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1.
The uptake of various, different-sized particles by macrophages was studied using the electron microscope. In addition to observing normal cells, cells were examined which had been inhibited by exposing them to low temperature (4°C), and to a number of metabolic poisons. It was found that large particles (> 01 μm) enter the cells and are contained in large vesicles (0·1–5 μm). Small particles (< 50 nm) may also enter the cells by this process. They enter most frequently, however, by passing into small (~ 70 nm) vesicles. These may later coalesce and their contents adhere to give a second kind of large vesicle. The various inhibitors prevented the ingestion of the large particles (and of the small particles en masse) into large vesicles, but did not prevent their initial adsorption onto the plasma membranes. They did not prevent nearly normal numbers of small particles from entering the pre-existing small vesicles, nor their subsequent fusion into the second class of large vesicles.  相似文献   

2.
A new light microscope–temperature‐controlled chamber (LM–TCC) has been constructed. The special feature of the light microscope–temperature‐controlled chamber is the Peltier‐element temperature control of a specimen holder for biological samples, with a volume capacity of 1 mL. This system has marked advantages when compared to other approaches for temperature‐controlled microscopy. It works in a temperature range of −10°C to +95°C with an accuracy of ±0.1°C in the stationary phase. The light microscope–temperature‐controlled chamber allows rapid temperature shift rates. A maximum heating rate of 12.9°C min−1 and a maximum cooling rate of 6.0°C min−1 are achieved with minimized overshoots (≤1.9°C). This machinery operates at low cost and external coolants are not required. Especially with samples absorbing irradiation strongly, temperature control during microscopy is necessary to avoid overheating of samples. For example, leaf segments of Ficaria verna exposed to 4500 μmol photons m−2 s−1 in a standard microscopic preparation show a temperature increase (δT) of 18.0°C, whereas in the light microscope–temperature‐controlled chamber this is reduced to 4°C. The kinetics of microscope‐light induced δT are described and infrared thermography demonstrates the dissipation of the temperature. Chloroplasts of the cold adapted plant Ranunculus glacialis show the tendency to form stroma‐filled protrusions in relation to the exposure temperature. The relative number of chloroplasts with protrusions is reduced at 5°C when compared to 25°C. This effect is reversible. The new light microscope–temperature‐controlled chamber will be useful in a wide range of biological applications where a rapid change of temperature during microscopic observations is necessary or has to be avoided allowing a simulation of ecologically relevant temperature scenarios.  相似文献   

3.
Background: The impact of burns and colds on human skin microcirculation and histomorphology has not been compared as yet. Reflectance confocal microscopy (RCM) enables in vivo insight in human skin on cellular and subcellular levels. We evaluated analogies and differences of thermal injuries on microcirculation and histomorphology in vivo using RCM. Methods: Local superficial burn (6 female, 4 male; aged 28.4 ± 2.9 years, burn group) versus superficial cold (4 female, 6 male; aged 30.4 ± 5.2 years, cold group) was induced on the dorsum of the hand in an experimental immersion hand model. In vivo RCM was performed prior (control), immediately (t1) and 15 minutes (t2) following thermal injury to evaluate: Individual blood cell flow (IBCF), functional capillary density (FCD), epidermal thickness (ET), and granular cell size (GCS). Results: In the burn group, IBCF was increased at t1 (78.02 ± 2.60/min) and remained elevated at t2 (84.16 ± 3.04/min). In the cold group, IBCF decreased at t1 (12.62 ± 2.12 min) and increased at t2 (74.24 ± 3.14/min, P < 0.05) compared to the controls (58.23 ± 3.21/min). FCD was 6.74 ± 0.52/mm2 in controls and increased at both t1 (7.82 ± 0.72/mm2) and t2 (8.02 ± 0.81/mm2) in the burn group. In the cold group, FCD decreased at t1 (2.60 ± 0.42/mm2) and increased at t2 (7.92 ± 0.44/mm2, P < 0.05). ET increased at both t1 (43.12 ± 4.08 μm, P > 0.05) and t2 (47.26 ± 4.72 μm, P < 0.05) in the burn group. In the cold group, ET decreased at t1 (39.92 ± 3.14 μm, P > 0.05) and increased at t2 (44.72 ± 4.06 μm, P < 0.05) compared to the controls (41.26 ± 3.82 μm). Control GCS was 726.9 ± 59.4 μm2 and increased at both t1 (739.8 ± 69.8 μm2, P > 0.05) and t2 (762.6 ± 71.4 μm2, P < 0.05) in the burn group. In the cold group, GCS decreased at t1 (712.4 ± 53.8 μm2, P > 0.05) and increased at t2 (742.6 ± 64.8 μm2, P < 0.05). Conclusions: Superficial burn induces more cellular destruction and cold leads to huge fluctuation in tissue perfusion, however, with moderate impact on histomorphology. The effect on dermal capillaries suggests a selective neural control and cold injuries might down‐regulate this system, much more than burns can activate it. Microsc. Res. Tech., 2011. © 2011 Wiley‐Liss, Inc.  相似文献   

