Showing papers by "University of Birmingham published in 1987"

Differences in B cell growth phenotype reflect novel patterns of Epstein-Barr virus latent gene expression in Burkitt's lymphoma cells

Abstract: Recently established Epstein-Barr virus (EBV)-positive Burkitt's lymphoma (BL) cell lines, carrying chromosomal translocations indicative of their malignant origin, have been monitored for their degree of in vitro progression towards a more 'lymphoblastoid' cell surface phenotype and growth pattern, and for their expression of three EBV latent gene products which are constitutively present in all virus-transformed normal lymphoblastoid cell lines (LCLs). BL cell lines which stably retained the original tumour biopsy phenotype on serial passage were all positive for the nuclear antigen EBNA 1 but did not express detectable amounts of two other 'transforming' proteins, EBNA 2 and the latent membrane protein (LMP). This novel pattern of EBV gene expression was also observed on direct analysis of BL biopsy tissue. All three viral proteins became detectable, however, in BL cell lines which had progressed towards a more LCL-like phenotype in vitro. This work establishes a link between B cell phenotype and the accompanying pattern of EBV latent gene expression, and identifies a novel type of EBV:cell interaction which may be unique to BL cells.

Seasonal temperatures in Britain during the past 22,000 years, reconstructed using beetle remains

Abstract: Seasonal and mean annual temperatures can be reconstructed from radiocarbon-dated beetle remains to yield a synthesis of the palaeoclimatic history of Britain over the last 22,000 years. The reconstructions agree well with independent evidence from periglacial features and provide a detailed picture of the glacial to interglacial transition 14,500–9,000 years ago.

LIGHT AND TEMPERATURE DEPENDENCE OF THE CARBON TO CHLOROPHYLL a RATIO IN MICROALGAE AND CYANOBACTERIA: IMPLICATIONS FOR PHYSIOLOGY AND GROWTH OF PHYTOPLANKTON

Abstract: Summary The carbon:chlorophyll a ratio (C:chl a or θ) is a sensitive indicator of physiological state in microalgae. The dependence of θ on photon flux density (PFD or I) and temperature in exponentially growing nutrient-sufficient microalgae can be described by an empirical equation with four coefficients. C:chl a increases linearly with increased light level at constant temperature and decreases exponentially with increased temperature at constant light level. Both the slope (ɛ) and intercept (θ0) of linear regressions of θ on photon flux density increase at low temperature. The intercept, θ0, increases from 6 to 40 g of carbon per gram of chlorophyll a (g C g chl a−1) between 30 and 0 °C and ɛ increases by over an order of magnitude from 004 to 1·9 g C g chl a−l m2 s μol photon−1 over the same temperature range. Low-temperature chlorosis can be interpreted as an adaptive response in the allocation of cell resources between temperature-independent biophysical reactions involved in light-harvesting and temperature-dependent biochemical reactions. This response also reduces the potential for photoinhibitory damage at high light levels which can be exacerbated by low temperatures. The range of values for θ in nature has not been adequately determined because of difficulty in separating phytoplankton from detritus, bacteria and microzooplankton. Based on the laboratory observations summarized in this paper, it would appear that use of a single value of θ for phytoplankton is inappropriate for ecological studies. For example, at a PFD of 50 μmol m−2 s−1, θ increases from 10 to 130 g C g chl a−1 between 30 and 0 °C under nutrient-sufficient conditions. These conclusions are based on observations for eight diatoms, two green algae, one euglenoid and two cyanobacteria for which the appropriate data are available. In contrast to these groups, the dinofiagellates contain substantially less chlorophyll a The available data indicate that θ is about three times larger in dinoflagellates than in other algae under comparable PFDs at 20 °C. There are insufficient data available, however, to evaluate the light and temperature dependence of θ in dinoflagellates.

Magmatism at rifted continental margins

Abstract: The intense volcanism and uplift observed on many rifted continental margins, forming basaltic seaward-dipping reflector sequences, is accompanied by the emplacement of a thick igneous section at depth. Partial melting by decompression of passively upwelling asthenosphere that is hotter than normal because it is near a hotspot explains both the thickness of the new igneous crust and the initial elevation of the rifted margins.

Lipid peroxidation and mechanisms of toxicity.

