Phylogenetic inference: how much evolutionary history is knowable?

In order to reconstruct phylogenetic trees from extremely dissimilar sequences it is necessary to estimate accurately the extent of sequence divergence. In this paper a new method of sequence analysis, Markov triple analysis, is developed for determining the relative frequencies of nucleotide substitutions within the three branches of a three-taxon dendrogram. Assuming that nucleotide sites are independently and identically distributed and assuming a Markov model for nucleotide (or protein) evolution, it is shown that the unique Markov matrices can be reconstructed given only the joint probability distribution relating three taxa. (In the much simpler case involving only two taxa and two character states, Markov matrices can also be reconstructed, provided symmetry assumptions are placed on the elements of the matrices.) The method is illustrated using sequence data from the combined first and second codon positions derived from complete human, mouse, and cow mitochondrial sequences.      

Differences in the carbon tetrachloride-induced damage to components of the smooth and rough endoplasmic reticulum from rat liver

There is a higher activity of ethyl morphine N-demethylase (EM-ase) and cytochrome P-450 (P-450) reductase as well as higher P-450 content in the smooth endoplasmic reticulum (SER) than in the rough endoplasmic reticulum (RER). The extent of the irreversible binding of the¹⁴C from¹⁴CCl₄ to lipids and proteins, as well as the CCl₄-induced destruction of P-450 is more intense in SER than in RER while the opposite was found for glucose 6-phosphatase (G6P-ase) destruction. CCl₄-induced lipid peroxidation is as intense in SER as is in RER.¹⁴C from¹⁴CCl₄ gets irreversibly bound to ribosomal proteins.     

High yield expression of leptospirosis vaccine candidates LigA and LipL32 in the methylotrophic yeast <Emphasis Type="Italic">Pichia pastoris</Emphasis>

Background  

Leptospirosis, a zoonosis caused by Leptospira spp., is recognized as an emergent infectious disease. Due to the lack of adequate diagnostic tools, vaccines are an attractive intervention strategy. Recombinant proteins produced in Escherichia coli have demonstrated promising results, albeit with variable efficacy. Pichia pastoris is an alternative host with several advantages for the production of recombinant proteins.     

Interaction of ouabain with the Na(+) pump in intact epithelial cells

To determine the specificity and efficacy of [(3)H]ouabain binding as a quantitative measure of the Na(+) pump (Na(+), K(+)-ATPase) and as a marker for the localization of pumps involved in transepithelial Na(+)-transport, we analyzed the interaction of [(3)H]ouabain with its receptor in pig kidney epithelial (LLC-PK(1)) cells. When these epithelial cells are depleted of Na(+) and exposed to 2 muM [(3)H]ouabain in a Na(+)-free medium, binding is reduced by 90 percent. When depleted of K(+) and incubated in a K(+)- free medium, the ouabain binding rate is increase compared with that measured at 5 mM. This increase is only demonstable when Na(+) is present. The increased rate could be attributed to the predominance of the Na(+)-stimulated phosphorylated form of the pump, as K(+) is not readily available to stimulate dephosphorylation. However, some binding in the K(+)-free medium is attributable to pump turnover (and therefore, recycling of K(+)), because analysis of K(+)-washout kinetics demonstrated that addition of 2 muM ouabain to K(+)-depleted cells increased the rate of K(+) loss. These results indicate that in intact epithelial cells, unlike isolated membrane preparations, the most favorable condition for supporting ouabain binding occurs when the Na(+), K(+)-ATPase is operating in the Na(+)-pump mode or is phosphorylated in the presence of Na(+). When LLC-PK(1) cells were exposed to ouabain at 4 degrees C, binding was reduced by 97 percent. Upon rewarming, the rate of binding was greater than that obtained on cells kept at a constant 37 degrees C. However, even at this accelerated rate, the time to reach equilibrium was beyond what is required for cells, swollen by exposure to cold, to recover normal volume. Thus, results from studies that have attempted to use ouabain to eliminate the contribution of the conventional Na(+) pump to volume recovery must be reevaluated if the exposure to ouabain was done in the cold or under conditions in which the Na(+) pump is not operating.     

