bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viral Capsids and Envelopes: Structure and Function
Authors: Lucas William 
Published: April 2010

Abstract

Virus particles contain the viral genome packaged in a protein coat called the capsid. For some viruses, the capsid is surrounded by lipid bilayer that contains viral proteins, usually including the proteins that enable the virus to bind to the host cells. This lipid and protein structure is called the virus envelope, and is derived from the host cell membranes. The capsid and envelope play many roles in viral infection, including virus attachment to cells, entry into cells, release of the capsid contents into the cells, and packaging of newly formed viral particles. The capsid and envelope are also responsible for transfer of the viral genetic material from one cell to another. These structures also determine the stability characteristics of the virus particle, such as resistance to chemical or physical inactivation.

Key concepts:

Viral genetic material is packaged inside protein structures called capsids.

Viruses are divided into two groups: enveloped viruses are surrounded by an outer lipid membrane; nonenveloped viruses lack this membrane.

Where present, the envelope contains the viral proteins, which mediate binding to host cells. Where no envelope is present, this function is carried out by the outer capsid proteins. In general, nonenveloped viruses are more stable and can survive much longer in the environment.

Capsids and envelopes determine the method of viral entry into and exit from host cells.
Nerve‐dependent Tissue and Organ Regeneration
Authors: Mescher Anthony L 
Published: April 2010

Abstract

The anatomical and functional restoration of parts removed from an organism is known as regeneration. In the regenerating amphibian limb and in tissue regeneration in certain sensory organs, this process occurs under the influence of nerves. In other systems, such as liver regeneration and most instances of tissue repair, nerves are not required. One determinant of whether nerves are required for regenerative growth may be the degree of vascularization in the injured, responding tissue or organ. The early, nerve‐dependent blastema of the regenerating limb is almost completely avascular except in its overlying skin. The molecular basis of the nerves’ growth‐promoting effect is not known. Of the candidate molecules proposed, the nutritive factor
transferrin
, which is also released from capillaries, fits most closely to what is known of the neural effect in limb regeneration. Other candidates proposed as mediators of this activity include Fibroblast growth factors (FGFs),
neuregulins
and anterior gradient protein (nAG).

Key Concepts:

Amphibian limb regeneration and other examples of epimorphic (blastema‐based) regeneration usually depend on trophic factors provided by peripheral nerves.

All nerve types can supply the growth requirement, which appears to be a nutritive factor that sustains cell cycling rather than a mitogenic signal to trigger cell cycling in dedifferentiating limb cells.

Other nerve‐dependent regenerating systems, such as regeneration of taste buds and corneal repair, lack a direct, extensive vasculature.

Regenerating systems not requiring nerves, such as liver regeneration and seasonal regrowth of antlers, are not epimorphic and the regenerative process does not involve a blastema.

Candidate factors for the neural effect include neuregulins, the newt anterior‐gradient protein (nAG), and the plasma‐derived trophic factor transferrin.

Transferin is transported and released axonally and is required for cell cycle progression in a manner consistent with the effects of denervation on limb blastema cell proliferation.
Lens Induction
Authors: Kondoh Hisato 
Published: April 2010

AbstractLens tissue develops from the embryonic head ectoderm through its interaction with the retinal primordium, the optic vesicle. This developmental mechanism has served as a paradigm of embryonic tissues induction. The application of modern techniques for gene manipulation and monitoring gene activities in developing embryonic tissues have revealed the two optic vesicle‐dependent mechanisms that underlie the lens induction process: local activation of the cooperative transcription factorsSOX2(SRY‐related‐HMG‐box 2) andPAX6(paired box 6) in the head ectoderm; and elimination of the influence of the cephalic neural crest, which is otherwise inhibitory to lens development. Lens induction reciprocally influences the development of the optic vesicle and organizes the lens‐centered optic cup. The action ofSOX2andPAX6is also common to other lens‐generating processes, including during lens regeneration from the dorsal iris in the newt eye, and lens transdifferentiation from the pituitary primordium as occurs in certain mutant embryos.Key concepts:Tissue induction is the process of deriving new cell types from a tissue through interaction with another tissue.Transcription factors are proteins that regulate gene transcription by binding to the gene regulatory regions of DNA.Signalling molecules, which are often proteins, are secreted from a group of cells, bound by receptors on another group of cells, and cause changes in the cells that bind the molecules.
Immunity: Humoral and Cellular
Authors: Harrison Leonard C , Unglik Gary , Honeyman Margo C 
Published: April 2010

Abstract

The immune system evolved to recognise infectious pathogens. Discrimination between self and nonself is a critical property of the immune system that enables it to eradicate pathogens without harming the host. Immune responses to pathogens are affected initially by the innate immune system, which reacts rapidly to generic pathogen‐associated molecules and primes the adaptive immune system, which is slower to react but has exquisite specificity and memory. Here, we outline the spatial framework of the immune system and define its mobile and fixed elements. A range of cell types (including antigen‐presenting cells and lymphocytes) and soluble components (including complement, antibody, cytokine and chemokine proteins) circulate and communicate between the bone marrow and lymphoid tissue structures to maintain immune surveillance.

