Mitotic activity of the duodenal crypt enterocytes in mice transplanted with EA21a mammary carcinoma.

The presence of a tumor generally changes the mitotic activity of the normal cell population in mice. In the present work, the mitotic activity of the duodenal crypt enterocytes in EA21a mammary carcinoma-bearing mice was determined. The results show that there is a patent circadian variation in normal mice and, in the presence of the EA21a mammary tumor, cell proliferation is stimulated. Stimulation was evident in enterocytes from the intermediate as well as the superficial regions of the crypt. Some humoral factors produced by the transplanted tumor could interfere with the regulatory mechanism of the mitotic activity of duodenal crypt enterocytes.     

EARLY EFFECT OF MOSQUITO LARVAE EXTRACT ON MOUSE CELLS PROLIFERATIONIN VIVO

It has been demonstrated that mosquito larvae crude extract has an inhibiting effect on the mitotic rate of several mouse cell populations. The sampling period was 16–24h after treatment, when mitotic peak normally occurs. The present paper reports the effect of mosquito larvae crude extract on the proliferation of hepatocytes, renocytes, Lieberkhün crypt enterocytes, and sialocytes. In this case, the sampling period covered the dark phase of the day, during the first 12h after treatment. Colchicine-arrested metaphases were controlled at 20/04, 00/08 and 04/12 (Time of Day/Time Post Injection). The mitotic rate was significantly increased in hepatocytes and renocytes and inhibited in duodenum enterocytes. In view of the time chosen to administer the treatments and the time elapsed until sampling, we conclude a probable effect of the extract at the G₂-M point of the cell cycle.     

Isoprenaline-induced cell proliferation in mouse salivary glands: the effect of castration

The proliferative response to isoprenaline in the submaxillary and parotid glands of the Balb/c mouse has been studied in the intact male and female, and also in the male castrated one month prior to stimulation. The hyperplastic response of the acinar cells has been monitored by serial measurements of the flash tritiated thymidine labelling index and the mitotic index. Castration caused the atrophy of the granular ducts in the submaxillary gland, and therefore an increased predominance of the acini. At one month after castration the acini occupied an area almost 1.5-fold greater than that of the granular ducts, but this was not as great as in the intact female gland where acini occupied twice the area of the granular ducts. Hyperplasia was induced by a single injection of isoprenaline (0.3 mM/kg body weight). The response of the submaxillary gland in the intact male and intact female was very similar, DNA synthesis commencing 21-24 h after stimulation and mitotic activity first noted after 33-36 h. On the other hand, in the submaxillary gland of the castrated male, DNA synthesis began after only 18-21 h and mitotic activity after only 27-30 h. A metaphase arrest experiment with vincristine confirmed the more prompt response in the castrated animals; between 33-36 h after isoprenaline injection, the rate of entry of cells into mitosis was 4 cells/100 cells/h in the castrated group but only 0.4 cells/100 cells/h in the intact males. Thus castration appears to bestow a unique state of responsiveness upon the submaxillary gland to isoprenaline stimulation. The mechanisms underlying this change are not yet understood, for it is paradoxical that atrophy of a structural component rich in specific protein growth factors can alter the format of isoprenaline-induced hyperplasia in acinar cells that produce secretory glycoproteins.     

Synthesis and immunocytochemical localization of alpha 2u globulin in the duct cells of the rat submaxillary gland

Alpha 2u globulin, a protein of unknown function so far believed to be synthesized exclusively in the male liver under multihormonal control, is now shown to be localized by immunocytochemistry in the granular convoluted tubules of the adult male submaxillary gland. In addition, using Northern blot analysis, we have shown specific alpha 2u globulin mRNA sequences in the RNA extracted from the submaxillary gland. Thus, it is evident that the protein is being synthesized therein. Alpha 2u globulin was also detected in the submaxillary gland duct cells of adult female and immature animals of both sexes, all of which are known not to synthesize alpha 2u globulin in their livers. The present data have established that alpha 2u globulin is synthesized in the rat submaxillary gland and indicate that the control of alpha 2u globulin gene expression in the rat liver and in the submaxillary gland is different.     

