[A study of the clinical factors which have the greatest effect on bronchial hyperresponsiveness in atopic asthma by multiple regression analysis]

We studied the clinical factors which have the greatest effect on bronchial hyperresponsiveness, with 37 atopic asthma patients (23 males and 14 females). They were from 13 to 59 years old. We measured the control value of the respiratory conductance (Grs.cont), the minimum dose of methacholine (bronchial sensitivity, Dmin), the linear slope of the Grs (= 1/Rrs) decreased (bronchial reactivity, SGrs) and SGrs/Grs.cont by the "Astograph" method (Chest 80, 600, 1981). Statistical analysis was performed by multiple regression analysis. Grs.cont, log Dmin, SGrs and SGrs/Grs.cont were regarded as objective variables. Age, onset age of asthma, period of disease, smoking history, family history of atopy, serum IgE, blood eosinophil counts, positive skin test counts, FEV1.0% and type of asthma attack (perennial or seasonal) were regarded as explanatory variables. The results were as follows: 1) The explanatory variable which showed the highest partial correlation coefficients, was the type of asthma attack in multiple regression analysis of Grs.cont and log Dmin (p < 0.05, p < 0.05). 2) Grs.cont of perennial asthma attack (0.247 +/- 0.064) was significantly lower than that of seasonal attack (0.318 +/- 0.097) (p < 0.02). Log Dmin of perennial asthma attack (-0.837 +/- 0.457) was significantly lower than that of seasonal attack (-0.254 +/- 0.429) (p < 0.005). Therefore in mild atopic asthma, the clinical factor which has the greatest effect on bronchial hyperresponsiveness is the type of asthma attack. We conclude that the existence of perennial asthma attacks is mostly related to increased bronchial hypersensitivity.

Non-competitive antagonism by hirsuteine of nicotinic receptor-mediated dopamine release from rat pheochromocytoma cells

Effects of hirsuteine, an indole alkaloid extracted from Uncaria genus, on nicotine- and high K-induced responses were investigated in rat pheochromocytoma PC12 cells. Hirsuteine (300 nM-10 microM) inhibited dopamine release evoked by 100 microM nicotine in a concentration-dependent manner. Hirsuteine did not produce a parallel shift of the concentration-response relationship curve for nicotine, but reduced maximal dopamine release. Dopamine release evoked by 60 and 155 mM KCl was also inhibited by hirsuteine, but the concentration necessary for significant inhibition was higher (more than 10 microM). Under whole cell voltage-clamp, hirsuteine reversibly inhibited inward currents activated by 100 microM nicotine. The current inhibition was slightly accelerated by hyperpolarization. The results suggest that hirsuteine non-competitively antagonizes nicotine-evoked dopamine release by blocking ion permeation through nicotinic receptor channel complexes. The blockade of Ca channels, which are activated during nicotine-evoked depolarization, may not play a major role in the antagonism.

Overproduction of biologically-active human nerve growth factor in Escherichia coli

A gene coding for human nerve growth factor (hNGF) was constructed for expression under control of the trp promoter in E. coli. The plasmid pTRSNGF contained a synthetic hNGF gene fused, in frame, to the region encoding the beta-lactamase signal peptide. The plasmid pTRLNGF contained the same coding sequence as hNGF attached downstream from the N-terminal fragment of the trp L gene. E. coli cells harboring pTRSNGF produced an amount of hNGF constituting 4% of the total cellular protein, and removed the beta-lactamase signal peptide. The mature protein hNGF was biologically active in the PC12h bioassay for neurite outgrowth. This biological activity was comparable to that of authentic mouse NGF. E. coli cells harboring pTRLNGF produced an amount of fusion protein hNGF constituting 25% of the total cellular protein. Although the fusion protein hNGF formed inclusion bodies in cells, dissolved fusion protein hNGF was active in neurite outgrowth from PC12h cells.

