1041 Impact of Spectral Contamination and Anatomical Location on Diagnostic Accuracy of Single-Voxel Spectroscopy in Pre-Operative Glioma Characterisation

Aim

Single-voxel spectroscopy (SVS) discriminates amongst brain tumours by measuring metabolite variations reflective of malignant transformation. However, spectral contamination may affect diagnostic accuracy, impacting radiological opinion of regions of interest (ROI) required to determine extent of surgical resection.

Method

A single-centre, retrospective, observational study, including 93 SVS meaningfully interpretable examinations between 2012 and 2018. Accuracy of lesion classification was assessed by comparison of histological diagnosis as reference standards against discrimination between entities and tumour grades by SVS, with consideration for voxel location, volume, and proximity to the calvaria or ventricular system. Quantification of metabolites was recorded as ratios, and visual inspection, qualitative and descriptive analysis were undertaken.

Results

SVS demonstrated high entity accuracy (100%) but lower grade accuracy (87%), ranging from periventricular (73%) vs non-periventricular (90%), and subcalvarial (86%) vs subcortical (88%) voxels. CSF contamination caused metabolite dilution and/or enhanced lactate signals from sub-arachnoid or ventricular CSF, especially in areas of increased brain-skull distance; lipid contamination from peri-calvarial fat and subcutaneous tissue resulted in enhanced lipid signals neighbouring areas of increased brain-scalp distance. Misclassified lesions were located regions of increased cranial concavity, reduced cerebral cortical thickness and inappropriate outer volume suppression (OVS). Voxel volume variation had no impact across cerebral coordinates (p=0.605), calvaria proximity (p=0.127) or ventricular proximity (p=0.367).

Conclusion

Spectral contamination significantly impacted grade accuracy, with metabolite dilution and enhance lactate and lipids signals leading to radiological under- and overestimation of glioma grade, respectively, thus indicating that avoidance of contaminating tissues and OVS are pivotal to adequate spectral quality for diagnostic accuracy.

1040 Metabolite Quantification and Entity and Grade Characterisation of Gliomas via Single-Voxel Spectroscopy for Pre-Operative Radiological Diagnosis

Aim

Brain tumours pose a diagnostic challenge, but single-voxel spectroscopy (SVS) provides a non-invasive tool to quantify brain metabolite variations reflective of neoplasia, such as NAA, choline (Cho), creatinine (Cr), lipids (Lip) and lactate (Lac). Inconsistency in spectroscopic research and time-patient pressures emphasises the need for reviewing SVS characterisation of gliomas for peri-operative decision-making.

Method

A single-centre, retrospective, observational study, including 93 SVS meaningfully interpretable examinations between 2012 and 2018 (PRESS, TE=35ms, 144ms). Spectroscopic diagnoses were compared to histopathologic reports for overall, entity and grade accuracy analysis. Metabolite ratios to Cr were recorded or obtained from peak area integrals.

Results

High accuracy of lesions discrimination was observed (83–98%). Significant metabolite variation for Cho/Cr (p=0.021) and Cho/NAA (p=0.013) was observed across grades (WHO Grade I-IV). Spectra of astrocytomas and oligodendrogliomas (grade II) were similarly characterised by high Cho, decreased NAA and Cr, and small-to-moderate Lac-Lip and mIns. In contrast, grade III anaplastic oligodendrogliomas (AO) were distinguished from anaplastic astrocytomas (AA) thanks to smaller Lac-Lip and mIns/Cr. Finally, glioblastoma multiforme (GBM, grade IV) displayed high Cho, decreased Cr, the lowest or virtually absent NAA, and the highest Lac-Lip. High-grade spectroscopy, such as enhanced Lac or Lac-Lip, may be an early indicator of grade transformation prior to reflection in histopathology in tumours, which were follow up prospectively.

Conclusion

This study enhanced spectral characterisation of gliomas and discrimination amongst low- and high-grade gliomas. Whilst these aid pre-operative radiological diagnoses, further research is required to investigate spectroscopy predictive of tumour genetics, now necessary for diagnosis.

