Lymphatic and Blood Vessels of the Aged Human Gingiva1

The lymphatic pathways in the gingivae from aged humans were traced by the use of the PAS reaction or iron hematoxylin stain, and their structural characteristics were compared to those of the blood microvasculature. In the young and aging gingivae the lymphatic capillaries originated in the connective tissue papillae of the lamina propria, and appeared as thin walled irregular shaped vessels. The adjacent blood capillaries in aged gingivae differed in that their walls were thicker and stained intensely Schiff positive than seen in young adult gingivae. The lymphatic capillaries emptied into thin walled collecting vessels of varying calibers that course through the lamina propria to reach the main conducting vessels that contained valves projecting within its lumen. The accompanying blood vessels were easily differentiated from the lymphatic vessels by the intense positive staining of their walls following exposure to the PAS reaction. Distended lymphatic vessels of different caliber were demonstrable in inflamed aging gingivae, suggesting that lymphatic vessels in the aged gingivae were able to provide a drainage system for excessive fluid, proteins, and other particulates from both non-injured and injured sites.     

The Application of Miller's Elastic Stain to Glycol Methacrylate Tissue Sections

The application of Miller's dilute elastic stain followed sequentially by Gill's III hematoxylin and a fast green counterstain produced a reliable and consistent method for differentially staining elastic fibers, nuclei, muscle and collagen in glycol methacrylate tissue sections. Evaluation of different methods of fixation and conditions of staining on animal tissue sections showed that elastic fibers in both perfusion and immersion fixed tissues can be intensely stained. The stability of Miller's elastic stain offers the potential of a commercially available histological stain reagent for coarse and fine elastic fibers in glycol methacrylate tissue sections.     

The application of Miller's elastic stain to glycol methacrylate tissue sections

The application of Miller's dilute elastic stain followed sequentially by Gill's III hematoxylin and a fast green counterstain produced a reliable and consistent method for differentially staining elastic fibers, nuclei, muscle and collagen in glycol methacrylate tissue sections. Evaluation of different methods of fixation and conditions of staining on animal tissue sections showed that elastic fibers in both perfusion and immersion fixed tissues can be intensely stained. The stability of Miller's elastic stain offers the potential of a commercially available histological stain reagent for coarse and fine elastic fibers in glycol methacrylate tissue sections.     

THE FINE STRUCTURE OF ELASTIC FIBERS

The fine structure of developing elastic fibers in bovine ligamentum nuchae and rat flexor digital tendon was examined. Elastic fibers were found to contain two distinct morphologic components in sections stained with uranyl acetate and lead. These components are 100 A fibrils and a central, almost amorphous nonstaining area. During development, the first identifiable elastic fibers are composed of aggregates of fine fibrils approximately 100 A in diameter. With advancing age, somewhat amorphous regions appear surrounded by these fibrils. These regions increase in prominence until in mature elastic fibers they are the predominant structure surrounded by a mantle of 100 A fibrils. Specific staining characteristics for each of the two components of the elastic fiber as well as for the collagen fibrils in these tissues can be demonstrated after staining with lead, uranyl acetate, or phosphotungstic acid. The 100 A fibrils stain with both uranyl acetate and lead, whereas the central regions of the elastic fibers stain only with phosphotungstic acid. Collagen fibrils stain with uranyl acetate or phosphotungstic acid, but not with lead. These staining reactions imply either a chemical or an organizational difference in these structures. The significance and possible nature of the two morphologic components of the elastic fiber remain to be elucidated.     