[Role of 99mTc-labeled RBC SPECT in the diagnosis of hepatic hemangioma--comparison with US, CT and angiography]

The roles of planar imaging and SPECT with 99mTc-labeled RBC, US, Dynamic CT and angiography in the diagnosis of hepatic hemangioma were evaluated. The study group consisted of 18 patients with a total of 40 hemangiomas and 13 patients with a total of 21 non-hemangiomas. Among these patients, 5 patients with a total of 8 hemangiomas and 10 patients with a total of 14 non-hemangiomas were diagnosed by operation and biopsy. In all 40 hemangiomas, sensitivity for planar imaging was 35%, SPECT 50%, US 53%, Dynamic CT 82% and angiography 81%, respectively. When the tumor size was greater than 2.2 cm by SPECT and 2.8 cm by planar imaging, their sensitivity for both methods was 100%. Specificity for planar imaging was 100%, SPECT 95%, US 81%, Dynamic CT 100% and angiography 83%, respectively. One patient with hepatocellular carcinoma diagnosed by angiography showed increased uptake on SPECT. Because of the highest accuracy for SPECT in hemangioma greater than 2.0 cm, SPECT should be considered to be the method of choice for noninvasive diagnosis of hemangioma.

Tetronothiodin, a novel cholecystokinin type-B receptor antagonist produced by Streptomyces sp. NR0489. I. Taxonomy, yield improvement and fermentation

Streptomyces sp. NR0489 produces tetronothiodin, a novel brain-type cholecystokinin receptor antagonist. This species was differentiated from its related species S. gelaticus, S. griseolus and S. hydrogenans on the basis of their cultural characteristics, such as the utilization of carbohydrates and the presence or absence of various enzymatic activities. We applied the DNA-DNA hybridization method using photobiotin, which proved the genetic difference between the four species mentioned above. The yield improvement effort including single colony isolation, mutation, and protoplast regeneration together with medium optimization resulted in more than an 81-fold increase of the productivity of tetronothiodin as compared to that of the wild type strain.

[Respiratory control in diffuse interstitial lung disease]

Whether the change of lung volume affect ventilatory responsiveness to chemical stimuli has not been studied in patients with interstitial lung disease (ILD). We measured the responses of minute ventilation (VE), tidal volume (VT), and occlusion pressure (P0.1) to hypercapnia (HCVR) and hypoxia (HVR) in these patients. Breathing efficiency (delta VE/delta P0.1) and effective compliance (delta VT/delta P0.1) were also measured under the same stimuli. 1) HCVR and HVR were measured in one female patient with hypersensitivity pneumonitis. VE responses during low VC phase (VC; 71% of predicted value) were similar to that during increased VC phase (VC; normal level) in both HCVR and HVR. However, VT responses of low VC phase were lower than those of increased phase, and P0.1 responses of low VC phase were higher than those of increased VC phase. Both breathing efficiency and effective compliance of low VC phase were lower than those of increased VC phase. 2) Thirty one patients with ILD were divided into two groups: low VC group; VC < 80% of predicted value, and normal VC group; VC > 80% of predicted value. HCVR and HVR were compared between two groups. Mean values of VE response to hypercapnia and hypoxia in low VC group were lower than those of in normal group, although they were not significantly different. VT response to hypercapnia and hypoxia were significantly lower of low VC group than those of normal VC group. Mean values of P0.1 responses to hypercapnia and hypoxia of low VC group were higher than those of normal VC group, although they were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

[Diagnostic value of a new myocardial perfusion agent, 99mTc-teboroxime (SQ30,217) in patients with coronary artery disease, utilizing a SPECT imaging protocol: a multicenter phase III clinical trial]

Technetium-99m teboroxime (TEBO) is a new technetium-based myocardial perfusion imaging agent, which has high myocardial extraction and rapid myocardial washout. Its rapid myocardial washout may necessitate rapid imaging protocols. This study was designed to perform exercise/rest SPECT imaging protocols with rapid data acquisition (from 2.8 +/- 1.4 min to 11.2 +/- 4.1 min after injection) in 171 patients with coronary artery disease, 15 patients with cardiomyopathy and 8 patients with other heart disease. The rapid imaging protocols resulted in a high prevalence of good image quality. The diagnostic value of TEBO was recognized from the high concordance of image findings with thallium-201 (201Tl) scintigraphy, 88.2% in the exercise protocol and 89.9% in the rest protocol. Also, the sensitivity and specificity of TEBO for detecting coronary artery disease were comparable (86.6% and 53.9%, respectively) with those of 201Tl (90.7% and 46.2%, respectively). No toxic effects of TEBO were observed in subjective and objective clinical findings and blood examinations. TEBO was finally evaluated to be useful in 98.4% of the patients. Thus, this agent has good clinical potential for myocardial perfusion imaging.

