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Biomedical subjects

W C de Bruijn

Publications and source records attributed to W C de Bruijn.

At least 19 recordsLinked to original sources
PubMed1992

Element analysis of the early stages of age-related macular degeneration.

The accumulation of basal laminar deposit (BLD) in the macula is considered to be a precursor of age-related macular degeneration. To learn more about the composition of BLD and the role of zinc in age-related macular degeneration, we investigated the elements in BLD, as well as in surrounding structures in 38 postmortem human maculae by electron-probe x-ray microanalysis. Basal laminar deposit and capillary vessel walls of the choriocapillaris appeared to contain no typical elements. Calcium, phosphorus, sulfur, zinc, and chlorine were detected in the lipofuscin granules in retinal pigment epithelium. Pigment granules of the retinal pigment epithelium and choroidal melanocytes contained predominantly sulfur and copper and, to a lesser degree, zinc, calcium, and iron. Local calcifications in Bruch's membrane were composed of large amounts of calcium and phosphorus and smaller amounts of zinc, iron, and chlorine. Metal-mirror fixation of the maculae, followed by freeze-drying and vapor fixation, showed additional amounts of sodium and potassium. From these experiments, no conclusions could be drawn about the origin of BLD. No relationship was found between the detection of zinc and the presence of BLD or drusen in the macula.

Adolescent↗
PubMed1992

Comparison of cytosolic products formed in rat liver in response to parenteral and dietary iron loading.

Two different methods were used to create a situation of iron (Fe) overload in rats. One group of rats received Fe dextran, and another group of rats received a carbonyl Fe-enriched diet. The ferritins present in the liver cytosol of these rats were isolated and compared. From each group, two cytosolic products were isolated with the use of ultracentrifugation: a cytosolic ferritin fraction (CF) and a (slower sedimenting) light ferritin fraction (CLF). There were no differences with respect to the protein coat (subunit composition and amino acid analysis). Analysis of the Fe core revealed that the two CF fractions were similar, whereas the two CLF fractions differed with respect to their Fe content and to the packing of their cores. The carbonyl CLF product contained less Fe atoms/molecule, which, moreover, seemed to be packed in a less compact way.

Amino Acids↗
PubMed1992

The role of iron in experimental porphyria and porphyria cutanea tarda.

Porphyria cutanea tarda (PCT) and experimental porphyria are characterized by a decreased activity of the enzyme uroporphyrinogen decarboxylase, and accumulation of uroporphyrins and heptacarboxylporphyrins in the liver. Iron (Fe) plays an important role in PCT and experimental porphyria. Biochemically and electron microscopically, we examined the relationship between Fe and porphyrins in liver tissue of C57BL/10 mice made porphyric by administration of iron dextran as Imferon (IMF), and in liver biopsies of patients with symptomatic PCT. Accumulation of uroporphyrins and heptacarboxylporphyrins, and an increased amount of Fe were observed in livers of mice treated with IMF and in liver biopsies of patients with PCT. In mice treated with IMF, the activity of uroporphyrinogen decarboxylase was decreased. Both in livers of mice treated with IMF and in livers of patients with PCT, needle-like structures, representing uroporphyrin crystals, were observed by electron microscopy. Uroporphyrin crystals and Fe (as ferritin) were observed in the same hepatocyte. Moreover, there was a striking morphological correlation between uroporphyrin crystals and ferritin-Fe, suggesting a role for (ferritin-)Fe in the pathogenesis of porphyria.

Animals↗
PubMed1992

The effect of two new semi-synthetic glycosaminoglycans (G871, G872) on the zeta potential of calcium oxalate crystals and on growth and agglomeration.

The effects of two new semisynthetic glycosaminoglycans (GAGs), G871 and G872, on the crystal growth and agglomeration of calcium oxalate monohydrate (COM) were studied in artificial urine in vitro. A constant composition crystallization system and a seeded crystal growth system were used to measure the rate of crystal growth and degree of agglomeration. The zeta potential on the crystal surface was measured using a Coulter DELSA 440 doppler electrophoretic light scattering analyzer. The previously reported GAG analogue, sodium pentosan polysulphate (SPP or SP54), was studied as a reference inhibitor of crystallization using the same systems. All three substances had a concentration-dependent effect on the zeta potential and on the rate of crystal growth and agglomeration of COM in artificial urine. G872 had a significantly greater effect than either G871 or SPP on all the measured parameters. It is suggested that semisynthetic GAGs, such as those reported in this paper may be of use in the prevention of the recurrence of calcium oxalate stones.

Calcium Oxalate↗
PubMed1992

Histologic features of the early stages of age-related macular degeneration. A statistical analysis.

