摘要:

In the first part of this study, metal bioaccumulation and metallothioneins were investigated in various organs of the red‐blooded teleost,Trematomus bernacchii,and the haemoglobinlessChionodraco hamatus.Hepatic metallothionein correlated positively with Cd, Cu, and Zn concentrations inT. bernacchii,whereas inC. hamatusit showed a positive correlation only with Cd. A metal‐linking protein with characteristics typical of metallothioneins was identified in the liver ofC. hamatusas well as ofT. bernacchii.In the second part, data on the amino acid sequence of the enzyme Superoxide dismutase (SOD) were analysed and compared with SOD sequences from other animals. In the third part, a low degree of tolerance against the toxic effects of copper was recorded in two cilates,Pleuronema coronatumandEuplotes rariseta,collected from Terra Nova Bay and cultured in the laboratory.

ISSN:1125-0003    

DOI:10.1080/11250000009356349

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Among Antarctic notothenioids, appreciable amounts of hepatic metallothionein were found in red‐blooded species, whilst very little metallothionein, if any, was detected in icefish. In contrast, high levels of metallothionein mRNA were revealed in both fishes by Northern blot analysis of total RNA. Phylogenetic analyses carried out on the metallothionein sequences obtained by using reverse‐transcriptase polymerase chain reaction on eight notothenioid species revealed that notothenioid metallothioneins can be divided into two groups, metallothionein‐I and metallothionein‐II, indicating that they arose from at least one gene duplication event occurring in the ancestral lineage of the Notothenioidei. A strong induction of metallothionein gene expression and metallothionein accumulation could be obtained in icefish injected with cadmium salt. Apparently, the expression of the genes encoding MT‐I and MT‐II in icefish liver is differentially regulated by cadmium. The discrepancy between metallothionein mRNA levels and amounts of metallothionein protein observed in icefish was observed also in red‐blooded species. InNotothenia coriiceps,the profile of metallothionein mRNA accumulation, as well as that of the metallothionein levels, differs substantially in different tissues suggesting the presence of an organ‐specific regulation of metallothionein genes.

ISSN:1125-0003    

DOI:10.1080/11250000009356350

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Cathepsin D was purified to homogeneity from the liver of Antarctic icefish by anion‐exchange chromatography followed by affinity chromatography on concanavalin‐A Sepharose. The N‐terminal sequence of this proteinase was used to design a primer to be employed in reverse‐transcriptase polymerase chain reaction together with liver RNA from two Antarctic Notothenioidei, the red‐bloodedTrematus bernacchiiand the haemoglobinless icefishChionodraco hamatus.The reaction mixture analysed by agarose gel electrophoresis, showed two bands of 1400 bp and 1200 bp. The open reading frame of the cloned cDNA, containing the 1400 bp fragment, encoded an aspartic proteinase showing sequence similarity with cathepsin D of other vertebrates. The nucleotide sequence of the 1200 bp fragment showed 58% identity with aspartic proteinase from other sources, but also features not found in homologous enzymes from other organisms. The temperature dependence of kinetic parameters was determined for the purified icefish cathepsin D. At temperatures between 8 and 50° C, the icefish proteinase had a higher specificity constant (kcat/Km) than human cathepsin D. The stability of both enzymes was measured at 50° C and half‐lives of 55 and 3 min were derived for icefish and human cathepsin D, respectively.

