Ultraviolet Radiation Effects on Ehrlich Ascites Tumor Cells : Observations Using a Flying Spot Ultraviolet Microscope

A flying spot ultraviolet microscope, employing a fast scan and pulsed operation of the raster, has been used to induce radiation damage in ascites tumor slide cultures, and to study by time-lapse cinematography the progressive stages of cell damage. The cells observed came from a strain (EF₇) of the Ehrlich ascites carcinoma. Irradiated cells were found to show a characteristic syndrome of damage, involving blebbing at the cell surface, while control cells in the adjacent areas of the preparation remained unchanged. The end of the blebbing period is marked by swelling of the cells, and the time taken for this phenomenon to occur was used as a measure of the severity of the damage. It was found that the time required for swelling is dependent on the size of the dose employed, as well as on the sensitivity of the cells. This latter sensitivity was found to decline as the physiological age of the tumor increased. If ultraviolet illumination below 255 mµ is excluded, no symptoms of damage occur, even when very large doses are used. These observations are discussed in relation to the nature of the system in the cell which is affected.     

Limitations of Fibrinogen-Polymyxin Medium in Detecting Coagulase-Positive Staphylococci in Raw Milk

A fibrinogen-polymyxin medium and Staphylococcus Medium 110 were used in the isolation of coagulase-positive staphylococci in raw milk. Results indicated that both media allow the growth of some rods and of many coagulase-negative cocci. A significantly greater number of coagulase-positive staphylococci were identified by the tube test than were revealed by halo formation on fibrinogen-polymyxin medium.     

STUDIES OF CYTOCHEMICAL LOCALIZATION OF SPECIFIC DEHYDROGENASES IN FROZEN,DISEASED TISSUES OF PINUS

Intracellular activity of individual dehydrogenases in frozen tissues of Pinus monticola and Cronartium ribicola was demonstrated by supplying a specific substrate and the appropriate pyridine-nucleotide-linked coenzyme. Freezing broke cell permeability barriers releasing endogenous coenzymes and substrates which had produced nonspecific enzymatic reduction of nitro blue tetrazolium by miscellaneous dehydrogenases throughout fresh tissues. Freezing enhanced specificity by accentuating the differences between control and treatment sections. Succinic, ethanol, glutamic, α-glycerophosphate, isocitric, lactic, malic, glucose-6-phosphate, and 6-phos-phogluconate dehydrogenases and NAD and NADP diaphorases were localized within cells of the blister rust fungus and its western white pine host. NAD- and NADP-linked forms of glutamic, isocitric, and malic dehydrogenases were also detected. The distribution and activity of the enzymes are described for cell types of host and pathogen. β-Hydroxybutyric and pyruvic dehydrogenases were not detected. Calcium and magnesium (5 × 10⁻³ m final conen) and zinc (1.5 × 10⁻⁵ m final concn) had little or no effect on localization. Amytal increased reduction by 6-phosphogluconate, glutamic, and ethanol dehydrogenases while azide depressed the reaction for the last enzyme. Cyanide augmented diformazan formation with succinate. Transhydrogenase was eliminated as a likely contributor to spurious localization in these frozen tissues. Enzymatically produced diformazan appeared on the surface of lipid droplets in cells of both organisms in fresh and frozen sections. The use and interpretation of data from frozen and fresh tissues in tetrazolium cytochemistry are discussed.     

A role for the thymic epithelium in the selection of pre-T cells from murine bone marrow

A rat thymic epithelial cell line IT45-R1 has been previously described as secreting soluble molecules that in vitro chemoattract rat hemopoietic precursor cells. The development of such an in vitro migration assay was based on the ability of cells to migrate across polycarbonate filters in Boyden chambers. In the present paper, by using the same strategy, we studied murine bone marrow cells capable of migrating in vitro toward IT45-R1 conditioned medium. The responding cells were shown to represent a minor bone marrow subpopulation characterized by a low capacity to incorporate tritiated thymidine in vitro (less than 10% of control). Moreover, this cell subset was considerably impoverished with respect to granulocyte-macrophage CFU (less than 7% of control) and pluripotent hemopoietic stem cells (less than 12% of control). Potential generation of T cells of donor-type in the lymphoid organs of irradiated recipients was measured by using C57BL/Ka Thy-1.1 and Thy-1.2 congenic mice. Thy-1.1 irradiated mice were injected intrathymically or intravenously with the selectively migrated cell subset of Thy-1.2 donor-type bone marrow cells. The use of an i.v. transfer route allowed us to show that these cells possess thymus-homing and colonization abilities. In a time-course study after intrathymic cell transfer, these migrated cells were able to generate Thy-1.2+ donor-type thymocytes represented by all cortical and medullary cell subsets in a single wave of repopulation from day 20 to day 30 after transfer, with a peak around days 23 to 25. The degree of repopulation closely resembled that seen with unfractionated bone marrow cells in terms of absolute numbers of donor cells per thymus (82% of control, 22 x 10(6) Thy-1.2+ cells) as well as in percent donor cells per thymus (105% of control). Thy-1.2+ cells were also detected in the lymph nodes and the spleens of reconstituted recipient mice. Taken together, these results support the idea that the supernatant of the established thymic epithelium IT45-R1 induces the migration of a murine bone marrow subset that contains hemopoietic stem cells already committed to the lymphoid lineage (i.e., pre-T cells).     

