The migration of intestinal intervillous epithelial cells labeled in the fetus was followed in neonatal mice. At 17 days of gestation, a first group of pregnant mice received three intraperitoneal injections of 3H-thymidine (150 microCi/injection) administered at 30 min intervals. Two mothers were sacrificed 3 hours after the first injection. Mice from different litters were also sacrificed on days 0, 2, 4, 8, 12, 14, and 16 after birth. A second group of pregnant mice was injected at 18 1/2 days of gestation and offspring were sacrificed on days 6, 8, 10, 12, 14, and 16 after birth. Segments of duodenum and ileum were fixed in glutaraldehyde, postfixed in osmium tetroxide, dehydrated, and embedded in Epon. Sections were stained with aldehyde fuchsin and processed for radioautography. By following the leading front and trailing edge of labeled cells in the longest villi of the duodenum and ileum, we observed that 1) extrusion zones become active immediately after birth and 2) the longest villi do not elongate until 10 days after birth in the duodenum and 14 days in the ileum, that is, when all labeled epithelial cells originally present in the fetus have been extruded. Moreover, by measuring the distance between the internal limit of the inner circular layer of smooth muscle and the intervillous epithelium at 17 days of gestation (12.95 +/- 1.18 microns) or the bottom of the crypts at day 3 (14.81 +/- 0.91 microns), we propose that crypts do not develop as downgrowths: rather the intervillous epithelium is reshaped and the crypt-villus junction moves upward, away from the muscularis externa.(ABSTRACT TRUNCATED AT 250 WORDS)

No abstract

To document regional structural and cellular proliferation changes in the developing mouse colon, tissues from fetal, suckling, and weanling mice were analyzed by light microscopy (LM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), [3H]-thymidine incorporation studies, and radioautography. The proximal and distal colon were studied independently at all ages. At 17-18 days of gestation, the mouse proximal colonic mucosa was projected into high and low longitudinal folds disposed in a V-shaped pattern. From birth up to 9 days, the mucosal folds observed by SEM can easily be misinterpreted as being a succession of high and low villus-like structures at LM level. TEM study confirmed the presence of highly specialized absorptive cells in the upper halves of the mucosal folds during this period. No recognizable crypts were noted at birth. Instead, LM and radioautography showed the presence of cell aggregates developing at the base of the epithelium at all levels of the mucosal folds. These cell aggregates evolved into rudimentary crypts giving fully differentiated crypts by day 16 with radiolabeled cells located in the midcrypt portion. As opposed to the proximal segment, a flat mucosa interspersed with well defined short crypts at birth was observed in the distal colon. During the following days, crypts further developed and by 16 days, the radiolabeled epithelial cells were still exclusively located at the base of the crypt. TEM observations illustrated that specialized cells as those found in the proximal segment did not differentiate in this segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Summary. Pregnant Swiss ICR mice were injected i.p. with 0.5 ~tg of epidermal growth factor (EGF) per g b.wt at 15,16 and 17 days of gestation and fetuses were removed at 18 days of gestation. EGF treatment had no effect on the weight of the fetuses and on the length of the small intestine. No modification of the protein and DNA contents was noted. However brush border alkaline phosphatase and trehalase activities were significantly increased as well as endoplasmic reticulum membrane-bound glucose-6-phosphatase.Epidermal growth factor (EGF) is a small polypeptide mitogen that has been isolated from the male mouse submaxillary gland 2 and from human urine 3. The presence of EGF in human Brunner's gland, shown by Elder et al. 4, suggests that EGF may have a role in mucosal growth and control of gastrointestinal secretion. In the adult male mouse Scheving et al. 5'6 have demonstrated that EGF rapidly stimulates DNA synthesis in some regions of the digestive tract. In the newborn mouse EGF stimulates ornithine decarboxylase activity in the stomach and duodenum 7 and accelerates the maturation of the intestinal mucosa 8. Using an organ culture method of fetal mouse small intestine, we have observed that EGF induces the differentiation of the rough endoplasmic reticulum in absorptive cells after 72 h of culture 9. The aim of this work was to determine the effect of EGF on the fetal mouse small intestine in utero by measuring the protein and DNA contents as well as enzymatic activities of the brush border and endoplasmic reticulum. Results were comparable with both products. Fetuses were removed at 18 days of gestation. The entire small intestine of the fetuses was removed, measured and cut into 3 equal parts. For each assay, the intestinal thirds of 5 fetuses were pooled, weighed and homogenized in 49 vol. of ice-cold red• water in an Omnimixer during 2 min at full speed. The homogenates were used immediately for enzymatic determinations. Protein was measured by the method of Lowry et al. l~ with bovine serum albumine as standard and DNA content was determined by the method of Burton" as modified by Giles Results and discussion. The effects of daily injections of EGF for 3 days beginning at 15 days of gestation have been studied in the small intestine of fetuses at 18 days of gestation. As shown in table 1 the weight of the EGFtreated fetuses, the length of their small intestine and the weight of the different intestinal segments are comparable to that of the controls. Furthermore no modification of the protein and DNA contents is noted along the small intestine. The development of some brush border membrane hydrolytic activities has been investigated. Significant increases of alkaline phosphatase and trehalase activities are recorded along the entire length of the small intestine following EGF treatment (table 2), except for trehalase activity in the distal thirds where the increase is nonsignificant. It is interesting to note that even though alkaline phosphatase and trehalase activities increase following EGF treatm...

