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Biomedical subjects

G F Vrensen

Publications and source records attributed to G F Vrensen.

At least 91 records · Page 5Linked to original sources
PubMed1992

Effects of human epidermal growth factor on endothelial wound healing of human corneas.

Paired human donor corneas (age, 73 +/- 12 yr), preserved in organ culture medium, were used to evaluate the effect of human epidermal growth factor (hEGF) on endothelial wound closure rate (WCR), on morphometric parameters (cell size, shape, and density), and on cell division in the wound area. The endothelium of the corneas was mechanically wounded (area, 4.9 +/- 0.9 mm2). For each pair, one cornea was treated with 10 ng/ml hEGF, while the mate served as control. WCR was assessed by daily staining of the corneas with trypan blue. Morphometric data were obtained after alizarin staining. Mitotic activity was assessed using 3H-thymidine autoradiography. Addition of hEGF significantly increased the WCR compared to the control group. In the closed wound (between 4-9 d), the mean cell size in the center averaged 1940 microns2 in the control group and 1287 microns2 in the hEGF-treated group (P less than 0.01). Fifteen days after wounding, the mean cell sizes averaged 1910 microns2 and 1427 microns2 in the control and hEGF-treated group, respectively (P less than 0.01). All corneas exposed to hEGF had higher endothelial cell densities than the control corneas. In the early stages of wound closure, the cells in the transitional zone in hEGF-treated corneas had a somewhat more elongated shape. However, hEGF did not affect the final cell shape within the closed wound. Autoradiographic results revealed that hEGF accelerated DNA-synthesis, although only to a limited extent. The results indicate that, in human corneas, hEGF promotes endothelial wound healing predominantly by cell migration, at least in corneas from senior donors.

Adult↗
PubMed1991

Ultrastructural identification of trigeminal nerve terminals in the pterygopalatine ganglion of rats: an anterograde tracing and immunohistochemical study.

Trigeminal nerve terminals in the rat pterygopalatine ganglion (PPG) were ultrastructurally identified using anterograde tracing with Phaseolus vulgaris-leucoagglutinin (PHA-L). Electron microscopic immunohistochemistry was used to demonstrate the presence of substance P (SP) and calcitonin gene-related peptide (CGRP) in nerve terminals of the PPG. Adjacent to the rostral part of the PPG an additional minor area was described. Perikarya in this minor rostral part were more spherical and had irregular outlines. Ultrastructurally, the glial enwrapment of the nerve terminals seemed to be more loosely arranged in comparison to that in the major rostral part of the PPG. With PHA-L, numerous labelled nerve fibres and terminals were found in all parts of the PPG. The ultrastructure of these terminals was uniform, many of them showing synaptic contacts. Numerous terminals in the PPG were SP-positive, whereas only a few were CGRP-positive. Fibres stained positive for both neuropeptides. The PPG is shown to be synaptically innervated by sensory fibres arising in the trigeminal ganglion, with the strong suggestion of SP and CGRP acting as neurotransmitters. A modulatory interaction between the autonomic and sensory system, resembling an axon reflex mechanism in the peripheral nervous system is endorsed.

Animals↗
PubMed1991

Nuclear breakdown during terminal differentiation of primary lens fibres in mice: a transmission electron microscopic study.

The pre and post-natal development of wild type mouse lenses was studied by transmission electron microscopy, with special emphasis on denucleation of primary lens fibres. Denucleation of primary fibres is characterized by nuclear accumulation of small granules, most likely nucleosomes, which are condensed to osmiophilic bodies in the nucleus and in the cytoplasm. The osmiophilic bodies are laid down in apposition to the fibre membrane and are invaded by vesicles and granules, which probably contain proteolytic enzymes. Part of the breakdown products are extruded into the extracellular space, transported to the anterior and posterior poles where they might be finally digested or discarded from the lens. The morphology of the denucleation process of primary fibres is different from the gradual fading of nuclei in secondary fibres as described by Kuwabara and Imaizumi (1974: Invest. Ophthalmol. Vis. Sci. 13, 973-81).

Animals↗
PubMed1991

Age-related changes in local water and protein content of human eye lenses measured by Raman microspectroscopy.

