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Biomedical subjects

E Thorud

Publications and source records attributed to E Thorud.

At least 55 records · Page 3Linked to original sources
PubMed1982

Circadian rhythms in mouse epidermis: variation in the numbers of basal and differentiating cells, cell density, and cell loss.

In histologic sections from hairless mouse epidermis, the total epidermal cell number and the numbers of basal and differentiating cells were determined per unit length, and cell density was calculated. Sampling was made every 2 h during 2 successive 24-h spans. All parameters showed circadian changes during both 24-h spans. The cell numbers per unit length and the cell density showed both high values around 12(00), some hours subsequent to the peak of mitotic activity. The loss rate of epidermal nucleated cells was calculated from first harmonic sine curves fitted to the circadian changes in total epidermal cell number and to the mitotic rate. The loss rate showed a circadian rhythm with increased values from after 16 00 to after 00(00). This implies that there is a circadian variation in the transition of differentiating cells into horny materials, and hence in cell differentiation.

Animals↗
PubMed1981

Inhibition of methylcholanthrene-induced skin carcinogenesis in hairless mice by dimethyl sulfoxide.

Hairless mice were given 5 topical applications of 470 nmol 20-methylcholanthrene (MCA) at one week intervals. In one experimental group the MCA was dissolved in reagent grade acetone alone, in another group it was dissolved in a mixture consisting of 50% acetone and 50% dimethyl sulfoxide (DMSO). A control group received the mixed solvent alone. The animals were observed for development of papillomas and malignant tumors during 75 weeks. The group treated with MCA in acetone/DMSO had a higher mortality than the two other groups. The admixture of 50% DMSO to the solvent had a significant inhibitory effect on tumor and cancer rates and on cancer yield, whereas no effect could be observed on the tumor yield. Hence, 50% DMSO in the solvent has a moderate, but significant, inhibitor effect on MCA-induced skin carcinogenesis. Similar inhibitory effect of DMSO on the promotion phase in two stage-carcinogenesis protocols have been reported in the literature. The biochemical mechanisms behind this effect are unknown.

Animals↗
PubMed1981

Epidermis extracts (chalone) inhibit cell flux at the the G1-S, S-G2 and G2-M transitions in mouse epidermis.

Epidermal cell flux at the G1-S, S-G2 and G2-M transition was examined during the first 4 hr after injection of epidermis extract. The flux parameters were estimated by a combination of several methods. The G1-S and S-G2 transit rates were calculated on the basis of a double labelling technique with [3H]TdR, the G2-M flux by means of colcemid and the relative proportion of cells in the S or G2 phase by means of flow cytometry. All experiments were performed both in early morning and late evening, corresponding to maximum and minimum rates of epidermal cell proliferation in the hairless mouse. The epidermis extract inhibited the S-G2 and G2-M transit rates to the same degree, while the inhibition of cell flux at the G1-S transit was consistently stronger. In general, the inhibition of cell flux at the different transitions was most pronounced when the rate of cell proliferation was low and vice versa.

Animals↗
PubMed1981

Evidence of rapid and slow progression of cells through G2 phase in mouse epidermis: a comparison between phase durations measured by different methods.

Percentage labelled mitosis (PLM) measurements were initiated at four different times during a 24-hr period and continued for 24 hr in hairless mouse epidermis. Estimates of G2 and S phase durations (mean TG2 and mean TS) were calculated. A significant number of labelled mitoses (10--20%) was seen after 30 min in all four PLM measurements and the estimated mean TG2 varied from 1.4 to 2.5 hr and was in agreement with values from PLM measurements in other epithelial tissues. These mean TG2 values were much shorter than expected from [3H]TdR double labelling experiments and from a multiparameter cell kinetic study in hairless mouse epidermis and did not reflect the circadian variations seen in these studies. The differences in estimates of phase durations can be explained by postulating two G2 cell populations; one with a rapid and another with a slow rate of cell cycle progression. The cells with the higher rate are mainly registered by the PLM method, whereas those with the lower rate largely escape detection by this method. TG2 estimates from PLM measurements in mouse epidermis therefore do not reflect the phase duration of the entire G2 population. It is also concluded that circadian variations in TS can not be accurately registered by the PLM method.

Animals↗
PubMed1980

Flow cytometry (FCM) of human epidermal cells. A preparation method for epidermal cells and demonstration of circadian variations in the proportion of S-phase cells.

A suction blister technique on the abdominal skin to separate pure human epidermis from its basement membrane is described. After incubation with proteolytic enzymes (trypsin, pepsin) and mechanical shaking, isolated cells and nuclei were stained with ethidium bromide. DNA-specific fluorescence was measured in a flow cytometer using UV excitation light. Cell-cycle phase distributions were obtained from the resulting histograms using a planimetric method. The proportion of cells with an S-phase DNA content showed circadian variations with peak values shortly before noon, and lower values during the rest of the 24 h period.

Blister↗
PubMed1980

Perturbation of cell cycle progression in mouse epidermis prior to the regenerative response.

