Development of contemporary issues courses: pitfalls and opportunities.

The development and teaching of contemporary issues courses provide unique opportunities for expanding influence, service to the university, and professional development. During the last decade, there has been a proliferation of such courses centered on the issue of human exploitation of animals. The Ohio State University's general education curriculum, initiated in 1990, includes a requirement that senior students complete a 5-credit course in the category Issues of the contemporary world. Currently, 28 courses are offered in this category, and 5 are from the College of Food, Agricultural, and Environmental Sciences. Our course, entitled Issues concerning the use of animals by humans, was the first from the college included in this category. The course has been offered continuously since 1990-4 quarters per year since 1992. Challenges included gaining approval of the course through a special oversight committee, enhancing visibility of the course outside the college, instructor education, and control of personal biases. The development of this type of course is, necessarily, a continuous process. Instruction of this course has been challenging, enlightening, and exceedingly rewarding. Instructors of similar courses at 11 other universities reported experiences similar to ours.

Autocrine mitogen IgEGF cooperates with c-myc or with the Hcs locus during hepatocarcinogenesis in transgenic mice.

Hepatocarcinogenesis is deterministic in transgenic mice expressing in the liver gene construct Alb-DS4 that encodes autocrine growth factor IgEGF (D Stern et al. (1987), Science 235: 321-324), causing their death within 7.1 months. Hepatic expression of construct AAT-myc encoding murine c-myc causes liver cancer in 44% of the mice at 14.8 months. Cooperation of these genes was evident in CD2F1 transgenics bearing Alb-DS4 plus AAT-myc, in which accelerated hepatocellular carcinoma (HCC) formation caused death of all mice within 4.4 months. Alb-DS4 also cooperates with the Hcs locus, which in C3H/HeJ mice mediates high susceptibility to spontaneous hepatocarcinogenesis, causing accelerated formation of HCC to which mice succumbed at 5.1 months. Thus, genes that predispose to HCC formation cooperate in transgenic mice and their interaction is a key to understand mechanisms that cause liver cancer.

Heavy metal content (Hg2+, Cd2+, Pb2+) in various body parts: its impact on cholinesterase activity and binding glycoproteins in the grasshopper Aiolopus thalassinus adults.

Various toxicological symptoms were observed in Aiolopus thalassinus (Fabr.) adults which resulted from either contaminated soil or from being fed HgCl2-, CdCl2-, and PbCl2-treated diet. Many insects had abnormal wings which were present until the F3 untreated generation. Heavy metals were stored in different body parts, most of Cd2+ and Hg2+ were found in the testes, followed by the gut. Lead was enriched in all organs and body parts of the treated grasshoppers compared to the control. The highest lead concentrations were found in testes, wings, gut, and ovaries. In the treated generation ChE activity was reduced to about 23% compared to the untreated grasshoppers. In contrast to this, lead increased ChE activity to about 14%. In the following F2 untreated adults, ChE activity was normal; no long-term effect was found. In the supernatant of treated adults a Cd-type glycoprotein was found which can bind Cd ions; its MW was determined by electrophoresis and reference proteins at about 14,450 Da.

Long-term effects of heavy metals in food on developmental stages of Aiolopus thalassinus (Saltatoria: Acrididae).