The Raman microspectroscopic method was used to determine the local water and protein content in human lenses. In 18 lenses of varying age position-defined water/protein content measurements were carried out along the visual and the equatorial axis. A main characteristic of the human lens is its constant and relatively low protein content. In addition this constant nuclear value is reached within a short distance from the capsular surface. For statistical analysis of age-related changes the data points in individual lenses were piecewise linearized. (1) The mean nuclear water content was calculated from the data points in the inner 80% of the visual axis. (2) The steep drop in water content was linearized using a least-squares linear regression approach. The distance between lenticular surface and the intersection of the regression line with the line representing the nuclear mean was denominated as surface layer width. It proved that: (i) the mean nuclear water content significantly increased with age, (ii) the width of the surface layer was age independent in the anterior and posterior poles of the visual axis, and (iii) in the equatorial axis the surface layer width significantly decreased with age. Seven human lenses with small opaque spots were also investigated. The opaque spots proved to have a normal-for-site water content and some of them were flanked at their capsular side by a zone with a high-for-site water content.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Morphologic effects of bacteriochlorin a and light in vivo on intraocular melanoma.

To study the development of tissue and cell damage, the early morphologic changes induced by photodynamic therapy (PDT) with the new photosensitizer bacteriochlorin a (BCA) were investigated in Greene hamster melanoma implanted in the anterior eye chamber of white rabbits up to 24 hr after BCA-PDT, using light and electron microscopy. Immediately after BCA-PDT, intracellular spaces were enlarged, and blood vessels were clotted with swollen erythrocytes. By electron microscopy, it was found that some mitochondria had fused inner and outer membranes, and the cristae mitochondriales were affected. With time, the severity of the tissue and cell damage increased, leading to almost complete tumor necrosis after 24 hr. The direct mitochondrial damage and the vascular damage induced by BCA-PDT probably both contribute to tumor necrosis.

Animals↗
PubMed1990

Pre- and post-ganglionic nerve fibres of the pterygopalatine ganglion and their allocation to the eyeball of rats.

The origin, course and distribution of pre- and postganglionic neurons of the pterygopalatine ganglion (PPG) in the rat were studied using acetylcholinesterase staining, wheat germ agglutinin coupled to horseradish peroxidase (WGA-HRP) histochemistry and autoradiography. These methods were used in a selected and planned fashion to reveal details concerning the innervation of the lacrimal gland and portions of the eye. The PPG in rats consists of a rostral triangular portion and additional perikarya surrounding the distal part of the major petrosal nerve. Fibres from the superior cervical ganglion (SCG) reach the PPG via the inferior petrosal sinus. Application of WGA-HRP was made after transections: (1) rostral to the PPG; and (2) caudal to the PPG. The first of these applications labelled mainly fibres in the PPG; the second application labelled preganglionic parasympathetic brainstem neurons dorsolateral to the facial nucleus (i.e. the lacrimal nucleus), rostral cells in the SCG and trigeminal sensory fibres. WGA-HRP injections of the lacrimal gland, the conjunctiva and the anterior chamber of the eye all labelled cells in different parts of the PPG. This means that the PPG contains sensory and sympathetic nerve fibres and that the PPG has a topographical organisation along the rostrocaudal axis. Isotope injections of the PPG anterogradely labelled fibres passing through the ciliary ganglion that innervated the conjunctiva, the limbus and parts of the choroid.

Acetylcholinesterase↗
PubMed1990

Fluorophotometric assessment of blood-retinal barrier function after white light exposure in the rabbit eye.

Fluorophotometry was performed in 14 rabbits after exposure of one eye to white light with an energy insufficient to cause visible phototoxic retinal damage as determined by ophthalmoscopy and fundus photography. Fluorescence measurements in the vitreous were performed before and 1 hr after i.v. injection of fluorescein. Ratios between the fluorescein concentrations in the exposed and in the non-exposed fellow eye were calculated after correction for the autofluorescence. The average ratio directly after light exposure had significantly increased (P = 0.005) as compared to pre-exposure values and was maximal one day after exposure (P less than 0.005). Four days after exposure the ratios had returned to pre-exposure values (P greater than 0.05). A significant linear correlation between age and the ratios directly after exposure was found (r = -0.67; P less than 0.01). Signs of phototoxic retinal damage were not found on ophthalmoscopy and fundus photography, nor on light and electron microscopic examination of the retinal pigment epithelium, neuro-retina or retinal capillaries 1 and 4 days after light exposure. A fluorophotometric assessment of the blood-retinal barrier (BRB) function after white light exposure appeared to be a more sensitive parameter of light-induced damage than morphological examination since light exposures at retinal irradiance levels below the threshold for ultrastructural damage resulted in a temporary BRB dysfunction that could be detected by fluorophotometry but not by the other methods.

