Effect of supplementing live Saccharomyces cerevisiae yeast on performance, rumen function, and metabolism during the transition period in Holstein dairy cows.

Dairy cows have to face several nutritional challenges during the transition period, and live yeast supplementation appears to be beneficial in modulating rumen activity. In this study, we evaluated the effects of live yeast supplementation on rumen function, milk production, and metabolic and inflammatory conditions. Ten Holstein multiparous cows received either live Saccharomyces cerevisiae (strain Sc47; SCY) supplementation from -21 to 21 d from calving (DFC) or a control diet without yeast supplementation. Feed intake, milk yield, and rumination time were monitored until 35 DFC, and rumen fluid, feces, milk, and blood samples were collected at different time points. Compared with the control diet, SCY had increased dry matter intake (16.7 vs. 19.1 ± 0.8 kg/d in wk 2 and 3) and rumination time postpartum (449 vs. 504 ± 19.9 min/d in wk 5). Milk yield tended to be greater in SCY (40.1 vs. 45.2 ± 1.7 kg/d in wk 5), protein content tended to be higher, and somatic cell count was lower. In rumen fluid, acetate molar proportion was higher and that of propionate lower at 21 DFC, resulting in increased acetate:propionate and (acetate + butyrate):propionate ratios. Cows in the SCY group had lower fecal dry matter but higher acetate and lower propionate proportions on total volatile fatty acids at 3 DFC. Plasma analysis revealed a lower degree of inflammation after calving in SCY (i.e., lower haptoglobin concentration at 1 and 3 DFC) and a likely better liver function, as suggested by the lower γ-glutamyl transferase, even though paraoxonase was lower at 28 DFC. Plasma IL-1ß concentration tended to be higher in SCY, as well as Mg and P. Overall, SCY supplementation improved rumen and hindgut fermentation profiles, also resulting in higher dry matter intake and rumination time postpartum. Moreover, the postcalving inflammatory response was milder and liver function appeared to be better. Altogether, these effects also led to greater milk yield and reduced the risk of metabolic diseases.

Impact of dry-off and lyophilized Aloe arborescens supplementation on plasma metabolome of dairy cows.

Positive effects have been observed as a result of Aloe arborescens supplementation in the dry-off phase in dairy cows. Metabolomic approaches can provide additional information about animal physiology. Thus, we characterized plasma metabolome around dry-off in 12 cows supplemented (AL) or not (CTR) with 10 g/d of lyophilized A. arborescens with an untargeted metabolomic approach. Overall, 1658 mass features were annotated. Regardless of treatment, multivariate statistics discriminated samples taken before and after dry-off. Overall, 490 metabolites were different between late lactation and early dry period, of which 237 were shared between AL and CTR. The most discriminant compounds (pentosidine and luteolin 7-O-glucoside) were related to the more fibrous diet. Pathway analysis indicated that pyrimidine and glycerophospholipid metabolisms were down-accumulated, suggesting reduced rumen microbial activity and liver load. Samples from AL were discriminated from CTR either the day of dry-off or 7 days after. At dry-off, aloin and emodin were the most discriminant metabolites, indicating that Aloe's bioactive compounds were absorbed. Seven days later, 534 compounds were different between groups, and emodin was among the most impacted. Pathway analysis highlighted that glycerophospholipid, pyrimidine, and folate metabolisms were affected. These results might indicate that Aloe has positive effects on liver function and a modulatory effect on rumen fermentation.

The auditory space in the motor system.

Sensory events in the space around us trigger specific motor patterns directed toward or away from the spatial location of the sensory source. Spatially-defined sensorimotor associations are well-known in the visual domain but less so for the auditory modality. In particular no spatially-directed audio-motor association has been described for the upper limb. We tested the instantaneous directional tuning of the corticospinal system by means of single-pulse transcranial magnetic stimulation (TMS) over the left motor cortex in 16 healthy volunteers while at rest. We recorded the lateral accelerations of the TMS-evoked movement by means of an accelerometer placed on the forearm. Acoustic stimuli (pure tone frequency=1000Hz, duration=50ms) coming from 25 different directions lying in the axial anterior half-plane at the height of the participant's ears were played on earphones. The entire set of sound directions covered a span of 160° (±80° where 0° is the frontal direction) at a fixed azimuth angle. Six different intervals between sound onset and TMS (0, 25, 50, 100, 150 and 200ms) were tested for each sound direction. Significant correlations were found between sound origin and TMS-evoked arm accelerations only when TMS was delivered 50ms prior to sound onset. We show the presence in the upper limb motor system of auditory spatial tuning. Sound information accesses the motor system at very short latency, potentially compatible with both a subcortical and a cortical origin of the response. The use of TMS-evoked accelerations allowed us to disclose a strict directional tuning in audio-motor associations.

