Urinary acid-base excretion deciphers high acid load from colonic bicarbonate loss in intestinal failure patients with ileocolonic anastomosis - Guidance for composition of parenteral support

BACKGROUND & AIMS

Acid-base disturbances are common in short bowel (SB) patients due to increased intestinal bicarbonate loss. However, the resulting systemic acid load has not been quantified. Base excess is used to monitor metabolic acid-base disturbances but inadequately reflects the acid load. Our aim was to investigate the systemic acid/base load in SB-patients to obtain quantitative estimates to guide the composition of parenteral support.

METHODS

We calculated total acid load in SB patients by summing 24-h urinary net acid excretion (NAE) and the provision of base equivalents in parenteral support. We then compared differences among anatomical SB-types: jejunostomy (SB-J), jejunocolostomy (SB-JC), and jejunoileostomy (SB-JIC). 47 urine samples from 34 SB patients were analyzed for bicarbonate (HCO3-), ammonium (NH4+), and titratable acid (TA) concentrations. NAE was calculated as (TA + NH4+) - HCO3-. Mixed-effects repeated-measures models were used to statistically examine differences between SB-types and associations with parenteral nutrition and NAE. A healthy cohort served as control.

RESULTS

In comparison to SB-J, SB-JC patients had a 4.1 mmoL/l lower base excess (95% CI: -6.3 to -1.8) and an 84.5 mmol/day higher total acid load (CI: 41.3 to 127.7). There were no significant differences between SB-JIC and SB-J regarding base excess, NAE, or total acid load. Higher amounts of infused acetate, sodium, and chloride, but not the acetate/chloride ratio, were associated with lower NAE and higher base excess.

CONCLUSIONS

Due to increased colonic bicarbonate loss, patients with SB-JC have a ∼4.4-fold higher acid load than healthy controls. The ion transport mechanisms mediating this bicarbonate loss from the remaining colon need further experimental investigation. NAE could be a useful tool to adjust base infusion in SB.

Genomic Analysis of Inbreeding and Coancestry in Nordic Jersey and Holstein Dairy Cattle Populations

In recent years, Genomic Selection (GS) has accelerated genetic gain in dairy cattle breeds worldwide. Despite the evident genetic progress, several dairy populations have also encountered challenges such as heightened inbreeding rates and reduced effective population sizes. The challenge has been to find a balance between achieving substantial genetic gain while managing genetic diversity within the population, thereby mitigating the negative effects of inbreeding depression. This study aims to elucidate the impact of GS on pedigree and genomic rates of inbreeding (ΔF) and coancestry (ΔC) in Nordic Jersey (NJ) and Holstein (NH) cattle populations. Furthermore, key genetic metrics including the generation interval (L), effective population size (Ne), and future effective population size (FNe) were assessed between 2 time periods, before and after GS, and across distinct animal cohorts in both breeds: females, bulls, and approved semen-producing bulls (AI-sires). Analysis of ΔF and ΔC revealed distinct trends across the studied periods and animal groups. Notably, there was a consistent increase in yearly ΔF for most animal groups in both breeds. An exception was observed in NH AI-sires, which demonstrated a slight decrease in yearly ΔF. Moreover, NJ displayed minimal changes in yearly ΔC between the periods, whereas NH exhibited elevated ΔC values across all animal groups. Particularly striking was the substantial increase in yearly ΔC within the NH female population, surging from 0.02% to 0.39% between the periods. Implementation of GS resulted in a reduction of the generation interval across all animal cohorts in both NJ and NH breeds. However, the extent of reduction was more pronounced in males compared with females. This reduction in generation interval influenced generational changes in ΔF and ΔC. Bulls and AI-sires of both breeds exhibited reduced generational ΔF between periods, in contrast to females that demonstrated an opposing pattern. Between the periods, NJ maintained a relatively stable Ne, 29.4 before and 30.3 after GS, while NH experienced a notable decline from 54.3 to 42.8. Female groups in both breeds displayed a negative Ne trend, while males demonstrated either neutral or positive Ne developments. Regarding FNe, NJ exhibited positive FNe development with an increase from 40.7 to 57.2. The opposite was observed in NH, where FNe decreased from 198.8 to 42.7. In summary, it was evident that the genomic methods could detect differences between the populations and changes in ΔF and ΔC more efficiently than pedigree methods. GS implementation yielded positive outcomes within the NJ population regarding the rate of coancestry but the opposite was observed with NH. Moreover, analysis of ΔC data hints at the potential to decrease future ΔF through informed mating strategies. Conversely, NH faces more pressing concerns, even though ΔF remains comparatively modest in contrast to what has been observed in other Holstein populations. These findings underscore the necessity of genomic control of inbreeding and coancestry with strategic changes in the Nordic breeding schemes for dairy to ensure long-term sustainability in the forthcoming years.

Secretin: a hormone for HCO3- homeostasis

Secretin is a key hormone of the intestinal phase of digestion which activates pancreatic, bile duct and Brunner gland HCO3- secretion. Recently, the secretin receptor (SCTR) was also found in the basolateral membrane of the beta-intercalated cell (B-IC) of the collecting duct. Experimental addition of secretin triggers a pronounced activation of urinary HCO3- excretion, which is fully dependent on key functional proteins of the B-IC, namely apical pendrin and CFTR and the basolateral SCTR. Recent studies demonstrated that the SCTR knock-out mouse is unable to respond to an acute base load. Here, SCTR KO mice could not rapidly increase urine base excretion, developed prolonged metabolic alkalosis and exhibited marked compensatory hypoventilation. Here, we review the physiological effects of secretin with distinct focus on how secretin activates renal HCO3- excretion. We describe its new function as a hormone for HCO3- homeostasis.

Post-intervention Adherence to the New Nordic Renal Diet among patients with chronic kidney disease, stages 3 and 4

The New Nordic Renal Diet (NNRD) is a meal pattern reduced in phosphorus, protein, and sodium for patients with moderate chronic kidney disease. The NNRD showed improvements in metabolic, and physiological outcomes after 26-weeks intervention. In the original study, participants were randomized to NNRD (n = 30), or control (habitual diet) (n = 30). The aim of this study was to explore adherence to the NNRD 3 months after cessation of intervention (follow-up). Fifty-seven participants completed the follow-up visit, which consisted of fasting blood samples and 24 h urine samples. At follow-up, there was no longer a significant reduction in 24 h urine phosphorus excretion in the NNRD group. From intervention to follow-up, 24 h urine phosphorus increased by 63 mg in the NNRD group, vs. -24.1 mg in the control group, between-group difference 87.1 mg (-10.1, 184.3, p = 0.08). Our findings show that more active intervention is needed to support adherence and maintain beneficial effects of the NNRD.

