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PubMed1994

A motor-driven miniature multiple microelectrode manipulator for recording from the cortical neuropile of the awake monkey in operant behavior paradigms.

An improved version of the Blum and Feldman multiple microelectrode manipulator is described. The main innovation is a design based on miniaturization and light weight (75 g), which allows head mounting with minimal disturbance to the animal in awake monkey operant behavior studies. The major features of the previously described model are preserved: simultaneous independent manipulation of four microelectrodes, in order to record from at least four single units, that may be crosscorrelated. With the new design better adjustment of intermicroelectrode distances for studies of interneural distances of 300 microns to 7 mm, and an easier automatic, computer-controlled monitoring of distances transversed into the brain are possible.

Animals↗

PubMed1992

Detection of polymorphisms of human DNA after polymerase chain reaction by miniaturized SDS-PAGE.

PCR followed by SDS-PAGE in miniaturized non-denaturing gels permits in some cases the identification of single base pair substitutions in small DNA fragments and therefore, the study of human DNA polymorphisms. The usefulness of the system in forensic science is investigated by typing the HLA-DQA1 locus and the VNTR recognized with the probe pMCT118 (locus D1S80) and it shows to be advantageous over previously published methods for typing the MCT118 system, whereas in HLA-DQA1 typing for forensic casework, both dot-blot with ASO probes and this method could be complementary.

Base Sequence↗

PubMed1994

A rise in postsynaptic Ca2+ potentiates miniature excitatory postsynaptic currents and AMPA responses in hippocampal neurons.

We have investigated the site of expression of the potentiation of excitatory postsynaptic currents (EPSCs) induced by the activation of postsynaptic voltage-sensitive Ca2+ channels, by examining the effect of depolarizing pulses on miniature (m) EPSCs and responses to AMPA. Application of voltage pulses caused a approximately 2.5-fold increase in the mean amplitude of mEPSCs. This NMDA receptor-independent potentiation of mEPSC amplitudes was transient, returning to control values within 30-40 min. The potentiation was associated with a decrease in the number of small amplitude events and an increase in the number, as well as the maximum amplitude, of the larger events, with no apparent change in mEPSC kinetics. Accompanying the increase in mEPSC amplitudes, there was a 1.6-fold increase in the apparent frequency of events. Voltage pulse-induced potentiation was completely blocked by the inclusion of the Ca2+ chelator BAPTA in the recording pipette. Responses to repeated applications of AMPA were also potentiated following the application of voltage pulses, and the time course of this potentiation was similar to that observed with the mEPSCs. Our data indicate that rises in intracellular Ca2+ that occur independently of NMDA receptor activation can result in a potentiation of quantal size, which is due to an increase in the postsynaptic sensitivity of non-NMDA receptors.

Animals↗

PubMed1996

Considerations in miniaturizing simplified agro-ecosystems for advanced life support.

Miniaturizing the Earth's biogeochemical cycles to support human life during future space missions is the goal of the NASA research and engineering program in advanced life support. Mission requirements to reduce mass, volume, and power have focused efforts on (1) a maximally simplified agro-ecosystem of humans, food crops, and microbes; and, (2) a design for optimized productivity of food crops with high light levels over long days, with hydroponics, with elevated carbon dioxide and other controlled environmental factors, as well as with genetic selection for desirable crop properties. Mathematical modeling contributes to the goals by establishing trade-offs, by analyzing the growth and development of experimental crops, and by pointing to the possibilities of directed phasic control using modified field crop models to increase the harvest index.

Agriculture↗

PubMed1990

Miniaturization of a liquid membrane sensor for the determination of bile acids.

The preparation of a compound liquid ion exchanger used for the miniaturization of bile acid sensitive microelectrode is described. The liquid ion exchanger is 2% benzyldimethylhexadecylammonium cholate in decanol/0.1 M hexadecyltributylammonium taurocholate in 5% hexachlorobenzene, 0.5% bromoacetanilide O-dichlorobenzene. The slopes, detection limits, selectivity coefficients, drifts and response time of the various bile acid sensitive microelectrodes are evaluated and compared.

Bile Acids and Salts↗

PubMed1991

A miniature Clark-type oxygen electrode using a polyelectrolyte and its application as a glucose sensor.