The evolution of ultimobranchial bodies in Holtzman rats during the first 64 weeks after birth was studied by reconstructing three-dimensional models from serial sections stained by the periodic acid-Schiff technique.Radio-autography with 125I was made to see if ultimobranchial cells and/or follicular cells lining the lumen of mixed follicles were able to iodinate proteins. The term ultimobranchial body designates herein an embryonic vesicular structure (derived from the third pharyngeal pouch) whose wall is made of stratified squamous epithelium. During the first week after birth, the vesicular ultimobranchial body elongates rapidly and becomes a canal or a duct. During the second week, cell desquamation brings about local dilatations in the lumen of these ducts; with further enlargement ultimobranchial follicles will appear. In one-day-old rats, mixed follicles are present. Only the follicular component of mixed follicles iodinates proteins as is shown by radioautography. The reconstructed models enlarge rapidly up to the 56th day after birth at which time their weight has increased nineteenfold. These same models show that the three morphological components of ultimobranchial parenchyma, namely ducts, follicles and mixed follicles, are in continuity within the thyroid parenchyma. The formation of new thyroid follicles after birth and the possiblility that the ultimobranchial parenchyma may function as an endocrine gland of holocrine type are discussed.

No abstract

In order to gain insight into the earliest pathological changes underlying the development of autoimmune aspermatogenic orchitis (AIAO) the blood-testis barrier was studied by light and electron microscopy, freeze-etching, and cytochemical techniques early (from 1 to 8 days after adjuvant treatment of isoimmunization). At later times (16 to 21 days) the study was carried out by light microscopy only. Adult male guinea pigs were used either as controls or immunized with Freund's complete adjuvant alone or together with pertussis vaccine. An additional group comprised animals immunized with a suspension of isologous spermatozoa emulsified in Freund's complete adjuvant and with pertussis vaccine. Ultrastructural studies of the testes of experimental animals showed, at earlier periods, apparently normal Sertoli junctions. However, in the adluminal compartment, distended gaps were seen between the facing membranes of adjacent Sertoli cells. At later periods, a massive destruction of the germinal cells were observed. In freeze-fracture replicas, the Sertoli junctions of testes belonging to all the experimental groups were characterized by an irregular network of occasionally interrupted strands of particles associated with the P face (PF). Large concavities determined distensions between interconnecting ridges. The gap junctions were increased in number and in surface. Tracer studies using horseradish peroxidase showed that the marker permeated the myoid cells of a greater proportion of tubules than in control animals. Within the seminiferous epithelium there was only a limited passage of the marker towards the lumina of the tubules. Yet the tracer was always excluded from the adluminal compartment by the Sertoli tight junctions. Our observations suggest the possibility that the FCA causes a loosening of the Sertoli junctions. This condition could enhance exchanges between two antigenically different cellular compartments and, thus, favor occurrence of an autoimmune reaction when cytotoxic factors are experimentally induced, as in iso- or autoimmunization.

We evaluated six commercially available tissue culture media in their capacity to support villi morphogenesis and enterocyte differentiation during duodenal development of the fetal mouse in vitro: McCoy's 5A, Medium 199, Swim's S77, Trowell T8, Leibovitz L-15, and RPMI-1640. The duodenal segments were resected at 15 d gestation, before the formation of intestinal villi. In the segments cultured with the first four media, no villi differentiated even at 72 h culture. The number of epithelial cells per transverse section of the explants did not increase at 24 h and thereafter the number of epithelial cells decreased, except with McCoy's 5A. With the Leibovitz and RPMI media, rudimentary villi differentiated at 24 h of culture and they attained their longest length at 48 h. With the RPMI medium, the number of epithelial cells doubled at 24 h of culture and with Leibovitz medium it doubled at 48 h. At the fine structural level absorptive cells remained poorly differentiated with all the media studied. Goblet cells were easily identified after 24 h culture; they had a well developed rough endoplasmic reticulum and numerous mucous granules. Endocrine cells differentiated in culture and they were loaded with secretion granules. It was concluded that the small intestine of the fetal mouse can be kept in organ culture for at least 72 h. Full maturation of absorptive cells seemed to require some additional factor(s) as they remained poorly differentiated with all the media studied. Because well differentiated endocrine cells were present in all the explants, it appeared that gastrointestinal hormones do not affect villi morphogenesis and absorptive cells differentiation.