[Pneumonitis caused by hydrocarbon inhalation]. / Pneumopathies par inhalation d'hydrocarbures volatiles.

INTRODUCTION: Kerosene pneumonitis is rare. It most commonly occurs in children who have ingested a hydrocarbon by accident. In adults, pneumonitis caused by aspiration of incompletely vaporized kerosene may be seen in fire-eaters can cause pneumonitis. CASE REPORTS: We report six cases of fire-eater's pneumonitis, from our region, due to hydrocarbon inhalation. CONCLUSIONS: This inhalational pulmonary insult has classical clinical manifestations. The frequency of cases, particularly in tourist areas that host street festivals, is probably underestimated. Its tendency to spontaneously resolve questions the need for antibiotics and corticosteroids.

Expression of insulin-like growth factor-I in rat glioma cells is associated with change in both immunogenicity and apoptosis.

Insulin-like growth factor I (IGF-I), has a role in cellular differentiation and is also expressed in neoplastic transformation of glioma cells. We recently demonstrated inhibition in expression of cellular IGF-I after transfection with vectors that incodes a segment of the human IGF-I RNA in antisense orientation. The transfected cells expressed increased levels of both MHC-I and B7 molecules. In this paper we show that IGF-I antisense transfected cells also become apoptotic. Moreover, the phenomenon of programmed cell death is related to the phenomenon that results in increased expression of MHC-I and B7 molecules. Co-transfection of rat glioma cells with the vector expressing IGF-I antisense RNA and with vectors encoding the expression of MHC-I and B7 antisense cDNA suppressed the expression of both of these molecules and was associated with a decrease in apoptosis.

Seizure-related opening of the blood-brain barrier produced by the anticholinesterase compound, soman: new ultrastructural observations.

Previous macroscopic and light microscopic observations established that the organophosphate soman, an irreversible inhibitor of cholinesterases, produces seizure-related opening of the blood-brain barrier (BBB) to proteins. In Wistar rats, this BBB alteration was found to be reversible. This alteration was greatest during the first hour of seizures, and was topographically limited to sensitive areas such as the thalamus. In contrast, the hippocampus remained free of any vascular leakage. The present study is an attempt to elucidate, in rat thalamus, the subcellular mechanisms involved in soman-induced BBB alteration. A combination of three ultrastructural approaches was used: examination of ultra-thin sections, freeze-fracture, and post-embedding protein A-gold immunocytochemistry of the endogenous, normally exclusively blood-borne, albumin. Our findings show that soman-induced seizure activity produced no discernible structural change in the endothelial tight junctions, whereas it unambiguously increased the number of endothelial vesicles. Finally, immunolabelled albumin clearly crossed the endothelium, but was not systematically found inside the endothelial vesicles. Altogether, the present ultrastructural study confirms that soman can alter the integrity of the BBB, and demonstrates that the blood-to-brain passage of proteins does not mainly derive from the opening of tight junctions. Although transcytosis is clearly increased through the cerebral endothelium, there is little evidence that blood-borne proteins penetrate the brain in this way. The actual mechanisms of transport thus remain to be clarified.

Bacterial toxins modifying the actin cytoskeleton.

Numerous bacterial toxins recognize the actin cytoskeleton as a target. The clostridial binary toxins (Iota and C2 families) ADP-ribosylate the actin monomers causing the dissociation of the actin filaments. The large clostridial toxins from Clostridium difficile, Clostridium sordellii and Clostridium novyi inactivate, by glucosylation, proteins from the Rho family that regulate actin polymerization. In contrast, the cytotoxic necrotic factor from Escherichia coli activates Rho by deamidation and increases the formation of actin filaments. The enterotoxin of Bacteroides fragilis is a protease specific for E-cadherin and it promotes the reorganization of the actin cytoskeleton. The bacterial toxins that modify the actin cytoskeleton induce various cell disfunctions including changes in cell barrier permeability and disruption of intercellular junctions.