ISSN:1125-0003    

DOI:10.1080/11250000009356351

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Glutamate dehydrogenase (GDH) was purified from the liver of the teleostChaenocephalus aceratus(Notothenioidei: Channichthyidae) and the microorganismPsychrobactersp. TAD1, from Antarctic marine and terrestrial environments, respectively. GDH isolated fromC. aceratusliver had a hexameric molecular structure very similar to that of other vertebrates and displayed preference for NAD+, a feature shared with other fish enzymes. The bovine and fish GDH activity and stability were differently affected by temperature and hydrostatic pressure. At low temperatures, the specific activity of fish GDH was higher than that measured with the homologous bovine enzyme.Psychrobactersp. TAD1 showed a feature quite unusual in bacteria, i.e. the presence of two distinct GDHs specific either for NADP+or for NAD+. NADP+‐dependent GDH was purified and characterised. It has a hexameric structure with a subunit molecular weight similar to that described for this class of GDHs and a specific activity at low and moderate temperatures similar to that measured with the homologous enzyme fromEscherichia coli.The kinetic properties of NADP+‐dependent GDH ofPsychrobactersp. TAD1 and the presence of another NAD+‐dependent GDH suggest that, during the cold‐adaptation process, this enzymatic function acquired a pattern of changes different from that ofC. aceratus.

ISSN:1125-0003    

DOI:10.1080/11250000009356352

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A well known characteristic of the oxidative metabolism of Antarctic fishes is their preferential utilization of the lipid metabolic pathway. Since oxidative metabolism may lead to a significant production of oxygen‐derived free radicals, which may have several harmful effects on biological structures, it seemed worthwhile to investigate the presence, in various tissues from different Antarctic fishes, of those ions and molecules which are known to be at the basis of the antioxidant defense mechanisms. Hence, the Coenzyme Q and trace elements (selenium, copper, and zinc) content of tissues from several Antarctic fishes was determined and compared with that of non‐Antarctic species. Unlike temperate fishes, in which the Coenzyme Q is Q10, all the Antarctic species examined displayed the homolog Q9form. This particular finding was related to the difference in the crystallisation temperature existing between Coenzyme Q10and Coenzyme Q9. Taken together, the results indicate a higher level of antioxidant defenses for Antarctic species, with respect to temperate fishes. This may be considered a stimulating basis for further studies on the adaptation mechanisms centered on the oxidative metabolism of organisms living in extreme environments.

ISSN:1125-0003    

DOI:10.1080/11250000009356353

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This research dealing with fish, bird and mammal hemoglobins is in the framework of the study of the molecular basis of cold adaptation in Antarctic organisms. The study of hemoglobin structural and functional properties in Antarctic teleosts allowed a correlation of amino acid sequence, multiplicity, and oxygen‐binding features with ecological constraints. Amino acid sequences of α and β chains were analysed to build phylogenetic trees, while the organisation and expression of globin genes was studied. The respiratory proteins of Antarctic birds were investigated, in relation with the oxygen demands arising from their characteristic behaviour (diving or flight) and, in general, from the extreme conditions of the Antarctic habitat. The study of Weddell seal hemoglobins indicated that the combined effect of carbon dioxide, organic phosphates and temperature optimises oxygen delivery to all tissues in spite of their relative heterothermia. The crystallographic structure of the carbonmonoxy derivative ofTrematomus newnesimajor hemoglobin was resolved, giving new insight into the study of the Root effect. The molecular models of skua hemoglobins revealed the presence of a second, additional phosphate binding site located between the two α chains, paving the way to further studies.

ISSN:1125-0003    

DOI:10.1080/11250000009356354

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This work reports recent data on mechanisms of cold adaptation exhibited by the Antarctic teleostsTrematomus bernacchiiandChionodraco hamatus.Analysis of fatty acid in intestinal mucosa brush border suggested that an increase in unsaturated fatty acid could be a mechanism for the preservation of cell membrane integrity and functionality. The investigation of several transporters involved in the regulation of cell homeostasis (Na+/K+‐AT‐Pase, Na+‐D‐glucose cotransport, Na+/H+exchanger and Ca++‐AT‐Pase) showed kinetic characteristics that could explain part of the adaptation of these proteins to work at low temperature. The activity of carbonic anhydrase, involved in pH control both at intra‐cellular and systemic level, was related to plasma buffer capacity.

