Lay Perspectives on Receiving Different Types of Genomic Secondary Findings: a Qualitative Vignette Study.

Genome-wide sequencing may generate secondary findings (SFs). It is recommended that validated, clinically actionable SFs are reported back to patients/research participants. To explore publics' perspectives on the best ways to do this, we performed a vignette study among Finnish adults. Our aim was to explore how lay people react to different types of hypothetical genomic SFs. Participants received a hypothetical letter revealing a SF predisposing to a severe but actionable disease-cardiovascular disease (familial hypercholesterolemia, long QT syndrome) or cancer (Lynch syndrome, Li-Fraumeni syndrome). Participants (N = 29) wrote down their initial reactions, and discussed (N = 23) these in focus groups. Data were analyzed using inductive thematic analysis. Reactions to hypothetical SFs varied according to perceived severity and familiarity of the diseases. SFs for cancer were perceived as more threatening than for cardiovascular diseases, but less distressing than risk for psychiatric or neurological disorders, which participants spontaneously brought up. Illness severity in terms of lived experience, availability of treatment, stigma, and individual's responsibility to control risk were perceived to vary across these disease types. In addition to clinical validity and utility, SF reporting practices need to take into account potential familiarity and lay illness representations of different diseases. Illness representations may influence willingness to receive SFs, and individuals' reactions to this information.

"I would like to discuss it further with an expert": a focus group study of Finnish adults' perspectives on genetic secondary findings.

Lowered costs of genomic sequencing facilitate analyzing large segments of genetic data. Ethical debate has focused on whether and what kind of incidental or secondary findings (SFs) to report, and how to obtain valid informed consent. However, people's support needs after receiving SFs have received less attention. We explored Finnish adults' perspectives on reporting genetic SFs. In this qualitative study which included four focus group discussions (N = 23) we used four vignette letters, each reporting a genetic SF predisposing to a different disease: familial hypercholesterolemia, long QT syndrome, Lynch syndrome, and Li-Fraumeni syndrome. Transcribed focus group discussions were analyzed using inductive thematic analysis. Major themes were immediate shock, dealing with worry and heightened risk, fear of being left alone to deal with SFs, disclosing to family, and identified support needs. Despite their willingness to receive SFs, participants were concerned about being left alone to deal with them. Empathetic expert support and timely access to preventive care were seen as essential to coping with shock and worry, and disclosing SFs to family. Discussion around SFs needs to concern not only which findings to report, but also how healthcare systems need to prepare for providing timely access to preventive care and support for individuals and families.

Effect of centralization on long-term survival after resection of pancreatic ductal adenocarcinoma.

BACKGROUND: Centralization of pancreatic surgery has resulted in improved short-term outcomes in a number of healthcare systems. The aim of this study was to see whether hospital volume influenced long-term prognosis, use of adjuvant therapy or histopathological evaluation of patients undergoing surgical resection for pancreatic ductal adenocarcinoma (PDAC). METHODS: Patients undergoing surgical resection of PDAC in Finland between 2002 and 2008 were identified from national registers. Demographic, histopathological, operative and oncological data were recorded, and the histopathological slides of patients who survived for more than 4 years were reviewed. Operative volume was defined according to the annual rate of pancreatoduodenectomy as: high-volume centres (HVCs; 20 or more resections per year), medium-volume centres (MVCs; 6-19 resection annually) and low-volume centres (LVCs; 5 or fewer resections annually). RESULTS: Some 467 patients who had undergone resectional surgery for PDAC at 22 centres were included. Patient demographics and resection types did not differ between centres. Thirty- and 90-day mortality rates were significantly lower in HVCs compared with LVCs: 0 versus 5·5 per cent (P = 0·001) and 2·5 versus 11·0 per cent (P = 0·003) respectively. Tumours in HVCs were generally at a more advanced stage than those in LVCs (stage IIB: 65·7 versus 40·6 per cent respectively; P < 0·001), but with no greater use of adjuvant therapy. Significantly more patients survived for 2 years (43·3 versus 29·7 per cent; P = 0·034) and 3 years (25·4 versus 14·1 per cent; P = 0·045) after surgery in HVCs than in LVCs. More information was missing in the histopathological reports from LVCs and MVCs than in those from HVCs (P ≤ 0·002). CONCLUSION: Both short- and long-term survival was significantly better for patients operated on in HVCs. Histopathological analysis appears to be more comprehensive in HVCs.