4.
The dimensions and numbers of vesicles were determined in the blood capillary endothelium of the gastrocnemii muscle of dogs. These results permitted more accurate calculations of the number of vesicles crossing the endothelium in one direction/sec/(μm2 (~6·2), and of the median vesicular attachment time (~8 sec). The probability of fusion occurring when a vesicle contacts a plasma membrane (α= 0·004) was unchanged: hence it was concluded, from the mean cellular width (0·21 μm) and the calculated cytoplasmic viscosity (~0·1 poise), that ~49% of the vesicles starting from one side reached the other one, and that their median transit time was ~1 sec.  相似文献   

5.
Mature spermatozoa traits and morphology of endangered Albanian water frog, Pelophylax shqipericus, have been characterized for the first time through phase contrast microscopy, as part of successful implementation of in vitro fertilization technique for this species. The basic morphology of P. shqipericus spermatozoa consists of an elongated, thick, smooth‐edged, and solid‐staining head, continuing with a thin and long tail which usually extends 2.48 times the head length. The acrosome was not clearly discernible so the measurements were done on the head as a whole, while the middle section was better visible. Average length of head, including the acrosome and midsection was estimated to be 11.78 μm ± 0.32, while the tail length resulted 29.24 ± 1.75 μm. The average thickness of the head was shown to be 3.45 μm. The total sperm length resulted to be 41.02 ± 1.83 μm. The average sperm concentration was estimated of 25.5 × 106/ml. Sperm amount, survival rate and motility were also measured. The sperm survival rate was maximal immediately after preparation of the suspension and tended to decrease over time of storage, reaching 50% after 72 hr. Decreased sperm motility seemed to follow the same trend as sperm viability. Sperm traits resulted to be very similar both in size and in shape with those of “Lessonae” frog group, one of the lineages of Western Palearctic species complex, suggesting a strong phylogenetic relationship among these species.  相似文献   

6.
Objective: Until now, high resolution reflectance confocal‐laser‐scanning microscopy (CLSM) was used for observation of cutaneous morphology in vivo and in real time. We hypothesized that CLSM also allows observation of dynamic processes of cutaneous microcirculation. Methods: Reflectance CLSM (Vivascope1500; Lucid, Rochester, NY) was performed in 24 young male habitual smokers (23 years, range: 19–26, body mass index 23.9 ± 4.04) with relatively limited cigarette exposure (mean: 3.1 ± 2.4 pack‐years). Eight matched nonsmokers served as controls. The quantitative blood cell flow and the diameter of capillary loops were determined prior (baseline), during, as well as 5 and 10 min after smoking. Results: Baseline value for blood cell flow was 55.50 ± 2.33 cells/min, and decreased over 45% during smoking (30.43 ± 3.76/min; P = 0.02). They were still 22% lower (43.33 ± 2.45/min; P = 0.01) 5 min after smoking and exceeded baseline values 10 min after smoking by 13% (63.00 ± 3.10/min; P > 0.05). The baseline values for capillary loop diameter (9.03 ± 0.22 μm) decreased by 21% (7.18 ± 0.28 μm; P = 0.03) during smoking, remained about 9% (8.23 ± 0.18 μm; P = 0.01) lower 5 min after smoking and exceeded baseline values insignificantly by 4% (9.38 ± 0.28 μm; P > 0.05) 10 min after smoking. There were no significant differences to the controls. Conclusion: Reflectance CLSM enables qualitative and quantitative observation of dynamic processes of cutaneous microcirculation on histomorphological level. Microsc. Res. Tech., 2009. © 2008 Wiley‐Liss, Inc.  相似文献   

