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L C Junqueira

Publications and source records attributed to L C Junqueira.

At least 37 records · Page 2Linked to original sources
PubMed1983

Biology of collagen-proteoglycan interaction.

The purpose of this article is to review our knowledge to date of collagen-proteoglycan interaction. Many topics have been taken into account in order to provide a reasonably complete picture of this highly complex subject. Basic information about collagen biology, and an overview of the current concepts and advances regarding proteoglycans, have served as a basis to elucidate collagen-proteoglycan interaction. The bases of some methods of study have been reviewed in order to provide a fuller understanding of the results that are cited in this article. The experimental models and biological examples discussed herein demonstrate that collagen-proteoglycan interaction is essential to the extracellular matrix resiliency. The organization of these macromolecules is critical: collagen molecules become assembled into fibrils, fibrils aggregate to form fibers, fibers associate into bundles of fibers, and proteoglycans in the ground substance play a major role in the ordering process; on the other hand, glycosaminoglycans (GAGs) are composed of repeating monomers--GAGs linked to a same protein core form a proteoglycan--which, in turn, may bind to a hyaluronic acid molecule to form a proteoglycan aggregate together with other proteoglycans. Further growth of these complex macromolecules at higher hierarchical levels occurs by interaction of collagen with proteoglycans. A striking correlation between the tissue distribution of the genetically-distinct types of interstitial collagen and the occurrence of the different GAGs (which argues strongly in favour of a specific interaction) is demonstrated comprehensively in this review. Tissues composed of collagen type I possess small amounts of proteoglycans which contain almost exclusively dermatan sulfate; while tissues containing only collagen type II have high amounts of chondroitin sulfates. Collagen type III is the major fibrillary constituent of tissues that possess intermediate levels of proteoglycans, which contain great amounts of heparan sulfate. The histochemical and ultrastructural equivalents of these interactions have been emphasized in order to permit an interpretation of the morphologic aspects that can contribute to distinguishing these macromolecular components when studying tissue sections either under the light microscope or by aid of electron microscopy.

Animals↗
PubMed1983

Histochemical and morphological studies on a new type of acellular cartilage.

A new type of cartilage was found participating in a valve-like system inside the conus arteriosus of the fresh water sting ray, Potamotrygon sp.. This cartilage possesses no chondrocytes and its matrix is perforated by vascular channels that ramify dendritically forming canaliculi. The acellular cartilage does not possess perichondrium but, rather, it is attached to a basement membrane-like structure. The cartilaginous matrix contains collagen fibrils that strongly interact with the chondroitin sulfate of the ground substance. The histochemical and biochemical findings suggest that not all of the glycosaminoglycans present in the acellular cartilage are bound to protein cores to form proteoglycans.

Animals↗
PubMed1982

The influence of tissue section thickness on the study of collagen by the Picrosirius-polarization method.

The influence of tissue section thickness on the color and intensity of birefringence displayed by collagen in tissue sections studied by means of the Picrosirius-polarization method, is reported in this paper. When dermal collagen sections of different thicknesses (ranging from 0.25 to 11 micrometers) were studied by this method, it became evident that not only did the intensity of birefringence increase proportionally to tissue section thickness, as was to be expected, but also a gradual shift in color from green through a yellow to red could be observed as tissue section thickness increased. The limitations of the Picrosirius-polarization method for the localization of collagen types I, II, and III in routinely used histological slides is discussed, showing that this method is useful for the study of the distribution of the different types of interstitial collagen in normal adult vertebrate organs.

Animals↗
PubMed1982

Fine structure and histochemistry of the tail fin ray in teleosts.

Ultrastructural and histochemical studies performed on the skeletal elements of the tail fins of six representative species of teleosts enabled the following observations to be made. The electron microscopic pattern of amorphous substance deposition, and the diameter of the collagen fibrils, in lepidotrichia closely resemble those which are typical of cartilage. In addition, lepidotrichia contain chondroitin sulfate AC as the only sulfated glycosaminoglycan, and this glycosaminoglycan shows high levels of interaction with collagen, both features being characteristic of cartilage. Furthermore, the histochemical data presented in this paper suggest that not all of the glycosaminoglycans present in lepidotrichia are bound to protein cores to form proteoglycans. Each actinotrichium consists of a single ultrastructural entity of remarkable width and, thus, is not composed of a bundle of discretely separated collagen fibrils but rather of hyperpolymerized collagen molecules. This aspect differs from the arrangement pattern of all the other interstitial collagens, suggesting that actinotrichia may contain a new type of collagen.

