Expression of <Emphasis Type="Italic">c-fos</Emphasis> as an index of functional interaction of the frontal cortex and limbic cerebral structures in the course of food-procuring stereotyped movements in rats

We estimated expression of the c-fos gene (a marker of increase in neuronal activity) and manifestations of the histochemical reaction to NADPH-diaphorase (a marker of NO-generating neurons) in the medial prefrontal cortex (MPFC) and forebrain limbic structures of rats in the norm, in the state of starvation, and during realization of long-lasting (60 min) periodic (several times per minute) food-procuring movements of the forelimb. The starvation state or realization of motivated stereotyped forelimb movements were related to significant bilateral increases (P < 0.05) in the levels of c-fos expression in the anterior olfactory (AOP) and cortical (ACo) nuclei and the central (Ce) and basolateral (BLA) nuclei of the amygdala, and also in the pyriform (Pyr), prelimbic (PrL), and inferior limbic (IL) cortices. The described findings demonstrate that the high Fos immunoreactivity in the MPFC and amygdalar structures is related to the motivation state in animals and reflects the active involvement of limbic cerebral structures in the formation of motor programs and also in the stabilization and realization of operant reflexes. Neirofiziologiya/Neurophysiology, Vol. 40, No. 3, pp. 256–259, May–June, 2008.     

Topography of Fos-Immunoreactive and NADPH-d-Reactive Neurons in the Limbic Structures of the Basal Forebrain and in the Hypothalamus during Realization of Motivated Operant Movements in Rats

We estimated in rats the expression of early gene c-fos (marker of neuronal activation) and NADPH-diaphorase activity (NO-synthase marker) in the limbic structures of the basal forebrain and in the hypothalamus. Estimations were performed in the norm, in the state of starvation, and after realization of long-lasting (repeated 4 to 12 times per minute for 30 min) motivated stereotyped food-procuring forelimb movements. In food-deprived animals, a significantly greater (Р < 0.05), as compared with the control, number of Fos-immunoreactive (Fos-ir) and NADPH-diaphorase-reactive (NADPH-dr) neurons was observed in limbic structures, namely in the medial septum (MS), nuclei of the vertical and horizontal branches of the diagonal fascia (VDB and НDB), magnocellular preoptic nucleus (MCPO), complex of the substantia innominata−basal nucleus of Meynert of the pallidum, SI-GP(B), as well as in the laterodorsal tegmental nucleus (LDTg), medial part of the pallidum (MGP), paraventricular and lateral nuclei of the hypothalamus (Pa and LH), and islands of Calleja (ICj and ICjM). In the limbic structures and pontine nuclei of rats of the experimental group (that performed operant movements), greater mean densities of labeled neurons were found in the succession LDTg < SI < MCPO < GP(B) < MS < VDB < HDB. The maximum mean density of Fos-ir neurons (13.8 ± 0.9 labeled nuclei within 200 × 200 μm² area) was found in the HDB. In the hypothalamic nuclei of starving rats, c-fos expression was two times higher than that in the control. After realization of operant movements, the intensity of expression in the LH was somewhat smaller, while in the Ра it was higher. The maximum density of NADPH-dr neurons was observed in the Pa (303.4 ± 18.7 cells), in the ICj and ICjM (287 ± 11.6 and 260 ± 8.7 neurons, respectively), and in the MGP (93 ± 6.7 labeled cells). When analyzing the distribution of labeled neurons in experimental rats, we found high densities of double-labeled cells (Fos + NADPH-d positivity) in the Pa, MGP, ICj, and ICjM. Such specificity of changes in the c-fos expression and NADPH-d reactivity in the hypothalamus correlates, perhaps, with the formation of motivation signals related to a delay in food accessibility and supply of food. Modifications of neuronal activity in limbic structures reflect involvement of the latter in the formation of motor programs for food-procuring movements and their realization. Neirofiziologiya/Neurophysiology, Vol. 41, No. 1, pp. 32–40, January–February, 2009.     

