Regional Heterogeneity of D2-Receptor Signaling in the Dorsal Striatum and Nucleus Accumbens

Dopamine input to the dorsal and ventral striatum originates from separate populations of midbrain neurons. Despite differences in afferent inputs and behavioral output, little is known about how dopamine release is encoded by dopamine receptors on medium spiny neurons (MSNs) across striatal subregions. Here we examined the activation of D2 receptors following the synaptic release of dopamine in the dorsal striatum (DStr) and nucleus accumbens (NAc) shell. We found that D2 receptor-mediated synaptic currents were slower in the NAc and this difference occurred at the level of D2-receptor signaling. As a result of preferential coupling to Gαo, we also found that D2 receptors in MSNs demonstrated higher sensitivity for dopamine in the NAc. The higher sensitivity in the NAc was eliminated following cocaine exposure. These results identify differences in the sensitivity and timing of D2-receptor signaling across the striatum that influence how nigrostriatal and mesolimbic signals are encoded across these circuits.

The Brassica napus blackleg resistance gene LepR3 encodes a receptor-like protein triggered by the Leptosphaeria maculans effector AVRLM1

LepR3, found in the Brassica napus cv 'Surpass 400', provides race-specific resistance to the fungal pathogen Leptosphaeria maculans, which was overcome after great devastation in Australia in 2004. We investigated the LepR3 locus to identify the genetic basis of this resistance interaction. We employed a map-based cloning strategy, exploiting collinearity with the Arabidopsis thaliana and Brassica rapa genomes to enrich the map and locate a candidate gene. We also investigated the interaction of LepR3 with the L. maculans avirulence gene AvrLm1 using transgenics. LepR3 was found to encode a receptor-like protein (RLP). We also demonstrated that avirulence towards LepR3 is conferred by AvrLm1, which is responsible for both the Rlm1 and LepR3-dependent resistance responses in B. napus. LepR3 is the first functional B. napus disease resistance gene to be cloned. AvrLm1's interaction with two independent resistance loci, Rlm1 and LepR3, highlights the need to consider redundant phenotypes in 'gene-for-gene' interactions and offers an explanation as to why LepR3 was overcome so rapidly in parts of Australia.

Domestication bottlenecks limit genetic diversity and constrain adaptation in narrow-leafed lupin (Lupinus angustifolius L.)

In contrast to most widespread broad-acre crops, the narrow-leafed lupin (Lupinus angustifolius L.) was domesticated very recently, in breeding programmes isolated in both space and time. Whereas domestication was initiated in Central Europe in the early twentieth century, the crop was subsequently industrialized in Australia, which now dominates world production. To investigate the ramifications of these bottlenecks, the genetic diversity of wild (n = 1,248) and domesticated populations (n = 95) was characterized using diversity arrays technology, and adaptation studied using G × E trials (n = 31) comprising all Australian cultivars released from 1967 to 2004 (n = 23). Principal coordinates analysis demonstrates extremely limited genetic diversity in European and Australian breeding material compared to wild stocks. AMMI analysis indicates that G × E interaction is a minor, albeit significant effect, dominated by strong responses to local, Western Australian (WA) optima. Over time Australian cultivars have become increasingly responsive to warm, intermediate rainfall environments in the northern WA grainbelt, but much less so to cool vegetative phase eastern environments, which have considerably more yield potential. G × E interaction is well explained by phenology, and its interaction with seasonal climate, as a result of varying vernalization responses. Yield differences are minimized when vegetative phase temperatures fully satisfy the vernalization requirement (typical of eastern Australia), and maximized when they do not (typical of WA). In breeding for WA optima, the vernalization response has been eliminated and there has been strong selection for terminal drought avoidance through early phenology, which limits yield potential in longer season eastern environments. Conversely, vernalization-responsive cultivars are more yield-responsive in the east, where low temperatures moderately extend the vegetative phase. The confounding of phenology and vernalization response limits adaptation in narrow-leafed lupin, isolates breeding programmes, and should be eliminated by widening the flowering time range in a vernalization-unresponsive background. Concomitantly, breeding strategies that will widen the genetic base of the breeding pool in an ongoing manner should be initiated.

