Cardiorespiratory responses to acute hypoxemia in the chronically catheterized fetal llama at 0.7-0.9 of gestation

PURPOSE: To compare hard-copy digital chest radiographs obtained with a selenium-based system with wide-latitude asymmetric screen-film radiographs for detection of pulmonary nodules. MATERIALS AND METHODS: Fifty patients undergoing thoracic computed tomography (CT) for suspected pulmonary nodules were recruited to undergo both digital and screen-film posteroanterior (PA) and lateral chest radiography. Three chest radiologists blinded to the CT results independently reviewed each digital and screen-film radiograph, identified each nodule, and graded their confidence for its presence. RESULTS: Seventy-eight pulmonary nodules (mean diameter, 1.5 cm; range, 0.5-3.5 cm; 62 soft tissue, 16 calcified) were identified with CT in 34 patients, while 16 patients had clear lungs. The mean sensitivity for the detection of all nodules by all readers (PA and lateral) was 66% (95% Cl, 54%, 76%) for digital radiographs and 64% (95% Cl, 52%, 74%) for screen-film radiographs. Differences between the two techniques were not statistically significant (P > .05, Student t test). There was no difference in mean false-positive-true-positive ratios (PA, 0.35; lateral, 0.53) or positive predictive values (PA, 74%; lateral, 65%), and no significant difference (P > .05) was seen in mean reader confidence rating. CONCLUSION: In detecting pulmonary nodules, radiologists perform comparably with selenium-based digital and wide-latitude asymmetric screen-film radiographs.     

Metabolism of glucose, fructose and lactate in vivo in chronically cannulated foetuses and in suckling lambs

1. Chronically cannulated sheep foetuses and suckling lambs were injected with 14C-labelled glucose, fructose or lactate, and sequential blood samples taken under conditions of minimal stress and without anaesthesia. 2. Gluconeogenesis from lactate was not detectable in foetal sheep, but the pathway was active in suckling lambs. 3. Fructose utilization rates were low in foetal sheep, with no measurable conversion into glucose or lactate. 4. The high rates of irreversible loss of both glucose and lactate in the foetus were decreased in suckling lambs. Radioactivity from labelled glucose entered both the lactate and fructose pools in foetal sheep, and entered the lactate pool in suckling lambs. 5. A model is proposed in which carbon flow between glucose, fructose and lactate has been quantified in foetal sheep.     

Decreased response to phototherapy for neonatal jaundice in breast-fed infants

OBJECTIVE: To evaluate the efficacy of phototherapy for nonhemolytic hyperbilirubinemia in breast-fed and formula-fed infants and infants receiving formula and breast milk. DESIGN: Prospective study. SETTING: Nursery for healthy infants. METHOD: Full-term healthy infants with nonhemolytic hyperbilirubinemia (bilirubin concentration, >255 micromol/L [14.9 mg/dL] or 222 micromol/L [13.0 mg/dL] at ages younger than 48 hours) were treated with conventional phototherapy by using daylight fluorescent lamps. Three groups of infants were studied: group 1, formula-fed infants; group 2, breast-fed infants; and group 3, infants receiving formula and breast milk. All patterns of feeding started at birth. Phototherapy was terminated only when bilirubin concentrations had decreased to less than 185 micromol/L (10.8 mg/dL); the minimum exposure period was 24 hours. RESULTS: A total of 163 infants were studied: group 1, 79; group 2, 34; and group 3, 50. The age at the start of exposure was comparable in all groups. The mean+/-SD weight loss as a percentage of birth weight was as follows: group 1, 2.8%+/-5.0%; group 2, 6.1%+/-3.4%; and group 3, 3.2%+/-2.6%. The duration of exposure to phototherapy was as follows: group 1, 54.1+/-20.8 hours; group 2, 64.6+/-25.1 hours; and group 3, 54.9+/-21.5 hours; the 24-hour rate of decrease in the bilirubin concentration was as follows: group 1, 18.6%+/-11.7%; group 2, 17.1%+/-9.6%; and group 3, 22.9%+/-9.4%. The overall rate of decrease in the bilirubin concentration for the duration of exposure to phototherapy was as follows: group 1, 0.8%+/-0.3% per hour; group 2, 0.6%+/-0.3% per hour; and group 3, 0.8%+/-0.3% per hour. Weight loss at the start of phototherapy was significantly greater in group 2 compared with group 1 (P<.001) and group 3 (P<.001), although the hemoglobin and hematocrit values were comparable. The duration of exposure to phototherapy was not significantly different in the 3 groups (P=.06); however, the duration of exposure of group 2 infants was 10 hours more than that of the other 2 groups. The 24-hour rate of decrease in the bilirubin concentration in group 3 was significantly better than that of group 2 (P = .007) and group 3 (P = .02); the rates of decrease for groups 2 and 3 were similar (P = .52). The overall rate of decrease in the bilirubin concentration during the duration of exposure to phototherapy in group 2 was significantly less than that of group 1 (P = .002) and group 3 (P<.001); the rates for groups 1 and 3 were similar (P = .35). The postexposure rebound bilirubin concentrations were comparable in all groups during the first 2 days; however, the duration of moderate jaundice in group 2 was more prolonged. CONCLUSIONS: The response to phototherapy of group 2 infants was significantly slower than that of group 3 and group 1 infants; this response was still of adequate efficacy. The addition of formula to the feedings for totally breast-fed infants, without suspension of breast-feeding, would enhance the efficacy of phototherapy and reduce exposure time.     

