Synchrone Replikation aller Chromosomen beiXenopus laevis

Summary Autoradiographics showed synchronous replication of all chromosomes inXenopus laevis.     

A histochemical study of immune destruction of the lymphopoietic system

Zusammenfassung Eine auffallende Zunahme von -Galactosidase kommt im lymphoetischen Säuger-Gewebe im Zusammenhang mit der immunologischen Auflösung dieses Systems vor. Die hernach auftretende Proliferation retikulärer Zellen steht im Zusammenhang mit der Regeneration dieses Organs. Diese Zellen enthalten eine reichliche Anzahl lysosomatischer Enzyme (z.B. -Galactosidase).

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This investigation was supported in part by Public Health Service Research Grants Nos. Ca 02624 and CA 02903 from the National Cancer Institute and in part by an institutional grant to the Detroit Institute of Cancer Research Division of the Michigan Cancer Foundation from the United Foundation of Greater Detroit, and Detroit General Hospital Research Corporation. Newaygo County Cancer Association. We wish to express our gratitude for stenographic assistance to Mrs.Connie Malucusky and MissPatricia Warzocha.     

Identification of an emerin–β-catenin complex in the heart important for intercalated disc architecture and β-catenin localisation

How mutations in the protein emerin lead to the cardiomyopathy associated with X-linked Emery-Dreifuss muscular dystrophy (X-EDMD) is unclear. We identified emerin at the adherens junction of the intercalated disc, where it co-localised with the catenin family of proteins. Emerin bound to wild type β-catenin both in vivo and in vitro. Mutating the GSK3β phosphorylation sites on β-catenin abolished this binding. Wild type but not mutant forms of emerin associated with X-EDMD were able to reduce β-catenin protein levels. Cardiomyocytes from emerin-null mice hearts exhibited erroneous β-catenin distribution and intercalated disc architecture. Treatment of wild type cardiomyocytes with phenylephrine, which inactivates GSK3β, redistributed emerin and β-catenin. Emerin was identified as a direct target of GSK3β activity since exogenous expression of GSK3β reduced emerin levels at the nuclear envelope. We propose that perturbation to or total loss of the emerin–β-catenin complex compromises both intercalated disc function and β-catenin signalling in cardiomyocytes.     

Asa Issie, Aramis and the origin of Australopithecus

The origin of Australopithecus, the genus widely interpreted as ancestral to Homo, is a central problem in human evolutionary studies. Australopithecus species differ markedly from extant African apes and candidate ancestral hominids such as Ardipithecus, Orrorin and Sahelanthropus. The earliest described Australopithecus species is Au. anamensis, the probable chronospecies ancestor of Au. afarensis. Here we describe newly discovered fossils from the Middle Awash study area that extend the known Au. anamensis range into northeastern Ethiopia. The new fossils are from chronometrically controlled stratigraphic sequences and date to about 4.1-4.2 million years ago. They include diagnostic craniodental remains, the largest hominid canine yet recovered, and the earliest Australopithecus femur. These new fossils are sampled from a woodland context. Temporal and anatomical intermediacy between Ar. ramidus and Au. afarensis suggest a relatively rapid shift from Ardipithecus to Australopithecus in this region of Africa, involving either replacement or accelerated phyletic evolution.     

A Teleonic Management Framework for Organizations

The hierarchical organization (HO) that has provided the prevailing model for business management for most of this century has been challenged repeatedly during the last 20 to 30 years. Matrix Management (MM), Total Quality Management (TQM), and Business Process Reengineering (BPR) are just three in the long line of approaches that have been suggested to remedy some of the problems with HO. Although these approaches have showed great promise, they either have been abandoned (MM), are on their way out (TQM), or are experiencing serious problems (BPR) in a large number of organizations that have tried to implement them. Yet many of these organizations have managed to make these approaches work. It is suggested in this paper that the main reasons for the failures do not lie in the models themselves, each of which have considerable merits, but in the absence of an overall theoretical framework, within which the various models could be validated and amalgamated. The authors are of the opinion that teleonics (proposed by Járos and Cloete, 1987) could serve as the basis for such a framework, which could thus be called the Teleonic Management Framework (TMF).     

Cytosolic pH regulates root water transport during anoxic stress through gating of aquaporins

Flooding of soils results in acute oxygen deprivation (anoxia) of plant roots during winter in temperate latitudes, or after irrigation, and is a major problem for agriculture. One early response of plants to anoxia and other environmental stresses is downregulation of water uptake due to inhibition of the water permeability (hydraulic conductivity) of roots (Lp(r)). Root water uptake is mediated largely by water channel proteins (aquaporins) of the plasma membrane intrinsic protein (PIP) subgroup. These aquaporins may mediate stress-induced inhibition of Lp(r) but the mechanisms involved are unknown. Here we delineate the whole-root and cell bases for inhibition of water uptake by anoxia and link them to cytosol acidosis. We also uncover a molecular mechanism for aquaporin gating by cytosolic pH. Because it is conserved in all PIPs, this mechanism provides a basis for explaining the inhibition of Lp(r) by anoxia and possibly other stresses. More generally, our work opens new routes to explore pH-dependent cell signalling processes leading to regulation of water transport in plant tissues or in animal epithelia.     

Deficiency in short-chain fatty acid beta-oxidation affects theta oscillations during sleep

In rodents, the electroencephalogram (EEG) during paradoxical sleep and exploratory behavior is characterized by theta oscillations. Here we show that a deficiency in short-chain acyl-coenzyme A dehydrogenase (encoded by Acads) in mice causes a marked slowing in theta frequency during paradoxical sleep only. We found Acads expression in brain regions involved in theta generation, notably the hippocampus. Microarray analysis of gene expression in mice with mutations in Acads indicates overexpression of Glo1 (encoding glyoxylase 1), a gene involved in the detoxification of metabolic by-products. Administration of acetyl-L-carnitine (ALCAR) to mutant mice significantly recovers slow theta and Glo1 overexpression. Thus, an underappreciated metabolic pathway involving fatty acid beta-oxidation also regulates theta oscillations during sleep.     

A mutation creating a potential illegitimate microRNA target site in the myostatin gene affects muscularity in sheep

Texel sheep are renowned for their exceptional meatiness. To identify the genes underlying this economically important feature, we performed a whole-genome scan in a Romanov x Texel F2 population. We mapped a quantitative trait locus with a major effect on muscle mass to chromosome 2 and subsequently fine-mapped it to a chromosome interval encompassing the myostatin (GDF8) gene. We herein demonstrate that the GDF8 allele of Texel sheep is characterized by a G to A transition in the 3' UTR that creates a target site for mir1 and mir206, microRNAs (miRNAs) that are highly expressed in skeletal muscle. This causes translational inhibition of the myostatin gene and hence contributes to the muscular hypertrophy of Texel sheep. Analysis of SNP databases for humans and mice demonstrates that mutations creating or destroying putative miRNA target sites are abundant and might be important effectors of phenotypic variation.