ISSN:1125-0003    

DOI:10.1080/11250000009356355

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Ferritin from the spleen of the Antarctic teleostTrematomus bernacchiiis an iron storage protein composed of a single sub‐unit type whose amino N‐terminal sequence is blocked, as in L‐type mammalian and fish ferritin polypeptide chains. The partial amino acid sequence reveals a high similarity with the cDNA‐deduced sequence of the M chain (L‐type) ofSalmo salarand the H1 chain ofSalmo gairdneriferritins. Like those of the latter sub‐units, theT. bernacchiichain contains the ferroxidase center, typical of mammalian H chains, and the glutamate residues of the iron micelle nucleation site, typical of mammalian L chains. It follows that, at variance with the mammalian ferritins, a single chain suffices to carry out both ferritin functions. In accordance with the sequence data, theT. bernacchiiferritin homopolymer is endowed with a high rate of iron oxidation and a high iron accumulation capacity.

ISSN:1125-0003    

DOI:10.1080/11250000009356356

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Physiological adaptation of Antarctic teleosts to cold environment was studied with regard to the presence of regulatory peptides involved in (i) cardiac and ion‐water homeostasis, (ii) brain, (iii) intestine, and (iv) gonads. Immunoreactivity for different regions of the Atrial Natriuretic Peptide was detected in the heart ofTrematomus bernacchii, Chionodraco hamatus, Cryodraco antarcticus,andChampsocephalus gunnari,while immunoreactivity for other regulatory peptides (i.e., endothelin‐1, somatostatin‐14, and galanin) appeared to be widely distributed in the cardio‐vascular system. Osmoregulatory peptides (somatostatin‐14, prolactin, atrial natriuretic peptide, galanin, and urotensin II) were localised by immunohistochemistry in the urinary bladder and gills. From studies on the distribution of the pituitary specific transcription factor 1 and adenohypophysial hormones (growth hormone, prolactin, and gonadotropin releasing hormone) in the brain and pituitary ofTrematomus bernacchiiandPagothenia coriiceps,it was evident that the pituitary specific transcription factor 1 acts as a developmental regulator of the anterior pituitary, responsible for growth hormone and prolactin cell commitment, differentiation, and gene expression. This coexistence appeared to be a unique trait of Antarctic teleosts. Analyses of the distribution and localisation of gastrointestinal hormones and neuropeptides (insulin, glucagon, pancreatic polypeptide, somatostatin, vasoactive intestinal polypeptide, pituitary adenylate cyclase activating peptide, and peptide histidine isoleucine) in adults ofChionodraco hamatus, Pagetopsis mascropterus,andNotothenia coriiceps,and larvae ofPleuragramma antarcticumshowed that most of the immunoreactive nerve fibres in Notothenioids are of extrinsic type. Ultrastructural analysis ofChionodraco hamatus, Champsocephalus gunnari,andNotothenia coriicepsmale gametes showed some peculiar aspects in the head of the spermatozoa. Studies on the spermatogenesis indicated a shifted circannual cycle in the icefishes and in the red blooded fishes: when spermato‐genensis is completed in the icefish, in the red blooded teleosts the testis is not in reproductive activity as shown by the positive immunoreaction for Fibroblast Growth Factor and its receptor 1 in spermatogonia and Sertoli cells ofChionodraco hamatusand the lack of positivity inTrematomus bernacchii.

ISSN:1125-0003    

DOI:10.1080/11250000009356357

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The conduction properties of peripheral nerves from the Arctic fish species Arctic eelpouts (Lycodessp.), snake bleeny(Lumpenus lampretaeformis) and Polar cod (Boreogadus saida), permanently adapted to low temperatures, were studied. The temperature dependence of the conduction velocity was 1.82 to 2.16, which is similar to that described for Mediterranean fishes and, at their physiological temperature, the conduction velocity of Arctic fishes is about one half of that of temperate fishes, suggesting that this neurophysiological function is not cold adapted in those Arctic fish species.

ISSN:1125-0003    

DOI:10.1080/11250000009356358

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor