cells. The stable transfection of MDA-MB-231 with an expression vector encoding ST6GalNAc I induces the expression of STn antigen at the cell surface. The expression of STn short cuts the initial O-glycosylation pattern of these cell lines, by competing with the Core-1 beta1,3-galactosyltransferase, the first enzyme involved in the elongation of O-glycan chains. Moreover, we show that STn expression is associated with morphological changes, decreased growth and increased migration of MDA-MB-231 cells.

The human sialyltransferase family

The human genome encodes probably more than 20 different sialyltransferases involved in the biosynthesis of sialylated glycoproteins and glycolipids but to date only 15 different human sialyltransferase cDNAs have been cloned and characterized. Each of the sialyltransferase genes is differentially expressed in a tissue-, cell type-, and stage-specific manner to regulate the sialylation pattern of cells. These enzymes differ in their substrate specificity, tissue distribution and various biochemical parameters. However, enzymatic analysis conducted in vitro with recombinant enzyme revealed that one linkage can be synthesized by multiple enzymes. We present here an overview of these human genes and enzymes, the regulation of their occurrence and their involvement in several physiological and pathological processes.

Common antiviral cytotoxic t-lymphocyte epitope for diverse arenaviruses

Members of the Arenaviridae family have been isolated from mammalian hosts in disparate geographic locations, leading to their grouping as Old World types (i.e., lymphocytic choriomeningitis virus [LCMV], Lassa fever virus [LFV], Mopeia virus, and Mobala virus) and New World types (i.e., Junin, Machupo, Tacaribe, and Sabia viruses) (C. J. Peters, M. J. Buchmeier, P. E. Rollin, and T. G. Ksiazek, p. 1521-1551, in B. N. Fields, D. M. Knipe, and P. M. Howley [ed.], Fields virology, 3rd ed., 1996; P. J. Southern, p. 1505-1519, in B. N. Fields, D. M. Knipe, and P. M. Howley [ed.], Fields virology, 3rd ed., 1996). Several types in both groups-LFV, Junin, Machupo, and Sabia viruses-cause severe and often lethal human diseases. By sequence comparison, we noted that eight Old World and New World arenaviruses share several amino acids with the nucleoprotein (NP) that consists of amino acids (aa) 118 to 126 (NP 118-126) (RPQASGVYM) of LCMV that comprise the immunodominant cytotoxic T-lymphocyte (CTL) epitope for H-2(d) mice (32). This L(d)-restricted epitope constituted >97% of the total bulk CTLs produced in the specific antiviral or clonal responses of H-2(d) BALB mice. NP 118-126 of the Old World arenaviruses LFV, Mopeia virus, and LCMV and the New World arenavirus Sabia virus bound at high affinity to L(d). The primary H-2(d) CTL anti-LCMV response as well as that of a CTL clone responsive to LCMV NP 118-126 recognized target cells coated with NP 118-126 peptides derived from LCMV, LFV, and Mopeia virus but not Sabia virus, indicating that a common functional NP epitope exists among Old World arenaviruses. Use of site-specific amino acid exchanges in the NP CTL epitope among these arenaviruses identified amino acids involved in major histocompatibility complex binding and CTL recognition.

Natural autoreactive B cells in transgenic mice reproduce an apparent paradox to the clonal tolerance theory

Naturally occurring autoreactive B cells are thought to be physically eliminated or rendered functionally silent through different mechanisms of tolerance. However, multireactive low affinity natural autoantibody-producing B cells seem to escape these mechanisms in normal adults and could constitute the B cell pool from which pathological autoantibodies can emerge. To analyze this apparent paradox to the clonal tolerance theory, we have made two transgenic mouse lines (mu(k), mudelta(k)) producing a natural low affinity multireactive human autoantibody. These models enable us to test both the central tolerance mechanisms (reactivity with single-stranded DNA) and the peripheral tolerance mechanisms after Ag administration. Not only are the multireactive B cells not deleted in the bone marrow, they circulate and remain in the periphery even after the prolonged administration of Ag, the presence of membrane IgD increasing the number of mature autoreactive B cells. Self-reactive B cells are shown to be autoantigen ignorant both in vivo and in vitro, but they are not anergic because they can be easily activated through both B cell receptor-dependent and -independent pathways. Thus, these mouse lines reproduce an apparent paradox to the clonal tolerance theory meriting further investigation of the biological significance of this phenomenon.

