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PubMed2006

Characterization of hepatic drug-metabolizing activities of Bama miniature pigs (Sus scrofa domestica): comparison with human enzyme analogs.

We used various substrates and selective inhibitors of human cytochrome P450 (CYP) isozymes as probes to study the metabolism of liver microsomes from Chinese Bama miniature pigs. Nifedipine oxidation (NOD) and testosterone 6beta-hydroxylation (6beta-OHT) activities were similar between human liver microsomes and those from Bama miniature pigs. However, compared with those from humans, liver microsomes from Bama miniature pigs showed decreased phenacetin O-deethylation, coumarin 7-hydroxylation, and chlorzoxazone 6-hydroxylation activities, whereas dextromethorphan O-demethylation activity was increased. Ketoconazole selectively inhibited NOD and 6beta-OHT activities in microsomes from Bama pigs, and 8-methoxypsoralen and tranylcypromine inhibited coumarin 7-hydroxylation in pig microsomes. However, furafylline and quinidine failed to selectively inhibit phenacetin O-deethylation and dextromethorphan O-demethylation in microsomes from Bama pigs, whereas chlormethiazole more efficiently inhibited coumarin 7-hydroxylation activity than chlorzoxazone 6-hydroxylation in pig microsomes. Our results suggest that liver microsomes from Chinese Bama miniature pigs are similar to those from humans in regard to metabolism of nifedipine and testosterone (both are probe substrates for human CYP3A4). In addition, chemical inhibitors used as specific probes for human P450 enzymes did not always show the same selectivity toward corresponding enzyme activities in liver microsomes from Bama pigs. However, ketoconazole (a potent inhibitor of human CYP3A4) could be used as a selective inhibitor probe for the NOD and 6beta-OHT activities in liver microsomes from Chinese Bama miniature pigs.

Adult↗
PubMed2000

Miniature mass analyzers

Increased efforts are being made to develop miniature mass spectrometers, including those which are hand-portable, and to retain the performance characteristics of traditional laboratory instruments as much as possible in the miniature instruments. This review of miniature mass analyzers emphasizes analytical performance and compares the relative merits of each type of miniature mass analyzer. Miniature instruments discussed include sector, Wien filter, time-of-flight, linear quadrupole, quadrupole ion trap and Fourier transform ion cyclotron resonance mass spectrometers, as well as combinations of and variations on these major types. Special considerations that apply to small mass analyzers are noted and suggestions are made regarding the possible future development of this field. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1995

How can exocytosis account for the actual properties of miniature synaptic signals?

It is broadly accepted that a postsynaptic "miniature" is the most elementary chemically transmitted signal and results from the all-or-none release of transmitter packaged in a single presynaptic vesicle. Hitherto, it has not been possible to directly verify this renowned representation, although it is consistent with evidence of vesicle traffic and, following an intense period of release, vesicle depletion. However, vesicle traffic involving molecular components similar to those implicated in transmitter release has been attributed to other functions including membrane repair. Furthermore, as a number of investigators have recently proposed, miniature signals recorded at peripheral and central synapses may actually reflect several rather than a single discharge of transmitter. It is not clear whether such putative multiple-discharge miniatures represent near-synchronous exocytoses of several vesicles or a burst of openings in a pore that couples a vesicle with the outer membrane. In any case, despite the popularity of the vesicular hypothesis, the molecular mechanism involved in synchronizing fast elementary secretion has not yet been elucidated. Interdependencies among subminiature discharges composing a miniature have suggested that the underlying process is a regenerative signal restricted to a presynaptic terminal unit, confirming Fatt and Katz's first speculation on miniatures, which was not vesicular exocytosis [Fatt and Katz (1952), J. Physiol., 117:109-128]. Here we discuss the possibility that this regenerative signal might be a localized cytosolic Ca2+ transient and attempt to reconcile this hypothesis with the exocytotic models proposed to explain fast transmitter release.

Animals↗
PubMed1996

Use of a miniaturized test system for determining acute toxicity of toxicity identification evaluation fractions.

A miniaturized test system was developed and used to determine the acute toxicity of effluent fractions separated by HPLC to Daphnia magna and Pimephales promelas. The miniaturized test system consists of exposing test organisms in 1 ml of test solution using 48-well microtiter plates for the test vessels. Several factors were investigated to determine the acceptability of this test system. These factors included organism biomass to test solution ratio, toxicity of the microtiter plates to the organisms, dissolved oxygen in the test solution, partitioning of the test chemicals to the walls of the test vessels, and dilution of the test solution when the organisms are transferred. Toxicity of four reference chemicals to D. magna and P. promelas was also determined using the miniaturized test systems. It was concluded that the test system could be miniaturized and still provide results comparable to those obtained when standard U.S. EPA test procedures were used. The major benefit of using the miniaturized test system is that less solution is required for conducting a toxicity test. This becomes important when only a small amount of test solution is available, as might occur during a toxicity identification evaluation, after an effluent has been fractionated by HPLC. Other benefits include less space required to conduct a test, less time necessary to prepare test solutions, and a reduced volume of waste for disposal.

