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At least 775 records · Page 43Linked to original sources
PubMed1989

Tungsten and molybdenum heteropolyacids as staining and contrasting agents: reactivity with epoxyresin-embedded cell and tissue structures.

In this work, we carry out a further approach to the knowledge of the reaction mechanism of phosphotungstic and phosphomolybdic acids (PTA and PMA), as well as some derivatives, with cell structures from epoxyresin-embedded materials. Applied on thin sections from glutaraldehyde-fixed tissues, PTA and PMA induced a strong electron contrasting reaction in spermatid acrosomes, goblet cell mucin, callose and plant cell walls, endexine, intine and starch granules. In light microscopy, the localization of heteropolyacids on these structures was achieved by treatments of semithin sections with suitable reducing agents (titanous sulfate, stannous chloride, sodium borohydride, or p-phenylenediamine) to form the mixed-valence heteropolyblues, or with Schiffs's reagent. The use of PTA-dye complexes (pyronin-PTA and Mallory's PTA-hematoxylin) also showed the same staining pattern. Taking into account the chemical characteristics of the PTA- and PMA-reactive tissue elements, the present results indicate that heteropolyacids selectively enter into the highest hydrophilic structures from non-polar epoxy-embedded sections; after brief washing, they appear predominantly retained in tissue structures containing a great amount of carbohydrate components.

Animals↗
PubMed1996

A comparative study of the transition between predentin and dentin, using various preparative procedures in the rat.

The appearance of the junction between predentin and dentin of rat incisors was investigated after chemical fixation (aldehyde), physical fixation (high pressure freezing and freeze substitution) and by histochemistry. Physical fixation revealed a 1-2 micron wide intermediary zone, in which only the collagen fibers were mineralized. In dentin, which looked denser and more homogeneous, both collagen fibers and intercollagenous spaces were mineralized. The intermediary layer could not been seen after aldehyde fixation. When cationic dyes were used during fixation in order to retain proteoglycans, a 0.5-5 micron border zone located at the junction between predentin and dentin was densely stained on the dentin side, whereas in dentin only the interglobular network displayed electron density. The periodic acid-thiocarbohydrazide-silver proteinate reaction, visualizing glycoproteins, and the phosphotungstic acid/chromic acid mixture, which reveals glycoproteins and phosphorylated proteins, produced extensive staining of the transitional zone located at the dentin edge, whereas staining was weaker in dentin. These morphological and histochemical investigations support the existence of an intermediary zone in which mineralization occurs. This transitional zone between predentin and dentin has specific properties; therefore we propose it be termed metadentin.

Aldehydes↗
PubMed2006

Receptors for leptin and estrogen in the subcommissural organ of rabbits are differentially modulated by fasting.

In rabbits, the fasting-dependent reduction of LH secretion is likely mediated by leptin and estrogens via receptors in the brain. For the first time, using immunohistochemistry, the presence and regulation of receptors for leptin (Ob-R) and estradiol-17beta subtype alpha (ERalpha) were studied in the subcommissural organ (SCO) of rabbits, which were fed either ad libitum (control) or fasted for 48 h (treated) to verify whether this brain structure is a potential site of integration for metabolism and reproduction. In control rabbits, the cytoplasm of glial cells lining the SCO evidenced strong Ob-R immunoreactivity, whereas both ependymal and hypendymal cells of this glandular-like structure were negative. The Ob-R positive glial cells were identified as fibrous astrocytes using the phosphotungstic acid-hematoxylin histochemical (PTAH) and glial fibrillary acidic protein (GFAP) immunohistochemical techniques. ERalpha immunoreactive nuclei were detectable exclusively in the specialized cells forming the SCO, whereas surrounding astrocytes and neurons were negative. Compared to controls, in fasted rabbits, the staining of Ob-R immunoreaction was reduced in the cytoplasm of positive astrocytes, but greatly enhanced in plasma membranes, whereas the number of ERalpha immunoreactive SCO cells was increased (13.2+/-2.7 vs. 5.2+/-2.0, P<0.01). Ependymal cells lining the third ventricle were negative for both Ob-R and ERalpha. Our results indicate, although indirectly, that the SCO, together with the astrocytes in close contact with this structure, is a likely target for nutritional and gonadal signals carried by leptin and estrogens, suggesting that these specialized glial cells may regulate reproduction and metabolism through mechanisms still unknown.

Animals↗
PubMed1983

Isolation and Identification of Plasma Membrane from Light-Grown Winter Rye Seedlings (Secale cereale L. cv Puma).

