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Biomedical subjects

C J Brinkman

Publications and source records attributed to C J Brinkman.

At least 19 recordsLinked to original sources
PubMed1994

Corneal eccentricity as a tool for the diagnosis of keratoconus.

Ninety-nine eyes with keratoconus of 64 patients were examined using the sagittal radii method to determine the corneal flattening and compared with 100 eyes of 50 healthy controls. To express the degree of this flattening, four numerical eccentricity (E) values for each eye were calculated. The highest E value of the four was chosen as a parameter for diagnosis of the disease. In keratoconus patients in whom the highest E values of keratoconus eyes were > or = 0.8, the specificity of the test was 98% and the sensitivity was 97%. This abnormal eccentricity was observed in keratoconus eyes with a visual acuity of 1.0, whereas slit-lamp examination showed no abnormalities. This study demonstrates that eccentricity can be helpful to diagnose keratoconus at an early stage.

Adolescent↗
PubMed1993

Therapy for ocular toxoplasmosis.

We conducted a prospective multicenter study of the efficacy of current therapeutic strategies for ocular toxoplasmosis in 149 patients. Treatment consisted of the following three triple-drug combinations: group 1, pyrimethamine, sulfadiazine, and corticosteroids; group 2, clindamycin, sulfadiazine, and corticosteroids; and group 3, trimethoprim, sulfamethoxazole and corticosteroids. Patients with peripheral retinal lesions were not treated systemically. No difference in the duration of inflammatory activity was observed between treated and untreated patients (P = .5). The most important factor predicting the duration of inflammatory activity was the size of the retinal lesion itself, independent of the treatment (P < .001). We found a reduction in size of the retinal inflammatory lesion for 49% of the pyrimethamine-treated patients (17 of 35) compared to 20% of the untreated patients (eight of 41) (P < .01). However, the most frequent occurrence of side effects was also associated with pyrimethamine medication (26%, nine of 35). The mean recurrence rate after three years of follow-up was 49% for all patients (60 of 122 patients), with no differences between treated and untreated patients (P = .6).

Adult↗
PubMed1993

Fundus pathology in neurosarcoidosis.

We describe the ocular symptomatology in 6 patients with neurosarcoidosis. All patients suffered from uveitis posterior or panuveitis. Ophthalmoscopy revealed multifocal chorioretinic lesions, periphlebitis, severe papilledema or an isolated chorioretinic process. The similarity with birdshot chorioretinopathy is described. Nuclear magnetic resonance imaging, computer assisted tomography and visual field examination can all contribute to the determination of neurological involvement in sarcoidosis.

Adolescent↗
PubMed1992

Analysis of the electroretinogram in toxoplasma retinochorioiditis.

The decision to use therapy in toxoplasma retinochorioiditis depends on the location of the active lesion and the presence of vitreous activity. In eyes with dense vitreous clouding it can be difficult to see whether the macular region is involved or not. In theory the localisation of a lesion can be estimated on the basis of the flash ERG. The standard flash electroretinogram was recorded in 23 patients with inactive toxoplasma retinochorioiditis lesions in the retina. In 17 cases a lesion was present within the central 12 degrees of the visual field, 8 of these had a reduced photopic ERG. In 15 patients lesions were found outside the central 12 degrees, in 8 of whom the scotopic ERG was reduced. We conclude that the ERG can be of use in indicating the scar location in patients with dense vitreous clouding.

Adolescent↗
PubMed1992

Pseudophakic endophthalmitis.

We performed a retrospective study on 45 patients admitted to the Rotterdam Eye Hospital and the Ophthalmic Department of the Academic Medical Center in Amsterdam with pseudophakic endophthalmitis. Vitreous loss during cataract extraction was associated with a significantly increased risk of postoperative endophthalmitis when compared with uncomplicated cataract extraction (p < 0.0001). The incidence of pseudophakic endophthalmitis in diabetic patients was not significantly higher as compared to non-diabetic patients. Vitrectomy in the treatment of postoperative endophthalmitis did not improve the final visual acuity, probably because of selection bias. Methicillin and cephazolin, used intravitreally against gram-positive organisms, failed to provide a good coverage for endophthalmitis due to Staphylococcus epidermidis.