Sex- and Age-Related Temporal Variations in Intestinal-Epithelium Proliferation in the Suckling Mouse

Intestinal-crypt enterocytes are a cell population undergoing constant renewal in the mouse. Both adult and 28 d old animals have been shown to exhibit circadian rhythms in cell proliferative indices, but there are only scant data on the 24 h mitotic activity in the small and large intestine of younger mice. The present studies were thus undertaken in order to characterize the proliferative pattern of enterocytes in the duodenum and colon of 7 and 14 d old males and females of the C3H/S strain. Animals of each sex and from each age group were sacrificed every 4 h during a 24 h span, with each animal receiving an injection of colchicine 4 h before sacrifice. Samples of duodenum and colon were removed and processed for hematoxylin–eosin staining. Twenty longitudinally sectioned crypts within each sample were analyzed, and the mitotic indices of both cell populations from each animal were estimated. The arithmetic mean±SEM for each experimental group were then calculated and the statistical significance of differences between the means assessed by ANOVA and Student t-tests. We observed a greater daily mitotic activity in the duodenum than the colon, and moreover enterocytic proliferation in both those regions was greater in 14 than 7 d old animals. Twenty-four hour variations in mitotic activity occurred in all the experimental groups and tissues except for the large intestine of 7 d old females. Finally, the temporal profile of epithelium proliferation in the suckling mouse varied with age, sex, and site of the intestine studied.     

Sex- and age-related temporal variations in intestinal-epithelium proliferation in the suckling mouse

Intestinal-crypt enterocytes are a cell population undergoing constant renewal in the mouse. Both adult and 28 d old animals have been shown to exhibit circadian rhythms in cell proliferative indices, but there are only scant data on the 24 h mitotic activity in the small and large intestine of younger mice. The present studies were thus undertaken in order to characterize the proliferative pattern of enterocytes in the duodenum and colon of 7 and 14 d old males and females of the C3H/S strain. Animals of each sex and from each age group were sacrificed every 4 h during a 24 h span, with each animal receiving an injection of colchicine 4 h before sacrifice. Samples of duodenum and colon were removed and processed for hematoxylin-eosin staining. Twenty longitudinally sectioned crypts within each sample were analyzed, and the mitotic indices of both cell populations from each animal were estimated. The arithmetic mean±SEM for each experimental group were then calculated and the statistical significance of differences between the means assessed by ANOVA and Student t-tests. We observed a greater daily mitotic activity in the duodenum than the colon, and moreover enterocytic proliferation in both those regions was greater in 14 than 7 d old animals. Twenty-four hour variations in mitotic activity occurred in all the experimental groups and tissues except for the large intestine of 7 d old females. Finally, the temporal profile of epithelium proliferation in the suckling mouse varied with age, sex, and site of the intestine studied.     

Epithelial cell kinetics in the descending colon of the rat

Epithelial cell loss was induced in the descending colon of the rat by temporary ischaemia to investigate whether this would lead to an increase in crypt cell proliferation. Shortly after the temporary ischaemia the number of cells per crypt was markedly reduced, and it was shown that the cell loss occurred mainly from the non-proliferating upper half of the crypt. The number of cells per crypt reached control values again after 24-48 h. There was a marked increase in proliferative activity, as reflected by the labelling index after 3HTdR and by the mitotic index, with peak values at 16 and 24 h after ischaemia. After 48 h the proliferative indices were normal again. The increase in crypt cell proliferation was characterized by an increase in the labelling index as well as in the mitotic index per crypt cell position. No enlargement of the proliferative cell compartment in the crypt was observed. It is most likely then that the increase in crypt cell proliferation was brought about by a shortening of the cell cycle, since the growth fraction in the lower half of the crypt approaches 1.0. The possible implications of the present data for the control of colonic cell proliferation and colonic carcinogenesis are discussed.     

Effects of tumors on the daily mitotic activity of mouse pars intermedia

We have investigated the effects of EA21a and EA34 mammary carcinomas on daily PI cell proliferation in mice. Animals were divided into groups grafted with either EA34 or EA21a carcinomas (and a non-grafted control group). They were all injected intraperitoneally with 2 microg colchicine per g of body weight 4 h before sacrifice and the number of mitoses per 1000 nuclei was calculated. The mitotic index (MI) of pars-intermedia epithelial cells in control animals showed significant temporal variations. However, the MI from mice grafted with EA34 or EA21a carcinomas showed no such variation. There was no difference between the daily MIs of controls and tumor grafted groups. The absence of a 24 h mitotic activity curve in both EA21a and EA34 tumor-bearing animals demonstrates a lower level of synchronization of cells entering mitosis.     