An efficient high-throughput flow cytometric method for estimating DNA ploidy level in plants

We present an efficient high-throughput flow cytometric method that builds on previously published methods and permits rapid ploidy discrimination in plants. By using Brassica napus L. microspore-derived plants as an example, we describe how 192 leaf tissue samples may be processed and analyzed comfortably by one operator in 6 h from tissue sampling to ploidy determination. The technique involves placing young leaf samples in two 96-well racks, using a bead-beating procedure to release nuclei into a lysis solution, filtering the samples on 96-well filter plates, staining with propidium iodide, and then rapidly estimating DNA ploidy using a plate loader on a BD FACS-Canto II flow cytometer. Throughout the sample preparation process, multichannel pipetting allows faster and less error-prone sample handling. In two 96-well plates of samples, the histogram peaks of DNA content from flow cytometry were wellresolved in 189 of 192 samples tested (98.4%), with CV values ranging from 2.98% to 6.20% with an average CV of 4.35% (SD = 0.68%). This new method is useful in doubled haploid plant breeding programs where early discrimination of haploid and doubled haploid (i.e., diploid) plantlets can confer significantly improved operational efficiencies. We discuss how this method could be further refined including adapting the method to robotic sample processing.

Divergent patterns of allelic diversity from similar origins: the case of oilseed rape (Brassica napus L.) in China and Australia

Oilseed rape (Brassica napus) in Australia and China have similar origins, with introductions from Europe, Canada, and Japan in the mid 20th century, and there has been some interchange of germplasm between China and Australia since that time. Allelic diversity of 72 B. napus genotypes representing contemporary germplasm in Australia and China, including samples from India, Europe, and Canada, was characterized by 55 polymorphic simple sequence repeat (SSR) markers spanning the entire B. napus genome. Hierarchical clustering and two-dimensional multidimensional scaling identified a Chinese group (China-1) that was separated from "mixed group" of Australian, Chinese (China-2), European, and Canadian lines. A small group from India was distinctly separated from all other B. napus genotypes. Chinese genotypes, especially in the China-1 group, have inherited unique alleles from interspecific crossing, primarily with B. rapa, and the China-2 group has many alleles in common with Australian genotypes. The concept of "private alleles" is introduced to describe both the greater genetic diversity and the genetic distinctiveness of Chinese germplasm, compared with Australian germplasm, after 50 years of breeding from similar origins.

One-year outcome of auditory-tactile-visual-vestibular intervention in the neonatal intensive care unit: effects of severe prematurity and central nervous system injury

Thirty-seven infants with severe central nervous system injury or extreme prematurity were randomly assigned to a multisensory (auditory-tactile-visual-vestibular) intervention or control group. Intervention began in the hospital at 33 weeks' postconceptional age and continued twice daily in the home until 2 months' corrected age. Mother-infant interactions during feedings were videotaped, and the Bayley Scales of Infant Development were administered. Control mothers stimulated their infants more during feeding, but these significant differences dissipated by 4 months. The presence of periventricular leukomalacia was associated with significantly poorer mental development, regardless of group assignment. Experimental infants tended to exhibit better motor and mental performance and had 23% fewer cerebral palsy diagnoses at 1 year, but these trends were not statistically significant. The type of brain injury was more important in determining 1-year developmental outcome than type of postnatal experience, suggesting that periventricular leukomalacia presents a major challenge for infant development.

Short-term benefit from oral vancomycin treatment of regressive-onset autism

In most cases symptoms of autism begin in early infancy. However, a subset of children appears to develop normally until a clear deterioration is observed. Many parents of children with "regressive"-onset autism have noted antecedent antibiotic exposure followed by chronic diarrhea. We speculated that, in a subgroup of children, disruption of indigenous gut flora might promote colonization by one or more neurotoxin-producing bacteria, contributing, at least in part, to their autistic symptomatology. To help test this hypothesis, 11 children with regressive-onset autism were recruited for an intervention trial using a minimally absorbed oral antibiotic. Entry criteria included antecedent broad-spectrum antimicrobial exposure followed by chronic persistent diarrhea, deterioration of previously acquired skills, and then autistic features. Short-term improvement was noted using multiple pre- and post-therapy evaluations. These included coded, paired videotapes scored by a clinical psychologist blinded to treatment status; these noted improvement in 8 of 10 children studied. Unfortunately, these gains had largely waned at follow-up. Although the protocol used is not suggested as useful therapy, these results indicate that a possible gut flora-brain connection warrants further investigation, as it might lead to greater pathophysiologic insight and meaningful prevention or treatment in a subset of children with autism.

