bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular structures of xanthan and related polysaccharides
Authors: P.Millane R , Wang Bowei
Published: November 2023

Xanthan and related polysaccharides with various sidechains have been trapped in ordered conformations in oriented fibers. X-ray diffraction patterns from these fibers show that these polymers have molecular repeats and helix symmetries very similar to those of xanthan, but different molecular diameters. These results indicate that the conformations of all these polymers are similar, and show that the (1 3) branch point, rather than the detailed primary structure of the sidechain, is the important determinant of their ordered structures.
In vitro transcription with nuclear extracts from differentiated tissues
Authors: Sierra Felipe , Tian Jian-Min , Schibler Ueli
Published: November 2023

Much recent research in molecular biology is focusing on the molecular interactions that control transcription. Transcription of protein-coding genes is performed by RNA polymerase II (pol II). This enzyme, however, is not capable of recognizing bona fide promoters by itself. To do so, it requires protein-protein interactions with a number of ancillary factors (1). Some of these transcription factors, the so-called basal factors, are needed for the initiation of transcription at most promoters (2). In contrast, some promoter¬ specific regulatory proteins stimulate transcription of only a subset of genes. These latter transcription factors include, among others, tissue-specific regulatory proteins, supposed to play an important role during cellular differentiation (3). These molecules have the capability of recognizing and interacting with sequence-specific regions in the promoter or enhancer regions of genes (the so-called cis elements). Complex networks of these protein-DNA, as well as protein-protein, interactions lead to the final regulated level of expression of specific genes.
Transcriptional analysis using transgenic animals
Authors: Dillon Niall , Grosveld Frank
Published: November 2023

The ability to introduce a foreign gene into an organism, thus generating a genetically altered (transgenic) individual, is one of the major advances in genetics in recent years. The technology has now become widely used and has allowed a large number of fundamental biological questions to be addressed which could not have been tackled by other means. Because of their role as model organisms for genetic studies, mice and Drosophila have been the most widely used organisms for transgenic studies. This chapter will deal mainly with the practical aspects of using transgenic mice for the detailed analysis of transcription.
Diagnosis of amoebic infection
Authors: Warhurst D C
Published: November 2023

During the life cycle of the intestinal amoebae of man, the trophozoite or feeding stage multiplies by simple binary fission in the large intestine. It subsequently rounds up and develops a wall, to give the resistant infective form or cyst which withstands the conditions outside the body when it is excreted with the faeces. Nuclear division may or may not take place within the cyst. The infection is acquired by direct ingestion of faeces, or by ingestion of faecally contaminated food or water. When the cysts pass through the stomach acid they are unharmed and, after exposure to the secretions of the small intestine and bile, hatch in the large intestine to give rise to multiplying generations of trophozoites.
Migrating worms
Authors: Gillespie S H
Published: November 2023

Toxocara canis is an ascarid parasite of canids. In the dog, ingested eggs hatch in the stomach and invade the intestinal wall where larvae are carried to the liver and are distributed to the body via the bloodstream. Lung migration occurs and larvae are coughed up and swallowed, where larvae develop into adult worms in the intestines of the dog. Eggs passed in the faeces may or may not be fertilized (Plates 3e,f and 4a). This life cycle occurs mainly in younger dogs; over the age of six months, larval development is halted at the L2 stage and larvae migrate in the tissues before becoming dormant. In pregnant bitches, larvae are activated and migrate transplacentally to infect the pups after the 42nd day of gestation. In consequence, almost all pups are infected at the time of whelping (1).
Microfilariae
Authors: Denham D A
Published: November 2023

The conventional method of detecting and counting microfilariae has been to prepare ‘thick’ smears of either measured or unmeasured quantities of blood. When I first started work on filariasis in the laboratory I found this technique laborious and slow and began using the chamber system which was subsequently described and evaluated by Denham et al. (1).
Analysis of sites phosphorylated in vivo and in vitro
Authors: Hardie D Grahame , Campbell david G , Caudwell F Barry , Haystead Timothy A J
Published: November 2023

There are several compelling reasons why one might wish to analyse and identify the exact site and surrounding sequence at which a particular protein is phosphorylated, either in vivo,in isolated or cultured cells, or in purified cell-free systems: (a) Identification of the protein kinase(s) responsible for phosphorylation in vivoor in intact cells. Most proteins are phosphorylated by multiple protein kinases, and one method to identify the physiologically relevant protein kinase is to compare the locations of the sites phosphorylated in intact cells with those phosphorylated by a purified protein kinase in a reconstituted cell-free system. If the sites do not match, this approach conclusively rules out the involvement of that protein kinase, while if they do match this gives strong, although not conclusive, support for the view that the protein kinase is phosphorylating the protein.
Transneuronal mapping of neural circuits with alpha herpesviruses
Authors: Strick Peter L , Card J Patrick
Published: November 2023