Trimethoprim inhibits renal H+-K+-ATPase in states of K+ depletion

There is growing consensus that under physiological conditions, collecting duct H+ secretion is independent of epithelial Na+ channel (ENaC) activity. We have recently shown that the direct ENaC inhibitor benzamil acutely impairs H+ excretion by blocking renal H+-K+-ATPase. However, the question remains whether inhibition of ENaC per se causes alterations in renal H+ excretion. To revisit this question, we studied the effect of the antibiotic trimethoprim (TMP), which is well known to cause K+ retention by direct ENaC inhibition. The acute effect of TMP (5 µg/g body wt) was assessed in bladder-catheterized mice, allowing real-time measurement of urinary pH, electrolyte, and acid excretion. Dietary K+ depletion was used to increase renal H+-K+-ATPase activity. In addition, the effect of TMP was investigated in vitro using pig gastric H+-K+-ATPase-enriched membrane vesicles. TMP acutely increased natriuresis and decreased kaliuresis, confirming its ENaC-inhibiting property. Under control diet conditions, TMP had no effect on urinary pH or acid excretion. Interestingly, K+ depletion unmasked an acute urine alkalizing effect of TMP. This finding was corroborated by in vitro experiments showing that TMP inhibits H+-K+-ATPase activity, albeit at much higher concentrations than benzamil. In conclusion, under control diet conditions, TMP inhibited ENaC function without changing urinary H+ excretion. This finding further supports the hypothesis that the inhibition of ENaC per se does not impair H+ excretion in the collecting duct. Moreover, TMP-induced urinary alkalization in animals fed a low-K+ diet highlights the importance of renal H+-K+-ATPase-mediated H+ secretion in states of K+ depletion.NEW & NOTEWORTHY The antibiotic trimethoprim (TMP) often mediates K+ retention and metabolic acidosis. We suggest a revision of the underlying mechanism that causes metabolic acidosis. Our results indicate that TMP-induced metabolic acidosis is secondary to epithelial Na+ channel-dependent K+ retention. Under control dietary conditions, TMP does not per se inhibit collecting duct H+ secretion. These findings add further argument against a physiologically relevant voltage-dependent mechanism of collecting duct H+ excretion.

Design of a virtual data shelf to effectively explore a large database of 3D medical surface models in VR

PURPOSE

Medical researchers deal with a large amount of patient data to improve future treatment decisions and come up with new hypotheses. To facilitate working with a large database containing many patients and parameters, we propose a virtual data shelf, displaying the 3D anatomical surface models in an immersive VR environment.

METHODS

Thereby, different functionalities such as sorting, filtering and finding similar cases are included. To provide an appropriate layout and arrangement of 3D models that optimally supports working with the database, three layouts (flat, curved and spherical) and two distances are evaluated. A broad audience study with 61 participants was conducted to compare the different layouts based on their ease of interaction, to get an overview and to explore single cases. Medical experts additionally evaluated medical use cases.

RESULTS

The study revealed that the flat layout with small distance is significantly faster in providing an overview. Applying the virtual data shelf to the medical use case intracranial aneurysms, qualitative expert feedback with two neuroradiologists and two neurosurgeons was gathered. Most of the surgeons preferred the curved and spherical layouts.

CONCLUSION

Our tool combines benefits of two data management metaphors, resulting in an efficient way to work with a large database of 3D models in VR. The evaluation gives insight into benefits of layouts as well as possible use cases in medical research.

Health effects of the New Nordic Renal Diet in patients with stage 3 and 4 chronic kidney disease, compared with habitual diet: a randomized trial

BACKGROUND

Chronic kidney disease (CKD) leads to an accumulation of waste products and causes adverse cardiometabolic effects.

OBJECTIVES

We investigated the health effects of the New Nordic Renal Diet (NNRD), a novel meal pattern reduced in phosphorus, protein, and sodium.

METHODS

A 26-wk randomized trial compared the NNRD with a habitual diet. The NNRD group received weekly home deliveries of food and recipes. Monthly study visits included fasting blood samples, 24-h urine samples, blood pressure, and anthropometric measurements. Intention-to-treat analysis used linear mixed-effects models.

RESULTS

Sixty patients, mean estimated glomerular filtration rate (eGFR) 34 mL/min/1.73 m2 and body mass index of 25-27 kg/m2, were included and 58 completed. Metabolic syndrome was present in 53% (NNRD group) and 57% (control group). The NNRD group (n = 30) reduced their 24-h urine phosphorus excretion by 19% (-153 mg; 95% confidence interval [CI]: -210, -95), control group (n = 30) (no change), between-group difference -171 mg (95% CI: -233, -109; P < 0.001). Proteinuria was reduced by 39% in the NNRD group (-0.33 g/d; 95% CI: -0.47, -0.18), control group (no change), between-group difference -0.34 g/d (95% CI: -0.52, -0.17; P < 0.001). Plasma urea was reduced by -1.5 mmol/L in the NNRD group (95% CI: -2.1, -0.9), control group (no change), between-group difference -1.4 mmol/L (95% CI: -2.0, -0.7; P < 0.001). Systolic blood pressure fell by -5.2 mmHg in the NNRD group (95% CI: -8.4, -2.1), control group (no change), between-group difference -3.9 mmHg (95% CI; -7.6, -0.2; P = 0.04). The NNRD group lost -1.7 kg (95% CI: -2.6, -0.8), control group (no change), between-group difference -2.0 kg (95% CI: -3.0, -1.0; P < 0.001). There were no effects on eGFR during the 26-wk intervention.

CONCLUSION

NNRD in moderate CKD reduces phosphorus excretion, proteinuria, systolic blood pressure, and weight, mainly by reducing abdominal fat. This trial was registered at clinicaltrials.gov as NCT04579315.

Loss of the Secretin Receptor Impairs Renal Bicarbonate Excretion and Aggravates Metabolic Alkalosis in Mice during Acute Base-Loading

SIGNIFICANCE STATEMENT

During acute base excess, the renal collecting duct β -intercalated cells ( β -ICs) become activated to increase urine base excretion. This process is dependent on pendrin and cystic fibrosis transmembrane regulator (CFTR) expressed in the apical membrane of β -ICs. The signal that leads to activation of this process was unknown. Plasma secretin levels increase during acute alkalosis, and the secretin receptor (SCTR) is functionally expressed in β -ICs. We find that mice with global knockout for the SCTR lose their ability to acutely increase renal base excretion. This forces the mice to lower their ventilation to cope with this challenge. Our findings suggest that secretin is a systemic bicarbonate-regulating hormone, likely being released from the small intestine during alkalosis.

BACKGROUND

The secretin receptor (SCTR) is functionally expressed in the basolateral membrane of the β -intercalated cells of the kidney cortical collecting duct and stimulates urine alkalization by activating the β -intercalated cells. Interestingly, the plasma secretin level increases during acute metabolic alkalosis, but its role in systemic acid-base homeostasis was unclear. We hypothesized that the SCTR system is essential for renal base excretion during acute metabolic alkalosis.

METHODS

We conducted bladder catheterization experiments, metabolic cage studies, blood gas analysis, barometric respirometry, perfusion of isolated cortical collecting ducts, immunoblotting, and immunohistochemistry in SCTR wild-type and knockout (KO) mice. We also perfused isolated rat small intestines to study secretin release.

