An acute effect of triazolam on muscarinic cholinergic receptor binding in the human brain measured by positron emission tomography

An acute effect of triazolam, a potent benzodiazepine agonist, on cholinergic receptor binding in the human brain was measured by PET (positron emission tomography) using [11C]N-methyl-4-piperidylbenzilate ([11C]NMPB), a potent muscarinic cholinergic receptor antagonist. Two PET scans were performed in each subject: (1) control scan; (2) after oral administration of 0.5 mg triazolam or placebo. The previously discussed amnestic effect of triazolam was measured by immediate and delayed recall of meaningful and meaningless syllables. A compartment model employing the radioactivity in the cerebellum as an input function was used for the quantification of receptor binding. The binding parameter, k3, was decreased after triazolam administration in all measured regions, whereas no change was observed after placebo treatment. The reduction compared to the control study varied from 8.6 +/- 3.7% in the temporal cortex to 16.3 +/- 6.3% in the thalamus. Triazolam administration impaired both immediate and delayed recall of syllables, whereas placebo administration had no effects. Benzodiazepine agonists are reported to decrease the cortical acetylcholine release. The decrease of acetylcholine release in the synaptic cleft might be the explanation for the decreased binding of [11C]NMPB.

Dopamine D2 and serotonin S2 receptors in susceptibility to methamphetamine psychosis detected by positron emission tomography

Positron emission tomography (PET) was used to assess the role of dopamine D2 receptors in the striatum and serotonin S2 receptors in the frontal cortex in the susceptibility to methamphetamine-induced psychosis. Subjects were six men who had previously experienced methamphetamine psychosis (methamphetamine subjects) and 10 age- and sex-matched control subjects. The radiotracer used was 11C-N-methylspiperone. Although binding availability, assessed by dynamic analysis, in the two regions did not differ between the two groups, the ratio of binding availability in the striatum to that in the frontal cortex significantly decreased in the methamphetamine subjects as compared with the control subjects. These findings suggest that an imbalance in the activity of these two receptors may be related to the susceptibility to methamphetamine psychosis.

No age-related changes in human benzodiazepine receptor binding measured by PET with [11C]Ro 15-4513

The effects of age on the binding of [11C]Ro 15-4513, a partial inverse agonist of the central benzodiazepine receptor, were studied. Sixteen healthy male volunteers (21-78 years old) participated. Regional radioactivity in the brain was followed for 45 min by positron emission tomography after a bolus injection of [11C]Ro 15-4513. Similar tracer kinetics were observed in both young and old subjects. For the quantification of receptor binding in vivo, a compartment model, in which radioactivity in the pons was used as an input function, was applied. There were no significant changes in the binding potentials with age (P > 0.1) in ten brain regions. These observations delineate an interesting difference between central benzodiazepine (BZ) receptors and other neurotransmitter receptors in the human brain measured by PET that have been shown to have a reduction with age.

Dopamine D1 receptors in Parkinson's disease and striatonigral degeneration: a positron emission tomography study

Striatal dopamine D1 receptors were investigated in 11 patients with Parkinson's disease (PD), five patients with striatonigral degeneration (SND) and six age-matched controls by positron emission tomography and carbon-11 labelled SCH23390. The SND patients showed mean 12%, 21%, and 31% declines in the ratios of radioactivity in the caudate, anterior putamen, and posterior putamen compared with that in the occipital cortex. These ratios were not significantly altered in the PD patients. The results may explain the different therapeutic responses to levadopa between SND and PD patients, and this technique might prove useful for their differentiation.

Dopamine D1 receptors in Parkinson's disease and striatonigral degeneration: a positron emission tomography study

Striatal dopamine D1 receptors were investigated in 11 patients with Parkinson's disease (PD), five patients with striatonigral degeneration (SND) and six age-matched controls by positron emission tomography and carbon-11 labelled SCH23390. The SND patients showed mean 12%, 21%, and 31% declines in the ratios of radioactivity in the caudate, anterior putamen, and posterior putamen compared with that in the occipital cortex. These ratios were not significantly altered in the PD patients. The results may explain the different therapeutic responses to levadopa between SND and PD patients, and this technique might prove useful for their differentiation.