7.
M.M. Hamdy  R.B. Waterhouse 《Wear》1981,71(2):237-248
The fretting wear of Ti-6Al-4V and Inconel 718 was investigated with a sphere-on-flat configuration. The spherical surface was 100 mm in radius and in all tests was made of the same material as the flat. The normal load was 2.75 N and the frequency of the tangential movement was 50 Hz. Two amplitudes of slip were used, 10 and 40 μm. Tests were conducted in air at temperatures up to 600 °C for the titanium alloy and up to 540 °C for the nickel alloy. High temperature strain gauges enabled a continuous record of the tangential stress to be made and subsequent calculation of the coefficient of friction. Wear was assessed from measurement of the scar volume. At 280 and 540 °C at an amplitude of 40 μm the coefficient of friction and wear rate decreased to a low value on the nickel alloy. This only occurred at 540 °C for the lower amplitude of slip. Low friction and wear are associated with the formation of a “glaze” oxide, which requires a larger slip amplitude at lower temperatures for its formation.The titanium alloy generally exhibited higher coefficients of friction which continued to increase at 106 cycles, although wear rates at 200 °C and above were comparable with those on the nickel alloy. “Glaze” oxide begins to form at 200 °C and is well developed at 400 °C. At 600 °C breakdown occurs owing to local creep of the substrate.  相似文献   

8.
The effect of implantation of nitrogen ions (1.5 MeV) on the friction and wear characteristics of pure iron sliding against M-50 steel (unimplanted) was studied in a pin-on-disk sliding friction apparatus. Test conditions included room temperature (~25°C), a dry air atmosphere, a load of ½ kg (4.9 N), sliding velocities of 0.043 to 0.078 m/s (~15 to 25 rpm), a pure hydrocarbon lubricant (n-hexadecane), or a USP mineral oil and nitrogen ion implantation doses of 5 × 1015 and 5 × 1017 ions/cm2.

No differences in wear rates were observed in the low-dose (5 × 1015 ions/cm2) experiments. In the high-dose experiments (5 × 1017 ions/cm2), small reductions in initial (~40 percent) and steady-state (~20 percent) wear rates were observed for nitrogen-implanted iron riders as compared with unimplanted controls. No differences in average friction coefficients were noted for either dose.

Auger electron spectroscopy combined with argon ion bombardment revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 6 atomic percent at a depth of 8 × 10?7 m (0.8 μm). Similar analysis within the wear scar (~2.0 × 10?5 m subsurface) of an implanted rider after 20 μm of wear yielded only background nitrogen concentration. No inward migration of nitrogen ions was observed.  相似文献   

9.
Self-supporting ultralow density laser targets with an apparent density as low as 1 mg/cm3, a porous layer thickness of 60–500 μm, and a window diameter of 2.5 mm were prepared by thermally induced gelation of cellulose acetate solution in a mixture solvent between two glass slides using the mold casting method. In view of the low mechanical gel strength at a concentration of <0.2 wt %, supercritical drying of molded targets is carried out without separating the glass slides. For the target output to be radically increased, a new procedure has been developed based on rapid freezing of the solution on a metal brick from room temperature to–60°C and lower, down to–190°C, without initial gelation.  相似文献   

10.
Number, length, and diameters of dendritic spines of the granule cell in the dorsal leaf of the rat dentate gyrus were measured by using high-voltage electron microscope stereo images of 5-m?m-thick Golgi preparations with the aid of a three-dimensional image analyzer system. Spine densities of 2.02 ± 0.28, 2.28 ± 0.33, and 3.36± 0.35 per 1 μm at distal, middle, and proximal portions of the dendrite were obtained. These values were about 1.6-fold of the previous light microscopical report. Mean three-dimensional spine length were 1.244 ± 0.506 μm, 1.262 ± 0.563 μm, and 1.254 ± 0.584 μm at distal, middle, and proximal portions, respectively, which were about 1.4 times longer than those measured in two dimensions. By using measured morphometrical parameters of spines such as lengths, diameters, and population densities, total spine surface areas of 2.401 μm2, 2.806 μm2, and 4.180 μm2 per 1 μm of the dendrite at distal, middle, and proximal portions, respectively, were obtained. The total surface area of dendrite was about doubled by the addition of the spines at each dendritic portion. The advantageous features and the problems of the present method are discussed.  相似文献   

