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At least 1,207 records · Page 67Linked to original sources
PubMed1980

Miniature anion-exchange/centrifugation technique for the diagnosis of microfilaraemia in the field.

The miniature anion-exchange/centrifugation (AEC) technique, developed originally for the detection of low parasitaemias in laboratory rodents, was adapted to field use for the diagnosis of trypanosomiasis in man in Africa and was tested in The Gambia. During this field study it was found that microfilariae of Dipetalonema perstans could also pass through the anion exchange column and appear in the centrifugate as 'medusa heads'. One locality-group (Mansafa Bolon) showed a generally higher prevalence and prevalences in women over 40 years old were higher than in the corresponding male groups in every locality. The potential usefulness of this technique in epidemiological studies of filariasis and ways of improving the accuracy of numerical estimates are briefly discussed.

Adolescent↗
PubMed1984

The superiority of the miniature Anion-Exchange Centrifugation Technique for detecting low grade trypanosome parasitaemias.

The efficiency was tested of the Haematocrit Centrifugation Technique (HCT) and the miniature Anion-Exchange Centrifugation Technique (mAECT) for demonstrating trypanosomes in the blood of four antelopes experimentally infected with Trypanosoma brucei gambiense in Liberia. During simultaneous daily application of both methods over a period of six months, parasitaemias were detected on 12 occasions by HCT and on 73 occasions by mAECT during 473 examination days, thus indicating the superiority of the mAECT for the detection of low grade trypanosome infections.

Animals↗
PubMed1977

Accurate, rapid measurement of the fraction of unbound estradiol and progesterone in small volumes of undiluted serum at 37 degrees C by miniature steady-state gel filtration.

A method is described for the accurate, rapid measurement of the unbound fractions of estradiol and of progesterone in small volumes of plasma or serum at 37 degrees C by a miniature method of steady-state gel filtration. There is minimal perturbation of the equilibrium between bound and free hormone and no derived kinetic parameters are required. The method has been used to measure the unbound fraction of progesterone in plasma from women during the second and third trimesters of pregnancy and of estradiol in sera of developing female rats.

Animals↗
PubMed1990

Ultrasound effects on miniature end plate potential discharge frequency are contingent upon acoustic environment.

The effects of low level ultrasonic stimulation (250 mW cm-2; 1.5 MHz; continuous wave) on the frequency of miniature end-plate potential (MEPP) production, at the frog neuromuscular junction, have been examined in two situations. In a simple exposure environment, where the muscle was immersed in Ringer solution and stretched over a polyurethane resin base at room temperature, the ultrasound stimulus produced a marked increase in the MEPP discharge rate, with only a small concomitant rise (1.0-1.6 degrees C) in local temperature. Control temperature increases of a similar magnitude produced only small changes in the rate of MEPP production. The experiment was repeated in an environment with better defined field conditions. The muscle was suspended in a chamber sealed at the base with an acoustically transparent polycarbonate material, 0.05 mm thick, and contained in a thermostatically controlled bath lined with an acoustically absorbent material. In this situation, no increase in MEPP frequency was observed in response to ultrasonication, although the local measured temperature increase was similar in both magnitude and time course. It is suggested that these results may depend upon differences between standing wave conditions and free field progression of the beam through the sample.

Acetylcholine↗
PubMed1994

Miniature excitatory postsynaptic currents in bipolar cells of the tiger salamander retina.

The synapse between photoreceptor and bipolar cell is important for at least three reasons: (1) it is the first synapse in the visual pathway; (2) it is the best-known tonic chemical synapse; and (3) it has perhaps the most complex and highly organized synaptic morphology in the entire brain. Yet little is known about how neurotransmitter is released from this synapse. We present in this report evidence which suggests that the release of photoreceptor neurotransmitter, presumably glutamate, is probably mediated by clusters of synaptic vesicles which give rise to discrete miniature excitatory postsynaptic currents (MEPSCs) in bipolar cells. The MEPSCs are Ca(2+)-, osmotic- and CNQX-sensitive, and they share the same reversal potential (near -3 mV) as the glutamate-induced postsynaptic current. The frequency of MEPSCs increases upon presynaptic depolarization, and the mean peak conductance is about 54 pS. MEPSCs exhibit wide variations of amplitudes and durations, probably resulting from random variations of number of synaptic vesicles and the degree of synchronization in individual release clusters.

