Orcein-hematoxylin in iodized ferric chloride as a stain for elastic fibers, with metanil yellow counterstaining

Global Thrombosis Test: Occlusion by Coagulation or SIPA?

The global thrombosis test (GTT) is a point of care device that tests thrombotic and thrombolytic status. The device exposes whole blood flow to a combination of both high and low shear stress past and between ball bearings potentially causing thrombin and fibrin formation. The question arises as to whether thrombosis in the GTT is dominated by coagulation-triggered red clot or high shear-induced white clot. We investigated the nature of the thrombus formed in the GTT, the device efficacy, human factors use, and limitations. The GTT formed clots that were histologically fibrin-rich with trapped red blood cells. The occlusion time (OT) was more consistent with coagulation than high shear white clot and was strongly lengthened by heparin and citrate, two common anticoagulants. The clot was lysed by tissue plasminogen activator (tPA), also consistent with a fibrin-rich red clot. Changing the bead to a collagen-coated surface and eliminating the low shear zone between the beads induced a rapid OT consistent with a platelet-rich thrombus that was relatively resistant to heparin or tPA. The evidence points to the GTT as occluding primarily due to fibrin-rich red clot from coagulation rather than high shear platelet aggregation and occlusion associated with arterial thrombosis.

The role of neprilysin in regulating the hair cycle

In most mammals, each hair follicle undergoes a cyclic process of growing, regressing and resting phases (anagen, catagen, telogen, respectively) called the hair cycle. Various biological factors have been reported to regulate or to synchronize with the hair cycle. Some factors involved in the extracellular matrix, which is a major component of skin tissue, are also thought to regulate the hair cycle. We have focused on an enzyme that degrades elastin, which is associated with skin elasticity. Since our previous study identified skin fibroblast elastase as neprilysin (NEP), we examined the fluctuation of NEP enzyme activity and its expression during the synchronized hair cycle of rats. NEP activity in the skin was elevated at early anagen, and decreased during catagen to telogen. The expression of NEP mRNA and protein levels was modulated similarly. Immunostaining showed changes in NEP localization throughout the hair cycle, from the follicular epithelium during early anagen to the dermal papilla during catagen. To determine whether NEP plays an important role in regulating the hair cycle, we used a specific inhibitor of NEP (NPLT). NPLT was applied topically daily to the dorsal skin of C3H mice, which had been depilated in advance. Mice treated with NPLT had significantly suppressed hair growth. These data suggest that NEP plays an important role in regulating the hair cycle by its increased expression and activity in the follicular epithelium during early anagen.

Experimental Pseudomonas aeruginosa Infection of the Mouse Cornea

Pseudomonas aeruginosa infection of human cornea is rare but serious. The work of previous investigators using experimental infection primarily of rabbit cornea resulted in successful therapy for 10 to 50% of clinical cases. The advantage of using the mouse is demonstrated. The methods we adapted for characterizing the untreated experimental infection included: incising the cornea to enable establishing the infection; corneal examination with a steroscopic microscope; grading corneal pathology; qualitative and quantitative monitoring of the infecting bacteria by culturing and staining sectioned and dissected tissues. The characteristics of the tissue pathology, host response, and infection were similar to those reported for other animals and man. Corneal pathology was frequently nearly maximal 1 day after infection; host response involved a progression of events of long duration; pathology persisted well beyond the period of bacterial infection. The infection was essentially noncommunicable, and invasiveness was limited to the tissues of the incised eye. The results show the possibility of tests for invasiveness of clinical isolates and for screening for therapeutic and prophylactic measures.

Protease-resistant insulin-like growth factor (IGF)-binding protein-4 inhibits IGF-I actions and neointimal expansion in a porcine model of neointimal hyperplasia