Dopamine receptor agonists and antagonists enhance ATP-activated currents

The effects of dopamine and related compounds on ATP-activated channels were investigated in pheochromocytoma PC12 cells. Dopamine (10 microM) enhanced an inward current activated by 100 microM ATP. A similar enhancement of the ATP-activated current was observed with apomorphine (10 microM), a non-selective dopamine receptor agonist, with (+)-SKF-38393 (10 microM), a selective dopamine D1 receptor agonist, and with (-)-quinpirole (10 microM), a selective dopamine D2 receptor agonist. Moreover, (+)-SCH-23390 (30 microM), a dopamine D1 receptor antagonist, and (-)-sulpiride (30 microM), a dopamine D2 receptor antagonist, also enhanced the ATP-activated current. The results suggest that ATP-activated channels are modulated by dopaminergic mechanisms, and that this modulation cannot be attributed to any single class of dopamine receptors.

[Effects of alpha 2-agonist apraclonidine on norepinephrine levels in the rat iris-ciliary body]

In an attempt to estimate the in vivo catecholamine level in rat iris-ciliary body, animals were sacrificed by microwave irradiation which rapidly inactivates metabolic enzymes. Catecholamine levels in the iris-ciliary body were determined by high-performance liquid chromatography with electrochemical detection. The norepinephrine level in rat iris-ciliary body per gram tissue protein was 3.56 +/- 0.22 micrograms/g (21.1 +/- 1.3 nmol/g)(mean +/- SEM, n = 7). Neither dopamine nor epinephrine were detected. A single instillation of 5 microliters of an 0.05% apraclonidine (alpha 2-agonist) to one eye of a rat increased the norepinephrine level in the iris-ciliary body by 7.7% one hour after administration (p less than 0.05).

[Effects of atropine on acetylcholine levels in the rat iris-ciliary body]

In an attempt to estimate the in vivo acetylcholine level in rat iris-ciliary body, animals were sacrificed by microwave irradiation which rapidly inactivates metabolic enzymes. Acetylcholine levels in the iris-ciliary body were determined by high-performance liquid chromatography with electrochemical detection. The acetylcholine level in rat iris-ciliary body per gram tissue protein was 58.8 +/- 5.0 nmol/g (mean +/- SEM, n = 9). A single instillation of 5 microliters of an 0.05% atropine to one eye of a rat decreased acetylcholine level in the iris-ciliary body by 17% half an hour after administration (p less than 0.02).

Neurochemical and histological analysis of motor dysfunction observed in rats with methylnitrosourea-induced experimental cerebellar hypoplasia

Histological and neurochemical changes related to motor dysfunction observed in rats after neonatal treatment with nitrosoureas were examined. Neonatal rats received subcutaneous injections of methylnitrosourea (MNU: 0.125 mmol/kg, s.c.) or ethylnitrosourea (ENU: 0.25 mmol/kg, s.c.) daily at 4,5,6 and 7 days post partum, a period of cerebellar granule cell, stellate cell and basket cell formation. At 14 days and 45 days after birth, MNU-treated rats displayed a lowering in motor coordination skills measured by tests of retainment ability on a rod of 26 mm diameter, chinning-climbing ability on parallel rods or retainment ability on a rotating rod. Histological examination at 14 days after birth showed a cerebellar hypoplasia with reduced cellularity of the internal granule cell layer and a disperse disposition of Purkinje cells in the granule cell layer. Cerebellar growth and cerebellar content and concentration of DNA were remarkably reduced in the MNU-treated rat. The degree of the reduction in cerebellar content of glutamic acid paralleled the degree of the cerebellar hypoplasia at 14 and 45 days after birth. In contrast, the concentrations of gamma-aminobutyric acid, acetylcholine, 5-hydroxytryptamine and norepinephrine were significantly increased by MNU treatment. ENU treatment control did not exert any significant changes in the neurotransmitters and motor coordination. These results suggest that the motor dysfunctions observed in MNU treated rats are induced by unbalanced output activities from Purkinje cells to motor neurons.

