共查询到20条相似文献,搜索用时 31 毫秒
1.
Human lipoprotein(a) is a low density lipoprotein-like lipoprotein whose concentration in plasma is correlated with atherosclerosis. The characteristic protein component of lipoprotein(a) is apolipoprotein(a) (apo(a)) which is disulfide-linked to apolipoprotein B-100. Sequencing of rhesus monkey apo(a) cDNA suggests that this protein, like human apo(a), is highly similar to plasminogen. Sequence data suggests that a plasminogen-like protease activity and kringle 1-, 2-, 3-, and 5-like domains are unnecessary for apo(a) function, but a highly repeated kringle four-like domain is important. Liver is the major site of apo(a) RNA synthesis; reduced amounts of message were also found in testes and brain. Co-expression with apoB-100 and plasminogen in rhesus tissues is not mandatory. 相似文献
2.
Igor Karšaj Carlo Sansour Jurica Sorić 《Biomechanics and modeling in mechanobiology》2009,8(5):359-370
In this paper, a hyperelastic and thermodynamically consistent model for soft tissue is developed that is able to describe
the change of the initial orientation of the collagen fibres. Full numerical implementation is considered as well. The collagen
architecture is assumed to reorient driven by a specific thermodynamical force. The anisotropy is described by a strain energy
function, which is decomposed into a part related to the matrix and a part related to the fibres. The initial fibre orientation
is defined by a structural tensor, while the current orientation is described by a time-dependent structural tensor, which
results from the initial one by a rotational transformation. The rotation tensor is obtained via an integration process of
a rate tensor, which depends on an adequately defined thermodynamical force. The integration is achieved via an exponential
map algorithm, where it is shown that the rotation is necessarily a two-parametric one. Efficiency of the proposed formulation
is demonstrated using some numerical examples. 相似文献
3.
Some reaction cascades in biological systems are analyzed by a self-organized chemical model, an autocatalytic reaction. This model is described by the coupling of a primary system which stabilizes the initial stage of the reaction rapidly and a partial system which controls the primary system slowly. By the internal force caused by a trigger above the threshold, the coupled system in near-equilibrium is broken and changed into a new state. From the rate equation for the coupled system, a dimensionless nonlinear state equation, n = -n3 - un - v, is derived, where n is the concentration of intermediate, and u, v are dynamic variables of the system. This equation is similar to a nonequilibrium tri-molecular reaction. By using this chemical network theory, fibrin polymerization. F + F----fm----fp + X, where F is a fibrinogen molecule, fm is a fibrin monomer, fp is fibrin polymer, and X is small peptides released from fibrinogen, is discussed as an excellent example of the enzyme reaction cascade. 相似文献
4.
I shall argue that most religious ritual is a performance that not only invokes but also performs communication. The ethnographic material from which I derive this argument is from China, in particular the temple rituals of local festivals. My argument is that a deep obeisance of welcome and departure that is both like and not like the normal ritual of greeting marks a religious from a non-religious ritual occasion and place. It is a ritual doubling that makes the honoured guest also a host. Religious ritual is a medium, and as a medium it is double in another sense. It is deference and deferral, a repeated transmission of obeisance to authority that has the authority of repetition. As well as doubling, religious ritual is excessively communicative. The medium is a performance not only of invitation and departure but also of communicative response, and it repeats this communication as a test of communicative response over and over again. Religious ritual performs both the opening and closing of communication, both the seeking and the responsive reciprocation of gift offerings with bounteousness. It is shadowed by the possibility of no response, of giving offence, of being abandoned. This possibility is acknowledged by being prevented, while the possibility that the performers are their own responders is disavowed. 相似文献
5.
C H Regnier H Kolsky P D Richardson G M Ghoniem J G Susset 《Journal of biomechanics》1983,16(11):915-922
The purpose of this paper is to investigate the theoretical basis for the pressure-distension behavior of the urinary bladder. A finite strain theory is developed for hollow spherical structures and it is shown that the Treloar model is a good prototype only for rubber balloons. The pressure-extension ratio relationship is inverted to lead a general form of strain energy function, and fitted by an empirical relation involving one exponential. The following form of strain energy function is derived: W(lambda, lambda, lambda -2) = C1 (P(1), a) + P(1)C2 (a, lambda)ea(lambda -1). Where C1(P(1), a) is a constant (N m-2), P(1) is the initial pressure, a is the rate of pressure increase and C2 (a, lambda) a third degree polynomial relation. P(1) and a are experimentally determined through volumetric pressure-distension data. It is verified that this type of energy function is also valid for uniaxial loading experiments by testing strips coming from the same bladder for which P(1) and a were computed. There is a good agreement between the experimental points and the theoretical stress-strain relation. Finally, the strain energy function is plotted as a function of the first strain invariant and appears to be of an exponential nature. 相似文献
6.