Operant reflexes and expression of the <Emphasis Type="Italic">c-fos</Emphasis> gene in the amygdalar nuclei and insular cortex of rats

We studied manifestations of increased neuronal activity in the limbic structures of the rat brain related to realizations of operant reflexes by the animals. After rats had performed repeated operant foodprocuring movements, the mean numbers of Fos-immunoreactive neurons within sections of the central and basolateral amygdalar nuclei, insular cortex, substantia innominata, and paraventricular hypothalamic nucleus significantly exceeded the control values. In the ipsilateral (with respect to the working forelimb) central nucleus of the amygdala, the mean number of such neurons within a 40-μm-thick slice was nearly an order of magnitude greater than in the control (42.2 ± 2.4 and 4.5 ± 0.4 labeled units, respectively). In the agranular insular and granular/disgranular cortical zones at the contralateral site, the numbers of labeled neurons exceeded control values by about three times (94.6 ± 8.2 vs 31.6 ± 2.2 and 103.5 ± 4.5 vs 39.6 ± ± 2.4 immunopositive cells, respectively). These findings confirm the hypothesis on the direct involvement of the subcortical structures and limbic cortex zones in the control of somato-cardiovascular integration during the performance of operant reflexes by the animals.     

Changes in the Expression of <Emphasis Type="Italic">с-fos</Emphasis> and NADPH-Diaphorase Activity in Rat Hippocampal Structures Related to Food Deprivation and Realization of Operant Food-Procuring Movements

The expression of early c-fos gene (marker of neuronal activation) and NADPH-diaphorase reactivity (NADPH-dr) was studied in various hypothalamic structures of rats in the norm, in the state of starvation, and after realization of long-lasting (repeated 4 to 12 times per minute for 30 min) motivated stereotyped food-procuring forelimb movements. In rats in the starving state, as compared with the control, the densities (number of units within a 200 × 200 μm² test area of a 40-μm-thick slice) of Fos-immunoreactive (Fos-ir) neurons in the parvicellular part of the paraventricular nucleus (Ра), supraoptic (SO), and medial preoptic (МРО) nuclei, anterior hypothalamic region (АН), and lateral hypothalamic nucleus (LH) were significantly greater (Р < 0.05) than in the control. In the dorsomedial (DMD) and ventromedial (VMHD) hypothalamic nuclei, this index did not differ from control values. After the performance of intense unilateral operant movements, higher densities of labeled neurons (as compared with that in control and starving animals) were observed in the PаAP, SO, МРО, and DMD, while smaller densities were observed in the LH and VMH. NADPH-dr neurons (i.e., NO synthase-containing cells) were observed in many hypothalamic nuclei; the maximum density of such NO-generating neurons was found in the Pa, SO, MPO, and DMD. The overwhelming majority of Fos-ir and NADPH-dr neurons in neurons was observed after realization of stereotyped food-procuring movements in the Ра and SO. This specificity of changes in the number of Fos-irand NADPH-dr neurons in the hypothalamic nuclei reflects, perhaps, the involvement of these structures in the control of autonomic functions in the course of realization of operant reflexes and adaptation of the function of the cardiovascular system to the corresponding intense physical and emotional loading.     

Excitatory and inhibitory neuron imbalance in the intrauterine growth restricted fetal guinea pig brain: Relevance to the developmental origins of schizophrenia and autism

Neurodevelopmental disorders such as schizophrenia and autism are thought to involve an imbalance of excitatory and inhibitory signaling in the brain. Intrauterine growth restriction (IUGR) is a risk factor for these disorders, with IUGR onset occurring during critical periods of neurodevelopment. The aim of this study was to determine the impact of IUGR on excitatory and inhibitory neurons of the fetal neocortex and hippocampus. Fetal brains (n = 2) were first collected from an unoperated pregnant guinea pig at mid-gestation (32 days of gestation [dg]; term ∼67 dg) to visualize excitatory (Ctip2) and inhibitory (calretinin [CR] and somatostatin [SST]) neurons via immunohistochemistry. Chronic placental insufficiency (CPI) was then induced via radial artery ablation at 30 dg in another cohort of pregnant guinea pigs (n = 8) to generate IUGR fetuses (52 dg; n = 8); control fetuses (52 dg; n = 7) were from sham surgeries with no radial artery ablation. At 32 dg, Ctip2- and CR-immunoreactive (IR) cells had populated the cerebral cortex, whereas SST-IR cells had not, suggesting these neurons were yet to complete migration. At 52 dg, in IUGR versus control fetuses, there was a reduction in SST-IR cell density in the cerebral cortex (p = .0175) and hilus of the dentate gyrus (p = .0035) but not the striatum (p > .05). There was no difference between groups in the density of Ctip2-IR (cortex) or CR-IR (cortex, hippocampus) neurons (p > 0.05). Thus, we propose that an imbalance in inhibitory (SST-IR) and excitatory (Ctip2-IR) neurons in the IUGR fetal guinea pig brain could lead to excitatory/inhibitory dysfunction commonly seen in neurodevelopmental disorders such as autism and schizophrenia.     