A miniature Clark-type oxygen electrode was fabricated by anisotropically etching silicon. A two-gold-electrode configuration was used and a double-layered gas-permeable membrane was formed directly on the electrolyte, poly(vinyl-4-ethylpyridinium bromide) in the sensitive area. These materials improved the electrode's stability in long-term storage and sterilization tolerance to a practical level. The 90% response time averaged 80 s and residual current 10%, with a good linear calibration curve. The oxygen electrode was also used to make an integrated sensor for the simultaneous determination of glucose and oxygen. The glucose sensor's response time was 50-110 s, with good linearity in glucose concentrations between 56 microM and 1.1 mM at 37 degrees C, pH 7.0.

Biosensing Techniques↗

PubMed1992

Calibration in dogs of a subcutaneous miniaturized glucose sensor using a glucose meter for blood glucose determination.

The feasibility of calibrating a glucose sensor by using a wearable glucose meter for blood glucose determination and moderate variations of blood glucose concentration was assessed. Six miniaturized glucose sensors were implanted in the subcutaneous tissue of conscious dogs, and the parameters used for the in vivo calibration of the sensor (sensitivity coefficient and extrapolated current in the absence of glucose) were determined from values of blood glucose and sensor response obtained during glucose infusion. (1) Venous plasma glucose level and venous total blood glucose level were measured simultaneously on the same sample, using a Beckman analyser and a Glucometer II, respectively. The regression between plasma glucose (x) and whole blood glucose (y) was y = 1.12x-0.08 mM (n = 114 values, r = 0.96, p = 0.0001). The error grid analysis indicated that the use of a Glucometer II for blood glucose determination was appropriate in dogs. (2) The in vivo sensitivity coefficients were 0.57 +/- 0.11 nA mM-1 when determined from plasma glucose, and 0.51 +/- 0.07 nA mM-1 when determined from whole blood glucose (t = 1.53, p = 0.18, n.s.). The background currents were 0.88 +/- 0.57 nA when determined from plasma glucose, and 0.63 +/- 0.77 nA when determined from whole blood glucose (t = 0.82, p = 0.45, n.s.). (3) The regression equation of the estimation of the subcutaneous glucose level obtained from the two methods was y = 1.04x + 0.56 mM (n = 171 values, r = 0.98, p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1996

Novel hexacyanoferrate (III)-modified carbon electrodes: application in miniaturized biosensors with potential for in vivo glucose sensing.

We adapted a new technology for the modification of carbon base electrodes for use as probe-type, potentially implantable glucose sensors. Carbon rods (diameter 0.3 mm) were modified by repeated potential cycling in 0.1 M potassium hexacyanoferrate (III). The modified-carbon electrodes were sealed in plastic pipette tips with an exposed reaction area where glucose oxidase was immobilized using glutaraldehyde. An outer membrane of Nafion, followed by 15% (w/v) polyurethane, was applied over the enzyme layer. The miniature modified-carbon glucose sensors displayed a sensitivity to glucose in phosphate-buffered saline of 91.4 +/- 19 nA/mM (mean +/- SEM) and a linear range up to 5.3 +/- 1 mM glucose when operated at 750 mV versus a silver/silver chloride reference. Corresponding, unmodified-carbon based glucose sensors displayed a lower sensitivity of 20.7 +/- 3 nA/mM with a linear range up to 3.8 +/- 0.5 mM. The modified-carbon glucose sensors responded to glucose when operated in plasma but with a reduced sensitivity compared with that in buffered saline. Glucose sensors displayed good stability for up to 6.5 days during continuous operation in 5 mM buffered glucose solution. Interference from ascorbate and 4-acetamidophenol at both physiological and pharmacological ranges was significantly lower at the modified-carbon base electrodes than that at the unmodified-carbon base electrodes. Also, the relatively large effect of ascorbate and 4-acetamidophenol at the unmodified-carbon base electrode was reduced considerably when the base electrode was coated with glucose oxidase, Nafion and polyurethane membranes.

Acetaminophen↗

PubMed2004

A prospective multicenter clinical trial to evaluate the safety and effectiveness of the implantable miniature telescope.

