Basic Structural Differences Research Articles

Mechanisms of Ammonia Excretion Across Fish Gills

Although it has been a subject of considerable research, many questions regarding the mechanism(s) of ammonia excretion (JAmm) across fish gills remain unresolved. Recent advances improving our understanding of the linkage between CO2 and ammonia excretion, and the likelihood that H+-ATPases are present in freshwater fish gills, should improve our understanding about mechanisms of branchial JAmm. Moreover, basic differences in gill structure and function between freshwater- and seawater-adapted fishes are probably reflected by dissimilar mechanisms of JAmm. In fresh water, JAmm likely proceeds exclusively by NH3 diffusion down favorable blood-to-expired gill water PNH3 gradients. The carbonic anhydrase-catalyzed hydration of excreted CO2 augments JAmm by generating H+ that trap NH3 (as NH4+) as it diffuses into the gill water. To a lesser extent, the active extrusion of H+, via branchial H+-ATPase's, might also facilitate JAmm. The probable absence of electroneutral Na+/H+ exchange on the apical epithelia, makes branchial Na+/NH4+ exchange unlikely in freshwater fishes. In marine fishes, JAmm likely occurs via passive NH3 diffusion but NH4+ diffusion is also important, owing to the much higher cationic permeability of the gills of seawater fishes. The high Na+ concentrations of seawater indicate that apical Na+/NH4+ exchange is also possible in marine fishes. Finally, substitution of NH4+ for K+ on basolateral Na+:K+ATPase's and/or Na+/2Cl−/K+ co-transporters could also contribute to JAmm by marine fishes.

Intraparty Preferences, Heterogeneity, and the Origins of the Modern Congress: Progressive Reformers in the House and Senate, 1890-1920

In this article, the emergence of the modern Congress, characterized by a seniority system, strong committees, and weak party leadership, is linked to changes in external electoral forces. Specifically, we argue that the changes in both House and Senate organization were driven by the rise of heterogeneity within the dominant Republican party. We show that the centralized systems of Cannonism and Aldrichism were incompatible with the heterogeneous preferences created by the rising numbers of Progressive Republicans, causing both Houses to reform their systems of allocation of desirable committee posts. Furthermore, the differing modes of change between the Houses are due to basic differences in structure.

96/04596 Biomarkers assemblage in relation to coal rank

A set of 30 maceral concentrates consisting of 5 exinites (sporinites), 14 vitrinites and 11 inertinites (fusinites and semifusinites) was analyzed by Curie-point pyrolysis mass spectrometry in combination with computerized multivariate statistical analysis techniques. Seventeen samples, representing sink/flotation concentrates of 7 different coals, were obtained through the British National Coal Board, whereas the remaining samples represent cesium-chloride density-gradient centrifugation fractions of two different U.S. coals prepared at the University of Utah.It is found that vitrinites, (semi)fusinites and, to some extent, sporinites show qualitatively similar rank-related changes, such as a decrease in dihydroxybenzene signals and an increase in napthalene signals with increasing rank. In fact, the overall pyrolysis MS patterns of inertinities show a close similarity to those of vitrinites of corresponding carbon content (as obtained from higher rank coals).Notwithstanding these similarities, however, the presence of basic differences in maceral structure is indicated by relatively minor but characteristic peak series in the liptinite (sporinite) as well as inertinite samples. Whereas inertinite spectra show relatively pronounced peak series at the high mass end of the spectrum which can be tentatively identified as representative of polynuclear aromatic compounds, sporinites are characterized by series of branched aliphatic and/or alicyclic polyenic hydrocarbons, possibly representing isoprenoids and related biomarker compounds.

Characterisation of the double genome structure of modern sugarcane cultivars (Saccharum spp.) by molecular cytogenetics.

