79 research outputs found
Ricardo Miledi - an outstanding neurophysiologist of 20th-21st centuries (1927-2017)
No full textRicardo Miledi (16.09.1927-18.12.2017) is an outstanding neurophysiologist and biophysicist who made a great contribution to the study of synaptic transmission functions. He proved the key role of сalcium ions in the release of neuromediators, developed methods of receptor expression and membrane fragments integration into large oocytes that provided huge possibilities for thousands of researchers to study subtle mechanisms of transmembrane proteins function in norm and pathology. Ricardo Miledi received his MD degree in the National Autonomous University of Mexico and in 1954 he defensed his dissertation on the study of electrical nature of cardiac fibrillation in the National Institute of Cardiology (Mexico). In 1956-1958 he underwent training in Canberra Health Research Institute (Australia) in the laboratory headed by John Eccles (Nobel Prize 1963). In 1958 R. Miledi was invited to the Department of biophysics of University College London where in cooperation with Bernard Katz (Nobel Prize 1970) made a number of important discoveries in the analysis of acetylcholine receptor expression in denervated mucle; determination of the role of calcium in neuromediators release; analysis of membrane noise on neuromediator application to neuromuscular synapses; study of the effect of antibodies from patients with myasthenia gravis on neuromuscular transmission. In the early 1980s Ricardo Miledi implemented the method of functional expression in Xenopus frog oocytes of receptors and ion channels from messenger ribonucleic acid (mRNA). His heritage running the gamut is presented in more than 500 articles.</jats:p
Ricardo Miledi - Bibliography from Ricardo Miledi. 15 September 1927 — 18 December 2017
No full textFor nearly five decades, Ricardo Miledi was among the foremost researchers in elucidating how nerves transmit signals across synapses. Born in Chihuahua, Mexico, he qualified as a medical doctor, obtained a PhD with Arturo Rosenblueth and then, while in Canberra with John Eccles FRS, was invited by Bernard Katz FRS to join the Biophysics department at University College London, where he stayed from 1958 to 1984. Both independently and with Katz, he demonstrated that influx of calcium into the presynaptic nerve terminal is the essential trigger for the release of the neurotransmitter that carries signals across to the postsynaptic cell. He found that cutting the nerve to a frog's muscle increased the number and distribution of its muscle acetylcholine (ACh) receptors, which he purified and established as membrane proteins. Together with Katz, he introduced the technique of membrane noise analysis to determine the properties of the individual ion channels opened by ACh, providing the first functional characterization of a single receptor with integral ion channel. With Eric Barnard (FRS 1981), he pioneered a new approach facilitating the study of neurotransmitter receptors and ion channels by ‘transplanting’ them from brain and other tissues into large Xenopus oocyte cells by injection of messenger RNA. After moving to the University of California, Irvine, in 1984, he helped to establish the Mexican Institute for Neurobiology at Querétaro. Working in Irvine and Mexico he extended this oocyte expression technique to incorporate transplanted brain membranes, particularly from patients with epilepsy or other neurological disorders. He received many honours for his work, including the Royal Medal (1998), but was happiest working in his lab applying his extraordinary technical skills and imagination to study synaptic transmission and inspiring a generation of neuroscientists
Microtransplantation of cellular membranes from squid stellate ganglion reveals ionotropic GABA receptors
No full textAuthor Posting. © Marine Biological Laboratory, 2013. This article is posted here by permission of Marine Biological Laboratory for personal use, not for redistribution. The definitive version was published in Biological Bulletin 224 (2013): 47-52.The squid has been the most studied cephalopod, and it has served as a very useful model for investigating the events associated with nerve impulse generation and synaptic transmission. While the physiology of squid giant axons has been extensively studied, very little is known about the distribution and function of the neurotransmitters and receptors that mediate inhibitory transmission at the synapses. In this study we investigated whether γ-aminobutyric acid (GABA) activates neurotransmitter receptors in stellate ganglia membranes. To overcome the low abundance of GABA-like mRNAs in invertebrates and the low expression of GABA in cephalopods, we used a two-electrode voltage clamp technique to determine if Xenopus laevis oocytes injected with cell membranes from squid stellate ganglia responded to GABA. Using this method, membrane patches containing proteins and ion channels from the squid's stellate ganglion were incorporated into the surface of oocytes. We demonstrated that GABA activates membrane receptors in cellular membranes isolated from squid stellate ganglia. Using the same approach, we were able to record native glutamate-evoked currents. The squid's GABA receptors showed an EC50 of 98 μmol l–1 to GABA and were inhibited by zinc (IC50 = 356 μmol l–1). Interestingly, GABA receptors from the squid were only partially blocked by bicuculline. These results indicate that the microtransplantation of native cell membranes is useful to identify and characterize scarce membrane proteins. Moreover, our data also support the role of GABA as an ionotropic neurotransmitter in cephalopods, acting through chloride-permeable membrane receptors.Grass Foundation Fellowships to
L.C. and A.L. (www.grassfoundation.org). L.C. was additionally
supported by the Ph.D. in Neurophysiology program
of the University of Rome “La Sapienza.” All authors
were Grass Fellows. This work was supported by Ministero
della Sanita` Antidoping and PRIN project 2009 (to E.P.)
