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901.
L S Kwok 《Journal of theoretical biology》1989,139(4):573-574
902.
L S Kwok 《Proceedings. Biological sciences / The Royal Society》1990,242(1305):141-147
Stromal swelling in human, cat, and rabbit cornea is biphasic, interpretable as an elementary cusp catastrophe proposed by Thom, with t* = log t and Q* = log Q (stromal charge Q, time t) as control parameters, and H0.5 (hydration H) as the state variable. A thermodynamic potential with two attractor regions, each with a local minimum, governs corneal stromal swelling. Transitions follow a 'saturation convention' whereby the second minimum is preferred upon availability. Corneal swelling is an example of a space-equivalent unfolding, where the transition plane moves in time. It is proposed that the transition plane coincides with the uncoupling of interfibrillary linkages or 'springs' in the corneal stroma, and is associated with a critical hydration of ca. 10 kg H2O per kilogram dry mass, and stromal charge ca. 1 x 10(-7) mol electrons. 相似文献
903.
904.
Debora Napoli Leonardo Lupori Raffaele Mazziotti Giulia Sagona Sara Bagnoli Muntaha Samad Erika K Sacramento Joanna Kirkpartick Elena Putignano Siwei Chen Eva Terzibasi Tozzini Paola Tognini Pierre Baldi Jessica CF Kwok Alessandro Cellerino Tommaso Pizzorusso 《EMBO reports》2021,22(1)
The authors regret having omitted grant attributions in the original publication. The funding section is herewith updated to reflect the change. “Funding attributed to Tommaso Pizzorusso was provided by EPIGEN Flagship project and PRIN2017HM8FA, funding attributed to Alessandro Cellerino was provided by Fondazione Pisa ETHERNA project, funding attributed to Pierre Baldi was provided by NIH (grant NIH ), funding attributed to Jessica Kwok was provided by the Leverhulme Trust project grant (RPG‐2018‐100).” GM123558相似文献
905.
906.
907.
Regulation of rat liver microsomal cholesterol 7 alpha-hydroxylase: presence of a cytosolic activator 总被引:2,自引:0,他引:2
Microsomal cholesterol 7 alpha-hydroxylase (EC 1.14.13.7) in rat liver was assayed by a single-isotope-incorporation method, and factors influencing its activity were studied. Crude cytosol contained a non-catalytic activator which was heat-stable and on-dialyzable. This activator enhanced cholesterol 7 alpha-hydroxylase catalytic activity. The stimulatory property of this cytosolic activator was not altered by cholestyramine feeding, and was retained after fractionation by ammonium sulfate of saturation up to 65%. 3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) stimulated hydroxylase activity at concentrations up to 90 micro M. ATP at concentration greater than 1.2 mM inhibited hydroxylase activity. NaF was stimulatory at concentrations up to 50 mM with a maximum stimulatory effect at 10 mM, and was antagonistic in effect to ATP. HMG-CoA and ATP at the above inhibitory concentrations and higher abolished the activating effect of the cytosolic factor. 相似文献
908.
Hoi Fei Kwok Peter Jurica Antonino Raffone Cees van Leeuwen 《Cognitive neurodynamics》2007,1(1):39-51
Spontaneous activity in biological neural networks shows patterns of dynamic synchronization. We propose that these patterns
support the formation␣of a small-world structure—network connectivity␣optimal for distributed information processing. We␣present
numerical simulations with connected Hindmarsh–Rose neurons in which, starting from random connection distributions, small-world
networks evolve as a result of applying an adaptive rewiring rule. The rule connects pairs of neurons that tend fire in synchrony,
and disconnects ones that fail to synchronize. Repeated application of the rule leads to small-world structures. This mechanism
is robustly observed for bursting and irregular firing regimes. 相似文献
909.
An experimental procedure and method of analysis are presented for calibration of a thin-beam force transducer. The beam transducer
can be produced and calibrated with a minimum coefficient of 10 ng (10−5 dyne) force per micron (10−4 cm) deflection, i.e.,k
B∼0.1 dyne/cm. Since beam deflections on the order of 0.1 μm can be detected, forces of a few nanograms can be resolved. Such
forces are common in mechanical experiments on microscopic bodies, e.g., biological cells, artificial membrane capsules, droplets,
etc. 相似文献
910.
Neuropeptide Y (NPY) is present in both extrinsic sympathetic adrenergic nerve terminals and intrinsic nerves of the gastrointestinal (GI) tract. Based on this localization a number of functions have been attributed to GI NPY including regulation of blood flow, intestinal fluid and electrolyte transport, and motility. There is nothing currently known, however, about the regulation of its secretion from GI nerves. The effect of cholinergic agonists and antagonists on secretion of NPY immunoreactivity (NPY-IR) from the isolated perfused rat stomach was investigated in the present study. Perfusate samples were extracted and concentrated on SepPak cartridges. Basal levels of NPY-IR varied between 98 and 147 fmol/min. Release was stimulated by high potassium concentrations (50 mM) and acetylcholine (ACh; 1 microM). ACh-induced secretion was unaffected by atropine, but inhibited by hexamethonium. Further evidence for a nicotinic component in the regulation of NPY-IR secretion was obtained by the finding of hexamethonium-induced reduction in basal secretion and stimulation of secretion by 1,1-dimethyl-4-phenyl-piperazinium (DMPP). In conclusion, cholinergic agonists and antagonists can modulate gastric NPY-IR secretion, and the cholinergic stimulatory effects are probably mediated via nicotinic receptor stimulation at the level of the intrinsic ganglia. 相似文献