A novel concentric double-barrelled calcium-selective microelectrode for small cells

A novel concentric design of double-barrelled Ca2+-selective microelectrode, with an inner pipette tip that protrudes beyond an outer one, has recently been developed and is described. This configuration of pipettes was produced from concentric capillaries in one step using a horizontal pipette puller. For the tip of the inner barrel to protrude, Corning 1724 aluminosilicate glass was selected, as it has a higher melting point than the 1723 glass which is used for the outer barrel. To reduce electrode resistance the inner capillary was best made with a triangular shape. It was preferentially silanized in a dry box by injection of methyltrichlorosilane into only the inner barrel. The Ca2+ neutral carrier-based liquid membrane (ETH 1001) was back-filled from the tip to the shank of the inner pipette and above this CaCl2 solution was added. KCl, which contained EGTA and was buffered to pCa 7, was used to fill the reference barrel. These Ca2+ electrodes showed linear response with slope approximately equal to 30 mV for changes in Ca2+ concentration between 10(-3) and 10(-7) M in the presence of constant [K+]. They offer a number of advantages including a low noise level achieved by the presence of the external concentric KCl electrode, and a simple mechanical structure that allows applications to a variety of small cells.     

Tip size of ion-exchanger based K+-selective microelectrodes. I. Effects on selectivity

Double-barreled ion-exchanger based K+-selective microelectrodes (K+ ISMs) of a variety of tip diameters were used to study the dependency of ion selectivity upon tip size. The selectivity of K+ ISMs depended on tip size and barrel configuration. Within the range of tip diameters tested (approximately 0.5-6 micron) all K+ ISMs constructed of two barrels glued side by side ("figure-eight glass") exhibited sensitivity to K+ and NH4+. Figure-eight K+ ISMs with tip diameters less than 1.5 micron were not sensitive to tetramethylammonium, tetraethylammonium, or choline, whereas K+ ISMs with tip diameters greater than or equal to 1.5 micron sensed all of the quaternary amines. Tip size dependent selectivity was not present in K+ ISMs made from thick septum theta glass. The explanation for tip size dependent changes in ion selectivity is unknown but a discussion of theoretical possibilities is given.     

SKIN BIOPSY SAMPLING OF BELUGA WHALE CARCASSES: ASSESSMENT OF BIOPSY DARTING FACTORS FOR MINIMAL WOUNDING AND EFFECTIVE SAMPLE RETRIEVAL

Different combinations of biopsy tip lengths (20, 25 mm) and diameters (5, 6, 7 mm), crossbow draw weights (23, 45, 68 kg) and distances (1.5–15 m) were tested on fresh beluga carcasses to determine factors affecting the success of biopsy retrieval and the extent of wounding. Tips with smaller diameters and longer lengths were found to be more likely to retrieve a skin sample, while the draw weight of the crossbow had a significant effect on the severity of the wound. The samples obtained from all biopsy darts tested yielded sufficient amounts of DNA for genetic analysis (20–109 μg) with the highest yield coming from the germinativum spinosum layer. For beluga whales we recommend using a tip of 5 mm in diameter, 25 mm in length, and a draw weight of 23 kg at close range.     

Flow microfluorometric and light-scatter measurement of nuclear and cytoplasmic size in mammalian cells.

A technique for rapid measurement of nuclear and cytoplasmic size relationships in mammalian cell populations has been developed. Based on fluorescence staining of either the nucleus alone or in combination with the cytoplasm using two-color fluorescence methods, this technique permits the simultaneous determination of nuclear and cytoplasmic diameters from fluorescence and light-scatter measurements. Cells stained in liquid suspension pass through a flow chamber at a constant velocity, intersecting a laser beam which excites cell fluorescence and causes light scatter. Depending upon which analysis procedure is used, optical sensors measure nuclear fluorescence and light scatter (whole cell size) or two-color nuclear and cytoplasmic fluorescence from individual cells crossing the laser beam. The time durations of signals generated by the nucleus and cytoplasm are converted electronically into signals proportional to the respective diameters and are displayed as frequency distribution hitograms. Illustrative examples of measurements on uniform microspheres, cultured mammalian cells and human exfoliated gynecologic cells are presented.     

