History of Cells Research
In the light microscope level of the chemical composition of cells, form, structure and function of the subjects. Study the biology of cell structure and function of branches. Cells are composed of organic form and function of the basic unit of their own turn, composed of many parts. Studies on the structure of it are not only to know what parts, and to further find out the composition of each part. Accordingly, not only to know of functional cells function as a whole, but also to understand the different parts of the functional relationship.
Organism's physiological functions and all life phenomena are based on cell-based expression. Therefore, regardless of the organism's genetic, developmental and physiological knowledge, or as a medical basis for the pathology, pharmacology and agriculture, breeding, cytology are essential.
Foundation stage
Most cells are very small, beyond the limits of human vision.Cells must be observed with a microscope. However, in recognition of the objective existence of cells before, can not know the object observed under the microscope is the cell. So in 1677 A.van Leeuwenhoek used his microscope to create a simple animal, "sperm", without knowing it is a cell. Cell (cell, derived from the Latin cella intent of the gap, a small room) the word is 1667 R. Hook in the observation section to see the cork cork containing a small room and to the named.
In fact, these small rooms are not living structure, but the gap posed by the cell wall, but the cell was followed down this term. In the cytology of the Enlightenment, with a simple microscope, although it observed that many small objects ─ ─ such as bacteria, ciliates, etc., but the main purpose is to observe some of the developmental phenomena, such as the butterfly's metamorphosis, the sperm and egg structure.
Due to the limitations of the microscope was observed not precise enough, with the shackles of religious belief, but these observations support the first theory into dogma. Some people claimed to see a small reflection in the sperm of the "villain" that this individual will develop into fine commentators ─ ─ CD; Some people also believe that "bad people" exist in the egg, egg ─ ─ CD commentators. Into effect on the first lasted 100 years, hindering people in R.Hook on the basis of further understanding of the cell, until 1827 К.M. Bell found that mammalian eggs, the cell itself began to be carefully observed. In this period developed the achromatic objective lens, the introduction of magenta (carmine) and hematoxylin as the nuclear dye coloring and slicer and slice technology start-ups are fine for the observation of cells to create more favorable conditions. In a mucus-like cells are the precursors of go through a kind of processes such as crystallization, and the first to produce nuclear (also found in nucleolus). He and the plant cell as a community, like hydra, like insect groups. In his letter, inspired by Shi Wanjian animals and plants are formed by the cells. He accumulated a large number of facts that both the structure and growth of consistency, in 1839 proposed a cell theory. At the same time, the Czech animal physiologist JE Purkinje put forward the concept of protoplasm; German zoologist CTE von Siebold (1845) concluded that protozoa are single cells.RC German pathologist Feier Xiao (1855) on the basis of connective tissue in the study that "all cells come from cells" of the famous, and the creation of cellular pathology. German zoologist M. Schulze in 1861, a definition of the cell: "cell is a mass of protoplasm with the characteristics of all life, in which the nucleus." This stage can be said for more than cytology foundation stage. The further development of cytology, the first is to deepen the understanding of cell structure. Because it must have a correct understanding of the structure can then explore their function.
Morphological study
From the mid-19th century to early 20th century, the nucleus of cell structure, especially the research, progress has been made. German botanist EA 1875 first described the plant cells coloring objects and concluded that the same species each have a certain number of colored objects; In 1885 the German scholar C. La Buer constant number of objects made color patterns.
1880 Bala Nieci Ji describes the color of the spiral structure of the object, the following year found the dye tablets Pfizer Cina, until 1888 W. Walter Dyer only then colored objects in the nuclear officially named chromosomes. German scholar H. Henkin 1891 germ cells in insects observed X chromosome, 1902 WL Stevens, EB Wilson and other found a Y chromosome.
