Multidisciplinary Consensus on the Management of Non-Invasive Respiratory Support in the COVID-19 Patient

Acute respiratory failure due to COVID-19 pneumonia often requires a comprehensive approach that includes non-pharmacological strategies such as non-invasive support (including positive pressure modes, high flow therapy or awake proning) in addition to oxygen therapy, with the primary goal of avoiding endotracheal intubation. Clinical issues such as determining the optimal time to initiate non-invasive support, choosing the most appropriate modality (based not only on the acute clinical picture but also on comorbidities), establishing criteria for recognition of treatment failure and strategies to follow in this setting (including palliative care), or implementing de-escalation procedures when improvement occurs are of paramount importance in the ongoing management of severe COVID-19 cases. Organizational issues, such as the most appropriate setting for management and monitoring of the severe COVID-19 patient or protective measures to prevent virus spread to healthcare workers in the presence of aerosol-generating procedures, should also be considered. While many early clinical guidelines during the pandemic were based on previous experience with acute respiratory distress syndrome, the landscape has evolved since then. Today, we have a wealth of high-quality studies that support evidence-based recommendations to address these complex issues. This document, the result of a collaborative effort between four leading scientific societies (SEDAR, SEMES, SEMICYUC, SEPAR), draws on the experience of 25 experts in the field to synthesize knowledge to address pertinent clinical questions and refine the approach to patient care in the face of the challenges posed by severe COVID-19 infection.

180-day risk of mortality in older patients admitted to short-stay units: the 6-Month Short-Stay Unit (6M UCE) Score

OBJECTIVES

To develop a multidimensional score to assess risk of death for patients of advanced age 180 days after their admission to short-stay units (SSUs).

MATERIAL AND METHODS

Prospective, multicenter, observational and analytical study of a cohort of patients aged 75 years or older who were admitted to 5 Spanish SSUs between February 1 and April 30, 2014. We recorded demographic and clinical data as well as geriatric assessment scores. A multilevel logistic regression model was developed to identify independent factors associated with 180-day mortality. The model was used to construct a scale for scoring risk.

RESULTS

Data for 593 patients with a mean (SD) age of 83.4 (5.9) years entered the model; 359 (60.7%) were women. Ninety-two patients (15.5%) died within 180 days of SSU admission. Factors included in the final risk score were age over 85 years (1 point), male sex (1), loss of appetite or weight loss in the 3 months before admission (1), acute confusional state (2), functional dependence for basic activities of daily living at admission (2), and pressure ulcers (2). Low risk was indicated by a score of 0 to 2 points, intermediate risk by 3 to 5 points, and high risk by 6 to 9 points. Mortality rates at 180 days in these 3 risk groups were 5%, 18%, and 54%, respectively. The area under the receiver operating characteristic curve for the model after boots trapping was 0.72 (95% CI, 0.65-0.78).

CONCLUSION

The SSU score could be useful for stratifying risk of death within 6 months of SSU admission of older patients, so that type of care can be tailored to risk.

[Spanish short-stay-units: results according to department designated to manage the unit]

OBJECTIVES

To compare the efficiency of short-stay units (SSUs) managed by different departments within hospitals.

MATERIAL AND METHODS

Cross-sectional study in 40 hospitals with SSUs. From June 1 to December 31, 2012,we gathered data on clinical caseloads and management. Variables directly related to efficiency were mean length of stay, bed rotation index, and weekend discharge rate.

RESULTS

Forty SSUs were studied; 25 (62.5%) were managed by the hospital's emergency department (ED), 9 (22.5%) were managed by the internal medicine department (IMD), 5 (12.5%) were independent, and 1 was jointly managed by the hospital's ED and the IMD. A total of 45 140 patients were discharged from the SSUs. The most common diagnoses were exacerbation of chronic heart or respiratory disease, urinary tract infection, and respiratory infection. Age was the only variable that was related to the hospital department designated to manage these SSUs. The mean ages by management type were as follows: independent SSUs (75.6 years) vs ED-managed SSUs (67.2 years) vs IMD-managed SSUs (57.8 years) (P=.02). Group-by-group comparisons showed that the mean length of stay was shorter in ED-managed SSUs than in IMD-managed units (2.65 vs 3.73 respectively; P=.047), and overall mortality was lower in IMD-managed SSUs than in ED-managed SSUs (0.64% vs 3%; P=.033). However, unforeseen mortality (after excluding patients under palliative care or judged to be in the final hours of life) did not differ significantly between groups.

CONCLUSION

We did not detect important differences between SSUs managed by different departments in the hospitals in this series. However, mean length of stay was found to be shorter in ED-managed SSUs than in IMD-managed units.

[Effect of subglottic air insufflation on subglottic pressure during swallowing]

OBJECTIVE

To determine whether there are differences between subglottic pressure during swallowing with and without air insufflation via a subglottic catheter in tracheostomized patients.

DESIGN

A prospective, randomized cross-over study was made.

SETTING

Adult Intensive Care Units.

PARTICIPANTS

Patients requiring mechanical ventilation and tracheostomy with a subglottic catheter, and with tolerance to deflation of the balloon and a speaking valve placed over the opening of the tracheostomy tube.

INTERVENTIONS

Subglottic pressure was measured during swallowing of a thickened solution with and without the delivery of airflow through the subglottic catheter.

MAIN VARIABLE

Subglottic pressure during swallowing.

RESULTS

Twelve out of 14 patients showed higher subglottic pressure values during swallowing with air insufflation. Two patients showed no differences between both conditions. Median (Med) values of subglottic pressure for the first, second and third swallow were 5, 4 and 4.5 cmH2O (Med 4.5 cmH2O) without air insufflation, and 8, 5.5 and 7.5 cmH2O (Med 5.5 cmH2O) with air insufflation, respectively (Wilcoxon, Z=-3.078; p=.002).

CONCLUSION

In a group of tracheostomized patients, air insufflation via a subglottic catheter increased subglottic pressure levels measured during swallowing.