Masseteric repetitive nerve stimulation in the diagnosis of myasthenia gravis.

OBJECTIVE: (1) to develop a method for masseteric repetitive nerve stimulation (RNS) and to obtain normative data for amplitude and area decrement of the muscle (M) response. (2) To investigate myasthenia gravis (MG) patients with masseteric RNS. Masticatory muscles are frequently affected in MG, but no RNS test is available to investigate this district. METHODS: Fifteen healthy subjects and 17 MG patients were examined. The masseteric nerve was stimulated by a monopolar needle (cathode), inserted between the mandibular incisure and the zygomatic arch, and a surface electrode (anode), on the contralateral cheek. Masseteric M response was recorded using surface electrodes on the muscle belly and below the mandibular angle. Stimuli were delivered at 3 Hz in trains of 9, at rest and after isometric effort. RESULTS: Normal subjects: mean amplitude decrement was 0.3+/-1.2% at rest, and 1.9+/-1.3% after isometric effort. PATIENTS: 15 patients (88%) were positive on masseteric RNS; in 3 of these it was the only positive RNS test. The extent of decrement observed in masseter muscle was significantly greater than in trapezius muscle. CONCLUSIONS: Masseteric RNS is a simple and well-tolerated procedure; it offers a new possibility in testing the cranial muscles in disorders of neuromuscular transmission.

Muscle reinnervation following neonatal nerve crush. Interactive effects of glycosaminoglycans and insulin-like growth factor-I.

This study shows that glycosaminoglycans promote muscle reinnervation following neonatal sciatic nerve injury. Such an effect appears to be mediated by insulin-like growth factor-1. The glycosaminoglycan moiety of proteoglycans is a constituent of the basal lamina active on nerve regeneration by means of the interaction with laminin and with several growth factors. We have previously shown that supplementation of glycosaminoglycans affects neuronal degeneration and regeneration. In this study we report that following neonatal lesion of the rat sciatic nerve glycosaminoglycan treatment promoted extensor digitorum longus muscle reinnervation with consequent improvement of muscle morphology. In saline-treated rats, reinnervation was only partial and there was a marked muscle fibre atrophy. In addition glycosaminoglycan treatment of lesioned rats increased insulin-like growth factor-I messenger RNA and protein in the reinnervated muscle, and insulin-like growth factor-I and insulin-like growth factor binding protein-3 plasma levels. Similarly, treatment of nerve lesioned rats with insulin-like growth factor-I promoted muscle reinnervation and prevention of muscle fibre atrophy, higher levels of insulin-like growth factor-I in the reinnervated muscle and of insulin-like growth factor-I and insulin-like growth factor binding proteins in plasma. These data suggest that glycosaminoglycans are potent stimulants of muscle reinnervation and that their effects may be mediated by increased levels of insulin-like growth factor-I.

Effect of long-term administration of Hexarelin on the somatotrophic axis in aged rats.

The growth hormone-releasing peptide Hexarelin (Hexa; 80 micrograms/kg-1, s.c.) was administered for 30 and 60 days to old rats. The GH-releasing effect of Hexa was maintained during chronic treatment. At the end of the treatment, old rats were administered once with Hexa which elicited a greater GH response in rats chronically treated with the peptide than in those receiving a placebo. Pituitary GHmRNA concentrations were significantly lower in the older rats than in the younger animals, irrespective of Hexa treatment, while the GH protein content was similar in all the groups studied. The same was true for hypothalamic GHRH, whose synthesis was reduced in all the older animals but not in the young, in the presence of maintained concentrations of the peptide. Somatostatin mRNA concentrations were significantly higher in the hypothalami of older rats and administration of Hexa for 30 or 60 days brought the concentrations of somatostatin mRNA of aged rats to 'young' levels. Treatments with Hexa failed to alter the circulating levels of IGF-1. The data reported in this article indicate that long-term treatment with Hexa normalized some biological indices of somatotrophic function in aged rats.

