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Biomedical subjects

J B Schweitzer

Publications and source records attributed to J B Schweitzer.

At least 19 recordsLinked to original sources
PubMed2001

Neural activity related to drug craving in cocaine addiction.

BACKGROUND: Crack cocaine dependence and addiction is typically associated with frequent and intense drug wanting or craving triggered by internal or environmental cues associated with past drug use. METHODS: Water O 15 positron emission tomography (PET) studies were used to localize alterations in synaptic activity related to cue-induced drug craving in 8 crack cocaine-dependent African American men. In a novel approach, script-guided imagery of autobiographical memories were used as individualized cues to internally generate a cocaine craving state and 2 control (ie, anger and neutral episodic memory recall) states during PET image acquisition. RESULTS: The mental imagery of personalized drug use and anger-related scripts was associated with self-ratings of robust drug craving or anger, and comparable alterations in heart rate. Compared with the neutral imagery control condition, imagery-induced drug craving was associated with bilateral (right hemisphere amygdala activation greater than left) activation of the amygdala, the left insula and anterior cingulate gyrus, and the right subcallosal gyrus and nucleus accumbens area. Compared with the anger control condition, internally generated drug craving was associated with bilateral activation of the insula and subcallosal cortex, left hippocampus, and anterior cingulate cortex and brainstem. A brain-wide pixel-by-pixel search indicated significant positive and negative correlations between imagery-induced cocaine craving and regional cerebral blood flow (rCBF) in distributed sites. CONCLUSIONS: The collected findings suggest the craving-related activation of a network of limbic, paralimbic, and striatal brain regions, including structures involved in stimulus-reward association (amygdala), incentive motivation (subcallosal gyrus/nucleus accumbens), and anticipation (anterior cingulate cortex).

Adult↗
PubMed2001

Attention-deficit/hyperactivity disorder.

ADHD continues to be one of the most common psychiatric disorders in children and is recognized increasingly as a common psychiatric disorder in adults. Diagnosis of the disorder requires careful consideration of other psychiatric and medical disorders that may mimic symptoms of ADHD. Comorbid disorders are common in patients with ADHD and require careful attention. A recommended diagnostic evaluation for children and adults includes the completion of a psychiatric interview, rating scales from multiple informants, and often individually tailored psychologic testing. Pharmacologic treatment options include the first-line stimulant agents for adults and children and TCAs and atypical antidepressants as second-line agents. Behavioral interventions may help reduce ADHD symptoms and address comorbid conditions in children. Future research is needed to identify the optimal psychosocial treatment for adults with ADHD.

Adult↗
PubMed2001

The impact of hypercarbia on the evolution of brain injury in a porcine model of traumatic brain injury and systemic hemorrhage.

Carbon dioxide is perhaps the most potent available modulator of cerebrovascular tone and thus cerebral blood flow (CBF). These experiments evaluate the impact of induced hypercarbia on the matching of blood flow and metabolism in the injured brain. We explore the hypothesis that hypercarbia will restore the relationship of CBF to metabolic demand, resulting in improved outcome following traumatic brain injury (TBI) and hemorrhage. A behavioral outcome score, hemodynamic, metabolic, and pathologic parameters were assessed in anesthetized and ventilated juvenile pigs. Animals were assigned to either normocarbia or hypercarbia and subdivided into TBI (via fluid percussion) with or without hemorrhage. The experimental groups were TBI; TBI + 40% hemorrhage (40%H); TBI + hypercarbia (CO2); and TBI + 40%H + CO2. Hemorrhaged animals were resuscitated with blood and crystalloid. Hypercarbia was induced immediately following TBI using 10% FiCO2. The normocarbic group demonstrated disturbance of the matching of CBF to metabolism evidenced by statistically significant increases in cerebral oxygen and glucose extraction. Hypercarbic animals showed falls in the same parameters, demonstrating improvement in the matching of CBF to metabolic demand. Parenchymal injury was significantly decreased in hypercarbic animals: 3/10 hypercarbic versus 6/8 normocarbic animals showed cerebral contusions at the gray/white interface (p = 0.05). The hypercarbic group had significantly better behavioral outcome scores, 10.5, versus 7.3 for the normocarbic groups (p = 0.005). The decreased incidence of cerebral contusion and improved behavioral outcome scores in our experiments appear to be mediated by better matching of cerebral metabolism and blood flow, suggesting that manipulations modulating the balance of blood flow and metabolism in injured brain may improve outcomes from TBI.