Abstract: Aerobic organisms by definition require oxygen, and the importance of iron in aerobic respiration has long been recognized, but despite their beneficial roles, these elements can pose a real threat to the organism. During oxygen reduction, reactive species such as O2-. and H2O2 are formed readily. Iron can combine with these species, or with molecular oxygen itself, to generate free radicals which will attack the polyunsaturated fatty acids of membrane lipids. This oxidative deterioration of membrane lipids is known as lipid peroxidation. To protect itself against this form of attack, the organism possesses several types of defense mechanisms. Under normal conditions, these defenses appear to offer adequate protection for cell membranes, but the possibility exists that certain foreign compounds may interfere with or even overwhelm these defenses, and herein could lie a general mechanism of toxicity. This possible cause of toxicity is discussed in relation to other suggested causes.

Second malignancies following testicular cancer, ovarian cancer and Hodgkin's disease: an international collaborative study among cancer registries.

Abstract: Eleven population-based cancer registries tabulated second cancers among 133,411 patients diagnosed with testicular cancer, ovarian cancer or Hodgkin's disease between 1945 and 1984 Overall, 3,157 second cancers were observed, as compared with 2,420 expected at least one year after the first cancer Survivors of testicular and ovarian cancer experienced 30% and 20% more cancers respectively than the general population comparison group, and patients previously diagnosed with Hodgkin's disease had an 80% excess of cancer No information was available either on treatment for the first cancer, or other risk factors However, temporal patterns in the risk of specific second cancers were analysed, with particular reference to the possible role of therapy for the first cancer Leukaemia of the acute or non-lymphatic type, which has been previously linked to alkylating agent therapy, occurred in excess following all 3 first cancers, as did non-Hodgkin's lymphoma (overall relative risks of 61 and 18 respectively, with considerably higher relative risks following Hodgkin's disease) Other cancers for which important and plausibly therapy-induced excesses occurred were lung cancer following Hodgkin's disease (relative risk 19), breast cancer following Hodgkin's disease (relative risk 14) and bladder cancer following ovarian cancer and Hodgkin's disease (relative risks 17 and 22 in women, respectively) Rarer sites at which striking excesses occurred were the salivary gland, thyroid, bone and connective tissue There were smaller, but clear excesses for cancers of the rectum and colon following ovarian cancer and testicular cancer, skin cancer following Hodgkin's disease, and kidney cancer following ovarian cancer Overdiagnosis, misclassification of metastases and confounding by other risk factors were all considered as explanations of observed excesses Nonetheless, it appeared that there are clear excess risks for cancers other than acute leukaemia which must be ascribed to therapy for the first cancer, especially in view of the possible under-reporting in registry material Case-control studies are under way to provide information on the role of specific aspects of therapy

Late Cretaceous and paroxysmal Cretaceous/Tertiary extinctions

Abstract: The various geological signatures at Cretaceous/ Tertiary time including iridium and other associated elements, microspherules, and shock deformation features are compatible with the suggestion that the transition is marked by a period of intense volcanism. The volatile emissions from this volcanism would lead to acid rain, reduction in the alkalinity and pH of the surface ocean, global atmospheric temperature changes, and ozone layer depletion. These environmental effects coupled with those related to the major sea level regression of the late Cretaceous provide the framework for an explanation of the selective nature of the observed extinction record.

Paraquat poisoning: clinical features and immediate general management.

Abstract: In contrast to 10-15 years ago most cases of paraquat poisoning are now due to deliberate self-poisoning with parasuicidal or suicidal intent rather than to accidental ingestion. Less commonly, poisoning may follow careless handling of paraquat during occupational use. Although paraquat can be absorbed through the skin if improperly handled, poisoning usually follows ingestion and has rarely been reported after subcutaneous, intravenous or intraperitoneal injection. Clinically, three degrees of intoxication may be distinguished. Mild poisoning occurs after the ingestion or injection of less than 20 mg of paraquat ion/kg body weight. In these cases patients are either asymptomatic or symptoms are confined to the gastrointestinal system. All patients recover fully. Moderate to severe poisoning usually follows the ingestion (rarely injection) of 20-40 mg of paraquat ion/kg body weight. Non-specific symptoms of ill health together with local gastrointestinal symptoms precede the development of renal failure (which may recover spontaneously) and pulmonary fibrosis which may not be manifest for days or weeks. Death occurs in the majority of cases but is usually delayed for 2-3 weeks. Acute fulminant poisoning follows the ingestion of substantial quantities of paraquat (greater than 40 mg of paraquat ion/kg body weight). In addition to local symptoms, multiple organ (cardiac, respiratory, hepatic, renal, adrenal, pancreatic, neurological) failure occurs. Death may supervene within hours and is never delayed for more than a few days. Initial general management has four priorities.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine receptors in human thymic myoid cells in situ: An immunohistological study