Key Concepts:

The immune system is designed to recognise, react to and eradicate ‘nonself’, in particular infectious pathogens.

The immune system comprises fixed and mobile elements.

The elements of the immune system sequentially mediate innate immunity, providing acute, generic defences and adaptive immunity, providing highly specific, long‐lasting defences.

The specificity and diversity of adaptive immunity is based on genetic polymorphism of the receptors for antigens on T and B cells and of the major histocompatibility complex (MHC) molecules that bind antigenic peptides recognised by the T‐cell receptor.

Nonspecific costimulation via surface‐interacting molecules or soluble cytokines and chemokines shapes the differentiation of T and B cells in the adaptive immune response.
Plant Defences against Herbivore Attack
Authors: Schardl Christopher L , Chen Feng 
Published: April 2010

Abstract

Plants deploy a number of defences against attack by insects and other herbivores. Direct defence is conferred by plant products and structures that deter or kill the herbivores. Chemical toxins and deterrents vary widely among plant species, and some typical toxins include alkaloids, terpenoids, steroids, phenylpropanoids and precursor compounds that, on damage of the plant tissue, can be degraded to cyanide or other toxic molecules. Physical defences include thorns, barbs and unpalatable tissues. Other defences are indirect, such as defensive symbioses with microbes, harbouring protective ants or recruitment of parasitoids and predators that attack the herbivores. Recent experiments, and deployment of transgenic plants with Bt toxins, demonstrate the potential for novel plant defences in agriculture.

Key Concepts:

Plants employ various direct and indirect mechanisms to defend against herbivores.

Direct defences include chemical defences and physical defences such as tissue toughness, thorns and barbs.

Chemical defences against herbivores are numerous and diverse.

Direct chemical defences can be toxic or deterrent to herbivores, or reduce nutritive value of the plant tissues.

Some chemical defences act indirectly, for example, by attracting wasps that are parasitic to the herbivores.

According to optimal defence theory, young tissues of high value to plant fitness tend to be chemically defended, whereas older tissues have relatively strong physical defences.

Chemical defences, especially induced chemical defences, are tightly regulated mainly through the jasmonate signalling pathway.
Eicosanoid Biosynthesis
Authors: Fernandez Ana Z , Fatima Garces Maria , Alvarado‐Castillo Claudia P , Estrada Omar 
Published: April 2010

AbstractEicosanoids are the major products derived from the cellular metabolism of arachidonic acid by the enzymescyclooxygenase,lipoxygenaseandepoxygenases. The eicosanoids comprise several compounds, which include prostaglandins, thromboxanes, prostacyclins, leukotrienes, lipoxins and epoxyeicosatrienoic acids. They represent the major group of metabolically active lipids, exerting their functions through different mechanisms, that is by receptor binding and intracellular signalling pathway modulation. Their effects are diverse, acting on every cell of the body, with a short half‐life. A tight regulation on the processes of formation and inactivation or clearance is fundamental to prevent the exacerbation of their effects. Although initially they were strictly linked to inflammatory processes, recent evidences point out their homeostatic counterpart. Thus, there are eicosanoids involved in vasoconstriction/vasodilatation balance, thrombotic/antithrombotic balance and inflammation/anti‐inflammation balance. This article will focus on the enzymes involved in the formation of these lipids.Key concepts:Eicosanoids are important lipid mediators involved in cellular homeostasis.Most eicosanoid effects are mediated through specific receptors.Inhibition or activation of the key enzymes involved in the biosynthesis of eicosanoids has encouraged the development of new therapeutics approaches.
Quaternary Life on Land
Authors: Elias Scott A 
Published: April 2010

AbstractThe Quaternary is the most recent geologic period. The glaciations that characterise this period began about 2.6 million years ago. There have been roughly 50 glacial–interglacial cycles during the Pleistocene Epoch which comprised all of the Quaternary except the current interglacial interval, the Holocene. Pleistocene biota mostly responded to the series of rapid dramatic climatic changes by migrating to regions of acceptable climate. The constant reshuffling of biological communities led to the formation of many combinations of species for which there is no modern analogue. The end of the last glaciation saw the extinction of large numbers of large mammals (the Pleistocene megafauna) in Eurasia, Australia and the New World. The Late Pleistocene saw the rise and geographic dispersal of humans, including Neanderthals in Europe and southwest Asia, and modern humans who spread out of Africa into Europe, Asia, Australia and eventually the New World.Key concepts:Rapid climate change characterised most of the Quaternary.The Quaternary and Late Tertiary saw the evolution of modern ecosystems.Nonanalogue biological communities formed during the Pleistocene, as the ranges of individual species responded independently to climate change.The Late Pleistocene–Holocene transition saw a major extinction event among megafaunal mammals.The Pleistocene was also the most important interval of human evolution and dispersal.
Petals
Authors: Drea Sinéad 
Published: April 2010

