Effect of Vesicle Size on the Cytolysis of Cell-Penetrating Peptides (CPPs)

A specific series of peptides, called a cell-penetrating peptide (CPP), is known to be free to directly permeate through cell membranes into the cytosol (cytolysis); hence, this CPP would be a potent carrier for a drug delivery system (DDS). Previously, we proposed the mechanism of cytolysis as a temporal and local phase transfer of membrane lipid caused by positive membrane curvature generation. Moreover, we showed how to control the CPP cytolysis. Here, we investigate the phospholipid vesicle's size effect on CPP cytolysis because this is the most straightforward way to control membrane curvature. Contrary to our expectation, we found that the smaller the vesicle diameter (meaning a higher membrane curvature), the more cytolysis was suppressed. Such controversial findings led us to seek the reason for the unexpected results, and we ended up finding out that the mobility of membrane lipids as a liquid crystal is the key to cytolysis. As a result, we could explain the cause of cytolysis suppression by reducing the vesicle size (because of the restriction of lipid mobility); osmotic pressure reduction to enhance positive curvature generation works as long as the membrane is mobile enough to modulate the local structure. Taking all the revealed vital factors and their effects as a tool, we will further explore how to control CPP cytolysis for developing a DDS system combined with appropriate cargo selection to be tagged with CPPs.

4-Phenylbutyric acid protects against neuronal cell death by primarily acting as a chemical chaperone rather than histone deacetylase inhibitor

This letter describes the mechanism behind the protective effect of 4-phenylbutyric acid (4-PBA) against endoplasmic reticulum (ER) stress-induced neuronal cell death using three simple 4-(p-substituted phenyl) butyric acids (4-PBA derivatives). Their relative human histone deacetylase (HDAC) inhibitory activities were consistent with a structural model of their binding to HDAC7, and their ability to suppress neuronal cell death and activity of chemical chaperone in vitro. These data suggest that 4-PBA protects against neuronal cell death mediated by the chemical chaperone activity rather than by inhibition of histone deacetylase.

Compensating Enthalpic and Entropic Changes Hinder Binding Affinity Optimization

A common strategy to improve the potency of drug candidates is to introduce chemical functionalities, like hydrogen bond donors or acceptors, at positions where they are able to establish strong interactions with the target. However, it is often observed that the added functionalities do not necessarily improve potency even if they form strong hydrogen bonds. Here, we explore the thermodynamic and structural basis for those observations. KNI-10033 is a potent experimental HIV-1 protease inhibitor with picomolar affinity against the wild-type enzyme (K(d) = 13 pm). The potency of the inhibitor is the result of favorable enthalpic (DeltaH = -8.2 kcal/mol) and entropic (-TDeltaS = -6.7 kcal/mol) interactions. The replacement of the thioether group in KNI-10033 by a sulfonyl group (KNI-10075) results in a strong hydrogen bond with the amide of Asp 30B of the HIV-1 protease. This additional hydrogen bond improves the binding enthalpy by 3.9 kcal/mol; however, the enthalpy gain is completely compensated by an entropy loss, resulting in no affinity change. Crystallographic and thermodynamic analysis of the inhibitor/protease complexes indicates that the entropy losses are due to a combination of conformational and solvation effects. These results provide a set of practical guidelines aimed at overcoming enthalpy/entropy compensation and improve binding potency.

Adaptive inhibitors of the HIV-1 protease

A significant obstacle to the efficacy of drugs directed against viral targets is the presence of amino acid polymorphisms in the targeted molecules. Amino acid polymorphisms may occur naturally due to the existence of variations within and between viral strains or as the result of mutations associated with drug resistance. An ideal drug will be one that is extremely effective against a primary target and maintains its effectiveness against the most important variations of the target molecule. A drug that simultaneously inhibits different variants of the target will lead to a faster suppression of the virus, retard the appearance of drug-resistant mutants and provide more efficacious and, in the long range, more affordable therapies. Drug molecules with the ability to inhibit several variants of a target with high affinity have been termed adaptive drugs (Nat. Biotechnol. 20 (2002) 15; Biochemistry 42 (2003) 8459; J. Cell. Biochem. S37 (2001) 82). Current drug design paradigms are predicated upon the lock-and-key hypothesis, which emphasizes shape complementarity as a way to attain specificity and improved binding affinity. Shape complementarity is accomplished by the introduction of conformational constraints in the drug molecule. While highly constrained molecules do well against a unique target, they lack the ability to adapt to target variations like those originating from naturally occurring polymorphisms or drug-resistant mutations. Targeting an array of closely related targets rather than a single one while still maintaining selectivity, requires a different approach. A plausible strategy for designing high affinity adaptive inhibitors is to engineer their most critical interactions (for affinity and specificity) with conserved regions of the target while allowing for adaptability through the introduction of flexible asymmetric functionalities in places facing variable regions of the target. The fundamental thermodynamics and structural principles associated with this approach are discussed in this chapter.