Aged↗
PubMed1992

Uveitis and systemic disease.

A prospective study was conducted of 865 patients with uveitis to determine the frequency of associated systemic diseases and to assess the value of limited laboratory screening of these patients. All patients underwent a standard diagnostic protocol followed--when indicated--by special tests and procedures performed in order of likelihood ('tailored approach'). For 628 patients (73%) a specific diagnosis was established based on history, ophthalmologic examination, and laboratory and radiographic studies. A definite association with systemic disease was determined for 220 patients (26%). A relationship with a subclinical systemic disorder could be presumed in 201 cases (23%) and a well-established clinical uveitis entity without a recognisable systemic disorder was present in 207 cases (24%). For 237 patients (27%) a diagnosis could not be determined. The most frequently observed systemic diseases were sarcoidosis (7%) and HLA-B27-associated seronegative spondylarthropathies (6%). Presumed or definite toxoplasmosis was encountered in 10% of cases. HLA-B27-associated acute anterior uveitis was the most common clinical entity (17%). In the majority of cases the presence of a systemic disease was not suspected prior to eye involvement and was only recognised after the subsequent diagnostic procedures.

Adolescent↗
PubMed1991

Paradox of enhanced contractility in postischemic rat hearts with depressed function.

Depressed function of postischemic hearts may be related to incomplete recovery of coronary perfusion. To circumvent this factor we studied the properties of papillary muscles under controlled extracellular conditions. First, recovery of function was measured in postischemic rat hearts. Next, a muscle was dissected and superfused in a bath. After 40 min of ischemia, recovery of cardiac output was generally zero. Muscles from this group were relaxed or showed small contractures. After 20-30 min of ischemia recovery of coronary flow and cardiac output was 50-100%, and the isolated muscles showed the following properties (compared with Langendorff-perfused controls): 1) increased force at normal or low [Ca2+]; 2) action potential and postextrasystolic potentiation were unchanged, which indicates that Ca2+ influx per beat was unchanged; 3) the decay of potentiation was slowed, indicating a reduced rate of Ca2+ extrusion via Na(+)-Ca2+ exchange. This implies intracellular Ca2+ accumulation and explains the increased force. Postischemic enhancement of contractility (isovolumic pressure) was demonstrated also in whole heart preparations. We conclude that mild injury by preceding ischemia leads to enhanced contractility (Ca2+ accumulation), advanced injury to local contractures, and finally to a general contracture (Ca2+ overload). Recovery of heart function and coronary flow probably depends on the number and size of local contractures.

Action Potentials↗
PubMed1990

Cataract extraction in patients with chronic posterior uveitis.

The surgical management of cataract in patients with chronic posterior uveitis is described. Of 41 eyes, 88% acquired improvement of the visual acuity 4 months postoperatively, which then remained stable in most of the cases during a follow-up of one year. The type of cataract extraction, extracapsular or intracapsular, did not influence these results, nor did the implantation of an intraocular lens. Recurrence of the uveitis occurred in about one third of the cases. Postoperative complications consisted of macular edema, retinal detachment and vitreous hemorrhage.

Adult↗
PubMed1990

The influence of vitrectomy and lensectomy on experimental uveitis.

A secondary immune response in the rabbit eye can be provoked by intravenous injection of the antigen, previously injected intravitreally. The inflammation process consists of iris hyperemia, pericorneal redness and cellular and proteinous exudates in the anterior chamber and vitreous. The influence of vitrectomy combined with lensectomy or preceded by extracapsular lens extraction on the character of the secondary immune response has been studied in the rabbit eye. Both eyes of adult rabbits were injected intravitreally with human serum albumin. Five to ten weeks later, when the primary inflammation process had vanished, the vitreous and the lens were removed from the right eye in one group of animals. In a second group of rabbits, an extracapsular lens extraction was performed upon both eyes, later followed by vitrectomy of the right eye. Four weeks later all animals received an intravenous booster injection with human serum albumin. The eyes which still contained the vitreous developed a secondary inflammation consisting predominantly of cells and fibrin clots in the anterior chamber however without flare. On the contrary, the eyes which underwent vitrectomy developed a flare in the anterior chamber with only a few cells detectable. Analysis of cells and protein in the anterior chamber and histological evaluation supported the clinically observed differences between both eyes. These results suggest that the persistence of the vitreous is associated with the reactivation of a secondary immune response. Vitrectomy combined with lensectomy or preceded by extracapsular lens extraction leads to increased passive transfer of proteinous material through the vessels.

