On conditional and intrinsic autoregressions

Gaussian conditional autoregressions have been widely used inspatial statistics and Bayesian image analysis, where they areintended to describe interactions between random variables atfixed sites in Euclidean space. The main appeal of these distributionsis in the Markovian interpretation of their full conditionals.Intrinsic autoregressions are limiting forms that retain theMarkov property. Despite being improper, they can have advantagesover the standard autoregressions, both conceptually and inpractice. For example, they often avoid difficulties in parameterestimation, without apparent loss, or exhibit appealing invariances,as in texture analysis. However, on small arrays and in nonlatticeapplications, both forms of autoregression can lead to undesirablesecond-order characteristics, either in the variables themselvesor in contrasts among them. This paper discusses standard andintrinsic autoregressions and describes how the problems thatarise can be alleviated using Dempster's (1972) algorithm oran appropriate modification. The approach represents a partialsynthesis of standard geostatistical and Gaussian Markov randomfield formulations. Some nonspatial applications are also mentioned.     

Evidence for Reversible Tyrosine Protein Phosphorylation in the Okadaic Acid-Producing Marine Dinoflagellate Prorocentrum lima

ABSTRACT. The protist Prorocentrum lima , a primary producer of the tumour promoter okadaic acid, is a member of the dinoflagellate class of marine microorganisms. Herein, we have identified and characterized a protein tyrosine kinase (designated PLIK 1A) in P. lima that autophosphorylates almost exclusively on tyrosine residues. PLIK 1A was shown to have an approximate molecular mass of 38 kDa by SDS-PAGE and a native molecular mass within the range of 47–55 kDa by Superdex-75 gel filtration. Phosphoamino acid analysis of autophosphorylated PLIK 1A revealed the presence of phosphotyrosine and autophosphorylated PLJK 1A reacted with monoclonal anti-phosphotyrosine antibodies in a Western immunoblot. In addition, two protein tyrosine phosphatases were identified in P. lima that had apparent molecular masses within the ranges of 150–168 kDa and 73–82 kDa as determined by Superdex-200 gel filtration. These P. lima phosphatases, termed PLPTP-I and PLPTP-II, efficiently dephosphorylated tyrosine phosphorylated myelin basic protein. owever, only PLPTP-I was capable of dephosphorylating the tyrosine phosphorylated substrate angiotensin. Both PLPTP-I and PLPTP-II were able to dephosphorylate tyrosine autophosphorylated PLIK 1A. These data provide the first evidence for reversible tyrosine protein phosphorylation in P. lima by protein tyrosine kinases and phosphatases     

Temperature-controlled open-top chambers for global change research

To enable experiments on the interactive effects of elevated atmospheric CO₂ and increased air temperature on physiological processes in trees to be carried out, we altered the standard design of open-top chambers by replacing blowers with evaporative coolers and in-line heaters, with a feedback control system to maintain ambient or elevated air temperatures within the chambers. Ambient and elevated (+ 4 °C) temperature regimes were attained consistently and reliably throughout the growing season, with high reproducibility between chambers. From May through December the average of nearly 300,000 temperature measurements was 18.5 °C in ambient air, 18.9 ± 0.6 °C in six ambient chambers, and 22.4 ± 0.9 °C in six elevated temperature chambers. The difference in soil temperature between ambient and elevated chambers was 1.2 °C. Absolute humidity (vapour pressure) in the chambers was higher than that of ambient air, but it was generally similar between temperature treatments. Vapour pressure deficit therefore was higher in elevated temperature chambers than in ambient chambers, and this difference is considered an inseparable part of the temperature treatment. The addition of a temperature control system to open-top chambers removes what has been an important flaw in this important tool for global change research.     