Animals↗
PubMed2003

Design of a miniature implantable left ventricular assist device using CAD/CAM technology.

In this study, we developed a new miniature motor-driven pulsatile left ventricular assist device (LVAD) for implantation into a Japanese patient of average build by means of computer-aided design and manufacturing (CAD/CAM) technology. A specially designed miniature ball-screw and a high-performance brushless DC motor were used in an artificial heart actuator to allow miniaturization. A blood pump chamber (stroke volume 55 ml) and an inflow and outflow port were designed by computational fluid dynamics (CFD) analysis. The geometry of the blood pump was evaluated using the value of index of pump geometry (IPG) = (Reynolds shear stress) x (occupied volume) as a quantitative index for optimization. The calculated value of IPG varied from 20.6 Nm to 49.1 Nm, depending on small variations in pump geometry. We determined the optimum pump geometry based on the results of quantitative evaluation using IPG and qualitative evaluation using the flow velocity distribution with blood flow tracking. The geometry of the blood pump that gave lower shear stress had more optimum spiral flow around the diaphragm-housing (D-H) junction. The volume and weight of the new LVAD, made of epoxy resin, is 309 ml and 378 g, but further miniaturization will be possible by improving the geometry of both the blood pump and the back casing. Our results show that our new design method for an implantable LVAD using CAD/CAM promises to improve blood compatibility with greater miniaturization.

Computer-Aided Design↗
PubMed1988

Stationary and non-stationary occurrences of miniature end plate potentials are well described as stationary and non-stationary Poisson processes in the mollusc Navanax inermis.

Protractor muscles in the gastropod mollusc Navanax inermis exhibit typical spontaneous miniature end plate potentials with mean amplitude 1.71 +/- 1.19 (standard deviation) mV. The evoked end plate potential is quantized, with a quantum equal to the miniature end plate potential amplitude. When their rate is stationary, occurrence of miniature end plate potentials is a random, Poisson process. When non-stationary, spontaneous miniature end plate potential occurrence is a non-stationary Poisson process, a Poisson process with the mean frequency changing with time. This extends the random Poisson model for miniature end plate potentials to the frequently observed non-stationary occurrence. Reported deviations from a Poisson process can sometimes be accounted for by the non-stationary Poisson process and more complex models, such as clustered release, are not always needed.

Action Potentials↗
PubMed2005

Anxiolytic-hypnotic drug use associated with trust, social participation, and the miniaturization of community: a multilevel analysis.

The concept of social capital has gained wide interest in public health research in recent years. However, we suggest a concept that was introduced and developed by Fukuyama, named "miniaturization of community", as an alternative to that of social capital. The concept of miniaturization of community emphasizes that a high level of social participation can be accompanied by a low level of trust, both at the individual and at the community level, which may in turn result in social disorder and lack of social cohesion. When society becomes more disordered, people may tend to feel more insecure and anxious. Use of anxiolytic-hypnotic drugs (AHDs) could under such circumstances be a coping strategy. In this study, we first wanted to investigate whether the contextual component of the miniaturization of community concept (i.e. area high social participation and low trust) is associated with individual AHD use, over and above individual characteristics. Secondly, we aimed to study whether people living in the same municipality share a similar probability of AHD use, after adjusting for individual characteristics, and if so, how large this contextual phenomenon is. We used data on 20,319 women and 17,850 men aged 18-79 years from 58 municipalities in six regions in central Sweden, who participated in the Life & Health year 2000 postal survey. We applied multilevel logistic regression analysis with individuals at the first level and areas at the second level. Our results suggest that living in an area with a high level of miniaturization of community seems to be associated with individual AHD use, beyond people's individual characteristics including their own level of social participation and trust. The concept of miniaturization of community may be an extension of the classic concept of social capital and may increase our understanding of contextual effects on health.

Adolescent↗
PubMed1976

Local anesthetic alteration of miniature endplate currents and endplate current fluctuations.