Profound neuronal plasticity in response to inactivation of the dopamine transporter

The dopamine transporter (DAT) plays an important role in calibrating the duration and intensity of dopamine neurotransmission in the central nervous system. We have used a strain of mice in which the gene for the DAT has been genetically deleted to identify the DAT's homeostatic role. We find that removal of the DAT dramatically prolongs the lifetime (300 times) of extracellular dopamine. Within the time frame of neurotransmission, no other processes besides diffusion can compensate for the lack of the DAT, and the absence of the DAT produces extensive adaptive changes to control dopamine neurotransmission. Despite the absence of a clearance mechanism, dopamine extracellular levels were only 5 times greater than control animals due to a 95% reduction in content and a 75% reduction in release. Paradoxically, dopamine synthesis rates are doubled despite a decrease of 90% in the levels of tyrosine hydroxylase and degradation is markedly enhanced. Thus, the DAT not only controls the duration of extracellular dopamine signals but also plays a critical role in regulating presynaptic dopamine homeostasis. It is interesting to consider that the switch to a dopamine-deficient, but functionally hyperactive, mode of neurotransmission observed in mice lacking the DAT may represent an extreme example of neuronal plasticity resulting from long-term psychostimulant abuse.     

Organ blood flow redistribution in response to hypoxemia in neonatal piglets

This study was designed to determine the effects of severe hypoxemia on newborn piglet visceral blood flow. While the hemodynamic effects of a severe hypoxemic insult are well characterized in newborn animals, its impact on organ perfusion in premature infants is not well characterized. Cannulas were placed in the femoral vessels and left atrium of term (1-14 days old) and prematurely delivered (cesarean section at 90% of term gestation) piglets. After stabilization, some animals were subjected to 1 h of ventilator-controlled hypoxia (yielding PaO2 approximately = 30-40 torr) followed by 30 min of reoxygenation; the remaining animals served as unchallenged controls. Radiolabeled microspheres were injected in all animals at times 0 min (baseline), 5 and 60 min (hypoxia), and 90 min (reoxygenation). Blood flows (mL/min/g tissue) to organs were determined using reference organ techniques. Control animals displayed no alterations in any of the variables monitored. Throughout the experimental period, organ blood flows were almost uniformly lower (p<.05, ANOVA) in premature versus term animals. The trend toward increased cerebral and cardiac blood flows during hypoxia observed in the premature piglets was similar to that of term animals, but of lower magnitude. In term piglets, hypoxia produced an immediate and significant (*p<.05) decline in small-intestinal blood flow followed by autoregulatory escape (2.02+/-0.17 mL/min/g at time 0, 1.56+/-0.15 mL/min/g at 5 min hypoxia, 1.88+/-0.18 mL/min/g at 60 min hypoxia, 2.26+/-0.19 mL/min/g at 30 min reoxygenation), an effect not readily observed in the premature piglets (0.48+/-0.10 mL/min/g at time 0, 0.44+/-0.07 mL/min/g at 5 min hypoxia, 0.46+/-0.10 mL/min/g at 60 min hypoxia, 0.42+/-0.08 mL/min/g at 30 min reoxygenation). However, mucosal blood flows measured in these younger animals declined throughout the experimental period to almost 50% of baseline, compared to a complete restoration to baseline blood flow observed following reoxygenation of term piglets. Intestinal blood flow in premature infants is small when compared to term animals, and alterations in small intestinal blood mucosal flow induced by hypoxia appear less well tolerated by the premature animals. Taken together, this may in part account for the increased risk of developing intestinal ischemic diseases in premature infants who are even temporarily exposed to a severe hypoxic challenge.     

