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Biomedical subjects

A Kato

Publications and source records attributed to A Kato.

At least 631 records · Page 35Linked to original sources
PubMed1984

Influence of the input function on the calculation of the local cerebral metabolic rate for glucose in the deoxyglucose method.

We describe here a modification of Sokoloff's deoxyglucose method which requires fewer blood samples but does not diminish accuracy. To calculate the local cerebral metabolism for glucose (LCMRglu), the input function containing the initial peak must be known. This requires many blood samples for accurate definition. To estimate the influence of the peak on the LCMRglu, a dummy input function was generated by extrapolating the data points after 2 min back to 0 min. Next, a biexponential curve, fitted to a reduced number of samples, was applied for the input function. The error introduced into the LCMRglu by using these different approximations was analyzed with an error function derived from an operational equation. The results indicate that the error of LCMRglu caused by neglecting the peak is less than 3%. Furthermore, the error of LCMRglu resulting from use of the biexponential approximation is a function of LCMRglu: the error decreases as the LCMRglu increases and remains at less than 3% even when only seven data points are used (half the usual number of the standard method). Finally, the LCMRglu was calculated by the biexponential curve-fitting, using the experimental data, and compared with that calculated by Sokoloff's computer program. Both methods were in good agreement. This modified method offers great advantage for simultaneous measurement of CMRglu, CBF, and other physiological parameters by means of the multiple tracer autoradiographic technique in the small laboratory animal.

Animals↗
PubMed1984

An improved approach for measurement of regional cerebral rate constants in the deoxyglucose method with positron emission tomography.

A new experimental approach was designed to measure regional rate constants for [18F]2-fluoro-2-D-deoxyglucose in the three-compartment model. A programmed infusion was used to keep the plasma tracer concentration constant for the first 20 min. Positron emission tomography images of the brain were taken every minute for 20 min in a low-resolution mode, then every 15-20 min for 2-3 h in a medium-resolution mode. Two simplified operational equations for the calculation of the regional rate constants were derived that incorporated the contribution of the vascular compartment to tissue activity. The first equation was applied to data collected during the initial 20 min (when the concentration of plasma tracer was constant) to estimate the values of k1*, k2*, k3*, and the fraction of the vascular compartment. The second equation was applied to data collected during the whole experimental period to find the value of k4* and to provide a better estimate of k3*. The regional rate constants measured experimentally in three dogs and a brain tumor patient agreed well with those in the literature. This method permits estimation of the local CMRglu under pathological conditions using regionally measured rate constants and provides new information on the pathophysiological meaning of the rate constants.

Aged↗
PubMed1984

Renal vein thrombosis in stillborn infant of diabetic mother.

A second rare autopsy case of renal vein thrombosis in a stillborn female infant of a diabetic mother and the first after oxytocin induction is reported. Correlative light and electron microscopic studies were conducted. Extensive thrombosis from main to small cortical branches of the left renal vein was encountered causing hemorrhagic infarction of the left kidney. Newly formed hemorrhagic infarction and thrombosis of several small veins in the cortex of the right kidney were discovered. Hyperplasia of the pancreatic islets of Langerhans was observed. The literature was reviewed and the pathogenesis and clinical aspects were discussed.

Adult↗
PubMed1984

[Evaluation of amputation techniques for the study of limb regeneration in the newt and toad].

A comparison between forelimb amputations through the radius-ulna and the humerus was made in the adult newt, Cynops pyrrhogaster pyrrhogaster and the young toad, Xenopus laevis. Newts regenerated their forelimbs after the amputations and the new parts resembled the old in structure and function. Toads regenerated their forelimbs incompletely after the amputations. The new parts lacked joints and fingers showing a simply elongate pattern. The effect of re-amputation of exposed bone on the regeneration was evaluated in the adult newt. A left forelimb was amputated through the humerus and the exposed bone which protruded from the cut surface due to the relationships of the soft tissues, was then re-amputated a few minutes later. A right forelimb of the same individual was simply amputated without re-amputation of the exposed bone. Newts regenerated both forelimbs simultaneously. The new parts resembled the old in structure and function.

Amputation, Surgical↗
PubMed1984

Presence of prelymphoma cells in the bone marrow of the lymphomagenic virus-treated AKR mouse.

