A puzzling feature of Colloidal Iron positive and Alcian Blue negative material

Summary A puzzling feature of Colloidal Iron positive and Alcian Blue negative substance is encountered in yolk sac of young larvae of a fish —Tilapia mossambica. This yolk material is PAS positive (proved to be due to neutral mucopolysaccharide) and negative to Toluidine Blue, Azure A (pH 2 to 4.5), Aldehyde Fuchsin and AB pH 1. More work is necessary to establish the exact chemical nature of the CI positive material.     

Tunicate Endostyles: Histochemistry of Acidic Glycoproteins Re-examined in Ciona intestinalis and Styela plicata

Previous reports of tunicate endostyles have suggested that they contain little or no acidic glycoproteins in the glandular zones. The endostyles of Ciona intestinalis and Styela plicata were examined after anhydrous fixation with cyanuric chloride. Polyanions were stained with alcian blue (AB) at pH 2.5 or azure A, while sulfomucins were stained with high-iron diamine (HID) or AB at pH 1.0. Endostyles were also tested for sensitivity to acid hydrolysis (AH) and saponification. In Ciona zones 2 and 4 sometimes demonstrated positive HID and AB 1.0 responses. Almost invariably zone 6 was AB+ at pH 2.5; zones 2 and 4 were frequently responsive to AB, but less intense. Each of these 3 zones, when AB+, was sensitive to AH. Responses by zones 3 and 5 to AB (pH 2.5), azure A and saponification suggest that these zones contain mostly nuclear material. In secretory zones 2, 4 and 6 histological responses are consistent with the histochemistry of sialomucins. Zones 1 and 8 had sulfated material in the apical edges in both animal groups. Among the fixatives used for Ciona, only anhydrous fixation demonstrated most of the positive responses to polyanion-sensitive stains.     

Histochemistry of carbohydrates in the epithelium lining the bulbourethral gland of the rat

The histochemistry of carbohydrates has been studied in the epithelium lining the bulbourethral gland of the rat by means of light- and electron-microscopic methods. The results obtained show that the cytoplasms of the epithelial cells contain neutral and acidic carbohydrates. The neutral carbohydrates exhibited positive reactions with periodic acid-Schiff and periodic acid-thiosemicarbazide-silver proteinate, whereas the acidic carbohydrates reacted positively with alcian blue (AB; pH 1.0 and 2.5) and dialyzed iron. Most neutral carbohydrates were found to be glycoproteins localized within the secretory granules. The acidic carbohydrates consist of at least two types, AB (pH 1.0)-reactive sulfated and AB (pH 2.5)-reactive nonsulfated carbohydrates; most nonsulfated carbohydrates were determined to be sialic acid. The acidic carbohydrates were also localized within the secretory granules.     

Mucopolysaccharide histochemistry of Musca domestica

Summary While studying the distribution of acid mucopolysaccharides (AMPS) in the prepupal larva of the housefly, Musca domestica nebulo (Fahr.) using routine histochemical methods, the authors found that except for the midgut cells, dorsal pharyngeal epithelium and the thick connective tissue of the brain, the ganglia and the imaginal discs, in all other cells studied, an AMP is present which is neither a sulfomucin, a sialomucin nor a hyaluronic acid. Its alcian blue (AB) staining is abolished by active methylation and is not restored by saponification; it is not abolished by mild acid hydrolysis; it stains -metachromatically with Azure A at pH 4.5 and lightly with Azure A at pH 1.5, with weak toluidine blue and with aluminium sulfate-methylene blue; it is unstained by aldehyde fuchsin (AF) and safranin O (Saf. O) in AB-AF, AF-AB and AB-Saf.O procedures; it is positive to colloidal iron but is negative to periodic acid Schiff reaction in all probability; and its AB staining is abolished by saponification (KOH treatment) without prior methylation. Pending further work to exactly characterize this AMP, it is tentatively referred to as KOH-labile AMP. The significance of its distribution is discussed.     

