Hypofrontality and cognitive impairment in schizophrenia: dynamic single-photon tomography and neuropsychological assessment of schizophrenic brain function.

Regional cerebral blood flow (rCBF) was assessed in 40 chronic male schizophrenic patients (20 medicated, 20 unmedicated) and 31 matched normal controls with Dynamic Single-photon Emission Computed Tomography (D-SPECT). Blind analyses of normalized color-coded tomograms revealed significant bifrontal and bitemporal rCBF deficits in the patient group. Frontal flow deficits were most prominent in paranoid patients (n = 21) and right temporal deficits were most prominent in nonparanoid patients (n = 19). These relative regional declines were observed within the context of significantly elevated hemispheric blood flow in schizophrenics compared with controls. Reduced left frontal rCBF was associated with neuropsychological impairment on the Wisconsin Card Sorting Test and Luria-Nebraska Battery. Increased hemispheric CBF was correlated with the presence of positive schizophrenic symptoms. Medication status was unrelated to rCBF. These findings demonstrate that hypofrontality has important implications for cognitive function in some schizophrenic individuals.

Hsp70 mRNA induction is reduced in neurons of aged rat hippocampus after thermal stress.

Levels of heat-shock 70 mRNAs, relative to those of 18S rRNA, were quantitated in specific cell types of hippocampus of adult and aged rats subjected to identical heat shock regimens. Body temperature changes in response to the heat stress were no different in adult and aged rats. In control rats, as well as 3 h after initiation of heat shock in both adult and aged rats, relative levels of the constitutively synthesized heat-shock cognate 70 (hsc70) mRNA were highest in hippocampal neurons and much lower in glia. No heat-shock protein 70 (hsp70) mRNAs were present in any cell type of control adult or aged rats. In heat-shocked adult rats, the relative levels of the heat-shock-inducible hsp70 mRNAs were highest in a subpopulation of glia, intermediate in granule cells of the dentate gyrus, and lowest in pyramidal cells of Ammon's horn. Relative levels of hsp70 mRNA were several-fold lower in the dentate gyrus granule cells of aged rats compared to relative levels in controls and were also reduced in many pyramidal cells of the hippocampus but not in hippocampal glia. These findings suggest that some neuronal populations in the hippocampus may be at increased risk for stress-related injury in the aged animal.

Dephosphorylation of purified brain tyrosine hydroxylase by rat striatal extracts.

Tyrosine hydroxylase (TH) was purified from bovine brain and enzymatically phosphorylated in vitro. Radioactively phosphorylated TH was dephosphorylated by rat tissue extracts. Of tissues examined, rat corpus striatal extracts were highest in specific activity in the TH dephosphorylating assay. Phosphorylated histone did not inhibit dephosphorylation of TH by rat striatal extracts. The thermal decay of dephosphorylating activity of rat striatal extracts varied with substrate, with TH dephosphorylating activity most unstable of the activities assayed. The results suggest that TH can be enzymatically dephosphorylated and that, in corpus striatum, this process differs quantitatively from the dephosphorylation of phosphohistone and phosphoprotamine.

Distribution of catecholamine-containing neurons in the normal human hypothalamus.

We have studied the distribution of catecholamine-containing neurons in the hypothalamus of 8 normal adult human brains, using Schmorl's stain for melanin and immunohistochemical staining for tyrosine hydroxylase (TH). TH immunoreactive perikarya were found in the wall of the third ventricle, in the areas in which dopaminergic neuroendocrine neurons are found in other primate species. Many of these neurons contained melanin pigment, and the percentage increased with age. Other melanin-pigmented neurons in the same distribution did not stain for TH, suggesting that postmortem TH immunostaining may not be sufficiently sensitive to visualize all catecholaminergic neurons. A separate group of larger TH-positive perikarya was seen in the lateral hypothalamic area. These may correspond to the incerto-hypothalamic dopamine neurons in other primate species. Only rare melanin-pigmented neurons were seen in this cell group, even at 66 years of age. Our data indicate that the hypothalamic neuroendocrine dopamine neurons in the human brain are distributed in a pattern similar to that in other primate species, and that both postmortem tyrosine hydroxylase and melanin staining provide an incomplete but representative sampling of the periventricular-arcuate cell group.

Identification of dopamine-containing cell bodies in the dorsal and median raphe nuclei of the rat brain using tyrosine hydroxylase immunochemistry.