The phenomenon of cell division, at that time has been seriously and a careful analysis. German botanist W. Hofmeister 1867 in plants, A. Schneider 1873 in animals, were more detailed account of indirect division; German scientist W. Cell Fu Leming found the chromosome in 1882, after the vertical split of the proposed name of the mitotic division instead of indirectly, E. Haeuser describes the distribution of chromosomes when the indirect split; After him, EAto mitosis into until now GM of the early, mid, late, late; He and other scholars also observed in plant meiosis, after further research and finally distinguish between haploid and diploid chromosome number. Studies on the cytoplasm, the nucleus as far less thorough. Although the German biologist O.Hurt Vichy 1875 discovered centrosome, but when it is the evolution of mitosis is the future study of mitosis before they get a more detailed understanding.
As Gorky found what he called Apparato reticulare interno (later known as Golgi apparatus) and structure (1895), before the invention of the electron microscope for its existence, has been controversial. Because of this structure must be fixed in the cell after a fixed dose, then silver or after osmium tetroxide staining can show someone that it is the artifact; But the observation of living cells or with live or frozen sections stained in the secretory cells of a certain position they are certainly able to see this structure. On mitochondria, since 1897 is C. Benda discovered and named after its existence for more consistent advice. After a certain number of cells in the fixative after fixation, can be certain dyes can also be observed in vivo.
However, in the shape of various optical microscopes, or a linear or granular, or a bunch of particles; As to whether there is a variety of animal cells in all organisms or cells, was not yet conclusive. Understanding on their own cytoplasm even worse.
Although there have been various theories, but they do not reflect the true situation. For example, C. Frohman 1865 that contains fibrous material woven into a framework or mesh. W. Fu Leming 1882 mistakenly see the mitochondria, spindle and fixed samples of other fibrous structure, by extension, that is buried in the cytoplasm of the filamentous matrix compositions. German organization scientist R. Altman 1886 and even that some small particles is the simplest, live, "the basic cellular organisms," because of their special way of concentration and composition of cells;
This could also be mistaken as the mitochondria, and secretory and storage granules. Easier for people to accept the 1888 German zoologist O. Bi Qili cellular or foam theory: the cytoplasm is more viscous material (transparent quality hyalopla-sm) to form the honeycomb structure consisting of fine, which is full of other known cellular fluid (enchylema) of the material. This doctrine to some extent realistic, because the Bi Qili not based on the concept of a fixed specimen investigation, but according to the in vivo observation of the protozoans.
The cytoplasm of protozoa is indeed the sun worm-shaped foam, on single-cell protozoan is the question debated almost half a century, until 1875 study by the Bi Qili, ciliates before it would be sure to maintain the doctrine of foam so the longest time. The structure of the cytoplasm also recalled two cases. 1899 Garnier in the study of various types of glandular cells with basophilic cytoplasm and found the presentation of dynamic filamentous or rod-like structure, that this is not the cytoplasmic inclusions, but part of the cytoplasm, thus named for the moving mass, and a detailed account of this. This is half a century later, under the electron microscope the cytoplasm of the structure proved to be true, that the endoplasmic reticulum, but was not given due attention. Wei Late in 1902 a detailed description of the different animal stripes muscle sarcoplasmic reticulum, is long forgotten, until the application of electron microscopy, in 1960, only fully evaluated the accuracy of his observations.
Understanding of the structure of the cytoplasm to the nucleus or chromosomes lag behind the knowledge of the situation did not improve long-term. Especially after the early 20th century, with the cytogenetic separation, reorganization, chain, exchange of chromosomal and other genetic phenomena, based on more in-depth understanding of a chromosome. H. Powell Mar 1933 in mosquitoes found in the basal cells of the venturi multi-line chromosomes. 1934 TS Painter in Drosophila, RL Gold HW Bi Musi in chironomids, also found in this structure. Multi-line chromosome is present in some dipteran larvae gland cells in the large chromosomes in Drosophila and its length is about 100 times the normal chromosomes, each chromosome consists of many (can be more to 400) stained fibers in the whole show on the chromosome bands stained deep and shallow room with stained area.