11.
This in vitro study aimed to quantify water loss at histological points in ground sections of normal enamel during air drying at room temperature (25°C) and relative humidity of 50%. From each of 10 ground sections of erupted permanent human normal enamel, three histological points (n = 30) located at 100, 300 and 500 μm from enamel surface and along a transversal following prisms paths were characterized regarding the mineral, organic and water volumes. Water loss during air drying was from 0 to 48 h. Drying occurred with both falling and constant‐drying rates, and drying stabilization times (Teq) ranged from 0.5 to 11 h with a mean 0.26 (±0.12)% weight loss. In some samples (n = 5; 15 points), Teq increased as a function of the distance from the enamel surface, and drying occurred at an apparent diffusion rate of 3.47 × 10?8 cm2 s?1. Our data provide evidence of air drying resulting in air replacing enamel's loosely bound water in prisms sheaths following a unidirectional water diffusion rate of 3.47 × 10?8 cm2 s?1 (from the original enamel surface inward), not necessarily resulting in water evaporating directly into air, with important implications for transport processes and optical and mechanical properties.  相似文献   

12.
The tribological behavior of self-mated Ti3SiC2 is investigated from ambient temperature to 800?°C at a sliding speed of 0.01?m/s in air. The results show that at the temperatures lower than 300?°C, friction coefficient and wear rates are as high as 0.95 and 10?3?mm3/N?m, respectively. With the temperature increasing to 600?°C, both the friction coefficient and wear rates show consecutive decrease. At 700 and 800?°C, friction coefficient and wear rates are 0.5 and 10?6 mm3/N?m, respectively. According to the wear mechanism, the tribological behavior of Ti3SiC2 can be divided into three regimes: mechanical wear-dominated regime from ambient temperature to 300?°C characterized by pullout of grains; mixed wear regime (mechanical wear and oxidation wear) from 400 to 600?°C; and tribo-oxidation-dominated wear regime above 700?°C. The tribo-oxides on the worn surfaces involve oxides of Si and Ti. And, species transformation occurs to these two oxides with the increasing temperature. In the competition oxidation of elements Ti and Si, Si is preferably oxidized because of its high active position in the crystal structure. Additionally, plastic flow is another notable characteristic for the tribological behavior of self-mated Ti3SiC2.  相似文献   

13.
This work describes an analysis of titanium dioxide (TiO2) thin films prepared on silicon substrates by direct current (DC) planar magnetron sputtering system in O2/Ar atmosphere in correlation with three‐dimensional (3D) surface characterization using atomic force microscopy (AFM). The samples were grown at temperatures 200, 300, and 400°C on silicon substrate using the same deposition time (30 min) and were distributed into four groups: Group I (as‐deposited samples), Group II (samples annealed at 200°C), Group III (samples annealed at 300°C), and Group IV (samples annealed at 400°C). AFM images with a size of 0.95 μm × 0.95 μm were recorded with a scanning resolution of 256 × 256 pixels. Stereometric analysis was carried out on the basis of AFM data, and the surface topography was described according to ISO 25178‐2:2012 and American Society of Mechanical Engineers (ASME) B46.1‐2009 standards. The maximum and minimum root mean square roughnesses were observed in surfaces of Group II (Sq = 7.96 ± 0.1 nm) and Group IV (Sq = 3.87 ± 0.1 nm), respectively.  相似文献   

14.
15.
Fatigue curves in the presence of fretting have been determined on the alloy Ti-6Al-4V in fluctuating tension under a mean stress of 247 MN m?2 at 20, 200, 400 and 600 °C. The fatigue strengths at 107 cycles at temperatures of 200 and 400 °C are the same, namely ±77 MNm?2. At 600 °C the fatigue strength under these conditions falls to ±70 MNm?2. The normal fatigue strength also shows a considerable fall off at this temperature. Scanning electron microscope observations show that failure is associated with the formation of ridges on the surface which develop into piles of platelets. This process is apparent at 200 °C but becomes accelerated at the higher temperatures and leads to large accretions of platelets at 600 °C in curious formations resembling an elephant's trunk.  相似文献   

