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1.
To ascertain the properties of an excitable membrane of the soma of giant neurons of mollusks, experiments were carried out to study the effect of conditioning shift of the membrane potential on the mechanism of action-potential generation. The effect of conditioning was assessed from changes in the action-potential curve and its first derivative, as well as from the curve of transmembrane currents under voltage clamp conditions. It was found that a change in membrane potential evokes at least two reactions which have opposite effects on the mechanism of generation of action potentials. These reactions evidently have different time characteristics. One of these does not differ notably from the reaction recorded for other excitable structures, and is manifested in the activation (with hyperpolarization) or inactivation (with depolarization) of the mechanism generating action potentials. The other reaction contributes either to an increase (with depolarization) or a decrease (with hyperpolarization) in the efficiency of this mechanism. Conditioning polarization also has a marked effect on the system responsible for repolarization of the membrane during generation of action potentials. This effect is manifested in a change in the reaction of this system to tetraethylammonium ions. The specific membrane systems sustaining excitability and reacting to changes in the strength of the membrane's electrical field were found to be very inert. After a shift in the potential to a given stable level a rearrangement, lasting sometimes tens of seconds, takes place in the membrane.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 1, pp. 91–99, January–February, 1970. 相似文献
2.
V P Lozovo? V A Kozlov V A Trufakin A V Shurlygina 《Biulleten' eksperimental'no? biologii i meditsiny》1986,102(7):82-84
The correlative analysis of diurnal rhythms of cell number and adenylate cyclase cellular activity was performed in the thymus, spleen and peripheral blood of Swiss mice, intact or thymectomized at the age of 3 months. The existence of somehow synchronized diurnal rhythms of cAMP exchange and cell recirculation was found in the peripheral lymphocyte pool and in the thymus. Diurnal rhythm of cAMP synthesis in peripheral lymphocytes was regulated by the thymus. Thymectomy led to desynchronization of recirculating processes and cyclic nucleotide metabolism in immunocompetent cells. 相似文献
3.
The levels of endogenous phytohormones and respiratory rate in nine sorts of flowers such as Cymbidium faberi Rolfe, Nopalxochia ackermannii Kunth and others were investigated both at full bloom and senescence and meanwhile the effect of exogenous phytohormones on prolonging the blossoms and promoting ethylene production were tested. There is a high content of endogenous ethylene in all the long-lived flowere, about 3–16 folds higer than the short-lived ones. There is a high level of ABA at full blooming flowers of short-lived flowers, in which there is no or only some cytokinins in it, but the ratio of CTK (6BA+zeatin)/ABA is smaller(l.7). The endogenous ABA reached a much higher level at senescence in all nine sorts of flowers, so it is reasonable to consider that it is ABA which plays an important role of regulation in controlling flower's senescence. There is a much higher level of GA3 and zeatin in the long-lived flowers which is not demonstrated in the shortlived ones. The respiratory rate is one of the factors controtling the longevity of flowers, but it does not play a decided role. Application of 6BA and zeatin prolongs distinctly orchid’s longevity, however exogenous IAA through the promotive action on ethylene production, evidently extends the longevity of the flowers of the Nopalxochia ackermannii Kunth. 相似文献
4.
Henry B. F. Dixon 《The Biochemical journal》1973,131(1):149-154
A simple case is considered in which the rate of a two-step reaction depends on pH because the intermediate formed in the first step has to gain (or lose) a proton before it can react in the second step, and in which the rate-determining step therefore changes with pH. The curves of reaction rate against pH are shown to be symmetrical, and the sharpest peak possible has a width at half its height of 1.53pH units, i.e. of 2log(3+2 radical2). Any particular curve for this situation proves to be identical with a curve that could be generated for the pH-dependence of a single-step reaction in which the rate is proportional to the concentration of a particular ionic form of a reactant. Curves for the latter situation, however, can have forms impossible for the former case in which the rate-determining step changes, but only if the protonations that activate and deactivate the reactant are co-operative. The peak can then become even sharper, and its width at half its height can fall to 1.14pH units, i.e. to 2log(2+ radical3). 相似文献
5.