Effects of seasonal acclimatization on temperature dependence of cardiac excitability in the roach, Rutilus rutilus.

Temperature sensitivity of electrical excitability is a potential limiting factor for performance level and thermal tolerance of excitable tissues in ectothermic animals. To test whether the rate and rhythm of the heart acclimatize to seasonal temperature changes, thermal sensitivity of cardiac excitation in a eurythermal teleost, the roach (Rutilus rutilus), was examined. Excitability of the heart was determined from in vivo electrocardiograms and in vitro microelectrode recordings of action potentials (APs) from winter and summer roach acclimatized to 4 and 18°C, respectively. Under heat ramps (3°C h(-1)), starting from the acclimatization temperatures of the fish, heart rate increased to maximum values of 78±5 beats min(-1) (at 19.8±0.5°C) and 150±7 beats min(-1) (at 28.1±0.5°C) for winter and summer roach, respectively, and then declined in both groups. Below 20°C, heart rate was significantly higher in winter than in summer roach (P<0.05), indicating positive thermal compensation. Cardiac arrhythmias appeared with rising temperature as missing QRS complexes, increase in variability of heart rate, episodes of atrial tachycardia, ventricular bradycardia and complete cessation of the heartbeat (asystole) in both winter and summer roach. Unlike winter roach, atrial APs of summer roach had a distinct early repolarization phase, which appeared as shorter durations of atrial AP at 10% and 20% repolarization levels in comparison to winter roach (P<0.05). In contrast, seasonal acclimatization had only subtle effects on ventricular AP characteristics. Plasticity of cardiac excitation appears to be necessary for seasonal improvements in performance level and thermal resilience of the roach heart.

Highly recurrent mutations of SGK1, DUSP2 and JUNB in nodular lymphocyte predominant Hodgkin lymphoma.

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL)-a subtype of Hodgkin lymphoma (HL)-is characterized by a low content of tumor cells, the lymphocyte predominant (LP) cells. Transformation into diffuse large B-cell lymphoma (DLBCL) occurs in about 10% of patients. We performed whole-genome mutation analysis of the DLBCL components from two composite lymphomas consisting of clonally related NLPHL and DLBCL as a means to identify candidate tumor suppressor genes and oncogenes in NLPHL. The analysis of LP cells for selected mutations of the DLBCL revealed that most mutations are also present in the LP cells, indicating a close relationship between the two components. The analysis of 62 selected genes in NLPHL by targeted ultra-deep sequencing revealed three novel highly recurrently mutated genes (each mutated in ~50% of cases), that is, DUSP2, SGK1 and JUNB. SGK1 was expressed in the LP cells of primary NLPHL cases and in the NLPHL cell line DEV. Administration of an SGK1 inhibitor induced apoptosis in the NLPHL cell line DEV and the DLBCL cell line Farage, suggesting a pathogenetic role of SGK1 in the LP and DLBCL cells. In summary, the present study identifies SGK1, DUSP2 and JUNB as novel key players in the pathogenesis of NLPHL.

Gill tissue lipids of salmon (Salmo salar L.) presmolts and smolts from anadromous and landlocked populations.