Characterization of the hypothalamo-pituitary-IGF-I axis in rats made obese by overfeeding.

Obesity is coupled to several disturbances of the endocrine axes. It has previously been shown that genetically obese Zucker male rats have an impaired secretion of growth hormone (GH), probably originating from a primary reduction of hypothalamic GH-releasing hormone (GHRH) function and resulting in a decrease of GH gene expression and release. We sought to evaluate the somatotropic function in another model of experimental obesity. Normal male Sprague-Dawley rats were fed an energy-rich highly palatable diet for 7 months until they reached body weights overlapping those reported for obese Zucker rats. They were then evaluated for different indices of the hypothalamo-pituitary-somatomedin-C (IGF-I) axis. At the end of the overfeeding period, rats were divided into overtly obese (obese group) and overweight (overweight group) rats according to the degree of overweight and the Obesity Lee Index, while rats fed ad libitum with the standard pellet chow served as controls. Acute administration of a supramaximal dose of GHRH (2 micrograms/rat i.v.) elicited a significantly (at least P < 0.05) lower plasma GH rise in the overweight and obese groups compared with the controls although no difference was seen in the pituitary GH content and gene expression and plasma concentrations of free IGF-I in the two experimental groups vs the controls. In addition, evaluation of hypothalamic GHRH and somatostatin mRNAs (slot-blot hybridization) did not show any significant differences between the three groups. Of the different metabolic indices investigated, plasma glucose and insulin concentrations were significantly (P < 0.01) higher in the obese than in the overweight and control groups. A sharp decrease in plasma testosterone levels, together with a reduction in testis weight, was seen in both groups of rats fed the palatable diet compared with the controls. These findings underline the 'peripheral' feature of the hyposomatotropinism of rats chronically fed an energy-rich diet, and may account for the reversibility of the GH impairment in many obese subjects once a normal body weight has been restored. Moreover, the peripherally-driven hyposomatotropinism of these rats is in sharp contrast with the hypothalamic-driven GH secretory impairment of the obese Zucker rats.

In vivo microdialysis of the hypothalamus: a suitable method to study the function of hypophysiotropic neurons in the rat.

Brain microdialysis is a method commonly exploited by neuropharmacologists to study the mechanism of action and preclinical features of centrally acting drugs. It allows measurement of chemical messengers released into the extracellular space, providing a first approximation of neuronal function in selected areas. In this study we have applied the microdialysis of the hypothalamus to evaluate the release of somatostatin from neurosecretory neurons which are involved in growth hormone regulation and validated this method with different challenges.

Growth hormone secretion is differently affected in genetically obese male and female rats.

Growth hormone (GH) secretion is markedly blunted in obesity. Reportedly, genetically obese Zucker rats show a reduced GH secretion due to an impaired function of hypothalamic neurons producing the GH-releasing hormone (GHRH). The aim of this work was: (1) to compare the in vitro GH responsiveness to GHRH in genetically obese female versus male Zucker rats and, (2) to evaluate the function of hypothalamic GHRH and somatostatin and of pituitary receptors for these neurohormones as assessed by the effectiveness of GHRH and somatostatin on adenylate cyclase (AC) activity. Baseline GH secretion of pituitaries obtained from male and female obese rats was not different and similar to that present in lean counterparts. Stimulation with 10(-7) M GHRH elicited a significantly lower GH secretion from the pituitaries of obese male rats but induced a similar GH secretion from the pituitaries of lean and obese female rats. In these pituitaries, GH concentration was similar in obese versus lean male and female rats [corrected]. A sex-related difference was also evidenced when plasma concentrations of somatomedin C (IGF-I) were evaluated. Obese male rats had lower IGF-I concentrations than lean counterparts, while this was not the case for obese versus lean female rats. Evaluation of AC activity following GHRH disclosed a lower activation in obese than in lean male rats, whereas in the females the enzyme activation was higher in obese than in lean animals. Conversely, the inhibitory effect of somatostatin on forskolin-stimulated AC was similar in pituitary membranes of obese and lean rats of both sexes.(ABSTRACT TRUNCATED AT 250 WORDS)