Cultivated sugarcane clones (Saccharum spp., 2n=100 to 130) are derived from complex interspecific hybridizations between the species S. officinarum and S. spontaneum. Using comparative genomic DNA in situ hybridization, we demonstrated that it is possible to distinguish the chromosomes contributed by these two species in an interspecific F1 hybrid and a cultivated clone, R570. In the interspecific F1 studied, we observed n + n transmission of the parental chromosomes instead of the peculiar 2n + n transmission usually described in such crosses. Among the chromosomes of cultivar R570 (2n = 107-115) about 10% were identified as originating from S. spontaneum and about 10% were identified as recombinant chromosomes between the two species S. officinarum and S. spontaneum. This demonstrated for the first time the occurrence of recombination between the chromosomes of these two species. The rDNA sites were located by in situ hybridization in these two species and the cultivar R570. This supported different basic chromosome numbers and chromosome structural differences between the two species and provided a first bridge between physical and genetical mapping in sugarcane.

Structure and identification of root bark of Quercus robur L.

The root bark structure of Quercus robur L. was analysed at different stages of root development and compared to the structure of stem bark. Root bark thickness varied considerably between different roots. Sclereid quantity decreased with increasing distance from the stem, which means it increased with age. Visible growth increments diminished with increasing distance from the stem. In lateral roots crystal quantity decreased with increasing distance from the stem. In lateral roots secondary phloem fibre length, sieve tube member length, and sieve tube diameter showed no regular trend. There were only a few basic structural differences between root and stem bark. The zone of cell differentiation (cell expansion, lignification) was wider in root bark; sieve tube collapse was delayed. In lateral root bark fewer sclereids were formed. The first-formed periderm often originated from deeper cell layers. Thus, primary elements were lacking after periderm formation. In root bark the phellem cell walls were of equal thickness. Thus, phellem lacked visible growth increments. Root bark phellem cells were slightly larger. The root phelloderm was more distinct. The secondary phloem fibres were slightly shorter than those in stem bark. Sieve tube members of stem and root bark were of similar length and diameter. The qualitative bark anatomical characters of oak root bark are suitable for root identifications. Due to minor structural differences between root and stem bark the characters must be used with care.

A theoretical analysis of the effect of forest structure on synthetic aperture radar backscatter and the remote sensing of biomass

Stand level forest canopy structure as measured by the size, density, and distribution of the stems, branches, and leaves may have a strong effect on SAR backscatter. This study used the Michigan Microwave Canopy Scattering model (MIMICS) and forest canopy biometric data from tropical and subtropical broadleaf forests to simulate a series of forest stands having equivalent above ground biomass while still exhibiting substantial structural differences. The model stands were made to represent a wide range of basic structural differences found in Earth’s broadleaf forests. The radar response to these structural differences is shown for the NASNJPL AIRSAR P-, L-, and C-band quadpol. configuration at incidence angles of 20°, 40°, and 60°. Results for three sets of equal-biomass-foreststands were generated: five structural types having a total above ground biomass of 5 kg/m2 (50 tonha), three structural types at 15 kg/m2 (150 tonsha), and three structural types at 30 kg/m2 (300 tonsha). Simplified model input were used to reduce the number of geometric variables tested across the range of structural types. The potential effect that extreme structural differences might have on the biomass signal and saturation threshold was assessed. Results indicate that structure can have a considerable effect on the SAR return for forests with equivalent above ground biomass. Differences in backscatter of up to 18 dB were predicted for some bands and polarizations. A forest canopy structural descriptor derived from the vegetation surface area to volume ratio (SAN), which is a measure of stuctural consolidation, appears to explain the differences in backscatter. In many vegetation stands structural consolidation is directly related to an increase in biomass during the thinning phase of forest succession. This structural effect may explain the good relationship between SAR backscatter and biomass in these cases.

The A-domain of beta 2 integrin CR3 (CD11b/CD18) is a receptor for the hookworm-derived neutrophil adhesion inhibitor NIF.

