Stereospecific Glucocorticoid Binding to Subcellular Fractions of the Sensitive and Resistant Lymphosarcoma P1798

WE have shown that in vitroexposure of cells of these PI798 tumours to physiological doses of glucocorticoids produces significant inhibition of DNA, RNA and protein metabolism^1–3 and glucose uptake^{2, 4} only in the glucocorticoid-sensi-tive tumour. These glucocorticoid-induced inhibitions can be correlated with the inhibition of growth and subsequent regression and dissolution of the sensitive tumour. In this study we have carried out competition experiments using the two 11-hydroxy isomers of Cortisol which have been shown to have the requisite stereospecific restraints necessary to show specific glucocorticoid binding⁵. It would be reasonable to suppose that both the 11α and 11β-isomers of Cortisol would compete almost equally for nonspecific binding sites of triamcinolone acetonide. But since only 11β-cortisol has glucocorticoid activity, only this isomer could compete with triamcinolone acetonide for specific binding. Thus, the difference in displacement caused by these two 11-hydroxy isomers is an indication of the specific binding of ³H-triamcinolone acetonide to different fractions of the PI 798 tumour.     

The Concept of Messenger RNA and Cytodifferentiation

The messenger RNA hypothesis serves as a concrete model of genefunction which may be of real use to the developmental biologist.The hypothesis posits that the product of a gene is an RNA moleculewith a base sequence complementary to the sequence of nucleotidebases in the DNA. The operations and restrictions which definea messenger are discussed. Animal and embryonic cells, whileconforming in general to the predictions, display certain variationsfrom the original hypothesis, such as difficulties in obtainingdirected synthesis of protein in vitro, greater stabilityofthe messenger RNA, association of active ribosomes with lipoproteinmembranes, and a possible heterogeneity of ribosomes. Some recent studies on messenger RNA in sea urchins and frogembryos are discussed, with special reference to the natureand importance of the RNA synthesized during cleavage, the significanceof new ribosome synthesis, and the potential importance of controlmechanisms at the 'translational level for regulation of newprotein synthesis The latter point is illustrated further by a discussion of theinitiation of synthesis of hemoglobin in the chick embryo. Theapplication of drugs and antimetabolites which derange and inhibitRNA synthesis (actinomycin, 8-azaguanine, 5-fluorouracil, and5-bromodeoxyuridine) shows that 8 hours prior to its onset,the synthesis of hemoglobin is independent of the synthesisof RNA of high molecular weight. The initiation of hemoglobinsynthesis is probably regulated at the translational level.Preliminary experiments using the heme precursor, delta-amino-levulinicacid, show that heme may be limiting for the onset of hemoglobinsynthesis.     

Programmed DNA Degradation and Nucleolar Biogenesis Occur in Distinct Organelles During Macronuclear Development in Tetrahymena

ABSTRACT. Programmed DNA rearrangements, including DNA degradation, characterize the development of the soma from the germline in a number of developmental systems. Pddl p (programmed DNA degradation 1 protein), a development-specific polypeptide in Tetrahymena , is enriched in developing macronuclei (anlagen) and has been implicated in DNA elimination and nucleolar biogenesis. Here, immunocytochemistry and fluorescent in situ hybridization (FISH) were employed to follow Pddl p and two nucleolar markers (Nopp52 and rDNA) during macronuclear development. Both Pdd 1p and Nopp52 localize to subnuclear structures, each of which resemble nucleoli. However, while true nucleoli form and persist during development, Pdd 1p-positive structures are only present for a brief period of macronuclear differentiation. Accordingly, two distinct organelles can be recognized in anlagen: (1) Pdd 1p-positive structures, which lack Nopp52 and rDNA, and (2) developing nucleoli which contain rDNA and Nopp52 but lack Pdd 1p. Taken together with recent data corroborating Pdd 1p's role in DNA elimination, we favor the hypothesis that Pdd 1p structures are unique, short-lived organelles, likely to function in programmed DNA degradation and not in nucleolar biogenesis.     

When One Form is Between Two Others: An Application of Biorthogonal Analysis

SYNOPSIS. This essay presents a method for measuring the degreeto which one biological outline form lies in between two others.The procedure does not measure forms separately, but rathercompares pairs of tensors expressing D'Arcy Thompson's "Cartesiantransformations" according to the biorthogonal formalism ofBookstein. In analogy with conventional methods, betweennessis computed as a similarity score, the cosine of a non- Euclideanangle between the tensors. The new quantities, size-betweennessand shapebetweenness, enable comparisons of form series againsta priori orderings intra- and interspecifically     

Heterozygosity for recessive lethals in homosporous fern populations: Thelypteris palustris and Onoclea sensibilis

Sporophytes from natural populations of Thelypteris palustris and Onoclea sensibilis were subjected to breeding tests to reveal the presence of recessive lethal alleles in their genotypes. All sporophytes were found to be heterozygous for recessive sporophytic lethals. Despite the capability for producing completely homozygous genotypes by intragametophytic self-fertilization, ferns in natural populations seem to retain considerable genetic loads of deleterious recessive alleles. It is suggested that natural selection operates to strongly favour heterozygous rather than homozygous sporophytes under most conditions.     

