Fine Structure of Selected Marine Pseudomonads and Achromobacters

The fine structure of more than 20 marine pseudomonads and more than 15 achromobacters was examined. Under the conditions extant, clear differences between members of these two groups were seen. The pseudomonads displayed the characteristic gram-negative morphology: the cell wall was irregularly undulant and the cytoplasmic membrane more nearly planar, ribonucleoprotein (RNP) particles were loosely packed throughout the periphery of the cytoplasm, and the deoxyribonucleic acid (DNA) was axially disposed. Cell division appeared to be by constriction. Some strains characteristically produced evaginations or blebs of the cell wall. Occasionally, thick, densely stained ring structures were seen which are possibly analogous to mesosomes. In contrast, the achromobacters demonstrated a regularly undulant outer cell wall element and a planar inner wall. The cytoplasmic membrane was thin and not readily observed. RNP particles were densely stained and tightly packed in the cytoplasm; the DNA was most often lobate in disposition. Cellular division was mediated by the formation of a septum which consisted of the cytoplasmic membrane and the inner element of the cell wall. Mesosomes were observed in all of the strains examined. Dense inclusion bodies were also seen in many strains.     

Fine Structure of Cardiac Sarcomeres in the Black Widow Spider Latrodectus mactans

Fine structural characteristics of the cardiac muscle and its sarcomere organization in the black widow spider, Latrodectus mactans were examined using transmission electron microscopy. The arrangement of cardiac muscle fibers was quite similar to that of skeletal muscle fibers, but they branched off at the ends and formed multiple connections with adjacent cells. Each cell contained multiple myofibrils and an extensive dyadic sarcotubular system consisting of sarcoplasmic reticulum and T‐tubules. Thin and thick myofilaments were highly organized in regular repetitive arrays and formed contractile sarcomeres. Each repeating band unit of the sarcomere had three apparent striations, but the H‐zone and M‐lines were not prominent. Myofilaments were arranged into distinct sarcomeres defined by adjacent Z‐lines with relatively short lengths of 2.0 μm to 3.3 μm. Cross sections of the A‐band showed hexagon‐like arrangement of thick filaments, but the orbit of thin filaments around each thick filament was different from that seen in other vertebrates. Although each thick filament was surrounded by 12 thin filaments, the filament ratio of thin and thick myofilaments varied from 3:1 to 5:1 because thin filaments were shared by adjacent thick filaments.     

转Bt基因棉田节肢动物群落营养层及优势功能团的组成与变化

1998年在河北南皮棉区转Bt基因棉棉田和常规棉综防田的生物群落变化的研究表明,与常规棉综防田相比,转Bt基因棉棉田的节肢动物种类增加30.7%,功能团多样性增加66.9%,天敌类和中性节肢动物类的丰富度分别增加97.6%和158.0%,害虫类的丰富度减少45.7%。就功能团的种群数量来看,主要害虫棉铃虫、蚜虫和蓟马种群数量分别减少98.9%、69.0%和72.6%;而次要害虫害蝽、粉虱、叶蝉类昆虫的种群数量分别增加了2.2、3.2和14.8倍,棉花生长中期,转Bt基因棉棉田中的基位物种丰富度大于中位和顶位物种;常规棉田中的差异则更大,出现天敌控制“空缺”。综合分析表明,转Bt基因棉棉田生态系统比常规棉综防田稳定;转Bt基因棉棉田的中性节肢动物和次要害虫在害虫－天敌的营养链中起到了重要的调控作用。     

Neuromuscular Systems in Molluscs

Molluscs have become increasingly popular in the study of centralneural mechanisms. More recently, there have been attempts torelate activity in central neurons with behavior in animalsof this phylum. The latter studies necessitate an understandingof the effectors of such behaviors. This requires not only informationabout the neuromuscular junction, but also an awareness of thecapabilities of the muscles themselves. Therefore, we have discussedsome structural and related functional characteristics of molluscanmuscle. We suggest that invertebrate mucles might be comparedon three scales: the amount of myofilament organization, theamount of vesicular specialization and organization, and theamount of paramyosin. We have considered some characteristicsof the widely-studied sustained contraction, known as "catch."Finally, we have discussed the neuromuscular junction—thetypes of junctions, the multiplicity of innervation, and someaspects of pharmacology. The results of such a study indicatedmany areas in which further research is essential before wecan understand behavior in terms of activity in the centralnervous system.     

