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W van Dijk

Publications and source records attributed to W van Dijk.

At least 19 recordsLinked to original sources
PubMed2006

Laser wakefield acceleration: the injection issue. Overview and latest results.

External injection of electron bunches into laser-driven plasma waves so far has not resulted in 'controlled' acceleration, i.e. production of bunches with well-defined energy spread. Recent simulations, however, predict that narrow distributions can be achieved, provided the conditions for properly trapping the injected electrons are met. Under these conditions, injected bunch lengths of one to several plasma wavelengths are acceptable. This paper first describes current efforts to demonstrate this experimentally, using state-of-the-art radio frequency technology. The expected charge accelerated, however, is still low for most applications. In the second part, the paper addresses a number of novel concepts for significant enhancement of photo-injector brightness. Simulations predict that, once these concepts are realized, external injection into a wakefield accelerator will lead to accelerated bunch specs comparable to those of recent 'laser-into-gasjet' experiments, without the present irreproducibility of charge and final energy of the latter.

Journal Article↗
PubMed2005

Interlaboratory comparison of three methods for the determination of the radon exhalation rate of building materials.

In this study three methods for the determination of the radon (222Rn) exhalation rate of building materials are compared. All three are so-called purge-and-trap methods in which the sample is enclosed in a container from which the exhaled radon is continuously purged by a constant flow of nitrogen gas. The outflowing radon is directed through a trapping agent, and the radon exhalation rate is subsequently calculated from the trapped activity. The main differences between the three methods are the trapping agent (silica gel, charcoal), trapping temperature (liquid nitrogen, room temperature), trapping period (30 min to 10 d), analytical method to determine the trapped activity (liquid scintillation counting, gamma ray spectrometry, total gamma counting) and the sample counting times (1 to 16 h). The repeatability and intralaboratory reproducibility are determined for one of the methods and amount to 3.1% and 4.3%, respectively. The intralaboratory reproducibility, derived from five samples with a radon release rate up to 450 microBq s(-1), was found to be 5.6% on average (range 3 to 8%). These figures are close to the combined standard uncertainty of the individual results that vary between 3 to 6%, depending on the method and method variables such as trapping period and the uncertainty of the calibration source. Furthermore, another 10 commercially available building materials were analyzed to investigate the correlation between the applied methods. Using linear regression analysis, it was found that the slope deviated not more than 10% from the one to one correspondence line. The results show that measurements of the exhalation rate can be carried out with a large degree of accuracy provided sufficient care is taken for a well-documented standard method.

Calibration↗
PubMed2003

Cloning and expression of a functional estrogen receptor-alpha from African catfish (Clarias gariepinus) pituitary.

An African catfish (Clarias gariepinus) estrogen receptor-alpha (cfERalpha) cDNA fragment was amplified by RT-PCR, in combination with a modified 3'-RACE procedure, on total RNA extracted from pituitary. This cDNA fragment was used to screen an African catfish pituitary cDNA library. A clone was obtained that contained an open-reading frame coding for a 620 amino acid cfERalpha protein with a deduced molecular mass of 68.1 kDa. In addition, a partial African catfish estrogen receptor-beta (cfERbeta) cDNA fragment was amplified by RT-PCR on total RNA extracted from testis. Neighbor-joining analysis was used to infer a phylogenetic classification for cfERalpha and cfERbeta. The tree obtained indicated that there are two major clusters of vertebrate ERs: ERalpha and ERbeta. Within each cluster, teleost and tetrapod ER sister clades could be distinguished. The cfERalpha clustered with other teleost ERalphas, whereas cfERbeta clustered with other teleost ERbetas. The ligand-induced transcriptional activity of cfERalpha was demonstrated in a transient gene expression assay using cells in which an acute estrogenic response was created by co-transfecting cultures with recombinant cfERalpha cDNA expression vector constructs in the presence of an estrogen-dependent reporter plasmid. Real-time, quantitative PCR revealed that cfERalpha transcripts were most abundantly expressed in pituitary, while in all other tIssues tested the relative cfERalpha mRNA levels were less than approximately 5% of the level obtained in pituitary. Moreover, we found that, during pubertal development, the relative cfERalpha mRNA levels gradually increased in African catfish pituitary.

