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Biomedical subjects

P Visser

Publications and source records attributed to P Visser.

At least 37 records · Page 2Linked to original sources
PubMed1996

Cell fusion in space: plasma membrane fusion in human fibroblasts during short term microgravity.

During short-term microgravity in sounding rocket experiments (6 min.) the cytoskeleton undergoes changes and therefore it is possible that cell processes which are dependent on the structure and function of the cytoskeleton are influenced. A cell fusion experiment, initiated by a short electric pulse, was chosen as a model experiment for this sounding rocket experiment. Confluent monolayers of primary human skin fibroblasts, grown on coverslips, were mounted between two electrodes (distance 0.5 cm) and fused by discharging a capacitor (68 micro F; 250 V; 10 msec) in a low conductive medium. During a microgravity experiment in which nearly all the requirements for an optimal result were met (only the recovery of the payload was delayed) results were found that indicated that microgravity during 6 minutes did not influence cell fusion since the percentage of fused products did not change during microgravity. Within the limits of discrimination using morphological assays microgravity has no influence on the actin/cortical cytoskeleton just after electrofusion.

Actins↗
PubMed1994

Structural relation between HDL-binding proteins in porcine liver.

We have found strong evidence for a relation between three high-density lipoprotein (HDL)-binding proteins of 90, 110, and 180 kDa in porcine liver that were detected by ligand blotting. Because HDL-binding proteins with identical molecular masses were detected in human liver, all subsequent experiments were performed with porcine liver proteins. An antiserum raised against a highly purified preparation of the 90-kDa HDL-binding protein, designated 90-PC, showed cross-immunoreactivity with the 110- and 180-kDa HDL-binding proteins. Purified protein preparations of the 90-, 110-, and 180-kDa HDL-binding proteins were obtained and analyzed by polyacrylamide gel electrophoresis with sodium dodecyl sulfate. Under nonreducing conditions these preparations showed protein bands with the expected molecular masses. Reduction of these preparations resulted in protein bands of 90 kDa. Ligand blotting experiments with 125I-HDL showed protein bands of 90, 110, and 180 kDa under nonreducing conditions and a 90-kDa protein band in all three preparations under reducing conditions. Immunoblotting experiments with 90-PC antiserum resulted in a similar pattern. The three protein preparations were then subjected to cyanogen bromide cleavage and the resulting peptides separated on gel. Immunoblotting with the 90-PC antibody revealed a pattern of protein bands that was remarkably similar in all three protein preparations. Immunohistochemical localization studies with the 90-PC antibody showed that the HDL-binding proteins were present both at the borders of the sinusoids as well as within the hepatocellular plates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Cortisone-induced islet cell hyperplasia in hamsters.

Pancreatic islet cell hyperplasia was studied in hamsters during one to eight weeks of cortisone treatment. Measurement of serum glucose and insulin; pancreatic insulin, glucagon, somatostatin, pancreatic polypeptide as well as islet tissue morphometry were performed. Serum glucose was highest at week 2, followed by mild to moderate hyperglycemia. Serum insulin was increasingly higher from week 1 to week 8. Pancreatic insulin was maximal at week 5 then declined through week 8 in the presence of beta cell neurosis in markedly hyperplastic islets. Pancreatic concentration of somatostatin and pancreatic polypeptide moderately increased more than the control levels; however, compared with the controls, glucagon was reduced by cortisone treatment. Effect of cortisone in the four types of islet cells is discussed, particularly on beta cell hyperplasia, which appears to be a response to decreased insulin binding to the target organs with no changes in receptor concentration.

Animals↗
PubMed1984

Combined sialidase (neuraminidase) and beta-galactosidase deficiency. Clinical, morphological and enzymological observations in a patient.

A patient with combined deficiency of sialidase and beta-galactosidase is described. This now 39-year-old man, who is of Japanese origin, showed gradually progressive clinical features from the age of six years. Many of these features are commonly found in sialidosis type 2 or in GM1-gangliosidosis. Both sialidase and beta-galactosidase activities were deficient in leucocytes and cultured fibroblasts. Leucocytes of his mother showed activities of both enzymes in the lower limit of the control range. Morphologically, the pattern of storage products in a skin biopsy resembled in many respects that seen in GM1-gangliosidosis. Moreover, storage products which could be typical of sialidosis were also observed. Since the patient showed angiokeratomata, the morphological findings were compared with those specific to Fabry's disease, but no similarities were found. An enzymological diagnosis of the disease is most reliable on cultured fibroblasts, discriminating it from sialidosis type 2 and GM1-gangliosidosis. In view of recent findings, leucocytes seem to be less suitable for the establishment of the diagnosis galactosialidosis.

Adult↗
PubMed1983

Monoclonal antibodies against human beta-glucocerebrosidase.

Monoclonal antibodies were obtained against the membrane-bound lysosomal enzyme beta-glucocerebrosidase (acid beta-glucosidase), which is deficient in Gaucher's disease. BALB/c mice were immunized with homogeneous enzyme protein extracted from a sodium dodecyl sulphate/polyacrylamide gel. The mice were subsequently hyperimmunized with partially purified enzyme prior to fusion of spleen cells with myeloma cells. After fusion, 32 primary hybrid cell populations were obtained which continued to produce antibodies against beta-glucocerebrosidase after prolonged time of culture. All antibodies reacted with both native and denatured enzyme. Four primary cell populations were subcloned and the antibodies produced were characterized. The antibodies were all four of the IgG1 subclass. Three of these antibodies bind to protein A whereas one does not. The results of binding assays indicated that three of the antibodies react with the same antigenic domain (epitope 1), but the fourth with a different one (epitope 2). Probably two antigenic determinants are present in epitope 1 since one of the antibodies with specificity for epitope 1 is inactivated after iodination by the chloramine-T procedure whereas a second one is not.

Animals↗
PubMedDate not supplied

The use of microwave irradiation with low formalin concentrations to enhance the conversion of dopamine into norsalsolinol in rat brain: a pilot study.

The fixation of the neurotransmitter dopamine in the central nervous system by perfusion with formalin solutions seems to take place mainly via the formalin-induced condensation product norsalsolinol. In the present investigation the influence of microwave irradiation of the formalin-induced condensation of dopamine was studied in vitro and in vivo by making use of different, relatively low, formalin concentrations. It appeared that in vitro and in vivo the dopamine conversion was complete with 4% formalin and no influence of microwaves was noted. However, by making use of much lower formalin concentrations (0.2% and 0.4%) the condensation of dopamine was strongly augmented, in vitro (200%) and in vivo (at least 500%) using microwave techniques. There was a considerable loss in non-microwaved tissue (30%) after perfusion in vivo. This was lower (10%) in microwaved tissue. In experiments with perfused brain tissue which allowed a more complete calculation, a loss was found. This might be caused by a strong binding of dopamine and/or norsalsolinol to tissue components or to side reactions that could not be traced by the present experimental techniques.

Animals↗
PubMedDate not supplied

Otitic barotrauma.

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Barotrauma↗
PubMedDate not supplied

Mood and Sleep. I. Effects of the menstrual cycle.

Four female subjects were studied during eight nights each at corresponding days of the menstrual cycle. No clear cycle effects could be discerned in the sleep variables of the subjects as a group. In one subject, however, a U-shaped course of negative mood was found during the menstrual cycle, together with an enhanced percentage of stage 2 sleep and a lowered percentage of slow wave sleep at the time of the menses. In the three other subjects' cycles no such cyclic variations in the mood or sleep variables were found.

Adult↗