Biomineralization Processes

1989 ◽  
Author(s):  
Heinz A. Lowenstam ◽  
Stephen Weiner
Keyword(s):  
Continuous Spectrum ◽  
Convergent Evolution ◽  
Common Ancestor ◽  
External Medium ◽  
The Other ◽  
Mineral Formation ◽  
Mineralization Processes ◽  
Established Fact ◽  
Different Sources ◽  
Almost Continuous

The large number of different minerals formed by organisms from almost 50 different phyla described in Chapter 2 should in itself discourage anyone from searching for the mechanism of biomineralization. On the other hand, the survey of macromolecules used by many organisms to control mineralization (Chapter 2), even though limited primarily to carbonate- and phosphate-bearing mineralized hard parts, shows that similar and rather unusual acidic glycoproteins and proteoglycans are widely utilized in biomineralization. This raises the possibility that many organisms may have adopted common approaches or strategies for regulating mineral formation. We do not know whether this arose as a result of divergence from a common ancestor or is a product of convergent evolution in which many different phyla independently began utilizing similar macromolecules for controlling mineralization (see Chapter 12). Either way we view the diversity in biomineralization as the product of a very broad and almost continuous spectrum of processes that organisms use to control mineralization. This ranges from no apparent control at one end to, it seems, control over every detail at the other. However, this is achieved by a fairly limited number of different basic processes used in various combinations and ways to produce a unique final product. This last statement is, we readily admit at this point in time, more an act of faith than an established fact. In this chapter we will try to identify and/or speculate about some of these basic processes. We will draw upon material from many different sources, and, in particular, we will refer whenever possible to the more detailed descriptions of mineralization processes given in the chapters that follow. As a consequence, this chapter may also be used by the reader as a guide toward more discriminating reading on selected topics in the remainder of the book. The spectrum of biomineralization processes can in principle be easily divided into cases in which control is exercised in some way over mineralization and those in which it is not. In practice the differentiation is not that simple as all organisms do exercise some control at one level or another, even if it simply involves, for example, removing from the cell some undesirable metabolic end-product or ion that combines with another ion in the external medium and precipitates.

D. The Line Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 207-244
Author(s):  
R. P. Kraft
Keyword(s):  
Variable Stars ◽  
The Other ◽  
Line Spectrum ◽  
Afternoon Session ◽  
Empirical Information ◽  
Pulsating Variable Stars ◽  
Almost Continuous ◽  
Informal Approach

(Ed. note:Encouraged by the success of the more informal approach in Christy's presentation, we tried an even more extreme experiment in this session, I-D. In essence, Kraft held the floor continuously all morning, and for the hour and a half afternoon session, serving as a combined Summary-Introductory speaker and a marathon-moderator of a running discussion on the line spectrum of cepheids. There was almost continuous interruption of his presentation; and most points raised from the floor were followed through in detail, no matter how digressive to the main presentation. This approach turned out to be much too extreme. It is wearing on the speaker, and the other members of the symposium feel more like an audience and less like participants in a dissective discussion. Because Kraft presented a compendious collection of empirical information, and, based on it, an exceedingly novel series of suggestions on the cepheid problem, these defects were probably aggravated by the first and alleviated by the second. I am much indebted to Kraft for working with me on a preliminary editing, to try to delete the side-excursions and to retain coherence about the main points. As usual, however, all responsibility for defects in final editing is wholly my own.)

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

Immunological Relationship Between Plasminogen Activator Inhibitors from Different Sources

1987 ◽  
Vol 57 (01) ◽  
pp. 029-034 ◽  
Author(s):  
Göran Urdén ◽  
Joanna Chmielewska ◽  
Tomas Carlsson ◽  
Björn Wiman
Keyword(s):  
Plasminogen Activator ◽  
Polyclonal Antibodies ◽  
Active Form ◽  
Polyclonal Antiserum ◽  
The Other ◽  
Hep G2 ◽  
Inhibitor Activity ◽  
Tissue Plasminogen ◽  
Immunological Relationship ◽  
Different Sources