RESULTS

In wild-type mice, secretin acutely increased urine pH and pendrin function in isolated perfused cortical collecting ducts. These effects were absent in KO mice, which also did not sufficiently increase renal base excretion during acute base loading. In line with these findings, KO mice developed prolonged metabolic alkalosis when exposed to acute oral or intraperitoneal base loading. Furthermore, KO mice exhibited transient but marked hypoventilation after acute base loading. In rats, increased blood alkalinity of the perfused upper small intestine increased venous secretin release.

CONCLUSIONS

Our results suggest that loss of SCTR impairs the appropriate increase of renal base excretion during acute base loading and that SCTR is necessary for acute correction of metabolic alkalosis. In addition, our findings suggest that blood alkalinity increases secretin release from the small intestine and that secretin action is critical for bicarbonate homeostasis.

The AE4 transporter mediates kidney acid-base sensing

The kidney plays a key role in the correction of systemic acid-base imbalances. Central for this regulation are the intercalated cells in the distal nephron, which secrete acid or base into the urine. How these cells sense acid-base disturbances is a long-standing question. Intercalated cells exclusively express the Na⁺-dependent Cl^-/HCO₃^- exchanger AE4 (Slc4a9). Here we show that AE4-deficient mice exhibit a major dysregulation of acid-base balance. By combining molecular, imaging, biochemical and integrative approaches, we demonstrate that AE4-deficient mice are unable to sense and appropriately correct metabolic alkalosis and acidosis. Mechanistically, a lack of adaptive base secretion via the Cl^-/HCO₃^- exchanger pendrin (Slc26a4) is the key cellular cause of this derailment. Our findings identify AE4 as an essential part of the renal sensing mechanism for changes in acid-base status.

Variation and genetic control of individual recombination rates in Norwegian Red dairy cattle

Meiotic recombination is an important evolutionary mechanism that breaks up linkages between loci and creates novel haplotypes for selection to act upon. Understanding the genetic control of variation in recombination rates is therefore of great interest in both natural and domestic breeding populations. In this study, we used pedigree information and medium-density (∼50K) genotyped data in a large cattle (Bos taurus) breeding population in Norway (Norwegian Red cattle) to investigate recombination rate variation between sexes and individual animals. Sex-specific linkage mapping showed higher rates in males than in females (total genetic length of autosomes = 2,492.9 cM in males and 2,308.9 cM in females). However, distribution of recombination along the genome showed little variation between males and females compared with that in other species. The heritability of autosomal crossover count was low but significant in both sexes (h² = 0.04 and 0.09 in males and females, respectively). We identified 2 loci associated with variation in individual crossover counts in female, one close to the candidate gene CEP55 and one close to both MLH3 and NEK9. All 3 genes have been associated with recombination rates in other cattle breeds. Our study contributes to the understanding of how recombination rates are controlled and how they may vary between closely related breeds as well as between species.

Challenged Urine Bicarbonate Excretion as a Measure of Cystic Fibrosis Transmembrane Conductance Regulator Function in Cystic Fibrosis

BACKGROUND

In cystic fibrosis (CF), renal base excretion is impaired. Accordingly, challenged urine bicarbonate excretion may be an in vivo biomarker of cystic fibrosis transmembrane conductance regulator (CFTR) function.

OBJECTIVE

To evaluate the association between challenged bicarbonate excretion and clinical characteristics at baseline, quantify the CFTR modulator drug elexacaftor/tezacaftor/ivacaftor-induced changes of challenged bicarbonate excretion after 6 months of treatment, and characterize the intraindividual variation in healthy adults.

DESIGN

Prospective observational study.

SETTING

Cystic fibrosis clinic, Aarhus University Hospital, Denmark.

PATIENTS

Fifty adult patients with CF starting CFTR modulator therapy with elexacaftor/tezacaftor/ivacaftor between May 2020 and June 2021.

MEASUREMENTS

Quantification of urine bicarbonate excretion after an acute oral sodium bicarbonate challenge before and 6 months after elexacaftor/tezacaftor/ivacaftor treatment.

RESULTS

At baseline, challenged urine bicarbonate excretion was associated with several CF disease characteristics. Bicarbonate excretion was higher in patients with residual function mutations. A higher bicarbonate excretion was associated with better lung function, pancreatic sufficiency, and lower relative risk for chronic pseudomonas infections. Elexacaftor/tezacaftor/ivacaftor treatment increased bicarbonate excretion by 3.9 mmol/3 h (95% CI, 1.6 to 6.1 mmol/3 h), reaching about 70% of that seen in healthy control participants. In healthy control participants, individual bicarbonate excretion at each visit correlated with the individual mean bicarbonate excretion. The median coefficient of variation was 31%.

LIMITATION

Single-center study without a placebo-controlled group.

CONCLUSION

Although further studies are needed to address the performance and sensitivity of this approach, this early-stage evaluation shows that challenged urine bicarbonate excretion may offer a new, simple, and safe quantification of CFTR function and the extent of its pharmacologic improvement. Elexacaftor/tezacaftor/ivacaftor partially restores renal CFTR function in patients with CF, likely resulting in decreased risk for electrolyte disorders and metabolic alkalosis.

PRIMARY FUNDING SOURCE

Innovation Fund Denmark.

Dietary K+ acts as a genuine diuretic

K⁺ balance in mammals relies on regulated renal K⁺ excretion matching unregulated fluctuating K⁺ intake. Upon a K⁺ rich meal, rapid and powerful K⁺ excretion is needed. Renal K⁺ secretion is stimulated by the increased tubular flow. We speculated that high K⁺ intake acutely increases urinary flow to stimulate K⁺ excretion.

METHODS

Mice were K⁺ challenged through diets or gavage. Post K⁺ loading urinary output, osmolarity, [K⁺ ]_u , [Na⁺ ]_u , plasma osmolarity, [copeptin]_p , [K⁺ ]_p , and [Na⁺ ]_p were measured. To locate the mechanism of K⁺ -induced diuresis in the glomerular/tubular system we measured creatinine excretion and assessed functional transport in isolated perfused TALs and CDs during an acute [K⁺ ]_bl switch from 3.6 to 6.5 mM. Molecular adaptations of transport proteins involved in water reabsorption were investigated by immunoblotting.

RESULTS

(1) Mice switched from a 1% to 2% K⁺ diet increased diuresis within 12 hours and reciprocally reduced diuresis when switched from 1% to 0.01% K⁺ diet. (2) A single K⁺ gavage load, corresponding to 25%-50% of daily K⁺ intake, induced 100% increase in diuresis within 30 minutes. This occurred despite augmented plasma osmolarity and AVP synthesis. (3) K⁺ gavage did not change GFR. (4) In isolated perfused TALs, shifting [K⁺ ]_bl from 3.6 to 6.5 mM did not affect AVP-induced NaCl transport. (5) In sharp contrast, in isolated perfused CDs, shifting [K⁺ ]_bl from 3.6 to 6.5 mM markedly reduced CD AVP sensitivity, ie inhibited water absorption.

CONCLUSION

Dietary K⁺ loading induces a rapidly on-setting diuresis. The mechanism of K⁺ -induced diuresis involves desensitization of the CD to AVP.