How to measure the increase in elastic system fibres in the lamina propria of the uterine cervix of pregnant rats

As the uterus enlarges to accommodate the growing fetus during pregnancy, the cervix behaves essentially as a barrier. During ripening and delivery, it needs to become soft and distensible to allow dilation and the passage of the conceptus. As the transformations of the collagen-containing fibres are known to be essential for ripening and delivery, it has been hypothesized that the elastic system fibres, owing to their intrinsic mechanical properties (reversible extensibility), could be involved in the shape-recovering process immediately after delivery. In sections stained by Weigert's resorcin-fuchsin (with previous oxidation), we describe the elastic system fibres in the lamina propria of the rat uterine cervix. They are distributed following different patterns when in the endocervix or in the ectocervical-vaginal region. A third distinctive pattern (named the 'elastic tendon') is described here for the first time in the uterine-cervical transition. A special morphometrical protocol has been designed in order to overcome problems during the quantification process. Using the so-called intercept counting method, it was possible to demonstrate that the elastic system fibres are increased in the cervix at the end of pregnancy. They may be involved in the immediate shape-recovering of the cervix after delivery as well as in helping to strengthen the anchoring of the epithelium to the lamina propria, thus minimizing birth trauma.

Phenotypic modulation of fibroblastic cells in the mucous layer of the human uterine cervix at term

The uterine cervix is a dynamic structure with a high capacity to adapt to different, even opposing, roles during the sequence of physiological events of gestation (for example, acting as a barrier to retain the fetus during pregnancy and dilating to allow delivery at term). Histoarchitectural changes of the uterine cervix allow its successful adaptation. The aim of this study was to investigate whether fibroblastic cell plasticity, described in the lamina propria of the rat uterine cervix at term, could be observed in women too. Biopsy specimens of non-pregnant and intrapartum human cervices were studied under the transmission electron microscope, and cytoskeletal differentiation markers were identified by immunohistochemistry under the light microscope. Desmin-positive cells were present in the mucous layer of the cervix during labour. These cells displayed cytoplasmic processes (typical of myofibroblasts) that also stained positively for vimentin. The main ultrastructural features for defining the myofibroblast under the electron microscope were also observed in these cells. However, cervices of non-pregnant women contained resident fibroblasts at the same location. Examination of the differentiation repertoire of fibroblastic cells in the mucous layer of the uterine cervix resulted in the characterization of myofibroblasts at term. The implications of the plasticity of fibroblastic-myofibroblastic cells in the physiological changes displayed in the uterine cervix during pregnancy, labour and postpartum involution require further investigation.

Differential distribution of the fibres of the collagenous and elastic systems and of glycosaminoglycans in the rat pubic joint

The pubic joint of male and female rats was studied at the light- and electron microscopical levels using methods that selectively disclose the extracellular matrix fibres and glycosaminoglycans. The interpubic tissue showed no difference between sexes (including pregnant and intrapartum females). The medial ends of the pubic bones were covered by articular caps of hyaline cartilage that blended in the midline. The whole articular cartilage was covered dorsally and ventrally (as well as craneally and caudally) by a typical perichondrium. The differential distribution of the fibres of the collagenous and elastic systems in the pubic joint agreed with the results reported in the literature for other rat cartilages. Collagen fibres, composed mainly of type-I collagen, were localised to the fibrous perichondrium and bone. Type-II collagen was localised to the central nucleus of hyaline cartilage, whereas reticulin fibres (rich in type-III collagen) were found in the adventitial loose connective tissue adherent to the most superficial layer of the perichondrium. The central nucleus of hyaline cartilage possessed the two types of elastic-related fibres: elaunin fibres were localised mainly to the chondrogenic layer of the perichondrium, whereas oxytalan fibres were found in the matrix that surrounded the chondrocytes. The bulk of the glycosaminoglycans present in the pubic joint cartilage corresponded to hyaluronic acid and chondroitin sulphate. The propriety of classification of the rat pubic joint as a true synchondrosis (instead of symphysis), and the fact that the unaltered pelvis of the rat seems to be adequate for normal parturition, are discussed.

Relaxin has a minor role in rat mammary gland growth and differentiation during pregnancy

Growth and differentiation of mammary gland is associated with numerous hormones and a variety of cell-cell, cell-matrix interactions. This study addressed the role of relaxin (Rlx) on these processes. Morphologic and biochemical changes that occur throughout the second half of pregnancy are reported. Temporal patterns and spatial distributions of markers useful to evaluate proliferation, secretion, and collagen remodeling were established. To evaluate the role of Rlx, an ablation/replacement animal model was used. Considering Rlx secretion pattern, two periods were selected: d 11 through d 13, and d 20 through d 23. In the stroma, the extracellular compartment showed changes associated with the lack of Rlx. Collagen remodeling within the lobuloalveolar structure, measured by a significant increase in collagen birefringence, decreased at d 12, d 21, and d 22. Parenchymal structures were less sensitive to the absence of Rlx than stroma. Epithelial cell proliferation was lower in Rlx-deficient rats only at d 12, and alpha-lactalbumin expression decreased at d 21 and d 22. Both lobuloalveolar diameter and percentage of area occupied by these structures showed no changes. In the absence of Rlx, some of the studied markers showed statistically significant differences in scattered days; these do not make clear trends. No differences were found on d 23 on any of the studied parameters suggesting that compensatory mechanisms might be activated to overcome the effects of the absence of Rlx. Unlike the critical role of Rlx either in uterine cervix dilation or in nipple development during rat pregnancy, Rlx had a minor role in growth and differentiation of rat mammary gland.

Characterization of fibroblastic cell plasticity in the lamina propria of the rat uterine cervix at term

Different organs contain fibroblasts with specific features and functions, indicating the complexity of fibroblast biology. In the rat cervical stroma, fibroblasts are preferentially located in the fibrous ring that surrounds the mucous layer. The purpose of this study was to investigate the morphological features and immunophenotype of fibroblastic cells of the uterine cervix in cycling, pregnant, and postpartum rats. Expression of the cytoskeletal proteins desmin, vimentin, and alpha-smooth muscle actin (alpha-SMA) were studied by immunohistochemistry. The optical density of immunohistochemical staining was quantified by image analysis. The ultrastructural features of fibroblastic cells were observed under transmission electron microscopy. Cervical fibroblastic cells always expressed vimentin and desmin but never alpha-SMA. During the first half of pregnancy (Day 5 [D5] to D14), desmin intensity values were similar to those of cycling and postpartum fibroblasts. In contrast, a strong expression of desmin was found from D15 to D22, with maximal expression at term (D23). Immunohistochemical expression for vimentin was constant throughout pregnancy and showed no differences with cycling and postpartum uterine cervices. Stromal cells from cycling and early pregnant rats displayed ultrastructural features characteristic of typical fibroblasts. In contrast, at the end of pregnancy, fibroblasts differentiated and showed increased secretory characteristics, reaching the ultrastructural features of a myofibroblast. Based on the differential expression of desmin and the electron microscopic observations, the foregoing results showed a modulation of the fibroblastic phenotype in the uterine cervix during pregnancy. To our knowledge, this is the first report that addresses the presence of myofibroblasts derived from resident fibroblasts in the fibrous ring of the rat uterine cervix. Fibroblastic-myofibroblastic cell plasticity may have implications in the physiological changes displayed in the uterine cervix during pregnancy, parturition, and postpartum involution.

