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Biomedical subjects

D A Wilson

Publications and source records attributed to D A Wilson.

At least 91 records · Page 5Linked to original sources

Jejunal obstruction caused by a Pythium insidiosum granuloma in a mare.

An 8-year-old Missouri Fox Trotter mare was examined because of intermittent, low-grade abdominal pain and weight loss for 3 months. Incomplete jejunal obstruction, caused by a granulomatous mass in the wall of the jejunum, was identified during exploratory celiotomy. Pythium insidiosum was identified as the cause of the granuloma. This case suggests that enteric pythiosis may develop in horses that are geographically distant from the Gulf Coast.

Animals↗

Bilateral 6-OHDA lesions of the locus coeruleus impair associative olfactory learning in newborn rats.

On postnatal day 4 (PN4) Wistar rat pups were anesthetized and received bilateral infusions of 6-OHDA into the locus coeruleus or received vehicle infusions. On PN6 pups were trained in a classical conditioning paradigm with intra-oral milk infusions as the UCS and citral odor as the CS. Pups were trained in either 'paired', 'odor-only', 'milk-only' or 'backward' (milk then odor) conditions. On PN7 acquisition of a learned odor preference to the CS was tested in a two-odor choice test. HPLC analysis showed that locus coeruleus lesions significantly reduced olfactory bulb NE content but had no effect on olfactory bulb DA or 5-HT levels compared to controls. Pups receiving locus coeruleus lesions did not differ in behavioral response patterns during training compared to their littermate, vehicle controls. However, locus coeruleus lesions impaired acquisition of conditioned odor preferences. These results suggest that NE output from the locus coeruleus is critical for early olfactory learning.

Analysis of Variance↗

Preserved cognitive skills in dementia of the Alzheimer type.

OBJECTIVE: To describe preserved cognitive skills in patients with dementia. DESIGN: Case series. SETTING: Community clinic. PATIENTS: Five patients who met National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for probable Alzheimer's disease and were claimed to retain a cognitive skill. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Standard neuropsychological tests and individualized measures of patient's skilled behaviors. For patients who remained skilled at games, performance was compared with that of normal controls in direct competition. For the patient-trombonist, raters compared premorbid and postmorbid recordings of his play. RESULTS: One patient continued to play the trombone in a Dixieland band, although he could not name well-known numbers that he played. Another continued to solve adult jigsaw puzzles. A third patient retained skill at canasta, the fourth at dominoes. The fifth patient remained a skillful contract bridge player, although he could not name the suits or articulate simple bidding rules. Four patients had impaired performance on standard anterograde and remote memory and naming tests but performed normally on pursuit rotor and letter fluency tests. Mini-Mental State Examination scores for these patients ranged from 10 to 22. One patient refused neuropsychological testing but displayed his skill. CONCLUSIONS: Together with previous studies of preserved piano playing or painting skills, our findings indicate that a broad range of complex cognitive abilities may be preserved in patients with dementia of the Alzheimer type who cannot perform simpler actions.

Aged↗

Nitric oxide synthase does not contribute to cerebral autoregulatory phenomenon in anesthetized dogs.

Nitric oxide (NO) is a potent vasodilator produced by nitric oxide synthase (NOS). We tested the following hypotheses: (1) cerebral blood flow (CBF) is NO dependent, (2) NO contributes to CBF autoregulation, and (3) NO participates in the neurohypophysial vasodilator response to hypotension. Three groups of sodium pentobarbital anesthetized dogs were studied using microspheres. In 7 dogs, N omega-nitro-L-arginine methyl ester (L-NAME; 40 mg/kg, i.v.) increased mean arterial pressure (MAP) by 12%. Cerebrovascular resistance (CVR) increased more than MAP, resulting in a 20 +/- 4% reduction (range 12-67%) in baseline CBF. In unblocked conditions, actively autoregulated regions (e.g. cortex, white matter, median eminence) demonstrated a correlation between CVR and MAP whereas passive regions (neural lobe) did not. NOS block did not effect the relationship between MAP and CVR in most brain regions. However, a significant relationship between CVR and MAP developed in neural lobe after NOS block. Abrupt hypotension increased neural lobe blood flow to 239 +/- 37% control at 3 min, despite NOS block. These results show that baseline cerebral vessel tone depends upon NOS activity. Enhanced NO release cannot explain either cerebral autoregulation or the transient hyperperfusion seen in neural lobe immediately following rapid hemorrhage.