The molecular mechanism of CFTR- and secretin-dependent renal bicarbonate excretion

This review summarizes the newly discovered molecular mechanism of secretin-stimulated urine HCO₃ ^- excretion and the role of cystic fibrosis transmembrane conductance regulator (CFTR) in renal HCO₃ ^- excretion. The secretin receptor is functionally expressed in the basolateral membrane of the HCO₃ ^- -secreting β-intercalated cells of the collecting duct. Here it activates a fast and efficient secretion of HCO₃ ^- into the urine serving to normalize metabolic alkalosis. The ability to acutely increase renal base excretion is entirely dependent on functional pendrin (SLC26A4) and CFTR, and both proteins localize to the apical membrane of the β-intercalated cells. In cystic fibrosis mice and patients, this function is absent or markedly reduced. We discuss that the alkaline tide, namely the transient urine alkalinity after a meal, has now received a clear physiological explanation.

NBCn1 Increases NH4 + Reabsorption Across Thick Ascending Limbs, the Capacity for Urinary NH4 + Excretion, and Early Recovery from Metabolic Acidosis

BACKGROUND

The electroneutral Na⁺/HCO₃ ^- cotransporter NBCn1 (Slc4a7) is expressed in basolateral membranes of renal medullary thick ascending limbs (mTALs). However, direct evidence that NBCn1 contributes to acid-base handling in mTALs, urinary net acid excretion, and systemic acid-base homeostasis has been lacking.

METHODS

Metabolic acidosis was induced in wild-type and NBCn1 knockout mice. Fluorescence-based intracellular pH recordings were performed and NH₄ ⁺ transport measured in isolated perfused mTALs. Quantitative RT-PCR and immunoblotting were used to evaluate NBCn1 expression. Tissue [NH₄ ⁺] was measured in renal biopsies, NH₄ ⁺ excretion and titratable acid quantified in spot urine, and arterial blood gasses evaluated in normoventilated mice.

RESULTS

Basolateral Na⁺/HCO₃ ^- cotransport activity was similar in isolated perfused mTALs from wild-type and NBCn1 knockout mice under control conditions. During metabolic acidosis, basolateral Na⁺/HCO₃ ^- cotransport activity increased four-fold in mTALs from wild-type mice, but remained unchanged in mTALs from NBCn1 knockout mice. Correspondingly, NBCn1 protein expression in wild-type mice increased ten-fold in the inner stripe of renal outer medulla during metabolic acidosis. During systemic acid loading, knockout of NBCn1 inhibited the net NH₄ ⁺ reabsorption across mTALs by approximately 60%, abolished the renal corticomedullary NH₄ ⁺ gradient, reduced the capacity for urinary NH₄ ⁺ excretion by approximately 50%, and delayed recovery of arterial blood pH and standard [HCO₃ ^-] from their initial decline.

CONCLUSIONS

During metabolic acidosis, NBCn1 is required for the upregulated basolateral HCO₃ ^- uptake and transepithelial NH₄ ⁺ reabsorption in mTALs, renal medullary NH₄ ⁺ accumulation, urinary NH₄ ⁺ excretion, and early recovery of arterial blood pH and standard [HCO₃ ^-]. These findings support that NBCn1 facilitates urinary net acid excretion by neutralizing intracellular H⁺ released during NH₄ ⁺ reabsorption across mTALs.

Impaired renal HCO3 - secretion in CFTR deficient mice causes metabolic alkalosis during chronic base-loading

AIM

Cystic fibrosis patients have an increased risk of developing metabolic alkalosis presumably as a result of altered renal HCO₃ ^- handling. In this study, we directly assess the kidneys' ability to compensate for a chronic base-load in the absence of functional CFTR.

METHODS

Comprehensive urine and blood acid-base analyses were done in anaesthetized WT mice or mice lacking either CFTR or pendrin, with or without 7 days of oral NaHCO₃ loading. The in vivo experiments were complemented by a combination of immunoblotting and experiments with perfused isolated mouse cortical collecting ducts (CCD).

RESULTS

Base-loaded WT mice maintained acid-base homeostasis by elevating urinary pH and HCO₃ ^- excretion and decreasing urinary net acid excretion. In contrast, pendrin KO mice and CFTR KO mice were unable to increase urinary pH and HCO₃ ^- excretion and unable to decrease urinary net acid excretion sufficiently and thus developed metabolic alkalosis in response to the same base-load. The expression of pendrin was increased in response to the base-load in WT mice with a paralleled increased pendrin function in the perfused CCD. In CFTR KO mice, 7 days of base-loading did not upregulate pendrin expression and apical Cl^- /HCO₃ ^- exchange function was strongly blunted in the CCD.

CONCLUSION

CFTR KO mice develop metabolic alkalosis during a chronic base-load because they are unable to sufficiently elevate renal HCO₃ ^- excretion. This can be explained by markedly reduced pendrin function in the absence of CFTR.

Benzamil-mediated urine alkalization is caused by the inhibition of H+-K+-ATPases

Epithelial Na⁺ channel (ENaC) blockers elicit acute and substantial increases of urinary pH. The underlying mechanism remains to be understood. Here, we evaluated if benzamil-induced urine alkalization is mediated by an acute reduction in H⁺ secretion via renal H⁺-K⁺-ATPases (HKAs). Experiments were performed in vivo on HKA double-knockout and wild-type mice. Alterations in dietary K⁺ intake were used to change renal HKA and ENaC activity. The acute effects of benzamil (0.2 µg/g body wt, sufficient to block ENaC) on urine flow rate and urinary electrolyte and acid excretion were monitored in anesthetized, bladder-catheterized animals. We observed that benzamil acutely increased urinary pH (ΔpH: 0.33 ± 0.07) and reduced NH₄⁺ and titratable acid excretion and that these effects were distinctly enhanced in animals fed a low-K⁺ diet (ΔpH: 0.74 ± 0.12), a condition when ENaC activity is low. In contrast, benzamil did not affect urine acid excretion in animals kept on a high-K⁺ diet (i.e., during high ENaC activity). Thus, urine alkalization appeared completely uncoupled from ENaC function. The absence of benzamil-induced urinary alkalization in HKA double-knockout mice confirmed the direct involvement of these enzymes. The inhibitory effect of benzamil was also shown in vitro for the pig α₁-isoform of HKA. These results suggest a revised explanation of the benzamil effect on renal acid-base excretion. Considering the conditions used here, we suggest that it is caused by a direct inhibition of HKAs in the collecting duct and not by inhibition of the ENaC function.NEW & NOTEWORTHY Bolus application of epithelial Na⁺ channel (EnaC) blockers causes marked and acute increases of urine pH. Here, we provide evidence that the underlying mechanism involves direct inhibition of the H⁺-K⁺ pump in the collecting duct. This could provide a fundamental revision of the previously assumed mechanism that suggested a key role of ENaC inhibition in this response.

ENaC expression correlates with the acute furosemide-induced K+ excretion

BACKGROUND

In the aldosterone-sensitive distal nephron (ASDN), epithelial sodium channel (ENaC)-mediated Na+ absorption drives K+ excretion. K+ excretion depends on the delivery of Na+ to the ASDN and molecularly activated ENaC. Furosemide is known as a K+ wasting diuretic as it greatly enhances Na+ delivery to the ASDN. Here, we studied the magnitude of acute furosemide-induced kaliuresis under various states of basal molecular ENaC activity.