[A case of chronic persistent cough (CPC) caused by gastroesophageal reflux (GER) (including a study of CPC caused by suspected GER)]

A patient, an 80-year-old female, had complained of a cough for 20 weeks, and was not cured by cough medicine. Gastroesophageal reflux was considered as the cause of the cough because of her symptoms and gastrointestinal fiberscopy (GIF) and barium meal studies. She made favorable progress on a histamine H2 blocker and cysapurid for 4 weeks. Therefore we diagnosed her cough as caused by gastroesophageal reflux. We also studied the incidence of chronic persistent cough in patients suspected of gastroesophageal reflux because of symptoms and GIF results. Among 676 cases examined by GIF at Niigata-kenritsu Myoko Hospital, we detected 7 cases who complained of heartburn and in whom we observed hiatal hernia and reflux esophagitis by GIF. Only one of them, the present case, complained of a cough. CPC caused by gastroesophageal reflux is not seen frequently, but the possibility of GER as the cause of CPC should be considered.

Sustained damage to energy metabolism of brain regions after microsphere embolism in rats

BACKGROUND AND PURPOSE

Information on sustained damage to cerebral function and metabolism after cerebral ischemia is useful for prophylaxis and therapeutics of cerebral infarction. The purpose of the present study was to induce sustained damage to brain regions after cerebral ischemia in experimental animals. For this purpose, we examined animal behavior and cerebral energy metabolism following microsphere embolism in rats.

METHODS

We injected 900 microspheres (48 microns in diameter) into the right internal carotid artery of 110 rats and determined the time course of changes in the rats' behavior and the energy metabolism of the cortex, striatum, and hippocampus of both hemispheres. We injected the same volume of vehicle, without microspheres, into 28 sham-operated rats; there were 14 nonoperated control rats.

RESULTS

Peak increase in lactate content and decrease in adenosine triphosphate and creatine phosphate of these brain regions of the right hemisphere were seen on the first day after microsphere embolism, whereas peak increases in glucose and glycogen contents of these regions were observed on the third day. Most of the metabolic alterations in all these regions continued for up to 28 days after operation, although they recovered toward control levels with time after the operation. The extent and trend of metabolite changes of the right hemisphere after microsphere embolism were similar in the three brain regions. In the left hemisphere, similar metabolic changes were observed, but to a lesser degree. The time course of changes in behavioral scores following microsphere embolism revealed marked stroke-like symptoms on the first day and relatively rapid disappearance of the symptoms with time after embolism.

CONCLUSIONS

Microsphere embolism is capable of inducing widespread, sustained damage to energy metabolism of brain regions.

Extracellular adenosine 5′-triphosphate-evoked glutamate release in cultured hippocampal neurons

Characteristics of extracellular ATP-evoked electrical responses in rat hippocampal neurons were investigated. Extracellular ATP (100 microM) induced a rapid depolarization followed by repetitive firings of spikes in these cells under whole-cell current-clamp. In whole-cell voltage-clamp experiments, ATP activated 2 types of inward currents that were inhibited by P2-purinoceptor blocker suramin (300 microM). One is a small (about -20 pA) sustained current which is insensitive to tetrodotoxin (TTX), and the other is a large (-100 to -300 pA) transient current which abolished in the presence of 3 microM TTX. The ATP-induced transient current was blocked by 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX; 30 microM), a non-N-methyl-D-aspartate (non-NMDA) receptor antagonist. ATP failed to induce the transient current in the cell which showed the desensitization to quisqualic acid (QA; 10 microM), a non-NMDA receptor agonist. These findings suggest that ATP directly activates small sustained currents, and indirectly induces the transient currents by evoking glutamate release.

Inhibition of ion channels by hirsutine in rat pheochromocytoma cells

Effects of hirsutine, an alkaloid that produces a potent ganglion blocking effect, were investigated using rat pheochromocytoma PC12 cells. Hirsutine (1 to 10 microM) suppressed dopamine-release evoked by 100 microM nicotine. In voltage-clamped cells, hirsutine (1 to 10 microM) inhibited the inward current activated by 100 microM nicotine. Hirsutine was equipotent to hexamethonium in blocking the nicotine-activated current. The voltage-dependency of the nicotine activated current was not modified by hirsutine. Effects of hirustine on other ion channels were tested to determine its selectivity. Inward currents mediated through ATP-activated channels were scarcely affected by hirsutine (up to 100 microM). However, hirustine (10 microM) inhibited Ba currents passing through Ca channels and K currents activated by depolarizing voltage steps. The results suggest that hirsutine potently blocks nicotinic receptor-channels, but hirsutine also inhibits voltage-gated Ca and K channels. Roles of the inhibition of these channels in the pharmacological effects of hirsutine were discussed.