The use of alpha herpesviruses for defining functionally interconnected populations of neurones has generated considerable interest in recent years (1). Two of the most attractive aspects of using viruses for circuit definition are the fact that they pass transneuronally and replicate in synaptically linked populations of neurones. Thus, the virus is transported through a multi-synaptic pathway and the signal, (i.e. intracellular concentration of virus) progressively increases with time (Figures 1 and 2). These two attributes are clearly superior to those offered by other neuronal tracers which have been shown to pass transneuronally. Wheatgerm agglutinin horseradish peroxidase (WGA-HRP) and the C fragment of tetanus toxin (CTT) are both known to cross synapses, but they do so in such limited amounts that it is at times difficult to identify synaptic transfer with confidence. For these reasons, there has been a dramatic increase in the number of studies which have utilized herpesviruses to characterize functionally distinct populations of neurones.
Histochemistry of endogenous enzymes
Authors: Vincent S R
Published: November 2023

Enzyme histochemistry is the art of performing biochemical reactions on tissue sections, thereby providing the precise localization of particular enzymes. Given the cellular complexity of the nervous system, histochemical methods have played a key role in the biochemical dissection and mapping of various neurochemically distinct cell types. Enzyme histochemistry, like other histochemical techniques, is always a compromise between preserving enzyme activity and maintaining adequate histological structure. Thus aldehyde fixation is often used for two purposes, to preserve cellular morphology, and to prevent diffusion of otherwise soluble enzymes. However, it must always be borne in mind that such fixation can inhibit or destroy enzyme activity.
Serum-free media for neuronal cell culture
Authors: Butler Michael
Published: November 2023

The first reported work on the growth of cells in vitro was in 1907 by Harrison (1) who was able to suspend an explant of the spinal cord of a frog embryo from a microscope slide. This ‘hanging drop technique’ enabled the growth of the neuronal cells to take place within a fibrin matrix resulting from the application of a drop of lymph fluid. The observed cell growth was supported by the nutrients provided by the supernatant remaining from the clotted lymph.
Correlative electrophysiological and biochemical studies in neuronal cell lines
Authors: Dunn Philip M , Coote Paul R , Wood John N
Published: November 2023

Neuronal excitation is usually evoked by a chemical interaction with a specific membrane-associated receptor that results in an alteration in ion fluxes, a change in the transmembrane potential and a self-propagating wave of depolarization mediated by the activation of voltage-gated ion channels (1). The initial depolarizing event may occur through the direct action of a ligand on a receptor that has intrinsic channel activity, or indirectly through the medium of intracellular second messengers.
The molecular biology of influenza viruses and paramyxoviruses
Authors: Paterson Reay G , Lamb Robert A
Published: November 2023

Orthomyxoviruses and paramyxoviruses are important aetiological agents of disease in man and animals. Each year disease outbreaks caused by these viruses result in extensive morbidity and mortality. In recent years major advances have been made in our knowledge and understanding of the structure and function of orthomyxovirus and paramyxovirus genes and the proteins that they encode. In particular, the complete genome sequences of many strains of influenza A, B, and C viruses and paramyxoviruses have been obtained. The expression of cDNA copies of individual genes has led to the elucidation of coding strategies used by these viruses and has also permitted study of the synthesis and maturation of many virally-encoded proteins in the absence of other virus gene products.
Molecular analysis of immunodeficiency viruses
Authors: Schulz Thomas F , Spire Bruno
Published: November 2023

The rapid expansion of our knowledge of human and animal immunodeficiency viruses over the last decade would not have been possible without the availability of methods developed by molecular biologists. In this chapter we summarize some of the more commonly used molecular biological techniques employed with these viruses. As it would go beyond the remit of this chapter to list every technique that could fall under this definition, we refer the reader to some of the excellent molecular biology manuals (1, 2) for the more basic methods. The term immunodeficiency virus usually refers to animal or human lentiviruses, although a number of other viruses can also cause transient states of immunodeficiency. Table 1 contains a list of these lentiviruses. From a technical point of view, the techniques discussed in this chapter can be applied to all the viruses in this group, although some details (for example tissue culture conditions) may differ with individual viruses or virus strains. Most of the protocols in this chapter are based on our experience with the human immunodeficiency viruses HIV-1 and HIV-2.
Types of growth factor activity: detection and characterization of new growth factor activities
Authors: Mckay I A
Published: November 2023

This book concerns itself with peptide molecules which transmit signals between animal cells. Despite the fact that these molecules may function as growth stimulators and/or growth inhibitors and that they may modulate differentiated functions of cells, they have come to be known collectively as growth factors. Many such factors have already been described (see Appendix J), so it is the aim of this chapter to outline ways of characterizing a new factor with the emphasis on avoiding re-characterization of existing factors. Details of the individual methods involved will be covered in the following chapters or in other books of the Practical Approach series.
Induction of DNA synthesis and cell division in quiescent cells in response to small peptide growth factors
Authors: Corps Anthony N , Brown Kenneth D
Published: November 2023