Composition of membrane lipids from the gills of juvenile Atlantic salmon (Salmo salar) in presmolt and smolt phases of development was compared among anadromous and non-anadromous populations. Three stocks migrating from spawning rivers to either lake (landlocked stock), brackish water or full strength sea water were grown under common garden conditions, and gill lipids and their acyl and alkenyl chains were examined in February (presmolts) and at the end of May (smolts) by mass spectrometry and gas-liquid chromatography. The most remarkable changes upon transition from the presmolt phase to the smolt phase were: (i) increase in the cholesterol/phospholipid ratio, (ii) decrease in the abundance of phosphatidylinositol (PI) content, (iii) increase in the amount of sulfatides, (iv) increase in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) species with two highly unsaturated acyl chains, and finally (v) convergence of interstock differences in PC and PE species composition towards a similar lipid composition. Increases in the gill membrane content of cholesterol and sulfatides are discussed as pre-adaptation of salmon gills for salt-secretion, which may occur by increases in membrane microdomains (rafts) harboring ion channels and pumps. The decreases of PI were likely related to adjusting the gill membrane permeability to ions by diminishing prostanoid production. The similarity of those changes among three salmon stocks and the convergence of initially (presmolt phase) different PC and PE species profiles between the stocks towards similar lipid composition suggests that smoltification process of the gill epithelium is largely similar in anadromous and landlocked populations.

Cigarette smoking and risk of Hodgkin lymphoma and its subtypes: a pooled analysis from the International Lymphoma Epidemiology Consortium (InterLymph).

BACKGROUND: The etiology of Hodgkin lymphoma (HL) remains incompletely characterized. Studies of the association between smoking and HL have yielded ambiguous results, possibly due to differences between HL subtypes. PATIENTS AND METHODS: Through the InterLymph Consortium, 12 case-control studies regarding cigarette smoking and HL were identified. Pooled analyses on the association between smoking and HL stratified by tumor histology and Epstein-Barr virus (EBV) status were conducted using random effects models adjusted for confounders. Analyses included 3335 HL cases and 14 278 controls. RESULTS: Overall, 54.5% of cases and 57.4% of controls were ever cigarette smokers. Compared with never smokers, ever smokers had an odds ratio (OR) of HL of 1.10 [95% confidence interval (CI) 1.01-1.21]. This increased risk reflected associations with mixed cellularity cHL (OR = 1.60, 95% CI 1.29-1.99) and EBV-positive cHL (OR = 1.81, 95% CI 1.27-2.56) among current smokers, whereas risk of nodular sclerosis (OR = 1.09, 95% CI 0.90-1.32) and EBV-negative HL (OR = 1.02, 95% CI 0.72-1.44) was not increased. CONCLUSION: These results support the notion of etiologic heterogeneity between HL subtypes, highlighting the need for HL stratification in future studies. Even if not relevant to all subtypes, our study emphasizes that cigarette smoking should be added to the few modifiable HL risk factors identified.

A significant role of sarcoplasmic reticulum in cardiac contraction of a basal vertebrate, the river lamprey (Lampetra fluviatilis).

AIM: Cardiac contraction and relaxation are mediated by rapidly changing calcium concentration around the myofibrils. In comparison with endotherms, ectothermic hearts are more strongly dependent on extracellular calcium for contraction suggesting this trait might represent the primitive vertebrate mode of cardiac activation. This study tests the hypothesis that intracellular calcium stores play a minor role in cardiac excitation-contraction coupling of a basal vertebrate, the lamprey (Lampetra fluviatilis). METHODS: Contribution of sarcoplasmic reticulum to cardiac calcium management was examined by measuring the ryanodine sensitivity of contraction, determining the number of cardiac ryanodine receptors and their calcium sensitivity, assessing the size of sarcoplasmic reticulum calcium stores in enzymatically isolated cardiac myocytes and qualitative electron microscopic observations of sarcoplasmic reticulum in cardiac muscle. RESULTS: An extensive network of nonjunctional sarcoplasmic reticulum around myofibrils and numerous junctional sarcoplasmic reticulum couplings at the periphery of the myocytes was present in atrial and ventricular muscle of the lamprey heart. High numbers of ryanodine receptors were present in atrial (0.16 ± 0.04 nmol mg(-1) prot) and ventricular membranes (0.27 ± 0.03) (P < 0.01), and 10 µm ryanodine inhibited large part of contraction force in atrial (37.8 ± 5.7%) and ventricular (49.2 ± 6.5%) muscle. CONCLUSION: Sarcoplasmic reticulum is well developed in the lamprey heart and plays a significant role in cardiac calcium management. This suggests that in the common ancestor of vertebrates, cardiac excitation-contraction coupling could have been fairly strongly dependent on sarcoplasmic reticulum calcium stores. Functionally, this trait might be associated with high cardiac output and active predatory lifestyle of the lamprey.