Abstract: Myoid cells were studied by double immunofluorescence in sections of thymus from 47 patients with myasthenia gravis and 15 control subjects, using polyclonal sheep anti-troponin T and monoclonal antibodies to troponin I, striated muscle myosin, and acetylcholine receptor (AChR). The myoid cells were rare and located mainly in the medulla, and most were clearly positive for AChR; labeling was similar with four individual monoclonal antibodies specific for extrajunctional AChR and five that also recognize endplate AChR. They were mostly keratin-positive and consistently HLA-DR-negative. In the myasthenia gravis samples, the myoid cells were similar but largely confined to medullary epithelial areas; AChR labeling was slightly weaker, but otherwise they did not differ noticeably from those of control subjects. A preliminary finding was of even rarer AChR-positive/HLA-DR-positive antigen-presenting (possibly) cells seen in 9 of 9 myasthenia gravis samples and in none of 9 control samples. Although myoid-cell AChR appears antigenically similar to extrajunctional muscle AChR, and must therefore express the epitopes that myasthenics' antibodies recognize, these cells do not appear to be foci of immunological stimulation in myasthenia gravis.

New type B isolates of Epstein-Barr virus from Burkitt's lymphoma and from normal individuals in endemic areas.

Abstract: Summary All Epstein—Barr virus (EBV) isolates can be classified as type A or type B depending upon the identity of their EBV nuclear antigen (EBNA) 2 protein. The great majority of isolates examined to date encode an EBNA 2A protein like that of the reference type A strain B95-8. Type B virus strains, encoding an antigenically distinct EBNA 2B protein, have as yet only been rescued from rare Burkitt's lymphoma (BL) cell lines of African origin (Jijoye, AG876). Our recent finding that type B isolates are less efficient than type A in in vitro transformation assays prompted us to determine (i) the relative contribution the two types of virus make to the incidence of BL in endemic areas of Africa (Kenya) and New Guinea and (ii) the relative incidence of infection with these two types in the normal population in these same areas. On the first point, EBNA 2 gene typing using specific DNA probes showed that four of ten recently established Kenyan BL cell lines and two of four BL cell lines from New Guinea carried type B virus isolates. To address the second point, spontaneous lymphoblastoid cell lines were established from the blood of normal virus carriers and typed for EBNA 2 at the protein level; a significant proportion (> 20%) of the normal population in both the above BL-endemic areas were infected with type B isolates. This is the first indication of the widespread nature of type B virus infection in any community and the first isolation of such viruses from a non-BL source. The reproducible size of the EBNA 2B protein encoded by all type B isolates irrespective of their geographical origin, and of the EBNA 1 protein encoded by all type B isolates from one area, contrasted markedly with the extreme variability in the size both of EBNA 2A and of EBNA 1 seen generally among type A isolates. This suggests that the number of type B virus strains in existence worldwide could be quite limited. Most importantly, the data suggest that type B viruses, despite their relatively poor performance in in vitro transformation assays, can contribute at least as efficiently as can type A viruses to the pathogenesis of BL.

The penetration of light through soil

Abstract: There has been little written on the penetration of light through soil. In this review, we attempt to collate most of the work that has been published on this topic in order to stimulate further research and to clarify the often-confused literature. Light penetration can be measured directly with, for example, a spectroradiometer, or indirectly by using germination of light-sensitive seeds or the presence of growing algae as bioindicators. Although the penetration of light through soil is greatly affected by factors such as soil moisture content and particle size and colour, it generally appears that physiologically and ecologically significant amounts of light rarely penetrate more than 4–5 mm through the soil, and may often penetrate much less than this. Any penetration beyond 10 mm would generally not be significant, especially as most soils are covered with litter, algae or lichens, or are shaded from direct sunlight. However, for some light-stimulated geo-tropic responses of roots, which can be sensitive to very low fluences, the penetration of light to greater depths could well be significant. The role of light in soil in directing root growth is also discussed.

