Astrocyte–neuron interactions in neurological disorders

Astrocytes have long been considered as just providing trophic support for neurons in the central nervous system, but recently several studies have highlighted their importance in many functions such as neurotransmission, metabolite and electrolyte homeostasis, cell signaling, inflammation, and synapse modulation. Astrocytes are, in fact, part of a bidirectional crosstalk with neurons. Moreover, increasing evidence is stressing the emerging role of astrocyte dysfunction in the pathophysiology of neurological disorders, including neurodegenerative disease, stroke, epilepsy, migraine, and neuroinflammatory diseases.     

Transposition of c-abl oncogene in a case of masked Ph chromosome duplicated in blastic phase

Summary A female with chronic myelocytic leukemia (CML) in blastic phase (BP) showed a masked Ph chromosome that had originated by a translocation between chromosomes 8 and 22, with no obvious involvement of chromosome 9. A duplication of the masked Ph and trisomy 13 were present as additional anomalies. The karyotype on peripheral blood unstimulated cultures was 48,XX,t(8;22)(p12;q11),+13,+der(22) t(8;22)/47,XX,t(8;22)(p12;q11),+der(22)t(8;22). While the duplication of the Ph is a frequent finding in BP of CML, we did not find any other case in the literature with duplication of a masked Ph. In situ hybridization with c-abl and bcr probes showed that a 3 bcr sequence was translocated to the der(8) chromosome, while the c-abl oncogene was transposed to the masked Ph.     

The Mr 17500 region of the A chain of urokinase is required for interaction with a specific receptor in A431 cells

We have found the existence of specific receptors for the plasminogen activator, urokinase, in A431 human epidermoid carcinoma cells, cultures in plasminogen-free conditions. Two subsets of receptors have been recognized on the basis of 125I-labelled urokinase binding analysis: about 1 X 10(3) high-affinity (Kd = 5.0 X 10(-11) M) and 1 X 10(5) low-affinity (Kd = 9 X 10(-9) M) receptors per cell. The electron microscopic observation of a urokinase: ferritin conjugate has shown single and clustered receptors at the cell surface. Down-regulation of the receptors (T1/2 = 3.77 h) follows the binding of urokinase. The binding does not involve an intact catalytic site and is inhibited by a monoclonal antibody against the Mr 17500 proteolytic fragment of the A chain of urokinase.     

Flow cytometric evaluation of proliferative activity and ploidy in myelodysplastic syndromes and acute leukemias

Propidium iodide (PI) DNA distribution of bone marrow (BM) cells was studied by flow cytometry (FCM) in 36 patients without hematologic or malignant disease (normal BM) and in 172 patients with anemias (36 pts), myelodysplastic syndromes (MDS) (33 pts) and acute leukemia (AL) at diagnosis (60 pts), remission (24 pts) and relapse (19 pts). White blood cells from normal male subjects were used as an external diploid reference standard (median CV = 3.8). Patients with normal BM, anemias, MDS and acute leukemia at diagnosis had tritiated thymidine labeling index (LI) and most with MDS and AL had also evaluable cytogenetics performed on the same BM sample used for FCM. In normal BM, median aliquot of cells with PI-DNA content intermediate between the diploid and the tetraploid value (2n-4n cells %) was 15.7. The ratio between the fluorescence intensity of the G0/1 peak of normal BM cells and the fluorescence intensity of the G0/1 peak of the reference standard (FI ratio) ranged from 93 to 1.05 (mean +/- 2SD). The 2n-4n cell % was higher than normal in anemias (p less than .001), lower in leukemias (p less than .001) and widely scattered in MDS. A linear correlation was found between 2n-4n cell % and LI, with 2n-4n cell % value higher than LI. The FI ratio was lower than normal in anemias (p less than .05), higher in AL with normal cytogenetics (p less than .02) and broadly scattered in MDS with normal cytogenetics. From our experience, PI-DNA-FCM is a simple and adequate method to evaluate proliferative activity in hematologic diseases. Nevertheless, caution must be taken in attributing small changes in FI ratio to aneuploidy, since they are found in anemias and in MDS and AL with normal cytogenetics, possibly due to differences in PI uptake by different cell types.     

Involvement of chondroitin sulphate in preventing adhesive cellular interactions

Glycosaminoglycans isolated from native non-adhesive surfaces of both endothelial and mesothelial origin and from endothelial cells cultured in vitro were analyzed by electrophoresis and characterized by chemical and enzymatic breakdown. All the surfaces examined expose in vivo chondroitin 6-sulphate as the main glycosaminoglycan. Under in vitro culture, the exposure of chondroitin sulphate is reduced. Paper chromatography of hydrolysis products upon degradation by chondroitinase AC shows equal amounts of both 6- and 4-sulphated disaccharides. At the same time, the surfaces lose their non-adhesiveness to leukocytes. The addition of fibroblast growth factor to endothelial monolayers restores both non-adhesiveness to leukocytes and exposure of chondroitin sulphate. These results seem to indicate that the exposure of chondroitin sulphate is important in preventing cellular adhesion.     

The SWISS-2DPAGE database of two-dimensional polyacrylamide gel electrophoresis, its status in 1995.

SWISS-2DPAGE is a database of proteins identified on two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). The current release contains 343 entries of human, yeast (Saccharomyces cerevisiae) and Escherichia coli origin, as well as virtual entries for each of the protein sequences in the SWISS-PROT database.     

Three chromosomes' (7;9;22) rearrangement and the origin of the Philadelphia chromosome

Summary A woman with chronic myelocytic leukemia had the Philadelphia chromosome and a complex four-break—three-chromosome rearrangement. The q32q34 portion of chromosome 9 is translocated to band q22 of chromosome 7, and at the end of this segment is attached the deleted q11 qter portion of chromosome 22. A review of 12 cases of the Philadelphia chromosome originating by the rearrangement of three or more chromosomes reveals that chromosomes 9 and 22 are always involved, while the third chromosome is a different one in each case. We discuss the hypothesis that the 22q segment is always specifically attached to band 9q34 wherever this portion of 9q is transposed.Address for offprint requests: Prof. M. Fraccaro, Gruppo Euratom, Via Forlanini, 14, I-27100 Pavia, Italy     

Effect of ubiquinone extraction on ubiquinol-1 oxidase activity in beef heart mitochondria

Extraction of endogenous ubiquinone with different methods does not influence ubiquinol oxidase activity in lyophilized mitochondria in terms ofK _M, although a decrease ofV _max is sometimes observed. Experiments with submitochondrial particles from a UQ-deficient mutant ofS. cerevisiae confirm the results with UQ-depleted mitochondria and support the idea that endogenous ubiquinone is not required for the oxidation of exogenous ubiquinols by complex III.