An ammonia-sensing air gap microelectrode

An ammonia-sensing air gap microelectrode has been designed on the basis of a neutral carrier pH-sensing inner electrode. This electrode has a tip diameter of 2 to 5 microns, has a simple design, is easy to fabricate, and has a long shelf life. Its response to ammonium is linear in the range 3 x 10(-5) to 10(-2) M and its response time (95%) is 10 to 15 s. The electrode was converted to a microsensor for urea by immobilization of urease within its tip. The linear response to urea ranged from 3 x 10(-4) to 10(-2) M and the response time was 15 to 20 s.     

Squeezed flow preconcentration for probe tip biosensors

The preconcentration of analytes improves sensing using probe tips. In this work, we report a method based on creating a squeeze flow between a cylinder and circular coverslip to preconcentrate material at the liquid–gas interface while allowing a probe tip to be readily inserted there. In verification tests using enhanced green fluorescent protein, this capacity is proven. We estimated a 9.7 times increase in probability for fluorophores to be picked up at the tip using inference from fluorescence intensity distributions found. The method is expeditious, simple, and inexpensive, and it does not require any electrical energy source to operate.     

Effect of indenter size on elastic modulus of cartilage measured by indentation

Our preliminary indentation experiments showed that the equilibrium elastic modulus of murine tibial cartilage increased with decreasing indenter size: flat-ended 60 deg conical tips with end diameters of 15 microm and 90 microm gave 1.50+/-0.82 MPa (mean+/-standard deviation) and 0.55+/-0.11 MPa, respectively (p<0.01). The goal of this paper is to determine if the dependence on tip size is an inherent feature of the equilibrium elastic modulus of cartilage as measured by indentation. Since modulus values from nonindentation tests are not available for comparison for murine cartilage, bovine cartilage was used. Flat-ended conical or cylindrical tips with end diameters ranging from 5 microm to 4 mm were used to measure the equilibrium elastic modulus of bovine patellar cartilage. The same tips were used to test urethane rubber for comparison. The equilibrium modulus of the bovine patellar cartilage increased monotonically with decreasing tip size. The modulus obtained from the 2 mm and 4 mm tips (0.63+/-0.21 MPa) agreed with values reported in the literature; however, the modulus measured by the 90 microm tip was over two and a half times larger than the value obtained from the 1000 microm tip. In contrast, the elastic modulus of urethane rubber obtained using the same 5 microm-4 mm tips was independent of tip size. The equilibrium elastic modulus of bovine patellar cartilage measured by indentation depends on tip size. This appears to be an inherent feature of indentation of cartilage, perhaps due to its inhomogeneous structure.     

从X线片研究不同类型的体育运动对胫骨内、外径的影响

本文对45名男少年(依其从事运动情况分为举重、跳跃组,不从事专项运动者为普通组)胫骨正位和侧位X线片进行了观察、测量,并对三组胫骨的髓腔径、内外横径比和内外矢状径比等指标进行了统计分析。结果表明:不同机能对髓腔大小的影响既在某些方面相似,又在另一些方面出现不同的趋势;对内外径比的某些方面也有不同影响;内外径比变化趋势并非国外某些学者所记载的以8:11最为适宜。     

Metabolic constraints on the recovery of sensitivity after visual pigment bleaching in retinal rods

The shutoff of active intermediates in the phototransduction cascade and the reconstitution of the visual pigment play key roles in the recovery of sensitivity after the exposure to bright light in both rod and cone photoreceptors. Physiological evidence from bleached salamander rods suggests this recovery of sensitivity occurs faster at the outer segment base compared with the tip. Microfluorometric measurements of similarly bleached salamander rods demonstrate that the reduction of all-trans retinal to all-trans retinol also occurs more rapidly at the outer segment base than at the tip. The experiments reported here were designed to test the hypothesis that these two phenomena are linked, e.g., that slowed recovery of sensitivity at the tip of outer segments is rate limited by the reduction of all-trans retinal and results from a shortage of cytosolic nicotinamide adenine dinucleotide phosphate (NADPH), the reducing agent for all-trans retinal reduction. Extracellular measurements of membrane current and sensitivity were made from isolated salamander rods under dark-adapted and bleached conditions while intracellular NADPH concentration was varied by dialysis from a micropipette attached to the inner segment. Sensitivity at the base and tip of the outer segment was assessed before and after bleaching. After exposure to a light that photoactivates 50% of the visual pigment, rods were completely insensitive for nearly 10 minutes, after which the base recovered sensitivity and responsiveness with a time constant of ∼200 seconds, but tip sensitivity recovered more slowly with a time constant of ∼680 seconds. Dialysis of 5 mM NADPH into the rod promoted an earlier recovery and eliminated the previously observed tip/base difference. Dialysis of 1.66 mM NADPH failed to eliminate the tip/base recovery difference, suggesting the steady-state NADPH concentration in rods is ∼1 mM. These results indicate the inner segment is the primary source of reducing equivalents after pigment bleaching, with the reduction of all-trans retinal to all-trans retinol playing a key step in the recovery of sensitivity.     