Architectural remodelling in acute and chronic interstitial lung disease: fibrosis or fibroelastosis?

AIMS

Pulmonary fibrosis in acute and chronic lung disease has been much investigated, but little attention has been directed at the elastic tissue in these situations. Our aim was to verify whether elastic deposition accompanies collagen deposition in the repairing process of acute and chronic lung injury.

METHODS AND RESULTS

We measured, by image analysis, the content of fibres of the collagenous and elastic systems of the alveolar septum in histological slides sampled from autopsied lungs, using the picrosirius-polarization method and Weigert's resorcin-fuchsin stain, respectively. Five groups were studied: I, 10 normal patients; II, 10 patients with cardiogenic pulmonary oedema; III, 23 adult respiratory distress syndrome (ARDS) patients in the early phase; IV, 14 ARDS patients in the late fibroproliferative phase; and V, 10 idiopathic pulmonary fibrosis patients. The first two groups were used as controls. The content of fibres of the collagenous and elastic systems was significantly increased in groups IV and V as compared to the other groups.

CONCLUSIONS

Our results indicate that deposition of elastic system fibres is present in the fibroproliferative phase of ARDS and in usual interstitial pneumonia and suggest that this event may contribute to the alveolar mechanical dysfunction and remodelling that occur in acute and chronic interstitial lung disease.

Estrogen and progesterone modulation of eosinophilic infiltration of the rat uterine cervix

Ripening of the rat cervix involves widespread collagenolysis that follows an eosinophilic leukocyte infiltration. The hormonal control of these events is not well understood. The aims of this study were to investigate the mechanism through which progesterone (P) and 17beta-estradiol (E(2)) modulate eosinophilic invasion and to determine if this event is protein synthesis mediated. Cervical eosinophilic invasion was measured in intact rats during the second half of pregnancy and compared with values from ovariectomized (O) pseudopregnant (PSP) rats treated with P and E(2) in doses that mimicked the levels of pregnancy. Other O-PSP rats were treated with an E(2) antagonist (tamoxifen) and the antiprogestin RU-486. To study the role of protein synthesis in eosinophilic invasion of the cervix, rats were treated with actinomycin-D (an inhibitor of mRNA synthesis), and animals were sacrificed on D21 or D22 to evaluate eosinophilic invasion. Rats treated with E(2) showed high levels of infiltration and tamoxifen blocked this E(2) effect. On the other hand, P antagonized the stimulatory effects of E(2) on eosinophilic invasion, however when the P and E(2) treated rats were injected with RU-486 the inhibitory effect of P was reversed. In intact pregnant rats a sharp rise in eosinophilic infiltration was detected on D23, 20 h after the fall of serum P. Finally, E(2) treated rats injected with actinomycin-D had no invasion of eosinophils. In conclusion, the estrogen-triggered eosinophil invasion is affected by the classic estrogen receptor antagonist tamoxifen and by the mRNA synthesis blocker actinomycin-D suggesting a genomic action of E(2). Furthermore, the estrogen effect is blocked by P and this inhibition is reversed by RU-486.

[Distribution of financial resources according to the productivity (determined by bibliometry) in the Medical Research Laboratories of the Hospital das Clínicas da Faculdade de Medicina da Universidad de São Paulo (Brazil)]

A challenge that research managers have to face is how to "reallocate" agency budgets in order to bring them in line with the results of performance reviews. Research policies must develop a strategic plan describing their goals, devise yardsticks to measure their progress, and tie that performance to allocate research funds with some degree of priority. Though Brazil already has a substantial presence in world's science, scientific enterprise must be used to strengthen it. The first step should be to raise standards in Brazilian science by concentrating the resources on supporting excellence. A strategy to judge biomedical research productivity should include tactics to disclose whether the resulting publications have appeared in the field's most respected, peer-reviewed journals. A pilot project to road-test the above-discussed ideas on performance measurements was conducted at the Laboratories of Medical Research (Clinical Hospital, University of São Paulo School of Medicine). These Laboratories perform a vast proportion of biomedical research at the country's largest University. This article illustrates that confidence in fairness and consistency with which funds are now being allocated has helped to improve productivity, thus showing that this strategy is fruitful.

Collagen-affecting drugs impair regeneration of teleost tail fins

Regenerating tail fins were studied in two species of teleosts, Tilapia rendalli and Cyprinus carpio, treated with indomethacin, aspirin, dexamethasone, penicillamine, and beta-aminoproprionitrile, drugs known to disrupt collagen metabolism in mammals. Collagen was studied under the light microscope by the Picrosirius-polarization method and also under the electron microscope. In general, these drugs disturbed the deposition and organization of collagen fibrils leading to abnormally thin or practically absent lepidotrichia and actinotrichia, and also to disorganized fibrous connective tissue. The resulting disorganization of the collagenous scaffolding of the regenerating dermoskeleton was probably responsible for a secondary effect on blastema distalization and on the general fin ray patterning that were also observed. The foregoing observations suggest that the stromal histoarchitecture of the regenerate plays a vital role in fin regeneration and indicate that these drugs may be useful in studying the extracellular matrix-cell interactions at the cellular and molecular level. In addition, the present findings provide a basis for developing different biological models by using teleost fin regeneration.

Morphometric study of the regeneration of individual rays in teleost tail fins

The results obtained using morphometric variables which describe fin ray regeneration patterns are reported for individual fin ray amputations in the goldfish (Carassius auratus) and zebrafish (Brachydanio rerio). Classical and updated experiments are compared to verify previous morphogenetic models of cell tractions (Oster et al. 1983) or epidermis-mesenchyme induction (Saunders et al. 1959) applied to the limb of other vertebrates. Position-dependent patterns within the fin of Carassius auratus are analysed under a comparative protocol using morphometric methods. Conditions in which the apical epidermis is separated from blastema may differentiate small fin rays, thus suggesting this epidermis is involved in blastemal formation. Blastemal cells differentiating as lepidotrichia forming cells (LFCs) may also be related to morphological changes in covering epidermis. Long-range interactions from neighbouring fin ray blastemas or short-range interactions within the blastema, may be postulated through the analysis of segmentation.

