Influx of leukocytes and platelets in an evolving brain infarct (Wistar rat).

The results of several experimental studies of focal ischemia and anecdotal observations suggest that leukocytes may contribute to the injury initiated by an arterial occlusion. The timing and the nature of leukocyte responses in evolving brain infarcts (either human or experimental) are incompletely characterized. This is a study of experimental brain lesions in 96 Wistar rats that underwent occlusion of a large intracranial artery for variable intervals ranging between 30 minutes and 7 days. The experimental model, based on the occlusion of a middle cerebral artery ostium via the insertion of a nylon monofilament through the external carotid artery, does not require opening the skull; therefore, the inflammatory response is not influenced by the effects of craniotomy and changes in intracranial pressure are only those induced by the ischemic lesion. All 96 animals having the same type of arterial occlusion developed an ischemic brain lesion (limited to the territory of the corresponding artery) that evolved into an area of extensive neuronal necrosis over a period of 6 to 12 hours followed by pan-necrosis (infarct) approximately 60 hours later. In this study, leukocytes (in particular polymorphonuclear cells) were detected in the microvessels (capillaries and venules) of the ischemic hemisphere as early as 30 minutes after the arterial occlusion. Numbers of intravascular neutrophils peaked at 12 hours, whereas intraparenchymal granulocytes were most numerous at 24 hours; a few granulocytes were visible in the brain infarct as late as day 7. Circulating monocytes were first detected within the capillaries/venules of the ischemic area after 4 to 6 hours. Platelet aggregates were more abundant in the arterial than the venous side of the circulation, and luminal obstruction of arteries by platelet aggregates became noticeable only 48 hours after the arterial occlusion. Fibrin thrombi were conspicuous for their absence. These observations provide the background for studies that will attempt to unravel the relationship between the biological responses of leukocytes and neuronal necrosis secondary to focal ischemia.     

The paraventricular nucleus of hypothalamus mediates the pressor response to noradrenergic stimulation of the medial prefrontal cortex in unanesthetized rats

The medial prefrontal cortex (MPFC) is a structure that is also involved in cardiovascular modulation. The injection of norepinephrine (NE) into the prelimbic (PL) area of the MPFC of unanesthetized rats evokes a pressor response which is mediated by acute vasopressin release. Vasopressin is synthesized by magnocellular cells of the paraventricular (PVN) and supraoptic nucleus (SON) of the hypothalamus. In the present study, we endeavored to determine which vasopressin-synthesizing hypothalamic nucleus is involved in the pressor pathway activated after NE injection into the PL area of the MPFC. We report here that lidocaine microinjection into the SON did not change the pressor response evoked by NE injection into the PL. However, the response to NE was blocked by prior injection of lidocaine or CoCl₂ into the PVN, indicating that this area is responsible for the mediation of this pressor response. A neuroanatomic experiment in which the neuronal tracer biotinylated dextran amine (BDA) was microinjected into the MPFC showed a lack of axons or neuronal cell bodies in the PVN, indicating that there are no direct connections between the PL area of the MPFC and the PVN. The results suggest that the PVN is involved in the mediation of the pressor response to NE in the PL area and that this pathway must relay in other brain structures before reaching the PVN.     

Estimating the relative frequency of leukodystrophies and recommendations for carrier screening in the era of next‐generation sequencing

Leukodystrophies are a heterogeneous group of heritable disorders characterized by abnormal brain white matter signal on magnetic resonance imaging (MRI) and primary involvement of the cellular components of myelin. Previous estimates suggest the incidence of leukodystrophies as a whole to be 1 in 7,000 individuals, however the frequency of specific diagnoses relative to others has not been described. Next generation sequencing approaches offer the opportunity to redefine our understanding of the relative frequency of different leukodystrophies. We assessed the relative frequency of all 30 leukodystrophies (associated with 55 genes) in more than 49,000 exomes. We identified a relatively high frequency of disorders previously thought of as very rare, including Aicardi Goutières Syndrome, TUBB4A‐related leukodystrophy, Peroxisomal biogenesis disorders, POLR3‐related Leukodystrophy, Vanishing White Matter, and Pelizaeus‐Merzbacher Disease. Despite the relative frequency of these conditions, carrier‐screening laboratories regularly test only 20 of the 55 leukodystrophy‐related genes, and do not test at all, or test only one or a few, genes for some of the higher frequency disorders. Relative frequency of leukodystrophies previously considered very rare suggests these disorders may benefit from expanded carrier screening.     

