Nigrostriatal proteasome inhibition impairs dopamine neurotransmission and motor function in minipigs

Parkinson's disease (PD) is characterized by degeneration of dopaminergic neurons in the substantia nigra leading to slowness and stiffness of limb movement with rest tremor. Using ubiquitin proteasome system inhibitors, rodent models have shown nigrostriatal degeneration and motor impairment. We translated this model to the Göttingen minipig by administering lactacystin into the medial forebrain bundle (MFB). Minipigs underwent positron emission tomography (PET) imaging with (+)-α-[¹¹C]dihydrotetrabenazine ([¹¹C]DTBZ), a marker of vesicular monoamine transporter 2 availability, at baseline and three weeks after the unilateral administration of 100 μg lactacystin into the MFB. Compared to their baseline values, minipigs injected with lactacystin showed on average a 36% decrease in ipsilateral striatal binding potential corresponding to impaired presynaptic dopamine terminals. Behaviourally, minipigs displayed asymmetrical motor disability with spontaneous rotations in one of the animals. Immunoreactivity for tyrosine hydroxylase (TH) and HLA-DR-positive microglia confirmed asymmetrical reduction in nigral TH-positive neurons with an inflammatory response in the lactacystin-injected minipigs. In conclusion, direct injection of lactacystin into the MFB of minipigs provides a model of PD with reduced dopamine neurotransmission, TH-positive neuron reduction, microglial activation and behavioural deficits. This large animal model could be useful in studies of symptomatic and neuroprotective therapies with translatability to human PD.

Acute presentation of craniopharyngioma in children and adults in a Danish national cohort

We aimed to study the occurrence of acute-onset symptoms at initial presentation in a national Danish cohort of patients with childhood- or adult-onset craniopharyngioma, and to investigate potential risk factors for acute presentation. Medical records of 189 consecutive patients (39 children, 150 adults) presenting with craniopharyngioma during the period 1985-2004 were reviewed, and data regarding initial symptoms, neuroimaging results, vision and pituitary function were systematically collected. Acute symptoms preceding hospital admission were noted. Subgroup analyses were based on age, gender and calendar year period. Potential risk factors for acute presentation were analysed through uni- and multivariate analyses. Acute symptoms were reported in 24 (13%) patients. Acute visual symptoms, headache, nausea or vomiting were most frequently reported, and acute symptoms were more frequent among children (28%) than among adults (9%) (P < 0.01). There were no differences according to sex or calendar year period. Hydrocephalus was present in half of childhood cases and one-fifth of adult patients (P < 0.001). Intra-tumour haemorrhage was seen in two cases. Acute symptoms were more frequent among patients with tumours occupying the third ventricle (P < 0.01), radiologic signs of calcification (P < 0.05) or hydrocephalus (P < 0.01). In multivariate analysis, however, only childhood onset (P < 0.05) and calcification (P < 0.05) were independent risk factors for acute presentation. Craniopharyngioma presented with acute symptoms in 13% of patients. Childhood onset and radiologic signs of calcification were independent risk factors for acute presentation. Intra-tumour haemorrhage was rare.

Scanning tunneling microscopy reveals single-molecule insights into the self-assembly of amyloid fibrils

Many severe diseases are associated with amyloid fibril deposits in the body caused by protein misfolding. Structural information on amyloid fibrils is accumulating rapidly, but little is known about the assembly of peptides into fibrils at the level of individual molecules. Here we investigate self-assembly of the fibril-forming tetrapeptides KFFE and KVVE on a gold surface under ultraclean vacuum conditions using scanning tunneling microscopy. Combined with restrained molecular dynamics modeling, we identify peptide arrangements with interesting similarities to fibril structures. By resolving individual peptide residues and revealing conformational heterogeneities and dynamics, we demonstrate how conformational correlations may be involved in cooperative fibril growth. Most interestingly, intermolecular interactions prevail over intramolecular interactions, and assembly of the phenyl-rich KFFE peptide appears not to be dominated by π-π interactions. This study offers interesting perspectives for obtaining fundamental single-molecule insights into fibril formation using a surface science approach to study idealized model systems.