Animals↗
PubMed1990

Inherited syndrome of microcephaly, dyskinesia and pontocerebellar hypoplasia: a systemic atrophy with early onset.

A neurodegenerative disease is reported in 5 related families, belonging to a Dutch genetic isolate. Seven children (5 females, 2 males) had microcephaly, spastic pareses, severe extrapyramidal dyskinesia and failure to acquire any voluntary skills. Four died during childhood. Marked pontocerebellar hypoplasia and progressive cerebral atrophy were found by computed tomography of the brain. Autopsy in one case revealed widespread, progressive loss of neurons affecting the olivopontoneocerebellar system more severely than any other part of the brain, accounting for the macroscopic pontocerebellar hypoplasia. A neocortical biopsy from another patient indicated that rough endoplasmic reticulum in neurons as the earliest ultrastructural target of the pathological process. This study confirms the disease as an inherited neuronal degeneration with very early, probably prenatal onset.

Atrophy↗
PubMed1990

Crystalline cataract and uncombable hair. Ultrastructural and biochemical findings.

A 7-year-old girl was found to have a progressive axial crystalline cataract located in the embryonal, fetal, and infantile nucleus. She also had the unknown association of crystalline cataract with uncombable hair. Samples of the aspirate after extracapsular cataract extraction (ECCE) showed elongated, trigonal crystals on scanning electron microscopy. On transmission electron microscopy, the crystals were surrounded by a membrane sometimes consisting of up to 30 concentric layers. The crystals were found to contain carbon, oxygen, nitrogen, sulfur, and disulfide bonds. The findings suggest that a major constituent of the crystals was a sulfur-containing aminoacid, probably cystine. Protein analysis of the remaining lens material showed elevated alpha-, beta 2-, and gamma 2- crystallin levels. Analysis of the hair root status showed hair loss in the resting phase of the hair cycle with abnormal sheathing in most hairs that were in the growth phase.

Cataract↗
PubMed1990

Early morphogenesis of persistent hyperplastic tunica vasculosa lentis and primary vitreous. A transmission electron microscopic study.

This report provides transmission electron microscopic observations on the early pathogenesis of persistent hyperplastic tunica vasculosa lentis/persistent hyperplastic primary vitreous (PHTVL/PHPV) in affected canine fetuses at days 28-44 postcoitum. The retrolental tissue by which this anomaly is characterized consists of loosely arranged fibroblasts in a randomly oriented meshwork of collagenous fibrils. Some of these cells contain melanosomes at day 44. In one day-44 eye, cells of neuroectodermal origin (Müller cells; fibrous astrocytes) were observed. From day 37 onward, the posterior subcapsular part of the lens contains rounded, increased intercellular spaces, resembling vacuoles, which deform the shape of the lens fibers. The posterior lens capsule develops normally until day 30. From day 35 onward the capsule has an amorphous ultrastructure, as opposed to the clearly laminated ultrastructure in reference eyes at day 35. In addition, the capsule's thickness increases until day 35, and, instead of growing thicker, decreases thereafter. Based on these results, it is hypothesized that a primary metabolic disorder in the lens fibers, subsequently leading to the formation of an abnormal posterior lens capsule, constitutes the primary defect in the sequence of events leading to PHTVL/PHPV.

Animals↗
PubMed1989

The allocation of nerve fibres to the anterior eye segment and peripheral ganglia of rats. I. The sensory innervation.

