508 research outputs found

    Vorrichtung zur Beobachtung der dreidimensionalen Bewegung von Objekten, die in einer Flüssigkeit gehalten sind

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    Vorrichtung zur Beobachtung der dreidimensionalen Bewegung von Objekten (2), die in einer Flüssigkeit gehalten sind und deren Bewegung abhängig ist von den in der Flüssigkeit herrschenden örtlichen Eigenschaften wie der Temperatur, der chemischen Zusammensetzung oder den Lichtverhältnissen, wobei die Vorrichtung umfasst:- eine Beobachtungkammer (5) zur Aufnahme der mit den Objekten (2) versehenen Flüssigkeit,- eine erste Belichtungseinrichtung (6) mit einer Lichtquelle (7), eingerichtet zur lokalen Änderung der Eigenschaften in der Flüssigkeit,- eine optische Aufnahmeeinheit (12), eingerichtet zur optischen Erfassung der Objekte (2) in der Flüssigkeit, dadurch gekennzeichnet,dass die erste Belichtungseinrichtung (6) eingerichtet ist, gezielt eine Lichtmenge in einer gewünschten dreidimensionalen Verteilung in die Flüssigkeit der Beobachtungskammer (5) einzubringen, wobei die Flüssigkeit Bestandteile aufweist, die bei Einwirkung von optischen Lichtstrahlen einer bestimmten Wellenlänge ihre Eigenschaften ändern unddass die optische Aufnahmeeinheit eingerichtet ist, die Bewegung der Objekte (2) räumlich zu erfassen und in entsprechende elektronische Signale umzuwandeln

    Gating by Cyclic Gmp and Voltage in the α Subunit of the Cyclic Gmp–Gated Channel from Rod Photoreceptors

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    Gating by cGMP and voltage of the α subunit of the cGMP-gated channel from rod photoreceptor was examined with a patch-clamp technique. The channels were expressed in Xenopus oocytes. At low [cGMP] (<20 μM), the current displayed strong outward rectification. At low and high (700 μM) [cGMP], the channel activity was dominated by only one conductance level. Therefore, the outward rectification at low [cGMP] results solely from an increase in the open probability, Po. Kinetic analysis of single-channel openings revealed two exponential distributions. At low [cGMP], the larger Po at positive voltages with respect to negative voltages is caused by an increased frequency of openings in both components of the open-time distribution. In macroscopic currents, depolarizing voltage steps, starting from −100 mV, generated a time-dependent current that increased with the step size (activation). At low [cGMP] (20 μM), the degree of activation was large and the time course was slow, whereas at saturating [cGMP] (7 mM) the respective changes were small and fast. The dose–response relation at −100 mV was shifted to the right and saturated at significantly lower Po values with respect to that at +100 mV (0.77 vs. 0.96). Po was determined as function of the [cGMP] (at +100 and −100 mV) and voltage (at 20, 70, and 700 μM, and 7 mM cGMP). Both relations could be fitted with an allosteric state model consisting of four independent cGMP-binding reactions and one voltage-dependent allosteric opening reaction. At saturating [cGMP] (7 mM), the activation time course was monoexponential, which allowed us to determine the individual rate constants for the allosteric reaction. For the rapid rate constants of cGMP binding and unbinding, lower limits are determined. It is concluded that an allosteric model consisting of four independent cGMP-binding reactions and one voltage-dependent allosteric reaction, describes the cGMP- and voltage-dependent gating of cGMP-gated channels adequately

    Cyclic nucleotide-regulated channels (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