Evidence that gonadotropin-releasing hormone stimulates gene expression and levels of active nitric oxide synthase type I in pituitary gonadotrophs, a process altered by desensitization and, indirectly, by gonadal steroids.

To determine the site and mechanism of action of gonadal steroids on pituitary nitric oxide synthase type I (NOS I), present in both gonadotrophs and folliculo-stellate cells, the effects of castration and steroids were examined in male rats, in the presence of a GnRH antagonist (Antarelix). Western analysis showed a rapid and substantial increase with time, after orchidectomy, of NOS I protein, the concentration doubling in 24 h and reaching a maximal 4- to 5-fold increase after 3-7 days, followed by a progressive decline after 2 weeks. Testosterone or estradiol replacement, or administration of GnRH antagonist, totally abolished the effects of castration, demonstrating a mediation of the steroid effects via GnRH. In noncastrated rats, steroids and the GnRH antagonist also caused a reduction in the levels of NOS I (by 50-60%), consistent with inhibition of endogenous GnRH stimulation. In marked contrast, administration of a potent GnRH agonist (Triptorelin) to intact rats increased the levels of NOS I. A time-course study with a long-lasting formulation showed that rise in NOS I developed rapidly after a lag of approximately 5 h, with a 2-fold increase detectable after 8 h and a maximal 4.5-fold after 48 h. The level declined afterwards in a manner consistent with homologous desensitization that may occur in the continuous presence of GnRH; however, the profile was different and delayed compared with those of gonadotropin release. As observed for NOS I protein, NOS I messenger RNA concentration was increased by castration or GnRH agonist and reduced by steroids or GnRH antagonist. Taken together, these data demonstrate that steroids indirectly regulate NOS I messenger RNA and protein levels, through the hypothalamic modulation of GnRH, which represents the primary regulator of NOS I. No effect of steroids on NOS I was seen in the posterior lobe. NADPH-diaphorase histochemistry coupled to immuno-identification of the cells revealed that the treatments affecting the concentration of NOS I concomitantly altered the activity but exclusively in gonadotrophs and not in folliculo-stellate cells (which do not respond to GnRH), reinforcing the idea that GnRH played a major regulatory role. Expression in gonadotrophs of a GnRH-dependent NOS I and the ensuing production of nitric oxide represents a potentially novel signaling pathway for the neuropeptide in the anterior pituitary, consistent with the previously reported GnRH-induced cGMP production, the role of which remains to be evaluated.

Altered gap and tight junctions in human thyroid oncocytic tumors: a study of 8 cases by freeze-fracture.

Human oncocytic tumors of the thyroid gland may be either adenomas or carcinomas. The morphology and the ultrastructure of these oncocytes are well-known. Numerous studies have demonstrated the role of gap and tight junctions in experimental and human carcinogenesis; however, the junctional complexes of the oncocytic tumors have never been studied. The aim of this study is to analyze gap and tight junctions in the oncocytic tumors of the thyroid. Because they are morphologically similar, whether benign or malignant, they offer an attractive model for studying the junctional complexes in both benign and malignant lesions. Eight oncocytic human thyroid tumors were collected and studied by freeze-fracture. Four of these cases were benign and four were malignant. Four cases of normal gland were also studied to represent the control group. Normal tight and gap junctions were described for the control group. No gap junctions could be found for the oncocytic tumors. Furthermore, alterations of the tight junctions were described; especially focal tights in the oncocytic adenomas and well organized and labyrinthic tight junctions in the oncocytic carcinomas. The lack of gap junction in the benign as well as in the malignant oncocytomas may suggest that the absence of gap junction is not sufficient for malignancy. The alterations of the tight junctions found in the oncocytic tumors of the thyroid are similar to those observed in poorly differentiated tissues or tumors, and may suggest a cellular regression rather than a tumorogenic factor.