Heart rate variability in preterm brain-injured and very-low-birth-weight infants

Heart rate variability (HRV) reflects the complex interplay of the sympathetic and parasympathetic innervation of the heart. Developmental maturation of the fetus and newborn results in predictable alterations in the neural cardiac control of heart rate. Furthermore, patterns of HRV are closely correlated to clinical outcome in several pathologic situations. The first aim of this study was to characterize the maturational patterns of HRV in a group of developmentally at-risk newborns (those with severe hemorrhagic or ischemic brain injury and extremely immature, low-birth-weight infants). Secondly, we sought to determine whether a correlation exists between HRV and length of hospital stay, diagnosis of cerebral palsy, and neurodevelopmental test scores at 1-year corrected age. Time domain indices of HRV were computed longitudinally from 32 to 37 weeks of corrected gestational age in 19 very low birth weight, preterm infants. Among the 19 infants studied, 7 infants had no evidence of brain injury, 7 infants had periventricular leukomalacia (PVL), 3 infants had grade III/IV intraventricular hemorrhage (IVH), and 2 infants had both IVH and PVL. Neurologic injuries were documented using ultrasound and neurodevelopmental progress was followed through 1 year of corrected gestational age. A multivariate repeated measures analysis was performed to determine the relationship between the type of perinatal brain injury and neurodevelopmental status at 1 year of corrected gestational age. The type of perinatal brain injury was highly correlated to specific patterns of HRV with multivariate regression models producing adjusted r(2) values ranging from 0.63 to 0.99. The type of perinatal brain injury was highly correlated to the developmental outcome measures (p < 0.0000) with PVL patients having the lowest neurodevelopmental scores, IVH patients having the highest scores, and noninjured infants having midrange, grossly normal values. Using ANOVA, HRV was correlated to outcome, but individual comparisons revealed statistical significance only for the noninjured group (p < 0.04). However, multivariate models, which characterized outcome within each brain injury group, were highly significant (adjusted r (2) ranged from 0.23 to 0.89). In summary, the type of perinatal brain injury determined the pattern of HRV and HRV was highly correlated to length of hospital stay and neurodevelopmental function assessed at 1 year of corrected gestational age.

Developmental intervention for preterm infants diagnosed with periventricular leukomalacia

Preterm infants with periventricular leukomalacia (PVL) were evaluated to determine whether multi-sensory stimulation is safe and to assess whether it improved neurobehavior and neurodevelopment. Thirty preterm infants with documented PVL were randomly assigned to control (n= 15) or experimental (Group E) (n= 15) groups at 33 weeks post-conceptional age. Group E infants received 15 minutes of auditory, tactile, visual, and vestibular (ATVV) intervention twice a day, five days a week, for four weeks during hospitalization. Repeated measures ANOVA demonstrated that Group E infants experienced significant increases in heart and respiratory rate and a 0.72% drop in hemoglobin saturation, coinciding with a significant behavioral state shift from sleep to alertness during intervention. No differences were identified in neurobehavioral function and neurodevelopment, indicating that Group E suffered no injury. Group E had an average hospital stay nine days shorter than that of controls, with the associated cost savings of $213,840. The earlier hospital discharge indicates that ATVV intervention promotes alertness without compromising physiologic status in vulnerable infants.

Responses of preterm infants to unimodal and multimodal sensory intervention

PURPOSE

To examine the immediate responses of preterm infants to two forms of unimodal [auditory only (A) and tactile only (T)] and two forms of multimodal sensory stimulation [auditory, tactile and visual (ATV); auditory, tactile, visual and vestibular (ATVV)].

METHOD

A convenience sample of 54 clinically stable preterm infants (33-34 postconceptional weeks) was randomly assigned to 1 of 5 experimental groups [Control (C); (A); (T); (ATV); and (ATVV)]. Stimulation was applied for 15 minutes once daily for 4 consecutive days.

