共查询到20条相似文献,搜索用时 0 毫秒
1.
Summary The pineal of lower vertebrates characteristically contains true and modified photoreceptors with functional und structural homologies to retinal photoreceptors. Afferent nerves convey photic information from the pineal to sensory areas of the brain stem. Light also influences synthetic activity within the organ, controlling the rhythm in melatonin production which is generated endogenously. The molecular mechanisms underlying this rhythmic event are described and the hypothesis advanced that the pineal transduces several forms of environmental stimulus involved in the regulation of rhythmic function. 相似文献
2.
R. Fundele E. Jägerbauer G. Jarms 《Cellular and molecular life sciences : CMLS》1985,41(11):1471-1472
Summary The phosphoglycerate mutase isozyme patterns from cyclostomata, cartilaginous and bony fish were analyzed. The observed patterns indicate that a duplication of a single ancestral gene coding for phosphoglycerate mutase took place during the evolution of the gnathostome vertebrates. 相似文献
3.
W W Burggren 《Experientia》1988,44(11-12):919-930
In very few instances can the cardiovascular systems of adult 'lower' vertebrates serve as direct models for development in 'higher' vertebrates, primarily because numerous evolutionary specializations for preferential distribution of cardiac output between systemic tissues and gas exchange organs occur in the highly derived circulation of most extant lower vertebrates. Yet, the extensive literature on the cardiovascular anatomy and physiology of aquatic and air breathing fishes, amphibians and reptiles offers important conceptual insights into both patterns and mechanisms of development in birds and mammals. The primary contribution of such studies to the student of developing bird and mammal circulations is the clear demonstration that surprisingly complex hemodynamic function can develop from supposedly 'simple' cardiovascular systems typified by incompletely divided heart chambers. Thus, the hemodynamics of embryonic bird and mammal circulations should be determined by measurement, rather than inferred from structure. 相似文献
4.
5.
6.
H. Underwood 《Cellular and molecular life sciences : CMLS》1990,46(1):120-128
Summary The pineal has been identified as a major circadian pacemaker within the circadian system of a number of lower vertebrates although other pacemaking sites have been implicated as well. The rhythmic synthesis and secretion of the pineal hormone, melatonin, is suggested as the mechanism by which the pineal controls circadian oscillators located elsewhere. Both light and temperature cycles can entrain the pineal melatonin rhythm. The pineal, therefore, acts as a photo and thermoendocrine transducer which functions to synchronize internal cycle with cycles in the environment. A model is presented which portrays the pineal as a major component of a multioscillator circadian system and which suggests how these multiple circadian clocks are coupled to each other and to cycles of light and temperature in the external world. 相似文献
7.
H Underwood 《Experientia》1990,46(1):120-128
The pineal has been identified as a major circadian pacemaker within the circadian system of a number of lower vertebrates although other pacemaking sites have been implicated as well. The rhythmic synthesis and secretion of the pineal hormone, melatonin, is suggested as the mechanism by which the pineal controls circadian oscillators located elsewhere. Both light and temperature cycles can entrain the pineal melatonin rhythm. The pineal, therefore, acts as a photo and thermoendocrine transducer which functions to synchronize internal cycle with cycles in the environment. A model is presented which portrays the pineal as a major component of a 'multioscillator' circadian system and which suggests how these multiple circadian clocks are coupled to each other and to cycles of light and temperature in the external world. 相似文献
8.
H. Underwood 《Cellular and molecular life sciences : CMLS》1989,45(10):914-922
Summary The pineal has been identified as a major circadian pacemaker within the circadian system of a number of lower vertebrates although other pacemaking sites have been implicated as well. The rhythmic synthesis and secretion of the pineal hormone, melatonin, is suggested as the mechanism by which the pineal controls circadian oscillators located elsewhere. Both light and temperature cycles can entrain the pineal melatonin rhythm. The pineal, therefore, acts as a photo and thermoendocrine transducer which functions to synchronize internal cycle with cycles in the environment. A model is presented which portrays the pineal as a major component of a multioscillator circadian system and which suggests how these multiple circadian clocks are coupled to each other and to cycles of light and temperature in the external world. 相似文献
9.
