Antigen Binding Lymphocytes in Congenitally Athymic (Nude) Mice

THE autoradiographic detection of the binding of various radiolabelled antigens to a proportion of lymphocytes from animals not exposed to those antigens (“nonprimed” lymphocytes) is well documented^1–4. Such lymphocytes are thought to have patches of surface immunoglobulin, primarily IgM, which act as specific receptors for antigen^5,6. A proportion at least of these unprimed lymphocytes are immunologically competent as shown in vivo^7,8 and hence are true antigen reactive cells. Most assays have used peripheral lymphocyte suspensions from tissues of man, mouse, rat and chicken, not enriched or fractionated in any way for the two distinct lines of lymphocytes, thymic derived (T) and non-thymic derived (B)⁹. It is not clear whether antigen-binding cells (ABC), detected in routine assays where autoradiographs are exposed for 1–2 weeks, are of both T and B cell type or are predominantly of only one type. Experiments using unlabelled and radiolabelled immunoglobulin antisera with isolated T and B cells have inferred specific antigen binding on both populations although T cells seem to have far fewer antigen binding receptors than B cells¹⁰.     

Selective <Emphasis Type="Italic">in vitro</Emphasis> Methylation of Rat Chromatin Associated Historie after Partial Hepatectomy

IT is thought that chromosomal proteins may be involved in the control of genetic activity^1,2, but certain facts about their metabolism in mammals^3–5 and insects^6,7 indicate that de novo synthesis of histones may not be an important determinant in the modulation of genetic activity.     

The Development of Protein Bodies in the Storage Tissues1

Homogenates of the developing endosperms of maize, wheat, andbarley and of developing cotyledons of peas have been separatedon sucrose density gradients. Protein bodies have been recognizedby their content of storage proteins, their density, and theirappearance under the electron microscope. The distribution ofthe endoplasmic reticulum was followed by measuring NADH-cytochromec reductase. Glutamate dehydrogenase, catalase, and triose phosphatedehydrogenase—respectively marker enzymes for mitochondria,microbodies, and plastids—were also present in the gradients.Differences were found between the different species with respectto the association between the endoplasmic reticulum and thestorage proteins. There was no evidence for any vacuolar markerenzymes associated with the cereal protein bodies. The proteinbodies of wheat and barley appear to be similar to each otherbut differ from maize in that the latter have much more endoplasmicreticulum associated with them. In contrast the protein bodiesof peas co-sediment with vacuolar marker enzymes.     

Maintenance Respiration and Carbon Balance of Plants at Low Levels of Sodium Chloride Salinity

The daily course of carbon influx and efflux was measured inyoung plants of Phaseolus vulgaris, Xanthium strumarium, Zeamays, and Atriplex halimus, exposed to low levels of salinity(NaCl) and varying daytime light intensities. Maintenance respiration(R_M) was calculated. In Phaseolus, Xanthium, and Atriplex, R_Mrose with increasing salinity, approximately up to those levelsof salinity above which apparent signs of toxicity appear. Athigher levels of salinity R_M declined. There was no responseof R_M to salinity in Zea. At the levels of salinity tested,salinity did not affect the ratio of growth respiration to photosynthesis. At –5 x 10⁵ Pa of NaCl salinity, the increase in R_M inXanthium was calculated to account for 24% of the growth reductioncaused by salt. The remainder could be ascribed to reduced photosynthesis.The increase of R_M is considered to be indicative of an adaptivemechanism, not present in the very salt-sensitive Zea.     

Starch Metabolism, Respiration, and Shoot Formation in Tobacco Callus Cultures

The starch content of shoot-forming and non-shoot-forming tobacco callus cultured in light and darkness was determined. A variety of carbohydrates and cytokinins incorporated into the culture medium were effective in bringing about starch accumulation and shoot formation in the tissue. In addition, the respiratory activity of the callus, grown in the presence or absence of gibberellic acid, was measured. A strong correlation between the starch content of the tissue, its rate of respiration, and shoot formation was observed.     

Confirmation by Chemical Synthesis of the Structure of 4-Ipomeanol,a Lung-toxic Metabolite of the Sweet Potato, <Emphasis Type="Italic">Ipomoea batatas</Emphasis>

WE have described the lung and liver toxicity of mould-damaged sweet potatoes and characterized briefly some abnormal metabolites responsible for these phenomena^1–4. The respiratory tract toxin, 4-ipomeanol (1-[3-furyl]-4-hydroxy-1-pentanone) (VI), may be responsible for the typical lung oedema of cattle that are fed mouldy sweet potatoes as well as a similar pathological state in mice fed or injected with the pure compound.     

A molecular phylogeny of the genus Apis suggests that the Giant Honey Bee of the Philippines,A. breviligula Maa,and the Plains Honey Bee of southern India,A. indica Fabricius,are valid species

Two new taxa have been added to the existing molecular phylogenies of the genus Apis. The new phylogeny supports the accepted phylogenetic relationships of {dwarf honey bees [giant honey bees (cavity‐nesting honey bees)]}. Based on Bayesian and maximum parsimony trees, our analysis supports recognition of Apis indica, the Plains Honey Bee of south India, as a separate species from A. cerana. Our analysis also supports recognition of the Giant Philippines Honey Bee, A. breviligula, as a separate species from A. dorsata.