RESULTS

Outcome measures included pulse (PR) and respiratory rate (RR), oxygen saturation, behavioral state (BS), and body temperature. Repeated measures ANOVA identified significant differences among the groups during intervention for PR (p < .001), RR (p = .01), and BS (p < .02). Infants receiving any intervention with a tactile component showed increasing arousal (change in BS), and increased PR and RR during stimulation. Group T infants had higher proportions of PR > 180 while Group ATVV had higher proportions of PR < 140 (p = .0001). Group ATVV showed increased alertness following stimulation (24%) in contrast to having the least alertness during stimulation (11%).

CONCLUSIONS

Tactile stimulation alone may be too arousing for these infants while the addition of vestibular stimulation may modulate arousal and facilitate optimal arousal prior to feeding.

Infant stimulation: modification of an intervention based on physiologic and behavioral cues

Research involving developmental intervention with premature infants in the hospital has traditionally taken two paths: application of a sensory stimulation protocol and individualized assessment and treatment. This article describes a new method that combines some of the philosophical strengths of these two approaches. A decision tree is presented to standardize the modifications of a developmental intervention based on physiologic and behavioral cues.

Environmental influences on the developing premature infant: theoretical issues and applications to practice

The neonatal intensive-care unit (NICU) environment may interfere with the maturation and organization of premature infants' central nervous systems and may fail to meet these infants' developmental needs. In particular, immature distance receptors (i.e., hearing and vision) may receive overwhelming stimulation, whereas more mature tactile and vestibular pathways receive little stimulation. Furthermore, research on fetal learning suggests that the NICU environment should sensitively address requirements for learning by providing contingent experience. Nurses are ideally suited to reorganize the NICU and intervene to optimize infants' growth and development.

Patterns of physiologic and behavioral response of intermediate care preterm infants to intervention

PURPOSE

To determine the safety of a developmental intervention for use with preterm infants and feasibility of a time sampling procedure.

METHODOLOGY

An experimental design was used to test an intervention with clinically stable 33-34-week postconceptional age infants over a 4-day period. Repeated outcome measures included pulse rate, oxygen saturation levels, and infant behavioral state.

FINDINGS

The intervention resulted in significant differences in infant behavioral state with the experimental group achieving more alertness. Physiologic parameters remained within normal limits both during and after the intervention.

CONCLUSIONS

The protocol was found to be safe for implementation with clinically stable preterm infants. Behavioral state findings suggest the potential for the intervention to promote alertness. Results suggest that changes in oxygen saturation and pulse rate were dependent upon changes in behavioral state.

Neuropsychologic abnormalities in children with congenital central hypoventilation syndrome

We hypothesized that intellectual, neurodevelopmental, and visual-motor tests would be able to characterize the scope and nature of central nervous system involvement in children with congenital central hypoventilation syndrome. Age-appropriate intellectual (Brazelton Neonatal Behavioral Assessment, Bayley Scales of Infant Development, Wechsler Preschool and Primary Scale of Intelligence-Revised and Wechsler Intelligence Scale for Children--Revised), neurodevelopmental (Halsted-Reitan neuropsychologic battery), and visual-motor (Beery visual-motor integration test) tests were given to 17 children with congenital central hypoventilation syndrome (age 0.1 to 14.3 years). We found a broad range in IQ and developmental quotient, from greater than the 85th percentile to less than the 5th percentile, with discrepancies noted between verbal and performance measures. Multiple asymmetries and deficiencies of motor performance, not consistently related to handedness, were also found. Significant eye-hand coordination deficits were uncommon, but general performance was well below average. Full, verbal, and performance IQs and developmental quotients greater than or equal to 70 and less than 70 were compared by chi-square analysis with other associated conditions, including hours of ventilatory support, duration of initial hospitalization, growth, pulmonary hypertension, seizures, brain atrophy, central and peripheral hearing deficits, and ophthalmologic abnormalities; no statistically significant associations were found. These results lend support to the hypothesis that congenital central hypoventilation syndrome is a diffuse central nervous system process. However, the effects of transient hypoxia and associated conditions on neurodevelopmental test results cannot be excluded with certainty.

