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Biomedical subjects

I Molenaar

Publications and source records attributed to I Molenaar.

At least 37 records · Page 2Linked to original sources
PubMed1981

Human brain in tissue cultures. VI. Presence of glial fibrillary acidic protein in subcultivated human fetal brain cells as demonstrated by immunofluorescent and immunoperoxidase staining.

Glial fibrillary acidic protein (GFAP) was present in cell cultures derived from human fetal brain tissue as determined by indirect immunofluorescence (IF) and immunoperoxidase (IP) staining using rabbit anti-human GFAP antisera. The IF and IP techniques were comparable in localizing the cytoplasmic distribution and the frequent perinuclear concentration of GFAP in brain cells. The horseradish peroxidase technique was more sensitive and a 1:20-1:40 dilution of anti-GFAP serum could be applied in the initial step of the peroxidase staining as compared to a 1:10 dilution of anti-GFAP serum for IF staining. Sequential studies of subcultivated human fetal brain cell lines by these techniques indicated that some brain cell lines become GFAP-negative rapidly, whereas other cell lines remain GFAP-positive for no less than ten subcultivations in vitro. GFA protein was never present in any PML-SV40-transformed human brain cells.

Animals↗
PubMed1981

Nutritional myopathy in ducklings: a growth rate-dependent symptom of "tissue peroxidosis' due to a net nutritional shortage of vitamin E plus selenium in skeletal muscle.

Although low dietary vitamin E is an absolute prerequisite for the occurrence of nutritional myopathy in ducklings, it was found that the myopathy can be prevented if the vitamin E depletion does not start before 2 weeks of age and if the dietary selenium content is not too low (greater than 74 ppb). Under these circumstances growth remained normal and the animals stayed alive during the experimental period of 14 weeks, despite low levels of vitamin E in serum, liver, and muscle. The weekly growth rate of the nondeficient duckling, as derived from the growth curve, is extremely high during the first 2 weeks of age with a distinct peak during the 2nd week followed by a steep fall during the 3rd week. In vitamin E-deficient ducklings tissue vitamin E dilution curves were calculated by mathematic transformation of the growth curve. Th results suggest that a critical net nutritional shortage of vitamin E plus selenium in skeletal muscle causes myopathy in ducklings. It is proposed that nutritional myopathy should be considered as a symptom of "tissue peroxidosis' and not as a symptom of vitamin E deficiency per se.

Age Factors↗
PubMed1980

The graft-versus-host reaction in the rabbit spleen. Ultrastructural evidence for two differentiated T-cell lines.

Lethally irradiated (900 rads), bone-marrow-protected rabbits were given allogeneic thymocytes intravenously. Autoradiography by means of local splenic infusion of (H3) thymidine revealed progeny of two differentiated T-cell lines. Electron microscopy confirmed these observations in detail. An analogy with cellular immunity reactions in an "isolated T-cell system", performed in draining lymph nodes after a variety of antigenic stimuli is presented. The functional properties of these T-blasts and their lymphoid descendants are discussed.

Animals↗
PubMed1980

A model for the glomerular filter.

The model for the glomerular filter presented here is based on the relationship between basement membrane collagen and fibrillar collagen. The glomerular basement membrane collagen is produced by the epithelial cell and present on its surface in a staggered organization as in fibrillar collagen. Binding and aggregation of the collagen molecules with a matrix protein results in a large (+/- 50 nm) meshwork controlled by collagen molecules and bound to the cell surface. Because the matrix proteins bind GAGs, the aggregates are recognizable as anionic sites. A continued production of glomerular basement membrane material will cause a movement towards the endothelial side accompanied with a degradation. This degradation results in a loss of carbohydrates, digesting of alpha-molecules in the triple helices and a loss of anionic sites. The loss of carbohydrates leads to cross-linking and narrowing of the meshes in the direction of the endothelial side of the GBM. Final digestion results in fragmented helices which will pass the GBM and probably be reabsorbed by the epithelial cells or which will pass the slit diaphragm. The slit diaphragm, a staggered collagen structure in plane, functions as a bridge between the epithelial foot processes and is able to regulate the flow and pressure.

Animals↗
PubMed1978

Site of initiation of the plasma cell reaction in the rabbit lymph node. Ultrastructural evidence for two distinct antibody forming cell precursors.