Chronic nifedipine dosing enhances cephalexin bioavailability and intestinal absorption in conscious rats

Cephalexin, a beta-lactam antibiotic, is rapidly absorbed via the di-and tripeptide intestinal transporters, as for many peptidomimetic drugs. Acute nifedipine has been shown to increase intestinal absorption of several beta-lactams: amoxicillin and cefixime in humans, and cephalexin in the rat. We showed previously that the nervous system was involved in the increasing effect of nifedipine on cephalexin intestinal absorption in anesthetized rats. The aim of the present study was 2-fold: 1) to investigate whether the effect of nifedipine is maintained in conscious rats, and 2) to determine whether the nifedipine effect will persist during chronic nifedipine administration. Acute and chronic oral administration of nifedipine significantly increased oral cephalexin area under the plasma concentration-time curve (34 and 25%, respectively) and maximum concentration in plasma (57 and 51%, respectively), while the distribution and elimination parameters of intra-arterial cephalexin were not affected by acute or chronic nifedipine administration. In conclusion, acute nifedipine effect on intestinal absorption of cephalexin is independent of anesthesia in rats. Since nifedipine could still enhance cephalexin intestinal absorption after a 7-day b.i.d. treatment, it can be envisaged to apply this effect to increase bioavailability of poorly absorbed peptidomimetic drugs in man.

Relationships of immunoglobulins E and G sensitization to respiratory function in dairy farmers

An impairment of respiratory function has been demonstrated in dairy farmers. The objective of this study was to evaluate the relationship of allergy to respiratory function in dairy farmers in a longitudinal study conducted in the Doubs (France). A cohort of male dairy farmers constituted in 1990 was re-evalued in 1995. Subjects completed a medical and occupational questionnaire, and a spirometry test in both 1990 and 1995, in 1995 they were also subjected to immunological tests. Relationships between immunological variables and respiratory function were studied by a multiple linear regression model adjusted for age, smoking status, respiratory symptoms, altitude and occupational exposure. Amongst the 394 subjects of the initial cohort, 330 were included in the longitudinal study and 320 had immunological tests. Log immunoglobulin (Ig) E was negatively correlated with the 1995 respiratory function parameters (p<0.05 for forced expiratory volume in one second (FEV1) and FEV1/vital capacity (VC). Immunoglobulin (Ig) G response to Aspergillus fumigatus detected by enzyme-linked immunosorbent assay (ELISA) was negatively correlated to 1995 respiratory function parameters (VC: p<0.01; FEV1: p<0.001; FEV1/VC: p<0.01). There was a positive relationship between IgG antibodies against Aspergillus fumigatus and the mean annual decline in FEV1 (p<0.01) and FEV1/VC (p<0.01). To conclude, allergy may play a role in the impairment of respiratory function in dairy farmers of the Doubs and sensitization to Aspergillus fumigatus seems to constitute an independent risk factor for the development of airflow obstruction in this occupational setting.