Among the most frequently used model systems for the study of cell growth control are a number of mouse embryo-derived fibroblastic cell lines, termed 3T3 cells. The terminology reflects the original experiments designed to derive and maintain cells in a non-transformed, non-tumourigenic state, (i.e. cells which depended on the presence of serum for their growth, which did not overgrow each other, and which did not cause tumours when injected into recipient animals). It was found that passaging the cells every three days at 3 x 105cells/5 cm dish maintained the cells in optimum condition by those criteria (1).
Clonal and long-term cultures using human bone marrow
Authors: Coutinho L H , Gilleece M H , Wynter E A De , Will A , Testa N G
Published: November 2023

Much of our current knowledge concerning the regulation of normal haemopoiesis and its alteration in disease has resulted from advances in techniques for culturing human haemopoietic cells in vitro. The establishment of clonogenic assays for progenitor cells in semi-solid culture medium was instrumental in the identification of the haemopoietic growth factors as well as in the characterization of their biological activities. These may be better defined when serum-deprived medium and highly purified cell populations are used (see Chapter 2). In addition, these clonal assays provide quantitative and qualitative means of analysing the haemopoietic progenitor cells in a whole range of clinical settings (1-3).
Imaging gene expression in neural grafts
Authors: Sirinathsinghji D J S , Dunnett S B
Published: November 2023

In recent years considerable attention has been devoted to the development of techniques for the implantation of embryonic neural tissue into the adult mammalian brain as a tool for replacing damaged host tissue and repairing damaged neuronal circuits. Indeed, several studies have shown that embryonic neurones grafted into the mammalian brain can survive, grow, differentiate, and reverse many of the structural, biochemical, physiological, and behavioural deficits associated with experimental or genetic neuronal loss (1). This method thus has immense relevance to the possible treatment of human neurodegenerative disease. In addition, it is a powerful technique for the neurobiologist for the exploration of the basic cellular, receptor, and molecular mechanisms regulating the development and functional organization of specific neuronal systems within the brain.
The role of cellular transcription factors in the regulation of human immunodeficiency virus gene expression
Authors: Nabel Gary J
Published: November 2023

The human immunodeficiency virus (HIV) is dependent on its host cell for the synthesis and processing of viral RNA. Steady-state levels of viral RNA can be regulated by several mechanisms, including the rate of transcriptional initiation, elongation, processing, export, and packaging. Diverse regulatory mechanisms have, therefore, evolved to control viral RNA during HIV replication. These events play a critical role in the regulation of viral replication. Relative to the human genome, the genomic complexity of HIV is relatively small, <0.001% in size. To regulate viral gene expression specifically, the virus has evolved its own regulatory gene products. These viral trans-activators are also dependent upon cellular factors that interact with viral proteins and cis-acting DNA and RNA regulatory elements to further modulate HIV gene expression. These mechanisms of regulation are diverse. For example, the Tat trans-activator affects the ability of a cellular transcription complex to elongate and inhibits premature termination of the HIV transcript (1, 2, Chapter 4). The Rev gene product, on the other hand, does not affect the synthesis of viral RNA but acts with cellular factors on an RNA structure after formation of the primary transcript (3, 4, Chapter 5). For these trans-activators, an intimate association has evolved between host cell factors and viral gene products. These essential trans-activators are synthesized only after viral transcription has been initiated. The regulation of the initiation of HIV transcription also plays an important role in the viral life cycle.
Cell surf ace carbohydrates: cell-type specific expression
Authors: Fukuda Minoru
Published: November 2023

Cell surface carbohydrates are major components of the outer surface of mammalian cells and these carbohydrates are very often characteristic of cell types. Carbohydrate structures change dramatically during mammalian development. Specific sets of carbohydrates are expressed at different stages of differentiation and in many instances these carbohydrates are recognized by specific antibodies, thus providing differentiation antigens (1-4). In mature organisms, expression of distinct carbohydrates is eventually restricted to specific cell types, providing cell-type-specific carbohydrates. Aberrations in these cell surface carbohydrates are associated with various pathological conditions, including malignant transformation.
Carbohydrate recognition in cell-cell interaction
Authors: Lowe John B
Published: November 2023

Mammalian cell surfaces are decorated with complex carbohydrate molecules, also known as oligosaccharides or glycoconjugates. These molecules display a remarkable degree of structural diversity, that is in turn a function of the cell type, or tissue, or particular stage of development of the cell or tissue. Observations demonstrating that cell surface oligosaccharide structure varies with the differentiation state or lineage of a cell suggest that these molecules play important roles in mediating information transfer into and out of the cell.
|Mechanisms of DNA transposition
Authors: Plasterk Ronald H A
Published: November 2023

All organisms studied in any detail have been found to contain transposons, discrete segments of DNA that can move within genomes. Transposons can be viewed as molecular parasites, the smallest units of selection: single (or a few) genes that move around by using all functions of the host (building blocks, energy, the replication apparatus), and that only provide the factors that are needed for the recognition of the border between themselves and their host DNA, and for the initiation of events that result in their own spread within the host genome. The only necessary explanation for their existence is that they have survived, but this does not exclude the possibility that, like many other parasites, transposons could be anywhere on the scale between parasitism and symbiosis, and thus be for their hosts either a nuisance, or an indispensable helper, or both.
| Eukaryotic transposable elements as tools to study gene structure and function
Authors: Kaiser Kim , Sentry John W , Finnegan David J
Published: November 2023