Zusammenfassung Blutdruck und Durchmesser der Aorta abdominalis wurden in vivo bei Ruhe und während Sympathikusreizung zur Berechnung der Wandstärke und-Spannung direkt registriert. 相似文献
10.
11.
12.
Germline development in vertebrates and invertebrates 总被引:13,自引:0,他引:13
In all animals information is passed from parent to offspring via the germline, which segregates from the soma early in development
and undergoes a complex developmental program to give rise to the adult gametes. Many aspects of germline development have
been conserved throughout the animal kingdom. Here we review the unique properties of germ cells, the initial determination
of germ cell fates, the maintenance of germ cell identity, the migration of germ cells to the somatic gonadal primordia and
the proliferation of germ cells during development in vertebrates and invertebrates. Similarities in germline development
in such diverse organisms as Drosophila melanogaster, Caenorhabditis elegans, Xenopus laevis and Mus musculus will be highlighted.
Received 11 December 1998; received after revision 25 January 1999; accepted 25 January 1999 相似文献
13.
14.
Boris Strilić Tomáš Kučera Eckhard Lammert 《Cellular and molecular life sciences : CMLS》2010,67(19):3209-3218
The cardiovascular system developed early in evolution and is pivotal for the transport of oxygen, nutrients, and waste products
within the organism. It is composed of hollow tubular structures and has a high level of complexity in vertebrates. This complexity
is, at least in part, due to the endothelial cell lining of vertebrate blood vessels. However, vascular lumen formation by
endothelial cells is still controversially discussed. For example, it has been suggested that the lumen mainly forms via coalescence
of large intracellular vacuoles generated by pinocytosis. Alternatively, it was proposed that the vascular lumen initiates
extracellularly between adjacent apical endothelial cell surfaces. Here we discuss invertebrate and vertebrate cardiovascular
lumen formation and highlight the possible modes of blood vessel formation. Finally, we point to the importance of a better
understanding of vascular lumen formation for treating human pathologies, including cancer and coronary heart disease. 相似文献
15.
Sangeeta Chauhan Xinde Zheng Yue Ying Tan Boon-Hui Tay Shuhui Lim Byrappa Venkatesh Philipp Kaldis 《Cellular and molecular life sciences : CMLS》2012,69(22):3835-3850
Successful completion of the cell cycle relies on the precise activation and inactivation of cyclin-dependent kinases (Cdks) whose activity is mainly regulated by binding to cyclins. Recently, a new family of Cdk regulators termed Speedy/RINGO has been discovered, which can bind and activate Cdks but shares no apparent amino acid sequence homology with cyclins. All Speedy proteins share a conserved domain of approximately 140 amino acids called “Speedy Box”, which is essential for Cdk binding. Speedy/RINGO proteins display an important role in oocyte maturation in Xenopus. Interestingly, a common feature of all Speedy genes is their predominant expression in testis suggesting that meiotic functions may be the most important physiological feature of Speedy genes. Speedy homologs have been reported in mammals and can be traced back to the most primitive clade of chordates (Ciona intestinalis). Here, we investigated the evolution of the Speedy genes and have identified a number of new Speedy/RINGO proteins. Through extensive analysis of numerous species, we discovered diverse evolutionary histories: the number of Speedy genes varies considerably among species, with evidence of substantial gains and losses. Despite the interspecies variation, Speedy is conserved among most species examined. Our results provide a complete picture of the Speedy gene family and its evolution. 相似文献
16.
G. L. Waldbott 《Cellular and molecular life sciences : CMLS》1966,22(12):835-837
Zusammenfassung Fluor- und Kalziumwerte in verkalktem Aortengewebe wurden mit denen von makroskopisch normal erscheinendem Aortengewebe verglichen. Der Fluorgehalt der Aorta verschiedener Personen zeigte grosse individuelle Schwankungen, die unabhängig vom Kalziumgehalt waren. Eine direkte Korrelation des Aortenfluors mit dem Lebensalter wurde festgestellt. Die statistische Auswertung der Untersuchungen vonCall et al.2 ergab, dass der Fluorgehalt der Aorta unabhängig von demjenigen des Skelettes ist.
