Problems of body-weight estimation in fossil primates

Body-weight estimates of fossil primates are commonly used to infer many important aspects of primate paleobiology, including diet, ecology, and relative encephalization. It is important to examine carefully the methodologies and problems associated with such estimates and the degree to which one can have confidence in them. New regression equations for predicting body weight in fossil primates are given which provide body-weight estimates for most nonhominid primate species in the fossil record. The consequences of using different subgroups (evolutionary “grades”) of primate species to estimate fossil-primate body weights are explored and the implications of these results for interpreting the primate fossil record are discussed. All species (fossil and extant) were separated into the following “grades”: prosimian grade, monkey grade, ape grade, anthropoid grade, and all-primates grade. Regression equations relating lower molar size to body weight for each of these grades were then calculated. In addition, a female-anthropoid grade regression was also calculated for predicting body weight infernales of extinct, sexually dimorphic anthropoid species. These equations were then used to generate the fossil-primate body weights. In many instances, the predicted fossil-primate body weights differ substantially from previous estimates.     

Structure of a protein catalyzing the formation of 11 cis-retinal in the visual cycle of invertebrate eyes

A pigment made up of a protein able to bind retinal as well as retinol is described. The molecule consists of a dimer with a molecular weight of 50,000 which binds one molecule of retinal. The binding site for retinal is a Schiff base buried in the interior of the protein. Retinol is probably bound to the protein in the same site as for retinal, although not covalently, as suggested by the absorbance spectra. The protein, extracted from honeybee retina, is involved in visual pigment metabolism, and its structure may elucidate the mechanism of the stereospecific photoisomerization of all trans-retinal to 11-cis-retinal.     

Pheophytin-mediated energy storage of photosystem II particles detected by photoacoustic spectroscopy

The photoacoustic (PA) characteristics (energy storage and heat dissipation) of photosystem II (PSII) core-enriched particles from barley were studied (i) in conditions where there was electron flow, i.e., in the presence of a combination of the electron acceptor K₃ Fe (CN)₆, referred to as FeCN, and the electron donor diphenylcarbazide (DPC), and (ii) in conditions where electron flow was suppressed, i.e., in the absence of FeCN and DPC. The experimental data show that a decrease of heat dissipation with a minimum at 540 nm can be interpreted as energy storage resulting from the presence of pheophytin (Pheo) in the PSII particles. On account of the capability of the PA method to measure the energy absorbed by the chromophores which is converted to heat, it is suggested that the PA detection of Pheo present in the PSII complex will permit to clarify the function of processes involving non-radiative relaxation of excited states in P680-Pheo-Q_A interactions.Abbreviations -Car -Carotene - Chl Chlorophyll - DPC Diphenylcarbazide - EPR Electron Paramagnetic Resonance - FeCN potassium ferricyanide - HEPES N-2-hydroxyethylenepiperazine-N-2-ethanesulfonate - P680 reaction center of PSII - PA Photoacoustic - Pheo pheophytin - PSI photosystem I - PSII photosystem II - Q_A primary electron acceptor of PSII     

Purification of bovine liver histidyl-tRNA synthetase, the Jo-1 antigen of polymyositis: size of the whole enzyme and its characteristic proteolytic fragments

We have recently reported the marked increase in frequency which can be achieved in the detection of the anti-Jo-1 antibody of polymyositis in serum samples by replacing commercial mixtures of cytoplasmic and nuclear antigens with the purified antigen, histidyl-tRNA synthetase. The present paper describes a method for purifying this antigen and an investigation of its size. Molecular masses previously reported for the enzyme have varied from 85-154 kDa and subunit molecular masses varying from 40-77 kDa have been observed. Several of these fragments are of sizes similar to those of a number of other autoantigens commonly observed in connective tissue diseases. Since the clinical identification of these autoantigens often relies exclusively on size determination by Western blotting, we have characterized the commonly occurring fragments of histidyl-tRNA synthetase lest they confuse such identification. It is concluded that histidyl-tRNA synthetase, like many other aminoacyl-tRNA synthetases, is subject to severe proteolysis during extraction procedures. Several characteristic fragments (Mr = 80, 75, 61, 55, 50 and 45 kDa) result, a finding that provides a satisfactory explanation of the various values previously reported. The intact bovine enzyme is a dimer of molecular mass close to 160 kDa.     