METHODS

C57/Bl6J mice were subjected to different dietary regimens that regulate molecular ENaC expression and activity levels. The animals were anesthetized and bladder-catheterized. Diuresis was continuously measured before and after administration of furosemide (2 µg/g BW) or benzamil (0.2 µg/g BW). Flame photometry was used to measure urinary [Na+ ] and [K+ ]. The kidneys were harvested and, subsequently, ENaC expression and cleavage activation were determined by semiquantitative western blotting.

RESULTS

A low K+ and a high Na+ diet markedly suppressed ENaC protein expression, cleavage activation, and furosemide-induced kaliuresis. In contrast, furosemide-induced kaliuresis was greatly enhanced in animals fed a high K+ or low Na+ diet, conditions with increased ENaC expression. The furosemide-induced diuresis was similar in all dietary groups.

CONCLUSION

Acute furosemide-induced kaliuresis differs greatly and depends on the a priori molecular expression level of ENaC. Remarkably, it can be even absent in animals fed a high Na+ diet, despite a marked increase of tubular flow and urinary Na+ excretion. This study provides auxiliary evidence that acute ENaC-dependent K+ excretion requires both Na+ as substrate and molecular activation of ENaC.

Improved dairy cattle mating plans at herd level using genomic information

From 2012 to 2018, 223 180 Montbéliarde females were genotyped in France and the number of newly genotyped females increased at a rate of about 33% each year. With female genotyping information, farmers have access to the genomic estimated breeding values of the females in their herd and to their carrier status for genetic defects or major genes segregating in the breed. This information, combined with genomic coancestry, can be used when planning matings in order to maximize the expected on-farm profit of future female offspring. We compared different mating allocation approaches for their capacity to maximize the expected genetic gain while limiting expected progeny inbreeding and the probability to conceive an offspring homozygous for a lethal recessive allele. Three mate allocation strategies (random mating (RAND), sequential mating (gSEQ€) and linear programing mating (gLP€)) were compared on 160 actual Montbéliarde herds using male and female genomic information. Then, we assessed the benefit of using female genomic information by comparing matings planned using only female pedigree information with the equivalent strategy using genomic information. We measured the benefit of adding genomic expected inbreeding and risk of conception of an offspring homozygous for a lethal recessive allele to Net merit in mating plans. The influence of three constraints was tested: by relaxing the constraint on availability of a particular semen type (sexed or conventional) for bulls, by adding an upper limit of 8.5% coancestry between mate pairs or by using a more stringent maximum use of a bull in a herd (5% vs 10%). The use of genomic information instead of pedigree information improved the mate allocation method in terms of progeny expected genetic merit, genetic diversity and risk to conceive an offspring homozygous for a lethal recessive allele. Optimizing mate allocation using linear programming and constraining coancestry to a maximum of 8.5% per mate pair reduced the average coancestry with a small impact on expected Net Merit. In summary, for male and female selection pathways, using genomic information is more efficient than using pedigree information to maximize genetic gain while constraining the expected inbreeding of the progeny and the risk to conceive an offspring homozygous for a lethal recessive allele. This study also underlines the key role of semen type (sexed vs conventional) and the associated constraints on the mate allocation algorithm to maximize genetic gain while maintaining genetic diversity and limiting the risk to conceive an offspring homozygous for a lethal recessive allele.

Impaired Renal HCO3 - Excretion in Cystic Fibrosis

BACKGROUND

Patients with cystic fibrosis (CF) do not respond with increased urinary HCO₃ ^- excretion after stimulation with secretin and often present with metabolic alkalosis.

METHODS

By combining RT-PCR, immunohistochemistry, isolated tubule perfusion, in vitro cell studies, and in vivo studies in different mouse models, we elucidated the mechanism of secretin-induced urinary HCO₃ ^- excretion. For CF patients and CF mice, we developed a HCO₃ ^- drinking test to assess the role of the cystic fibrosis transmembrane conductance regulator (CFTR) in urinary HCO₃ ^-excretion and applied it in the patients before and after treatment with the novel CFTR modulator drug, lumacaftor-ivacaftor.

RESULTS

β-Intercalated cells express basolateral secretin receptors and apical CFTR and pendrin. In vivo application of secretin induced a marked urinary alkalization, an effect absent in mice lacking pendrin or CFTR. In perfused cortical collecting ducts, secretin stimulated pendrin-dependent Cl^-/HCO₃ ^- exchange. In collecting ducts in CFTR knockout mice, baseline pendrin activity was significantly lower and not responsive to secretin. Notably, patients with CF (F508del/F508del) and CF mice showed a greatly attenuated or absent urinary HCO₃ ^--excreting ability. In patients, treatment with the CFTR modulator drug lumacaftor-ivacaftor increased the renal ability to excrete HCO₃ ^-.

CONCLUSIONS

These results define the mechanism of secretin-induced urinary HCO₃ ^- excretion, explain metabolic alkalosis in patients with CF, and suggest feasibility of an in vivo human CF urine test to validate drug efficacy.

Itch relief in patients with psoriasis: effectiveness of calcipotriol plus betamethasone dipropionate foam

BACKGROUND

Itch is common in psoriasis, adversely affecting health-related quality of life (HRQoL) and sleep.

OBJECTIVE

We evaluated the efficacy of topical fixed-dose combination calcipotriol 50 μg/g plus betamethasone dipropionate 0.5 mg/g cutaneous foam (Cal/BD foam) on itch, itch-related sleep loss and HRQoL vs. foam vehicle.

METHODS

We pooled data from three Phase II/III trials (NCT01536886/NCT01866163/NCT02132936) of Cal/BD foam vs. foam vehicle in adults with mild-severe psoriasis. For itch-related analyses, patients with baseline itch visual analogue scale (VAS) >40 (range 0-100) were analysed. Outcomes included the following: itch VAS reduction >40, ≥70% improvement in itch (Itch70) or itch-related sleep loss, 75% improvement in modified Psoriasis Area and Severity Index (excluding head; mPASI75) and Dermatology Life Quality Index (DLQI) scores 0/1 through 4 weeks.

RESULTS

Of 837 patients, 800 had baseline itch VAS >0 (Cal/BD foam, n = 610; foam vehicle, n = 190); 484 had baseline itch VAS >40. There was no correlation between itch VAS score and mPASI at baseline (R²  = 0.021). In patients with baseline itch VAS >40, more patients achieved itch VAS reduction >40 in the active vs. vehicle group from Day 5 onwards (Day 5: 57.5% vs. 40.2% [P < 0.05]; Week 4: 83.0% vs. 45.8% [P < 0.001]). More Cal/BD-foam-treated patients achieved Itch70 at Day 3 (34.2% vs. 22.5%; P < 0.05) through to Week 4 (79.3% vs. 38.1%; P < 0.001). In patients with baseline itch VAS >40 and sleep loss >20, improvements in itch-related sleep loss occurred at Week 1 and continued through 4 weeks. Itch-related improvements occurred before improvements in mPASI75. There were significant differences in the proportion of Cal/BD-foam- vs. foam-vehicle-treated patients with baseline DLQI >10 (n = 172 vs. n = 50) achieving DLQI ≤1 (25.0% vs. 4.0%; P = 0.001) and DLQI 0 (17.4% vs. 2.0%; P = 0.006) at Week 4.