The A-domain is a approximately 200-amino acid peptide present within structurally diverse proadhesive proteins including seven integrins. A recombinant form of the A-domain of beta 2 integrins CR3 and LFA-1 has been recently shown to bind divalent cations and to contain binding sites for protein ligands that play essential roles in leukocyte trafficking to inflammatory sites, phagocytosis and target cell killing. In this report we demonstrate that the neutrophil adhesion inhibitor, NIF produced by the hookworm Ancyclostoma caninium is a selective CD11b A-domain binding protein. NIF bound directly, specifically and with high affinity (Kd of approximately 1 nM) to recombinant CD11b A-domain (r11bA). The binding reaction was characterized by rapid association and very slow dissociation, and was blocked by an anti-r11bA monoclonal antibody. No binding was observed to rCD11aA. The NIF-r11bA interaction required divalent cations, and was absent when the mutant r11bA D140GS/AGA (that lacks divalent cation binding capacity) was used. The NIF binding site in r11bA was mapped to four short peptides, one of which being an iC3b binding site. The interaction of NIF with CR3 in intact cells followed similar binding kinetics to those with r11bA, and occurred with similar affinity in resting and activated human neutrophils, suggesting that the NIF epitope is activation independent. Binding of NIF to CR3 blocked its ability to bind to its ligands iC3b, fibrinogen, and CD54, and inhibited the ability of human neutrophils to ingest serum opsonized particles. NIF thus represents the first example of a disintegrin that targets the integrin A-domain, and is likely to be used by the hookworm to evade the host's inflammatory response. The unique structure of NIF, which lacks a disintegrin motif, emphasizes basic structural differences in antagonists targeting A+ and A- integrins, that should be valuable in drug design efforts aimed at generating novel therapeutics. Identification of the region in NIF mediating A-domain binding should also be useful in this regard, and may, as in the case of disintegrins, unravel a new structural motif with cellular counterparts mediating important physiologic functions.

Age and adjustment to night work.

The study was designed to examine the effects of age on sleep and the circadian rhythms during consecutive night shifts. Two groups of letter sorters (19-29 (n = 7) and 53-59 (n = 7) years of age were studied in a sleep laboratory under closely controlled conditions. After two baseline days, circadian adjustment to three night shifts was monitored by continuous measurement of rectal temperature, salivary melatonin, and sleep-wakefulness during the night shifts. Age was significantly related to the adjustment to night work of rectal temperature minimum and of self rated sleepiness. Young subjects delayed their temperature phase and decreased sleepiness more than the older subjects. Age was also significantly related to an increase of alertness and to the feeling of being refreshed after the day sleep. Although there were basic differences in sleep duration and structure between the age groups, the latter did not change across the night shifts. Aging decreases the ability to recover after several, but not after the first night shift.

SAPPHO updated — project SAPPHO phase II

Abstract Project SAPPHO consists of a comparative analysis of ‘paired’ successful and unsuccessful technological innovations, where one half of the pair is a commercial success and the other a commercial failure. In phase I of the project twenty-nine pairs were investigated, seventeen in chemical processes and twelve in scientific instruments. Five main areas of difference between successful and unsuccessful innovators emerged which related to the innovator's understanding of user needs, efficiency of development, characteristics of managers, efficiency of communications and marketing and sales efforts. In phase II, the project has been extended to include a new total of forty-three pairs, twenty-two in chemical processes and twenty-one in scientific instruments. The results of phase I have been confirmed with the same five underlying factors emerging as strongly differentiating between success and failure and with some inter-industry differences becoming clearer. These differences, by and large, relate to the basic structural and environmental differences which exist between the two industries. Following the statistical analysis a subjective review was made of thirty-four failure cases, and those factors which contributed maximally to the individual failures were identified. The results of this exercise support the results of the statistical analysis, but they also highlight some new and significant factors. Finally, some of the more important of the many hypotheses which have been forwarded as offering explanations for innovative success were tested in the tight of the phase II SAPPHO results.

Internal Anatomy of Meiopriapulus fijiensis (Priapulida)