Daily Variations in Colchicine‐Induced Apoptosis in Duodenal Crypts

Apoptotic cell death can be induced by several agents, among them colchicine, a microtubule disrupting‐drug that affects continuously renewing cell populations, such as the intestinal crypt enterocytes. The objectives of this investigation were (1) to confirm in vivo colchicines‐inductive effect and (2) to determine the existence of 24 h variations in the crypt enterocytes apoptotic indices. The study was done on C3H/S male adult mice housed under standardized conditions. Starting at midnight until the end of a circadian period, subgroups of mice were sacrificed after having been injected with colchicine or saline i.p. 4 h beforehand. Duodenal samples were processed for hematoxylin‐eosin staining and TUNEL technique. In order to score the number of apoptosis, the longitudinal sections of the crypts were divided into three regions comprised, respectively, of tiers 1–4, 5–12, and 13–20, proceeding from the bottom to the top of the crypt. Values of each lot were expressed as mean±SEM. A highly significant statistical difference in apoptotic indices was found for colchicine‐treated animals. The 24 h curve for colchicine‐induced apoptosis displayed qualitative and quantitative differences compared to other inducer agents. Highest apoptotic indices were found in the deepest crypt regions. Daily variations were observed in all the crypt sectors of the colchicine‐treated animals and in tiers 5–12 of the saline controls. The present work demonstrates that the colchicine cytotoxicity due to its apoptotic‐inducing effect depends on the dosing time during the 24 h in this mouse strain.     

Daily variations in colchicine-induced apoptosis in duodenal crypts

Apoptotic cell death can be induced by several agents, among them colchicine, a microtubule disrupting-drug that affects continuously renewing cell populations, such as the intestinal crypt enterocytes. The objectives of this investigation were (1) to confirm in vivo colchicines-inductive effect and (2) to determine the existence of 24 h variations in the crypt enterocytes apoptotic indices. The study was done on C3H/S male adult mice housed under standardized conditions. Starting at midnight until the end of a circadian period, subgroups of mice were sacrificed after having been injected with colchicine or saline i.p. 4h beforehand. Duodenal samples were processed for hematoxylin-eosin staining and TUNEL technique. In order to score the number of apoptosis, the longitudinal sections of the crypts were divided into three regions comprised, respectively, of tiers 1-4, 5-12, and 13-20, proceeding from the bottom to the top of the crypt. Values of each lot were expressed as mean +/- SEM. A highly significant statistical difference in apoptotic indices was found for colchicine-treated animals. The 24 h curve for colchicine-induced apoptosis displayed qualitative and quantitative differences compared to other inducer agents. Highest apoptotic indices were found in the deepest crypt regions. Daily variations were observed in all the crypt sectors of the colchicine-treated animals and in tiers 5-12 of the saline controls. The present work demonstrates that the colchicine cytotoxicity due to its apoptotic-inducing effect depends on the dosing time during the 24 h in this mouse strain.     

Iron regulatory protein as an endogenous sensor of iron in rat intestinal mucosa. Possible implications for the regulation of iron absorption.