The length of the tail of bacteriophages is controlled by a protein which acts as a molecular ruler. The needle of the injectisome, which is assembled by the polymerization of subunits that are exported through the nascent injectisome, is functionally related to the tail of bacteriophages. Interestingly, its length is controlled by a protein, which is itself exported and acts as a molecular ruler that is coupled to a substrate specificity switch. The bacterial flagellum is evolutionarily related to the injectisome. The length of the hook is also controlled by a secreted protein. This protein acts as a substrate specificity switch and, possibly, also as a ruler. 相似文献
7.
Williams RJ 《Acta biochimica Polonica》2004,51(2):281-298
Signalling concerns the transfer of information from one body, a source, to another, a receiver in order to stimulate activity. The problem arises with the word information. It is defined as what is transferred in a sequence of things, say between people, e.g. words or signs. The idea of signalling between people is then obvious but it is not clear in cell biology. Information transfer, signalling, is required for the organisation of all cellular activity but we must ask what is transferred and how is it transmitted and received? Sometimes it is assumed that all information, i.e. organisation in a cell, is represented in the DNA sequence. This is incorrect. We shall show that the environment is a second source of information concerning material and energy. The receiving party from both DNA and the environment is general metabolism. The metabolism then signals back and sends information to both DNA and uptake from the environment. Even then energy is needed with machinery to send out all signals. This paper examines the way signalling evolved from prokaryotes through to man. In this process the environmental information received increased to the extent that finally the brain is a phenotypic as much as a genotypic organ within a whole organism. By phenotypic we mean it is organised by and interactive with information from the environment. 相似文献
8.
The ribosomal protein S27a (RPS27a) is cleaved from the fusion protein ubiquitin–RPS27a (Ub–RPS27a). Generally, Ub and RPS27a are coexpressed as a fusion protein but function independently after Ub is cleaved from RPS27a by a deubiquitinating enzyme. As an RP, RPS27a assembles into ribosomes, but it also functions independently of ribosomes. RPS27a is involved in the development and poor prognosis of various cancers, such as colorectal cancer, liver cancer, chronic myeloid leukemia, and renal carcinoma, and is associated with poor prognosis. Notably, the murine double minute 2/P53 axis is a major pathway through which RPS27a regulates cancer development. Moreover, RPS27a maintains sperm motility, regulates winged aphid indirect flight muscle degeneration, and facilitates plant growth. Additionally, RPS27a is a metalloprotein and mercury (Hg) biomarker. In the present review, we described the origin, structure, and biological functions of RPS27a. 相似文献
9.
Masahiro Tanaka 《Journal of theoretical biology》1984,110(4):619-635
What is information for living organisms? An answer to this question is given on a physical basis and a contrast between genetic information and sensory information is stressed with a relation to information theory. A simple model of an environment of living organisms is investigated on the basis of communication systems model proposed by the author and a cost of information transmission is taken into consideration through capacity cost theory. It is shown that channel capacity of information theory can be interpreted as an environment, and furthermore that a large diversity of genetic messages needs a large capacity of the environment. In addition, a definition of life in terms of information is proposed and a unified view on life processes is suggested. 相似文献
10.
The question of virginity testing in Turkey 总被引:2,自引:0,他引:2
Pelin SS 《Bioethics》1999,13(3-4):256-261
Pre-marital sex for a woman is regarded as wrong in my country. As a result, it is socially forbidden for a woman to engage in this act. In order to present a woman as a virgin on her marriage day, she is subjected to pressure, and put under control both by her family and societal norms. However, a man is free and never made to suffer any of the above. A woman found to be a virgin on her first night of marriage is seen as a normal person while one suspected to have lost her virginity is made to undergo a series of medical examinations to bring clarity to her situation. 相似文献
11.
Fluorescence polarization immunoassay (FPA) is a homogeneous immunoassay useful for rapid and accurate detection of antibody or antigen. The principle of the assay is that a fluorescent dye (attached to an antigen or an antibody fragment) can be excited by plane-polarized light at the appropriate wavelength. As a rule, a small molecule rotates faster when in solution than a larger molecule. The rotation rate may be assessed by measuring light intensity in the vertical and horizontal planes. Generally, the time it takes a molecule to rotate through a given angle is an indication of its size. When a small molecule that rotates rapidly is bound to a larger molecule, the rotation rate is decreased and this decrease is measured. Because it is a primary antigen-antibody interaction, the rate of reaction is very rapid and usually a result may be obtained in minutes. This technology was applied to the detection of antibody to Brucella abortus in serum and milk, providing for the first time a rapid primary binding assay that is cost effective for use in the field. 相似文献
12.