Cell kinetic perturbations that resulted in a wave of increased cell division during the 6-8 hr lag period prior to regenerative DNA replication in mouse epidermis were examined. The epidermis was stimulated to proliferate by adhesive tape stripping, and flow cytometric DNA measurements of isolated epidermal basal cells counting of mitoses, of Colcemid arrested metaphases and of labeled mitoses among basal cells in histologic sections were made. The results showed that mitotic peaks that occur in the prereplicative period subsequent to tape stripping can be explained by a delay in cell progression through the S phase, followed by subsequent release and partial synchrony in further cell cycle progression. Early peaks of mitoses in epidermis stimulated to proliferate should therefore not, without further evidence, be assumed to originate from cells triggered into division from a resting G2 compartment. The results also indicate an initial delayed cell progression through the G2 phase, whereas the mitotic duration seemed to be initially reduced, indicating that the DNA synthesis phase and the G2 phase are parts of the epidermal cell cycle that may be most vulnerable to various types of influences.

Animals↗
PubMed1980

Perturbation of cell cycle progression in mouse epidermis prior to the regenerative response.

Cell kinetic perturbations that resulted in a wave of increased cell division during the 6--8 hr lag period prior to regenerative DNA replication in mouse epidermis were examined. The epidermis was stimulated to proliferate by adhesive tape stripping, and flow cytometric DNA measurements of isolated epidermal basal cells, counting of mitoses, of Colcemid arrested metaphases and of labeled mitoses among basal cells in histologic sections were made. The results showed that mitotic peaks that occur in the pre-replicative period subsequent to tape stripping can be explained by a delay in cell progression through the S phase, followed by subsequent release and partial synchrony in further cell cycle progression. Early peaks of mitoses in epidermis stimulated to proliferate should therefore not, without further evidence, be assumed to originate from cells triggered into division from a resting G2 compartment. The results also indicate an initial delayed cell progression through the G2 phase, whereas the mitotic duration seemed to be initially reduced, indicating that the DNA synthesis phase and the G2 phase are parts of the epidermal cell cycle that may be most vulnerable to various types of influences.

Animals↗
PubMed1980

The stathmokinetic method in vivo. Time-response with special reference to circadian variations in epidermal cell proliferation in the hairless mouse.

Groups of hairless mice were injected i.p. with a stathmokinetic dose of 0.15 mg colcemid at seven different times of the day and animals killed 0, 15 and 30 min, 1, 2, 3 and 4 hr after the injection. The proportion of cells in metaphase and ana/telophase was determined in histological sections. The results showed a transient accumulation of metaphases about 30 min after the injection, followed by an increase in metaphases from 1 to 4 hr. Therefore, no value before 1 hr after the colcemid injection should be used in calculations of the mitotic rate. The presence of circadian rhythms with high mitotic activity in the morning and low activity in the evening was confirmed. It is shown by regression analyses that the accumulation period of 4 hr is sufficiently short to reflect circadian variations in epidermal cell proliferation and that the 4-hr accumulation value alone is sufficient to estimate the mitotic rate.

Animals↗
PubMed1979

Flow cytofluorometric analysis of a human aneuploid cell line growing in vitro and in intraperitoneal diffusion-chambers.

An aneuploid established cell line originating from human skin (NCTC 3075) was cultivated in vitro culture and in intraperitoneal diffusion chambers in hamsters. In in vitro cell culture a near tetraploid cell line dominated. Shortly after implantation into the diffusion chambers in the peritoneal cavity of hamsters a selective lysis of cells with near tetraploid DNA content occurred, with a relative increase of a diploid subline. After 5 days in the hamster a tetraploid cell line again dominated as in in vitro culture. The use of flow cytofluorometry for ploidy analysis and changes in cell cycle traverse is demonstrated. The possible use of this model system in studies of response to therapy is discussed.

Aneuploidy↗
PubMed1979

Internal cysts and fistulae of branchial origin.

Cysts and fistulae related to the second and third pharyngeal pouches are described. These anomalies probably occur more often than presumed. Unilateral recurring infections of the tonsillar region, including parapharyngeal abscess, may be caused by anomalies related to the second pouch. Third pouch anomalies are located in the piriform recess. Cysts may reach a size that causes obstruction to the larynx and hypopharynx, while diverticulae cause few symptoms.

Adult↗
PubMed1979

Circadian rhythms in mouse epidermal basal cell proliferation. Variations in compartment size, flux and phase duration.

Several kinetic parameters of basal cell proliferation in hairless mouse epidermis were studied, and all parameters clearly showed circadian fluctuations during two successive 24 hr periods. Mitotic indices and the mitotic rate were studied in histological sections; the proportions of cells with S and G2 phase DNA content were measured by flow cytometry of isolated basal cells, and the [3H]TdR labelling indices and grain densities were determined by autoradiography in smears from basal cell suspensions. The influx and efflux of cells from each cell cycle phase were calculated from sinusoidal curves adapted to the cell kinetic findings and the phase durations were determined. A peak of cells in S phase was observed around midnight, and a cohort of partially synchronized cells passed from the S phase to the G2 phase and traversed the G2 phase and mitosis in the early morning. The fluctuations in the influx of cells into the S phase were small compared with the variations in efflux from the S phase and the flux through the subsequent cell cycle phases. The resulting delay in cell cycle traverse through S phase before midnight could well account for the accumulation of cells in S phase and, therefore, also the subsequent partial synchrony of cell cycle traverse through the G2 phase and mitosis. Circadian variations in the duration of the S phase, the G2 phase and mitosis were clearly demonstrated.

