Showing papers in "Cellular and Molecular Life Sciences in 1992"
TL;DR: An attempt is made to review the presently known, completely identified crustacean neuropeptides with regard to structure, function and distribution.
Abstract: In this article, an attempt is made to review the presently known, completely identified crustacean neuropeptides with regard to structure, function and distribution. Probably the most important progress has been made in the elucidation of a novel family of large peptides from the X-organ-sinus gland system which includes crustacean hyperglycemic hormone (CHH), putative molt-inhibiting hormone (MIH) and vitellogenesis (=gonad)-inhibiting hormone (VIH). These peptides have so far only been found in crustaceans. Renewed interest in the neurohemal pericardial organs has led to the identification of a number of cardioactive/myotropic neuropeptides, some of them. unique to crustaceans. Important contributions have been made by immunocytochemical mapping of peptidergic neurons in the nervous system, which has provided evidence for a multiple role of several neuropeptides as neurohormones on the one hand and as local transmitters or modulators on the other. This has been corroborated by physiological studies. The long-known chromatophore-regulating hormones, red pigment concentrating hormone (RPCH) and pigment-dispending hormone (PDH), have been placed in a broader perspective by the demonstration of an additional role as local neuromodulators. The scope of crustacean neuropeptide research has thus been broadened considerably during the last years.
470 citations
TL;DR: Evidence from several cell types suggests that endocytosis may be coupled to autophagy to a variable extent, and that the amphisome may play a central role as a collecting station for material destined for lysosomal degradation, as indicated by ultrastructural evidence.
Abstract: Autophagic degradation of cytoplasm (including protein, RNA etc.) is a non-selective bulk process, as indicated by ultrastructural evidence and by the similarity in autophagic sequestration rates of various cytosolic enzymes with different half-lives. The initial autophagic sequestration step, performed by a poorly-characterized organelle called a phagophore, is subject tofeedback inhibition by purines and amino acids, the effect of the latter being potentiated by insulin and antagonized by glucagon. Epinephrine and other adrenergic agonists inhibit autophagic sequestration through a prazosin-sensitive α1-adrenergic mechanism. The sequestration is also inhibited by cAMP and by protein phosphorylation as indicated by the effects of cyclic nucleotide analogues, phosphodiesterase inhibitors and okadaic acid.
400 citations
TL;DR: InE.
Abstract: In E. coli, protein degradation plays important roles in regulating the levels of specific proteins and in eliminating damaged or abnormal proteins. E. coli possess a very large number of proteolytic enzymes distributed in the cytoplasm, the inner membrane, and the periplasm, but, with few exceptions, the physiological functions of these proteases are not known. More than 90% of the protein degradation occurring in the cytoplasm is energy-dependent, but the activities of most E. coli proteases in vitro are not energy-dependent. Two ATP-dependent proteases, Lon and Clp, are responsible for 70-80% of the energy-dependent degradation of proteins in vivo. In vitro studies with Lon and Clp indicate that both proteases directly interact with substrates for degradation. ATP functions as an allosteric effector promoting an active conformation of the proteases, and ATP hydrolysis is required for rapid catalytic turnover of peptide bond cleavage in proteins. Lon and Clp show virtually no homology at the amino acid level, and thus it appears that at least two families of ATP-dependent proteases have evolved independently.
369 citations
TL;DR: This review article deals with recent developments in molecular and physiological aspects of chitinases from plants, fungi, bacteria, insects and fishes.
Abstract: This review article deals with recent developments in molecular and physiological aspects of chitinases from plants, fungi, bacteria, insects and fishes
343 citations
TL;DR: It appears, at least for penguins and seals, that the duration of the fast may be limited by changes that occur in biochemical regulation near the end of theFasts in these animals are closely interrelated.