The effect of the local anesthetic QX222 on the kinetics of miniature endplate currents and acetylcholine induced endplate current fluctuations was studied in voltage clamped cutaneous pectoris muscle of Rana pipiens. Both the endplate current fluctuation spectra and the miniature endplate current decay consisted of two or three components depending upon the holding potential and local anesthetic concentration. The cutoff frequency of each spectral component was equal to the decay rate of its corresponding constituent of the miniature endplate current. Comparison of the relative amplitudes of the spectral and miniature endplate components indicated that QX222 did not act by creating two kinetically distinct populations of acetylcholine receptors. QX222 action could be explained by alteration of the acetylcholine receptors such that they sequentially change conformation form one open state to another. A specific case in which QX222 binds to the open state of the acetyl-choline receptor creating a blocked state, was found to account for the observed relationship between the relative amplitudes of the miniature endplate current and spectral components, as well as the previously observed voltage and concentration sensitivity of the decay rates of endplate current components.

Anesthetics, Local↗
PubMed2001

Modulation of miniature inhibitory postsynaptic currents by isoflurane in rat dissociated neurons with glycinergic synaptic boutons.

The effects of a volatile anesthetic, isoflurane, on glycinergic miniature inhibitory postsynaptic currents (IPSCs) were investigated in mechanically dissociated rat trigeminal nucleus neurons with intact glycinergic interneuronal presynaptic nerve terminals. The nystatin-perforated patch recording configuration was used to record the miniature IPSCs under voltage-clamp conditions. Isoflurane shifted in a parallel fashion the glycine (Gly) concentration-response curve of enzymatically dissociated neurons to the left without changing the maximum response. Isoflurane reversibly increased the frequency of the miniature IPSCs and prolonged the decay time constant without affecting the mean amplitude. The increase in the frequency of miniature IPSCs in the presence of isoflurane was also observed in Ca(2+)-free external solution. Thapsigargin prohibited the facilitatory effect of isoflurane on the miniature IPSC frequency. It is concluded that isoflurane increases the Ca(2+) concentration in the glycinergic presynaptic nerve terminal by enhancing the release and/or suppressing the uptake of Ca(2+) into stores.

Anesthetics, Inhalation↗
PubMed2003

Social capital and the miniaturization of community among daily and intermittent smokers: a population-based study.

BACKGROUND: The impact of social participation, trust, and the miniaturization of community on daily and intermittent smoking was investigated. METHODS: The 2000 public health survey in Scania is a cross-sectional study. A total of 13,715 persons answered a postal questionnaire, which represents 59% of the random sample. A logistic regression model was used to investigate the association between the social capital variables and daily and intermittent smoking. The multivariate analysis was performed by using a logistic regression model to investigate the importance of possible confounders (age, country of origin, education, and snuff consumption) on the differences in daily and intermittent smoking between high versus low social participation, trust, and their four combination categories. The differences in the prevalences of the 13 social participation subitems between the high social capital and miniaturization of community categories were compared by t tests. RESULTS: Daily smoking is negatively associated with both social participation and trust, while intermittent smoking is positively associated with social participation and negatively associated with trust. This latter combination, named "the miniaturization of community," is an indirect measure of the ideologically and culturally increasingly narrow forms of social participation that excludes generalised trust to other people. Study circles, meetings of organisations, theatre/cinema, arts exhibition, and gathering of relatives are more prevalent in the high social capital category, while visit(s) to night club/entertainment is more prevalent in the miniaturization of community category. CONCLUSIONS: Low social capital is associated with daily smoking. "The miniaturization of community," i.e., high social participation and low trust, is significantly associated with intermittent smoking. The results have direct implications for smoking prevention strategies.

Adult↗
PubMed2001

Trade-offs in miniature quadrupole designs.

Pressing needs for miniature mass spectrometers became apparent during the last decade in process monitoring and control, space exploration, and environmental screening. Besides the small footprint, common requirements include low cost, low power consumption, field portability, reliability, autonomy, and ease-of-use. Design concepts and construction technologies of miniaturized quadrupole sensors were guided by cost reduction requirements without sacrifice of performance. The first miniature and complete quadrupole mass spectrometer system was introduced as the Micropole sensor. The concept featured a novel technique to assemble and operate multiple miniature quadrupoles in parallel. The short analyzer length offers a significant advantage by enabling direct mass filtering at pressures up in the 10(-2) torr range. High voltages at higher frequencies (10-20 MHz) are required for acceptable mass resolving powers. Additional trade-offs were uncovered in miniature sensors leading to designs optimized for each class of applications. Real time ray tracing of ions injected and filtered in the quadrupole field is used early in the design stage to predict the performance and reliability of the device.