IGF-I has been shown to play a role in the progression of atherosclerosis in experimental animal models. IGF-binding protein-4 (IGFBP-4) binds to IGF-I and prevents its association with receptors. Overexpression of a protease-resistant form of IGFBP-4 has been shown to inhibit the ability of IGF-I to stimulate normal smooth muscle cell growth in mice. Based on these observations, we prepared a protease-resistant form of IGFBP-4 and infused it into hypercholesterolemic pigs. Infusion of the protease-resistant mutant inhibited lesion development by 53.3 +/- 6.1% (n = 6; P < 0.01). Control vessels that received an equimolar concentration of IGF-I and the protease-resistant IGFBP-4 showed no reduction in lesion size compared with control lesions that were infused with vehicle. Infusion of a nonmutated form of IGFBP-4 did not significantly inhibit lesion development. Proliferating cell nuclear antigen analysis showed that the mutant IGFBP-4 appeared to inhibit cell proliferation. The area occupied by extracellular matrix was also reduced proportionally compared with total lesion area. Immunoblotting revealed that the mutant IGFBP-4 remained intact, whereas the wild-type IGFBP-4 that was infused was proteolytically cleaved. Further analysis of the lesions revealed that a marker protein, IGFBP-5, whose synthesis is stimulated by IGF-I, was decreased in the lesions that received the protease-resistant, IGFBP-4 mutant, whereas there was no change in lesions that received wild-type IGFBP-4 or the mutant protein plus IGF-I. These findings clearly illustrate that infusion of protease-resistant IGFBP-4 into the perilesion environment results in inhibition of cell proliferation and attenuation of the development of neointima. The findings support the hypothesis that inhibiting IGFBP-4 proteolysis in the lesion microenvironment could be an effective means for regulating neointimal expansion.

Dexamethasone-induced changes in lung function are not prevented by concomitant treatment with retinoic acid

Alveolarization is impaired in rats treated with dexamethasone (Dex) on postnatal days 4-13, but concomitant treatment with all-trans retinoic acid (RA) increases alveolar number. To determine whether morphological changes induced by Dex and/or RA predict changes in lung function at 1 mo, we assessed resting breathing parameters, dynamic compliance, ventilation required to maintain O(2) saturation at > or = 90%, and pressure-volume curves of air-filled lungs. During resting breathing, mean tidal volume per gram was greater in Dex + RA-treated rats than in controls (P < 0.05). Dynamic compliance was also greater in Dex- and Dex + RA-treated rats than in controls or RA-treated rats (P < 0.02). In Dex- and Dex + RA-treated rats, we observed increased hysteresis ratios (P < or = 0.006), air trapping (P < 0.05), and lung volumes at 5 and 13.5 cmH(2)O pressure (P < 0.001) and decreased elastic recoil (P < 0.007). The effect of Dex on elastic recoil was greater in female than in male rats (P = 0.006). Despite impaired septation, O(2) saturation was not compromised in Dex- or Dex + RA-treated rats. Thus lung function changes induced by Dex treatment during alveolarization were not prevented by concomitant treatment with RA.

The role of elastases secreted by fibroblasts in wrinkle formation: implication through selective inhibition of elastase activity

We have previously demonstrated that decreases in skin elasticity, accompanied by increases in the tortuosity of elastic fibers, are important early events in wrinkle formation. In order to study the role of elastases in the degeneration of elastic fibers during wrinkle formation we examined the effects of an inhibitor of skin fibroblast elastase, N-phenethylphosphonyl-L-leucyl-L-tryptophane (NPLT), on wrinkle formation in hairless mice skin following UV irradiation. Dorsal skins of hairless mice were exposed daily to UV light for 18 weeks at doses of 65-95 mJ/cm2 and treated topically with 100 microL of 1 mM NPLT immediately after each UV irradiation. Wrinkles on dorsal skins were evaluated from week 6 through week 18. The daily exposure of mouse skin to UV light with less than 1 minimal erythemal dose significantly enhanced the activity of elastase in the exposed skin by week 4, and the elevated levels of elastase activity were significantly reduced by the in vitro incubation with NPLT in a dose-dependent manner to a level similar to that in unexposed mice skin, indicating that NPLT can efficiently inhibit the UV-inducible elastase activity. Topical application of NPLT significantly suppressed wrinkle formation when compared with vehicle controls by week 15 of treatment (P < 0.05). Histochemistry of elastic fibers with Orcein staining demonstrated that there were no obvious decreases of the fine elastic fibers in UV-exposed NPLT-treated skin in contrast to their marked decreases in the UV-exposed vehicle-treated skin. These findings suggest that skin fibroblast elastase plays a decisive role in wrinkle formation through the degeneration of elastic fiber.

