bluuebunny/crossref_metadata_2025_split huggingface dataset:
Birnaviruses
Authors: Delmas Bernard 
Published: February 2015

Abstract

Birnaviruses are bisegmented double‐stranded
RNA
viruses infecting animals belonging to different vertebrate and invertebrate phyla. Most of the research efforts on birnaviruses have focused on infectious bursal disease virus (
IBDV
), which is responsible for important losses in the poultry industry. Another economically important birnavirus is infectious pancreatic necrosis virus (
IPNV
) of salmonids. Other birnaviruses (<10) have been isolated from diseased animals, established cell lines or identified by deep sequencing. The reverse genetic systems that have been engineered for
IBDV
and
IPNV
at the end of the 1990s have been powerful tools to dissect the molecular biology of these viruses. During these past 10 years, resolution of the
3D
‐structures of several birnavirus proteins (including their unique replicase/transcriptase, their protease, their capsid protein and ultimately their complete capsid) by X‐ray radiocrystallography,
NMR
and cryo‐electron microscopy shed light on important properties and characteristics of these viruses.

Key Concepts

Birnaviruses are nonenveloped double‐stranded RNA viruses with representatives able to infect animals of invertebrate and vertebrate phyla, but not yet found infecting mammals.

The birnavirus capsid possess a T = 13
laevo
icosahedral symmetry.

Entry of birnavirus into a cell is mediated by a capsid‐associated peptide that deforms and perforates membranes.

The birnavirus virus protein 4 (VP4) protease possess a serine‐lysine catalytic dyad and is homologous to the protease domain of bacterial and organelle ATP‐dependent Lon proteases.

The birnavirus capsid protein VP2 is structurally homologous to the capsid protein of positive‐strand viruses, just like the T = 3 nodaviruses and T = 4 tetraviruses.

The palm subdomain‐based active site of the birnavirus RNA‐dependent RNA‐polymerases is internally permuted to the unique C‐A‐B motif arrangement, a feature shared with permutotetraviruses, a group of positive‐strand RNA viruses.

The capsid proteins of birnaviruses display a high structural polymorphism of their assemblies.
Hepatitis Delta Virus
Authors: Taylor John Marston 
Published: February 2015

Abstract

Several viruses are important causes of acute and chronic infections of the human liver.
Hepatitis delta virus
(
HDV
) is a most unusual agent that is found only in association with

Hepatitis B virus (
HBV
)

.
HDV
can make
HBV
infections more damaging to the liver.
HDV
needs the envelope proteins of
HBV
to achieve virus assembly and infection of new susceptible cells. Thus,
HDV
infections can be prevented with the vaccine against
HBV
envelope proteins.
HDV
has an
RNA
genome that is unique in that it is very small (around 1700 nucleotides) and has a circular conformation. This genome is replicated via redirection of host
RNA
polymerase activity to act on
RNA
templates. This replication is fundamentally different from that of
HBV
, which involves reverse transcription.

Key Concepts

HDV is unlike any other animal virus.

HDV has similarities and yet distinct differences from viroids, agents that infect plants.

HDV only encodes one protein and yet by RNA editing creates an essential second protein.

HDV replicates by redirecting host RNA polymerase activity.

HDV can make HBV infections more pathogenic.
Cellular Thermodynamics: The Molecular and Macroscopic Views
Authors: Wolfe Joe 
Published: February 2015

Abstract

On the macroscopic scale, biology obeys thermodynamics, and this article introduces the laws of thermodynamics and its macroscopic variables, including entropy. The molecular description is often more directly useful to biologists. So this article explains Boltzmann's distribution, which describes how the proportion of molecules having a particular energy depends on energy and temperature, and quantifies the compromise between minimising energy and maximising entropy. This simple law is then used to explain and quantify several aspects of the function and structure of cells. These include Årrhenius' law for reaction rates, the Nernst equation for electrochemical equilibria, and hydraulic and osmotic equilibria between solutions with different compositions. It also explains the equilibrium between different phases (solid, liquid and vapour), the aggregations of molecules in self‐assembly, aspects of the stability and mechanical homeostasis of membranes and entropic forces in biomolecules.