Africa↗
PubMed2002

Cloning and spatiotemporal expression of the follicle-stimulating hormone beta subunit complementary DNA in the African catfish (Clarias gariepinus).

The gene and cDNA encoding a putative follicle-stimulating hormone beta subunit (cfFSHbeta) from African catfish (Clarias gariepinus) were cloned. Similar to other FSHbeta genes, the cfFSHbeta gene consisted of three exons interrupted by two introns. The cfFSHbeta cDNA coded for a mature protein of 115 amino acids. The 12 cysteines that are required for the typical tertiary folding of glycoprotein hormone beta subunits were positionally conserved in cfFSHbeta. The cfFSHbeta mRNA expression was exclusively detected in the pituitary and was detectable before pubertal development was initiated. The cfFSHbeta transcript levels increased in particular during early stages of puberty and reached constantly high levels after the first appearance of spermatids in the testis. The cfFSHbeta mRNA-positive cells were localized in the proximal pars distalis. Castration of mature males caused elevated cfFSHbeta mRNA levels that were decreased by steroid replacement. Previous work indicated that the African catfish is an interesting model to study the regulation of gonadal functions because cfLH is able to activate both the catfish luteinizing hormone receptor (cfLH-R) and follicle-stimulating hormone receptor (cfFSH-R). Because cfFSH purification has failed so far, ongoing studies are directed toward the production of recombinant cfFSH. After all, the developmental and hormonal regulation of cfFSHbeta transcript levels opens the possibility for physiologically relevant actions of the putative cfFSH, next to the presumptive bifunctionally acting cfLH.

Amino Acid Sequence↗
PubMed2002

Gonadotropin-releasing hormone does not directly stimulate luteinizing hormone biosynthesis in male African catfish.

Besides gonadotropin release, GnRH stimulates gonadotropin subunit gene transcription and translation in gonadotrophs. In the African catfish, Clarias gariepinus, chicken GnRH-II (cGnRH-II: [His5,Trp7,Tyr8]-GnRH) and catfish GnRH (cfGnRH: [His5,Asn8]-GnRH) are two endogenous forms of GnRH. Studying their effects on LH subunit steady-state mRNA levels, LH de novo synthesis, and LH release in primary pituitary cell cultures of adult males, we found that cGnRH-II hardly influenced the steady-state levels of LH subunit mRNAs or LH de novo synthesis, although it stimulated LH release. Although cfGnRH stimulated LH secretion as well, high concentrations-although apparently still within the physiologic range-reduced LH transcript levels and de novo synthesis in primary pituitary cell cultures. In vivo experiments demonstrated a biphasic response of LH subunit transcript levels after a single GnRH injection: a decrease after 2 h was followed by an increase at 8 h. When the testes were removed before GnRH treatment, however, LH transcript levels remained depressed at 8 h after GnRH injection, indicating that the secondary increase in LH transcript levels depends on the presence of the testes. We conclude that the up-regulation of LH production subsequent to GnRH stimulation in adult male African catfish is mediated by factors originating from the testis. Previous work suggests that aromatizable androgens may play an important role in this context. Under the present experimental conditions, however, GnRHs had no, or an inhibitory, direct effect on LH production in catfish gonadotrophs.

Animals↗
PubMed2001

Differences in sulfation patterns of heparan sulfate derived from human bone marrow and umbilical vein endothelial cells.