Two times sublethal total body-X-irradiation with weekly local thymus irradiation established a T-cell deprived experimental model in rabbits. Humoral immunity reactions in draining lymph nodes have been analyzed histologically and at the submicroscopical level after challenge with Salmonella Java vaccine, horse spleen ferritin, horse-gamma-globulin, a chemical sensitizer oxazolone (2 phenyl-4-ethoxymethylene-5-oxazolone) and after skin allografting respectively. The time sequence studies in these animals with an 'isolated B-cell system' are compared with similar experiments in normal non-irradiated rabbits. The site of initiation of the thymus-independent and thymus-dependent plasma cell response is established in the lymph node. The (ultra)structural features of the antibody forming (-B-)cell precursors, the marginal zone cells, are described and discussed. The differentiating off-spring of two (sub)microscopically recognizable plasma cell lines is presented.

Animals↗
PubMed1978

Electron microscopy of cellular immunity reactions in B-cell deprived rabbits. Thymus derived antigen reactive cells, their micro-environment and progeny in the lymph node.

Three times sublethal total body X-irradiation with thymus shielding--at 14 days' intervals--established an 'isolated T-cell system'. Cellular immunity reactions in draining lymph nodes of rabbits have been analyzed at the ultrastructural level after challenge with horse spleen ferritin, the chemical sensitizer, 2-phenyl-4-ethoxymethylene-5-oxazolone and after skin allografting. A basic pattern of interdigitating cells (IDC) is described as a specific constituent of the thymus-dependent areas of peripheral lymphoid tissue. Their ultrastructural features and presumable functional relationship to the afferent loop of cellular immunity reactions are presented. The differentiation pathway of two T-cell lines is shown and discussed in relation to cellular and thymus-dependent humoral immunity reactions.

Animals↗
PubMed1978

Cells of origin of propriospinal fibers and of fibers ascending to supraspinal levels. A HRP study in cat and rhesus monkey.

In the spinal cord of cat and rhesus monkey the cells of origin of long and short propriospinal fibers and those of the spinal fibers ascending to supraspinal levels were identified by means of retrograde HRP labeling after large unilateral HRP-injections, i.e. in the spinal white and grey matter at different levels, in the pons and in the dorsal column nuclei. The findings indicate the existence of the following arrangement. Long ascending supraspinal fibers arise mainly from neurons in the dorsal grey (laminae I-IV and the medial parts of laminae V and VI) as well as from neurons in the medial part of the ventral grey (lamina VIII), in Clarke's column and in the spinal border cell area. Some neurons in the dorsal grey projects to the dorsal column nuclei, which in turn distribute fibers back to the spinal cord. Long propriospinal fibers mainly derived from neurons in the medial part of the ventral grey (lamina VIII), while short propriospinal fibers are characteristically derived from neurons in the intermediate zone (lateral halves of laminae V and VI and lamina VII). The neurons located laterally in laminae V-VII distribute fibers mainly ipsilaterally, while those located medially in lamina VII distribute them to some degree bilaterally. The findings in cats with transections of either the dorsal or the ventral halves of the spinal white matter (both above and below the injected segment), show that the fibers from the dorsal grey and the lateral parts of laminae V-VII travel mainly through the dorsal half of the white matter, while those from the medial part of lamina VII and from lamina VIII travel mainly through the ventral half.

Afferent Pathways↗
PubMed1978

The use of polyethyleneimine for demonstration of anionic sites in basement membranes and collagen fibrils.

Strong cationic polyethyleneimine (PEI) is used to trace anionic sites in lung, choroid plexus, glomeruli, blood vessels and also on collagen fibrils. In the mentioned tissues, PEI is found in the basement membranes with a spacing identical to that found on collagen fibrils. It is assumed that the acid endgroups of tropocollagen molecules are responsible for the binding of PEI.

Animals↗
PubMed1977

Biochemical and ultrastructural aspects of the inhibited phagocytosis by neutrophil granulocytes in acute brain-damaged patients.

In a study of 60 head-injured patients inhibition of phagocytosis by neutrophil granulocytes was observed over a period of up to 5 weeks. This inhibition of phagocytosis could be correlated with the severity of head injury as well as with the state of unconsciousness at the time of the investigation. No correlation was found between neutrophil granulocyte counts and the inhibition of phagocytosis. A good correlation could be demonstrated between the level of lumbar CSF 5-HIAA and the inhibition of phagocytosis. After in vitro incubation with albumin the cells showed a recovery of phagocytosis. Electron micrographs of the cells showed ultrastructural appearances suggesting a changed permeability of the plasma membrane and, in addition, alterations in the cytoplasmic region beneath the plasma membrane. It is suggested that head injury may influence the pituitary-adrenal system and the autonomic nervous system, giving changes of neutrophil function and of neurotransmitter metabolism; these changes may represent an adaptation mechanism.

Adolescent↗
PubMed1977

Polyethyleneimine as tracer particle for (immuno) electron microscopy.