Scanning and transmission microscopical analyses of the major organ systems of Meiopriapulus fijiensis were performed. The most important findings included the presence of an epithelium-lined multichambered system surrounding a portion of the foregut, a complex foregut structure with an eight-ridged pattern extending into the polythyridium, and a gland located anteriorly in the midgut. The ultrastructural organization of the protonephridia and the ovaries is more similar to macrobenthic priapulids than to members of other meiobenthic taxa. The flagellated spermatozoa are of a primitive type, having a globular nucleus, a cap-shaped acrosome, and four mitochondria. This suggests external fertilization, which stands in contrast to internal fertilization known for Tubiluchus. Our knowledge of the ultrastructure of meiobenthic Priapulida is almost exclusively based on the analysis of Tubiluchus philippinensis van der Land, 1985 (see Alberti & Storch, 1983, 1986, 1988, 1989; Storch & Alberti, 1985a,b). Recently, some organ systems of the sedentary meiobenthic species Maccabeus tentaculatus Por, 1973 were analyzed by means of scanning and transmission electron microscopy (Wolter, 1987). Generally, there is a striking similarity between these two genera at the ultrastructural level. However, an analysis of the integument of Meiopriapulus fijiensis Morse, 1981, the only species of the third genus of meiobenthic Priapulida, revealed some basic differences in fine structure (Storch et al., 1989). The purpose of the present paper is to compare the ultrastructure of internal organs of Meiopriapulus fijiensis with corresponding organs of Tubiluchus and Maccabeus. Attention is focused only on features differing from the latter two. MATERIALS AND METHODS Living specimens of Meiopriapulus fijiensis were collected from the infralittoral zone at Korolevu Beach on Viti Levu, Fiji, and transported to Friday Harbor Laboratories, University of Washington, where they were maintained in seawater among sand grains in glass bowls at ambient room temperature. The authors gratefully acknowledge use of the priapulids collected in Fiji by Dr. G. Pauley and subsequently fixed for TEM by Mr. E. Meyh6fer (both of the University of Washington). We also acknowledge the technical assistance of Ms. R. Mummert (Heidelberg) and Mr. H. P. Dreyer (Kiel), and the field assistance of Ms. N. Helm (former Peace Corps volunteer, Western Samoa). This study was supported by a NATO Grant for Collaborative Research to V. Storch and R. P. Higgins, and a grant to R. P. Higgins (for field work in Fiji) from the Smithsonian Research Opportunities Fund. For M. P. Morse, this is Contribution No. 176, Marine Science Center, Northeastern University. TRANS. AM. MICROSC. Soc., 108(3): 245-261. 1989. ? Copyright, 1989, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.104 on Wed, 28 Dec 2016 18:06:34 UTC All use subject to http://about.jstor.org/terms TRANS. AM. MICROSC. SOC.

Minimal flows of finite almost periodic rank

AbstractThe totally minimal flow (X, T) is said to have finite almost periodic rank if there is a positive integer n such that whenever (x1, x2,…, xn+1) is an almost periodic point of the product flow (Xn+1, T×…×T) then, for some i≠j, xi, and xj are in the same orbit. The rank of (X, T) is the smallest such integer. If (Y, S) is a graphic flow, (Y, Sn) has rank |n| and it is shown that every finite rank flow has, modulo a proximal extension, a graphic power factor. Various classes of finite rank flows are defined, and characterized in terms of their Ellis groups. There are four disjoint types which have basic structural differences.

Characterization of coal maceral concentrates by curie-point pyrolysis mass spectrometry

A set of 30 maceral concentrates consisting of 5 exinites (sporinites), 14 vitrinites and 11 inertinites (fusinites and semifusinites) was analyzed by Curie-point pyrolysis mass spectrometry in combination with computerized multivariate statistical analysis techniques. Seventeen samples, representing sink/flotation concentrates of 7 different coals, were obtained through the British National Coal Board, whereas the remaining samples represent cesium-chloride density-gradient centrifugation fractions of two different U.S. coals prepared at the University of Utah. It is found that vitrinites, (semi)fusinites and, to some extent, sporinites show qualitatively similar rank-related changes, such as a decrease in dihydroxybenzene signals and an increase in napthalene signals with increasing rank. In fact, the overall pyrolysis MS patterns of inertinities show a close similarity to those of vitrinites of corresponding carbon content (as obtained from higher rank coals). Notwithstanding these similarities, however, the presence of basic differences in maceral structure is indicated by relatively minor but characteristic peak series in the liptinite (sporinite) as well as inertinite samples. Whereas inertinite spectra show relatively pronounced peak series at the high mass end of the spectrum which can be tentatively identified as representative of polynuclear aromatic compounds, sporinites are characterized by series of branched aliphatic and/or alicyclic polyenic hydrocarbons, possibly representing isoprenoids and related biomarker compounds.