OBJECTIVE: Heparan sulfates (HS), the polysaccharide side chains of HS proteoglycans, differ in structure and composition of sulfated domains among various tissue types, resulting in selective protein binding. HS proteoglycans on bone marrow endothelial cells (BMEC) could contribute to tissue specificity of the bone marrow endothelium and play a role in the presentation of chemokines such as stromal cell-derived factor-1 (SDF-1) and adhesion of hematopoietic progenitor cells after stem cell transplantations. We characterized differences in HS structure and SDF-1 binding between BMEC and human umbilical vein endothelial cells (HUVEC). MATERIALS AND METHODS: Expression of HS proteoglycans on human bone marrow microvessels was investigated by immunohistochemical staining. Comparison of three human BMEC cell lines with HUVEC and an HUVEC cell line was studied by flow cytometry using antibodies against different epitopes of the HS polysaccharide chain. HS proteoglycans were biochemically characterized after isolation from metabolically labeled cultures of the BMEC cell line 4LHBMEC and HUVEC. Binding of radiolabeled SDF-1 to 4LHBMEC and HUVEC and competition with heparins were investigated. RESULTS: Bone marrow microvessels constitutively expressed HS proteoglycans. Flow cytometric experiments showed differences in HS chain composition between BMEC and HUVEC. Biochemical characterization revealed more O-sulfation of the N-sulfated domains present in cell-associated HS glycosaminoglycans in 4LHBMEC compared to HUVEC. Binding experiments showed that 4LHBMEC bound more 125[I]-SDF-1 per cell than HUVEC. This could be inhibited largely by heparin and O-sulfated heparin and to a lesser extent by N-sulfated heparin. CONCLUSIONS: Cellular HS from BMEC differs in composition from HUVEC. We postulate that the presence of highly sulfated domains in the HS chains from BMEC contributes to tissue specificity of bone marrow endothelium in which HS may be involved in SDF-1 presentation and adhesion of hematopoietic progenitor cells.

Bone Marrow↗
PubMed2001

Increased alpha3-fucosylation of alpha1-acid glycoprotein in Type I diabetic patients is related to vascular function.

Diabetic mellitus is attended by the development of endothelial dysfunction which is suggested to be accompanied with a chronic low-degree of inflammation. During a chronic hepatic inflammatory response, specific changes in glycosylation of the acute phase protein alpha1-acid glycoprotein (AGP) can be detected. In this report we studied the changes in glycosylation of AGP in more detail and evaluated the relation between a change in glycosylation of AGP and urinary albumin secretion in Type I diabetic patients. The glycosylation of AGP, studied by crossed affinity immunoelectrophoresis (CAIE) and high pH anion exchange chromatography with pulse amperometric detection (HPAEC-PAD), showed an increase in alpha3-fucosylation. Staining with an antibody against sialyl Lewis(x) (sLe(x)) implied that part of the alpha3-fucosylation was present in a sLe(x)-conformation. In the group of Type I diabetic patients with increased urinary albumin excretion, a significant increase in alpha3-fucosylation of AGP (p<0.0005) could be detected. Therefore, the increased alpha3-fucosylation of AGP can be used as an additional marker for the development of vascular complications in Type I diabetic patients.

Adolescent↗
PubMed2001

Steroid hormones stimulate gonadotrophs in juvenile male African catfish (Clarias gariepinus).

In juvenile African catfish (Clarias gariepinus), the pituitary LH content strongly increased after the beginning of spermatogonial proliferation. We hypothesized that a signal of testicular origin is involved in stimulating the gonadotrophs. We investigated the effects of castration and sex steroid treatment on gonadotrophs in juvenile males by quantifying LH production and release and LH subunit transcript levels and by examining gonadotroph morphology and proliferation. Castration reduced but did not abolish the maturation-associated elevation in pituitary LH content. Treatment with testosterone but not with 11-ketotestosterone, an otherwise potent androgen in fish, reversed the castration-induced decrease of pituitary LH levels. An increased pituitary LH content was accompanied by an increased number of cytologically mature gonadotrophs. However, no evidence was found for gonadotroph proliferation, so that quiescent gonadotrophs may have become activated. Although 11-ketotestosterone treatments had no effect in castrated males, this androgen attenuated gonadotroph activation in intact males. Because androgen production in juvenile catfish is downregulated by treatment with 11-ketotestosterone, its inhibitory effects on gonadotrophs in gonad-intact males may be due to suppression of Leydig cell testosterone production, which appears to be a limiting factor for the activation of catfish gonadotrophs. Aromatizable androgens may have opposite effects on fish (stimulatory) and mammalian (inhibitory) gonadotrophs.