Journal Article↗
PubMed2000

Space charge effects on resolution in a miniature ion mobility spectrometer.

Miniaturization of ion mobility spectrometry (IMS) is expected to have many advantages, as well as difficulties, in the separation of chemical species at atmospheric pressure. We report the results of studies of a miniature ion mobility spectrometer that has a drift channel 1.7 mm in diameter, the smallest cross section reported to date. The miniature cell contains a homogeneous drift field and is operated at atmospheric pressure. The miniature IMS has been characterized by measuring both negative and positive ion spectra using a frequency-quadrupled Nd: YAG laser on samples of NO, O2, and methyl iodide; a useful resolution (> 10) was achieved with an operating voltage of 500 V. Peak broadening due to Coulomb repulsion was determined to have a major effect on the resolution of the miniature device.

Journal Article↗
PubMed2003

Miniature homeodomains: high specificity without an N-terminal arm.

Recently, we described a strategy for the design of miniature proteins that bind DNA and protein surfaces with high affinity and selectivity. This strategy involves identifying the functional epitope required for macromolecular recognition by a natural protein and presenting it on a small, stable protein scaffold. In previous work, high-affinity DNA recognition was achieved only when the miniature protein contained the complete functional epitope. Here we report a miniature homeodomain that recognizes its 6-bp target site in the nanomolar concentration range at 25 degrees C, despite the absence of DNA contact residues located along the homeodomain N-terminal arm. We conclude that miniature proteins can achieve high affinity and selectivity for DNA by design even when the functional epitope is incomplete by using pre-organization to effectively compensate for lost protein-DNA contacts. In this case it has been possible to miniaturize both the recognition surface and the structural framework of a globular protein fold.

Amino Acid Sequence↗
PubMed2004

High affinity, paralog-specific recognition of the Mena EVH1 domain by a miniature protein.

Many protein domains involved in cell signaling contain or interact with proline-rich sequences, and the design of molecules that perturb signaling pathways represents a foremost goal of chemical biology. Previously we described a protein design strategy in which the well-folded alpha-helix in avian pancreatic polypeptide (aPP) presents short alpha-helical recognition epitopes. The miniature proteins designed in this way recognize even shallow protein clefts with high affinity and specificity. Here we show that the well-folded type-II polyproline helix in aPP can present the short PPII-helical recognition epitope within the ActA protein of Listeria monocytogenes. Like miniature proteins that use an alpha-helix for protein recognition, the miniature protein designed in this way displays high affinity for a natural ActA target, the EVH1 domain Mena1-112, and achieves the elusive goal of paralog specificity, discriminating well between EVH1 domains Mena1-112, VASP1-115, and Evl1-112. Most importantly, the miniature protein competed with ActA in Xenopus laevis egg cytoplasmic extracts, decreasing actin-dependent motility of L. monocytogenes and causing extreme speed variations and discontinuous tail formation. Our results suggest that miniature proteins based on aPP may represent an excellent framework for the design of ligands that differentiate the roles of EVH1 domains in vitro and in vivo.

Amino Acid Sequence↗
PubMed2004

Miniature device for aqueous and non-aqueous solubility measurements during drug discovery.

PURPOSE: A miniature device was developed for the measurement of aqueous and non-aqueous equilibrium solubility during drug discovery. The solubility values obtained using the miniature device were compared to those obtained using the conventional shake-flask method. METHODS: The aqueous solubility of six structurally diverse compounds, the solubility of carbamazepine in various cosolvent systems, and the pH-solubility profile of saquinavir were determined using the miniature device. The device contains a multichannel cartridge pump and a Tygon tubing that is mounted on the pump with two ends linked by a syringe filter. The drug slurry was filled into the tubing and circulated inside, continually passing through the syringe filter. At the end of the experiment, the filtrate was collected and analyzed directly by High-Pressure Liquid Chromatography (HPLC). The solubility was also determined by the shake-flask method. RESULTS: The solubility values determined by the miniature device were in good agreement with those measured by the conventional shake-flask method. CONCLUSIONS: The miniature device provides a unique way of testing aqueous and non-aqueous equilibrium solubility in a microscale setting. With approximately 1 mg of compound, it is possible to determine the entire pH-solubility profile. The device is useful for solubility screening during lead optimization and candidate selection in early drug discovery, when compound supply is limited. It can also be used for screening solubility in non-aqueous systems to select vehicles for preclinical in vivo studies.

Anti-HIV Agents↗
PubMed2003

Long-term follow up of gastric low-grade mucosa-associated lymphoid tissue lymphoma by endosonography emphasizing the application of a miniature ultrasound probe.