Recording of intracellular Ca2+ from smooth muscle cells by sub-micron tip, double-barrelled CA2+-selective microelectrodes

Novel, double-barrelled Ca2+-selective microelectrodes with tip diameters of approximately 0.1 micron were constructed by using Simon's neutral Ca2+ ligand (ETH 1001). Concentric micropipettes were utilized for the first time for Ca2+-selective microelectrodes in which the Ca2+ ligand was incorporated into a protruding inner pipette, surrounded by an outer reference electrode. In addition, they were made from high resistance aluminosilicate glass tubing (Corning Code 1724). These Ca2+-selective electrodes had linear responses from pCa 3 to pCa 7 in the presence of constant [K+]. They provided on-line observation of changes in intracellular [Ca2+] and in the resting membrane potential in single smooth muscle cells isolated from toad stomach. The mean concentration of intracellular Ca2+ in resting cells was 163.6 +/- 20 nM (+/- SEM, n = 16). Doubling the intracellular Ca2+ level by exposure of cells to elevated [K+] was sufficient to cause shortening.     

Measuring air temperature in field studies

In order to find a simple technique for reducing errors in measurements of air temperature, experiments were performed in a wind tunnel using different sizes of thermocouples and a variety of shields. Thermocouples with a coat of clean, white enamel paint on the tip were simple and inexpensive, and they resulted in only small eroors due to radiation.     

Nuclear lamina—like filaments and nuclear matrix in allium cepa as revealed by scanning electron microscopy

In this study,freeze-fractured specimens of allium cepa root tip meristems were examined under the scanning electron microscope(SEM),This technique permitted the visualization of the outer membrane of the nuclear envelope with nuclear pore complexes and polyribosomes.Some of the cell nuclei prepared with this procedure had fissures of various widths on their nuclear envelopes through which the nuclear lamina-like filaments(LLF) undernearth the nucleoplasmic side of the envelopes were clearly visible.The diameters of these filaments veried between 25 and 125nm.Many of the LLFs showed granular thickenings at places,and were attached to the inner surface of nuclear envelope in some regions .Similar LLFs were also seen at the peripheries of the freeze-fractured faces of nuclei.Meanwhile,the spatial relation between the nuclear matrix filaments(NMF) and other nuclear structures(nucleoli,chromation and peripheral lamina-like filaments) was revealed in these fractured preparations.In addition,the methods and techniques in studying the nuclear lamina morphology and the roles played by NMFs in activities of various nuclear sturctures were discessed in brief.     

Estimation of Free, Conjugated, and Diffusible Indole-3-acetic Acid in Etiolated Maize Shoots by the Indolo-alpha-pyrone Fluorescence Method

Procedures for estimating free indoleacetic acid (IAA extracted from tissue homogenates by aqueous acetone), conjugated IAA (extracted by aqueous acetone and hydrolyzed by 1 n KOH), and diffusible IAA (diffused from the excised tissue into water), in shoots of etiolated 3-day-old maize (Zea mays L. cv. GH 390) seedlings are described, the indolo-alpha-pyrone fluorescence method being used to assay IAA. The reliability of the procedure is shown by comparative IAA determinations of the extracts using the gas chromatography-mass spectrometry method in which the methyl ester, heptafluorobutyryl derivative of IAA is assayed using the selected-ion-monitoring technique with deuterated IAA as an internal standard. A 3-millimeter-long coleoptile tip, a coleoptile with its included leaves and nodal region (whole coleoptile), and a mesocotyl each contains 0.2, 1.7, and 1.5 nanograms of free IAA, respectively. The whole coleoptile and the mesocotyl contain slightly less conjugated IAA than their content of free IAA. IAA diffuses from the coleoptile tip at the rate of 1.0 nanograms per tip per hour; from the base of the whole coleoptile and a set of leaves excised from a coleoptile, IAA diffuses at the rate of 0.62 and 0.17 nanogram per plant part per hour, respectively. The data obtained support the classical assumption that the coleoptile tip produces IAA. It is also suggested that some IAA is decomposed during its downward transport in the coleoptile.     

