The hypoxia response pathway in the Antarctic fish Notothenia coriiceps is functional despite a poly Q/E insertion mutation in HIF-1α.

Antarctic notothenioid fishes, inhabiting the oxygen-rich Southern Ocean, possess a polyglutamine and glutamic acid (poly Q/E) insertion mutation in the master transcriptional regulator of oxygen homeostasis, hypoxia- inducible factor-1α (HIF-1α). To determine if this mutation impairs the ability of HIF-1 to regulate gene expression in response to hypoxia, we exposed Notothenia coriiceps, with a poly Q/E insertion mutation in HIF-1α that is 9 amino acids long, to hypoxia (2.3 mg L-1 O2) or normoxia (10 mg L -1 O2) for 12 h. Heart ventricles, brain, liver, and gill tissue were harvested and changes in gene expression quantified using RNA sequencing. Levels of glycogen and lactate were also quantified to determine if anaerobic metabolism increases in response to hypoxia. Exposure to hypoxia resulted in 818 unique differentially expressed genes (DEGs) in liver tissue of N. coriiceps. Many hypoxic genes were induced, including ones involved in the MAP kinase and FoxO pathways, glycolytic metabolism, and vascular remodeling. In contrast, there were fewer than 104 unique DEGs in each of the other tissues sampled. Lactate levels significantly increased in liver in response to hypoxia, indicating that anaerobic metabolism increases in response to hypoxia in this tissue. Overall, our results indicate that the hypoxia response pathway is functional in N. coriiceps despite a poly Q/E mutation in HIF-1α, and confirm that Antarctic fishes are capable of altering gene expression in response to hypoxia.

A prospective study of type 2 diabetes, metformin use, and risk of breast cancer.

BACKGROUND: Type 2 diabetes (T2D) has been associated with increased breast cancer risk, but commonly prescribed antidiabetic medications such as metformin may reduce risk. Few studies have investigated T2D and medications together in relation to breast cancer. PATIENTS AND METHODS: Data came from 44 541 Sister Study participants aged 35 to 74 years at enrollment (2003-2009) who satisfied eligibility criteria, followed through 15 September 2017. Information on time-varying, self-reported, physician-diagnosed, prevalent and incident T2D, use of antidiabetic medications, and covariates was obtained from baseline and follow-up questionnaires. Incident breast cancers were confirmed with medical records. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated. RESULTS: During follow-up (median, 8.6 years), 2678 breast cancers were diagnosed at least 1 year after enrollment. There were 3227 women (7.2%) with prevalent and 2389 (5.3%) with incident T2D, among whom 61% (n = 3386) were ever treated with metformin. There was no overall association between T2D and breast cancer risk (HR 0.99; 95% CI, 0.87-1.13). However, T2D was associated with increased risk of triple-negative breast cancer (HR 1.40; 95% CI, 0.90-2.16). Compared with not having T2D, T2D with metformin use was not associated with overall breast cancer risk (HR 0.98; 95% CI, 0.83-1.15), but it was associated with decreased risk of estrogen receptor (ER)-positive breast cancer (HR 0.86; 95% CI 0.70-1.05) and increased risk of ER-negative (HR 1.25; 95% CI, 0.84-1.88) and triple-negative breast cancer (HR 1.74; 95% CI, 1.06-2.83). The inverse association with ER-positive cancer was stronger for longer duration (≥10 year) metformin use (HR 0.62; 95% CI, 0.38-1.01; P for trend = 0.09). Results were supported by sensitivity analyses. CONCLUSION: Our findings suggest that associations between T2D and breast cancer may differ by hormone receptor status and that associations between T2D and ER-positive breast cancer may be reduced by long-term metformin use.

Characterization of the hypoxia-inducible factor-1 pathway in hearts of Antarctic notothenioid fishes.