Using immunohistochemical methods with antibodies specific to tyrosine hydroxylase, we examined the distribution of dopaminergic cells in the dorsal and median raphe nucleus of the rat brain. Although dopamine-containing cell bodies were previously thought to be almost exclusively confined to the substantia nigra pars compacta, ventral tegmental area, and tuberoinfundibular system, we found numerous cell bodies which stained for tyrosine hydroxylase in the dorsal and median raphe nuclei.

Chronic cocaine administration depletes tyrosine hydroxylase immunoreactivity in the meso-limbic dopamine system in rat brain: quantitative light microscopic studies.

Chronic administration of cocaine (10 mg/kg, IP, every 12 hours for 10 consecutive days) produced a large decrease in tyrosine hydroxylase staining axons and terminal boutons in the frontal cortex and nucleus accumbens in rats. This treatment also produced a depletion of tyrosine hydroxylase immunoreactivity in the ventral tegmental area of the midbrain when examined 60 days following the final cocaine injection. These effects were quantitated using a Leitz Data Acquisition and Display System. This analysis revealed a 59% and 65% decrease in tyrosine hydroxylase positive staining terminal processes in the frontal cortex and nucleus accumbens, respectively. Furthermore, quantitative light microscopic analysis showed a 52% decrease in tyrosine hydroxylase positive material in the ventral tegmental area. These data demonstrate that chronic administration of cocaine produces a long-term, if not permanent, loss of tyrosine hydroxylase enzyme in both the cell bodies of the midbrain ventral tegmental area as well as in the nerve terminals in post-synaptic target regions of the forebrain.

Effects of chronic methamphetamine on the nigral-striatal dopamine system in rat brain: tyrosine hydroxylase immunochemistry and quantitative light microscopic studies.

Chronic administration of methamphetamine (20 mg/kg, IP, every 12 hours for 10 days) produced a large decrease in tyrosine hydroxylase staining axons and terminal boutons in the caudate nucleus in rats when examined 60 days following the final methamphetamine injection. This effect was quantitated using the Leitz Data Acquisition and Display System (DADS) revealing that there was a 74% decrease in tyrosine hydroxylase positive processes in the caudate nucleus. Furthermore, this treatment also produced a large decrease in the number of tyrosine hydroxylase positive staining neuronal perikarya in the pars compacta of the substantia nigra. This effect was also quantitative using the Leitz-(DADS) system, revealing a decrease of 89% in tyrosine hydroxylase positive material. These data demonstrate that chronic administration of methamphetamine produces a long-term loss of tyrosine hydroxylase enzyme in both the cell bodies of the substantia nigra and the nerve terminals in the caudate nucleus. Whether this effect is due to the degeneration of the neurons or some metabolic effect remains to be determined.

Tyrosine hydroxylase immunochemistry and quantitative light microscopic studies of the mesolimbic dopamine system in rat brain: effects of chronic methamphetamine administration.

Long-term treatment of rats with methamphetamine (20 mg/kg, IP, every 12 hours for 10 days) resulted in a large decrease in tyrosine hydroxylase staining axons and terminal boutons in the nucleus accumbens and frontal cortex, as well as the ventral tegmental area of the midbrain, when examined 60 days following termination of the drug treatment regimen. Quantitative analysis showed a 71 and 78% decrease in tyrosine hydroxylase staining processes in the nucleus accumbens and frontal cortex, respectively, and a 90% decrease in tyrosine hydroxylase positive material in the ventral tegmental area. Thus, tyrosine hydroxylase enzyme in both the cell bodies of the midbrain ventral tegmental area as well as in the nerve terminals in post-synaptic target regions of the forebrain is depleted by chronic methamphetamine administration.

Effects of tricyclic antidepressant treatment on tyramine-O-sulfate excretion in depressed patients.

The urinary excretion of tyramine-O-sulfate following an oral load of tyramine (Tyramine Challenge Test, 'TCT') was measured in a group of fourteen inpatients with unipolar and bipolar major depressive episode. TCT was done both during a pretreatment baseline period and following four weeks of treatment with tricyclic antidepressants. The change in TCT values after treatment correlated with improvement in depression. The previously described ability of TCT to discriminate between endogenous and nonendogenous depressed patients was confirmed at baseline. However, following tricyclic antidepressant treatment, TCT values were not significantly different between endogenous and nonendogenous patients.