Relation between interstitial myocardial collagen and the degree of clinical impairment in Chagas' disease

Cardiac performance is negatively associated with interstitial collagen in Chagas' cardiomyopathy. The magnitude of dysfunction is related to the degree of collagen, and this association seems to exhibit a threshold above it if definite cardiac deterioration occurs.

Use of the Picrosirius-polarization method to age fibrotic lesions in the hepatic granulomas produced in experimental murine schistosomiasis

The state of collagen aggregation in hepatic granulomas produced in experimental murine schistosomiasis and harvested at different phases of the disease was estimated by staining histological sections in Picrosirius and studying them under polarized light. Two different types of collagenous fibres appeared successively during granuloma evolution, the first population, of thin, weakly birefringent, greenish fibres being replaced by thicker collagen fibres which display a stronger yellow-red birefringence. A simple morphometric technique (a point-counting procedure) was used to quantify the two distinct populations of collagenous fibres. Curve-fitting procedures were then employed, using the state of collagen aggregation as the dependent variable and time as the independent variable. The results showed that there is a progressive organization of the collagenous scaffolding of hepatic granulomas, such that quantitative study of the degree of collagen organization allows an adequate determination of the age of each granuloma. The combination of the Picrosirius-polarization method with simple and efficient morphometric approaches will clearly provide useful information on the natural history of schistosomal granuloma scarring.

Dating of fibrotic lesions by the Picrosirius-polarization method. An application using the lesions of Lechiguana (bovine focal proliferative fibrogranulomatous panniculitis)

This work was designed to verify if a simple quantitative procedure to estimate the state of collagen aggregation is useful in describing the natural history of a fibrous process. For this purpose sixteen cases of Lechiguana lesion were used. Histochemical evaluation of the collagen content and its state of aggregation was done by the Picrosirius-polarization method. Morphometric studies were done by means of a point-counting procedure, which allowed the determination of the areal fraction of thin and thick collagenous fibers within Lechiguana lesions collected at different times of clinical evolution (14 days through 8 months). Early lesions are characterized by thin collagenous fibers. This population of slender fibers decreases later on, when thick fibers become more prevalent. Curve fitting procedures were employed using the state of collagen aggregation as the dependent variable and time as the independent variable. The best fitting was obtained by linear and exponential functions. Statistical analysis indicates that the quantitative study of the degree of collagen organization allows an adequate determination of the time course of Lechiguana lesions. We concluded that simple determinations of collagen aggregation provide numerical data that may be useful to build mathematical models relating time of evolution of the disease to fibrosis.

Differential distribution of elastic system fibers in control and bronchoconstricted intraparenchymatous airways in the guinea-pig lung

The elastic system fibers were studied at the light microscopic level by using Weigert's resorcin-fuchsin method after oxidation. This study was designed to describe the distribution of these fibers in intrapulmonary guinea-pig airways and to characterize their conformational changes during bronchoconstriction induced by methacholine aerosol. Airways present a palisade of elastic system fibers just beneath the epithelial basement membrane; these fibers are also present in the adventitial connective tissue. Thin fibers link the fibers located in the palisade among themselves and also connect them to those fibers located in the bronchial adventitial tissue, by traversing the airway smooth muscle. During bronchoconstriction, the fibers located beneath the epithelial basement membrane are divided into two components: one follows the epithelial invaginations towards airway lumen, while the other population remains attached through airway smooth muscle to the fibers located in the adventitial connective tissue. At the ultrastructural level, the findings corroborated those of the light microscopy and in addition, disclosed that typical mature elastic fibers and also elaunin fibers attach directly to the basal lamina, a feature that has not been reported previously in other tissues studied. This configuration is compatible with the idea that fibers of the elastic system restrict the mucosal folding during bronchoconstriction, and may also provide energy to restore airway configuration to its normal status after contraction.

Leukocyte infiltration and collagenolysis in cervical tissue from intrapartum sheep

Sheep uterine cervices and cervical mucus were heavily infiltrated by neutrophils during labour, whereas samples of cervices obtained from non-pregnant controls had no infiltrate. The neutrophilic infiltrate of the sheep uterine cervix at term was not homogeneously distributed throughout the organ: luminal mucus contained more neutrophils than tissues which, in turn, displayed a differential distribution, the superficial subepithelial layer being more heavily infiltrated than the deeper submucous layers. A widespread collagenolysis was observed in the sheep uterine cervix at term. The homogeneous morphological aspect of degradation of collagen fibres throughout the whole cervical stroma contrasted with the above-mentioned differential distribution of neutrophils. On the basis of previous reports showing that collagenolysis follows the leukocytic invasion of human and rat cervices at term, a possible role for the neutrophilic infiltrate of the sheep uterine cervix is discussed.

Organization of collagen and elastic fibers studied in stretch preparations of whole mounts of human visceral pleura

Fibers of the collagenous and elastic systems are most relevant in the double mechanical action of visceral pleura (VP), i.e. volume limitation and the generation of elastic recoil pressure. In this work we studied the organization of these fibrous components of VP in two situations: normal lungs and bullous disease. We employed histochemical methods on conventional histological slides and on thin spreads of whole mounts of visceral pleura. In addition, the scanning electron microscope was also used. According to our results, pleural function is made possible by the combination of both the elastic and collagenous fiber systems, each one having as intrinsic organizational pattern. Marked alterations of pleural bullous structure are observed with changes in lung volume. Fibers of the elastic and collagenous systems are clearly interdependent elements. Collagenous fibers are interwoven in a plaited structure that closely resembles the osiers of a wicker basket, indicating that collagen fibers allow for lung volume increase up to a point of maximal stretching of the system. The pleural contribution to lung elastic recoil pressure originates from the elastic network which turns back to its resting position when inspiratory pressures are negligible. The pleural immobility in bullous disease is associated with an almost complete absence of elastic fibers and the presence of very thick collagen fibers, suggestive of a cicatricial process, devoid of any characteristic pattern of distribution.

Urban air pollution enhances the formation of urethane-induced lung tumors in mice

This paper investigates the association between air pollution and lung neoplasia in an animal model. The experimental exposures were done in two locations with different air pollution profiles: a polluted area (downtown São Paulo) and a "clean" environment (Atibaia). Swiss mice were employed and urethane (3 g/kg) was used as carcinogenic substance. Two experiments were performed: Experiment I was designed to verify whether air pollution acts as initiator and/or promoter of lung cancer, using 300 mice; Experiment II employed 250 animals and aimed to verify if the effects of air pollution on the development of lung tumors was dose dependent. A significant effect of air pollution in augmenting lung carcinogenecity induced by urethane was observed. This effect was shown to be dose-dependent and reproducible on two different occasions. In addition, morphometric studies revealed that pollution may influence tumor phenotype. These results support the hypothesis that air pollution plays a significant role in the development of lung tumors.

