No abstract

Circadian rhythms in DNA synthesis are described for the tongue epithelium, five different regions of the alimentary canal (gut)--esophagus, stomach, duodenum, jejunum and rectum--and bone marrow in a group of BDF1 male mice. A circadian rhythm is also described for the mitotic index in the corneal epithelium in the same mice. The data document for the first time in the same animals the dramatic variation in cell division encountered from one region of the gut to another. This variation is seen in the amplitudes of the rhythms as well as in the over-all 24-hour means. On the contrary, the phasings of the rhythms in the different regions of the gut are remarkably similar. In this study, where the mice were standardized to 12 hours of light (0600-1800) alternating with 12 hours of darkness, the peak of the DNA-synthesis rhythm occurred around the time of transition from dark to light, and the trough around the time of transition from light to dark. The implications of these findings, and those of others, to the study of cell kinetics and to cancer chemotherapy are discussed.

No abstract

"Anatomizing" is a new verb some use to describe the breaking apart of a complex entity such as the human body, into isolated tidbits of information for study, which can never equal the complex, integrated whole. Although popular with first-year medical students, this practice of "tidbitting" anatomical information into easy to memorize facts or tables of facts does not prepare medical students for the inevitable task of dealing with the integrated structure-function of the human body, both normal and diseased, as patient managers. Examination questions drive the cognitive methods students will use to learn content. Asking students on examinations for recall of previously memorized tidbits fosters the cognitive learning behavior of only memorization. Examination questions, however, can be constructed that assess student understanding and integration of the content, that is, student use of cognitive and metacognitive methods of higher order learning that will foster high-quality learning producing better practitioners and lifelong learners. This kind of efficient student learning needs to begin in the first year of medical school.Learning more efficiently and at deeper levels of understanding is especially pertinent as the contact hours in anatomy courses continue to decrease.

A new patient and blood unit identification system designed to confirm the identity of crossmatched blood products and that of the intended recipient was evaluated. Six hundred seventy-two red cell concentrates were transfused to 312 patients. Participating hospital personnel and patients were interviewed regarding the use and benefit of this unique system, which incorporates a "lock-box" approach to the identification process. The product and procedure were accepted unanimously and enthusiastically, and three potential mistransfusions were avoided by use of the system during the limited period of observation. This type of approach to the identification process affords greater security than conventional practices and minimally burdens staff.

The frequency of labeled mitoses method (FLM) was used to study the cell kinetics in the stratified squamous epithelium of the mouse esophagus and tongue. FLMs were generated by injecting tritiated thymidine (TdR) at two different phases of the mouse circadian system: TdR was injected into one group of mice at 0900 and into a different, second group of mice at 2100. Three variables were monitored for each group; (1) the FLM, (2) the mitotic index and (3) the grain count over the labeled mitotic figures. In both the esophagus and the tongue there was a circadian rhythm in the mitotic index with the peak occurring during the first half of the diurnal phase and the trough occurring during the first half of the nocturnal phase. The FLM curves from each group revealed the following data.

Scheduling exams late in the window of opportunity does not appear to provide a performance advantage and may even be detrimental since these students are responsible for new content information in the course and in other concurrently running courses while they are preparing for a 'late' exam.

An analysis model to detect and quantify white cells (WBCs) in red cell concentrates (RBCC) drawn from units of blood that are highly depleted of WBCs is described. WBC detection is performed by fluorescence analysis of 50 microL of RBCC labeled with propidium iodide, a DNA/RNA fluorophore. Quantification is performed by regression analysis of standard dilutions of RBCC in substantially WBC-free red cells. This RBCC diluent is obtained by filtration of blood through a new medium. The method proves to be precise (CV = 7%), efficient (+/- 30 min/aliquot), and linear (r = 0.99) to 6 log10 WBC depletion of the native product. The current technique is preferable to those suggested previously, such as ficoll concentration, which requires the sacrifice of the unit of blood for counting purposes, and to earlier fluorescence analysis techniques that do not employ WBC-free red cell diluents. The latter do not monitor extremely low concentrations of WBCs because they lack adequate signal-to-noise discrimination. The sensitivity of the described method allows for monitoring of WBC depletion procedures with greater efficiency than is currently available commercially.