Newly hatched F1 nymphs of Aiolopus thalassinus (Fabr.) were fed on food treated with various concentrations of HgCl2, CdCl2, and PbCl2 until the end of adult life. Toxicological observations were followed in the F1 generation and in the F2 generation derived from the heavy metal-loaded F1 parents. The highest concentration of the heavy metal caused 100% mortality of the F1 adults within four weeks. The nymphal duration of the F1 and F2 generations was significantly prolonged after Hg and Cd exposure, but the F1 of the group treated with lead was not affected. The fresh body weight of adults was significantly reduced in the F1 generation of most treatments and in the resulting untreated F2. The lifespan of the F1 adults was shortened. In the F2 generation, although the lifespan was somewhat longer, generally it was still shorter than that of the control adults. The mean egg number laid by F1 adults fed on food contaminated with Hg or Cd was decreased. This decrease was more pronounced in the case of Cd than Hg. In the females fed on food treated with Pb the reduction of the number of egg pods was not remarkable. The hatchability of the eggs laid by F1 females was significantly reduced as compared to the control. The viability of the eggs laid by F2 adults was somewhat decreased due to either a reduced number of egg pods or to a lower rate of hatchability, especially in the case of Cd. The treated adults frequently displayed weakness in their legs, difficulties in walking, tremors, and nervous movements.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies of intestinal stem cells using normal, chimeric, and transgenic mice.

The mouse intestinal epithelium represents a continuous developmental system. Its four principal differentiated cell types--enterocytes, goblet, enteroendocrine, and Paneth cells--are derived from a common multipotent stem cell located near the base of monoclonal crypts. Members of these four lineages undergo rapid and perpetual renewal along an anatomically well-defined pathway. The gut epithelium provides a unique mammalian model for studying the biological features of stem cells (e.g., their ability to undergo asymmetric division, their enormous proliferative potential, their capacity for functional anchorage in a niche), examining how stem cell hierarchies are established and maintained in renewing cell populations, analyzing the relationships between passage through the cell cycle and lineage allocation (commitment), and defining the mechanisms that give stem cells a "positional address" along the cephalocaudal axis, allowing them to generate regional differences in the differentiation programs of their derived lineages (axial pattern formation).

Expression of SV-40 T antigen in the small intestinal epithelium of transgenic mice results in proliferative changes in the crypt and reentry of villus-associated enterocytes into the cell cycle but has no apparent effect on cellular differentiation programs and does not cause neoplastic transformation.

The mouse intestinal epithelium represents a unique mammalian system for examining the relationship between cell division, commitment, and differentiation. Proliferation and differentiation are rapid, perpetual, and spatially well-organized processes that occur along the crypt-to-villus axis and involve clearly defined cell lineages derived from a common multipotent stem cell located near the base of each crypt. Nucleotides -1178 to +28 of the rat intestinal fatty acid binding protein gene were used to establish three pedigrees of transgenic mice that expressed SV-40 large T antigen (TAg) in epithelial cells situated in the uppermost portion of small intestinal crypts and in already committed, differentiating enterocytes as they exited these crypts and migrated up the villus. T antigen production was associated with increases in crypt cell proliferation but had no apparent effect on commitment to differentiate along enterocytic, enteroendocrine, or Paneth cell lineages. Single- and multilabel-immunocytochemical studies plus RNA blot hybridization analyses suggested that the differentiation programs of these lineages were similar in transgenic mice and their normal littermates. This included enterocytes which, based on the pattern of [3H]thymidine and 5-bromo-2'-deoxyuridine labeling and proliferating nuclear antigen expression, had reentered the cell cycle during their migration up the villus. The state of cellular differentiation and/or TAg production appeared to affect the nature of the cell cycle; analysis of the ratio of S-phase to M-phase cells (collected by metaphase arrest with vincristine) and of the intensities of labeling of nuclei by [3H]thymidine indicated that the duration of S phase was longer in differentiating, villus-associated enterocytes than in the less well-differentiated crypt epithelial cell population and that there may be a block at the G2/M boundary. Sustained increases in crypt and villus epithelial cell proliferation over a 9-mo period were not associated with the development of gut neoplasms--suggesting that tumorigenesis in the intestine may require that the initiated cell have many of the properties of the gut stem cell including functional anchorage.

Toxicological studies on the long-term effects of heavy metals (Hg, Cd, Pb) in soil on the development of Aiolopus thalassinus (Fabr.) (Saltatoria: Acrididae).

