A simple fluorimetric assay for the determination of carbamoyl phosphate in tissue extracts is described. In the assay, production of ATP from carbamoyl phosphate and ADP by carbamate kinase is coupled to the formation of NADPH, using glucose, hexokinase, NADP+, and glucose-6-phosphate dehydrogenase. Production of NADPH in this system proved to be equal to the amount of carbamoyl phosphate present. 相似文献
Rapid eye movement sleep behavior disorder (RBD) is a parasomnia characterized by dream enactment behavior during rapid eye movement sleep, which is generally related to damage of pontomedullary structures. Idiopathic RBD is a well-established risk factor for neurodegenerative disease; at least 40-65% of patients with idiopathic RBD will develop a defined neurodegenerative phenotype over 10 years. This is almost always a “synucleinopathy” (Parkinson’s disease, dementia with Lewy bodies, or multiple system atrophy). Often, patients develop a syndrome with overlapping parkinsonism and cognitive impairment. The ability of RBD to predict disease has major implications for development of neuroprotective therapy, by providing a high-risk prodromal group for neuro-protective trials. In addition, it allows testing of other predictive markers of neurodegeneration. Recent prospective studies found that idiopathic RBD patients with abnormal olfaction at baseline had a 65% 5-year risk of developing neurodegenerative disease, compared with a 14% risk in those with normal olfaction. Those with abnormal color vision had a 74% risk of neurodegenerative disease compared with 26% in those with normal vision. Additionally, neuroimaging markers of the sub-stantia nigra including dopaminergic functional imaging and transcranial ultrasound have been able to predict imminent development of defined neurodegenerative disease in RBD, although sensitivity and lead time have not been established. Future studies will continue to expand the list of predictive markers of neurodegeneration and will better define specificity, sensitivity, and lead time of prodromal markers.
A selection of normal human tissues was investigated for the presence of lamins B1, B2, and A-type lamins, using a panel
of antibodies specific for the individual lamin subtypes. By use of immunoprecipitation and two-dimensional immunoblotting
techniques we demonstrated that these antibodies do not cross-react with other lamin subtypes and that a range of different
phosphorylation isoforms is recognized by each antibody. The lamin B2 antibodies appeared to decorate the nuclear lamina in
all tissues examined, except hepatocytes, in which very little lamin B2 expression was observed. In contrast to previous studies,
which suggested the ubiquitous expression of lamin B1 in mammalian tissues, we show that lamin B1 is not as universally distributed
throughout normal human tissues as was to be expected from previous studies. Muscle and connective tissues are negative, while
in epithelial cells lamin B1 seemed to be preferentially detected in proliferating cells. These results correspond well with
those obtained for lamin B1 in chicken tissues. The expression of A-type lamins is most prominent in well-differentiated epithelial
cells. Relatively undifferentiated and proliferating cells in epithelia showed a clearly reduced expression of A-type lamins.
Furthermore, most cells of neuroendocrine origin as well as most hematopoietic cells were negative for A-type lamin antibodies.
Accepted: 4 February 1997 相似文献
To investigate the relationship between a protein’s sequence and its biophysical properties, we studied the effects of more than 100 mutations in Avena sativa light-oxygen-voltage domain 2, a model protein of the Per-Arnt-Sim family. The A. sativa light–oxygen–voltage domain 2 undergoes a photocycle with a conformational change involving the unfolding of the terminal helices. Whereas selection studies typically search for winners in a large population and fail to characterize many sites, we characterized the biophysical consequences of mutations throughout the protein using NMR, circular dichroism, and ultraviolet/visible spectroscopy. Despite our intention to introduce highly disruptive substitutions, most had modest or no effect on function, and many could even be considered to be more photoactive. Substitutions at evolutionarily conserved sites can have minimal effect, whereas those at nonconserved positions can have large effects, contrary to the view that the effects of mutations, especially at conserved positions, are predictable. Using predictive models, we found that the effects of mutations on biophysical function and allostery reflect a complex mixture of multiple characteristics including location, character, electrostatics, and chemistry. 相似文献
We observed mixed groups of dark-eyed juncos (Junco hyemalis) and grey-headed juncos (Junco caniceps) at baited sites in northern Arizona during the non-breeding season. In interspecific and inter-racial conflicts, J. caniceps dorsalis was dominant to J. caniceps caniceps and to two races of dark-eyed juncos. Junco caniceps dorsalis also fed significantly faster than any of the other juncos. For both species, feeding rates were approximately the same in large and small mixed-species groups, though in larger groups, individual grey-headed juncos won conflicts at a higher rate and individual dark-eyed juncos lost conflicts at a higher rate. Also, dark-eyed juncos fed at a significantly lower rate in groups comprised mostly of grey-headed juncos than in groups of similar size but composed mostly of conspecifics. Residency times and recapture probabilities were similar for the two species, suggesting little difference in over-winter survival. 相似文献
Flooding results in induction of anaerobic metabolism in many higher plants. As an important component of anaerobic energy production, alcohol dehydrogenase (ADH) activity increases markedly in response to flooding in white clover, Trifolium repens. Significant inter-individual variation in flood-induced ADH activity exists in natural populations of T. repens. The genetic basis of this variation was analyzed by offspring-midparent regression of data from 75 greenhouse reared families; the estimated heritability of flood-induced ADH activity was 0.55 (±0.13). Genetic variation in flood-induced ADH activity has pronounced effects on physiological response and flood tolerance in this species. ADH activity is positively correlated with the rate of ethanol production, indicating that observed in vitro activity differences are manifested in in vivo physiological function. T. repens plants with higher ADH activities during flooding have greater flood tolerance (measured as growth rate when flooded/unflooded growth rate). Variation in ADH activity during flooding accounts for more than 79% of the variance in flood tolerance. On the basis of a limited field survey of populations occupying three sites differing in exposure to flooding conditions, individuals from site C, the most frequently flooded site, expressed significantly higher average ADH activity when flooded than individuals from site A, a site with no history of flooding. Since ADH activity levels are not correlated with electrophoretic mobility variation in T. repens, this work supports previous suggestions that regulatory variation in enzyme activity may play a central role in biochemical adaptations to environmental stress. 相似文献