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.

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.

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).

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.

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.

Economics of using bovine somatotropin in dairy cows and potential impact on the US dairy industry.

Budgets with a microcomputer spreadsheet were developed to evaluate the economics of bovine somatotropin use and to estimate the impact on US dairy cow numbers. Income over feed and variable costs increased with somatotropin use and low feed prices. With high feed prices, income responses were less favorable, and when combined with low milk prices, somatotropin use resulted in less income than from control cows. Price of somatotropin did not have a major effect on production costs. The number of cows needed to meet US milk requirements is primarily influenced by per capita consumption and production per cow. With continuing yearly increases in per capita consumption of 2 kg of milk equivalent and cow milk yields of 114 kg, the number of milk cows needed through 1992 remains at the 1987 figure of approximately 10.3 million. In the scenario of a 15% increase in milk yield due to somatotropin, 20% of cows receiving the hormone, and cows receiving the hormone being 10% above the national average of all cows; the number needed in 1992 is 9.77 million, or a drop of 5.4% from 1987. Somatotropin use will have a less drastic effect on cow numbers than originally predicted.

Mammary implant shell failure.

The author critically examined removed implants, and found that the sac of both inflatable and gel mammary implants may perforate due to wear or erosion.

Epinephrine inhibiting milk ejection in lactating cows.

Blood oxytocin was determined on 10 Holstein cows during normal milking and during milking when epinephrine was injected intravenously before or after udder stimulation. The average peak oxytocin concentration during normal milking was 399.7 muU/ml plasma and was reached at 1 min after teat cup application. Oxytocin concentration in blood plasma declined rapidly after peak concentration and dropped to 30.5 muU/ml plasma within 4 min after the start of milking. By 5 min after removal of the teat cups, it had declined to less than 4 muU/ml plasma. The administration of epinephrine, either before or after udder washing, inhibited milk ejection as indicated by milk production and oxytocin concentrations. Peak oxytocin concentrations were 1.05 muU/ml plasma 1 min after teat cup application when epinephrine was injected before udder washing and 8.6 muU/ml plasma at teat cup application when epinephrine was injected after udder washing. These results and the use of a beta receptor blocker to inhibit the effect of epinephrine at the myoepithelial cell level indicated that epinephrine inhibited release of oxytocin from the neurohypophysis.