Computational analysis of confined jet flow and mass transport in a blind tube.

A computational analysis of confined nonimpinging jet flow in a blind tube is performed as an initial investigation of the underlying fluid and mass transport mechanics of tracheal gas insufflation. A two-dimensional axisymmetric model of a laminar steady jet flow into a concentric blind-end tube is put forth and the governing continuity, momentum, and convection-diffusion equations are solved with a finite element code. The effects of the jet diameter based Reynolds number (Re(j)), the ratio of the jet-to-outer tube diameters (epsilon), and the Schmidt number (Sc) are evaluated with the determined velocity and contaminant concentration fields. The normalized penetration depth of the jet is found to increase linearly with increasing Re(j) for epsilon = O(0.1). For a given epsilon, a ring vortex that develops is observed to be displaced downstream and radially outward from the jet tip for increasing Re(j). The axial shear stress profile along the inside wall of the outer tube possesses regions of fixed shear stress in addition to a local minimum and maximum in the vicinity of the jet tip. Corresponding regions of axial shear stress gradients exist between the fixed shear stress regions and the local extrema. Contaminant concentration gradients develop across the ring vortex indicating the inward diffusion of contaminant into the jet flow. For fixed epsilon and Sc and Re(j) approximately 900, normalized contaminant flow rate is observed to be approximately twice that of simple diffusion. This model predicts modest net axial contaminant transport enhancement due to convection-diffusion interaction in the region of the ring vortex.     

Analysis of novel geometry-independent method for dialysis access pressure-flow monitoring

Background

End-stage renal disease (ESRD) confers a large health-care burden for the United States, and the morbidity associated with vascular access failure has stimulated research into detection of vascular access stenosis and low flow prior to thrombosis. We present data investigating the possibility of using differential pressure (ΔP) monitoring to estimate access flow (Q) for dialysis access monitoring, with the goal of utilizing micro-electro-mechanical systems (MEMS) pressure sensors integrated within the shaft of dialysis needles.

Methods

A model of the arteriovenous graft fluid circuit was used to study the relationship between Q and the ΔP between two dialysis needles placed 2.5–20.0 cm apart. Tubing was varied to simulate grafts with inner diameters of 4.76–7.95 mm. Data were compared with values from two steady-flow models. These results, and those from computational fluid dynamics (CFD) modeling of ΔP as a function of needle position, were used to devise and test a method of estimating Q using ΔP and variable dialysis pump speeds (variable flow) that diminishes dependence on geometric factors and fluid characteristics.

Results

In the fluid circuit model, ΔP increased with increasing volume flow rate and with increasing needle-separation distance. A nonlinear model closely predicts this ΔP-Q relationship (R² > 0.98) for all graft diameters and needle-separation distances tested. CFD modeling suggested turbulent needle effects are greatest within 1 cm of the needle tip. Utilizing linear, quadratic and combined variable flow algorithms, dialysis access flow was estimated using geometry-independent models and an experimental dialysis system with the pressure sensors separated from the dialysis needle tip by distances ranging from 1 to 5 cm. Real-time ΔP waveform data were also observed during the mock dialysis treatment, which may be useful in detecting low or reversed flow within the access.

Conclusion

With further experimentation and needle design, this geometry-independent approach may prove to be a useful access flow monitoring method.     

