Familial transmission of a 3q;22p translocation, with partial trisomy of chromosome 3 in the propositus

A family, carrying a balanced 3q;22p translocation, was detected through a propositus who showed multiple congenital malformations. As there are no previous references of similar cases where identification techniques were performed, the authors present this material for consideration in the delineation of clinical syndromes associated with specific chromosomal anomalies.     

A new variant of glucosephosphate isomerase deficiency.

A new variant of glucose-6-phosphate isomerase deficiency is described. The enzyme kinetics and properties were studied. Genetic and electrophoretic data pointed to a double heterozygous state in the patient. These data are compared to the other variants described in the literature until now.     

Incorporation of (3H)-arachidonic acid into cattle retina lipids: high uptake in triacylglycerols, diacylglycerols, phosphatidylcholine and phosphatidylinositol.

The incubation of (³H)-arachidonic acid-prelabeled cattle retinas for 20 min in the presence of glucose under a gas phase of 5% carbon dioxide in oxygen showed uneven labeling in lipid classes. Total phospholipids, acylglycerides and free fatty acids contained 35, 37 and 31 per cent of the total radioactivity. In phosphatidylinositol and phosphatidylcholine almost 70% of the polar lipid (³H)-arachidonate was recovered. About 70% of the total fatty acid esterified in retina lipids was found in diacylglycerols, triacylglycerols, phosphatidylinositol and phosphatidylcholine. It is concluded that the cattle retina “in vitro” takes up free arachidonic acid and that this fatty acid is further unevenly acylated into lipids.The apolar fatty acyl residues of lipids display an independent turnover and their composition may be modified by acylation-deacylation reactions. In several cellular lipids, a differential turnover of the fatty acids as compared with other lipid moieties has been indicated, such as the case of phosphatidylinositol (1–3) and cardiolipin (4). The latter is enriched in the inner mitochondrial membrane where energy conservation processes take place and the former has been implicated in synaptic transmission (5) and related with a protein identified as the acetylcholine receptor (6). In brain phosphoinositides tetraenoic molecular species are by far the largest (2) and an active acylation-deacylation cycle of arachidonic acid occurs (7). However data regarding retina phosphoinositides composition and metabolism is limited to: fatty acid distribution (8), to some studies on the phosphodiester metabolism by ³²p (9) and to a study reporting that in frog rod outer segments and retina, polyphosphoinositides are undetectable (10). The purpose of the present investigation was to observe the (³H)-arachidonic acid labeling of acylglycerides and of phosphoglyceride classes of cattle retina.     

Common and rare species respond to similar niche processes in macroinvertebrate metacommunities

Ecologists have long investigated why communities are composed of a few common species and many rare species. Most studies relate rarity to either niche differentiation among species or spatial processes. There is a parallel between these processes and the processes proposed to explain the structure of metacommunities. Based on a metacommunity perspective and on data on stream macroinvertebrates from different regions of Brazil, we answer two questions. 1) Are sets of common and rare species affected by similar niche and spatial processes? 2) How does the community composition of common and of rare species differ? The main hypothesis we test is that common species are mainly affected by environmental factors, whereas rare species are mostly influenced by dispersal limitation. We used variation partitioning to determine the proportion of variation explained by the environment and space in common and rare species matrices. Contrary to our expectations, evidence supported the idea that both common and rare species are affected mainly by environmental factors, even after controlling for the differing information content between common and rare species matrices. Moreover, the abundance of some common species is also a good predictor of variation in rare species matrices. Niche differences are unlikely to be the sole cause of patterns of rarity in these metacommunities. We suggest that sets of common and rare species react to similar major environmental gradients and that rare species also respond to processes that operate at a more fine‐grained spatial scale, particularly biotic interactions. We extend the view that species sorting is the dominant process structuring metacommunities and argue that future studies focusing on rarity would benefit from a metacommunity perspective.     

Munc18-1 promotes large dense-core vesicle docking.

Secretory vesicles dock at the plasma membrane before Ca(2+) triggers their exocytosis. Exocytosis requires the assembly of SNARE complexes formed by the vesicle protein Synaptobrevin and the membrane proteins Syntaxin-1 and SNAP-25. We analyzed the role of Munc18-1, a cytosolic binding partner of Syntaxin-1, in large dense-core vesicle (LDCV) secretion. Calcium-dependent LDCV exocytosis was reduced 10-fold in mouse chromaffin cells lacking Munc18-1, but the kinetic properties of the remaining release, including single fusion events, were not different from controls. Concomitantly, mutant cells displayed a 10-fold reduction in morphologically docked LDCVs. Moreover, acute overexpression of Munc18-1 in bovine chromaffin cells increased the amount of releasable vesicles and accelerated vesicle supply. We conclude that Munc18-1 functions upstream of SNARE complex formation and promotes LDCV docking.