16.
BACKGROUND: Splint immobilization of the forearm is often performed in clinical practice. Previous studies investigated the effect of immobilization on bone, cartilage, muscle, and tendon, however, the acute effects on human skin microcirculation and histomorphology remains elusive. METHODS: In 12 healthy, nonsmoking individuals (aged 29.7 ± 9.1 years) a randomly selected forearm was immobilized by splinting for 72 h, whereas the other forearm served as control. In vivo Reflectance‐Mode Confocal‐Microscopy (RMCM) was performed prior (baseline value) and postimmobilization to evaluate: quantitative blood cell flow; density of functional dermal capillaries; epidermal thickness; and granular cell size. RESULTS: At 72h forearm immobilization, quantitative blood cell flow was significantly reduced (42.86 ± 3.68 cells/min) compared to the control blood flow (53.11 ± 3.68 cells/min, P < 0.05) and dermal capillaries indicates less functional density (5.73 ± 0.63 capillaries/mm2) compared to the controls (7.04 ± 0.81 capillaries/mm2, P < 0.05). Histometric assessment reveals significantly thinner epidermis following immobilization compared to the control site (40.02 ± 2.91 vs. 46.64±3.09 µm, P < 0.05). Granular cell size was significantly altered at 72 h splinting (730.1 ± 42.53 µm2) compared to the control cell size at 770.2 ± 38.21 µm2. Comparison of baseline values of both forearms indicate statistically insignificance (P > 0.05) for each parameter. CONCLUSION: At 72 h splint immobilization, for the first time, significant adaptive mechanisms were evaluated on human skin microcirculation and histomorphology using in vivo RMCM. These adaptations may be considered as an incipient atrophy of the human skin. Long‐term effects of immobilization including the regenerative potential should be evaluated in further RMCM studies. Microsc. Res. Tech. 77:99–103, 2014. © 2013 Wiley Periodicals, Inc.  相似文献   

17.
Electron energy‐loss spectroscopy (EELS) has been used to characterize the electronic structure of charcoal phases at the nanoscale, thus demonstrating that the technique can be applied to environmental science. Activated charcoal is extensively used to remove pollutants from liquid and gaseous sewage. It is mainly obtained by activation of coke or charcoal produced from ligneous precursors. The present study concerns the use of by‐products of local Caribbean agriculture, such as sugar cane bagasse, fruit stones and seeds, for use as activated charcoal precursors. Charcoal phases are prepared by high‐temperature pyrolysis of lignocellulosic raw materials under a nitrogen gas flow. With the aim of optimizing the pyrolysis temperature and duration and oxygen content, the concentration of carbon sp2 hybridized chemical bonds and structural ordering have been followed by EELS for different treatment temperatures. To quantify the carbon sp2 content, near edge structure (NES) at the carbon K edge has been measured to determine the strength of π → π* and 1s → π* transitions. Three precursors of plant origin, shells of Terminalia catappa and Acrocomia karukerana and seeds of Psidium guajava, with the pyrolysis temperatures between 600 and 900 °C, were investigated. The fraction of carbon sp2 bonding is found to increase when the temperature rises from 600 °C to the range 700–750 °C and becomes stable at higher temperatures. For temperatures in excess of 700 °C, structural ordering probably occurs and well‐defined 1s → σ* NES is present, whose intensity increases with increasing preparation temperature. For the highest temperature of around 900 °C, the structure of the final product is less well organized than graphitized carbon but a few per cent of a highly ordered phase is found.  相似文献   

