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Biomedical subjects

R Bjerknes

Publications and source records attributed to R Bjerknes.

At least 73 records · Page 4Linked to original sources
PubMed1989

Migration of cells in the rat corneal epithelium.

The migration of cells in the rat corneal epithelium was studied using continuous labelling with tritiated thymidine [3H]TdR, during a 24 h period. Most mitoses resulted in 2 new basal cells. Cells leaving the basal cell layer moved vertically to the surface in all areas of the corneal epithelium. The first labelled cells reached the surface 3 days after the first injection of [3H]TdR. No stream of cells from the conjunctiva to the cornea in the limbal areas was observed, and no centripetal migration of epithelial cells in the cornea could be observed. After a cell has lost its attachment to the basement membrane, it is committed to be exfoliated in a few days without undergoing mitosis. Thus the slow centripetal migration of epithelial cells and the exchange of centrally located cells, as indicated by clinical findings and experimental studies, can only be explained by migration of basal cells.

Animals↗
PubMed1989

Cell kinetics during healing of corneal epithelial wounds.

After removing a circular area of the central corneal epithelium of the rat eye, the labelling indices and the mitotic rates were measured at various times after wounding, both in the cornea and in the adjacent conjunctival epithelium. The proliferative response was most marked in the corneal epithelium adjacent to the wound, but there was also a definite response in the epithelium covering the denuded areas, and in the conjunctival epithelium. The study demonstrated that the conjunctival epithelium. The study demonstrated that the conjunctiva itself plays a role in the healing of a central corneal epithelial wound. The similarities in the cellular response may indicate that both epithelia are under the influence of the same growth-suppressing factors (chalones), and must be looked upon as a unit. However, no support was found for the theory that the limbal area serves as a generative organ for the corneal epithelium.

Animals↗
PubMed1988

The labelling index is not always reliable. Discrepancies between the labelling index and the mitotic rate in the rat corneal epithelium after intraperitoneal and topical administration of tritiated thymidine and colcemid.

Many cell kinetic studies are based on the assumption that tritiated thymidine injected into an animal is available for incorporation into DNA for only a short time, and that it labels all cells in the S phase. The present study indicates that this is not the fact for the rat corneal epithelium. The labelling index (LI) declines considerably from the limbal area to the central cornea, while the mitotic rate is almost constant all over the corneal epithelium. The LI should therefore not be used as the only criterion in the assessment of proliferation rate.

Administration, Topical↗
PubMed1988

Cell renewal of the rat corneal epithelium. A method to compare corresponding corneal areas from individual animals.

A stathmokinetic method to study the mitotic rate in the corneal epithelium of the rat is described and applied. Horizontal and vertical diameter sections were used. In order to analyze the mitotic rate in the various parts of the corneal epithelium, each vision field (objective 100, eye piece 12.5), comprising 182 microns basement membrane, was regarded as a separate unit. Since the number of vision fields across the cornea varies from specimen to specimen, we constructed a mathematical method to correlate corresponding corneal areas from different eyes. Using this method it is shown that the mitotic rate is almost equal all over the cornea, with no definite reduction in the central areas. There is no area of significantly high proliferation rate, either in the limbal area or in the adjacent conjunctiva.

Animals↗
PubMed1988

Whipple's disease. Demonstration of a persisting monocyte and macrophage dysfunction.

A patient with Whipple's disease has been followed up for 4 years. Primary involvement was limited to the small intestines, and accumulation of periodic acid-Schiff-positive material, containing typical more or less intact bacillary bodies, was demonstrated within macrophages of affected tissue. After initial oxytetracycline treatment and clinical remission, the patient relapsed, with multiorgan affections. The antibiotic regimen was changed to chloramphenicol, followed by continuous trimethoprim-sulfamethoxazole. Flow cytometric studies showed persisting impairment of monocyte and macrophage intracellular degradation of bacteria during all the 4 years tested. After relapse, reduced activity of several brush border enzymes was demonstrated in distal duodenal biopsy specimens. After 17 months of continuous trimethoprim-sulfamethoxazole therapy complete clinical remission, regression of histopathologic abnormalities, and restoration of duodenal enzyme activities had occurred. The results demonstrate a persisting dysfunction of mononuclear phagocytes from a patient with Whipple's disease, suggesting a primary abnormality of cell-mediated immunity which may promote the susceptibility to the causative bacillus.

