Search results for "Oxygen transport"
showing 10 items of 63 documents
Closely related crabs from opposite niches adopt different mechanisms to adjust oxygen transport
2008
The successful colonization of new environments is often achieved through adaptations or key innovations of existing physiological or biochemical mechanisms. The oxygen supply in marine invertebrates represent a complex and deeply integrated system which plays a fundamental role in animal adaptive plasticity. In particular, species which inhabit highly stochastic environments as shallow water or intertidal bands, have to cope with extremely different regimes of oxygen availability and effectively maintain a stable aerobic metabolism. Within this framework, we have focused on comparative physiology of Portunid Crabs hemocyanin, to evaluate the role molecular heterogeneity and functional plas…
Monitoring of rheologic variables during postoperative high-dose brachytherapy for uterine cancer.
2004
Oxygenation of tumor tissue has recently been assed an important prerequisite for the effectiveness of radiotherapy in cervical cancer. Hyperviscosity is a common phenomenon in malignancy and a cause of reduced oxygen transport capacity that would favour tissue hypoxia. Hemorheological variables were serially tested preoperatively, during four cycles of fractionated adjuvant IR192 HDR after loading radiation (HDR-AL) of the vaginal vault (weekly intervals), and 6 months postoperatively in patients with cervical (n=12) and endometrial cancer (n=26). Women who were scheduled for benign tumor surgery served as controls (n=29). Preoperatively, in cervical and endometrial cancer patients, mean …
Immunological properties of oxygen-transport proteins: hemoglobin, hemocyanin and hemerythrin
2016
It is now well documented that peptides with enhanced or alternative functionality (termed cryptides) can be liberated from larger, and sometimes inactive, proteins. A primary example of this phenomenon is the oxygen-transport protein hemoglobin. Aside from respiration, hemoglobin and hemoglobin-derived peptides have been associated with immune modulation, hematopoiesis, signal transduction and microbicidal activities in metazoans. Likewise, the functional equivalents to hemoglobin in invertebrates, namely hemocyanin and hemerythrin, act as potent immune effectors under certain physiological conditions. The purpose of this review is to evaluate the true extent of oxygen-transport protein dy…
Entrapment and characterization of functional allosteric conformers of hemocyanin in sol–gel matrices
2016
Hemocyanins are giant oxygen transport proteins of molluscs and arthropods, which display high cooperativity and a complex pattern of conformations, generated by hierarchical allosteric interactions of their complex quaternary structure. A still unanswered question is the correlation between the functional properties of the postulated conformers and structural features that govern their oxygen binding, such as metal complex coordination. In this study we focus on the dodecameric hemocyanin of the crustacean Carcinus aestuarii, with the aim to obtain a functional and structural characterization of the individual conformational states giving rise to cooperativity, by entrapping hemocyanin int…
Muscle metabolic profile and oxygen transport capacity as determinants of aerobic and anaerobic thresholds
1988
Aerobic and anaerobic thresholds determined by different methods in repeated exercise tests were correlated with cardiorespiratory variables and variables of muscle metabolic profile in 33 men aged 20–50 years. Aerobic threshold was determined from blood lactate, ventilation, and respiratory gas exchange by two methods (AerT1 and AerT2) and anaerobic threshold from venous lactate (AnTLa), from ventilation and gas exchange (AnTr) and by using the criterion of 4 mmol·l−1 of venous lactate (AnT4mmol). In addition to ordinary correlative analyses, applications of LISREL models were used. The 8 explanatory variables chosen for the regression analyses were height, relative heart volume, relative …
Enthalpic and entropic contributions of water molecules to the functional T → R transition of human hemoglobin in solution
1992
Generalized solvent-mediated forces contribute to free energy at the functional T → R transition of human hemoglobin A (HbA). Their contribution is here sorted out quantitatively in both its enthalpic and entropic parts, along with the average number of water molecules involved. The latter (about 75 waters in average) must be considered together with HbA as one statistically defined functional unit for oxygen transport. Their configurations are expected to undergo frequent structural rearrangements. Lifetimes of statistically relevant configurations do not need to (although, of course, they may) exceed by more than a factor 5 the normal H-bond lifetimes of the pure solvent. Compared to the …
Screening the bulk properties and reducibility of Fe-doped Mn2O3 from first principles calculations
2017
Abstract Manganese oxides, particularly Mn 2 O 3 , have demonstrated great potential for oxygen carrier materials in chemical looping applications. The application of these materials in the industrial scale is hindered by thermodynamic restrictions related to the reoxidation process. This disadvantage can be overcome by doping the oxide with a guest cation. Iron is one of the most promising dopants, but the atomic-level understanding of its effects on the properties of α-Mn 2 O 3 is incomplete. Herein, we report a systematic GGA+U study of the bulk properties and reducibility of Fe x Mn 2-x O 3 (0 ≤ x ≤ 2) as a function of Fe dopant concentration. In particular, we focus on a representative…
Differential expression of the corticosteroid receptors GR1, GR2 and MR in rainbow trout organs with slow release cortisol implants
2012
The present study describes the transcriptional levels of the corticosteroid receptors (CRs) GR1, GR2 and MR in the different organs of the rainbow trout (Oncorhynchus mykiss) in response to a slow release of cortisol, throughout a 10-day period. We show that after short term (1 day after cortisol implantation), when the plasma levels of cortisol emulate an acute stress, the GR2 and MR expression levels were upregulated in the brain and head kidney tissues. This result reflects the role of these organs as regulators of the stress response. In general, the rest of the organs, especially gills, intestine, liver, muscle and spleen, showed decreased transcriptional levels of GR1, GR2 and MR, al…
Tissue gradients of energy metabolites mirror oxygen tension gradients in a rat mammary carcinoma model
2001
Abstract Purpose: It has been shown that oxygen gradients exist in R3230AC tumors grown in window chambers. The fascial surface is better oxygenated than the tumor surface. The purpose of the present study was to determine whether gradients exist for energy metabolites and other end points related to oxygen transport. Methods and Materials: Imaging bioluminescence was used to measure ATP, glucose, and lactate in cryosections of R3230AC tumors. Mean vessel density and hypoxic tissue fraction were assessed using immunohistochemistry. Tumor redox ratio was assessed by redox ratio scanning. Results: Lactate content and hypoxic fraction increased, whereas ATP, glucose, redox ratio, and vessel de…
Oxygen Transport in Tumors
1996
Experimental evidence suggests that the hypoxic fraction in solid tumors may influence its growth, may increase its malignant potential, and may reduce its sensitivity towards non-surgical treatment modalities (e.g., standard irradiation, certain anticancer drugs). The role of the tumor O2 status in radio-/chemotherapy and its impact on relevant tumor biological characteristics of tumors are summarized in Table 1.