The cellular response of lambs to Brucella ovis before and after birth

The immunological response of lambs to Brucella ovis before and after birth was investigated. The establishment of indwelling cannulas in the efferent prescapular lymphatic ducts of foetal lambs allowed continual monitoring of the immune response of a single lymph node. Foetal lambs in the last trimester of pregnancy were shown to mount a strong cell-mediated immune response to B. ovis. Lymphocytes from the challenged lymph node stimulated with B. ovis in vitro usually first reacted significantly and had highest [3H]-thymidine incorporation between 4 and 6 days after primary and secondary challenge, whereas, lymphocytes from the unchallenged node did not exhibit significant [3H]-thymidine incorporation until some 24 h later. Lymphocytes from these lambs challenged as foetuses still exhibited significant [3H]-thymidine incorporation in response to B. ovis for 4 to 5 months after birth. The proportion of surface immunoglobulin-positive cells in efferent prescapular lymph of unchallenged lambs ranged from 0.5 to 2.0% but after B. ovis challenge this proportion ranged from 2.7 to 8.7% between 4 to 6 days after challenge. By 9 to 12 days after challenge, the proportion had declined to pre-challenge values.     

The morphogenesis of motor rituals in rats treated chronically with the dopamine agonist quinpirole.

Rats injected repeatedly with the dopamine agonist quinpirole develop motor rituals that evolve through a cascade of 4 behavioral processes. The 1st involves increased activity. The 2nd involves increased path stereotypy, reflected in traveling repeatedly along the same few paths. The 3rd is an increase in the frequency of stopping in a few places, along with a decrease in stopping in other places. The 4th is a decrease in the repetition of movements performed in the specific stopping places. Altogether, these processes culminate in stereotypy, a typical short set of movements composed of a single performance of each movement type. Thus, stereotypy arises from changes in the temporal and spatial organization, but not the content, of behavioral patterns. These results provide a model for the development of motor rituals and their linkage to normal behavior and to the physical properties of the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of neonatal dopamine depletion on sensory inhibition in the rat

Central dopamine systems appear to play an important role in sensory information processing. In particular, the filtering (or gating) of repetitive auditory stimuli is modulated by pharmacological manipulations that affect dopaminergic neurotransmission. The present study further addressed the role of dopamine in auditory gating. Three-day-old male Sprague-Dawley rats, pretreated with desipramine, received intracisternal injections of 6-hydroxydopamine (6-OHDA; 75 micrograms in 10 microliters) or the vehicle. At 4 months of age the rats were implanted for evoked potential recording and auditory gating was assessed using a paired click paradigm. Neonatally administered 6-OHDA did not alter gating in the adult rats. However, unlike for the control group, systemic amphetamine (1.83 mg/kg, IP) failed to disrupt gating in the treated rats. Apomorphine (1.0 mg/kg, SC) disrupted gating in both groups. Neonatal 6-OHDA treatment caused significant reductions in dopamine levels in the striatum, nucleus accumbens, and substantia nigra/ventral tegmental regions. There was an inverse relationship between substantia nigra/ ventral tegmental area dopamine levels and auditory gating. Overall, the results suggest that amphetamine-induced auditory gating loss requires presynaptic dopamine release, but that the deficiency occurs through postsynaptic dopamine receptor activation.     

