Biomedical subjects

D R Appleton

Publications and source records attributed to D R Appleton.

At least 109 records · Page 6Linked to original sources

PubMed1977

The measurement of the cell cycle time in squamous epithelium using the metaphase arrest technique with vincristine.

In squamous epithelia with a single layer of germinative cells, the age distribution of cells in the cell cycle is shown to depend on the direction of the mitotic axis (i.e. a line joining the nuclei of daughter cells) relative to the plane of the basal layer. When axes are in the plane of the basal layer the age distribution is exponential; when cells divide at right angles to the plane of the basal layer, the age distribution is rectangular. When there is a ratio of vertical to horizontal axes, the age distribution is intermediate but can be calculated from knowledge of the proportion of axes in the plane of the layer. Squamous epithelia can be classified according to this arrangement of axes. When there are multiple layers of germinative cells, as in psoriasis, the age distribution is shown to be exponential to a good approximation, whatever the direction of the mitotic axes in the several layers. The importance of these observations is demonstrated by analysing metaphase arrest experiments with vincristine in the single layer of germinative cells in the mouse oesophagus, and in the several layers found in psoriatic epidermis. Choice of the wrong age distribution leads to an error of 6 h in the oesophagus and 23 h in psoriatic epidermis, when the mean cell cycle time is calculated. It is concluded that, in squamous epithelium, it is most important to know the age distribution before calculating the cell cycle time by methods involving measurement of the rate of entry of cells into mitosis or DNA synthesis.

Animals↗

PubMed1977

The effect of a single injection of hydroxyurea on cell population kinetics in the small bowel mucosa of the rat.

The effect of a single injection of hydroxyurea (HU) on cell population kinetics in the jejunal crypt of the rat was studied using autoradiography with tritiated thymidine and metaphase arrest with vincristine. HU appeared to act selectively on cells in the S phase producing inhibition of DNA synthesis and cell death. The deficit in proliferating cells was made good by a decrease in cell cycle time and an increase in growth fraction. Particular attention was paid to the basal, slowly cycling (and possibly clonogenic) crypt cells; early in the recovery sequence an increase in cell production rate was found in the base of the crypt. It is proposed that basal crypt cells, having survived cycle-specific insult because of long cell cycle times, proceed to repopulated the depleted proliferative compartment.

Animals↗

PubMed1977

An in vivo stathmokinetic study of cell proliferation in human gastric carcinoma and gastric mucosa.

Cell production rates were studied in a group of eleven patients with carcinoma of the stomach using an in vivo technique with vincristine. In normal pyloric mucosa estimates ranged from 8 to 15 cells/1000 cells/hr, and in the carcinomas from 3 to 24 cells/1000 cells/hr. Because of the very large variation in the data, comparison between individual tumours and normal mucosa is not regarded as being worth-while at this stage. The implications of these results for previous human in vivo stathmokinetic experiments are also discussed.

Adenocarcinoma↗

PubMed1976

Studies on the mechanism of diurnal variation of proliferative indices in the small bowel mucosa of the rat.

In the rat small bowel mucosa significant variation was found in both the labelling and the mitotic indices with time of day. The zenith and the nadir of labelling and mitotic activity coincided at 15.00 and 02.00 hours respectively. Small changes were found in the "cut-off" position, but this variation in proliferative compartment size was insufficient to account for the comparatively wider fluctuations in proliferative indices. Measurements of the rate of entry into mitosis, using metaphase arrest with vincristine at three widely separated times during the day, showed no significant change. Changes in the growth fraction or in the birth rate as measured cannot account for diurnal variation in the proliferative activity of the small bowel mucosa. We propose a hypothesis which involves diurnal fluctuations in the transit times through G1 and through G2.

Animals↗

PubMed1976

Cell proliferation in the prostate complex of the castrate mouse.