The ability of Antarctic notothenioid fishes to mount a robust molecular response to hypoxia is largely unknown. The transcription factor, hypoxia-inducible factor-1 (HIF-1), a heterodimer of HIF-1α and HIF-1ß subunits, is the master regulator of oxygen homeostasis in most metazoans. We sought to determine if, in the hearts of Antarctic notothenioids, HIF-1 is activated and functional in response to either an acute heat stress or hypoxia. The red-blooded Notothenia coriiceps and the hemoglobinless icefish, Chaenocephalus aceratus, were exposed to their critical thermal maximum (CTMAX) or hypoxia (5.0 ± 0.3 mg of O2 L-1) for 2 h. Additionally, N. coriiceps was exposed to 2.3 ± 0.3 mg of O2 L-1 for 12 h, and red-blooded Gobionotothen gibberifrons was exposed to both levels of hypoxia. Levels of HIF-1α were quantified in nuclei isolated from heart ventricles using western blotting. Transcript levels of genes involved in anaerobic metabolism, and known to be regulated by HIF-1, were quantified by real-time PCR, and lactate levels were measured in heart ventricles. Protein levels of HIF-1α increase in nuclei of hearts of N. coriiceps and C. aceratus in response to exposure to CTMAX and in hearts of N. coriiceps exposed to severe hypoxia, yet mRNA levels of anaerobic metabolic genes do not increase in any species, nor do lactate levels increase, suggesting that HIF-1 does not stimulate metabolic remodeling in hearts of notothenioids under these conditions. Together, these data suggest that Antarctic notothenioids may be vulnerable to hypoxic events, which are likely to increase with climate warming.

Interactions between a Polygenic Risk Score and Non-genetic Risk Factors in Young-Onset Breast Cancer.

Most gene-environmental studies have focused on breast cancers generally, the preponderance of which occur after age 50. Young-onset breast cancers (YOBC) tend to be aggressive and may be etiologically different. The goal of this analysis was to assess interactions between an established 77-SNP polygenic risk score (PRS) and non-genetic risk factors for YOBC. We constructed the PRS using a family-based study of 1,291 women diagnosed with breast cancer before age 50 and their parents and unaffected sisters. We used conditional logistic regression to analyze interactions between the PRS and 14 established risk factors. In further analyses we assessed the same interactions, but for invasive cancer, estrogen receptor (ER) positive cancer and with broader inclusion of racial/ethnic groups. Results showed a decreased association between the PRS and YOBC risk for women who had ever used hormonal birth control (odds ratio [OR] = 2.20 versus 3.89) and a stronger association between the PRS and YOBC risk in pre-menopausal women (OR = 2.46 versus 1.23). Restricting the analysis to ER+ cancers or invasive cancers or using samples from all ethnic groups produced similar results. In conclusion, the PRS may interact with hormonal birth control use and with menopausal status on risk of YOBC.

Oncologic treatment strategies and relative survival of patients with stage I-III rectal cancer - A EURECCA international comparison between the Netherlands, Belgium, Denmark, Sweden, England, Ireland, Spain, and Lithuania.

INTRODUCTION: The aim of this EURECCA international comparison is to compare oncologic treatment strategies and relative survival of patients with stage I-III rectal cancer between European countries. MATERIAL AND METHODS: Population-based national cohort data from the Netherlands (NL), Belgium (BE), Denmark (DK), Sweden (SE), England (ENG), Ireland (IE), Spain (ES), and single-centre data from Lithuania (LT) were obtained. All operated patients with (y)pTNM stage I-III rectal cancer diagnosed between 2004 and 2009 were included. Oncologic treatment strategies and relative survival were calculated and compared between neighbouring countries. RESULTS: We included 57,120 patients. Treatment strategies differed between NL and BE (p < 0.001), DK and SE (p < 0.001), and ENG and IE (p < 0.001). More preoperative radiotherapy as single treatment before surgery was administered in NL compared with BE (59.7% vs. 13.1%), in SE compared with DK (55.1% vs. 10.4%), and in ENG compared with IE (15.2% vs. 9.6%). Less postoperative chemotherapy was given in NL (9.6% vs. 39.1%), in SE (7.9% vs. 14.1%), and in IE (12.6% vs. 18.5%) compared with their neighbouring country. In ES, 55.1% of patients received preoperative chemoradiation and 62.3% postoperative chemotherapy. There were no significant differences in relative survival between neighbouring countries. CONCLUSION: Large differences in oncologic treatment strategies for patients with (y)pTNM I-III rectal cancer were observed across European countries. No clear relation between oncologic treatment strategies and relative survival was observed. Further research into selection criteria for specific treatments could eventually lead to individualised and optimal treatment for patients with non-metastasised rectal cancer.