Variation in the Fine Structure of a Marine Achromobacter and a Marine Pseudomonad Grown Under Selected Nutritional and Temperature Regimes

Certain features of the fine structure of a marine achromobacter and a marine pseudomonad were dependent upon the conditions of growth. Cells of achromobacter grown at 10 C in a low peptone-seawater (SW) medium displayed the characteristic morphology of the achromobacter: a regularly undulant outer element of the cell wall and a planar inner element, tightly packed ribonucleoprotein (RNP) particles in the cytoplasm, deoxyribonucleic acid (DNA) disposed in a lobate manner, and dense inclusion bodies. Few mesosomes, however, were seen. Cells of achromobacter grown at 10 C in a high peptone-SW medium had larger and more highly organized mesosomes. At 22 C, in a low peptone-SW medium, no mesosomes were seen, but the inclusions were more frequently seen and were larger in the achromobacter cells. At 22 C, in a high peptone-SW medium, these cells revealed the greatest variation in cellular morphology. They contained both small and large mesosomes, or no mesosomes, and both small and large inclusions, or no inclusions. Pseudomonad cells at 10 C in a low peptone-SW medium revealed a typical gram-negative morphology: double-layered, irregularly undulant cell wall; more nearly planar cytoplasmic membrane; densely stained, lightly packed RNP particles; finely fibrillar, axially disposed DNA; simple mesosomes. At 10 C, in a high peptone-SW medium, pseudomonad cells revealed associated strands of material and intracytoplasmic ringlike structures. At 22 C, in a low peptone-SW medium, pseudomonad cells had a more undulant cell-wall and a more nearly planar cytoplasmic membrane. At 22 C, in a high peptone-SW medium, these cells revealed prominent blebs of the cell wall.     

Spore Fine Structure in Clostridium cochlearium

The fine structure of Clostridium cochlearium was examined by use of thin sections, negative stains, and carbon replicas. Particular attention was given to details of the sporulation process and to fine structure of the spores. Spore coat formation was well advanced before the first evidence of cortex formation was noted. Three distinct spore coats were detected, the outermost of which was composed of seven layers. In addition, the spores possessed tubular appendages of variable length attached to one end of the spore. These differed in a number of respects from those described for other clostridia.     

Fine Structure and Spore Germination in Fusarium culmorum

The fine structure of the macroconidium of Fusarium culmorum(W. G. Smith) Sacc. is described. The presence of a mucilaginouscoat around the conidium and its expansion during germinationare confirmed. Studies of germinating conidia have shown changesin the numbers of organelles. The germ tube is shown to be formedfrom an entirely new wall laid down in the conidium, and theemergence of the germ tube is brought about by lysis of theoriginal condial wall.     

Status of Bone Mineral Density in Patients Selected for Cardiac Transplantation

ObjectiveTo determine the prevalence and correlates of low bone mineral density (BMD) in ambulatory outpatients with end-stage heart failure who were awaiting cardiac transplantation.MethodsFifty-five cardiac transplant candidates with end-stage heart failure were enrolled in this study. Bone mineral density at the lumbar spine and proximal femur was determined by dual-energy x-ray absorptiometry. Laboratory studies included serum alkaline phosphatase, calcium, intact parathyroid hormone, and 25-hydroxyvitamin D.ResultsThe mean proximal femur and lumbar spine Z scores were 0.3 ± 1.1 and 0.3 ± 1.5, respectively. The mean BMD was not lower than that of the age- and sex- matched reference population. Z scores were less than -1 in 23% at the lumbar spine and 15% at the proximal femoral neck. On the basis of T scores, osteopenia (T scores between -1 and -2.5) was present in 24% (confidence interval, 13% to 35%) of patients at the lumbar spine and in 20% (confidence interval, 10% to 30%) at the proximal femur; osteoporosis (T scores of less than -2.5) was present in 4% of the study population. Half of the patients in this study sample had elevated intact parathyroid hormone levels, and a third of the patients had low 25-hydroxyvitamin D levels.ConclusionLumbar spine and hip BMD measurements were not significantly low relative to age and sex in ambulatory patients with heart failure awaiting cardiac transplantation. (Endocr Pract. 2008;14:704-712)     

Fine Structure of Haemophilus vaginalis

Haemophilus vaginalis 594 has a trilaminar cell wall, ribosomes, a fibrillar nucleoid, and both convoluted and simple mesosome-like bodies. Polar bulbous enlargements of the cell and multiple cross wall formations may explain its pleomorphism.     

Fine Structure of Thiobacillus thiooxidans

Mahoney, Robert P. (Skidmore College, Saratoga Springs, N.Y.), and Mercedes R. Edwards. Fine structure of Thiobacillus thiooxidans. J. Bacteriol. 92: 487-495. 1966.-Thin section analysis of the chemosynthetic autotroph Thiobacillus thiooxidans revealed structures comparable to gram-negative heterotrophic bacteria. Although this species is unique in that it oxidizes elemental sulfur for energy, uses carbon dioxide as its sole source of carbon, and can withstand a pH of less than 1, thin sections revealed a profile of the cell envelope (cell wall and plasmalemma) similar to other gram-negative species which have more common physiological traits. The cell wall is composed of five layers with an overall width of approximately 200 A, and the plasmalemma appears as a conventional "unit membrane" with a width of about 85 A. Volutin granules and less-dense bodies of similar shape and size were frequently observed in close association with the nucleoplasm. The nature and function of these bodies are unknown at this time.     

