Microglial Reaction in the Rat Cerebral Cortex Induced by Cortical Spreading Depression

The response of microglial cells to cortical spreading depression (CSD) was studied in rat brain by immunocytochemistry. CSD was elicited for one hour by the topical application of 4M potassium chloride solution and the microglial reaction examined immunocytochemically after 4, 16, 24 and 72 hours. CSD was sufficient to induce a microglial reaction throughout the cortex at 24 hours. Activated microglial cells furthermore showed a striking de-novo expression of major histocompatibility complex class II antigens. In contrast, no microglial reaction was observed in the cortex of sham-operated animals. This microglial reaction in response to CSD was not associated with histologically detectable neuronal damage. These results support the view that microglial cells are extremely sensitive to changes of the brain microenvironment. Their activation may be related to changes of ion homeostasis in the brain which are not sufficient to trigger neuronal injury.     

Alpha-thalassemia/mental retardation syndrome in a 45,X male

An unbalanced Y;autosome translocation leading to a male with a 45,X karyotype is rare with about 30 published cases. A male with a 45,X karyotype as a result of a unique, submicroscopic, unbalanced Y;16 translocation is presented with alpha-thalassemia/mental retardation syndrome.     

Reproductive planning after genetic counselling: a perspective from the last decade

Studies from the last decade on factors influencing reproductive planning after genetic counselling were reviewed. Increased possibilities of DNA-analysis and prenatal diagnosis might have brought about a shift in the paramountcy of factors influencing reproductive planning after genetic counselling. In contrast to the literature in the seventies, the magnitude of the genetic risk was no longer found to be one of the decisive factors in postcounselling reproductive planning. Instead, the interpretation of the risk as high or low and the desire to have children appeared to be paramount. The impact of new developments in DNA-analysis in prenatal diagnosis and presymptomatic testing will be an important subject for future studies on factors influencing reproductive planning.     

Inactivation of the peroxisomal ABCD2 transporter in the mouse leads to late-onset ataxia involving mitochondria, Golgi and endoplasmic reticulum damage

ATP-binding cassette (ABC) transporters facilitate unidirectional translocation of chemically diverse substances, ranging from peptides to lipids, across cell or organelle membranes. In peroxisomes, a subfamily of four ABC transporters (ABCD1 to ABCD4) has been related to fatty acid transport, because patients with mutations in ABCD1 (ALD gene) suffer from X-linked adrenoleukodystrophy (X-ALD), a disease characterized by an accumulation of very-long-chain fatty acids (VLCFAs). Inactivation in the mouse of the abcd1 gene leads to a late-onset neurodegenerative condition, comparable to the late-onset form of X-ALD [Pujol, A., Hindelang, C., Callizot, N., Bartsch, U., Schachner, M. and Mandel, J.L. (2002) Late onset neurological phenotype of the X-ALD gene inactivation in mice: a mouse model for adrenomyeloneuropathy. Hum. Mol. Genet., 11, 499-505.]. In the present work, we have generated and characterized a mouse deficient for abcd2, the closest paralog to abcd1. The main pathological feature in abcd2-/- mice is a late-onset cerebellar and sensory ataxia, with loss of cerebellar Purkinje cells and dorsal root ganglia cell degeneration, correlating with accumulation of VLCFAs in the latter cellular population. Axonal degeneration was present in dorsal and ventral columns in spinal cord. We have identified mitochondrial, Golgi and endoplasmic reticulum damage as the underlying pathological mechanism, thus providing evidence of a disturbed organelle cross-talk, which may be at the origin of the pathological cascade.     