The lysosomal-associated membrane protein LAMP-1 is a novel differentiation marker for HC11 mouse mammary epithelial cells

HC11 cells are a model for mammary epithelial cell differentiation. Following treatment with the lactogenic hormones glucocorticoids, insulin and prolactin the HC11 cells synthesize milk proteins. Stereological analysis at the ultrastructural level suggested that lysosomal biogenesis was activated following lactogenic hormone treatment of HC11 cells. Differentiation was also accompanied by an increase in the cellular content of tri- and tetra-antennary oligosaccharides, which were reactive with isolectin L4 from Phaseolus vulgaris (L-PHA). The lysosomal-associated membrane glycoproteins LAMP-1 and LAMP-2 are the major carriers of this glycosylation pattern. An analysis of LAMP-1 and LAMP-2 expression levels showed that there was a dramatic increase in LAMP-1 following lactogenic hormone treatment of HC11 cells. The control of LAMP-1 expression is mainly post-transcriptional since the level of LAMP-1 RNA is not affected by lactogenic hormones. Stereological analysis also showed an increase in intermediate filament control of differentiated cells. Analysis of the cytokeratins expressed in differentiated cells suggests that HC11 cells have characteristics of a mammary-specific stem cell. Increase in lysosomal vesicles and their contents might play a role in intra- and extra-cellular remodeling, which is characteristic of cell differentiation.

The role of the collagenous and elastic system fibers in modulating bronchoconstriction

The distribution and conformational changes of the fibers of the collagenous and elastic systems in guinea pig airways after a contractile agonist challenge are described. We observed a distinct pattern of behavior within the mucosal fibers during bronchoconstriction. Part of the fibers of the two systems tend to follow the epithelial invaginations towards the airway lumen, while the remaining ones seem to be attached to the internal smooth muscle. These layers of fibers in the mucosa are interconnected to one another and to the adventitial network by slender fibers. We suggest that the configuration and behavior of these fibers during bronchoconstriction may contribute to airway reopening after the contractile stimulus has ceased. The possible role of this mechanism in the pathophysiology of human asthma is discussed.

Effect of aqueous and nonaqueous fixatives on the quantitative estimation of collagen-proteoglycan interaction in tissue sections

The present study was designed to assess the influence of aqueous and nonaqueous fixatives on the quantitative estimation of collagen-proteoglycan interaction in tissue sections. Tissues containing different collagen types and distinct sulfated proteoglycan classes were isolated from pig costal cartilage, human skin, and the inner muscular layer of dog small intestine and fixed using aqueous or nonaqueous methods. The results showed that the best fixation method was exposure to paraformaldehyde gas. When using aqueous fixatives, proteoglycans were lost to different degrees among the various tissues analyzed, reflecting differences in chemical properties of proteoglycan classes and/or in their interactions with other matrix components such as collagen.

Correlation of thyrotropin secretion with morphometric data of secretory granules from individual thyrotropes. An ultrastructural study on rat cells identified by reverse hemolytic plaque assay

We investigated the existence of functional subpopulations of thyrotropes in pituitary glands of male rats, also seeking to establish any correlation of thyrotropin secretion with morphometric data of secretory granules. Pituitary cells secreting thyrotropin were detected using a reverse hemolytic plaque assay. Population analysis of the plaque sizes (TSH secreted) of individual thyrotropes in control cultures from male rats revealed a unimodal frequency distribution. TRH added to the medium resulted in a shift to a bimodal distribution of sizes, consisting of small and large modes, but did not alter the fraction of plaque-forming thyrotropes. The plaque size of control cultures was the same as that of the fraction of TRH-stimulated thyrotropes forming small plaques. Because the extent of hemolysis is related to the amount of thyrotropin secreted by each individual thyrotrope, these results suggest that: a) all thyrotropes secrete thyrotropin even in the absence of a stimulatory dose of TRH; b) the thyrotrope subpopulation secreting small amounts of thyrotropin when incubated with TRH may be unresponsive to this stimulatory factor. After performing reverse hemolytic plaque assay, plaque-forming cells were subsequently processed for electron microscopy. Morphometric analysis of the secretory granules correlated well with plaque size (TSH secreted). It is thus concluded that the functional subtypes of thyrotropes can be recognized on the basis of their ultrastructural images.

Histochemical and ultrastructural study of the extracellular matrix fibers in patellar tendon donor site scars and normal controls

Lesions of the anterior cruciate ligament are extremely common and frequently demand surgical treatment in order to avoid disabling sequels. The use of a central one-third of the patellar tendon as an autograft for surgical reconstruction of a damaged cruciate ligament is common. Although several investigations in human and animal models have demonstrated long-term graft viability, there have been cases of loosening and rupture of the graft. In these occasions, a new substitute for the torn structure must be found. Owing to its inherent accessibility, the patellar tendon has been elected one of the choices of donor tissue. In order to evaluate the characteristics of the remaining scar, we performed a histochemical and ultrastructural study using biopsy material obtained from the central one-third of the donor tendon of 8 patients. This material was analyzed by comparing the ultrastructural picture with the results obtained using the specific method for collagen-containing fibers (Picrosirius-polarization) by light microscopy; four normal patellar tendons were used as controls. Despite the resemblance with the normal tissue, our results show that the healed tissue does not restore the tendon ad integrum, neither at the light microscopic nor at the electron microscopic levels. Structural differences can be responsible for biomechanical alterations. Impaired biomechanical properties can, at least partly, explain some of the clinical complications observed in patients submitted to this surgical technique. However, without performing biomechanical studies in this kind of tendons, we are neither allowed to encourage nor to reject the use of scars as donor tissue for a second surgery.

Regeneration of fin rays in teleosts: a histochemical, radioautographic, and ultrastructural study

Regeneration followed partial amputation of the tail fin in three representative species of teleosts. A systematic study, using histochemical methods, radioautography and transmission electron microscopy, disclosed the essentials of the natural history of regeneration of the fin soft-rays. At about 24 hours, epidermal cells had completely covered the cut edge. By the second day an apical epidermal cap was established. Beneath this cap a blastema was formed by about three days after amputation. A collagenous lepidotrichial matrix had begun to develop by 4 days after excision. Actinotrichia were first detected in the regenerates at 5 days. During these processes, the basal lamina of the epidermis played an important morphogenetic role. The cells responsible for the regenerate underwent regressive changes after form and function had been restored.