Abstract

Petals are often the most obvious organ within a flower because they provide visually arresting targets for varied pollinators and show corresponding adaptions in form, colour and scent. When present, they are located in the outer layers of a flower (the perianth) surrounding the male and female reproductive organs, the stamens and carpels. Their development is a consequence of a regulatory hierarchy of meristem determining genes, organ identity genes and downstream target genes. The gene hierarchy involves transcription factors from varied families and is regulated at transcriptional and posttranscriptional levels, involving microRNAs (
ribonucleic acids
) and targeted protein degradation. The nature of the gene and protein interactions determining and controlling many aspects of petal development have been teased apart in dicotyledonous flowers of

Arabidopsis

,

Antirrhinum

and

Petunia

and in recent years, this knowledge has been used to explore the evolution of these developmental genetic systems across the angiosperms.

Key concepts:

Molecular genetics has identified key regulators of petal development in model species.

Petal initiation and subsequent development is regulated by a range of transcription factor types.

Petal characteristics such as colour, shape and scent are related to pollination mechanisms.

Ethylene is important in petal senescence.
Epidermis: Outer Cell Layer of the Plant
Authors: Glover Beverley J 
Published: April 2010

Abstract

The epidermis is the protective outer layer of clonally related cells covering all plant organs. It is composed of a number of specialised cell types which differentiate from the basal epidermal cell in adaptively significant frequencies and patterns. The epidermis is unique in developing solely through anticlinal divisions, generating a sheet of cells overlying the rest of the plant. This sheet is connected biochemically to the cell layers below, with information exchange occurring in both directions. The specialised cell types within the epidermis develop either through communication among themselves, or, in some cases, through communication also with the underlying cell layers. Brief descriptions of the molecular genetic control of trichomes, stomata, root hairs and petal conical‐papillate epidermal cells are provided here, along with a summary of the role of the cuticle in epidermal cell morphology.

Key Concepts:

The plant epidermis is a single layer of clonally related cells.

Plant epidermis fulfils a basic protective function, but specialised cells within the epidermis have specific roles.

The aerial epidermis originates in the shoot apical meristem, the root epidermis in the root apical meristem and the seedling epidermis arises by isolation of the outer layer during embryogenesis.

Stomatal guard cells allow gas exchange, and their patterning is controlled by cell lineage‐based developmental mechanisms.

Trichomes protect the plant from herbivores, and their patterning is controlled by cell–cell interactions.

Root hairs increase surface area for water and nutrient uptake, and are patterned according to positional signals.

The cuticle overlying the epidermis can contribute to cell shape and function.
Immunodeficiency Disorders due to Antibody Deficiency (B‐lymphocyte Disorders)
Authors: Roberts Robert L 
Published: April 2010

Abstract

The majority of patients with primary immunodeficiency have a defect in their ability to make sufficient quantities of specific antibodies. This lack of specific antibodies is due to the lack of B lymphocytes, defects in B‐lymphocyte function, or inability of B lymphocytes to interact with T lymphocytes. Patients born with only antibody deficiency usually appear normal at birth due to maternal antibodies that crossed the placenta. They usually start developing more infections at around six months of age when maternal antibodies have been depleted, and they cannot make their own antibodies. Treatment may include prophylactic antibodies until diagnosis is confirmed or infusion of immunoglobulin, either by intravenous route or subcutaneously. When patients have antibody deficiency plus defects in T lymphocytes, the disease is usually more severe and will be further discussed in other articles.

Key Concepts:

The most severe form of antibody deficiency, Bruton's, requires regular infusions of IVIG starting in infancy.

Common variable immunodeficiency (CVID) is often associated with autoimmune disease as well as malignancies.

Less severe forms of B‐cell deficiency may be managed with prophylactic antibiotics.

Severe combined immunodeficiency (SCID) requires stem cell transplantation for treatment.