The age distribution, frequency, and correlation among histologic macular changes, including formation of a basal laminar deposit, drusen, and thickening and calcification of Bruch's membrane, were studied by light microscopy. The authors studied 182 unpaired postmortem human maculae from patients between 8 and 100 years of age. In addition, 45 maculae of contralateral eyes and the peripheral retina of 50 eyes were studied. In 92%, Bruch's membrane was thickened starting at age 19, and calcifications in this membrane were found in 59% starting at age 33. In 37% of the maculae, hard drusen were found starting at age 34. Soft drusen were found in 10% beginning at age 54. Basal laminar deposit was found in 39% of the maculae starting at age 40. All changes correlated strongly with age (P less than 0.0001). No sex differences were found. Fellow eyes showed similar aging changes (P less than 0.001). The presence of basal laminar deposit in the macula correlated with basal laminar deposit-like material in the peripheral retina (correlation coefficient, 0.39; P less than 0.003), whereas drusen in the macula correlated with drusen in the peripheral retina (correlation coefficient, 0.42; P = 0.001). Geographic atrophy was found in 6.6% of the eyes from subjects older than 70 years and subretinal neovascularization in 3.8%, especially in the maculae with basal laminar deposit.

Adolescent↗
PubMed1992

Correspondence analysis for quantification in electron energy loss spectroscopy and imaging.

Electron energy loss spectroscopy (EELS) is a technique to investigate the physical properties of material. Using this technique it is possible to detect the presence of a specific element in a specimen. When used in combination with an electron microscope, energy filtered images may be obtained, which in principle may be used to quantify the local element concentration. This involves a process of background correction, conventionally performed assuming a specific parametric behavior of the spectral intensity as a function of electron energy loss. In this article a parameter-free method is described for background correction based on the formalism of correspondence analysis. Such a method may be used in parts of the spectrum where the functional dependence of the spectral intensity is unknown. Use of this method for element detection has been suggested before. This article reports simulation experiments suggesting its suitability for quantitative determination of element distributions and element concentrations.

Image Processing, Computer-Assisted↗
PubMed1991

Is basal laminar deposit unique for age-related macular degeneration?

The ultrastructural nature and distribution of basal laminar deposit, considered to be a precursor of age-related macular degeneration, were studied in 42 human maculae. Basal laminar deposit was found from age 19 years on, not only between the retinal pigment epithelial cells and their basement membrane but also more often on the choriocapillary side of Bruch's membrane. No direct relationship was found with other aging changes, such as calcifications in Bruch's membrane, accumulation of lipofuscin granules, or drusen in the macular area. Material similar to basal laminar deposit can be found in the trabecular system, in the cornea, and also in many other organs and tissues. On a structural and morphometrical basis, we think that basal laminar deposit is similar to fibrous long-spacing collagen and thus does not seem to be a purely ocular abnormality.

Adolescent↗
PubMed1991

Morphometry, densitometry and pattern analysis of plastic-embedded histologic material from urothelial cell carcinoma of the bladder.

An image analysis method of grading histologic sections of bladder carcinoma was tested. The method was new in four respects. First, for fixation of the biopsies a coagulant fixative was used. Second, 2-microns plastic sections were used to ensure the reproducibility of nuclear imaging. Third, a new stereologic approach was used for calculation of the nuclear volume and DNA content. Fourth, for the classification rule the morphometric, densitometric and texture features were used in concert. The IBAS 2000 instrument was used for the measurements. Texture analysis of the chromatin patterns was performed using Markovian texture features. Using discriminant analysis, of 22 parameters, 2 morphometric, 2 densitometric and 3 texture features were selected for the classification rule. With them, 89% of the bladder carcinomas were correctly classified into the three grades. All grade III tumors were classified correctly. Among the features tested, the densitometry of the DNA had the highest F values. All of the grade III tumors and 45% of the grade II tumor group had DNA histograms indicating aneuploidy. This study showed that plastic-embedded material is well suited to morphometry and densitometry and can be used for quantitative grading of bladder carcinoma.

Carcinoma, Transitional Cell↗
PubMed1991

Iron and uroporphyrin in hepatocytes of inbred mice in experimental porphyria: a biochemical and morphological study.