Animals↗
PubMed1982

Collagen arrangement in cartilages.

The collagen arrangement of different cartilages of several mammals was studied by the Picrosirius-polarization method applied to tissue sections whose proteoglycans had been previously removed by enzymatic digestion. This procedure not only increases collagen birefringency but it also enhances the optimal resolution, permitting an accurate observation of the collagen disposition in this tissue. Our observations led to the conclusion that in the material studied at least five general patterns of collagen arrangement occur. When studied with the aid of electron microscopy, different cartilages showed variable values in their collagen fibril diameter. The results obtained suggest a greater variability in the collagen fibril diameters of those cartilages submitted to strong pressures.

Animals↗
PubMed1982

Biology of collagen.

Recent major advances in our knowledge of the biology of collagen considerably facilitated an understanding of the structure, function and pathology of connective tissues. This short review is designed as an introduction to current concepts and findings in collagen polymorphism, its biosynthesis, degradation, and interaction with the ground substance. Such a discussion will serve as a basis for a review of the current concepts and advances regarding the tissue distribution, and specific functional roles, of the different types of collagen, as well as the disorders of the connective tissue that involve collagen. We hope that this article will serve to grant the reader an opportunity to gain an overview of the developments in the research related to this fascinating protein. It was also our intention to show how much more remains to be learnt about the biology of collagen.

Animals↗
PubMed1981

Correlation of specific sulfated glycosaminoglycans with collagen types I, II, and III.

A qualitative and quantitative biochemical study of the glycosaminoglycans was performed in tissues constituted predominantly by one type of collagen, or in tissues containing mixtures of different types of collagen. The results obtained show the presence of dermatan sulfate, chondroitin sulfate, and heparin sulfate in tissues containing collagen types I, II, or III, respectively, suggesting a specific correlation of different glycosaminoglycans with these three types of collagen.

Animals↗
PubMed1981

Morphological and histochemical studies on the collagen in neurinomas, neurofibromas, and fibromas.

The collagen in neurinomas, neurofibromas was studied by optical and electron microscopy. Neurinomas were shown to be composed mainly of thin argyrophilic, weakly birefringent fibers formed by thin collagen fibrils. Fibromas presented only thick, non-argyrophilic, strongly birefringent fibers composed of thick collagen fibrils. Neurofibromas showed populations of the two above-mentioned types of fibers occupying different areas of their parenchyma. These results suggest that the collagen of neurinomas is mainly of type III, while fibromas present collagen type I, and neurofibromas are composed of both types of collagen.

Collagen↗
PubMed1981

Comparative morphologic and histochemical studies on the collagen of vertebrate arteries.

Arteries of representative species from the main vertebrate classes were studied by a method that quantitates collagen-proteoglycans interaction, by the histochemical Picrosirius polarization method and by electron microscopy. The collagen of the adventitia presents features which are characteristic of collagen type I. The collagen in the tunica media revealed histochemical and ultrastructural aspects which are typical of collagen type III. As these results were consistently observed in all species studied, they suggest the presence of a general structural pattern of collagen distribution in vertebrate arteries.

Animals↗
PubMed1980

Morphologic and histochemical evidence for the occurrence of collagenolysis and for the role of neutrophilic polymorphonuclear leukocytes during cervical dilation.

Biopsy specimens of nonpregnant and intrapartum human cervices were studied by electron microscopy, and by the Picrosirius-polarization method which is a specific procedure for the detection of collagen fibers in tissue sections. The results obtained demonstrate a marked reduction of collagen fibers in the intrapartum material as compared to the samples of nonpregnant cervices. Evidence that indicated the presence of a widespread collagenolysis in the intrapartum biopsy specimens was obtained by both optical and electron microscopy, thus suggesting that this might be the main cause of the changes in the cervix that permit it to dilate during parturition. The study of the neutrophilic polymorphonuclear leukocytes in the intrapartum biopsy specimens strongly suggested that these cells participate in this process.