Serum homovanillic acid levels in schizophrenic patients and normal control subjects.

Schizophrenic patients with an early age at onset of illness had low baseline levels of homovanillic acid (HVA) in serum compared with schizophrenic patients with a late age at onset. After adjustments were made for age at onset, there was a significant partial correlation between positive symptoms and serum HVA. The relationship between positive symptom scores and serum HVA was shifted to the left in the early onset patients, suggesting a relatively increased sensitivity of dopamine-associated response. Patients with severe negative symptoms also had an earlier age at onset and a trend toward lower serum HVA. This study found no difference between mean serum HVA values in schizophrenic patients and normal control subjects.

Cerebellar blood flow in schizophrenic patients and normal control subjects.

We used 133Xe dynamic single-photon emission computed tomography (DSPECT) to measure the resting cerebellar blood flow in 17 neuroleptic-free schizophrenic and schizophreniform patients and 13 normal control subjects. A subset of these subjects (11 patients and 7 control subjects) additionally underwent activation studies during the Wisconsin Card Sorting (WCS) and Number Matching (NM) tests. Baseline relative cerebellar blood flow was significantly lower in older patients than in age-matched control subjects. For absolute cerebellar flow, there was a significant difference between patients and control subjects in the overall activation response (patients: NM 13.4% increase, WCS 15.7% increase; control subjects: NM 3.1% decrease, WCS 0.0% change). This difference was more pronounced in older subjects. Cerebral blood flow significantly increased during NM (patients: 21.3% increase, control subjects: 6.5% increase) and WCS (patients: 16.5% increase, control subjects: 9.7% increase). The difference in the magnitude of cerebral NM activation between schizophrenic patients and control subjects, although not statistically significant, may call into question the appropriateness of using NM as a control task in schizophrenic patients. Finally, we found no differences between the effects of WCS and NM on cerebellar or cerebral blood flow. Because of the small number of subjects in each group, the results of this study should be interpreted cautiously.

Expression of heat shock protein 70 and heat shock cognate 70 messenger RNAs in rat cortex and cerebellum after heat shock or amphetamine treatment.

The expression of strictly inducible hsp70 mRNAs and constitutively expressed hsc70 mRNAs was compared in cerebellum and cerebral cortex of control rats, heat-shocked rats, and rats made hyperthermic with amphetamine. An hsc70-specific oligonucleotide probe identified a 2.55-kb mRNA in cerebellum and cerebral cortex of all rats. An hsp70-specific oligonucleotide probe identified a 3.05-kb mRNA and a 3.53-kb mRNA in cerebellum and cerebral cortex of heat-shocked and amphetamine-treated rats, but not in control rats. Quantitation demonstrated that both hsp70 and hsc70 mRNA levels, relative to 18S rRNA levels, were increased following each treatment. The relative levels of both mRNAs were higher in cerebellum than in cerebral cortex. In amphetamine-treated rats, hsc70 mRNA relative levels increased at body temperatures greater than 39 degrees C, whereas hsp70 mRNA synthesis was induced at temperatures greater than 40 degrees C. Total thermal response values and relative levels of both mRNAs were compared. The results suggested that both the transcription and turnover of hsp70 mRNAs differed between cerebellum and cerebral cortex. At equivalent total thermal response values, amphetamine-treated rats had higher relative levels of hsp70 mRNAs than heat-shocked rats, suggesting that amphetamine enhanced the induction of hsp70 mRNAs.

A human gene family with sequence homology to Drosophila melanogaster Hsp70 heat shock genes.

A growing literature describes the structure and regulation of prokaryotic and eukaryotic heat shock genes. We here report the isolation of several members of a human heat shock protein 70 (hsp 70) multigene family which contains at least 10 different genes and/or pseudogenes exhibiting sequence homology to the hsp70 gene of Drosophila melanogaster. Eight nonoverlapping recombinant lambda phages from a lambda-Charon4A human genomic library were studied by restriction mapping. One lambda clone was sequenced and characterized as a hsp70 pseudogene inserted into a rearranged human HindIII 1.9-kilobase repeated DNA sequence. This pseudogene is probably located on the X chromosome. Its predicted amino acid sequence shows extensive homology to those of Drosophila hsp70, trout hsp70, Xenopus hsp70, yeast hsp70, and some homology to the heat-inducible dnaK gene product of Escherichia coli. Amino acid homology is clustered, suggesting evolutionary conservation of domains critical to the function of this protein in both prokaryotic and eukaryotic cells.