SummaryPolyclonal antibodies have been raised against the inhibitor moiety in the purified complex between tissue plasminogen activator and its fast inhibitor (PA-inhibitor) in human plasma/ serum. A radioimmunoassay for quantitation of PA-inhibitor antigen was developed. The polyclonal antiserum and a previously described monoclonal antibody against the PA-inhibitor (14) have been used to study the immunological relationship between PA-inhibitors from plasma, serum, platelets, placenta extract and conditioned media from Hep G2 and HT 1080 cells. It was demonstrated that the ratio between PA-inhibitor activity and antigen varied considerably between the different sources. In the plasma samples studied, similar activity and antigen concentrations were found, suggesting that the PA-inhibitor in these samples mainly was in an active form. On the other hand the other sources seemed to contain variable amounts of inactive PA-inhibitor forms. Immunoadsorption experiments revealed that the PA-inhibitor (activity and antigen) from all the sources were specifically bound to the insolubilized antibodies (polyclonal and monoclonal). In no case, however, could active PA-inhibitor be eluted from the immunoadsorption columns. Also the competitive radioimmunoassays suggested that the PA-inhibitors from the different sources studied, were closely immunologically related.

On Biomineralization

1989 ◽  
Author(s):  
Heinz A. Lowenstam ◽  
Stephen Weiner
Keyword(s):  
Medical Research ◽  
Design Principles ◽  
Mineral Formation ◽  
Medical Problems ◽  
Basic Principles ◽  
Mineralized Tissues ◽  
Mineralization Processes ◽  
Archaeological Artifacts

Focusing on the basic principles of mineral formation by organisms, this comprehensive volume explores questions that relate to a wide variety of fields, from biology and biochemistry, to paleontology, geology, and medical research. Preserved fossils are used to date geological deposits and archaeological artifacts. Materials scientists investigate mineralized tissues to determine the design principles used by organisms to form strong materials. Many medical problems are also associated with normal and pathological mineralization. Lowenstam, the pioneer researcher in biomineralization, and Weiner discuss the basic principles of mineral formation by organisms and compare various mineralization processes. Reference tables listing all known cases in which organisms form minerals are included.

scholarly journals Interspecies Chromosome Mapping in Caprimulgiformes, Piciformes, Suliformes, and Trogoniformes (Aves): Cytogenomic Insight into Microchromosome Organization and Karyotype Evolution in Birds

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 826
Author(s):  
Rafael Kretschmer ◽  
Marcelo Santos de Souza ◽  
Ivanete de Oliveira Furo ◽  
Michael N. Romanov ◽  
Ricardo José Gunski ◽  
...  
Keyword(s):  
Convergent Evolution ◽  
Karyotype Evolution ◽  
Rare Events ◽  
Rare Event ◽  
Chromosome Mapping ◽  
The Other ◽  
Other Hand ◽  
Interchromosomal Rearrangement ◽  
Insight Into ◽  
Phalacrocorax Brasilianus

Interchromosomal rearrangements involving microchromosomes are rare events in birds. To date, they have been found mostly in Psittaciformes, Falconiformes, and Cuculiformes, although only a few orders have been analyzed. Hence, cytogenomic studies focusing on microchromosomes in species belonging to different bird orders are essential to shed more light on the avian chromosome and karyotype evolution. Based on this, we performed a comparative chromosome mapping for chicken microchromosomes 10 to 28 using interspecies BAC-based FISH hybridization in five species, representing four Neoaves orders (Caprimulgiformes, Piciformes, Suliformes, and Trogoniformes). Our results suggest that the ancestral microchromosomal syntenies are conserved in Pteroglossus inscriptus (Piciformes), Ramphastos tucanus tucanus (Piciformes), and Trogon surrucura surrucura (Trogoniformes). On the other hand, chromosome reorganization in Phalacrocorax brasilianus (Suliformes) and Hydropsalis torquata (Caprimulgiformes) included fusions involving both macro- and microchromosomes. Fissions in macrochromosomes were observed in P. brasilianus and H. torquata. Relevant hypothetical Neognathae and Neoaves ancestral karyotypes were reconstructed to trace these rearrangements. We found no interchromosomal rearrangement involving microchromosomes to be shared between avian orders where rearrangements were detected. Our findings suggest that convergent evolution involving microchromosomal change is a rare event in birds and may be appropriate in cytotaxonomic inferences in orders where these rearrangements occurred.