I appreciate the cooperation of Drs. E.Booth and J. R.Mc-Donald, pathologists at Hutzel and Harper Hospitals respectively, for furnishing the aorta specimens; D. L. J.Savage and Mr. J. M.Lucas of the Department of Statistics at Yale University for their statistical interpretation of my data; Dr. R. A.Kemp Harper, St. Bartholomew's Hospital, London, England, and Dr. G.Nalbone, Department of Industrial Medicine, University of Palermo, Italy, for furnishing the illustrations in Figures 1 and 2. 相似文献
I appreciate the cooperation of Drs. E.Booth and J. R.Mc-Donald, pathologists at Hutzel and Harper Hospitals respectively, for furnishing the aorta specimens; D. L. J.Savage and Mr. J. M.Lucas of the Department of Statistics at Yale University for their statistical interpretation of my data; Dr. R. A.Kemp Harper, St. Bartholomew's Hospital, London, England, and Dr. G.Nalbone, Department of Industrial Medicine, University of Palermo, Italy, for furnishing the illustrations in Figures 1 and 2. 相似文献
17.
18.
S. M. Armstrong 《Cellular and molecular life sciences : CMLS》1989,45(10):932-938
Summary Although pinealectomy has little influence on the circadian locomotor rhythms of laboratory rats, administration of the pineal hormone melatonin has profound effects. Evidence for this comes from studies in which pharmacological doses of melatonin are administered under conditions of external desynchronization, internal desynchronization, steady state light-dark conditions, and phase shifts of the zeitgeber. Taken together with recent findings on melatonin receptor concentration in the rat hypothalamus, particularly at the level of the suprachiasmatic nuclei, these results suggest that melatonin is a potent synchronizer of rat circadian rhythms and has a direct action on the circadian pacemaker. It is possible, therefore, that the natural role of endogenous melatonin is to act as an internal zeitgeber for the total circadian structure of mammals at the level of cell, tissue, organ, whole organism and interaction of that organism with environmental photoperiod changes. 相似文献
19.
Melatonin and circadian control in mammals 总被引:5,自引:0,他引:5
S M Armstrong 《Experientia》1989,45(10):932-938
Although pinealectomy has little influence on the circadian locomotor rhythms of laboratory rats, administration of the pineal hormone melatonin has profound effects. Evidence for this comes from studies in which pharmacological doses of melatonin are administered under conditions of external desynchronization, internal desynchronization, steady state light-dark conditions, and phase shifts of the zeitgeber. Taken together with recent findings on melatonin receptor concentration in the rat hypothalamus, particularly at the level of the suprachiasmatic nuclei, these results suggest that melatonin is a potent synchronizer of rat circadian rhythms and has a direct action on the circadian pacemaker. It is possible, therefore, that the natural role of endogenous melatonin is to act as an internal zeitgeber for the total circadian structure of mammals at the level of cell, tissue, organ, whole organism and interaction of that organism with environmental photoperiod changes. 相似文献
20.
Pineal melatonin rhythms and the timing of puberty in mammals 总被引:2,自引:0,他引:2
The direction of change in daylength provides the seasonal time cue for the timing of puberty in many mammalian species. The pattern of melatonin secretion from the pineal gland transduces the environmental light-dark cycle into a signal influencing the neuroendocrine control of sexual maturation. The change in duration of nocturnal melatonin secretion is probably the key feature of the melatonin signal which conveys daylength information. This information may also be used by neuroendocrine axes controlling seasonal changes in pelage colour, growth and metabolism. The mechanism of action of melatonin on neuroendocrine pathways is unknown. Although the ability to synthesize and secrete melatonin in a pattern that reflects the duration of the night may not occur until the postnatal period, the rodent and ovine foetus has the ability to respond in utero to photoperiodic cues to which its mother is exposed in late gestation. Transplacental passage of maternal melatonin is likely to be the mechanism by which photoperiodic cues reach the foetus. Species which do not exhibit seasonal patterns of puberty, such as the human, also secrete melatonin in a pattern which reflects the environmental light-dark cycle, but they do not respond reproductively to the seasonal melatonin information. 相似文献