Ambystoma↗
PubMed1983

A rapid miniature thin layer chromatography system for analysis of prostaglandins and lipoxygenase products.

We have developed a miniature thin layer chromatography system for rapidly identifying the major arachidonate metabolites in a radiolabeled form elaborated by cells or tissues. This system separates the total spectrum of cyclooxygenase products and several of the most commonly found lipoxygenase pathway metabolites, while retaining the fine resolution of larger-scale and more time-consuming procedures. It requires less than one hour for extraction of metabolites, chromatography, and counting.

Animals↗
PubMed1989

Interstrain inseminations and embryo transfers between the SLA miniature pig and standard crossbred pig.

The purpose of this study was to determine fertilization and karyotypes of embryos after interstrain insemination and survival of embryos after reciprocal transfers between the National Institutes of Health SLA miniature pig and standard crossbred pig. Recovery of viable embryos indicated fertilization rates were not different in the two strains. Karyotypes of cells from embryos of both strains had the same chromosome number. The wide variation (within animal) in developmental stages of embryos recovered from the SLA minipig suggests the possibility of a prolonged ovulation interval, or a super imposed recruitment of a second set of follicles ovulating a few hours later. Cystic endometrial hyperplasia in the SLA minipig reduced the number of embryos recovered due to mechanical blockage of the uterine horns, thus preventing adequate flushing. SLA minipig recipients with no morphological evidence of cystic endometrial hyperplasia have a similar pregnancy rate to the standard pig. Cystic endometrial hyperplasia may contribute to reduced reproductive efficiency of the SLA minipig as a result of a detrimental effect on early embryo development and/or implantation.

Journal Article↗
PubMed1986

Miniature load cells for the measurement of foot-ground reaction forces and centre of foot pressure during gait.

A knowledge of the function of the foot is essential for an understanding of the mechanics of gait. In particular it is necessary to measure the forces, and their directions, between the foot and the ground. Miniature shoe borne load cells were used to measure the centre of foot pressure of a normal subject, a below knee amputee and a polio patient. An analysis of the resulting force patterns has been found useful as a measure of a subject's functional mobility. This paper describes a system which has been developed to measure and analyse the distribution of the forces acting on the foot of a polio patient, an amputee and group of normal subjects.

Adult↗
PubMedDate not supplied

A miniaturized micro-fluorescence film balance for protein-containing lipid monolayers spread from a vesicle suspension.

In order to study protein-lipid monolayers at the air/water interface a miniaturized micro-fluorescence film-balance apparatus has been developed and combined with a modified technique of spreading and separating a monolayer from a vesicle suspension. The spreading method provides non-denaturing conditions for protein-lipids. When applied to protein-lipid vesicles, monolayers with incorporated proteins are obtained, and their thermodynamic parameters may be controlled in a well-defined way by film balance techniques. In the apparatus introduced, a movable microscope allows the observation of micro-fluorescence during the tracking of individual domains at the air/water interface of a fixed Langmuir trough. After the control of parameters such as subphase temperature, surface pressure and lateral molecule distribution, a monolayer may be transferred and immobilized on a planar solid support, making it accessible to optical surface-sensitive measuring methods as well as to electron microscopy and scanning probe techniques.

Lipids↗
PubMed1984

Successful ventricular application of the miniaturized controlled-delivery Accurel technique for sustained enhancement of cerebrospinal fluid peptide levels in the rat.

A recently developed small controlled-delivery peptide device has now been further miniaturized (3.5 mm3 rod) and its action has been tested in vitro and in vivo using vasopressin (VP) as experimental substance. In vitro immersion showed a constant and lasting release of VP for weeks, as had been described for larger devices. By introducing the mini-device into the lateral ventricle of rat brain and by sampling CSF via a permanent cannula in the cisterna magna, a steadily enhanced level of VP could be attained for CSF. These increased levels persisted for one week, but most likely continue for longer periods.