C-banding patterns of the karyotypes of two closely related wild flax species, Linum austriacum L. (2n = 18) and Linum grandiflorum Desf. (2n = 16), were studied. The karyotypes of both species were similar in the chromosome morphology and size. In each species, metacentric and acrocentric chromosomes (1.7-4.3 microns) and one satellite chromosome were observed. In the karyotypes of the species studied, all homologous chromosome pairs were identified, and quantitative ideograms were constructed. Eight chromosome pairs in the two species had similar C-banding patterns. A low level of intraspecific polymorphism in the intercalary and telomeric C-bands was shown in both species. The results indicate that the genomes of two flax species originated from one ancestral genome with the main chromosome number of 8 or 9. Apparently, the doubling of chromosome number or loss of one chromosome with subsequent redistribution of the chromosome material in the ancestral form resulted in the divergence into two species, L. austriacum L. and L. grandiflorum Desf. A considerable similarity of chromosomes in these species provides evidence for their close phylogenetic relatedness, which makes it possible to place them in one section within the Linum genus. 相似文献
6.
O. N. Mukhametova 《Journal of Ichthyology》2010,50(8):660-670
Ichthyoplankton surveys are made in lagoon water bodies of the south-eastern part of Sakhalin (the Vavai-Chibisan system of
lakes, Lake Tunaicha, Lake Izmenchivoe) from April until November 2002–2007. Comparative characteristics of ichthyoplankton
complexes in the ice-free period is given. In the investigated lagoon lakes, differences in the species composition of the
ichthyoplankton by the number and time of appearance of the maxima of abundance of eggs and larvae are noted, and also related
to morphological structure and hydrological conditions of water bodies. In lagoon lake Izmenchivoe with a salinity not less
than 26‰, the eggs and larvae of marine fishes only takes place while, in Vavai-Chibisan lakes, that of freshwater fishes
only takes place. In brackish lake Tunaicha, the lowest number of fish species reproduce. In the Vavai-Chibisan system and
in Lake Izmenchivoe, one maximum of abundance of ichthyoplankton in June is recorded and, in Lake Tunaicha, two maxima (the
highest in June and less expressed in August) are recorded. Irrespective of the species composition, the ichthyoplankton complexes
of lagoon lakes have general traits determined by hydrological conditions of water bodies and by their general origin and
geographic situation: prevalence of eggs and larvae of low boreal fish species, the maximum species diversity in the late
spring-early summer, and decrease of abundance in cooler years. 相似文献
7.
Dietary intakes of tomatoes and tomato products containing lycopene have been shown to be associated with decreased risk of chronic diseases such as cancer and cardiovascular diseases in numerous studies. Serum and tissue lycopene levels have also been inversely related to the risk of lung and prostate cancers. Lycopene functions as a very potent antioxidant, and this is clearly a major important mechanism of lycopene action. In this regard, lycopene can trap singlet oxygen and reduce mutagenesis in the Ames test. However, evidence is accumulating for other mechanisms as well. Lycopene at physiological concentrations can inhibit human cancer cell growth by interfering with growth factor receptor signaling and cell cycle progression specifically in prostate cancer cells without evidence of toxic effects or apoptosis of cells. Studies using human and animal cells have identified a gene, connexin 43, whose expression is upregulated by lycopene and which allows direct intercellular gap junctional communication (GJC). GJC is deficient in many human tumors and its restoration or upregulation is associated with decreased proliferation. The combination of low concentrations of lycopene with 1,25-dihydroxyvitamin D3 exhibits a synergistic effect on cell proliferation and differentiation and an additive effect on cell cycle progression in the HL-60 promyelocytic leukemia cell line, suggesting some interaction at a nuclear or subcellular level. The combination of lycopene and lutein synergistically interact as antioxidants, and this may relate to specific positioning of different carotenoids in membranes. This review will focus on the growing body of evidence that carotenoids have unexpected biologic effects in experimental systems, some of which may contribute to their cancer preventive properties in models of carcinogenesis. Consideration of solubility in vitro, comparison with doses achieved in humans by dietary means, interactions with other phytochemicals, and other potential mechanisms such as stimulation of xenobiotic metabolism, inhibition of cholesterogenesis, modulation of cyclooxygenase pathways, and inhibition of inflammation will be considered. This review will point out areas for future research where more evidence is needed on the effects of lycopene on the etiology of chronic disease. 相似文献
8.