Bronchopulmonary dysplasia and postnatal growth in extremely premature black infants

Bronchopulmonary dysplasia (BPD) may adversely affect the postnatal growth of the extremely premature infant; however, most studies have not controlled for birth weight. We studied 90 Black premature infants (mean birth weight 989 +/- 148 g). Weight was recorded biweekly until discharge and at 4, 8, and 12 months of age corrected for prematurity. Infants with BPD (N = 23) were contrasted with infants without BPD (N = 67). Data were modeled using the Count model: Stage I birth to term and Stage II term to 12 months. Birth weight was considered part of growth beginning in utero and multivariate analyses were used to control for BPD, gestational age, duration of hospitalization and socioeconomic status. After adjustment for birth weight, BPD did not explain the growth pattern. A lower gestational age was associated with a slower establishment of steady growth (P less than 0.01), while an increased duration of hospitalization was associated with a lower growth rate (P less than 0.05). Growth in stage II was not explained by study variables. 'Catch-up' growth was seen in both infants with and without BPD. We conclude that differences in growth among infants with BPD are mainly attributable to birth weight. We speculate that poorer growth may be seen in a sub-group of infants with severe BPD.

Cranial ultrasonography and the prediction of cerebral palsy in infants weighing less than or equal to 1200 grams at birth

The rôle of serial cranial ultrasonography in the prediction of cerebral palsy was examined in 116 surviving infants with birthweights less than or equal to 1200 g. All underwent serial real-time sonographic examinations of the brain on days one, five and 21, then monthly, until term corrected age. Intraventricular hemorrhage (IVH) was diagnosed in 48 infants, and three had periventricular leukomalacia. Of the 116 infants, 31 had ultrasound abnormalities at term. At 12 to 18 months corrected age 12 infants had cerebral palsy and 38 were classified as suspect; the other 66 were normal. There was a clear association between risk group, based on sonographic findings at term, and outcome. Infants with IVH whose cranial ultrasounds failed to become normal by term corrected age were at higher risk for cerebral palsy than those with normal examinations at term, regardless of the severity of IVH. Thus an abnormal ultrasound at term corrected age was highly predictive of cerebral palsy, especially among survivors of IVH. It remained the best predictor of cerebral palsy, even when other perinatal and neonatal variables were considered. In contrast, duration of mechanical ventilation, rather than sonographic findings, was the best predictor of suspect neuromotor status.

Maternally administered tactile, auditory, visual, and vestibular stimulation: relationship to later interactions between mothers and premature infants

Thirty-three mother-infant pairs were randomly assigned to one of three groups: control, talking, or interactive (RISS). The later treatment included massage, talking, eye contact and rocking. The intervention (RISS) was administered to determine whether mothers and their preterm infants who actively interacted with each other would differ on later maternal and infant behaviors. The talking and RISS treatments were administered at specified time intervals 24 hours after delivery. Prior to hospital discharge, mother-infant interaction was assessed during a feeding. Significant differences were identified among the three groups for maternal (p less than .03) and infant (p less than .05) behaviors. These results suggest that active maternal interaction with the premature infant may enhance specific components of mother-infant interaction.

Prolonged mechanical ventilation and intracranial hemorrhage: impact on developmental progress through 18 months in infants weighing 1,200 grams or less at birth

In this prospective, longitudinal study, the relative impact of intracranial hemorrhage and prolonged mechanical ventilation on developmental progress during the first 18 months of life of infants weighing 1,200 g or less at birth was examined. A total of 159 surviving infants were divided into two groups: infants with and those without intracranial hemorrhage. These groups were then subdivided into groups of infants receiving prolonged mechanical ventilation (greater than 21 days) and those mechanically ventilated for 21 days or less, thus creating four subgroups. Group 1 (intracranial hemorrhage and prolonged mechanical ventilation) and group 3 (intracranial hemorrhage and no prolonged mechanical ventilation) showed no statistically significant differences for severity of intracranial hemorrhage, persistence of ventriculomegaly, or presence of periventricular leukomalacia. A repeated-measures analysis of variance demonstrated a main effect for prolonged mechanical ventilation on outcome as measured by the Bayley Mental Development Index and Bayley Psychomotor Development Index at 4, 8, 12, and 18 months of age (corrected for prematurity). Forward stepwise regression revealed prolonged mechanical ventilation to the best predictor of Bayley indexes at all ages except 4 months of age, for which the Psychomotor Development Index was best predicted by length of hospitalization. No main effect for intracranial hemorrhage was demonstrated, but the motor performance of infants with intracranial hemorrhage declined significantly with age. By contrast prolonged mechanical ventilation was associated with uniformly poor performance at every age and serves as a powerful marker for poor developmental progress during the first 18 months of life in infants weighing 1,200 g or less at birth.