Photosynthesis of Ectocarpus siliculosus in red light and after pulses of blue light at high pH – evidence for bicarbonate uptake

Pulses of blue light cause stimulation of red light saturated photosynthesis in Ectocarpus siliculosus, because blue light activates the operation of a pathway for inorganic carbon (C_i) acquisition by inducing the mobilization of CO₂ from an intermediate metabolite. In the absence of exogenous C_i, photosynthetic rates roughly equal those of CO₂ release by respiration. In seawater of pH 9·5 (2·3 mol m^–3 total C_i, but concentrations of free CO₂ below 0·2 mmol m^–3), photosynthesis was clearly above these rates, although they were only ≈ 30% of those in normal seawater (≈ pH 8). The degree and the time course of the stimulations of photosynthesis by pulses of blue light were unaltered at high pH. Essentially the same characteristics were found after buffering or in the presence of acetazolamide, an inhibitor of extracellular carbonic anhydrase activity. Therefore, it is concluded that Ectocarpus is able to directly take up HCO₃^– in addition to CO₂ (uptake of CO₃^2– cannot be excluded). The dependence of photosynthesis on C_i at pH 9·5 was biphasic, with C_i below 0·2 mol m^–3 having no effect at all. In C_i-free seawater, the shapes of the stimulations after blue light pulses differed for pH 6, pH 8 and pH 9·5. At low pH, only the fast peak (maximum ≈ 5 min after blue light) was detected, whereas at high pH mainly the slow peak (maximum ≈ 20 min after blue light) was observed. At the intermediate pH 8, both peaks were present. As inhibition of total carbonic anhydrase by ethoxyzolamide brought out the fast peak of the stimulations at pH 9·5 it is concluded that the fast component was due to a transient disequilibrium of an intracellular pool of C_i which, after blue light, was fed by CO₂ released from the postulated storage intermediate.     

Seasonal variation in glycoconjugates of the pedal glandular system of the rayed Mediterranean limpet,Patella caerulea (Gastropoda: Patellidae)

Glycoconjugates secreted by the pedal system of the rayed limpet, Patella caerulea, were characterised in situ by histochemical and lectin-histochemical methods in individuals collected around the annual cycle, in November, March, and June. Stainings with periodic acid–Schiff (PAS), Alcian blue pH 2.5 (AB pH 2.5), Alcian blue pH 1.0 (AB pH 1.0), high-iron diamine–Alcian blue pH 2.5 and lectin binding assays with 9 lectins (Con A, WGA, succinylated-WGA, PNA, DBA, SBA, AAA, UEA-I, LTA) were performed. Four secreting cell types were observed in the sole, one in the peripheric region, and two in the sidewall. Glycoconjugate composition varied among cell types and also in one and the same cell type throughout the year. β-Elimination followed by PAS and AB pH 2.5 stainings indicated that most saccharidic chains were O-linked to the protein backbone. Secretion by sole and peripheric region was acidic, carboxylated and/or sulfated, whereas that of the sidewall was neutral. Glucosaminylated and 1,4-fucosylated residuals were predominant in the cell types along the year, 1,2-fucosylated residuals being observed only in the sidewall cells in June. Mannosylated and/or glycosylated residuals were observed in all cells mostly in November. Galactosylated/galactosaminylated residuals were present mostly in the sidewall cells and in the sole subepidermal mucocytes in June. Mannosylated and/or glycosylated residuals in November are probably linked to gonad maturation or to higher locomotion and foraging activity, whereas galactosaminylation in the sole cells and 1,2-fucosylation and glucosaminylation in the sidewall cells in June are linked to a prolonged stationary state, increasing water adsorption to counteract dehydration and/or to modulate microbial interactions.     