Differential serologic response to Mycoplasma ovipneumoniae and Mycoplasma arginini in lambs affected with chronic respiratory disease

BM 17.0744 (2,2-dichloro-12-(p-chlorophenyl)-dodecanoic acid) is a substance from a group of omega-substituted alkyl carboxylic acids with the general formula, ring-spacer-carboxylic acid. With BM 17.0744-a compound structurally unrelated to thiazolidinediones--antihyperglycemic and antihyperinsulinemic potency has been demonstrated in various animal models of type II diabetes. The antidiabetic effect is independent of the genetic background of the disease, gender, and animal species. The 24-hour blood glucose profile was dose- and time-dependently improved in ob/ob mice after a single and fourth oral administration of 0.3, 1, and 3 mg/kg/d. A dose-dependent reduction of hyperglycemia (10%, 15%, 28%, and 66%) was found in db/db mice after the fifth oral administration of 3, 10, 30, and 100 mg/kg/d. Hyperinsulinemia was reduced dose-dependently in yellow KK mice by 1%, 24%, 34%, and 66% after the fifth oral administration of 0.3, 1, 3, and 10 mg/kg/d. Overall glucose metabolism was predominantly higher in euglycemic-hyperinsulinemic clamp studies in obese fa/fa rats pretreated for 14 days with 10 mg/kg/d BM 17.0744. The data in diabetic and insulin-resistant animals suggest an improvement of insulin action that is supported by enhancement of insulin effects in vitro. There is no evidence of a risk for hypoglycemia in diabetic and metabolically healthy animals. Triglyceride (TG) and cholesterol were reduced in the serum of metabolically healthy rats, as well as serum lipids in db/db mice, which suggests this effect is independent of amelioration of the diabetic status. Lipid-lowering effects in diabetic and healthy animals show an additional property of BM 17.0744. Because of its antidiabetic and lipid-lowering potency, the substance is of great interest in treating the metabolic syndrome. Lipid decreases in rats are associated with a dose-dependent increase in carnitine acetyltransferase activity in the liver to about 100-fold (12.5 mg/kg/d). This together with hepatomegaly in small rodents may indicate peroxisomal proliferation, a phenomenon considered species-specific. Its relevance for humans is well documented for other classes of compounds including fibrates. Specific side effects of insulin sensitizers of the thiazolidinedione type, such as an increase in body weight and heart weight, could not be observed after 4-week oral application of BM 17.0744 in rats. In general, BM 17.0744 was well tolerated in the pharmacological dose range in all species tested.     

Increased cortisol response to exogenous adrenocorticotropic hormone in chronically stressed pigs: influence of housing conditions

In a longitudinal experiment, the influence of tethered housing (a condition of chronic stress) on the reactivity of the adrenal cortex to exogenous ACTH was investigated in gilts. To that end, the plasma cortisol response to synthetic ACTH (1-24; 10 micrograms/kg of BW; i.v. bolus injection via a permanent catheter) was determined before and after prolonged tethered housing. Two systems for tethered housing were used, one more restrictive than the other with regard to possibilities for visual and tactile contacts with conspecifics and visual control over the environment. The ACTH treatment induced a marked, transient plasma cortisol response in all gilts studied, irrespective of their housing conditions. Long-term tethered housing increased the ACTH-induced cortisol response. Possible effects of the experimental procedure or age-related effects could be excluded, because in control gilts, which were housed loose during the entire experimental period, the cortisol response to ACTH remained unaltered. The chronic stress-induced increase in the ACTH-induced cortisol response was considerably more pronounced and persistent in gilts that were deprived of possibilities for social contacts with conspecifics and visual control over the environment than in gilts with such possibilities. These data indicate that in tethered gilts adaptational changes occur at the level of the adrenal cortex that affect the ACTH-induced adrenocortical response. In addition, not only physical restraint but also restriction of social contact and visual control play an important role in the development of these changes.     