Animals↗
PubMed2000

Effects of cholinergic depletion on neural activity in different laminae of the rat barrel cortex.

The purpose of these experiments was to determine the effects of cholinergic depletion on spontaneous and evoked activity of neurons in the different layers of the posteromedial barrel subfield (PMBSF) of the rat somatosensory cortex. Acetylcholine neurons in nucleus basalis of Meynert (NBM) were selectively lesioned with an immunotoxin (IT), 192 IgG-saporin. Spontaneous activity was significantly lower in layers II-III, Va, and VI in IT-injected animals compared to control animals. Evoked activity was significantly lower in layers II-III, IV, Vb, and VI of IT-injected animals compared to control animals. The largest difference was observed in layer Vb. Thus, cholinergic depletion causes significant changes in the magnitude of spontaneous and evoked activity but these differences are not completely in register with one another.

Acetylcholine↗
PubMed2000

Neural activity related to anger in cocaine-dependent men: a possible link to violence and relapse.

This study examined the neural correlates of cue-induced anger in cocaine-dependent men in an initial investigation of possible neurobiological explanations for the putative association between cocaine addiction and violence. We used positron emission tomography (PET) to localize alterations in regional cerebral blood flow (rCBF) during mental imagery of a personal anger-associated scene and of an emotionally neutral scene in ten cocaine-dependent men. Compared to the emotionally neutral imagery control condition, anger was associated with marked decreases in rCBF in multiple areas of the frontal cortex (particularly the right inferior frontal gyrus), left posterior insula, left fusiform gyrus, and midbrain. Conversely, this same inferior frontal area was activated by anger imagery in nicotine-dependent men. Anger was also associated with increases in rCBF in the right fusiform gyrus, right and left middle occipital gyri, left post-central gyrus, left medial frontal gyrus, left cuneus, and in the left anterior cingulate gyrus. The study showed that cue-induced anger in cocaine-dependent men was associated with decreased activity in frontal cortical areas involved in response monitoring and inhibition. The lack of this association in nicotine-dependent men suggests a possible deficit in anger regulation associated with cocaine dependence and a possible link between cocaine dependence, violence, and relapse.

Adult↗
PubMed2000

Alterations in the functional anatomy of working memory in adult attention deficit hyperactivity disorder.

OBJECTIVE: The authors used a functional neuroimaging study with a working memory probe to investigate the pathophysiology of attention deficit hyperactivity disorder (ADHD). Their goal was to compare regional cerebral blood flow (rCBF) changes related to working memory in adults with and without ADHD. METHOD: Using [(15)O]H(2)O positron emission tomography (PET) studies, the authors compared the sites of neural activation related to working memory in six adult men diagnosed with ADHD and six healthy men without ADHD who were matched in age and general intelligence. RESULTS: Task-related changes in rCBF in the men without ADHD were more prominent in the frontal and temporal regions, but rCBF changes in men with ADHD were more widespread and primarily located in the occipital regions. CONCLUSIONS: These data suggest the use of compensatory mental and neural strategies by subjects with ADHD in response to a disrupted ability to inhibit attention to nonrelevant stimuli and the use of internalized speech to guide behavior.

Adult↗
PubMed1999

Synaptophysin immunoreactivity in temporal lobe epilepsy-associated hippocampal sclerosis.

