Different Layers Of Tissue Research Articles

Geometrical effects in mechanical characterizing of microneedle for biomedical applications

This paper proposes the design and implementation of MEMS (Micro Electro Mechanical Systems)-based in-plane silicon microneedles with explanation of integrated functionality for sensing the resistive forces offered by human skin. The proposed design dimensions are calculated by using the constraints of minimal microneedle dimension, force withstanding capabilities, and their relationship. The paper also proposes the novel fabrication process to realize the microneedles, along with the integrated sensors for sensing skin resistive forces at various depths. The idea of this microneedle prototype is based on the requirements of strength, robustness, minimal insertion pain, and tissue damage in patients. The fundamental constraints set the length of our proposed MEMS-based in-plane microneedle to be 600 μm. The design gives the optimal dimensions of length, width, and thickness both of microneedle and the channel running through it, while considering the influence of various mechanical forces. In addition, the skin also offers an opposing force on the microneedle, which changes with depth of microneedle, angle of insertion, and different layers of tissue penetrated. Three piezoelectric sensors are fabricated on the microneedle to give reliable skin resistance measurement for different insertion depth. Performance analysis is made to validate the proposed design approach for different microneedle geometries and sizes.

Organotypic raft cultures as an effective in vitro tool for understanding Raman spectral analysis of tissue.

There is a growing body of evidence showing that optical spectroscopy has the potential to be a useful in vivo diagnostic tool. Yet, so far there is no definitive cellular and biochemical understanding for the differences seen in the spectra from different tissue categories and disease states. In this study, we examine the use of organotypic raft cultures as an in vitro model of in vivo tissue conditions in an attempt to overcome some of the limitations of previously used methods. Organotypic raft cultures resembling normal and dysplastic epithelial cervical tissue were constructed and grown at an air-liquid interface for 2 weeks. Raman spectra of normal as well as dysplastic raft cultures were measured and compared with in vivo spectra from the corresponding tissue type. Histologic comparisons ensured that the raft cultures had similar structure and morphology to the corresponding intact tissue types. Raman spectra were also acquired from different layers of tissue. Spectral comparisons show that the Raman spectra of the raft cultures are similar to the spectra acquired from the cervix in vivo for both normal and dysplastic tissues. These results show that organotypic raft cultures are an effective and useful tool for the cellular and biochemical analysis of tissue spectroscopy.

Mast cells are present in epithelial layers of different tissues of the mollusc Anomalocardia brasiliana. In situ characterization of heparin and a correlation of heparin and histamine concentration.

Heparin, other sulphated glycosaminoglycans and histamine were extracted from various dissected organs of Anomalocardia brasiliana, a mollusc from the South Atlantic, and quantified. A good correlation between heparin and histamine content was found in the labial palp, intestine, ctenidium, mantle and foot tissues. The tissue location of metachromatic cells, putatively containing heparin, was identified histologically with Alcian Blue, Toluidine Blue, Masson trichrome, Haematoxylin-Eosin and PAS. Except for the foot, cells containing metachromatic granules were found in the epithelium surfaces of all the organs analysed. An in situ identification of heparin using nitrous acid and heparinase degradation has established unequivocally the presence of this compound in the metachromatic cells. The location of 'mast-like' cells at the epithelium surface of mollusc tissues exposed to the environment are very similar to the distribution of mammalian and other vertebrate mast cells and gives support to the suggestion for a role of mast cells in defense mechanisms.