Single and Multiple Visual Systems in Arthropods

Extraction of two visual pigments from crayfish eyes prompted an electrophysiological examination of the role of visual pigments in the compound eyes of six arthropods. The intact animals were used; in crayfishes isolated eyestalks also. Thresholds were measured in terms of the absolute or relative numbers of photons per flash at various wavelengths needed to evoke a constant amplitude of electroretinogram, usually 50 µv. Two species of crayfish, as well as the green crab, possess blue- and red-sensitive receptors apparently arranged for color discrimination. In the northern crayfish, Orconectes virilis, the spectral sensitivity of the dark-adapted eye is maximal at about 550 mµ, and on adaptation to bright red or blue lights breaks into two functions with λ_max respectively at about 435 and 565 mµ, apparently emanating from different receptors. The swamp crayfish, Procambarus clarkii, displays a maximum sensitivity when dark-adapted at about 570 mµ, that breaks on color adaptation into blue- and red-sensitive functions with λ_max about 450 and 575 mµ, again involving different receptors. Similarly the green crab, Carcinides maenas, presents a dark-adapted sensitivity maximal at about 510 mµ that divides on color adaptation into sensitivity curves maximal near 425 and 565 mµ. Each of these organisms thus possesses an apparatus adequate for at least two-color vision, resembling that of human green-blinds (deuteranopes). The visual pigments of the red-sensitive systems have been extracted from the crayfish eyes. The horse-shoe crab, Limulus, and the lobster each possesses a single visual system, with λ_max respectively at 520 and 525 mµ. Each of these is invariant with color adaptation. In each case the visual pigment had already been identified in extracts. The spider crab, Libinia emarginata, presents another variation. It possesses two visual systems apparently differentiated, not for color discrimination but for use in dim and bright light, like vertebrate rods and cones. The spectral sensitivity of the dark-adapted eye is maximal at about 490 mµ and on light adaptation, whether to blue, red, or white light, is displaced toward shorter wavelengths in what is essentially a reverse Purkinje shift. In all these animals dark adaptation appears to involve two phases: a rapid, hyperbolic fall of log threshold associated probably with visual pigment regeneration, followed by a slow, almost linear fall of log threshold that may be associated with pigment migration.     

Arthropods in contemporary and some fossil resins

More than 4800 arthropod inclusions were isolated and identified from resin of various contemporary conifer trees in various parts of northern Eurasia. Their composition is compared with that in representative collections of Baltic and Rovno ambers (Upper Eocene) and with that in Dominican amber (Lower Miocene). The original composition of inclusions of Dominican amber is reconstructed for the first time using a procedure intended to reduce the effect of human bias. Taphonomical characteristics of resins and their effects on the composition of inclusions are studied. The actuapaleontological approach reveals a trend towards a decrease in the relative abundance of arboreal springtails and nematoceran dipterans and an increase in that of the true bugs, beetles, lepidopterans, and hymenopterans (especially ants) between the Eocene and the present. Relative abundances of spiders and mites show no clear trend. The available data on other arthropods are still insufficient for elucidating evolutionary trends. Surprisingly, a small contemporary sample from Taimyr (N. Siberia) was inexplicably more similar to the Eocene amber than to other contemporary resins. No other significant differences in composition of inclusions, compared across different conifer genera or geographic areas, have been revealed. A more detailed comparison between contemporary and fossil hymenopteran and beetle inclusions reveals correlations with both age (= evolutionary change) and geography. The absolute dominance of ants, particularly Formicinae and Myrmicinae, and, among solitary hymenopterans, Ichneumonidae, Braconidae, and Pteromalidae, and a corresponding decline in the abundance of Scelionidae and Dolichoderinae in contemporary resins compared to amber reflect evolutionary changes. In contrast, the overwhelming abundance of Formicinae and consistent occurrence of sawflies in contemporary resins of northern Eurasia appear to be explained by geography. The Eocene assemblages of beetle inclusions are characterized by a wider and more variable set of dominant families, in sharp contrast to contemporary resins, which are uniformly dominated by Curculionidae, Chrysomelidae, and Staphylinidae. Additional analyses are needed to explain this difference.     

Decalcification at the Mantle-Shell Interface in Molluscs

Decalcification at the mantle-shell interface in Mercenariatnercenaria was studied through the changes in the chemicalcomposition of the extrapallial fluid, and by the measurementof Ca⁴⁵-deposition and solution. Measurements of O₂-tensiondemonstrated that the clam was anaerobic soon after the valveswere closed. Measurements of calcium, carbon dioxide, and hydrogenion concentration showed that all of these components of theextrapallial fluid increase with increasing time of closure.These measurements, and measurements of calcium and succinicacid in the tissues and fluids of the clam, indicated thatsuccinicacid produced by the anaerobic metabolism of the clam was neutralizedby the dissolution of previously deposited shell.     

Distribution of Acid Proteinase Activity in Molluscs

Acid proteinases with an optimum around pH 3 were demontrated in various tissues of 12 molluscan species. Enzymes strongly inhibited by pepstatin were predominant and the molecular weights of those from two species were in the region of 38,000–68,000, suggesting that they were cathepsin D-type proteinases.