Search PubMed⌕ Search

Biomedical subjects

L Bolund

Publications and source records attributed to L Bolund.

At least 127 records · Page 7Linked to original sources
PubMed1986

Close linkage between X-linked ectodermal dysplasia and a cloned DNA sequence detecting a two allele restriction fragment length polymorphism in the region Xp11-q12.

EDA (ectodermal dysplasia, anhidrotic) is an X-linked recessive disorder characterized by hypohidrosis, hypoor anodontia, and hypotrichosis. A possible linkage between the gene for EDA and a number of restriction fragment length polymorphisms (RFLPs) spread over the X chromosome was investigated in two Danish families segregating EDA. No recombination between the gene for EDA and our probe pTAK8, which detects a two allele polymorphism in the region Xp11-q12, was found in nine informative meiotic events (seven of which are phase known), giving a maximal lod score of 2.41 at a recombination fraction of 0.00. This juxtacentromeric location of the gene for EDA agrees well with the linkage data obtained with the other markers used in this study.

Adolescent↗
PubMed1986

Changes in proliferating cell subpopulations and mitotic activity in human epidermal cultures treated with epithelial growth inhibitors.

Labeling of cultured human epidermal cells with [3H]thymidine has revealed a dramatic heterogeneity among sorted S-phase cells. Cell kinetic studies have shown that these differences in labeling intensity most probably reflect differences in the rate of DNA synthesis, and cycling basal cells may be divided into subpopulations on this basis. Studies with growth stimulators have suggested that these subpopulations are involved in cell renewal or population expansion during early differentiation of the keratinocyte. In the present study the effects of an epidermal growth inhibitor purified from an epidermis extract and a kidney epithelial growth inhibitor obtained from conditioned medium of BSC-1 cell cultures were investigated. Both agents were shown to cause a dramatic decrease in mitotic activity in the epidermal cultures and also to diminish the proportion of S-phase cells with a strong thymidine incorporation (high rate of DNA replication). The effect of the BSC-1 growth inhibitor was furthermore shown to be counteracted by epidermal growth factor and cholera toxin.

Cell Differentiation↗
PubMed1985

Changes in basal cell subpopulations and tissue differentiation in human epidermal cultures treated with epidermal growth factor and cholera toxin.

Cell kinetic studies on cultured human epidermal cells have indicated that cycling basal cells may be divided into at least two subpopulations that seem to differ with respect to the rate of DNA replication. The present study was undertaken in order to elucidate the biological significance of these subpopulations. The proliferation characteristics of cultured basal cells were changed by the addition of epidermal growth factor (EGF) and cholera toxin to the culture medium. It was shown that EGF and cholera toxin stimulated the growth of human epidermal cells in culture. Simultaneously, the terminal differentiation of the cells was inhibited resulting in a reduced multilayering and a reduced formation of the cornified envelope. However, only minor differences in the protein synthesis pattern were observed between cultures maintained in the presence or absence of the growth stimulators. The effect of EGF and cholera toxin on the basal cell subpopulations was investigated after 3H-thymidine labelling followed by cell sorting and autoradiography. In the presence of EGF and cholera toxin dramatic changes were induced in the labelling pattern of sorted S-phase cells indicating significant alterations in the balance between the subpopulations of cycling basal cells. Our results with these substances are in accord with the hypothesis that the observed cell kinetic subpopulations may be related to regeneration or early events in the differentiation process of the keratinocyte.

Adult↗
PubMed1985

Basal-cell subpopulations and cell-cycle kinetics in human epidermal explant cultures.