Structural biology of the fibres of the collagenous and elastic systems

The different types of fibres of the collagenous and elastic systems can be demonstrated specifically in tissue sections by comparing the typical ultrastructural picture of each of the fibre types with studies using selective staining techniques for light microscopy. A practical modus operandi, which includes the recommended staining procedures and interpretation of the results, is presented. Micrographs and tables are provided to summarize the differential procedures. Reticulin fibres display a distinct argyrophilia when studied by means of silver impregnation techniques, and show up as a thin meshwork of weakly birefringent, greenish fibres when examined with the aid of the Picrosirius-polarization method. In addition, electron-microscopic studies showed that reticulin fibres are composed of a small number of thin collagen fibrils, contrasting with the very many thicker fibrils that could be localized ultrastructurally to the sites where non-argyrophilic, coarse collagen fibres had been characterized by the histochemical methods used. The three different fibre types of the elastic system belong to a continuous series: oxytalan-elaunin-elastic (all of the fibre types comprising collections of microfibrils with, in the given sequence, increasing amounts of elastin). The three distinct types of elastic system fibres have different staining characteristics and ultrastructural patterns. Ultrastructurally, a characteristic elastic fibre consists of two morphologically different components: a centrally located solid cylinder of amorphous and homogeneous elastin surrounded by tubular microfibrils. An oxytalan fibre is composed of a bundle of microfibrils, identical to the elastic fibre microfibrils, without amorphous material. In elaunin fibres, dispersed amorphous material (elastin) is intermingled among the microfibrils.

Nasal mucus clearance in rats: differences with sex and phase of the oestrous cycle

We studied the changes in airway mucus rheology and clearability, as well as in morphometric indices, between male rats and females in either the oestrous or dioestrous phases of the oestrous cycle. Three-month-old Wistar rats were studied and the phases of the oestrous cycle were determined based on analysis of vaginal smears stained by a modified Shorr's procedure. Nasal mucus samples were analysed by means of magnetic rheometry and determination of in vitro transport rate in the frog palate preparation. In situ clearance on the exposed nasal septum was also determined. The mucociliary velocity in situ was significantly affected by both sex and the oestrous cycle phase. In female rats, dioestrous phase clearance was significantly slower than the oestrous phase one. Clearance in male rats was faster than that of both the phases studied in females. Mucus rigidity of females in the oestrous phase was more rigid than that of females in the dioestrous phase and that of males. Mucus viscosity/elasticity ratio for deformations performed at high frequencies was greater for females in comparison with males. Cough clearability computed on the basis of rheological parameters was predicted to be more favourable in females. There were no significant differences between the three groups in mucociliary clearance in vitro. Morphometric studies of the nasal epithelium showed that epithelial and glandular volumes did not exhibit sex- or oestrous-phase-related differences, but the amount of epithelial acidic glycoproteins was lower in females in the oestrous phase in comparison with males and those in the dioestrous phase, the same trend being observed in the glands of the lamina propria.(ABSTRACT TRUNCATED AT 250 WORDS)

Volume fraction of dense-core granules correlates strongly with survival in disseminated (stage IV) neuroendocrine cell carcinomas of the lung of the well differentiated and small cell subtypes

In order to verify whether ultrastructural quantitative morphological indices of neuroendocrine cell carcinoma of the lung may help to predict survival in disseminated disease (Stage IV), 21 biopsy specimens were studied. Volume density of mitochondria and dense-core granules was assessed by a conventional point-counting procedure. Survival in months after biopsy was considered the dependent variable of age and of the morphometric parameters, in a multivariate linear regression analysis. The significance level was set at 5%. Survival was positively correlated (p = 0.011, multiple r = 0.686) with volume fraction of dense-core granules (p = 0.0025) and negatively correlated with volume fraction of mitochondria (p = 0.035), and also with age (p = 0.034). Our data indicate that survival is strongly dependent on the degree of neuroendocrine differentiation and of metabolic activity of tumour cells and that improved prognostic accuracy is provided by the use of quantitative analyses as compared with the conventional subtyping of malignant pulmonary neuroendocrine neoplasms.

Nuclear/cytoplasmic ratio correlates strongly with survival in non-disseminated neuroendocrine carcinoma of the lung

In order to verify whether quantitative morphological indices of neuroendocrine carcinoma of the lung may help to predict survival, 47 biopsies (from 37 males and 10 females; 16-82 years of age) were studied by light microscopy. Areal fractions of nuclei, cytoplasm, stroma, and blood vessels were determined using a standard point counting method. The counts were made in six non-coincident microscopic fields in each case, and the areal fractions of nuclei, of the entire tumour cell, stroma, blood vessels and the nuclear/cytoplasmic ratio were computed. In a multivariate linear regression analysis, survival in months after biopsy was considered the dependent variable of age and of all morphometric parameters listed above. The significance level was set at 5%. For all patients (disregarding staging) survival was negatively correlated (P < 0.001, multiple r = 0.5435) with age and nuclear/cytoplasmic ratio. When only patients with disease confined to the thorax (stages I, II and III) were taken into account, the accuracy of the function predicting survival increased considerably (P = 0.004, multiple r = 0.7957). The use of simple stereological methods, therefore, proved to be of value in predicting survival in patients with neuroendocrine carcinomas of the lung.

Morphological distinction between filaments that converge upon desmosomes and those that are attached to hemidesmosomes in the epidermis of anuran larvae and lampreys

Two populations of morphologically distinct intermediate filaments which are segregated into different compartments of the cytoplasm and which may attach to different junctional specialisations were observed in the basal layer cells of the epidermis of tadpoles of Rana catesbeiana, Rana temporaria, Bufo bufo, Leptodactylus flavopictus and Pseudis paradoxus and in the skin of the adult lamprey, Lampetra planeri. These two distinct populations of cytokeratin intermediate filaments were recognised on the basis of their diameter: the thicker intermediate filaments apparently attach themselves to hemidesmosomes whereas the thinner intermediate filaments apparently converge upon desmosomes, in a single cell. The fact that these findings were consistently observed in all the tadpoles of the five species examined and in adult lampreys, and also fit with data for newt larvae, argues in favour of the existence of a uniform structural pattern of distribution of morphologically distinct intermediate filaments in basal layer cells that is a general phenomenon in the epidermis of amphibian larvae.