18.
This research investigated the morphological, morphometric, and ultrastructural cardiomyocyte characteristics of male Wistar rats at 18 months of age. The animals were euthanized using an overdose of anesthesia (ketamine and xylazine, 150/10 mg/kg) and perfused transcardially, after which samples were collected for light microscopy, transmission electron microscopy, and high‐resolution scanning electron microscopy. The results showed that cardiomyocyte arrangement was disposed parallel between the mitochondria and the A‐, I‐, and H‐bands and their M‐ and Z‐lines from the sarcomere. The sarcomere junction areas had intercalated disks, a specific structure of heart muscle. The ultrastructural analysis revealed several mitochondria of various sizes and shapes intermingled between the blood capillaries and their endothelial cells; some red cells inside vessels are noted. The muscle cell sarcolemma could be observed associated with the described structures. The cardiomyocytes of old rats presented an average sarcomere length of 2.071 ± 0.09 μm, a mitochondrial volume density (Vv) of 0.3383, a mitochondrial average area of 0.537 ± 0.278 μm2, a mitochondrial average length of 1.024 ± 0.352 μm, an average mitochondrial cristae thickness of 0.038 ± 0.09 μm and a ratio of mitochondrial greater length/lesser length of 1.929 ± 0.965. Of the observed mitochondrial shapes, 23.4% were rounded, 45.3% were elongated, and 31.1% had irregular profiles. In this study, we analyzed the morphology and morphometry of cardiomyocytes in old rats, focusing on mitochondria. These data are important for researchers who focus the changes in cardiac tissue, especially changes owing to pathologies and drug administration that may or may not be correlated with aging. Microsc. Res. Tech., 2013. © 2012 Wiley Periodicals, Inc.  相似文献   

19.
Measurements were made of the diameters, numbers and other parameters of small, smooth-surfaced vesicles in the endothelium of blood capillaries and lymphatics, and in the mesothelial cells of the diaphragms of mice. Some measurements were also made on the aortic endothelium. With a few exceptions, there were no morphological differences between the various sites. It was found that between 25% and 35% of the non-nuclear cell volume was composed of vesicles, whose membranes accounted for about 55% of their volumes. Their internal volumes were ~ 70,000 nm3, totalling ~ 0·04 μm3/μm2 of luminal surface area. For each 1 μm2 there were ~ 135 vesicles attached to each surface membrane of the cell, and between ~ 200 and ~ 350 vesicles lying free in the cytoplasm. There was probably a slight amount of shrinkage during the preparation of the material, and the true linear dimensions were probably ~ 105% of those actually observed. Thus the values for the internal volumes were probably ~ 85,000 nm3 and ~005 μm3 respectively; the vesicular numbers were probably ~ 125 attached to each surface and between ~ 175 and ~ 300 free. The vesicles attached to the plasma membranes often had quite long stalks; these were estimated to be ~ 30 nm at the moment of rupture. Thus the vesicles must be released an appreciable distance away from the membrane. This modifies the conclusions of Shea & Karnovsky (1966), since it can now be shown that Brownian movement alone is capable of accounting for the release of the vesicles, their movements within the cells and their transportation of material. By combining these results with others estimating the endothelial permeability coefficients, it can be calculated that the average free lifetime of a vesicle is ~1½ sec, from union with one plasma membrane to the next. It can also be shown that the average time of such an attachment is ~ 2½ sec. There are many possible sources of error relating to these measurements; they must only be regarded as tentative. It appears likely, however, that they are of about the correct order of magnitude as they accord well with other data.  相似文献   

20.
针对脆性石英玻璃的微加工,利用自主研发的金刚石砂轮微尖端修整工艺,研发了光纤阵列石英玻璃微V槽磨削技术。分析了60°的微V槽形状偏差对光纤耦合损耗的影响,然后,研究了砂轮微尖端的误差补偿修整工艺。最后,实验分析了微V槽的磨削精度。理论分析显示:微V槽角度、间距和宽度的偏差分别控制在±0.42°、±1.04μm和±1.2μm以内时,耦合损耗小于0.5dB。实验结果表明:开发的数控磨削工艺可加工高精度的60°微V槽阵列;采用数控轨迹和角度补偿修整后,砂轮微尖端半径可平均达到10.46μm,角度精度为(60±0.22)°;对石英玻璃进行微磨削后,微V槽的角度偏差达到0.4°,尖端半径为10.5μm,宽度偏差为0.3μm,间距偏差为0.5μm,可保证光纤阵列的精密对接。  相似文献   

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