Characterization of Encephalitozoon (Septata) intestinalis Isolates Cultured from Nasal Mucosa and Bronchoalveolar Lavage Fluids of Two AIDS Patients

ABSTRACT. Microsporidia are obligate intracellular protozoan parasites that can cause opportunistic infections in AIDS patients. Species from five genera of microsporidia are presently known to infect man. One species, Septata intestinalis originally was detected in stool specimens of individuals with chronic diarrhea and subsequently was found to disseminate to the kidneys, lungs, and nasal sinuses. This organism has since been reclassified as Encephalitozoon and in this study, we report the culture of Encephalitozoon intestinalis from a bronchoalveolar lavage specimen and a nasal mucus aspirate of two AIDS patients living in the USA. The bronchoalveolar and nasal microsporidian isolates grew in several continuous cell lines including RK-13, MDCK, HT-29, Caco-2, Vero, and 1047. Transmission electron microscopy of the clinical and cell culture specimens revealed that the new isolates appeared to be E. intestinalis based on morphology and growth of organisms in septated membrane-bound parasitophorous vacuoles. The new E. intestinalis isolates were characterized and compared with the first isolated E. intestinalis that was cultured from stool to confirm their identity and to determine if there existed any minor differences, as seen in the closely related Encephalitozoon cuniculi strains. By the methods of sodium dodecyl sulfate-polyacrylamide gel electrophoresis staining for proteins and carbohydrates, Western blot immunodetection, and polymerase chain reaction-based methods with restriction endonuclease digestion, double-stranded DNA heteroduplex mobility shift analysis, and DNA sequencing of the ribosomal DNA intergenic spacer region, the new isolates were identical to each other and to the reference isolate of E. intestinalis. In addition, with any of these methods, the E. intestinalis organisms could be distinguished from the three E. cuniculi strains, Encephalitozoon hellem, and Vittaforma corneae, which is important for diagnostics, therapeutic strategies, and epidemiology.     

The Fine Structure of Four “Species” of Amoeba*

The fine structure of Amoeba discoides, Amoeba dubia, and Amoeba amazonas was studied and compared with that of Amoeba proteus. The different kinds of amebas showed general similarities but differed in the ultrastructural details of their organelles. With respect to fine structure, A. discoides was indistinguishable from A. proteus, while both A. dubia and A. amazonas had distinctive features. The nuclei of all had a prominent honeycomb-like fibrous lamina, but A. dubia differed from the others in the distribution of nucleoli within the nucleus. The mitochondria of A. amazonas were unusual in having a variable pattern of cristae, some being plate-like and others tubular. Golgi bodies in A. amazonas had a greater proportion of vesicles and a smaller number of cisternae than those of the others, while Golgi bodies in A. dubia had highly flattened cisternae without a lining of filamentous material such as is found in the other types. The plasma membrane of A. dubia also lacked the prominent filamentous cell coat common to A. proteus and other amebas. The relation between the Golgi apparatus and the cell coat and the significance of the degree of development of the cell coat for pinocytosis and other phenomena is considered. The experimental use of these cells, including the formation of hybrids by nuclear transplantation is discussed.     

Paradoxes in Western Creativity

Statistical data, showing percentages of creativity in the various arts and philosophy among different nations during the history of Western civilization, can now be presented. This covers the ground quantitatively which Kroeber's Configurations of Culture Growth covered qualitatively. The study not only reveals different patterns among nations, but indicates the nature of the problem to be overcome if mankind is to achieve a universal maximum release of creativity for all in the future.     

Honeyeater population changes in relation to food availability in the Jarrah forest of Western Australia

The numbers of honeyeaters present at particular sites in the Jarrah forest varied significantly from month to month, with peak abundance occurring between May and September. Numbers also varied from site to site, depending upon the major plant species present. Honeyeater abundance was not limited by arthropod availability, but in many instances was closely correlated with the availability of nectar, particularly that produced by Dryandra sessilis. Large honeyeaters, such as Anthochaera chrysoptera and Phylidonyris novaehollandiae, were generally most abundant at times and sites of greatest nectar production. Small honeyeaters, such as Acanthorhynchus superciliosis, were never abundant but were present for most of the year. The production of nectar between October and December was such that more honeyeaters could have been supported than were actually present. Low numbers at these times can be explained in terms of reduced foraging efficiency that would have resulted from more widely dispersed flowers, and the possible availability of more rewarding nectar resources at other sites.