Chemical and Physical Characteristics of Corn Silages and Their Effects on In Vitro Disappearance

Estimating the available energy in corn silage provides a unique challenge because the silage contains variable proportions of grain and stover, each of which can differ in availability due to chemical composition and physical form. The objectives of this study were to investigate relationships among chemical components and their relationships with in vitro disappearance of ground and unground dried silages, and to quantify minimally fragmented starch in corn silage and investigate its impact and that of mean particle size (MPS) on in vitro disappearance of unground silages. Thirty-two corn silages were selected to provide diversity in dry matter, protein, fiber, and MPS. Detergent fibers were highly correlated with each other and with nonfiber carbohydrates, and were used to develop prediction equations between these constituents. Sieves with apertures > or =4.75 mm were used to isolate intact kernels and large kernel fragments, which were collected and analyzed to measure minimally fragmented starch (Starch>4.75). Dividing Starch>4.75 by total starch defined the proportion of minimally fragmented starch (Starch>4.75/Total), which ranged from 9 to 100% with a mean of 52%. Starch>4.75/Total was positively correlated with MPS (r = 0.46). The inverse of Starch>4.75/Total is an index of kernel fragmentation. Silages were prepared as whole material or ground to pass through a 4- or 1-mm screen of a cutter mill. In vitro dry matter disappearance (IVDMD) was greater for ground than for whole samples (71.7 and 61.2%, respectively). Increased IVDMD for ground samples was attributed to greater in vitro neutral detergent fiber (NDF) and neutral detergent solubles (NDS) disappearances. The IVDMD of ground samples was related to NDF and acid detergent lignin (R2 = 0.80). The IVDMD of whole corn silage was related to acid detergent lignin, Starch>4.75, MPS, and dry matter. When IVDMD was partitioned into in vitro digestible NDS (IVdNDS) and in vitro digestible NDF, the IVdNDS of whole was not uniform or completely fermented. The difference in IVdNDS between ground and whole was related to Starch>4.75/Total. In conclusion, the proportion of minimally fragmented starch provides a corn silage fragmentation index that is related to the in vitro digestion of whole silages that, if validated by in vivo trials, may be a useful quantitative substitute for the qualitative processing adjustment factor that is used currently in summative equations for estimating the total digestible nutrients of corn silages.

Basolateral amygdala glutamatergic activation enhances taste aversion through NMDA receptor activation in the insular cortex

In conditioned taste aversion (CTA), a subject learns to associate a novel taste with visceral malaise. Brainstem, limbic and neocortical structures have been implicated in CTA memory formation. Nevertheless, the role of interactions between forebrain structures during these processes is still unknown. The present experiment was aimed at investigating the possible interaction between the basolateral nucleus of the amygdala (BLA) and the insular cortex (IC) during CTA memory formation. Injection of a low dose of lithium chloride (30 mg/kg, i.p.) 30 min after novel taste consumption (saccharin 0.1%) induces a weak CTA. Unilateral BLA injection of glutamate (2 microg in 0.5 microL) just before low lithium induces a stronger CTA. Unilateral injection of an N-methyl-d-aspartate (NMDA) receptor antagonist (AP5, 5 microg in 0.5 microL) in IC has no effect. However, AP5 treatment in IC at the same time or 1 h after the ipsilateral BLA injection reverses the glutamate-induced CTA enhancement. Injection of AP5 in IC 3 h after BLA injection does not interfere with the glutamate effect. Moreover, the CTA-enhancing effect of glutamate was also blocked by contralateral IC injection of AP5 at the same time. These results provide strong evidence that NMDA receptor activation in the IC is essential to enable CTA enhancement induced by glutamate infusion in the BLA during a limited time period that extends to 1 but not to 3 hours. These findings indicate that BLA-IC interactions regulate the strength of CTA. The bilateral nature of these amygdalo-cortical interactions is discussed.

Effects of the enantiomers of BayK 8644 on the charge movement of L-type Ca channels in guinea-pig ventricular myocytes