Its formation is due to nuclear mitosis (nuclear is not only the splitting of chromosomes split), so each chromosome is actually a multi-line formed by a number of chromosomes.This chromosome in size, is conducive to the fine structure of the chromosome analysis. In addition, also according to multi-line chromosome to determine its function bubble expansion activities. But at the same time, on the cytoplasm, remove it with a cell biological understanding of certain physiological functions, the understanding of the structure and not much progress.
This situation until the 1940s, the widely used electron microscopy, specimens embedded, sliced a gradual improvement of technology, have a great change. Through a lot of work, not only to clarify the past can be seen in the optical microscope but not see, or still controversial organelles such as mitochondria, Golgi apparatus, centrosome, endoplasmic reticulum, cilia, flagella and other structures, and also found that many had not seen the construction of the past, such as lysosome, peroxisome, ribosome, constitute the cytoskeleton of a variety of fiber, and electron microscopy to high pressure by 1 to 10 angstroms thickness of fibers support a variety of micro-beam system of organelles, in particular, saw a variety of cell membranes. In the past, never seen under the light microscope the cell membrane or nuclear membrane, but to judge according to the interface or the physical conditions of their existence, and in the electron microscope to determine all of the films are 75 to 100 angstroms thick, three-tier structure (called unit membrane).
Moreover, the various parts of a cell membrane are linked, plasma membrane and the endoplasmic reticulum, endoplasmic reticulum and Golgi, or nuclear membrane is connected.It is a double membrane, the inner and outer membrane composition, and has a certain structure of the nuclear pore, through which cytoplasmic material and nuclear material can be exchanged. In the plasma membrane between cells found on the link: desmosomes, tight junctions and gap junctions and so on. These structures combined with the cells or the exchange of material between cells; Etching technique using frozen, you can better observe them. 20 to 30 years time, the cytoplasm and organelles of the form has been very understanding. Of course, the widely used electron microscopy of the era, optical microscopy is still a powerful and indispensable tool.
Cytoskeleton, such as complete, is the use of fluorescent antibody in the optical microscope observations. In the meantime, progress on the nuclear research not too large. Although the structure of the nucleolus with the precise description, but on the chromatin, electron microscopy ultrathin sections can only see some color ideas ─ ─ chromatin should be cut off cross-section, see the complete chromatin structure.
The method makes use of spread chromatin spread, and can only see the thickness of the different fibers. Until the 1970s, was observed under the electron microscope nucleosome; Shortly thereafter, combined with biochemical extraction, observed the metaphase chromosome scaffold protein is the so-called core, DNA fibers which extend out to the surrounding ring. But how coagulation integrated chromatin chromosome, although there are different ideas ─ ─ such as some people think that because of staining time and again spiral of fiber (so-called super-helix), but the extent to which realistic, it is difficult to judge.
Research in this area, to a considerable extent driven by the other disciplines, the impact of the various disciplines can be roughly divided into several stages; of course, these stages can not be completely separated. Embryology affect cell function, did not like the study of structure, in a mass organization to find a cell for the study.
Egg is a cell, individual cells can not get to study the age, it is very convenient to use the material. As with the eggs, the role of the various parts of its course according to their impact on development in judgments. This involves embryo issues. However, if the sperm nucleus with the hybridization of dissimilar function, you need to determine the emergence of heterogeneous character, which relates to genetic problems. Early work in this area is basically carried out by the embryologist, which is characterized by comprehensive research, not simply from the perspective of the egg cell, but to get egg cells to research and development as genetic and other related issues. Some major problems have been mapped out, so in the academic thinking of the future have a profound effect. O.Vichy and R. Hurt Ludwig von Hurt brothers in 1887 for materials with a sea urchin, the first to see live eggs fertilized, and fertilization experiments were carried out for analysis.