Thermodynamic rules for the design of high affinity HIV-1 protease inhibitors with adaptability to mutations and high selectivity towards unwanted targets

Protease inhibitors are key components in the chemotherapy of HIV-1 infection. However, the long term efficacy of antiretroviral therapies is hampered by issues of patient compliance often associated with the presence of severe side effects, and above all by the appearance of drug resistance. The development of new protease inhibitors with high potency, low susceptibility to mutations and minimal affinity for unwanted targets is an urgent goal. The engineering of these adaptive inhibitors requires identification of the critical determinants of affinity, adaptability, and selectivity. Analysis of the binding database for existing clinical and experimental inhibitors has allowed us to address the following questions in a quantitative fashion: (1) Is there an optimal binding affinity? Or, are the highest affinity inhibitors necessarily the best inhibitors? (2) What is the dependence of optimal affinity on adaptability and selectivity? (3) What are the determinants of adaptability to mutations associated with drug resistance? (4) How selectivity against unwanted targets can be improved? It is shown that the optimal affinity is a function of the effective target concentration and the desired adaptability and selectivity factors. Furthermore, knowledge of the enthalpic and entropic contributions to the binding affinity to the wild type provides a way of anticipating the response of an inhibitor to mutations associated with drug resistance, and therefore, a valuable guideline for optimization.

Multidrug resistance to HIV-1 protease inhibition requires cooperative coupling between distal mutations

The appearance of viral strains that are resistant to protease inhibitors is one of the most serious problems in the chemotherapy of HIV-1/AIDS. The most pervasive drug-resistant mutants are those that affect all inhibitors in clinical use. In this paper, we have characterized a multiple-drug-resistant mutant of the HIV-1 protease that affects indinavir, nelfinavir, saquinavir, ritonavir, amprenavir, and lopinavir. This mutant (MDR-HM) contains six amino acid mutations (L10I/M46I/I54V/V82A/I84V/L90M) located within and outside the active site of the enzyme. Microcalorimetric and enzyme kinetic measurements indicate that this mutant lowers the affinity of all inhibitors by 2-3 orders of magnitude. By comparison, the multiiple-drug-resistant mutant only increased the K(m) of the substrate by a factor of 2, indicating that the substrate is able to adapt to the changes caused by the mutations and maintain its binding affinity. To understand the origin of resistance, three submutants containing mutations in specific regions were also studied, i.e., the active site (V82A/I84V), flap region (M46I/I54V), and dimerization region (L10I/L90M). None of these sets of mutations by themselves lowered the affinity of inhibitors by more than 1 order of magnitude, and additionally, the sum of the effects of each set of mutations did not add up to the overall effect, indicating the presence of cooperative effects. A mutant containing only the four active site mutations (V82A/I84V/M46I/I54V) only showed a small cooperative effect, suggesting that the mutations at the dimer interface (L10I/L90M) play a major role in eliciting a cooperative response. These studies demonstrate that cooperative interactions contribute an average of 1.2 +/- 0.7 kcal/mol to the overall resistance, most of the cooperative effect (0.8 +/- 0.7 kcal/mol) being mediated by the mutations at the dimerization interface. Not all inhibitors in clinical use are affected the same by long-range cooperative interactions between mutations. These interactions can amplify the effects of individual mutations by factors ranging between 2 and 40 depending on the inhibitor. Dissection of the energetics of drug resistance into enthalpic and entropic components provides a quantitative account of the inhibitor response and a set of thermodynamic guidelines for the design of inhibitors with a lower susceptibility to this type of mutations.

Structural and Thermodynamic Basis of Resistance to HIV-1 Protease Inhibition: Implications for Inhibitor Design

One of the most serious side effects associated with the therapy of HIV-1 infection is the appearance of viral strains that exhibit resistance to protease inhibitors. At the molecular level, resistance to protease inhibition predominantly takes the form of mutations within the protease molecule that preferentially lower the affinity of protease inhibitors with respect to protease substrates, while still maintaining a viable catalytic activity. Mutations associated with drug resistance occur within the active site cavity as well as distal sites. Active site mutations affect directly inhibitor/protease interactions while non-active site mutations affect inhibitor binding through long range cooperative perturbations. The effects of mutations associated with drug resistance are compounded by the presence of naturally occurring polymorphisms, especially those observed in non-B subtypes of HIV-1. The binding thermodynamics of all clinical inhibitors against the wild type protease, drug resistant mutations and non-B subtype HIV-1 proteases has been determined by high sensitivity isothermal titration calorimetry. In conjunction with structural information, these data have provided a precise characterization of the binding mechanism of different inhibitors and their response to mutations. Inhibitors that exhibit extremely high affinity and low susceptibility to the effects of mutations share common features and binding determinants even if they belong to different chemical scaffolds. These binding determinants define a set of rules and constraints for the design of better HIV-1 protease inhibitors.