The effects of the agonist enantiomer S(-)Bay K 8644 on gating charge of L-type Ca channels were studied in single ventricular myocytes. From a holding potential (Vh) of -40 mV, saturating (250 nm) S(-)Bay K shifted the half-distribution voltage of the activation charge (Q1) vs. V curve -7.5 +/- 0.8 mV, almost identical to the shift produced in the Ba conductance vs. V curve (-7.7 +/- 2 mV). The maximum Q1 was reduced by 1.7 +/- 0.2 nC/microF, whereas Q2 (charge moved in inactivated channels) was increased in a similar amount (1.4 +/- 0.4 nC/microF). The steady-state availability curves for Q1, Q2, and Ba current showed almost identical negative shifts of -14.8 +/- 1.7 mV, -18.6 +/- 5.8 mV, and -15.2 +/- 2.7 mV, respectively. The effects of the antagonist enantiomer R(+)BayK 8644 were also studied, the Q1 vs. V curve was not significantly shifted, but Q1max (Vh = -40 mV) was reduced and the Q1 availability curve shifted by -24.6 +/- 1.2 mV. We concluded that: a) the left shift in the Q1 vs. V activation curve produced by S(-)BayK is a purely agonistic effect; b) S(-)BayK induced a significantly larger negative shift in the availability curve than in the Q1 vs. V relation, consistent with a direct promotion of inactivation; c) as expected for a more potent antagonist, R(+)Bay K induced a significantly larger negative shift in the availability curve than did S(-)Bay K.

Differential involvement of cortical muscarinic and NMDA receptors in short- and long-term taste aversion memory

In conditioned taste aversion, an animal avoids a taste previously associated with toxic effects, and this aversive memory formation requires an intact insular cortex. In this paper, we investigated the possible differential involvement of cholinergic and glutamatergic receptors in the insular cortex in short-term memory (STM) and long-term memory (LTM) of taste aversion in rats. Taste aversion was induced by intraperitoneal administration of lithium chloride (a malaise-inducing drug) 15 min after experience with an unfamiliar taste. In order to test STM and LTM of taste aversion, taste stimulus was again presented 4 h and 72 h after lithium injection, respectively. During the acquisition, microinjection of the muscarinic antagonist, scopolamine, in the insular cortex before, but not after, the presentation of the new taste, abolished STM as well as LTM. Blockade of the NMDA receptor, in the insular cortex, by AP5 before, but not after, the presentation of the taste stimulus, impaired LTM but left STM intact. Moreover, when injected 1 h after malaise induction (i.e., during taste-illness association), AP5 disrupted both STM and LTM. These results suggest that activation of muscarinic receptors in the insular cortex is involved in the acquisition of taste memory, whereas NMDA receptors participate in taste memory consolidation. These data demonstrate that different neurochemical mechanisms subserve different memory phases. NMDA receptors are also probably involved in processing the visceral input, thus allowing subsequent taste-illness association. This indicates that in the same cortical area the same neurotransmitter system can be involved in distinct processes: taste memory consolidation vs. taste-illness association.

Twenty-four-hour-old lambs rely more on maternal behavior than on the learning of individual characteristics to discriminate between their own and an alien mother

Lambs can discriminate their own mother from an alien dam on the first day of life, suggesting the recognition of individual physical characteristics of the mother. Alternatively, their choice may depend on behavioral differences existing between the ewes because of their maternal selectivity. To clarify this, the ability of 24-hr-old lambs to discriminate between their own and an alien mother, that were either intact and accept only their own lamb at nursing (i.e., selective, n = 19) or anosmic, which nurse indiscriminately alien lambs as well as their own (i.e., nonselective, n = 24), was assessed by a 5-min, two-choice test. With intact dams, lambs spent significantly more time next to their own mother whereas this was not so in the presence of anosmic dams. Furthermore, in the intact group, the vocal activity by their own mother differed from that by the alien dam while this was not so in anosmic ewes. We conclude that 24-hr-old lambs rely more on the behavior of the ewes to select their dam than on their individual physical characteristics.

Extensive immunolesions of basal forebrain cholinergic system impair offspring recognition in sheep

The involvement of the basal forebrain cholinergic system has been extensively investigated in instrumental learning but little is known of its participation in social memory, especially in the memorization of individual traits of a conspecific. The present study tested in sheep its contribution to both instrumental learning and individual offspring recognition. Six weeks before parturition, ewes received injections of a specific cholinergic immunotoxin (ME20.4 IgG-saporin) into the lateral ventricles (150 microg) and in some cases additional immunotoxin injections into the nucleus basalis (11 microg/side). After 3 weeks of recovery, ewes were trained on a classical instrumental visual discrimination task known to be sensitive to cholinergic deficits. The formation of memory of offspring was assessed through both olfactory and visual/auditory recognition tasks. Olfactory recognition was tested by presenting at suckling successively an alien and the familiar lamb at 2 and 4 h after parturition. Visual/auditory recognition of the lamb was performed using a non-olfactory discrimination test between the familiar and an alien lamb after 12 h of mother-young contact. The lesion extent was assessed by counting choline acetyltransferase-immunopositive neurons in the basal forebrain and measuring the density of acetylcholinesterase fibers in different target areas. Results showed that immunotoxic lesions delayed acquisition of the instrumental visual discrimination. Moreover, olfactory recognition of the lamb was severely impaired while visual/auditory lamb recognition was marginally altered. There was no evidence for sensorimotor or motivational deficits. Importantly, impairment was observed in animals for which loss of basal forebrain cholinergic neurons and their efferent fibers was higher than 75%, while striatal cholinergic neurons and Purkinje cells were unaffected. This study provides evidence that the basal forebrain cholinergic system contributes not only to instrumental but also to social learning. In addition, the cholinergic modulation seems of importance for processing visual and olfactory modalities. However, since only extensive lesions affect performance, this indicates that the basal forebrain cholinergic system possesses substantial reserve capacity to sustain cognitive functions.