Animals↗
PubMed1979

Noise-induced hearing loss and the comprehension of speech in noise.

Subjects suffering from noise-induced hearing loss (NIHL) with or without hearing loss at 2 kHz were examined by speech audiometry with a three-digit test, bisyllabic and monosyllabic PB word lists in silence, and in USASI noise with a masking effect of 44 dB and 68 dB at 1 kHz. Subjects with up to 20 dB hearing loss at 2 kHz had almost the same speech comprehension in noise as normal hearing subjects. Subjects with hearing loss greater than 20 dB at 2 kHz had increasing discrimination loss at increasing noise levels. They also needed a signal-to-noise ratio better than normal-hearing persons would yield at the noise levels used. The evaluation of hearing disablement in occupational noise-included hearing loss should therefore be based for one-half on the results of speech audiometry in silence, and for the other half, in noise.

Adult↗
PubMed1978

Epidermla cell kinetics in hairless mice after bleomycin. I. Perturbations after different single doses.

Three different doses of bleomycin (BLM) (2,1, and 0.01 mg/animal) were injected ip into groups of hairless mice. Cell kinetic alterations in the basal layer of the epidermis were studied up to 10 days after BLM administration. The two highest doses of BLM affected the epidermal cell kinetics in a similar way but with different time courses. Only a moderate depression of the labeling index was observed during the first 24 hours. The results indicate that cells affected by BLM in the middle of the G1 phase are arrested in their subsequent S phase, and that thereafter an increase in the rate of DNA synthesis may occur in the arrested cells without increasing the number of cells in S phase. The percentage of cell accumulated in S and G2 phases as determined by flow cytofluorometry never exceeded 130% of control values with any of the doses. Phase durations were determined from percentage of labeled mitoses curves after the highest dose of BLM and were not significantly different from normal values, indicating that the accumulated cels are probably out of cycle and unable to proliferate again. Calculations based on cell counts and mitotic rate showed that the cells had a prolonged lifespan. No block and subsequent release of cells specifically caused by BLM were observed. BLM has a complex effect on the epidermis, and therefore does not seem to be a promising agent for cell synchronization as a basis for combination chemotherapy in vivo.

Animals↗
PubMed1976

Separation of mouse epidermal basal and differentiating cells for microflow fluorometric measurements: a methodologic study.

The DNA content of lymphocytes and of basal cells from normal hairless mouse epidermis was measured by microflow fluorometry (MFF). To obtain a relatively pure suspension of epidermal basal cells a combined mechanical and enzymatic method was used. The admixture of differentiating cells into the basal cell fraction after cell separation was 13%. The results were compared with those obtained with conventional Feulgen microspectrophotometry applied to basal cells and dermal lymphocytes in histologic sections. The results from both cytophotometric methods were in good agreement and clearly demonstrated the improved resolution obtained by using microflow fluorometry. When the lymphocytes were not treated with pepsin before being stained with ethidium bromide for MFF, the modal DNA value was consistently below that of the basal cells from the same specimen. Pepsin treatment of lymphocytes, however, increased their fluorescence intensity to the value of epidermal basal cells. The modal DNA value of Feulgen-stained dermal lymphocytes in histologic sections was consistently below that of epidermal basal cells from the same section. The advantage of pepsin treatment for obtaining higher resolution of DNA measurements of basal and differentiating epidermal cells and of lymphocytes was evaluated. The cell cycle distribution of basal cells from epidermis in different states of proliferative activity was determined. Changes in the proportion of cells in S phase were parallel to changes in the 3H-Tdr labeling index.

Animals↗
PubMedDate not supplied

Epidermal cell kinetics in hairless mice after bleomycin. II. Perturbations after multiple doses.

Bleomycin (BLM) at doses of 0.1 mg/animal was injected into hairless mice every 4 hours for 4 days. Epidermal cell cycle phase distributions were determined by flow cytofluorometric DNA measurements. Labeling indices and mean grain counts were determined by means of autoradiography, and mitotic rates were determined by demecolcine arrest of metaphases. A small, partially reversible accumulation of cells with G2 phase DNA content was observed subsequent to BLM administration. Most of the cells accumulated in G2 phase, however, seemed to stop proliferation and die in this phase. Thus, BLM does not fulfill the criteria for a good synchronizing agent in the hairless mouse epidermis. Flow cytofluorometry alone cannot determine whether piling up of cells in a particular cell cycle phase is true synchrony or an accumulation of lethally damaged cells. Several cell kinetic methods should be used to demonstrate real synchrony.

Animals↗