Showing papers on "Crypt published in 1974"

Continuous labelling studies on mouse skin and intestine.

Abstract: Data are presented for changes in absolute radioactivity levels and labelling indices (LI) in three tissues: jejunum, colon and dorsal skin in the mouse during conditions of repeated (every 3 hr for 168 hr) 3H-TdR (5 μCi) injections. The lengths of S and the cell cycle were estimated. The crypt and mucosal transit times were evaluated. There is a slowly cycling subpopulation in the crypt which may be the goblet cell precursors or a crypt stem cell population. The skin LI data cannot be fitted by a single straight line and the procedure of continuously handling or injecting the animals appears to result in a disturbance of the steady state. The liquid scintillation data for all samples showed some consistent and surprisingly large fluctuations and a clear deviation from linear uptake with increasing time.

Cryptogenic Cells and Proliferative Cells in Intestinal Epithelium

Abstract: SummaryThe number of cells in the mouse intestinal crypt that are capable of crypt regeneration after radiation damage was estimated to be 44+20−14, which is less than the known number of about 135 proliferating cells.A correction was considered necessary to measurements of crypt survival by the technique of microcolony assay to allow for the increase in the size of regenerating crypts.

The cell cycle time in the rat jejunal mucosa.

Abstract: The regional variation of the duration of cell cycle parameters was studied by constructing fraction of labelled mitoses curves at several levels in the jejunal crypt column of male Wistar rats. Prolonged Tc and Ts values were apparent only in the bottom eight cell positions, and these differences were shown to be significant compared with the remaining cell positions by analysing the data by the method of Gilbert (1972). Above cell position 8 the proliferating crypt cells showed effectively the same phase durations. For the whole crypt column Tc was 11.32 ± 0.14 (SE) and Ts 6.49 ± 0.10. Although variation in phase durations was confined to the basal portion of the crypt, the results essentially confirm the findings of Cairnie, Lamerton & Steel (1965a), and may be interpreted in terms of the slow cut-off model. The demonstration of prolonged Tc values in basal cell positions confirms the presence of a longer cycling subpopulation of cells at the bottom of the crypt.

Control of intestinal epithelial replacement: lack of evidence for a tissue-specific blood-borne factor

Abstract: The small intestine of rats was cut across in two places, about 14 and 50% of the length of the small intestine from the pylorus, and continuity was re-established by suturing the proximal and distal ends. The resulting sac of small intestine, averaging 36% of the total length of the small intestine, had its upper end closed off, and its lower end anastomosed, either to the intestine-in-continuity (an ‘intestine-sac’), or to the skin of the abdominal wall (a ‘skin-sac’). On the ninth post-operative day, the cell production rate in squashes of micro-dissected whole crypts of Lieberkuhn was measured by mitotic blockade with Colcemid. The rate of cell production in unoperated and sham-operated rats was 30 cells/crypt/hr, throughout the length of the small intestine. In the intestine in continuity, the rate increased to an average of 46 cells/crypt/hr above the anastomosis, and to 54 cells/crypt/hr below it. At the lower end of the ‘intestine-sac’, which drained into the intestine-in-continuity, the rate was 39 cells/crypt/hr, while in the lower end of the sac which drained to skin the rate of cell production was only 16 cells/crypt/hr. This significantly lower cell production rate in intestine which was not in contact with ingesta is taken to be evidence of the importance of local, rather than blood-borne factors in the control of epithelial replacement.

Effect of villus length on cell proliferation and migration in small intestinal epithelium.

Abstract: For the interpretation of data supporting the hypothesis of a feedback regulation of proliferative activity in intestinal crypts by the functional villus cell compartment the life span and migration rate of epithelial cells on villi of experimentally reduced length should be known. Autoradiographic studies and scintillation counting of isolated villi at different time intervals after 3H-thymidine labelling were carried out 36, 48 and 60 hr intervals after X-irradiation. The results showed that the life span of epithelial cells in rat small intestine (36–48 hr) is independent of the villus length. In villi of reduced length the migration rate of the epithelial cells was found to be decreased compared with controls. Changes in the migration rate in turn seem to be dependent on the production of epithelial cells in the crypt. Comparative studies on the recovery of crypt and villus epithelium after various doses (300 and 700 R) of X-radiation support the hypothesis that increased proliferative activity in the crypt cell compartment is related to a reduction of the number of functional villus cells below a critical villus length. The importance of these findings in the interpretation of data on (micro) biochemical analyses of certain cell differentiation characteristics during increased proliferative activity is discussed.

The influence of changing cell kinetics on functional differentiation in the small intestine of the rat a study of enzymes involved in carbohydrate metabolism

Abstract: The activity of a number of enzymes involved in carbohydrate metabolism was measured in different cellular compartments of the intestinal epithelium by microchemical techniques. The enzyme activities were related to different cell positions along crypt and villus and to cell age. Enzyme activities in proliferating, differentiating and functional cell compartments of the intestine of normal rats were compared with those in which the cell kinetics had been modified. The effect of increased proliferative activity within the crypt of normal animals was studied in the intestine during recovery after low radiation doses. The effect of increased life-span was investigated in germ-free animals. The specific activity of α-glucosidase, present in microvilli, was found to increase considerably during cell differentiation and subsequent cell migration along the villus. Its specific activity remained unchanged in isolated intestinal loops deprived of dissaccharide substrate for 6 weeks. Lactate dehydrogenase and, to a...

The crypt surface of blade-vent implants in clinical failure: An electron microscopic study

Abstract: An electron microscopic investigation was undertaken in an attempt to ascertain the nature of the blade-vent implant crypt wall in clinical failures. All observations were made on tissues removed from the crypt surface of endosseous metal implants placed in the jaws of both human subjects and rhesus monkeys. From the information currently available and the results obtained in this investigation, two conclusions appear to emerge with some degree of clarity. First, animal experimentation has demonstrated a highly vascular osteogenic connective tissue lining the implant crypt in clinically successful cases. Second, electron microscopic analysis of tissue obtained from both man and monkey and from all levels of the implant crypt surface of clinically failing blades revealed: (1) delayed osteogenesis, (2) epithelial cell migration along the entire crypt surface, (3) persistent inflammation, and (4) a thick subepithelial connective-tissue component composed of collagen fibers and inflammatory cells.

The Action of Nitrogen Mustard in Synchronized Intestinal Crypt Cells in Vivo

Abstract: The exposure to nitrogen mustard of synchronized crypt epithelial cells during various stages of the proliferative cycle induced distinctive morphological alterations in the intestinal mucosa. These structural abberrations were virtually identical regardless of the position of the crypt epithelial cells within the generation cycle at the time of drug administration and were indistinguishable from those induced in asynchronous populations. These findings indicate that nitrogen mustard can exert its cytotoxic effects not only throughout interphase but during the stage of nuclear division as well.