Plasma Proteins, Yolk Proteins and Metal-Binding Proteins

The extracellular fluid of the metazoans is not only a transport vehicle but also, for the majority of the body’s cells, their growth environment. Proteins play an important role here, providing colloid-osmotic pressure and acting as buffers. The most important parameter in this respect is their concentration which, depending upon the species, the developmental stage and the physiological conditions, can vary from less than 1 to more than 200 mg/ml (Table 5.1). In addition to these general functions, individual plasma proteins have various specific roles, e.g. in the transport of substances, in defence reactions, in blood clotting or in the solution of clots. At least in the case of the mor…

Extracellular Structural and Secretory Proteins

The extracellular matrices of animal tissues consist of networks of collagens and elastins, the meshes of which are filled with structural glycoproteins and glycosaminoglycans. The cells themselves are in direct contact with the basement membranes, which are specific regions of the extracellular matrix with a thickness of 20200 nm. The very varied compositions of the different extracellular matrices determine their mechanical characters and, in particular, their interactions with the cells [73]. The binding of cells to various matrix components is mediated by specific receptors on the cell surface and these recognize certain peptide sequences in the matrix proteins [141]. Several particular…

Toxic Proteins and Peptides

Many animals produce poisonous substances which, even at a relatively low dose, are deleterious or lethal to other organisms, including man. They may serve on the one hand to disable or kill prey, or on the other hand as a protection or defence against predators. These substances are mostly produced by special glands, and both poison reservoirs and specialized structures for delivering the secretion, e.g. stings or modified mouthparts or fangs, are usually also present. In accordance with the aims of this book, we will deal with the comparative biochemistry of the animal toxins as natural products with special structures and functions; a discussion of the mechanisms of their pharmacological…

Characterisation of a novel airway late phase model in the sensitized guinea pig which uses silica and Bordetella pertussis as adjuvant for sensitization.

The objective of the present investigation was to validate a novel model of allergic late phase reaction in the airways of conscious guinea pigs by monitoring airway function with CO2-forced respiration. In addition airway inflammation as one possible cause for the development of airway late phase reaction was characterized by a novel technique which consists of bronchoalveolar lavage via the orotracheal route. Guinea pigs were sensitized twice at 2-week intervals with ovalbumin in silica and Bordetella pertussis. Two weeks after the booster sensitization all guinea pigs showed an acute decrease of tidal volume under CO2-forced respiration 5-15 min after antigen challenge. In contrast 42 ou…

Sterols and Steroids

Sterols and steroids, like the terpenes and carotinoids, are isoprene derivatives. The sterols are components of the membranes of all eukaryotic cells and they bind and condense the phospholipid bilayer. The outer cell membrane is particularly rich in sterols, with a molar ratio of sterols to phospholipids of 0.8–0.1, compared with the usual value of 0.1–0.3 for intracellular membranes. The parent substance of all sterols is cholesterol (Fig. 16.1). The sterols are classified with the steroid hormones and bile salts as steroids because they also have the gonan (formerly steran) four-ring system and have their biosynthetic origin in cholesterol. Steroids with hormonal functions are known fro…

Dissociation of airway responsiveness and bronchoalveolar lavage (BAL) cell composition in sensitized guinea-pigs after daily inhalation of ovalbumin

Summary. The association between inflammatory cell influx, cell activation status and change of airway responsiveness to acelylcholine (ACh) after daily inhalation of ovalbumin (OA) in sensitized guinea–pigs was investigated. Starting 3 weeks after sensitization (OA at 50mg/kg s.c. + i.p.) guinea–pigs were exposed daily to 2% OA (10min: undercover of 0.5Smg/kg mepyramine i.p. 15min before OA) for 2 weeks. Concentration–response curves (CRCs) for inhaled ACh were performed 24 h after the last OA–challenge and 24 h after another single OA–inhalation 1 week later. CRCs for inhaled ACh were neither affected 24 h after the last OA challenge (daily for two weeks) nor 24 h after another OA–inhalat…

The metabolism of phenol and substituted phenols in zebra fish.