Polyethyleneimine (PEI) is proposed as a tracer for use in electron microscopical investigations. Relative small molecules are available (molecular weight 600-60,000). PEI is soluble in water; it is not visible in the electron microscope without further treatment, but can easily be detected as a particle by contrastting it with phosphotungstic acid or OsO4. Using PEI of a molecular weight of 40,000, particles of 10 nm diameter can be produced. The strong cationic character of PEI results in electrostatical binding to anionic sites. Hence perfusion and immersion of tissues with PEI of various molecular weights offers possibilities to either study the location of anionic sites or pathways of transport. Anionic sites could be demonstrated in the normal and pathologic glomerular basement membrane. Work on the use of PEI as a marker particle in immunoelectronmicroscopy is in progress.

Animals↗
PubMed1976

Changes of ventricular ependyma and choroid plexus in experimental hydrocephalus, as observed by scanning electron microscopy.

Hydrocephalus was induced in rats by the injection of silicone oil or kaolin suspension into the cisterna magna. One to 5 weeks later the walls of the lateral ventricles were studied with the scanning electron microscope after killing the animals by perfusion fixation. In contrast to controls, the hydrocephalic animals killed 1 or 2 weeks after injection showed degeneration of ependymal cilia and infestation of the ependymal and choroid plexus surface with reactive cells, which presumably may be identified as Kolmer phagocytic cells by their ultrastructural features as studied by the transmission electron microscope. A coating of debris on the surface of the choroid plexus in the hydrocephalic animals possibly bears upon the ciliary degeneration with consequent deficiency of the clearing effect of ciliary movement. In the longer surviving hydrocephalic animals regeneration of cilia seemed to have occurred.

Animals↗
PubMed1976

Selenium in in vitamin-E-deficient diets and the occurrence of myopathy as a symptom of vitamin E deficiency.

The occurrence of myopathy in vitamin-E-deficient ducklings, which is used for the determination of the degree of vitamin E deficiency, is depending on the selenium content of the diet. The selenium content of a semi-synthetic diet and its constituents was determined by neutron activation analysis, which showed to be an adequately sensitive and precise method of analysis for selenium. The casein compound was the main source of the selenium in the diet. Myopathy occurred with diets containing about 50 ppb Se; diets containing about 100 ppb Se failed to induce any signs of myopathy.

Animal Feed↗
PubMed1975

Morphology and size-distribution of sound and acid-treated enamel crystallites.

Citric acid dissolves crystallites of enamel by initially etching out approximately hexagonal holes in the core of the crystallites, parallel to their long axis. Such acid-treatment influences the crystallite diameter only slightly since the distribution of the diameters of crystallites with a hollow core is not essentially different from those found in sound enamel. In both cases, the average diameter is 37 nm. Crystallites having a central defect and an outer diameter of about 40 nm are split into two parts of approximatley 15 nm in diameter following acid treatment. The central defect is caused exclusively by the acid and not by damage from the electron beam, nor by a combination of acid treatment and electron beam damage.

Citrates↗
PubMed1975

The effect of vitamin E deficiency on permeability of mitochondria for phosphate.

We have investigated whether the earlier-found decreased unsaturation in mitochondrial membranes in vitamin E deficiency affects the permeability properties of mitochondria. The iso-osmotic swelling technique was used as a measure for the rate of uptake of substrates by these organelles. A significantly slower uptake could be observed of ammonium malate in the presence of phosphate and of ammonium phosphate. These changes in membrane permeability might give a clue to the mechanism of some metabolic abnormalities as seen in vitamin E deficiency in relating these abnormalities to specific membrane functions, e.g. an affection of carriers; for instance the phosphate carrier.

Ammonium Chloride↗
PubMed1975

Parallel tubular structures in lymphocytes. I. Occurrence in patients with Hodgkin's Disease.

Investigations with the electron microscope on peripheral blood of patients with Hodgkin's disease revealed parallel tubular structures in the cytoplasm of the lymphocytes, similar to those described in the literature. In normal subjects 2-9% of the lymphocytes were found to contain these structures. The number of such lymphocytes is increased in most patients as compared to normals. A correlation between an increase of inclusions containing lymphocytes and the histological or clinical classifications could not be established. An elevation of lymphocytes with tubular structures could be found in both favourable and unfavourable histological and clinical subgroups of Hodgkin patients, but especially in all groups with an unfavourable prognosis. The origin and function of the parallel tubular structures is still unknown, but their increase in lymphocytes of patients with Hodgkin's disease is of some interest in view of the involvement of these cells.

Cell Membrane↗