Duodenal enterocytes adjust intestinal iron absorption to the body's state of iron repletion. Here we tested how iron supply from the blood modulates the RNA-binding activity of iron regulatory proteins (IRP-1 and IRP-2) in immature duodenal rat enterocytes, and whether the modulation is compatible with the hypothesis that IRPs, in turn, may regulate the expression of iron transport proteins in maturating enterocytes during migration to the villus tips. Tissue uptake of parenterally applied 59Fe along the duodenal crypt-villus axis was compared to local IRP-1 and IRP-2 activity and to duodenal 59Fe transport capacity 12 h, 48 h, and 72 h after intravenous iron administration to iron-deficient rats. IRP-1 and IRP-2 activity was significantly increased in iron-deficiency. 59Fe administrated from the blood side was almost exclusively taken up by crypt enterocytes. Accordingly, the activity of IRP-1 decreased at this site 12 h after parenteral iron administration, but remained high at the villus tips. After 48 h the bulk of 59Fe containing enterocytes had migrated to the villus tips. Correspondingly, IRP-1 activity was decreased at duodenal villus tips after 48 h. IRP-2 activity also tended to decrease, though the change was statistically not significant. IRP-2 activity remained significantly higher at duodenal villus tips than in crypts, even after 72 h. Intestinal iron absorption capacity decreased with the same delay as IRP-1 activity after intravenous iron administration. In the ileum 59Fe uptake from the blood and IRP activity showed no significant difference between crypt and villus region. Luminal administration of iron decreased duodenal IRP-1 and IRP-2 activity at tips and crypts within 2 h. Thus, recently absorbed iron becomes available to cytosolic IRP during its passage through the enterocyte. Our results are compatible with a role of IRPs in gearing the expression of intestinal iron transporters in the duodenal brushborder to the body's state of iron repletion.     

G2 restriction point within populations of hepatocytes and tongue keratinocytes in young, growing mice

The authors studied the effect of either extracts from liver (LE) or the malignant tumour ES2 (TE) or plasma from intact mice (PI) or tumour-bearing animals (PT) on the mitotic activity of the hepatocytes and tongue keratinocytes in young, growing C3H/s male mice (28+/-1 days old). Animals standardized for periodicity analysis were injected intraperitoneally with either TE, LE, PI, PT, or saline (S) at 16:00 h with 0.01 ml of sample/g of body weight and were then killed at (time of day/h post-injection) 20:00/04, 00:00/08, and 04:00/12. Colchicine (2 microg/g) was injected 4 h before death. Samples of the liver and tongue from each animal were processed for histology and assessment of mitotic index. The results were expressed as colchicine-arrested metaphases/1000 nuclei. The TE and LE stimulated the mitotic activity of hepatocytes and tongue keratinocytes. Taking into account the time elapsed between the injections and the measurements made in these light-dark synchronized animals, we conclude that the increase in mitotic index observed in those tissues stemmed from a reinitiation of cell-cycle traverse in a subpopulation of G2-arrested, noncycling cells.     

Time dependency of 1,25(OH)2D3 induction of calbindin mRNA and calbindin expression in chick enterocytes during their differentiation along the crypt-villus axis

Quantitative methods of in situ hybridization and immunocytochemistry have been used to measure 1,25 dihydroxyvitamin D3 (1,25(OH)2D3) induction of calbindin mRNA and calbindin protein expressed in jejunal enterocytes at all points along the crypt-villus axis over a 24 h period. Small amounts of calbindin mRNA detected in vitamin D3 deficient (D-deficient) chick intestine increased rapidly to maximal values 8 h after hormone injection. The magnitude of this response was inversely related to age of enterocyte measured separately by injecting tritiated thymidine into D-deficient and 1,25(OH)2D3-injected birds. Enterocytes of all ages expressed small amounts of calbindin 3 h after hormone injection. This amount of calbindin then increased up to 24 h after hormone injection. Maximal calbindin expression took place in basal villus enterocytes. Later decrease in the ability of upper villus enterocytes to express calbindin was associated with a similar fall in calbindin mRNA expression. Previously it was suggested that inefficient translation to calbindin mRNA might take place in basal villus enterocytes 48 h after vitamin D injection. Present work using 1,25 (OH)2D3 shows that calbindin expression takes place at a constant rate during this early stage of enterocyte development. Secondary events limiting higher rates of calbindin synthesis in upper crypt and basal villus enterocytes remain to be identified.     

Amino acid metabolizing enzymes in rat submaxillary gland, normal or neoplastic, and in pancreas.

The activities of 12 enzymes, many related to ornithine metabolism, were measured in rat submaxillary gland, submaxillary gland tumors and pancreas. In submaxillary gland, the activities of arginase, ornithine aminotransferase, pyrroline-5-carboxylate reductase and glutamine synthetase were high, but no ornithine transcarbamylase or proline oxidase could be detected. In the fetal submaxillary gland, arginase was at almost adult levels while ornithine aminotransferase reached 50% of its adult value postnatally. Submaxillary tumors deviated from their cognate tissue by lower levels of amino acid metabolizing enzymes and by high concentrations of thymidine kinase. In pancreas, none of the pyrroline-5-carboxylate metabolizing enzymes were as high as in either liver or submaxillary gland. The outstanding activities were those of gamma-glutamyl transpeptidase and glutamate dehydrogenase. Although arginase activities in submaxillary gland and pancreas were quantitatively similar, they differed qualitatively: submaxillary gland contained the same variant as liver while the pancreatic isozymes resembled those of other nonhepatic tissues.     