Abstract: There are several groups of animals that are adapted for extremely long duration fasting as part of their reproductive cycle. Penguins, bears and seals routinely fast without food or water for months at time. However, they do not ‘starve’, as the biochemical implications of starving are very different from those of successful fasting. There are distinct biochemical adaptations in lipid, carbohydrate and especially protein metabolism that allow these animals to survive. It appears, at least for penguins and seals, that the duration of the fast may be limited by changes that occur in biochemical regulation near the end of the fast. In all of these species, the biochemistry of fasting and the ecological and behavioral demands of their breeding cycles are closely interrelated.
261 citations
TL;DR: Proteins sequestered by a non-selective bulk process within the lysosomes turn over with an apparent half-life of about 8 minutes and this rapid lysOSomal proteolysis is initiated by endopeptidases, in particular by the cathepsins D and L.
Abstract: Proteins sequestered by a non-selective bulk process within the lysosomes turn over with an apparent half-life of about 8 minutes and this rapid lysosomal proteolysis is initiated by endopeptidases, in particular by the cathepsins D and L. We describe also the cathepsins B and H which show mainly exopeptidase and only low endopeptidase activity. Especially cathepsin H is most probably the only lysosomal aminopeptidase in many cell types. Additionally, the properties of other mammalian lysosomal endo- and exopeptidases are compared. Finally, we discuss some of the conditions for the action of lysosomal proteases as the low intralysosomal pH, the high part of lysosomal thiol groups and the absence of intralysosomal proteinase inhibitors.
233 citations
TL;DR: Proteins of the Major Urinary Complex of the adult male mouse selectively bind the male pheromones 2-(sec-butyl)thiazoline and dehydro-exo-brevicomin, and concentrate them in urine.
Abstract: Proteins of the Major Urinary Complex of the adult male mouse (Mus musculus) selectively bind the male pheromones 2-(sec-butyl)thiazoline and dehydro-exo-brevicomin, and concentrate them in urine.
220 citations
TL;DR: Effects of the essential oils (EOs) extracted from eleven aromatic plants belonging to the Lamiaceae family were examined upon three different developmental stages of Drosophila auraria, showing insecticidal effects by preventing egg hatching, or by causing the death of larvae and adult flies.
Abstract: Effects of the essential oils (EOs) extracted from eleven aromatic plants belonging to the Lamiaceae family (common in the Greek flora) were examined upon three different developmental stages ofDrosophila auraria. All of the EOs examined exhibited insecticidal effects, either by preventing egg hatching, or by causing the death of larvae and adult flies. In several cases, malformation and/or prohibition of puparium formation was also observed.
180 citations
TL;DR: Small hummingbirds achieve the highest known mass-specific metabolic rates among vertebrate homeotherms, and their capacities for O2 and substrate delivery to muscle mitochondria, as well as mitochondrial oxidative capacities in these animals may be at the upper limits of what is structurally and functionally possible given the constraints inherent in vertebrate design.
Abstract: Resting and maximal mass-specific metabolic rates scale inversely with body mass. Small hummingbirds achieve the highest known mass-specific metabolic rates among vertebrate homeotherms. Maximal capacities for O2 and substrate delivery to muscle mitochondria, as well as mitochondrial oxidative capacities in these animals may be at the upper limits of what are structurally and functionally possible given the constraints inherent in vertebrate design. Such constraints on the evolutionary design of functional capacities may play an important role in determining the lower limits to vertebrate homeotherm size and the upper limits to mass-specific metabolic rate.
172 citations
TL;DR: It was found that the rate of oviposition of herbivorous mites was reduced on seedlings exposed to volatiles from infested seedlings, and predatory mites were attracted by exposeduninfested seedling.
Abstract: When infested by herbivorous mites, cotton seedlings produce volatile cues that elicit attraction of predatory mites. Experiments were carried out to elucidate how downwinduninfested conspecific seedlings are affected by these volatiles. It was found that the rate of oviposition of herbivorous mites was reduced on seedlings exposed to volatiles from infested seedlings. Moreover, predatory mites were attracted by exposeduninfested seedlings. These results strongly suggest that uninfested plants are better protected against herbivore attack when exposed to airborne chemicals released by their infested neighbours.