Evolution of the glutamine synthetase gene, one of the oldest existing and functioning genes

We performed molecular phylogenetic analyses of glutamine synthetase (GS) genes in order to investigate their evolutionary history. The analyses were done on 30 DNA sequences of the GS gene which included both prokaryotes and eukaryotes. Two types of GS genes are known at present: the GSI gene found so far only in prokaryotes and the GSII gene found in both prokaryotes and eukaryotes. Our study has shown that the two types of GS gene were produced by a gene duplication which preceded, perhaps by > 1000 million years, the divergence of eukaryotes and prokaryotes. The results are consistent with the facts that (i) GS is a key enzyme of nitrogen metabolism found in all extant life forms and (ii) the oldest biological fossils date back 3800 million years. Thus, we suggest that GS genes are one of the oldest existing and functioning genes in the history of gene evolution and that GSI genes should also exist in eukaryotes. Furthermore, our study may stimulate investigation on the evolution of "preprokaryotes," by which we mean the organisms that existed during the era between the origin of life and the divergence of prokaryotes and eukaryotes.

[Estimation of risk due to radiation exposure in the mass screening of cancer in Japan]

Five types of mass screening programs for cancer are performed under the auspices of the Adult Health Promoting Act of the Japanese Government. The cancers involved are those of stomach, uterus, lung, breast and colon. Radiological images are routinely used for the screening of stomach and lung cancers, and mammography will be employed in the near future. In this study, the risk due to radiation exposure in the above-mentioned screening programs was estimated for an individual who participates in the screening of each cancer annually. The dose absorbed at each screening was estimated and an additive risk model was used as the pattern of occurrence of radiation-induced cancers for simplicity. Safety was also estimated. Results showed that the risk of a shortened life-expectancy as a result of undergoing annual mass screening for breast, stomach and lung cancer was insignificant in comparison with the average life-expectancy of about 80 years for Japanese men and women, and much smaller than the benefit of mass screening expressed in terms of prolonged life-expectancy. However, it should be emphasized that a quality control program must be established to keep the dose absorbed at each X-ray screening examination as low as reasonably possible.

Age-related changes in human muscarinic acetylcholine receptors measured by positron emission tomography

The effects of age on the binding parameters of [11C]N- methyl-4-piperidylbenzilate ([11C]NMPB), a specific muscarinic cholinergic receptor ligand, were studied. Eighteen healthy male volunteers (18-75 years old) participated. Regional radioactivity in the brain was followed for 60 min by positron emission tomography (PET). Uptake of [11C]NMPB continuously increased in all brain areas with the exception of the cerebellum. For the quantification of receptor binding, a compartment model, in which radioactivity in the cerebellum was used as an input function, was used. The binding parameter, K3, of muscarinic acetylcholine receptors in eight brain regions (pons, hippocampus, frontal cortex, striatum, temporal cortex, thalamus, occipital cortex, parietal cortex) showed an age-related decrease of about 45% over the age range.

A new gel using super absorbent polymer for mapping the spatial dose distributions of electron beams by MR imager

A technique for mapping the spatial dose distribution with a magnetic resonance imager is presented. A ferrous sulphate solution with sulfuric acid was used as the detecting medium for radiation dose. To make a gel of the solution for filling up a cubic phantom, we developed a new gel component that is combined with a super absorbent polymer (Sumikagel N-100) and a cross-linked dextran gel (Sephadex G-200). In order to make the application for radiation treatment planning, mapping of the dose distribution was carried out using a Unix computer.

In vivo binding of [11C]Ro15-4513 in human brain measured with PET

Ro15-4513, an azide derivative of benzodiazepine antagonist flumazenil (Ro15-1788), and Ro15-1788 were labelled with carbon 11. Sequential PET scans following injection of [11C]Ro15-4513 or [11C]Ro15-1788 into normal male healthy volunteers were measured, and kinetic analysis using pons as a reference region was performed. [11C]Ro15-4513 was highly accumulated in frontal cortex, temporal cortex, hippocampus and relatively lower accumulation in occipital cortex, whereas almost homogeneous distribution of Ro15-1788 throughout cortex area was seen. The kinetic analysis revealed that such differences of regional distribution in brain between two labelled ligands were mainly due to the regional difference of the dissociation rate constants in vivo (k4). [11C]Ro15-4513 may be a useful tool for the in vivo study of benzodiazepine receptors in human brain.

