No photoinactivation of Propionibacterium acnes with soft laser treatment.
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Acne Vulgaris↗
Biomedical subjects
A Johnsson
Publications and source records attributed to A Johnsson.
The phenotypic characteristics of simian sarcoma virus-transformed human fibroblasts suggest that the v-sis gene product acts solely as a PDGF receptor agonist in cell transformation.
Previous studies have indicated that the oncogene v-sis of simian sarcoma virus (SSV) encodes a growth factor that is structurally and functionally similar to platelet-derived growth factor (PDGF). In the present investigation we have analysed the phenotypic characteristics of human foreskin fibroblasts transformed by SSV. It was found that the PDGF receptors were extensively down-regulated. This finding is consistent with a high, local, extracellular concentration of a PDGF-like factor, synthesized by the transformed cell. The receptors were up-regulated by suramin, a drug that is known to dissociate PDGF and the v-sis product from the PDGF receptors. A cell-associated v-sis product of mol. wt 24,000 was identified by immunoprecipitation with PDGF antibodies; release of this component was induced by a high concentration of exogenous PDGF, indicating that a fraction of the product is associated with the PDGF receptors. SSV was not found to be an immortalizing virus; when serially passaged, SSV-transformed cells had essentially the same life-span as their non-transformed counterparts. Moreover, SSV did not induce growth in soft agar beyond the level afforded by exogenously added PDGF. Thus, the present study favors the notion that SSV transformation is mediated by a growth factor that mimics PDGF but has no further cellular effects.
Cell Division↗
Efficient reversion of simian sarcoma virus-transformation and inhibition of growth factor-induced mitogenesis by suramin.
Simian sarcoma virus, an acutely transforming primate retrovirus with capacity to induce gliomas and sarcomas in experimental animals, has acquired its transforming properties by transducing the cellular gene sequences that encode one of the constituent chains of platelet-derived growth factor. Suramin, a drug used in the treatment of trypanosomiasis and onchocerciasis, has previously been reported to inhibit the interaction of platelet-derived growth factor with its cell surface receptor. We show here that suramin efficiently reverts the simian sarcoma virus-induced transformed phenotype in human and rat fibroblasts and propose that this is due to neutralization of an externalized v-sis product. Moreover, we show that suramin inhibits the action of a broad spectrum of growth factors.
Animals↗
Human melanoma cell lines of primary and metastatic origin express the genes encoding the chains of platelet-derived growth factor (PDGF) and produce a PDGF-like growth factor.
Normal human melanocytes and five human melanoma cell lines were analyzed for production of platelet-derived growth factor (PDGF)-like activity. Three of the melanoma cell lines released an activity that inhibited binding of 125I-labeled PDGF to human foreskin fibroblasts and stimulated [3H]thymidine incorporation in such cells. These activities were inhibited by the addition of anti-PDGF antibodies. All three factor-producing cell lines were derived from the same patient--one originated from the primary tumor (WM 115), and two were from individual lymph-node metastases (WM 239A and WM 266-4). The factor produced by WM 266-4 cells was characterized biochemically in detail. Immunoprecipitated, the metabolically labeled factor migrated in NaDod-SO4/gel electrophoresis as a homogeneous Mr 31,000 species, which under reducing conditions was resolved into two species of Mr 16,500 and Mr 17,000, implying a dimeric structure of the molecule. The factor was purified to homogeneity. Analysis by reverse-phase high-pressure liquid chromatography of reduced and alkylated factor revealed an elution pattern identical to that of PDGF A chains. Thus, the native molecule appears to be a homodimer of PDGF A chains. Blot-hybridization analysis of poly(A)+ RNA from the cell lines with 32P-labeled PDGF A chain and B chain (SIS product) cDNA probes revealed a relative abundance of B chain transcripts in the cell line originating from the primary tumor tissue only but expression of A chain in all three cell lines. We conclude that the two structural genes encoding each of the subunit chains of PDGF can be expressed in human melanoma cells and that the two genes can be independently expressed in such cells.