Depression of cardiac function after deep hypothermic circulatory arrest in deeply anesthetized neonatal lambs

Cardiac dysfunction is common after neonatal cardiac operations. Previous in vivo studies in neonatal animal models however, have failed to demonstrate decreased left ventricular function after ischemia and reperfusion. Cardiac dysfunction may have been masked in these studies by increased endogenous catecholamine levels associated with the use of light halothane anesthesia. Currently, neonatal cardiac operations are often performed with deep opiate anesthesia, which suppresses catecholamine surges and may affect functional recovery. We therefore examined the recovery of left ventricular function after ischemia and reperfusion in neonatal lambs anesthetized with high-dose fentanyl citrate (450 micrograms/kg administered intravenously). Seven intact neonatal lambs with open-chest preparation were instrumented with left atrial and left ventricular pressure transducers, left ventricular dimension crystals, and a flow transducer. The lambs were cooled (< 18 degrees C) on cardiopulmonary bypass (22 +/- 6 minutes), exposed to deep hypothermic circulatory arrest (46 +/- 1 minutes), and rewarmed on cardiopulmonary bypass (30 +/- 10 minutes). Catecholamine levels and indexes of left ventricular function were determined before (baseline) and 30, 60, 120, 180, and 240 minutes after termination of cardiopulmonary bypass. Levels of epinephrine, norepinephrine, and dopamine were unchanged from baseline values. Left ventricular contractility (slope of end-systolic pressure-volume relationship) was depressed from baseline value (31.7 +/- 9.3 mm Hg/ml) at 30 minutes (15.7 +/- 6.4 mm Hg/ml) and 240 minutes (22.7 +/- 6.4 mm Hg/ml) but unchanged between 60 and 180 minutes. Left ventricular relaxation (time constant of isovolumic relaxation) was prolonged from baseline value (19.0 +/- 3.0 msec) at 30 minutes (31.4 +/- 10.0 msec) and 240 minutes (22.1 +/- 2.8 msec) but unchanged between 60 and 180 minutes. Afterload (left ventricular end-systolic meridional wall stress) was decreased at 30, 60, and 240 minutes. Indexes of global cardiac function (cardiac output, stroke volume), preload (end-diastolic volume), and left ventricular compliance (elastic constant of end-diastolic pressure-volume relationship) were unchanged from baseline values. In deeply anesthetized neonatal lambs exposed to ischemia and reperfusion, left ventricular contractility, relaxation, and afterload are markedly but transiently depressed early after reperfusion and mildly depressed late after reperfusion.     

Influence of sleep states on laryngeal and abdominal muscle response to upper airway occlusion in lambs

This study was aimed at describing abdominal and laryngeal muscle responses to upper airway occlusion (UAO) in early life and the effect of sleep states on these responses. Twelve nonsedated, 9-26-d-old lambs were studied. We simultaneously recorded 1) airflow (pneumotachograph + face mask); 2) sleep states (electrocorticogram and electrooculogram); 3) abdominal muscle (external obliquus) electromyogram (EMG); and 4) glottic constrictor (thyroarytenoid) and dilator (posterior cricoarytenoid and cricothyroid) muscle EMGs. The pneumotachograph was repeatedly occluded for 15-30 s in wakefulness and natural sleep. We analyzed 90 occlusions during wakefulness (11 lambs), 28 during non-rapid eye movement (nREM) sleep (six lambs), and 23 during rapid eye movement (REM) sleep (five lambs). A phasic expiratory external obliquus EMG was present during baseline and progressively increased throughout UAO in wakefulness and nREM sleep, but not in REM sleep. Phasic thyroarytenoid EMG progressively increased during inspiratory efforts throughout UAO in wakefulness and nREM sleep, paralleling the increase in glottic dilator (posterior cricoarytenoid and cricothyroid) EMG. In contrast, glottic muscle response to UAO in REM sleep was severely blunted or disorganized by frequent swallowing movements. We conclude that UAO triggers complex and coordinated laryngeal and abdominal muscle responses during wakefulness and nREM sleep in lambs; these responses are largely absent, however, in REM sleep. These unique results, together with the defective arousal response in REM sleep, suggest that vulnerability to airway occlusion could be increased during REM sleep in early life. Possible implications for understanding severe postnatal apneas are discussed.     