170 citations
TL;DR: This review focuses on aspects of the formation, transport, detoxification and excretion of the two most important nitrogenous products of fishes: ammonia and urea.
Abstract: Catabolism of nitrogen-containing substances makes a major contribution to the oxidative metabolism in teleostean fishes. In this review, we focus on aspects of the formation, transport, detoxification and excretion of the two most important nitrogenous products of fishes: ammonia (NH3 plus NH4+) and urea. While NH4+ makes up the bulk of nitrogenous waste, it is in equilibrium with the highly toxic NH3. Ammonia is generated in the liver and excreted through branchial, surface and renal routes. Innocuous urea is derived through hepatic uricolysis or argininolysis and voided through kidney, gill, skin or faeces. Under conditions hampering the release of ammonia, such as exposure to exogenous ammonia, water limitation, or alkaline conditions, some teleosts detoxify ammonia through synthesis of urea by the ornithine-urea cycle in liver. Ammonia and possibly alanine are the prevalent vehicles of internal nitrogen transport. Glutamine is immaterial to interorgan nitrogen transport in fishes, but plays a transient role in the detoxification of ammonia by brain glutamine synthetase.
TL;DR: Hummingbirds have extremely specialized digestive traits that allow them to assimilate sucrose at high rates and with extremely high efficiency, whereas many nectar- and fruit-eating passerines prefer glucose and fructose, which seems to be associated with poor sucrose assimilation.
Abstract: Plants pollinated and dispersed by different groups of birds offer different kinds of sugars in nectar and fruit pulp. The preferences and physiological traits of avian pollinators and seed dispersers are broadly correlated with the sugar composition of the nectar and fruit that they feed on and appear to have influenced the evolution of the sugar composition of the rewards that plants offer. Hummingbirds prefer sucrose whereas many nectar- and fruit-eating passerines prefer glucose and fructose. Preference for hexoses in passerines seems to be associated with poor sucrose assimilation resulting from two physiological mechanisms: lack of intestinal sucrase activity and fast passage rates. Sucrase activity absence appears to be restricted to a single phylogenetic group (the sturnid-muscicapid lineage). Fast passage rates seem to be characteristic of many small frugivores and to hinder the assimilation of complex nutrients that require hydrolysis before absorption. Hummingbirds have extremely specialized digestive traits that allow them to assimilate sucrose at high rates and with extremely high efficiency. These specialized digestive traits appear not to be present in many nectar-feeding passerines.
TL;DR: The review focuses on the compartmentation of the reactions and the proteolytic fragmentation of lysosomal enzyme precursors, which is characterized mainly by modifications of carbohydrate side chains.
Abstract: Lysosomal enzymes are subjected to a number of modifications including carbohydrate restructuring and proteolytic maturation. Some of these reactions support lysosomal targeting, others are necessary for activation or keeping the enzyme inactive before being segregated, while still others may be adventitious. The non-segregated fraction of the enzyme is secreted and can be isolated from the medium. It is considered that the secreted lysosomal enzymes fulfill certain physiological and pathophysiological roles. By comparing the secreted and the intracellular enzymes it is possible to distinguish between the reactions that occur before and after the segregation. In this review the reactions that may influence the segregation are referred to as the early processing and those characteristic for the enzymes isolated from lysosomal compartments as the late processing. The early processing is characterized mainly by modifications of carbohydrate side chains. In the late processing, proteolytic fragmentation represents the most conspicuous changes. The review focuses on the compartmentation of the reactions and the proteolytic fragmentation of lysosomal enzyme precursors. While a plethora of proteolytic reactions are involved, our knowledge of the proteinases responsible for the particular maturation reactions remains very limited. The review points also to work with cells from patients affected with lysosomal storage disorders, which contributed to our understanding of the lysosomal apparatus.