Intestinal paracellular permeability during malnutrition in guinea pigs: effect of high dietary zinc.

BACKGROUND: Zinc has been shown to have beneficial effects in vitro on epithelial barrier function, and in vivo to reduce intestinal permeability in malnourished children with diarrhoea. AIMS: To determine whether malnutrition alters intestinal paracellular permeability, and whether zinc prevents such alterations. METHODS: Guinea pigs were fed a normal protein diet (NP group), a low protein diet (LP group), or a low protein diet enriched with 1800 ppm zinc (LPZn group) for three weeks. Intestinal permeability was measured on jejunal segments mounted in Ussing chambers by measuring ionic conductance and mucosal to serosal fluxes of 14C-mannitol, 22Na, and horseradish peroxidase. Tight junction morphology was assessed on cryofracture replicas. RESULTS: Mannitol and Na fluxes and ionic conductance increased in the LP group compared with the NP group but remained normal in the LPZn group. Accordingly, jejunal epithelia from the LP group, but not from the LPZn group, showed a small decrease in number of tight junctional strands compared with epithelia from the NP group. Neither malnutrition nor zinc treatment modified horseradish peroxidase fluxes. CONCLUSIONS: Malnutrition is associated with increased intestinal paracellular permeability to small molecules, and pharmacological doses of zinc prevent such functional abnormality.

Establishment of hepatic cell polarity in the rat hepatoma-human fibroblast hybrid WIF-B9. A biphasic phenomenon going from a simple epithelial polarized phenotype to an hepatic polarized one.

By immunofluorescence and freeze fracture methods, we have studied the establishment of hepatic cell polarity in WIF-B9 cells, a subclone of the WIF-B rat hepatoma-derived hybrid cell line. As previously shown (Ihrke et al. (1993) J. Cell Biol. 123, 1761-1775; Shanks et al. (1994) J. Cell Sci. 107, 813-825), these cells are a suitable model for in vitro studies of various hepatic functions, particularly polarity: in confluent cultures, the majority of cells form bile canaliculus-like structures; membrane domains are settled, according to plasma membrane protein localization similar to rat hepatocytes in situ. We here report that the establishment of WIF-B9 cell polarity is a slow progressive biphasic phenomenon. During the first days of culture, the majority of cells do not make bile canaliculus-like structures. However, they display a polarity similar to that of simple epithelial cells: apical membrane proteins and villin are found at the cell apex; basolateral ones, excluded from this area, are expressed in the remaining membrane area; the tight junction-associated protein ZO-1 and actin are concentrated at the boundary of these two poles, whereas E-cadherin is present at the lateral pole just under the apex. With time in culture, the number of cells expressing this simple epithelial polarized phenotype decreases progressively and, after 10-15 days, depending on the plating density, nearly all the cells express the typical hepatic polarized phenotype. The expression of these two phenotypes is mutually exclusive. Freeze-fracture replicas of both types of polarized cells show either macula occludens, fascia occludens (simple epithelial polarity) or zonula occludens (hepatic polarity), associated with gap junctions. In this last case, two or three continuous strands are generally present all around the bile canaliculus-like structures.

Analytical microscopy and environment. Current developments using bioindicators of pollution by stable and radioactive elements.