Distribution and co-localization of choline acetyltransferase and p75 neurotrophin receptors in the sheep basal forebrain: implications for the use of a specific cholinergic immunotoxin

The basal forebrain cholinergic system is involved in different forms of memory. To study its role in social memory in sheep, an immunotoxin, ME20.4 immunoglobulin G (IgG)-saporin, was developed that is specific to basal forebrain cholinergic neurons bearing the p75 neurotrophin receptor. The distribution of sheep cholinergic neurons was mapped with an antibody against choline acetyltransferase. To assess the localization of the p75 receptor on basal forebrain cholinergic neurons, the distribution of p75 receptor-immunoreactive neurons with ME20.4 IgG was examined, and a double-labeling study with antibodies against choline acetyltransferase and p75 receptor was undertaken. The loss of basal forebrain cholinergic neurons and acetylcholinesterase fibers in basal forebrain projection areas was assessed in ewes that had received intracerebroventricular injections of the immunotoxin (50, 100 or 150 microg) alone, as well as, in some of the ewes treated with the highest dose, with bilateral immunotoxin injections in the nucleus basalis (11 microg/side). Results indicated that choline acetyltransferase- and p75 receptor-immunoreactive cells had similar distributions in the medial septum, the vertical and horizontal limbs of the band of Broca, and the nucleus basalis. The double-labeling procedure revealed that 100% of the cholinergic neurons are also p75 receptor positive in the medial septum and in the vertical and horizontal limbs of the band of Broca, and 82% in the nucleus basalis. Moreover, 100% of the p75 receptor-immunoreactive cells of these four nuclei were cholinergic. Combined immunotoxin injections into ventricles and the nucleus basalis produced a near complete loss (80-95%) of basal forebrain cholinergic neurons and acetylcholinesterase-positive fibers in the hippocampus, olfactory bulb and entorhinal cortex. This study provides the first anatomical data concerning the basal forebrain cholinergic system in ungulates. The availability of a selective cholinergic immunotoxin effective in sheep provides a new tool to probe the involvement of basal forebrain cholinergic neurons in cognitive processes in this species.

Learning of olfactory cues is not necessary for early lamb recognition by the mother

Ewes identify their young through the use of different sensory modalities. Olfactory recognition, which mediates selective acceptance at the udder, is established at 4 h postpartum (pp). Visual and auditory cues are involved in recognition at a distance, which is evident at 12 h pp. This study investigates whether anosmic ewes are able (a) to develop visual and auditory recognition and (b) to restore selective acceptance of their lamb at the udder. Visual and auditory recognition was assessed in anosmic and intact ewes at 12 h and 24 h pp by a test of two choices: their own and an alien lamb. Selectivity at allowing suckling was tested by presenting successively an alien and the familiar lamb at 4 h, 3 days, and 1 month pp. In the two-choice recognition test, at both 12 h and 24 h pp, anosmic as well as intact ewes showed a preference for their familiar lamb. Although anosmic ewes showed no difference in their acceptance of alien and familiar lambs for suckling at 4 h and 3 days pp, they nursed the alien lamb less at 1 month pp and showed more rejection behaviors toward it. Thus, visual, auditory, or both those types of recognition can be rapidly established, independent of olfactory recognition. Moreover, differential behavior of anosmic ewes toward their own versus an alien lamb at the udder at 1 month suggests that vision and audition may compensate to some extent for the loss of olfaction.

Reciprocal positive regulation of hypoxia-inducible factor 1alpha and insulin-like growth factor 2

Hypoxia-inducible factor 1 (HIF-1) activates transcription of genes encoding glucose transporters, glycolytic enzymes, vascular endothelial growth factor, and other proteins involved in O2 homeostasis and tumor progression. The expression and transcriptional activity of the HIF-1alpha subunit is regulated by the cellular O2 concentration. We demonstrate that insulin, insulin-like growth factor (IGF)-1, and IGF-2 induce expression of HIF-1alpha, which is required for expression of genes encoding IGF-2, IGF-binding protein (IGFBP)-2 and IGFBP-3. These data provide a novel mechanism by which HIF-1alpha overexpression may occur in tumor cells and contribute to an autocrine growth factor loop.