CONCLUSION

Compared with foam vehicle, Cal/BD foam offers more rapid and effective itch relief, with associated significant improvements in sleep and DLQI.

Rapid onset of action of calcipotriol/betamethasone dipropionate cutaneous foam in psoriasis, even in patients with more severe disease

BACKGROUND

The effectiveness of topical therapies in psoriasis is dependent on, amongst other factors, patient adherence. Together with treatment effectiveness and reduction of symptoms, speed of onset and health-related quality of life (HRQoL) are important influencers of adherence.

METHODS

This pooled analysis of three Phase II/III trials evaluated the efficacy of topical fixed-dose combination calcipotriol 50 μg/g plus betamethasone dipropionate 0.5 mg/g cutaneous foam (Cal/BD foam) vs. foam vehicle at early timepoints in mild-to-severe psoriasis using clinically meaningful modified Psoriasis Area and Severity Index (mPASI) and Dermatology Life Quality Index (DLQI) targets.

RESULTS

A greater proportion of Cal/BD-foam- vs. foam-vehicle-treated patients achieved absolute mPASI targets 0 (15.1% vs. 1.0%), ≤1 (41.4% vs. 5.2%), ≤3 (78.5% vs. 29.2%) and ≤5 (90.2% vs. 62.5%) at week 4 (P < 0.001; all targets). Significant differences between Cal/BD-foam- vs. foam-vehicle-treated patients were observed as early as week 1 in those achieving mPASI ≤1 (6.8% vs. 1.5%; P < 0.01), ≤3 (40.4% vs. 22.8%; P < 0.001) and ≤5 (69.7% vs. 50.8%; P < 0.001). In patients with more severe psoriasis (baseline mPASI >10), a greater proportion of Cal/BD-foam- vs. foam-vehicle-treated patients achieved mPASI ≤1 (20.2% vs. 5.9%; P < 0.05), ≤3 (49.2% vs. 8.8%; P < 0.001) and ≤5 (63.7% vs. 26.5%; P < 0.001) at week 4. In patients with severely impaired HRQoL (baseline DLQI >10), a greater proportion of Cal/BD-foam- vs. foam-vehicle-treated patients achieved target DLQI ≤1 or 0 (week 4: DLQI ≤1, 25.0% vs. 4%; P = 0.001; DLQI 0, 17.4% vs. 2.0%; P = 0.006).

CONCLUSION

We report rapid onset of action and greater efficacy with Cal/BD foam vs. foam vehicle, even in patients with more severe psoriasis, manageable with topical treatments. This may support physician management of patient expectations and improve patient adherence, translating into overall topical treatment effectiveness.

Hydrochlorothiazide and acute urinary acidification: The "voltage hypothesis" of ENaC-dependent H+ secretion refuted

AIM

The "voltage hypothesis" of H⁺ secretion states that urinary acidification following increased Na⁺ delivery to the collecting duct (CD) is ENaC dependent leading to transepithelial voltage-dependent increase in H⁺ secretion. We recently showed that furosemide acidifies the urine independently of ENaC activity. If the voltage hypothesis holds, hydrochlorothiazide (HCT) must acidify the urine. We here tested the acute effect of HCT on urine pH under normal and high ENaC expression.

METHODS

Mice subjected to a control or a low-Na⁺ diet were anesthetized and infused (0.5 mL h^-1 ) with saline. Catheterization of the urinary bladder allowed real-time measurement of diuresis and urine pH. Mice received either HCT (1 mg mL^-1 ) or vehicle. Urinary Na⁺ and K⁺ excretions were determined by flame photometry. ENaC expression levels were measured by semi-quantitative Western blotting.

RESULTS

(1) HCT increased diuresis and natriuresis in both diet groups. (2) K⁺ excretion rates increased after HCT administration from 18.6 ± 1.3 to 31.7 ± 2.5 μmol h^-1 in the control diet group and from 23.0 ± 1.3 to 48.7 ± 3.0 μmol h^-1 in the low-Na⁺ diet group. (3) Mice fed a low-Na⁺ diet showed a marked upregulation of ENaC. (4) Importantly, no acute changes in urine pH were observed after the administration of HCT in either group.

CONCLUSION

Acute administration of HCT has no effect on urine pH. Similarly, substantial functional and molecular upregulation of ENaC did not cause HCT to acutely change urine pH. Thus, an increased Na⁺ load to the CD does not alter urine pH. This supports our previous finding and likely falsifies the voltage hypothesis of H⁺ secretion.

Does the DSA reconstruction kernel affect hemodynamic predictions in intracranial aneurysms? An analysis of geometry and blood flow variations

BACKGROUND

Computational fluid dynamics (CFD) blood flow predictions in intracranial aneurysms promise great potential to reveal patient-specific flow structures. Since the workflow from image acquisition to the final result includes various processing steps, quantifications of the individual introduced potential error sources are required.

METHODS

Three-dimensional (3D) reconstruction of the acquired imaging data as input to 3D model generation was evaluated. Six different reconstruction modes for 3D digital subtraction angiography (DSA) acquisitions were applied to eight patient-specific aneurysms. Segmentations were extracted to compare the 3D luminal surfaces. Time-dependent CFD simulations were carried out in all 48 configurations to assess the velocity and wall shear stress (WSS) variability due to the choice of reconstruction kernel.

RESULTS

All kernels yielded good segmentation agreement in the parent artery; deviations of the luminal surface were present at the aneurysm neck (up to 34.18%) and in distal or perforating arteries. Observations included pseudostenoses as well as noisy surfaces, depending on the selected reconstruction kernel. Consequently, the hemodynamic predictions show a mean SD of 11.09% for the aneurysm neck inflow rate, 5.07% for the centerline-based velocity magnitude, and 17.83%/9.53% for the mean/max aneurysmal WSS, respectively. In particular, vessel sections distal to the aneurysms yielded stronger variations of the CFD values.

CONCLUSIONS

The choice of reconstruction kernel for DSA data influences the segmentation result, especially for small arteries. Therefore, if precise morphology measurements or blood flow descriptions are desired, a specific reconstruction setting is required. Furthermore, research groups should be encouraged to denominate the kernel types used in future hemodynamic studies.

Evolving gene banks: improving diverse populations of crop and exotic germplasm with optimal contribution selection

We simulated pre-breeding in evolving gene banks - populations of exotic and crop types undergoing optimal contribution selection for long-term genetic gain and management of population genetic diversity. The founder population was based on crosses between elite crop varieties and exotic lines of field pea (Pisum sativum) from the primary genepool, and was subjected to 30 cycles of recurrent selection for an economic index composed of four traits with low heritability: black spot resistance, flowering time and stem strength (measured on single plants), and grain yield (measured on whole plots). We compared a small population with low selection pressure, a large population with high selection pressure, and a large population with moderate selection pressure. Single seed descent was compared with S0-derived recurrent selection. Optimal contribution selection achieved higher index and lower population coancestry than truncation selection, which reached a plateau in index improvement after 40 years in the large population with high selection pressure. With optimal contribution selection, index doubled in 38 years in the small population with low selection pressure and 27-28 years in the large population with moderate selection pressure. Single seed descent increased the rate of improvement in index per cycle but also increased cycle time.