Properties and structure of vitrites from coking coals of the High Silesian Coal Basin

Investigations of the properties and structure of vitrites separated from gas coal type 33 (International class 632), gas-coking coal type 34 (Int. class 634) and orthocoking coals type 35.1 and 35.2 (Int. class 535 and 433) from the High Silesian Coal Basin are presented. Basic differences in properties and structure appear between the vitrite of gas coal and the other vitrites. Vitrites from orthocoking coals are characterized by the highest degree of aromatic unit condensation, the packing of aromatic lamellas and by the highest height of crystallites. The process of continuous thermosolvolysis of these vitrites with chloroform was carried out. Properties and structure of the extracts and extraction residues are also presented. The increase of the aromatic character of the extracts with increase of the rank of the parent vitrites is observed.

Liposarcomas

A series of atypical lipomas, well-differentiated/dedifferentiated liposarcomas, and myxoid/round cell liposarcomas were examined by light and electron microscopy in order to understand better the marked variation in histologic growth patterns exhibited by adipose tissue neoplasms. We found that they were composed of a mixture of adipocytes and nonfat-storing mesenchymal cells or were predominantly made up of only one of these cell types. From these and other published observations, we feel that 1) myxoid/round cell liposarcomas are composed of adipocytes; 2) spindle cell lipomas, atypical lipomas, and well-differentiated liposarcomas are composed of a mixture of the two cell types; and 3) the dedifferentiated regions of well-differentiated liposarcomas are composed of nonfat-storing mesenchymal cells. The basic structural differences of the two cell types and the quantitative variations when they occur in mixtures seem to account for the marked variations in neoplastic growth patterns.

Computer-Aided Analysis of Curriculum Structure

This paper presents a structural analysis of the undergraduate curriculum of the Department of Chemical Engineering at the University of Houston. Structural models are developed for the curriculum based on two different sets of information regarding prerequisite relations among courses; (i) prerequisite relations identified by professors, and (ii) prerequisite relations stated in the official university catalog. The basic structural differences between the two models are identified by matrix manipulations. Also developed, is a Bayesian approach to derive a ‘posterior curriculum structure’ based on students’ empirical opinions about prerequisite relations. The Bayesian approach evaluates the ‘strength’ of prerequisite relations when used in conjunction with the basic difference identification method.

The Sub-Family Arundinoideae and Its Position in Relation to a General Classification of the Gramineae

The traditional scheme of classification for the grasses is one based upon spikelet morphology. This provides a means of identifying species and genera and of grouping them into tribes. A well-known example of a tribal scheme based entirely upon spikelet morphology is that of Hubbard in Hutchinson (1934). By the time Hubbard's work was produced the presence of parallel evolution within the family was recognized, although not always understood as no criteria were available which might reveal true affinities. Thus genera of the Pogae and Eragrostideae had for a long time been intermingled, as had genera of the Aveneae and Danthonieae. A land-mark in grass classification was established by Avdulow in 1931; he demonstrated the value of cryptic characters. Working primarily on chromosome counts he related them to tribal groups within the family, supplementing the counts with cytological and anatomical information. This approach revealed a major division between tropical and temperate grasses. Since Avdulow's pioneering work a great variety of characters has been proposed by various authors, covering the fields of anatomy, cytology, biochemistry and physiology. These have been summarized and reviewed by Prat (1960), Auquier (1963) and others. They mostly confirm Avdulow's broad groups, but many of them are indistinct or difficult to assess, and are of little help in differentiating critical groups or formulating precise circumscriptions. However among them is a group of characters derived from the leaf anatomy, which has been shown to be of considerable significance in practical taxonomy. Differences in leaf-blade anatomy were recognized by Duval-Jouve (1875) but not credited with any taxonomic significance until Avdulow re-deployed them. Since Avdulow, a mass of observations has been accumulated by various authors, of which by far the most extensive treatise is the compendium on grass anatomy of Metcalfe (1960). In this paper the terminology used is largely taken from Metcalfe's work. From the observations reported it is apparent that certain character combinations predominate, and various modern authors such as Pilger (1954), Prat (1960) and Gould (1968) have sought to employ these basic differences in leaf structure for the grouping of tribes into sub-families.