Key Concepts

Cells and components that are physically close together are often approximately in thermal and chemical equilibrium, which allows some powerful observations about their properties.

Cells and tissues sometimes approximate steady state: they input and output energy and matter at approximately equal rates and vary little over time.

Entropy measures the ‘uselessness’ of energy: the biosphere survives by converting energy with low entropy (light from the sun) into energy with high entropy (waste heat lost to the atmosphere and to space).

Entropy also quantifies disorder – but only at a molecular level.

The Boltzmann energy distribution leads directly to a number of important laws and effects relevant to cell biology:

Årrhenius' law of reaction rates,

ion equilibria,

osmotic pressure,

phase equilibria, and

molecular oligamerisation and aggregation.
Iron Deficiency
Authors: Bridges Kenneth R 
Published: February 2015

Abstract

Iron deficiency is a leading cause of anaemia, affecting more than half a billion people worldwide. Depletion of iron stores precedes impaired production of iron‐containing proteins, most importantly haemoglobin. The two important stages of iron deficiency are (1) depletion of iron stores without anaemia and (2) depletion of iron stores with anaemia. The gastrointestinal tract mediates iron uptake into the body but is also the major source of iron loss and iron deficiency. Although anaemia is the most commonly recognised consequence of iron deficiency, injury to other organs has serious consequences that include fatigue, weakness and developmental delay in infants. Maternal iron deficiency during pregnancy can result in poor neonatal low iron stores and heightened risk of neurocognitive impairment. Oral iron supplements are the most convenient form of replacement but attention should be directed to the preparation as tolerance varies greatly depending on the specific iron salt.

Key Concepts

Iron is the second most common metal in the surface of the earth, but absorption is a challenge due to the low solubility of iron salts.

Gastric acidity and weak iron chelators, such as ascorbic acid, greatly facilitate iron absorption that occurs primarily in the duodenum and upper jejunum.

Gastrointestinal blood loss is the most common cause of iron deficiency.

Females of reproductive age suffer a high rate of iron deficiency due to menstrual blood loss.

Iron deficiency often produces anaemia in which extremely low haemoglobin levels are tolerated because of the slow rate of fall from the normal range.

Growth and developmental delay are particularly serious consequences of iron deficiency during infancy, often occurring in the wake of substantial maternal iron deficiency during gestation.

Oral iron is the most convenient form of replacement but often is poorly tolerated when sulphate is the anion in the salt.

A dramatic decline has occurred in serious complications of intravenous iron replacement, including anaphylaxis, with the advent of newer formulations.
Chromatographic Techniques
Authors: Lewis Alastair C 
Published: February 2015

Abstract

Chromatography achieves the physical separation of chemical components in a mixture for either analytical or preparative purposes, based on the unique degree of interaction between each component and the separating medium. Chromatography can be used to isolate a wide range of different chemicals, from permanent gases to macromolecules, metals, ions and organic and inorganic compounds. Chromatography uses gases, liquids or supercritical fluids as the mobile phase to carry analytes through the separating medium, commonly referred to as the column. In the case of liquid chromatography, the column is often a packed tube, and in gas chromatography a wall‐coated capillary. Chromatography is used in many different application areas and is one of the most commonly used laboratory techniques. Chromatography is often coupled with mass spectrometry as a detector.

Key Concepts

Materials found in nature and from man's activities are often highly complex mixtures of different chemicals; isolating and quantifying individual components in such mixtures is a very common measurement requirement.

Chromatography is an analytical method in which a physical separation of individual components in a mixture is achieved.

A sample mixture is solvated in a fluid, which is used to carry it through a separating medium often referred to as a column. The solvating fluid is referred to as the mobile phase and the separating medium as the stationary phase.

Each analyte may interact (e.g. by adsorption) to a unique degree with the stationary phase, resulting in the physical separation of the mixture into its component parts.

The separating medium is often found in the form of a packed column of stationary‐phase material, open tubular column with a wall coating or as a planar coated plate.