TL;DR: Evidence suggests matching of capacities between different steps in carbohydrate metabolism, and between the intestine, liver, kidneys, and spleen, is a testable hypothesis of economic design, useful in detecting and explaining cases of apparently uneconomic design.
Abstract: Natural selection tends to eliminate unutilized capacities because of their costs. Hence we ask how large are the reserve capacities by which biological capacities exceed natural loads, and how closely are related biological capacities matched to each other. Measured capacities (Vmax values) of small intestinal brush-border nutrient transporters are typically around twice their natural loads (dietary intakes of their substrates); the ratio is higher for a transporter of a hyperessential nutrient. Preliminary evidence suggests matching of capacities between different steps in carbohydrate metabolism, and between the intestine, liver, kidneys, and spleen. Symmorphosis — the postulated matching of capacities to each other and to loads — is a testable hypothesis of economic design, useful in detecting and explaining cases of apparently uneconomic design.
TL;DR: The production of large numbers of males in the thelytokous speciesEncarsia formosa was induced by feeding antibiotics to their mothers and insemination does not occur.
Abstract: The production of large numbers of males in the thelytokous speciesEncarsia formosa was induced by feeding antibiotics to their mothers. The males induced by antibiotic treatment produce sperm and sometimes mate with females, but insemination does not occur.
TL;DR: The modified thioflavine S method presented here (easy and cheap to perform), the morphological appearance of the stained neurofibrillary tangles and senile plaques is greatly improved and the intense contrast between stained lesions and background permits an accurate automatic quantification of NFT and SP using a computer-assisted image analysis system.
Abstract: Large differences are usually observed when standard staining methods for a number of pathological lesions in neurodegenerative disorders are compared. With the modified thioflavine S method presented here (easy and cheap to perform), the morphological appearance of the stained neurofibrillary tangles (NFT) and senile plaques (SP) is greatly improved. Furthermore, the intense contrast between stained lesions and background obtained with this technique permits an accurate automatic quantification of NFT and SP using a computer-assisted image analysis system.
TL;DR: Green leaf volatiles were shown to interrupt responses to aggregation pheromones of three species of bark beetles which infest pines in the southern United States, and this is the first report of an interruptant for Ips species and the only report of a phersomone interruptant active for both Ips and Dendroctonus species.
Abstract: Green leaf volatiles were shown to interrupt responses to aggregation pheromones of three species of bark beetles (Coleoptera: Scolytidae) which infest pines in the southern United States [the southern pine beetle,Dendroctonus frontalis Zimm.; the four-spined engraver,Ips avulsus (Eichhoff); and the five-spined engraver,Ips grandicollis (Eichhoff)]. The order of effectiveness of the compounds tested for each species was hexanal>hexanal+hexan-1-ol>hexan-1-ol. Neither hexanal, hexan-1-ol nor hexanal+hexan-1-ol was as effective in interrupting pheromone responses ofD. frontalis as verbenone, a known inhibitor of this species. Other than interspecific chemical signals, this is the first report of an interruptant forIps species, and the only report of a pheromone interruptant active for bothIps andDendroctonus species.
TL;DR: The marine mollusc Aplysia was used to investigate the role of peptidergic co-transmission in feeding behavior, and it was demonstrated that the peptides modify the relationship between muscle contraction amplitude and relaxation rate so as to maintain optimal motor output when the intensity and frequency of feeding behavior change.
Abstract: Despite their ubiquitous presence in the central and peripheral nervous systems, the behavioral functions of peptide co-transmitters remain to be elucidated. The marine molluscAplysia, whose simple nervous system facilitates the study of the neural basis of behavior, was used to investigate the role of peptidergic co-transmission in feeding behavior. Several novel modulatory neuropeptides were purified, and localized to identified cholinergic motorneurons. Physiological and biochemical studies demonstrated that these peptides are released when the motorneourons fire at frequencies that occur during normal behavior, and that the peptides modify the relationship between muscle contraction amplitude and relaxation rate so as to maintain optimal motor output when the intensity and frequency of feeding behavior change.