DEVELOPMENT OF MUCILAGINOUS SURFACES IN EUGLENOIDS. I. STALK MORPHOLOGY OF COLACIUM MUCRONATUM1

The envelope and stalk of Colacium mucronatum Bourr. & Chad, were examined in living cells with light microscopy and in fixed preparations with scanning electron microscopy using critically point dried (CPD) and freeze dried (FD) preparations. The envelope of palmelloid cells is formed over the entire cell surface by many individual strands attached at right angles to areas of articulation of the pellicular strips. Strands were observed to anastomose on the posterior tip of otherwise naked cells. Stalks of living cells in India ink preparations had an optically dark inner core with a lighter outer sheath. In FD stalks a definite inner core was not evident, whereas CPD stalks had an outer surface composed of thick strands which may be the collapsed and aggregated strands of the FD stalks. In both there was also an amorphous matrix. The stalk forms from the aggregation of many strands from the anterior cell tip back to a point encompassing the cell surface anterior to a cross section of the tip 9 μm diam. The outer surface of the stalk comes from the pellicular surface joining that area and the core from the cell tip in the area of the canal opening. Any possible participation of the inner canal surface in stalk formation could not be determined because of the great density of the mucilage at the cell-tip/stalk junction.     

Pressurised aeration in wetland macrophytes: Some theoretical aspects of humidity-induced convection and thermal transpiration

The pressurised gas-flows, humidity-induced convection (HIC) and thermal transpiration (TT), which are important for aeration and for greenhouse gas emissions in some wetland macrophytes, are described and discussed. Results obtained from simple mathematical modelling of the processes are presented to illustrate some of their more relevant features. It is emphasised that both processes require the presence of a micro-porous partition having a significantly greater resistance to pressure flow than to diffusion. In particular it is shown that whilst the potential to pressurise by these processes is inversely related to the pore diameters of the partition, the maximum gas flows are generated where pore diameters range from 0.1 to 0.2 μm. Where partitions are a surface feature (e.g. emergent macrophytes) a dominant role for HIC is predicted; where partitions are an embedded feature (e.g. water-lilies) it is deduced that HIC will still play a significant role, but the contribution of TT could be greater.     

Effect of mercury on pollen germination and tube growth in <Emphasis Type="Italic">Lilium longiflorum</Emphasis>

Pollen development and germination were adversely affected by the presence of mercury, whereas low-concentrations stimulated the whole procedure. Mercury caused morphological anomalies during the tube growth, characterized by irregularly increasing diameters and swelling tips. The main effect was the anomalous cell wall formation at the tip where a substantial number of organelles were found reducing the secretory vesicles. The dense organelle concentration caused a significant reduction of cytoplasmic movement integrity, and the cytosol streaming was gradually reduced or stopped completely. Electron dense, multilamellar myelin-like structures (MMS) of membranous material were frequently present, in close contact with plasmalemma or away from it. A loose network of fibrillar material and spherical aggregates mostly at the tip region were observed which progressively were loosened into the surrounding medium. Elevated mercury concentrations can affect plant reproduction, resulting in anomalies in gamete development and consequently loss of plant biodiversity.     

Optical bio-sniffer for ethanol vapor using an oxygen-sensitive optical fiber

An optical bio-sniffer for ethanol was constructed by immobilizing alcohol oxidase (AOD) onto a tip of a fiber optic oxygen sensor with a tube-ring, using an oxygen sensitive ruthenium organic complex (excitation, 470 nm; fluorescent, 600 nm). A reaction unit for circulating buffer solution was applied to the tip of the device. After the experiment in the liquid phase, the sniffer-device was applied for gas analysis using a gas flow measurement system with a gas generator. The optical device was applied to detect the oxygen consumption induced by AOD enzymatic reaction with alcohol application. The sensor in the liquid phase was used to measure ethanol solution from 0.50 to 9.09 mmol/l. Then, the bio-sniffer was calibrated against ethanol vapor from 0.71 to 51.49 ppm with good gas-selectivity based on the AOD substrate specificity. The bio-sniffer with the reaction unit was also used to monitor the concentration change of gaseous ethanol by rinsing and cleaning the fiber tip and the enzyme membrane with buffer solution.     

江豚眼的解剖学和组织学研究

统计结果表明:与黄海沿岸种群江豚相比,长江种群江豚眼中央至吻端的平均距离显著较小,与长江弱光环境相适应。长江种群平均眼裂高比较小,眼球平均相对水半径比较短,而前后径比较长。眼球较趋近于圆球型。视觉较近视。在显徽与亚显微结构方面未发现两种群之间有差异。江豚无典型的视锥,而具有细胞核和内节呈视锥状、外节呈视杆状的一种中间型视细胞。