Optimal left ventricular lead positioning during cardiac resynchronisation therapy; a comparison of 2 methods

Background/Introduction

Superior response to CRT and improved clinical outcomes can be achieved when placing the left ventricular (LV) lead at the site of latest mechanical activation and avoiding regions of scar during cardiac resynchronisation therapy (CRT). The site of latest mechanical activation can be identified using speckle-tracking echocardiography, whilst the area of latest electrical activation can be assessed by measuring QLV, the time from the initial deflection of the surface QRS complex to sensing at the LV lead electrode. It remains unclear if the two techniques are interchangeable and whether the site of latest mechanical activation is related to the site of latest electrical activation, or sensed electrical signals correspond to sites of scar.

Purpose

To determine whether electrical targeting of LV lead position corresponds to echo-guided mechanical targeting and whether myocardial electrogram signals can predict areas of myocardial scar

Methods

This was a pilot study of patients receiving CRT, in sinus rhythm with severe LV impairment (ejection fraction ≤35%) and left bundle branch block (LBBB) with QRS ≥130ms. Ethics approval was obtained, and written consent was sought. Participants underwent echocardiographic speckle-tracking 2-dimensional radial strain imaging to identify amplitude and time to peak contraction of posterior, posterolateral, lateral, anterolateral and anterior segments. During CRT implant, the sensed R wave and QLV were measured at the respective branch of the coronary sinus, where the anatomy permitted. The site of latest mechanical was compared to the site of latest electrical activation and classified as concordant (same site), adjacent (within 1 segment), or remote (2 segments away). The strain amplitude was compared to the sensed R wave and time to mechanical activation with QLV.

Results

Seventeen patients (13 male) were studied, mean age 74.2 (SD 8.7). Mean QRS was 161 ms (SD 18), mean PR 186 ms (SD 37). A modest and significant positive correlation was found between the site of latest mechanical and latest electrical activation (Pearson r=0.66, p 0.004). The site of latest electrical activation was concordant with latest mechanical activation in 13 patients (76.5%), adjacent in 4 patients (23.5%) and remote in none. There was no apparent association between sensed R wave and strain amplitude (Pearson r=0.2, p=0.12) or between QLV and time to mechanical activation (Pearson r=0.1, p=0.5).

Conclusion

A significant positive correlation was found between the site of latest mechanical and latest electrical activation in patients undergoing CRT implant. Electrical targeting might be a suitable alternative to mechanical targeting particularly when imaging is not available, however, does not appear to discriminate scar. Future larger studies are needed to confirm our findings and determine whether QLV can be used as an alternative method for targeting LV lead placement.

Funding Acknowledgement

Type of funding sources: None.

P–574 Examination of inter centre variation in PGT-A “no result rate” and efficacy of rebiopsy - Analysis of 22,833 samples 2015–2019

Study question

Are there significant differences in PGT-A “no result” rates and clinical outcomes following rebiopsy between ART clinics, and do rebiopsied embryos perform better than transferring with no result?

Summary answer

There is significant differences between clinics in terms of “no result rate” in PGT-A and utilisation of rebiopsy. What is known already: With any testing platform used in PGT-A, there is always a chance that a sample will not yield a result and rebiopsy may be considered to ascertain an embryos cytogenetic status. Studies have demonstrated rebiopsy yields results and adds to embryos genetically suitable for transfer. Clinical outcome data, however, remains scarce, leading to difficulty for clinics in benchmarking their performance when rebiopsied embryos are transferred.

Study design, size, duration

A retrospective analysis was performed of trophectoderm samples submitted for PGT-A via NGS over a 5yr period, 2015–2019. The no result (NR) rate was calculated per year and per clinic. Clinics were contacted for follow up data on NR embryos in terms of usage and clinical outcomes. Clinical outcomes from rebiopsied embryos were compared with those transferred as NR without rebiopsy.

Participants/materials, setting, methods

Data was collected on 22833 trophectoderm samples, submitted by 30 IVF laboratories. NR rate was analysed by year and by clinic. Clinics were asked if NR embryos had undergone rebiopsy, and if so if they had survived warming and rebiopsy. Clinics were asked if embryos selected for transfer had survived (re)warming, and to provide clinical follow-up including hCG test, clinical pregnancies, miscarriage and livebirth. The two tailed Fishers exact test was used for statistical analysis.