Hexazonium pararosaniline as a fixative for animal tissues

Hexazonium pararosaniline is a valuable reagent that has been used in enzyme activity histochemistry for 50 years. It is an aqueous solution containing the tris-diazonium ion derived from pararosaniline, an aminotriarylmethane dye, and it contains an excess of nitrous acid that was not consumed in the diazotization reaction. Other investigators have found that immersion for 2 min in an acidic (pH 3.5) 0.0015 M hexazonium pararosaniline solution can protect cryostat sections of unfixed animal tissues from the deleterious effects of aqueous reagents such as buffered solutions used in immunohistochemistry, while preserving specific affinities for antibodies. In the present investigation hexazonium pararosaniline protected lymphoid tissue and striated muscle against the damaging effects of water or saline. The same protection was conferred on unfixed sections treated with dilute nitrous or hydrochloric acid in concentrations similar to those in hexazonium pararosaniline solutions. Model tissues (solutions, gels or films containing gelatin and/or bovine albumin) responded predictably to well known cross-linking (formaldehyde) or coagulant (mercuric chloride) fixatives. Hexazonium pararosaniline solutions prevented the dissolution of protein gels in water only after 9 or more days of contact, during which time considerable swelling occurred. It is concluded that there is no evidence for a “fixative” action of hexazonium pararosaniline. The protective effect on frozen sections of unfixed tissue is attributable probably to the low pH of the solution.     

A new method for surface staining large slices of fixed brain using a copper phthalocyanine dye

Here we describe a method for gross staining of gray matter in slices of formaldehyde-fixed human brain. After protection of white matter with 4% phenol at 60°C for 5 min followed by a cold water wash, the gray matter was stained for 10-15 min at 20-25°C with 1% aqueous copper(II) phthalocyanine tetrasulfonic acid tetrasodium salt (CPTS). The staining resisted all attempts to be washed from the gray matter. Stained slices can be stored indefinitely in slightly acidified water, or plastinated as permanent dry specimens.     

Adults of European ant‐like stone beetles (Coleoptera: Staphylinidae: Scydmaeninae) Scydmaenus tarsatus Müller & Kunze and Scydmaenus hellwigii (Herbst) prey on soft‐bodied arthropods

Scydmaenine beetles are commonly described as predators specialized in capturing and feeding on armored mites of the order Oribatida, and documented cases of feeding on other live arthropods have not been known. Based on laboratory observations and a broad choice of Acari (armored and soft‐bodied) and other soil arthropods, food preferences and associated behavior of two scydmaenine species are clarified and described. Adults of Scydmaenus tarsatus ignored oribatid and mesostigmatan mites, but readily attacked and fed on a soft‐bodied Rhizoglyphus sp. (Acaridae), and on small springtails, especially on Ceratophysella denticulata (Hypogastruridae). A water drinking behavior was observed for this species, not reported previously in any Staphylinidae. Scydmaenus hellwigii ignored all tested Acari (including Rhizoglyphus) and scavenged on dead neanurine collembolans or freshly cut pieces of large springtails; a long term culture was maintained by feeding beetles with isotomid springtails. Previously reported strict specialization of Scydmaenus as a predator on Oribatida was not confirmed and it is concluded that the studied species feed on live soft‐bodied organisms and scavenge on dead arthropods.     

A qualitative study of trends in patient preferences for the management of the partially dentate state

Objective: To identify factors influencing attitudes of partially dentate adults towards dental treatment in Ireland. Background: People are retaining more teeth later in life than ever before. Management of partially dentate older adults will be a major requirement for the future and it is important to determine factors which may influence patients’ attitudes to care. Methods: Subjects: A purposive sample of 22 partially dentate patients was recruited; 12 women and 12 men, ranging in age from 45 to 75 years. Data Collection: Semi‐structured individual interviews. Results: Dental patients have increasing expectations in relation to (i) a more sophisticated approach to the management of missing teeth and (ii) their right to actively participate in decision making regarding the management of their tooth loss. There is some evidence of a cohort effect with younger patients (45–64 years) having higher expectations. Conclusions: The evidence of a cohort effect within this study in relation to higher patient expectations indicates that both contemporary and future patients are likely to seek a service based on conservation and restoration of missing teeth by fixed prostheses.     

Spontaneous coronary artery dissection: long stenting in a patient with polycythemia vera

Spontaneous coronary artery dissection is a rare cause of myocardial ischemia or sudden cardiac death. We describe a patient with polycythemia vera and a chronic spontaneous coronary artery dissection who was treated with successful angioplasty and long stenting.