Animals↗
PubMed1990

Ocular inflammatory activity following different techniques of lens extraction and vitrectomy in rabbits.

The ocular inflammatory activity following different techniques of lens extraction and vitrectomy was studied in rabbits recovered from primary uveitis. Primary uveitis was induced by intravitreal injection of human serum albumin. After five to ten weeks, when the eyes were completely quiet, vitrectomy combined with lensectomy in one session or extracapsular lens extraction followed by vitrectomy was performed in different groups of rabbits. The most intense postoperative inflammatory process was encountered following removal of the lens independently of the route of extraction (via the ciliary body or via the anterior chamber). Vitrectomy via the ciliary body led to a minimal postoperative inflammation which resolved within 7 days. From these results we concluded that vitrectomy in primarily sensitized rabbit eyes can be performed without intense postoperative complications.

Animals↗
PubMed1988

Assessment of hemodynamic function and tolerance to ischemia in the absence or presence of calcium antagonists in hearts of isoproterenol-treated, exercise-trained, and sedentary rats.

The effects of cardiac hypertrophy on the structure, function and tolerance to ischemia of rat hearts have been investigated. Multiple injections of low doses of isoproterenol (ISO) resulted in an increase of heart weight/body weight ratio by 60%, and a decrease of myocardial creatine kinase activity by 25%, as compared to normal rats. Compared to age-matched control rats, rats submitted to a swimming program had a higher heart weight by 20%, but similar values of heart weight to body weight ratio. In isolated perfusion, the functional capacities of hearts from ISO-treated rats were severely depressed compared to normal rat hearts whereas exercise-trained rat hearts performed as well or even better than control hearts. The functional recovery of ISO-treated hearts following cardioplegia-induced arrest for 20 min at 37 degrees C was significantly worse than the recovery of normal hearts, but hearts of exercise-trained rats showed a significantly better recovery than control hearts. Exercise training results in improvement of myocardial blood supply resulting in better preservation of the heart during ischemia, compared to normal hearts. Addition of a combination of verapamil and diltiazem to the cardioplegic solution followed by ischemic arrest for 20 min at 37 degrees C resulted for ISO-treated rat hearts in an improved recovery of cardiac output (99%) compared to cardioplegia in the absence of these drugs (72%). In exercise-trained and control rat hearts, calcium antagonists improved the recovery from cardioplegic arrest of cardiac output from 90% to 92% and from 71% to 87%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Factors influencing the quantitative determination of tear proteins by high performance liquid chromatography.

HPLC analysis of human tears allows tear protein profiles to be obtained within ten minutes. A tear protein profile normally consists of 4 major peaks: IgA, lactoferrin, protein G and lysozyme. Although it is a rapid method, the use of High Performance Liquid Chromatography in the (quantitative) determination of proteins in tears is influenced by various factors. The day to day variability of the quantitative use, ranges between 7 and 9% for the various tear proteins. Combining the HPLC method with a convenient collection method such as sponges or Schirmer strips, showed that the sponges and some of the Schirmer strips used in this study eluted significant material absorbing light at 280 nm. No statistical difference was observed in the HPLC protein profiles of tears collected with Schirmer strips or with sponges. Using sponges has the advantage that they can absorb almost twice as much tears in a same period of time as Schirmer strips. HPLC analysis of human tear proteins is not accurate when there is albumin leakage as in traumatic sampling with Schirmer strips or in inflammatory states. The I-125 column which was used in our study is not able to separate lactoferrin and albumin, which may cause an overestimation of lactoferrin in inflammatory conditions. The study presented here indicates that for quantitative use of HPLC in epidemiological tear protein research better separating protein gel filtration columns are needed.

