Deficits in striatal dopamine D(2) receptors and energy metabolism detected by in vivo microPET imaging in a rat model of Huntington's disease.

Functional imaging by repeated noninvasive scans of specific (18)F tracer distribution using a high-resolution small-animal PET scanner, the microPET, assessed the time course of alterations in energy utilization and dopamine receptors in rats with unilateral striatal quinolinic acid lesions. Energy utilization ipsilateral to the lesion, determined using scans of 2-deoxy-2-[(18)F]fluoro-d-glucose uptake, was compromised severely 1 week after intrastriatal excitotoxin injections. When the same rats were imaged 5 and 7 weeks postlesion, decrements in energy metabolism were even more prominent. In contrast, lesion-induced effects on dopamine D(2) receptor binding were more progressive, with an initial upregulation of [3-(2'-(18)F]fluoroethyl)spiperone binding apparent 1 week postlesion followed by a decline 5 and 7 weeks thereafter. Additional experiments revealed that marked upregulation of dopamine D(2) receptors consequent to quinolinic acid injections could be detected as early as 3 days after the initial insult. Postmortem markers of striatal GABAergic neurons were assessed in the same rats 7 weeks after the lesion: expression of glutamic acid decarboxylase and dopamine D(1) receptor mRNA, as well as [(3)H]SCH-23,390 and [(3)H]spiperone binding to dopamine D(1) and D(2) receptors, respectively, detected prominent decrements consequent to the lesion. In contrast, by 7 weeks postlesion [(3)H]WIN-35,428 binding to dopamine transport sites within the striatum appeared to be enhanced proximal to the quinolinic acid injection sites. The results demonstrate that functional imaging using the microPET is a useful technique to explore not only the progressive neurodegeneration that occurs in response to excitotoxic insults, but also to examine more closely the intricacies of neurotransmitter activity in a small animal model of HD.

In vivo imaging of neuronal activation and plasticity in the rat brain by high resolution positron emission tomography (microPET).

The study of neural repair and neuroplasticity in rodents would be enhanced by the ability to assess neuronal function in vivo. Positron emission tomography (PET) is used to study brain plasticity in humans, but the limited resolution and sensitivity of conventional scanners have generally precluded the use of PET to study neuroplasticity in rodents. We now demonstrate that microPET, a PET scanner developed for use with small animals, can be used to assess metabolic activity in different regions of the conscious rodent brain using [18F]fluorodeoxyglucose (FDG) as the tracer, and to monitor changes in neuronal activity. Limbic seizures result in dramatically elevated metabolic activity in the hippocampus, whereas vibrissal stimulation results in more modest increases in FDG uptake in the contralateral neocortex. We also show that microPET can be used to study lesion-induced plasticity of the brain. Cerebral hemidecortication resulted in diminished relative glucose metabolism in the neostriatum and thalamus ipsilateral to the lesion, with subsequent, significant recovery of metabolic function. These studies demonstrate that microPET can be used for serial assessment of metabolic function of individual, awake rats with a minimal degree of invasiveness, and therefore, has the potential for use in the study of brain disorders and repair.

Development of a crossed corticotectal pathway following cerebral hemispherectomy in cats: a quantitative study of the projecting neurons.