Amino Acid Oxidoreductases↗

Rat spinal cord neurons contain nitric oxide synthase.

We describe the distribution and characteristics of nitric oxide synthase-containing neurons in rat spinal cord using a polyclonal affinity-purified antibody against rat cerebellar nitric oxide synthase. Numerous neurons were stained throughout the entire rostrocaudal extent of the spinal cord. Cell bodies, dendrites and axons stained in a uniform manner. Nitric oxide synthase immunoreactivity was intense in neurons of laminae I-IV and X throughout the entire spinal cord. Neurons in the intermediolateral cell column of the thoracic and lumbar spinal cord were also intensely stained for nitric oxide synthase. The sacral cord demonstrated substantial nitric oxide synthase immunostaining within lamina VII. For the entire cord, scattered neurons in laminae V, VI, VII, and VIII were weakly positive. In addition, punctate nitric oxide synthase staining throughout laminae I, III and surrounding some large motor neurons in the ventral horn suggested the presence of nitric oxide synthase at synapses. Axons and dendritic terminals located in the gray and white matter were also stained. The majority of nitric oxide synthase positive neurons in the intermediolateral cell column were double-labelled by subcutaneously injected FluoroGold confirming that these cells were preganglionic autonomic neurons. Most NADPH-diaphorase-stained neurons were also nitric oxide synthase-positive. The distribution of nitric oxide synthase-containing neurons in spinal cord suggests that nitric oxide plays a role in spinal cord neurotransmission including: preganglionic sympathetic and parasympathetic, somatosensory, visceral sensory and possibly motor pathways. In particular, the autonomic nervous system appears enriched with nitric oxide synthase immunoreactivity. The precise role of each neuron type remains to be demonstrated in physiologic and pathophysiologic paradigms.

Amino Acid Oxidoreductases↗

The locus coeruleus, norepinephrine, and memory in newborns.

Use of learned odor cues by newborn rats is critical for pup survival. Rat pups acquire approach responses to maternal odors through an associative conditioning mechanism. This learned behavioral response is accompanied by a modification of olfactory bulb neural response patterns to the learned odor. Both the behavioral and neural response changes involved and require norepinephrine release in the olfactory bulb. The source of this norepinephrine is the locus coeruleus. It is proposed that the unique response properties of the locus coeruleus during the early postnatal period in the rat may facilitate acquisition of these critical early memories.

Animals↗

Neurobiology of associative learning in the neonate: early olfactory learning.

Mammalian neonates have been simultaneously described as having particularly poor memory, as evidenced by infantile amnesia, and as being particularly excellent learners with unusually plastic nervous systems that are easily influenced by experience. An understanding of the neurobiological constraints and mechanisms of early learning may contribute to a unified explanation of these two disparate views. Toward that end, we review here our work on the neurobiology of learning and memory in neonates. Specifically, we have examined the neurobiology of early learning using an olfactory classical conditioning paradigm. Olfactory classical conditioning in neonates at the behavioral level conforms well with the requirements and outcomes of classical conditioning described in adults. Furthermore, specific neural correlates of this behavioral conditioning have been described including anatomical and physiological changes, neural pathways, and modulatory systems. In this Review, we outline the behavioral paradigm, the identified neural correlates, and apparent mechanisms of this learning. Finally, we compare the neurobiology of early learning with that reported for mature animals, with specific reference to the role of US-CS convergence, memory modulation, consolidation, and distributed memory.

