Molecular mechanism for the production of multiple form of MM creatine kinase

Summary Incubation of human, canine or rabbit MM creatine kinase with carboxypeptidase-N or B resulted in the production of 2 additional enzyme forms with increased anodal migration on polyacrylamide gels. The C-terminal amino acid of tissue MM creatine kinase from all 3 species was shown to be lysine, a specific substrate for carboxypeptidase-N and B.     

Affinity chromatography of monoamine oxidase

Summary A method is described for the purification of pig liver monoamine oxidase by affinity chromatography, using a colum with covalently bound pargyline.Acknowledgment. The authors wish to thank the University Research Council for financial support.     

Collagen of the calcified layer of human articular cartilage

Summary The distribution patterns of collagen types I, II and III were studied using immunofluorescent staining techniques in human articular cartilage, including the calcified layer. Tissue taken from femoral heads was stained with the appropriate antiserum. Adjacent sections were stained with von Kossa or Alizarin red to determine the distribution of calcium salts. Results indicate that endochondral ossification at this site occurs by calcium being deposited initially within a matrix of type II collagen.     

Hypothermia induced in mice by enzyme-mediated depletion of serotonin

Injection of a purified serotonin (and tryptophan)-degrading enzyme into mice produced a pronounced hypothermia when the mice were maintained at 22 degrees C, but not at 30 degrees C. Brain levels of serotonin and tryptophan were strikingly depleted, but concentrations of norepinephrine and dopamine remained unchanged.     

Germline gain-of-function mutations in SOS1 cause Noonan syndrome

Noonan syndrome, the most common single-gene cause of congenital heart disease, is characterized by short stature, characteristic facies, learning problems and leukemia predisposition. Gain-of-function mutations in PTPN11, encoding the tyrosine phosphatase SHP2, cause approximately 50% of Noonan syndrome cases. SHP2 is required for RAS-ERK MAP kinase (MAPK) cascade activation, and Noonan syndrome mutants enhance ERK activation ex vivo and in mice. KRAS mutations account for <5% of cases of Noonan syndrome, but the gene(s) responsible for the remainder are unknown. We identified missense mutations in SOS1, which encodes an essential RAS guanine nucleotide-exchange factor (RAS-GEF), in approximately 20% of cases of Noonan syndrome without PTPN11 mutation. The prevalence of specific cardiac defects differs in SOS1 mutation-associated Noonan syndrome. Noonan syndrome-associated SOS1 mutations are hypermorphs encoding products that enhance RAS and ERK activation. Our results identify SOS1 mutants as a major cause of Noonan syndrome, representing the first example of activating GEF mutations associated with human disease and providing new insights into RAS-GEF regulation.     

The recent expansion of Pluto's atmosphere

Stellar occultations--the passing of a relatively nearby body in front of a background star--can be used to probe the atmosphere of the closer body with a spatial resolution of a few kilometres (ref. 1). Such observations can yield the scale height, temperature profile, and other information about the structure of the occulting atmosphere. Occultation data acquired for Pluto's atmosphere in 1988 revealed a nearly isothermal atmosphere above a radius of approximately 1,215 km. Below this level, the data could be interpreted as indicating either an extinction layer or the onset of a large thermal gradient, calling into question the fundamental structure of this atmosphere. Another question is to what extent Pluto's atmosphere might be collapsing as it recedes from the Sun (passing perihelion in 1989 in its 248-year orbital period), owing to the extreme sensitivity of the equilibrium surface pressure to the surface temperature. Here we report observations at a variety of visible and infrared wavelengths of an occultation of a star by Pluto in August 2002. These data reveal evidence for extinction in Pluto's atmosphere and show that it has indeed changed, having expanded rather than collapsed, since 1988.     

Human cdc2 protein kinase is a major cell-cycle regulated tyrosine kinase substrate

cdc2 is a catalytic subunit of a protein kinase complex, called the M-phase promoting factor, that induces entry into mitosis and is universal among eukaryotes. In HeLa cells, cdc2 is shown to be the most abundant phosphotyrosine-containing protein and its phosphotyrosine content is subject to cell-cycle regulation. One site of cdc2 tyrosine phosphorylation in vivo is selectively phosphorylated by pp60c-src in vitro.     

Dynamics of collapsing and exploding Bose-Einstein condensates.

When atoms in a gas are cooled to extremely low temperatures, they will-under the appropriate conditions-condense into a single quantum-mechanical state known as a Bose-Einstein condensate. In such systems, quantum-mechanical behaviour is evident on a macroscopic scale. Here we explore the dynamics of how a Bose-Einstein condensate collapses and subsequently explodes when the balance of forces governing its size and shape is suddenly altered. A condensate's equilibrium size and shape is strongly affected by the interatomic interactions. Our ability to induce a collapse by switching the interactions from repulsive to attractive by tuning an externally applied magnetic field yields detailed information on the violent collapse process. We observe anisotropic atom bursts that explode from the condensate, atoms leaving the condensate in undetected forms, spikes appearing in the condensate wavefunction and oscillating remnant condensates that survive the collapse. All these processes have curious dependences on time, on the strength of the interaction and on the number of condensate atoms. Although the system would seem to be simple and well characterized, our measurements reveal many phenomena that challenge theoretical models.