Expression and distribution of carbohydrate sequences in chick germ cells: a comparative study with lectins and the NC-1/HNK-1 monoclonal antibody

The expression of end-chain sugar residues and of oligosaccharidic sequences has been investigated in chick germ cells at critical stages during the migration, proliferation and sexual differentiation of these cells. Fluorescent lectins and indirect immunofluorescence studies using the NC-1/HNK-1 monoclonal antibody indicate a remarkable control of glycosylation during germ cell embryonal life. Besides a retained expression of glucose/mannose residues, it was found that alpha- and beta-galactose residues, N-acetyllactosamine and N-N' diacetylchitobiose sequences as well as the sulfated trisaccharidic NC-1 epitope were detectable in a stage-specific pattern. Present at a very high density in the cytoplasm and on the surface of the early germ cells at premigrative and migratory stages, the staining for these carbohydrate sequences gradually disappeared when the germ cells settled and proliferated in the developing gonadal primordia. The disaccharide Gal beta 1----3 Gal NAc was exclusively detected in migrating PGCs. In sexualized gonads, acetyllactosamine and/or diacetylchitobiose were similarly reexpressed in both oogonia and spermatogonia. Spermatogonia displayed beta-galactose residues and a high immunoreactivity with the NC1 Mab, indicating modulations in PGC glycosylations related to the acquisition of sexual phenotypes. In addition NC-1 was found to be expressed in the somatic component of the undifferentiated gonad and in the testis interstitial gland.     

A proenkephalin A-derived peptide analogous to bovine adrenal peptide E from frog brain: Purification, synthesis, and behavioral effects

A peptide derived from the posttranslational processing of proenkephalin A was isolated from an extract of the brain of the European green frog Rana ridibunda and its primary structure established as: Tyr-Gly-Gly-Phe-Met-Arg-Arg-Val-Gly-Arg¹⁰-Pro-Glu-Trp-Trp-Gln-Asp-Tyr-Gln-Lys-Arg²⁰-Tyr-Gly-Gly-Phe-Met. The structure was confirmed by chemical synthesis. The peptide represents an amphibian equivalent of bovine adrenal peptide E [preproenkephalin A (206–230)-peptide] but the sequence contains two amino acid substitutions (Met¹⁵ → Gln and Leu²⁵ → Met) compared with the mammalian peptide. The data support previous hypotheses that the Leu-enkephalin sequence is not present in preproenkephalin A of amphibians. Intracerebroventricular injections of frog peptide E (10 and 100 ng) in mice had no significant effect on horizontal locomotor activity. The peptide, in doses up to 1 μg, had no effect on latency of escape jumping in the hot plate test and the peptide (100 ng) did not modify responses (paw licking, rearing, and escape jumping) in morphine-treated mice.     

How drought events during the last century have impacted biomass carbon in Amazonian rainforests

During the last two decades, inventory data show that droughts have reduced biomass carbon sink of the Amazon forest by causing mortality to exceed growth. However, process-based models have struggled to include drought-induced responses of growth and mortality and have not been evaluated against plot data. A process-based model, ORCHIDEE-CAN-NHA, including forest demography with tree cohorts, plant hydraulic architecture and drought-induced tree mortality, was applied over Amazonia rainforests forced by gridded climate fields and rising CO₂ from 1901 to 2019. The model reproduced the decelerating signal of net carbon sink and drought sensitivity of aboveground biomass (AGB) growth and mortality observed at forest plots across selected Amazon intact forests for 2005 and 2010. We predicted a larger mortality rate and a more negative sensitivity of the net carbon sink during the 2015/16 El Niño compared with the former droughts. 2015/16 was indeed the most severe drought since 1901 regarding both AGB loss and area experiencing a severe carbon loss. We found that even if climate change did increase mortality, elevated CO₂ contributed to balance the biomass mortality, since CO₂-induced stomatal closure reduces transpiration, thus, offsets increased transpiration from CO₂-induced higher foliage area.