Billingen (Lower Arenig/Lower Ordovician) acritarchs from the East European Platform and their palaeobiogeographic significance

Billingen (Lower Arenig/Lower Ordovician) sediments of the St. Petersburg region, northwest Russia and the Leba area, northern Poland of the East European Craton yield acritarch assemblages, which are largely homogenous though displaying minor compositional differences that probably reflect a gradient from inner to outer shelf environments. Comparison with coeval acritarch microflora from the Yangtze Platform, South China, shows an overall similarity between Baltoscandian and South Chinese phytoplankton. The widespread uniformity in the fossil microphytoplankton may be related to the extensive global 'evae' sea-level transgression, which characterized the Billingen time. This suggests that during the Tremadoc through early Arenig times, acritarch assemblages displayed essentially an undifferentiated cold-water and oceanic character along the whole margin of Perigondwana in the South, as well as on the South Chinese and Baltic platforms, at middle latitudes (Mediterranean oceanic Realm). Despite this overall similarity, however, some typical taxa of the high-latitude Mediterranean Province (Arbusculidium, Coryphidium and Striatotheca) occur in South China, but are absent in Baltica. This discrepancy is explained as caused by differences in climatic and physiographic conditions that prevailed at the two palaeocontinents at this time. The inferred pattern of oceanic circulation during the Lower Ordovician is consistent with the palynological evidence of a prevailing warmer climate in Baltica than in South China, although the two palaeocontinents occupied the same palaeolatitudinal position.     

Nuclear-magnetic-resonance study of the histidine residues of S-peptide and S-protein and kinetics of 1H-2H exchange of ribonuclease A.

1H NMR spectroscopy at 100 MHz was used to determine the first-order rate constants for the 1H-2H exchange of the H-2 histidine resonances of RNase-A in 2H2O at 35 degrees C and pH meter readings of 7, 9, 10 and 10.5. Prolonged exposure in 2H2O at 35 degrees C and pH meter reading 11 caused irreversible denaturation of RN-ase-A. The rate constants at pH 7 and 9 agreed reasonably well with those obtained in 1H-3H exchange experiments by Ohe, J., Matsuo, H., Sakiyama, F. and Narita, K. [J. Biochem, (Tokyo) 75, 1197-1200 (1974)]. The rate data obtained by various authors is summarised and the reasons for the poor agreement between the data is discussed. The first-order rate constant for the exchange of His-48 increases rapidly from near zero at pH 9 (due to its inaccessibility to solvent) with increase of pH to 10.5 The corresponding values for His-119 show a decrease and those for His-12 a small increase over the same pH range. These changes are attributed to a conformational change in the hinge region of RNase-A (probably due to the titration of Tyr-25) which allows His-48 to become accessible to solvent. 1H NMR spectra of S-protein and S-peptide, and of material partially deuterated at the C-2 positions of the histidine residues confirm the reassignment of the histidine resonances of RNase-A [Bradbury, J. H. & Teh, J. S. (1975) Chem. Commun., 936-937]. The chemical shifts of the C-2 and C-4 protons of histidine-12 of S-peptide are followed as a function of pH and a pK' value of 6.75 is obtained. The reassignment of the three C-2 histidine resonances of S-protein is confirmed by partial deuteration studies. The pK' values obtained from titration of the H-2 resonances of His-48, His-105 and His-119 are 5.3, 6.5 and 6.0, respectively. The S-protein is less stable to acid than RNase-A since the former, but not the latter, shows evidence of reversible denaturation at pH 3 and 26 degrees C. His-48 in S-protein titrates normally and has a lower pK than in RN-ase-A probably because of the absence of Asp-14, which in RN-ase-A forms a a hydrogen bond with His-48 and causes it to be inaccessible to solvent, at pH values below 9.     

The sequestration of Ca2+ by mitochondria in rat heart cells

Rat heart ventricular cells, purified by Percoll density gradient centrifugation, were incubated in the presence of 1.3 mM CaCl2. After 20 min incubation, samples of the cells were lysed in medium containing 0.3 mM digitonin, ruthenium red and EGTA, and a mitochondrial fraction was isolated at intervals thereafter. Extrapolation of the mitochondrial 45Ca2+ contents to zero time enabled the endogenous 45Ca2+ to be estimated at the time of cell lysis. The lysis conditions yielded essentially complete release of lactate dehydrogenase from the cells, but caused negligible damage to the mitochondria as judged by their retention of glutamate dehydrogenase, and their ability to accumulate and retain Ca2+ in the absence of ruthenium red and EGTA. The data indicate that about 13% of total cell Ca2+ only may be mitochondrial in vivo.     

Edinburgh emergency asthma admission service.

In December 1968 an emergency service was set up in Edinburgh to enable patients with severe asthma to be admitted to hospital without delay. Up to 31 August 1975, 82 such patients had been admitted on 162 occasions, on 116 without the intervention of a general practitioner. The service is extended to patients particularly at risk of developing fatal asthma, and since it began no patient has died from asthma outside hospital. One patient, however, died from tension pneumothorax that developed after admission. We believe that similar services should be available throughout Britain.     

