Clastogen-induced chromosomal breakage as a marker for first trimester prenatal diagnosis of Fanconi anemia

Summary Using cultured trophoblast cells obtained by chorionic villus biopsy, we diagnosed Fanconi anemia (FA) in two pregnancies and excluded it in eight pregnancies at risk for the syndrome. Baseline chromosomal breakage and breakage induced by diepoxybutane (DEB) were analyzed. Increased breakage was used as a marker for the syndrome. Our results were unambiguous and provide a reliable method for prenatal detection of FA in the first trimester of pregnancy.     

Abnormal electrophoretic mobility of spectrin tetramers in hereditary elliptocytosis

Summary Hereditary elliptocytosis (HE) is a genetically determined disorder of the red cell membrane. The main protein which composes the proteinaceous skeleton of the membrane is an elongated molecule named spectrin which is a heterodimer composed of two chains, and . In the membrane spectrin dimers are associated head-to-head to form tetrameric structures. We and other authors have reported that spectrin studied from many HE patients exhibited a dimer self-association defect (type I HE). A mutation in the head of the spectrin chain was mostly found in type I HE. We have previously described one of the three known spectrin pathological variants shown on mild tryptic digest pattern. This variant was characterized by the appearance of an abnormal 65,000-dalton peptide (Sp ^I/65). Using nondenaturating gel electrophoresis, we describe in this paper a triplicated pattern of the spectrin tetramer bands which is found in heterozygous HE cases displaying the 65,000-dalton variant. Study of a homozygous case allowed us to characterize the electrophoretic mobility of the abnormal symmetrical spectrin tetramer (₂ ^I/65-₂) and to study the correlation between the fraction of this abnormal symmetrical tetramer found in heterozygous patients and the amount of the 65,000-dalton peptide observed in spectrin tryptic digests.     

Enzymatic deconjugation of catecholamines in human and rat plasma and red blood cell lysate

We have developed a method for enzymatic hydrolysis of both sulfated and glucuronidated catecholamines in plasma and red blood cell lysate. Hydrolysis occurs in the course of the radioenzymatic assay for catecholamines. In human plasma, catecholamines are conjugated almost entirely with sulfate while, in rat plasma, glucuronides are the main conjugates of epinephrine and dopamine but not norepinephrine. Rat plasma contains less percent conjugated catecholamine than human plasma. Human red blood cell lysate contains less conjugated catecholamine than plasma, whereas free E in lysate exceeds that of plasma and free NE has same level both in plasma and lysate. This method is useful in detecting total (free + sulfated + glucuronidated) catecholamines and the nature of conjugated catecholamines.     

Stimulation of Free Fatty Acid and Diacylglycerol Accumulation in Cerebrum and Cerebellum During Bicuculline-Induced Status Epilepticus. Effect of Pretreatment with α-Methyl-p-Tyrosine and p-Chlorophenylalanine

The pool size and composition of free fatty acids (FFA) and diglycerides (DG) from the cerebrum and cerebellum of rats undergoing bicuculline-induced seizures were studied. A fourfold increase in cerebral FFA occurred 3-4 min after bicuculline injection; arachidonic and stearic acids were the principal fatty acids accumulated. Cerebellar FFA also increased, but to a lesser extent. An increased production of arachidonic acid took place in the cerebrum as a function of time after bicuculline injection. Other fatty acids produced were oleic, palmitic, and docosahexaenoic acids. A twofold increase in cerebral arachidonic acid was seen at the time of the first generalized tonic-clonic convulsion. However, a 13- to 17-fold increase in arachidonic acid was seen approximately 5-6 min after bicuculline injection. The rise in other FFA was much smaller. Stearoyl- and arachidonoyl-DG were also accumulated. The drug alpha-methyl-p-tyrosine was found to (a) potentiate the bicuculline-stimulated release of cerebellar FFA, and (b) inhibit by 70% the production of stearoyl- and arachidonoyl-DG in the cerebrum and cerebellum. Basal production of FFA was stimulated by p-chlorophenylalanine, but the drug had no effect on the bicuculline-induced changes. Hydrolysis of phospholipids enriched in stearoyl-arachidonoyl groups, such as phosphatidylinositol of excitable membranes, may be stimulated during seizures.     

Selective inactivation of the 3'' to 5'' exonuclease activity of Escherichia coli DNA polymerase I by heat

Heat selectively inactivates the 3' to 5' exonuclease activity of E. coli DNA polymerase I, resulting in reduced dNTP turnover and lower fidelity of replication of homopolymer and natural DNA templates.     

Research on genetic abnormality in the hemolytic form of hereditary elliptocytosis with homozygosity for the spectrin alpha I/74 variant

We have undertaken to identify the spectrin gene mutation in a patient with a severe hemolytic form of Hereditary Elliptocytosis with homozygosity for the spectrin alpha I/74 variant. This variant corresponds to the presence of a 74,000 peptide which is produced during mild tryptic digestion of spectrin by cleavage at the Arginine-39 of the alpha I/80,000 domain of the spectrin alpha chain (595 amino acids). We hypothesized that the alpha I/74 mutation would be closed to the cleavage site Arg-39. A genomic library built with the patient's DNA was screened with a probe corresponding to a fragment of the alpha spectrin gene. Two clones were isolated, one being of paternal, the other of maternal origin. The subclones obtained contained the alpha spectrin gene exons 2 and 3 which encode for the first 88 amino-acids of the spectrin alpha I domain. The sequences obtained did not show any abnormality. The implications of these results are discussed.     

The plasma membrane of myxosporidian valve cells: freeze fracture data

Freeze fracturing of Myxosporidian spores reveals the occurrence of a continuous layer of transmembrane particles all over the surface area of the valve cells which form the spore envelope. These particles are densely packed all over the P face membrane. Due to their polygonal outline, their diameter (6-7 nm) and their central core, they resemble the particles forming the connections of gap junctions which metabolically couple the neighboring cells in animal tissues. In the present report, the role of the transmembrane particles is still hypothetical. However, they might represent a membrane structural specialization of the spores which are submitted to osmotic variations of the fluid external medium. Furthermore similar transmembrane particles are observed at the level of the septate junction which seals the valve cells. In this occurrence, they are arranged in a series of 40 double rows parallel to the suture of the spore envelope. These findings support the view that Myxosporidia are Metazoa and raise the problem of their origin.