A Study of Glutathione <Emphasis Type="Italic">S</Emphasis>-transferase pi Expression in Central Nervous System of Subjects with Amyotrophic Lateral Sclerosis Using RNA Extraction from Formalin-Fixed,Paraffin-Embedded Material

The expression of glutathione S-transferase pi (GST pi), an enzyme responsible for inactivation of a large variety of toxic compounds was studied in spinal cord, motor and sensory brain cortex obtained from patients who died in the course of amyotrophic lateral sclerosis (ALS). The studies were performed on formalin-fixed, paraffin-embedded (FFPE) and freshly frozen tissues. The method of RNA isolation from FFPE was modified. A significant decrease of GST pi-mRNA expression was found in cervical spinal cord and motor brain cortex of ALS subjects comparing to analogue control tissues (P < 0.01), as well as in motor cortex of ALS subjects comparing to their sensory cortex (P < 0.05). In spinal cords the decrease in GST pi-mRNA expression was accompanied by a decrease of GST pi protein level. Results indicated lowered GST pi expression on both mRNA and protein levels in the regions of nervous system affected by ALS. The non-properly inactivated by GST toxic electrophiles and organic peroxides may thus contribute to motor neurons damage.     

Mechanisms of corticofugal control of the activity of “vagal” viscerosensory neurons in theNucleus tractus solitarii

In experiemnts on cats under chloralose-nembutal anesthesia, we studied viscerosensory neurons in thenucl. tractus solitarii identified by their responses to stimulation of then. vagus. The responses of these cells to stimulation of the secondary sensorimotor cortex (zoneS2) and dorsal regions of field 25 of the limbic cortex (DLC) were recorded. A substantial part of the “vagal” viscerosensory units demonstrated convergent properties and responded toS2 and DLC stimulations by phasic responses. The short latencies of these responses were indicative of oligosynaptic and, in some cases, even monosynaptic transmission of corticofugal influences on a considerable part of such neurons. Using paired stimulation allowed us to demonstrate that the effects of stimulation of the visceral afferent fiber undergo long-lasting suppression exerted by descending corticofugal volleys. The mechanisms of cortical control of the activity of bulbar viscerosensory neurons are discussed.     

Activation of Neurons of the Medullary Centers of the Autonomic Nervous System Related to Motivated Operant Movements Realized by Rats

Using the corresponding techniques, we visualized Fos-immunoreactive (Fos-ir) and NADPH diaphorasereactive (NADPH-dr) neurons in the medullary centers of the autonomic nervous system (ANS) of rats, which performed repetitive operant movements (catching of food globules from the manger by the left forelimb under conditions of high food motivation). Animals were trained to perform operant movements in 30 min-long everyday sessions during 12 days. The duration of a single food-procuring movement was about 600 msec. Realization of the operant reflex was accompanied by clearly expressed motivational/affective reactions. The heart rate (HR) in the course of each operant movement sharply dropped (on the 10th day of training, by 12%, on average) with subsequent recovery of this parameter within 3–4 sec. In the course of 30-min-long training sessions, the mean HR gradually decreased (in the examined group, 7%, on average) within an interval from the 5th to the 20th min with subsequent recovery until the end of the training session. The mean numbers of Fos-ir neurons in the medullary nuclei of the ANS (Sol, IRt, CVL, RVL, Amb, 10, and MdD) of rats performing food-procuring movements (n = 4) were significantly (P < 0.05) greater than those in the control, and the intensities of c-fos expression in these structures corresponded to the following succession: Sol > IRt > CVL+RVL/CVL > RVL. Large Fos-ir neurons were observed in the dorsal motor nucleus of the n. vagus (10) and in the Amb/RAmb nuclei. In a considerable proportion of neurons of the Sol and single cells of the 10 and Amb, we observed double labeling (Fos-ir + NADPH-dr). Thus, operant food-procuring movements are accompanied by episodes of bradycardia related to each separate realization; in addition, a long-lasting tonic decrease in the HR developed. These autonomic reactions are mediated by the abovementioned medullary ANS nuclei. It is supposed that the respective weakening of inhibitory sympathetic effects on spindle receptors of the muscles involved in realization of the above operant movements can provide facilitation of generation of proprioceptive impulsation, facilitation of monosynaptic spinal reflexes, and, finally, an increase in the efficacy of targeted limb movements directed toward food procurement.     