Cell Line↗
An action spectrum for blue and near ultraviolet inactivation of Propionibacterium acnes; with emphasis on a possible porphyrin photosensitization.
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Light↗
Porphyrin photosensitization of bacteria.
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Dose-Response Relationship, Drug↗
Platelet-derived growth factor agonist activity of a secreted form of the v-sis oncogene product.
We have compared the functional properties of a growth factor partially purified from medium conditioned by simian sarcoma virus-transformed cells with those of platelet-derived growth factor (PDGF). The factor mimicked the effects induced by PDGF: it bound to and activated human fibroblast PDGF receptors and stimulated DNA synthesis. These activities were specifically inhibited by PDGF antibodies and thus elicited by a factor(s) immunologically related to PDGF. The factor behaved as a secretory protein, since about 95% of the receptor-binding activity was found in the medium after a 48-hr serum-free incubation. Structural characterization of the PDGF-like activity revealed a Mr 24,000 intracellular protein and two polypeptides of Mr 13,000 and 11,500 released into the medium. The Mr 13,000 component bound to human fibroblasts; this binding was competitively inhibited by PDGF. The data support the possibility that oncogene products may elicit transforming activity by interacting with the normal cellular mitogenic pathway.
Animals↗
Platelet-derived growth factor: mechanism of action and relation to oncogenes.
Recent studies of platelet-derived growth factor (PDGF) have revealed several structural and functional similarities between this growth factor or components linked to its mechanism of action and certain oncogene products: PDGF itself has a structural homology with the transforming protein of simian sarcoma virus, the PDGF receptor has a functional homology (tyrosine kinase activity) with a family of oncogene products, and PDGF induces the expression of the cellular counterparts of myc and fos. In addition, several tumour cell lines have been found to produce PDGF-like growth factors, which may cause autocrine stimulation of growth. We interpret these findings as indicating that regulatory components along the PDGF-dependent mitogenic pathway may have oncogenic properties if they are inappropriately expressed or activated.
Cell Line↗
The c-sis gene encodes a precursor of the B chain of platelet-derived growth factor.
The relationship between platelet-derived growth factor (PDGF) and the proto-oncogene c-sis has been determined by amino acid sequence analysis of PDGF and nucleotide sequence analysis of c-sis genomic clones. The nucleotide sequences of five regions of the human c-sis gene which are homologous to sequences of the transforming region (v-sis) of simian sarcoma virus (SSV) were determined. By alignment of the c-sis and v-sis nucleotide sequences the predicted amino acid sequence of a polypeptide homologous to the putative transforming protein p28sis of SSV was deduced. Both predicted sequences use the same termination codon and additional coding sequences may lie 5' to the homologous regions. Amino acid sequence analysis of the PDGF B chain shows identity to the amino acid sequence predicted from the c-sis sequences over 109 amino acid residues. Polymorphism may exist at two amino acid residues. These results suggest that c-sis encodes a polypeptide precursor of the B chain. A partial amino acid sequence of the PDGF A chain is also described. This chain is 60% homologous to the B chain and cannot be encoded by that part of c-sis which has been sequenced but could be encoded by sequences which lie 5' to the five regions of v-sis homology in c-sis, or at a separate locus.
Amino Acid Sequence↗
Influence of pH on porphyrin production in Propionibacterium acnes.
Propionibacterium acnes was grown on Eagle's medium for 4-15 days at pH 5.3-7.2 The porphyrin production was measured both by direct fluorometry and by high pressure liquid chromatography (HPLC). The greatest concentration of porphyrins was produced at pH 6.1. Protoporphyrin was the dominant porphyrin species present in the bacteria in all samples. The relative amount of coproporphyrin was greatest at pH 6.7 after 4 days of incubation. In human skin there are local variations in the pH; therefore our findings may be of importance for porphyrin production in acne.
Chromatography, High Pressure Liquid↗
Period lengthening of human circadian rhythms by lithium carbonate, a prophylactic for depressive disorders.