Main results and the role of chance

There was a wide range in sample numbers submitted by clinics over the time period, ranging from 9 samples through to 2633. In tclinics submitting over 500 samples the NR rate ranged from 0.6% to 7.4%, and in the those submitting 100–499 samples it ranged from 1.1% to 5.8%. Both these differences proved to be statistically significant (p < 0.05) between the best and worst performing clinics, and shows that a gap in performance exists between clinics. Less than 50% of NR embryos underwent rebiopsy. While the majority of embryos undergoing rebiopsy yielded a result (92.3%) and 31.4% of these were euploid or mosaic, almost half still remain in storage. The rate of livebirth/ongoing implantation in the rebiopsy group is 35.5% and 17.1% in the non rebiopsy group, illustrating a non significant trend towards a higher chance of implantation and livebirth in the rebiopsy group. Of 58 patients undergoing rebiopsy without any euploids in their initial cycle, 18 had a euploid embryo identified for future use. The additional manipulations involved in rebiopsy do not impact on survival at warming for transfer, but clinical outcomes in rebiopsied embryos appear poorer than those where a result was generated at first biopsy.

Limitations, reasons for caution

Despite starting with 22833 samples, 1115 of which were classified as NR, there were only 31 rebiopsied and 42 NR embryos transferred. It was therefore not possible to analyse transfer data by clinic or by embryo quality.

Wider implications of the findings: Rebiopsy yields genetic results and embryos suitable for patient use, including for patients who produced no other euploid/mosaic embryos in their cycle. However, it is not offered/performed in many cases. Clinical outcome data must continue to be compiled and analysed to confirm performance exceeds transfer of NR embryos.

Trial registration number

Not applicable

Pituitary tumour types in dogs and cats

Pituitary tumours are common in dogs and are being increasingly recognized in cats. Pituitary tumours are usually classified as adenomas and should only be classified as carcinomas when there is evidence of metastatic spread of the tumour, which is rare. Despite the benign nature of most pituitary tumours, they can still compress or invade neighbouring tissues. Pituitary tumours can be functional (hormonally active) or non-functional (hormonally silent). The aim of this review was to provide an overview of the different pituitary tumour types in dogs and cats that have been reported in the literature. In dogs, the most common pituitary tumour type is the corticotroph adenoma, which can cause pituitary-dependent hypercortisolism. In cats, the most common pituitary tumour is the somatotroph adenoma, which can cause hypersomatotropism, and the second-most common is the corticotroph adenoma. A lactotroph adenoma has been described in one dog, while gonadotroph, thyrotroph and null cell adenomas have not been described in dogs or cats. Hormonally silent adenomas are likely underdiagnosed because they do not result in an endocrine syndrome. Tools used to classify pituitary tumours in humans, particularly immunohistochemistry for lineage-specific transcription factors, are likely to be useful to classify canine and feline pituitary tumours of unknown origin. Future studies are required to better understand the full range of pituitary adenoma pathology in dogs and cats and to determine whether certain adenoma subtypes behave more aggressively than others. Currently, the mechanisms that underlie pituitary tumorigenesis in dogs and cats are still largely unknown. A better understanding of the molecular background of these tumours could help to identify improved pituitary-targeted therapeutics.

Determination of Patulin in Apple Juice

A method is described for the quantitative analysis of patulin in apple juice involving ethyl acetate extraction followed by derivatization of the patulin and subsequent GLC analysis of the derivative. Preparation of 3 derivatives, the silyl ether, acetate, and chloroacetate, is described. Using the acetate derivative and the hydrogen flame detector, recoveries of patulin in spiked apple juice are 90% or better and the detection limit is about 0.7 μg/ml