High-energy phosphate metabolism of the myocardium in normal subjects and patients with various cardiomyopathies--the study using ECG gated MR spectroscopy with a localization technique

Nuclear magnetic resonance spectroscopy (MRS) is a new technique for the evaluation of myocardial metabolism. Recently, localized MRS has been clinically available to measure by a non-invasive method the relative concentrations of the high-energy phosphate metabolites in the myocardium. We performed ECG gated P-31 MRS using ISIS (image-selected in vivo spectroscopy) in 15 normal volunteers, 12 patients with hypertrophic cardiomyopathy, 12 with left ventricular hypertrophy, 6 with dilated cardiomyopathy and 11 with specific heart muscle disease. Myocardial peak height ratios of PCr/gamma-ATP, Pi/gamma-ATP and PCr/Pi were measured. Myocardial P-31 MRS demonstrated a significant decrease in the ratio PCr/ATP in patients with hypertrophic cardiomyopathy and specific heart muscle disease as compared with normal subjects, indicating myocardial metabolic disturbance in these patients. The ratio of PCr/ATP in patients with dilated cardiomyopathy did not differ significantly from that of normal subjects. However, exercise MRS revealed a marked decrease of PCr peak in an asymptomatic patient with dilated cardiomyopathy, which may indicate a latent metabolic disturbance in the myocardium of dilated cardiomyopathy.

[Intramuscular degeneration process in Duchenne muscular dystrophy--investigation by longitudinal MR imaging of the skeletal muscles]

Intramuscular degeneration process of Duchenne dystrophy skeletal muscles was investigated by longitudinal skeletal muscle imaging with high-field-strength NMR-CT of 1.5 Tesla. Thigh muscles in 10 cases ranging in age from 4 to 19 years were examined by T1-weighed longitudinal images (TR = 215-505 ms, TE = 19-20 ms). Following results were obtained: (1) Skeletal muscle degeneration was depicted as high signal intensity area reflecting its high fat contents. (2) These high signal intensity areas had a longitudinally streaky appearance in parallel direction with myofibers. (3) These findings were more prominent toward myotendon junction than muscle bellies. (4) Skeletal muscle degeneration progressed rapidly between 7 to 10 years of age, and reached a plateau after that.

[Preliminary specification of X-ray CT for lung cancer screening (LSCT) and its evaluation on risk-cost-effectiveness]

In Japan mass screening for lung cancer is widely performed by chest X-ray film of 10 x 10 cm, with sputum cytology for high-risk groups. However, the effectiveness of the present mass screening program for lung cancer has been less than expected, although some date have shown improvement of the survival rate as a result of mass screening. We propose a new X-ray CT method of screening for lung cancer called Lung Cancer Screening CT (LSCT). The preliminary specifications for LSCT are as follows: scan speed is within 10 sec for a 40 cm length with a 1 cm slice thickness, and the absorption dose for lung is less than 1 cGy. A computer-assisted diagnostic system is necessary for image reading. The risk-benefit analysis of LSCT indicates that Japanese men and women over 45 years old can be screened in 1992 and thereafter. The cost per person.year of LSCT screening is estimated to be 1.4 x 10(6) yen for a population incidence rate of 50 x 10(-5) person/year and average life expectancy of 30 years. In 1992 the above condition will be satisfied by men aged 55 years old and above, but not by women of any age. We believe that LSCT should be developed further and tested in the high-risk group of men with an incidence rate of 100 x 10(-5) persons/year or more.

[Evaluation of performance in diagnosis of pneumoconiosis using FCR (Fuji Computed Radiography)]

The purpose of this study was to determine the applicability of the FCR system to the diagnosis of pneumoconiosis. In the study, images of pneumoconiosis obtained by FCR were collected from the Rosai Hospital for Silicosis, and the distribution, shape and size of small opacities of pneumoconiosis were determined by three of the authors. An image data base was prepared, and diagnosis of pneumoconiosis using FCR test films was performed by 12 physicians with reference to reduced ILO films. Among the data obtained, data relating to profusion were analyzed. The results were compared with those obtained in the previous study. It was found that, if suitable image processing was carried on FCR test films, profusion could be classified with an accuracy equal to that of the diagnosis of pneumoconiosis with usual full-size films. It was necessary to establish standard films obtained by FCR in order to improve the accuracy of diagnosis of pneumoconiosis using FCR.