Eukaryotic genomes were once considered invariant. The discovery that they contain transposable elements, powerful agents of genetic change, showed this not to be the case. Transposition into coding sequence is an obvious source of variability. Transposable elements also cause chromosome rearrangement, due to a variety of mechanisms including imprecise excision and exchange between elements at different locations. Although such events normally occur in a more or less random manner, and at low frequencies, it is possible to harness transposable elements as tools for genome manipulation. This is best illustrated by the P element of Drosophila. In our discussion of P, and of similar elements from plants, we hope to indicate what might be achieved in any eukaryotic organism of interest.
Hybridization strategy
Authors: Anderson Margaret L M
Published: November 2023

Nucleic acid hybridization on filters has formed the basis of a range of experimental techniques that have been instrumental in developing our understanding of gene structure and function. The procedure is widely applicable having being used for many years for screening genomic and cDNA libraries, for Southern and Northern blot hybridizations, dot blot hybridizations, and hybrid selection. Techniques are constantly being refined to allow the range of applications to be extended and more recent applications have included genome mapping and sequencing (1) and the detection of mutations in diagnostic medicine (2).
Analysis of gene expression by blotting techniques
Authors: Kim Kwang-soo , Febbraio Maria , Han Tae-Hee , Wessel Thomas C , Park Dong H , Joh Tong H
Published: November 2023

Expression of eukaryotic genes is regulated developmentally, positionally, and temporally. In addition, the pattern of gene expression can be altered significantly by intracellular and extracellular stimuli. This regulation is achieved during transcription and processing of the mRNA product as well as during translation and post-translational modification of the resulting protein. Several major mechanisms are involved, including the limited expression of transcription and translation factors, phosphorylation, the expression of necessary co-factors, and control of RNA and protein degradation. Accurate analyses of specific mRNA transcripts and their protein products are, therefore, essential if one is to understand the mechanisms whereby individual genes are regulated.
PCR MIMICs: competitive DNA fragments for use in quantitative PCR
Authors: Siebert Paul D , Kellogg David E
Published: November 2023

Competitive PCR has emerged as a valuable method for determining the relative levels of mRNAs; for example, the change in mRNA expression levels or to estimate the actual number of mRNA molecules. Perhaps the greatest advantage of competitive PCR is that useful data can be obtained during either the exponential phase or plateau phase of PCR amplification
Construction of cloning and expression vectors
Authors: Hadfield Christopher
Published: November 2023

Numerous different types of cloning and expression vectors have been made for yeast and the majority are widely distributed amongst the international yeast research community. In the main, these are shuttle vectors that are able to propagate, and be selected for, in both yeast and Escherichia coli. This dual host capability has enabled yeast vectors to be constructed on the back of existing E. coli vectors and, in addition, has enabled recombinant derivatives to be made using efficient and powerful E. coli host-vector cloning strategies before introduction of the finished product into yeast.
High efficiency transformation with lithium acetate
Authors: Gietz R Daniel , Woods Robin A
Published: November 2023

The transformation of lithium acetate (LiAc) treated yeast cells with plasmid DNA was first reported in 1983 (1). The procedure was less efficient than transformation of cells converted to sphaeroplasts by treatment with Zymolyase (2, 3), but was simpler and faster. The original procedure, and subsequent improvements reported by a number of workers, involved a pre-incubation of the cells in LiAc, followed by an incubation in LiAc plus plasmid DNA, then by the addition of polyethylene glycol (PEG), and finally by exposure to a heat shock. The yields of transformants with this procedure rarely exceeded 1 × 10/µg plasmid DNA (4), compared with 2 × 105/µg for the sphaeroplast procedure (5). In 1989 it was reported that inclusion of single-stranded carrier nucleic acids (DNA or RNA) in the transformation reaction increased the efficiency of the LiAc procedure dramatically; to 1 x 10 transformants/ µg (6). Further modifications to this ‘LiAc/ssDNA/PEG’ method reduced the time required and increased the efficiency more than 20 fold (7, 8). The current version of the method, described here, is markedly simpler and has yielded up to 2.2 x 107 transformants/µg plasmid DNA.
Protein blotting using polyvinylidene fluoride membranes
Authors: Mansfield Michael A
Published: November 2023

Transfer of proteins from a polyacrylamide gel to a microporous membrane preserves the resolution of the electrophoretic transfer and permits further analysis using a broad array of techniques. Polyvinylidene fluoride (PVDF) was described as a protein blotting substrate in 1986 (1) and was found to be compatible with protocols defined for blotting to nitrocellulose (2). PVDF is a Teflon-type polymer composed of the basic repeating unit shown below Proteins interact with the polymer non-covalently through dipolar and hydrophobic interactions. PVDF is chemically compatible with the aqueous buffer systems used in electroblotting and immunodetection. Since PVDF is resistant to most organic solvents, however, it can withstand harsh chemical conditions in which nitrocellulose membranes dissolve or decompose. For this reason, the methods available for protein analysis on PVDF membranes are much more extensive (Table I; see (3) for review).
Transfer and blocking conditions in immunoblotting
Authors: Van Dam A
Published: November 2023