Long-term-stable ether-lipid vs conventional ester-lipid bicelles in oriented solid-state NMR: altered structural information in studies of antimicrobial peptides

Recently, ether lipids have been introduced as long-term stable alternatives to the more natural, albeit easier degradable, ester lipids in the preparation of oriented lipid bilayers and bicelles for oriented-sample solid-state NMR spectroscopy. Here we report that ether lipids such as the frequently used 14-O-PC (1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine) may induce significant changes in the structure and dynamics, including altered interaction between peptides and lipids relative to what is observed with the more conventionally used DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) bilayers. Such effects are demonstrated for the antimicrobial peptide novicidin, for which 2D separate-local-field NMR and circular dichroism experiments reveal significant structural/conformational differences for the peptide in the two different lipid systems. Likewise, we observe altered secondary structure and different temperature-dependent membrane anchoring for the antimicrobial peptide alamethicin depending on whether the peptide is reconstituted into ester or ether lipids. Such observations are not particularly surprising considering the significant difference of the lipids in the phosphorus headgroup and they may provide important new insight into the delicate peptide-membrane interactions in the systems studied. In contrast, these observations reinforce the need to carefully consider potential structural changes in addition to long-term stability prior to the selection of membrane environment of membrane proteins in the analysis of their structure and dynamics. In more general terms, the results underscore the necessity in structural biology to address both the protein and its environments in studies relating structure to function.

Craniopharyngioma: historical notes

For centuries tumors have been described which today with some confidence can be diagnosed as craniopharyngiomas. It was not until 1904 Erdheim described what he called 'hypophysial duct tumors', and which Cushing later gave the name craniopharyngioma. The first operation for this neoplasm took place in 1909. It soon became evident that the outcome of surgery was rather dismal with high mortality and morbidity rates-even after corticosteroid therapy became available around 1950. Radiotherapy was introduced and later refined as radiosurgery. This paper presents a short survey of the accumulation of knowledge of craniopharyngiomas.

Excess mortality in women with pituitary disease: a meta-analysis

BACKGROUND

Increased mortality has been reported in patients with pituitary disease, with some studies showing higher standard mortality rates (SMR) in women than in men.

OBJECTIVE

To assess overall SMR for men and women with benign pituitary disease without excessive ATCH or GH secretion and to investigate associations between SMR and time period of diagnosis.

DESIGN

From searches in PubMed, Embase and Web of Science databases, and reference lists of major reviews and original articles, we included original studies providing SMR values and 95% confidence intervals (CI) for men and women separately. Thirty articles were studied in detail. Six studies were eligible for the meta-analysis of sex-specific mortality, and seven for the analysis of association between SMR and diagnosis period.

RESULTS

Individual studies (total 5412 patients) reported total SMR values (men and women together) ranging from 1.21 to 3.80. SMR varied from 0.98 to 3.36 in men and from 2.11 to 4.54 in women. Weighted SMR values were significantly higher in women (2.80; CI 2.59-3.02) than in men (2.06; CI 1.94-2 20) (P < 0.0001). SMR was negatively correlated with first year of diagnosis in individual studies (partial correlation analysis controlling for sex, P = 0.017), and approached normal in recent studies in men but not in women.

CONCLUSIONS

In our meta-analysis of patients with pituitary disease without ACTH or GH excess, SMR was significantly higher in women than in men. SMR reached normal levels in men treated in recent decades, but remained elevated in women.

Complement activation by the amyloid proteins A beta peptide and beta 2-microglobulin

Complement activation (CA) has been reported to play a role in the pathogenesis of Alzheimer's disease (AD). To investigate whether CA may contribute to amyloidogenesis in general, the CA potential of different amyloid fibril proteins was tested. CA induced by A beta preparations containing soluble protein, protofilaments and some fibrils or only fibrils in a solid phase system (ELISA) was modest with a slow kinetics compared to the positive delta IgG control. Soluble A beta induced no detectable CA in a liquid phase system (complement consumption assay) while fibrillar A beta caused CA at 200 mg/ml and higher concentrations. Soluble beta 2-microglobulin (beta 2M) purified from peritoneal dialysates was found to be as potent a complement activator as A beta in both solid and liquid phase systems while beta 2M purified from urine exhibited lower activity, a difference which may be explained by differences observed in SDS-resistant oligomers and isoforms. Soluble Amyloid A-protein caused no significant CA. A beta and beta 2M activated complement via the classical pathway. The modifying influence by amyloid-associated molecules on A beta-induced CA was also investigated, but neither serum amyloid P component nor heparan sulfate did significantly alter the A beta-induced CA. The results indicate that not only fibrillar A beta but also oligomers of, in particular, beta 2M from patients with dialysis-associated amyloidosis are capable of inducing CA at supra-physiological concentrations.

