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PubMed2001

Effect of tetraalkylammonium derivative of 6-methyluracil on amplitude and temporal parameters of miniature endplate potentials in frog neuromuscular junction.

The effect of C-547, a tetraalkylammonium derivative of 6-methyluracil, a novel highly selective acetylcholinesterase inhibitor, on frog neuromuscular junction was studied. In concentrations 10(-9)-10(-7)M the preparation increased the amplitude and temporal parameters of miniature endplate potentials. In contrast to the effect of C-574 on purified acetylcholinesterase from mammals, the effect of this agent on frog neuromuscular junction was reversible. In a concentration of 10(-6)M the preparation apart from anticholinesterase activity produced a parasympatholytic effect manifested in a decrease in amplitude and decay time constant of miniature endplate potentials accompanied by a decrease in spontaneous transmitter secretion. After washout, the parasympatholytic effect recovered more slowly, but disappeared more rapidly compared to anticholinesterase activity. These findings suggest that parasympatholytic effect of C-547 results from direct action on receptor-channel complexes in the endplate membrane.

Acetylcholinesterase↗
PubMed2000

Presynaptic calcium stores underlie large-amplitude miniature IPSCs and spontaneous calcium transients.

The cellular mechanisms responsible for large miniature currents in some brain synapses remain undefined. In Purkinje cells, we found that large-amplitude miniature inhibitory postsynaptic currents (mIPSCs) were inhibited by ryanodine or by long-term removal of extracellular Ca2+. Two-photon Ca2+ imaging revealed random, ryanodine-sensitive intracellular Ca2+ transients, spatially constrained at putative presynaptic terminals. At high concentration, ryanodine decreased action-potential-evoked rises in intracellular Ca2+. Immuno-localization showed ryanodine receptors in these terminals. Our data suggest that large mIPSCs are multivesicular events regulated by Ca2+ release from ryanodine-sensitive presynaptic Ca2+ stores.

Animals↗
PubMed2006

Scaling and the design of miniaturized chemical-analysis systems.

Micrometre-scale analytical devices are more attractive than their macroscale counterparts for various reasons. For example, they use smaller volumes of reagents and are therefore cheaper, quicker and less hazardous to use, and more environmentally appealing. Scaling laws compare the relative performance of a system as the dimensions of the system change, and can predict the operational success of miniaturized chemical separation, reaction and detection devices before they are fabricated. Some devices designed using basic principles of scaling are now commercially available, and opportunities for miniaturizing new and challenging analytical systems continue to arise.

Animals↗
PubMed1983

Training generative repertoires within agent-action-object miniature linguistic systems with children.

This study investigated processes responsible for generative language acquisition through the use of a miniature linguistic system. The miniature linguistic system consisted of nonsense syllables and concrete-enactive, agent-action referents. The purpose of Experiment 1 was to determine (a) whether children would recombine agent and action constituents to produce novel utterances and (b) whether children would generate further extensions of the linguistic system (e.g., agent-action-object sentences) following training of a novel syntactic construction. Four children (aged 8:8, 7:4, 4:9, and 4:5) produced novel utterances to describe untrained agent-action referents. They also progressed from agent-action learning to producing agent-action-object sentences after training on only one or two examples of this sentence type with the appropriate referents. Experiment 2 explored conditions more likely to facilitate recombinative generalization among preschoolers. In particular, how a history of lexical learning affects subsequent language learning was investigated with seven 4-year-olds. Results indicated that a history of lexical learning greatly enhanced generative production of untrained agent-action utterances. In addition, all seven children learned new syntactic rules to generate three-word utterances, regardless of the orderings of agent, action, and object words. Implications for developing efficient language remediation programs are discussed.

Child↗
PubMed1997

Miniature head-mounted microphone for voice perturbation analysis.

The miniature head-mounted microphone has become the microphone of choice in clinics, laboratories, and professional work settings where voice amplification or recording is needed and subject mobility is desirable. In this study, a miniature head-mounted condenser microphone was compared to a larger, professional grade stand-mounted condenser microphone for perturbation analysis. Amplitude and frequency perturbation measures of human phonation were made for comparison. The results indicate that only small differences exist between the two microphones. The only exception is when there is significant head movement, in which case the head-mounted microphone offers an advantage. Errors associated with variable source-to-microphone distance can therefore be reduced without losing baseline quality in transducing voice signals for analysis.

Amplifiers, Electronic↗
PubMed1997

Cytogenetic study of 30 patients with multiple myeloma: comparison of 3 and 6 day bone marrow cultures stimulated or not with cytokines by using a miniaturized karyotypic method.