Long-term effects of soil treated with 0.12-12 ppm HgCl2, 2-100 ppm CdCl2 and 25-500 ppm PbCl2 on the development, reproductive capacity and viability of Aiolopus thalassinus (Fabr.) (grasshoppers) during two successive generations were studied. The hatching rate of nymphs developed from eggs laid in treated soil was significantly reduced. Mercury was the most effective in reducing the hatching rate followed by cadmium and lead. The newly hatched nymphs, which developed in the heavy-metal-treated soil, were transferred to and reared in separate cages in order that toxicological effects could be followed through the next two generations without any further treatment. No significant increase was observed in percent mortality during both the F1 and F2 nymphal stages resulting from Hg, Cd and Pb treatment. The nymphs were more tolerant than the eggs and adults to the cumulative effect of heavy metals. The mean durations of the F1 and F2 nymphal stages were prolonged in all Hg and Cd treatments, but such a prolongation in the Pb treatments was found only in F1 nymphs, those developed from the two highest soil PbCl2 concentrations (250 and 500 ppm). The adult fresh weight of the F1 and F2 generations was significantly low in the case of the Hg and Cd treatments. The lifespan of the F1 and F2 adults developed from eggs laid in Hg-, Cd- and Pb-treated soil was significantly shortened and thus the number of egg pods was reduced in comparison with the control. The hatchability of nymphs developed from eggs laid by the F1 generation was significantly lower than that of the untreated control. No significant decrease in the hatching rate was found for the eggs laid by the F2 generation, except at the highest soil concentrations of the three metals. The metal content of eggs laid by the F1 generation increased significantly with increasing soil concentrations of the three metals. In the F2 generation eggs the heavy metal content was reduced in all cases; this indicates a dilution of the metal concentration in successive generations if no further exposure takes place.

Ethylnitrosourea-induced mutations in vivo involving the Dolichos biflorus agglutinin receptor in mouse intestinal epithelium.

A mutagenesis assay system is introduced based on the induction of mutations in somatic cells of mouse small intestine using ethylnitrosourea (ENU). F1 mice heterozygous for the Dolichos biflorus agglutinin (DBA) locus (Dlb-1a/Dlb-1b) encoding the DBA cell surface receptor, were treated in utero on either day 7, day 9 or day 11 post coitum. Mutant intestinal cell populations of adult mice were visualised in whole-mount preparations by the absence of histochemical staining using peroxidase-labelled Dolichos biflorus agglutinin. Loss of staining is attributed to mutagenesis of the Dlb-1b allele in the heterozygote. This system allows one to evaluate mammalian mutagenesis in vivo at a single locus. Mutant cell populations appeared as discrete groups of 'striped' villi, each stripe comprising cells derived from unstained crypt stem cells (cf. Schmidt et al., 1985a). A spontaneous mutation level was noted in untreated controls which was found to differ significantly from that recorded in mice treated with the mutagen (P less than 0.01). The mutation scores were highly consistent among mice and a small number of animals (i.e., 16) were sufficient to detect mutagenic effects of ENU. Thus, the advantages which accrue from the assay are (1) the ability to detect small clones of mutant cell populations in the intestine (i.e., cells derived from a single mutated crypt); (2) a small number of tested mice are required to generate a conclusive result, especially when compared to the mammalian spot test (Fahrig, 1978).

On the clonal origin of tumours--lessons from studies of intestinal epithelium.

Clonal studies of adult chimaeric mouse epithelium have demonstrated the monoclonal composition of crypts of Lieberkühn. In neonatal life, however, polyclonal crypts have been found, indicating that crypts are of polyclonal origin. We here relate these findings to studies of mosaic tissues which have addressed the question whether solid tumours are of monoclonal or polyclonal origin. The issues has so far remained unresolved because the expected frequencies of polyclonal tumours, given polyclonal origins, have not previously been estimated. A general approach for the calculation of such expected values is suggested. The consistent reports of tumours with polyclonal components suggest that autocrine or paracrine mechanisms play an important role during tumorigenesis.