[Primary hyperoxaluria type 1 detected by liver biopsy]

PH1 is caused by deficiency of the liver-specific peroxisomal enzyme alanine: glycoxylate aminotransferase (AGT). Early onset with progressive renal failure and systemic oxalosis is typical. We report a case of a 42 year-old man with PH1 in whom liver biopsy and DNA-analysis showed reduced AGT-activity and homozygosity for the polymorphism C154T and the point mutation G630A. The patient seems to respond to pyridoxine treatment. We suggest that clinical suspicion of PH1 be pursued with a diagnostic liver biopsy.

Isoforms of murine and human serum amyloid P component

Isoelectric focusing (IEF) and immunofixation of murine serum amyloid P component (SAP), purified and in serum, showed a distinct and strain-dependent isoform pattern with up to seven bands (pI 5.1-5.7). Neuraminidase treatment caused a shift of the isoforms to more basic pI values, but did not affect their number. When the acute-phase response was analysed in three mouse strains, CBA/J and C3H/HeN initially showed seven SAP isoforms in serum and C57BL/6 J three or four. The responses in all three strains peaked at day 2 and were normalized within 14 days. On days 2 and 4, CBA/J and C3H/HeN mice showed one more acidic isoform and an increase in the concentration of the most basic isoform. C57BL/6 J mice exhibited two to three new isoforms during the acute-phase response. This appears to be the first demonstration of the physiological existence of SAP isoforms. In contrast, demonstration of isoforms of human SAP required the presence of urea and higher SAP concentrations. TEF and immunofixation of SAP monomers showed five to eight isoforms, ranging from pI 4.7-5.7. IEF of SAP in human serum resulted in a less distinct pattern and more acidic isoforms. As with murine SAP, neuraminidase treatment caused a shift of the isoforms, but no reduction in isoform number. Two-dimensional gel electrophoresis confirmed the existence of multiple isoforms of human SAP monomers.

[D-vitamin and vitamin D deficiency among Asian immigrants]

Vitamin D deficiency, often complicated by osteomalacia, among Asian immigrants (especially females) is now also recognized in the Nordic countries. The article reviews the history of vitamin D featuring its discovery as well as a contemporary perspective, and describes the complex etiology of the disease. The symptoms, diagnostic approach and recommended treatment are also summarized.

An in vitro cellular system for generation of AA-amyloid

Different conditions for establishing a cell culture system for generation of AA-amyloid were investigated. The most effective system was based on peritoneal macrophages from CBA/J mice that had received repeated injections of Hammersten casein, with subsequent cultivation of the cells at high density, high levels of acute phase serum, and neutral pH. Staining with Congo red, thioflavin T, and anti-AA revealed amyloid-like structures associated with macrophage clusters. The structures increased in number and size from day 2 to 6 of cell cultivation. The concentration of apoSAA in the culture medium fell markedly in the amyloid-producing cell cultures, while the SAP concentration was not reduced. The described cell culture system can be useful in studies of the influence of chaperone molecules and other factors or the formation and degradation of amyloid fibrils.

Calcium-dependent and -independent binding of the pentraxin serum amyloid P component to glycosaminoglycans and amyloid proteins: enhanced binding at slightly acid pH

Serum amyloid P component (SAP), a member of the pentraxin family of proteins, binds calcium-dependently to several ligands including glycosaminoglycans (GAG's). We have investigated the influence of pH on the Ca2(+)-dependent binding of SAP to solid phase GAG's and amyloid fibril proteins (AA and beta2M) by ELISA. An increase in the dose-dependent binding of SAP to heparan sulfate, AA-protein and beta2M was observed as the pH decreased from 8.0 to 5.0. Furthermore, a lower, but significant Ca2(+)-independent binding of SAP to heparan sulfate, dermatan sulfate, AA protein and the amyloid precursor protein beta2M was observed. This binding was also enhanced at slightly acid pH, most pronounced at pH 5.0. The results of this study indicate that SAP can exhibit both Ca2(+)-dependent and -independent binding to ligands involved in amyloid fibril formation and that the binding is enhanced under conditions of slightly lowered pH.

