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Developmental changes in the calcium currents in embryonic chick ventricular myocytes 总被引:1,自引:0,他引:1
Summary Using the patch-clamp technique, we recorded whole-cell calcium current from isolated cardiac myocytes dissociated from the apical ventricles of 7-day and 14-day chick embryos. In 70% of 14-day cells after 24 hr in culture, two component currents could be separated from totalI
Ca activated from a holding potential (V
h) of –80 mV. L-type current (I
L) was activated by depolarizing steps fromV
h –30 or –40 mV. The difference current (I
T) was obtained by subtractingI
L, fromI
Ca.I
T could also be distinguished pharmacologically fromI
L in these cells.I
T was selectively blocked by 40–160 m Ni2+, whereasI
L was suppressed by 1 m D600 or 2 m nifedipine. The Ni2+-resistant and D600-resistant currents had activation thresholds and peak voltages that were near those ofI
T andI
L defined by voltage threshold, and resembled those in adult mammalian heart. In 7-day cells,I
T andI
L could be distinguished by voltage threshold in 45% (S cells), while an additional 45% of 7-day cells were nonseparable (NS) by activation voltage threshold. Nonetheless, in mostNS cells,I
Ca was partly blocked by Ni2+ and by D600 given separately, and the effects were additive when these agents were given together. Differences among the cells in the ability to separateI
T andI
L by voltage threshold resulted largely from differences in the position of the steady-state inactivation and activation curves along the voltage axis. In all cells at both ages in which the steady-state inactivation relation was determined with a double-pulse protocol, the half-inactivation potential (V
1/2) of the Ni2+-resistant currentI
L averaged –18 mV. In contrast,V
1/2 of the Ni2+-sensitiveI
T was –60 mV in 14-day cells, –52 mV in 7-dayS cells, and –43 mV in 7-day NS cells. The half-activation potential was near –2 mV forI
L at both ages, but that ofI
T was –38 mV in 14-day and –29 mV in 7-day cells. Maximal current density was highly variable from cell to cell, but showed no systematic differences between 7-day and 14-day cells. These results indicate that the main developmental change that occurs in the components ofI
Ca is a negative shift with, embryonic age in the activation and inactivation relationships ofI
T along the voltage axis. 相似文献
4.
Summary The present study deals with cytological observations, DNA and protein synthesis in artificially activated sea urchin eggs. The eggs were activated by means of Loeb's double treatment with butyric acid and hypertonic sea water. Most of the eggs ofHemicentrotus pulcherrimus divided when the chromosomes duplicated after formation of the first monaster and other eggs divided at a later cell cycle. In the eggs ofTemnopleurus toreumaticus, however, haploid division at the first cell cycle was observed predominantly.Activated eggs that were treated for 25 min with hypertonic sea water showed a marked uptake of3H-thymidine during the two periods of 30–40 min and 90–100 min after the double treatment. These periodic changes in the3H-thymidine uptake paralleled morphological changes within the nucleus. However, these periods of increased uptake were not observed in the eggs treated with hypertonic sea water for 60 min. During exposure to hypertonic sea water, the3H-thymidine-uptake by eggs activated with butyric acid decreased gradually. When the uptake of14C-valine by eggs was measured, a very low level was seen in unfertilized eggs. The level of uptake increased strikingly when the eggs were activated with butyric acid but was suppressed by the hypertonic treatment. However, removal of the eggs to sea water allowed the uptake to return to the former high level. This pattern suggests that the hypertonic treatment has an inhibitory effect on the synthesis of protein (or enzymes) which obstruct cleavage induction. 相似文献
5.
A winter geometrid moth, Inurois punctigera, shows sympatric and genetically isolated seasonal populations (i.e. early‐ and late‐winter populations) in the cold regions of Japan, whereas it shows only mid‐winter populations in the warm regions. Variation in adult flight phenology on a large geographic scale along latitudinal environmental gradients has been described, but the phenological variation on a more local scale along altitudinal environmental gradients has not yet been characterized. In the present study, we assessed the flight phenology at high‐ and low‐elevation areas in Mt. Rokko, Hyogo, Japan. First, we revealed that flight period was not disrupted in mid‐winter, even at high‐elevation areas (>660 m) but the population abundance was much lower in high‐elevation areas than in low‐elevation areas. Then, in the following two seasons, we investigated I. punctigera abundance, winter harshness (i.e. winter temperature) and their host plant abundance in nine closely located stations in Mt. Rokko. A generalized linear mixed model analysis indicated a greater effect of winter temperature on I. punctigera abundance compared to available food resources, suggesting that differences in winter harshness among elevation shapes the gradient of I. punctigera abundance along altitude. Our findings suggest that harsh conditions during winter function as selective agents on mid‐winter types of I. punctigera, and this could be involved in the divergence between sympatric early‐ and late‐winter populations of I. punctigera. 相似文献
6.