TL;DR: The sum of the contents of the three D-amino acids in a plasma sample correlated with the serum creatinine level of the subject, and no D-Amino acid was shown to be present in the plasma proteins.
Abstract: Twelve neutral free amino acids, i.e. serine, threonine, glutamine, asparagine, alanine, proline, methionine, tyrosine, valine, leucine, isoleucine and phenylalanine, were surveyed for the presence of D-enantiomers in plasma samples from patients with renal diseases and from normal subjects. D-serine, D-alanine and D-proline were found in the patient's plasma. The highest concentrations (D/L ratio) of D-serine, D-alanine and D-proline were 0.2362, 0.2087 and 0.0986, respectively. The sum of the contents of the three D-amino acid was shown to be present in the plasma proteins.
TL;DR: It is demonstrated for the first time ahair cycle-dependent gene and protein expression of proopiomelanocortin in mouse skin in vivo and β-endorphin antigen was localized in the sebaceous gland in a hair cycle dependent manner.
Abstract: We demonstrate for the first time a hair cycle-dependent gene and protein expression of proopiomelanocortin in mouse skin in vivo. Northern blot detected POMC mRNA with an apparent size of 0.9 kb in anagen but not telogen skin. Western blot emphasized a specific protein of 30–33 kDa recognized by anti β-endorphin in late but not early anagen or telogen skin. By immunocytochemistry, β-endorphin antigen was localized in the sebaceous gland in a hair cycle dependent manner.
TL;DR: The synthesis of a set of proteins called the heat shock proteins (hsp) is induced and they are required for repairing the damage resulting from stress.
Abstract: When prokaryotic or eukaryotic cells are submitted to a transient rise in temperature or to other proteotoxic treatments, the synthesis of a set of proteins called the heat shock proteins (hsp) is induced. The structure of these proteins has been highly, conserved during evolution. The signal leading to the transcriptional activation of the corresponding genes is the accumulation of denatured and/or aggregated proteins inside the cells after stressful treatment. The expression of a subset of hsp is also induced during early embryogenesis and many differentiation processes.
TL;DR: The antimitotic agent taxol was tested for toxicity towards fungi from different taxonomic groups and found to be particularly active against oomycete fungi and in germinating zoospore cysts of the oomyCetePhytophthora capsici the mechanism of action ofTaxol was shown to involve inhibition of mitosis, presumably resulting from an effect on microtubules.
Abstract: The antimitotic agent taxol was tested for toxicity towards fungi from different taxonomic groups and found to be particularly active against oomycete fungi. In germinating zoospore cysts of the oomycete Phytophthora capsici the mechanism of action of taxol was shown to involve inhibition of mitosis, presumably resulting from an effect on microtubules. Various taxol analogues with deleted A-ring C-13 side chain substituents were tested for toxicity towards P. capsici and Aphanomyces cochlioides to provide insight into structural features required for activity. The importance of the side chain was shown by the much lower activity as compared to taxol of analogues lacking all or part of the side chain. The effect of stereochemistry at the C-2' position on fungitoxicity towards oomycetes was similar to that reported previously on mammalian microtubule assembly.
TL;DR: Concepts include results from quantitative structure-activity relationships (QSAR), pharmacokinetics, ecophysiology and general biology, molecular genetic aspects and selection, and finally the structure of communities and man-made alterations in them.
Abstract: The fate of environmental pollutants — the various isotopes of elements, and inorganic or organic compounds — is a fundamental aspect of ecology and ecotoxicology, and bioaccumulation is a phenomenon often discussed in this context. Human activities have drastically altered natural concentrations of many substances in the environment and added numerous new chemicals. An understanding of the processes of bioaccumulation is important for several reasons. 1) Bioaccumulation in organisms may enhance the persistence of industrial chemicals in the ecosystem as a whole, since they can be fixed in the tissues of organisms. 2) Stored chemicals are not exposed to direct physical, chemical, or biochemical degradation. 3) Stored chemicals can directly affect an individual's health. 4) Predators of those organisms that have bioaccumulated harmful substances may be endangered by food chain effects. While former theories on the processes of bioaccumulation focused on single aspects that affect the extent of accumulation (such as the trophic level within the food chain or the lipophilicity of the chemical), modern theories are based on compartmental kinetics and the integration of various environmental interactions. Concepts include results from quantitative structure-activity relationships (QSAR), pharmacokinetics, ecophysiology and general biology, molecular genetic aspects and selection, and finally the structure of communities and man-made alterations in them.