Adult↗
PubMed1988

The influence of technical procedures on cell countings in the rat corneal epithelium: a statistical analysis.

We have performed a statistical analysis on cell counts from different areas of the rat corneal epithelium by using the number of cells per high power microscopical vision field (1250 x) as a unit. Each vision field consisted of 182 micron basal membrane. The number of vision fields varied from 29 to 39 in the horizontal and vertical diameter sections used. Only small variations were found in the number of cells from the different vision fields inside one single section. This confirm the extreme regularity of this epithelium. However, when comparing different sections, even from the same eye, the variations were much greater. Further, sections prepared for autoradiography showed a 10% reduction of the number of cells compared with the sections only stained with hematoxylin. A large proportion of the variation in the cell counts must be a result of the technical procedures, and is thus not an intrinsic property of the corneal epithelium. This conclusion may also be valid in cell counts from other epithelial structures.

Animals↗
PubMed1988

The dimer of hemoregulatory peptide (HP5B) stimulates mouse and human myelopoiesis in vitro.

A synthetic analogue of a pentapeptide associated with mature granulocytes has been described earlier and shown to suppress myelopoietic colony formation in vitro in concentrations from 10(-13) to 10(-6) M. By oxidation of the peptide, a dimer will rapidly occur by formation of disulfide bridges between cysteine residues. We here demonstrate that this dimer has the opposite effects of the monomer. For both mouse and human granulocyte-macrophage colony-forming units (CFU-GM), a dose-dependent enhancement of colony formation was observed in the dose range 10(-16) to 10(-5) M, where a saturation level was reached above 10(-8) M. At low doses of colony-stimulating activity (CSA) and in the linear stimulating phase, an up to ten times increase of colony formation was seen, whereas at higher doses the effect was less pronounced. Also at the plateau level of CSA stimulation an increased colony yield was seen. All types of colonies were stimulated. The dimer itself had no colony-stimulating factor activity and was not toxic to bone marrow cells in suspension cultures up to 24 h. Upon reduction of the dimer by use of sulfhydryl compounds, inhibitory effects on CFU-GM were restored. The peptide had no effect on the phagocytic process in human granulocytes, including attachment and internalization of bacteria or Zymosan particles. The monomerdimer equilibrium of hemoregulatory peptide may constitute a new mechanism for proliferative regulation of myelopoietic cells.

Agar↗
PubMed1987

A synthetic hemoregulatory peptide (HP5B) inhibits human myelopoietic colony formation (CFU-GM) but not leukocyte phagocytosis in vitro.

A synthetic analog of a hemoregulatory peptide associated with mature human granulocyte (HP5B) has been investigated for inhibitory effects on human myelopoietic stem cells in vitro. In addition, it has been tested for effects on phagocytosis by human granulocytes and monocytes by use of an automatic flow cytometric method. A dose-dependent inhibition of colony formation was found after preincubation of bone marrow cells for 1 h at 37 degrees C in the range 10(7) -10(-11) mol/l. Above or below these concentrations, no inhibitory effects were seen. The degree of inhibition varied from experiment to experiment, indicating variable responsiveness of the donor cells. Maximal effect was of magnitude 90% inhibition, and the optimal dose was 10(7) mol/l. The peptide had no effect on the kinetics of phagocytosis by measurements of the uptake of fluorescent Zymosan particles or Staphylococcus aureus. This may indicate a selective effect on the precursor cells, with no effect on the functional state of their progeny, the granulocytes and monocytes.

Bone Marrow Cells↗
PubMed1987

Serum opsonins to group B meningococci.