Mucopolysaccharide histochemistry of rat tooth germs

Summary The histochemical distribution and localization of acid mucopolysaccharides and glycoproteins have been studied in rat tooth germs and lower joints. After fixation, sections were stained with PAS, alcian blue-PAS, colloidal iron, colloidal iron-PAS, colloidal iron-Feulgen, azure A and safranin O. Prior to staining, sections were incubated in hyaluronidase, pepsin and papain. A 2 hour incubation in pepsin greatly enhanced AB or CI basophilia in the stellate reticulum and the enamel-dentinal junction. These findings demonstrated that some acidic radicals of the polysaccharides are partially blocked by basic proteins. Hyaluronidase did not completely destroy the alcian blue or colloidal iron positive material whereas azure A metachromasia was completely removed. These results indicated that AB and/or CI stained substrates different from those revealed by azure A.With 10 Figures in colourThis work was supported by Grant No. D-1325 of the National Institutes of Health, Bethesda, Maryland.On leave of absence at the University of Rome Medical School, Viale Regina Elena 287-A, Rome, Italy.     

Histochemistry of glycosaminoglycans in cartilage ground substance

Summary The critical-electrolyte-concentration staining method using Alcian blue (AB) was applied to etched semithin Epon-embedded sections. The distribution of various glycosaminoglycans (GAGs) was studied in hyaline, elastic, cellular and fibrous cartilage obtained from humans and rodents. The staining patterns in semithin sections were found to correspond to those obtained using paraffin-embedded material. Lectin histochemistry was performed on consecutive sections. The following peroxidase-labelled lectins were used: Ricinus communis A I, Arachis hypogaea, Ulex curopaeus A I, Triticum vulgaris, Helix pomatia, Limax flavus, and concanavalin A. The lectin-binding capacity of cartilaginous ground substance was found to be low, as was expected on account of the few free sugar residues of GAGs. Chondroitin sulphate, the most widely distributed GAG, did not exhibit lectin staining. The lectin-binding site (positive staining for all lectins tested except H. pomatia) observed corresponded to areas positive forkeratan sulphate, as shown by AB staining in preceding or following sections. The pronounced lectin binding seen in cellular structures and the inner territorial matrix regions is considered to be due to higher concentrations of oligosaccharides involved in the metabolism of GAGs.Supported by the Hochschuljubiläumsstiftung der Stadt Wien     

Histochemistry of glycosaminoglycans in cartilage ground substance. Alcian-blue staining and lectin-binding affinities in semithin Epon sections

The critical-electrolyte-concentration staining method using Alcian blue (AB) was applied to etched semithin Epon-embedded sections. The distribution of various glycosaminoglycans (GAGs) was studied in hyaline, elastic, cellular and fibrous cartilage obtained from humans and rodents. The staining patterns in semithin sections were found to correspond to those obtained using paraffin-embedded material. Lectin histochemistry was performed on consecutive sections. The following peroxidase-labelled lectins were used: Ricinus communis A I, Arachis hypogaea, Ulex europaeus A I, Triticum vulgaris, Helix pomatia, Limax flavus, and concanavalin A. The lectin-binding capacity of cartilaginous ground substance was found to be low, as was expected on account of the few free sugar residues of GAGs. Chondroitin sulphate, the most widely distributed GAG, did not exhibit lectin staining. The lectin-binding sites (positive staining for all lectins tested except H. pomatia) observed corresponded to areas positive for keratan sulphate, as shown by AB staining in preceding or following sections. The pronounced lectin binding seen in cellular structures and the inner territorial matrix regions is considered to be due to higher concentrations of oligosaccharides involved in the metabolism of GAGs.     

Alcianblue/PAS or PAS/alcianblue?

Summary The combined alcian blue (AB)/PAS technic is widely used for the detection and characterization of mucosubstances in tissue sections. Mostly the sequence AB/PAS is used, occasionally also the reserved sequence PAS/AB. The present study shows clearly that the sequence of the combined technic, i.e. AB/PAS or PAS/AB is substantially influencing the results. So it could be demonstrated that by using the combination PAS/AB originally PAS-positive and AB-negative reacting mucosubstances become AB-posltive. This could be caused by periodic acid oxidation followed by addition of hydrogen sulfite to aldehyde group thus providing secondary basophilic resp. AB positive material.     