UNLABELLED: Hexachlorobenzene-induced porphyria is iron dependent and characterized by the decreased activity of uroporphyrinogen decarboxylase and the accumulation of porphyrins in the liver. To examine the relationship between iron and porphyrins in liver tissue, we performed a biochemical and morphological (histological, ultrastructural and morphometrical) study in the livers of C57BL/10 mice. Mice were treated with hexachlorobenzene, iron dextran or the combination of hexachlorobenzene and iron dextran. An accumulation of porphyrins and an increased total iron content were found not only in the livers of mice treated with hexachlorobenzene and iron dextran but also in mice treated with iron dextran alone. In contrast, the amount of porphyrins was only slightly increased in the livers of mice treated with hexachlorobenzene alone. Needle-like structures, representing uroporphyrin crystals, were observed, histologically and ultrastructurally, in hepatocytes of mice treated with hexachlorobenzene and iron dextran and with iron dextran alone. Uroporphyrin crystals and ferritin iron were found in the same hepatocyte. A single uroporphyrin crystal, surrounded by ferritin iron, was observed in a hepatocyte of a mouse treated with hexachlorobenzene alone. Both in the livers of mice treated with hexachlorobenzene and iron dextran and in the livers of mice treated with iron dextran alone, morphometrical analysis showed that an increased area fraction of uroporphyrin crystals was associated with an increased area fraction of ferritin iron in hepatocytes. CONCLUSIONS: In C57BL/10 mice, experimental porphyria can be induced by iron overload alone; uroporphyrin crystals and ferritin iron are located in the same hepatocyte; and the morphological co-occurrence of uroporphyrin crystals and ferritin iron in hepatocytes suggests a role for iron (as ferritin) in the pathogenesis of porphyria.

Animals↗
PubMed1990

Ultrastructural localization of calcium and Ca(2+)-ATPase activity in gonadotropes and stellate cells of the catfish pituitary.

In the pituitary of the African catfish, Clarias gariepinus, calcium precipitates were ultrastructurally visualized with the oxalate-pyroantimonate procedure (OPP). The presence of calcium in these precipitates was validated with several methods, including "Electron Energy Loss Spectrometry" (EELS). In the OPP-treated tissue calcium precipitates were seen in a) non-secretory stellate cells and b) gonadotropic (GTH-) cells. In the latter the amount of precipitate is generally low, but stimulation of the gonadotropin release, either in vivo or in vitro, resulted in a considerable increase. This increase is discussed in relation to the role of calcium as second messenger in the GTH-cells. Ca(2+)-ATPase was exclusively represented in stellate cells and GTH-cells, its strongest activity associated with the plasma membrane and with the membranes of the endoplasmic reticulum. The localization of this enzyme is discussed in relation to its role in the regulation of the intracellular calcium concentration in the GTH-cells. The stellate cells are considered to be involved in the regulation of extracellular calcium concentrations in the pituitary.

Animals↗
PubMed1990

Analysis of iron-containing compounds in different compartments of the rat liver after iron loading.

The livers of iron-loaded rats were fractionated and a cytosolic fraction, a lysosomal fraction, a siderosomal fraction and haemosiderin were obtained. All iron-containing compounds from these fractions were isolated and their morphology, Fe/P ratios, iron core diameter and peptide content were compared. The cytosolic fraction contained ferritin (CF) and a slower sedimenting, light ferritin (CLF). The lysosomal fraction also contained ferritin (LF) and a slower sedimenting light ferritin (LLF). The siderosomal fraction contained ferritin (SF), a faster sedimenting non-ferritin iron compound (SIC) and haemosiderin (HS). SIC and HS did not resemble ferritin as much as the other products did, but were found to be water-insoluble aggregates. The Fe/P ratios of CF and CLF were lower than the Fe/P ratios of LF and LLF and these in turn had lower Fe/P ratios than SF, SIC and HS. The iron core diameter of the cytosolic ferritin was increased after lysosomal uptake. The iron core diameters of the siderosomal products were smaller. CLF, CF, LF, LLF and SF contained one kind of subunit of approximately 20.5 kDa. SIC and HS contained other peptides in addition to the 20.5-kDa subunit. The results indicate that storage of ferritin molecules is not limited to the cytosolic compartment, but is also the case in the lysosomes. Extensive degradation of the ferritin molecule seems to be confined to the siderosomes.

Animals↗
PubMed1989

Effect of phlebotomy on the ferritin iron content in the rat liver as determined morphometrically with the use of electron energy loss spectroscopy.

Phlebotomy of untreated and iron-loaded rats results in a significant decrease in total liver iron. In iron-loaded rats a marked decrease in iron-containing particles is observed ultrastructurally in lysosomes and cytoplasm of hepatic sinusoidal cells but not in parenchymal cells. This remarkable phenomenon was further investigated in a morphometric study, based on element-specific (iron) distribution images made in situ in the parenchymal cell by means of electron energy loss spectroscopy. With the use of this technique it could be shown that in spite of phlebotomy the ferritin iron content of the iron-loaded liver parenchymal cell is not decreased.

Animals↗
PubMed1989

Ultrastructural electron probe X-ray microanalytical reaction product identification of three different enzymes in the same mouse resident peritoneal macrophage.

