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991.
To determine a possible relationship between organismal and molecular
evolution, the divergence patterns of gene families were examined by taking
special notice of functional difference, tissue distribution, and
intracellular localization of the members. A phylogenetic analysis of 25
different gene families revealed interesting patterns of divergence of
these families: Most gene duplications giving rise to different functions
antedate the vertebrates-arthropods separation. On the other hand, in a
group of members carrying virtually identical function to one another but
differing in tissue distribution (tissue- specific isoform), most gene
duplications have occurred independently in each of vertebrates and
arthropods after the separation of the two animal groups. In family members
encoding molecules localizing in cell compartments (compartmentalized
isoforms), the gene duplications antedate the animals-fungi separation. In
the cases of the Ca2+ pump and rab subfamilies, the compartmentalized
isoforms were shown to have diverged during the early evolution of
eukaryotes. A phylogenetic analysis of the tissue-specific isoforms from 26
different subfamilies revealed extensive gene duplications and rapid rates
of amino acid substitutions in the early evolution of chordates before the
separation of fishes and tetrapods. On the contrary, the genetic variations
are relatively low in the later period. This pattern of evolution observed
at the molecular level is correlated well with that of tissue evolution
based on fossil evidence and morphological data, and thus evolution at the
two levels may be related.
相似文献
992.
993.
994.
995.
Stability increments of 3' dangling ends on the core helices AUGCAU at various Na+ concentrations are reported. The results show that all 3' dangling ends except 3'U dangling at low Na+ concentrations can stabilize the helix and this stabilization is very sequence dependent. 相似文献
996.
997.
A gene of Penicillium funiculosum encoding an endoglucanase was cloned and expressed in Escherichia coli using the lacZ promoter of vector pUC 18. The gene product hydrolyzed carboxymethyl cellulose and showed strong cross reactivity with P. funiculosum anticellulases. 相似文献
998.
The results of the examination of sputum induced by the inhalation of nebulized hypertonic saline in the diagnosis of Pneumocystis carinii pneumonia (PCP) are presented. In suspected cases of PCP in patients who were either HIV antibody positive or were receiving immunosuppressive therapy, 46 induced sputum specimens were stained using both Grocott's modified Gomori methenamine silver nitrate (GMS) and immunofluorescence staining. In 12 specimens P. carinii cysts were detected by both methods, in four specimens by GMS staining only and in five specimens by immunofluorescence only. The sensitivity of induced sputum examination in the detection of P. carinii cysts was increased by using both of these staining methods on each sputum specimen and the need for more invasive methods of diagnosis was reduced. 相似文献
999.
1000.
V. A. Marchenko V. B. Fenik N. N. Preobrazhenskii M. M. Seredenko 《Neurophysiology》1995,27(5-6):307-314
Inspiratory activity generated by superfusedin situ semi-isolated medullo-spinal preparations of newborn (one-day-old) and four- to five-day-old rats was recorded from then. phrenicus before and after transverse sectioning of the ventrolateral part of the medulla (VLPM) at different levels. Under similar experimental conditions, the frequency of inspiratory discharges (ID) and their integral intensity, reflecting the volume and temporal parameters of inspiration, are much lower in one-day-old rats, as compared with those in four- to five-day-old animals. Specific roles of different VLPM levels in respiration control in young rats are demonstrated. Transection of the VLPM below the most rostral VLPM portion, corresponding to theM chemosensitive zone, caused a significant increase in the ID frequency and a decrease in the ID integral intensity. Transection performed below the intermediate VLPM region, corresponding to theS chemosensitive zone, resulted in a significant decrease in both ID frequency and ID integral intensity, up to total ID blockade in 5 of 12 1-day-old preparations. This finding can be interpreted as an indication of morphofunctional immaturity of the respiratory network in the caudal VLPM regions in newborn animals. Comparative analysis of ID pattern showed that this activity in one-day-old rats is more or less gasping-like, while that in four- to five-day-old animals is eupnoe-like. The results allow us to conclude that the level of maturity of morphofunctional organization of medullary respiratory networks considerably differs in newborn and older animals. The mechanisms responsible for formation and control of respiratory activity in early postnatal period of rats are discussed.Neirofiziologiya/Neurophysiology, Vol. 27, No. 5/6, pp. 387–395, September–December, 1995. 相似文献