1. The metabolism of five phenols in zebra fish was studied after uptake from the medium. The results showed no qualitative differences to other Cyprinid fish species, only the oxidation rate seemed to be lower. 2. Phenyl glucuronide, phenyl sulphate, and quinol sulphate were identified as metabolites of phenol. 3. Identified metabolites of 2-cresol were 2-cresyl glucuronide, 2-cresyl sulphate, and 2-hydroxybenzoic acid in trace amounts. 4. Only the glucuronide and sulphate conjugates were detected as metabolites of 4-nitrophenol, 4-chlorophenol, and pentachlorophenol.

Effect of substituted phenols on transaminase activity in the fish,Leuciscus idus melanotus L.

Influence of bacteria on the metabolite pattern of phenol in zebra fish (Brachydanio rerio)

Summary An investigation was performed on the potential influence of bacteria in the medium on the metabolism of phenol in zebra fish. The results obtained in vitro and in vivo show that bacteria may influence biotransformation studies of xenobiotics by fish in different manner. First, it was shown that phenol conjugates were deconjugated. Hydrolysis of phenyl glucuronide was observed both in vitro and in vivo. Deconjugation of phenyl sulphate was found to a minor extent merely under in vitro conditions. Second, the xenobiotic itself, in this case phenol, was degradated to CO2. The proportion did not lead to a significant removal of the test compound of the fish. Zusammenfassung Einflus von…

The Structural Variety and Metabolism of Proteins

Individual eukaryote cells contain in the order of 104 different proteins, and each animal species contains an even greater number due to differences between the tissues of an individual and between the individuals themselves; furthermore, the protein spectrum changes during the course of development. The number of different proteins to be found in extant organisms may be as high as 1012. The description of this variety, its origin and biological significance is the most extensive theme in comparative biochemistry. This chapter will concern itself with the possibilities for structural variation and the general metabolism of proteins; further chapters will deal with comparative studies of in…

Elimination and distribution of different substituted phenols by frog (Rana temporaria) and crayfish (Astacus leptodactylus)

The Structure and Metabolism of Carbohydrates

Compared with the variety of carbohydrates in plants, relatively few sugars or sugar derivatives are regularly found in animals either free or as components of more complex compounds. However, it is possible that sugars originating from plants in the diet are transiently retained in animals and distort the normal sugar spectrum. Approximately a dozen sugars and sugar derivatives are regularly found in animals: the pentoses d-ribose and 2-deoxy-d-ribose; the hexoses d-glucose, d-galactose, d-mannose, d-fructose and l-fucose; the uronic acids d-glucuronic acid and l-iduronic acid; and the hexosamines d-glucosamine and d-galactosamine. In addition, d-erythrose, d-ribulose, d-xylulose and d-sed…

Kinetic studies on the elimination of different substituted phenols by goldfish (Carassius auratus)

Metabolism of chlorobenzene and hexachlorobenzene by the zebra fish, Brachydanio rerio.

It is now becoming evident that in many cases metabolites have a greater toxic potential than the parent xenobiotic exposed. For this reason, the knowledge of biotransformation pathways of xenobiotics plays a substantial role in environmental monitoring programs. The zebra fish (Brachydanio rerio, Hamilton-Buchanan) has received increased attention as a model species for freshwater fish in environmental surveillance programs to evaluate potential health and impacts of anthropogenic chemicals. The metabolism of phenol and various substituted phenols in zebra fish has recently been studied. The purpose of the present study was to examine the metabolism of chlorobenzene and hexachlorobenzene (…