The Involvement of Calcium Transport Systems of the Plasma Membrane in Calcium Exchange in Neurons of the <Emphasis Type="Italic">Carassius gibelio</Emphasis> Cerebellum

We studied the role of Na⁺/Ca²⁺ exchanger (NCX) and Ca²⁺-ATPase of the plasma membrane (РМСА), known to be the most important intracellular systems controlling calcium exchange in cerebellar neurons of a fish species tolerant to hypoxia, Carassius gibelio. In our experiments, we used the corresponding blockers of these transport systems, ions of lithium and lanthanum. The intracellular Ca2+ concentration ([Ca²⁺] _і ) was measured using a calcium-sensitive dye, Fura-2AM, and a microfluorescence technique. We found that neurons of the Carassius cerebellum possess an effective system of cleaning of the cytoplasm from excessive Ca²⁺, which is provided by both NCX and РМСА functioning in the plasma membrane. Under conditions of the blockade of functioning of РМСА using lanthanum, the basal Ca²⁺ level in the cells increased, on average, by 31.4% with respect to the control, independently of the duration of test depolarizations. After switching off of the NCX functioning by the replacement of sodium ions in the extracellular solution by lithium ions, the Ca²⁺ level in the cell increased by 36.6% with respect to the control (also independently of the duration of depolarization). The obtained data indicate that the functioning of РМСА and NCX in Carassius cerebellar neurons significantly influences the intracellular calcium exchange providing the maintenance of an adequate basal Ca2+ level in these neurons.     

Decolorization of structurally different textile dyes by Aspergillus niger SA1

The fungal strain, Aspergillus niger SA1, isolated from textile wastewater sludge was screened for its decolorization ability for four different textile dyes. It was initially adapted to higher concentration of dyes (10–1,000 mg l⁻¹) on solid culture medium after repeated sub-culturing. Maximum resistant level (mg l⁻¹) sustained by fungal strain against four dyes was in order of; Acid red 151 (850) > Orange II (650) > Drimarene blue K₂RL (550) > Sulfur black (500). The apparent dye removal for dyes was seen largely due to biosorption/bioadsorption into/onto the fungal biomass. Decolorization of Acid red 151, Orange II, Sulfur black and Drimarine blue K₂RL was 68.64 and 66.72, 43.23 and 44.52, 21.74 and 28.18, 39.45 and 9.33% in two different liquid media under static condition, whereas, it was 67.26, 78.08, 45.83 and 13.74% with 1.40, 1.73, 5.16 and 1.87 mg l⁻¹ of biomass production under shaking conditions respectively in 8 days. The residual amount (mg l⁻¹) of the three products (α-naphthol, sulfanilic acid and aniline) kept quite low i.e., ≤2 in case AR 151 and Or II under shaking conditions. Results clearly elucidated the role of Aspergillus niger SA1 in decolorizing/degrading structurally different dyes into basic constituents.     

Changes in dendritic spine density on layer 2/3 pyramidal cells within the cingulate cortex of late pregnant and postpartum rats

A rapid upregulation of astrocytic protein expression within area 2 of the cingulate cortex (Cg2) of the maternal rat occurs within 3 h postpartum and persists throughout lactation. Previous studies have shown that similar changes in astrocytic proteins can signal changes in local synapses and dendritic spines. Thus, here we used the Golgi-Cox impregnation technique to compare spine density in layer 2 and 3 pyramidal cells of Cg2, the CA1 region of the hippocampus and the parietal cortex (ParCx) among metestrus, late pregnant (LP), 3-hour postpartum (3H PP) and 16-day postpartum rats (D16 PP). Rats in the 3H PP group had higher numbers of dendritic spines/10 μm on the apical dendrites of pyramidal neurons in both Cg2 and CA1 than the other groups, which did not differ. A similar pattern was observed in basilar dendrites but this failed to reach significance. In Cg2, Sholl analysis revealed that rats in the D16 PP group had a significantly greater extent of dendritic arborization in the basilar region than any other group. These data suggest that the changes in astrocytic proteins that occur in Cg2 in the postpartum period are associated with neuronal plasticity in pyramidal layers 2 and 3.     