Muscle Logic: New Knowledge Resource for Anatomy Enables Comprehensive Searches of the Literature on the Feeding Muscles of Mammals

Background

In recent years large bibliographic databases have made much of the published literature of biology available for searches. However, the capabilities of the search engines integrated into these databases for text-based bibliographic searches are limited. To enable searches that deliver the results expected by comparative anatomists, an underlying logical structure known as an ontology is required.

Development and Testing of the Ontology

Here we present the Mammalian Feeding Muscle Ontology (MFMO), a multi-species ontology focused on anatomical structures that participate in feeding and other oral/pharyngeal behaviors. A unique feature of the MFMO is that a simple, computable, definition of each muscle, which includes its attachments and innervation, is true across mammals. This construction mirrors the logical foundation of comparative anatomy and permits searches using language familiar to biologists. Further, it provides a template for muscles that will be useful in extending any anatomy ontology. The MFMO is developed to support the Feeding Experiments End-User Database Project (FEED, https://feedexp.org/), a publicly-available, online repository for physiological data collected from in vivo studies of feeding (e.g., mastication, biting, swallowing) in mammals. Currently the MFMO is integrated into FEED and also into two literature-specific implementations of Textpresso, a text-mining system that facilitates powerful searches of a corpus of scientific publications. We evaluate the MFMO by asking questions that test the ability of the ontology to return appropriate answers (competency questions). We compare the results of queries of the MFMO to results from similar searches in PubMed and Google Scholar.

Results and Significance

Our tests demonstrate that the MFMO is competent to answer queries formed in the common language of comparative anatomy, but PubMed and Google Scholar are not. Overall, our results show that by incorporating anatomical ontologies into searches, an expanded and anatomically comprehensive set of results can be obtained. The broader scientific and publishing communities should consider taking up the challenge of semantically enabled search capabilities.     

Repression of CD2 gene expression is mediated by an AP-2 related factor

Tissue specific and developmental expression of the CD2 gene is tightly regulated during T cell development. DNase I hypersensitivity analysis has revealed the presence of two sites (DHS1 and 2) located 5' to the CD2 gene which have been reported to be implicated in the developmental regulation of expression of CD2. The location of DHS2 marks the position of the minimal promoter whereas DHS1 is located approximately 1800 bp upstream. We show that repressor and derepressor activities are contained within the region of DNA marked by DHS1. The repressor is capable of regulating homologous and heterologous promoters regardless of orientation. This activity is entirely dependent upon the presence of an AP-2 binding site as mutation of this site resulted in a loss of repressor activity. A nuclear factor found in Jurkat cells specifically binds this site but was shown to be serologically distinct from AP-2.     

Modelling mammary metabolism in the dairy cow to predict milk constituent yield, with emphasis on amino acid metabolism and milk protein production: model construction

Previous efforts to simulate mammary metabolism have focused on energy, mostly considering amino acids (AA) in aggregate. The main objective of this work was to build a model of mammary metabolism, based on data from arterio-venous difference studies, which considered AA in sufficient detail to predict yields of milk solids. The model contains 19 state variables and considers the removal of 37 metabolites from blood, including 22 AA. It is driven by blood flow and arterial concentrations, and outputs include milk protein, milk lactose, and three classes of milk fat (by chain length). The model was parameterized using a balance version of it and the mean observations from four arterio-venous difference experiments, with a limited number of assumptions, and evaluated against these experiments. In assembling the balance model, milk protein output was not predicted satisfactorily, as some essential AA were not present in quantities great enough to support the rates of milk protein synthesis observed experimentally. Tryptophan showed the greatest deficit, followed by tyrosine plus phenylalanine, methionine, and histidine. In addition, significant quantities of pyruvate were needed to synthesize serine, glycine, and alanine. The supply of alpha-ketoglutarate plus glutamate to synthesize proline and glutamine was provided in part by catabolism of arginine; the remainder was derived from catabolism of other AA and energetic substrates.     

A single low dose of X-rays induces high frequencies of genetic instability (aneuploidy) and heritable damage (apoptosis), dependent on cell type and p53 status

We harvested and analyzed cells from four different non-transformed cell lines surviving a single X-ray exposure. Evidence of radiation-induced karyotype instability was observed in 100% of C3H 10T1/2 fibroblast clones and 11.3% of V79 fibroblast clones. Heritable damage: predisposition to apoptosis, but not karyotype instability, was induced in TK6 (p53(wt/wt)) and WTK1 (p53(mut/mut)) human B-lymphoblastoid cell clones. The studies indicate: (1) genetic instability and/or heritable damage are induced in cells exposed to radiation at a high frequency, and induction of genetic instability is not limited to morphologically transformed cells [Radiat. Res. 138 (1994) S105; Radiat. Environ. Biophys. 36 (1998) 255]; (2) sensitivity to genetic instability and heritable damage depend on cell type; (3) checkpoint stringency and p53 status significantly influence the frequency of radiation-induced genetic instability and heritable damage; (4) in some cell lines, damage induced by low doses of radiation (below 2 Gy) leads to heritable cytotoxic and genotoxic effects in 100% of cells exposed. The data suggest that mammalian cells misinterpret damage induced by ionizing radiation as if it were a physiological cell signal. This contrasts strongly with the response of mammalian cells to damage induced by other types of DNA-toxic agents where damage-specific repair mechanisms are activated.