1,744 research outputs found
Medial Ganglionic Eminence Progenitors Transplanted into Hippocampus Integrate in a Functional and Subtype-Appropriate Manner.
Medial ganglionic eminence (MGE) transplantation rescues disease phenotypes in various preclinical models with interneuron deficiency or dysfunction, including epilepsy. While underlying mechanism(s) remains unclear to date, a simple explanation is that appropriate synaptic integration of MGE-derived interneurons elevates GABA-mediated inhibition and modifies the firing activity of excitatory neurons in the host brain. However, given the complexity of interneurons and potential for transplant-derived interneurons to integrate or alter the host network in unexpected ways, it remains unexplored whether synaptic connections formed by transplant-derived interneurons safely mirror those associated with endogenous interneurons. Here, we combined optogenetics, interneuron-specific Cre driver mouse lines, and electrophysiology to study synaptic integration of MGE progenitors. We demonstrated that MGE-derived interneurons, when transplanted into the hippocampus of neonatal mice, migrate in the host brain, differentiate to mature inhibitory interneurons, and form appropriate synaptic connections with native pyramidal neurons. Endogenous and transplant-derived MGE progenitors preferentially formed inhibitory synaptic connections onto pyramidal neurons but not endogenous interneurons. These findings demonstrate that transplanted MGE progenitors functionally integrate into the postnatal hippocampal network
Classical Extended Conformal Algebras Associated with Constrained KP Hierarchy
We examine the conformal property of the second Hamiltonian structure of
constrained KP hierarchy derived by Oevel and Strampp. We find that it
naturallygives a family of nonlocal extended conformal algebras. We give two
examples of such algebras and find that they are similar to Bilal's V algebra.
By taking a gauge transformation one can map the constrained KP hierarchy to
Kuperschmidt's nonstandard Lax hierarchy. We consider the second Hamiltonian
structure in this representation. We show that after mapping the Lax operator
to a pure differential operator the second structure becomes the sum of the
second and the third Gelfand-Dickey brackets defined by this differential
operator. We show that this Hamiltonian structure defines the W-U(1)-Kac-Moody
algebra by working out its conformally covariant form.Comment: NHCU-HEP-94-28, 19 pages (Plain TeX
Gelfand-Dikii Brackets for Nonstandard Lax Equations
We generalize the construction of Gelfand-Dikii brackets to the case of
nonstandard Lax equations. We also discuss the possible origin of Kac-Moody
algebras present in such systems.Comment: 11 pages, Preprint no. UR1347, ER40685-79
Harsh parenting, deviant peers and adolescent risky behavior: understanding the meditational effect of adolescent attitudes and intentions
The current study examined mechanisms proposed to explain the roles of harsh parenting and association with deviant peers on adolescent involvement in tobacco, alcohol use and risky sexual behaviors. Prospective, longitudinal data came from youth who participated throughout adolescence (n= 451). Information regarding observed harsh parenting and adolescent\u27s relations with their peers was assessed in early adolescence (13 years), adolescent attitudes and intentions about risky behavior was assessed during middle adolescence (15 years), and engagement in risky behavior was assessed in late adolescence (18 years). Adolescent\u27s gender, parents\u27 education, parent tobacco and alcohol use and early adolescent\u27 involvement in risky behaviors were used as control variables. Both harsh parenting and involvement with deviant peers was directly related to adolescent engagement in tobacco use, alcohol use and sexual behavior. Also, adolescent attitudes and intentions mediated this relationship. That is, harsh parenting and involvement with deviant peers was no longer associated with risky behavior once attitudes and intentions about risky behaviors was added in the model. This was true even after parent substance use and adolescent early involvement in risky behaviors were taken into account
Extremely High Energy Neutrinos and their Detection
We discuss in some detail the production of extremely high energy (EHE)
neutrinos with energies above 10^18 eV. The most certain process for producing
such neutrinos results from photopion production by EHE cosmic rays in the
cosmic background photon field. However, using assumptions for the EHE cosmic
ray source evolution which are consistent with results from the deep QSO survey
in the radio and X-ray range, the resultant flux of neutrinos from this process
is not strong enough for plausible detection. A measurable flux of EHE
neutrinos may be present, however, if the highest energy cosmic rays which have
recently been detected well beyond 10^20 eV are the result of the annihilation
of topological defects which formed in the early universe. Neutrinos resulting
from such decays reach energies of the grand unification (GUT) scale, and
collisions of superhigh energy neutrinos with the cosmic background neutrinos
initiate neutrino cascading which enhances the EHE neutrino flux at Earth. We
have calculated the neutrino flux including this cascading effect for either
massless or massive neutrinos and we find that these fluxes are conceivably
detectable by air fluorescence detectors now in development. The
neutrino-induced showers would be recognized by their starting deep in the
atmosphere. We evaluate the feasibility of detecting EHE neutrinos this way
using air fluorescence air shower detectors and derive the expected event rate.