The effect of single and of multiple doses of prednisolone tertiary butyl acetate on cell population kinetics in the small bowel mucosa of the rat.

The effect of single and of multiple doses of prednisolone upon cell population kinetics in the rat jejunal crypt was investigated, using autoradiography and stathmokinetic techniques with vincristine. Single injections of prednisolone (2.5 mg/kg body weight) induced a depression both flash thymidine labelling and mitotic indices; this change was shown to be due to a decreased cell production rate. Recovery of these proliferative indices occurred over seven days after injection; measurement of crypt size parameters showed a transient decrease in crypt population. Multiple daily injections of prednisolone (1 mg/kg body weight) produced a more sustained decrease in labelling and mitotic indices, which lasted as long as injections were continued (7 days); stathmokinetic techniques showed decreases in cell production rates, and the crypt population was also depressed throughout this period. It is concluded that prednisolone depresses cell proliferative rates in rat jejunal mucosa.     

Mitogenic action of tumour necrosis factor-alpha and interleukin-8 on explants of human duodenal mucosa

Our aim is to examine whether tumour necrosis factor-alpha (TNF-alpha) and interleukin affect the mitotic activity in explants of human duodenal mucosa and to estimate the release of cytokines from explants incubated with TNF-alpha. Biopsy specimens of normal duodenal mucosa were taken from 19 subjects that underwent upper endoscopy for investigation of dyspeptic symptoms or chronic gastrointestinal bleeding. The specimens were processed following guidelines for organ culture technique. Paired biopsy specimens from 12 subjects were cultured for 23 h to achieve steady state and thereafter the explants were incubated 25 h with 10(-13)-10(-9) M of TNF-alpha or IL-8. Mitoses were arrested in the metaphase by adding vincristine sulphate for the last three hours. The explants were then fixed and processed for microdissection. Fifteen crypts were microdissected and the total number of metaphases was determined using the whole crypt as reference volume. The number of metaphases per crypt was also estimated in explants incubated with 10(-10) M TNF-alpha in the presence of anti-IL-8 antibodies. Additional duodenal explants from seven subjects were incubated with 10(-10) M TNF-alpha for 25 h. Thereafter the release of IL-1-beta, IL-6, IL-8 and interferon gamma (IFN-gamma) into the culture medium was measured by enzyme immunoassay and expressed as pg/mg protein. TNF-alpha and IL-8 significantly increased the number of metaphases/crypts (P<0.0001). The addition of anti-IL-8 slightly reduced the number of metaphases/crypt compared to the values observed in the explants incubated with 10(-10) M TNF-alpha alone (P<0.0001). The number of metaphases/crypt in the explants incubated with 10(-10) M TNF-alpha in the presence of anti-IL-8 antibodies was, however, markedly and significantly higher than that of the controls (P<0.000). TNF-alpha induced the release of IL-8 (P<0.01) and IL-6 (P<0.05) from the duodenal explants. TNF-alpha and IL-8 are potent mitogens to human small intestinal crypts. The mitogenic action of TNF-alpha is primarily a direct effect of the cytokine and only to a minor extent mediated by a secondary production of IL-8 in the duodenal explant. Our findings indicate that TNF-alpha and IL-8 may participate in the regulation of cell proliferation in the human small intestinal epithelium.     