Molecular Vibrations of Polymers

Vibrational spectroscopy provides information on three important aspects of polymers, that is, their chemical composition, the geometric arrangement of atoms in space (physical structure), and the interatomic forces associated either with valence bonding or intermolecular interactions. The theory and experimental procedures developed so far for application of vibrational spectroscopy to small molecules and their crystals carry over to polymeric systems, with important differences that have to do with the unique structures exhibited by polymers. In this review, the theory of molecular vibrations of polymeric molecules is presented in a manner that emphasizes the basic structural differences between these molecules and their low-molecular-weight analogues. In particular, recent approaches to calculations of the frequencies of polymers with irregular conformational defects are reviewed. On the experimental side, the focus is on those experimental tech­ niques which, because of recent developments in instrumentation, per­ mit new or improved measurements. The most significant recent devel­ opments involve digital data acquisition and analysis, and the recent availability and use of Fourier transform infrared spectroscopy (FTIR). The improved specificity of infrared spectroscopy, achieved mainly through application of spectral subtraction techniques to high signal-to­ noise digital data, has led to a renewed interest in determinations of the chemical composition of macromolecular systems, including the nature of the bonding of chromophores in the polymer chain. Chemical com­ position descriptions rely on correlations between frequencies and specific chemical groups as, for example, the C = 0 stretching frequency of the carbonyl group. Although developing such correlations is a rather old topic, and one in which much progress and payoff have been

A comparative study of the production structure of the cotton textile industry in India and the USA

This paper attempts a comparison of production structures of the cotton textile industries in India and the USA, using the input‐output framework. There are studies of comparative production structures in an economy but a disaggregated study has not been attempted for a particular industry. Almost all studies of the international comparisons of production structure have revealed that there are structural similarities between developed and less developed countries in spite of wide differences in per capita income and in levels of development. These similarities may not persist at an industry level and it could be that the chosen product‐mix and techniques conceal the basic differences in production structure of a developing and a developed economy in the economy‐wide study.

SAPPHO updated - project SAPPHO phase II

Project SAPPHO consists of a comparative analysis of ‘paired’ successful and unsuccessful technological innovations, where one half of the pair is a commercial success and the other a commercial failure. In phase I of the project twenty-nine pairs were investigated, seventeen in chemical processes and twelve in scientific instruments. Five main areas of difference between successful and unsuccessful innovators emerged which related to the innovator's understanding of user needs, efficiency of development, characteristics of managers, efficiency of communications and marketing and sales efforts. In phase II, the project has been extended to include a new total of forty-three pairs, twenty-two in chemical processes and twenty-one in scientific instruments. The results of phase I have been confirmed with the same five underlying factors emerging as strongly differentiating between success and failure and with some inter-industry differences becoming clearer. These differences, by and large, relate to the basic structural and environmental differences which exist between the two industries. Following the statistical analysis a subjective review was made of thirty-four failure cases, and those factors which contributed maximally to the individual failures were identified. The results of this exercise support the results of the statistical analysis, but they also highlight some new and significant factors. Finally, some of the more important of the many hypotheses which have been forwarded as offering explanations for innovative success were tested in the tight of the phase II SAPPHO results.

An electron microscopic study of the circulatory system in Nereis japonica.

Blood vessels in Nereis japonica were studied by electron microscopy. It was found that blood vessels regardless of location were similar in the basic organization of the basal lamina and the usual presence of collagen fibrils on the vessel wall. Differences arise, depending on whether the outside of the basal lamina is covered by peritoneal cells, by gut epithelium, or by epidermis. These relate to the location of the vessels in mesenteries, gut or epidermis, but do not reflect basic structural differences in the vessels themselves. Furthermore, it was concluded that true endothelial cells do not exist in the circulatory system of Nereis japonica and that, in this respect, the system is essentially different from that of vertebrates, in which endothelial cells line the vessels of a closed circulatory system. These considerations lead to the further conclusion that the vascular lumen in Nereis is essentially interstitial space and that the system, which has been known as a typical "closed" circulatory system in annelids, is actually an open circulatory system. Peritoneal cells covering the walls of internal vessels show various degrees of muscular differentiation and those possessing myofilaments may be called "myomesothelial cells."