The Quilon Limestone,Kerala Basin,India: an archive for Miocene Indo‐Pacific seagrass beds

Reuter, M., Piller, W.E., Harzhauser, M., Kroh, A., Rögl, F. & ?ori?, S. 2010: The Quilon Limestone, Kerala Basin, India: an archive for Miocene Indo‐Pacific seagrass beds. Lethaia, Vol. 44, pp. 76–86. The facies of the fossiliferous Quilon Limestone in SW India is described for the first time in detail at the Padappakkara‐type locality. Facies (fossiliferous, micrite‐rich, bioturbated sediment with intercalated sand pockets) and faunal composition (epiphytic foraminifers, seagrass feeding Smaragdia gastropods, bioimmuration of celleporiform bryozoan colonies) indicate a seagrass environment. The large discoidal archaiasin foraminifer Pseudotaberina malabarica, in particular, is considered as a proxy for seagrass communities. Recent seagrasses have their centre of generic richness in the Indo‐Pacific where they cover wide areas in the tidal and shallow sub‐tidal zones. However, their geological record is only fragmentary and their palaeobiogeographic distribution has a big stratigraphical gap in the Miocene Western Indo‐Pacific region. The described nannoplankton flora and planktonic foraminifers from the Quilon Formation demonstrate that the deposition of the studied seagrass bed occurred in nannoplankton biozone NN3. This timing suggests formation during the closure of the Tethyan Seaway. The Quilon Limestone is thus an early Western Indo‐Pacific seagrass bed and an important step in reconstructing the history of seagrass communities. □Quilon Formation, Pseudotaberina malabarica, seagrass facies, Burdigalian, Indo‐Pacific.     

SELECTION OF COLONY SITES AND NEST SITES BY COMMON TERNS STERNA HIRUNDO IN OCEAN COUNTY, NEW JERSEY

Common Terns nested on 34 of 259 saltmarsh islands along 46 miles of Ocean County coastline, New Jersey. They nested on low islands of Spartina with less than 12%, windrow ranging in size from 0.6 to 108 acres. All islands selected by terns faced at least two miles of open water from at least one direction. Selection of islands seemed a response to vegetation, size, distance to the nearest island, distance to the nearest shore and exposure to open water. Of the 225 islands without nesting terns, only three fulfilled appropriate criteria. Eighty per cent of nests were situated on windrow. Terns laid larger clutches on windrow compated to those nesting in Spartina. Nearest neighbour distance on islands with low predation varied from 85 to 485 cm and was a function of space, vegetation, and the size of the island. Terns nested closer together on windrow compared with Spartina. Considering all colonies, the mean nearest neighbour distance negatively correlated with the number of nests. Skimmers, Oystercatchers, Laughing Gulls, and Herring Gulls nested in some of the tern colonies. All tern colonies on islands also occupied by nesting Herring Gulls suffered over 10% egg-loss by predation. Proportionally more nests were preyed upon in windrow than in Spartina. Clutch sizes in nests in windrow on islands with predation were significantly lower than those in windrow on islands without predation, even though clutch sizes in Spartina were similar on islands with and without predation. Flooding by exceptional high tides destroyed significantly more nests in Spartina than in windrow. The nests that survived in Spartina were built deeper, and their rim heights were higher than nests destroyed by tides. Choice of colony and nest sites is discussed in terms of the balance of two selection pressures: predation and tidal flooding. Tern nests on windrow are more exposed to predators, but safer from flooding, whereas those nests in Spartina are more susceptible to flooding and less vulnerable to predators. The recent invasion of Herring Gulls into Ocean County has significantly increased the rate of nest predation among affected colonies of Common Terns. It is possible that in future years the terns' behaviour may be modified in response to this new selective pressure.     

Cardiopulmonary Gas Exchange in the Turtle: A Model Analysis

The performance of the cardiorespiratory gas exchange systemof the turtle, Pseudemys scripla, at rest and at three bodytemperatures (15, 25, 35°C), was assessed in reference totheory and experimental data. The primary processes governinggas exchange(ventilation, perfusion, diffusion) were found tobe uniformly balanced in regard to CO₂ exchange. This was nottrue for O₂ transport where, at higher body temperature, thesystemis characterized by underventilation and overperfusionin conjunction with declining O₂ saturation levels. Adjustmentsin convection of air or blood, which favor improvement in arterialO₂ saturation levels, are incompatible with stability of theCO₂stores and acid-base state. The latter were preserved acrossthe temperature range. Comparisons between bird, mammal, andturtle illustrate close similarity in the relative roles ofthe primary processes governing CO₂ exchange. This persistsin the face of wide differences inmetabolic intensity, cardiopulmonaryarchitecture and complexity, and body temperatures characterizingthe species which were compared. The close control of carbondioxide transport may reflect a fundamental adjustment to airbreathing by lungs as primitive vertebrates emerged from waterto the terrestrial domain. From a regulatory point of view thestudy emphasizes the importance of both structural and functionalcontrol of CO₂ homeostasis. It does not rule out regulatoryfeatures which may insure more effective O₂ transport; however,the latter are not evident within the context of the steadystate assumptions underlying this analysis.