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    Cyclic nucleotide-gated (CNG) channels are responsible for signalling in the primary sensory cells of the vertebrate visual and olfactory systems.CNG channels are voltage-independent cation channels formed as tetramers. Each subunit has 6TM, with the pore-forming domain between TM5 and TM6. CNG channels were first found in rod photoreceptors [69, 98], where light signals through rhodopsin and transducin to stimulate phosphodiesterase and reduce intracellular cyclic GMP level. This results in a closure of CNG channels and a reduced &#8216;dark current&#8217;. Similar channels were found in the cilia of olfactory neurons [153] and the pineal gland [60]. The cyclic nucleotides bind to a domain in the C terminus of the subunit protein: other channels directly binding cyclic nucleotides include HCN, eag and certain plant potassium channels.Hyperpolarisation-activated, cyclic nucleotide-gated (HCN)The hyperpolarisation-activated, cyclic nucleotide-gated (HCN) channels are cation channels that are activated by hyperpolarisation at voltages negative to ~-50 mV. The cyclic nucleotides cyclic AMP and cyclic GMP directly activate the channels and shift the activation curves of HCN channels to more positive voltages, thereby enhancing channel activity. HCN channels underlie pacemaker currents found in many excitable cells including cardiac cells and neurons [56, 164]. In native cells, these currents have a variety of names, such as Ih, Iq and If. The four known HCN channels have six transmembrane domains and form tetramers. It is believed that the channels can form heteromers with each other, as has been shown for HCN1 and HCN4 [2]. High resolution structural studies of CNG and HCN channels has provided insight into the the gating processes of these channels [117, 121]. A standardised nomenclature for CNG and HCN channels has been proposed by the NC-IUPHAR subcommittee on voltage-gated ion channels [88]

    Cyclic nucleotide-regulated channels (CNG) in GtoPdb v.2021.3

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    Cyclic nucleotide-gated (CNG) channels are responsible for signalling in the primary sensory cells of the vertebrate visual and olfactory systems. CNG channels are voltage-independent cation channels formed as tetramers. Each subunit has 6TM, with the pore-forming domain between TM5 and TM6. CNG channels were first found in rod photoreceptors [83, 120], where light signals through rhodopsin and transducin to stimulate phosphodiesterase and reduce intracellular cyclic GMP level. This results in a closure of CNG channels and a reduced &#8216;dark current&#8217;. Similar channels were found in the cilia of olfactory neurons [181] and the pineal gland [71]. The cyclic nucleotides bind to a domain in the C terminus of the subunit protein: other channels directly binding cyclic nucleotides include hyperolarisation-activated, cyclic nucleotide-gated channels (HCN), ether-a-go-go and certain plant potassium channels.The HCN channels are cation channels that are activated by hyperpolarisation at voltages negative to ~-50 mV. The cyclic nucleotides cyclic AMP and cyclic GMP directly bind to the cyclic nucleotide-binding domain of HCN channels and shift their activation curves to more positive voltages, thereby enhancing channel activity. HCN channels underlie pacemaker currents found in many excitable cells including cardiac cells and neurons [64, 192]. In native cells, these currents have a variety of names, such as Ih, Iq and If. The four known HCN channels have six transmembrane domains and form tetramers. It is believed that the channels can form heteromers with each other, as has been shown for HCN1 and HCN4 [2]. High resolution structural studies of CNG and HCN channels has provided insight into the the gating processes of these channels [139, 146, 140]. A standardised nomenclature for CNG and HCN channels has been proposed by the NC-IUPHAR Subcommittee on voltage-gated ion channels [108]

    Cyclic nucleotide-regulated channels (CNG) in GtoPdb v.2023.1

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    Cyclic nucleotide-gated (CNG) channels are responsible for signalling in the primary sensory cells of the vertebrate visual and olfactory systems. CNG channels are voltage-independent cation channels formed as tetramers. Each subunit has 6TM, with the pore-forming domain between TM5 and TM6. CNG channels were first found in rod photoreceptors [83, 120], where light signals through rhodopsin and transducin to stimulate phosphodiesterase and reduce intracellular cyclic GMP level. This results in a closure of CNG channels and a reduced &#8216;dark current&#8217;. Similar channels were found in the cilia of olfactory neurons [181] and the pineal gland [71]. The cyclic nucleotides bind to a domain in the C terminus of the subunit protein: other channels directly binding cyclic nucleotides include hyperolarisation-activated, cyclic nucleotide-gated channels (HCN), ether-a-go-go and certain plant potassium channels.The HCN channels are cation channels that are activated by hyperpolarisation at voltages negative to ~-50 mV. The cyclic nucleotides cyclic AMP and cyclic GMP directly bind to the cyclic nucleotide-binding domain of HCN channels and shift their activation curves to more positive voltages, thereby enhancing channel activity. HCN channels underlie pacemaker currents found in many excitable cells including cardiac cells and neurons [65, 192]. In native cells, these currents have a variety of names, such as Ih, Iq and If. The four known HCN channels have six transmembrane domains and form tetramers. It is believed that the channels can form heteromers with each other, as has been shown for HCN1 and HCN4 [2]. High resolution structural studies of CNG and HCN channels has provided insight into the the gating processes of these channels [139, 146, 140]. A standardised nomenclature for CNG and HCN channels has been proposed by the NC-IUPHAR Subcommittee on voltage-gated ion channels [108]

