Ruth E. Shrader

Zinc-Deficient Embryos: Reduced Thymidine Incorporation

The 12-day-old embryos of rats with a deficiency of zinc showed a reduced uptake of tritiated thymidine when compared with controls, as shown by liquid scintillation and autoradiography. The high incidence of gross congenital malformations resulting from zinc deficiency may thus be caused by DNA impaired DNA synthesis.

CONGENITAL MALFORMATIONS OF THE NERVOUS SYSTEM IN ZINC-DEFICIENT RATS

Publisher Summary This chapter discusses congenital malformations of the nervous system in zinc-deficient rats. Zinc deficiency appears to have a most marked effect on growing or proliferating tissues. Young weanling rats in a rapid stage of growth are severely affected by zinc deficiency and show extreme retardation or cessation of growth. Similarly, there is a complete arrest of ovarian maturation in the female and of spermatogenesis in the male. The deleterious effect of zinc deficiency on rapidly growing tissues is also very pronounced in the embryo. In an experiment described in the chapter, zinc deficiency in pregnant rats resulted in a high rate of embryonic death, severe intrauterine growth retardation, and a high incidence of congenital malformations affecting every organ system. In the experiment, rat embryos from zinc-deficient females showed a reduced uptake of tritiated thymidine when compared with controls, as measured by liquid scintillation and autoradiography.

Early Postnatal Development of the Intestine in Progeny of Protein-Deprived Rats

Development of the small intestine was studied in newborn, and 4-, 8-, and 12-day-old young of rats fed diets, during gestation, containing 24 or 4% casein as the source of protein. Newborn prenatally protein-deprived rats had shorter, narrower intestines, reduced numbers of villi per unit length, shorter villi, and reduced numbers of absorptive cells and crypt cells. These differences had disappeared by the age of 12 days in adequately fed pups that had survived to that age.

Lactic and Malic Dehydrogenases in Testes of Zinc-Deficient Rats

Summary The activities of LDH and MDH were evaluated in the testes of zincdeficient and control rats by both spectrophotometric and histochemical methods. There was no significant decrease in the activities of these enzymes by either method in the testes of rats fed the zinc-deficient ration for 28 days as compared with rats fed the zincsupplemented diet ad libitum or in restricted amounts. Histological changes were observed in the testes of zinc-deficient rats consisting of decreased tubule size, spermatogonic arrest, nuclear chromatolysis in spermatids and secondary spermatocytes, and pyknotic epithelial cells. The testes of restricted or ad libitum-fed controls appeared normal. The evidence presented does not support the hypothesis that reduced activity of these enzymes is a primary cause of the physiological and morphological changes observed in zinc deficiency.

Drinking-Straw Molds for Embedding Multiples of Longitudinal Segments for Cryostat Sectioning

It is often desirable to obtain cryostat cross sections of tubular structures, such as oviduct, uterus, esophagus, or small intestine, and to retain the sequential relationships of such sections. In this laboratory the following technic which has been used on rat and mouse tissues from newborn and weanling animals has proved to be rapid, inexpensive, and productive of uniformly excellent results.

Cryostat Sectioning; Modification of the Antiroll Plate

A replaceable antiroll plate and holder have been designed for use in the Ames Lab-Tek cryostat which replace the plastic plate supplied with the instrument and insure a flawless, properly aligned plate for maximum efficiency in thin section cutting. A metal plate holder is attached to the existing screw-driven bracket provided with the instrument by the manufacturer. Glass plates made from one half of a 1.5 × 3 inch microscope slide are coated on the leading edge with spray-on Teflon and provided with tape spacers. These plates slip into the holder and can be adjusted for angular inclination and alignment with the cutting edge by movement within the holder or manipulation of the adjustment screw.