Every scientist who performs immunoblotting techniques wishes to resolve proteins as distinguishable bands or spots at the site where specific antigen antibody reactions occur. Additionally, no background staining should be obtained on other parts of the blot. Owing to a number of problems, distinct immunoblot patterns are not always obtained, and sometimes it is even difficult to distinguish specific staining from background reactions. These problems are, in the first place, related to the fact that the interaction between the blotting matrix and blotted antigens is not covalent, so that proteins can be lost from the matrix. Secondly, the antibody can often only react with the antigen if it is not denatured too much.
Proteins of the neuronal cytoplasmic and membrane associated cytoskeleton
Authors: Ha Yes Nandini V L , Holmes Fiona E , Roobol Anne , Carden Martin J , Baines Anthony J
Published: November 2023

In this chapter we present a compilation of methods that are of general use in the isolation of some components of the cytoskeleton in brain. The methods chosen illustrate the preparation of proteins that are not only of specific use in the analysis of, for example, neuronal function, but also are of use as archetypes in studies of protein assemblies relevant to a wide variety of cell types. The properties of brain microtubules and brain spectrin are taken to represent paradigms for the activities and role in structural assemblies of the corresponding proteins in non-neuronal tissue. On the other hand, the properties of neurofilaments and synapsin I are those of neurone-specific proteins. A problem with cytoskeletal proteins is that they do not possess defining enzyme activitesspectrin and neurofilament polypeptides, for example, containno known enzyme activites, and although tubulin has GTPase activity, this does not uniquely define the protein. In giving methods for purifying these proteins it is not possible to quote standard units of any activity to ensure that the protein has been correctly identified and purified. In the methods described below, we have therefore relied on describing the expected pattern of polypeptides on SDS-polyacrylamide gel electrophoresis, and have, where appropriate, given commercial sources of antibodies which can be used to test the identity of the purified proteins. In the case of tubulin and neurofilaments, their defining characteristic is their appearance in the electron microscope, and we recommend that microtubule and neurofilament
Immunocytochemical techniques for the study of the nervous system
Authors: Priestley J V
Published: November 2023

At the time of writing of the first edition of this book, immunocytochemistry was the main histochemical technique used in studies of the nervous system. With the possible exception of receptor autoradiography, it had largely replaced other localization procedures including previously popular techniques such as transmitter uptake autoradiography and amine fluorescence histochemistry. However, in the past ten years another revolution has taken place and the technique of in situ hybridization, which received only passing reference in the first edition, now merits a chapter of its own (Chapter 4). Journals are full of in situ hybridization papers and the casual observer could be forgiven for thinking that immunocytochemistry has, in its turn, been replaced by in situ hybridization. This is not the case, but what is true is that the experimenter now has two powerful and complementary techniques to choose from (Table 1). For certain tasks in situ hybridization is a more appropriate tool than immunocytochemistry. This is particularly so for studies of changes in expression following pharmacological or physiological manipulation and may be true for certain cell body distribution studies. However the simplicity and speed of immunocytochemical procedures, the fact that many different types of molecule can be localized, and the high resolution obtained, make immunocytochemistry still the method of choice for most anatomical and cytological studies. Any substance to which antibodies can be generated can be localized, ranging from single amino acids or nucleotides, through proteins and polysaccharides, to organelles or cells of unknown and/or complex composition (Table 2). In addition immunocytochemistry can be combined with numerous other histochemical and anatomical procedures, providing powerful tools for deciphering chemical neuroanatomy (4-6).
Investigation of mitochondrial defects in brain and skeletal muscle
Authors: Clark J b. , Bates T E , Boakye P , Kuimov A , Land J M
Published: November 2023

In recent years there has been a considerable upsurge of interest in defects of the mitochondrial respiratory chain and their clinical consequences. This has been in part due to an increased awareness of the mitochondrial myopathies and encephalopathies, a heterogeneous group of human muscle and brain disorders. Patients with these diseases present with muscle fatigue and exercise intolerance together with ataxia and dementia in the case of encephalopathies (1-3). The other reason is the sequencing of the mitochondrial DNA (mtDNA) and the realization that it codes for 13 subunits of the mitochondrial oxidative phosphorylation system. This means that this mitochondrial system is unique in the biological world in being coded for by both the nuclear and mitochondrial genome. Furthermore, patients suffering from these conditions provide ‘natural windows’ on the role of oxidative as distinct to glycolytic ATP production in the energy homeostasis of different tissues.
The effect of guar gum on the stability of emulsions prepared with physiological surfactants; L-a-phosphatidylcholine and sodium taurocholate
Authors: Fillery-Travis A J , Moulson S J , Foster L H , Robins M M
Published: November 2023

