Inactivation pattern of the fragile X in heterozygous carriers

Summary Chromosome analysis with conventional staining, G-banding, and R-banding with 5-bromodeoxyuridine (BrdU) incorporation were performed on the lymphocytes of ten females, who were heterozygous for the fragile X-chromosome. Mental development of these females varied greatly: moderate to severe mental retardation was found in one and moderate mental retardation in four females. Normal to borderline intelligence was found in three and normal intelligence was noted in two further females. The discrepancy in percentage of active fragile X-chromosomes in the five females with moderate mental retardation was found to be 60–100% (mean value: 80%). The three women with normal to borderline intelligence showed a corresponding discrepancy from 57 to 86% (mean value: 77%) of active fragile X-chromosomes. Finally, two female heterozygotes for fragile X with normal intelligence showed 70 and 76% (mean value 73%) of active fragile X-chromosomes. The phenotypic features also did not seem to correspond with the X-chromosome inactivation pattern. Based on the data obtained, we suggest that there is no evident correlation between the frequency of the active fragile X chromosomes and the mental status of these females.     

Ultrastructural immunocytochemical evidence for peptidergic neurotransmission in the pond snail Lymnaea stagnalis

Summary Three neuronal systems of the pond snail Lymnaea stagnalis were immunocytochemically investigated at the ultrastructural level with the unlabeled peroxidase-antiperoxidase technique. Preliminary electrophysiological and cell-filling investigations have shown that a cluster of neurons which reacts positively with an antiserum against the molluscan cardio-active peptide FMRFamide, sends axons to the penis retractor muscle. In this muscle anti-FMRF-amide (aFM) positive axons form neuro-muscular synapses with (smooth) muscle fibers. The morphological observations suggest the aFM immunoreactive system to be involved in peptidergic neurotransmission. In the right parietal ganglion a large neuron (LYAC) is penetrated by aFM positive axons which form synapse-like structures (SLS) with the LYAC. The assumption that the SLS represent the morphological basis for peptidergic transmission is sustained by the observation that iontophoretical application of synthetic FMRFamide depolarizes the LYAC. The axons of a group of pedal anti-vasopressin (aVP) positive cells run in close vicinity to the cerebral ovulation (neuro-)-hormone producing cell system (CDC system) Synapses or SLS between the two systems were not observed. The fact that (bath) application of arg-vasopressin induces bursting in the CDC, may indicate that the vasopressin-like substance of the aVP cells is released non-synaptically.     

Malformative syndrome associated with a ring 10 chromosome and a translocated 10q/19 chromosome

Summary A male newborn with a ring 10 chromosome is described. The distal part of the long arm of chromosome 10, deleted during ring formation (10q25), is translocated to the short arm of chromosome 19.     

Familial occurrence of severe ulnar aplasia and lobster claw feet: A new syndrome

Summary In this paper we describe a previously unreported association of ulnar defect and lobster-claw deformity of the feet, occurring in four males belonging to two generations of the same family. Minor expression of the same ulnar reduction defect in female relatives suggests X-linked recessive inheritance, but an autosomal dominant with irregular expression cannot be excluded.Aspirant N.F.W.O.     

Localization of acid phosphatase in Saccharomyces cerevisiae: a clue to cell wall formation.

Acid phosphatase is present in two layers of the cell envelope of Saccharomyces cerevisiae. These are separated by another layer, which is free of acid phosphatase. We have evidence that the cell wall is built up in two stages, which are independent. In the first stage, the cell wall is built up during the formation of the bud. Glucanase vesicles are involved in this process. In the second stage, a thick layer is deposited at the inside against the new cell wall. This results in the thick, rigid wall of the mature yeast cell. This latter layer is probably assembled on the outer surface of the plasmalemma.     