Large performance variation does not affect outcome in the Finnish cervical cancer screening programme.

OBJECTIVE: Cytology screening for prevention of cervical cancer can reduce incidence and mortality by more than 80% in settings with good organization and rigorous quality control. Audit studies are essential for reaching and maintaining a high quality of screening. The aim of this study was to evaluate variation in performance indicators by screening laboratory and assess the impact on the effectiveness of screening as indicated by cervical intraepithelial neoplasia grade 3 and above (CIN3+) rates after a negative screen. METHODS: Seven cytology screening laboratories operating during 1990-1999 with a total of 953 610 screening tests performed were included in the study. By linking screening and cancer register files, all cases of CIN3+ diagnosed in the screened population were identified. For 395 CIN3+ cases with a preceding negative screen and 787 controls, a re-evaluation of smears was undertaken to uncover false negative screening tests. Performance parameters and rates of CIN3+ after a negative screen were analysed for interlaboratory heterogeneity. RESULTS: The rates of follow-up recommendations and referrals varied by up to 3.6- (2.8-10.2%) and 4.0-fold (0.03-0.12%), respectively. CIN1, CIN2 and CIN3+ screen detection rates differed by up to 8.5- (0.02-0.17%), 5.4- (0.05-0.25%) and 3.3-fold (0.05-0.18%). False negative rates determined by re-evaluation showed up to 2.1-fold differences (29-62%). Rates of CIN3+ after a negative screen (0.023-0.048%) and as a proportion of total CIN3+ (15-31%) in the screened population were low and did not vary significantly. CONCLUSIONS: There were large variations in the sensitivity-specificity trade-off between laboratories, reflected in all performance indicators as well as in the test validity estimates of the re-evaluation phase, but not in screening effectiveness. Even though performance variations do not always have an impact on the effectiveness of screening, they lead to variations in cost, treatment and psychological burden, and should be addressed.

Electrophysiological properties and expression of the delayed rectifier potassium (ERG) channels in the heart of thermally acclimated rainbow trout.

In ectotherms, compensatory changes in ion channel number and activity are needed to maintain proper cardiac function at variable temperatures. The rapid component of the delayed rectifier K+ current (IKr) is important for repolarization of cardiac action potential and, therefore, crucial for regulation of cellular excitability and heart rate. To examine temperature plasticity of cardiac IKr, we cloned the ether-à-go-go-related gene (ERG) channel and measured its electrophysiological properties in thermally acclimated rainbow trout (Oncorhynchus mykiss; omERG). The present findings demonstrate a complete thermal compensation in the whole cell conductance of the atrial IKr in rainbow trout acclimated to 4 degrees C (cold acclimation) and 18 degrees C (warm acclimation). In situ hybridization indicates that transcripts of the omERG channel are present throughout the muscular tissue of the heart, and quantitative PCR shows increased expression of the omERG in cold-acclimated trout compared with warm-acclimated trout. In both acclimation groups, omERG expression is higher in atrium than ventricle. In addition, the omERG has some functional features that support IKr activity at low temperatures. Voltage dependence of steady-state activation is completely resistant to temperature changes, and steady-state inactivation and activation kinetics are little affected by temperatures below 11 degrees C. Collectively, these findings suggest that high density of cardiac IKr is achieved by cold-induced increase in the number of functional omERG channels and inherent insensitivity of the omERG to temperature below 11 degrees C. These adaptations are probably important in maintaining high heart rates and proper excitability and contractility of trout cardiac myocytes in the cold.

Fish cardiac sodium channels are tetrodotoxin sensitive.