Prelymphoma cells (PLC) are defined as cells which give rise to lymphoma cells but are not in themselves autonomous. They are present in the bone marrow of young AKR mice, a strain with a high natural incidence of thymic lymphoma. PLC are identified by transfer of AKR bone marrow into 400-rad-treated F1 recipients, one of the parents being AKR. Normal 1-month-old AKR bone marrow cells result in thymic lymphomas of AKR type in the hybrid recipients after latent periods of 6 to 16 months. In the present study, PLC resulting in lymphoma of AKR type 3 to 4 months after inoculation to irradiated hybrids are described. They are consistently found in the bone marrow of 21- to 28-day-old AKR mice treated at 3 to 5 days of age with a lymphomagenic virus, SL3-3. Long-term culture of these bone marrow cells allows the survival of totipotent hemopoietic stem cells but not of PLC. Thymic stromal remnants prepared from the 21- to 28-day-old virus-treated mice efficiently replicate oncogenic virus; however, they do not contain PLC. This was determined by grafting the remnants to irradiated and nonirradiated hybrid recipients. No AKR type lymphomas developed in the grafted mice. We conclude that the bone marrow of young oncogenic virus-treated AKR mice contains PLC modified by oncogenic virus so that they can produce thymic lymphomas after a shorter latent period than can PLC found in 1-month-old normal AKR mice. The modified PLC are not derived from totipotent marrow stem cells or sequestered in the thymic stroma of virus-treated mice.

Animals↗
PubMed1984

[Quantitative double tracer autoradiographic technique for the simultaneous measurement of local cerebral blood flow and local cerebral glucose utilization using 14C-IAP and 18F-FDG].

We have reported a quantitative double tracer autoradiographic technique for the simultaneous measurement of local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCGU) using 14C-IAP and 18F-FDG respectively. Six awake normal rats and 3 left middle cerebral artery (MCA) occluded rats were used for this experiments. A 50-hold greater radioactivity of 18F was administered and the first exposure was done for 2 hours to obtain a 18F image. Three days later (39 half-lives of 18F), a second exposure was done for 5 to 6 days to obtain the 14C image. Tissue concentration of 14C was measured relative to the commercially available 14C-methyl methacrylate standards. 18F standards were prepared in each experiment. Cross contamination of 14C in the first exposure was less than 2% in the normal state and less than 4% even in the uncoupling condition. The values obtained by this methods for LCBF and LCGU agreed closely with those obtained by a single tracer technique previously reported in the literature. The technique outlined in this paper also provided local glucose utilization flow ratio (LGFR) for the first time. LGFR was obtained by dividing the LCGU image by LCBF image and was expressed as percent mumol/ml. The mean LGFR of control rats was 76 +/- 8% mumol/ml. In a MCA occlusion group, LGFR of ischemic cortex increased until 2 to 3 times higher than that of contralateral non-ischemic cortex. Oxygen glucose index image which was obtained from the LCGU and A-V differences of O2 showed that approximately half of the glucose was metabolized anerobically.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

[Local blood flow and capillary permeability in the experimental meningeal carcinomatosis].

Local blood flow and capillary permeability of the rats with meningeal carcinomatosis were studied with macroautoradiography, and relationship between blood flow, permeability and effects of chemotherapy is discussed. Experimental meningeal carcinomatosis was induced in the Wistar rats by inoculating Walker 256 tumor into cisterna magna. One to 12 days after inoculation, rats were used for measurements of blood flow (by 14C- iodoantipyrine) and capillary permeability (by 14C-alpha-aminoisobutyric acid). Images of autoradiography and corresponding histological appearances were analyzed. In the early stage of tumor growth (2 to 3 days after inoculation), a few layers of tumor cells were identified in the ambient cistern. Blood flow in the vicinity of the tumor cell layer was noted, but no increase in capillary permeability was found. In the middle stage of tumor growth (3 to 5 days after inoculation), 10 to 20 layers of the tumor cell was noted in the ambient cistern. Blood flow in the tumor was evident and capillary permeability began to increase. In the late stage of tumor growth (6 to 12 days after inoculation), a mass of the tumor cells was noted in the ambient cistern. In this stage, blood flow in the tumor was similar to that of cerebral gray matter and capillary permeability increased markedly. Brain adjacent to the tumor also showed increase in capillary permeability. The result correlated well to the previous result of experimental chemotherapy. Form those data, lipid soluble drugs which cross blood-brain barrier readily are recommended for the early stage of meningeal carcinomatosis, and water soluble drugs which has limitations to cross blood-brain barrier can not be recommended.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

[Development of ACNU-resistant meningeal gliomatosis models: establishment of resistant rat glioma subline against ACNU].