Treating canine Cushing's syndrome: Current options and future prospects

Naturally occurring hypercortisolism, also known as Cushing's syndrome, is a common endocrine disorder in dogs that can be caused by an adenocorticotrophic hormone (ACTH)-producing pituitary adenoma (pituitary-dependent hypercortisolism, PDH; 80-85% of cases), or by an adrenocortical tumor (ACT; 15-20% of cases). To determine the optimal treatment strategy, differentiating between these two main causes is essential. Good treatment options are surgical removal of the causal tumor, i.e. hypophysectomy for PDH and adrenalectomy for an ACT, or radiotherapy in cases with PDH. Because these options are not without risks, not widely available and not suitable for every patient, pharmacotherapy is often used. In cases with PDH, the steroidogenesis inhibitor trilostane is most often used. In cases with an ACT, either trilostane or the adrenocorticolytic drug mitotane can be used. Although mostly effective, both treatments have disadvantages. This review discusses the current treatment options for canine hypercortisolism, and considers their mechanism of action, efficacy, adverse effects, and effect on survival. In addition, developments in both adrenal-targeting and pituitary-targeting drugs that have the potential to become future treatment options are discussed, as a more selective and preferably also tumor-targeted approach could have many advantages for both PDH and ACTs.

Mean Platelet Volume and Size Distribution and Their Sensitivity to Agonists in Patients with Coronary Artery Disease and Congestive Heart Failure

Mean platelet volume was related to platelet count in patients with myocardial infarction (n = 55) and patients with congestive heart failure (n = 9). 18 patients with acute myocardial infarction were tested at admission and 4-7 days later, together with 13 patients with chronic stable angina and 10 patients with chest pain which was not related to coronary artery disease. In citrated blood a relative reduced frequency of large platelets (>13 fl) occured in patients with acute myocardial infarction at admission but was not seen during recovery or in patients with chronic stable angina. This suggests consumption of large platelets at time of thrombus formation. No relation was found between plasma catecholamine levels and mean platelet volumes. Effects of serotonine, adrenaline and CGP 28392, a calcium agonist, on platelet volume distributions were determined. Sensitivity of platelets to adrenaline was increased in patients with acute myocardial infarction on admission and reduced 4-7 days later, while in patients with congestive heart failure reactivity to both serotonine and adrenaline were reduced. This indicates a fast down-regulation during the early recovery phase of myocardial infarction and chronically in congestive heart failure.

Steroidogenic factor-1 inverse agonists as a treatment option for canine hypercortisolism: in vitro study

Hypercortisolism is one of the most commonly diagnosed endocrinopathies in dogs, and new targeted medical treatment options are desirable. Steroidogenic factor-1 (SF-1), an orphan nuclear hormone receptor, is a key regulator of adrenal steroidogenesis, development, and growth. In pituitary-dependent hypercortisolism (PDH), high plasma ACTH concentrations increase the transcriptional activity of SF-1. In adrenal-dependent hypercortisolism, SF-1 expression is significantly greater in dogs with recurrence after adrenalectomy than in those without recurrence. Inhibition of SF-1 could therefore be an interesting treatment option in canine spontaneous hypercortisolism. We determined the effects of 3 SF-1 inverse agonists, compounds IsoQ A, #31, and #32, on cortisol production, on the messenger RNA (mRNA) expression of steroidogenic enzymes and SFs, and on cell viability, in primary adrenocortical cell cultures of 8 normal adrenal glands and of 3 cortisol-secreting adrenocortical tumors (ATs). To mimic PDH, the normal adrenocortical cell cultures were stimulated with ACTH. The results show that only compound #31 inhibited cortisol production and SF-1 target gene expression in non-ACTH-stimulated and ACTH-stimulated normal adrenocortical cells but did not affect cell viability. In the AT cell cultures, the effects of #31 on cortisol production and target gene expression were variable, possibly caused by a difference in the SF-1 mRNA expressions of the primary tumors. In conclusion, inhibition of SF-1 activity shows much promise as a future treatment for canine hypercortisolism.