The Adrenal Gland in Dogs with Hyperadrenocorticalism; A Pathologic Study

Bilateral adrenocortical hyperplasia was present in 24 of 27 dogs with hyperadrenocorticalism. Two dogs had a unilateral adenoma, and one had a carcinoma of the adrenal cortex.

Bilateral cortical hyperplasia was diffuse or nodular. The difference between the two patterns of hyperplasia was not associated with any consistent varation in the clinical or endocrinologic features. In the three dogs with adrenal cortical neoplasia there was marked cortical atrophy of the contralateral adrenal gland. Extracapsular nodular hyperplasia was common in the adrenals of dogs with hyperadrenocorticalism and also in older control dogs without endocrine disease. Ten of the dogs with bilateral adrenocortical hyperplasia were examined postmortem; two had a chromophobe adenoma of the pituitary, but no pituitary lesion was found in the others.

The Computational Fluid Dynamics Rupture Challenge 2013—Phase I: prediction of rupture status in intracranial aneurysms

BACKGROUND AND PURPOSE

Rupture risk assessment for intracranial aneurysms remains challenging, and risk factors, including wall shear stress, are discussed controversially. The primary purpose of the presented challenge was to determine how consistently aneurysm rupture status and rupture site could be identified on the basis of computational fluid dynamics.

MATERIALS AND METHODS

Two geometrically similar MCA aneurysms were selected, 1 ruptured, 1 unruptured. Participating computational fluid dynamics groups were blinded as to which case was ruptured. Participants were provided with digitally segmented lumen geometries and, for this phase of the challenge, were free to choose their own flow rates, blood rheologies, and so forth. Participants were asked to report which case had ruptured and the likely site of rupture. In parallel, lumen geometries were provided to a group of neurosurgeons for their predictions of rupture status and site.

RESULTS

Of 26 participating computational fluid dynamics groups, 21 (81%) correctly identified the ruptured case. Although the known rupture site was associated with low and oscillatory wall shear stress, most groups identified other sites, some of which also experienced low and oscillatory shear. Of the 43 participating neurosurgeons, 39 (91%) identified the ruptured case. None correctly identified the rupture site.

CONCLUSIONS

Geometric or hemodynamic considerations favor identification of rupture status; however, retrospective identification of the rupture site remains a challenge for both engineers and clinicians. A more precise understanding of the hemodynamic factors involved in aneurysm wall pathology is likely required for computational fluid dynamics to add value to current clinical decision-making regarding rupture risk.

Composite-light-pulse technique for high-precision atom interferometry

We realize beam splitters and mirrors for atom waves by employing a sequence of light pulses rather than individual ones. In this way we can tailor atom interferometers with improved sensitivity and accuracy. We demonstrate our method of composite pulses by creating a symmetric matter-wave interferometer which combines the advantages of conventional Bragg- and Raman-type concepts. This feature leads to an interferometer with a high immunity to technical noise allowing us to devise a large-area Sagnac gyroscope yielding a phase shift of 6.5 rad due to the Earth's rotation. With this device we achieve a rotation rate precision of 120  nrad s(-1) Hz(-1/2) and determine the Earth's rotation rate with a relative uncertainty of 1.2%.

Genetic characterization of a herd of the endangered Danish Jutland cattle

In this paper we present results from a genetic characterization of a herd of the Danish Jutland cattle breed named the Kortegaard herd (n = 135; 57 males and 78 females). The herd is genotyped on the Bovine HD BeadChip microarray with 697,548 evenly spaced SNP across the bovine genome. The aim of the study was to characterize the genetic profile of the Kortegaard herd, which has been closed for several generations, by quantifying the degree of genetic homogeneity within the herd and to compare its genetic profile to that of other cattle breeds. A total of 868 animals from the Angus, Belgian Blue, Charolais, Friesian, Hereford, Holstein, Holstein-Friesian crosses, Limousin, and Simmental breeds was used for genetic profile comparisons. The level of genetic variation within the breeds were quantified by the expected heterozygosity (H(E)), observed heterozygosity (H(O)), average minor allele frequency (MAF), the degree of polymorphism, and runs of homozygosity (ROH), which are contiguous lengths of homozygous genotypes of varying length. Interestingly, the Kortegaard herd had the lowest within-breed genetic variation (lowest H(E), H(O), and MAF), showed moderate levels of short ROH (<5 Mb), and had the highest mean long ROH (>5 Mb) compared to all the other breeds. This is possibly due to recent consanguineous matings, a strong founder effect, and a lack of gene flow from other herds and breeds. We further examined whether the observed genetic patterns in the Kortegaard herd can be used to design breeding strategies for the preservation of the genetic pool by focusing on a subset of SNP outside homozygote regions. By calculating the pairwise identical-by-state between all possible matings, we designed a breeding plan that maximized heterozygosity in the short term. The benefits and limitations of such a breeding strategy are discussed.

Indirect genetic effects and kin recognition: estimating IGEs when interactions differ between kin and strangers

Social interactions among individuals are widespread, both in natural and domestic populations. As a result, trait values of individuals may be affected by genes in other individuals, a phenomenon known as indirect genetic effects (IGEs). IGEs can be estimated using linear mixed models. The traditional IGE model assumes that an individual interacts equally with all its partners, whether kin or strangers. There is abundant evidence, however, that individuals behave differently towards kin as compared with strangers, which agrees with predictions from kin-selection theory. With a mix of kin and strangers, therefore, IGEs estimated from a traditional model may be incorrect, and selection based on those estimates will be suboptimal. Here we investigate whether genetic parameters for IGEs are statistically identifiable in group-structured populations when IGEs differ between kin and strangers, and develop models to estimate such parameters. First, we extend the definition of total breeding value and total heritable variance to cases where IGEs depend on relatedness. Next, we show that the full set of genetic parameters is not identifiable when IGEs differ between kin and strangers. Subsequently, we present a reduced model that yields estimates of the total heritable effects on kin, on non-kin and on all social partners of an individual, as well as the total heritable variance for response to selection. Finally we discuss the consequences of analysing data in which IGEs depend on relatedness using a traditional IGE model, and investigate group structures that may allow estimation of the full set of genetic parameters when IGEs depend on kin.

Abstract P5-09-11: BP1, a homeoprotein, regulates estrogen receptor alpha and induces estrogen independence

Introduction: BP1 is a member of the homeobox gene family of transcription factors. Our recent studies have shown that BP1 may play a role in breast cancer cell survival, aggressiveness and metastasis. BP1 protein (pBP1) is expressed in 80% of invasive ductal breast tumors. Moreover, 100% of inflammatory breast tumors are BP1 positive. These data led us to define the mechanism of BP1-related tumorigenesis and aggressiveness in breast cancer.