Induction in vivo of resistance of C6 rat glioma and 9L rat glioma to ACNU [1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride] was studied and ACNU-resistant rat meningeal gliomatosis models were developed by using these resistant glioma sublines. Rapid acquisition of resistance to the agent was present at 2nd transplant generation in both glioma lines. Cellular resistance to ACNU remained unchanged in the absence of drug over 5 transplant generations in vivo in spite of the fact that the drug treatment was discontinued at the 5th generation after a complete resistance was induced. On the other hand, the degree of resistance of 9L resistant subline established by only once ACNU treatment was found to be decreased after 5 transplant generations in vitro. Degree of resistance at the cellular level was observed with each subline by in vitro technique and compared with each other. Each subline was found to have different degree of resistance: 9L resistant subline showed higher resistance than C6 resistant subline, and the differences in degree of resistance between 9L resistant subline and C6 resistant subline were approximately 750 and 20, respectively, when they were expressed as ratios of IC50 (drug concentration for 50% growth inhibition) for the resistant subline to the original one.

Animals↗
PubMed1984

Pharmacokinetics of positron-labeled 1,3-bis(2-chloroethyl)nitrosourea in human brain tumors using positron emission tomography.

The nitrosoureas are widely used in the chemotherapy of brain tumors, two of the most common being 1,3-bis(2-chloroethyl)nitrosourea and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea. However, we do not understand how these compounds work, nor do we know which part of the molecule has antitumor activity. In six patients with brain tumor, we measured the kinetic behavior of positron-labeled 1,3-bis(2-chloroethyl)nitrosourea in both the tumor and the normal brain with the aid of positron emission tomography; we also analyzed the distribution of radioactivity in plasma. We found the clearance of total radioactivity from the tumor to be significantly slower than from the contralateral brain and plasma, indicating a different rate of 1,3-bis(2-chloroethyl)nitrosourea decomposition in the tumor than in normal brain.

Brain Neoplasms↗
PubMed1983

Overlap and cotranscription of the genes for the beta and epsilon subunits of tobacco chloroplast ATPase.

The nucleotide sequences of the genes for the beta and epsilon subunits of tobacco chloroplast ATPase have been determined. The coding regions for the beta and epsilon subunits contain 1494 bp (498 codons) and 399 bp (133 codons), respectively. The 3' end of the beta-coding region overlaps by one nucleotide with the 5' end of the epsilon-coding region. The overlapping termination and initiation codons are ATGA. The beta and epsilon genes are cotranscribed as a 2.7-kb polycistronic mRNA. The amount of the beta and epsilon mRNA in the chloroplast is about one-twentieth that of the LS mRNA.

Base Sequence↗
PubMed1983

Flow properties of hemolysate-loaded liposome suspensions.

Sheep hemolysate-loaded liposomes were prepared by a modified interfacial deposition technique. The mean diameter of the liposomes was estimated to be about 310 nm. Sheep hemolysate-loaded liposomes were called artificial red blood cells (ARBC). The flow properties of the ARBC suspension (pH 7.4) were measured with a concentric cylinder-type rorational viscometer at low shear rates and were compared with those of sheep red blood cell (SRBC) suspension (pH 7.4). It was revealed that the flow type of the ARBC suspension (pH 7.4) was of pseudoplastic as in the case of SRBC suspension (pH 7.4). The relative viscosity of the ARBC suspension as a function of particle concentration in the medium was linear and fitted fairly well with the Einstein equation. However, the relative viscosity of SRBC suspension was increased more gradually with increasing particle concentration, and was well presented by the Brinkman equation as a function of particle concentration for concentrated suspensions. It was suggested that this would be due to the difference in particle-particle interaction between the two types of suspensions. The flow properties of the mixed suspensions of the ARBC and SRBC in the suspending medium (pH 7.4) with and without dextran were measured. It was revealed that the relative viscosity of the mixed suspension is reduced with increasing mixing ratio of the ARBC in the suspension, suggesting that the flow properties of the mixed suspension of the ARBC and SRBC are dependent on the ARBC rather than dextran.

Animals↗