Androgens↗
PubMed2001

Specific glycosylation of alpha(1)-acid glycoprotein characterises patients with familial Mediterranean fever and obligatory carriers of MEFV.

BACKGROUND: Familial Mediterranean fever (FMF) is a periodic febrile disorder, characterised by fever and serositis. The acute phase response during attacks of FMF results from the release of cytokines, which in turn induce increased expression and changed glycosylation of acute phase proteins. A recent study indicated that attacks in FMF are accompanied by a rise of plasma concentrations of serum amyloid A (SAA) and C reactive protein (CRP), which remain significantly raised during remission relative to healthy controls. Another study suggested that obligatory heterozygotes also display an inflammatory acute phase response. OBJECTIVE: To determine the state of inflammation in homozygotic and heterozygotic MEFV genotypes. METHODS: CRP and SAA were studied by enzyme linked immunosorbent assay (ELISA). The glycosylation of the acute phase protein, alpha(1)-acid glycoprotein (AGP), was visualised with crossed affinoimmunoelectrophoresis with concanavalin A as diantennary glycan-specific component and Aleuria aurantia lectin as fucose-specific affinity component. RESULTS: FMF attacks were associated with an increase (p<0.05) in the serum inflammation parameters CRP, SAA, and AGP. The glycosylation of AGP showed an increase (p<0.05) in fucosylated AGP glycoforms, whereas the branching of the glycans remained unaffected. The glycosylation of AGP in the MEFV carrier group, compared with that in a healthy control group, was characterised by a significant increase (p<0.05) in branching of the glycans, whereas the fucosylation remained unaffected. CONCLUSION: The findings suggest an FMF-specific release of cytokines, resulting in a different glycosylation of AGP between a homozygotic and heterozygotic MEFV genotype.

Adolescent↗
PubMed2000

GnRH stimulates LH release directly via inositol phosphate and indirectly via cAMP in African catfish.

In African catfish, two gonadotropin-releasing hormone (GnRH) peptides have been identified: chicken GnRH (cGnRH)-II and catfish GnRH (cfGnRH). The GnRH receptors on pituitary cells producing gonadotropic hormone signal through inositol phosphate (IP) elevation followed by increases in intracellular calcium concentration (¿Ca(2+)(i)). In primary pituitary cell cultures of male African catfish, both cGnRH-II and cfGnRH dose dependently elevated IP accumulation, ¿Ca(2+)(i), and the release of the luteinizing hormone (LH)-like gonadotropin. In all cases, cGnRH-II was more potent than cfGnRH. The GnRH-stimulated LH release was not associated with elevated cAMP levels, and forskolin-induced cAMP elevation had no effect on LH release. With the use of pituitary tissue fragments, however, cAMP was elevated by GnRH, and forskolin was able to stimulate LH secretion. Incubating these fragments with antibodies against cfGnRH abolished the forskolin-induced LH release but did not compromise the forskolin-induced cAMP elevation. This suggests that cfGnRH-containing nerve terminals are present in pituitary tissue fragments and release cfGnRH via cAMP signaling on GnRH stimulation, whereas the GnRH receptors on gonadotrophs use IP/¿Ca(2+)(i) to stimulate the release of LH.

Animals↗
PubMed2000

Gonadotropin-releasing hormone fibers innervate the pituitary of the male African catfish (Clarias gariepinus) during puberty.