A Modified Verhoeff-Van Gieson Elastin Histochemical Stain to Enable Pulmonary Arterial Hypertension Model Characterization

Optimal histochemical staining is critical to ensure excellent quality stained sections to enable light microscopic and histomorphometric image analysis. Verhoeff-van Gieson is the most widely used histochemical stain for the visualization of vascular elastic fibers. However, it is notoriously difficult to differentiate fine elastic fibers of small vasculature to enable histomorphometric image analysis, especially in organs such as the lung. A tissue fixation procedure of 10% neutral buffered formalin with subsequent fixation in 70% ethanol further compounds the problem of small vessel staining and identification. Therefore, a modified Verhoeff’s elastin stain was developed as a reliable method to optimally highlight the internal and external elastic laminae of small arteries (50-100 µm external diameter) and intra-acinar vessels (10-50 µm external diameter) in 3 µm thick lung tissue sections from models of pulmonary arterial hypertension. This modified Verhoeff’s elastin stain demonstrated well-defined staining of fine elastic fibers of pulmonary blood vessels enabling subsequent histomorphometric image analysis of vessel wall thickness in small arteries and intra-acinar vessels. In conclusion, modification of the standard Verhoeff-van Gieson histochemical stain is needed to visualize small caliber vessels’ elastic fibers especially in tissues fixed in 10% neutral buffered formalin followed by additional fixation in 70% ethanol.Key words: Histochemical stain, histomorphology, lung, Verhoeff-van Gieson, elastin     

Aging affects different human muscles in various ways. An image analysis of the histomorphometric characteristics of fiber types in human masseter and vastus lateralis muscles from young adults and the very old

This study is an attempt to objectively evaluate age-related changes in human muscles by use of histomorphometric methods. Aging in humans induces dramatic transformations in the skeletal muscles but little is known as to whether or not the aging processes per se may affect all muscles equally. In this study aging of two human muscles with different functions, origin and nerve supply is compared. Sections were cut from masseter and vastus lateralis muscles obtained from young adults aged 18-24 years and from the very old aged 90-102 years. Muscle fiber types were classified with the traditional myofibrillar ATPase staining. Various histomorphometric parameters of the different fiber types in human masseter and vastus lateralis muscle sections were obtained by image analyses to evaluate the age-related changes in the muscle fibers. The following variables were calculated: the number of each fiber type per photographed area; the area of each fiber and two indicators for the shape of the muscle fibers. In the aging muscles there was no relative preferential loss of a fiber type. High numbers of intermediate ATPase-stained fibers (IM fibers) were found in some old vastus muscles but were only sporadic in young vastus muscles. However, there was no change in the percentage distribution of intermediate ATPase-stained fibers when young and very old human masseter muscles were compared. Incubation of the sections with antimyosin antibodies showed that the IM fibers in old masseter and old vastus contained different myosin heavy chains. Thus ATPase activity and anti-myosin staining displayed a somewhat different pattern of fiber type distribution. The main changes in the shape and area indicated that type I fibers in the masseter became more circular while in the vastus they decreased significantly in size. The type II fibers in the vastus became very small and deviated significantly from circularity whereas the type II fibers in the masseter only exhibited a decrease in the size of the fibers. Histomorphometric measurements show that aging affects different human muscles in various ways.     

Further evidence of oxygen diffusion as the determining factor in the relation between disk thickness and respiration of potato tissue

The effect of oxygen tension above atmospheric pO₂ on the development of respiratory capacity in potato disks has been examined. Raising the oxygen tension of the aqueous environment to 40% during the aging of 2.0 mm or 3.0 mm thick disks at 25° progressively increased the respiration rate of the tissue as shown by subsequent assay in 100% oxygen. Disks 3.0 mm thick showed a greater response to increased pO₂ than did 2.0 mm disks. A comparison of center 1.0 mm sections excised from 3.0 mm disks after aging, showed that the respiration rate of internal tissue from disks aged in high pO₂ was approximately 40% greater than such tissue aged with atmospheric pO₂. The characteristic inverse relationship between respiration rate and thickness in aged disks can be modified from a concave-downwards curve to a convex-downwards curve by pretreating the tissue with increased pO₂, thus indicating that raising the pO₂ during aging can increase the thickness threshold at which the transition from tissue manifesting the respiratory characteristics of thin disks to that manifesting the characteristics of thick disks, occurs. Similarly increased pO₂ during aging can modify the hyperbolic relationship obtaining between pretreatment temperature in the range 10° to 25° and respiratory capacity of aged 3.0 mm disks, to approximate to the linear relationship observed with 0.75 mm disks. It is concluded that the development of respiratory capacity in disks between 0.75 mm and 3.0 mm thick is restricted by oxygen dificiency and that the characteristic inverse relationship between respiration rate and thickness in aged disks is largely attributable to this factor, the influence of which is discernible both on the development of respiratory capacity and on its subsequent assay.     