Chromosomal radiosensitivity of breast cancer with a CHEK2 mutation

Recently, multiple studies have shown that a sequence variant in CHEK2 (CHEK2 1100delC) plays a role in the susceptibility to breast cancer. This mutation should confer about a twofold increased breast cancer risk in women and a 10-fold increased risk in men. Because the CHEK2 gene plays a critical role in DNA damage repair and the CHEK2 1100delC variant confers susceptibility to breast cancer, we investigated if patients carrying the CHEK2 1100delC mutation are characterized by an enhanced chromosomal radiosensitivity. To this end, familial breast cancer patients, sporadic breast cancer patients, and healthy women, considered in our previously studied to determine their chromosomal radiosensitivity with the G2 and G0-MN assay, were all tested in present study for the presence of the CHEK2 1100delC variant. The 1100delC variant was detected in none of the 100 healthy individuals, in 1 of 100 (1%) unselected breast cancer patients and in 3 of 78 (3.8%) breast cancer patients with a family history of breast cancer. The breast cancer patients with the CHEK2 1100delC genotype had a mean radiation-induced yield of chromatid breaks that was not significantly different from that of the healthy control group. Although the mean yield of micronuclei (MN) was significantly higher compared to the healthy control group, this higher mean MN yield was due to a single patient who had a very high number of MN compared to the parallel control. Our data suggest that breast cancer patients with a CHEK2 1100delC mutation are in general not characterized by a distinct enhanced chromosomal radiosensitivity. These conclusions are, however, very preliminary, because of the small numbers of CHEK2 1100delC breast cancer patients studied.     

Fertilization and early embryology: Effects of persistent chlorinated hydrocarbons on fertility and embryonic development in the rabbit

The commercial polychlorinated biphenyl (PCB) formulation Aroclor1260 (4 mg/kg body weight), technical grade dichlorodiphenyltrichloroethane(DDT; 3 mg) and Lindane (-hexachlorocyclohexane; 0.8 mg) wereadministered orally, either separately or in combination, tosexually mature female rabbits three times per week for 12–15weeks. Oviductal and uterine luminal fluid, cleavage stage embryos(day 1 post coitum), blastocysts (day 6), fetuses, exocoelicfluid and placentae (day 11) were analysed, firstly for chlorinatedhydrocarbon residues, and secondly for embryonic and fetal development.The doses applied were well tolerated by the treated animals.PCB and DDT accumulated in uterine secretions (day 6) but notin oviductal luminal fluid (day 1). Both chlorinated hydrocarbonswere found in preimplantation blastocysts. Residues in day 11fetuses were 16- (DDT) or 18-fold (PCB) higher than in day 6blastocysts. Significant amounts were also detected in placentaltissue and in exocoelic fluid. A specific accumulation of thehighly chlorinated biphenyl congener no. 180 was noted in fetuses,placentae and exocoelic fluid. The clear accumulation of thechlorinated hydrocarbon compounds in luminal fluid and embryonictissue is contrasted by rather weak effects on fertility. Nostatistically significant differences between treated animalsand controls were observed for fertilization rate and pre- andpost-implantation (up to day 11 post coitum) losses. However,in females exposed to PCB, a 20% higher loss of blastocystswas noticed, as compared with controls (P > 0.05). This effectwas shown on day 6 of embryonic development and may be due tothe embryotoxic activities of PCB.     

Resolution and conservation of mismatches in DNA end joining

DNA end joining is a major pathway for the elimination of double-strandbreaks from chromosomal DNA of higher eucaryotic cells. Extractsof Xenopus laevis eggs rejoin such breaks even when their shortsingle-stranded termini are expected to form imperfectly matchedoverlaps. However, end-joined products cloned in Escherichiacoli, necessarily give rise to perfectly matched products. Thereforeit has not been possible to determine whether the end joiningprocess creates mismatched products, perfectly matched (resolved)products or both. To investigate whether mismatch resolutionwas the result of the X. laevis end joining process or of activitiesof the bacterial host we used denaturing gradient gel electrophoresisto analyse joined products. We found that the end joining processdoes include mismatch resolution, the degree of which varieswith regard to the nature of the original overlap structure.Mismatches 3' to a gap are completely resolved, mismatches 3'to a nick and 5' to a nick or gap are resolved to some extentbut are generally conserved. Mismatches between base matchesare always conserved. These findings suggest competing processesof ligation, DNA fill-in synthesis or exonucleolytic excisionof mismatched bases next to a gap or nick. At mismatches 3'to a nick the probability of ligation is greater than that ofexcision while at mismatches 3' to a gap the probability ofexcision is greater than elongation of a given mismatch. Atmismatches 5' to nicks or gaps it appears that ligation or elongationand ligation, respectively, are the most probable pathways butproducts resulting from mismatch excision, elongation and ligationare also detected. ⁵To whom correspondence should be addressed