Early diagnosis is essential in preventing long‐term disability or early death
Brain Death and the Vegetative State
Authors: Jellinger Kurt A 
Published: April 2010

Abstract

A brain‐dead patient is unconscious, has lost the capacity to breathe (apnoea) and requires mechanical respiration; even with full supportive treatment his heart will soon stop, usually only after a few days. The widely accepted definition of brain death (BD) equates it with death of a person and renders legally the removal of organs for transplantation. Evidence‐based criteria for the clinical diagnosis of BD and the use of confirmatory tests are available. A patient in the vegetative state is unconscious but has his eyes open and can breath on his or her own, but requires artificial feeding, automatic‐vegetative functions and some active functions of the severely damaged brain being preserved. Its diagnosis is based on repeated clinical observations and modern neuroimaging tests. Given adequate treatment persons in a vegetative state can survive for years and may recover towards the minimally conscious state or even can regain (in)complete recovery.

Key Concepts:

Brain death is the expression of irreversible loss of brain function.

Brain death is a precisely defined clinical diagnosis based on generally accepted criteria.

When the clinical diagnosis is unequivocal, no additional confirmatory tests (angiography, electroencephalography, transcranial Doppler sonography or magnetic resonance angiography) are necessary.

Causes of brain death are traumatic brain injury, cerebral haemorrhage and systemic hypoxia, and frequently associated with brain oedema and raised intracranial pressure damaging the brainstem.

The widely accepted legal definition of brain death equates it with death of a person.

Brain death diagnosis depends on adequate observation times (6–24 h or more), and its declaration has to be made by two adequately experienced physicians.

Unequivocal diagnosis of brain death generally renders legally the removal of organs for transplantation.

The vegetative state consists of continuing unconsciousness with no evidence of awareness and no possibility for communication, with the eyes open, spontaneous breathing and preserved brainstem autonomic functions.

Causes of the vegetative state are various types of severe acute brain damage (head injury, systemic hypoxia or encephalitis) or progressive brain damage (terminal states of Alzheimer or Huntington disease, demyelinating, metabolic, inflammatory diseases or severe malformations).

The diagnosis of the vegetative state depends on repeated clinical examinations and demands considerable skills; it can be supported by electroencephalography and modern neuroimaging methods showing severe drop of cerebral metabolism.

Given adequate treatment, persons in a vegetative state can survive for years and some may recover towards the minimal conscious state or may even show (in)complete recovery with various degrees of incapacity.
Cytomegalovirus Infections in Humans
Authors: Griffiths Paul D 
Published: April 2010

Abstract

Cytomegalovirus (CMV) is a herpesvirus that causes severe disease in the immunocompromised because virus replication is normally held in check by cell‐mediated immune responses. Patients receiving immunosuppressive drugs to allow allo‐transplantation, patients with AIDS (acquired immunodeficiency syndrome) or fetuses with immature immune responses are therefore at risk of developing CMV end‐organ disease. A high viral load is required for CMV end‐organ disease to develop. Ganciclovir is a potent inhibitor of CMV replication and can be used either for prophylaxis or for preemptive therapy (administering the drug when CMV is detected in the blood). Both of these strategies effectively control CMV end‐organ disease in transplant patients. A phase II study of a prototype CMV vaccine has recently published encouraging results, suggesting that CMV infection may ultimately be preventable by means of universal immunisation.

Key Concepts:

CMV viraemia precedes CMV end‐organ disease.

Prompt treatment of CMV viraemia prevents end‐organ disease.

The probability of end‐organ disease is nonlinear with respect to viral load.

This threshold relationship is seen also in babies with congenital CMV infection and hearing loss.

Prompt treatment of congenital CMV infection can reduce the risk of progressive hearing loss.
Thalassaemias
Authors: Weatherall David J 
Published: April 2010

Abstract

The thalassaemias are the commonest genetic disorders in humans and present an increasing public health problem in the tropical countries in which they occur at a high frequency. There are many different forms of thalassaemia, all resulting from mutations of the genes which are responsible for regulating the structure and synthesis of haemoglobin. These diseases are all transmitted in a Mendelian fashion; parents, who are symptomless carriers, each pass on a defective gene to a severely affected offspring. The extremely high frequency of these diseases reflects natural selection whereby symptomless carriers are more resistant to different forms of malaria. A better understanding of the genetic basis of these diseases has led to improvements in their prevention and symptomatic treatment.

Key Concepts:

The haemoglobinopathies, thalassaemia and sickle cell disease, are by far the commonest genetic disorders.

These diseases have reached their high frequency mainly due to natural selection through heterozygote protection against malaria.

Thalassaemias consist of several different disorders, each due to many different underlying mutations of the globin genes.

All the severe forms of thalassaemia show a remarkable clinical variability which reflects both genetic modifiers, adaption to anaemia and the environment.

All the different forms of thalassaemia can be identified in fetal life and hence prenatal diagnosis is possible.

A cure of thalassaemia is only possible by bone marrow transplantation when suitable donors are available.

Most serious forms of thalassaemia are amenable to symptomatic treatment with transfusion and drugs to remove excess iron.