Production of pulmonary vasodilation by tolazoline, independent of nitric oxide production in neonatal lambs

OBJECTIVE: To determine whether tolazoline reduces pulmonary vascular resistance (PVR) by means of endogenous nitric oxide production. DESIGN: Thirty newborn lambs (2 to 7 days of age) were anesthetized with pentobarbital, and their lungs were ventilated through an endotracheal tube. Intravascular catheters were placed in the left ventricle, descending aorta, right atrium, and pulmonary artery for continuous monitoring of intravascular pressures. Cardiac output was measured with radiolabeled microspheres. Arterial carbon dioxide pressure and pH were maintained in a normal range throughout the experiments. Animals were randomly assigned to the following groups: group 1, lungs ventilated with a hypoxic gas mixture and administered tolazoline; group 2, given N omega-nitro-L-arginine (L-NA) (5 mg/min intravenously for 60 minutes) and tolazoline; group 3, given L-NA with hypoxia and tolazoline. Acetylcholine (0.5 microgram/kg) was injected into the right atrium to assess pulmonary nitric oxide synthase activity before and after the L-NA infusion. Data were analyzed by analysis of variance. RESULTS: L-NA inhibited the acetylcholine-induced reduction in mean pulmonary artery pressure (MPAP) by more than 75%. Hypoxia and L-NA increased both MPAP and PVR. Tolazoline produced immediate reductions in both MPAP and PVR in all three groups (group 1, 27% +/- 3% and 50% +/- 5%; group 2, 34% +/- 5% and 50% +/- 6%; and group 3, 31% +/- 4% and 46% +/- 5%, respectively). CONCLUSIONS: These results suggest that tolazoline produces vasodilation independent of nitric oxide production. Understanding the mechanism by which tolazoline produces pulmonary vasodilation may provide insight into the clinical use of this drug and information regarding other potential endogenous mediators of pulmonary vasomotor tone in the neonate.     

Repeated isolation stress in the neonatal rat: Relation to brain dopamine systems in the 10-day-old rat.

Isolation of the rat pup from the nest and dam for one hour per day from PN 2–9 is a useful paradigm for producing stress in the neonate. These previously isolated rats respond to an amphetamine challenge with alterations in activity at the juvenile stage or as adults. Furthermore, when dopamine release is measured in the nucleus accumbens, juveniles release 3 times more dopamine after amphetamine than do controls. This study describes changes in behavior and brain dopamine systems at PN 10. Experiment 1 determined an appropriate amphetamine dose that could be used for behavioral activation at PN 10. Experiment 2 produced significant evidence of enhanced behavioral activation after the isolation paradigm and indicated that brain regions innervated by the mesolimbic dopamine system, septum, and hypothalamus display increased dopamine turnover and that the nigrostriatal pathway is less active. Likewise, in Experiment 3, in vivo microdialysis of the nucleus accumbens indicated that previously isolated pups respond to an amphetamine challenge with a several-fold increase in dopamine release over a 4-hour session. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of neonatal dopamine depletion on spatial ability during ontogeny.

Investigated the effects of neonatal dopamine (DA) depletion on spatial discrimination tasks. Ss were lesioned at 3 and 6 days of age with intraventricular 6-hydroxydopamine preceded by Desipramine. In Exp 1, Ss were tested before weaning for the ability to spontaneously alternate in a T maze both in the presence of their home cage shavings and with a screen covering the shavings. Lesioned Ss were significantly impaired in their ability to spontaneously alternate. Control and lesioned Ss both showed a decrease in performance when the screen prevented full access to the shavings and the magnitude of the impairment was significantly greater for the lesioned animals. In Exp 2, Ss were tested after weaning in an appetitively motivated task in T maze. The task required both a functional working and reference memory. Lesioned Ss were impaired on both the working and the reference components of the task; however, the magnitude of the impairment was greater in the working memory task. Results suggest that early lesions of general DA systems produce deficits in tasks requiring spatial alternation behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ventilation style on surfactant metabolism and treatment response in preterm lambs