The present investigation deals with the effect of testosterone on each of the tissue components of the bursa of Fabricius: the endodermal epithelium, the mesenchyme, and the hemopoietic stem cells. Tissue combination experiments between testosterone-treated endoderm and normal mesenchyme and vice versa have shown that the androgen damages irreversibly the bursal epithelium. The latter is not seeded by hemopoietic stem cells and cannot undergo follicle formation when treated with high doses of testosterone. This occurs even if it is associated with a nontreated bursal mesenchyme. On the contrary, associations of testosterone-treated mesenchyme with normal endoderm result in normal bursa histogenesis. By using an original test of viability for lymphoid cells based on the application of the quail-chick marker system, we demonstrate that disappearance of hemopoietic cells in the endoderm results from their expulsion from the bursa and not from their death in situ. The conspicuous effect of testosterone on the bursa of Fabricius can be related to the levels of androgen receptors found in the organ. Typical cytosol androgen receptors are demonstrated in both bursal endoderm and mesoderm, although the amount in the former is higher. The concentration of binding sites in the bursa is >10 times higher than that in other organs such as lung and small intestine whose development is not affected by testosterone, contrasting with glucocorticosteroid receptor (measured by labeling with dexamethasone) found in the same concentration in all tissues. 相似文献
9.
10.
N A Babenko 《Ukrainski? biokhimicheski? zhurnal》1989,61(3):85-90
The metabolism of nuclear phospholipid acyl components of liver in uneven-aged rats was studied in vitro under different dietary fat implications. The activity of phospholipases A1 and A2 in the nuclei was found to sharply increase in animals pretreated with excess of fat. The incorporation of labelled palmitic, oleic, linoleic and arachidonic acid into nuclear phospholipids is under control of age and diet manipulations. The observed changes in the level of fatty acids metabolism are more pronounced in cell nuclei of the young rat liver. The lipid composition of cell nuclei in the test 3-month old animals does not differ from that of the control animals. At the same time dietary implications induce deep changes in the composition of nuclear lipids in 24-months old animals. 相似文献
11.
Regulation of the extent of splicing of influenza virus NS1 mRNA: role of the rates of splicing and of the nucleocytoplasmic transport of NS1 mRNA. 总被引:6,自引:2,他引:4
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Influenza virus NS1 mRNA is spliced by host nuclear enzymes to form NS2 mRNA, and this splicing is regulated in infected cells such that the steady-state amount of spliced NS2 mRNA is only about 10% of that of unspliced NS1 mRNA. This regulation would be expected to result from a suppression in the rate of splicing coupled with the efficient transport of unspliced NS1 mRNA from the nucleus. To determine whether the rate of splicing of NS1 mRNA was controlled by trans factors in influenza virus-infected cells, the NS1 gene was inserted into an adenovirus vector. The rates of splicing of NS1 mRNA in cells infected with this vector and in influenza virus-infected cells were measured by pulse-labeling with [3H]uridine. The rates of splicing of NS1 mRNA in the two systems were not significantly different, strongly suggesting that the rate of splicing of NS1 mRNA in influenza virus-infected cells is controlled solely by cis-acting sequences in NS1 mRNA itself. In contrast to the rate of splicing, the extent of splicing of NS1 mRNA in the cells infected by the adenovirus recombinant was dramatically increased relative to that occurring in influenza virus-infected cells. This could be attributed largely, if not totally, to a block in the nucleocytoplasmic transport of unspliced NS1 mRNA in the recombinant-infected cells. Most of the unspliced NS1 mRNA was in the nuclear fraction, and no detectable NS1 protein was synthesized. When the 3' splice site of NS1 mRNA was inactivated by mutation, NS1 mRNA was transported and translated, indicating that the transport block occurred because NS1 rRNA was committed to the splicing pathway. This transport block is apparently obviated in influenza virus-infected cells. These experiments demonstrate the important role of the nucleocytoplasmic transport of unspliced NS1 mRNA in regulating the extent of splicing of NS1 mRNA. 相似文献
12.