The development of the catfish gonadotropin-releasing hormone (cfGnRH) fiber network in the pituitary of male African catfish (Clarias gariepinus) was investigated in relation to puberty. Double immunolabeling studied by confocal laser scanning microscopy revealed a concomitant development of gonadotropes and of pituitary cfGnRH innervation during the first wave of spermatogenesis. Catfish GnRH-immunoreactive fibers in the proximal pars distalis (PPD) of the pituitary were initially observed at the age of 10 weeks (onset of spermatogonial proliferation) and gradually reached the adult pattern at the age of 20 weeks (spermatozoa present in the testis). The content of cfGnRH-associated peptide (cfGAP, part of the prohormone) in the pituitary similarly increased during puberty. At the electron microscopical level, fibers containing cfGAP-ir granules came into close proximity of the gonadotropes at 18 weeks of age. In vitro studies indicated a progressively increasing basal and cfGnRH-stimulated luteinizing hormone (LH) secretion during pubertal development. The LH secretion patterns were similar in response to exogenous cfGnRH (0.1 microM) or to endogenous cfGnRH, the release of which was induced by forskolin (1 microM). Castration experiments demonstrated that the innervation of the pituitary with cfGnRH fibers continued after surgery, accompanied by an increase in the cfGAP levels. However, gonadotrope development was retarded, suggesting a differential regulation of the two maturational processes. Since testosterone stimulates both processes, other testicular factors may also be involved. Puberty-associated changes in LH release patterns appear to reflect changes in the GnRH sensitivity and in the pool of releasable LH, while availability of cfGnRH does not appear to be a limiting factor.

Animals↗
PubMed1999

Plasma concentration of C-reactive protein is increased in type I diabetic patients without clinical macroangiopathy and correlates with markers of endothelial dysfunction: evidence for chronic inflammation.

Moderately increased plasma concentrations of C-reactive protein are associated with an increased risk of cardiovascular disease. C-reactive protein, its relation to a low degree of inflammatory activation and its association with activation of the endothelium have not been systematically investigated in Type I (insulin-dependent) diabetes mellitus. C-reactive protein concentrations were measured in 40 non-smoking patients with Type I diabetes without symptoms of macrovascular disease and in healthy control subjects, and in a second group of Type I diabetic patients (n = 60) with normo- (n = 20), micro- (n = 20) or macroalbuminuria (n = 20). Differences in glycosylation of alpha1-acid glycoprotein were assayed by crossed affinity immunoelectrophoresis. Activation of the endothelium was measured with plasma concentrations of endothelial cell markers. The median plasma concentration of C-reactive protein was higher in Type I diabetic patients compared with healthy control subjects [1.20 (0.06-21.64) vs. 0.51 (0.04-9.44) mg/l; p<0.02]. The Type I diabetic subjects had a significantly increased relative amount of fucosylated alpha1-acid glycoprotein (79+/-12% vs. 69+/-14% in the healthy control subjects; p<0.005), indicating a chronic hepatic inflammatory response. In the Type I diabetic group, log(C-reactive protein) correlated significantly with von Willebrand factor (r = 0.439, p<0.005) and vascular cell adhesion molecule-1 (r = 0.384, p<0.02), but not with sE-selectin (r = 0.008, p = 0.96). In the second group of Type I diabetic patients, increased urinary albumin excretion was associated with a significant increase of von Willebrand factor (p<0.0005) and C-reactive protein (p = 0.003), which were strongly correlated (r = 0.53, p<0.0005). Plasma concentrations of C-reactive protein were higher in Type I diabetic patients without (clinical) macroangiopathy than in control subjects, probably due to a chronic hepatic inflammatory response. The correlation of C-reactive protein with markers of endothelial dysfunction suggests a relation between activation of the endothelium and chronic inflammation.

Adult↗
PubMed1998

Inflammation-induced expression of sialyl LewisX is not restricted to alpha1-acid glycoprotein but also occurs to a lesser extent on alpha1-antichymotrypsin and haptoglobin.

