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Metabolic responses to food deprivation and refeeding in juveniles of Rutilus rutilus (Teleostei: Cyprinidae) (1993)

Méndez, Gabriela ; Wieser, Wolfgang

Springer

Environmental biology of fishes 36 (1993), S. 73-81

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ISSN: 1573-5133

Keywords: Tissue water ; Protein ; Glycogen ; Enzymes of energy metabolism ; Stress ; Adaptation ; Recovery

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Synopsis Effect of food deprivation and refeeding on metabolic parameters were studied in juvenile Rutilus rutilus, weighing 280–460 mg. Tissue hydration increased with the length of the starvation period, reaching a new steady state after 4–5 weeks. Total protein concentration remained constant at about 60% of dry body mass. The concentration of glycogen decreased during food deprivation, a new steady state being reached at about 30% of control values after 4 weeks. Refeeding caused a dramatic increase of glycogen concentration which exceeded the value in fed controls by 6- to 9-fold. This is seen as a tactic for rapid storage of food energy, to be used later for the synthesis of body materials. With respect to their responses to food deprivation the 12 enzymes investigated formed four groups: (1) activity unaffected by food deprivation or refeeding (COX, THIOL, CK, GOT); (2) activity drops to about 60% of control value during the initial phase of food deprivation but remains constant thereafter (PK, LDH, Pase); (3) slow but continuous decrease in activity during the whole period of starvation, i.e. up to 7 weeks (PFK, OGDH, CS, FBPase); (4) activity increases during food deprivation, decreases again upon refeeding (GPT). A model is discussed which distinguishes between four phases in the general response of young fish to food deprivation and refeeding: stress, transition, adaptation, and recovery.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00005981

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Control of mitochondrial and cellular respiration by oxygen (1995)

Gnaiger, Erich ; Steinlechner-Maran, Rosmarie ; Méndez, Gabriela ; [et al.]

Springer

Journal of bioenergetics and biomembranes 27 (1995), S. 583-596

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ISSN: 1573-6881

Keywords: Oxygen limitation ; p 50 ; critical oxygen pressure ; respirometry ; polarographic oxygen sensor ; human endothelial cells ; rat liver mitochondria ; intracellular $$p_{O_2 } $$ ; oxygen gradients ; kinetics ; nonequilibrium thermodynamics

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Physics

Notes: Abstract Control and regulation of mitochondrial and cellular respiration by oxygen is discussed with three aims: (1) A review of intracellular oxygen levels and gradients, particularly in heart, emphasizes the dominance of extracellular oxygen gradients. Intracellular oxygen pressure, $$p_{O_2 } $$ , is low, typically one to two orders of magnitude below incubation conditions used routinely for the study of respiratory control in isolated mitochondria. The $$p_{O_2 } $$ range of respiratory control by oxygen overlaps with cellular oxygen profiles, indicating the significance of $$p_{O_2 } $$ in actual metabolic regulation. (2) A methodologically detailed discussion of high-resolution respirometry is necessary for the controversial topic of respiratory control by oxygen, since the risk of methodological artefact is closely connected with far-reaching theoretical implications. Instrumental and analytical errors may mask effects of energetic state and partially explain the divergent views on the regulatory role of intracellular $$p_{O_2 } $$ . Oxygen pressure for half-maximum respiration,p 50, in isolated mitochondria at state 4 was 0.025 kPa (0.2 Torr; 0.3 ΜM O2), whereasp 50 in endothelial cells was 0.06–0.08 kPa (0.5 Torr). (3) A model derived from the thermodynamics of irreversible processes was developed which quantitatively accounts for near-hyperbolic flux/ $$p_{O_2 } $$ relations in isolated mitochondria. The apparentp 50 is a function of redox potential and protonmotive force. The protonmotive force collapses after uncoupling and consequently causes a decrease inp 50. Whereas it is becoming accepted that flux control is shared by several enzymes, insufficient attention is paid to the notion of complementary kinetic and thermodynamic flux control mechanisms.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02111656

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Pseudomonas aeruginosa clinical and environmental isolates constitute a single population with high phenotypic diversity. (2014)

Christian Santos-Medellín; María-Victoria Grosso-Becerra; Abigail González-Valdez; José-Luis Méndez; Gabriela Delgado; Rosario Morales-Espinosa; Luis Servín-González; Luis-David Alcaraz; Gloria Soberon-Chavez

BioMed Central

In: BMC Genomics

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Publication Date: 2014-04-29

Description: Background: Pseudomonas aeruginosa is an opportunistic pathogen with a high incidence of hospital infections that represents a threat to immune compromised patients. Genomic studies have shown that, in contrast to other pathogenic bacteria, clinical and environmental isolates do not show particular genomic differences. In addition, genetic variability of all the P. aeruginosa strains whose genomes have been sequenced is extremely low. This low genomic variability might be explained if clinical strains constitute a subpopulation of this bacterial species present in environments that are close to human populations, which preferentially produce virulence associated traits. Results: In this work, we sequenced the genomes and performed phenotypic descriptions for four non-human P. aeruginosa isolates collected from a plant, the ocean, a water-spring, and from a dolphin stomach. We show that the four strains are phenotypically diverse and that this is not reflected in genomic variability, since their genomes are almost identical. Furthermore, we performed a detailed comparative genomic analysis of all the seven previously completed P. aeruginosa genomes with the four strains studied in this work by means of describing its core and pan-genomes. Conclusions: Contrary to what has been described for other bacteria, we found that P. aeruginosa's core genome is constituted by a high proportion of genes and that its pan-genome is thus relatively small. Considering the high degree of genomic conservation between isolates of P. aeruginosa from diverse environments, including human tissues, some implications for the treatment of infections are discussed. This work also represents a methodological contribution for the genomic study of P. aeruginosa, since the pan-genome database of protein comparisons is provided.

Electronic ISSN: 1471-2164

Topics: Biology