Telephone-based weight loss support for patients with knee osteoarthritis: a pragmatic randomised controlled trial.

OBJECTIVE: To determine the effectiveness of telephone-based weight loss support in reducing the intensity of knee pain in patients with knee osteoarthritis, who are overweight or obese, compared to usual care. DESIGN: We conducted a parallel randomised controlled trial (RCT), embedded within a cohort multiple RCT of patients on a waiting list for outpatient orthopaedic consultation at a tertiary referral hospital in NSW, Australia. Patients with knee osteoarthritis, classified as overweight or obese [body mass index (BMI) between ≥27 kg/m2 and <40 kg/m2] were randomly allocated to receive referral to an existing non-disease specific government funded 6-month telephone-based weight management and healthy lifestyle service or usual care. The primary outcome was knee pain intensity measured using an 11-point numerical rating scale (NRS) over 6-month follow-up. A number of secondary outcomes, including self-reported weight were measured. Data analysis was by intention-to-treat according to a pre-published analysis plan. RESULTS: Between May 19 and June 30 2015, 120 patients were randomly assigned to the intervention (59 analysed, one post-randomisation exclusion) or usual care (60 analysed). We found no statistically significant between group differences in pain intensity [area under the curve (AUC), mean difference 5.4, 95%CI: -13.7 to 24.5, P = 0.58] or weight change at 6 months (self-reported; mean difference -0.4, 95%CI: -2.6 to 1.8, P = 0.74). CONCLUSIONS: Among patients with knee osteoarthritis who are overweight, telephone-based weight loss support, provided using an existing 6-month weight management and healthy lifestyle service did not reduce knee pain intensity or weight, compared with usual care. TRIAL REGISTRATION NUMBER: ACTRN12615000490572.

Informal caregiving in head and neck cancer: caregiving activities and psychological well-being.

The purpose of this study was to quantify the general cancer support activities that long-term carers of head and neck cancer (HNC) survivors engage in; and the relationships between these care activities and psychological well-being. Respondents answered a survey detailing their caring activities, the amount of time that they spent on those activities and how comfortable they felt engaging in them. Psychological well-being was assessed by the Depression Anxiety Stress Scales-21. A total of 197 carers took part in the study. The majority (76%) were women, mean age 57.4. Mean time since diagnosis was 6.2 years. In the past month, 45% of carers did not spend any extra time per week helping their relative/friend with general caring activities such as cleaning the house; 31% spent 1-19 hr/week and 23% spent 20 or more hours/week doing so. Most carers were comfortable assisting their relative/friend, though more carers felt uncomfortable assisting with HNC-specific support tasks (31% uncomfortable helping with medication) compared with general support tasks (7% uncomfortable helping with appointments). Feeling uncomfortable with head and neck-specific care tasks was a significant predictor of experiencing depression and anxiety.

Hypoxia-Inducible Factor-1α in Antarctic notothenioids contains a polyglutamine and glutamic acid insert that varies in length with phylogeny.

The long evolution of the Antarctic perciform suborder of Notothenioidei in the icy, oxygen-rich waters of the Southern Ocean may have reduced selective pressure to maintain a hypoxic response. To test this hypothesis, cDNA of the key transcriptional regulator of hypoxic genes, hypoxia-inducible factor-1α (HIF-1α), was sequenced in heart ventricles of the red-blooded notothenioid, Notothenia coriiceps, and the hemoglobinless icefish, Chaenocephalus aceratus. HIF-1α cDNA is 4500 base pairs (bp) long and encodes 755 amino acids in N. coriiceps, and in C. aceratus, HIF-1α is 3576 bp long and encodes 779 amino acids. All functional domains of HIF-1α are highly conserved compared to other teleosts, but HIF-1α contains a polyglutamine/glutamic acid (polyQ/E) insert 9 amino acids long in N. coriiceps and 34 amino acids long in C. aceratus. Sequencing of this region in four additional species, representing three families of notothenioids, revealed that the length of the polyQ/E insert varies with phylogeny. Icefishes, the crown family of notothenioids, contain the longest polyQ/E inserts, ranging between16 and 34 amino acids long, whereas the basal, cold-temperate notothenioid, Eleginops maclovinus, contains a polyQ/E insert only 4 amino acids long. PolyQ/E inserts may affect dimerization of HIF-1α and HIF-1ß, HIF-1 translocation into the nucleus and/or DNA binding.