Ecotoxicological investigations were performed on three sets of bioindicators. The first one concerns marine pollution of invertebrates (molluscs: the mussel Mytilus edulis and related species, crustaceans: the crab Liocarcinus puber and related species), contaminated by stable or radioactive elements originating from wastes discharged into sea water. The second one concerns freshwater pollution of vertebrates (fish: the brown trout Salmo trutta fario), contaminated by aluminium dissolved in rivers, as a consequence of an atmospheric pollution by acid rain. The third one concerns the atmospheric pollution of trees by plutonium (Casuarina equisetifolia). Mechanisms involved in the uptake, storage and elimination processes of these toxicants were studied, with a special emphasis on cellular and subcellular aspects of concentration sites. Two microanalytical methods were employed: Secondary Ion Mass Spectrometry (SIMS), using the ion microscope and the ion microprobe, and X-ray spectrometry using the electron microprobe (EMP). In marine organisms, the target organs and tissues of bioaccumulation of stable and radioactive elements (238U, 239Pu and 241Am), were shown to be mainly digestive gland, gill and exoskeleton. The target organelles were shown to be spherocrystals and lysosomes. Amoebocytes, enzymatically equipped with lysosomal phosphatase, were involved in the phagocytic clearance of metal pollutants. In trout, insolubilisation of Al phosphate within lysosomes and a high metal concentration within bones were observed. The tree Casuarina equisetifolia exhibits a particular ability to concentrate atmospheric plutonium within its leaves.

Compared effects of extracellular K+ ions and soman, a neurotoxic, on cerebral astrocyte morphology. An in vitro study.

One of the roles of astrocytes in the maintenance of perineuronal ionic balance during intense neuronal activity occurring after injection of convulsant agents like soman. Soman is an irreversible cholinesterase inhibitor and induces brain damage with early swelling of astrocytic perivascular processes. Mature astrocytes are easily characterized on freeze-fracture replicas owing to the presence of regular geometric aggregates of intramembranous particles: the 'orthogonal arrays' (OAs). In primary cultures of astrocytes OA distribution is homogeneous throughout the plasma membrane. A present hypothesis (see review in Risau and Wolburg, 1990) considers that these OAs are associated with channels controlling potassium ion concentration in the cerebral parenchyma. We have investigated the effects of extracellular concentrations of K+ ions identical to those observed during neuronal activity on primary cultures of astrocytes and effects induced by soman. High concentrations of K+ ions (60 mM) as well as soman exerted direct effects on astrocytic plasma membranes: K+ ion influx within astrocytes induces a partial disaggregation of OAs and more acutely than soman. Neither K+ ions nor soman induce swelling of astrocytic end-feet.

The supra-ependymal innervation is not responsible for the repression of tight junctions in the rat cerebral ependyma.

Classically, the contiguous epithelial cells show intercellular tight junctions (TJ) positioned as a continuous belt of cell-cell contacts at the boundary of apical and basolateral plasma membranes. Among the epithelia, the "typical" cerebral ependyma is very peculiar due to the absence of TJ, in contrast to the ependyma of the circumventricular organs (e.g. choroid plexus and the subcommissural organ) which shows well differentiated TJ. Since the "typical" ependyma is covered in the rat with a plexus of intraventricular nervous fibres not present at the surface of the circumventricular organs, we hypothesized local repression of TJ by molecules (serotonin, GABA, etc.) released by the supra-ependymal varicosities. Neither the denervation of the "typical" ependyma nor the ex vivo activation of protein kinase C (which increases the transepithelial resistance as it has been reported in other epithelia) produced junctional fibrils as shown by freeze-fracture. As the protein ZO-1 was not detectable in the "typical" ependyma by immunocytochemistry, there is probably repression of the genes responsible for TJ biosynthesis by unidentified endogenous factors.

Tumour necrosis factor-alpha induces morphological and functional alterations of intestinal HT29 cl.19A cell monolayers.

TNF-alpha is a widely distributed proinflammatory cytokine, involved in many disease states. Although it has widely distributed effects, a precise mechanism of action has never been described, in particular at the epithelial level. Morpho-functional changes of the intestinal epithelial monolayer HT29 cl.19A exposed to TNF-alpha were therefore assessed, using electron microscopy (including freeze-fracture replica analysis), as well as measurement of mannitol, Na+ and horseradish peroxidase fluxes across intestinal HT29 cl.19A cell monolayers using Ussing chambers. TNF-alpha receptors were induced on HT29 cl.19A cells by a small non-toxic dose of IFN-gamma (5 U/ml). After 4 h of the combined presence of TNF-alpha (10 ng/ml) and IFN-gamma (5 U/ml), the tight junction structure was altered as shown by a significant decrease in the average strand number measured in the apico-basal direction (5.50 +/- 2.70 vs 3.73 +/- 1.39 in control and treated cells respectively, P < 0.0001) and by a significant decrease in junctional depth (0.27 +/- 0.14 and 0.17 +/- 0.10 microns in control and treated cells respectively, P < 0.0001). These results are in agreement with a decrease in number of 'kiss' sites between contiguous membranes of TNF-alpha treated cells observed in ultrathin sections.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of nitric oxide in the neuropathology in soman intoxication.