Cytogenetics in multiple myeloma (MM) cases are generally difficult to perform due to the low proliferation index of malignant plasma cells (PC) in most cases. Although IL-6 and GM-CSF stimulate the in vitro proliferation of malignant plasma cells, their usefulness for improving cytogenetic results in multiple myeloma patients remains questionable, because results which compare various culture conditions in a sufficient number of patients are not available. By using a miniaturized karyotypic method, we compared in 30 multiple myeloma patients the number and percentage of clonal abnormal mitoses obtained from 3 and 6 d bone marrow cultures performed without or with two combinations of cytokines: IL-6 + GM-CSF or IL-6 + GM-CSF + IL-2 + IL-4 + TNFalpha. The percentage of patients with an abnormal karyotype, which varied with the Durie and Salmon stage of the disease, as well as the type of numerical and structural karyotypic abnormalities that we detected, were in agreement with published results. The detection of clonal karyotypic abnormalities was better after 3d of culture without cytokine than in all other culture conditions. The higher percentage of patients at all stages of MM with an abnormal karyotype in our study (76.6%) than in previous ones (20% to 60%) is largely explained by the large number of mitoses analysed in six different culture conditions due to the use of a miniaturized karyotypic method.

Bone Marrow↗
PubMed2001

Miniaturized tests for computer-assisted identification of motile Aeromonas species with an improved probability matrix.

AIMS: To develop miniaturized tests for the phenotypic identification of motile Aeromonas species using an improved probability matrix. METHODS AND RESULTS: Conventional tests were miniaturized for use in 96-well plates, and their performance assessed using 60 aeromonads comprising type and reference strains as well as clinical, fish and water isolates. A revised probability matrix for Aeromonas hybridization groups 1-14, including A. allosaccharophila, A. bestiarum, A. encheleia and A. popoffii, was developed. Using 26 tests, all the reference strains were correctly identified with the revised probability matrix, and 80% of the isolates were correctly identified at a Willcox probability level of 95%. CONCLUSION: The compact test format, coupled with a robust identification matrix, provides a convenient basis for identifying motile aeromonads. SIGNIFICANCE AND IMPACT OF THE STUDY: The identification system for identifying aeromonads will be of use to medical and veterinary laboratories undertaking disease diagnosis.

Aeromonas↗
PubMed2005

Reducing risk in infant cardiopulmonary bypass: the use of a miniaturized circuit and a crystalloid prime improves cardiopulmonary function and increases cerebral blood flow.

Advances in perfusion strategies have played an important role in improving outcomes following repair of complex congenital heart defects. The influence of cooling strategy, temperature, duration of circulatory arrest, and specific method of cerebral perfusion on neurologic morbidity have been extensively characterized. Similarly, the ability of pharmacologic agents to modulate the post-cardiopulmonary bypass (CPB) inflammatory response has been previously elucidated in both the laboratory and clinical arena. However, modification of the circuit and priming components have received comparably less attention. We recently showed that employment of a miniaturized circuit and a bloodless prime reduce inflammation and have salutary effects on cardiopulmonary function following hypothermic low-flow perfusion (HLF), and that this circuit may also improve cerebral protection following both deep hypothermic circulatory arrest and HLF. The current report, therefore, reviews current strategies utilized to minimize post-CPB inflammation and highlights the empirical evidence from our laboratory demonstrating the beneficial role of a miniaturized extracorporeal circuit in this context.

Animals↗
PubMedDate not supplied

[Cryosurgical ablation of bone tissue with a newly developed miniature cryoprobe--adaptation of the method for use in bones in vitro and in vivo].

AIM: Up to now, modern miniature cryoprobes have been used successfully for local destruction of soft tissue tumors without damaging adjacent healthy tissue. In this study, the methodology of cryoablation was applied to bone and the freezing effect as well as the cooling capacity of the probe was examined in vivo and in vitro. METHODS: Freezing was performed by cooling one or two probes, with a diameter of 3.2 mm to -180 degrees C with liquid nitrogen. The cooling capacity of the probes was determined under thermic control by an in vitro measurement on human bone, followed by an in vivo measurement on femoral and tibia bones of a sheep. RESULTS: The in vitro freezings achieved a sufficient tissue cooling using one or two cryoprobes. The simultaneous use of 2 probes resulted in a synergistic effect between the probes. According to the body heat, the registered temperature curves, during the in vivo freezings, showed a more flat trend. Nevertheless, temperatures below -50 degrees C were achieved at a distance of 1 cm from the probe due to the synergistic effect. Local or systematical intraoperative complications have not been observed. CONCLUSION: An adequate tissue cooling of bone matrix can be achieved within in vivo freezings through the use of one or more miniature cryoprobes so that the use of this probe could possibly become an alternative or supplement to the surgical resection of pathologic bone processes.

Animals↗
PubMed1999

Image-guided surgery of the skull base using a novel miniature position sensor.