Overcoming drug resistance in HIV-1 chemotherapy: the binding thermodynamics of Amprenavir and TMC-126 to wild-type and drug-resistant mutants of the HIV-1 protease

Amprenavir is one of six protease inhibitors presently approved for clinical use in the therapeutic treatment of AIDS. Biochemical and clinical studies have shown that, unlike other inhibitors, Amprenavir is severely affected by the protease mutation I50V, located in the flap region of the enzyme. TMC-126 is a second-generation inhibitor, chemically related to Amprenavir, with a reported extremely low susceptibility to existing resistant mutations including I50V. In this paper, we have studied the thermodynamic and molecular origin of the response of these two inhibitors to the I50V mutation and the double active-site mutation V82F/I84V that affects all existing clinical inhibitors. Amprenavir binds to the wild-type HIV-1 protease with high affinity (5.0 x 10(9) M(-1) or 200 pM) in a process equally favored by enthalpic and entropic contributions. The mutations I50V and V82F/I84V lower the binding affinity of Amprenavir by a factor of 147 and 104, respectively. TMC-126, on the other hand, binds to the wild-type protease with extremely high binding affinity (2.6 x 10(11) M(-1) or 3.9 pM) in a process in which enthalpic contributions overpower entropic contributions by almost a factor of 4. The mutations I50V and V82F/I84V lower the binding affinity of TMC-126 by only a factor of 16 and 11, respectively, indicating that the binding affinity of TMC-126 to the drug-resistant mutants is still higher than the affinity of Amprenavir to the wild-type protease. Analysis of the data for TMC-126 and KNI-764, another second-generation inhibitor, indicates that their low susceptibility to mutations is caused by their ability to compensate for the loss of interactions with the mutated target by a more favorable entropy of binding.

Quantitative structure-activity relationship study of N-(3-oxo-3,4-dihydro-2H-benzo[1,4]thiazine-6-carbonyl)guanidines as potent Na/H exchange inhibitors

We have previously reported that N-(4-isopropyl-2,2-dimethyl-3-oxo-3,4-dihydro-2H-benzo[1,4]oxazine-6-car bonyl)guanidine (4b) methanesulfonate salt (KB-R9032) is a potent and highly water-soluble Na/H exchange inhibitor. In a series of studies on Na/H exchange inhibitors, we designed and synthesized N-(3-oxo-3,4-dihydro-2H-benzo[1,4]thiazine-6-carbonyl)guanidines (5) as more potent inhibitors with high water-solubility. The design strategy for 5 was based on a quantitative structure-activity relationship (QSAR) study, involving the proportional relationship between the biological activity and hydrophobicity of the ring structure of compounds 4. As expected, compounds 5 showed more potent activity than 4. It was found by using the QSAR analysis that 5 were about five-fold more potent than 4. The increase in potency of compounds 5 well agreed with our previous QSAR analysis result. The most potent derivative was the methanesulfonate salt 5d of the 4-isopropyl derivative (IC50=0.0091 microM). And in addition to the in vitro study, 5d showed significant protective activity against a rat acute myocardial infraction model.

Synthesis and quantitative structure-activity relationships of N-(3-oxo-3,4-dihydro-2H-benzo[1,4]oxazine-6-carbonyl)guanidines as Na/H exchange inhibitors

N-(3-Oxo-3,4-dihydro-2H-benzo[1,4]oxazine-6-carbonyl)guanidines 4 were prepared and tested for Na/H exchange inhibitory activities in order to clarify the structure-activity relationship (SAR). Quantitative SAR (QSAR) analysis of 6-carbonylguanidines 4 indicated that the length of the 4-substituent was parabolically related to activity and that the calculated optimum 4-substituents were propyl, ethyl and isopropyl groups. This SAR was similar to the SAR of the 2- and 4-substituents of 7-carbonylguanidine derivatives 3, although the position relative to the essential guanidinocarbonyl group was different. Larger 2-substituents, such as a phenyl group were unfavorable. The most potent derivative in this series was N-(4-isopropyl-2,2-dimethyl-3-oxo-3,4-dihydro- 2H-benzo[1,4]oxazine-6-carbonyl)guanidine 4 g, with an IC50 value of 0.12 microM. The methanesulfonate salt (KB-R9032) of 4g had excellent water-solubility and showed anti-arrhythmia activity against a rat acute myocardial infarction model. KB-R9032 was selected for further investigation as a therapy for ischemia-reperfusion induced injury.

Design, synthesis and quantitative structure-activity relationship study of N-(3-oxo-3,4-dihydro-2H-benzo[1,4]oxazine-7-carbonyl)guanidine derivatives as potent Na/H exchange inhibitors

Inhibition of the Na/H exchanger is a promising approach for treating ischemia-reperfusion injury, but no clinical agent is yet available. Recently, we established the structural requirements for potent inhibitors of the Na/H exchanger. In the present work, we designed N-(3-oxo-3,4-dihydro-2H-benzo[1,4]oxazine-7-carbonyl)guanidine 3a as a new lead compound for potent inhibitors with good water-solubility, based on the previous information. During the structural optimization, care was taken to keep the hydrophobicity (clogP) in the range of about 1.5-2.0, which is considered optimum for good bioavailability. Various derivatives of 3a were synthesized and the quantitative structure-activity relationship (QSAR) was studied. The QSAR result indicated that the lengths of the substituents at the 2- and the 4-positions of the 2H-benzo[1,4]oxazine ring are parabolically related to activity. The most potent compounds were (R) and/or (S)-N-(2-ethyl-4-isopropyl(or ethyl)-3-oxo-3,4-dihydro-2H-benzo[1,4]oxazine-7-carbonyl)guanidines 3q-t with IC50 values of 0.036-0.073 microM. The water-solubility of the hydrochlorides and methanesulfonates is 3-5 mg/ml, which is sufficient for therapeutic use.