If you were to consider the cytoplasm and nucleus in the developing role of the TH Boveri horse roundworm found in the reduction of chromatin analysis of the phenomenon, the factors that affect the reduction found in the cytoplasm. In addition, the blastomeres may be numbered to track the origin of each blastomere cell lineage work on a variety of egg yolk content of their cleavage of different types of studies have pointed out that the distribution of eggs in the cytoplasm, affecting the direction of the spindle , decided to form a cleavage plane, determine the type of cleavage.
Moreover, in some especially suitable for the formation of the egg can be seen in various organs of the material already in the layout of the egg, cleavage after every ball and split the formation of organs that will be a certain correspondence. All of these suggest that the genetic potential of the nucleus is equivalent, but in later development, through the cytoplasm or cell-cell interactions will be subject to different regulation.
For the role of the nucleus has also been fully valued. 1887 German experimental embryologist TH Boveri was the sea urchin egg two sperm, according to the chromosome in each blastomere in the distribution and development of individual blastomeres that are qualitatively different from each chromosome, the chromosome is a personality. Using sea urchin eggs, TH Morgan finished 1896 ─ ─ artificial parthenogenetic egg without fertilization can also be developed.
To block non-fertilized egg nucleus or mutant sperm, cytoplasm and nucleus of development in their respective role in the observed larvae have shown that the resulting characteristics of the father. All these show the importance of the nucleus. All in all the achievements of that time, in 1883 the German embryologist W. Lu had expressed this idea: "Not only chromosomes and various parts of each chromosome, for determining an individual's development, physiology and morphology may have been important."
1887 German zoologist A. Weismann proposed the hypothesis of germplasm. Although this hypothesis was later overturned experimental study, but the hypothesis presented in the decision between the child and then there is some genetic link to be found thinking. Remove the impact of academic thinking in order to solve the problem of embryology, cytology also provides an important experimental method, which is tissue culture. American embryologists RG Harrison in 1907 to study the creation of nerve fiber growth in vitro methods, and later by American physiologist A. Karel take over, to develop into specialized technology.
After 30 years has increasingly shown its importance, and today, not only all aspects of living cells, even in terms of many other disciplines is essential technology. he impact of genetics rediscovered GJ 1900 endel's research achievements, the genetics of a strong impetus to the progress of cytology. merican geneticist and embryologist TH organ studied fruit fly genetics, found that occasional eyed individuals are always male; combined with the existing, knowledge on sex chromosomes, males appear to explain the dirty looks, began to explain genetic phenomena from the cells, genetic factors may be located on the chromosome.
Cytology and genetics linked genetically to be quantitative and physiological concepts, from cytology to be qualitative, material and narrative concepts, and gradually produce cytogenetics. 1920 U.S. cell scientist WS Sutton further pointed out that the genetic factor and the parallels between chromosome behavior, necessarily mean that genetic factors located on chromosomes, and that if two pairs of factors in the same chromosome, they may follow or may not follow Mendelian laws of inheritance, indicating a chain of concepts, deepened on meiosis in particular on chromosome pairing, chromosome exchange research.
In addition, the discovery of radiation phenomena (X-ray, radium radiation, ultraviolet light), temperature can cause mutations in fruit flies, the mutation frequency is high due to more conducive to experimental study of chromosomes. After radiation caused by various mutations, including gene displacement, inversion and deletion, etc. can be found in the chromosome basis. The use of mutant and wild-type hybrid and its offspring for statistical processing, you can calculate the gene sequencing of chromosome map.