Animals↗
PubMedDate not supplied

Detection of sub-miniature endplate potentials by harmonic analysis.

In phrenic nerve-diaphragm preparations from young rats and mice, long-term recordings of miniature endplate potentials (MEPPs) from single synapses were performed. Amplitude histograms obtained from these experiments were analysed with respect to the presence of multiple peaks which are believed to reflect quantal transmitter release. This was accomplished by subjecting MEPP amplitude histograms as well as matched random number histograms to Fourier analysis; harmonics in the MEPP amplitude distribution were considered valid only if they exceeded those of the random number distribution. In 9 out of 11 experiments, substantial evidence for the existence of preferred amplitudes was obtained; in two cases, however, it was completely missing. Applying our method to a series of promising MEPP amplitude histograms selected from the literature, we found a similar relationship between positive and negative results. We also noted a fairly constant relationship between the size of the elementary sub-MEPPs and the mean amplitude of the bell-MEPPs, named so according to the Gaussian shape of their amplitude distribution.

Animals↗
PubMed1986

A miniaturized cryoprobe for functional neuronal blockade in freely moving animals.

We have developed a miniature cryoprobe for blockade of neuronal structures. The cryoprobe uses Freon as a cooling medium and consists of concentric double stainless steel cannulae, a shaft heater coil and a tip thermocouple. The cryoprobe tip temperature is controlled by adjusting Freon flow supplying the cryoprobe by an automobile fuel injector and electronic control circuit, and is displayed on a temperature monitor. Tissue temperatures, determined by thermocouples, ranged from 8.5 degrees C near the cryoprobe tip to 20 degrees C 2.5 mm distal to the tip. The cryoprobe shaft is maintained at body temperature by means of a shaft heater coil and a heater control circuit. The cryoprobe offers advantages of ease of construction, and allows cooling of neuronal structures in freely moving animal preparations.

Animals↗
PubMed1995

Miniature microdrive for extracellular recording of neuronal activity in freely moving animals.

The new design of a removable miniature microdrive for extracellular recordings of single-unit activity in freely moving animals with high-impedance electrodes is presented. The construction permits very simple installation and removal of the microelectrodes, rapid fixation of the microdrive on the animals skull and rapid removal after recording. The microdrive provides vertical positioning of the electrode without rotations and lateral shifts, stable recordings of single units for several hours and the possibility to change the penetration track 20-30 times in the same animal. The 3.2-mm diameter of the microdrive cylinder permits the installation of several units simultaneously. The weight of the microdrive with the base is 115 mg. The microdrive permits penetrations to any desired depth.

Animals↗
PubMed1995

A method of estimating the rate of miniature end-plate potential occurrences based on parametric time series modeling.

This paper presents a parametric method of estimating the rate of miniature end-plate potential (MEPP) occurrences. We consider the case where the rate of MEPP occurrences is raised by the constant deporalization of presynaptic terminals by using high-concentration potassium solutions. Under such conditions, since MEPP occurrences cannot be identified by eye due to waveform superposition, it is necessary to estimate the rate with the aid of statistical techniques instead of counting the occurrences by eye. In this paper it is assumed according to the literatures that the MEPP data are modeled as a stationary Poisson impulse process filtered by the linear system the impulse response function of which is the sum of two exponentials. Then, the discretized MEPP data are shown to be a second-order autoregressive (AR(2)) process, driven by the sum of 2 first-order moving average (MA(1)) processes (the residual time series). An explicit formula for estimating the rate can be derived by combining the second- and third-order moments of the residual time series. The validity of the proposed estimation method is verified through Monte Carlo simulations in which the rate is varied ranging from 100 to 10,000 s-1. Likewise, the proposed method is applied to estimation of the rate of actual MEPP data, which were observed at the frog's neuromuscular junction under high-concentration potassium solutions.

Animals↗
PubMed1994

Miniature endplate currents at the newly formed neuromuscular junction in Drosophila embryos and larvae.