Other processes for producing deeply penetrating air showers constitute a
negligible background.Comment: 33 pages, including 12 eps figures, LaTe
Floating-disk parylene microvalve for self-regulating biomedical flow controls
A novel self-regulating parylene micro valve is presented in this paper with potential applications for biomedical flow controls. Featuring a free-floating bendable valve disk and two-level valve seat, this surface-micromachined polymeric valve accomplishes miniature pressure/flow rate regulation in a band-pass profile stand-alone without the need of power sources or active actuation. Experimental data of underwater testing results have successfully demonstrated that the microfabricated in-channel valve can regulate water flow at 0-80 mmHg and 0-10 µL/min pressure/flow rate level, which is perfectly suitable for biomedical and lab-on-a-chip applications. For example, such biocompatible microvalve can be incorporated in ocular implants for control of eye fluid drainage to fulfill intraocular pressure (IOP) regulation in glaucoma patients
Microfabricated Implantable Parylene-Based Wireless Passive Intraocular Pressure Sensors
This paper presents an implantable parylene-based wireless pressure sensor for biomedical pressure sensing applications specifically designed for continuous intraocular pressure (IOP) monitoring in glaucoma patients. It has an electrical LC tank resonant circuit formed by an integrated capacitor and an inductor coil to facilitate passive wireless sensing using an external interrogating coil connected to a readout unit. Two surface-micromachined sensor designs incorporating variable capacitor and variable capacitor/inductor resonant circuits have been implemented to realize the pressure-sensitive components. The sensor is monolithically microfabricated by exploiting parylene as a biocompatible structural material in a suitable form factor for minimally invasive intraocular implantation. Pressure responses of the microsensor have been characterized to demonstrate its high pressure sensitivity (> 7000 ppm/mmHg) in both sensor designs, which confirms the feasibility of pressure sensing with smaller than 1 mmHg of resolution for practical biomedical applications. A six-month animal study verifies the in vivo bioefficacy and biostability of the implant in the intraocular environment with no surgical or postoperative complications. Preliminary ex vivo experimental results verify the IOP sensing feasibility of such device. This sensor will ultimately be implanted at the pars plana or on the iris of the eye to fulfill continuous, convenient, direct, and faithful IOP monitoring
Implantable Unpowered Parylene MEMS Intraocular Pressure Sensor
This paper presents the first implantable, unpowered, parylene-based micro-electro-mechanical-systems (MEMS) pressure sensor for intraocular pressure (IOP) sensing. From in situ mechanical deformation of the compliant structures, this sensor registers pressure variations without power consumption/transduction. Micromachined high-aspect-ratio thin-walled tubes in different geometric layouts are exploited to obtain a high-sensitivity pressure response. An integrated packaging method has been successfully developed to realize suture-less implantation of the device. In vitro testing results have demonstrated that the IOP sensor can achieve 0.67 degree/mmHg angular sensitivity with a spiral-tube design, 3.43 µm/mmHg lateral sensitivity with a long-armed-tube design, and 0.38 µm/mmHg longitudinal sensitivity with a serpentine-tube design. This IOP sensor is designed to be implanted in the anterior chamber of the eye and anchored directly on the iris so that, under incident visible light, the pressure response of the implant can be directly observed from outside the eye, which enables faithful and unpowered IOP monitoring in glaucoma patient
Implantable parylene-based wireless intraocular pressure sensor
This paper presents a novel implantable, wireless,
passive pressure sensor for ophthalmic applications. Two
sensor designs incorporating surface-micromachined
variable capacitor and variable capacitor/inductor are
implemented to realize the pressure sensitive components.
The sensor is monolithically microfabricated using parylene
as a biocompatible structural material in a suitable form
factor for increased ease of intraocular implantation.
Pressure responses of the microsensor are characterized
on-chip to demonstrate its high pressure sensitivity (> 7000
ppm/mmHg) with mmHg level resolution. An in vivo animal
study verifies the biostability of the sensor implant in the
intraocular environment after more than 150 days. This
sensor will ultimately be implanted at the pars plana or iris of
the eye to fulfill continuous intraocular pressure (IOP)
monitoring in glaucoma patients
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