Caracterizacion electrofisiologica del receptor a serotonina de celulas gliales del cerebro adulto
No full textExpresion de genes para los receptores a glicina durante el desarrollo del sistema nervioso de la rata
No full textPhysiological characterization of human muscle acetylcholine receptors from ALS patients
No full textAmyotrophic lateral sclerosis (ALS) is characterized by progressive degeneration of motor neurons leading to muscle paralysis. Research in transgenic mice suggests that the muscle actively contributes to the disease onset, but such studies are difficult to pursue in humans and in vitro models would represent a good starting point. In this work we show that tiny amounts of muscle from ALS or from control denervated muscle, obtained by needle biopsy, are amenable to functional characterization by two different technical approaches: "microtransplantation" of muscle membranes into Xenopus oocytes and culture of myogenic satellite cells. Acetylcholine (ACh)-evoked currents and unitary events were characterized in oocytes and multinucleated myotubes. We found that ALS acetylcholine receptors (AChRs) retain their native physiological characteristics, being activated by ACh and nicotine and blocked by alpha-bungarotoxin (alpha-BuTX), d-tubocurarine (dTC), and galantamine. The reversal potential of ACh-evoked currents and the unitary channel behavior were also typical of normal muscle AChRs. Interestingly, in oocytes injected with muscle membranes derived from ALS patients, the AChRs showed a significant decrease in ACh affinity, compared with denervated controls. Finally, riluzole, the only drug currently used against ALS, reduced, in a dose-dependent manner, the ACh-evoked currents, indicating that its action remains to be fully characterized. The two methods described here will be important tools for elucidating the role of muscle in ALS pathogenesis and for developing drugs to counter the effects of this disease
Microtransplantation of acetylcholine receptors from normal or denervated rat skeletal muscles to frog oocytes.
No full textCell membranes, carrying neurotransmitter receptors and ion channels, can be ‘microtransplanted’
into frog oocytes. This technique allows a direct functional characterization of the
originalmembrane proteins, togetherwith any associated molecules theymay have, still embedded
in their natural lipid environment. This approach has been previously demonstrated to be very
useful to study neurotransmitter receptors and ion channels contained in cellmembranes isolated
from human brains.Here, we examined the possibility of using themicrotransplantation method
to study acetylcholine receptors from normal and denervated rat skeletal muscles.We found that
the muscle membranes, carrying their fetal or adult acetylcholine receptor isoforms, could be
efficiently microtransplanted to the oocyte membrane, making the oocytes become sensitive to
acetylcholine. These results show that oocytes injected with skeletalmuscle membranes efficiently
incorporate functional acetylcholine receptors, thus making the microtransplantation approach
a valuable tool to further investigate receptors and ion channels of human muscle diseases
<b>’Anomalous</b><b>’ </b><b>non-quantal endplate </b><b>potentials </b>
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