TL;DR: Defensive secretions (allomones) from first-instar nymphs of stink bugs in the subfamily Pentatominae contain (E)-4-oxo-2-decenal as a major constituent, whereas this compound is absent from later instars.
Abstract: Defensive secretions (allomones) from first-instar nymphs of stink bugs in the subfamily Pentatominae contain (E)-4-oxo-2-decenal as a major constituent, whereas this compound is absent from later instars. In contrast, first instars ofEdessa meditabunda (Edessinae) produce allomones like those of later instars. The C6 and C8 (E)-4-oxo-2-alkenals are common, characteristic exocrine compounds of nymphal and adult Heteroptera, but (E)-4-oxo-2-decenal is previously unknown as a major natural product for which a biological role has yet to be established.
TL;DR: Recent findings on AKH inactivation and metabolism, as well as onAKH prohormone processing and biosynthesis are summarized.
Abstract: Adipokinetic hormones AKH I (pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-Thr-NH2) and AKH II (pGlu-Leu-Asn-Phe-Ser-Trp-Gly-Thr-NH2) are synthesized by neurosecretory cells (NSC) of the corpora cardiaca (CC) in the locust,Schistocerca gregaria. These NSC constitute a homogeneous ‘peptide factory’ as each cell synthesizes both AKH I and AKH II. This homogeneity makes the CC an excellent system in which to study aspects of neuropeptide biosynthesis. This report summarizes recent findings on AKH inactivation and metabolism, as well as on AKH prohormone processing and biosynthesis.
TL;DR: The results confirm that mucus can be regarded as a gel with finite pores, but that it does not constitute an absolute barrier to even high molecular weight solutes.
Abstract: A diffusion chamber technique based on time-lag analysis for the estimation of effective diffusion coefficients of radiolabelled macromolecules of varying molecular weights through native mucus gel is reported. For all solutes studied, a reduction in effective diffusion coefficients was observed with a retardation of solute flux in both aqueus and mucus layers. Over the molecular weight range of solutes investigated (126–186 000 Daltons), a consistent effect of molecular weight was evident with regard to the retarding effect of mucus. No apparent or absolute molecular weight cut-off for macromolecular transfer was exhibited. However, at high molecular weights (>30 000 Daltons) the retardation was greatly enhanced. The results confirm that mucus can be regarded as a gel with finite pores, but that it does not constitute an absolute barrier to even high molecular weight solutes.
TL;DR: HSWS seems to offer some form of cerebral recovery, with the prefrontal cortex being particularly implicated, and the hSWS characteristics of certain forms of major psychiatric disorders may well endorse this prefrontal link.
Abstract: Recent findings concerning human slow wave sleep (hSWS-stages 3+4; delta EEG activity) are critically reviewed. Areas covered include the significance of the first hSWS cycle; hSWS in extended sleep; relationship between hSWS, prior wakefulness and sleep loss; hSWS influence on sleep length; problems with hSWS deprivation; influence of the circadian rhythm; individual differences in hSWS, especially, age, gender and constitutional variables such as physical fitness and body composition. Transient increases in hSWS can be produced by increasing both the quality and quantity of prior wakefulness, with an underlying mechanism perhaps relating to the waking level of brain metabolism. Whilst there may also be thermoregulatory influences on hSWS, hypotheses that energy conservation and brain cooling are major roles for hSWS are debatable. hSWS seems to offer some form of cerebral recovery, with the prefrontal cortex being particularly implicated. The hSWS characteristics of certain forms of major psychiatric disorders may well endorse this prefrontal link.