Preferential states of longitudinal tension in the outer tissues of Taraxacum Officinale (Asteraceae) peduncles

We tested Wilhelm Hofmeister's hypothesis that the outer layers of herbaceous stem tissues are held in a preferential state of longitudinal tension by more internal stem tissues that are held in a reciprocal state of compression. We measured (1) the biaxial stiffness of dandelion peduncles that were barometrically inflated with a Scholander pressure bomb, and (2) the stiffness and mechanical behavior of different layers of tissues that were surgically manipulated as longitudinal strips placed in uniaxial tension. Hofmeister's hypothesis predicts that stems will shorten and expand in girth as their volume transiently increases (due to barometric or hydrostatic inflation), that they will longitudinally rupture when excessively inflated, and that the principal stiffening agents in their outer tissues will be aligned in the longitudinal direction with respect to stem length. Our experiments confirmed these predictions: (1) the longitudinal strains observed for inflated peduncles were negative and smaller than the circumferential strains such that stems contracted in length and expanded in girth, (2) peduncles longitudinally ruptured when excessively inflated, (3) surgical experiments indicated that the epidermis was stiffer in longitudinal tension than any other immature peduncle tissue and was as stiff as any other tissue region in mature stems, and (4) microscopic analyses showed that the net orientation of cellulose microfibrils in the cell walls of the outer region of stem tissues was parallel to stem length. A strong positive correlation existed between the tensile stiffness of tissues and the net orientation of cell wall microfibrils.

Targeted damage effects of high intensity focused ultrasound (HIFU) on liver tissues of Guizhou province miniswine

HIFU can pass through tissues and accurately damage target tissues inside organisms. This article reports on the oriented damage effects of HIFU upon miniswine internal and external liver tissues, and suggests a new conception of the ‘biological focal field’. The results revealed that: (1) HIFU can be used to damage accurately liver tissues under the guide of a B-modal ultrasound device; (2) the scope of the injury is connected with sound intensity and irradiation time; and (3) the different layers of tissue through which the ultrasound has passed remain undamaged.

A hand-held drilling tool for orthopedic surgery

A novel hand-held drilling tool devoted to orthopedic surgery is presented in this paper. The starting point of the study is the conjecture that the invasiveness of interventions might be reduced by adding sensing, reasoning, and control capabilities to existing tools, in order to obtain controlled penetration in the patient's body and automatic discrimination among layers of different tissues. Due to the particular environment in which the tool is to work, the requirements in terms of human friendliness and safety impose a careful design of the human-machine interface. The proposed approach to the development of a mechatronic tool for surgery is discussed, with emphasis on the functionality and performance of the device and the limited-usage expertise required. New applications for the proposed concepts in nonsurgical environments requiring hand-held tools are foreseen.

Modelling Binary, Knudsen and Transition Regime Diffusion Inside Complex Porous Media

The problem of gaseous diffusion inside complex porous media arises in the modeling of many chemical processes (e.g. Chemical Vapor Infiltration (CVI), heterogeneous catalysis in porous catalysts, filtration, etc...). A program computing effective diffusivities in the bulk, Knudsen and transition regimes has been designed and tested, which uses a Monte-Carlo mean-square-displacement algorithm. The porous medium has been represented from a special interpretation of a computer 3D discretized image. Simulations were carried out in a typical case of complex structured porous medium: a stacking of tissues (e. g. 2D woven fiber preform for CVI-densified composite materials). The results are presented as tortuosity factors, i.e. deviations from an equivalent medium made of straight cylindrical pores. The evolution of the diffusivities with the geometrical parameters of the tissues, and with the stacking mode has also been studied. It appears that the perpendicular diffusivity is closely related to the proportion of matching holes between different layers of tissue. The intermediate regime appears for Knudsen numbers lying between 100 and 10 -1 . In this domain, the Bosanquet formula only gives a good description if the Knudsen number is multiplied by a factor γ = 1/4. This phenomenon had been reported, to a lesser extent, for unidirectional random fiber packings.

Computer model of cardiac repolarization processes and of the recovery sequence

A computer model simulating both excitation and recovery processes within a block of heart muscle tissue has been developed and implemented on different IBM PC AT compatible computers. The model incorporates blocks of tissue consisting of several thousand elements and introduces phenomena which are completely or partly omitted in other existing cardiac electrophysiology models. These phenomena include the electric anisotropy of the tissue, different durations of repolarization in different layers of tissue, and the different shapes of action potential which correspond to cells excited when not fully recovered. Implementation of the model on small personal computers requires the use of a special data structure management and an effective algorithmic background. The program of the model is written in PASCAL and uses dynamically allocated data structures and the asynchronous simulation technique of event planing. These techniques are described in detail. The model has been used in various experiments. Results of simulation studies are presented in the form of modeled three-lead electrocardiographic records. The experimental series which are described include basic patterns of regular activation sequences, modeling of premature beats, simulation of effects due to fast pacing, models of ischemia and infarction, simulation of reentry mechanisms with a special reference to the initiation of ventricular fibrillation, and models of late potentials. The future development of more realistic models of the cardiac recovery process is also discussed.