Detection of antileukoprotease in connective tissue of the lung

An indirect immunofluorescence technique was applied to frozen sections of central and peripheral human lung tissue to search for extracellular localizations of antileukoprotease (ALP). Two monoclonal anti-ALP antibodies recognizing different epitopes and polyclonal anti-ALP antibodies were used. ALP was found to be localized along elastic fibers in alveolar septa, and also along elastic fibers in the walls of bronchi, bronchioles and blood vessels. Serous cells of bronchial submucosal glands showed labelling as well. In frozen sections of liver and spleen no label was found. Cells and elastic fibers were not labelled when lung tissue sections were processed with polyclonal or monoclonal anti-ALP antibodies, that were blocked with purified ALP before the immunostaining. The association of ALP with elastic fibers of human pulmonary connective tissue is of importance in understanding the role of the inhibitor in the defense of the lung parenchyma against the action of proteolytic enzymes, which is thought to result in emphysema.     

Detection of antileukoprotease in connective tissue of the lung

Summary An indirect immunofluorescence technique was applied to frozen sections of central and peripheral human lung tissue to search for extracellular localizations of antileukoprotease (ALP). Two monoclonal anti-ALP antibodies recognizing different epitopes and polyclonal anti-ALP antibodies were used. ALP was found to be localized along elastic fibers in alveolar septa, and also along elastic fibers in the walls of bronchi, bronchioles and blood vessels. Serous cells of bronchial submucosal glands showed labelling as well. In frozen sections of liver and spleen no label was found. Cells and elastic fibers were not labelled when lung tissue sections were processed with polyclonal or monoclonal anti-ALP antibodies, that were blocked with purified ALP before the immunostaining. The association of ALP with elastic fibers of human pulmonary connective tissue is of importance in understanding the role of the inhibitor in the defense of the lung parenchyma against the action of proteolytic enzymes, which is thought to result in emphysema.     

Fluorescent staining of elastic tissue with Rhodamine B and related xanthene dyes

Summary Frozen sections, cut at 8 from various fresh tissues, were dried for 5 minutes over sulfuric acid, and then stained for 4 minutes in a 0.1% aqueous solution of Rhodamine B (Chroma) at pH 8.O. After soaking twice in butanol for 2 minutes each, the sections were kept on a warmer at 60° C for 2 minutes and then mounted in oil of cedar. Under ultraviolet microscopy, elastic fibers selectively stained yellow-orange against a pale blue background. No autofluorescence of elastic fibers was observed in guinea pig, rat, hamster or rabbit tissue in contrast to the autofluorescence of elastic fibers typically seen in human tissue.Similar fluorescent staining of the elastic tissue could be achieved by using a number of related xanthene dyes including pyronine, eosin B, acridine orange, pholoxin, phloxin B. More distantly related auranine O and thiazol yellow G were likewise used with success as fluorochromes for elastic fibers.Supported by a John A. Hartford Foundation Grant.     

Macroscopic and histological investigation of guanaco footpads (Lama guanicoe,Müller 1776)