Acute and chronic inflammation-induced expression of sialyl LewisX has already been shown to occur on alpha1-acid glycoprotein. We now demonstrate that this phenomenon is not restricted to alpha1-acid glycoprotein but also occurs on two other acute-phase proteins. ie on alpha1-antichymotrypsin and on haptoglobin. The level of expression of sialyl LewisX on these proteins was lower than on alpha1-acid glycoprotein, in all likelihood because alpha1-acid glycoprotein is the only acute-phase protein containing tetraantennary glycans. No expression of sialyl LewisX was detectable on alpha1-protease inhibitor, a protein with a high diantennary glycan content. Non-sialylated LewisX was not detectable on these major acute-phase proteins in any of the conditions studied. This indicates that the majority of the a3-linked fucose residues are present as sialyl LewisX on alpha1-acid glycoprotein, alpha1-antichymotrypsin and haptoglobin. The absolute contribution to the total phenotype in plasma of protein containing this determinant in a multivalent form was highest for alpha1-acid glycoprotein. This leads us to propose that alpha1-acid glycoprotein is, among the acute-phase proteins studied, the one with the highest potential for interference with the extravasation of leukocytes by binding to the selectins.

Acute-Phase Proteins↗
PubMed1998

Sialyl Lewis(x) epitopes do not occur on acute phase proteins in mice: relationship to the absence of alpha3-fucosyltransferase in the liver.

Mice are frequently used in models for the study of immunological processes related to inflammation. Since it is known that the degree of fucosylation of human acute phase proteins (APPs) is altered as a consequence of an inflammatory response, we have undertaken this study to gain more insight into the fucosylation of acute phase proteins as it occurs in mouse liver. Mice carrying the cluster of the three genes encoding human alpha1-acid glycoprotein (AGP), one of the well known APPs, were used and the fucosylation of AGP was assessed. A complete absence of fucosylation on the transgenic human AGP was found, which is in sharp contrast to AGP in human serum, of which a major proportion is normally alpha3-fucosylated. Remarkably, a large proportion of mouse AGP did contain fucose residues. Fucosylation was also detected on another APP, mouse protease inhibitor (PI). Alpha3-fucosylation of the transgenic human AGP can be achieved in vitro, using an alpha3/4-fucosyltransferase (alpha3/4-FucT) isolated from human milk, showing that the glycoprotein is not intrinsically resistant to fucosylation. Upon subsequent measurement of the activities of the possible fucosyltransferases present in liver membranes of parent and transgenic mice, only an N-linked-core alpha6-FucT and no alpha2-, alpha3- or alpha4-FucT activity was detected. This indicates that fucose residues found on the mouse serum proteins AGP and PI, which are synthesized in the liver, are most probably in alpha6-linkage to the core chitobiosyl unit. Interestingly, both alpha6- and alpha3-FucT activity was detectable in human liver membranes. None of the above mentioned findings were influenced by the induction of an acute phase response by administration of bacterial lipopolysaccharide. This study shows that: (a) alpha6-FucT is probably a protein specific-glycosyltransferase, since mouse AGP, but not human AGP, may be used as an acceptor; (b) in contrast to human liver, mouse liver does not express any alpha3-FucT-activity, thereby making the mouse incapable of producing the Sialyl Lewis(x) epitope on APPs, which is an important part of the inflammatory reaction in humans. This last finding indicates that the mouse is not suitable as a model for the study of those phenomena related to inflammation in humans, in which glycosylation of acute phase proteins could play a significant role.

Acute-Phase Proteins↗
PubMed1997

Do synovial fluid acute phase proteins from patients with rheumatoid arthritis originate from serum?