A hypothetical mechanism for the partial sparing of visual function in the contralateral visual field following cerebral hemispherectomy early in life is the formation of a new corticotectal pathway arising from the remaining primary visual cortex (areas 17 and 18) that projects to the contralateral superior colliculus. To test this hypothesis, the left superior colliculus of intact adult and neonatal (5-15 days old) cats and of adult cats with a left cerebral hemispherectomy sustained neonatally (7-9 days old) or in adulthood, was injected with WGA-HRP and the brains were processed for combined TMB/DAB histochemistry. The primary visual cortex was examined, labelled neurons were counted and the cross sectional area of their somata was measured. The left primary visual cortex of intact adult animals exhibited a mean of 959.68 labelled cells +/- 406.5 (S.E.), with a mean soma size of 366.7 microns2 +/- 131.2. For the neonatal intact cats, there was a mean of 75.31 +/- 21.08 cells within the left primary visual cortex which exhibited a mean soma size of 249.56 microns2 +/- 68.18. The peak cell size distribution for both intact groups was similar at 300 microns2. Virtually no labelled neurons were detected in the right primary visual cortex of intact animals (neonatal or adult). For neonatal-hemispherectomized cats, the remaining right primary visual cortex exhibited a mean cell count of 351.09 +/- 126.3 cells, with a mean soma size of 436.1 microns2 +/- 131.5, and a peak cell size distribution of 400 microns2. Finally, for adult-hemispherectomized animals, the contralateral primary visual cortex exhibited 68.27 +/- 20.13 neurons having a mean soma size of 486.6 microns2 +/- 143.2 with a peak cell size distribution of 500 microns2. These results indicate that reorganization of the corticotectal pathway occurs in both adult- and neonatal-hemispherectomized cats but is more pronounced in neonatal-lesioned animals. In addition, the cells of origin of this reorganized pathway tended to be larger, perhaps in response to a greater axonal arborization.

Cerebral hemidecortication alters expression of transforming growth factor alpha mRNA in the neostriatum of developing rats.

Transforming growth factor alpha (TGF alpha) is a mitogenic polypeptide which acts at the epidermal growth factor receptor to produce its biologic effects. Recent studies have demonstrated that TGF alpha may act as a neurotrophic factor. Cerebral hemispherectomy (hemidecortication) is performed on some children with intractable epilepsy. Prior studies have demonstrated improved functional recovery in both children and animals when the surgery is performed at a very early age. In order to test whether TGF alpha may be involved in the functional recovery of the neostriatum following cerebral hemidecortication, we performed in situ hybridization for TGF alpha mRNA on brains of rats which underwent hemispherectomy at postnatal day (P) 6 or P12 or in adulthood, and sacrificed one, 7, or 30 days following surgery. Normal striatal expression in control animals was very high at P6 and then decreased throughout development. In animals undergoing lesion at earlier ages (P6 and P12), TGF alpha mRNA expression was first depressed in the ipsilateral neostriatum one day after surgery and then elevated to supranormal levels 7 and 30 days after surgery. Maximal decreases (40% below contralateral neostriatum) were seen in animals lesioned at P12 and sacrificed the next day. Maximal elevations (60% greater than opposite neostriatum) were seen in animals operated on at P6 and sacrificed 30 days post surgery. Expression in the adult animal was only mildly affected, with a 20% increase found in the ipsilateral caudate 7 days after the lesion, but no significant changes after one or 30 days survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Benzodiazepine receptor binding following chronic treatment with naloxone, morphine and met-enkephalin in normal rats.

The effects of chronic administration of naloxone, morphine and met-enkephalin on benzodiazepine (BDZ) receptor binding in rat brain were determined 2 and 50 days after treatments were accomplished. Two days after naloxone treatment (75 micrograms/h s.c. for 14 days), enhanced BDZ receptor binding was observed in cingulate, frontal, piriform, entorhinal and sensorimotor cortices; amygdala complex, hippocampus, substantia nigra and central gray. Two days after morphine treatment (20 mg/kg i.p. daily for 6 days), increased BDZ receptor binding was detected in cingulate, frontal, piriform, entorhinal and sensorimotor cortices; amygdala complex, hippocampus and substantia nigra. Two days after met-enkephalin treatment (10 micrograms/h i.c.v. for 6 days) enhanced BDZ receptor binding was shown only in sensorimotor cortex. No significant changes were observed 50 days after the treatments were completed. These data indicate an important interaction between GABAergic and opioid peptide systems.

Tumorigenicity in the nude mouse of cocultures derived from two nontumorigenic cell types, human pituitary adenomas and mouse C3H 10T1/2 fibroblasts.