The distribution of sensory trigeminal nerve fibres in the anterior eye segment and the autonomic eye related ganglia, i.e. the parasympathetic ciliary and pterygopalatine ganglia and the sympathetic superior cervical ganglion, was studied in rats. For this the trigeminal ganglion was injected with tritiated leucine and wheat germ agglutinin coupled to horseradish peroxidase (WGA-HRP). After injection of WGA-HRP into the trigeminal ganglion, ganglion cell somata in the superior cervical and the pterygopalatine ganglion were labelled. As labelling of these cell bodies with WGA-HRP is the result of retrograde transport it must be assumed that cell bodies in these ganglia project to the trigeminal ganglion. [3H]Leucine injection into the trigeminal ganglion revealed the presence of labelled nerve fibres in the pterygopalatine ganglion and the nodose ganglion i.e. the sensory ganglion of the vagus nerve. Labelled nerve fibres were absent in the ciliary and superior cervical ganglion. As [3H]leucine labelling of nerve fibres is the result of anterograde transport exclusively, it can be concluded that trigeminal nerve fibres project to the nodose ganglion and the pterygopalatine ganglion, but not to the ciliary and superior cervical ganglion. In the retrobulbar structures, sensory nerve fibres occurred between the inferior oblique and the lateral rectus muscle and were present medial to the medial rectus muscle. Within the anterior eye segment, sensory nerve fibres were found in the cornea epithelium, stroma and adjacent to the endothelium. In addition, labelled fibres were found in the anterior stroma of the ciliary body, throughout the iris up to the pupillary border and in the conjunctiva. Most sensory nerve fibres which innervate the cornea, the iris and the ciliary body traverse the ciliary cleft.

Animals↗
PubMed1989

The allocation of nerve fibres to the anterior eye segment and peripheral ganglia of rats. II. The sympathetic innervation.

The sympathetic innervation of the peripheral ganglia related to the eye, i.e. the trigeminal ganglion, the ciliary ganglion and the pterygopalatine ganglion, and of the anterior eye segment was studied in rats. Selective labelling of sympathetic nerves was obtained by means of injection of [3H]leucine into the superior cervical ganglion. Bundles of sympathetic nerve fibres were found in the trigeminal ganglion and the pterygopalatine ganglion but were absent in the ciliary ganglion. In addition individual sympathetic nerve fibres, which may have contacts with trigeminal ganglion cells, were found between the ganglion cell bodies all over the trigeminal ganglion indicating a sympathetic innervation of this ganglion. In the anterior eye segment, there appeared to be a sympathetic innervation of the ciliary cleft, the ciliary body and the iris. Within the ciliary body sympathetic nerve fibres innervate the central stroma and the stroma of the ciliary processes. Labelled sympathetic nerve fibres were also observed in the stroma of the iris and were most abundant in its periphery. Most sympathetic fibres reach the iris and ciliary body by way of the base of the ciliary body. Only few sympathetic fibres are present in the ciliary cleft. No sympathetic innervation of the cornea was found.

Adrenergic Fibers↗
PubMed1989

Satellite cells as blood-ganglion cell barrier in autonomic ganglia.

In a preliminary study a difference in the uptake and transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) between the trigeminal ganglion and the superior cervical ganglion was observed. After injection of WGA-HRP and HRP into the trigeminal ganglion, peroxidase was found in the space between the satellite cell processes and the ganglion cells. The ganglion cells showed pinocytosis and uptake of WGA-HRP and HRP. In the superior cervical ganglion WGA-HRP and HRP were found alongside the satellite cells but were absent in the space between satellite cells and ganglion cells. Intravenous injection revealed the presence of HRP in the space between sensory ganglion cells and their satellite cells of the trigeminal and nodose ganglion whereas HRP was absent in the space between autonomic ganglion cells and their satellite cells of the superior cervical, medial cervical and pterygopalatine ganglion although HRP lined the satellite cell membranes. By means of electron microscopy, satellite cell processes in the superior cervical ganglion were found to enwrap ganglion cells very tightly with a marginal space between both cell types. Satellite cells and their processes were mutually anchored by numerous tight junctions. In the trigeminal ganglion the extracellular space between ganglion cells and satellite cells was larger and satellite cells were found to be more loosely arranged around the ganglion cells. Satellite cell processes were only occasionally linked by tight junctions. It is concluded that satellite cells in autonomic ganglia comprise an effective barrier for WGA-HRP and HRP and probably large molecules in general. This barrier is absent in sensory ganglia.

