Peripartal Endocrinology in the Mare and Foetus

The endocrine profiles in the periparturient mares are dominated by increasing concentrations of progestagens and decreasing oestrogens. These hormones are produced by precursors from the foetus, metabolized by the placenta and act primarily on the maternal uterus. The circulating concentrations of hormones in maternal plasma, generally, represent a small proportion of those metabolized by the foetus and utero-placental tissues. There is clear evidence that the foetal hypothalamo-pituitary-adrenal (HPA) axis initiates the process of foetal maturation and the hormonal cascade which culminates in parturition at term. The endocrine changes associated with abnormal pregnancy and abortion in late pregnancy are less well understood, as are the hormonal treatments needed to avert these problems. Further work is needed to establish the biological role of the various hormones present in pregnant mares and, in particular, those hormones which control myometrial quiescence.     

Physiological traits in preterm calves during their first week of life

Morbidity and mortality of preterm neonatal calves are higher than of calves born at normal term, possibly and in part due to immaturity of physiological functions. Physiological parameters were therefore studied during the first week of life in seven preterm calves, born on day 277 of gestation after dams were injected prostaglandin F2alpha and flumethason. Calves were fed colostrum of the first milking for the first 3 days and from day 4 to day 7 the same colostrum diluted with milk replacer. Body weight increased during the first week of life by 2.2 kg. Heart rate and respiratory rate were always relatively high, whereas values of rectal temperature, blood gases, haematological, metabolic and endocrine traits were in the range and behaved similarly as is the experience in full-term neonatal calves. Major exceptions were glucose and insulin, the concentrations of which barely rose postprandially, and growth hormone, the responses of which to growth hormone releasing factor analogue 1-29 were extremely variable and in part very small. In conclusion, calves born 2 week before normal term that survived the first week of life, although physiologically immature, were well able to handle ingested nutrients and to control their metabolism.     

Growth performance, metabolic and endocrine traits, and absorptive capacity in neonatal calves fed either colostrum or milk replacer at two levels

Colostrum (CO) contains high amounts, whereas whole milk and milk replacer (MR) contain small amounts, of bioactive and growth-promoting substances, such as IGF-I. An experiment was designed to study the effects of feeding CO or MR on the first 3 d to neonatal calves, followed by whole milk up to d 7, at low and high density. Intestinal absorptive capacity, plasma metabolite and hormone concentrations, and growth performance were measured during the 1st wk of life. Body weight increased (P < .05) similarly in calves fed low or high amounts of CO but did not rise in MR-fed calves. Loose feces were more frequent (P < .05) and absorption of xylose on d 5 was lower (P < .01) in MR- than in CO-fed calves, but there were no effects of feeding density within CO-fed or within MR-fed groups. However, high feeding density within CO-fed groups enhanced (P < .05) total protein, globulin, triglyceride, cholesterol, and insulin concentrations, whereas in the initially high and low MR-fed groups only plasma glucose and insulin after the first meal and plasma NEFA on d 2 were modified (P < .05) by different feeding density. Thus, feeding different amounts of CO partly influenced protein and fat metabolism in calves during the 1st wk of life, but it did not measurably affect intestinal function. However, feeding different amounts of MR, in the absence of CO, barely affected metabolic and endocrine traits and absorptive capacity. Thus, high density CO feeding, and therefore a high supply of nutrients, together with greater amounts of bioactive and growth-promoting substances influenced neonatal metabolism and growth more than a high density of MR feeding containing only small amounts of bioactive and growth-promoting substances. Factors in addition to nutrient density seem to be important for the development of neonatal calves.     