There is substantial evidence that the presence of non-starch polysaccharides (NSP) in the human diet can reduce the rate of lipid absorption within the gut with subsequent benefits for health {1). During digestion in the small intestine the lipid forms an emulsion whose interface is subjected to changes in both the nature and concentration of surfactants available. The presence of other interferring species such as NSP and partially digested proteins may also affect the interfacial composition and properties. This work represents the first part of a study to model the emulsions formed during gut transit and characterise the influence of NSP on their stability and behaviour.
Polysaccharide gums: their modulation of carbohydrate and lipid metabolism and role in the treatment of diabetes mellitus
Authors: Ellis P R
Published: November 2023

It is well known that the addition of polysaccharide gums, such as guar gum, to a carbohydrate meal reduces post-prandial hyperglycaemia in healthy and diabetic subjects. Moreover, diabetic patients administered these gums with their normal diet have shown significant long-term improvements in glycaemic control and lipid metabolism. Improved glycaemic control and a reduction in plasma cholesterol are thought to lessen the risk of developing the late complications of diabetes (e.g. cardiovascular disease, nephropathy). The physiological activity of gums depend on their capacity to increase digesta viscosity in the stomach and small intestine. Dietary supplements of polysaccharide gum in solution are extremely unpalatable. To improve palatability, pharmaceutical preparations have been designed to hydrate slowly when mixed with a drink and thus reduce viscosity in the mouth. However, some of these were found to be clinically ineffective. The efficacy of gums can be improved by incorporating them into foods. Recently, novel plant foods, rich in non-starch polysaccharides, have been studied and found to have marked therapeutic properties. A soluble extract of one of these, a leguminous food from Africa, appears to have similar rheological properties to that of guar gum.
Gelation and retrogradation of concentrated starch gels
Authors: Keetels C J A M , Vliet T Van
Published: November 2023

The gelation and retrogradation of concentrated starch systems have been studied by determining the mechanical properties at small and large deformations. During heating, the moduli of potato and wheat starches first increased and then decreased. Several phenomena that can affect these rheological properties have been evaluated. The rigidity of the swollen wheat starch granules was higher than the rigidity of the swollen potato starch granules. During ageing, the rigidity of the potato starch granules increased more rapidly, resulting in a cross-over of the moduli. A possible explanation of these phenomena is that native wheat starch granules contain more entanglements between the starch molecules. The eating quality of bread and other products with a high starch content changes during storage. These changes are often related to a change in the fracture or yielding properties of the product. For instance, during the staling of bread, the crumb firms and becomes more crumbly. The decrease in eating quality is, at least in part, caused by recrystallization of starch in the processed food. This recrystallization process is called retrogradation.
The influence of caseins on the rheology of x-carrageenan gels
Authors: Lynch M Gerard , Mulvihill Daniel M
Published: November 2023

The carrageenans form a group of highly sulphated polysaccharides isolated from the cell walls of various genera of marine algae of the class Rhodophyceae. 1C-Carrageenan is composed of a nearly perfect alternating sequence of 1,3-linked - β-galactose 4-sulphate and 1,4- linked 3,6 anhydro- α-D-galactose residues (1). Major applications of carrageenans have developed as a result of their ability to complex with other macromolecules, particularly proteins. Most of such uses involve milk based systems in which carrageenans can be used as stabilisers, viscosity builders or gelling agents (2). Their mode of action is not simply through modification of solution properties as there is evidence that they interact with casein micelles (3,4).
Rheology and structure of gellan-alginate co-gels
Authors: Papageorgiou M , Gothard M G , Willoughby L E , Kasapis S , Richardson R K , Morris E R
Published: November 2023

Sodium alginate dissolved in calcium chloride solution at 90°C shows ‘weak gel’ properties similar to those of ordered xanthan, and circular dichroism spectra indicate formation of calcium polyguluronate ‘egg-box’ dimers even at this elevated temperature. The solutions show a sharp increase in rigidity (G’) on cooling, and convert to permanent gels on storage at low temperature. The gels attain maximum hardness at -40% calcium conversion (for alginate with a polyguluronate content of -58%), and their elasticity can be readily controlled by adjustment of Ca2+ concentration around this optimum value. Incorporation of moderate concentrations of gellan (0.1 - 0.3% w/v in combination with 2% w/v alginate and 5 mM trisodium citrate sequestrant) increases the strength of the gels, but does not significantly change their elasticity, indicating that the gellan acts as a strong ‘filler’ in an alginate matrix. The composition-dependence of G’ and hardness (yield stress), and the response of the mixed gels to incorporation.
Gelation of food macromolecules: effects of sugars on the gelation of agarose and mixtures of konjac glucomannan and carrageenan
Authors: Nishinari Katsuyoshi , Tomohisa A T , Aka Y , Watase Mineo , Kohyama Kaoru , Iida Hiroki , Williams Peter A , Phillips Glyn O
Published: November 2023

Effects of sugars on gelation of agarose were studied by differential scanning calorimetry (DSC) and dynamic viscoelastic measurements. It was suggested that the number of junction zones was increased, and that the size of junction zones became smaller by the addition of sucrose. As a result of this, the rotational freedom of parallel links which constitute a zipper was decreased. The increment of melting or setting temperature per unit concentration of sugars was correlated linearly with the dynamic hydration number of the sugars.