UV radiation induces two major classes of pyrimidine dimers: the pyrimidine [6-4] pyrimidone photoproduct (6-4 product) and the cyclobutane pyrimidine dimer (CPD). Many organisms produce enzymes, termed photolyases, that specifically bind to these damage products and split them via a UV-A/blue light-dependent mechanism, thereby reversing the damage. These photolyases are specific for either CPDs or 6-4 products. A gene that expresses a protein with 6-4 photolyase activity in vitro was recently cloned from Drosophila melanogaster and Xenopus laevis. We report here the isolation of a homolog of this gene, cloned on the basis of sequence similarity, from the higher plant Arabidopsis thaliana. This cloned gene produces a protein with 6-4 photolyase activity when expressed in Escherichia coli. We also find that a previously described mutant of Arabidopsis (uvr3) that is defective in photoreactivation of 6-4 products carries a nonsense mutation in this 6-4 photolyase homolog. We have therefore termed this gene UVR3. Although homologs of this gene have previously been shown to produce a functional 6-4 photolyase when expressed in heterologous systems, this is the first demonstration of a requirement for this gene for photoreactivation of 6-4 products in vivo.     

In vivo release of dopamine and its metabolites from rat striatum in response to domoic acid

The microdialysis technique was used to examine the effect of the neurotoxin domoate, an analog of glutamic acid, on striatal dopamine activity. Our results show that the intracerebral administration of different concentrations of domoate (100 and 500 microM) produced increases in the extracellular levels of dopamine associated to decreases in the extracellular levels of its metabolites dihydroxyphenylacetate and homovanillate from rat striatum. These changes seem to be related according to a time sequence, indicating a possible effect on the metabolism of dopamine. Changes were also observed in locomotor activity (cycling behavior, sniffing around and chewing) in rats during the domoate infusion. The physiological mechanism by which domoate increased dopamine release remains to be worked out.     

Experience in a neonatal intensive care unit affects pain response

OBJECTIVE: To determine the effect of being in the neonatal intensive care unit (NICU) on pain responses in infants of 32 weeks' postconceptual age (PCA). DESIGN: A cross-sectional comparative design was used. SETTING: Two level III NICUs, each in metropolitan, university teaching hospitals. PATIENTS: Infants of 32 weeks' PCA born within the past 4 days (the newly born group; n = 53) were compared with infants of the same PCA who had been born 4 weeks earlier (the earlier-born group: n = 36) and had spent that time in an NICU. OUTCOME MEASURES: Heart rate, oxygen saturation levels, and facial actions were used as outcomes in a between-group repeated measures analysis of variance across the heel stick procedure. Background variables of Apgar, weight at birth and data collection, severity of illness, age group, and total number of invasive procedures were entered into a stepwise regression. RESULTS: The two groups responded differently to the heel stick: the earlier-born infants had less behavioral manifestations of pain than the newly born infants. The number of invasive procedures was the primary factor that explained those behavioral differences, with Apgar as a second explanatory factor. The earlier-born infants had higher heart rates and lower oxygen saturation than the newly born infants before as well as during the procedure. These physiological differences were explained by the perinatal factors of age at birth and birth weight. CONCLUSION: Preterm infants who spend PCA weeks 28 through 32 in an NICU are less mature in their pain response than newborn premature infants of 32 weeks' PCA. Greater frequency of invasive procedures is associated with behavioral immaturity, whereas birth factors are associated with physiological immaturity.     

Nucleus accumbens dopamine modulates response rate but not response timing in an interval timing task.

While previous work has demonstrated that systemic dopamine manipulations can modulate temporal perception by altering the speed of internal clock processes, the neural site of this modulation remains unclear. Based on recent research suggesting that changes in incentive salience can alter the perception of time, as well as work showing that nucleus accumbens (NAc) shell dopamine (DA) levels modulate the incentive salience of discriminative stimuli that predict instrumental outcomes, we assessed whether microinjections of DA agents into the NAc shell would impact temporal perception. Rats were trained on either a 10-s or 30-s temporal production procedure and received intra-NAc shell microinfusions of sulpiride, amphetamine, and saline. Results showed that NAc DA modulations had no effect on response timing, but intra-NAc shell sulpiride microinfusions significantly decreased response rates relative to saline and amphetamine. Our findings therefore suggest that neither NAc shell DA levels, nor the resultant changes in incentive salience signaled by this structure, impact temporal control. (PsycINFO Database Record (c) 2011 APA, all rights reserved)