Structural requirements for potential Na/H exchange inhibitors obtained from quantitative structure-activity relationships of monocyclic and bicyclic aroylguanidines

The quantitative structure-activity relationship (QSAR) of N-(3-amino-6-chloro-5-ethylisopropylaminopyrazine-4-carbonyl) guanidine (EIPA) 1ac and its derivatives as Na/H exchange inhibitors was analyzed using th steric parameters and an indicator variable. The results indicated that bicyclic aroylguanidines might have Na/H exchange inhibitory activity. Therefore, various bicyclic aroylguanidines were synthesized and tested for Na/H exchange inhibitory activity. The QSAR study of the bicyclic aroylguanidines showed that hydrophobic bicyclic rings seemed to be preferable for potent activity. The hydrophobicity of the aroyl ring moiety was thought to be particularly important. Thus, the QSAR of EIPA and its derivatives was re-analyzed using hydrophobicity and steric parameters. The results indicated that high hydrophobicity of the pseudo-ring moiety and a substituent of appropriate length at the position corresponding to the 5-position of the naphthalene ring enhance the activity. As expected from the results, 5-bromo-2-naphthoylguanidine 3b and 5-methoxy-2-naphthoylguanidine 3c exhibited strong activity. These findings will be helpful to design new, potent Na/H exchange inhibitors.

Physiological correlation between glycyrrhizin, glycyrrhizin-binding lipoxygenase and casein kinase II

By means of glycyrrhizin (GL)-affinity column chromatography, a GL-binding lipoxygenase (gbLOX) was selectively purified from the partially purified soybean LOX-1 fraction. Polypeptide analysis of the purified gbLOX by SDS-PAGE detected two distinct polypeptides (p96 and p94), which were identical to LOX-3 as determined by their partial N-terminal amino acid sequences. Moreover, it was found that (i) phosphorylation of gpLOX by casein kinase II (CK-II) is significantly stimulated by 3 microM GL, but inhibited by 30 microM GL or 10 microM oGA; and (ii) gbLOX activity is enhanced when the enzyme is phosphorylated by CK-II in the presence of 3 microM GL. These results suggest that (i) CK-II is a kinase responsible for the activation of gbLOX through its specific phosphorylation; and (ii) GL is one of the regulatory substances for specific phosphorylation of gbLOX (LOX-3) by CK-II in plant cells.

Design and syntheses of a series of novel serotonin3 antagonists

From a structural comparison study between serotonin and serotonin3 (5-HT3) antagonists using a two-dimensional grid template composed of regular hexagons, we deduced structural modification patterns from agonists to antagonists, and designed new 5-HT3 antagonist prototypes. Among them, 2-(4-methyl-1-piperazinyl)-1-butylbenzimidazole (6) was identified as a lead compound which has potent 5-HT3 antagonistic activity comparable to that of granisetron. Using a quantitative structure-activity relationships method, we optimized the structure of 6 and selected 6-amino-5-chloro-1-isopropyl-2-(4-methyl-1-piperazinyl)benzimidazole dimaleate (69, KB-6933), one of the most potent and long-acting 5-HT3 antagonists, as a candidate drug.

[Structure-activity relationship of flavonoids in suppressing rat liver lipid peroxidation]

145 flavonoids were studied for their inhibitory effects on the iron-induced lipid peroxidation in mitochondria obtained from rat livers. Of these compounds tested, 30, 57, 59, 67, 70, 72, 77, 102 and 110 (ED50 < or = 0.5 nmol/mg prot) showed distinctly more potent inhibitory activity than baicalein (ED50 < or = 5 nmol/mg prot) and 59 and 72 (ED50 < or = 0.05 nmol/mg prot) exhibited the most potent activity. In order to elucidate the relationships between substituents on the flavonoid skeleton and the biological activity, the quantitative structure-activity relationships (QSAR) were analyzed by the adaptive least-squares (ALS) method for 142 flavonoids. The analysis has shown that the presence of the 1,4- and 1,2-hydroquinone in A-ring and/or B-ring of flavonoids and hydrophobicity of the molecule are responsible for the in vitro inhibitory activity.

Structural modification patterns from agonists to antagonists and their application to drug design--a new serotonin (5-HT3) antagonist series

Structural variations from agonists to their selective antagonists seemed to follow certain patterns. To analyze the variation patterns in the structural modification processes in past examples as well as to utilize the "common" variation patterns as possible principles to design new selective antagonistic drugs, the structures of agonists and their antagonists were superimposed on a two-dimensional grid template composed of regular hexagons and the topological similarities and dissimilarities of substructural elements between agonists and antagonists were examined. Between several pairs of neurotransmitter amines and their "selective" antagonists, similar patterns were disclosed in their structural modification processes. The generalized structural modification patterns were successfully applied as guiding principles to design and identify a new prototype structure of the 5-HT3 antagonist. The prototype structure was optimized by use of QSAR procedures leading to a compound which shows a potent antiemetic activity as well as a powerful gastrointestinal-motility modulation.