Small Nitrogenous Compounds

Because of the constant turnover of proteins, protein-bound and free amino acids exist in a dynamic equilibrium. The intracellular pool of free amino acids, which is replenished by the hydrolysis of existing proteins, by uptake from the intercellular space and by de novo synthesis, is available for protein synthesis and for the many other metabolic processes dependent upon amino acids. The concentration of free amino acids is always lower than that of the protein-bound residues, one limiting factor being the strong osmotic effects of such low molecular weight compounds. Thus, there is no specific amino acid store in an organism; it is more the case that enzymes and structural proteins thems…

Metabolism of phenol in the terrestrial snail Cepaea nemoralis L

1. The metabolism of phenol in the terrestrial snail Cepaea nemoralis was studied after injection into the haemocoel of the dorsolateral foot region. 2. Excreted metabolites, and metabolites extracted from the body, were analysed by h.p.l.c. In addition to phenyl beta-D-glucoside, arbutine (quinol beta-D-glucoside), a new conjugate of phenol, was detected.

Proteins of Muscle and the Cytoskeleton

The contractile elements of striated vertebrate skeletal muscle, the myofibrils, contain thin filaments, which are 6 nm in diameter and consist mainly of actin, and thicker myosin filaments with a diameter of 16 nm (Fig. 10.1). During muscle contraction, the filaments undergo a sliding movement relative to each other (sliding filament mechanism). This is brought about by the reversible formation of bridges between the myosin molecules and the actin filaments, which bind, change their conformation and then dissociate (bridge cycle). The required energy is supplied by the hydrolysis of ATP. The sliding distance (step size) per molecule of ATP hydrolysed is controversial; the most recent measu…

The Subject Matter and Methods of Comparative Biochemistry

The diversity of living organisms, the abundance of forms, colours and phenotypes, is one of the most impressive aspects of our world. Since ancient times, science has concerned itself with the ordering and classification of this diversity. At first, only those structures and processes which were recognizable without any special apparatus could be compared; the invention of the light microscope and the electron microscope introduced new dimensions and new opportunities for comparison. Finally, progress to the molecular level became possible with the development of methods of biochemical analysis. Different comparative biological disciplines arose, each with particular goals and methods. The…

Excretion and metabolism of phenol, 4-nitrophenol and 2-methylphenol by the frogs Rana temporaria and Xenopus laevis.

1. Rana and Xenopus excrete 90-95% dose, and metabolize 50-65% dose of phenol, 4-nitrophenol and 2-methylphenol within 24 h, to about the same extent. 2. Kinetic data for the excretion of phenols from both species fit a two-compartment model. The elimination constants of Rana and Xenopus are not significantly different. 3. Metabolism is mostly conjugation by glucuronidation and sulphation of the original phenols. Additionally, oxidations leading to dihydroxyphenols and benzoic acid from 2-methylphenol, and reduction of 4-nitrophenol occur, followed by conjugation. 4. There is an important difference between the metabolite patterns of Rana and Xenopus in that the latter is unable to glucuron…

Nucleic Acids and Nuclear Proteins

DNA deserves the most attention in any book dealing with molecular variety in animals. The complete genetic information of the organism is encoded in the order of the bases, and with it also is the whole spectrum of genetically determined variation within and between individuals. One can view DNA as a text in which each of the four letters at each position has a unique meaning. Some information and variety is lost en route from the DNA via RNA to the proteins and the complex morphological and physiological characters because only part of the DNA is transcribed into RNA, and not all RNA codes for proteins; furthermore, the genetic code is degenerate and the 64 possible triplet codons define …

Ester Hydrolases, ATPases and Carboanhydrases

Many biomolecules are esterified with carbonic acid, phosphoric acid or sulphuric acid. The enzymes responsible for the hydrolytic cleavage of the esters are the carboxylester hydrolases, phosphoesterases and sulphatases. In addition to the phosphomonoesterases, we will also consider the phosphodiesterases and nucleases that are specific for cAMP and cGMP, as well as the ATPases that cleave phosphoric acid anhydride bonds. The ion-transporting ATPases will be discussed together with comparative biochemical data on ion channels. The chapter ends with a discussion of carboanhydrases.