Hungry, but not thirsty, rats prefer flavors paired with ethanol

The present experiments examined the reinforcing effects of an ethanol (EtOH) unconditioned stimulus (UCS) on conditioned flavor preferences in food-deprived rats and in water-deprived rats. In Experiment 1A food and water deprived animals received distinct conditioning treatments. One half of the animals were intragastrically intubated with EtOH (0.5 g/kg), and thereafter allowed 20 min free access to similar flavored drinking solutions. Remaining animals were intubated with distilled water. All animals received 15 presentations of an EtOH-paired flavor. A two-bottle preference test was subsequently used to evaluate preferences or aversions to flavors paired with EtOH in food-deprived and water-deprived animals. Results of Experiment 1A showed that food-deprived animals preferred the flavor associated with EtOH. Conversely, preferences for EtOH-paired flavors were not established in water-deprived animals. In Experiment 1B deprivational states of animals used in Experiment 1A were reversed without further drug training. Following a two week habituation period to deprivation state animals again received a two-bottle preference test to re-evaluate preferences or aversions to the EtOH-paired flavors. Results of those manipulations indicated that an ethanol aversion was established in the water-deprived animals. Those results indicated that water-deprived animals of Experiment 1B reversed their EtOH-paired flavor preference when the caloric need associated with food deprivation conditions was eliminated. Since deprivational state determined the development of EtOH preferences, the present results indicate that caloric need may play an initial role in establishing conditioned preferences for EtOH.     

A dinucleotide mutation in the endothelin-B receptor gene is associated with lethal white foal syndrome (LWFS); a horse variant of Hirschsprung disease

Lethal white foal syndrome (LWFS) is a congenital anomaly of horses characterized by a white coat colour and aganglionosis of the bowel, which is similar to Hirschsprung disease (HSCR). We decided to investigate possible mutations of the endothelin-B receptor gene ( EDNRB ) in LWFS as recent studies in mutant rodents and some patients have demonstrated EDNRB defects. First, we identified a full-length cDNA for horse EDNRB . This cDNA fragment contained a 1329 bp open reading frame which encoded 443 amino acid residues. The predicted amino acid sequence was 89, 91 and 85% identical to human, bovine and mouse as well as rat EDNRB respectively, but only 55% identical to the human, bovine and rat endothelin A receptor (EDNRA). Secondly, sequence analysis, together with allele-specific PCR and the amplification- created restriction site (ACRS) technique, revealed a dinucleotide TC-- >AG mutation, which changed isoleucine to lysine in the predicted first transmembrane domain of the EDNRB protein. This was associated with LWFS when homozygous and with the overo phenotype when heterozygous.      

Seroprevalence of viral hepatitis C in polytransfused patients at Central University Hospital of Brazzaville

The viral C hepatitis is a disease which is often asymptomatic but with a very high risk of death. A prospective survey on multitransfused patients with a high transfusional risk has been conducted between May 1st and September 30th, 2001 in the medical services of the Hospital of Brazzaville. It deals with 252 samples of blood taken on 132 multitransfused patients and 120 control cases who have never been transfused. The screening of antibodies has been performed with ELISA technique by using 2 sensitive tests: the monolisa anti-HCV plus version 2 (Bio-Rad) and BIOTEC HCV a.b. Only monolisa is registered by AFSSAPS. The survey shows a overall seroprevalence of 13.9%: multitransfused patients: 26 out of 132 (19.7%) and control cases 9 out of 120 (7.5%). The prevalence of anti-HCV antibodies is practically similar in both series. It is low among control cases before 20 years old, but important in this same group when the patients are multitransfused. It is very significant among adult control cases, indicating the probability of other transmission modes in this age bracket. Patients suffering from hemoglobinopathy (sickle cell) and from malignant hemopathy paid an heavy toll to the virus with respectively 16.9% and 22% of prevalence even if the sampling is restricted. This results point out the necessary implementation of a systematic screening of all the main viruses before transfusion.     

Neuronal injury after photoactivation of photofrin II.

Photodynamic therapy has been used in the management of patients with malignant brain tumors even though the effects of this form of treatment on the adjacent normal brain are incompletely characterized. The authors examined, in sequential experiments, morphologic alterations affecting the cerebral cortex in rats injected with Photophrin II and exposed to light. Initially, minimal cell alterations, including cisternal swelling of both endoplasmic reticulum and Golgi apparatus, involved only neurons located in the superficial layers of the cerebral cortex exposed to light. These changes spread, over a period of several hours, from the surface to the bottom of the cortex and eventually involved the entire cortical segment exposed to light. The earliest structural signs of lethal injury to neurons developed over a period of 18 hours after porphyrins had been photoactivated and astrocytes had been severely damaged. Signs of lethal injury to neurons included an increase in the number of mitochondrial cristae and appearance of amorphous electron-dense deposits within swollen mitochondria. The appearance of these alterations was followed by segregation of intracytoplasmic organelles and fragmentation of nuclear and cytoplasmic membranes. The tissue changes, including those involving neurons, eventually progressed to coagulation necrosis at 48 hours. These observations suggest that prophyrins injected to rats (48 hours before photoactivation) cause swelling and necrosis of astrocytes. This is followed by neuronal necrosis, which appears at two time intervals; the initial neuronal necrosis occurs after the astrocytic disintegration. A second type of neuronal alteration appears after microvessels become thrombosed and ischemia is likely to develop.     