Chromatographic methods are very commonly coupled with detectors such as mass spectrometry, which allows for the quantification and identification of analytes as they elute from the column.
Müller,J F T(Fritz)
Authors: West David A 
Published: February 2015

AbstractFritz Müller (1822–1897), German naturalist, was one of the great Darwinians of the nineteenth century. Educated in math and science in what was then part of Prussia, he emigrated to Brazil in 1852; in the forests and ocean of the province of Santa Catarina, he found a rich diversity of organisms for study, especially marine and freshwater Crustacea, insects and flowering plants. From original observations of morphology, development, physiology and behaviour, he documented the power of natural selection in the evolution of adaptations. He encountered Darwin'sOrigin of Speciesin its German translation in 1861, tested its salient points in the Crustacea and endorsed them. Although he and Darwin were half a world apart, they recognised many common interests through correspondence and publications, and Müller became Darwin's closest intellectual kin.
N
atta,
G
iulio
Authors: Pasquon Italo 
Published: February 2015

Abstract
Italian polymer chemist (1903–1979) who developed the theory and technology of stereospecific polymerisation. Stereospecific polymerisation has been a revolution in the field of macromolecular chemistry. Besides the discoverer, Natta was its undisputed ruler. With his brilliant insights and tireless work, he was able to guide and coordinate the interdisciplinary work of his collaborators to the discovery and the study of more than a hundred new polymers, over a period of 15 years. The synthesis of isotactic polypropylene was the last great discovery – in terms of economic importance – still possible in the traditional field of industrial chemistry. For several years, the most significant results obtained in the field of stereospecific polymerisation continued to come from Natta's laboratories. Since then, the stereospecific polymerisation continues even nowadays to be the subject of study.
History of Classical Genetics
Authors: Harman Oren , Lamm Ehud 
Published: February 2015

Abstract

Classical genetics has its origin in the 1850s and 1860s, when the Moravian monk Gregor Mendel attempted to formalise the rules of inheritance governing plant hybridisation. In 1909, the Danish biologist Wilhelm Johannsen proposed that there are two sources of variation: one arising from the action of the environment and the other due to variations in Mendel's hereditary factors – entities Johannsen called ‘genes’. When Mendel's laws were rediscovered in 1900, breeding experiments were wedded to cytological observation of chromosomes in the nucleus of organisms – most notably in the fruit fly – and classical genetics was born. The chromosome theory of inheritance that was formulated as a result of this work stated that genes are located linearly on chromosomes and that chromosomal dynamics underlie the patterns of Mendelian inheritance. Towards mid‐century, this work culminated in models of what genes do, and what they are made of.

Key Concepts

Classical genetics refers to the study of the laws of hereditary transmission in living organisms.

Classical genetics has its origin in Gregor Mendel's papers on inheritance in peas, published in 1866.

The chromosome theory of inheritance states that genes are located on chromosomes and that chromosomal dynamics underlie the patterns of Mendelian inheritance.

The ‘genotype’ is the totality of all the organism's genes, whereas the ‘phenotype’ are the characters displayed, which are products of both the underlying genes and the actions of the environment.

A fundamental observation in classical genetics was the ‘one gene, one enzyme’ relationship. It is now known that the relationship between genes and proteins is much more complex.
Splicing of Pre‐m
RNA
Authors: Tu Chi‐Chiang , Tarn Woan‐Yuh 
Published: February 2015

Abstract

The majority of eukaryotic messenger
RNAs
(m
RNAs
) are initially transcribed as intron‐containing precursor m
RNAs
(pre‐m
RNAs
). Removal of introns from each pre‐m
RNA
by splicing is necessary to generate a mature m
RNA
. Pre‐m
RNA
splicing is catalysed by the spliceosome, a large ribonucleoprotein complex that contains five small nuclear
RNAs
and numerous protein factors and forms anew on each intron of nascent transcripts. In higher eukaryotes, alternative splicing of pre‐m
RNA
generates multiple m
RNA
isoforms from a single gene and is regulated by cellular
RNA
‐binding proteins. Alternative splicing not only increases proteome diversity but also has the potential to regulate gene expression levels post‐transcriptionally. Thus, alterative splicing may have a great impact on a wide range of physiological and developmental processes. Defects in pre‐m
RNA
splicing underlie a considerable number of genetic diseases and cancers and may fine‐tune disease severity.