We have previously devised a semiquantitative grading system for hippocampal sclerosis (HS) in specimens resected for intractable temporal lobe epilepsy. The grades range from zero to four based on the amount and distribution of neuronal loss and gliosis. In the present study hippocampal sections from 25 patients who had temporal lobe epilepsy and had previously been assigned a grade were examined with synaptophysin immunohistochemistry, and the synaptic content in specific hippocampal fields was correlated with the results of the HS grading system. There was evidence of both significant synaptic loss and increased synaptic density in different fields of the hippocampus with increasing HS. A marked decrement of synaptic inmmunostaining was present in fields CA1 and CA4 that were highly correlated with HS grade. Sector CA4 seemed to respond in a more graded or continuous way to the pathological insults occurring in temporal lobe epilepsy than did CA1, which appeared to exhibit an all or nothing response. Also, while the width of the outer part of the molecular layer of the dentate (mid) gyrus decreased with increasing HS grade, the inner part of the mid became wider and showed an increased synaptic density so that the overall width of the mid was increased in the high-grade group. We conclude that quantitative measurement of synaptic loss in CAI and CA4 using synaptophysin immunohistochemistry is a sensitive method for detecting HS and correlates well with the empirically derived HS grading scale, with CA4 exhibiting a more graded response than CA1. In addition, a plasticity response in the inner part of the mld in patients with high-grade HS has been confirmed and quantitated.

Adult↗
PubMed1999

Prediction of presence of hippocampal sclerosis from intracarotid amobarbital procedure memory asymmetry scores and epilepsy on set age.

Identification of the pathological status of the hippocampus prior to surgery is important since the absence of hippocampal sclerosis (HS) carries risks to memory function following anterior temporal lobectomy (ATL). We studied 62 patients undergoing ATL (31 L, 31 R) for intractable epilepsy of temporal lobe origin in whom no pathology was identified apart from HS. An intracarotid amobarbital procedure (IAP) was performed as part of the preoperative evaluation. All patients were left hemisphere dominant for language. IAP memory testing was according to the protocol of Loring. We examined IAP memory asymmetry scores at four levels of difference (<2, > or =2, > or =4, > or =6) as a function of the presence (HS+) or absence (HS-) of HS. A logistic regression analysis was performed with HS+ as the dependent variable, and age at onset of epilepsy, age at time of surgery, gender, side of surgery and significant IAP memory asymmetry as independent variables. At each level of memory asymmetry, onset age and memory asymmetry were the only predictors of HS+. Younger age at onset was associated with HS+. Curves were constructed showing probability of HS+ for age at onset for each level of asymmetry. These can be used to predict the likelihood of presence of HS based on age at onset of epilepsy and the IAP memory asymmetry score. It is concluded that IAP memory asymmetry scores reflect the functional and pathological status of the hippocampus, and greater asymmetry increases the probability of finding HS in the resected hippocampus.

Adult↗
PubMed1999

Secondary neurologic injury resulting from nonhypotensive hemorrhage combined with mild traumatic brain injury.

Although the emergency physician often treats patients with multiple injuries, there are relatively few clinically relevant models that mimic these situations. To describe the changes after a hemorrhagic insult superimposed on traumatic brain injury (TBI), anesthetized and ventilated juvenile pigs were assigned to 35% hemorrhage (35H), TBI (via fluid percussion); TBI + 35H, and TBI + 40H (40% hemorrhage). Animals were resuscitated with shed blood and crystalloid. Hemodynamic, metabolic, behavioral, and histologic parameters were assessed for 48 h. In TBI, mean arterial pressure (MAP) was not significantly different from baseline. For TBI + 40H, MAP fell by 60% (p < 0.05). This was corrected with resuscitation. Interestingly, TBI + 35H did not show a fall in MAP, while in 35H, MAP was reduced similarly to the TBI + 40H group. ICP was elevated only initially in the TBI group. In TBI + 40H and TBI + 35H, ICP increased markedly with resuscitation, remaining elevated for 60 min. ICP remained at baseline with 35 H. Hemorrhagic focal cerebal contusions at the gray-white interface were observed in 3/5 of TBI + 40H and 5/7 of TBI + 35H. Despite the presence of subarachnoid hemorrhage (SAH) in all the animals in the TBI alone group, none of these animals demonstrated grossly discernible intraparenchymal injury. There was no evidence of intracranial injury in the 35H group. Only in animals receiving a secondary insult of hemorrhage following the primary TBI were cerebral contusions found. These experiments demonstrate the evolution of cerebral contusions as a form of secondary neurologic injury following resuscitation from traumatic brain injury and hemorrhage, even in the absence of significant blood pressure changes.

Animals↗
PubMed1998

Synaptophysin immunohistochemistry densitometry measurement in resected human hippocampus: implication for the etiology of hippocampal sclerosis.