New Insights in the Functional Zonation of the Canine Adrenal Cortex

BACKGROUND

Current understanding of adrenal steroidogenesis is that the production of aldosterone or cortisol depends on the expression of aldosterone synthase (CYP11B2) and 11β-hydroxylase cytochrome P450 (CYP11B1), respectively. However, this has never been studied in dogs, and in some species, a single CYP11B catalyzes both cortisol and aldosterone formation. Analysis of the canine genome provides data of a single CYP11B gene which is called CYP11B2, and a large sequence gap exists near the so-called CYP11B2 gene.

OBJECTIVES

To investigate the zonal expression of steroidogenic enzymes in the canine adrenal cortex and to determine whether dogs have 1 or multiple CYP11B genes.

ANIMALS

Normal adrenal glands from 10 healthy dogs.

METHODS

Zona fasciculata (zF) and zona glomerulosa (zG) tissue was isolated by laser microdissection. The mRNA expression of steroidogenic enzymes and their major regulators was studied with RT-qPCR. Southern blot was performed to determine whether the sequence gap contains a CYP11B gene copy. Immunohistochemistry (IHC) was performed for 17α-hydroxylase/17,20-lyase (CYP17).

RESULTS

Equal expression (P = .62) of the so-called CYP11B2 gene was found in the zG and zF. Southern blot revealed a single gene. CYP17 expression (P = .05) was significantly higher in the zF compared with the zG, which was confirmed with IHC.

CONCLUSIONS AND CLINICAL IMPORTANCE

We conclude that there is only 1 CYP11B gene in canine adrenals. The zone-specific production of aldosterone and cortisol is probably due to zone-specific CYP17 expression, which makes it an attractive target for selective inhibition of cortisol synthesis without affecting mineralocorticoid production in the zG.

P-glycoprotein-associated resistance to taxol and taxotere and its reversal by dexniguldipine-HCl, dexverapamil-HCl, or cyclosporin A

A series of different human MDR (multidrug-resistant) cell lines including a HeLa-MDR1 transfectant which exhibit high overexpression of the MDR1/P-glycoprotein gene, but no enhanced expression of the MRP (multidrug resistance associated protein) gene, showed different ratios of relative resistances to the taxanes taxol and taxotere. Using these cell lines the chemosensitizing efficacies of several structurally different chemosensitizers, i.e. the dihydropyridine dexniguldipine-HC1 (B8509-035), its main pyridine metabolite M1 (B8909-008), the cyclic peptide cyclosporin A, or the phenylalkylamine dexverapamil-HCl, were examined applying a 72 h tetrazolium based colorimetric MTT-assay, or a 96 h sulforhodamine B assay. Remarkably, we observed in some instances that the modulating efficacy of a particular chemosensitizer was strongly dependent on the cell line used for experimentation. Thus, dexniguldipine-HCl efficiently modulated taxane resistances of the ovarian carcinoma MDR cell line 2780AD in the submicromolar concentration range, whereas cyclosporin A and the other chemosensitizers were rather ineffective. Dexniguldipine-HCl or cyclosporin A, however, both showed a similarly strong modulating activity on the HeLa-MDR1 transfectant in clear contrast to the effects observed using the pyridine B8909-008, or dexverapamil-HCl, respectively, at the same final concentrations. Our results point to additional, as yet unidentified factors beyond the expression levels of P-glycoprotein which could contribute to the susceptibility of MDR cells to a combined treatment using taxanes and different chemosensitizing compounds. This result appears to be important considering the clinical application of chemosensitizers for combination therapy of tumors of different origin.

Genetic variation in PLAG1 associates with early life body weight and peripubertal weight and growth in Bos taurus

Variation at the pleiomorphic adenoma gene 1 (PLAG1) locus has recently been implicated in the regulation of stature and weight in Bos taurus. Using a population of 942 outbred Holstein-Friesian dairy calves, we report confirmation of this effect, demonstrating strong association of early life body weight with PLAG1 genotype. Peripubertal body weight and growth rate were also significantly associated with PLAG1 genotype. Growth rate per kilogram of body weight, daily feed intake, gross feed efficiency and residual feed intake were not significantly associated with PLAG1 genotype. This study supports the status of PLAG1 as a key regulator of mammalian growth. Further, the data indicate the utility of PLAG1 polymorphisms for the selection of animals to achieve enhanced weight gain or conversely to aid the selection of animals with lower mature body weight and thus lower maintenance energy requirements.