Key Concepts

In most eukaryotic pre‐mRNAs, the coding sequences (exons) are interrupted by stretches of non‐coding sequences (introns).

The spliceosome uses a two‐step transesterification reaction to remove introns and join exons of pre‐mRNAs.

The snRNAs and several conserved spliceosomal protein factors are implicated in the key catalytic steps of splicing.

Alternative splicing extends proteome diversity and regulates gene expression levels.

Alternative splicing is determined by interplay between
trans
‐acting regulatory factors and
cis
‐elements of pre‐mRNAs.

Alteration of
cis
‐elements and aberrant control of
trans
‐acting factors can lead to diseases.
Medical Genetics in Britain: Laying the Foundation (1940s–1960s)
Authors: Zallen Doris T 
Published: February 2015

Abstract

Medical genetics refers to the use of genetic information in the health care setting. This includes research efforts to understand the genetic basis of human illness. It also includes clinical services that use genetic knowledge to provide an assessment of risk for the occurrence of gene‐based disorders, determine an individual's actual genetic status, select treatments and put forth strategies for disease prevention. In Britain, medical genetics as an area of specialty arose out of the activities begun in three separate settings during the period from mid‐1940s through the 1960s: the Clinical Genetics Research Unit at the Institute of Child Health in London, the Paediatric Research Unit at Guy's Hospital in London and the Nuffield Unit of Medical Genetics at the University of Liverpool Medical School. The research programmes and clinical commitments of these separate units, along with the strong links connecting them, provided the foundation on which present‐day medical genetics is built and paved the way for the introduction of “genomic medicine” into twenty‐first century health care.

Key Concepts

Medical genetics, as an area of speciality, emerged late in the twentieth century in Britain largely through the efforts of physicians who, for the most part, had no formal training in genetics but who recognised its importance.

Activities undertaken at three separate medical units, each emphasising different aspects of genetics (pedigree analysis, cytogenetics and genetic variation associated with common disorders), formed the foundation on which medical genetics, as an entity, developed.

Medical genetics was able to grow and establish itself more widely because of the many different types of close interactions among the members of the three founding groups and the support received from existing medical institutions.
Nucleolus: Structure and Function
Authors: Olson Mark OJ , Dundr Miroslav 
Published: February 2015

Abstract

The nucleolus is the nuclear subdomain that assembles ribosomal subunits in eukaryotic cells. The nucleolar organiser regions of chromosomes, which contain the genes for pre‐ribosomal ribonucleic acid (
rRNA
), serve as the foundation for nucleolar structure. The nucleolus disassembles at the beginning of mitosis, its components disperse in various parts of the cell and reassembly occurs during telophase and early
G1
phase. Ribosome assembly begins with transcription of pre‐
rRNA
. During transcription, ribosomal and non‐ribosomal proteins attach to the
rRNA
. Subsequently, there is modification and cleavage of pre‐
rRNA
and incorporation of more ribosomal proteins and
5S rRNA
into maturing pre‐ribosomal complexes. The nucleolus also contains proteins and
RNAs
that are not related to ribosome assembly and a number of new functions for the nucleolus have been identified. These include assembly of signal recognition particles, sensing cellular stress and transport of human immunodeficiency virus 1 (
HIV
‐1) messenger
RNA
.

Key Concepts

The nucleolus, whose primary function is to assemble ribosomes, is the largest structure in the cell nucleus.

The nucleolus organiser regions of chromosomes, which harbour the genes for pre‐rRNA, are the foundation for the nucleolus.

All active nucleoli contain at least two ultrastructural components, the nucleolar dense fibrillar component representing early pre‐ribosomal complexes and the granular component containing more mature pre‐ribosomal particles.

Most nucleoli in higher eukaryotes also contain fibrillar centres, which are the interphase equivalents of the nucleolus organiser regions.