PURPOSE: To evaluate the safety and preliminary efficacy of a novel visual prosthetic device, the Implantable Miniature Telescope, IMT (by Dr Isaac Lipshitz) (IMT), in a phase I trial in patients with significant bilateral central vision impairment from late-stage age-related macular degeneration (AMD). The IMT is designed to reduce the relative size of the scotoma by rendering enlarged (threefold) central visual field images over the central and peripheral retina. DESIGN: Prospective, multicenter, open-label clinical trial. METHODS: In this prospective, multicenter phase I trial, 14 patients aged 60 or older with bilateral geographic atrophy or disciform scar AMD, cataract, and best-corrected visual acuity (BCVA) between 20/80 and 20/400 had an IMT implanted in one eye. Distance and near BCVA, endothelial cell density, and quality of life, measured as activities of daily life (ADL), were evaluated preoperatively and postoperatively. RESULTS: At 12 months, 10 (77%) of 13 patients gained 2 more lines of either distance or near BCVA, and eight (62%) of 13 patients gained 3 or more lines in either distance or near BCVA. Mean endothelial cell density decreased by 13%. All adverse events resolved without sequelae. ADL scores improved in the majority of patients. CONCLUSION: The results of this phase I trial support further evaluation of the IMT in a larger study population with late-stage AMD. A phase II/III trial is in progress.

Activities of Daily Living↗

PubMed2004

Results of the use of the Ex-PRESS miniature glaucoma implant in technically challenging, advanced glaucoma cases: a clinical pilot study.

PURPOSE: To report results of implantation of the Ex-PRESS Miniature Glaucoma Implant (Optonol, Neve Ilan, Israel) shunt directly under the conjunctiva in advanced glaucoma. DESIGN: Noncomparative case series. METHODS: Chart review of eleven cases of Ex-PRESS implantation. Outcome measures included intraocular pressure (IOP), complications, visual acuity, and additional interventions. Failure was defined as unacceptably high IOP requiring revision or explantation. RESULTS: Four patients (36%) failed. Ten (91%) experienced hypotony during postoperative week one. In the seven nonfailures, mean pre and postoperative IOPs were 30.3 +/- 9.3 mm Hg and 13.6 +/- 4.4 mm Hg, respectively (P = .006). The logMAR visual acuity did not change significantly from baseline to follow up (logMAR 1.1 +/- 0.9 and 1.4 +/- 0.9, respectively, P = .13). There were no intraoperative complications. Postoperative complications in the 11 eyes included choroidal detachment in 3 (27%) and suprachoroidal hemorrhage in 2 (18%). Of the 7 successful cases, additional interventions were required in 4 (57%). CONCLUSIONS: Despite significant IOP reduction, the incidence of complications following Ex-PRESS implantation directly under the conjunctiva was unacceptably high in this group of patients.

Conjunctiva↗

PubMed2006

Treatment of choroidal neovascularization through the implantable miniature telescope.

PURPOSE: To report a case of thermal laser photocoagulation of a choroidal neovasacular membrane through the implantable miniature telescope (IMT). DESIGN: Interventional case report. METHODS: Focal thermal laser photocoagulation was performed. Complete ablation of the neovascular lesion, visual acuity, and integrity of the IMT were assessed. RESULTS: An 81-year-old woman with a history of IMT implantation for advanced geographic atrophy related to age-related macular degeneration developed an extrafoveal choroidal neovascular lesion. The patient underwent focal laser photocoagulation through the telescope without complication. Three months after treatment, no evidence of recurrence was noted, and visual acuity remained at 20/200. The IMT was not altered by the treatment. CONCLUSIONS: Focal thermal laser photocoagulation through an IMT can successfully treat choroidal neovascularization without damaging the device.

Aged, 80 and over↗

PubMed2005

Alaryngeal speech aid using an intra-oral electrolarynx and a miniature fingertip switch.