Gastroparesis and functional dyspepsia: excerpts from the AGA/ANMS meeting

BACKGROUND

Despite the relatively high prevalence of gastroparesis and functional dyspepsia, the aetiology and pathophysiology of these disorders remain incompletely understood. Similarly, the diagnostic and treatment options for these two disorders are relatively limited despite recent advances in our understanding of both disorders.

PURPOSE

This manuscript reviews the advances in the understanding of the epidemiology, pathophysiology, diagnosis, and treatment of gastroparesis and functional dyspepsia as discussed at a recent conference sponsored by the American Gastroenterological Association (AGA) and the American Neurogastroenterology and Motility Society (ANMS). Particular focus is placed on discussing unmet needs and areas for future research.

Effects of a multi-component exercise program and calcium-vitamin-D3-fortified milk on bone mineral density in older men: a randomised controlled trial

SUMMARY

We examined the independent and combined effects of a multi-component exercise program and calcium-vitamin-D(3)-fortified milk on bone mineral density (BMD) in older men. Exercise resulted in a 1.8% net gain in femoral neck BMD, but additional calcium-vitamin D(3) did not enhance the response in this group of older well-nourished men.

INTRODUCTION

This 12-month randomised controlled trial assessed whether calcium-vitamin-D(3)-fortified milk could enhance the effects of a multi-component exercise program on BMD in older men.

METHODS

Men (n = 180) aged 50-79 years were randomised into: (1) exercise + fortified milk; (2) exercise; (3) fortified milk; or (4) controls. Exercise consisted of high intensity progressive resistance training with weight-bearing impact exercise. Men assigned to fortified milk consumed 400 mL/day of low fat milk providing an additional 1,000 mg/day calcium and 800 IU/day vitamin D(3). Femoral neck (FN), total hip, lumbar spine and trochanter BMD and body composition (DXA), muscle strength 25-hydroxyvitamin D and parathyroid hormone (PTH) were assessed.

RESULTS

There were no exercise-by-fortified milk interactions at any skeletal site. Exercise resulted in a 1.8% net gain in FN BMD relative to no-exercise (p < 0.001); lean mass (0.6 kg, p < 0.05) and muscle strength (20-52%, p < 0.001) also increased in response to exercise. For lumbar spine BMD, there was a net 1.4-1.5% increase in all treatment groups relative to controls (all p < 0.01). There were no main effects of fortified milk at any skeletal site.

CONCLUSION

A multi-component community-based exercise program was effective for increasing FN BMD in older men, but additional calcium-vitamin D(3) did not enhance the osteogenic response.

The use of proton NMR as an alternative for the amino acid analysis as identity test for peptides

Proton NMR was evaluated as an alternative to amino acid analysis as an identity test for peptides. Proton NMR can readily distinguish and identify all peptides currently described in the European Pharmacopoeia (Ph. Eur.). A comparison with amino acid analysis as an identity test is presented.

The use of clinical risk factors enhances the performance of BMD in the prediction of hip and osteoporotic fractures in men and women

BMD and clinical risk factors predict hip and other osteoporotic fractures. The combination of clinical risk factors and BMD provide higher specificity and sensitivity than either alone. INTRODUCTION AND HYPOTHESES: To develop a risk assessment tool based on clinical risk factors (CRFs) with and without BMD.

METHODS

Nine population-based studies were studied in which BMD and CRFs were documented at baseline. Poisson regression models were developed for hip fracture and other osteoporotic fractures, with and without hip BMD. Fracture risk was expressed as gradient of risk (GR, risk ratio/SD change in risk score).

RESULTS

CRFs alone predicted hip fracture with a GR of 2.1/SD at the age of 50 years and decreased with age. The use of BMD alone provided a higher GR (3.7/SD), and was improved further with the combined use of CRFs and BMD (4.2/SD). For other osteoporotic fractures, the GRs were lower than for hip fracture. The GR with CRFs alone was 1.4/SD at the age of 50 years, similar to that provided by BMD (GR = 1.4/SD) and was not markedly increased by the combination (GR = 1.4/SD). The performance characteristics of clinical risk factors with and without BMD were validated in eleven independent population-based cohorts.