Effects of baicalein and alpha-tocopherol on lipid peroxidation, free radical scavenging activity and 12-O-tetradecanoylphorbol acetate-induced ear edema

The effects of baicalein, a flavonoid, and alpha-tocopherol (vitamin E) on lipid peroxidation in rat forebrain homogenates, on free radical scavenging action against diphenyl-p-picrylhydrazyl (DPPH), and on 12-O-tetradecanoylphorbol acetate (TPA)-induced ear edema in mice were studied. Baicalein inhibited lipid peroxidation in forebrain homogenates, DPPH-induced free radical and TPA-induced ear edema as potently as did quercetin and nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, and more potently than BW755C, a mixed cyclooxygenase and lipoxygenase inhibitor. Lipid peroxidation in forebrain homogenates, DPPH-induced free radical and TPA-induced ear edema were also inhibited by alpha-tocopherol. Flavone showed no reaction. These results suggest that lipid peroxidation may play an important role in the pathogenesis of TPA-induced ear edema in mice.

Catecholamine responses to histamine infusion in man

To evaluate the effects of histamine-induced hypotension on plasma catecholamine levels, eight normal men, aged 20 to 40 years, were infused with incremental doses of histamine starting at 0.2 microgram/kg/min at a 30 degree tilt position with monitoring of blood pressure (BP) and heart rate. Histamine dosage was increased every 5 minutes by 0.1 to 0.2 microgram/kg/min until mean BP fell greater than 15 mm Hg or a dosage of 1.6 micrograms/kg/min was reached. Plasma catecholamine samples were taken between the fourth and fifth minute of each histamine dosage. Identical measurements were made during nitroglycerin-induced hypotension in these subjects. Histamine produced threefold greater increases in heart rate and plasma norepinephrine (NE) levels than did nitroglycerin for comparable decreases in BP. Although NE levels increased twofold to fivefold from baseline with histamine infusion, epinephrine levels increased minimally at the highest doses or not at all. Our data demonstrate that histamine selectively releases NE from adrenergic nerve terminals without significant adrenal catecholamine release. We suggest that neural NE release plays an important role in the cardiac effects of histamine.

Potential nootropic agents, 4-alkoxy-2-(1-piperazinyl)quinazoline derivatives

A series of 4-alkoxy-2-(1-piperazinyl)quinazoline derivatives was synthesized and evaluated for its ability to reverse a scopolamine-induced learned impairment in a one-trial passive avoidance task (antiamnestic activity). 2-(4-Allyl-1-piperazinyl)-4-pentyloxyquinazoline (4) showed more potent antiamnestic activity than such reference compounds as aniracetam, idebenone and bifemelane at a wide dose range (1-30 mg/kg]. Compound 4 also exhibited potent anticonvulsive and antihypoxic activities, and was selected as the most promising nootropic candidate agent.

Selective effect of KB-2796, a new calcium entry blocker, on cerebral circulation: a comparative study of the effects of calcium entry blockers on cerebral and peripheral arterial blood flows

The effects of a new calcium entry blocker, KB-2796, on cerebral and peripheral circulation were compared with those of four other calcium entry blockers (flunarizine, cinnarizine, nicardipine, and diltiazem) and also papaverine in anesthetized dogs. KB-2796 increased the vertebral blood flow to the same extent as the other drugs. KB-2796 and the other drugs increased the coronary blood flow, although the effect of KB-2796 was obviously weaker than that of the other drugs. The dose of KB-2796 producing a 30% increase in coronary blood flow was about 20 times higher than that producing an equivalent increase in vertebral blood flow. KB-2796 and the other calcium entry blockers caused a moderate increase in both femoral and common carotid blood flow. The renal artery showed a biphasic response to all drugs, which consisted of an initial decrease and a subsequent increase in the flow. From these results, it is suggested that KB-2796 is a new type of calcium entry blocker that selectively affects the cerebral circulation. It is also concluded that calcium entry blockers have a different spectrum of vasodilatory action on coronary and cerebral vascular beds and that a selective coronary vasodilatory action is not a common feature among all calcium entry blockers.

Novel 4-substituted 2-piperazinylquinazolines as potent anticonvulsive and antihypoxic agents

Several types of quinazoline derivatives were prepared and examined for anticonvulsive and antihypoxic activities. Many compounds showed potent anticonvulsive activity, and their anticonvulsive profile is similar to that of phenytoin. The analysis of quantitative structure-activity relationships indicated that the anticonvulsive activity was parabolically related to the lipophilicity of the compounds. Most of the 4-alkoxyquinazolines showed potent anticonvulsive and antihypoxic activities. It is confirmed that there is a good correlation between the potencies of these activities.

Retrograde thrombosis of feeding arteries after removal of arteriovenous malformations

Five cases of retrograde thrombosis of former feeding arteries after removal of an arteriovenous malformation (AVM) are reported. The clinical features of these patients were studied and compared to those of 71 patients without this complication. The following characteristics were found to correlate with retrograde thrombosis: 1) advancing age of the patient; 2) large AVM size; and 3) markedly dilated and elongated feeders. It is suggested that the slow flow in the former feeding arteries that was observed immediately after AVM removal and pathological changes in these vessels due to long-standing hemodynamic stresses contributed to the development of retrograde thrombosis. Neurological manifestations related to retrograde thrombosis were noted in three of the five cases. Although infrequent, this complication should be considered as a serious possibility following removal of an AVM.

Novel 4-phenoxy-2-(1-piperazinyl)quinazolines as potent anticonvulsive and antihypoxic agents

A series of 4-phenoxy-2-(1-piperazinyl)quinazolines was synthesized and examined for anticonvulsive and antihypoxic activities. Many of the compounds exhibited potent anticonvulsive activity comparable to that of carbamazepine or phenytoin. Among them, 4-phenoxy-2-(4-propyl-1-piperazinyl)quinazoline (5w) was selected as the most promising candidate antiepileptic drug with few side effects. It seemed that potent anticonvulsive activity was a prerequisite for potent antihypoxic activity.