Animals↗

Norepinephrine and posttraining memory consolidation in neonatal rats.

Wistar rat pups, aged Postnatal Day 5, were trained in an olfactory associative learning task with citral odor as the conditioned stimulus (CS) and intraoral infusions of milk as the unconditioned stimulus (US). Following a 30-min training session, pups were injected with either the norepinephrine beta-receptor antagonist propranolol or the beta-receptor agonist isoproterenol. Pups were tested 24 hr later for an acquired relative odor preference for the CS. Propranolol injected immediately following training impaired memory for the CS in a dose-dependent manner. This posttraining effect lasted less than 4 hr. Isoproterenol injected immediately after training also impaired memory performance, even at very low doses. These results suggest that posttraining levels of norepinephrine play a critical role in memory consolidation in the newborn, with elevations or decrements in noradrenergic activity resulting in impaired memory.

Aging↗

Cerebrovascular responsiveness to CO2 in Haemophilus influenzae type b meningitis in rabbits.

The effect of experimental meningitis on regional cerebral blood flow (rCBF), cerebral metabolic rate for oxygen (CMRO2), and cerebrovascular responsiveness to CO2 was determined in pentobarbital-anesthetized rabbits. The animals were inoculated intracisternally with saline (control) or log-phase Haemophilus influenzae type b (Hib). Eighteen hours later rCBF was determined with radiolabeled microspheres at normocapnia, hypocapnia, and hypercapnia. Cerebrovascular responses to hypocapnia and hypercapnia were assessed by calculating the change in cerebrovascular resistance per millimeter mercury change in PaCO2. At all CO2 levels, meningitis (M) was associated with elevated CBF compared with control (C: 47.5 +/- 3.0, M: 60.9 +/- 4.5 ml.100 g-1.min-1 at normocapnia, P < 0.01). Regional differences were present. In forebrain, the hyperemia in meningitis was confined to the superficial cortical grey matter. When compared with control, meningitis was not associated with altered vasoreactivity during hypocapnia (C: -0.026 +/- 0.006, M: -0.026 +/- 0.008 mmHg.ml-1 x 100 g-1.min-1.mmHg PaCO2(-1)) or hypercapnia (C: -0.037 +/- 0.004, M: -0.026 +/- 0.008 mmHg.ml-1 x 100 g.min.mmHg PaCO2(-1)). CMRO2 in meningitis was not significantly different from control (C: 3.53 +/- 0.29, M: 3.51 +/- 0.22 ml O2.100 g-1.min-1). These findings indicate that cerebrovascular responsiveness to CO2 is preserved in experimental Hib meningitis. Furthermore, enhanced CBF together with unchanged CMRO2 indicates that "luxury" cerebral perfusion is present in this model of bacterial meningitis.

Animals↗

Neural correlates of memory for odor detection conditioning in adult rats.

Adult male Wistar rats were trained in a simple odor detection task, with peppermint odor serving as either an S+, S- or as a randomly presented odor. Twenty-four hours after the last training session, rats were injected with [14C]2-deoxyglucose and exposed to the odor. Mean relative 2-deoxyglucose uptake to the odor was enhanced in the pars dorsalis of the anterior olfactory nucleus of S+ and S- trained rats compared to controls. In contrast, no differences in uptake were detected in either odor-specific focal regions of the olfactory bulb glomerular layer, the pyriform cortex, or the hippocampus.

Animals↗

Light spectral quality effects on the growth of potato (Solanum tuberosum L.) nodal cuttings in vitro.