Inhibitory action of peripheral-type benzodiazepines on dopamine release from PC12 pheochromocytoma cells

Characteristics of the benzodiazepine inhibition of dopamine (DA) release in PC12 cells were investigated. Diazepam inhibited DA release evoked by high concentrations of extracellular K+ in a dose-dependent manner (IC50, 10 microM). Ro 5-4864 [7-chloro-1,3-dihydro-1-methyl-5-(p-chlorophenyl)-2H-1,4-benzodiazepine- 2-one], a peripheral-type benzodiazepine, also inhibited DA release effectively. PK 11195 [1-(2-chlorophenyl)-N-methyl-N-(1-methyl-propyl)-3-isoquinoline carboxamide], a benzodiazepine generally considered a peripheral-type benzodiazepine receptor antagonist, did not antagonize the inhibition induced by diazepam, but rather inhibited DA release itself. On the other hand, the central-type benzodiazepines, clonazepam and Ro 15-1788 (ethyl-8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5a] [1,4]benzodiazepine-3-carboxylate) did not affect the DA release. Diazepam, Ro 5-4864 and PK 11195 also inhibited a Ba(++)-current carried by voltage-gated Ca++ channels, and diazepam suppressed an increase in intracellular Ca++ evoked by 80 mM extracellular K+ as measured by the fura-2 method. These results suggest that the inhibitory action of diazepam and other benzodiazepines on DA release from PC12 cells may be mediated through one type of peripheral-type benzodiazepine receptors which are coupled to voltage-gated Ca++ channels and that these receptors may not necessarily be the same as those in other tissues.

[Angiotensin converting enzyme (ACE) inhibitor-induced cough in non-smoking hypertensive patients]

The author studied the characteristics of ACE inhibitor-induced cough in 41 non-smoking hypertensive patients. For at least 6 months, 20 patients (10 males and 10 females) were treated with enalapril, and 21 (11 males and 10 females) with aracepril. The results were as follows. 1) ACE inhibitor-induced cough was induced in 7 cases (1 male and 6 females). The incident rate of cough was 17.1%. ACE inhibitor-induced cough was not significantly related to past allergic history or to the beta-adrenergic blocker therapy. The laboratory findings of the cough sufferers--such as eosinophil percent in venous blood, serum GOT and GPT, urea nitrogen, creatinine, renal function (PSP excretion test and creatinine clearance), and pulmonary function (%FVC, FEV1.0% and %V25)--were not significantly different from those of the non-coughers. 2) Inhibitory effects of ipratropium bromide inhalation of ACE inhibitor-induced cough were noted in 83.3% of the patients, but their coughs did not completely disappear. From these findings, the pathogenesis of this cough may be related to be as follows. The cough seems to be related to the release of acetylcholine from vagal nerve terminals or to the stimulation of irritant receptors and vagal reflex. 3) Chronic persistent cough or bronchial asthma did not occur after stopping the treatment with ACE inhibitors. The mean follow-up period was 15.6 months.

Integrated microscopic-macroscopic pharmacology of monoclonal antibody radioconjugates: the radiation dose distribution

