A hydraulic powered microtome in a commercial freezer; an improved cryostat for large sections

A new chamber method for mounting tissue sections

We describe a method for mounting tissue sections onto slides that is faster and especially useful for those sections too thin or too large to be mounted easily by conventional methods. We have devised a chamber system for mounting tissue sections onto slides under buffer solution. Because of the buoyancy of sections in the buffer solution and the elimination of fluid surface tension, it is easy to move, turn, unfold, and spread even quite large or thin tissue sections. In-solution-mounting in this chamber also greatly reduces the force of the brush tip used to maneuver sections onto the slide, thus resulting in less damage to the tissue sections. This chamber greatly facilitates mounting multiple tissue sections onto a single slide. The new method is applicable to protocols that stain tissue sections either before (e.g. cytochrome oxidase) or after (e.g. cresyl violet) section mounting.

Teratogenicity of 3,3-dimethyl-1-phenyltriazene: distribution in rats and rat embryos

3,3-Dimethyl-1-phenyltriazene (DMPT) is a methylating agent which is carcinogenic, teratogenic and mutagenic which, in the rat, provides a reproducible animal model with which to study the basis of chemically-induced micrognathism. The basis of teratogenic organotropism of DMPT and other methylating teratogens is unknown. The present study was undertaken to determine if limited chemical distribution within the embryo was responsible for the organotropism of DMPT. Whole-embryo autoradiographs and liquid scintillation analysis indicated that although DMPT may have some limitations of chemical distribution within the embryo, these limitations are not sufficient to explain its teratogenic organotropism.

Application of whole-body autoradiography in toxicology

Whole-body autoradiography enables the drugs and toxicants to be distributed throughout the animal. Good results are obtained with this technique. However, certain artifacts can occur that could lead to misinterpretation, and these must be known. These artifacts are described. From the metabolic point of view, autoradiography provides data on the distribution kinetics of a compound and the elimination of radioactivity in various organs. These data are a guide for quantitative research into the metabolism of a compound. From the toxicological point of view, it must be admitted that the main purpose of this technique is to reveal the sites of retention of radioactivity. Such specific organ retention could be the consequence of the activation of a minor metabolite into a very reactive compound. If this is so, it is a specific organ effect which could not be studied by other techniques and could lead the way to a more specific organ effect which could not be studied by other techniques and could lead the way to a more appropriate line of research in the study of chronic toxicity. However, it must be recalled that the fact that a compound is retained by a specific organ does not always mean that the compound exerts a toxic effect upon the said organ. With this technique, distribution study can be performed on pregnant animals, and it provides us with more data concerning the transplacental passage of radioactive metabolites. All these aspects of the technique clearly indicate that whole-body autoradiography should be insisted upon during the early stages of development of new molecules. Successive experiments could then lead to selecting the best experimental conditions for metabolic pharmacokinetics and studies in toxicology.

Localization and histochemical correlation of 73As by whole-body autoradiography in mice

Whole-body sagittal sections of mice administered [73As] H3AsO4 intravenously were processed for autoradiography and histochemistry for glucose-6-phosphatase or alkaline phosphatase. The intense localization of 73As in bone, kidney cortex, intestinal mucosa, and hair follicles corresponded exactly with the histochemical activity of glucose-6-phosphatase and alkaline phosphatase in sections containing no arsenic. The activity of glucose-6-phosphatase was inhibited in all of these sites in sections containing arsenic.

Whole-body autoradiography of the distribution of 125 I-thyrocalcitonin in mice

The distribution of 125I-thyrocalcitonin in male mice was studied by whole-body autoradiography. At six minutes after injection the highest accumulation of radioactivity was seen in the renal cortex, liver, blood, thyroid gland, bile, and urine. At 20 and 60 minutes there was a rapid decline of radioactivity in the blood and liver and a decided increase in the submaxillary gland, stomach, thyroid gland, urine, and bile. No specific sites of accumulation were noted in bone. Incubation of labeled thyrocalcitonin with mouse serums for as long as 60 minutes revealed significant alteration of the chromatoelectrophoretic properties but no detectable deiodination. Rapid deiodination and degradation of the hormone in blood and other tissues restricted interpretation of the autoradiograms at later time intervals.