BACKGROUND AND AIMS: Endoscopic ultrasonography (EUS) is a useful tool for the evaluation of gastric wall infiltration including gastric lymphoma. The aims of this study were to characterize gastric low-grade mucosa-associated lymphoid tissue (MALT) lymphoma according to EUS findings and to evaluate the role of a miniature ultrasound probe in the long-term follow up. METHODS: From January 1994 to March 2002, 20 patients were proven to have gastric low-grade MALT lymphoma. Endoscopic ultrasonography was performed with a conventional echoprobe and/or a miniature ultrasound probe for initial staging and a miniature ultrasound probe was performed during follow up. All patients positive for Helicobacter pylori received a 2-week course of omeprazole, amoxicillin and clarithromycin. RESULTS: Helicobacter pylori infection was found in 17 (85%) patients. In all patients, H. pylori was eradicated after treatment. Initial EUS showed significantly greater wall thickness (6.1 +/- 3.0 mm) in MALT lymphoma patients when compared with control (2.8 +/- 0.3 mm). The infiltrative patterns included wall thickening (3.5-14.1 mm) in 18 patients: stage E-I1 in 16 (mucosa and/or submucosa), stage E-I2 in one and stage E-II in one. Complete regression of MALT lymphoma following treatment for H. pylori was noted in 14 patients, with a mean duration of 11.3 +/- 9.1 months. Follow-up miniature ultrasound probe sonography showed comparative reduction in wall thickness (P < 0.05). CONCLUSIONS: Endoscopic ultrasonography plays a valuable role in the initial staging and long-term follow up of gastric low-grade MALT lymphoma. The application of a miniature ultrasound probe enables adequate evaluation in the majority of these patients, with additional benefits.

Adult↗
PubMed1998

Intracellular calcium stores modulate miniature GABA-mediated synaptic currents in neonatal rat hippocampal neurons.

The whole-cell configuration of the patch clamp technique was used to record miniature gamma-aminobutyric acidA (GABAA) receptor-mediated currents (in tetrodotoxin, 1 microM and kynurenic acid 1 mM) from CA3 pyramidal cells in thin hippocampal slices obtained from postnatal (P) day (P6-9) old rats. Switching from a Ca2+-containing to a nominally Ca2+-free medium (in which Ca2+ was substituted with Mg2+, in the presence or in the absence of 100 microM EGTA) did not change significantly the frequency or amplitude of miniature events. Superfusion of thapsigargin induced a concentration-dependent increase in frequency but not in amplitude of tetrodotoxin-resistant currents that lasted for the entire period of drug application. Mean frequency ratio (thapsigargin 10 microM over control) was 1.8+/-0.5, (n = 9). In nominally Ca2+-free solutions thapsigargin was ineffective. When bath applied, caffeine (10 mM), reversibly reduced the amplitude of miniature postsynaptic currents whereas, if applied by brief pressure pulses, it produced an increase in frequency but not in amplitude of spontaneous GABAergic currents. Superfusion of caffeine (10 mM) reversibly reduced the amplitude of the current induced by GABA (100 microM) indicating a clear postsynaptic effect on GABAA receptor. Superfusion of ryanodine (30 microM), in the majority of the cells (n = 7) did not significantly modify the amplitude or frequency of miniature events. In two of nine cells it induced a transient increase in frequency of miniature postsynaptic currents. These results indicate that in neonatal hippocampal neurons, mobilization of calcium from caffeine-ryanodine-sensitive stores facilitates GABA release.

Animals↗
PubMed2001

Possible mechanisms of miniaturization during androgenetic alopecia or pattern hair loss.

In androgenetic alopecia, or pattern hair loss, follicles undergo miniaturization, shrinking from terminal to vellus-like hairs. Traditionally, this process is thought to progress gradually over a number of follicular cycles. However, it is unlikely that miniaturization can be explained only by a series of progressively shorter anagen cycles. Simple calculations show that this process would take too long for significant miniaturization to occur secondary to shorter anagen cycles alone, especially in view of the latent lag period seen in pattern hair loss that occurs between the loss of a telogen hair and the appearance of an anagen hair. Evidence is presented to support a new concept that miniaturization is an abrupt, large-step process that also can be reversed in 1 hair cycle, as has been shown clinically, with confirmatory histologic evidence, in patients with pattern hair loss responding to finasteride treatment. It is hypothesized that the miniaturization seen with pattern hair loss may be the direct result of reduction in the cell number and, hence, size of the dermal papilla.

Alopecia↗