Image-guided navigational systems have been a useful adjunct for minimally invasive surgery of the skull base. A novel miniature position sensor has been developed that uses a low magnetic field for real-time tracking of surgical instruments. The 1.7-mm-diameter sensor attached to the position and orientation system (Magellan(R), Biosense, Inc., Johnson and Johnson Co., Baldwin Park, CA) was deployed through various surgical instruments or used in a hand-held fashion with a malleable shaft probe. We report on our experience using this electromagnetic system in a series of lesions of the sella and clivus. After patient/image registration, the system was consistently accurate to within 2 mm. We have found this system to be particularly advantageous in endoscopic surgery of cystic lesions of the skull base, where access is limited and anatomy may be distorted. In three patients, this device obviated the need for an extensive external surgical approach. Case histories are presented, which illustrate the specific advantages this miniature system provides during skull base surgery.

Journal Article↗
PubMed1998

A miniature metal-ceramic x-ray source for spacecraft instrumentation.

Definitive mineralogical identification of materials with x-ray diffraction and fluorescence on remote planetary probes requires the development of a rugged miniature x-ray source that complies with the mass, power, thermal, and electrical management constraints imposed by space missions. Conventional x-ray tubes are generally fragile, glass-envelope designs with heat-sensitive seals. They are too brittle and bulky for planetary missions, and usually require cumbersome and power-consuming cooling systems. Here we describe the development of a novel, rugged miniature x-ray source employing a ceramic BeO substrate upon which a metal target material is deposited. Conventional thermionic emission and high-voltage acceleration of electrons to strike the metal target material produce an x-ray yield comparable to conventional x-ray tubes. Thermal management of the x-ray source is achieved with the excellent heat transport properties of the BeO target substrate coupled with a passive heatpipe.

Beryllium↗
PubMed2004

Vascularized thymic lobe transplantation in miniature swine: thymopoiesis and tolerance induction across fully MHC-mismatched barriers.

As the major site of self-nonself discrimination in the immune system, the thymus, if successfully transplanted, could potentially carry with it the induction of central tolerance to any other organ or tissue from the same donor. We have recently developed a technique for transplantation of an intact, vascularized thymic lobe (VTL) in miniature swine. In the present study, we have examined the ability of such VTL allografts to support thymopoiesis and induce transplantation tolerance across fully MHC-mismatched barriers. Six miniature swine recipients received fully MHC-mismatched VTL grafts with a 12-day course of tacrolimus. Three of these recipients were thymectomized before transplantation and accepted their VTL allografts long-term, with evidence of normal thymopoiesis. In contrast, three euthymic recipients rejected their VTL allografts. Donor renal allografts, matched to the donor VTL grafts, were transplanted without immunosuppression into two of the three thymectomized recipients, and one of the three euthymic recipients. These renal allografts were accepted by thymectomized recipients, but rejected by the euthymic recipient in an accelerated fashion. This study thus demonstrates that successful transplantation of a vascularized thymus across a fully MHC-mismatched barrier induces tolerance in this preclinical, large-animal model. This procedure should enable studies on the role of the thymus in transplantation immunology as well as offer a potential strategy for tolerance induction in clinical transplantation.

Animals↗
PubMed2003

Developmental loss of miniature N-methyl-D-aspartate receptor currents in NR2A knockout mice.

The N-methyl-d-aspartate (NMDA) glutamate receptor (NMDAR), long implicated in developmental plasticity, shows decay time kinetics that shorten postnatally as NR2A subunits are added to the receptor. Neither the mechanism nor immediate effect of this change is known. We studied developing NMDAR currents by using visual neurons in slices from NR2A knockout (NR2AKO) and WT mice. Both strains show increased dendritic levels of synaptic density scaffolding protein PSD-95 with age. Dendritic levels of NR2A increased at the same time in WT and immunoprecipitated with PSD-95. PSD-95NMDAR binding was significantly decreased in the NR2AKO. Moreover, NMDAR miniature currents (minis) were lost and rise times of NMDAR evoked currents increased in mutant mice. Age-matched WT cells showed NR2A-rich receptors predominating in minis, yet slow NR2B mediated currents persisted in evoked currents. Disrupting photoreceptor activation of retinal ganglion cells eliminated increases in PSD-95 and NR2A in superior collicular dendrites of WT mice and slowed the loss of miniature NMDAR currents in NR2AKOs. These data demonstrate that NMDARs that respond to single quantal events mature faster during development by expressing the NR2A subunit earlier than NMDARs that respond to evoked release. We hypothesize that NR2A-rich NMDARs may be localized to the center of developing synapses by an activity-dependent process that involves the targeting of PSD-95 to the postsynaptic density. Neonatal receptors become restricted to perisynpatic or extrasynaptic sites, where they participate primarily in evoked currents.

Animals↗
PubMed1978

Sugar pucker geometries at the intercalation site of propidium diiodide into miniature RNA and DNA duplexes in solution.