Materials and Methods: MCF-7/O1, O2 and O4 cells overexpressing BP1 and control V1 and V2 cells were tested for growth in estrogen free media, malignant potential and invasiveness using cell viability assays, soft agar assays and matrigel assays, respectively. To determine the influence of BP1 overexpression on tumor characteristics, empty vector cells (V1) and overexpressor cells (O2 and O4) were injected into the fat pads of athymic nude mice. Mice were supplemented with estrogen pellets or were unsupplemented. Chromatin immunoprecipitation assays (ChIP) were used to validate the binding of pBP1 to ERa and EP300. The effects of BP1 expression on ERα and EP300 were investigated using immunoblotting and qRT-PCR. Effects of BP1 overexpression on tamoxifen sensitivity were measured using the MTT assay.

Results: Cells overexpressing BP1 showed higher viability (p&lt;0.05) when grown in the absence of serum, greater invasive potential (p&lt;0.05) and formed larger and more rapidly growing colonies (p&lt;0.0001) compared with cells containing the empty vector. Tumors were larger in mice receiving O1, O2 or O4 cells than in mice receiving V1 or V2 cells (p&lt;0.0001). There was also a positive correlation between BP1 mRNA levels and tumor size in patients (p = 0.01). 20% of mice injected with O2 or O4 developed tumors in the absence of estrogen, in contrast to control mice which did not develop tumors. Several mechanisms of estrogen independence related to BP1 were established: (1) an indirect mechanism, in which BP1 stabilizes ERα protein by transcriptional activation of p300, and (2) a direct mechanism, in which BP1 binds to the first intron of ERα and upregulates ERα RNA and protein expression. In addition, breast cancer anti-estrogen resistance 1 (BCAR1) RNA expression was higher in O2 as compared to V1 cells. Consistent with these findings, O2 cells exhibited increased proliferation when treated with tamoxifen, while V1 cells showed growth inhibition.

Conclusion: High BP1 levels can lead to estrogen independence in ER positive breast cancer cells and tumors in mice by at least two mechanisms, indirect and direct, and are associated with resistance to tamoxifen. These results suggest that BP1 may be an important therapeutic target in ER positive breast cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-09-11.

Characterization of the genetic profile of five Danish dog breeds

This investigation presents results from a genetic characterization of 5 Danish dog breeds genotyped on the CanineHD BeadChip microarray with 170,000 SNP. The breeds investigated were 1) Danish Spitz (DS; n=8), 2) Danish-Swedish Farm Dog (DSF; n=18), 3) Broholmer (BR; n=22), 4) Old Danish Pointing Dog (ODP; n=24), and 5) Greenland Dog (GD; n=23). The aims of the investigation were to characterize the genetic profile of the abovementioned dog breeds by quantifying the genetic differentiation among them and the degree of genetic homogeneity within breeds. The genetic profile was determined by means of principal component analysis (PCA) and through a Bayesian clustering method. Both the PCA and the Bayesian clustering method revealed a clear genetic separation of the 5 breeds. The level of genetic variation within the breeds varied. The expected heterozygosity (HE) as well as the degree of polymorphism (P%) ranked the dog breeds in the order DS>DSF>BR>ODP>GD. Interestingly, the breed with a tenfold higher census population size compared to the other breeds, the Greenland Dog, had the lowest within-breed genetic variation, emphasizing that census size is a poor predictor of genetic variation. The observed differences in variation among and within dog breeds may be related to factors such as genetic drift, founder effects, genetic admixture, and population bottlenecks. We further examined whether the observed genetic patterns in the 5 dog breeds can be used to design breeding strategies for the preservation of the genetic pool of these dog breeds.

Most of the benefits from genomic selection can be realized by genotyping a small proportion of available selection candidates

We reasoned that marginal returns from genomic selection diminish as the proportion of genotyped selection candidates increases and breeding values (BV) based on a priori information are used to choose candidates that are genotyped. We tested this premise by stochastic simulation of breeding schemes that resembled those used for pigs. We estimated rates of genetic gain and inbreeding realized by genomic selection in breeding schemes where candidates were phenotyped before genotyping and 0 to 100% of the candidates were genotyped based on predicted BV. Genotyping was allocated to male and female candidates at ratios of 100:0, 75:25, 50:50, 25:75, and 0:100. For genotyped candidates, a direct-genomic value (DGV) was sampled with reliabilities 0.10, 0.50, and 0.90. Ten sires and 300 dams with the largest BV after genotyping were selected at each generation. Selection was for a single trait with heritability 0.20. We found that the marginal returns did diminish as genotyping proportion was increased, while the rate at which the returns diminished slowed as DGV became more reliable. With DGV reliability 0.10, genotyping as little as 5% of the selection candidates realized 86% of the additional genetic gain and 67% of the reduction in inbreeding that was realized by genotyping 100% of the candidates. All of the genetic gain and reduction in inbreeding was realized by genotyping 40 and 50% of the candidates. When the reliability was increased to 0.90, genotyping 20% of the candidates was required to realize 76% of the genetic gain and 85% of the reduction in inbreeding. Genotyping 50% of the selection candidates with DGV reliability 0.90 realized 91% of the genetic gain and 94% of the reduction in inbreeding. Regardless of DGV reliability, returns at small genotyping proportions of 0.5 to 10% were maximized when only male candidates were genotyped. At the large genotyping proportions of 20 to 50%, returns were maximized by genotyping both males and females. Our findings indicate that, provided a priori information is available, only 5 to 20% of the selection candidates need to be genotyped to realize most of the benefits from genomic selection. At these genotyping proportions, it is best to target males in schemes when selection intensity for males is greater than females. Our findings should benefit breeders because they suggest that large investments in genotyping are not required to reap most of the benefits from genomic selection.

Oral transmission as a route of infection for viral haemorrhagic septicaemia virus in rainbow trout, Oncorhynchus mykiss (Walbaum)

Surveys among wild marine fish have revealed occurrence of viral haemorrhagic septicaemia virus (VHSV) infections in a high number of diverse fish species. In marine aquaculture of rainbow trout, preying on invading wild fish might thus be a risk factor for introduction and adaptation of VHSV and subsequent disease outbreaks. Our objective was to determine whether an oral transmission route for VHSV in rainbow trout exists. Juvenile trout were infected through oral, waterborne and cohabitation transmission routes, using a recombinant virus strain harbouring Renilla luciferase as reporter gene. Viral replication in stomach and kidney tissue was detected through bioluminescence activity of luciferase and qRT-PCR. Replication was detected in both tissues, irrespective of transmission route. Replication patterns, however, differed among transmission routes. In trout infected through oral transmission, replication was detected in the stomach prior to kidney tissue. In trout infected through waterborne or cohabitation transmission, replication was detected in kidney prior to stomach or in both tissues simultaneously. We demonstrate the existence of an oral transmission route for VHSV in rainbow trout. This implies that preying on invading infected wild fish is a risk factor for introduction of VHSV into marine cultures of rainbow trout.