An effective method for the isolation of plasma membrane from light-grown winter rye seedlings (Secale cereale L. cv Puma) was established using a liquid two-polymer phase separation. The conditions for the specific partition of plasma membrane into the polyethylene glycol-enriched upper phase were examined, including variations in the polymer concentration, buffer system, pH, and NaCl addition in the phase partition system. The most effective phase partition system for the isolation of plasma membrane from winter rye consisted of 5.6/5.6% (w/w) polyethylene glycol 4000/dextran T500 in 0.25 molar sucrose-10 millimolar potassium phosphate-30 millimolar NaCl (pH 7.8), repeated once. When the isolated plasma membrane was centrifuged on a linear sucrose density gradient, a single band was found at the 34% (w/w) sucrose layer (1.141 grams per cubic centimeter) which co-fractionated with the pH 6.5-ATPase.Identification of plasma membrane was performed by the combination of phosphotungstic acid-chromic acid stain and specific binding of N-1-naphthylphthalamic acid. Based on morphometrical observations after phosphotungstic acid-chromic acid stain, the isolated plasma membrane consisted mostly of vesicles of high purity. The isolated plasma membrane also showed extremely high specificity for N-1-naphthylphthalamic acidbinding, 10-fold higher than other membranes. It was also confirmed that there is a distinct difference in properties between plasma membrane and other membranes. The endomembranes such as from chloroplasts, mitochondria, and endoplasmic reticulum were observed to be highly sensitive to Zn(2+) ion and lower pH, which resulted in an abrupt aggregation of membranes. On the contrary, plasma membrane was very stable to these treatments and no aggregation was observed. These unique properties of isolated plasma membrane are generally observed in a wide variety of plant species and can be utilized for the assessment of the purity of preparations of isolated plasma membranes and for their identification.

Journal Article↗
PubMed1978

Protein degradation in normal and beige (Chediak-Higashi) mice,.

The beige mouse, C57BL/6 (bg/bg), is an animal model for the Chediak-Higashi syndrome in man, a disease characterized morphologically by giant lysosomes in most cell types. Half-lives for the turnover of [(14)C]bicarbonate-labeled total soluble liver protein were determined in normal and beige mice. No significant differences were observed between the normal and mutant strain for both rapidly and slowly turning-over classes of proteins. Glucagon treatment during the time-course of protein degradation had similar effects on both normal and mutant strains and led to the conclusion that the rate of turnover of endogenous intracellular protein in the beige mouse liver does not differ from normal. The rates of uptake and degradation of an exogenous protein were determined in normal and beige mice by intravenously injecting (125)I-bovine serum albumin and following, in peripheral blood, the loss with time of phosphotungstic acid-insoluble bovine serum albumin and the parallel appearance of phosphotungstic acid-soluble (degraded) material. No significant differences were observed between beige and normal mice in the uptake by liver lysosomes of (125)I-bovine serum albumin (t((1/2)) = 3.9 and 2.8 h, respectively). However, it was found that lysosomes from livers of beige mice released phosphotungstic acid-soluble radioactivity at a rate significantly slower than normal (t((1/2)) = 6.8 and 3.1 h, respectively). This defect in beige mice could be corrected by chronic administration of carbamyl choline (t((1/2)) = 3.5 h), a cholinergic agonist which raises intracellular cyclic GMP levels. However, no significant differences between normal and beige mice were observed either in the ability of soluble extracts of liver and kidney to bind [(3)H]cyclic GMP in vitro or in the basal levels of cyclic AMP in both tissues. The relevance of these observations to the presumed biochemical defect underlying the Chediak-Higashi syndrome is discussed.

Animals↗
PubMed2002

Type-I cryoglobulinemia-like histopathologic changes in tick bites: a useful clue for tissue diagnosis in the absence of tick parts.

BACKGROUND: The histopathologic findings of localized reactions to tick bites may present as diagnostic dilemmas, especially if there is no history of a tick bite, or if the tick's mouthparts are not present in the biopsied skin. OBJECTIVE: Skin biopsies of patients with a clinical history of a tick bite were selected and reviewed with the aim of detecting a common histopathologic denominator which could serve as a useful clue to the diagnosis, especially when the tick's mouthparts are absent. METHODS: Hematoxylin and eosin-stained slides of 15 skin biopsies of tick bites were retrieved from three dermatopathology and pathology laboratories. Where additional paraffin-embedded tissue was available, additional sections were also stained with periodic acid-Schiff (PAS) and phosphotungstic acid-hematoxylin (PTAH). RESULTS: In every case in which adequate tissue was available (13/ 15 biopsies), the capillaries and postcapillary venules of the superficial and deep vascular plexi adjacent to the attachment's site were filled with thrombi. Fibrin thrombi were seen in association with other more numerous thrombi characterized by homogeneous eosinophilic hyaline material similar to the cryoprecipitate present in type I (monoclonal) cryoglobulinemia. All thrombi were positive for PAS and PTAH; however, the latter staining was minimally present in the hyaline thrombi. In most cases, the site of the tick bite showed ulceration, with an underlying wedge-shaped superficial and deep perivascular and occasionally interstitial mixed lymphohistiocytic infiltrate. In addition, there were eosinophils, numerous neutrophils and extravasated erythrocytes. Other findings included suppurative necrosis (7/15) cases, giant-cell reaction (one case), fat necrosis (one case) and eccrine gland necrosis (one case). CONCLUSIONS: Vascular eosinophilic hyaline thrombi were found to be a frequent histologic manifestation of a tick bite. This finding may be related to the secretory products of the tick's saliva during inoculation. We believe that a tick bite should be suspected when focal intravascular hyaline occlusion is observed, and that it should be included in the differential diagnosis of type I (monoclonal) cryoglobulinemia, even if there is no history of a tick bite or if tick parts are not present in the skin biopsy specimen.

Adult↗