The surface of guanaco footpads is characterized by hairless skin with up to 4‐mm‐thick stratum corneum that protects from abrasion. The horny layer is pliable and elastic, and ensures firm contact with irregular ground. It is padded with a particular structure of the subcutaneous layer, the digital cushion. The flat cushions of each of the two digits are of elongated ovate shape, each about 45‐mm long, up to 20‐mm wide, and 8‐mm thick. The cushions are lined by a 1–2‐mm‐thick capsule that resembles a tunica albuginea. The capsule consists of coarse collagen fibers, with elastic fibers absent. The cushion capsule and dermis approach each other, and fuse along a line that runs parallel to the longitudinal axes of cushion and digit. Loose connective tissue rich in elastic fibers and acidic glycosaminoglycans separates dermis and cushion capsule lateral to the narrow interconnecting zone. The cushion capsule encloses cloudy yellowish, gelatinous material. Microscopy shows bundles of elastic fibers in abundant mucinous matrix. Tightly gathered elastic bundles adjoin the inner surface of the capsule. Rough cords of elastic fibers branch out from there and traverse to the opposite side. The cushion is pressed flat, and elastic fibers are stretched when bearing weight. With relief of load, elastic fibers contract and reset the cushion's shape. Contractile cells are absent. A resistant capsule and easily malleable mucinous contents establish the functioning as a gel pad. Mucinous connective tissue between elastic fiber bundles contains abundant basophilic matrix. Hyaluronan, chondroitin sulfate, and dermatan sulfate are main matrix constituents. Spindle‐shaped or stellate fibroblasts contain vimentin, S100 protein, and neuron specific enolase. Moprhology, staining characteristics and synthesis activities of these cells meet the criteria to be classified as myxoid cells. The connective tissue in guanaco digital cushions represents myxoid tissue. J. Morphol. 276:331–341, 2015. © 2014 Wiley Periodicals, Inc.     

Cytological Staining Procedures Applicable to Methacrylate-Embedded Tissues

Experiments indicate that osmic-fixed, plastic-embedded sections are suitable for examination in the light microscope. Nuclei, mitochondia, cellular membranes and cytoplasmic granules are readily demonstrable by phase microscopy. Connective tissue stains permit the identification of elastic and collagenous fibers. Glycogen and other carbohydrate-containing structures are demonstrable by the periodic acid-Schiff and the ammoniacal silver nitrate procedures. It is, therefore, possible to cross-check individual structures by comparing alternate thick and thin sections, examined in the light microscope and electron microscope respectively. Several other advantages pertain to plastic embedded tissues. The sections compare favorably in translucency and in their lack of distortion with material embedded in celloidin, yet the procedure is simpler and much more rapid. Sections of any desired thinness can be prepared, and alternate thick and thin sections are easily forthcoming. When examined in the phase-contrast microscope, mitochondrial preparations become routinely available without the uncertainties of most of the mitochondrial staining methods. It appears, therefore, that plastic embedding should find a useful place among the methods for light microscopy as well as in the armamentarium of the electron microscopist.     

Rapid-freezing and malachite green-acrolein-osmium tetroxide freeze-substitution fixation improve visualization of extracellular lipids in rat incisor pre-dentin and dentin

Rat incisor tissue sections were fixed by a modified version of the malachite green-aldehyde method (MGA) composed of rapid-freezing, malachite green-acrolein staining, and osmium tetroxide freeze-substitution (Fr.MGAO). In the pre-dentin, a thick, dense network of branched fibrous structures was observed. Cryotechniques allowed visualization of complexes about twice as thick and dense as the aggregates visualized on MGA-treated sections. Pretreatment of rapid-frozen samples with methanol before freeze-substitution fixation and staining prevented staining of the complexes otherwise revealed by the Fr.MGAO method. Electron-dense material stained by this procedure resisted de-mineralization with EDTA, while intramitochondrial granules and dentin crystallites were dissolved. EDTA treatment demonstrated unequal distribution of Fr.MGAO staining in dentin in the form of tiny dots underlining the collagen fibers. These results support the concept that rapid-freezing, followed by staining and freeze-substitution fixation, improves preservation of the phospholipids visualized as extracellular matrix components in pre-dentin and dentin of rat incisors.     