Adjuvant chemotherapy and relative survival of patients with stage II colon cancer - A EURECCA international comparison between the Netherlands, Denmark, Sweden, England, Ireland, Belgium, and Lithuania.

BACKGROUND: The aim of the present EURECCA international comparison is to compare adjuvant chemotherapy and relative survival of patients with stage II colon cancer between European countries. METHODS: Population-based national cohort data (2004-2009) from the Netherlands (NL), Denmark (DK), Sweden (SE), England (ENG), Ireland (IE), and Belgium (BE) were obtained, as well as single-centre data from Lithuania. All surgically treated patients with stage II colon cancer were included. The proportion of patients receiving adjuvant chemotherapy was calculated and compared between countries. Besides, relative survival was calculated and compared between countries. RESULTS: Overall, 59,154 patients were included. The proportion of patients receiving adjuvant chemotherapy ranged from 7.1% to 29.0% (p < 0.001). Compared with NL, a better adjusted relative survival was observed in SE (stage II: relative excess risks (RER) 0.53, 95% confidence interval (CI) 0.44-0.64; p < 0.001), and BE (stage II: RER 0.84, 95% CI 0.76-0.92; p < 0.001), and in IE for patients with stage IIA disease (RER 0.80, 95% CI 0.65-0.98; p = 0.03). CONCLUSION: The proportion of patients with stage II colon cancer receiving adjuvant chemotherapy varied largely between seven European countries. No clear linear pattern between adjuvant chemotherapy and adjusted relative survival was observed. Compared with NL, SE and BE showed an improved adjusted relative survival for stage II disease, and IE for patients with stage IIA disease only. Further research into selection criteria for adjuvant chemotherapy could eventually lead to individually tailored, optimal treatment of patients with stage II colon cancer.

Coagulation-driven platelet activation reduces cholestatic liver injury and fibrosis in mice.

BACKGROUND: The coagulation cascade has been shown to participate in chronic liver injury and fibrosis, but the contribution of various thrombin targets, such as protease activated receptors (PARs) and fibrin(ogen), has not been fully described. Emerging evidence suggests that in some experimental settings of chronic liver injury, platelets can promote liver repair and inhibit liver fibrosis. However, the precise mechanisms linking coagulation and platelet function to hepatic tissue changes following injury remain poorly defined. OBJECTIVES: To determine the role of PAR-4, a key thrombin receptor on mouse platelets, and fibrin(ogen) engagement of the platelet αII b ß3 integrin (αIIb ß3 ) in a model of cholestatic liver injury and fibrosis. METHODS: Biliary and hepatic injury was characterized following 4 week administration of the bile duct toxicant α-naphthylisothiocyanate (ANIT) (0.025%) in PAR-4-deficient mice, mice expressing a mutant form of fibrin(ogen) incapable of binding integrin αII b ß3 (Fibγ(Δ5) ), and wild-type mice. RESULTS: Elevated plasma thrombin-antithrombin and serotonin levels, hepatic fibrin deposition, and platelet accumulation in liver accompanied hepatocellular injury and fibrosis in ANIT-treated wild-type mice. PAR-4 deficiency reduced plasma serotonin levels, increased serum bile acid concentration, and exacerbated ANIT-induced hepatocellular injury and peribiliary fibrosis. Compared with PAR-4-deficient mice, ANIT-treated Fibγ(Δ5) mice displayed more widespread hepatocellular necrosis accompanied by marked inflammation, robust fibroblast activation, and extensive liver fibrosis. CONCLUSIONS: Collectively, the results indicate that PAR-4 and fibrin-αII b ß3 integrin engagement, pathways coupling coagulation to platelet activation, each exert hepatoprotective effects during chronic cholestasis.

Bladder cancer in renal allograft recipients: risk factors and outcomes.