The production of serum opsonins and other antibodies to serogroup B serotype 15 meningococci was examined in 7 patients with serogroup B serotype 15 meningococcal disease and 7 volunteers immunized with a vaccine containing outer membrane proteins from serogroup B serotype 2b and 15 meningococcal strains complexed with polysaccharides from serogroups A, C, Y and W-135 meningococci. Serum opsonic activity was measured by a flow cytometric phagocytosis technique, using unfixed serogroup B Neisseria meningitidis labelled with fluorescein isothiocyanate. Serum antibodies to outer membrane complexes prepared from the meningococcal test strain, B:15:P1.16, were measured by an enzyme linked immunosorbent assay. The mean number of bacteria per phagocyte increased from 9.7 to 17.3 (mean difference 7.6, p less than 0.001) when the meningococci were opsonized with convalescent sera compared to sera obtained during the acute illness, and from 8.0 to 15.4 (mean difference 7.4, p less than 0.001) when opsonized with sera from immunized versus pre-immunized volunteers. The patients had insignificant amounts of serum antibodies to the group B meningococcal test strain on admission to hospital. Two weeks later all had a marked increase in IgG, IgM and IgA serum antibodies. Vaccination caused a marked increase in serum IgG antibodies. Serum opsonic activity and IgG levels were still high 6 weeks after the acute illness/immunization. A correlation was observed between serum opsonic activity and IgG antibody levels (r = 0.883, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Phagocytic capacity of normal and malignant rat glial cells in culture.

The phagocytic capacity of 4 continuous rat glioma cell lines (BT2C, BT4Cn, BT5c, and 9L) and normal BD IX fetal rat glial cells in culture has been studied. This was done by flow cytometric measurements of single cells from monolayer cultures having ingested fluorescent bacteria, zymosan particles, red blood cells, or fragments of normal glial cells. In addition, phagocytosis was studied in a three-dimensional culture system. The BT4Cn, BT5C, and 9L cell lines were tumorigenic and invasive both in vivo and in organ culture in vitro. In contrast, BT2C has shown variable tumorigenicity and does not seem to be invasive. The phagocytic capacity of the cell lines was compared to their destructive properties during invasion. Depending on the particle type, 30-40% of the normal glial cells were phagocytic. The fractions of phagocytic glioma cells were dependent on the particle type and the prey load. Of the invasive cell lines, BT5C showed high phagocytic activity both in monolayer and three-dimensional cultures. Two of the invasive cell lines (BT5C and 9L) had about the same fraction of phagocytic cells as normal glial cells. These 2 cell lines showed highly destructive growth during invasion. In contrast, the third invasive cell line (BT4Cn) had almost no phagocytic cells. The BT4Cn cells showed single-cell invasion with little destruction of target tissue. The noninvasive cell line (BT2C) showed low phagocytic activity, and almost no destruction was observed in the border zone between tumor cells and normal tissue. Phagocytosis seems to be an inherent property of both normal and malignant glial cells, although the fraction of phagocytic cells varies from one cell line to another. In organ culture high phagocytic capacity of invasive glioma cells seems to be related to destructive activity on the normal brain tissue during invasion.

Animals↗
PubMed1985

Impaired bacterial degradation by monocytes and macrophages from a patient with treated Whipple's disease.

A patient with Whipple's disease is described, and multiparameter flow cytometric examinations of several of the patient's phagocyte functions 3 and 9 mo after the start of oxytetracycline therapy are reported. Almost no intracellular degradation of Escherichia coli or Streptococcus pyogenes proteins and DNA occurred after ingestion by the patient's monocytes and macrophages. In addition, only minor digestion of phagocytized zymosan particles was detected. The mononuclear intracellular degradation was equally impaired 3 and 9 mo after the start of therapy. The monocyte and macrophage phagocytosis and intracellular killing, and all granulocyte phagocyte functions tested, were normal. The impaired mononuclear degradation of ingested material that was measured is consistent with the accumulation of periodic acid-Schiff-positive bacterial degradation products seen in macrophages of affected tissues in vivo, and suggests a key role of macrophage dysfunction in the pathogenesis of Whipple's disease.