CONCLUSIONS

The models developed provide the basis for the integrated use of validated clinical risk factors in men and women to aid in fracture risk prediction.

Euthanasia: the legal issues

The legal status of euthanasia is frequently deliberated. It remains unlawful in Britain and advocates for a change in the law are vigorously opposed by those who argue that it should remain unchanged. An objective account, in which current law and arguments for and against change are exposed, is essential to inform the euthanasia debate. In this article the legal issues concerning euthanasia are examined and arguments raised by proposed changes in the law are considered.

Voluntary euthanasia: ethical concepts and definitions

Euthanasia is a highly emotive and contentious subject, giving rise to a great deal of debate. However, despite its frequent exposure in public and professional media, there appears to be a lack of clarity about the concepts and definitions used in the euthanasia debate. This suggests that discussions on this subject are inadequately informed and ineffectual. The ethical focus of the euthanasia debate concerns the moral legitimacy of 'voluntary euthanasia'. This article provides an overview and clarification of some of the key ethical issues at the centre of that debate.

The role of NADPH oxidase in carotid body arterial chemoreceptors

O(2)-sensing in the carotid body occurs in neuroectoderm-derived type I glomus cells where hypoxia elicits a complex chemotransduction cascade involving membrane depolarization, Ca(2+) entry and the release of excitatory neurotransmitters. Efforts to understand the exquisite O(2)-sensitivity of these cells currently focus on the coupling between local P(O2) and the open-closed state of K(+)-channels. Amongst multiple competing hypotheses is the notion that K(+)-channel activity is mediated by a phagocytic-like multisubunit enzyme, NADPH oxidase, which produces reactive oxygen species (ROS) in proportion to the prevailing P(O2). In O(2)-sensitive cells of lung neuroepithelial bodies (NEB), multiple studies confirm that ROS levels decrease in hypoxia, and that E(M) and K(+)-channel activity are indeed controlled by ROS produced by NADPH oxidase. However, recent studies in our laboratories suggest that ROS generated by a non-phagocyte isoform of the oxidase are important contributors to chemotransduction, but that their role in type I cells differs fundamentally from the mechanism utilized by NEB chemoreceptors. Data indicate that in response to hypoxia, NADPH oxidase activity is increased in type I cells, and further, that increased ROS levels generated in response to low-O(2) facilitate cell repolarization via specific subsets of K(+)-channels.

Characterization of the DGAT1 Mutations and the CSN1S1 Promoter in the German Angeln Dairy Cattle Population

The identification of quantitative trait loci (QTL) and genes with influence on milk production traits has been the objective of various mapping studies in the last decade. In the centromeric region of Bos taurus autosome (BTA) 14, the acyl-CoA:diacylglycerol acyltransferase1 gene (DGAT1) has been identified as the most likely causative gene underlying a QTL for milk fat yield and content. Recently, a second polymorphism in the promoter of DGAT1 emerged as an additional source of variation. In this study, the frequencies and the effects of alleles at the DGAT1 K232A and at the DGAT1 promoter variable number of tandem repeat (VNTR) locus on BTA14, and of alleles at the CSN1S1 (alpha(S1)-casein-encoding gene) promoter on BTA6 in the German Angeln dairy cattle population were investigated. Analyzed traits were milk, fat, protein, lactose, and milk energy yield, fat, protein, lactose, and milk energy content and somatic cell score. The lysine variant of the DGAT1 K232A mutation showed significant effects for most of the milk production traits. A specific allele of the DGAT1 promoter VNTR showed significant effects on the traits lactose yield and content, milk energy content, and SCS compared with the other alleles. Additionally, a regulation mechanism between the DGAT1 K232A mutation and the DGAT1 promoter VNTR was found for fat yield and content, which could be caused by an upper physiological bound for the effects of the DGAT1 gene. At the CSN1S1 promoter, 2 of 4 alleles showed significant allele substitution effects on the milk yield traits.