AIM: Sodium current (I(Na)) of the mammalian heart is resistant to tetrodotoxin (TTX) due to low TTX affinity of the cardiac sodium channel (Na(v)) isoform Na(v)1.5. To test applicability of this finding to other vertebrates, TTX sensitivity of the fish cardiac I(Na) and its molecular identity were examined. METHODS: Molecular cloning and whole-cell patch-clamp were used to examine alpha-subunit composition and TTX inhibition of the rainbow trout (Oncorhynchus mykiss) cardiac Na(v) respectively. RESULTS: I(Na) of the trout heart is about 1000 times more sensitive to TTX (IC50 = 1.8-2 nm) than the mammalian cardiac I(Na) and it is produced by three Na(v)alpha-subunits which are orthologs to mammalian skeletal muscle Na(v)1.4, cardiac Na(v)1.5 and peripheral nervous system Na(v)1.6 isoforms respectively. Oncorhynchus mykiss (om) omNa(v)1.4a is the predominant isoform of the trout heart accounting for over 80% of the Na(v) transcripts, while omNa(v)1.5a forms about 18% and omNa(v)1.6a only 0.1% of the transcripts. OmNa(v)1.4a and omNa(v)1.6a have aromatic amino acids, phenylalanine and tyrosine, respectively, in the critical position 401 of the TTX binding site of the domain I, which confers their high TTX sensitivity. More surprisingly, omNa(v)1.5a also has an aromatic tyrosine in this position, instead of the cysteine of the mammalian TTX-resistant Na(v)1.5. CONCLUSIONS: The ortholog of the mammalian skeletal muscle isoform, omNa(v)1.4a, is the predominant Na(v)alpha-subunit in the trout heart, and all trout cardiac isoforms have an aromatic residue in position 401 rendering the fish cardiac I(Na) highly sensitive to TTX.

Tobacco smoking, alcohol drinking and Hodgkin's lymphoma: a European multi-centre case-control study (EPILYMPH).

We analysed the effects of tobacco and alcohol in the aetiology of Hodgkin's lymphoma (HL), based on 340 cases and 2465 controls enrolled in Spain, France, Italy, Germany, Ireland and Czech Republic, between 1998 and 2004. Current smokers showed a significantly increased odds ratio (OR) of HL of 1.39 (95% confidence interval (CI) = 1.04-1.87). Analyses were also conducted separately for subjects younger than 35 years (179 cases) and for older subjects (161 cases). For subjects below age 35, no association was observed between tobacco and HL, whereas for older subjects, ever-smokers experienced a doubled risk of HL as compared to never smokers and the OR of HL for current smoking was 2.35 (95% CI = 1.52-3.61), with suggestion of a dose-response relationship. A protective effect of alcohol was observed in both age groups. The OR for ever-regular drinking was 0.58 (95% CI = 0.38-0.89) for younger subjects and 0.50 (95% CI = 0.34-0.74) for older subjects. There was no evidence of interaction between tobacco and alcohol. Our results are consistent with previous studies, suggesting a protective effect of alcohol on HL. An effect of tobacco was suggested for HL occurring in middle and late age, although this finding might have occurred by chance.

Surgery in the air--evacuating Finnish tsunami victims from Thailand.

In connection with the Asian tsunami disaster on December 26, 2004, a specially equipped Finnair B-757 airplane capable of evacuating badly injured patients was remodeled into an ambulance airplane. The vehicle could take up to 22 severely injured or ill patients and intensive care and limited surgical procedures could be provided to the patients. The plane was manned with a civilian medical team of 37 physicians and nurses. The plane left for Thailand to evacuate the most severely injured Finnish citizens within 10 hours of the evacuation decision. A total of 14 patients including 4 critically ill (two on ventilator) were transferred to Helsinki within 32 hours of takeoff. The medical team included a general, an orthopedic and a plastic surgeon. Soft tissue wounds, some of them severely infected, were the most common injuries, followed by extremity fractures and head injuries. The surgical procedures that were performed mid-air included wound surgery, to remove necrotic tissue, and external fixation and fasciotomy for a lower extremity fracture. The facilities under these circumstances would allow performing life-saving procedures to maintain airway and breathing, and surgical procedures of the soft tissues, extremity and pelvic fractures. Cavitary surgery would require additional equipment and resources.

Lymphoma in patients with dermatitis herpetiformis and their first-degree relatives.

