The functional state of thymus cells following microwave exposure of endocrine glands

Following local microwave exposure (460 MHz, 120 mW/cm2) of rabbits using fluorescent probes and chemiluminescent analysis, conformational rearrangements in nuclear and cytoplasmic membranes and in thymus cell chromatin of the animals as well as changes in the intensity of the lipid free radical peroxidation were seen. The character of the changes observed depended both on the localization of the exposure and on the number of exposures.     

An in vitro study of functional maturation of murine thymus cells.

Critical time of onset of thymus cell functions in ontogeny was studied in vitro. Collaborative function in an antibody response and ability to induce a graft-versus-host (GvH) response by murine thymocytes from different stages of ontogeny were investigated. Thymocytes from as early as 16-day mouse embryos were capable of collaborating in the antibody response to sheep-erythrocyte-antigen in vitro following 24 h of pretreatment with concanavalin A (con A). By contrast, maturation of thymus cell function as measured by competence to induce a graft-versus-host reaction, was first manifested by newborn thymus cells, and pretreatment with con A did not facilitate the maturation of this thymus cell function. Experiments to understand the effect of con A on the expression of cell surface antigens have also been reported. Con A-treated thymus cells of different ontogenic stages tested were less susceptible to killing by anti-theta serum than nontreated thymus cells; reverse was true with anti-H-2 serum. The significance of the differential susceptibility of con A-treated thymus cells to anti-sera treatment and the finding that mouse thymocytes can provide helper function as early as the 16th day of gestation have been discussed.     

Stepwise development of committed progenitors in the bone marrow that generate functional T cells in the absence of the thymus

We identified committed T cell progenitors (CTPs) in the mouse bone marrow that have not rearranged the TCRbeta gene; express a variety of genes associated with commitment to the T cell lineage, including GATA-3, T cell-specific factor-1, Cbeta, and Id2; and show a surface marker pattern (CD44+ CD25- CD24+ CD5-) that is similar to the earliest T cell progenitors in the thymus. More mature committed intermediate progenitors in the marrow have rearranged the TCR gene loci, express Valpha and Vbeta genes as well as CD3epsilon, but do not express surface TCR or CD3 receptors. CTPs, but not progenitors from the thymus, reconstituted the alphabeta T cells in the lymphoid tissues of athymic nu/nu mice. These reconstituted T cells vigorously secreted IFN-gamma after stimulation in vitro, and protected the mice against lethal infection with murine CMV. In conclusion, CTPs in wild-type bone marrow can generate functional T cells via an extrathymic pathway in athymic nu/nu mice.     

Pole cells of Drosophila melanogaster in culture. Normal metabolism, ultrastructure, and functional capabilities.

The metabolism, ultrastructure, and function of mass-isolated pole cells were examined during short-term culture in vitro. In addition to demonstrating that these cells functioned normally in culture, a number of new features of embryonic pole cells were discovered. Cell populations isolated from Renografin density gradients were incubated in medium containing tritiated valine, uridine, or thymidine. Although pole cells incorporated similar amounts of valine into protein as other embryonic cells throughout the first 6 hr in culture, they began to synthesize RNA only after 2 hr in culture. Approximately 30% of the pole cells synthesized DNA in vitro and this synthetic activity occurred largely during the first hour of culture. An ultrastructural analysis of colcemid-treated cells showed that 10% of the pole cells divide shortly after placement in culture. During pole cell culture in vitro, polar granules and nuclear bodies fragment and disperse so that they are eventually not detected in these cells. These changes also occur during pole cell development in vivo. Finally, we have obtained 25 to 33% germ line mosaicism among the fertile adults which were derived from embryos receiving transplantation of isolated pole cells before and after culture in vitro. These results demonstrate that these cells are able to follow their normal developmental program in vitro and are able to give rise to functional germ cells in vivo.     

Heterogeneity of epithelial cells in the human thymus

Summary To evaluate interrelationships among epithelial cells, and between morphology and function in the microenvironment, we studied the ultrastructural morphology of epithelial cells in sections of human thymus from donors aged 2 months to 31 years. Six types of epithelial cells were observed: subcapsular-perivascular (type 1); pale (type 2); intermediate (type 3); dark (type 4); undifferentiated (type 5); and large-medullary (type 6). Cells of types 2, 3 and 4 were found throughout the organ. The type-2 to -4 epithelial cells may represent various stages in a differentiation process. In this, type-2 cells are very active and type-4 cells are possibly degenerating elements. Type-4 cells can also contribute to Hassall's corpuscles. Type-5 cells were located mainly in the cortico-medullary region and showed the morphological characteristics of undifferentiated elements. Type-6 cells were located exclusively in the medulla and displayed characteristics of cellular activity. Small Hassall's corpuscles consisted of type-6 epithelial cells; in larger corpuscles many nuclei of type-6 cells were found. Cells of types 2 and 6 contained tubular structures (diameter approximately 20 nm).Concerning the function of thymus epithelial cells, the features associated with protein synthesis observed in cellular types 2 and 6 make them likely candidates for humoral factor-producing and/or secreting elements. In addition, type-2 and -3 cells in the cortex appear to contribute to a special pattern of epithelium-lymphocyte interaction (thymic nurse cells), as demonstrated by the intracytoplasmic location of lymphocytes in the epithelial cells. The various steps in intrathymic T-cell maturation occur at locations in a microenvironment composed of morphologically distinct epithelial cells.     

Histamine-content of Gomori-positive cells in the rat thymus

As revealed by a Reinecke-salt histochemical reaction and by immunocyto-chemistry, the Gomori-positive cells in the rat thymus contain histamine. The identity of Gomori-positive and histamine-containing cells was shown in histological preparations and tissue cultures.     

