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We describe how the histology course we teach to first-year medical students changed successfully from using glass slides and microscopes to using virtual slides and virtual microscopes. In 1988, we taught a classic medical histology course. Subsequently, students were loaned static labeled images on projection slides to introduce them to their microscope glass slides, and we made laser disks of histological images available in the teaching lab. In 2000, we placed the static labeled images and laboratory manual on the Web. We abandoned the Web-based approach in 2001. Faculty selected specific areas on microscope glass slides in student collections for scanning at a total magnification of 40, 100, 200, or 400. Christopher M. Prince of Petro Image, LLC, scanned the glass slides; digitized, encoded, and compressed (95%) the images; and placed them on CD-ROMs. The scanned images were viewed up to a magnification of 400 using the MrSID viewer (LizardTech software) and the computer as a virtual microscope. This viewer has many useful features, including effective microscope and telescope functions that provide greater versatility for sample study and speed in localizing structures than was possible with the actual microscope. Image detail is indistinguishable from that viewed under the light microscope at equivalent magnifications. Static labeled images were also placed on CD-ROMs to introduce students to the virtual slides. AN OVERVIEW OF TEACHING MEDICAL HISTOLOGY IN THE 20TH CENTURYMedical histology has been a longstanding basic science course in the medical school curriculum worldwide. Changes in histology course materials during the 20th century have reflected improvements in histological techniques and slide preparation as well as developments in light microscopes and associated photomicroscopy. Transmission and scanning electron photomicrographs were used in teaching histology during the second half of the 20th century. Changes in course content during the 20th century initially emphasized new knowledge of structure as observed at the light and electron microscope levels. Faculty members subsequently incorporated more histophysiology and histopathology into their courses to emphasize newly acquired information on the function and clinical relevance of the cells and tissues being studied. The presentation of a significant amount of cell biology also has been incorporated into textbooks and courses. Changes that were incorporated during the 1980s and 1990s have occurred at the same time as an emergence of pressures from the Liaison Committee on Medical Education (LCME) and local university administrators to decompress the curriculum and reduce student-faculty contact hours in courses, including histology. At a significant number of medical schools, financial constraints have resulted recently in only partial replacement of retiring faculty, and the teaching loads of remaining faculty, therefore, have increased.During the latter part of the 20th century and the beginning of the 21st century, there has been a rapi...

We have investigated the cell types in mouse testis and ovary in which the c-mos protooncogene is normally transcribed. Blot hybridization analysis of electrophoretically fractionated RNAs from testes of mice with defects in germ-cell development and from prepubertal and adult mice indicated that c-mos was transcribed during male germ-cell development. Analysis of purified populations of spermatogenic cell types detected c-mos RNA in the earliest haploid postmeiotic germ cell, the round spermatid, indicating that c-mos was expressed transiently during spermatogenesis. c-mos RNA was detected by blot hybridization in the ovaries of prepubertal mice and decreased in relative concentration following gonadotropin-stimulated proliferation of granulosa cells. These results suggested that c-mos was transcribed in oocytes and were confirmed by detection of high levels of c-mos RNA in isolated grown oocytes. Thus, c-mos is expressed in both male and female germ cells, suggesting possible roles for this protooncogene in meiosis, germ-cell development, fertilization, and early embryogenesis.Cellular oncogenes have been identified by three approaches: (i) as homologs of retroviral oncogenes, (ii) as genes that induce transformation upon transfection of cultured cells, and (iii) as genes that are frequently altered in neoplasms by DNA rearrangement or amplification (see refs. 1-3 for reviews). Together, these approaches have identified 40-50 cellular genes that, as activated oncogenes, can induce at least some aspects of neoplastic transformation. The formation of activated oncogenes from their normal cellular homologs (termed protooncogenes) can occur as a consequence of changes in the regulation of gene expression, point mutations resulting in single amino acid substitutions, or DNA rearrangements resulting in the synthesis of recombinant fusion proteins from which portions of the normal amino acid sequence have been deleted.A physiologic role for normal cellular progenitors of four oncogenes, sis, erbB, fms and erbA, is indicated by their identification as the genes encoding platelet-derived growth factor, epidermal growth factor receptor, macrophage colony-stimulating factor receptor, and thyroid hormone receptor, respectively (4-9). However, normal functions of other protooncogenes remain obscure. While some protooncogenes are expressed in many types of proliferating cells, others display more restricted patterns of expression, suggesting that they may function in specific developmental pathways.An example of developmental regulation of a protooncogene is provided by the expression of high levels of a unique c-abl transcript during postmeiotic differentiation of male germ cells (10). A possible role for another protooncogene, c-mos, in reproductive processes is suggested by its specific transcription in testes and ovaries of adult mice (11). The testis and ovary contain specialized, hormonally responsive somatic cells, Sertoli and Leydig cells in the male and granulosa cells in the female, as well as germ cells (...