BACKGROUND: Solid organ transplant recipients have an increased cancer risk owing to immunosuppression and oncogenic viral infections. We report on the incidence and types of bladder cancer in kidney transplant recipients in Ireland, describing possible additional risk factors and outcomes in these patients. METHODS: We identified kidney transplant recipients diagnosed with de novo bladder cancer between January 1, 1994, and July 31, 2012, by integrating data from the Irish National Cancer Registry and National Renal Transplant Registry. We calculated the standardized incidence ratio (SIR) and examined patient and tumor characteristics and 1-year survival rate. RESULTS: Fifteen patients were diagnosed with de novo bladder cancer during the study period, representing 0.48% of kidney transplant recipients. The SIR was 2.5 (95% CI, 1.4-4.2; P < .001). The mean interval between transplantation and diagnosis of bladder tumor was 8.6 years and mean age at time of diagnosis was 55.7 years. Sixty percent of patients were male. The tumor types were transitional cell carcinoma (9 patients), squamous cell carcinoma (3 patients), adenocarcinoma (1 patient), carcinoma in situ (1 patient), and diffuse large B-cell lymphoma (1 patient). Beside immunosuppression, risk factors associated with bladder cancer were urogenital disease (6 patients), cyclophosphamide exposure (2 patients), BK nephropathy (1 patient), analgesic nephropathy (1 patient), and extensive smoking (1 patient). Eight patients underwent radical cystectomy for invasive tumors, with resection of other pelvic organs in 7 patients. Mortality rate within the first year was 40%. CONCLUSION: Bladder cancer occurred more commonly in kidney transplant recipients with a predominance of aggressive tumors and a high mortality. In patients with preexisting risk factors such as urologic abnormalities and cyclophosphamide exposure careful assessment before transplantation and vigilant monitoring posttransplantation with a low threshold for cystoscopy may improve outcomes.

Hearts of some Antarctic fishes lack mitochondrial creatine kinase.

Creatine kinase (CK; EC 2.7.3.2) functions as a spatial and temporal energy buffer, dampening fluctuations in ATP levels as ATP supply and demand change. There are four CK isoforms in mammals, two cytosolic isoforms (muscle [M-CK] and brain [B-CK]), and two mitochondrial isoforms (ubiquitous [uMtCK] and sarcomeric [sMtCK]). Mammalian oxidative muscle couples expression of sMtCK with M-CK, creating an energy shuttle between mitochondria and myofibrils. We hypothesized that the expression pattern and activity of CK would differ between hearts of red- and white-blooded Antarctic notothenioid fishes due to their striking differences in cardiac ultrastructure. Hearts of white-blooded icefishes (family Channichthyidae) have significantly higher mitochondrial densities compared to red-blooded species, decreasing the diffusion distance for ATP between mitochondria and myofibrils and potentially minimizing the need for CK. The distribution of CK isoforms was evaluated using western blotting and maximal activity of CK was measured in mitochondrial and cytosolic fractions and tissue homogenates of heart ventricles of red- and white-blooded notothenioids. Transcript abundance of sMtCK and M-CK was also quantified. Overall, CK activity is similar between hearts of red- and white-blooded notothenioids but hearts of icefishes lack MtCK and have higher activities of M-CK in the cytosol compared to red-blooded fishes. The absence of MtCK may compromise cardiac function under stressful conditions when ATP supply becomes limiting.

Relationship between hair cortisol and perceived chronic stress in a diverse sample.

Hair cortisol (CORT) is a biomarker of chronic stress via long-term alterations in hypothalamus-pituitary-adrenal axis activity. Relationships to perceived stress measures, however, have rarely been specifically investigated. A diverse sample of 135 adults participated in a study assessing relationships between chronic stress indicator CORT to perceived stress and health indicators. CORT was not correlated to single perceived domain indices but with a global stress composite. Differences in objective and subjective measures were found for sociodemographics: racial/ethnic identity, sex and socioeconomic status (SES). Race by SES interactions predicted both CORT and perceived stress, but produced a complex and partially unanticipated pattern of results. For minorities, low and high SES showed the highest CORT, with mid-SES showing the lowest CORT; there was little change in perceived stress at all levels of SES. For non-minorities, mid-SES showed the highest CORT, with decreases in both CORT and perceived stress in high SES. The unanticipated findings of deleterious outcomes for high SES minorities highlight the importance of investigating potential stressors and moderators, including perceived discrimination and social identity. Moreover, these results suggest that CORT may not always correlate with single stress indices but may provide a global assessment of chronic stress, with implications for the allostatic load literature.