We developed and evaluated an intra-oral electrolaryngeal speech aid system for those who could not acquire common alaryngeal speech or for early post-surgery speech rehabilitation. Our system consisted of a denture-base intra-oral vibrator, a wireless miniature fingertip switch and a controller. To produce natural speech, the fingertip switch produced binary commands of voicing and accent and the controller implemented the pitch generation model using the commands. We first estimated the intelligibility of consonant-vowel syllables produced by our system. We then obtained the feedback about the system from the Japanese users on the basis of their daily life use, and evaluated the possibility and acceptability as an alaryngeal speech aid. Although the users were less satisfied at the intra-oral electrolarynx, the intelligibility of the intra-oral electrolarygeal speech was comparable to that of transcervical electrolaryngeal speech, and most of them were willing to employ it if they lost their current electrolaryngeal speech. According to the feedbacks from the users, a completely wire-free system and less eye-catching designs would make the prosthesis more acceptable. These results placed the intra-oral electrolarynx as a useful option of alaryngeal speech aids and encouraged the further development of the intra-oral electrolarynx.

Aged↗

PubMed2004

Application of a miniature biochip using the molecular beacon probe in breast cancer gene BRCA1 detection.

We report for the first time the application of a biochip using the molecular beacon (MB) detection scheme. The usability of this biochip novel detection system for the analysis of the breast cancer gene BRCA1 is demonstrated using molecular beacon probes. The MB is designed for the BRCA1 gene and a miniature biochip system is used for detection. The performance of the biochip-MB detection system is evaluated. The optimum conditions for the MB system for highest fluorescence detection sensitivity are investigated for the detection system. The detection of BRCA1 gene is successfully demonstrated in solution and the limit of detection (LOD) is estimated as 70 nM.

Biosensing Techniques↗

PubMed2005

Microtubule self-organisation by reaction-diffusion processes in miniature cell-sized containers and phospholipid vesicles.

Under appropriate conditions, in vitro microtubule preparations self-organise over macroscopic distances by a process of reaction and diffusion. To investigate whether such self-organisation can also occur in objects as small as a cell or an embryo we carried out experiments in miniature containers of cellular dimension. When assembled under self-organising conditions in wells of 120-500 microm, microtubules developed organised structures. Self-organisation is strongly affected by shape, being highly favoured by elongated forms. In wells of more complex shape, geometrical factors may either oppose or strengthen one another and so inhibit or reinforce self-organisation. Microtubules were also assembled within phospholipid vesicles of 2-5 microm diameter. Under self-organising conditions, we observed large shape changes from spheroids to long tubes (50-100 microm) and intertwined coils. We conclude that self-organisation of microtubules by reaction-diffusion processes can occur in containers of cellular dimensions and is capable of strongly deforming the cellular membrane.

Animals↗

PubMed2006

GABAergic miniature postsynaptic currents in septal neurons show differential allosteric sensitivity after binge-like ethanol exposure.

Binge-like ethanol treatment of septal neurons blunts GABAAR-mediated miniature postsynaptic currents (mPSCs), suggesting it arrests synaptic development. Ethanol may disrupt postsynaptic maturation by blunting feedback signaling through immature GABAARs. Here, the impact of ethanol on the sensitivity of mPSCs to zolpidem, zinc and 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha-OH-DHP) was tested. The decay phase of mPSCs showed concentration-dependent potentiation by zolpidem (0.03-100 microM), which was substantially blunted after ethanol exposure. Since zolpidem potentiation exhibited a substantial age-dependent increase in untreated neurons, this finding supported the idea that ethanol arrests synaptic development. GABAAR alpha1 subunit protein also increased with age in untreated neurons, paralleling enhanced sensitivity to zolpidem. Surprisingly, alpha1 levels were not reduced by binge ethanol even though mPSCs were relatively zolpidem-insensitive. Zinc (3-30 microM) decreased mPSC parameters in a concentration- and age-related manner with older untreated cells showing less inhibition. However, there was no increase in mPSC zinc sensitivity after binge ethanol as would be expected if a general arrest of synaptic maturation had occurred. 3alpha-OH-DHP (3-1000 nM) induced concentration-dependent potentiation of mPSC decay. Although potentiation was age-independent, binge ethanol treatment exaggerated sensitivity to this neurosteroid. Finally, chronic picrotoxin pretreatment (100 microM) intended to mimic GABAAR inhibition from ethanol pretreatment did not significantly change mPSC modulation by zolpidem, zinc or 3alpha-OH-DHP. These results suggest that binge ethanol treatment selectively arrests a subset of processes important for maturation of postsynaptic GABAA Rs. However, it is unlikely that ethanol causes a broad arrest of postsynaptic development through a direct inhibition of GABAAR signaling.