Flux quantization in a high- T c superconductor

Abstract: We have observed the quantization of magnetic flux in a high-Tc yttrium-based ceramic superconductor1 and obtain a value for the flux quantum in this material. The value of the flux quantum, h/2e where h is Planck's constant and e is the electron charge, implies that the charge carriers of superconductivity are electron pairs.

Understanding Jurassic Organic-rich Mudrocks—New Concepts using Gamma-ray Spectrometry and Palaeoecology: Examples from the Kimmeridge Clay of Dorset and the Jet Rock of Yorkshire

Abstract: Palaeoecology and gamma-ray spectrometry have been combined to study the controls on deposition of two well-known Jurassic organic-rich mudrocks. Portable gamma-ray spectrometry allows the rapid measurement of K, U and Th in the field. Th and K are contained mainly in the detrital clay fraction of the mudrocks and the Th/K ratio is found to decrease slightly with increasing water depth and distance from shoreline. Measured values of U have a detrital and an ‘authigenic’ component. Sediments deposited under anoxic conditions are consistently enriched in ‘authigenic’ U. Non-detrital ‘authigenic’ U has been estimated by the relative enrichment of U over Th, which is assumed to be immobile and present entirely in the detrital fraction.

Increased Diene Conjugates in Diabetic Subjects with Microangiopathy

Abstract: Free radicals are highly reactive unstable chemical species which have been implicated in the vascular damage associated with several disease states. Diene conjugates, probable products of free radical activity on lipids, were measured spectrophotometrically in 26 diabetic patients with microangiopathy, 36 uncomplicated diabetic patients, and 36 healthy controls. Total diene conjugates and diene conjugate to triglyceride ratios were significantly elevated in diabetic patients with microangiopathy (0.57 +/- 0.08 and 0.31 +/- 0.14 OD units/ml respectively; mean +/- SD) when compared with patients without complications (0.32 +/- 0.10, p less than 0.001, and 0.17 +/- 0.06, OD units/ml, p less than 0.011). There was no difference in total diene conjugation and their ratio to triglycerides between healthy controls and uncomplicated diabetic patients and the results were not influenced by the type of diabetes or level of diabetic control. Diene conjugate ratios repeated in 14 patients on two occasions, 6 weeks apart, with stable metabolic control were consistent. Increased diene conjugation suggesting increased free radical activity is associated with microangiopathy and this may have pathogenetic implications.

Radiations and extinctions in relation to environmental change in the marine Lower Jurassic of northwest Europe

Abstract: A diversity and turnover analysis has been undertaken for a number of invertebrate groups in the Liassic of northwest Europe. There is a more or less steady rise in diversity from the early Hettangian through to the Pliensbachian, followed by a marked decline into the early Toarcian, after which it tends once more to increase. Ammonites stand out from the other invertebrates as having had an exceptionally high rate of turnover, with very short species durations.Increase of neritic habitat area due to rise of sea level, and recolonization following the end-Triassic mass extinction event appear to be the promoters of diversity increase or radiation. Severe reductions of neritic habitat area with associated environmental deterioration, related either to episodic marine regressions or spreads of anoxic bottom waters, and bound up respectively with sea-level fall and rise, are seen as the prime factors responsible for increase of extinction rate. While the environmentally sensitive ammonites were affected by even minor regressions, the other, more eurytopic groups were evidently more resistant to these. The only event that warrants the term mass extinction, affecting nearly all the benthos and nekton but not the plankton, correlates precisely with the early Toarcian anoxic event. Several episodes can be recognized of migrations of organisms into Europe following extinctions.

Anaerobic respiration in the Rhodospirillaceae: characterisation of pathways and evaluation of roles in redox balancing during photosynthesis