Binding of complement proteins C1q and C4bp to serum amyloid P component (SAP) in solid contra liquid phase

Serum amyloid P component (SAP), a member of the conserved pentraxin family of plasma proteins, binds calcium dependently to its ligands. The authors investigated SAPs interaction with the complement proteins C4b binding protein (C4bp) and C1q by ELISA, immunoelectrophoresis and electron microscopy. Binding of these proteins to SAP was demonstrated when SAP was immobilized using F(ab')2 anti-SAP, but not when SAP reacted with these proteins in liquid phase; thus the binding to human SAP was markedly phase state dependent. Presaturation of solid phase SAP with heparin, which binds SAP with high affinity, did not interfere with the subsequent binding of C4bp or C1q to SAP. In contrast, collagen I and IV showed partial competition with the binding of C1q to SAP. Using fresh serum, immobilized native SAP bound C4bp whereas binding of C1q/C1 could not be demonstrated. Altogether the results indicate that firm binding of C1q and C4bp to SAP requires that SAP is presented on a solid phase, that C1q and C4bp react with sites distinct from the heparin binding site, and that C1q and collagen I share binding sites on SAP. Immobilized native SAP, aggregated SAP and SAP-heparansulphate complexes induced no detectable complement activation.

Isolation and characterization of porcine mannan-binding proteins of different size and ultrastructure

The authors report on the purification and characterization of mannan- binding proteins (MBP) isolated from porcine serum. The MBPs were purified by use of PEG precipitation, affinity chromatography on mannan-Sepharose, protein A- and anti-porcine IgM-Sepharose followed by gel filtration. The MBP proteins were collagenase sensitive and showed gamma 1-gamma 2-electrophoretic mobility. The MBP designated pMBP-28 had a molecular mass of 28 kDa when analysed on SDS-PAGE under reducing conditions and eluted corresponding to a molecular mass of approximately 700 kDa on gel filtration chromatography. Electron micrographs of pMBP-28 revealed an oligomeric protein similar to rodent MBP-A and human MBP but with a predominance of penta- and hexameric molecules. Another protein designated pMBP-27 was composed of peptides of 27 kDa and had an Mr of 300-350 kDa on gel filtration chromatography. Electron microscopy of pMBP-27 showed dimer and trimer molecules; the trimers without distinct stalk regions. The N-terminal 26(pMBP-27) and 24(MBP-28) amino acid residues showed 54% and 58% identity with human MBP.pMBP-28 showed a higher degree of sequence similarity to rat and mouse MBP-A (60% identity) than to mouse and rat MBP-C (41-45% identity). Both pMBPs exhibited Ca2+-dependent binding to D-mannose immobilized on agarose but no significant binding to N-acetyl-D-glucosamine- or fucose-agarose. The results further suggested the presence of a third pMBP which copurified with pMBP-27 but this protein was not sequenced.

An electron microscopic study of clinical Paget's disease of the nipple

An ultrastructural study of the epidermis from eight patients with clinical Paget's disease of the nipple supports the epidermotropic theory. There was no evidence that the Paget's cells originated from keratinocytes. We propose the hypothesis that Paget's cells represent transformed ductal cells, from the subjacent lactiferous ducts of the nipple, which have migrated into the epidermis, either as neoplastic cells or as normal ductal cells with secondary in situ transformation in the epidermis.

Native human serum amyloid P component is a single pentamer

Serum amyloid P component (SAP) and C-reactive protein (CRP) are members of the pentraxin protein family. SAP is the precursor protein to amyloid P component present in all forms of amyloidosis. The prevailing notion is that SAP in circulation has the form of a double pentameric molecule (decamer) whereas CRP is a single pentameric molecule. We have investigated by gel permeation chromatography the M(r) of SAP in freshly collected human serum and of SAP purified by carbohydrate affinity chromatography and anion exchange chromatography. SAP was monitored by quantitative immunoelectrophoresis and ELISA, and SAP peak fractions were analysed by use of SDS-PAGE, Western blotting, and electron microscopy. The results indicate that native SAP circulates as a single pentamer, a part of which forms complexes with C4b-binding protein. The properties of SAP changed during purification as indicated by rocket immunoelectrophoresis and electron microscopy. Thus, electron micrographs of purified SAP showed a predominance of decamers. However, the decamer form of SAP reversed to single pentamers when purified SAP was incorporated into SAP-depleted serum.