Small and large deformation rheological measurements on mixed systems of kappa-carrageenan and konjac glucomannan with different molecular weights suggested that gels of this mixture consist of a carrageenan network strengthened by weak interaction of konjac glucomannan with carrageenan. carrageenan-rich mixtures (CAR content> 70%) showed two exothermic peaks in the cooling DSC curves.
A performance test for carrageenan as a stabilizer for calcium-sensitive proteins
Authors: Lee Sui-Chen , Hansen Poul M T
Published: November 2023

The physical stability of fluid and frozen foods may be improved by the addition of different types of food hydrocolloids, either singly or in blends. With increased use of hydrocolloids in the food industry, a trend has developed toward using blends of different types to maximize stabilizer performance. Since different hydrocolloids may be expected to perform in different manners it is useful to develop performance tests which will accurately measure tha specific function of individual components or provide an index for their combined effects.
Dessert gels prepared from alginate and gellangum
Authors: Tega D Or , Sanderson G R
Published: November 2023

Water dessert gels prepared by cooling solutions containing either sodium alginate or gellan gum are well known. Gel formation is brought about by ion-mediated interchain association. Although calcium is the only ion suitable for the alginate gels, the gellan gum gels can be prepared using a variety of ions, notably calcium or magnesium. Recent studies have investigated the role of calcium and magnesium ions in gelation brought about by cooling solutions of sodium alginate, KELCOGEL gellan gum and a mixture of the two polymers. From the resulting understanding of how these ions partition between the polymers and sequestrant, a key ingredient in the formulation of these dessert gels, a range of dessert gels prepared from a combination of gellan gum and alginate have been developed. The characteristics of these gels are described.
Calcium sensitivity of high ester citrus pectins
Authors: Rolin C
Published: November 2023

High ester pectins may differ considerably in their calcium sensitivity, i.e. their ability to become viscous in solution by addition of ca++, This is known to be due to a heterogeneous distribution of ester groups which in turn is related to the action of esterase in the fruit raw material.
Purification and characterization of barley limit dextrinase during malting
Authors: Kristensen M , Svensson B , Larsen J
Published: November 2023

Different forms of barley limit dextrinase, LD, with different affinities for 3-cyclodextrin and different specific activities have been purified. They are single polypeptides with apparent molecular weights to 105 kD and isoelectric points around 4.5. Antibodies raised towards one of the purified proteins recognize a single polypeptide of 105 kD in crude barley extracts. LD is synthesized in developing kernels and during germination. The proteins appear in soluble and bound forms, and the bound forms can be extracted by addition of dithiothreitol or a cystein-protease.
Decreased diacetyl production in lager brewing yeast by integration of the ILV5 gene
Authors: Goossens E , Debourg A , Villanueba K D , Masschelein C A
Published: November 2023

Beer maturation, the rate-limiting step in the production process, is mainly required in order to remove the vicinal diketones (VDK), diacetyl and 2,3-pentanedione. Amplification of the ILVS gene has previously been shown to reduce the VDK production very efficiently.
Instability of the brewers yeast genome
Authors: Pedersen Mogens Bohl
Published: November 2023

Investigations of brewers yeast DNA have shown that different types of genetic changes occur in the genomes. Such genetic changes might give rise to instabilities and, therefore, affect the performance of the brewing yeast during fermentation. Some of the genetic changes have been monitored by electrophoretic karyotyping and by restriction fragment length polymorphism (RFLP) studies. Differences in chromosome lengths and number of different types of chromosomes Vin brewers yeast have been studied in order to find a plausible model/explanation for such changes. Changes in number of chromosomes V were monitored by the RFLP patterns of various URA3 alleles.
Continuous production of acidified wort for alcohol-free beer using immobilised lactic acid bacteria
Authors: Pittner H , Back W , Swinkels W , Meersman E , Dieren B van , Lommi H
Published: November 2023

Under German “Reinheitsgebot” regulations the use of biologically acidified wort is the only technological possibility to correct the pH of mash and wort; in addition, this will improve the taste of the finished beer. Based on experience in using continuously operated bioreactors in other applications (easier process control, higher efficiency) a pilot installation was used for continuous production of acidified wort with immobilised lactic acid bacteria.
Protease activity in beer and correlation to foam
Authors: Muldbjerg Marianne , Melda! Morten , Breddam Klaus , Sigsgaard Poul
Published: November 2023

A novel and very sensitive method for measuring protease activity in beer has been developed. The assay is based on fluorogenic substrates, designed specifically for yeast proteinase A, which previously has been shown to degrade foam-active proteins in beer. The corresponding enzyme was isolated from unpasteurized beer. Samples of different beers brewed on different yeast strains have been collected from production and from two litre fermentation. During 3 weeks of maturation a number of analyses have been carried out, e.g. protease activity and foam half-life. The results showed a correlation between increased protease activity and decreased foam stability. Furthermore, a dependence of the yeast strain on the amount of secreted protease was found.
The laser scanning: a new approach for detection of beer spoilers
Authors: Laurent F , Drocourt J L , Jakobsen M , Peladan F , Meersman E , Vasconcelos L de , Timmermans P
Published: November 2023