Isolation and characterization of novel glycoproteins from fish epidermal mucus: correlation between their pore-forming properties and their antibacterial activities

In fish, a layer of mucus covers the external body surface contributing therefore, among other important biological functions, to the defense system of fish. The prevention of colonization by aquatic parasites, bacteria and fungi is mediated both by immune system compounds (IgM, lysozyme, etc.) and by antibacterial peptides and polypeptides. We have recently shown that only the hydrophobic components of crude epidermal mucus of fresh water and sea water fish exhibit strong pore-forming properties, which were well correlated with antibacterial activity [N. Ebran, S. Julien, N. Orange, P. Saglio, C. Lemaitre, G. Molle, Comp. Biochem. Physiol. 122 (1999)]. Here, we have isolated novel glycosylated proteins from the hydrophobic supernatant of tench (Tinca tinca), eel (Anguilla anguilla) and rainbow trout (Oncorhynchus mykiss) mucus. The study of their secondary structure was performed by circular dichroism and revealed structures in random coil and alpha-helix in the same proportions. When reconstituted in planar lipid bilayer, they induced the formation of ion channels. This pore-forming activity was well correlated with a strong antibacterial activity (minimal inhibitory concentration < 1 microM for the three proteins) against both gram-negative and gram-positive bacteria. Our results suggest that fish secrete antibacterial glycoproteins able to kill bacteria by forming large pores (several hundreds to thousands of pS) in the target membrane.

Non-small cell lung cancer: a study of long-term survival after vinorelbine monotherapy

This study reports the results of 120 patients with inoperable non-small cell lung cancer treated with Navelbine at a dose of 25-30 mg/m(2)/week in a single-drug chemotherapy regimen. Surgery was contraindicated due to staging or to concomitant morbidity. Twenty patients achieved survival greater than or equal to 18 months, and one patient obtained exceptional survival of more than 120 months. The mean dose intensity of Navelbine in long-term survivors was 21.61 mg/m(2)/week. Objective response to Navelbine was found by multivariate analysis to be a prognostic factor for survival beyond 18 months. Weight loss of more than 5 kg of corporal weight was an unfavorable prognostic factor in patients with metastatic disease.

[Non-small-cell bronchial cancers: long-term survival after single drug chemotherapy with vinorelbine]

We studied a cohort of 120 patients with inoperable non-small-cell lung cancer treated with vinorelbin at the dose of 25-30 mg/m2/week in a single drug chemotherapy regimen. Surgery was contraindicated due to staging or to concomitant morbidity. Twenty patients survived 18 months or more. One survivor responded exceptionally, surviving 120 months. The mean dose intensity of Vinorelbine in long-term survivors was 21 mg/m2/week. Objective response was found at multivariate analysis to be a prognostic factor for survival beyond 18 months. Weight loss (< 5 kg) was an unfavorable prognostic factor in patients with metastases.

Neural modulation of cephalexin intestinal absorption through the di- and tripeptide brush border transporter of rat jejunum in vivo

Intestinal absorption of beta-lactamine antibiotics (e.g., cefixime and cephalexin) has been shown to proceed through the dipeptide carrier system. In a previous study, nifedipine (NFP), an L-type calcium channel blocker, enhanced the absorption of cefixime in vivo but not in vitro, and it was suggested that neural mechanisms might be involved in the effect of NFP. The aim of the present study was to assess the involvement of the nervous system on the intestinal absorption of cephalexin (CFX). To investigate this, we used a single-pass jejunal perfusion technique in rats. NFP and diltiazem enhanced approximately 2-fold the plasma levels of CFX in treated rats versus untreated controls. NFP also increased approximately 2-fold the CFX level in portal plasma and increased urinary excretion of CFX, thus indicating that CFX did effectively increase CFX intestinal absorption. Perfusing high concentrations of dipeptides in the jejunal lumen competitively reduced CFX absorption and inhibited the enhancement of CFX absorption produced by NFP. Hexamethonium and lidocaine inhibited the effect of NFP, whereas atropine, capsaicin, clonidine, and isoproterenol enhanced CFX absorption by the same order of magnitude as NFP. Thus, complex neural networks can modulate the function of the intestinal di- and tripeptide transporter. Sympathetic noradrenergic fibers, intestinal sensory neurons, and nicotinic synapses are involved in the increase of CFX absorption produced by NFP.