Alcianblue/PAS or PAS/alcianblue? Remarks on a classical technic used in carbohydrate histochemistry

The combined alcian blue (AB)/PAS technic is widely used for the detection and characterization of mucosubstances in tissue sections. Mostly the sequence AB/PAS is used, occasionally also the reserved sequence PAS/AB. The present study shows clearly that the sequence of the combined technic, i.e. AB/PAS or PAS/AB is substantially influencing the results. So it could be demonstrated that by using the combination PAS/AB originally PAS-positive and AB-negative reacting mucosubstances become AB-positive. This could be caused by periodic acid oxidation followed by addition of hydrogen sulfite to aldehyde group thus providing secondary basophilic resp. AB positive material.     

In vivo visualization of bonghan ducts inside blood vessels of mice by using an Alcian blue staining method

An in vivo method using Alcian blue (AB) was developed for visualizing floating threadlike tissues inside blood vessels of mice. These novel structures called intravascular Bonghan ducts (IBHDs) are considered as extension of acupuncture meridians. For in vivo imaging of IBHDs, AB solution (pH 7.4) that stains mucopolysaccharides like hyaluronic acid was used. After injecting AB solution into the femoral vein of a mouse, the threadlike structures, stained deep blue, inside the inferior vena cava. The histological results, such as hematoxylin, eosin, and AB staining, show the compositions of the cells and the extracellular matrix in the IBHD. Further studies are needed to investigate their physiological functions, especially in relation with those of other circulatory systems.     

The histochemistry of urea-unmasked glycosaminoglycans in the skin of the eel, Anguilla japonica

In the connective tissues of the dermis and subcutis of the eel skin, the histochemistry of urea-unmasked glycosaminoglycans has been studied by means of combined staining and enzyme digestion procedures. The staining procedures employed were alcian blue (AB) pH 1.0, AB pH 2.5, aldehyde fuchsin (AF), periodic acid-Schiff (PAS), AB pH 2.5-PAS, high iron diamine (HID) and low iron diamine (LID) methods, whereas the enzymes used were Streptomyces and testicular hyaluronidases, chondroitinases ABC and AC and keratanase. The results obtained have shown that a substantial amount of dermatan sulfate and a relatively small amount of hyaluronic acid, chondroitin, chondroitin sulfate A and/or C were the glycosaminoglycans involved in the connective tissues of the eel skin and that the tissues were devoid of keratan sulfate.     

Endometrial and endocervical secretion: the search for histochemical differentiation

OBJECTIVE: To determine the ideal histochemical stain to differentiate between non-neoplastic and neoplastic endocervix and endometrium. STUDY DESIGN: A total of 90 cases representing nonneoplastic cervix, non-neoplastic endometrium, endocervical adenocarcinoma and endometrial adenocarcinoma were stained with toluidine blue (TB); methylene blue (MB); mucicarmine (MUC); periodic acid-Schiff before and after diastase digestion (PAS, PAS-D); Alcian blue, pH 2.5 (AB); and periodic acid-Schiff after Alcian blue, pH 2.5 (PAB). Cases were blinded and randomly divided between two pathologists for evaluation of the staining and the staining distribution of the glandular epithelium by means of a 36-color scheme. RESULTS: The majority of non-neoplastic endocervix samples stained blue with MB (57%), fuchsia with MUC (70%), magenta with PAS (77%) and PAS-D (73%) and dark turquoise with AB (70%). The majority of non-neoplastic endometrium samples stained slate blue with TB (60%) and pink with PAS-D (53.3%). There is statistical difference (p < 0.05) in the color of the epithelium and secretions between the non-neoplastic cervix and endometrium. The malignant glands of endocervical origin could be differentiated significantly (p = 0.043) from non-neoplastic endocervical epithelium by MUC. The epithelium of the non-neoplastic endometrium is significantly differentiated from malignant endometrium using TB (p = 0.015) and MB (p = 0.038). Endocervical carcinoma could be significantly differentiated from endometrial carcinoma by MB. The staining in endocervical adenocarcinoma and endometrial carcinoma was predominantly present in both apical and cytoplasmic locations compared to their non-neoplastic counterparts (endocervix, p = 0.003; endometrium, p = 0.049). CONCLUSION: This study showed that a panel of histochemical stains could differentiate glandular cells of endocervical epithelium from endometrium.     