The microbial analysis of beer poses a number of problems: large volumes must be analysed; only specific beer spoilers are obtained with traditional plate count are delayed. of interest and results In order to overcome these problems and allow on immediate answer, Chemunex in collaboration with his Eclair contract members, is developing a new approach based on a combination of laser scanning and appropriate fluorescent markers for specific detection of beer spoilers.
Biological safety when working with HIV
Authors: Butler P J G
Published: November 2023

Human immunodeficiency virus (HIV) is classified as a dangerous pathogen and rightly placed in a high hazard group. Fortunately, experience has shown that the likelihood of acquiring an infection during normal laboratory work is small, if appropriate precautions are observed. In practice, more infections have occurred in clinical work than in laboratories, even when allowance is made for the numbers of workers involved. In part, at least, this is due to the fact that laboratory workers should know where any HIV is located in the laboratory. Care in the primary containment of all HIV specimens and adequate inactivation and decontamination before any materials are removed from containment and released to workers not expecting to work with HIV are obviously central to all safety procedures.
Isolation and biological characterization of primary HIV-1 isolates
Authors: Schuitemaker Hanneke
Published: November 2023

In the early years of HIV-1 research most of the virological studies were performed using a few T cell line adapted HIV-1 strains since primary isolation of HIV-1 with CD4-positive T cell lines as target cells was only successful in a small proportion of AIDS patients (1). Subsequent studies using PHA-stimulated PBMC indicated that many HIV-1 isolates were unable to grow in CD4-positive T cell lines (2). With the introduction of refinements to this isolation technique, and improvement of the sensitivity of the assays for the detection of HIV-1 in cultures, it has become possible to recover virus from HIV-1 seropositive persons, even in their asymptomatic period, with a 90-100% efficiency (3, 4). Primary HIV-1 isolates differ in their biological properties such as their ability to induce cell fusion (syncytia) in primary T cells, their replication rate, and their tropism for T cell lines and promonocytic cell lines (5).
Detection of viral RNA by the polymerase chain reaction (PCR)
Authors: Arrigo Salvatore J
Published: November 2023

The polymerase chain reaction (PCR) (1) has allowed sensitive and quantitative detection of low abundance RNAs. HIV-1 RNAs can be detected using oligonucleotide primer pairs specific for individual RNAs. The ability to detect low copy numbers of RNA allows for the quantitation of viral RNAs in both transfected and infected cells. Comparisons of RNA production can be performed using total, nuclear, cytoplasmic, or virion RNA. This facilitates the analysis of mutations on the RNA and virion production. We have used RNA PCR analysis extensively to examine the production of HIV-1 RNAs in transfected and infected lymphoid cells in culture (2—7). We have found that the sensitivity of this assay system is superior to other classical RNA detection techniques such as northern hybridization, nuclease SI and ribonuclease protection, and primer extension assays. In contrast to these other procedures, this procedure routinely can be performed in a few hours, resulting in data the same day the experiment was initiated. This procedure is also amenable to high throughput in that up to 96 samples can be assayed at the same time. In this chapter, some basic uses of PCR for the detection of HIV-1 RNAs in vitro will be covered.
The application of mass spectrometry to the analysis of peptides bound to MHC molecules
Authors: Cox Andrea L , Buczko Eric L , Engelhard Victor H , Shabanowitz Jeffrey , Hunt Donald F
Published: November 2023

Cellular ‘self’ and foreign proteins are constantly being degraded and the resulting peptides presented by MHC molecules on the cell surface. Cytotoxic T-lymphocytes recognize cells that express new antigens as a result of viral infection, cellular transformation, or tissue transplantation. Sequence analysis of peptides presented to the immune system in association with class I MHC molecules is an important initial step in the design and development of peptide vaccines or other immune regulators effective against such disease states as AIDS, cancer, and autoimmune disorders. Identification of peptides associated with a particular disease is challenging because these antigens are usually present in a complex mixture dominated by peptides derived from normal cellular proteins. In the case of HLA-A2.1, extraction of peptides from the MHC cleft results in over 10000 distinct peptides (6).
Glutathione peroxidase: activity and steady-state level of Mrna
Authors: Clair Daret K St , Chow Ching K
Published: November 2023

Glutathione peroxidase (glutathione: H2O2 oxidoreductase, EC 1.11.1.9) was first reported by Mills in 1957 in erythrocytes (1) and later in the liver of various species (2). The enzyme catalyses the reduction of hydroperoxides by reduced glutathione (GSH) to their corresponding alcohols. The ability of GSH peroxidase to reduce various hydroperoxides has led to the proposal of the role of the enzyme in protecting tissues against oxidative damage to critical biomembranes and macromolecules (3, 4).