Cultured human epidermal cells were studied by cell sorting and autoradiography after different 3H-thymidine (3H-dThd)-labelling procedures and after labelling with DNA precursors that are incorporated via salvage or de novo pathways. It was shown that 3H-dThd incorporation was the best measure of the rate of DNA replication. Dose-response experiments with pulse and continuous labelling revealed that all S- and G2-phase cells were cycling, whereas some 20% of the cells stayed in G1-phase for long periods of time. Most, if not all of these cells were probably non-proliferating differentiated keratinocytes. At least two subpopulations of S-phase cells could be discriminated on the basis of the rate of incorporation of DNA precursors. The difference in precursor incorporation did not seem to be caused by differences in nucleotide metabolism but rather to reflect true differences in the rate of DNA replication. Continuous labelling experiments showed that these subpopulations also were apparent in the G1- and G2-phases. Studies of the grain-count distribution revealed that cells that appeared to move rapidly through the S-phase moved slowly through the G2-phase, and vice versa. Cells stained with acridine orange were subjected to a two-parameter analysis in the cell sorter by simultaneous measurement of the DNA and RNA fluorescence. Autoradiography of sorted cells revealed that, on average, cells with low RNA contents incorporated 3H-dThd at a higher rate than cells with high RNA contents.

Acridine Orange↗
PubMed1985

DNA synthesis rate changes during the S phase in mouse epidermis.

The in vivo DNA synthesis rate throughout the S phase of mouse epidermal cells was investigated. Epidermal basal cells were isolated at various times of the day from normal animals injected with [3H]TdR 30 min before sacrifice, and from pulse-labelled animals with regenerating and growth-inhibited epidermis. The cells were analysed by DNA flow cytometry combined with cell sorting. Cells from successive fractions of the S phase were sorted on glass slides and subjected to quantitative [3H]TdR autoradiography. The results confirmed the presence of unlabelled (slowly replicating) cells in the S phase, the proportion of which was circadian stage-dependent with minimum values at midnight and in the early morning. The DNA synthesis rate throughout the S phase showed a general trend with high values in the mid-fractions, a pattern which was similar in normal and in growth perturbed epidermis. In the early morning the DNA synthesis rate pattern was bimodal with maxima both in the first and second half of the S phase, with a corresponding trough in mid-S. At this time of day the cell progression rate through S is at its maximum, indicating a relationship between the overall DNA synthesis rate and the rate distribution pattern through S.

Animals↗
PubMed1984

Subpopulations of slowly cycling cells in S and G2 phase in mouse epidermis.

Evidence has been presented supporting the existence of heterogeneity in cell-cycle progression in mouse epidermis, The present study was undertaken to characterize this heterogeneity in more detail. Hairless mice were continuously labelled with tritiated thymidine every 4 hr for 4 days. Basal cell suspensions were prepared from slices of mouse skin at intervals during the experiment and subjected to DNA flow cytometry. Cell-cycle analysis was combined with sorting of cells from windows in G1, S and G2 phase, and the proportion of labelled cells within each window was determined in autoradiographs. Reanalysis and resorting to control the purity of of sorted fractions were performed. Computer simulations of the data were made using a mathematical model assuming different S and G2 phase characteristics. A good fit to the data was only obtained when heterogeneity in mouse epidermal cell-cycle progression was assumed, indicating the existence of slowly traversing, distinct subpopulations of cells in G2 and S phase. These cells are assumed to contribute to about 40% of all cells in S phase and to about 70% of all in G2 phase. The estimated residence times in the resting states were 38 and 32 hr in S and G2 phase, respectively. Two-parameter sorting based on DNA and light scatter indicated that slowly cycling cells were larger than the average. There is no evidence of significant subpopulations of permanently non-proliferating keratinocytes in any of the cell-cycle phases.

Animals↗
PubMed1983

Morphological and functional differentiation in epithelial cultures obtained from human skin explants.