The effect of lithium carbonate on the circadian system of man was studied. Four out of eight volunteers living without time cues in isolated huts in the arctic showed a lengthening of the periods of the body temperature rhythm, activity rhythm, and sleep/wakefulness rhythm by c. 1 h. Four of the participants did not show a change in the periods between the placebo and lithium ingestion phases. Two subjects who did not receive lithium salt showed internal desynchronization between the temperature rhythm and the sleep/wakefulness rhythm. Extreme isolation in bunkers is not necessary to allow free running of the circadian system in man. The sleep/wakefulness rhythm, which is very easy to record, was a reliable indicator of the circadian system in the internally-synchronized state.
Antidepressive Agents↗
Platelet-derived growth factor: identification of constituent polypeptide chains.
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Blood Platelets↗
Manic-depressive states and daily temperature. Some circadian studies.
Proceeding from the hypothesis of disturbed circadian rhythms in endogenous depression, we observed the oral temperature of four patients in a long-term study. The results showed the following: 1) Depression is linked to higher mean daily temperatures compared with normal states. In manic states, the mean daily temperature is even higher than in depressive states. Sleep deprivation as effective treatment causes a decrease in mean daily temperature. 2) The daily temperature maximum changes its position in depressive states. This is interpreted as indicating a disturbed circadian system. 3) A period shorter or longer than 24 h cannot be observed in depressive states.
Adult↗
Separation of human monocytes on density gradients of Percoll.
Monocytes from human blood have been isolated by centrifugation in Percoll. A one-step procedure has been designed to isolate the cells from 7 ml of blood. when 5% of the white blood cells are assumed to be monocytes, an estimated average yield of 100% and a purity of 20% is achieved. The contaminating cells are almost exclusively lymphocytes. By a two-step procedure the monocytes can be obtained 90% pure with an approximate yield of 35%. The cells can be used for tissue culture without washing and they display the usual properties of mononuclear phagocytes in vitro.
Blood Coagulation↗
Computer simulation of circumnutations--behaviour under different g's and comparison with experiment.
The influence of different g-forces on helical growth movements--circumnutation--of sunflower seedlings is treated. Predictions from a model, describing the movements as geotropic overshoot movements, are given. Results from tests of the assumptions are given. These results as well as results in the literature do not contradict the model. The need for more precise centrifuge tests under otherwise free fall conditions is emphasized.
Computer Simulation↗
Effect of lithium carbonate on circadian periodicity in humans.
Five groups of two volunteers lived during four weeks under arctic summer conditions (Spitsbergen) isolated in huts, without time information. They received lithium carbonate or placebo. All showed free-run of their circadian temperature and activity/rest rhythms with periods longer than 24 hours. Under lithium carbonate, a period-lengthening effect can be shown. This could help to understand theprophylactic effect of lithium salts in manic-depressive episodes.
Body Temperature↗
Vitamin A transporting plasma proteins and female sex hormones.
Retinol-binding protein, prealbumin, and sex steroid plasma levels have been estimated daily in four women during the course of a normal menstrual cycle and in three women during treatment with combined oral contraceptives. The retinol-binding protein level showed a bicyclic variation during the menstrual cycle, whereas for prealbumin no consistent pattern of variation was observed. Oral contraceptive therapy induced a significant increase of retinol-binding protein which was correlated with the increase of vitamin A. The increase was about 35% for the formulation containing synthetic estrogen as compared with 15% for the one with natural estrogen. In relation to retinol-binding protein, the plasma level of prealbumin showed a less rapid increase but the final increment after oral contraceptive therapy appeared to be of the same magnitude for both proteins.
Adult↗
Circumnutations under free-fall conditions in space?
Regular growth movement, so-called circumnutation, of plants and plant organs is a very general phenomenon. The origin of circumnutations is, however, unclear. Three different types of model are discussed in relation to some experimental results on circumnutations. It is suggested that an experiment in space, under free-fall conditions, should be done on different species showing circumnutations in order to discriminate between the models.
Gravitation↗