Intoxication with organophosphorus (0P) anticholinesterase agents such as soman triggers irreversible lesions in some cerebral areas. Administration of soman at the LD 50 leads to an increased activity of NADPH-diaphorase (= NO-synthase) in the cerebral endothelial cells from the 6th hour after poisoning. This activity culminates after 24 h, whereas variations in this enzymatic activity are not easily detectable in NADPH-diaphorase positive neurons. Since soman triggers astrocytic oedema leading to a possible decrease in the local cerebral blood flow, it is likely that the induction of endothelial NO-synthase exerts an antagonistic effect, since NO is a vasodilator.

Effects of soman on cerebral astrocyte plasma membranes: a freeze-fracture study.

Astrocytes are identifiable on freeze-fracture by regular geometric aggregates of uniform intramembranous particles (IMP), the 'orthogonal arrays' (OA). These OAs are considered to be potassium channels that maintain the ionic balance around neurons. After subcutaneous administration of a single near LD50-dose of soman in rats, neurotoxic epileptogenic irreversible cholinesterase inhibitor, replicas showed a significant decrease in OA density in the convulsed animals. This dissociation by soman confirms that OA are a particularly labile membranes specialization. Frequent clumping of IMP and numerous cleavage planes were observed; this could be the result of an interaction between the liposoluble poison and membrane phospholipid fluidity.

Contribution of peripheral macrophages and microglia to the cellular reaction after mechanical or neurotoxin-induced lesions of the rat brain.

Lesions of the central nervous system result in invasion of peripheral phagocytes and/or in situ activation and proliferation of microglia, depending on the direct or indirect nature of the injury. Neurotoxins which are widely used to induce neurodegeneration have been reported to elicit a pure microglial reaction when administered intraventricularly. However, the mechanical lesion at the injection site, although remote from the lesioned area, could give access to blood-derived cells. Therefore, this study compares the phagocytic reaction occurring after a traumatic lesion of the brain causing a breakdown of the blood-brain barrier (BBB), or after degeneration of the inferior olivary neurons induced by intraperitoneal administration of 3-acetylpyridine, a process that respects the integrity of the BBB as suggested by the results of intravascular injection of Evans blue. The identification of the macrophages at the lesion site used specific binding of the B4 isolectin from Griffonia simplicifolia, preloading of the peripheral monocytes/macrophages with trypan blue, and characteristic morphological features. In traumatically lesioned rats, the lectin-labeled macrophages were mainly large rounded peripheral cells recruited 1-3 days postlesion, whereas in chemically lesioned rats, the cellular reaction appeared 24-36 h postinjection and peaked between 3 and 12 days before undergoing a slow decline. Lectin binding and morphological characteristics indicated that these small cells were reactive microglia. These results confirm that a brain injury leaving the BBB intact involves essentially the recruitment and/or the proliferation of microglia.

Variation in the expression of c-fos after intoxication by soman. Comparative study using in situ hybridization and immunohistochemistry.