Yoshiro Naito Hisashi Sawada Makiko Oboshi Aya Fujii Shinichi Hirotani Toshihiro Iwasaku Yoshitaka Okuhara Akiyo Eguchi Daisuke Morisawa Mitsumasa Ohyanagi Takeshi Tsujino Tohru Masuyama 《PloS one》2013,8(10)
Although iron is reported to be associated with the pathogenesis of chronic kidney disease, it is unknown whether iron participates in the pathophysiology of nephrosclerosis. Here, we investigate whether iron is involved in the development of hypertensive nephropathy and the effects of iron restriction on nephrosclerosis in salt- loaded stroke-prone spontaneously hypertensive rats (SHRSP). SHRSP were given either a normal or high-salt diet for 8 weeks. Another subset of SHRSP were fed a high-salt with iron-restricted diet. SHRSP given a high-salt diet developed severe hypertension and nephrosclerosis. As a result, survival rate was decreased after 8 weeks diet. Importantly, massive iron accumulation and increased iron content were observed in the kidneys of salt-loaded SHRSP, along with increased superoxide production, urinary 8-Hydroxy-2′-deoxyguanosine excretion, and urinary iron excretion; however, these changes were markedly attenuated by iron restriction. Of interest, expression of cellular iron transport proteins, transferrin receptor 1 and divalent metal transporter 1, was increased in the tubules of salt-loaded SHRSP. Notably, iron restriction attenuated the development of severe hypertension and nephrosclerosis, thereby improving survival rate in salt-loaded SHRSP. Taken together, these results suggest a novel mechanism by which iron plays a role in the development of hypertensive nephropathy and establish the effects of iron restriction on salt-induced nephrosclerosis. 相似文献
7.
Furochi H Tamura S Mameoka M Yamada C Ogawa T Hirasaka K Okumura Y Imagawa T Oguri S Ishidoh K Kishi K Higashiyama S Nikawa T 《FEBS letters》2007,581(30):5743-5750
Intact osteoactivin, a novel type I membrane glycoprotein, were shed at a dibasic motif in the juxtamembrane region in C2C12 myoblasts. Extracellular fragments were secreted into the culture media by a putative metalloprotease. Extracellular fragments of osteoactivin, but not control protein, induced matrix metalloprotease-3 (MMP-3) expression in NIH-3T3 fibroblasts. Epidermal growth factor (ERK) kinase inhibitors inhibited the osteoactivin-mediated MMP-3 expression, whereas the extracellular fragment of osteoactivin activated ERK1/2 and p38 in the mitogen-activated protein kinase pathway. Our results suggest that the extracellular fragments of osteoactivin produced by shedding act as a growth factor to induce MMP-3 expression via the ERK pathway in fibroblasts. 相似文献
8.
We have recently shown that autophagy is induced by ischemia and reperfusion in the mouse heart in vivo. Ischemia stimulates autophagy through an AMP activated protein kinase (AMPK)-dependent mechanism, whereas reperfusion after ischemia stimulates autophagy through a Beclin 1-dependent, but AMPK-independent, mechanism. Autophagy plays distinct roles during ischemia and reperfusion: autophagy may be protective during ischemia, whereas it may be detrimental during reperfusion. We will discuss the role of AMPK in mediating autophagy during myocardial ischemia in vivo. 相似文献
9.
Miyata Seiko Otake Hironao Fujishiro Hiroshige Iwamoto Kunihiro Noda Akiko Sone Michihiko Ozaki Norio 《Sleep and biological rhythms》2022,20(3):403-411
Sleep and Biological Rhythms - Sleep problems and obstructive sleep apnea (OSA) increase with age and disturb life in old age. Positional therapy is one option to treat OSA, but the differences in... 相似文献
10.
Seiko Miyata Sayumi Kawai Kumiko Honda Kunihiro Iwamoto Norio Ozaki 《Biological Rhythm Research》2019,50(2):171-179
Insufficient sleep and irregular sleep/wake rhythm are common problems among university students. We investigated the effect of sleep/wake rhythm and excessive daytime sleepiness (EDS) on the cortical oxygenation as measured by near-infrared spectroscopy (NIRS) and cognitive performance in university students. Peak- and integral values by a word fluency task were measured with NIRS. EDS was evaluated by the Epworth sleepiness scale (ESS), and performance function was evaluated using N-back task. Peak cerebral oxygenation was significantly correlated with ESS, bedtime, wake-up time, and median time of sleep. Accuracy on 2-back task was significantly correlated with integral value. Peak- and integral values were significantly lower, and bedtime and median time of sleep were significantly delayed in the EDS group than in the non-EDS group. EDS accompanied by delayed sleep/wake rhythm and short sleep duration may play an important role in decreasing daytime brain activity and cognitive performance. 相似文献