An SI epidemic model for a host with two viral infections circulating within the population is developed, analyzed, and numerically simulated. The model is a system of four differential equations which includes a state for susceptible individuals, two states for individuals infected with a single virus, one which is vertically transmitted and the other which is horizontally transmitted, and a fourth state for individuals infected with both viruses. A general growth function with density-dependent mortality is assumed. A special case of this model, where there is no coinfection and total cross immunity, is thoroughly analyzed. Several threshold values are defined which determine establishment of the disease and persistence at equilibrium for one or both of the infections within the host population. The model has applications to a hantavirus and an arenavirus that infect cotton rats. The hantavirus is transmitted horizontally whereas the arenavirus is transmitted vertically. It is shown through analysis and numerical simulations that both diseases can be maintained within a single host population, where individuals can be either infected with both viruses or with a single virus. 相似文献
13.
Whitaker TB 《Molecular biotechnology》2003,23(1):61-71
It is difficult to obtain precise and accurate estimates of the true mycotoxin concentration of a bulk lot when using a mycotoxin-sampling
plan that measures the concentration in a small portion of the bulk lot. A mycotoxin-sampling plan is defined by a mycotoxin
test procedure and a defined accept/reject limit. A mycotoxin test procedure is a complicated process and generally consists
of several steps: (a) a sample is taken from the lot, (b) the sample is ground (comminuted) in a mill to reduce particle size,
(c) a subsample is removed from the comminuted sample, and (d) the mycotoxin is extracted from the comminuted subsample and
quantified. Even when using accepted test procedures, there is variability associated with each step of the mycotoxin test
procedure. Because of this variability, the true mycotoxin concentration in the lot cannot be determined with 100% certainty
by measuring the mycotoxin concentration in a sample taken from the lot. The variability for each step of the mycotoxin test
procedure, as measured by the variance statistic, is shown to increase with mycotoxin concentration. Sampling is usually the
largest source of variability associated with the mycotoxin test procedure. Sampling variability is large because a small
percentage of kernels are contaminated and the level of contamination on a single seed can be very large. Methods to reduce
sampling, sample preparation, and analytical variability are discussed. 相似文献
14.
The cosmetic split-thickness skin graft donor site 总被引:3,自引:0,他引:3
Hallock GG 《Plastic and reconstructive surgery》1999,104(7):2286-2288
Any split-thickness skin graft donor site is obvious to some degree because of pigment alterations and, at the worst, it can develop hypertrophic scarring. A predictably superior aesthetic result is possible if this site is converted to a full-thickness defect followed by primary closure, because a linear scar is the only residuum. Using a modified tumescent technique, the groin can also be readily used as a split-thickness donor site if a thin graft is preferred; it captures the attributes of an ideal donor site in which pain is diminished, healing rapid, and the scar inconspicuous, just as when it is used as a full-thickness skin graft donor site. 相似文献
15.
Waliszewski P 《Bio Systems》2005,82(1):61-73
The emergence of Gompertzian dynamics at the macroscopic, tissue level during growth and self-organization is determined by the existence of fractal-stochastic dualism at the microscopic level of supramolecular, cellular system. On one hand, Gompertzian dynamics results from the complex coupling of at least two antagonistic, stochastic processes at the molecular cellular level. It is shown that the Gompertz function is a probability function, its derivative is a probability density function, and the Gompertzian distribution of probability is of non-Gaussian type. On the other hand, the Gompertz function is a contraction mapping and defines fractal dynamics in time-space; a prerequisite condition for the coupling of processes. Furthermore, the Gompertz function is a solution of the operator differential equation with the Morse-like anharmonic potential. This relationship indicates that distribution of intrasystemic forces is both non-linear and asymmetric. The anharmonic potential is a measure of the intrasystemic interactions. It attains a point of the minimum (U(0), t(0)) along with a change of both complexity and connectivity during growth and self-organization. It can also be modified by certain factors, such as retinoids. 相似文献
16.
Lectin affinity electrophoresis is a powerful technique to investigate the interaction between a lectin and its ligand. Affinity
electrophoresis results from the reduced mobility of a charged species owing to its interaction with an immobile species.
In this protocol, a two-dimensional lectin affinity electrophoresis experiment is described that affords separation of oligosaccharides.
The first-dimension is composed of a weak, polyacrylamide, capillary tube gel containing a lectin. The example described involves
a mixture of fluorescently labeled disaccharides. The mobility of only the lectin-binding disaccharide is reduced affording
a separation in the first-dimension. The tube gel is then extruded and placed onto the second-dimension gradient polyacrylamide
gel and subjected to electrophoresis. Mobility in the second-dimension is dependent on molecular size and visualization is
by fluorescence under transillumination. This method is also applicable, with appropriate modifications, for the separation
and analysis of glycopeptides and glycoproteins. 相似文献
17.