D1 dopamine receptor binding in mood disorders measured by positron emission tomography

D1 dopamine receptor binding in mood disorders was studied by positron emission tomography (PET) using 11C-SCH23390. Ten patients with bipolar mood disorders and 21 normal controls were studied in the drug-free state. The patients were in euthymic (N = 6), depressed (N = 3) and manic (N = 1) states. Regional radioactivity in the brain was followed for 40 min by PET. A two-compartment model was used to obtain the binding potential (k3/k4) for the striatum and frontal cortex. The binding potentials for the frontal cortex for the patients were significantly lower than those for normal controls, whereas those for striatum were not significantly different. These findings suggest that D1 dopamine receptors in the frontal cortex may be in a different state in patients with bipolar mood disorders.

[The group study of diagnostic efficacy of cerebro-vascular disease by I-123 IMP SPECT images obtained with ring type SPECT scanner--the ROC analysis on the diagnosis of perfusion defect and redistribution]

We performed two image reading experiments in order to investigate the diagnostic capability of I-123 IMP SPECT obtained by the ring type SPECT scanner in cerebro-vascular disease. Fourteen physicians diagnosed SPECT images of 55 cases with reference to clinical neurological informations, first without brain XCT images and second with XCT images. Each physician detected perfusion defects and redistributions of I-123 IMP and assigned a confidence level of abnormality for these SPECT findings by means of five rating method. From results obtained by ROC analysis, we concluded as follows: (1) Generally, I-123 IMP SPECT is a stable diagnostic modality in the diagnosis of cerebro-vascular disease and the image reading of XCT had no effects on the diagnosis of SPECT on the whole of physician, (2) However, there were unnegligible differences among individuals in the detectability of findings and the effect of XCT image reading, (3) Detectability of redistribution of I-123 IMP was lower than that of perfusion defect and inter-observer variation in the diagnostic performance for redistribution was larger than that of perfusion defect. The results suggest that it is necessary to standardize diagnostic criteria among physicians for redistribution of I-123 IMP.

Lesion of the nucleus basalis magnocellularis does not affect cerebral cortical blood flow in rats

The effects of a unilateral ibotenic acid lesion of the nucleus basalis magnocellularis (NBM) on blood flow of the cerebral cortex and striatum were studied at 2, 4, 8 and 16 weeks after the lesion in conscious rats. In the cerebral cortex, no side-to-side difference in blood flow was observed, though cholinergic enzyme activity was markedly reduced on the side of the lesion. The results suggest that NBM lesion produces disturbance of cholinergic neurons in the cerebral cortex without significant alteration of blood flow.

Comparison of complete amino acid sequences and receptor-binding properties among 13 serotypes of hemagglutinins of influenza A viruses

We determined the sequences of 7 serotypes (H4, H6, H8, H9, H11, H12, and H13) of hemagglutinin (HA) genes, which have not been reported so far. The coding regions consisted of 1692 nucleotides in H4, 1698 in H6, 1695 in H8, 1680 in H9, 1695 in H11, 1692 in H12, and 1698 in H13, and specified 564, 566, 565, 560, 565, 564, and 566 amino acids, respectively. By comparison of amino acid sequences, 13 HA serotypes could be divided into two families, i.e., an H1 group (H1, H2, H5, H6, H8, H9, H11, H12, and H13) and an H3 group (H3, H4, H7, and H10). The relationship was essentially similar to that reported by Air from the comparison of 80 amino-terminal amino acid sequence of 12 HA serotypes (G.M. Air, 1981, Proc. Natl. Acad. Sci. USA 78, 7639-7643). Though a considerable amino acid sequence difference exists between certain HA serotypes, several amino acid residues in fusion peptides (HA2(1-11)) and receptor-binding sites (HA1(98), -134, -138, -153, -183, and -195) were shown to be conserved among the 13 HA serotypes. Human H1 and avian H3, H4, H8, and H10 viruses preferentially bound NeuAc alpha 2,3Gal sequences, whereas human H2 and H3 and avian H6 and H9 viruses bound NeuAc alpha 2,6Gal sequences, although the amino acid residues at position 226 of human H2 and avian H6 and H9 serotype HAs are glutamine. These results show that the amino acid residue at position 226 is not necessarily a determinant of receptor specificity for all serotypes.

Quantitative measurement of uptake of radiolabeled monoclonal antibody by means of planar data

Data obtained from planar images were used to measure the uptake of monoclonal antibody in organs and tumors. Background counts included in the region of interest were eliminated, and the attenuation of the photons emitted by the radionuclide through the intervening tissues was compensated for. The background counts and the intensity of the attenuation were determined from the results of phantom studies and numerical integration with a personal computer. The quantitative uptake of 111In labeled anti-melanoma Monoclonal Antibody (ZME-018) in a melanoma lesion, the liver, and the bone marrow of a patient was measured by the planar method which we developed.