Synaptophysin (SY) is a protein expressed at presynaptic vesicles. SY immunohistochemistry (IHC) was undertaken in surgically resected hippocampal specimens from 25 patients with intractable epilepsy. All were investigated with chronic ictal EEG videotelemetry, which showed a temporal onset in each case, and all had normal magnetic resonance imaging (MRI). The density of reaction product of SY IHC was used to generate optical density (OD) measurements as an estimate of synaptic density in CA1 and CA4 fields (ODCA1 and ODCA4), and inner third and outer two-thirds of the molecular layer of the dentate gyrus (ODIML and ODOML). There was significant correlation between ODCA1 (r=0.619, P=0.001) and ODCA4 (r=0.639, P=0.001) and onset age of epilepsy. There was no correlation between ODCA1 and duration of epilepsy. There was correlation between ODCA4 and duration (r=-0.412, P=0.041), but partial correlations showed no significant correlation between ODCA4 and duration when controlling for onset, although correlation between ODCA4 and onset when controlling for duration remained significant (r=0.536, P < 0.01). Univariate ANOVA revealed onset age to be the only predictor of ODCA1 and ODCA4. Chronological age and duration were not predictors. There was no correlation between ODIML or ODOML and either onset age or duration. ODIML and ODOML were not predicted by onset age, duration or chronological age. These findings support the hypothesis that the major cause of hippocampal sclerosis is an age specific insult rather than the result of repeated seizures.

Adult↗
PubMed1997

Effects of cholinergic depletion on glutamic acid decarboxylase immunoreactivity in the somatosensory cortex of rats.

The purpose of these experiments was to determine the effects of cholinergic depletion on the morphology and staining density of barrels formed by glutamic acid decarboxylase-positive neuropil in the posteromedial barrel subfield of the somatosensory cortex. The density and distribution of glutamic acid decarboxylase immunoreactive neuropil were examined after highly selective lesions of cholinergic neurons in the nucleus basalis of Meynert with an immunotoxin, IgG 192-saporin. Glutamic acid decarboxylase immunoreactivity was also examined in animals subjected to a whisker-pairing experience and lesion of acetylcholine inputs from the nucleus basalis of Meynert. Seven to 9 weeks after intraventricular injection of the immunotoxin, animals were perfused with a zinc aldehyde fixative and glutamic acid decarboxylase immunoreactivity was examined in 30-micron tangential sections. Cholinergic depletion caused reduced glutamic acid decarboxylase immunoreactivity in selective regions of the posteromedial barrel subfield. The density of neuropil and cell bodies immunoreactive for glutamic acid decarboxylase was significantly reduced in septa and perimeters of barrel walls. The length, width, and area of barrels were reduced 10-20% in cholinergic-depleted animals compared with controls. The density of glutamic acid decarboxylase immunoreactivity in the hollow of barrels was not affected by this treatment. Whisker pairing did not significantly change the density of glutamic acid decarboxylase immunoreactivity in barrels. These observations are discussed in regard to how long-term cholinergic depletion affects the function of different fiber systems in the posteromedial barrel subfield cortex and how some sensory functions may be comprised.

Acetylcholine↗
PubMed1997

Effects of cholinergic depletion on experience-dependent plasticity in the cortex of the rat.