This study was performed in order to gain insight into the occurrence, glycosylation and the possible origin of the acute-phase proteins alpha1-acid glycoprotein (AGP) and alpha1-protease inhibitor (PI) in sera and synovial fluid from patients with rheumatoid arthritis (RA). Therefore paired sera and synovial fluid samples from patients with RA, and paired synovial fluid samples from right and left knees of patients with varying degrees of arthritis were studied. Crossed affinity immunoelectrophoresis (CAIE) was used with concanavalin A and Aleuria aurantia lectin for the detection of the degree of branching and fucosylation, respectively, and the monoclonal CSLEX-1 for the detection of Sialyl Lewis(X) (SLe(X)) groups on AGP. For PI, not only CAIE, but also high-pressure-anion-exchange chromatography with pulsed amperometric detection was used to study the glycosylation. It was established that the concentrations of AGP and PI were increased in the serum of RA patients compared to normal healthy controls, but that the concentration of both proteins, as well as albumin, was significantly lower in synovial fluid than in serum. Furthermore, the type of glycosylation of both AGP and PI found in RA was significantly different from that found in normals, with increased fucosylation, but there were no major differences in the degree of branching of AGP- or PI-glycans in RA, compared to normals. No differences in glycosylation could be established between serum and synovial fluid in RA. For PI an increased fucosylation was found, both in serum and synovial fluid, using both methods of detection, and it could be established that only the alpha1-->3- and not the alpha1-->6-fucosylation of PI was affected by RA. The increased fucosylation of AGP resulted in an increased expression of SLe(X) on AGP-glycans. Since the alpha1-->3-fucosylation of AGP was significantly increased in both serum and synovial fluid from RA patients, and this correlated with systemic but not with local disease parameters, it can be suggested that acute phase proteins in synovial fluid are most probably of hepatic origin.

Adult↗
PubMed1997

Pituitary gonadotrophs are strongly activated at the beginning of spermatogenesis in African catfish, Clarias gariepinus.

Pituitary gonadotrophs were studied in male African catfish between 1 and 37 wk of age using antisera against the LH subunits for immunohistological and radioimmunological purposes, and cRNA probes for in situ hybridization. Immunoreactive material was already detectable at the earliest age examined. In juveniles, the signal for the common glycoprotein alpha subunit (GP alpha) was stronger than that for the LH beta subunit. Accordingly, an excess of radioimmunoassayable GP alpha 100 times that of LHbeta was recorded in the pituitary. Using in situ hybridization, the mRNAs were detected 7 (GP alpha) and 13 (LHbeta) wk after hatching. Detection of LHbeta mRNA coincided with a 300-fold increase in the pituitary content of LHbeta and intact LH, whereas GP alpha increased only 15-fold. The number of gonadotrophs per pituitary and the amount of LH per gonadotroph also increased strongly. The strong, initial increase in pituitary LH levels was always associated with the presence of spermatocytes. However, in a limited number of cases (3 out of 12 fish), the pituitary LH content was low despite the presence of spermatocytes. The number of gonadotrophs, the staining intensities (reflecting protein and mRNA), and the pituitary LH content kept increasing, although at a reduced rate, until completion of the first wave of spermatogenesis. In view of the excess of GP alpha over LHbeta, we conclude that expression of the two subunits is regulated in part by different mechanisms, and that expression of LHbeta is rate-limiting for the amount of intact LH. The strong activation of the gonadotrophs shortly after meiosis opens the possibility that a signal of testicular origin stimulates LH expression, in particular its beta subunit. In the absence of a FSH-like gonadotropin in catfish, we propose that LH covers all functions requiring gonadotropic regulation in the African catfish.

Animals↗
PubMed1996

Glycosylation of alpha 1-acid glycoprotein in septic shock: changes in degree of branching and in expression of sialyl Lewis(x) groups.

The occurrence of differences in acute-phase response, with respect to concentration and glycosylation of alpha 1-acid glycoprotein (AGP) was studied in the sera of patients, surviving or not from septic shock. Crossed affino-immunoelectrophoresis was used with concanavalin A and Aleuria aurantia lectin for the detection of the degree of branching and fucosylation, respectively, and the monoclonal CSLEX-1 for the detection of sialyl Lewisx (SLeX) groups on AGP. Septic shock apparently induced an acute-phase response as indicated by the increased serum levels and changed glycosylation of AGP. In the survivor group a transient increase in diantennary glycan content was accompanied by a gradually increasing fucosylation and SLeX expression, comparable to those observed in the early phase of an acute-inflammatory response. Remarkably, in the non-survivor group a modest increase in diantennary glycan content was accompanied by a strong elevation of the fucosylation of AGP and the expression of SLeX groups on AGP, typical for the late phase of an acute-phase response. Our results suggest that these changes in glycosylation of AGP can have a prognostic value for the outcome of septic shock.

Acute-Phase Reaction↗