Multiple isoforms of the human pentraxin serum amyloid P component

Human serum amyloid P component (SAP) isolated from 20 healthy individuals was analyzed by anion exchange chromatography and isoelectric focusing (IEF) in order to investigate the existence of multiple forms of SAP and interindividual structural differences. Anion exchange chromatography showed one major and several minor subpopulations of SAP. IEF of all SAP isolates showed a previously unreported degree of heterogeneity with six isoelectric forms (pKi range 5.5-6.1) and with minor interindividual differences in respect of isoelectric points. Total enzymatic deglycosylation of SAP reduced the number of bands in IEF to two indicating the existence of two types of polypeptide chains.

Calcium-enhanced aggregation of serum amyloid P component and its inhibition by the ligands heparin and heparan sulphate. An electron microscopic and immunoelectrophoretic study

Serum amyloid P component (SAP) is a pentraxin found in the circulation and in all forms of amyloid deposits. Its physiological and pathophysiological functions are largely unknown. Electron microscopy showed purified human SAP to consist of double pentameric discs compatible with the results of size chromatography. The formation of double pentamers did not require calcium ions. The outer diameter of the discs arranged face-to-face was 11.6 nm and the inner diameter 3.2 nm. The thickness of single and double pentamers was 4.1 and 8.7 nm, respectively. Quadruple pentamers were occasionally seen. The self-aggregation of human SAP molecules was investigated in the presence and absence of calcium ions at different concentrations. In calcium-free solutions few and mostly small SAP aggregates were seen. After addition of calcium at increasing concentration the aggregates grew in size and crystalline-like structures were formed already at 2 mM calcium. At 25 mM calcium, large aggregates with a crystalline array occasionally exhibiting cylinders predominated. Binding of the ligands heparin and heparan sulphate to SAP completely abolished the calcium-enhanced aggregation, but the distribution of the SAP molecules was affected, resulting in strands or groups of adjacent molecules. The electrophoretic mobility of SAP was moreover significantly altered after its calcium-dependent reaction with these ligands. We conclude that purified SAP has a tendency to double pentamer formation and self-aggregation also in the absence of calcium ions. However, aggregation is greatly enhanced even at low concentrations (2 mM) of calcium. SAP's tendency to self-aggregation is abolished after its binding to heparin or heparin sulphate. Furthermore, our TEM studies indicate that purified human SAP freed of its natural ligands has the double pentameric form, whereas the electrophoretic investigations suggest that SAP's interaction with low-molecular-weight natural ligands in serum prevents homodimerization and self-aggregation.

Biochemical and ultrastructural studies of the C-type lectin bovine conglutinin

The aim of this study was to correlate the supramolecular organization of conglutinin (BK) with its primary and tertiary structure and to gain more knowledge of functionally important regions of the molecule. BK analyzed by SDS-PAGE under standard reducing conditions (40 mM DTT) showed a major band at 43 kDa and weaker bands at 86 and 180 kDa. In contrast, reduction with 6-50 mM L-cysteine resulted in 37-kDa subunits indicating the presence of intrachain disulfide bonds within this subunit. Hydroxylamine treatment indicated presence of ester bonds in the 86- and 180-kDa subunits. Collagenase digestion and SDS-PAGE under reducing and nonreducing conditions resulted in bands of 20 and 15 kDa, respectively, indicating the presence of intrachain, rather than interchain, disulfide bonds in the carboxy terminus. Deglycosylation and glycan differentiation analysis of BK revealed the presence of O-linked glycans of GalNAc and alpha (2-3) linked sialic acid type, whereas no N-linked glycans were demonstrated. Binding experiments with GlcNAc-gold suggested that multivalency is required for carbohydrate binding to BK. Electron microscopy showed mostly tetramers, 96 nm in diameter, but also mono-, di-, and trimers were seen. The tetramers consisted of 40-nm strands, each with a peripheral globular head composed of subunits and connected to a common central lobe built from four ring-formed structures. The strands occasionally showed two bends, one close to the central lobe and another 25 nm from the lobe. These bends most likely correspond to the interrupted Gly-Xaa-Yaa repeats at residues 38 and 123.

Grafting of human autogenous keratinocytes cultured in vitro

A rapid method of producing epithelial material suitable for covering skin defects after burns and avulsions is presented. In vitro grown keratinocytes suspended as single cells in human plasma were applied to the wound surface and covered with distended meshed xenograft. In this way it was possible in five clinical cases to obtain 25-80% epithelial coverage of wounds up to 200 times as wide as the donor area.