Age Factors↗

PubMed2005

Establishment and characterization of endothelial cell lines from the aorta of miniature pig for the study of xenotransplantation.

Pig endothelial cells are the first cells to interact with human immune components after organ xenotransplantation, which is a procedure currently considered to be the best treatment option for end-stage organ failure. It is, therefore, essential to study the mechanisms of molecular interaction between pig endothelial cells and human immune components, in order to overcome xenograft rejection. The aim of this study was to establish immortalized pig aortic endothelial cell lines, in order to facilitate future in vitro studies of human anti-pig immune responses. Endothelial cell lines were established following the transfection of primary endothelial cells isolated from the aortas of the Minnesota miniature pig with plasmid pRNS-1 carrying genes for neomycin resistance and the SV40 large T antigen. The immortalized cell lines showed a relatively rapid doubling time (17.6h) and the endothelial cell phenotype, as indicated by the formation of typical cobblestone monolayers and by the constitutive expression of PECAM-1 and the von Willebrand factor. Flow cytometric analysis demonstrated the constitutive expression of SLA class I and CD86, whereas the expression of E-selectin and SLA class II was only induced after stimulation with human TNF-alpha and pig IFN-gamma, respectively. On the other hand, no CD80 expression was detected in the primary cells or cell lines in the presence or absence of either human TNF-alpha or pig IFN-gamma. A vigorous human T cell proliferation against these cell lines was observed in the mixed lymphocyte-endothelial cell culture. These results suggest that pig endothelial cells, immortalized by the introduction of SV40 T, retain their original characteristics, except for the acquired property of immortalization, and that they may be useful for future in vitro studies of xenogeneic human anti-pig immune responses.

Animals↗

PubMed2005

Ion-channel noise places limits on the miniaturization of the brain's wiring.

The action potential (AP) is transmitted by the concerted action of voltage-gated ion channels. Thermodynamic fluctuations in channel proteins produce probabilistic gating behavior, causing channel noise. Miniaturizing signaling systems increases susceptibility to noise, and with many cortical, cerebellar, and peripheral axons <0.5 mum diameter [1, 2 and 3], channel noise could be significant [4 and 5]. Using biophysical theory and stochastic simulations, we investigated channel-noise limits in unmyelinated axons. Axons of diameter below 0.1 microm become inoperable because single, spontaneously opening Na channels generate spontaneous AP at rates that disrupt communication. This limiting diameter is relatively insensitive to variations in biophysical parameters (e.g., channel properties and density, membrane conductance and leak) and will apply to most spiking axons. We demonstrate that the essential molecular machinery can, in theory, fit into 0.06 microm diameter axons. However, a comprehensive survey of anatomical data shows a lower limit for AP-conducting axons of 0.08-0.1 microm diameter. Thus, molecular fluctuations constrain the wiring density of brains. Fluctuations have implications for epilepsy and neuropathic pain because changes in channel kinetics or axonal properties can change the rate at which channel noise generates spontaneous activity.

Animals↗

PubMed2005

Miniaturized test system for soil respiration induced by volatile pollutants.

A miniaturized method based on 96-well microtitre plates was developed and used to study respiration in pristine and contaminated soils following addition of volatile substrates. Small soil samples were exposed to fuel components, which were volatilized from spatially separate reservoirs of 2,2,4,4,6,8,8-heptamethylnonane (HMN) as an organic carrier. Respiration was determined as CO(2) production by means of a pH-indicator and bicarbonate-containing agar, or as (14)CO(2) evolution from (14)C-labelled substrates. Substrate concentrations inducing maximum microbial activity or inhibition were determined and CO(2) production profiles examined by multivariate analysis. When high concentrations of fuel components were applied, distinction of hydrocarbon exposed soils from unexposed soil was achieved within 6 h of incubation. With low concentrations, adequate distinction was achieved after 24 h, probably as a result of community adaptation. Nutrient limitation was identified with the (14)C method for toluene, and the optimal N and P amendment determined. Further potential applications of this rapid and inexpensive method are outlined.

Bacterial Physiological Phenomena↗