Characterization of an acid-labile, thermostable β-glycosidase from Thermoplasma acidophilum

A recombinant putative β-galactosidase from Thermoplasma acidophilum was purified as a single 57 kDa band of 82 U mg⁻¹. The molecular mass of the native enzyme was 114 kDa as a dimer. Maximum activity was observed at pH 6.0 and 90°C. The enzyme was unstable below pH 6.0: at pH 6 its half-life at 75°C was 28 days but at pH 4.5 was only 13 h. Catalytic efficiencies decreased as p-nitrophenyl(pNP)-β-d-fucopyranoside (1067) > pNP-β-d-glucopyranoside (381) > pNP-β-d-galactopyranoside (18) > pNP-β-d-mannopyranoside (11 s⁻¹ mM⁻¹), indicating that the enzyme was a β-glycosidase.     

Differential responsiveness of metabotropic glutamate receptors coupled to phosphoinositide hydrolysis to agonists in various brain areas of the adult rat

The effects of metabotropic glutamate receptor (mGluR) agonists on inositol phosphates (IP) accumulation were investigated in slices of the cerebral cortex, hippocampus, striatum and cerebellum of adult Sprague-Dawley rats. EC₅₀ values for 1S, 3R-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) did not differ significantly between various brain areas (range 10⁻⁵ M), quisqualate was the most potent in all the brain areas (range 10⁻⁷−10⁻⁶ M), except the cerebellum (10⁻⁵ M), ibotenate was the most potent in the striatum (range 10⁻⁶ M) and the least potent in the cerebral cortex and hippocampus (range 10⁻⁴ M). The efficacy in the four brain areas showed the following trend of ranking order for ACPD and quisqualate: hippocampus > striatum > cerebral cortex > cerebellum, and for ibotenate: hippocampus > cerebral cortex > striatum > cerebellum, although the observed differences reached the level of statistical significance only in the case of ACPD (hippocampus and striatum vs cerebellum) and ibotenate (hippocampus vs cerebellum). Co-incubation of the agonists at maximally effective concentrations in any pairwise combination resulted in no substantial additivity of IP accumulation. D,L-1-amino-3-phosphonopropionic acid (AP3) and D,L-2-amino-4-phosphonobutyric acid (AP4) at 0.5 mM concentration antagonized ACPD-induced IP accumulation by about 70 and 45%, respectively, without differences between brain areas. On the other hand, the antagonistic effects ofl-serine-o-phosphate (SOP) at 1 mM concentration were the highest in the hippocampus (75%) and the lowest in the cerebellum (25%). The comparative data indicate considerable regional receptor heterogeneity, in terms of different ratios of response to the agonists (but not antagonists, except SOP). There is a robust responsiveness of mGluRs not only in the hippocampus and cerebral cortex, but also in the striatum which exhibits the highest affinity to both quisqualate and ibotenate.     

Association of interleukin 4 VNTR polymorphism and HIV/AIDS in a north Indian seropositive patients

Despite different efforts made to intervene with the deadly nature of HIV/AIDS, all attempts remained unsuccessful due to complexity of the viral host interactions. The solution to HIV-1 pandemic is still to come, thus to assist the efforts being made to intervene with the deadly nature of the virus, different factors responsible for the disease burdens have to be looked into a systematic manner. As a result, the present study aimed to find out the association of IL-4 VNTR polymorphism with HIV-1 susceptibility and rate of disease progression. Three hundred cases and an equal number of sex and age matched controls were included for this study. The polymerase chain reaction assay was utilized to genotype IL-4 VNTR. The results of this study showed statistically significant variation among cases and controls in the distribution of the Rp2/Rp2 genotype (OR = 0.36, 95% CI = 0.18–0.69; P value = 0.0014) indicating, thereby, a possibility of reduced risk of HIV-1 susceptibility. Thus, Rp2/Rp2 genotype of the IL-4 might have a role to play in reducing risk of HIV-1 susceptibility among a north Indian population.     