The effect of light spectral quality on the growth of in vitro nodal cuttings of potato (Solanum tuberosum L.) cultivars Norland, Superior, Kennebec, and Denali were examined. The different light spectra were provided by Vita-Lite fluorescent (VF) (a white light control), blue fluorescent (BF), red fluorescent (RF), low-pressure sodium (LPS), and a combination of low-pressure sodium plus cool-white fluorescent lamps (LPS/CWF). For all cultivars, stem lengths after 4 wk were longest under LPS, followed by RF, LPS/CWF, VF, and BF (in descending order). Microscopic studies revealed that cells were shortest when cultured in BF or VF environments, and were longest in RF or LPS lamp environments. The highest number of axillary branches occurred on plantlets grown with LPS or LPS/CWF, whereas the lowest number occurred with BF. No leaf or stem edema (callus or gall-like growths) occurred with LPS or LPS/CWF lighting, and no edema occurred on cv. Norland plantlets, regardless of lighting. Results suggest that shoot morphologic development of in vitro grown potato plants can be controlled by controlling irradiant spectral quality.

Cells, Cultured↗

Role of the amygdala complex in early olfactory associative learning.

Although olfactory associative conditioning in newborn rats produces marked structural and functional changes in the olfactory bulb, recent evidence suggests that extrabulbar circuits must be involved in storing these early memories. The present experiments examined the role of the amygdala complex on early olfactory learning. Bilateral amygdala lesions or sham lesions were performed on Postnatal Day (PN) 5. On PN6, pups were trained in a standard classical conditioning paradigm associating odor with tactile stimulation. Behavioral testing on PN7 revealed that amygdala lesions blocked odor preferences but had no effect on conditioned behavioral activation. Similar sized neocortical lesions did not impair odor preferences. Importantly, amygdala lesion effects on learned odor preferences could be reversed by extensive overtraining. These results suggest that the amygdala complex plays a critical role in modulating associative learning as early as the first postnatal week in the rat.

Aging↗

Battery acid burns of the upper gastro-intestinal tract.

Strong acid ingestion produces distinctly different injuries from alkali burns. Alkali burns are well described but the lack of literature on the diagnosis and management of acid burns is apparent. This retrospective review of 18 patients with battery acid (30% sulphuric acid) ingestion showed no correlation between the severity of the symptomatology and the degree of injury. The quantity of acid needed to cause a significant upper GIT burn was more than 200 ml. Previous reports that acid spared the oesophagus due to rapid transit were disproved, since oesophageal involvement was found in 55% (10/18). Deep burns rather than circumferential burns resulted in stricture formation. The major injury site was the gastric antrum with 4 patients (23%) requiring surgical intervention to restore function.

Adolescent↗

Extracellular potassium activity and cerebral blood flow during moderate hypoglycemia in anesthetized dogs.

Moderate hypoglycemia (MH) may be associated with blunting of cerebral hypocapnic vasoconstriction. Coincident with this change, electroencephalogram (EEG) flattening occurs. Previous reports show that brain extracellular potassium activity ([K+]o) increases in association with the onset of isoelectricity during severe hypoglycemia and that K+ increases cause pial vessel vasodilation. Using a model of MH, we tested the hypothesis that increases in [K+]o (approximately 15 mM) correlate with blunting of cerebral hypocapnic vasoconstriction. Cerebral blood flow (CBF), [K+]o, and EEG were measured during normocapnia [arterial Pco2 (Paco2) = 35 Torr)] and hypocapnia (PaCO2 = 15 Torr) in MH (< 2 mM) and normoglycemic dogs. During MH, increases in [K+]o occurred in association with EEG flattening (from 4.2 +/- 0.5 to 13.8 +/- 3.8 mM). During normoglycemia and MH without [K+]o elevations, hypocapnic vasoconstriction occurred. [K+]o elevations with MH were associated with increased CBF and decreased vascular resistance (146 +/- 5 and 42 +/- 2% of control, respectively) during normocapnia, and blunting of cerebral hypocapnic vasoconstriction (93 +/- 16% normocapnic control) when [K+]o increased during hypocapnia. This study shows that increases in [K+]o during MH are necessary for both normocapnic increases in CBF and blunting of cerebral hypocapnic vasoconstriction. Increases in [K+]o may represent a mechanism for decreases in cerebral vascular resistance during MH.