TL;DR: The hypothesis that obesity and type II diabetes may be treated effectively with bromocriptine when administered at the proper times and dosages is supported.
Abstract: Obese postmenopausal female volunteers were given timed daily oral dosages of bromocriptine, and tested for reduction of body fat stores. This dopamine agonist has been shown to reset circadian rhythms that are altered in obese animals and to reduce body fat levels in several animal models. The participants were instructed not to alter their existing exercise and eating behavior during treatment. Skinfold measurements were taken on 33 subjects as indices of body fat. The measurements (e.g., suprailiac) were reduced after six weeks by about 25%, which represents a reduction of 11.7% of the total body fat. These dramatic decreases in body fat, which are equivalent to that produced by severe caloric restriction, were accompanied by more modest reductions of body weight (2.5%), indicating a possible conservation of protein that is usually lost as a consequence of such caloric restriction. The effects of bromocriptine treatment on body fat and hyperglycemia were also examined in non-insulin dependent diabetics being treated with oral hypoglycemics (7 subjects) or insulin (7 subjects). Total body fat was reduced by 10.7% and 5.1% in diabetics on oral hypoglycemics and insulin, respectively, without any significant reductions in body weight. Hyperglycemia was reduced in most of the 15 diabetic subjects treated leading to euglycemia and even cessation of hypoglycemic drugs in 3 of the 7 subjects during 4-8 weeks of bromocriptine treatment. These findings support the hypothesis that obesity and type II diabetes may be treated effectively with bromocriptine when administered at the proper times and dosages.
TL;DR: The results suggest that the enzyme is involved in the elimination of free D-serine in the cerebellum, as well as in the presence of D-enantiomers of neutral common amino acids in the brain.
Abstract: The physiological role of D-amino acid oxidase (EC 1. 4. 3. 3) in mouse brain is described. The presence of D-enantiomers of neutral common amino acids was surveyed in the brain. D-serine was shown to be present at high concentration only in regions where the enzyme activity was low. In normal mice whose D-amino acid oxidase activity was much higher in the cerebellum than in the cerebrum, free D-serine content was apparently lower in the cerebellum than in the cerebrum. In mice of a mutant strain lacking D-amino acid-oxidase activity, the free D-serine level was remarkably high both in the cerebrum and cerebellum. The results suggest that the enzyme is involved in the elimination of free D-serine in the cerebellum.
TL;DR: The biochemical adaptations that enableDeep-sea animals to exploit diverse deep-sea habitats and that help establish biogeographic patterning in the deep- sea are discussed.
Abstract: Deep-sea ecosystems contain unique endemic species whose distributions show strong vertical patterning in the case of pelagic animals and sharp horizontal patterning in the case of benthic animals living in or near the deep-sea hydothermal vents. This review discusses the biochemical adaptations that enable deep-sea animals to exploit diverse deep-sea habitats and that help establish biogeographic patterning in the deep-sea. The abilities of deep-sea animals to tolerate the pressure and temperature conditions of deep-sea habitats are due to pervasive adaptations at the biochemical level: enzymes exhibit reduced perturbation of function by pressure, membranes have fluidities adapted to deep-sea pressures and temperatures, and proteins show enhanced structural stability relative to homologous proteins from cold-adapted shallow-living species. Animals from the warmest habitable regions of hydrothermal vent ecosystems have enzymes and mitochondria adapted to high pressure and relatively high temperatures. The low metabolic rates of bathypelagic fishes correlate with greatly reduced capacities for ATP turnover in locomotory muscle. Reduced light and food availability in bathypelagic regions select for low rates of energy expenditure in locomotory activity. Deep-sea animals thus reflect the importance of biochemical adaptations in establishing species distribution patterns and appropriate rates of metabolic turnover in different ecosystems.