BACKGROUND: The risk for lymphoma is increased in both dermatitis herpetiformis (DH) and in coeliac disease. The lymphoma most associated with coeliac disease is enteropathy-associated T-cell lymphoma. OBJECTIVES: To study the occurrence and type of lymphoma in a large series of patients with DH and their first-degree relatives. METHODS: The occurrence of lymphoma was studied in 1104 patients consecutively diagnosed with DH in two university hospitals during 1969-2001. A questionnaire was sent to 341 patients to examine the occurrence of lymphoma in their 1825 first-degree relatives. To analyse whether the DH patients with lymphoma had adhered to a gluten-free diet similarly to the patients without lymphoma, two age- and sex-matched patients with DH served as controls for each index case. Data on the gluten-free diet were collected from prospectively completed dietary forms and also from medical records. RESULTS: Eleven (1%) patients contracted lymphoma 2-31 years after the diagnosis of DH. Eight had B-cell-type lymphoma, two enteropathy-associated T-cell lymphoma and one remained unclassified due to missing material. Three (0.2%) of the first-degree relatives contracted lymphoma, all B-cell type. The 11 DH patients with lymphoma had adhered to a gluten-free diet significantly less strictly than the DH controls without lymphoma. CONCLUSIONS: The present study documents that patients with DH can have both B- and T-cell lymphoma. The DH patients with lymphoma had not adhered as strictly to the gluten-free diet as the control patients without lymphoma. The occurrence of lymphoma in the first-degree relatives was lower than in the patients with DH.

Prognostic significance of antrum-predominant gastritis in functional dyspepsia.

BACKGROUND: The role of Helicobacter pylori infection in functional dyspepsia is still controversial, and subgroups of patients with functional dyspepsia who may benefit from H. pylori eradication should be identified. Patients with functional dyspepsia and antrum-predominant H. pylori-positive chronic gastritis, it has been argued, have fewer symptoms after eradication therapy. In the present study, we analysed the clinical significance of antrum-predominant gastritis on the long-term prognosis of functional dyspepsia. METHODS: Consecutive unselected dyspeptic patients were investigated in primary care and the patients with functional dyspepsia were enrolled in this long-term follow-up study. Altogether 182 patients were recruited: 65 with normal histology of the stomach, 36 with antrum-predominant gastritis, 21 with corpus-predominant gastritis and 60 with pangastritis. Patients' medical histories were reviewed after 6 to 7 years, with total number and outcome of repeated investigations analysed. At the end of follow-up, all patients were invited for voluntary gastroscopy. RESULTS: At the end of follow-up, the proportion of asymptomatic patients ranged from 21% (normal histology) to 26% (antrum-predominant gastritis). No statistically significant differences between groups appeared in regard to re-visits or to proportion of patients examined by sigmoideo- or colonoscopy during follow-up. Patients with antrum-predominant gastritis less often underwent upper endoscopy. Peptic ulcer was more frequent (P = 0.05) in patients with antrum gastritis than in other groups, but no other differences existed among any organic gastrointestinal findings. No significant differences between subgroups appeared among the 30% of patients using drugs for upper abdominal complaints during the previous year. CONCLUSIONS: Functional dyspepsia has an excellent long-term prognosis. Antrum-predominant gastritis in functional dyspepsia seems to carry an increased risk for peptic ulcer, and for this group in particular, H. pylori eradication should be considered. This finding requires confirmation in future studies performed in primary care.

Effects of chronic hypoxia on inward rectifier K(+) current ( I(K1)) in ventricular myocytes of crucian carp (Carassius carassius) heart.