Transmembrane Transport and Release of GABA in the Brain of Rats Subjected to Postnatal Hypoxia

We studied the effects of early postnatal hypoxia on the efficiency of active GABA transport through the plasma membrane of synaptic terminals (synaptosomes) isolated from the cerebral cortex, hippocampus, and thalamus of rats and on non-stimulated and Ca²⁺-stimulated GABA release. The state of hypoxia was induced by exposure of 10- to 12-day-old rats to a respiratory medium with low O₂ content (4% О₂ and 96% N₂) for 12 min (up to the initiation of clonico-tonic seizures). Animals were taken in the experiment 8 to 9 weeks after an episode of hypoxic stress. The intensity of transmembrane transport of GABA was estimated according to accumulation of [³Н]GABA in a coarse synaptosomal fraction. The process was characterized by calculation of the Michaelis constant K _m and also of the initial (within the 1st min) and maximum rates of accumulation of [³Н]GABA. The means of the initial rate of [³Н]GABA accumulation in preparations from the thalamus, cortex, and hippocampus were 205.5 ± 8.8, 266.2 ± 29.6, and 302.3 ± 31.2 pmol/min⋅mg protein, respectively. Hypoxic stress influenced the rates of accumulation of [³Н]GABA in synaptic terminals from the cortex and hippocampus but not in those from the thalamus. According to the characteristics of the response to hypoxic stress, all experimental animals could be classified into two groups. In some rats, accumulation of [³Н]GABA in both cortical and hippocampal synaptosomes decreased insignificantly (by about 15%), while in other animals this parameter increased significantly (by nearly 50%) for the cortex and decreased by 21.5%, on average, for the hippocampus. The affinity of the transporter with respect to [³Н]GABA in the cortex and hippocampus was nearly the same and showed no changes under the influence of hypoxia. The non-stimulated release of [³Н]GABA after the influence of hypoxia increased in all structures, while the depolarization-induced Ca²⁺-dependent release of [³Н]GABA was intensified only in synaptosomes from the cerebral cortex. The mechanisms of development of modifications of GABA-ergic processes under the influence of hypoxic stress in the course of the perinatal period are discussed. Neirofiziologiya/Neurophysiology, Vol. 40, No. 4, pp. 293–302, July–August, 2008.     

The Corynebacterium glutamicum insertion sequence ISCg2 prefers conserved target sequences located adjacent to genes involved in aspartate and glutamate metabolism

An IS element, termed ISCg2, was identified in the chromosome of Corynebacterium glutamicum ATCC 13032. After screening a cosmid library of the C. glutamicum ATCC 13032 genome, six copies of ISCg2 including their flanking regions were sequenced and analyzed. ISCg2 is 1636 bp in length and has 26-bp imperfect inverted repeats flanked by 3-bp direct repeats. By comparisons with other IS elements, ISCg2 was classified as a member of the IS30 family of insertion sequences. The six copies of ISCg2 were identical at the nucleotide level and were located in intergenic, AT-rich regions of the chromosome. The regions in which the six copies of ISCg2 were inserted displayed significant similarities. This similarity extends over a region of 65 bp, which was assumed to be the target region for ISCg2. Interestingly, five of the six copies of ISCg2 were located adjacent to genes that may be involved in aspartate and glutamate metabolism or its regulation. Investigation of the distribution of ISCg2 showed that the IS element is restricted to certain C. glutamicum strains. Analysis of various integration regions indicates active transposition of ISCg2 in C. glutamicum. Received: 7 April 1999 / Accepted: 17 June 1999     

The Distribution of Corticocortical,Thalamocortical, and Callosal Inputs on Identified Motor Cortex Output Neurons: Mechanisms for Their Selective Recruitment

Motor cortex neurons were identified antidromically in anesthetized cats by their axonal projections to one of six targets: (1) somatosensory cortex, (2) opposite motor cortex, (3) red nucleus, (4) lateral reticular nucleus, (5) spinal cord, and (6) ventrolateral thalamus. Three inputs to motor cortex were tested for their influences on the identified cortical efferent neurons. The tested inputs originated from ipsilateral somatosensory cortex, opposite motor cortex, and ventral thalamus. Subthreshold effects of input pathways were detected by monitoring latency variations of antidromic responses.

The three afferent sources, when activated by electrical stimulation, were not equally effective on motor cortex neurons. Ipsilateral corticocortical and thalamocortical excitation were found for the majority of neurons; the influenced proportions ranged from 55% to 100%, according to the target of the output neurons. Effects from the opposite hemisphere were found for only 5% to 30% of the neurons in the same projection classes.