Miniature endplate currents (mepcs) were recorded in embryos and larvae of Drosophila melanogaster with the patch clamp technique in the whole cell configuration from abdominal ventral oblique muscles. Shortly after nerve-muscle contacts (16 h after egg laying) mepcs were small and infrequent. The mean amplitude of mepcs increased abruptly during late embryonic stages but did not change any further up to second instar larvae. The amplitude distribution of mepcs was skewed toward larger amplitudes and changed drastically to a more broader distribution at the time of hatching, but did not change any further. These muscle cells were found to be electrically coupled to those in the rostral neighbor segment. The synaptic current has a fast rising phase and decayed with a single exponential throughout the developmental period examined. The decay time constant increased with amplitude but the rise time did not. Neither the rise time nor the decay time constant changed with development. Many synaptic currents decayed in a stepwise manner revealing underlying single channel events. Two discrete steps were discerned, with amplitudes of about 7.6 and 16 pA at -60 mV. These two types of channels were observed throughout the stages examined.

Animals↗
PubMed1994

Development of a miniature bioreactor for continuous culture in a space laboratory.

A new type of miniature bioreactor for continuous culture of yeast cells in space laboratories has been developed. Silicon microtechnology has permitted the integration of numerous functions and systems in a volume of 87 x 63 x 63 mm3 and a weight of 610 g. The 100 ml of fresh medium can be delivered at variable flow rates to the cultivation chamber (volume 3 ml) by means of a micropump. The culture is agitated by a magnetic stirrer. Microsensors monitor pH, temperature and redox potential. The decrease of pH occurring during the cultivation of Saccharomyces cerevisiae is compensated electrochemically. A window allows the inspection of the culture status. Samples of up to 1 ml can be drawn through a silicone rubber septum. The data measured by the sensors are transmitted on-line to the ground station during operations in space. The bioreactor had to fulfil several requirements related to the safety regulation of the space agencies. In particular, new materials had to be selected and tested for their biocompatibility. The instrument has now passed all space and biological qualification tests and will be used in an experiment selected by ESA for the International Microgravity Laboratory-2 Mission in Spacelab in July 1994. This paper gives the results of the functional and biological tests and a detailed description of the instrument.

Fermentation↗
PubMed1976

The toxicity of brominated sesame oil and brominated soybean oil in miniature swine.

Miniature swine were fed brominated sesame oil at dietary levels of 0, 5, 25, 50 or 500 mg/kg of body weight for 17 weeks and brominated soybean oil at levels of 0, 5, 50 or 500 mg/kg of body weight for 28 weeks. Growth rate and food intake were decreased only at the high dose level in the brominated sesame oil study. In both studies, signs of lethargy and ataxia occurred in pigs fed the highest dose, and were probably due to a dose-related increase in serum bromine concentrations. Marked elevations in lactic dehydrogenase (LDH), serum glutamic-oxalacetic transaminase (SGOT) and serum glutamicpyruvic transaminase (SGPT) values were seen at the highest dose level with both substances and these enzyme activities were increased at the 50 mg/kg dose level in the brominated sesame oil study. Histopathologic lesions were confined to animals given the highest dose level of either oil. Marked fatty degeneration of the hepatic plate cells and renal tubular epithelial cells were seen in both studies. In the brominated sesame oil study, neutral fat was moderately increased in the myocardium of the pigs fed 500 mg/kg. However, marked diffuse accumulation of LDH, marked diffuse fatty degeneration and focal degeneration, and/or necrosis of individual or small groups of cardiac muscle fibers were seen in the group fed brominated soybean oil at 500 mg/kg. A moderate to marked testicular atrophy was also observed in this group. A dose-related accumulation of total and hexane-soluble bromine was observed in all tissues examined in both studies; the highest concentrations occurred in adipose tissue of the pigs given the highest dose level. Kidneys, livers, hearts and thyroids of these groups also contained large amounts of bromine. In pigs given the 50 mg/kg dose level, total and hexane-soluble bromine concentrations were higher in the brominated sesame oil study than in the longer brominated soybean oil study and may be responsible for the elevations in LDH, SGPT and SGOT activities in this group.

Animals↗