Accurate dosimetry is essential for the assessment of radioimmunotherapy. Most often studied to date has been the macroscopic dosimetry related to organ and tumor distribution of the radiolabeled antibody, but the question of microscopic dose heterogeneity is also important. To address the latter issue, we have taken an integrated approach to the pharmacology, taking into account whole-body distribution, transcapillary transport, percolation through the tumor interstitial space, antigen-antibody interaction, and antibody metabolism. The first step is to simulate the spatial antibody concentration profile in a tumor as a function of time after i.v. (e.g., bolus) injection, using reasonable values for the parameters involved. The second step is to calculate, also as a function of time, the absorbed radiation dose distribution resulting from each concentration profile. Parameter values for IgG pharmacology and a radiation point source function for 131I are used to explore the effect of antibody distribution profiles on absorbed dose in the tumor. The geometry simulated corresponds to a spherical nodule of densely packed tumor cells. Absorbed doses are calculated for radiation from a single nodule (e.g., a micrometastasis or prevascular primary tumor) and for a cubic lattice of such nodules (e.g., corresponding to nodular lymphoma). As noted in our previous studies, there is a "binding site barrier." Binding to antigen retards antibody percolation into the nodules; high antibody affinity tends to decrease percolation and give a higher absorbed dose near the surface of each nodule. Heterogeneous antibody distribution results in a heterogeneous absorbed dose. This is more apparent in the case of radiation from a single nodule than it is for radiation from within an array of nodules. Dehalogenation results in a lower absorbed dose over time, and the effect is more apparent at later times after injection. PERC-RAD, the computer program package developed for these analyses, provides a convenient and flexible way to assess the impact of macroscopic and microscopic parameters on the distribution of radioimmunoconjugates and on the consequent profile of absorbed radiation dose in tumors. This mathematical model and the general principles developed here can be applied as well to other radiolabeled biological ligands.

An analysis of monoclonal antibody distribution in microscopic tumor nodules: consequences of a "binding site barrier"

Rational in vivo application of monoclonal antibodies for diagnosis and therapy of cancer requires an understanding of both the global and microscopic pharmacology of macromolecular ligands. Here, we introduce a new mathematical model for antibody distribution into small, prevascular, densely packed nodules (representing either primary or metastatic tumor). For the analysis, we link together several aspects of antibody pharmacology: the global (whole body) pharmacokinetics; transcapillary transport into normal tissue interstitium surrounding the nodule; diffusion into the nodule; nonspecific binding and/or partitioning; specific binding to tumor antigen; metabolism; and lymphatic outflow from the tissue space. Input parameter values are estimated from experimental studies in vitro, in animals, and in clinical trials. Our aim is to explore the sensitivity of antibody localization to variation in three of the important parameters of this model: the rate of transcapillary transport; the rate of lymphatic outflow; and the antigen density. Predictions based on this analysis include the following: (a) High rates of transcapillary transport influx or low rates of lymphatic efflux will enhance antibody percolation into the tumor nodule at early times after injection and increase the average antibody concentration in the tumor at all times; (b) Changes in antibody influx rate will affect the antibody distribution in the tumor at earlier times than do changes in the efflux rate; (c) Reducing the antigen concentration will increase the uniformity of antibody penetration but lower the average concentration in the tumor at all times after injection; and (d) Counter to intuition, lowering the antigen concentration can increase the peak concentrations achieved toward the center of the nodule. If, in addition, there is any metabolism of bound antibody, the concentration-time integral (i.e., the "area under the curve") for the center of the nodule will also be increased by decreasing the antigen concentration. These predictions directly reflect the "binding site barrier" hypothesis of Weinstein et al. (Ann. NY Acad. Sci., 507: 199-210, 1987) and Fujimori et al. (Cancer Res., 49:5656-5663, 1989; J. Nucl. Med., 31:1191-1198, 1990). In general, and perhaps surprisingly until one considers the problem carefully, the parameters governing antibody percolation can have opposite effects on the uniformity of antibody distribution at early and late times. These calculations, using the PERC program set, were done for antibodies, but we believe that the "binding site barrier" will also prove important for other injected macromolecules, for at least some highly bindable injected small molecules, for lymphokines and cytokines released from transfected cells injected in vivo, and, indeed, for endogenous species such as the autocrine-paracrine factors.

Inhibition of Ca-channels by diazepam compared with that by nicardipine in pheochromocytoma PC12 cells

The effects of diazepam on voltage-gated Ca channels were studied in PC12 pheochromocytoma cells using whole-cell voltage-clamp techniques. An inward current activated by a depolarizing voltage step to +10 mV from a holding potential of -60 mV in 10.8 mM Ba was larger than that activated in 10.8 mM Ca. The Ba current was completely blocked by a low concentration of Cd (30 microM) and was also sensitive to nicardipine (100 nM to 10 microM). Diazepam (1-100 microM) inhibited the Ba current in a concentration-dependent manner. Neither diazepam nor nicardipine affected the current-voltage relationship or the dependence on holding potentials of the Ba current. Both slightly accelerated the inactivation time course of the Ba current. When diazepam was applied to the cells in combination with nicardipine, the observed inhibition agreed with a value predicted assuming independent blockade by diazepam and by nicardipine. These results suggest that diazepam inhibits Ca channels in a manner similar to nicardipine, but that the binding sites for diazepam are different from those for nicardipine.