Abstract: Recent discoveries relating to pathways of anaerobic electron transport in the Rhodospirillaceae are reviewed. The main emphasis is on the organism Rhodobacter capsulatus ∗∗ but comparisons are made with Rhodobacter sphaeroides ∗∗ f. sp. denitrificans and Rhodopseudomonas palustris. The known electron acceptors for anaerobic respiration in Rhodobacter capsulatus are trimethylamine-N-oxide (TMAO), dimethyl sulphoxide (DMSO), nitrate and nitrous oxide. In each case respiration generates a proton electrochemical gradient and in some cases can support growth on non-fermentable carbon sources. However, the principal objective of this review is to discuss the possibility that, apart from a role in energy conservation, anaerobic respiration in the photosynthetic bacteria may have a special function in maintaining redox balance during photosynthetic metabolism. Thus the electron acceptors mentioned above may serve as auxiliary oxidants: (a) to maintain an optimal redox poise of the photosynthetic electron transport chain; (b) to provide a sink for electrons during phototrophic growth on highly reduced carbon substrates. Molecular properties of the nitrate reductase, nitrous oxide reductase and a single enzyme responsible for reduction of TMAO and DMSO are discussed. These enzymes are all located in the periplasm. Electrons destined for all three enzymes can originate from the rotenone-sensitive NADH dehydrogenase but do not proceed through the antimycin- and myxothiazol-sensitive cytochrome bc1 complex. It is likely, therefor, that the pathways of anaerobic respiration overlap with the cyclic photosynthetic electron transport chain only at the level of the ubiquinone pool. Redox components which might be involved in the terminal branches of anaerobic respiration are discussed.

Recombinant human interleukin 5 is an eosinophil differentiation factor but has no activity in standard human B cell growth factor assays.

Abstract: Following the observation that mouse interleukin 5 (IL5) is active as a B cell growth factor (BCGF) as well as an eosinophil differentiation factor, this work was carried out to test recombinant human IL5 for BCGF activity. A highly active, partially purified batch of recombinant human IL5 was prepared and tested for BCGF activity in four laboratories. This batch gave a 50% endpoint of 1:77,450 in the human eosinophil differentiation assay, 1:983 in the mouse eosinophil differentiation assay and 1:42 in the mouse BCL1 assay, thus demonstrating that, like mouse IL5, human IL5 has cross-species activity. By comparison with the assays in the mouse this batch would be expected to have 50% maximal human BCGF activity of about 1:4000. In each assay a known positive factor was used as a positive control, and there was no inhibitory activity in the preparation. However, despite the activity towards the mouse B cell lymphoma, the results showed no detectable activity in a panel of assays used to identify human BCGF and B cell differentiation factors. These assays included (a) proliferation assays with tonsillar or splenic B cells in the presence of the co-stimulators anti-mu or phorbol myristate acetate; (b) a restimulation assay in which tonsillar B cells are first activated with either Staphylococcus aureus Cowan 1 or a mixture of phorbol dibutyrate and ionomycin, or splenic B cells are first activated with anti-mu; (c) production of immunoglobulin by B cells in a restimulation assay with Staphylococcus aureus Cowan 1; (d) production of immunoglobulin by the Epstein-Barr virus-transformed B lymphoblastoid CESS cell line; (e) the ability to stimulate proliferation of chronic lymphocytic leukemia (B-CLL) cells freshly explanted from three different patients; (f) the ability to stimulate the B lymphoma (L4) cell line and the mature B cell (HBF1) line, and (g) the ability to replace T cells in specific antibody responses. It therefore seems unlikely that recombinant human IL5 is either a growth or a differentiation factor for human B cells, and raises the interesting question of the biological significance of the BCGF activity of this factor in the mouse.

Discovery of hard X-ray emission from supernova 1987A

Abstract: We report the discovery of hard X-rays from the region of the supernova SN1987A in the Large Magellanic Cloud. The observations were made from the Mir-Kvant observatory 'Rontgen'. Hard X-rays were first observed on 10 August 1987 and SN1987A then became the main target of the observatory. Up to 15 September 1987, a total of 115 pointings on 21 days were made. The flux showed little variation during the observation period. The measured spectrum extends from 20 keV to 300 keV and is extremely hard, having a photon power law index of ˜1.4. At low energies the spectrum becomes even flatter and there is indication of a cutoff between 10 and 25keV. The luminosity over the energy range 20–300 keV is ˜2x1038 erg s–1 (assuming a distance of 55 kpc). The error box for the hard source has a (2σ) radius of 10 arc min and contains SN1987A. The results have important implications for current models of SN1987A.

End-Cretaceous Mass Extinction Event: Argument for Terrestrial Causation

Abstract: The end-Cretaceous mass extinctions were not a geologically instantaneous event and were selective in character. These features are incompatible with the original Alvarez hypothesis of their being caused by a single asteroid impact that produced a world-embracing dust cloud with devastating environmental consequences. By analysis of physical and chemical evidence from the stratigraphic record it is shown that a modified extraterrestrial model in which stepwise extinctions resulted from encounter with a comet shower is less plausible than one intrinsic to the earth, involving significant disturbance in the mantle.