Animals↗

Vasopressin and oxytocin: modulators of neurohypophysial blood flow.

We examined the role of arginine vasopressin (AVP) as a mediator of neurohypophysial (NH) blood flow regulation in anesthetized dogs. First, we evaluated the NH hyperemia that occurs during hemorrhagic hypotension in the presence (n = 7) and absence (n = 7) of the selective AVP-V1 receptor antagonist [d(CH2)5Tyr(Me)]AVP. AVP-V1 blockade did not alter NH transient or steady-state flow responses to a standardized decrease to 80 mmHg mean arterial blood pressure. We then determined whether exogenous AVP alters NH and regional cerebral blood flow (CBF) (n = 8). Sequential intracarotid infusions resulted in sagittal sinus blood AVP concentrations ranging from 6.97 +/- 3.3 x 10(3) to 2.45 +/- 0.47 x 10(6) pg/ml. No change in NH blood flow (control 428 +/- 162 vs. 487 +/- 75 ml.min-1.100 g-1) was observed even at the highest blood level. However, CBF at the highest AVP level increased from a control value of 20 +/- 3 to 40 +/- 4 ml.min-1.100 g-1, while cerebral oxygen consumption remained unchanged. Administration of a selective AVP-V1 receptor antagonist, [d(CH2)5Tyr(Me)]AVP, blocked AVP-induced elevation in CBF in a third set of dogs (n = 5). Oxytocin was also given by intracarotid infusion at a constant rate (1-200 micrograms/ml) in a final group (n = 5). NH blood flow was unchanged at all doses, whereas CBF increased from control (24 +/- 2 to 38 +/- 5 ml.min-1.100 g-1) at the highest dose. (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Cranial hemophilic pseudotumor. Case report.

Hemophilic pseudotumor is a rare complication of hemophilia occurring in 1% to 2% of individuals with a severe factor VIII or IX deficiency. This pseudotumor has been defined as a progressive cystic swelling involving muscle that is produced by recurrent hemorrhage and may be accompanied by roentgenographic evidence of bone involvement. The case is presented of a 12-month-old child with mild factor VIII deficiency (10% of normal factor VIII activity), who developed a pseudotumor of the skull.

Bone Diseases↗

Effects of human immunodeficiency virus and immune status on magnetic resonance imaging of the brain in hemophilic subjects: results from the hemophilia growth and development study.

To determine the effects of hemophilia and human immunodeficiency virus (HIV) infection on the nervous system, the authors examined the relationship of brain magnetic resonance imaging (MRI) findings to immunologic function and neurologic examination findings. Baseline examinations included physical and neurologic examination, immunologic and virologic testing, and MRI of the brain. On neurologic examination, muscle atrophy was considered to be related to hemophilia if adjacent joints had arthropathy due to bleeding. Muscle atrophy was considered non-hemophilia-related if unrelated to arthropathy or if muscle atrophy was diffuse. Subjects were boys aged 6 to 19 years, enrolled in a multicenter study of the effects of hemophilia and HIV infection on growth and development, all with congenital coagulopathies requiring factor infusions. Three hundred ten subjects had complete data including neurologic examination, T-cell subsets, HIV antibodies, and MRI. Subjects with HIV infection whose CD4+ counts were < 200/microL were compared with subjects with HIV infection and CD4+ counts > or = 200/microL and with HIV-negative subjects, all of whom had CD4+ counts > 200/microL. MRI studies were normal in 230. Abnormal MRI studies were more frequent in HIV-positive subjects with CD4+ counts < 200 (29.4% abnormal compared with 17% in HIV-positive subjects with CD4+ counts > or = 200 and 15.3% in HIV-negative subjects). Diffuse atrophy accounted for most of the excess abnormalities in HIV-positive subjects with CD4+ counts < 200 (77.3% of abnormal scans). Diffuse atrophy on MRI was associated with decreased muscle bulk on neurologic examination, but not with abnormal tendon reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