Distribution of elastic system fibres in the rat tail tendon and its associated sheaths

The distribution of elastic, elaunin and oxytalan fibres in tendons and tendon sheaths was studied by means of light and electron microscopy. The different fibres were characterised by comparing their typical ultrastructural pictures with a combination of selective staining techniques for light microscopy with the appropriate enzymatic digestions. Since it was observed that the rat tail tendon and its associated sheaths are not homogeneous structures from the point of view of the distribution of the elastic system fibres, a systematic description of the differential distribution of the oxytalan, elaunin and elastic fibres in the tendon and in the endo-, peri-, epi- and paratendineum is presented. Mature elastic fibres are present in the tendon and in the para-, epi- and endotendineum, whereas these fibres could not be detected in the peritendineum. Very many elaunin fibres are characteristically recognised in the endotendineum; these fibres are present in the peritendineum and in the tendon fascicles too, while the epi- and paratendineum are devoid of elaunin fibres. The peri- and endotendineum contain numerous oxytalan fibres, whereas these fibres are absent from the tendon fascicles and the epi- and paratendineum. The functional implications of the foregoing findings are discussed.

Progesterone promotes a massive infiltration of the rat uterine cervix by the eosinophilic polymorphonuclear leukocytes

Rat uterine cervices contained an eosinophilic infiltrate during labor, whereas samples of cervices obtained from nonpregnant controls had no infiltrate. A heavy eosinophilic invasion, which closely resembled that of the cervix uteri at term, could be reproduced in ovariectomized rats following progesterone administration, but not in spayed rats injected with estrogen. Light and electron microscopic evidence showing a widespread collagenolysis in the cervical stroma at term is presented. This collagenolysis follows the eosinophilic invasion. On the basis of these observations, a possible role for the eosinophilic infiltrate of the uterine cervix is discussed.

A note on the histochemical and morphological characterization of the asbestoid degeneration of cartilage

Using only one histologic preparation and under the light microscope, the simple Picrosirius-polarization method permitted the histochemical characterization of the collagenous nature of amianthoid fibers in file cases of salivary gland tumors. In this regard the foregoing results agree with the electron microscopic and X-ray diffraction observations recorded in the literature. Not only did the Picrosirius-polarization method permit the precise characterization of the collagenous nature of asbestoid change but it was also useful for studying the degree of collagen polymerization in the lesion. Collagen molecules in the amianthoid fibers showed hyperpolymerization whereas the molecules in the compact areas were disoriented. Since the foregoing results demonstrate that the Picrosirius-polarization method is a simple and sensitive procedure for detecting asbestoid change in cartilage sections obtained from paraffin-embedded tissues, the usefulness of this technique for studying file cases is evident.

Morphologic evidence that disruption of the Golgi apparatus in PFHR 9-tumor cells causes disturbance in the traffic through this organelle

PFHR 9 is a murine teratocarcinoma-derived tumor which produces basement membrane components. Electron microscopy of the tumor cells disclosed a disorganization of the Golgi complex whose saccules, instead of being flattened, round up into 0.13 micron-wide spherical vesicles (SV). Their shape does not permit the normal stacking of parallel cisternae, and thus these SV become intermingled with transport vesicles (TV) which measure 44 nm in diameter. The cytoplasm of these tumor cells contains numerous multivesicular bodies (MVB) of varying size (ranging from 0.3 to 2.6 micron), which occupy 7% of the cellular volume. These MBV are packed with very many small vesicles similar in all aspects to the TV, and also contain a few larger vesicles which resemble the altered Golgi saccules (SV). Since these MVB display morphologic evidence for gradual lysis of their contents and strongly react with the cytochemical method for acid phosphatase, it is assumed that MVB are autophagic vacuoles which result from the accumulation of TV. This seems to be a unique example of a disease of the Golgi stack, with consequent accumulation and disposal of this material via autophagic vacuoles.

Effects of ovarian steroids on vaginal smears in the rat

A correspondence between the appearance of vaginal smears and the layers of the epithelium from which the cells had desquamated was established in untreated rats during the estrous cycle, in control ovariectomized rats and in spayed rats injected with either estrogen or progesterone. The technique for preparing and staining the smears (modified Shorr's staining procedure) is outlined. A simplified system of classification which allows the accurate identification of the various stages of the reproductive state in the rat is described. Standing estrus, as well as the influence of estrogen on spayed rats, is characterized by marked cornification of the cells and the disappearance of leukocytes. At the end of estrus, the cornified layer is sloughed off and invasion by leukocytes occurs. During diestrus, as well as in untreated ovariectomized rats, the vaginal contents consistently lack cornified cells whereas leukocytes are very plentiful. Proestrus follows diestrus: the vaginal smear is devoid of leukocytes and characterized by nucleated epithelial cells. Pregnancy, as well as the influence of progesterone on ovariectomized rats, is also characterized by epithelial growth and desquamation but at different rates, resulting in the presence of intermediate cells, and polymorphs and mucus forming a noticeable background to the smear. Since vaginal smears display cell pictures characteristic for each hormone after administration of estrogen or progesterone, exfoliate cytology is a good indicator of the stage of the reproductive state in the rat.

A morphologic and histochemical study of the mesentery in the guinea pig

The guinea pig mesentery is a uniform, continuous, thin (18 micron) sheet of connective tissue covered by a single layer of flattened mesothelial cells on both surfaces. Tight and gap junctions provide for cell-to-cell adhesion among mesothelial cells. These cells possess numerous micropinocytotic vesicles; a conspicuous basal lamina separates the mesothelium from the underlying connective tissue. Most of the material found between the two serous coverings consisted of a three-dimensional meshwork of abundant collagenous fibers intermingled with a sparse net of very thin (0.4 micron) elastic fibers. Two distinct populations of collagen fibrils are segregated into different compartments of the mesentery. One population is formed of thick (56 nm) fibrils which associate to form closely packed fibers. The second population, composed of loosely arranged thin (38 nm) fibrils which do not become assembled into fibers, is found underlying the basal lamina that separates the mesothelium from the connective tissue. These observations strongly suggest that the mesentery contains both collagens type I and type III. The guinea pig mesentery contains 6.8 mg of sulfated glycosaminoglycans/g dry weight. Most of these glycosaminoglycans (78%) were identified as dermatan sulfate, whilst the rest (22%) corresponded to heparan sulfate.

Distribution of elastic system fibers in the peripheral nerves of mammals

Various nerves of 6 representative species of mammals (including the human) were studied by the comparative association of the selective staining methods of light microscopy with the ultrastructural observation after tannic acid-glutaraldehyde fixation, which provided a reliable means of characterizing the different elastic system fibers. Although mature elastic fibers are not present in nerves, elastic-related fibers are frequently observed: oxytalan fibers are found mainly in the endoneurium, whereas elaunin fibers predominate in the epineurium. These fibers are longitudinally disposed, in a parallel orientation to the axons. The fact that these findings were consistently observed in the nerves of all species studied argues strongly in favor of the existence of a uniform structural pattern of distribution of elastic system fibers in nerves as a general phenomenon in mammals.