Many neurons (36 of 81, or 44%) were excited from more than one source, but few (5 of 37, or 14%) were influenced by all three possible sources of input, even in small regions of cortex innervated by all three of the inputs. Among 19 electrode tracks where all three inputs were present, there were only 2 tracks where all the neurons shared the same combination of inputs. Even for neurons in closest anatomical proximity (“clusters”), it was unusual (only 7 of 25 clusters) for all the neurons to have the same input pattern. Among the seven clusters where all the neurons shared the same input pattern, five of the clusters projected to the same target. These variable combinations of inputs to motor cortex neurons support the conclusion that efferent neurons could be recruited selectively from separate cortical layers or from within clusters of nearby neurons, according to the target of their axonal projection.     

Association between variants in the 5′-untranslated region of the bovine <Emphasis Type="Italic">MC4R</Emphasis> gene and two growth traits in Nanyang cattle

Melanocortin-4 receptor (MC4R) is one of five G-protein-coupled receptors binding melanocortins that is implicated in the control of feeding behavior and energy homeostasis. Six cattle populations (n = 594), including four Chinese indigenous breeds, Chinese Holstein, and a meat type breed (Angus), were used to detect single nucleotide polymorphisms in 5′-untranslated region of MC4R gene by means of PCR–SSCP and DNA sequencing. Four linked SNPs (g.[−293C>G; −193A>T; −192T>G; −129A>G]) were identified. The g.−293C>G and g.−129A>G could be genotyped with a PCR–RFLP using TaiI in three combined genotypes (AA, AB and BB). The two linked SNPs were associated with body weight and daily gain in Nanyang aged 6 months (P < 0.05), but they had no significant effect on body weight and daily gain in Nanyang aged 24 months (P > 0.05).     

Fumonisins in Maize in Relation to Climate,Planting Time and Hybrids in Two Agroecological Zones in Zambia

Field experiments in the high rainfall zone (HRZ) and the medium rainfall zone (MRZ) in Zambia were designed to determine the natural occurrence of fumonisins (FB_1–2) in Zambian maize hybrids, accumulation of FB_1–2 resulting from artificial inoculation with Fusarium verticillioides and effects of climate and planting time on FB_1–2 in maize. Combined FB_1–2 concentrations varied from 0 to 13,050 ng/g, with an overall mean of 666 ng/g. Maize from the HRZ had low incidences of FB_1–2-positive samples (mean 41%) which contained FB_1–2 below 500 ng/g. In the MRZ, higher incidences (mean 97%) and concentrations (40% of samples >1,000 ng/g) were recorded in two out of three years. There was no correlation between mean location FB_1–2 concentrations in individual years and precipitation, number of rain days or monthly precipitation. Postponing the planting time with 10 or 20 days did not significantly affect FB_1–2 concentration, but it reduced the yields in some years.     

Effect of 7-Nitroindazole Sodium on the Cellular Distribution of Neuronal Nitric Oxide Synthase in the Cerebral Cortex of Hypoxic Newborn Piglets

Cerebral hypoxia results in generation of nitric oxide (NO) free radicals by Ca⁺⁺-dependent activation of neuronal nitric oxide synthase (nNOS). The present study tests the hypothesis that the hypoxia-induced increased expression of nNOS in cortical neurons is mediated by NO. To test this hypothesis the cellular distribution of nNOS was determined immunohistochemically in the cerebral cortex of hypoxic newborn piglets with and without prior exposure to the selective nNOS inhibitor 7-nitroindazole sodium (7-NINA). Studies were conducted in newborn piglets, divided into normoxic (n = 6), normoxic treated with 7-NINA (n = 6), hypoxic (n = 6) and hypoxic pretreated with 7-NINA (n = 6). Hypoxia was induced by lowering the FiO₂ to 0.05–0.07 for 1 h. Cerebral tissue hypoxia was documented by decrease of ATP and phosphocreatine levels in both the hypoxic and 7-NINA pretreated hypoxic groups (P < 0.01). An increase in the number of nNOS immunoreactive neurons was observed in the frontal and parietal cortex of the hypoxic as compared to the normoxic groups (P < 0.05) which was attenuated by pretreatment with 7-NINA (P < 0.05 versus hypoxic). 7-NINA affected neither the cerebral energy metabolism nor the cellular distribution of nNOS in the cerebral cortex of normoxic animals. We conclude that nNOS expression in cortical neurons of hypoxic newborn piglets is NO-mediated. We speculate that nNOS inhibition by 7-NINA will protect against hypoxia-induced NO-mediated neuronal death.