A filamentous network surrounding secretory granules from mast cells

A freezing-thawing method for rupturing mast cells has made it possible to show that each of the secretory granules is surrounded by a regular network of filaments forming a basket-like structure. The filaments attach to the membrane with hook-like structures. Immunoelectron microscopy of intact mast cells shows that actin occurs mainly in the subplasmalemmal space, whereas in ruptured cells it is seen around granules, indicating that the granule network might consist of actin.

The involvement of protein kinase C in exocytosis in mast cells

Diacylglycerol generated from inositolphospholipid hydrolysis and tumor-promoting phorbol esters stimulate protein kinase C. The synthetic diacylglycerol 1-oleoyl-2-acetyl-rac-glycerol and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) have been used in pure rat peritoneal mast cells. Both caused histamine release associated with exocytosis. The release by the stimulation of protein kinase C alone in the absence of secretagogues was slow although up to 50% of the histamine content was released by TPA in 120 min. Remarkable potentiation of histamine release was observed when the mast cells were preincubated with TPA before exposure to the calcium ionophore A23187. The potentiation of histamine release corresponded with an intensification of exocytosis. The potentiation is consistent with a participation of protein kinase C in the secretory process. An inhibitory effect due to protein kinase C activity was also demonstrated using TPA and mast cells from sensitized rats. When sensitized mast cells preincubated with 50 nM TPA for 5 min were exposed to the antigen, the histamine release was substantially reduced compared to the sum of the release by the antigen and TPA or by the antigen alone. There was a corresponding decrease in exocytosis. The inhibition of exocytosis and histamine release seems to reflect a regulatory function of protein kinase C for the termination of the response, as demonstrated in other types of cells apparently acting through an inhibition of inositolphospholipid hydrolysis.

Reorganization of the subplasmalemmal cytoskeleton in association with exocytosis in rat mast cells

The subplasmalemmal cytoskeleton in mast cells has been studied by scanning electron microscopy of the internal side of the plasma membrane. Rearrangement of the dense subplasmalemmal network of actin filaments took place following cell activation by compound 48/80 and secretion of histamine. The rearrangement was a withdrawal of the subplasmalemmal cytoskeleton from the exocytotic sites and the development of bare, filament-free areas around the sites. In calcium-depleted mast cells we demonstrated a dense network that was difficult to break. Activation of the calcium-depleted cells by compound 48/80 did not induce rearrangement of the network, and in parallel there was no secretion of histamine.

Ultrastructure of psoriatic epidermis

The ultrastructure of human affected and unaffected psoriatic epidermis was studied in skin biopsies from 5 patients and 3 normal controls. Transmission electron microscopic investigations revealed abnormalities in all cell layers of the affected epidermis. Common to psoriatic keratinocytes from affected epidermis was the reduction of tonofilaments. The essential ultrastructural changes were located in the stratum granulosum and stratum corneum. Thus, absence of the fusion between the keratohyalin granules and the tonofilaments was found in stratum granulosum. The keratinocytes of the stratum corneum showed a large accumulation of ribosomes and vesicles resembling lipid vesicles.

Surface ultrastructure of cultures of affected psoriatic keratinocytes, unaffected psoriatic keratinocytes and normal keratinocytes

The surface structure of 11-12 days old cultures from biopsies of normal skin and uninvolved psoriatic skin was investigated by scanning electron microscopy. The keratinocytes formed flat, thin, and well-organized layers of elongated, tightly apposed cells. Newly-formed cells with few and short microplicae and microvilli were seen at the colony periphery. On the maturing cells towards the colony center, the number and size of microplicae or microvilli increased gradually. No differences were found between the structures on normal keratinocytes and keratinocytes from uninvolved psoriatic skin, but in keratinocytes from involved psoriatic skin glomerulus-like rolled microplicae occasionally were found.

Effects of dimethylsulfoxide (DMSO), nocodazole, and taxol on mast cell histamine secretion

Nocodazole depolymerized microtubules and increased the number of microfilaments, and dimethylsulfoxide increased the number of microfilaments. Both drugs inhibited compound 48/80-induced histamine release from rat mast cells. Taxol, which increased the number of microtubules, had no effect on histamine release. These observations support the view that microtubules may not be directly involved in secretion, but apparently an increased number of microfilaments is associated with a decreased capacity of the mast cells for histamine release. We suggest that microfilaments have to be depolymerized or rearranged before secretion can take place.