Nitric oxide synthase is not expressed, nor up-regulated in response to cold acclimation in liver or muscle of threespine stickleback (Gasterosteus aculeatus).

There are three isoforms of the enzyme nitric oxide synthase (NOS) in mammals: endothelial NOS (eNOS), inducible NOS (iNOS) and neuronal NOS (nNOS). All three isoforms oxidize arginine to citrulline in a reaction producing nitric oxide (NO), which regulates multiple signaling pathways and physiological functions in mammals. Less is known about NOS in fishes, in which the existence of eNOS is controversial. Nevertheless, multiple adjustments occur during cold acclimation of fishes, several of which are known to be mediated by eNOS and NO in mammals, including mitochondrial biogenesis, vasodilation and angiogenesis. We hypothesized that if NOS was present, and NO stimulated these pathways in fishes, then the activity of NOS would increase during cold acclimation. To test this hypothesis, we measured the activity and mRNA levels of NOS in three tissues (liver, oxidative muscle, glycolytic muscle) known to undergo mitochondrial biogenesis and/or angiogenesis. Measurements were made in the threespine stickleback, Gasterosteus aculeatus acclimated to either warm (20°C) or cold (8°C) temperature for 9weeks. Cold-acclimated fish were harvested on days 1-3, and at weeks 1, 4 and 9 at 8°C, while warm-acclimated fish were harvested on day 0 and after 9 weeks at 20°C. Transcript levels of NOS were quantified using quantitative real-time PCR, and NOS activity was measured using a radiochemical assay, which detected the rate of catabolism of (14)C-labeled arginine. Neither NOS activity nor transcripts were detected in oxidative muscle or glycolytic muscle of warm- or cold-acclimated stickleback, although transcript levels of nNOS and NOS activity were detected in brain. Arginine catabolism was detected in liver of animals held at 10°C and 20°C for 9weeks, but was due to arginase activity, rather than NOS. Consistent with this, NOS transcripts were undetectable in liver. The absence of NOS in liver and muscles of stickleback indicates that signaling molecules other than NO likely mediate physiological changes during cold acclimation in stickleback.

The molecular basis of aerobic metabolic remodeling differs between oxidative muscle and liver of threespine sticklebacks in response to cold acclimation.

We sought to determine the molecular basis of elevations in aerobic metabolic capacity in the oxidative muscle and liver of Gasterosteus aculeatus in response to cold acclimation. Fishes were cold- or warm-acclimated for 9 wk and harvested on days 1, 2, and 3 and weeks 1, 4, and 9 of cold acclimation at 8 degrees C, and on day 1 and week 9 of warm acclimation at 20 degrees C. Mitochondrial volume density was quantified using transmission electron microscopy and stereological techniques in warm- and cold-acclimated fishes harvested after 9 wk at 20 or 8 degrees C. Changes in aerobic metabolic capacity were assessed by measuring the maximal activity of citrate synthase (CS) and cytochrome-c oxidase (COX) in fishes harvested throughout the acclimation period. Transcript levels of the aerobic metabolic genes CS, COXIII, and COXIV, and known regulators of mitochondrial biogenesis, including peroxisome proliferator-activated receptor-gamma coactivators-1alpha and -1beta (PGC-1alpha and PGC-1beta), nuclear respiratory factor-1 (NRF-1), and mitochondrial transcription factor-A were measured in fishes harvested throughout the acclimation period using quantitative real-time PCR. The maximal activities of CS and COX increased in response to cold acclimation in both tissues, but mitochondrial volume density only increased in oxidative muscle (P < 0.05). The time course for changes in aerobic metabolic capacity differed between liver and muscle. The expression of CS increased within 1 wk of cold acclimation in liver and was correlated with an increase in mRNA levels of NRF-1 and PGC-1beta. Transcript levels of aerobic metabolic genes increased later in oxidative muscle, between weeks 4 and 9 of cold acclimation and were correlated with an increase in mRNA levels of NRF-1 and PGC-1alpha. These results show that aerobic metabolic remodeling differs between liver and muscle in response to cold acclimation and may be triggered by different stimuli.

Muscle fine structure may maintain the function of oxidative fibres in haemoglobinless Antarctic fishes.