A multi-line chromosome found in the chromosome opens new avenues of research. In determining a number of chromosomes is the bold line, the paired chromosomes, the one it conducted a detailed study of the structure and found the online coloring dye particles, dye particles of many gathered into adjacent bands, dyeing line Although difficult to see, but if appropriate staining can be seen under ultraviolet light, or they are not straight and parallel, but a very loose spiral. The other hand, can be derived according to linkage group on chromosome map using so-called gene sequencing methods and morphology of salivary gland chromosome map match up. Hybridization and cell morphology can be perfectly cross-checked in a multi-line chromosomes to see more specifically the exact situation of gene sequencing, each band is actually not only contains a gene. Moreover, some mutations due to genetic effects such as the location bar eye mutant (bar-eye) is the first multi-line chromosomes in obtaining evidence In the search for the genetic basis of the material under the impetus of chromosome research in surface spread out, not only the material for genetic research, and many other animal and plant species (some statistics about 12,000 species of vascular plants and 500 kinds of mammals ) cell division (meiosis), chromosome behavior, chromosome maps have been studied. Species of the same genus, the number of chromosomes is often the same. However, in the same family or the number of species ranges, or in this case is another case of multiple (polyploidy). The same individual in all chromosomes, at first glance seemed to be no big difference, but careful examination is different, so you can accurately tell the number of chromosomes of a species, the shape and size of each chromosome, and can number them line up. Can compare the genetic relationship of different species of chromosomes, thus finding the evolutionary relationships of species; Karyotype that closely related species, the chromosome number may be exactly the same, but may be very significant differences, in the latter case, after careful study of the total can find the original form, and thus derived from a variety of forms.
In plants, there are three known mutations: polyploidy, a chromosome breaks into several small or vice versa several small chromosomes assembled into a large and a doubling of the chromosome. Sometimes these three mutations and subspecies and species formation.In addition, plant polyploidy research has led to use various methods, such as chemicals, temperature, radiation-induced generation of polyploidy in some plants has received the application value. Carried out extensive studies of chromosome morphology, but also for male and female sex to find cellular basis of the decision. The impact of cell physiology, experimental methods used at this stage the rest of the function of cells, did not get satisfactory results.
Not observed with a microscope the cell membrane, cytoplasm can only judge the material exchange with the outside world of its existence, and permeability of certain substances in order to determine some of its features. As generally easy to fat-soluble substances into the cell, may have speculated that the cell membrane lipids or lipids from the hole formed. Have different molecular weight as the difficulty of the material into the cells of different molecular weight ─ ─ difficult to enter; Speculated that the cell membrane like a filter layer, which prevents large molecules into the cells of the hole In addition, once under the electrolyte, such as positive ions and negative ions on cell permeability, and cellular environment can affect the acidity, resulting in changes in positive and negative ion permeability, charge hypothesis put forward to explain this extremely complex cell permeability process.
As for the phagocytosis of solid particles, through simulation, for example, drops of chloroform phagocytic amoeba that this is due to the surface of cells to foreign bodies greater than the surrounding environment of adhesion, adhesion caused by the local membrane surface tension changes that are swallowed foreign body. These ideas, even then it seems, are in the passive permeability in the cell membrane; But cells also going against the diffusion gradient or concentration gradient active intake or discharge of certain substances. So also envisaged that there may be a cell needs energy in the process, they are of great significance for these processes, but it was still no information.
At that time the understanding of cellular respiration are mainly restricted to the food through a variety of enzymes to produce heat. Knowing that in the process of several enzymes, such as certain dehydrogenase, oxidase, cytochrome a, c, b, and thus understand the burning of food in the cell not by a sudden all the energy in the oxidation the form of heat release out, but gradually through a small stage, step by step to obtain and use a small amount of energy. This process of transfer as many enzymes as oxygen, hydrogen acceptance, redox system, and added to the total respiration process can proceed, and be micro-regulation.
The impact of other disciplines in the early 1940s, other disciplines of technical methods has been used for cytological studies, opened up a new situation, the formation of some new areas. The first is the application of electron microscopy had a super-microscopic morphology. Belgian zoologist J.Brad Xie, proceeding from embryology, the use of specific staining method (Unna, Feulgen) of nucleic acids in the developing meaning. Almost at the same time, the Swedish biochemist TO Kasiposong according to various substances on the absorption of certain wavelengths, creating a UV spectrophotometer cell, to detect proteins, DNA and RNA in the cells of these substances exist. If we say that the former can be characterized according to staining, the latter can be done based on quantitative absorption. Essence of their work to draw attention to nucleic acids in cell growth and differentiation in the role of attention.