Differential histologic diagnosis of osteoid. A study on human osteosarcoma collagen by the histochemical picrosirius-polarization method

Using only one histologic preparation and under the light microscope, the simple method described here permits a distinction between osteoid and other tissue components that can be mistaken for osteoid. Osteoid from both normal osteogenesis and osteosarcomas is disclosed by the picrosirius-polarization method as a three-dimensional network of randomly arranged, thin, short, weakly birefringent collagenous structures which shine against a dark background. These morphologic features can be used as a precise diagnostic criterion for the differential diagnosis between osteoid and other materials which resemble osteoid by other staining techniques. This precise characterization of osteoid is of great importance since the presence of osteoid is used as a criterion for the differential diagnosis of osteosarcomas. Not only does this method permit the precise characterization of osteoid but it is also useful for studying collagen distribution in osteosarcomas. In this regard the foregoing results agree with the immunofluorescence observations recorded in the literature.

Morphological, histochemical and biochemical observations on the connective tissue matrix of in situ and isolated hepatic granulomas in experimental murine schistosomiasis

The connective tissue matrix of hepatic granulomas from Swiss mice, each infected with 20 Schistosoma mansoni cercariae, was examined using morphological, histochemical and biochemical methods, during the evolution of the disease. Evidence was obtained by both light and electron microscopy that suggested the presence of two different collagen populations which appeared successively during granuloma evolution. Morphological features suggesting the occurrence of collagenolysis were observed at the final stage of granuloma development. The connective tissue matrix of schistosome granulomas was devoid of elastic system fibres. Schistosome egg granulomas contain dermatan sulphate-proteoglycan.

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.

Specific attachment of morphologically-distinct intermediate filaments to desmosomes and hemidesmosomes in the epidermis of the tadpole of the anuran, Pseudis paradoxus

Polarization microscopy disclosed the presence of strongly birefringent intracellular structures in the basal cells of the epidermis of the tadpole of the anuran Pseudis paradoxus. The electron microscopic picture of the birefringent structures showed that they were composed of thick intermediate filaments (average diameter: 11.2 +/- 0.8 nm) oriented in a parallel disposition to form closely packed bundles which attached to the hemidesmosomes present on the basal surface of the cells of the basal layer of the epidermis. Thinner intermediate filaments (average diameter: 8.2 +/- 0.8 nm) were localized to the cortical zone of the cytoplasm; these thinner intermediate filaments converged upon the sites of cell-to-cell adhesion (desmosomes).

Distribution of elastic system fibers in hyaline and fibrous cartilages of the rat

Rat hyaline and fibrous cartilages whose glycosaminoglycans had been removed by hyaluronidase digestion were studied by comparing the ultrastructural features with the observation of sections stained by selective methods for elastic system fibers under the light microscope. Except for the fibrous layer in the perichondrium of tracheal hyaline cartilage, where elastic fibers were found, no elastic fibers could be detected in the cartilages studied. However, cartilaginous tissues contained oxytalan and elaunin fibers. A distinct pattern of distribution of the above-mentioned elastic-related fibers could be observed in both kinds of cartilages. Hyaline cartilages possess oxytalan fibers in the extracellular matrix that surrounds the chondrocytes, whereas elastic fibers were localized in the fibrous layer of the perichondrium that encloses the cartilage. Elaunin fibers could be detected in the transition (chondrogenic) layer adjacent to the perichondrium. The methods used disclosed the presence of oxytalan and elaunin fibers running along the periphery of the collagen bundles in fibrocartilage.

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.

Evidence for collagen molecular orientation in basement membranes

The following basement membranes (BMs) from representative species of the main vertebrate classes were studied by the Picrosirius-polarization method: lens capsule, Reichert's membrane and glomerular BMs. A distinct birefringence was consistently observed in all BMs from all species studied by this method. The results reported provide a strong evidence for collagen macromolecular orientation in BMs. Heparitin sulphate was the only glycosaminoglycan detected in dogs lens capsules.

A histochemical and electron microscopic study on the collagen of nerves in the domestic fowl

The collagen in the endoneurium is present as argyrophilic reticular fibres, which show up as thin, weakly birefringent greenish fibres when studied by aid of the Picrosirius-polarization method, and are composed of loosely arranged thin collagen fibrils. The epineurium consists of thick non-argyrophilic collagen fibres, which display a strong birefringence of red or yellow colour when studied by the aid of the Picrosirius-polarization method, and consist of closely packed thick collagen fibrils. These characteristics strongly suggest that the reticular fibres in the endo- and perineurium are composed mainly of collagen Type III, whereas collagen Type I predominates in the epineurium. The fact that these observations on birds are consistent with the descriptions available in the literature for fish, amphibians, reptiles and mammals, argues in favour of the existence of a uniform structural pattern of collagen distribution that is a general phenomenon in vertebrate nerves.

Structure of the tail fin in teleosts

A morphologic study of the structure of the tail fin in eight species of teleosts was performed by aid of the Picrosirius-polarization method, which is a specific histochemical method for the detection of collagen in tissue sections. This structure is composed mainly of skeletal elements, the fin rays, covered by skin. Fin rays are bound to each other and to the surrounding tissues by a series of collagenous ligaments forming a complex, highly pliable and resistant structure. Although the general structural pattern of tail fins was consistent in all species studied, the comparative aspects reported in this paper show that variations in the form and size of their components are responsible for the morphologic diversities which are closely related to specific functional adaptations. Morphometric data on the number and size of actinotrichia in normal adult specimens are presented.

Dermal collagen distribution. A histochemical and ultrastructural study

Normal skin biopsy specimens obtained from 5 representative species of mammals, including man, were studied by the silver impregnation technique for reticulin fibers, by the histochemical Picrosirius-polarization method which is specific for collagen, and by transmission electron microscopy. The finely woven meshwork of argyrophilic reticulin fibers present in the adventitial dermis showed characteristics which are typical of collagen type III, when studied by aid of the Picrosirius-polarization method and by electron microscopy. On the other hand, the coarse collagen fibers of the deeper layers displayed ultrastructural and histochemical aspects which are characteristic of collagen type I. The foregoing observations support previous biochemical and immunohistologic findings, strongly suggesting that collagen type III is found mainly in the upper dermis while collagen type I predominates in the deeper layers.