Clinical and functional studies have strongly suggested that acetylcholine input from the nucleus basalis of Meynert is important for the cortex's adaptive response to experience. The purpose of this study was to investigate the effects of depletion of acetylcholine inputs from nucleus basalis of Meynert on experience-dependent plasticity in the cortex of young adult male rats. The posteromedial barrel subfield in the primary somatosensory cortex was studied. Experience-dependent plasticity was elicited using a whisker-pairing paradigm in which all whiskers except D2 and D3 were trimmed daily. Plasticity within barrel D2 of the posteromedial barrel subfield was measured using the electrophysiological extracellular recording technique. An index of plasticity was determined in two ways: as an increase in the magnitude of evoked activity to stimulation of whisker D2 and as a bias in the ratio of evoked activity for stimulation of paired whisker D3 and cut whisker D1 (D3/D1). Whiskers D2, D3 and D1 were stimulated (deflected) by a Chubbuck electromechanical stimulator. Cholinergic neurons in the nucleus basalis of Meynert were selectively lesioned with an immunotoxin, 192 IgG-saporin, injected into the left lateral ventricle. Lesions of cholinergic neurons in the nucleus basalis of Meynert were verified using choline acetyltransferase immunocytochemistry and radioenzymatic assay. Experience-dependent plasticity was significantly reduced in cholinergic-depleted animals. The magnitude of evoked activity to stimulation of whisker D2 increased by 16-100% in control animals compared with 0-20% in cholinergic-depleted animals. Similarly, compared to a 60-100% increase in the D3/D1 ratio of evoked activity for phosphate-buffered saline-injected control animals, cholinergic-depleted rats showed no significant increase in the D3/D1 ratio (0-15%) after undergoing the whisker-pairing paradigm. After whisker trimming, the D3/D1 response ratio in immunotoxin-treated animals was essentially the same as in control animals that had not been subjected to the whisker-pairing paradigm. This study showed that no significant plasticity response was observed in the absence of cholinergic input from the nucleus basalis of Meynert. The mechanisms of the action of acetylcholine in cortical plasticity are still not known, but we hypothesize that this type of plasticity is activity dependent and is significantly enhanced in the presence of acetylcholine.

Acetylcholine↗
PubMed1997

Differentiating central neurocytoma. Case report.

In 1976 a patient underwent partial resection of an intraventricular tumor that showed central neurocytoma. No other tumor pattern was observed. In 1994 this patient underwent a second operation for removal of the tumor, at which time foci of tumor were diagnosed as central neurocytoma and ganglioglioma. This is the first reported case of differentiation of central neurocytoma into ganglioglioma, a sequence of events termed differentiating central neurocytoma.

Adult↗
PubMed1996

The effects of immunolesions of nerve growth factor-receptive neurons by 192 IgG-saporin on sleep.

Low-affinity nerve growth factor (NGF) receptors are present on the cholinergic neurons of the basal forebrain. We studied the effects of 192 IgG-saporin, a specific immunotoxin for the NGF receptor-positive, cholinergic basal forebrain neurons, on sleep, the power spectrum of the electroencephalogram (EEG), and body temperature. After 3 d baseline recordings, 12 male rats were injected intracerebroventricularly with 4 micrograms 192 IgG-saporin. EEG, motor activity, and brain temperature were recorded for 23 h on the first, third, fifth, and seventh day after the treatment. 192 IgG-saporin did not affect the total daily amounts but altered the circadian distribution of sleep. On days 1 and 3 after the injection of the immunotoxin, the amount of non-rapid-eye-movement sleep (NREMS) and rapid-eye-movement sleep (REMS) increased during the dark period, whereas during the light both NREMS and REMS decreased. On day 5, these changes were less pronounced and sleep completely returned to the baseline by day 7. The EEG was suppressed in each frequency band and each vigilance state, and, in contrast to sleep, these changes in EEG persisted for 7 days. Brain temperature was decreased from day 3. These results suggest that NGF receptor-positive, cholinergic basal forebrain neurons are not necessary for the maintenance of total sleep time but contribute to the generation of normal EEG and the maintenance of brain temperature.

Analysis of Variance↗
PubMed1996

Use of a token economy to increase compliance during hemodialysis.

We report the effects of using a token economy to treat noncompliant behavior in a 10-year-old male hemodialysis patient. The results of an ABAB design indicated that the intervention increased compliant behavior during both treatment phases and that compliance was maintained at 3- and 6-month follow-up observations.

Child↗
PubMed1995

Loss of p75 nerve growth factor receptor mRNA containing neurons in rat forebrain after intraventricular IgG 192-saporin administration.

Cholinergic neurons of the basal forebrain express the p75 (low affinity) nerve growth factor receptor (NGFr) on the cell surface. It has been previously shown that an immunotoxin that recognizes the p75 NGFr, IgG 192-saporin, eliminates these neurons as judged by a variety of techniques after intraventricular injection into rat brain. Here we show that this loss of neurons can also be identified by detecting the disappearance of the p75 NGFr mRNA utilizing a non-radioactive in situ hybridization method.

Animals↗