Determination of the Number of Conserved Chromosomal Segments Between Species

Genetics ◽  
2001 ◽  
Vol 157 (3) ◽  
pp. 1387-1395 ◽  
Author(s):  
Sudhir Kumar ◽  
Sudhindra R Gadagkar ◽  
Alan Filipski ◽  
Xun Gu
Keyword(s):  
Statistical Approach ◽  
Common Ancestor ◽  
Chromosomal Rearrangements ◽  
Structural Similarity ◽  
The Other ◽  
Segment Length ◽  
Human Genomes ◽  
Genomic Divergence ◽  
Human And Mouse

AbstractGenomic divergence between species can be quantified in terms of the number of chromosomal rearrangements that have occurred in the respective genomes following their divergence from a common ancestor. These rearrangements disrupt the structural similarity between genomes, with each rearrangement producing additional, albeit shorter, conserved segments. Here we propose a simple statistical approach on the basis of the distribution of the number of markers in contiguous sets of autosomal markers (CSAMs) to estimate the number of conserved segments. CSAM identification requires information on the relative locations of orthologous markers in one genome and only the chromosome number on which each marker resides in the other genome. We propose a simple mathematical model that can account for the effect of the nonuniformity of the breakpoints and markers on the observed distribution of the number of markers in different conserved segments. Computer simulations show that the number of CSAMs increases linearly with the number of chromosomal rearrangements under a variety of conditions. Using the CSAM approach, the estimate of the number of conserved segments between human and mouse genomes is 529 ± 84, with a mean conserved segment length of 2.8 cM. This length is <40% of that currently accepted for human and mouse genomes. This means that the mouse and human genomes have diverged at a rate of ∼1.15 rearrangements per million years. By contrast, mouse and rat are diverging at a rate of only ∼0.74 rearrangements per million years.

The Origins of Political Trust in East Asian Democracies: Psychological, Cultural, and Institutional Arguments

2016 ◽  
Vol 17 (3) ◽  
pp. 410-426 ◽  
Author(s):  
EUNJUNG CHOI ◽  
JONGSEOK WOO
Keyword(s):  
National Economy ◽  
Social Trust ◽  
Political Representation ◽  
East Asian ◽  
Political Trust ◽  
The Other ◽  
Social Psychological ◽  
High Level ◽  
The Empirical Analysis ◽  
Different Sources

AbstractWhile the importance of social and political trust has been well documented, there is a lack of scholarly consensus over where trust originates. This article tests three theoretical arguments – social-psychological, social-cultural, and political institutional – on the origin of political trust against three East Asian democracies (Japan, South Korea, and Taiwan). The empirical analysis from the AsiaBarometer survey illustrates that political institutional theory best explains the origin of political trust in East Asian cases. Citizens of these East Asian democracies have a high level of political trust when they believe that their governments perform well in management of the national economy and political representation of elected officials. Meanwhile, social-psychological and social-cultural theories explain the origins of social trust, but not political trust. The evidence reveals that socially trusting people are not automatically politically trusting; social trust and political trust originate from different sources and do not transform from one to the other.

scholarly journals Clonal analysis of the serogroup B meningococci causing New Zealand's epidemic

2005 ◽  
Vol 134 (2) ◽  
pp. 377-383 ◽  
Author(s):  
K. H. DYET ◽  
D. R. MARTIN
Keyword(s):  
Genetic Diversity ◽  
New Zealand ◽  
16S Rrna ◽  
Meningococcal Disease ◽  
Common Ancestor ◽  
Clonal Complex ◽  
Clonal Analysis ◽  
The Other ◽  
Disease Rates ◽  
Sequence Types