The nucleolus disassembles at the beginning of mitosis and begins to reassemble in telophase.

Ribosome assembly begins with the transcription of pre‐rRNA by RNA polymerase I.

Ribosomal and non‐ribosomal proteins and 5S RNA associate with the pre‐rRNA during and after transcription.

The pre‐rRNA is modified and processed into rRNA with the aid of non‐ribosomal proteins and small nucleolar RNAs.

The nucleolus has numerous other functions including assembly of signal recognition particles, modification of transfer RNAs and sensing cellular stress.
Microtubule Organisation inDictyostelium
Authors: Gräf Ralph 
Published: February 2015

AbstractDictyostelium amoebae contain a radial array of microtubules emanating from a single microtubule‐organising centre called centrosome that is bound to the cytosolic face of the nucleus. Their centrosome contains no centrioles but consists of a layered core surrounded by a corona harbouring microtubule nucleation centres. It duplicates in prophase of a closed mitosis and organises a central spindle that drives centrosome separation and chromosome segregation. Dictyostelium microtubules exhibit a differential dynamic behaviour during interphase. Growth and shrinkage is observed only in the periphery but not in the pericentrosomal region. During mitosis, when centrosomes possess no corona, microtubules behave quite dynamically in formation of a central spindle and astral microtubules. Microtubules are associated with a couple of conserved proteins (MAPs), which are involved in centrosome biogenesis and the cross talk of microtubule tips with the actin cell cortex. The latter becomes evident in cytokinesis, when centrosomes with their attached microtubules participate in the positioning of cleavage furrows.Key ConceptsDictyostelium amoebae contain a nucleus‐associated centrosome that serves as the only microtubule‐organising centre.The Dictyostelium centrosome contains no centrioles, but consists of a three‐layered core structure surrounded by a microtubule‐nucleating corona.If compared to the three major plaques of the yeast spindle pole body, the entire core structure of the Dictyostelium centrosome appears equivalent to the central plaque, while the corona plays a similar role as the inner and outer plaques.Dictyostelium centrosomes duplicate at the onset of mitosis.Dictyostelium amoebae show a closed type of mitosis with a persisting nuclear envelope.Dictyostelium microtubules are quite dynamic during mitosis but show growth and shrinkage only in the periphery during interphase.Microtubule plus ends regulate actin dynamics at the cell cortex.Dictyostelium amoebae are a useful model to study the role of the centrosome and microtubules in cell dynamics and disease.
Cerebral Palsy: Treatments and Therapeutics
Authors: Feather‐Schussler Danielle N , Ferguson Tanya S 
Published: February 2015

AbstractCerebral palsy (CP) is a non‐progressive motor disorder affecting approximately 3 out of every 1000 infants in the United States. Although it is classified as a motor disorder, the deficits are caused by pre‐ or neonatal brain injury. Unfortunately, there is no cure forCPand currently, symptom management is the only treatment option available. As research begins to unravel the underlying causes and cellular changes leading toCP, potential treatments and therapeutics can be investigated to prevent brain damage following insults. Today, only two therapies are approved for use in the hospital setting: hypothermia and magnesium sulphate. Both of these therapies attempt to lessen the brain damage by slowing processes of inflammation and cell death. Other potential therapies are in clinical trials to test safety and efficacy for use in humans. Some drugs have shown promise in animal models; however, they have not yet been tested in humans. Researchers are searching for a cure.Key ConceptsThere is no cure for cerebral palsy and currently approved treatments target the symptoms of cerebral palsy, not the underlying causes.Hypothermia and magnesium sulphate are the only two therapeutics used in the hospital setting to slow or lessen brain damage following labour and delivery complications.Therapeutics targeting the excitatory amino acid neurotransmitter glutamate, along with glutamate receptor and transporter expression and function, appear to be promising.Drug treatments targeting growth factors and endogenous proteins may be beneficial to reduce cell death leading to cerebral palsy.Because inflammation plays a role in cerebral palsy, drug treatment that reduces the inflammatory response may also reduce brain damage following insults.