Animals↗
PubMed1989

Local variation in absolute water content of human and rabbit eye lenses measured by Raman microspectroscopy.

Raman spectra were obtained from fresh, fixed and sliced rabbit lenses and from human lens slices. For all lenses and lens slices the ratio R, defined as the Raman intensity at 3390 cm-1 divided by the Raman intensity at 2935 cm-1, was measured at different locations along the visual and equatorial axis. The ratios R were transformed to absolute water mass percentages by measuring solutions with known protein concentrations. It was shown that fixation and slicing have very little effect on the absolute water content of the lenses. The values obtained for the absolute water content are comparable to values given in literature. It was also shown that the water content in rabbit and human lenses rapidly decreases from the immediate anterior and posterior subsurface region to the deep superficial cortex and is relatively constant in the nucleus. Raman microspectroscopy appears to be a reliable method for the measurement of the absolute water content of small volumes on defined positions in the lens. This can be very useful when analyzing the possible relation between local variations in water content and the occurrence of opacities in the lens.

Animals↗
PubMed1989

Raman microspectroscopy of fixed rabbit and human lenses and lens slices: new potentialities.

Raman spectroscopy is a non-invasive, non-destructive technique for the study of the macromolecular composition of tissues. Raman spectra were obtained from intact fresh and paraformaldehyde fixed rabbit lenses and from thin slices prepared from these lenses. In addition the Raman spectrum of an intact 82-yr-old human lens was compared with a slice of the same lens. It appeared that fixation with paraformaldehyde had only a minor qualitative effect on the Raman spectra and that Raman spectra of intact lenses and lens slices were comparable. It was also shown that in the slice of the old human lens the fluorescence, due to chromophores, could be reduced so that a reliable Raman spectrum could be obtained. The use of slices improves the accuracy of the position at which Raman spectra are recorded and fixation extends the time available for Raman analysis which is particularly important for the study of human lenses. Moreover, slicing enables Raman analysis of old human lenses, which up to now was thought to be impossible due to the overwhelming fluorescence of the chromophores present in these lenses.

Aged↗
PubMed1989

Free running Neodymium-YAG laser coagulation of the human fovea. A light and electron microscopic study.

Free Running Neodymium-Yttrium Aluminum Garnet (FR Nd-YAG) laser coagulation of the macula was performed in seven human eyes. Follow-up varied from 1 to 15 days. Damage to the outer retinal layers was apparent immediately after exposure whilst that in the inner retinal layers developed subsequently. The choriocapillaris and major choroidal vessels were occluded. Visual acuity changed in an unpredictable way.

Adult↗
PubMed1988

The innervation of the rabbit's anterior eye segment: a retrograde tracing study.

The differential innervation of the distinct elements of the anterior segment of the rabbit eye, i.e. cornea, conjunctiva, ciliary body, iris, and trabecular meshwork, was studied using horseradish peroxidase-wheatgerm agglutinin (HRP-WGA) as a tracer. HRP-WGA was injected into the anterior chamber, the conjunctiva, or the cornea, and the animals were killed after 6 to 96 hr. The HRP-WGA localization was studied at the light and electron microscopic level. Injection into the anterior chamber led to an ubiquitous spread of the tracer in all elements of the anterior segment, resulting in a consistent retrograde labelling of neurons in the trigeminal (sensory), superior cervical (sympathetic) and ciliary (parasympathetic) ganglion. Neurons in the proximal part of the pterygopalatine ganglion (parasympathetic) were labelled only when the injected tracer was present in the conjunctiva. Varying survival times after corneal injection were used to establish restricted corneal uptake. Up to 16 hr after corneal injection, HRP-WGA was limited to the cornea and led to the exclusive labelling of neurons in the trigeminal ganglion, indicating that the central cornea has an almost exclusive sensory innervation. The trigeminal sensory neurons projecting to the cornea were restricted to a small antero-medial part of the trigeminal ganglion. Electron microscopy revealed four different cell types in the trigeminal ganglion. However, distinct elements of the anterior segment did not project to specific cell types.

Animals↗