Cell proliferation during 100 h of continuous androgen challenge was studied in the seminal vesicle and coagulating gland of Balb/c mice castrated 3 days or 14 days prior to the first daily injection of 250 mug testosterone propionate. Continuous labelling with [3H] thymidine indicated that the seminal vesicle was almost totally responsive to androgen, as early as 3 days after castration, whereas the androgen sensitivity of the coagulating gland increased from 30% at 3 days after castration to 85% at 14 days after castration. In both tissues the magnitude of the proliferative reaction could be related to the extent of cell loss prior to stimulation. The duration of the pre-replicative phase in the response of the seminal vesicle to androgen was 20-25 h both at 3 and 14 days after castration. In the coagulating gland the pre-replicative phase was 40 h at 3 days after castration and 20 h at 14 days after castration. The maximum uptake of [7alpha-3H] testosterone administered to mice 3 days after castration was significantly greater (P less than 0-01) in the seminal vesicle compared to the coagulating gland. At 14 days the seminal vesicle and coagulating gland exhibited a similar capacity for uptake. The in vivo metabolism of [7alpha-3H] testosterone was studied by thin layer chromatography 30 min and 120 min after administration. A high proportion of the radioactivity extracted from all the tissues was associated with highly polar steroids. At 3 days after castration, the seminal vesicle, 2 h after administration of radioactive testosterone, retained a much higher proportion of radioactivity associated with dihydrotestosterone than did the coagulating gland. The localization of steroid in mice 3 days after castration was studied by dry-mount autoradiography at intervals up to 2 h after the injection of [1,2,6,7(n)-3H]-testosterone. A heavier deposition of silver grains was observed over autoradiographs of the seminal vesicle. In the seminal vesicle the grains were primarily located over nuclear areas whereas in the coagulating gland the grains were diffusely distributed over both nuclear areas and over cytoplasmic areas.

Animals↗

PubMed1976

A comparison of short and long haemodialysis.

Two groups of patients treated by short (Milan) and long (Newcastle) haemodialysis were compared for incidence of symptoms and biochemical control. Short dialysis corrected urea and creatinine as well but control of potassium and phosphate were similar. The only apparent penalties to be paid by short dialysis patients were a higher incidence of itching, tingling or numbness, impairment of vibratory sense and difficulty in controlling blood pressure. The short dialysis group had higher haemoglobin and less dyspnoea, muscle weakness and dizziness after dialysis.

Adult↗

PubMed1975

Cell population kinetics in the mouse jejunal crypt.

The time parameters of the cell cycle were determined in the jejunal crypts of male Balb/c mice by an FLM experiment. The cell cycle time was 12.42 +/- 0.11 h, and the duration of DNA synthesis was 7.61 +/- 0.99 (mean values +/- S.E.). A stathmokinetic technique using vincristine gave a value of Tc of 11.8 h. The growth fraction (Ip) calculated from cycle parameters and the labelling index was 0.61, while a value of Ip estimated from a labelling index distribution curve was 0.65. For the whole crypt a value of 0.86 h was obtained for the duration of mitosis, longer than that in the rat. The mitotic duration was found to vary with cell position, but values of between 0.8 and 1.2 h prevailed throughout the proliferative compartment; values in the basal cell positions appeared shorter. Apparent cell cycle times were longest in the basal cell positions. A value for crypt migration rate calculated from a cumulative birth rate curve was 1.48 cell positions per h, compared with a value of 1.8 +/- 0.27 cell positions per h as measured from movement of the 50% peak value on the labelling index distribution curve with time after tritiated thymidine. The crypt cell production rate was calculated from microdissected and squashed crypts to be about 14 cells per crypt per h. There was a total crypt population of 282 +/- 65 (S.E.) cells, of which 172 were proliferative.

Animals↗

PubMed1975

Cell population kinetics in the rat jejunal crypt.

Cell kinetics in the jejunal crypt of the male Wistar rat were studied using autoradiographic techniques with tritiated thymidine and a stathmokinetic technique with vincristine. The migration rate measured by following the movement of the 50% peak on the labelling index distribution curve with time after injection of tritiated thymidine gave a value of 1-43 +/- 0-14 (SE) cell positions per hour, compared with a value from a cumulative birth rate of 1-78 cell positions per hour. Tht crypt column length was 32-9 +/- 0-2 cells and the column count was 22-3 +/- 0-2. This measurement gave a total crypt population of 734 cells, compared with an estimate of 650 +/- l from direct observation of squashed, microdissected crypts. In each crypt 22-5 +/- 0-5 mitoses were present, and the crypt cell production rate was 32 cells per crypt per hour; this latter value was confirmed using two independent techniques. The crypt growth fraction calculated from the durations of phases of the cell cycle and the labelling index was 0-62. A value of 0-61 was found from the labelling index distribution curve. As assessed from crypt squashes, there were 403 proliferating cells per crypt.