Differentiation of epithelial cells in the mouse thymus

Summary The foetal and post-natal development of the mouse thymus was studied with the electron microscope paying particular attention to the differentiation of the epithelial cells. At about 13 days' gestation, the thymus was composed principally of undifferentiated epithelial cells and some lymphoblasts. The latter accumulated rapidly but did not show much evidence of mitotic activity until after the development of differentiated cortical epithelial cells which appeared during the 15th day of gestation. Further differentiation of epithelial cells did not occur until near term when medullary cystic epithelial cells appeared, and post-natally when small Hassall's corpuscles were developed. Undifferentiated and dividing epithelial cells were seen in the medulla and were present in all postnatal animals examined.This is publication number 1400 from the Walter & Eliza Hall Institute of Medical Research.The author is grateful to Prof. G. J. V. Nossal, Dr. J. F. A. P. Miller and Dr. P. J. Russell for their interest and assistance with various aspects of this study. Special thanks are due to Miss Mary Bravington for her skilled technical assistance. This investigation was supported by grants from the Jane Coffin Childs Memorial Fund for Medical Research and the National Health and Medical Research Council of Australia. The Electron Microscope Laboratory was equipped and supported by grants from the Australian Research Grants Committee, J. B. Were and Sons and the Potter Foundation.     

Saprotrophic capabilities as functional traits to study functional diversity and resilience of ectomycorrhizal community

In an accompanying editorial Dr Petr Baldrian made a case casting doubt on our recent work addressing the saprophytic potential of ectomycorrhizal (EM) fungi. Dr Baldrian’s statements illustrate a very valid truth: the book is still very much open on this subject. The point he raised that the only logical reason for these fungi to be responding to high carbon demand or decreased host photosynthetic capacity by up-regulating enzymes is for the purpose of carbon acquisition is valid as well. Despite this, he makes the case that there is no compelling evidence that EM fungi exhibit saprophytic activity. The concept central to Dr Baldrian’s conclusion is that even though some EM fungi possess the genes necessary for saprophytic behaviour and may even express these genes, EM fungi do not inhabit a position in the soil column that provides access to usable substrate. In this paper we present both previously published and newly obtained data that demonstrate that this assumption is erroneous, and we present arguments that place the saprophytic potential of EM fungi within a broad ecological context.     

Morphological phenotypes and functional capabilities of submandibular parenchymal cells of the ferret investigated by protein, mucosubstance and enzyme histochemistry

Submandibular glands obtained post-mortem from mature ferrets of both sexes were examined with the use of light microscopical histochemical methods for proteins, mucosubstances and enzymes associated with cell functions or organelles. Demilunar cells showed carboxylated mucosubstances that were mainly non-sulphated, and diffuse activity for peroxidase, E600-sensitive esterase and acid phosphatase. Thiol groups were also detected in these cells. Central acinar cells showed sulphated mucosubstances, disulphides and reticular staining for thiamine pyrophosphatase. Intercalary ducts showed diffuse activity for NADH and NAD(P)H dehydrogenases. Striated ducts contained protein, tryptophan, disulphides, neutral mucosubstances and E600-sensitive esterase periluminally. Basally, the striated ductal cells showed variable activity for peroxidase, cytochrome oxidase, succinate dehydrogenase and acid phosphatase. Basolateral plasma membranes of these cells exhibited ouabain-sensitive Na,K-ATPase activity. The collecting ducts were characterized by variable periluminal staining for acid phosphatase, -glucuronidase, acid -galactosidase and E600-resistant esterase. The results suggest that the histological appearances of the acini of the submandibular gland of the ferret are dependent on the synthesis of secretory acid glycoproteins, that the striated ducts are involved with the secretion of tryptophan-rich product comprising neutral glycoproteins and showing esterase activity and with marked transport of ions and that the collecting ducts are involved with absorption.     

The role of the thymus in the maintenance of natural killer cells in vivo

This report describes a model for investigating the role of the thymus in regulating natural killer (NK) cell activity in vivo. Evidence is presented that the thymus can regulate NK cells, and that at least some NK cells can develop without thymic help. Marrow from thymectomized rats depleted of circulating T cells by thoracic duct cannulation was transplanted into rats without a thymus (1 degree ATX.BM). These 1 degree ATX.BM rats had NK cell levels above controls 3 months after reconstitution but markedly depressed NK cell levels by 9 months. When 1 degree ATX.BM marrow was used to reconstitute rats with or without a thymus, those without a thymus (2 degrees ATX.BM) exhibited low NK cell levels after 3 months, and a similar result was obtained when 2 degrees ATX.BM marrow was used to reconstitute 3 degrees ATX.BM rats. The low NK cell levels in 2 degrees and 3 degrees ATX.BM rats were due to a deficiency in spontaneously cytotoxic NK cells, as they had normal numbers of interferon-responsive pre-NK cells. Spleen cells from 2 degrees and 3 degrees ATX.BM rats produced less interferon than control spleen cells when cultured with P815 tumor cells in vitro. However, 2 degrees and 3 degrees ATX.BM rats had higher numbers of large granular lymphocytes than controls despite their low NK cell levels. In marked contrast to 2 degrees and 3 degrees ATX.BM rats, spleen cells from 4 degrees ATX.BM rats had higher levels of cytotoxicity and a higher frequency of both spontaneously cytotoxic and pre-NK cells than controls. The 4 degrees ATX.BM rats also had the highest frequency of large granular lymphocytes in the spleen.