Insulin, chemotherapy, and the mechanisms of malignancy: the design and the demise of cancer

The endogenous molecular biology of cancer cells involves autocrine and paracrine secretion of insulin and insulin-like growth-factors I and II, which subserve energy production and growth stimulation, respectively, in these cells. These activities confer on cancer its malignant potential, working as they do autonomously, free from higher levels of integrated control. Taking advantage of cancer's mechanisms of malignancy by employing exogenous insulin as a biologic response modifier, it is possible to potentiate the cytotoxic effects of chemotherapeutic agents for improved treatment of cancer. A synergy between certain membrane and metabolic effects of insulin on cancer cell molecular biology increases anticancer drug efficacy, and it does so with reduced doses of the drugs, enhancing their safety. This treatment strategy has been applied abroad over the last five decades with very promising clinical results.     

A role for lymphotoxin beta receptor in host defense against Mycobacterium bovis BCG infection

To investigate the role of membrane lymphotoxin (LT)alpha1 / beta2 and its LTbeta receptor (LTbetaR) in the protective immune response to Mycobacterium bovis bacillus Calmette-Guérin (BCG) infection, we have used a soluble fusion molecule (LTbetaR-IgG1). LTbetaR-Ig treatment interferes with granuloma formation mainly in the spleen by inhibiting macrophage activation and nitric oxide synthase activity. In addition, a large accumulation of eosinophils was observed in the spleen of LTbetaR-Ig-treated infected mice. Decreased blood levels of IFN-gamma and increased IL-4 were also observed, suggesting that the LTbetaR pathway is important in BCG infection to favor a Th1 type of immune response. The treatment of transgenic mice expressing high blood levels of a soluble TNFR1-IgG3 fusion protein with LTbetaR-Ig resulted in a still higher sensitivity to BCG infection, and extensive necrosis in the spleen. In conclusion, these results suggest that the LTbetaR and the TNFR pathways are not redundant in the course of BCG infection and protective granuloma formation: the LTbetaR pathway appears to be important in spleen granuloma formation, whereas the TNFR pathway has a predominant role in other tissues.     

Totally implantable venous access ports: frequency of complications and analysis of bacterial contamination after ablation

Totally implantable venous access ports (TIVAP) are valuable medical devices for long-term intravenous treatment such as parenteral nutrition, cancer chemotherapy or antiviral therapy. Implantation and use of these devices are each associated with infectious or mechanical complications. AIMS OF THE STUDY: To determine the frequency of complications and to analyze bacterial contamination of different parts of TIVAP (tip, septum, internal lumen of the port). MATERIAL AND METHODS: Clinical charts of patients, which TIVAP was removed between April 20th to December 31st 2003, were retrospectively reviewed. Infectious complications (local and septicemic) and non-infectious complications (i.e. obstruction, thrombosis, drug extravasation...) were defined using clinical and/or microbiological criteria. Quantitative culture from different parts of the TIVAP was performed. RESULTS: One hundred and ten patients (age 57 +/- 14-years-old, 94.3% cancers) were included, corresponding to 57,018 catheter-days: 39.1% had one or more non-infectious complications (density incidence: 0.86 for 1000 catheter-days). Among the 49 complications, obstruction, thrombosis, extravasations and malposition accounted for 30.6%, 30.6% 4.1% and 6% of cases. Twenty-one patients (19.1%) had an infectious complication: 11 were local and 14 were systemic (density incidence 0.43 for 1000 catheter-days). Bacteria responsible for TIVAP-associated bacteraemia were coagulase negative staphylococci (N = 2), Staphylococcus aureus susceptible to methicilline (N = 3), micrococci (N = 1), corynebacteria (N = 1) or Gram-negative bacilli (N = 8). Comparison of quantitative culture of the different parts of TIVAP with a threshold at 10(3) CFU/ml showed that culture of tip, septum and port has a sensitivity of 47.6% 57.1% and 61.9 %, respectively and a specificity of 100% 92.1% and 92.1%, respectively for the diagnosis of TIVAP infection. CONCLUSION: Complications associated to TIVAP are frequent but incidence that we have reported is comparable with previous studies. Analysis of internal lumen of the port is the most sensitive method for the diagnosis of TIVAP-associated infections.