Histamine release from saponin-permeabilized rat mast cells by calcium

The first effect of receptor activation on the mast cell surface, initiating histamine secretion, is an increase in the cytosol Ca2+ concentration. It should then be possible to induce histamine secretion by calcium alone, if the calcium permeability of the cell membrane could be increased without any significant interference with the physiological cell functions. This was achieved in the present study by adding low concentrations of saponin (0.0005% and 0.001% w/v) to the medium. When calcium was added to the saponin-permeabilized cells, around 40% histamine release occurred with 0.25 mM extracellular calcium (free Ca2+ 0.15 mM). The release was inhibited by antimycin A (1 microM). Transmission electron microscopy showed formation of vacuoles containing granules stripped of their membranes, which characterize a secretory response. The observations are consistent with a limited increase in the calcium permeability of the cell membrane for a brief period. There was apparently an increase in the cytoplasmic calcium concentration, which acted through calmodulin, since the histamine release induced by calcium from the permeabilized mast cells could be inhibited by a calmodulin-antagonist, mepacrine (10-30 microM).

Calmodulin in mast cells and its role in histamine secretion

Calmodulin content and distribution in rat peritoneal mast cells was determined by radioimmunoassay. Isolated pure mast cells were disrupted by sonication and the total calmodulin content and its distribution were determined. Calmodulin bound to the membranes was released by heating with 0.1% Lubrol PX to 95 degrees C for 5 min. The total calmodulin content of mast cells was found to be 160 +/- 14 ng/10(6) cells (9.4 +/- 0.82 pmoles/10(6) cells). The highest amount (68%) was present in the supernatant representing the cytosol. The next highest amount (26%) was found in the composite fraction consisting of mitochondria, endoplasmic reticulum, Golgi vesicles and plasma membrane (100,000 g pellet). The mast cell granules contained 4% of the total calmodulin. Trifluoperazine (TFP) was used as an antagonist to explore the role of calmodulin in histamine secretion. At 10 microM concentration, TFP caused a negligible spontaneous histamine release by its membrane effect. TFP (10 microM) inhibited histamine release by all the three secretagogues used, but the degree of inhibition varied: 60% with antigen, 40% with compound 48/80 and 20% with ionophore A23187. It is suggested that the TFP effect is due to calmodulin-antagonism and interference with the activation of enzymes, essential to the secretory process.

Cytoskeletal studies on Lowicryl K4M embedded and Affi-Gel 731 attached rat peritoneal mast cells

The subplasmalemmal network in mast cells consists of irregularly arranged 6-7 nm filaments (actin) connected by thinner filaments. In places oblique filaments with crossbridges or short, perpendicular filaments (11-12 nm) connect cell and granule membrane. Filaments attaching subplasmalemmal network to cell membrane divide like a Y and attach cell membrane end-on with a conical, hook-like bending. Each granule is surrounded by a regular network of filaments.

Electron microscopical study of rat mast cell maturation

The development of peritoneal mast cells in rats in the early post-natal period was found to take 7-8 weeks. A slightly shorter time was needed for the reappearance of mature peritoneal mast cells following their total destruction in adult rats. In both groups of animals mast cell ultrastructure was studied in successive phases of development. The maturation process was gradual, but no well-defined morphological stages could be demonstrated. The morphology of young peritoneal mast cells seems to indicate that they arise in the peritoneal fluid from macrophage-like cells.

Electron microscopic study of the regeneration in vivo of rat peritoneal mast cells after histamine secretion

Peritoneal mast cells regenerate their histamine granules in 5-6 weeks after intraperitoneal injection of the degranulating agent compound 48/80. In the beginning of the regeneration the small exocytic cavities containing the non-secreted granule remnants coalesce to a single large cavity. Later on this cavity decreases in size and becomes a small vacuole containing a very condensed material. After two weeks of regeneration mast cells are already capable of another secretory event.