Heterogeneity of monoclonal antibody distribution and radiation dose in tumors: a modeling analysis

For successful use of monoclonal antibodies and their conjugates for diagnosis and therapy, it is helpful to understand both macroscopic and microscopic aspects of antibody distribution. Antibody distribution in a tumor is simulated by splicing together information on global pharmacokinetics, transport across the capillary wall, diffusive penetration through the tumor interstitial space, and antigen-antibody interaction. One interesting implication of this simulation is a microscopic dosimetry for radioimmunotherapy. The information of microscopic radioconjugate distribution will enable us to calculate absorbed dose in a tumor at the microscopic scale. The first step is to simulate the spatial antibody concentration profile in a tumor as a function of time after intravenous (bolus) injection, using reasonable values for the parameters involved. The second step is to calculate, also as a function of time, the absorbed radiation dose distribution resulting from each concentration profile. Parameter values for IgG pharmacology and a radiation point source function for I-131 are used to explore the effect of affinity on the antibody distribution and consequent absorbed dose in the tumor. The geometry simulated corresponds to a spherical nodule of densely packed tumor cells. Absorbed doses are calculated for radiation from a single nodule and for a cubic lattice of such nodules. This modeling analysis demonstrates that 1) antigen-antibody binding in tumors can retard antibody percolation; 2) high antibody affinity at a given dose tends to decrease antibody percolation and result in a heterogeneous distribution; 3) heterogeneous antibody distribution results in heterogeneous absorbed dose. This is more apparent in the case of radiation from a single nodule or small tumors. PERC and PERC-RAD, the computer program packages developed for these analyses, provide a convenient and flexible way to assess the impact of macroscopic and microscopic parameters on the distribution of immunoconjugates (PERC) and the consequent absorbed radiation dose in tumors (PERC-RAD). This mathematical model and the general principles developed here can be applied as well as to other biological ligands and beta-emitters.

Steady-state kinetics of autoxidation of NAD(P)H initiated by hydroperoxyl radical, the acid form of superoxide anion radical

Rates of autoxidation of NAD(P)H initiated by hydroperoxyl radical, the acid form of superoxide anion radical which was generated by xanthine/xanthine oxidase, followed a typical autoxidation kinetic equation. Second-order rate constants for the reactions of NADPH and NADH with hydroperoxyl radical were found to be 9.82 +/- 0.13 x 10(4) M-1s-1 and 9.26 +/- 0.58 x 10(4) M-1s-1 at 25 degrees C, respectively. Rates of the reactions between NAD(P)H and superoxide to give degraded products other than NAD(P)+ were also investigated.

Antagonism by reactive blue 2 but not by brilliant blue G of extracellular ATP-evoked responses in PC12 phaeochromocytoma cells

1. The effects of reactive blue 2 and brilliant blue G, which have been shown to block extracellular ATP-evoked responses, were investigated to discover whether these compounds act as P2-purinoceptor antagonists in PC12 phaeochromocytoma cells. 2. Reactive blue 2 (10 to 100 microM) suppressed the ATP-stimulated dopamine secretion from PC12 cells in a dose-dependent manner. The concentration-response curve for ATP was shifted to the right and the maximal response was decreased by reactive blue (30 and 100 microM). Brilliant blue G (up to 100 microM) did not significantly affect the secretion. 3. Reactive blue 2 (10 to 100 microM) suppressed the ATP-activated inward current recorded from the voltage-clamped cells in a concentration-dependent manner. Brilliant blue G (up to 100 microM) did not affect the current. 4. The results suggest that reactive blue 2 but not brilliant blue G is a P2-purinoceptor antagonist in PC12 cells. The purinoceptors in these cells may be the same type as those involved in ATP-evoked smooth muscle relaxation, judging from the antagonism by reactive blue 2.