AIDS primary central nervous system lymphoma: molecular analysis of the expressed VH genes and possible implications for lymphomagenesis

AIDS-associated primary central nervous system lymphomas are late events that have an extremely poor prognosis. Despite different hypotheses, the brain localization of these B cell lymphomas remains an enigma. To better define the cell origin of the lymphomas and the possible role of the B cell receptor (BCR) in the brain localization and/or in the oncogenic transformation, we analyzed the V region genes of the Ig heavy chain expressed by lymphoma cells in five randomly selected patients. After amplifying the rearranged VHDJH DNA by PCR, cloning, and sequencing of the amplified products, we observed that: 1) of the five lymphomas analyzed, four were clearly monoclonal; 2) there was no preferential use of one peculiar VH family or one peculiar segment of gene; 3) the mutation analysis showed that an Ag-driven process occurred in at least two cases, probably before the oncogenic event; and 4) there was no intraclonal variability, suggesting that the hypermutation mechanism is no longer efficient in these lymphoma B cells. Taken together, our results suggest that distinct Ags could be recognized by the BCR of the lymphoma cells in different patients and that, if the Ags are responsible for the brain localization of these B cells bearing mutated BCR, other factors must be involved in B cell transformations in primary central nervous system lymphoma.

Pore-forming properties and antibacterial activity of proteins extracted from epidermal mucus of fish

Among several biological functions, the epidermal mucus of fish may play an important role in host defense, particularly in the prevention of colonization by parasites, bacteria and fungi. In previous work, two hydrophobic proteins of 27 and 31 kDa were isolated from carp mucus. This study identified a strong antibacterial activity (0.16-0.18 microM) well correlated with pore-forming properties. Here this work was extended to other fish species, four fresh water fish and one sea water fish. After a first step of purification, water-soluble and hydrophobic material were separated, and both fractions were analyzed by SDS-PAGE and capillary electrophoresis. Only the hydrophobic component induced pore-forming activity, when reconstituted in planar lipid bilayers. This pore-forming activity was well correlated to a strong antibacterial activity against several bacteria strains. These results suggest that fish secrete antibacterial proteins able to permeabilize the membrane of the target cell and thus act as a defense barrier.

Ionophore properties of OmpA of Escherichia coli

Both porins OmpA1, from wild-strain K12 Escherichia coli, and OmpA2, from a K12 derivative deficient in both OmpF and OmpC, are able to form ion channels in virtually solvent-free membranes. The conductance has been shown to vary in a discrete fashion with different single increment values especially with OmpA2. This behaviour seems to indicate, beside monomers, the presence of aggregates of different sizes. The estimated small pore diameter (0.6-0.7 nm) for the monomeric would explain the weak permeability of this narrow channel toward different solutes. OmpA protein, from experiments of ion selectivity and zero-current potential, is determined weakly anion selective.

Synthetic analogues of alamethicin: effect of C-terminal residue substitutions and chain length on the ion channel lifetimes

In a previous study, a synthetic analogue of the peptaibol alamethicin, in the sequence of which all alpha-aminoisobutyric acid (Aib) were substituted by leucine residues and the C-terminal residue modified, was shown to display the same single-channel behaviour as alamethicin in planar lipid bilayer, except that the sublevel lifetimes were much reduced. New analogues differing in their C-terminal residue (Phe-NH2, Pheol, Trp-NH2) have now been tested for their single channel properties in neutral lipid bilayers. The conductance amplitudes and open channel lifetimes do not differ significantly from the previous analogue. Thus, the nature of the last residue, which may be located near the membrane interface, does not seem to play an important role in the destabilisation of the conducting aggregate observed after the Aib substitution by Leu. Since the deletion of one residue (Glu18) in the 14-20 moiety induces a slight decrease of the increment between the conductance levels, but has no effect upon the channel lifetimes, this residue and the length of this segment do not interfer much with the channel lifetime of peptaibols. In conclusion the factors influencing the aggregate stability may be sought in the helix-helix interactions.