Adult↗
PubMed1987

Quantification of myocardial necrosis and cardiac hypertrophy in isoproterenol-treated rats.

Administration of a single high dose or multiple low doses of isoproterenol (ISO) to rats induces myocardial necrosis and cardiac hypertrophy. To assess the extent of necrosis we measured myocardial activities of creatine kinase (CK) and aspartate aminotransferase (AST) in the first days after ISO-treatment. After a single high dose and multiple low doses of ISO, necrosis was 10% and 25%, respectively. To quantify the degree of hypertrophy we measured heart weight and myocyte volume, and calculated cardiac CK, AST and DNA content up to 50 days after ISO-treatment. After a single high dose and multiple low doses of ISO, myocyte volume increased by 27% and 92%, respectively, while heart weight increased by 15% and 56%, respectively. As in this model hypertrophy is associated with focal necrosis, heart weight gain underestimates the actual increase of myocyte volume.

Animals↗
PubMed1985

Modulation of experimental allergic encephalomyelitis in Lewis rats by monoclonal anti-T cell antibodies.

The effect of monoclonal antibodies to different T lymphocyte populations of the rat on the induction and the course of experimental allergic encephalomyelitis (EAE) was investigated. EAE was induced by injection of guinea pig spinal cord in adjuvant. Subcutaneous injections of monoclonal antibodies to all peripheral T lymphocytes (W3/13) abrogated or prevented the development of clinical EAE. Similar results were obtained in animals injected with monoclonal antibodies to T helper cells (W3/25) mixed with monoclonal antibodies to T nonhelper cells (OX8). Animals treated with either W3/25 or OX8 developed clinical EAE as the control rats (subcutaneous injected with normal mouse serum). Histological examination after the acute stage revealed no significant differences between rats treated prophylactically with W3/13, W3/25 or OX8 and rats injected with normal mouse serum. Animals treated prophylactically with a mixture of W3/25 and OX8 developed, on the whole, EAE with less histological severity compared to the control animals. Treatment of rats after the onset of the first clinical symptoms of EAE (tail flaccidity) with W3/13 resulted in a less fatal course of the disease. Compared to surviving rats injected with mouse serum (controls) the number of infiltrates were reduced in these rats treated therapeutically.

Animals↗
PubMed1985

The effect of myelin basic protein on the protease inhibitors alpha 1 antitrypsin and alpha 2 macroglobulin.

The effect of myelin basic protein (MBP) of central nervous tissue on the protease inhibitors, alpha 1 antitrypsin (a1AT) and alpha 2 macroglobulin (a2M) was studied in vitro. For this purpose, 2 characteristics of the protease inhibitors were used, viz. their pattern after isoelectric focusing and their trypsin-binding capacity. Both features of purified a2AT disappeared in the presence of MBP. The tests with a2M revealed that the formation and stability of the complex between a2M and protease were reduced. The results of this study suggest that MBP causes an increase in proteolytic activity by inactivating protease inhibitors. The potential relevance of these results for demyelinating processes in man and animal is discussed.

Animals↗
PubMed1984

Lymphocyte subpopulations in multiple sclerosis: spontaneous and mitogen-induced activity.

Lymphocytes of chronic progressive multiple sclerosis (MS) patients and healthy persons were isolated by nylon-wool column filtration followed by density centrifugation. Incubating part of these lymphocytes with 2- aminoethyliso thiouronium bromide hydrobromide-treated sheep erythrocytes resulted in two other subfractions, the rosette-forming (E+) lymphocytes and the nonrosette -forming (E-) lymphocytes. Increased spontaneous activity was observed with the nonfractionated lymphocyte populations and with the E+- and E- -cell fractions of MS patients compared to the corresponding cell populations of controls following a culture period of one or several days. Phytohemagglutinin- and pokeweed mitogen-induced stimulation of these different lymphocyte fractions was the same in MS patients and controls. No influence of disease activity could be found on the immune parameters. Characterization of the different lymphocyte populations with monoclonal anti-human T-cell antibodies demonstrated a prevalence for helper T cells in forming rosettes.

Adult↗