Measurement of renal blood flow by cine computed tomography

Renal blood flow can be a major determinant of solute and water excretion. Several methods have been developed during the last 20 to 30 years to measure renal blood flow in experimental animals and in man [1–4]. The distribution of renal blood flow to the cortex and medulla may also influence sodium excretion [5]. Regional flow rates have therefore also been measured [1, 5–7]. However, doubts have been expressed as to the accuracy of these measurements, partly due to theoretical problems and partly because of disagreement in results between techniques [1, 6]. The recent availability of cine–computed tomography (CT) [8, 9] offers a promising new approach to measuring renal blood flow in man and experimental animals. With short scanning time and a high repetition rate, this technique can record indicator dilution curves in major vessels as well as in different layers of tissue using contrast material as a soluble indicator. CT images give a cross sectional view of the anatomy, eliminating the superimposition problem commonly encountered with other techniques. In addition, selective cannulation of renal vessels can be avoided due to the superb contrast resolution of CT scanners, which allows for opacifying vessels and tissues with only small amounts of contrast medium. The goal of the present study was to explore the capability of high speed CT scanning for measuring regional, renal blood flow in the dog.

Modeling the vibration response of the hand due to hand‐induced vibration

The mechanical response characteristics of the hand due to vibration directed into the hand by a vibrating handle was modeled as a three‐degree‐of‐freedom, mass‐spring‐damper system for vibration in each of three mutually orthogonal directions. The coupling that existed between the three mass elements and the relative values of the different components of the mechanical model correlated very well with the actual coupling and the physical relations that exist between the different layers of tissues in the fingers and hand. The model indicated that the mechanical response of the hand due to hand‐induced vibration was a function of the direction of the vibration relative to the hand and a function of the manner in which the vibrating handle was clasped. The model implied that vibration directed into the hand at frequencies below 100 Hz was transmitted through the different layers of tissues in the hand into the skeletal system and then up the arm. Vibration energy at frequencies above 100 Hz tended to be isolated to the tissued directly in contact with the vibrating handle.

Consideration of Body Dose in Radiation Therapy

In modem radiation therapy, we usually designate the treatment, by the dose per unit volume of the tissue we wish to radiate (relative to the per cent of erythema skin dose viz e). It is evident that a certain dose of this kind can be given in a number of different ways. The amount of radiation absorbed by the entire body or total body dose is however dependent upon what “fields” we choose for reaching the desired “tumor dose” and the general reaction of the patient. For instance, the change in the blood picture has more to do with the “total body dose” than with the “tumor dose.” We therefore consider it important to keep record of the “total body dose” as well as of the “tumor dose.” The question arises how the unit for the body dose ought to be defined and how the total dose ought to be figured. Wintz has recently published an article1 in which he calls attention to the importance of the body dose. He uses a certain unit “a.” The unit we have been using for some time is approximately 100 times smaller. I have designated it Ax and have defined it in the following way. The X -ray tube is excited by 200 kv. (measured with sphere-gap) alternating 60 cycle current with double way rectification and the rays filtered through 0.5 mm. copper and 5 mm. wood. If an erythema dose is given on the skin of a 10 × 10 cm. field then 100 Ax will be absorbed by the first 5 cm. of tissue presupposing that it is surrounded in all directions by tissue so that a very small part of the scattered radiation is lost laterally. A variation in the distance between the target and the skin does not influence the “body dose” enough to be considered as long as the whole ray cone passes entirely through the tissue. The absorption by different layers of tissue is given in Table 1.