Cavitary periventricular leukomalacia: incidence and short-term outcome in infants weighing less than or equal to 1200 grams at birth

One hundred surviving infants with birthweights less than or equal to 1200 g were examined longitudinally, using real-time ultrasonography of the brain. Five infants were diagnosed as having cavitary periventricular leukomalacia (PVL). One infant expired within a month following discharge; the remaining four entered a follow-up program and received developmental assessments. Three infants had moderate-severe spastic diplegia and the fourth had spastic quadriplegia. Cavitary PVL can be diagnosed in vivo and predicts future motor delay or cerebral palsy. Since the typical site of PVL involves the optic radiations, and the incidence of visual-perceptual disturbances is high in premature infants, further research is needed to explore the possible relationship between these two abnormalities.

Two year longitudinal followup of premature infants weighing less than or equal to 1,200 grams at birth: sequelae of intracranial hemorrhage

Intracranial hemorrhage (ICH) is a major problem for the premature infant, occurring in more than one-third of surviving infants weighing less than or equal to 1,500 g at birth. The literature on perinatal ICH, as it relates to neurodevelopment outcome, is briefly reviewed, and preliminary results from our two-year followup of 75 less than or equal to 1,200-g infants are summarized. An analysis of pathophysiology, diagnosis, classification, and followup indicates that risk for ICH and its sequelae increases as gestational age and birth weight decrease. Hydrocephalus apparently no longer presents significant risk beyond that conveyed by the original hemorrhage. However, persistent posthemorrhagic ventriculomegaly and/or periventricular abnormalities serve as significant "markers" of risk for neuromotor delay through two years of age. In contrast, recovery of normal ventricular morphology by term gestational age apparently indexes a degree of recovery from ICH and predicts a more normal developmental outcome through the first two postnatal years.

Intracranial hemorrhage and neurodevelopmental outcome at one year in infants weighing 1200 grams or less. Prognostic significance of ventriculomegaly at term gestational age

Seventy-five surviving infants weighting 1200 g or less at birth were followed up longitudinally, employing real-time ultrasonographic examination of the brain from birth to term corrected gestational age. Evaluations using the Milani-Comparetti Motor Developmental Screening Test and developmental testing using the Bayley Scales of Infant Development were performed at 4, 8, and 12 months corrected age. Thirty-five (46.7%) of the infants were diagnosed to have intracranial hemorrhage (ICH). These infants were significantly smaller and lighter and were mechanically ventilated close to five times longer than infants without ICH. ICH was predictive of poorer developmental outcome through the first postnatal year. ICH infants had significantly lower Bayley motor scores at both 4 and 12 months. Sixteen of the 20 who scored less than 84 on one or both of the Bayley Scales at one year had a history of ICH. When infants with hemorrhage and normal ventricles at term (ICH-no VM) were compared to infants with hemorrhage and ventriculomegaly at term (ICH-VM), the poorest motor outcome was seen in the ICH-VM group. Only the ICH-VM group showed motor performance significantly poorer than the non-ICH group at 12 months of age. Regardless of severity of hemorrhage, the data suggested an added risk for poorer developmental outcome in ICH survivors who had ventriculomegaly or abnormal periventricular morphology at term. Thus, intracranial hemorrhage per se indicates significantly greater risk of short-term motor sequelae continuing through the first four postnatal months, but persistently abnormal ventricles serve as a more significant "marker" of risk for longer term neuromotor delays at one year corrected age.(ABSTRACT TRUNCATED AT 250 WORDS)