Flocks of birds are highly variable in shape in all contexts (while travelling, avoiding predation, wheeling above the roost). Particularly amazing in this respect are the aerial displays of huge flocks of starlings (Sturnus vulgaris) above the sleeping site at dawn. The causes of this variability are hardly known, however. Here we hypothesise that variability of shape increases when there are larger local differences in movement behaviour in the flock. We investigate this hypothesis with the help of a model of the self-organisation of travelling groups, called StarDisplay, since such a model has also increased our understanding of what causes the oblong shape of schools of fish. The flocking patterns in the model prove to resemble those of real birds, in particular of starlings and rock doves. As to shape, we measure the relative proportions of the flock in several ways, which either depend on the direction of movement or do not. We confirm that flock shape is usually more variable when local differences in movement in the flock are larger. This happens when a) flock size is larger, b) interacting partners are fewer, c) the flock turnings are stronger, and d) individuals roll into the turn. In contrast to our expectations, when variability of speed in the flock is higher, flock shape and the positions of members in the flock are more static. We explain this and indicate the adaptive value of low variability of speed and spatial restriction of interaction and develop testable hypotheses. 相似文献
13.
Gorlenko VM 《Mikrobiologiia》2004,73(5):633-643
The tendencies in the study of anoxygenic photosynthesizing bacteria (APB) are considered in the review in the historical aspect, since APB discovery till present day. The contribution made by the researchers of the Institute of Microbiology, Russian Academy of Sciences, to the study of the phylogeny, ecology, and morphophysiological diversity of APB is noted. At present, the molecular-biological approaches play a decisive role in ecology and taxonomy. The most important task at the modem stage of the development of microbiology is to maintain the continuity of the historically formed classical approaches in the study of APB diversity. 相似文献
14.
Immobilization of a hind limb of the cat in the resting position was found to result in morphological changes in the nerve supplying the medial head of the gastrocnemius muscle. A reduction in the diameter of the larger myelinated fibres (greater than 12 micrometers) concomitant with a reduction in the mean fibre diameter of the nerve were observed. This reduction in the mean fibre diameter of the nerve was found to be directly proportional to the period of immobilization. Prolonged immobilization beyond 8 weeks, resulted in the splitting of the myelin lamellae, formation of myelin rings and figures in some of the larger axons in addition to an abundant increase in collagen. These structural changes indicate a definite neural involvement in the disuse atrophy of the muscle as a result of immobilization extending for a period of 8 weeks and above. 相似文献
15.
P A Motavkin 《Biulleten' eksperimental'no? biologii i meditsiny》1976,81(2):244-246
Melanophores in the arteries of the base of the brain of kittens displayed pronounced variations in size and shape in response to the peripheral electrical stimulation of the vagus and the sympathetic nerves. These melanophores changed their size and shape under the influence of acetylcholine and noradrenaline solutions in vitro too. The present experiments showed melanophores to have a double effector innervation. 相似文献
16.