Short-term intensive consolidation therapy after all-trans retinoic acid in acute promyelocytic leukemia

Complete remission induced by all-trans retinoic acid (ATRA) in acute promyelocytic leukemia is short lived, and several consolidation chemotherapy courses usually are given to reduce the relapse rate. To assess the value of short-term intensive consolidation, 38 patients with newly diagnosed acute promyelocytic leukemia entered a prospective study in which induction therapy with ATRA immediately was followed by a single course of mitoxantrone plus high-dose cytarabine (3 g/m2 every 12 hours, days 1-4), with no further treatment. Complete remission was achieved in 31 patients (81.6%) after a median time of 49 days of ATRA (to which chemotherapy was added at entry in 10 patients with leukocytosis). Thirty patients received the planned consolidation course. After a median follow-up of 36 months, four of these patients have relapsed and 24 are still in first complete remission, for an estimated disease-free survival of 75% at 60 months. The authors conclude that this single course consolidation of ATRA-induced remission provides excellent long-term control of acute promyelocytic leukemia.

Afferents to the rostral olfactory bulb in sheep with special emphasis on the cholinergic, noradrenergic and serotonergic connections

The olfactory bulb (OB) is involved in the processing of olfactory information particularly through the activation of its afferents. To localize their cell origin in sheep, a specific retrograde fluorescent tracer, Fluoro-Gold, was injected into the olfactory bulb of seven ewes. By using immunocytochemical techniques, retrogradely labeled neurons were colocalized with choline acetyltransferase, tyrosine hydroxylase, dopamine-beta-hydroxylase and serotonin to characterize cholinergic, noradrenergic and serotonergic Fluoro-Gold-labeled neurons. Most afferents originated from the ipsilateral side of the injection site. The OB received major inputs from the anterior olfactory nucleus (AON), the piriform cortex (PC), the olfactory tubercle, the diagonal band of Broca (DBB) and the amygdala. Other retrogradely labeled neurons were observed in the taenia tecta, the septum, the nucleus of the lateral olfactory tract, the preoptic area, the lateral hypothalamic area, the mediobasal hypothalamus, the lateral part of the premammillary nucleus, the paraventricular nucleus of the hypothalamus, the paraventricular thalamic nucleus, the central grey, the substantia nigra (SN), the ventral tegmental area (VTA), the lateral nucleus to the interpeduncular nucleus (IIP), the raphe and the locus coeruleus (LC). Contralateral labeling was also found in the AON, the PC, the SN compacta, the VTA, the IIP and the LC. Cholinergic Fluoro-Gold-labeled neurons belonged to the horizontal and vertical branch of the DBB. Noradrenergic afferents came from the LC and serotoninergic afferents came from the medial raphe nuclei and the 1IP. These data are discussed in relation with olfactory learning in the context of maternal behavior in sheep.

Isolation of Prothoteca zopfii from a case of bovine mastitis in Brazil

The isolation of Prothoteca zopfii, an algae lacking chlorophyll, from bovine mastitic milk, is described herein. The isolation was performed on 8% sheep blood agar, following incubation at 37 circC for 48 h. Based on biochemical tests, susceptibility to clotrimazole, and light and electron microscopic observation of cellular morphology the algae was identified as P. zopfii. The affected animal did not improve following treatment and had to be eliminated.

Postacquisition scopolamine treatments reveal the time course for the formation of lamb odor recognition memory in parturient ewes

Institut National de Recherche Agronomique/Centre National de la Recherche Scientifique Within 4 hr after parturition, ewes learn to recognize the odor of their lamb. Whether scopolamine, a muscarinic antagonist, interferes with lamb odor retention was studied. After 4 hr of mother-young contact, ewes were separated from their lambs for 3 hr. During separation, they received intramuscular injections of saline, methylscopolamine (peripheral muscarinic antagonist), or scopolamine. Only scopolamine (100 microg/kg) prevented subsequent lamb recognition. To assess whether this effect depended on the duration of the learning phase, mothers remained with their lambs for 4, 8, or 16 hr before the 3-hr separation period and the scopolamine treatments. Ewes treated after 4 or 8 hr of contact displayed disturbed lamb recognition, whereas those having 16 hr of contact did not. Activation of central muscarinic receptors is therefore important for the formation of lamb odor recognition memory during a critical period of less than 16 hr postpartum.