Determination of the different components of cadmium short‐term uptake by roots

As the various components of the cadmium (Cd) root sink have not been clearly described, there is a need to precisely measure the respective contributions of apoplast and symplast to short‐term root Cd uptake and to explain the linear component of the absorption isotherms. A new method of fractionating Cd in roots was applied to two plant species with contrasting abilities to accumulate Cd: maize (Zea mays) and a Cd‐hyperaccumulating ecotype of alpine pennycress (Noccaea caerulescens). Their roots were exposed for 1 h to increasing concentrations of labeled Cd. Series of desorption baths were used to obtain the root apoplastic Cd in combination with a brief freezing step in liquid nitrogen to separate the intracellular metal from the apoplastic one. The apoplastic uptake accounted for 15% to 82% and for 48% to 96% of the total Cd uptake of maize and of alpine pennycress roots, respectively. In the case of maize, the concentration‐dependent symplastic net flux fitted a biphasic Michaelis‐Menten function, while in the case of alpine pennycress, a Michaelis‐Menten‐plus‐linear function proved a better fit. The second component of the symplastic net flux may reflect absorption through a low‐affinity transport system. Short‐term Cd uptake by roots is dominated by the high‐affinity transport system for exposure concentrations below 1 μM for maize and 0.2 μM for alpine pennycress, while cell‐wall binding prevailed for higher exposure concentrations.     

Properties of chemically and physically treated wheat gluten films

Chemical (vapors of formaldehyde), physical (temperature, UV and gamma radiation), and aging treatments were applied to wheat gluten films. Changes in film mechanical properties, water vapor permeability, solubility, and color coordinates were investigated. An aging of 360 h led to a 75 and 314% increase in tensile strength and Young's modulus, respectively, and a 36% decrease in elongation. Severe thermal (above 110 degrees C, 15 min) and formaldehyde treatments highly improved the mechanical resistance of the films. Under these conditions, up to 376 and 654% increase in tensile strength and Young's modulus and up to 66% decrease in elongation have been observed. Water solubility was only slightly modified, whereas water vapor permeability was not affected. Color coordinates of films heated above 95 degrees C changed to a great extent. An almost total insolubilization of proteins in sodium dodecyl sulfate occurred for heat- and formaldehyde-treated films, due to the modification of protein network leading to changes in properties of the films.     

Effectiveness of passive gas-scavenging canisters attached to isoflurane anesthesia systems under standard-use conditions in a laboratory animal facility

Chronic exposure to trace levels of waste anesthetic gases has been linked to higher incidences of neurologic and reproductive dysfunction, hepatic and renal toxicity, and neoplasia in health care professionals. We have shown that low levels of isoflurane emissions are likely in conventional laboratory animal treatment rooms during the use of standard anesthesia delivery systems equipped with activated charcoal canisters for passive gas scavenging. In the present study, we surveyed the effectiveness of canisters (attached to well‐maintained precision isoflurane vaporizers) in current use throughout our AAALAC‐accredited laboratory animal facility. Canisters (Omnicon f/air) had been weighed prior to use and then attached to dual‐loop systems (face mask and induction box circuits) from 1 week to 6 months of service. Isoflurane emissions were measured using a pre‐calibrated, portable infrared spectrophotometer by attaching each canister to the face‐mask circuit, occluding the face mask and closing the stopcock to the induction circuit, and running the system at uniform isoflurane concentration (2%) and oxygen flow rate (1 L minute^?1). Samples were taken in animal procedure rooms (size range, 45–80 m³) in which the air turnover rate ranged between 20 and 30 nonrecirculating changes per hour. Nine of the 60 canisters (15%) in current use were found to have exceeded the manufacturer's recommended use‐life (defined as a weight increase of 50 g). Of these nine, seven canisters did not scavenge isoflurane at all (indicated by emissions greatly exceeding 100 ppm). Isoflurane was not detected in the operator's breathing zone under normal use conditions (i.e. gas directed to both circuits at once). Of the 51 canisters that had not exceeded their rated use‐life, 12 (23.5%) exhausted isoflurane at >2 ppm. Our data show that (i) the potential for exposure to waste isoflurane emissions will depend on the configuration of the delivery system and that (ii) enhanced attention to canister surveillance may be warranted even in well‐run facilities.