    The steering gaits of sperm

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    Sperm are highly specialized cells, which have been subject to substantial evolutionary pressure. Whereas some sperm features are highly conserved, others have undergone major modifications. Some of these variations are driven by adaptation to mating behaviours or fitness at the organismic level. Others represent alternative solutions to the same task. Sperm must find the egg for fertilization. During this task, sperm rely on long slender appendages termed flagella that serve as sensory antennas, propellers and steering rudders. The beat of the flagellum is periodic. The resulting travelling wave generates the necessary thrust for propulsion in the fluid. Recent studies reveal that, for steering, different species rely on different fundamental features of the beat wave. Here, we discuss some examples of unity and diversity across sperm from different species with a particular emphasis on the steering mechanisms. This article is part of the Theo Murphy meeting issue ‘Unity and diversity of cilia in locomotion and transport’

    Islam Progresif dalam Gerakan Sosial Dawam Rahardjo (1942-2016)

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    The phenomenon of poverty and injustice that continues until now, making a lot of Muslim figures to think again about Islamic thought. The Indonesian Islamic figure, one of the serious discussions of this issue is M. Dawam Rahardjo—for instance, we called Dawam. Based on the problem, this study focuses on the concept of thinking and implementation of Progressive Islam Dawam by reviewing, analyze, and discussing his work with a historical sociological approach. This research is descriptive-analytical with the qualitative method which is reinforced through in-depth interview. The results show that Dawam’s thought is part of Progressive Islam. He accepted the reality of the modern world, such as pluralism, liberalism, and secularism, then embraced all three in the strengthening of religiosity in society. Dawam is one of the Islamic leaders who have contributed to social change. Implementation can be seen from various works that concern Islamic renewal and community empowerment. His attitude and behavior can be seen in the institutions he leads—LSAF (Lembaga Studi Agama dan Filsafat) and LP3ES (Lembaga Penelitian, Pendidikan dan Penerangan Ekonomi dan Sosial). His criticism of the unjust political-economic order, accompanied by various solutions offered. Dawam’s idea in stemming the economic system that harms small people is the concept of cooperative development. Dawam chose the path of civil society and avoided political pragmatism. According to him, the Islamic struggle in the political path only tends to exploit religion for sectarian interests.Fenomena kemiskinan dan ketidakadilan yang masih berlanjut hingga saat ini, membuat banyak tokoh muslim berpikir ulang mengenai pemikiran keislaman. Tokoh Islam Indonesia, salah satu yang serius membincang persoalan ini adalah M. Dawam Rahardjo—selanjutnya Dawam. Berdasarkan soal tersebut, kajian ini fokus pada konsep pemikiran dan implementasi Islam Progresif Dawam dengan menelaah, mengkaji, dan membahas karyanya dengan pendekatan historissosiologis. Penelitian ini bersifat deskriptif-analitis dengan metode kualitatif yang diperkuat melalui wawancara mendalam. Hasilnya menunjukkan bahwa pemikiran Dawam bagian dari Islam Progresif. Ia menerima kenyataan dunia modern, seperti pluralisme, liberalisme, dan sekularisme, kemudian merengkuh ketiganya dalam penguatan keberagamaan di masyarakat. Dawam adalah salah satu tokoh Islam  yang memiliki andil dalam perubahan sosial. Implementasinya bisa dilihat dari berbagai karya yang concern pada pembaharuan Islam dan pemberdayaan masyarakat. Sikap dan perilakunya, dapat dilihat dalam lembaga yang ia pimpin—LSAF (Lembaga Studi Agama dan Filsafat) dan LP3ES (Lembaga Penelitian, Pendidikan dan Penerangan Ekonomi dan Sosial). Kritiknya atas tatanan ekonomi politik yang tidak adil, diiringi dengan berbagai solusi yang ditawarkan. Gagasan Dawam dalam membendung sistem ekonomi yang merugikan rakyat kecil adalah konsep pembangunan koperasi. Dawam milih jalur civil society, dan menghindari pragmatisme politik. Menurutnya, perjuangan keislaman di jalur politik hanya cenderung mengeksploitasi agama untuk kepentingan sektarian
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