Indomethacin enhances histamine-induced pulmonary hemodynamic changes

To determine the role of prostaglandins in porcine pulmonary hemodynamic changes caused by histamine, we compared responses to intravenous histamine with and without pre-treatment with the cyclo-oxygenase inhibitor, indomethacin. In anesthetized pigs, pulmonary artery pressure (Ppa), pulmonary arterial wedge pressure (Ppaw), left ventricular end diastolic pressure (Plved) and cardiac output (Q) were measured repeatedly for 30 minutes, following a 1 ml intrajugular injection of histamine 0.6 microM/kg (n = 6), the identical histamine dose after pre-treatment with indomethacin 5 mg/kg (n = 7), or normal saline (n = 5). Pulmonary arterial resistance (Ra) and pulmonary venous resistance (Rv) were calculated as (Ppa-Ppaw)/Q and (Ppaw-Plved)/Q respectively. Indomethacin pre-treatment caused 2-fold greater increases in Ra and Rv with histamine and more prolonged changes. We conclude that inhibition of a vasodilatory prostaglandin released from pulmonary endothelial cells results in unopposed pulmonary vasoconstriction, thereby augmenting pulmonary resistance changes due to histamine.

Benzylpiperazine derivatives. XI. Synthesis of compounds related to the metabolites of 1-[bis(4-fluorophenyl)methyl]-4-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride (KB-2796)

The metabolites of 1-[bis(4-fluorophenyl)methyl]-4-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride (KB-2796, 1), a cerebral vasodilator, and related compounds were synthesized to confirm the proposed structures. The structures of the metabolites (3-5) in rats were identified by means of synthesis of the authentic compounds.

Bioisosteric transformation of H1-antihistaminic benzimidazole derivatives

With the aim of obtaining new H1-antihistaminic agents, transformations of previously reported antihistaminic benzimidazoles were performed on the basis of the concept of bioisosterism. Among the compounds prepared, imidazo[4,5-b]pyridine (8) and 4(3H)-quinazolinone (11) exhibited significant H1-antihistaminic activity.

Quantitative structure-activity relationships of H1-antihistaminic benzimidazole derivatives

The quantitative structure-activity relationships (QSAR) of 2-(4-substituted-1-piperazinyl)benzimidazole derivatives for antihistaminic activity were examined. Taking into consideration the specific conformations of some derivatives, a significant correlation was obtained using Verloop's STERIMOL parameters B3 and L of the substituent at the 1-position of the benzimidazole nucleus. The results indicated that the derivatives having a substituent with a small breadth and an appropriate length at the 1-position showed potent activity. From the results, a model of the binding site is proposed. The QSAR of side effects (anticholinergic activity and central nervous system depressive effect) were also examined and the results showed that a sterically small substituent at the 1-position was required to decrease side effects.

Syntheses of the metabolites of 1-(2-ethoxyethyl)-2-(hexahydro-4-methyl-1H-1,4-diazepin-1-yl)-1H benzimidazole difumarate (KG-2413) and related compounds

The metabolites of 1-(2-ethoxyethyl)-2-(hexahydro-4-methyl-1H-1,4-diazepin-1-yl)-1H-b enzimidazole difumarate (KG-2413), which has a potent H1-antihistaminic activity, were predicted on the basis of metabolic studies of related compounds and were synthesized to aid in identification of the actual metabolites and for examination of their antihistaminic activity. Among the twelve compounds prepared, nine compounds were actually found as the metabolites of KG-2413 in rat urine. The antihistaminic activities of these metabolites were found to be lower than that of KG-2413.

[Clinical significance of intracranial hemorrhage caused by cerebral arteriovenous malformations: with special reference to intraventricular hemorrhage]

Forty-two cases with intracranial hemorrhage caused by cerebral arteriovenous malformation (AVM), which was diagnosed by CT scan, were reviewed with regard to the clinical significance of intracranial hemorrhage, especially intraventricular hemorrhage (IVH). Twenty-one patients were defined as poor risk cases whose level of consciousness at admission was 100 to 300 according to the Japan Coma Scale, whereas the remaining 21 patients were defined as good risk cases. Surgical excision of AVM was undertaken in 35 out of the 42 cases. Urgent surgical removal of intracerebral hematoma and AVM within 24 hours following onset was undertaken in 11 cases. In 14 patients, urgent continuous ventricular drainage was carried out. The effects of the following factors on the level of consciousness at admission, and on the result of AVM treatment were investigated to clarify the clinical significance of intracranial hemorrhage; 1) cast formation of 3rd and/or 4th ventricle, 2) volume of intraventricular hematoma, 3) accompanying intracerebral hematoma and 4) acute hydrocephalus. It was confirmed that all these factors significantly contributed to the development of serious disturbance of consciousness in the acute stage following intracranial hemorrhage. For good risk cases, the rate of patients who showed a good recovery or only moderate disability according to the Glasgow Outcome Scale reached 91%, whereas for poor risk cases, it was only 43%. The presence of large intracerebral hematomas of more than 4 cm in diameter accompanied with IVH was significantly correlated with the result of AVM treatment. The presence or absence of cast formation of 3rd and/or 4th ventricle, volume of intraventricular hematoma and acute hydrocephalus were not significantly related to the result of AVM treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of KB-2796, a new calcium antagonist, and other diphenylpiperazines on [3H]nitrendipine binding