Simultaneous cytochemical enzyme localization procedures for peroxidase (PO) plus acid phosphatase (AcP-ase) and/or aryl sulphatase (AS) have been investigated at the ultrastructural (EM) level. Electron probe X-ray microanalysis (EPMA) will identify and differentiate the reaction products. Dual reaction product localization of PO plus AcP-ase or alternatively PO plus AS have been obtained in the same mouse resident peritoneal macrophage. This has been acquired by first performing a PO-reaction followed by AcP-ase or followed by AS. In both cases PO-related reaction products (PODAB/Os or PODAB/Pt) were localized in nuclear envelope (NE) and rough endoplasmic reticulum (RER). Cells were identified by this reaction product as resident macrophages. Reaction products from the AcP-ase related cerium (AcP-aseCe), localized in lysosomes have been identified and differentiated from the PO-related osmium containing products. Similarly AS related barium (ASBa), localized in lysosomal structures and (R)ER was identified and differentiated. Triple reaction product localization of PO followed by AcP-ase plus AS could also be obtained. In this case, PO-related platinum containing reaction products (PODAB/Pt or PODAB/Os) in NE and RER has been identified and differentiated from the AcP-ase related lysosomal cerium (AcP-aseCe) and the AS related barium localized in lysosomal and (R)ER structures. Reversing the sequences in both dual cytochemical procedures: AcP-aseCe or ASBa followed by PODAB/Os (or PODAB/Pt) resulted in AcP-aseCe or ASBa activity related reaction products only. Reversing the sequence in the triple reaction procedures (ASBa followed by AcP-aseCe) resulted in the absence of the barium containing reaction products. By application of OsO4 postfixation with aminotriazole (ATR) additives the detrimental effects upon the various precipitates have been confirmed. In LM studies, using rat intestine and non-metal identification reactions for two of the enzymes (pararosaniline for AcP-ase, DAB for peroxidase), the influences of the metal ions used in EM were tested on the appearance of the coloured reaction products. Cerium ions used in EM for detection of AcP-aseCe activity have been shown to influence the PODAB visibility in LM and EM experiments. From the AS reaction media components neither barium ions nor p-nitro catachol sulphate influenced the LM visibility of the PO reaction.

Acid Phosphatase↗
PubMed1989

Studies on ferritin in rat liver and spleen during repeated phlebotomy.

1. The ferritin content of liver and spleen in normal and iron-loaded rats decreased during repeated phlebotomy. 2. During increased iron demand, ferritin is degraded in toto. 3. With the ESI and EELS technique the iron distribution was followed in different cell types and cellular compartments. 4. We have demonstrated two methods of iron mobilisation: (a) catabolism of lysosomal ferritin in toto and (b) delivery of ferritin from parenchymal cell into the bile and degradation of ferritin in toto.

Animals↗
PubMed1988

Descriptive light and electron microscopy of normal and clue-cell-positive discharge.

In women with clue-cell-positive discharge (CCPD), light-microscopical examination of the wet mount suggests a preference of bacteria for certain vaginal epithelial cells (VECs). To investigate this further, a light- and electron-microscopical study of patients and healthy controls was performed, with special emphasis on vitality and glycogen content of VECs and bacterial-epithelial cell interaction. Our study did not reveal morphologic differences between VECs of patients and controls. There was, however, a significant decrease in the percentages of vital and glycogen-containing VECs in CCPD (p less than 0.001), probably caused by an overgrowth of (anaerobic) bacteria. In CCPD vaginal bacteria preferably colonize vital VECs. This could account for the relatively low percentage of clue cells in this condition.

Female↗
PubMed1988

Extraneous background-correction program for matrix bound multiple point X-ray microanalysis.

A program is described that allows on-line determination of extraneous background in multiple point X-ray microanalytical matrices. The program is based upon the calculations of the extraneous background for the film (when present), the standard and the unknown by (100 sec.) point analysis. The program searches for a peak-free part of the spectrum in which the calculated value for the extraneous background is about equal to the value in this region of the spectrum (= be). On-line the contents of this be-region is subtracted from an unmanipulated continuum region in the vicinity of the element present in the unknown and standard (Pt). During the subsequently performed matrix analysis two arrays are acquired (P-b) and (b-be). From these two arrays, the Rx,st and subsequently the Rx,sp are calculated per pixel, which are converted to (be corrected) concentration arrays. In addition Z2/A-differences between standard and the analyzed specimen are corrected off-line. For each pixel the program judges whether the calculated concentration deviates from the value introduced for the standard. Once differences are registered, adequate corrections are made.

Animals↗
PubMed1987

An improved procedure for the X-ray microanalysis of acid phosphatase activity in lysosomes.

The useful detection of acid phosphatase activity with cerium as a capturing agent is confirmed. By introducing a freeze step in combination with a preincubation, reliably localized, lysosomal precipitates are obtained and aspecific ones prevented. Short (t less than 1 h) postfixation with either OsO4 plus K4Fe (CN)6 or OsO4 plus aminotriazole, added to lysosomal cerium localization a high membrane contrast. The detection of cerium by X-ray microanalysis is improved by a better spectral separation of the osmium (M alpha) and cerium (L alpha) peaks.

Acid Phosphatase↗