S W Melanson C H Yun M L Pezzementi L Pezzementi 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1985,81(1):87-96
The acetylcholinesterase activity of the fruit fly, Drosophila melanogaster, was characterized biochemically. The activity is associated with a glycoprotein which is divided between a detergent-extractable membrane-bound fraction and a soluble fraction. The acetylcholinesterase activity is concentrated in the head of the insect. Through pharmacological methods, greater than 95% of the cholinesterase is judged to be true acetylcholinesterase, and not pseudocholinesterase. As expected for an acetylcholinesterase, the enzyme has a high affinity for acetylthiocholine and is inhibited by excess concentrations of acetylthiocholine. The soluble enzyme is found predominantly as a 7.8 S form; a smaller amount of an approximately 6 S form is also present, and a greater than or equal to 14 S form may exist. The detergent-solubilized acetylcholinesterase has a sedimentation coefficient of 7.5 S in the presence of detergent. The thermal inactivation rates for the soluble and the membrane bound enzymes are markedly different. 相似文献
18.
Rob Lovering 《Bioethics》2020,34(3):242-251
Some people (e.g., Drs. Paul and Susan Lim) and, with them, organizations (e.g., the National Embryo Donation Center) believe that, morally speaking, the death of a frozen human embryo is a very bad thing. With such people and organizations in mind, the question to be addressed here is as follows: if one believes that the death of a frozen embryo is a very bad thing, ought, morally speaking, one prevent the death of at least one frozen embryo via embryo adoption? By way of a three-premise argument, one of which is a moral principle first introduced by Peter Singer, my answer to this question is: at least some of those who believe this ought to. (Just who the “some” are is identified in the paper.) If this is correct, then, for said people, preventing the death of a frozen embryo via embryo adoption is not a morally neutral matter; it is, instead, a morally laden one. Specifically, their intentional refusal to prevent the death of a frozen embryo via embryo adoption is, at a minimum, morally criticizable and, arguably, morally forbidden. Either way, it is, to one extent or another, a moral failing. 相似文献
19.
The utilization of ethanolamine and serine for ethanolamine phosphoglyceride synthesis by human Y79 retinoblastoma cells 总被引:2,自引:0,他引:2
M A Yorek R T Rosario D T Dudley A A Spector 《The Journal of biological chemistry》1985,260(5):2930-2936
Phospholipid synthesis was investigated in human Y79 retinoblastoma cells, a cultured cell line of retinal origin that retains many neural characteristics. Ethanolamine is taken up by Y79 cells through a high-affinity transport system and is utilized to synthesize ethanolamine and choline phosphoglycerides. High-affinity ethanolamine uptake has a K'm of 40.6 microM and a V'max of 1.06 nmol/min/mg protein, and the process is Na+ dependent. Choline is the only compound tested that reduced ethanolamine uptake, and very high choline concentrations were required to produce this effect. The cells incorporate ethanolamine into phosphatidylethanolamine and ethanolamine plasmalogen at equivalent rates, and the rates of catabolism of these phospholipids are similar. Only a small quantity of ethanolamine is incorporated into phosphatidylcholine, but the amount is not reduced by the addition of choline. Serine is incorporated into phosphatidylserine, which then is converted to phosphatidylethanolamine. Ethanolamine reduces but does not abolish this conversion. Unlike ethanolamine, only a small amount of serine is incorporated into ethanolamine plasmalogen. It is possible that the ethanolamine high-affinity uptake system is necessary to provide a neural cell with enough free ethanolamine for ethanolamine plasmalogen synthesis. 相似文献
20.
This paper investigates the formation of a segregated region for a specific set of input signals in a nerve field. The segregated region is formed by a feature detecting cell group which fires only for a specific set of input signals. This firing region is called the region of feature detecting cells for the corresponding input set. First, a basic self-organizing model is given. The model is composed of the first input layer, the second nerve cell layer with lateral inhibitory interactions (it is called a lateral-inhibition type nerve field) and an inhibitory nerve cell. An input signal is an-dimensional vector whose components assume continuous values. Next, the condition which gurantees the formation of a segregated region for a specific set of input signals is derived, and the properties of the model are discussed based on the derived condition. In addition, the behavior of the model is examined through computer-simulated experiments. The following observations are made: When a certain condition is satisfied, a segregated region is formed in the nerve field according to a specific set of input signals. By varying the parameters of learning, the region is formed depending on the similarity between input signals. The regions for similar input signals are formed near each other in the nerve field. The region is created depending on the occurence probability of the input signal and its norm. 相似文献