G G Polianskaia 《Tsitologiia》1988,30(6):732-738
A study was made of the karyotypic structure of sublines derived from the kangaroo rat's kidney (NBL-3) and skin fibroblasts of the Indian muntjac, available in the cell culture bank of the Institute of Cytology Acad. Sci. USSR. A comparative karyologic analysis was made of subline NBL-3 both contaminated with mycoplasma (NBLK) and decontaminated with antibiotics (NBLD). Authentic differences in cell distribution according to chromosome number in NBLK and NBLD variants were shown. Modal numbers of chromosomes are 11 and 17, respectively. The modal number for the Indian muntjac cell subline (MT) is 9. 60-80% of the cells had an identical karyotype (the main structural variant of the karyotype is MSVK). Using the G-banding technique, all the MSVK variants were shown to display constant karyotypes. In NBLK there are 5 pairs of homologous chromosomes and one metacentric. In NBLD, the number of homologous chromosomes increased in all the groups (hypotriploid karyotype). In subline MT 3 homologous chromosomes were found in groups I and IV, 2 in group III in addition to one X-chromosome. A comparison with the Indian muntjac karyotype showed the absence of marker chromosomes in MT. The analysis of additional SVK shows that the deviations from MSVK are caused mostly by changes in the number of homologous chromosomes within the groups. A study of the frequency of deviations in chromosome numbers observed in the groups from MSVK showed that different chromosomes were involved in karyotypic changes in the same way in the "low-chromosome" variants of NBLK and MT, and in different ways in NBLD. A comparison of the "premycoplasmic" variants of line NBL-3 with NBLK shows no differences in the parameters studied.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
17.
E Canon L G Timmermans 《Comptes rendus des séances de la Société de biologie et de ses filiales》1986,180(4):482-491
Using the Karnovsky and Roots modified by E1 Badawi and Schenk's technic for the cholinergic innervation and with the method of Lindvall and Bj?rklund modified by de la Torre and Surgeon for the adrenergic ones, we demonstrate the innervation of each tissular layer, in cervix, corpus and cornua of the uterus of the she-rat in pro-oestrus state. A statistic evaluation is established for the different areas. The density of cholinergic innervation is richer than the adrenergic one. The number of cholinergic fibers is maximum in the cervix. It decreases in corpus and cornua especially in the mucosal and sub-mucosal layers. The density of the muscular nervous network is predominant in the corpus versus the cervix. The number of adrenergic nerves is maximum in corpus it diminishes in the cervix and the cornua. In each region, the muscular adrenergic network domines over the other tissular layers. We confirm statistically morphometric non parametric observations of these other authors. 相似文献
18.
The tendencies in the study of anoxygenic photosynthetic bacteria (APB) are considered in the review in the historical aspect, from the discovery of APB till the present day. The contribution made by the researchers of the Institute of Microbiology, Russian Academy of Sciences, to the study of the phylogeny, ecology, and morphophysiological diversity of APB is noted. At present, molecular biological approaches play a decisive role in ecology and taxonomy. The most important task at the modern stage of the development of microbiology is to maintain the continuity of the historically formed classical approaches in the study of APB diversity. 相似文献
19.
The rate of oxidation of unithiol (sodium dimercaptopropansulfonate) by nitrite ion was determined in the course of the annual experiment at the Antarctic station Mirny in 1996-1997. The rhythmic fluctuations in the oxidation rate were found. It is shown that these fluctuations correlate with changes in the velocity of the Earth's forward-rotational movement by the action of the Sun and Moon. 相似文献
20.
G N Kryzhanovski? A A Shandra L S Godlevski? M Iu Karganov A M Mazarati R F Makul'kin 《Biulleten' eksperimental'no? biologii i meditsiny》1990,110(7):14-17
The peptide-containing fraction was emitted from the hippocampal and ventral mesencephalic region tissue of rats kindled with subconvulsant doses of corazol. Extracts were prepared by the help of hot acetic acid on the stage of generalized clonic-tonic seizure development. The intraventricular injection of VMR-extracts in relatively high dose increased seizure reactions which were induced in intact recipient rats by intraperitoneal corazol injection. The intraventricular injection of the extract in relatively low dose (100 times less) suppressed corazol-induced seizures in recipients. Data are discussed from the point of view of pathological epileptic system formation and the role played by peptides in supporting it's activity during pharmacological kindling. 相似文献