Adenosine triphosphatase in non-secreting and secreting mast cells

A Ca++-Mg++ ATPase has been demonstrated in the plasma membrane of rat peritoneal mast cells. The enzyme is localized by electron microscopy on the outer surface of the membrane. This agrees with the biochemical findings. A Ca++-Mg++ activated ATPase has also been shown to be present in the granule membrane. The optimal pH of the plasma membrane enzyme is close to the optimal pH for the histamine release. All the 14 inhibitors of plasma membrane ATPase tested - which caused varying degrees of inhibition of the enzyme - also inhibited histamine release induced by antigen, compound 48/80 and the divalent ionophore A23187. The conclusion from the study with the inhibitors is that a mild inhibition of the enzyme is compatible with histamine release, but a pronounced inhibition of the enzyme is always associated with inhibition of histamine release. ATP in low concentrations potentiates the release.

Surface morphology of rat peritoneal mast cells during in vitro regeneration after histamine secretion

Cell-surface morphology of regenerating mast cells was followed over a period of 48 h after histamine release. Control cells (not stimulated to secrete) were characterized by anastomosing folds of membrane of equal depth and width. During exocytosis these folds disappeared and were replaced by deep cup-shaped flaps of membrane evident in cells incubated for 10 min. During the first hours of regeneration these flaps fused mutually or with the plasma membrane. This activity suggests membrane retrieval, maybe specifically recycling the granule-type patches of membrane. Membrane-fusion activity was observed to some degree also after extended incubation. After 48 h of incubation the regeneration process was still not completed, as indicated by the fact that holes leading to intracellular cavities could still be found.

Electron microscopic study of the regeneration in vitro of rat peritoneal mast cells after histamine secretion

Regeneration of rat mast cells was studied by TEM from 10 s to 48 h after secretion of histamine induced by compound 48/80. During the first 2 h, small intracellular cavities, formed during compound exocytosis and containing non-membrane-bound remnants of the granules, tended to coalesce, and after 2 h of incubation regeneration started. After 6 h, all the cavities had fused into one large central cavity which contained the remnants of the granules and remained open to the exterior during the entire period. The plasma membrane microfolds which disappeared just after secretion were reformed during regeneration. They were apparently involved in endocytotic-like activity and coated vesicles also appeared beneath the plasmalemma (membrane recycling?). The fate of the granule remnants in the cavity is unknown, as regeneration was not completed after 48 h which is the longest survival time obtained so far in ultrastructural studies of mast cell regeneration in vitro.

High resolution scanning electron microscopy of elastic cartilage

The elastic cartilage of the rat epiglottis was studied with a high-resolution SEM technique. The chondrocytes were found to be anchored in their lacunae by fibrils running in from the territorial matrix. This matrix exhibited a dense network of fibrils arranged tangentially around the lacunar cavity. The fibrils of the inter-territorial matrix however, formed a three dimensional network of sheets with interconnecting fibrils. The SEM has shown up for the first time a substructure in the fibrils in the form of circular protuberances arranged circumferentially around the fibrils and forming ridges 12--19 nm apart. We suggest that the fibrils are collagen, and the protuberances are the proteoglycans attached to the collagen fibrils. Globules seen attached to the fibrils are most probably 'matrix granules' as observed in other kinds of cartilage. The total inability to visualize elastin with the high resolution SEM is puzzling.

Ultrahistochemistry of matrix vesicles in elastic cartilage

Matrix vesicles in the elastic cartilage of epiglottis were negative for acid phosphatase, alkaline phosphatase, and ATPase. This is in agreement with the very rare occurrence of mineralization of elastic cartilage. Only the lysosomes of the chondrocytes showed a positive reaction for acid phosphatase, and a positive reaction for alkaline phosphatase and ATPase was found in relation to the cells of the perichondrium.

The elastic cartilage in the normal rat epiglottis. I. Fine structure

Chondrocytes of the rat epiglottis contain large amounts of glycogen and lipids, which often make the cells resemble fat cells. The content of lipids is interpreted as being related to the function of the cells. The membranes of some of the large vacuoles are stained with ruthenium red. The cells give rise to long cytoplasmic processes. As in hyaline cartilage the intercellular substance consists of a fine network containing proteoglycan granules together with thicker cross striated fibers. Furthermore elastic fibers are found, consisting of amorphous and microfibrillar parts. In the matrix, both lysosome-like granules and more or less empty vesicles are observed. Accumulations of a finely particulate electron dense material and of a translucent amorphous material containing membrane bound granules are found in some lacunae situated in the outer part of the cartilage. These accumulations are possibly related to the development of collagenous and elastic fibers.