Dietary nitroprusside alleviates atherosclerosis in hypercholesterolemic Japanese quail (Coturnix coturnix japonica)

Male Japanese quail (Coturnix coturnix japonica), susceptible to cholesterol-induced atherosclerosis, were rendered hypercholesterolemic by feeding a diet containing 0.5% cholesterol in two experiments. Half the animals also received a dietary supplement of sodium nitroprusside ranging in concentration from 0.005% to 0.015%. After 10 weeks on the diets, serum was obtained for cholesterol analysis, the animals were killed, and the aortae removed and examined for the presence of atherosclerotic lesions. The number of animals having lesions and the severity of the lesions was reduced in a dose dependent manner among those animals receiving nitroprusside. Serum cholesterol was also reduced in response to increasing levels of dietary nitroprusside. These findings indicate that, in this model, dietary nitroprusside, a source of nitric oxide, can reduce the appearance and severity of atherosclerotic lesions in the aorta.

A role for neutrophil elastase in the progression of solar elastosis

Hairless (SKH-1) mice were mated with Beige (C57B/bb) mice to produce a hairless mouse deficient in neutrophil elastase (hhbb). These mice were exposed to 0.09J UVB irradiation for 5 months to see if neutrophil elastase was an important factor in elastin remodeling and development of solar elastoses. Analysis of peritoneal neutrophils confirmed that the hhbb mouse was deficient in elastase, retaining only 10% as much activity as the normal littermates (hhHb). Skin MPO activity was equally elevated in all the mice receiving UVB suggesting an equal influx of inflammatory cells. The absolute breaking strength of the skin in both the hhBb and hhbb mice was not altered by UVB treatment over the 5 month exposure period. Elastin quantitated biochemically as desmosine, or visualized histologically, was increased following UVB exposure in the normal mice. In the elastase deficient mice, however, the elastin fibers appeared to be unaffected by exposure to UVB irradiation at this level. The results suggest that neutrophil elastase is an important mediator in the development of solar elastosis resulting from continued exposure to UVB irradiation.

Developmental changes in tropoelastin gene expression in the rat lung studied by in situ hybridization

Gene expression for tropoelastin, the proprotein for elastin, was examined in the rat lung from 17 days of gestation (pseudoglandular stage) to adulthood by in situ hybridization using a rat-specific 35S-radiolabeled riboprobe. The tropoelastin message was present in vascular and airway smooth muscle, endothelial, septal interstitial, alveolar wall, and mesothelial cells but not in epithelial cells. With alveolar septal formation, the message in the interstitium increased progressively from 17 days of gestation, reaching a peak at 7 to 11 days postnatal. The signal in the arterial walls, in contrast, peaked between 19 days of gestation to 1 day postnatal and thereafter declined first from the outer media. The signal in general declined significantly by 21 days postnatal, and elastogenesis was virtually absent in the adult. These results support the idea that tropoelastin gene expression in the interstitium is closely associated with the centripetal progression of alveolarization, and the early postnatal decrease of tropoelastin expression in blood vessels corresponds with the sudden postnatal changes in the pulmonary hemodynamics. Furthermore, in the rat fetus and neonate, endothelial cells expressed the gene for tropoelastin and hence probably play a significant role in the formation of internal elastic lamina in vivo.

Histology of sun-damaged human skin

In glycomethacrylate sections of sun-exposed skin, we found the epidermis a sensitive index of damage. The stratum corneum of severely damaged skin was often compact and laminated, or gelatinous, and sometimes contained vesicles full of proteinous material. These vesicles arose from the enlarged and distinctly cellular-thick stratum lucidum. Sometimes there was no clear transition between the stratum lucidum and corneum. In the malpighian layer, cell heterogeneity, vacuolization, dysplasia, and zonal necrosis were common. The number of Langerhans cells was reduced in sun-damaged epidermis. The dermis had the usual disparate degrees of elastotic changes, with the formation of amorphous masses and the occurrence of fiber breakdown (fibrorhexis and fibrolysis). Macrophages among the elastotic masses contained coarse granules. When stained by means of the hematoxylin and Lee technique, the elastotic masses in the papillary dermis were pink or red but those in the mid dermis stained lilac to blue; all other elastic fibers stained pink or red. We found reticulin fibers predominantly around the elastotic masses and in areas of fibrorhexis and/or fibrolysis; a delicate collagenous fiber scaffolding supported the elastotic masses.