A massive and transitory increase in c-fos mRNA and Fos protein occurred in rats intoxicated by a single dose of soman (organophosphate compound and irreversible cholinesterase inhibitor) only in animals that had seizures. Comparison of immunohistochemistry that localizes Fos protein and of in situ hybridization that localizes its mRNA showed that there was an early and explosive expression of mRNA in many cerebral regions followed by transitory immunoreactivity in only some regions (piriform cortex, entorhinal area, hippocampus). The levels of mRNA and c-fos-like immunoreactivity decreased slowly and returned to basal level 24 h after soman administration.

Efficiency of liposomal ATP in cerebral ischemia: bioavailability features.

This study was performed to elucidate the mechanism by which adenosine triphosphate (ATP) encapsulated into liposomes was able to protect against experimental brain ischemia in the rat. After intracarotidal administration of liposomally entrapped ATP, the ATP blood level increased dramatically whereas no change was observed after administration of free ATP. This suggested that liposomes may protect ATP from its degradation by endothelial ectonucleotidases. On the other hand, it was observed that after administration of liposomally entrapped carboxyfluorescein (CF) to ischemic rats, the distribution of the brain fluorescence under the form of numerous punctiform structures was completely different from the diffuse fluorescence obtained with free CF injections. These data suggest that under certain hypoxic conditions the blood-brain barrier is open allowing the liposomes to reach the cerebral parenchyma. The mechanism of brain uptake is, however, still unclear: endothelial tight junctions opening or endothelial transcytosis.

Initial process of diffusion of small molecules from blood vessels to the meninges in the young rat.

Pathways taken by peripherally administered small molecules when entering the brain were investigated in 6-day-old rats by radioautography and fluorescence microscopy after intravenous administration and rapid freezing. L-[U-14C]Phenylalanine, [U-14C]sucrose and sodium fluorescein reached the brain within less than 5 seconds. These blood-borne molecules were found in the subarachnoid cisterns and the superficial parenchyma. These results suggest a special permeability of the arachnoid layer and/or the pial vessels. Phenylalanine alone reached the deep parenchyma because of the existence of a specific endothelial carrier.

Seizure-related opening of the blood-brain barrier induced by soman: possible correlation with the acute neuropathology observed in poisoned rats.

In rats poisoned with soman, an irreversible organophosphate anticholinesterase, acute changes in blood-brain barrier (BBB) permeability to proteins were investigated, using Evans Blue (EB)-labelled serum albumin and plasmatic gamma-immunoglobulin G (IgG) as indicators. Confirming previously published data, soman produced a conspicuous seizure-related and reversible BBB opening which was greatest after 30 to 60 min of paroxysmal electroencephalographic (EEG) discharges when signs of cerebral hyperactivity (epileptic EEG pattern, hyperoxia) were also at their height. Topographically, the protein leakage was bilateral and restricted to anatomically defined brain structures, some of which being thereafter sites of parenchymal edema and neuronal damage. In these areas (e.g., the thalamus), the edema is probably, at least in part, "vasogenic" in origin, and the possible contribution of the transient BBB opening to the neuronal lesions was questioned. On the other hand, the hippocampus, a region preferentially affected by the soman-induced acute neuropathology, was always free of any protein leakage, suggesting that the edema is unrelated to vascular damage and "cytotoxic" in nature. Finally, no topographic relationship was shown to exist between the increase in cerebrovascular permeability produced by soman and the histochemically-detected inhibition of the parenchymal total cholinesterases (ChE) or endothelial butyrylcholinesterase (BuChE).

Permeability of the normal rat brain, spinal cord and dorsal root ganglia microcirculations to immunoglobulins G.

The distribution of blood-borne immunoglobulins G (IgG) was studied in the cerebral cortex, pineal gland, spinal cord and dorsal root ganglia of normal Lewis rats using the detection of autologous anti-horseradish peroxidase (HRP) antibodies. This detection was performed by means of light and electron microscopy. This study demonstrated that, in the cerebral cortex and the spinal cord microcirculations, endothelial cells are a restrictive barrier against IgG while IgG are able to diffuse into the perivascular parenchyma of the pineal gland and spinal ganglia.