Some ectothermic vertebrates show unusually good tolerance to oxygen shortage and it is therefore assumed that they might, as a defense mechanism, decrease number or activity of ion channels in order to reduce membrane leakage and thereby ATP-dependent ion pumping in hypoxia. Although several studies have provided indirect evidence in favor of this 'channel arrest' hypothesis, only few experiments have examined activity of ion channels directly from animals exposed to chronic hypoxia or anoxia in vivo. Here we compare the inwardly rectifying K(+) current (I(K1)), a major leak and repolarizing K(+) pathway of the heart, in cardiac myocytes of normoxic and hypoxic crucian carp, using the whole-cell and cell-attached single-channel patch-clamp methods. Whole-cell conductance of I(K1) was 0.5 +/- 0.04 nS/pF in normoxic fish and did not change during the 4 weeks hypoxic (O2 < 0.4 mg/l; 2.68 mmHg) period, meanwhile the activity of Na(+)/K(+)ATPase decreased 33%. Single-channel conductance of the I(K1) was 20.5 +/- 0.8 pS in control fish and 21.4 +/- 1.1 pS in hypoxic fish, and the open probability of the channel was 0.80 +/- 0.03 and 0.74 +/- 0.04 ( P > 0.05) in control and hypoxic fish, respectively. Open and closed times also had identical distributions in normoxic and hypoxic animals. These results suggest that the density and activity of the inward rectifier K(+) channel is not modified by chronic hypoxia in ventricular myocytes of the crucian carp heart. It is concluded that instead of channel arrest, the hypoxic fish cardiac myocytes obtain energy savings through 'action potential arrest' due to hypoxic bradycardia.

Ryanodine and dihydropyridine receptor binding in ventricular cardiac muscle of fish with different temperature preferences.

Ca(2+)-induced Ca2+ release (CICR) mechanism of cardiac excitation-contraction (e-c) coupling is dependent on the close apposition between the sarcolemmal dihydropyridine receptors (DHPR) and the sarcoplasmic reticulum (SR) ryanodine receptors (RyR). In particular, high RyR/DHPR ratio is considered to reflect strong dependence on SR Ca2+ stores for the intracellular Ca2+ transient. To indirectly evaluate the significance of CICR in fish hearts, densities of cardiac DHPRs and RyRs were compared in ventricular homogenates of three fish species (burbot, rainbow trout, and crucian carp) and adult rat by [3H] PN200-110 and [3H] ryanodine binding. The density of RyRs was significantly (P<0.05) higher in the adult rat (124+/-10 channels/microm3 myocyte volume) than in any of the fish species. Among the fish species, cold-acclimated (4 degrees C) trout had more RyRs than burbot, and crucian carp. The density of DHPRs was highest in the trout heart. RyR/DHPR ratio was significantly (P<0.05) higher in rat (4.1+/-0.5) than in the fish hearts (varying from 0.97+/-0.16 to 1.91+/-0.49) suggesting that "mammalian type" CICR is less important during e-c coupling in fish ventricular myocytes. In rainbow trout, acclimation to cold did not affect the RyR/DHPR ratio, while in crucian carp it was depressed in cold-acclimated animals (4 degrees C; 0.97+/-0.16) when compared to warm-acclimated fish (23 degrees C; 1.91+/-0.49). Although RyR/DHPR ratios were relatively low in fish hearts, there was a close correlation (r2=0.78) between the RyR/DHPR ratio and the magnitude of the Ry-sensitive component of contraction in ventricular muscle among the fish species examined in this study.

Acute temperature change modulates the response of ICa to adrenergic stimulation in fish cardiomyocytes.

The purpose of this study was to investigate how the endogenous catecholamine adrenaline protects sarcolemmal Ca(2+) flux through the L-type Ca(2+) channel (I(Ca)) during acute exposure to cold in the fish heart. We examined the response of I(Ca) to adrenergic stimulation at three temperatures (7 degrees, 14 degrees, and 21 degrees C) in atrial myocytes isolated from rainbow trout acclimated to 14 degrees C. We found that I(Ca) amplitude varied directly with test temperature and was increased by adrenergic stimulation (AD; 5 nM and 1 microM) at all temperatures. However, I(Ca) was significantly more sensitive to adrenergic stimulation at the coldest test temperature. In fact, at 7 degrees C in the absence of AD, I(Ca) was extremely low. The addition of 1 microM AD increased peak I(Ca) 7.2-fold at 7 degrees C, 2.6-fold at 14 degrees C, and 1.6-fold at 21 degrees C and ameliorated the temperature-dependent difference in Ca(2+) influx across the cell membrane. We suggest that this increased adrenergic sensitivity is a critical compensatory mechanism that allows the rainbow trout heart to maintain contractility during acute exposure to cold temperatures. In particular, the tonic level of adrenergic stimulation provided by circulating plasma catecholamines (i.e., in the nM concentration range) may be crucial for effective excitation-contraction coupling in the cold cardiomyocyte.