A selective histochemical method for the quantitative estimation of elastic fibers by computerized morphometric analysis. Effect of colchicin treatment

A morphometric technique is reported that uses a new selective staining of the elastic system fibers in skin biopsy specimens to facilitate the quantitative evaluation of the volume fraction occupied by these elastic fibers in the tissue. The study of elastic fibers in the dermis of 30 patients, before and after six months of treatment with Colchicin, was carried out with a Quantimet 720 system. Preelastic (oxytalan and elaunin) fibers and mature elastic fibers were quantitated separately. Compared to the average volume fraction (surface occupied by the elastic fibers) before treatment with Colchicin (1.449 +/- 0.64%), the mean values after treatment were significantly increased (2.076 +/- 0.61%). The same results were found for the preelastic fibers: 0.807 +/- 0.51% before treatment and 1.025 +/- 0.54% after treatment. These results demonstrate the advantages of our monochromatic staining method for automatic quantitation of elastic fibers as well as the possibilities of the quantitative study of the elastic fibers in human dermis. This methodology should be applicable to other inherited or acquired diseases affecting skin elastic fibers as well as to other tissues containing elastic fibers.     

Resorption of elastic fibers in monkey gingival connective tissue: ultrastructural and immunocytochemical evidence

Little is known about the remodeling of elastic fibers in gingival connective tissue. In this study, elastic fibers in the lamina propria of monkey gingiva were examined by transmission electron microscopy and immunocytochemistry. Some elastic fibers were localized at invagination on the surface of the narrow processes of fibroblasts distributed among dense assemblies of collagen fibrils, and also within coated pits, which were pinching off as coated vesicles. At a higher magnification, the coated vesicles contained filamentous structures, as well as pentagonal structures similar those previously reported in elastic fibers. Immunoelectron microscopy demonstrated positive staining for fibrillin, one of the main components of microfibril, localized either in the coated pits or vesicles. These observations indicate that at least some elastic fibers were resorbed by fibroblasts, and that, in spite of the general belief that little remodeling of elastic fibers occurs under normal conditions, resorption of elastic fibers does occur in monkey gingival connective tissue. The functional significance of this is not yet clear, but it may be involved in facilitating the delicate and efficient adaptation of tissue to physical requirements during mastication.     

Preservation of elastic system fibers and of collagen molecular arrangement and stainability in an Egyptian mummy

The present findings show that both elastic system fibers and collagen markedly resisted change in tissues more than 2000 years old. The distribution of elastic fibers and elastic-related fibers (namely, oxytalan and elaunin fibers) in mummified tissues coincided with the observations made on the modern human tissues used as controls. The collagenous structures present in tissue sections obtained from the Egyptian mummy studied took on a deeply red colour when stained in the Picrosirius solution indicating that, as well as in the fresh controls, the basic groups in the collagen molecules were available for reacting with the strongly acidic dye Sirius Red. When viewed with polarized light, the collagen in the same tissue sections displayed an increased birefringence, which shows that the collagen molecules in mummified tissues maintain the oriented disposition which is typical of the modern human tissues used as controls. The methods employed have proved to be useful for the delineation of the elastic system fibers and of the collagenous scaffolding, which may be used as valuable landmarks in the study of the histoarchitecture of organs that have undergone considerable distortion.     

Mitochondrial DNA deletion mutations are concomitant with ragged red regions of individual, aged muscle fibers: analysis by laser-capture microdissection

Laser-capture microdissection was coupled with PCR to define the mitochondrial genotype of aged muscle fibers exhibiting mitochondrial enzymatic abnormalities. These electron transport system (ETS) abnormalities accumulate with age, are localized segmentally along muscle fibers, are associated with fiber atrophy and may contribute to age-related fiber loss. DNA extracted from single, 10 µm thick, ETS abnormal muscle fibers, as well as sections from normal fibers, served as templates for PCR-based deletion analysis. Large mitochondrial (mt) DNA deletion mutations (4.4–9.7 kb) were detected in all 29 ETS abnormal fibers analyzed. Deleted mtDNA genomes were detected only in the regions of the fibers with ETS abnormalities; adjacent phenotypically normal portions of the same fiber contained wild-type mtDNA. In addition, identical mtDNA deletion mutations were found within different sections of the same abnormal region. These findings demonstrate that large deletion mutations are associated with ETS abnormalities in aged rat muscle and that, within a fiber, deletion mutations are clonal. The displacement of wild-type mtDNAs with mutant mtDNAs results in concomitant mitochondrial enzymatic abnormalities, fiber atrophy and fiber breakage.     