ASSAY AND PROPERTIES OF 4-AMINOBUTYRIC-2-OXOGLUTARIC ACID TRANSAMINASE AND SUCCINIC SEMIALDEHYDE DEHYDROGENASE IN RAT BRAIN TISSUE

Abstract— The activity of 4-aminobutyric-2-oxoglutaric acid transaminase (GABA transaminase) and succinic semialdehyde dehydrogenase was determined in total rat brain homogenate. GABA transaminase activity was measured using a coupled enzyme method which utilizes endogenous succinic semialdehyde dehydrogenase to convert the formed succinic semialdehyde into succinate. The concurrently produced NADH was used as an estimate of GABA transaminase activity. This method could be used since it was shown that the dehydrogenase was about twice as active as the transaminase and because no significant accumulation of the intermediate succinic semialdehyde could be detected. GABA transaminase was inhibited by high ionic strength. In contrast NaCl decreased the apparent K _m and increased V _max for succinic semialdehyde dehydrogenase at high but not al low tissue concentrations. Increasing tissue concentration also resulted in a decrease of the apparent K _m, but did not change the V_max of succinic semialdehyde dehydrogenase and it is suggested that this enzyme can exist in two distinct states of aggregation, one with a high and one with a low affinity for succinic semialdehyde. The high affinity form of the enzyme is thought to prevent succinic semialdehyde from accumulation in the GABA transaminase assay. It is concluded that within certain limits the coupled enzyme method described here can be used for the assay of GABA transaminase activity.     

Recognition of different pools of phosphatidylglycerol in intact cells and isolated membranes of Acholeplasma laidlawii by phospholipase A2.

Phospholipase A2 (EC 3.1.1.4) from pig pancreas hydrolyzes phosphatidylglycerol in intact cells and isolated membranes of Acholeplasma laidlawii. Complete degradation of phosphatidylglycerol in intact cells at 37 degrees C does not result in lysis as shown by the retention of intracellular K+ ions and the cytoplasmic glucose-6-phosphatase, as well as the inability to detect activity of membrane-bound intracellular NADH-oxidase. A. laidlawii was grown on linoleic acid. Phospholipase A2 treatment of these cells at 5 degrees C, at which temperature the lipids are still in the liquid-crystalline state, results in a rapid breakdown of 50% of the phosphatidylglycerol. The residual phosphatidylglycerol can be hydrolyzed only at elevated temperatures and at much smaller rates, depending strongly on the incubation temperature. When membranes isolated from these cells are incubated at 5 degrees C, 70% of the phosphatidylglycerol is hydrolyzed immediately. The hydrolysis of the residual 30% is again strongly temperature dependent. Cells were grown on palmitate, elaidate, or oleate to investigate possible effects of the lipid phase transition on the accessibility of phosphatidylglycerol for phospholipase A2. Under conditions in which all the lipid is in the solid state, no hydrolysis occurs. When solid and liquid-crystalline lipid phases coexist, a limited hydrolysis of phosphatidylglycerol can be observed. The results demonstrate the disposition of phosphatidylglycerol in three different pools in the membrane of A. laidlawii. Phospholipase A2 has been used to discriminate between these pools and to estimate the amount of phosphatidylglycerol which is present in the liquid-crystalline phase. The present data, however, do not allow a definite localization of the phosphatidylglycerol pools.     

CMP-N-acetylneuraminic acid hydrolase, an ectoenzyme distributed unevenly over the hepatocyte surface.

The regional localization of CMP-N-acetylneuramic acid hydrolase at the hepatocyte surface was studied by using plasma membranes and hepatocytes isolated from rat liver. 1. By homogenization of the rat liver plasma membrane preparations and subsequent discontinuous sucrose gradient centrifugation, one light and two heavy membrane fractions were obtained. The origin of these three subfractions is discussed based on the specific activities in the three fractions of 5'-nucleotidase, alakaline phosphatase and Mg2+-ATPase and on electron microscopic examination of the fractions. Evidence is given suggesting that the light fraction is derived from the bile canalicular surface of the plasma membrane, and that the heavy fractions are derived predominantly from the sinusoidal and lateral surfaces of the liver cell membrane. CMP-AcNeu hydrolase was present at highest specific activity in one of the heavy subfractions. Therefore it is concluded that CMP-AcNeu hdyrolase is located preferentially in the sinusoidal and/or lateral plasma membrane parts of the liver cell. 2. Experiments with intact and disintegrated hepatocytes isolated from rat liver indicated that CMP-AcNeu hydrolase is located at the surface of the cell membrane, with its functional group directed to the outside.