We have evaluated the sugar pucker geometry at the intercalation site of propidium diiodide into the self-complementary dinucleoside monophosphate duplexes cytidylylguanosine and deoxycytidylyldeoxyguanosine as a function of the nucleotide/drug ratio in aqueous solution. Our solution results support the observation by Sobell and coworkers [Sobell, H.M., Tsai, C.C., Jain, S.C. & Gilbert, S.G. (1977) J. Mol. Biol. 114, 333--365] of a C3' endo (3'-5')C2' endo sugar pucker geometry in the 2:2 intercalation complex of ethidium bromide into the iodocytidylylguanosine duplex in the crystalline state. We demonstrate further that the mixed sugar pucker observed for the intercalation of propidium diiodide into the miniature RNA duplex in solution persists in the intercalative complex of this trypanocidal drug into the corresponding miniature DNA duplex in solution.

Deoxyribose↗
PubMed1999

Domain-domain communication in a miniature archaebacterial tRNA synthetase.

The three-dimensional structure of tRNA is organized into two domains-the acceptor-TPsiC minihelix with the amino acid attachment site and a second, anticodon-containing, stem-loop domain. Aminoacyl-tRNA synthetases have a structural organization that roughly recapitulates the two-domain organization of tRNAs-an older primary domain that contains the catalytic center and interacts with the minihelix and a secondary, more recent, domain that makes contacts with the anticodon-containing arm. The latter contacts typically are essential for enhancement of the catalytic constant k(cat) through domain-domain communication. Methanococcus jannaschii tyrosyl-tRNA synthetase is a miniature synthetase with a tiny secondary domain suggestive of an early synthetase evolving from a one-domain to a two-domain structure. Here we demonstrate functional interactions with the anticodon-containing arm of tRNA that involve the miniaturized secondary domain. These interactions appear not to include direct contacts with the anticodon triplet but nonetheless lead to domain-domain communication. Thus, interdomain communication may have been established early in the evolution from one-domain to two-domain structures.

Acylation↗
PubMed2002

Dosimetric characterization of a new miniature multileaf collimator.

The dosimetrical characteristics of a new miniature multileaf collimator (ModuLeaf MLC, MRC Systems GmbH, Heidelberg, Germany) attached to the accessory holder of a Siemens accelerator with 6 MV x-rays (PRIMUS, Siemens OCS, Concord, California, USA) have been investigated. In particular, those parameters which are important for the accuracy of the treatment such as output factors, penumbra, field edge precision and transmission/leakage were determined. These data can now be used to implement specific dose calculation procedures for this miniature multileaf collimator in treatment planning systems.

Humans↗
PubMed1998

Pediatric laparoscopy for nonpalpable testes with new miniaturized instruments.

New miniaturized pediatric telescopes (1.9 or 3.5 mm) and reusable instruments (3.5-mm trocars, scissors, graspers) were used for the first time in a prospective study to evaluate handling safety and efficacy in laparoscopic diagnosis of unilateral nonpalpable testes. The results were confirmed during the same anesthesia by open operation for either orchiopexy or removal of rudimentary spermatic cord structures. Laparoscopy in 13 boys revealed one abdominal testis, 5 vanishing testes, and 7 cases of inguinal retention associated with an open inner inguinal ring. The illumination and detail resolution of the minitelescope were excellent. The 3.5-mm instruments were fully functioning with regard to tissue dissection. No complications occurred. Without technical disadvantages but with increased safety for the patient, the new miniaturized pediatric laparocopic instruments indeed realize a step forward to minimal invasion in infants and children.

Child↗
PubMed1999

A micro-power precision amplifier for converting the output of light sensors to a voltage readable by miniature data loggers.

To record photosynthetically active radiation (PAR) simultaneously at a number of points throughout a forest canopy, we developed a simple, inexpensive (< $10 US) current-to-voltage converter that processes the current generated by a photodiode radiation sensor to a voltage range that is recordable with a miniature data logger. The converter, which weighs less than 75 g and has a volume of only 100 cm(3), is built around an ultra-low power OP-90 precision operational amplifier, which consumes less than 0.5 mA at 9 V when converting the output of a Li-Cor LI-190SA quantum sensor exposed to photosynthetically active radiation (PAR) of 2500 &mgr;mol m(-2) s(-1) or only 5 &mgr;A in low light. A small 9-V battery thus powers the amplifier for more than 1000 h of continuous operation. Correlations between photometer readings and voltage output from the current-to-voltage converter were high and linear at both high and low PAR. Sixteen Li-Cor LI-190SA quantum sensors each equipped with current-to-voltage converters and connected to a miniature data logger were deployed in the upper branches of a Panamanian tropical rainforest canopy. Each unit performed reliably during a one- or two-week evaluation.

Journal Article↗