Distribution of cholinergic and catecholaminergic nerves in the colon of the rat with aganglionosis.

We compared localization and distribution of putative cholinergic fibers by acetylcholinesterase and of adrenergic fibers visualized by the glyoxylic acid technique in the aganglionic segment using whole mount preparations of aganglionosis rat (AGR) and compared them with those of normal littermates. We also attempted simultaneous staining of acetylcholinesterase (AChE) and catecholamine fluorescence (C-F) on the same whole mount preparations to compare the differences in distribution pattern. All AGR used in this study had narrowed segments of the bowel extending from the distal ileum to the anus, and had no ganglion cells in these narrowed segments. In the intermuscular space, normally occupied with myenteric ganglion, of the narrowed distal colon and rectum, various sizes of nerve bundles and fibers reactive for AChE and C-F appeared to make coarse and irregular networks. These thick nerve bundles appeared to ascend to the proximal colon and disappeared in the cecum. In the distal ileum, almost totally absence of AChE positive nerve fibers, but a few fine C-F fibers, probably associated with blood vessels, were observed. By the method of simultaneous staining of AChE and C-F method in the whole mount preparations, the thick nerve bundles in the narrowed segments showed both of AChE positive and C-F positive. However, there were differences in peripheral fine nerve fibers in the segment; especially numerous perivascular C-F positive nerve fibers, but a few AChE positive ones were found. In the upper aganglionic narrowed segments, greatly diminished numbers of AChE positive and C-F positive nerve fibers were found in the circular muscle layer and in the submucosal layer. In the lower aganglionic narrowed segments, there were thick nerve bundles, forming irregular interlaced network. The role of these extrinsic nerve fibers in aganglionic segments is unclear.     

Contraction-free, fume-fixed longitudinal sections of fresh frozen muscle

Contraction damage occurring when longitudinal frozen sections of fresh unfixed muscles are thawed on microscope slides has limited histological examination of this tissue mainly to cross sections. Longitudinally oriented sections are advantageous for investigating properties that vary along the length of the muscle fibers. A fume fixation technique has been developed for preventing contraction of thick longitudinal frozen sections. The technique is compatible with histochemical staining of enzymes.     

Modifications of Erectile Tissue Components in the Penis during the Fetal Period

Background

The penile erectile tissue has a complex microscopic anatomy with important functions in the mechanism of penile erection. The knowledge of such structures is necessary for understanding the normal physiology of the adult penis. Therefore, it is important to know the changes of these penile structures during fetal development. This study aims to analyze the development of the main components of the erectile tissue, such as collagen, smooth muscle fibers and elastic system fibers, in human fetuses.

Methodology/Principal Findings

We studied the penises of 56 human fetuses aged 13 to 36 weeks post-conception (WPC). We used histochemical and immunohistochemical staining, as well as morphometric techniques to analyze the collagen, smooth muscle fibers and elastic system fibers in the corpus cavernosum and in the corpus spongiosum. These elements were identified and quantified as percentage by using the Image J software (NIH, Bethesda, USA). From 13 to 36 WPC, in the corpus cavernosum, the amount of collagen, smooth muscle fibers and elastic system fibers varied from 19.88% to 36.60%, from 4.39% to 29.76% and from 1.91% to 8.92%, respectively. In the corpus spongiosum, the amount of collagen, smooth muscle fibers and elastic system fibers varied from 34.65% to 45.89%, from 0.60% to 11.90% and from 3.22% to 11.93%, respectively.

Conclusions

We found strong correlation between the elements analyzed with fetal age, both in corpus cavernosum and corpus spongiosum. The growth rate of these elements was more intense during the second trimester (13 to 24 WPC) of gestation, both in corpus cavernosum and in corpus spongiosum. There is greater proportional amount of collagen in the corpus spongiosum than in corpus cavernosum during all fetal period. In the corpus spongiosum, there is about four times more collagen than smooth muscle fibers and elastic system fibers, during all fetal period studied.