Small intestinal and pancreatic microstructures are modified by an intraduodenal CCK-A receptor antagonist administration in neonatal calves

The aim of the present study was to investigate the role of CCK on the upper gut and pancreas microstructure and on pancreatic juice secretion in neonatal calves assessed by a repetitive intraduodenal administration of FK480, a CCK-A receptor antagonist, during the first 6 days of life. The experiment was performed on 10 neonatal calves surgically fitted with a pancreatic accessory duct catheter and duodenal cannulas. Calves were sacrificed on day 7 for tissue sampling. Treatment with FK480 resulted in: reduction of preprandial pancreatic juice secretion at days 1-3, smaller size of pancreatic acini and number of cells per acinus, reduction in intestinal crypt depth (except in the duodenal bulb), numerous modifications of intestinal villi length and width, lower mitotic index of crypt cells, and increased number and size of enterocytes with 'empty vacuoles'. In conclusion, the blockade of CCK-A receptors during early life both reduced pancreatic exocrine secretion and induced complex changes in pancreatic microstructure. The influence of CCK on the upper gut microstructure in neonatal calves could be either direct via activation of CCK-A receptors located in the mucosa of the upper gut or indirect by modulation of the secretion of pancreatic juice.     

Element concentration changes in mitotically active and postmitotic enterocytes. An x-ray microanalysis study

Unfixed freeze-dried and uncoated tissue sections of the mouse duodenum were suspended across a hole in a carbon planchet and analyzed in a scanning electron microscope fitted with energy-dispersive x-ray analytical equipment. Computer analysis of the x-ray spectra allowed elemental microanalysis of the nucleus, cytoplasm, and late anaphase-early telophase chromatin regions in the cryptal and villus enterocytes. Elemental concentrations (mmol/kg dry wt) were measured for Na, Mg, P, S, Cl, K, and Ca. None of the elements were compartmentalized preferentially in either the nucleus or the cytoplasm of interphase enterocytes of crypts or in postmitotic enterocytes of villi. In contrast, Ca, S, and Cl are detectable in significantly higher concentrations in mitotic chromatin of dividing enterocytes of the crypt as compared to surrounding mitotic cytoplasm, but Na, Mg, and P are in lower concentrations in the mitotic chromatin as compared to mitotic cytoplasm. Interphase enterocytes of crypts have higher concentrations of Mg, P, and K, and lower concentrations of Na than do postmitotic enterocytes of villi.     

Cell proliferation in chicken intestinal epithelium occurs both in the crypt and along the villus

The location of cell proliferation and differentiation in chicken small intestinal epithelium was examined using immunostaining, measurement of DNA synthesis and brush-border enzyme activities. Chicken enterocytes were removed sequentially from the villus using a modification of the Weiser (1973) method. Alkaline phosphatase activity was relatively constant along the villus tip-crypt axis but decreased in the crypt fractions, whereas sucrase and maltase activities showed higher activity in the upper half of the villus and lower activity in the lower half of the villus and in the crypt. Immunostaining of proliferating cell nuclear antigen indicated the presence of proliferating cells both in the crypt and along the villus, including some activity in the upper portion; the crypt region exhibited a significantly higher number of proliferating cells. Labelled thymidine incorporation into cell fractions after 2 h incubation exhibited a similar pattern of proliferation, with the most active region observed in the crypt and proliferation activity decreasing along the villus. However, some activity was found in the upper half of the villus. After 17 h incubation, cells from the middle region of the villi showed greater proliferation ability than the 2 h incubation. These results indicate that, unlike mammals, chicken enterocyte proliferation is not localized only in the crypt region, and that the site of enterocyte differentiation is not precisely localized. Accepted: 22 January 1998     

Gene expression of divalent metal transporter 1 and transferrin receptor in duodenum of Belgrade rats

Regulation of iron absorption is thought to be mediated by the amount of iron taken up by duodenal crypt cells via the transferrin receptor (TfR)-transferrin cycle and the activity of the divalent metal transporter (DMT1), although DMT1 cannot be detected morphologically in crypt cells. We investigated the uptake of transferrin-bound iron by duodenal enterocytes in Wistar rats fed different levels of iron and Belgrade (b/b) rats in which iron uptake by the transferrin cycle is defective because of a mutation in DMT1. We showed that DMT1 in our colony of b/b rats contains the G185R mutation, which in enterocytes results in reduced cellular iron content and increased DMT1 gene expression similar to levels in iron deficiency of normal rats. In all groups the uptake of transferrin-bound iron by crypt cells was directly proportional to plasma iron concentration, being highest in iron-loaded Wistar rats and b/b rats. We conclude that the uptake of transferrin-bound iron by developing enterocytes is largely independent of DMT1.