The present study was undertaken to characterize primary epithelial cultures obtained from human skin explants as experimental systems for studies of the differentiation process. When human skin explants were incubated at 34-35 degrees C, fibroblastic growth was strongly inhibited, whereas the epithelial growth proceeded unchanged. The lateral growth of the epithelial cells could be divided into two phases - a migratory and a proliferative one. Only cultures incubated at 35 degrees C or below completed the morphological differentiation process before sloughing, whereas no qualitative difference in protein synthesis was observed between cultures incubated at temperatures from 33-37 degrees C. Cultured epidermal cells were labelled with 3H-thymidine and analysed by flow cytometry and cell sorting. Cells sorted from the S- and G2-phase populations were further analysed by autoradiography and a considerable heterogeneity as to the nuclear labelling was disclosed. A large fraction of S-phase cells were found to be totally unlabelled. The grain count distributions revealed similar cell cycle subpopulations as have been shown to occur in vivo. The relationship of these subpopulations to the differentiation process is discussed.

Autoradiography↗
PubMed1983

DNA synthesis in mouse epidermis: S phase cells that remain unlabeled after pulse labeling with DNA precursors progress slowly through S.

Epidermal basal cells from hairless mice were isolated after pulse labeling with tritiated DNA precursors and subjected to DNA flow cytometry combined with cell sorting. Cells were sorted from a window in the middle of the S phase, collected on glass slides, and subjected to autoradiography. Unlabeled cells in the middle of the S phase were found in normal mouse epidermis after optimal pulse labeling with tritiated thymidine [( 3H]dThd), in accordance with previous results. The proportion of unlabeled S phase cells was considerably increased among basal cells from mice treated with growth-inhibitory epidermal extracts. Reanalysis and re-sorting of cells previously sorted from mid S showed that unlabeled cells could not be accounted for by G1 contamination. Furthermore, labeling with precursors incorporated into DNA by "de novo" metabolic pathway [( 3H]Urd) did not reduce the proportion of unlabeled S phase cells, either when given alone or when given in combination with the precursor for DNA incorporated by the "salvage" pathway [( 3H]dThd). This strongly indicates that the unlabeled S phase cells do not synthesize DNA continuously, or are synthesizing DNA at a rate below the level of detection. A reduced proportion of unlabeled S phase cells was found in regenerating epidermis. This may be explained by a dilution effect caused by the 3-fold increase in the total number of cells within S phase at this condition. The observation that essentially all cells in mid S phase were labeled during 4 days of continuous labeling with [3H]dThd, indicates that cells in S phase that remain unlabeled after optimal pulse labeling are cycling, albeit slowly. Two-parameter sorting based on DNA and light scatter indicated that slowly cycling cells are larger than the average. These cells may represent a subpopulation of basal cells going through their last division cycle before differentiation.

Animals↗
PubMed1979

Origin of triploidy in spontaneous abortuses.

Fourteen triploid spontaneous abortuses were studied cytogenetically by sequential Q and C banding and the marker chromosomes were compared with those of the parents. The abortuses comprised all triploid cases in a series of 288 consecutive abortuses of the first 16 weeks of pregnancy occurring in one hospital. In 12 of the triploids the origin of the extra haploid set was conclusively determined, revealing six cases of dispermy, five failures in the first maternal and one failure in the first paternal meiotic division. The results were combined with those of five other studies comprising a total of 48 informative cases. Non-reduction in the second meiotic division seems to be of little or no significance in the origin of human triploidy. Dispermy is the predominant source, accounting for 40--50% of the triploid spontaneous abortuses. Non-reduction in the first meiotic division of the father seems to be the second-most frequent source although in the present material the corresponding maternal non-reduction is much more common.

Abortion, Spontaneous↗
PubMed1975

Synthesis of oviduct nuclear and chromatin proteins during steroid induced differentiation.

Synthesis of nuclear histones and nonhistones was studied in chick oviduct during stimulation with estrogen and progesterone. In estrogen primed chicks, as compared to progesterone primed chicks, oviduct nonhistones are enriched in polypeptides of 50,000 daltons and larger. A secondary stimulation with the steroids increases the amino acid incorporation into histones and nonhistones two to six fold. Injection with estrogen induces preferential labelling of nonhistone polypeptides at 50,000 to 60,000 daltons independent of the kind of primary stimulation. A secondary injection with progesterone increases the amounts of highly labelled polypeptides with a molecular weight of over 70,000 daltons.

Animals↗