Adult↗
PubMed1985

Phagocytosis by human leukocytes, phagosomal pH and degradation of seven species of bacteria measured by flow cytometry.

Phagocytosis by human leukocytes, phagosomal pH and degradation of seven species of bacteria were studied by a flow cytometric method. The percentage of phagocytosing leukocytes was similar for all bacterial strains examined, but Salmonella typhi and Neisseria meningitidis were more slowly phagocytosed than other bacteria. The phagosomal pH surrounding the different bacterial species 15 min after the start of phagocytosis were: Streptococcus pneumoniae 4.4; N. meningitidis 4.9; Str. pyogenes 5.1; Staphylococcus aureus 5.2; Escherichia coli 5.3; S. typhi 5.4; and Klebsiella pneumoniae 5.7. For longer incubation periods, the phagosomal pH remained nearly constant. Staph. aureus, E. coli and S. typhi were the most readily degraded of the species tested. The proteins of all bacteria were degraded more rapidly than their DNA as determined by measurements of the loss of fluorescein-isothiocyanate-fluorescence and ethidium bromide-fluorescence, respectively. The rate of degradation varied from one bacterial species to another. The degradation of proteins and DNA was maximal for bacteria residing in a phagosomal environment estimated to be between pH 5.2 and 5.4.

Bacteria↗
PubMed1985

Estimation of circadian variations in cell cycle phase durations in murine epidermal basal cells.

Circadian variations in the proliferative activity of squamous epithelia are well known. However, circadian variations in the duration of the various cell cycle phases (S, G2 and mitosis) have been disputed. The percent labelled mitoses method, which is traditionally used to obtain duration of cell cycle phases, is poorly suited for identification of circadian variations. Therefore methods combining changes in compartment size (cell cycle phase) and cellular flux through the compartments have been used. Three different methods using such data are presented. These incorporate various simplifying assumptions that cause methodological errors. Limits for use of the different methods are indicated. The use of all three methods gives comparable and pronounced circadian variations in the duration of S and G2 phase. These results are also compatible with circadian variations in the mitotic duration, but they may also represent artefacts due to sensitivity to model errors.

Animals↗
PubMed1984

Flow cytometric assay for combined measurement of phagocytosis and intracellular killing of Candida albicans.

A rapid quantitative flow cytometric (FCM) assay for the combined kinetic measurement of phagocytosis and intracellular killing of fluorescein-isothiocyanate (FITC) labelled Candida albicans is described. The fraction of phagocytosing leukocytes and the numbers of attached or internalized Candida albicans per phagocytosing leukocyte were quantified by FCM, using trypan blue and a fluorescence quenching technique. Results obtained by microscopy agreed with the FCM estimates of phagocytosis. Dead, but not live, Candida albicans stained by propidium iodide (PI). Thus, both viable and intracellularly killed fungi could be discriminated and measured by FCM. Phagocyte killing determined by the FCM assay correlated with killing measured by a standard microbiological test and by methylene blue staining. The method allows rapid and accurate testing of opsonic and phagocytic functions under both experimental and clinical conditions.

Candida albicans↗
PubMed1984

Phagocyte C3-mediated attachment and internalization: flow cytometric studies using a fluorescence quenching technique.

The dynamics of phagocyte C3-mediated attachment and internalization of fluorescein-isothiocyanate (FITC)-labelled zymosan particles was studied by a flow cytometric (FCM) fluorescence quenching technique, using trypan blue as quenching agent. Trypan blue effectively quenched the fluorescence of extracellular, i.e. free and phagocyte-attached, zymosan particles, but did not influence on the fluorescence of particles internalized by phagocytes. During phagocytosis, an average of 2 C3-coated zymosan particles were simultaneously attached to the phagocyte surface, and the number of attached particles could not be increased by increasing the zymosan to leukocyte ratio, the concentration of C3, the incubation time, or by inhibiting internalization by Cytochalasin B. Phagocyte C3-mediated internalization of zymosan particles was dependent on the concentration of complement, and in the presence of sufficient amounts of C3, internalization continued until saturation was reached at 11 particles per phagocyte.

Complement C3↗