Human pituitary adenoma tissues were not tumorigenic in the hormonally manipulated nude mouse. Mouse fibroblast cells (C3H 10T1/2) also did not form tumors when inoculated alone into nude mice. When these two tissues were cocultured and coinoculated into nude mice however, the majority of inocula developed progressively enlarging tumors which could be established in tissue culture and passaged through the nude mouse. These tumors were sarcomatous histologically and thus did not resemble any human pituitary adenoma tissue injected. In order to detect any human cells in these tumors, tumor genomic DNA was subjected to Southern analysis using human repetitive Alu and HGH DNA sequence probes. Southern blot analysis of the nude mouse derived tumor genomic DNA revealed no sizeable human DNA in the mouse tumor cell genome indicating the absence of significant numbers of human cells in the tumors or the transfer of human DNA to the mouse cells. The tumors therefore arose from transformed C3H 10T1/2 cells after coculture with the human pituitary adenoma cells. These results implied that the tumorigenic transformation of susceptible C3H 10T1/2 cells in the cocultures occurred as a result of the secretion by the adenoma cells of transforming substances in the culture media or the induction of tumorigenicity through direct cell-cell contact between the two cell types.

Serum factors from patients with systemic lupus erythematosus enhancing superoxide generation by normal neutrophils.

It has been suggested that human neutrophils exposed to performed immune complexes or activated complement fragments generate O2- anions in extracellular medium. In vivo studies have revealed that oxygen intermediates produced by immune complex-activated neutrophils play an important role in subsequent tissue damage. Since it is difficult to obtain direct evidence that O2- is released into plasma in patients with systemic lupus erythematosus (SLE), we studied the capacities of their sera to stimulate O2- release by human neutrophils in vitro. Sera from patients with SLE significantly enhanced O2- generation by neutrophils compared to normal sera. The enhancing activity of serum in the induction of increased O2- generation correlated positively with the presence of serum immune complexes and negatively with serum complement levels. The enhancing factors were analyzed by serum fractionation on Sephadex G-200 gel filtration, and were concluded to be immune complexes of intermediate size containing an activated complement fragment.

The synergistic contribution of macrophages and antibody to protection against Salmonella typhimurium during the early phase of infection.

The contribution of phagocytes and antibody to protection against Salmonella typhimurium during the early phase of infection in mice was analysed. Following intravenous injection, most of the bacteria were trapped in the liver and spleen within 10 to 60 min and killed within 6 h; surviving organisms began to multiply in these tissues after 24 h and reached a maximum at 5 to 7 d. The transient killing phase was abrogated by treatment with carrageenan, a macrophage blocker, but not by whole-body X-irradiation. These observations suggest that carrageenan-sensitive, but radio-resistant macrophages play an important role in the early phase of the infection. Actively immunized mice showed accelerated trapping and killing; the protection observed at the early stage of infection in immunized mice could be passively transferred to normal mice, whereas carrageenan-treated mice did not kill the bacterial even after receiving immune serum. It seems that the synergistic action of macrophages and antibody provided the main initial primary defence in immune animals.

Differing contribution of polymorphonuclear cells and macrophages to protection of mice against Listeria monocytogenes and Pseudomonas aeruginosa.

Bacterial growth and lethality of Listeria monocytogenes in mice were augmented by carrageenan-treatment and X-irradiation (8 J kg-1), whereas growth and lethality of Pseudomonas aeruginosa were augmented by X-irradiation but not by carrageenan-treatment. Protection against L. monocytogenes, at least in the early phases, appears to depend mainly on macrophages, since carrageenan depletes macrophages but not polymorphonuclear cells (PMN), whereas protection against P. aeruginosa appears to depend mainly on PMN. Ineffectiveness of PMN in elimination of L. monocytogenes is supported by histological examination and observation of intracellular killing in vitro.