An epidemic of meningococcal disease caused by serogroup B meningococci expressing the P1.7-2,4 PorA protein began in New Zealand in 1991. The PorA type has remained stable. Different porB have been found in association with the P1.7-2,4 PorA, although type 4 has been most common. The clonal origins of B:P1.7-2,4 meningococci isolated from cases during 1990 to the end of 2003 were analysed. In 1990, the year immediately preceding the recognized increase in disease rates, all three subclones (ST-41, ST-42, and ST-154) of the ST-41/44 clonal complex occurred among the five isolates of B:P1.7-2,4. The two sequence types, ST-42 and ST-154, continued to cause most disease throughout New Zealand. Isolates belonging to subclone ST-41 were mostly identified early in the epidemic and in the South Island. 16S rRNA typing indicated that isolates belonging to the subclones ST-41 and ST-154 share a common ancestor, with those typing as ST-42 more distantly related with some genetically ambiguous. It is possible that ST-41 and ST-154 may have evolved one from the other but evolution to ST-42 is more difficult to explain. It is possible that one or more of the ST types could have been introduced into New Zealand prior to the first detection of clinical cases in 1990. Genetic diversity may have occurred during carriage in the community.

Improved resolution of recalcitrant nodes in the animal phylogeny through the analysis of genome gene content and morphology

2021 ◽  
Author(s):  
Ksenia Juravel ◽  
Luis Porras ◽  
Sebastian Hoehna ◽  
Davide Pisani ◽  
Gert Wörheide
Keyword(s):  
Common Ancestor ◽  
Sister Group ◽  
The Other ◽  
Gene Content ◽  
Statistical Hypothesis ◽  
Phylogenetic Position ◽  
Last Common Ancestor ◽  
Statistical Hypothesis Testing ◽  
Animal Phylogeny ◽  
Phylogenetic Hypotheses

An accurate phylogeny of animals is needed to clarify their evolution, ecology, and impact on shaping the biosphere. Although multi-gene alignments of up to several hundred thousand amino acids are nowadays routinely used to test hypotheses of animal relationships, some nodes towards the root of the animal phylogeny are proving hard to resolve. While the relationships of the non-bilaterian lineages, primarily sponges (Porifera) and comb jellies (Ctenophora), have received much attention since more than a decade, controversies about the phylogenetic position of the worm-like bilaterian lineage Xenacoelomorpha and the monophyly of the "Superphylum" Deuterostomia have more recently emerged. Here we independently analyse novel genome gene content and morphological datasets to assess patterns of phylogenetic congruence with previous amino-acid derived phylogenetic hypotheses. Using statistical hypothesis testing, we show that both our datasets very strongly support sponges as the sister group of all the other animals, Xenoacoelomorpha as the sister group of the other Bilateria, and largely support monophyletic Deuterostomia. Based on these results, we conclude that the last common animal ancestor may have been a simple, filter-feeding organism without a nervous system and muscles, while the last common ancestor of Bilateria might have been a small, acoelomate-like worm without a through gut.

Arts and Crafts of the Medieval Kingdoms of Nubia

2021 ◽  
pp. 846-873
Author(s):  
Dobrochna Zielińska
Keyword(s):  
Middle Eastern ◽  
Wall Painting ◽  
Political Authority ◽  
The Other ◽  
Arts And Crafts ◽  
Byzantine Empire ◽  
Late Period ◽  
Artistic Production ◽  
12Th Century ◽  
Different Sources

After the collapse of the Meroitic Empire, three independent kingdoms arose within its former territory. Because of a lack of centralized political authority and artistic production, their early development, although based on the Meroitic inheritance, was determined by different sources of influence. From the 8th century two united northern kingdoms became a powerful state, which is also reflected in its art. Rising creativity from the 9th century onwards reflected local needs and ambitions. In the course of time, surrounded by Islamic neighbors, Nubian art on one hand remained independent in its forms of art, but on the other hand absorbed a new style and iconographic details, which is most visible in 12th-century wall painting. Most probably it reflected a changing lifestyle, inspired by the wider Middle Eastern world at that time. The late period, although characterized by much less activity and financial possibilities of individuals or communities, still shows flourishing activities of Nubian artists. Christian Nubian culture ended almost simultaneously with the Byzantine empire, leaving almost one thousand years of its unique heritage.

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