Animals↗

PubMed1975

Adequate dialysis.

Regular haemodialysis with the Kiil dialyser for 8-10 h three times a week is the present standard of adequate dialysis. In 100 patients treated by this regime there was no positive correlation between plasma urea and creatinine before or after dialysis and any of the symptoms of which these patients still complained. There are no grounds for believing that a further increase in dialysis would relieve residual symptoms. However, any reduction in current standards of dialysis should be justified by prolonged clinical trial of large groups of patients before they are accepted as equivalent in view of the infrequency of some uraemic manifestations such as pericarditis. The implications of the middle molecular hypothesis are discussed.

Adult↗

PubMed1975

The proliferative response of the coagulating gland of the castrated mouse under continuous androgen stimulation: an experimental and computer simulation model.

The proliferative response of the coagulating gland of the castrated male mouse has been examined during continuous treatment with testosterone propionate. Fourteen days after castration, s.c. daily injections of testosterone propionate were begun. Mitotic (Im) and labelling (IL) index values were obtained at 3 h intervals for up to 100 h after the initial injection. These showed a biphasic response, in which IL reached a maximum at 30 and 70 h, and Im at approximately 45 and 75 h. Fraction-labelled mitoses (FLM) curves were begun 24, 48, and 72 h after the first androgen injection. In each curve the first wave of labelled mitoses rose to 100% and showed a square form indicating little spread in the durations of the G2 and S phases. Values of 7.5, 1.3 and 0.7 h were obtained for the durations of DNA synthesis (ts), the post-synthetic period (tG2) and of mitosis (tm) respectively. In none of the FLM curves was it possible to demonstrate a second wave of labelled mitoses and direct measurement of the cell cycle time (Tc) was not obtained. Continuous tritiated thymidine labelling indices revealed that after a latent period of 25 h, DNA synthesis began and labelling rose rapidly to 80% by 45 h and then more slowly to 95% by 97 h. Cell population changes during androgen stimulation estimated from measurements of total glandular DNA indicated that the number of cells present in the glands remained constant during the first 30 h after stimulation and thereafter increased to approximately 2-3 times the original value. The data are compared with a mathematical model which assumes that the cell population of castrated mice when stimulated passes from a GO compartment through successive waves of DNA synthesis and mitosis. After each cell division the cells may leave or remain in the proliferative cycle. This model has been subjected to computer simulation using the cell cycle parameters obtained in the kinetic experiments. There was good agreement between the stimulation and experimental results in the Im and IL curves, continuous labelling, and total cell number experiments. The simulation of FLM curves was less successful. Although the first wave of labelled mitoses was clearly seen the model predicts a distinct second wave of labelled mitoses. It is concluded that this does not appear because of variation in the duration of G1.

Animals↗

PubMed1975

The effect of starvation and refeeding on cell population kinetics in the rat small bowel mucosa.

Male rats were starved for a period of 96 hours. Measurements of crypt cell population showed a small reduction during starvation. The growth fraction remained constant, but the total number of proliferating cells per crypt fell as a consequence of the reduction in crypt population. Both labelling and mitotic indices fell throughout the starvation period. The cell cycle time (Tc), measured by a stathmokinetic technique using vincristine, was increased from 10-4 hours in control rats to 14-7 hours after 96 hours' starvation. Upon refeeding, the proliferative indices were observed to rise. After a small initial fluctuation, the growth fraction remained constant. The crypt population remained substantially unchanged. Sixteen hours after refeeding, the cell cycle time was reduced to 6-5 hours. The hypoproliferative response to starvation is mediated solely by an increase in cell cycle time, and the response to refeeding is interpreted in terms of a reduction in Tc. Changes in the size of the proliferating population are considered not to play an important role in either response, although it is not possible to exclude entirely the presence of resting cells in the proliferative compartment itself.

Animals↗

PubMed1975