Muscle fine structure and metabolism were examined in four species of Antarctic fishes that vary in their expression of haemoglobin (Hb). To determine how locomotory pectoral muscles maintain function, metabolic capacity, capillary supply and fibre ultrastructure were examined in two nototheniid species that express Hb (Notothenia coriiceps and Gobionotothen gibberifrons) and two species of channichthyid icefish that lack Hb (Chaenocephalus aceratus and Chionodraco rastrospinosus). Surprisingly, icefish have higher densities of mitochondria than red-blooded species (C. aceratus, 53+/-3% of cell volume; C. rastrospinosus, 39+/-3%; N. coriiceps, 29+/-3%; G. gibberifrons, 25+/-1%). Despite higher mitochondrial densities the aerobic metabolic capacities per g wet mass, estimated from measurements of maximal activities of key metabolic enzymes, are lower in icefish compared to red-blooded species. This apparent incongruity can be explained by the significantly lower mitochondrial cristae surface area per unit mitochondrion volume in icefishes (C. aceratus, 20.8+/-1.6 microm(-1); C. rastrospinosus, 25.5+/-1.8 microm(-1)) compared to red-blooded species (N. coriiceps, 33.6+/-3.0 microm(-1); G. gibberifrons, 37.7+/-3.6 microm(-1)). Consequently, the cristae surface area per unit muscle mass is conserved at approximately 9 m(2)g(-1). Although high mitochondrial densities in icefish muscle do not enhance aerobic metabolic capacity, they may facilitate intracellular oxygen movement because oxygen is more soluble in lipid, including the hydrocarbon core of intracellular membrane systems, than in aqueous cytoplasm. This may be particularly vital in icefish, which have larger oxidative muscle fibres compared to red-blooded nototheniods (C. aceratus, 2932+/-428 microm(2); C. rastrospinosus, 9352+/-318 microm(2); N. coriiceps, 1843+/-312 microm(2); G. gibberifrons, 2103+/-194 microm(2)). These large fibres contribute to a relatively low capillary density, which is partially compensated for in icefish by a high index of tortuosity in the capillary bed (C. aceratus=1.4, N. coriiceps=1.1).

Effects of anoxia and the mitochondrion on expression of aerobic nuclear COX genes in yeast: evidence for a signaling pathway from the mitochondrial genome to the nucleus.

Eucaryotic cells contain at least two general classes of oxygen-regulated nuclear genes: aerobic genes and hypoxic genes. Hypoxic genes are induced upon exposure to anoxia while aerobic genes are down-regulated. Recently, it has been reported that induction of some hypoxic nuclear genes in mammals and yeast requires mitochondrial respiration and that cytochrome-c oxidase functions as an oxygen sensor during this process. In this study, we have examined the role of the mitochondrion and cytochrome-c oxidase in the expression of yeast aerobic nuclear COX genes. We have found that the down-regulation of these genes in anoxic cells is reflected in reduced levels of their subunit polypeptides and that cytochrome-c oxidase subunits I, II, III, Vb, VI, VII, and VIIa are present in promitochondria from anoxic cells. By using nuclear cox mutants and mitochondrial rho(0) and mit(-) mutants, we have found that neither respiration nor cytochrome-c oxidase is required for the down-regulation of these genes in cells exposed to anoxia but that a mitochondrial genome is required for their full expression under both normoxic and anoxic conditions. This requirement for a mitochondrial genome is unrelated to the presence or absence of a functional holocytochrome-c oxidase. We have also found that the down-regulation of these genes in cells exposed to anoxia and the down-regulation that results from the absence of a mitochondrial genome are independent of one another. These findings indicate that the mitochondrial genome, acting independently of respiration and oxidative phosphorylation, affects the expression of the aerobic nuclear COX genes and suggest the existence of a signaling pathway from the mitochondrial genome to the nucleus.

Relationship quality of aggressive children and their siblings: a multiinformant, multimeasure investigation.