Comparative histochemistry of the mucoproteic cells of the hypophysis from Rhamdia hilarii, Hypostomus punctatus, Prochilodus scrofa and Cyprinus carpio (Teleostei). Immunohistochemical identification of the gonadotropic cells

Adenohypophyseal cells showing positive histochemical reactions for mucosubstances were classified as type I-IV in Hypostomus (Plecostomus) punctatus (Loricariidae), Rhamdia hilarii (Pimelolidae), Prochilodus scrofa (Prochilodontidae) and Cyprinus carpio (Cyprinidae) according to cell shape, size, cytological characteristics and adenohypophyseal distribution. Cell types I and II are common to the four species, with each cell type showing very similar cytological and histochemical characteristics, in spite of different adenohypophyseal distribution of cell type II, according to the teleost species. Type I cells are globular basophils located in the proximal pars ditalis and are positive to PAS and Alcian blue pH 2.5 (AB) reactions, showing cytoplasmic vacuoles and changes in granule concentration in the mature phase of the gonadal cycle. The smaller type II cells are fusiform or oval basophils exhibiting a strong AB reaction but also reacting to PAS. Type III cells are located in the pars intermedia showing PAS-positive reaction. Considering different teleost species, these cells exhibit some variations specially in relation to cell size and shape which are not detected in mature male C. carpio. Otherwise cell type IV is only present in the rostral pars distalis of P. scrofa. They are weakly basophilic and negative to PAS, reacting strongly to AB. Only cell type I showed unequivocally positive immunohistochemical results with anti-salmon gonadotropin.     

A novelin vitro release technique for peptide-containing biodegradable microspheres

The purpose of this study was to develop and evaluate a dialysisin vitro release technique for peptide-containing poly(d, 1-lactide-coglycolide) (PLGA) microspheres (ms) that would correlate within vitro data. Using a luteinizing hormone- releasing hormone analogue (LHRH), Orntide acetate, solubility and stability were determined in 0.1 M phosphate buffer (PB), pH 7.4, and in 0.1 M acetate buffer (AB), pH 4.0, with highperformance liquid chromotography (HPLC), and peptide permeability through a dialysis membrane (molecular weight cut-off 300,000) was determined. Orntide ms were prepared by a dispersion/solvent extraction/evaporation method and characterized for drug content (HPLC), particle size distribution (laser diffraction method), and surface morphology (scanning electron microscopy).In vitro release was studied in PB using a conventional extraction method and with a new dialysis method in AB. Gravimetric analyses of polymer mass loss and matrix hydration, and peptide adsorption to blank PLGA ms (50∶50, M_w 28 022) were carried out in PB and AB upon incubation at 37°C. Serum Orntide and testosterone levels in rats after administration of Orntide ms were determined by radioimmunoassay. Orntide acetate solubility was influenced by pH; approximately 2.3 mg/mL dissolved in PB and >18 mg/mL in AB. Stability was pH- and temperature-dependent. The peptide was very stable at pH 4.0, 4°C, but degraded rapidly at pH 7.4,37°C. Peptide permeability through the dialysis membrane was accelerated by agitation and>95% equilibrium was reached within 48 hours. The overall release rate was higher with the dialysis method. Mass loss of the Orntide ms was faster in AB (50% loss in 3 weeks: 95% in 35 days) than in PB (65% in 35 days). In contrast, hydration after 35 days was 4-fold higher in PB. The nonspecific adsorption to blank ms was greater in PB (128 μ g Orntide/10 mg PLGA) compared with AB (<5 μ g Orntide/10 mg PLGA). Administration of 30-day Orntide PLGA ms to rats resulted in an initial serum Orntide level of 21 ng/mL after 6 hours and a C_max of 87 ng/mL after 6 days. Testesterone levels were suppressed immediately after ms administration (3 mg Orntide/Kg) from 5.2 ng/mL to 0.3 ng/mL (after 24 hours) and remained suppressed for 38 days. Orntide acetate solubility and degradation kinetics were markedly influenced by pH of the buffer systems and mass loss; matrix hydration, as well as the nonspecific adsorption to blank ms, was pH-dependent. Thein vitro release profile obtained with the dialysis method in AB correlated well with thein vivo data, therepy providing a more reliable prediction ofin vivo performance.     