A new method, fiber fractionation, has been used to isolate and separate cells. The (NUNC, Vanguard International Inc., Red Bank, N.J.) and hold the nylon fibers under tension (Fig. 1). This arrangement greatly facilitates the handling and subsequent use of the fibers. Surface contaminants were removed by 10-min extractions of the strung fibers, first with petroleum ether and then with carbon tetrachloride. In order to increase the reactivity of the nylon fibers, they were partially hydrolyzed with 3 N HCl for 30 min at room temperature (6). After thorough rinsing in H20, the fibers were placed in a Petri dish containing 2 ml of a solution of either Concanavalin A (Con A) or various antigens in 0.15 M NaCl (pH 6.0). Protein concentrations ranged from 0.05 mg/ml to 5 mg/ml; specific values are indicated for each experiment. A water-soluble carbodiimide, 1-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide metho-p-toluenesulphonate (Aldrich Chemical, Milwaukee, Wis.), was used to couple protein covalently to the nylon (7). 2 ml of this reagent in 0.15 M NaCl (pH 6.0) at a carbodiimide to protein

Cardiac fibroblasts are the most numerous cells in the heart and are critical in the formation and normal functioning of the organ. Cardiac fibroblasts are firmly attached to and surrounded by extracellular matrix (ECM). Mechanical forces transmitted through interaction with the ECM can result in changes of overall cellular shape, cytoskeletal organization, proliferation, and gene expression of cardiac fibroblasts. These responses may be different in the normally functioning heart, when compared with various pathological conditions, including inflammation or hypertrophy. It is apparent that cellular phenotype and physiology, in turn, are affected by multiple signal transduction pathways modulated directly by the state of polymerization of the actin cytoskeleton. Morphological changes in actin organization resulting from response to adverse conditions in fibroblasts and other cell types are basically descriptive. Some studies have approached quantifying changes in actin cytoskeletal morphology, but these have involved complex and difficult procedures. In this study, we apply image analysis and non-Euclidian geometrical fractal analysis to quantify and describe changes induced in the actin cytoskeleton of cardiac fibroblasts responding to mechanical stress. Characterization of these rapid responses of fibroblasts to mechanical stress may provide insight into the regulation of fibroblasts behavior and gene expression during heart development and disease.

Tumor necrosis factor (TNF) is a cytokine that mediates many of the metabolic responses after endotoxemia, septicemia, and tissue injury. The effect of TNF on testicular function was determined in a series of studies in which rhTNF (0, 2, and 4 X 10(5) units/kg/24 hours) was administered by continuous infusion to male Wistar rats maintained on total parenteral nutrition adequate for growing rats. Testicular weight and histology, and plasma luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone levels were determined at 1, 3, and 6 days. Testicular weight decreased within 24 hours and this was associated with a fall in plasma testosterone and increased LH and FSH levels. These changes persisted for 6 days, indicating a loss of testosterone-mediated negative feedback on gonadotropin release. Histologic examination demonstrated significant damage to the germ cells in the adluminal compartment of the seminiferous epithelium; extensive exfoliation of spermatocytes and spermatids occurred at day six. However the primary spermatogonia in the basal compartment were relatively spared. Damage to the seminiferous epithelium at earlier times was noted in some tubules. The decrease in testosterone concentration and increase in gonadotropin levels suggest that TNF interferes with Leydig cell function. Germ cell damage may be a direct effect of TNF on these cells or may occur through secondary mechanisms involving Leydig or Sertoli cell dysfunction.

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The complex topological association of Sertoli cells and spermatogenic cells in the testis suggests the existence of cell surface adhesion molecules that regulate cellular interactions within the seminiferous epithelium. The recent report of N-cadherin mRNA expression in the mouse testis implies the involvement of this known adhesion molecule in testicular cell binding. Accordingly, here we report that (1) N-cadherin is found on the surface membranes of rat spermatogenic cells and on Sertoli cells, and (2) that N-cadherin is a partial mediator of Sertoli cell-germ cell adhesion as tested in an in vitro cellcell binding assay. Antiserum directed against the N-cadherin cell adhesion recognition sequence was used for Western blot analysis of purified plasma membranes from Sertoli cells and from spermatogenic cells. Both membrane preparations exhibited reactivity at an appropriate M, of about 130 kDa. In addition, immunofluorescence assays demonstrated that both germ cells and Sertoli cells were labeled by anti-N-cadherin. Finally, the antiserum was included in a cytometer-assisted cell-cell binding test to determine its inhibitory ability. The antiserum consistently reduced specific testicular cell-cell adhesion by 30%-50%. This is the first demonstration that antibodies directed against the cadherin cell adhesion recognition sequence are capable of inhibiting cell-cell interactions. Pre-incubation of either rat Sertoli cells or spermatogenic cells alone was sufficient to achieve statistically significant inhibition of intercellular adhesion. We conclude, therefore, that N-cadherin is expressed by both Sertoli cells and spermatogenic cells and that N-cadherin is one of a number of regulatory molecules mediating local cellular associations in the mammalian seminiferous tubule. o 1993 Wiley-Liss, Inc.