Sibling influence on the learning and enactment of aggressive behavior has been consistently demonstrated in studies of sibling relationships. Available evidence suggests that, compared with nonaggressive children's sibling interactions, the sibling interactions of aggressive children are marked by more frequent, intense, and prolonged aggressive behaviors. Although research on normative and aggressive children's sibling interactions has increased recently, a number of limitations in this literature were addressed in this study by: (1) including both an aggressive and nonaggressive comparison group, (2) examining both positive and negative features of sibling relationships, (3) employing a multimethod/multiinformant approach to data collection, and (4) utilizing an improved self-report method. In support of our hypotheses and consistent with previous research, results showed that aggressive children's sibling relationships were marked by higher levels of observed conflict and lower levels of self-reported positive features. When gender was examined, results showed that older brother/younger sister dyads were characterized by higher levels of negative features and lower levels of positive features.

Quantification of diffusion distance within the spongy myocardium of hearts from antarctic fishes.

We developed a stereological method for quantifying diffusion distance within spongy myocardium. Using this method we compared the hearts of three species of Antarctic fishes that vary in expression of oxygen-binding proteins. We examined hearts from Gobionotothen gibberifrons, a red-blooded species whose ventricle has myoglobin (Mb), and hearts of two species of icefish that lack hemoglobin (Hb) and vary in expression of cardiac Mb; Chionodraco rastrospinosus expresses Mb, Chaenocephalus aceratus does not. Average diffusion distance within ventricular tissue is greater in red-blooded Antarctic teleosts (9.82 + or - 1.37 microm) compared with icefish (C. rastrospinosus, 6.20 microm + or - 0.86; C. aceratus, 6.23 + or - 0.41 microm). Average diffusion distance to a mitochondrion parallels this trend because mitochondria are uniformly distributed within cardiac muscle. Results show that loss of Hb is correlated with increased trabeculation of heart ventricle. Loss of Mb however, is not correlated with an increase in trabeculation of ventricular tissue, despite significant differences in cellular ultrastructure compared with species that express the protein.

The interplay among cardiac ultrastructure, metabolism and the expression of oxygen-binding proteins in Antarctic fishes.

We examined heart ventricle from three species of Antarctic fishes that vary in their expression of oxygen-binding proteins to investigate how some of these fishes maintain cardiac function despite the loss of hemoglobin (Hb) and/or myoglobin (Mb). We quantified ultrastructural features and enzymatic indices of metabolic capacity in cardiac muscle from Gobionotothen gibberifrons, which expresses both Hb and Mb, Chionodraco rastrospinosus, which lacks Hb but expresses Mb, and Chaenocephalus aceratus, which lacks both Hb and Mb. The most striking difference in cellular architecture of the heart among these species is the percentage of cell volume occupied by mitochondria, V(v)(mit,f), which is greatest in Chaenocephalus aceratus (36.53+/-2.07), intermediate in Chionodraco rastrospinosus (20.10+/-0.74) and lowest in G. gibberifrons (15.87+/-0.74). There are also differences in mitochondrial morphologies among the three species. The surface area of inner mitochondrial membrane per volume of mitochondria, S(v)(imm, mit), varies inversely with mitochondrial volume density so that S(v)(imm,mit) is greatest in G. gibberifrons (29.63+/-1.62 microm(-)(1)), lower in Chionodraco rastrospinosus (21.52+/-0.69 microm(-)(1)) and smallest in Chaenocephalus aceratus (20.04+/-0.79 microm(-)(1)). The surface area of mitochondrial cristae per gram of tissue, however, is greater in Chaenocephalus aceratus than in G. gibberifrons and Chionodraco rastrospinosus, whose surface areas are similar. Despite significant ultrastructural differences, oxidative capacities, estimated from measurements of maximal activities per gram of tissue of enzymes from aerobic metabolic pathways, are similar among the three species. The combination of ultrastructural and enzymatic data indicates that there are differences in the density of electron transport chain proteins within the inner mitochondrial membrane; proteins are less densely packed within the cristae of hearts from Chaenocephalus aceratus than in the other two species. High mitochondrial densities within hearts from species that lack oxygen-binding proteins may help maintain oxygen flux by decreasing the diffusion distance between the ventricular lumen and mitochondrial membrane. Also, high mitochondrial densities result in a high intracellular lipid content, which may enhance oxygen diffusion because of the higher solubility of oxygen in lipid compared with cytoplasm. These results indicate that features of cardiac myocyte architecture in species lacking oxygen-binding proteins may maintain oxygen flux, ensuring that aerobic metabolic capacity is not diminished and that cardiac function is maintained.