Thermal denaturation of native striatal tyrosine hydroxylase: increased thermolability of the phosphorylated form of the enzyme.

Tyrosine hydroxylase was purified from bovine corpus striatum. The native enzyme had a half-life of 15 +/- 3 min at 50 degrees C. Phosphorylation of tyrosine hydroxylase with protein kinase purified from both corpus striatum and heart activated the enzyme, but activity was rapidly lost with additional preincubation of the enzyme at 30 degrees C. Thermal denaturation studies indicated that phosphorylated tyrosine hydroxylase had a half-life of 5 +/- 2 min at 50 degrees C

Tyrosine hydroxylase: studies on the phosphorylation of a purified preparation of the brain enzyme by the cyclic AMP-dependent protein kinase.

Tyrosine hydroxylase [L-tyrosine, tetrahydropteridine: oxygen oxidoreductase (3-hydroxylating); EC 1.14.16.2](TH) was purified from bovine corpus striatum. The purification involved sequential DEAE cellulose, hydroxylapatite and CM Sephadex C-50 chromatography, followed by glycerol density gradient centrifugation. Final preparations appeared to be 90 to 100% pure as judged by polyacrylamide gel electrophoresis under denaturing conditions in acetic acid-urea. The enzyme was estimated to have a minimum molecular weight of approximately 60,000 daltons. Purified TH could be activated in vitro by incubation with magnesium adenosine triphosphate and the catalytic subunit of cyclic AMP-dependent protein kinase (ATP/protein phosphotransferase; EC 2.7.1.37). When the final purified preparation of TH was incubated under these conditions utilizing [gamma-32P]ATP, it was found to incorporate 0.7 to 0.9 mol of phosphorus/mol of protein. These results suggest that the activation of TH in the presence of phosphorylating conditions is due to its phosphorylation by cyclic AMP-dependent protein kinase.

Chronic cocaine administration depletes tyrosine hydroxylase immunoreactivity in the rat brain nigral striatal system: quantitative light microscopic studies.

Chronic administration of cocaine (10 mg/kg, i.p., every 12 h for 10 consecutive days) produced a large decrease in tyrosine hydroxylase-staining axons and terminal boutons in the caudate nucleus in rats when examined 60 days after the final cocaine injection. This effect was quantitated using the Leitz data acquisition and display system (DADS) which revealed that there was a 63% decrease in tyrosine hydroxylase-positive processes in the caudate nucleus. In addition, this cocaine treatment regimen produced a large decrease in the number of tyrosine hydroxylase-positive staining neuronal perikarya in the pars compacta of the substantia nigra. Use of the Leitz-DADS system revealed that there was a 51% decrease in tyrosine hydroxylase-positive material in the substantia nigra. These data demonstrated that chronic administration of cocaine produced a long-term loss of tyrosine hydroxylase in both the cell bodies of the substantia nigra and the nerve terminals of the caudate nucleus. Further studies are required to determine whether the observed changes are due to degeneration of the neurons or some metabolic effect.

Regional cerebral function and blood flow: complementary single photon emission computed tomography of the brain using xenon-133 and [123I]iodoamphetamine.

Regional cerebral function and blood flow can be imaged using isopropyl[123I]iodoamphetamine (IMP), or 133Xe (DSPECT), respectively. Both of these essentially non-invasive, quantitative, methods are suitable for many nuclear medicine laboratories. This study assessed the in vivo information about intracerebral disease provided by IMP and DSPECT techniques to determine the optimal diagnostic use of these modalities. Single photon emission computed tomograms of 53 subjects were acquired using similar displays for IMP and DSPECT data. Lobar tracer distributions were graded by three experienced observers and analyzed using a kappa statistic to eliminate chance agreements. Overall, both IMP and DSPECT had similar patterns. However, while similar, one or the other technique often displayed abnormalities not present on both. Although technical factors may account for some differences between the modalities, a case of arteriovenous malformation proves that discordant findings can result directly from tracer localization properties. Thus at least some discordances provide truly complementary diagnostic information lacking in either single study taken alone.