Characterization of neuropathology in ovine CLN5 and CLN6 neuronal ceroid lipofuscinoses (Batten disease)

Sheep with naturally occurring CLN5 and CLN6 forms of neuronal ceroid lipofuscinoses (Batten disease) share the key clinical features of the human disease and represent an ideal model system in which the clinical efficacy of gene therapies is developed and test. However, it was first important to characterize the neuropathological changes that occur with disease progression in affected sheep. This study compared neurodegeneration, neuroinflammation, and lysosomal storage accumulation in CLN5 affected Borderdale, CLN6 affected South Hampshire, and Merino sheep brains from birth to end-stage disease at ≤24 months of age. Despite very different gene products, mutations, and subcellular localizations, the pathogenic cascade was remarkably similar for all three disease models. Glial activation was present at birth in affected sheep and preceded neuronal loss, with both spreading from the visual and parieto-occipital cortices most prominently associated with clinical symptoms to the entire cortical mantle by end-stage disease. In contrast, the subcortical regions were less involved, yet lysosomal storage followed a near-linear increase across the diseased sheep brain with age. Correlation of these neuropathological changes with published clinical data identified three potential therapeutic windows in affected sheep—presymptomatic (3 months), early symptomatic (6 months), and a later symptomatic disease stage (9 months of age)—beyond which the extensive depletion of neurons was likely to diminish any chance of therapeutic benefit. This comprehensive natural history of the neuropathological changes in ovine CLN5 and CLN6 disease will be integral in determining what impact treatment has at each of these disease stages

Nitrogen balance of dairy cows divergent for milk urea nitrogen breeding values consuming either plantain or perennial ryegrass

Inefficient nitrogen (N) use from pastoral dairy production systems has resulted in environmental degradation, as a result of excessive concentrations of urinary N excretion leaching into waterways and N₂O emissions from urination events into the atmosphere. The objectives of this study were to measure and evaluate the total N balance of lactating dairy cows selected for milk urea N concentration breeding values (MUNBVs) consuming either a 100% perennial ryegrass (Lolium perenne L.) or 100% plantain (Plantago lanceolata L.) diet. Sixteen multiparous lactating HolsteinFriesian × Jersey cows divergent for MUNBV were housed in metabolism crates for 72 h, where intake and excretions were collected and measured. No effect of MUNBV was detected for total N excretion; however, different excretion characteristics were detected, per urination event. Low MUNBV cows had a 28% reduction in the concentration of urinary urea nitrogen (g/event) compared to high MUNBV cows when consuming a ryegrass diet. Cows consuming plantain regardless of their MUNBV value had a 62% and 48% reduction in urinary urea nitrogen (g/event) compared to high and low MUNBV cows consuming ryegrass, respectively. Cows consuming plantain also partitioned more N into faeces. These results suggest that breeding for low MUNBV cows on ryegrass diets and the use of a plantain diet will reduce urinary urea nitrogen loading rates and therefore estimated nitrate leaching values, thus reducing the environmental impact of pastoral dairy production systems

ABSENCE OF CIRCADIAN PATTERNS OF SECRETION OF MELATONIN OR CORTISOL IN WEDDELL SEALS UNDER CONTINUOUS NATURAL DAYLIGHT

Blood samples were obtained from adult female Weddell seals in McMurdo Sound, Antarctica, utilizing four different seals every 2 h for 24 h on two occasions in November 1987. Plasma levels of melatonin were mostly near zero, whereas the values for cortisol were high (2101 ± 54 and 1908 ± 108 (S.E.M.) nmol/l, n = 52). For both hormones there was no evidence of a diurnal pattern of secretion. Juvenile seals sampled in December 1985 also had no evidence of a diurnal secretion pattern of melatonin, but blood levels of melatonin were higher than in adults. The results indicate that secretion of melatonin in adult Weddell seals ceases during the Antarctic summer

Molecular forms of C-type natriuretic peptide in cerebrospinal fluid and plasma reflect differential processing in brain and pituitary tissues

C-type natriuretic peptide (CNP) is a paracrine growth factor widely expressed within tissues of the central nervous system. Consistent with this is the high concentration of CNP in cerebrospinal fluid (CSF), exceeding levels in the systemic circulation. CNP abundance is high in hypothalamus and especially enriched in pituitary tissue where – in contrast to hypothalamus – processing to CNP-22 is minimal. Recently we have shown that dexamethasone acutely raises CNP peptides throughout the brain as well as in CSF and plasma. Postulating that molecular forms of CNP would differ in central tissues compared to forms in pituitary and plasma, we have characterized the molecular forms of CNP in tissues (hypothalamus, anterior and posterior pituitary gland) and associated fluids (CSF and plasma) using size-exclusion high performance liquid chromatography (SE-HPLC) and radioimmunoassay in control (saline-treated) and dexamethasone-treated adult sheep. Three immunoreactive-CNP components were identified which were consistent with proCNP (1-103), CNP-53 and CNP-22, but the presence and proportions of these different fragments differed among tissues. Peaks consistent with CNP-53 were the dominant form in all tissues and fluids. Peaks consistent with proCNP, conspicuous in hypothalamic extracts, were negligible in CSF whereas proportions of low molecular weight immunoreactivity (IR) consistent with CNP- 22 were similar in hypothalamus, posterior pituitary gland and CSF. In contrast, in both plasma and the anterior pituitary gland, proportions of higher molecular weight IR, consistent with CNP-53 and proCNP, predominated, and low molecular weight IR consistent with CNP-22 was very low. After dexamethasone, proCNP like material – but not other forms – was increased in all samples except CSF, consistent with increased synthesis and secretion. In conclusion, immunoreactive forms of CNP in central tissues differ from those identified in anterior pituitary tissue and plasma – suggesting that the anterior pituitary gland may contribute to systemic levels of CNP in some physiological settings

Recovery of ovulation rate in ewes following their removal from an oestrogenic lucerne forage

Grazing ewes on lucerne crops that contain elevated coumestrol concentrations before and during their mating period can decrease ovulation rate, which results in fewer multiple birth lambs. In this experiment, the ovulation rate of ewes grazing a moderately oestrogenic (29.1 ± 2.88 mg coumestrol/kg DM) lucerne crop for 6 weeks was compared with those transferred to grass pasture for 1 or 3 weeks, and a Control group on grass throughout. Ordinal regression predicted an exponential relationship with a sharp initial increase in ovulation rate from 0 to 14 days on grass that levelled off when ewes were on grass for durations greater than 3 weeks. Of importance, moderate coumestrol levels in lucerne remained throughout the experiment, and liveweight was unaffected by grazing treatment. This experiment quantified the decrease in risk of impaired lambing performance due to moderately oestrogenic lucerne consumption in relation to time on grass before ovulation. Specifically, removal of ewes from lucerne 2 weeks before ovulation mitigated the risk of decreased lambing performance

Prediction of coumestrol content in unirrigated lucerne crops using weather variables

Elevated coumestrol levels in lucerne (Medicago sativa L.) can reduce the reproductive performance of ewes. A model to predict coumestrol content of lucerne between summer and late autumn was developed to assess the risk of a crop having elevated levels. Data from previous studies have shown fungal damage to be the major contributor to coumestrol levels, but the fungal infestation levels that can cause a risk to reproduction in sheep are difficult to quantify. A number of variables were tested and the sum of rainfall and days where relative humidity was over 95% at 0900 h was found to have the best fit with coumestrol content of lucerne crops. The model was then tested with independent data from the literature and field. A decision tree is proposed as a practical user-friendly guide to predict whether coumestrol content is above or below a risk threshold of 25 mg/kg DM