The effect of KB-2796, a new diphenylpiperazine calcium antagonist, on [3H]nitrendipine ([3H]NTD) binding was investigated in synaptosomal membranes prepared from the guinea pig cerebral cortex. KB-2796 inhibited [3H]NTD binding in a dose-dependent manner with an IC50 value of 86 nM. In this respect, KB-2796 was the most potent among the diphenylpiperazine derivatives tested. Saturation binding data indicated that this inhibition resulted from a decrease in the binding affinity without changes in the maximal number of binding sites. KB-2796, however, significantly increased the dissociation rate constant of [3H]NTD from radiolabeled membranes. This finding suggests that KB-2796 inhibits [3H]NTD binding by a negative heterotropic allosteric mechanism. Other diphenylpiperazines tested also showed similar inhibitory properties. Diphenylpiperazines may act at a site, which is different from the 1,4-dihydropyridine binding site, on the voltage-dependent calcium channel.

[A clinical study of severe cases of hemorrhagic cerebral arteriovenous malformations]

The clinical study was undertaken on 24 poor risk patients out of 69 cases with hemorrhagic cerebral arteriovenous malformations, AVMs, and the surgical problems of poor risk patients with the lesions were discussed. The 24 cases, 35%, out of 69 hemorrhagic AVMs cases showed disturbances of consciousness of 3 digits (100-300) according to the Japan Coma Scale at the time of admission. All cases of these poor risk patients were observed less than 24 hours after the onset of the symptoms. Fifteen of these 24 cases showed brainstem signs including anisocoria and/or decerebrate rigidity and/or respiratory arrest. Eighty-three per cent of 24 poor risk patients had serious neurological defects as a result of the first hemorrhage. Therefore, it was impossible to prevent serious state from occurring in poor risk patients. Of the 69 cases with hemorrhagic AVMs, 56 cases were operated upon. Although 90% out of 38 good risk patients whose level of consciousness was 0 to 30 according to the Japan Coma Scale showed good recovery, only 44% of 18 poor risk patients recovered well. It could not be said that the surgical treatment gave satisfactory results for the poor risk patients when compared with the surgical results of the good risk patients. In respect to the location of AVMs, all three poor risk patients with AVMs in the corpus callosum and the ventricles showed good recovery, whereas of the poor risk patients with AVMs in the cerebrum or the cerebellum, only 4 out of 9 cases (44%) and 1 out of 6 cases (17%) showed good recovery respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanical properties of porcine intralobar pulmonary arteries

The isobaric and isovolumetric properties of intrapulmonary arteries were evaluated by placing a highly compliant balloon inside arterial segments. The passive pressure-volume (P-V) curve was obtained by changing volume (0.004 ml/s) and measuring pressure. The isobaric active volume change (delta V) or isovolumetric active pressure change (delta P) generated by submaximal histamine was measured at four different transmural pressures (Ptm's) reached by balloon inflation. The maximal delta P = 11.2 +/- 0.6 cmH2O (mean +/- SE) was achieved at 30.8 +/- 1.2 cmH2O Ptm and maximal delta V = 0.20 +/- 0.02 ml at 16.7 +/- 1.7 cmH2O Ptm. The P-V relationships were similar when volume was increased after either isobaric or isovolumetric contraction. The calculated length-tension (L-T) relationship showed that the active tension curve was relatively flat and that the passive tension at the optimal length was 149 +/- 11% of maximal active tension. These data show that 1) a large elastic component operates in parallel with the smooth muscle in intralobar pulmonary arteries, and 2) the change in resistance associated with vascular expansion of the proximal arteries is independent of the type of contraction that occurs in the more distal arterial segments.

Serial changes in acute extradural hematoma size and associated changes in level of consciousness and intracranial pressure

The authors report the cases of 37 patients encountered during the past 4 years who exhibited acute extradural hematoma but were initially treated conservatively because no or only small hematomas were observed on admission. The frequency of hematoma enlargement, hematoma size, and changes in the level of consciousness and intracranial pressure (ICP) were examined in these patients. The hematomas enlarged in 24 (64.9%) of the 37 patients, and attained a maximum thickness of 25 mm or greater in 19 patients (51.3%). The level of consciousness could be closely observed during enlargement of the hematomas in 13 patients: the level remained unchanged in eight, deteriorated in two, and improved in three, indicating relative stability in the state of consciousness despite the marked changes in hematoma size. The patients whose hematoma enlarged after the initial examination included three who underwent initial CT examination 5 hours after the injury. In five patients enlargement of extradural hematomas was observed unexpectedly during conservative treatment under ICP monitoring. The ICP also remained stable in three patients until the follow-up examination, but showed a rapid increase in two after a period of stability. However, there was no difference in the final size of the hematomas between the patients showing an increase in ICP and those who did not. These findings suggest that extradural hematomas enlarge progressively at rates varying with the condition of the source of hemorrhage. Moreover, a period of stability in the level of consciousness, such as the lucid interval seen in patients with extradural hematoma, is considered to be a period during which compensatory mechanisms can maintain the stability of the intracranial condition during progressive enlargement of the hematoma.