A comparative light microscopic evaluation of oxytalan fiber staining with a variety of dye substances

Staining of oxytalan fibers in marsupial, eutherian and human periodontal ligaments was surveyed with 65 different dyes. Using the criteria of response to preoxidation, distribution, and morphologic appearance, 27 dye preparations in addition to the Gomori aldehyde-fuchsin, Taenzer-Unna orcein, and Weigert resorcin-fuchsin techniques displayed oxytalan fibers. With two exceptions all dyes were cationic and reacted with varying degrees of excellence with different animals. Most dyes produced their best staining results as concentrated solutions in 3% acetic acid, suggesting involvement of oxidatively engendered polyanions predominantly associated with an acid mucopolysaccharide component of the oxytalan fiber. The significance of carboxyl and sulfur-containing groups should not be overlooked in further studies aiming to elucidate oxytalan fiber chemistry and microstructure. This study supported the view that oxytalan fibers belong to the family of elastic tissues and represent a biologically important system within the periodontal ligament.

Differential patterns of elastic fibers in scarring and non-scarring alopecias

Elastic fiber stain (acid alcoholic orcein) reveals diagnostically significant differences between several types of alopecia of the scalp. A short outline of elastic fiber distribution on the normal hair follicle emphasizes the elastic coat of the follicular isthmus, the sparsity of elastic fibers on the cyclic lower portion of the hair root, and the presence in the neck of the dermal papilla of an elastin-like body which is formed anew with each hair cycle. This body provides a marker of the gradual shortening of successive anagen hairs in male pattern alopecia. Patterns of elastic fibers in the perifollicular and interfollicular dermis are helpful in differentiating idiopathic pseudopelade of Brocq from pseudopeladic states secondary to lupus erythematosus and other disease processes. Within the idiopathic group, the development of elastic fibres on the lower cyclic portion of the hair root identifies a sub-group that may have a different, non-inflammatory pathogenesis and is provisionally designated as fibrosing alopecia.

The skin of the giraffe

The skin of the giraffe has the same general histological structure as that of other mammals, but there are notable features. The skin is heavily pigmented with the epidermis, pilary canals, and the outer cell layer of the apocrine duct richly melanized. Furthermore, melanotic dendritic cells are frequently found in the sebaceous glands, the entire length of the external root sheath, and the secretory tubules of the apocrine glands. The thick skin has a papillary dermis that extends to just beneath the secretory coils of the apocrine glands and bulbs of hair follicles and an equally thick reticular layer below these structures. The hair follicles do not grow in clusters, and with some regional variations, have associated sebaceous glands, apocrine glands, and arrectores pilorum muscles. Only the large hairs have a prominent medulla. In such specialized regions as the eyelids, nose, and lips, the apocrine glands are surrounded by cholinesterase-reactive nerves but the glands on the general body surface are not. The only specialized nerve receptors are hair follicle end organs found on every hair of the eyelids, nose, and lips, but only rarely elsewhere.

The host cell response in the local graft-versus-host reaction induced in the kidneys of F 1 rats by parental thoracic duct lymphocytes

Radioautographs of infiltrative cells in the kidneys of (Lewis x BN)F(1) rats labeled with tritiated thymidine (TdR(3)H) before the subcapsular injection of parental (Lewis) thoracic duct lymphocytes (TDL) showed a predominantly host-proliferative response by 4 days after grafting. The immediate renal incorporation of TdR(3)H was used to measure the local graft-vs.-host (GVH) reactions. Substantial reactions could still be induced in the face of the considerable degree of leukopenia after 400 R whole body gamma-irradiation. These results suggest that radioresistant cells are capable of carrying on the appropriate host activities and that the weakness of GVH reactions induced after higher doses of irradiation may be due to impairment of the mitotic mechanism of host cells. The importance of circulating leukocytes as a source of immunogenic stimulation was nevertheless substantiated by inducing local GVH reactions with Lew TDL in chimeric parental-type rats that had been repopulated with F(1) bone marrow. This result also emphasizes the nonspecific nature of tissue destruction in the renal GVH reaction in confirmation of Elkins. In this and other situations in which B cells were the predominant F(1) type elements available for interaction with parental-type TDL the reactions were nearly equivalent or equivalent to those in the appropriate controls. Typical local GVH reactions could be induced in heavily irradiated hosts by an inoculum of combined parental and F(1)-type TDL in the apparent absence of mononuclear phagocytes. The possible relationship between the activation of host lymphocytes, the involvement of B cells, and the nonspecific nature of tissue damage in the renal GVH is discussed.