Biologic and structural evaluation of 80 surgically excised human umbilical vein grafts

Human umbilical vein is a valuable alternative to autogenous saphenous vein in lower-limb revascularization. However, the long-term patency is not as good. To understand better the reasons for this, the authors studied the biologic and structural changes occurring in 80 segments of human umbilical vein (HUV) grafts excised from 70 patients. Morphologic, histologic and scanning electron microscopy examinations were performed on each specimen. It was noted that increasing duration of implantation was associated with greater encapsulation and less surrounding inflammatory reaction. Twenty-six percent of clinically noninfected grafts were found to harbour bacteria. Bacteremic colonization was often in the folds of the luminal surface. As a result of these findings, the authors emphasize the need for complete excision of clinically infected grafts. Anastomoses between HUV segments are discouraged because they are associated with a high frequency of infection and a corresponding decrease in duration of implantation. Delamination of the wall was common, and such sites may represent areas at risk for further degradation. Continued surveillance of the biologic and structural changes occurring in excised grafts remains an important method in increasing our understanding of the evolutive complications of HUV grafts.

Interaction of tachykinins with their receptors studied with cyclic analogues of substance P and neurokinin B

The activities of two groups of cyclic agonists of substance P (SP) have been studied. The disulfide bridge constraints have been designed on the basis of conformational studies on SP and physalaemin indicating an alpha-helical structure for the core of these two tachykinins (group I) and a folding of the C-terminal carboxamide towards the side chains of the glutamines 5 and 6 (group II). Only peptides simulating the alpha-helix present substantial potencies. [Cys3,6]SP is as active as SP in inhibiting 125I-labeled Bolton and Hunter SP-specific binding on rat brain synaptosomes and on dog carotid bioassay, two assays specific for the neurokinin 1 receptor. Moreover, [Cys3,6]SP is as potent as neurokinin B in inhibiting 125I-labeled Bolton and Hunter eledoisin-specific binding on rat cortical synaptosomes as well as in stimulating rat portal vein, two tests specific for the neurokinin 3 receptor. Interestingly, in contrast to neurokinin B, [Cys3,6]SP is a weak agonist of the neurokinin 2 receptor subtype, as evidenced by its binding potency in inhibiting 3H-labeled neurokinin A-specific binding on rat duodenum and in inducing the contractions of the rabbit pulmonary artery, a neurokinin 2-type bioassay. To increase the specificity of the cyclic analogue [Cys3,6]SP positions 8 and 9 were modified. [Cys3,6, Tyr8, Ala9]SP is slightly less selective than SP for the neurokinin 1 receptor subtype. [Cys2,5]neurokinin B constitutes a selective cyclic agonist for the neurokinin 3 receptor. The very weak potencies of the peptides from group II indicate that a certain degree of flexibility in the C-terminal moiety is required. Collectively, these results suggest that the neurokinin 1 and neurokinin 3 tachykinin receptors may recognize a similar three-dimensional structure of the core of the tachykinins. Different orientations of the common C-terminal tripeptide may be related to the selectivity for the different receptor subtypes.

Influence of the amino acids of substance P in the recognition of its receptor: affinities of synthesized SP analogues for the specific 125I-BHSP binding site on rat brain synaptosomes

Substance P analogues have been synthesized, by solid-phase methodology, in order to get a better knowledge of the structural requirements for the 125I-BHSP binding on rat brain synaptosomes. Assuming that the core of SP exists in an alpha-helicoidal structure three major points should be underlined: the SP receptor recognizes probably the side of the helix bearing the two side chains of Phe and Phe; the arginine guanidinium interacts with either a carboxylate or a phosphate function of the binding site; the C-terminal tripeptide undergoes a conformational change allowing the interactions of the C-terminal amide with a carboxylate and that of the sulfur atom with an electrophile of the binding site. The specificity of these peptides have been further estimated by comparing their binding potencies to those observed for the 125I-BHE specific binding on rat cortical synaptosomes and their bioactivities on guinea-pig ileum.