Investigations on circumferential microfilament bundles in rat retinal pigment epithelium

The presence of contractile proteins in normal rat retinal pigment epithelium has been studied using fluorescence and electron microscopy. Investigations using the F-actin binding toxin, phallacidin, coupled to the fluorochrome nitrobenzoxadiazole, revealed a band of fluorescence at or near the cell membrane. Immunofluorescent observations with anti-myosin and anti-alpha-actinin antisera gave similar results. Electron microscopy employing glutaraldehyde-8% tannic acid fixation revealed the presence of a circumferential microfilament band beneath the pigment epithelial apical surface that is closely associated with the plasma membrane and junctional complexes. Freeze-fracture studies confirmed the relationship of this band to the junctional complexes. The microfilament band measures approximately 0.5 micron +/- 0.2 micron in width and is composed of numerous 6 to 7 nm filaments. Some microtubules are seen in regions around the band, but no organelles appear to be associated with this structure. In en face sections through the zonula adherens, the circumferential microfilament band is associated with 30-nm electron-dense particles that are bound to the internal side of the membrane. Morphological evidence suggests that these may serve in anchoring the band to the membrane and assist in aligning the microfilament bands of adjoining cells. In the subapical cytoplasm, a microfilament bundle network was detected that interfaced with the circumferential microfilament band. In some cases, pigment epithelium was incubated in media-199 containing 25 to 50 ng/ml phallacidin prior to fixation. Circumferential microfilament bands of tissues treated in this manner exhibited a striated appearance.     

Temperature regulation in a burrow-nesting tropical seabird,the Wedge-tailed Shearwater (Puffinus pacificus)

Summary At low air temperatures (2.3–13.9°C), Wedge-tailed Shearwaters (Puffinus pacificus) shivered and their oxygen consumption increased to as much as 283% of the mean value (0.77 ml O₂/g·h) within the thermoneutral zone of air temperature (23–34°C). The minimal thermal conductance of the tissues and plumage was similar to the value predicted from the body mass (320.5 g). The oxygen consumption of the birds within their thermoneutral zone was lower than predictions based on body mass. At elevated air temperatures, the shearwaters panted at respiratory frequencies as high as 260 respirations/min; maximal respiratory frequencies were not invoked until the birds had become hyperthermic. During exposure to a hot environment, the oxygen consumption of the birds increased and in most instances the shearwaters were not able to lose heat equivalent to their concurrent metabolic heat production.Symbols and abbreviations BMR basal metabolic rate - C _total total thermal conductance - f respiratory frequency - TEWL total evaporative water loss - T _st stomach temperature - T _re rectal temperature     

Genetic study on indole-3-acetic acid production by ectomycorrhizal Hebeloma species: inter- and intraspecific variability in homo- and dikaryotic mycelia

Summary Interspecific variability of indole-3-acetic acid (IAA)-synthesizing activity was examined within 12 wild strains of different Hebeloma species. Interstrain variability was studied within 11 wild strains of Hebeloma cylindrosporum (Romagnési) and intrastrain variability was considered by using 20 homokaryotic and 50 controlled dikaryotic mycelia belonging to the progeny of one laboratory fruiting strain of this species.The range of variation of IAA-synthesizing activity was of the same order of magnitude within the four groups considered. No correlation was detected between, on one hand, the IAA-synthesizing activity of the mycelia and, on the other hand, their taxonomic position, their geographic origin, or their host plant.Within the progeny of one H. cylindrosporum fruiting strain, 15 of the 50 controlled dikaryons presented an activity higher than that of the original dikaryon. The variation among dikaryons could not be strictly related to the variation in parental homokaryons, indicating that genetic control of this activity probably involves a nonadditive component. Significant additive and nonadditive components of the genetic variation were detected, each of them representing about 50% of the total variation. The nonadditive heritable component could not be explained by a model involving only dominance.     

Antitrypanosomal action of cis-diamminedichloroplatinum (II) analogs

The present report deals with the alterations produced by cis-diamminedichloroplatinum (II) (DDP), and 2 of its analogs: cis-Pt(II)(tranylcypromine)2Cl2 and cis-Pt(II)(benzothiazole)2Cl2 in cultured epimastigote forms of Trypanosoma cruzi. Studies have been performed at the ultrastructural level and the inhibitory effect of these complexes on macromolecule synthesis, evaluated by 3H-thymidine, 3H-uridine, and 3H-leucine incorporation, has been investigated. DDP at concentrations of 50 and 100 micrograms/ml does not inhibit significantly the incorporation of radioactive precursors, but a clear decrease was observed with the 2 analogs. Eight hours of treatment at a concentration of 10 micrograms/ml rendered in all 3 cases an increase in autophagic vacuoles and lipids as well as an abnormal condensation of the nucleus chromatin.