Cervix Uteri↗
PubMed1980

Histochemical and morphological characterization of reticular fibers.

The results presented in this paper show that collagen fibers can be clearly distinguished from reticular fibers using the picrosirius-polarization method. A morphologic and morphometric study of these two types of fibers with electron microscopy shows that reticular fibers are characterized by the smaller diameter of their fibrillar components and the higher content of interfibrillar material, resulting in a loose arrangement of the fibrils. The evidences presented suggest that the amorphous matrix in which fibrils are embedded is responsible for the silver impregnation of reticular fibers. Our results show that the matrix of reticular fibers is characteristically rich in heparitin sulfate, and that the glycosaminoglycans present show a high interaction with the fibrillar component of these fibers.

Animals↗
PubMed1980

Quantitation of collagen - proteoglycan interaction in tissue sections.

Since the dye Sirius Red reacts with the basic groups of collagen, and it is possible to hydrolyze the proteoglycans bound to collagen by enzymatic digestion, a method was developed to quantitate the collagen-proteoglycan interaction in tissue sections. The method consists of measuring, with a spectrophotometer, the amount of dye bound to control and papain-digested tissue sections. The difference observed between the results obtained in control and digested sections is considered to be due to the unmasking of basic groups of collagen originally bound to proteoglycans. The initial results show a variability of this interaction in different tissues. They also suggest a reduction of collagen-proteoglycan interaction in atherosclerotic lesions.

Animals↗
PubMed1980

The collagen of permanently damaged nerves in human leprosy.

The collagen of nerve biopsies from ten leprosy patients was studied by the Picrosirius-polarization method and electron microscopy. It was observed that leprosy promotes a marked increase in nerve collagen content. Despite the changes induced by this disease, the localization of collagen types I and III in the endo-, peri-, and epineurium remains the same as in normal nerves.

Biopsy↗
PubMed1979

Do Schwann cells produce collagen type III?

The fact that collagen from both normal nerve endoneurium and Schwann cell tumours present characteristics of collagen type III, suggests that Schwann cells produce this type of collagen.

Animals↗
PubMed1979

The collagen of the vertebrate peripheral nervous system.

Nerves and ganglia from a variety of fish, amphibian, reptilian and mammalian species were studied by optical and electron microscopy. Observations using the Picrosirius-polarization method strongly suggest that two different types of collagen fibers are present in the connective tissues of nerves and ganglia. Electron microscopy of nerves and ganglia showed the presence of two different collagen fibril populations, distinguishable on the basis of diameter, located in different compartments of these structures. Thicker fibrils are present in nerve and ganglionic epineurium. Thinner fibrils are present in the endoneurium, surrounding nerve fibers and ganglionic cells, and between the concentric layers of perineurial cells. These results were consistently observed in all species studied and very probably represent a general phenomenon in vertebrates.

Amphibians↗
PubMed1979

Picrosirius staining plus polarization microscopy, a specific method for collagen detection in tissue sections.

Sirius Red, a strong anionic dye, stains collagen by reacting, via its sulphonic acid groups, with basic groups present in the collagen molecule. The elongated dye molecules are attached to the collagen fibre in such a way that their long axes are parallel. This parallel relationship between dye and collagen results in an enhanced birefringency. Examination of tissue sections from 15 species of vertebrates suggests that staining with Sirius Red, when combined with enhancement of birefringency, may be considered specific for collagen. An improved and modified method of staining with Sirius Red is presented.

Animals↗
PubMed1978

Differential staining of collagens type I, II and III by Sirius Red and polarization microscopy.

Organs of fish, amphibian, reptile, bird and mammals when stained by Sirius Red and studied with polarization microscopy present different colors in regions where collagens I, II and III have been described. Collagen type I presented a yellow, orange or red color while collagen type III appeared green. Collagen type II, present in cartilage and chondrosarcoma showed a variable color according to the tissue and the species. Its color and morphology however always permitted its clear distinction from collagens type I and type III.

Animals↗