Fiber capillarization relative to mitochondrial volume in diaphragm of shrew.

The objective was to examine fiber capillarization in relation to fiber mitochondrial volume in the highly aerobic diaphragm of the shrew, the smallest mammal. The diaphragms of four common shrews [Sorex araneus; body mass, 8.2 +/- 1.3 (SE) g] and four lesser shrews (Sorex minutus, 2.6 +/- 0.1 g) were perfusion fixed in situ, processed for electron microscopy, and analyzed by morphometry. Capillary length per fiber volume was extremely high, at values of 8,008 +/- 1,054 and 12,332 +/- 625 mm(-2) in S. araneus and S. minutus, respectively (P = 0.012), with no difference in capillary geometry between the two species. Fiber mitochondrial volume density was 28.5 +/- 2.3% (S. araneus) and 36.5 +/- 1.4% (S. minutus; P = 0.025), yielding capillary length per milliliter mitochondria values (S. araneus, 27.8 +/- 1.5 km; S. minutus, 33.9 +/- 2.2 km; P = 0.06) as high as in the flight muscle of the hummingbird and small bats. The size of the capillary-fiber interface (i.e., capillary surface per fiber surface ratio) per fiber mitochondrial volume in shrew diaphragm was also as high as in bird and bat flight muscles, and it was about two times greater than in rat hindlimb muscle. Thus, whereas fiber capillary and mitochondrial volume densities decreased with increased body mass in S. araneus compared with S. minutus Soricinae shrews, fiber capillarization per milliliter mitochondria in both species was much higher than previously reported for shrew diaphragm, and it matched that of the intensely aerobic flight muscles of birds and mammals.

Effects of adenosine on the contractility of normoxic rainbow trout heart.

Temperature strongly affects oxygen solubility in water, oxygen convection in the blood and locomotor activity of the fish. Since oxygen supply and demand are temperature dependent, it was hypothesized that the purinergic control of the heart, one of the most important mediators in oxygen-limited conditions, might also show temperature dependence. Therefore, the present study examines the effects of adenosine (Ado), a purinergic agonist, on the contractile and electrical activity of the thermally acclimated trout ( Oncorhynchus mykiss Walbaum) heart. The fish were acclimated to either 4 degrees C or 17 degrees C and the experiments were conducted at the acclimation temperatures of the animals. In spontaneously beating hearts, Ado had a negative chronotropic and a positive inotropic effect in warm-acclimated rainbow trout while no response was detected in cold-acclimated trout. In paced atrial and ventricular preparations, Ado had a negative inotropic effect in both warm- and cold-acclimated fish, and the response was strongest in the atria of warm-acclimated trout. Ado shortened the duration of contraction 12-14% in atrial preparations but had no effect in ventricular muscle. Ado (10(-4) mol l(-1)) increased the density of the inwardly rectifying K(+) current from -3.5+/-0.6 pA pF(-1) to -8.4+/-1.4 pA pF(-1) (at -120 mV) in atrial myocytes of warm-acclimated trout but was without effect in atrial myocytes of cold-acclimated trout (-2.4+/-0.8 pA pF(-1) vs. -2.1+/-0.9 pA pF(-1)). Ado had no effect on K(+) currents of ventricular cells in either acclimation group. These results indicate that the effects of Ado on cardiac contractility and electrical activity are stronger in warm-acclimated than in cold-acclimated trout when measured at the physiological body temperatures of the fish. The balance between oxygen demand and supply of the heart might be better in the cold where more environmental oxygen is available and the power of the muscles is weaker thereby reducing the need for the purinergic control of the heart. Temperature-dependence of Ado response in the trout heart warrants that temperature should be taken into consideration when the purinergic system of the ectotherms is studied.