Quantitative in vivo analysis of benzodiazepine binding sites in the human brain using positron emission tomography

Central-type benzodiazepine binding sites were characterized in a single normal human subject, using positron emission tomography (PET) and the radiolabelled benzodiazepine antagonist, carbon-11 labelled flumazenil ([11C] Ro 15-1788). The subject was scanned using tracer alone and tracer plus 4 different concentrations of unlabelled Ro 15-1788, including one concentration of unlabelled Ro 15-1788, chosen to produce maximum displacement of [11C] Ro 15-1788 from specific binding sites. Concentrations of free, unmetabolized [11C] Ro 15-1788 in plasma were estimated using a simple extraction and ultrafiltration method. Radioactivity in the regional exchangeable pool in brain was estimated under non-saturation conditions from the ratio of radioactivity in brain to plasma, under saturation conditions and the kinetics of free ligand in plasma. The specific binding was, then, estimated by the difference between the total radioactivity in brain and exchangeable pool radioactivity. Scatchard analyses were performed to yield Bmax and Kd values under pseudo-equilibrium conditions, which was observed as an increase of specific binding/free with reduction in specific binding. In cerebral cortex and cerebellum, the Bmax values were about 62-73 nmol/l and the Kd values were 3.6-6 nM in the estimation of free ligand in plasma and 12-15 nM in the estimation of exchangeable pool in brain, as free in brain.

[Isolation of human immunodeficiency virus type 1 (HIV-1) from seropositive hemophiliac Japanese]

We reported some biological properties of HIV-1 isolated from 16 hemophiliac Japanese and accidentally infected one mother. Peripheral mononuclear cells (PMCs) were obtained from them, one with AIDS, one with lymphadenopathy and the others were asymptomatic carriers. CD 8 depleted PMCs were obtained by panning methods. They were cocultivated with PHA-stimulated PMCs from seronegative donors. Fifteen HIV-1 isolates were obtained from 17 cases. Recovery rate was 87.5%. The replication rate of HIV-1 from AIDS patient was faster than other isolates from asymptomatic carriers. They did not from plaques on MT 4 cells. The host range study showed that all fifteen isolates infected primary macrophages and only two simultaneously infected human T cell line (MT 2). None of them showed infectivity to other T cell, B cell or monocytic cell lines. Although our study population was rather small, these results suggested that the majority of seropositive hemophiliac Japanese were already infected by HIV-1 and had the risk for the development of AIDS. Moreover, we recognized that HIV-1 from hemophiliac Japanese showed characteristic biological features, i,e, such as 1) weak cytopathic effects, 2) narrow host range and 3) tropism to primary macrophages. It is suggested that they may belong to a unique subtype of HIV-1 and their selective infectivity to primary macrophages have some relation to the clinical status of seropositive hemophiliacs. Further study is necessary to clarify these points.

Robustness of maximum likelihood tree estimation against different patterns of base substitutions

In the maximum likelihood (ML) method for estimating a molecular phylogenetic tree, the pattern of nucleotide substitutions for computing likelihood values is assumed to be simpler than that of the actual evolutionary process, simply because the process, considered to be quite devious, is unknown. The problem, however, is that there has been no guarantee to endorse the simplification. To study this problem, we first evaluated the robustness of the ML method in the estimation of molecular trees against different nucleotide substitution patterns, including Jukes and Cantor's, the simplest ever proposed. Namely, we conducted computer simulations in which we could set up various evolutionary models of a hypothetical gene, and define a true tree to which an estimated tree by the ML method was to be compared. The results show that topology estimation by the ML method is considerably robust against different ratios of transitions to transversions and different GC contents, but branch length estimation is not so. The ML tree estimation based on Jukes and Cantor's model is also revealed to be resistant to GC content, but rather sensitive to the ratio of transitions to transversions. We then applied the ML method with different substitution patterns to nucleotide sequence data on tax gene from T-cell leukemia viruses whose evolutionary process must have been more complicated than that of the hypothetical gene. The results are in accordance with those from the simulation study, showing that Jukes and Cantor's model is as useful as a more complicated one for making inferences about molecular phylogeny of the viruses.