In developed on the basis of their work from the cell chemistry, the chemical composition of cells, and morphological studies can complement each other, some additional understanding of cell structure. Chromosome analysis with multi-line, under UV light and the camera shows nucleolar staining particles containing DNA, contrast dye line with only little or even none. With protease (possibly impure) digestion can make them dissolve, so the line has been mistaken for dyeing protein composition. Furthermore, UV absorption spectra can be accurately measured according to paragraph chromosomes (euchromatin and heterochromatin) the percentage of certain amino acids.
Euchromatin paragraphs seem to contain higher molecular weight globulin type proteins, and heterochromatin paragraphs which have more types of low molecular weight of histone proteins. Then know that this is the separation of conditions at the time the product is a small amount of ribosomes and endoplasmic reticulum component of the complex. Nevertheless, on mitochondrial and microsomal studies so that many of the basic biochemical processes in the cytoplasm rather than in the nucleus carried out.
This approach combined with in-depth study of the morphology of cells in the process leading to a more profound understanding. The application of radioisotopes for the study of cell metabolism has opened up new avenues. From their participation into the cell material can be accurately track the synthesis, transport, storage and use of materials. For example, using this method shows that phosphorus compounds are not in mitosis, but in the interval, shortly before the split into the reference, and then was assigned to the sub-nuclei. From this number, and the results obtained with other isotopes, the cells may be inferred that the operation of some important material. Although in the 1930s, tissue culture have a greater development, but only to develop tissue, normal tissue can not develop a single cell, but not yet fully demonstrated its importance.
Studies using cultured cells in a whole lot (in situ) can not be looked into, such as cell nutrition, exercise, behavior, relationships between cells and so on. Almost all kinds of organizations, including some invertebrates (squid, sea squirt, fruit fly, etc.), have been training too. In good condition from the tissue culture grow a variety of cells, the growth is different. Basically, from the form can be divided into three types, epithelial, connective tissue and cell migration (such as lymphocytes, monocytes and macrophages). Sometimes the normal tissue culture cells appear not in the performance characteristics of an organism, such as enhanced if the medium contains surfactant material, a variety of tissue cells obtained the ability to swallow.
But they remain the unique nature and potential, because if you change the training environment or animals moving back to the original site will still be as it was growing. 1940s began to research carried out from the biochemical functions of each part of the cell work, resulting in biochemical cytology. the first to use the homogenate in a suitable solution to cell ─ ─ mechanical grinding and differential centrifugation methods, in addition to suits the nucleus can also be mitochondrial, microtonal and transparent quality of several parts.
They are to conduct research on some of the material and understand the existence and distribution of enzymes and certain metabolic processes in what parts. Separation was more successful is the mitochondria, as measured with an electron microscope has been rough on their size and learn in this organelle in the biochemical process, recognizing their importance for energy metabolism. Macrodomes had been mistaken for an organelle. It is worth mentioning that in the culture of fibroblast growth is also affected by substrate effects. In general they are radically aimlessly grown from the tissue.
However, if the manual to make sure the medium is under the direction of tension, or in the substrate on the artificial system of signs, the cell or along the direction of tension along the traces of the growth out. This phenomenon may be used to explain the overall function of connective tissue and tendons to adapt; they are always in tension in the direction the growth, differentiation. It can be seen, for cell research in the use of electron microscopy in the submicroscopic structure after in-depth, and in the application of biological technology in the functional aspects of the in-depth, has been for the cell biology at the molecular level, cell research the formation of the phenomenon of life to create the conditions. So later, in molecular genetics and molecular biology under the influence of outstanding achievement, cell biology of this new discipline quickly formed.