Influence of carbon supply on the stimulation of light-saturated photosynthesis by blue light in Laminaria saccharina: implications for the mechanism of carbon acquisition in higher brown algae

In saturating irradiances of red light, photosynthesis of Laminaria saccharina (L.) Lamouroux was stimulated by low irradiances of continuous blue light only when the supply of dissolved inorganic carbon (DIC) was limiting. The degree of this stimulation was inversely proportional to the logarithm of the concentration of free CO₂, whether this was adjusted by varying the total DIC or the pH at a given DIC concentration. The final pH reached in a closed system was higher in blue light than in red light. Both acetazolamide and ethoxyzolamide suppressed the responses to blue light almost completely, but reduced photosynthesis in red light by only 30%. Buffering the pH of the seawater also suppressed the stimulation of photosynthesis by blue light without affecting the photosynthetic rate in red light. The transient stimulation of O₂ evolution by a blue light pulse was not accompanied by a corresponding increase in CO₂ consumption. These observations could be explained if, in analogy to the mechanism proposed for Ectocarpus (Schmid, Mills & Dring 1996, Plant Cell and Environment 19,373–382, this issue, accompanying paper), photosynthesis was supported by a blue-light-activated release of CO₂ from an internal store. We suggest that the store is located in the vacuoles of the cortical tissue of the blades. The main photosynthetic tissue, however, is in the overlying meristoderm, and blue-light-activated mobilization of the store could stimulate O₂ evolution only if periplasmic carbonic anhydrase was available to facilitate CO₂ uptake from the cortex.     

Electrostatic interactions in leucine zippers: thermodynamic analysis of the contributions of Glu and His residues and the effect of mutating salt bridges

Electrostatic interactions play a complex role in stabilizing proteins. Here, we present a rigorous thermodynamic analysis of the contribution of individual Glu and His residues to the relative pH-dependent stability of the designed disulfide-linked leucine zipper AB(SS). The contribution of an ionized side-chain to the pH-dependent stability is related to the shift of the pK(a) induced by folding of the coiled coil structure. pK(a)(F) values of ten Glu and two His side-chains in folded AB(SS) and the corresponding pK(a)(U) values in unfolded peptides with partial sequences of AB(SS) were determined by 1H NMR spectroscopy: of four Glu residues not involved in ion pairing, two are destabilizing (-5.6 kJ mol(-1)) and two are interacting with the positive alpha-helix dipoles and are thus stabilizing (+3.8 kJ mol(-1)) in charged form. The two His residues positioned in the C-terminal moiety of AB(SS) interact with the negative alpha-helix dipoles resulting in net stabilization of the coiled coil conformation carrying charged His (-2.6 kJ mol(-1)). Of the six Glu residues involved in inter-helical salt bridges, three are destabilizing and three are stabilizing in charged form, the net contribution of salt-bridged Glu side-chains being destabilizing (-1.1 kJ mol(-1)). The sum of the individual contributions of protonated Glu and His to the higher stability of AB(SS) at acidic pH (-5.4 kJ mol(-1)) agrees with the difference in stability determined by thermal unfolding at pH 8 and pH 2 (-5.3 kJ mol(-1)). To confirm salt bridge formation, the positive charge of the basic partner residue of one stabilizing and one destabilizing Glu was removed by isosteric mutations (Lys-->norleucine, Arg-->norvaline). Both mutations destabilize the coiled coil conformation at neutral pH and increase the pK(a) of the formerly ion-paired Glu side-chain, verifying the formation of a salt bridge even in the case where a charged side-chain is destabilizing. Because removing charges by a double mutation cycle mainly discloses the immediate charge-charge effect, mutational analysis tends to overestimate the overall energetic contribution of salt bridges to protein stability.