Airway responsiveness to intravenous and inhaled acetylcholine in the guinea pig after cigarette smoke exposure

Exposure of conscious guinea pigs to cigarette smoke results in bronchial hyperresponsiveness. To examine the mechanisms involved, we measured airway responses to increasing doses of intravenous or inhaled acetylcholine in guinea pigs exposed to cigarette smoke (n = 20) or to air (n = 20). After exposure the guinea pigs were anesthetized, paralyzed, and studied in a pressure-sensitive body plethysmograph while ventilated through a tracheostomy. Two and 6 puffs of an aerosol of increasing concentrations (0.05 to 500 micrograms/ml) of acetylcholine were delivered via the tracheostomy. Intravenous acetylcholine was delivered in boluses of 0.1 ml of increasing concentrations (0.5 to 50,000 micrograms/ml) via a catheter in an external jugular vein. Pulmonary resistance (RL), dynamic compliance (Cdyn), and heart rate (HR) were measured at baseline (after aerosolized or intravenous saline) and after each dose of acetylcholine. The peak responses to both inhaled and intravenous acetylcholine were rapid in onset (less than 15 s), short-lived (3 to 4 breaths), and were noncumulative. The baseline RL, Cdyn, and HR were not different in the smoke and air exposure groups. In the intravenous acetylcholine group, there were no differences in RL, Cdyn, and HR responses between the air and smoke exposure groups. In the inhaled acetylcholine group, the dose-response curve was shifted to the left (p less than 0.05) and reached a higher maximal response (p less than 0.01) after smoke exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

A massive dose of vincristine

An esophageal cancer patient with bilateral lungs and neck lymph nodes metastases received 24 mg of vincristine instead of vinblastine because of the similarity between the two names, and survived multiorgan derangement. Serious states of central and peripheral neuropathy with muscle atrophy, gastrointestinal disorder, bone marrow suppression and mucocutaneous involvement were all encountered. Although hypotension and syndrome of inappropriate secretion of antidiuretic hormone (SIADH) were not observed as vincristine's side actions, toxicity to the myocardium, which has not been documented, was suggested in our case. These toxic impairments, however, subsided clinically within a month, except for paresthesia in the peripheral extremities. The effectiveness of the chemotherapy was remarkable against both the esophageal cancer and the metastatic lesions. No unintentional overdose of a drug, needless to say, should happen, and in order to minimize its possibility, it would be advisable for chemotherapy to be administered only by an experienced physician who is able to check the dose and concentration.

Comparative effects of leukotrienes on porcine pulmonary circulation in vitro and in vivo

The present study examined the effect of leukotrienes on porcine pulmonary vasculature both in vivo and in vitro. In vitro studies using isolated vascular strips demonstrated that pulmonary arterial smooth muscle contracted to leukotriene C4 (LTC4), whereas pulmonary vein smooth muscle did not. Pulmonary arterial contraction was due to both the direct action of LTC4 and secondarily generated thromboxane A2 (TxA2). In vivo, LTC4 injection caused a pronounced but transient increase in pulmonary arterial pressure and pulmonary arterial wedge pressure (Ppw), with a smaller effect on left ventricular end-diastolic pressure. Effects of LTD4 were smaller with comparable pressure changes at all three sites, suggesting a primary cardiac effect. Like LTC4, histamine caused a disproportionate increase in Ppw vs. left ventricular end-diastolic pressure. These observations suggest that LTC4 causes pulmonary venoconstriction in vivo despite its lack of effect on pulmonary vein smooth muscle in vitro. This discrepancy may be due to venoconstrictor effects of TxA2 generated from upstream pulmonary arterial vessels.

[New knowledge on the calcium pyrophosphate dihydrate (CPPD) crystal deposition disease in the cervical ligamentum flavum]

A case of 64-year-old Japanese woman with cervical radiculomyelopathy caused by the deposition of both calcium pyrophosphate dihydrate (CPPD) and hydroxyapatite crystals in the cervical ligamentum flavum is reported. The patient developed paresthesia in her both hands and gait disturbance in the previous six months. Neurological examination revealed generalized hyperreflexia and hypesthesia in the C7 region. Neuroradiologically, two nodular opacifications were shown in the C3-4 and C5-6 level. CT scan revealed linear and symmetrical calcifications in the C3-4 and nodular calcifications in the C5-6 level. En bloc laminectomy was performed and the patient was discharged from the hospital with improvements of neurological symptoms. Specimens of the spinal laminae and ligamenta flava were studied by light microscopy, scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (X-MA) on SEM, and an X-ray diffraction study was carried out on the crystals. The results showed A. CPPD crystal depositions throughout the ligamenta flava together with a minimal thickening of the ligaments. The deposition was seen in the midzone of the ligaments forming a plate-like distribution and forming lines in the cut surface, the latter coincided well with the CT finding at the C3-4 level. B. The nodule (7 X 6 X 6 mm in size) at the C5-6 level was composed of two crystals, CPPD and hydroxyapatite, the latter being encased by the former. The thickness of the CPPD layer was quite thin varying from 10 to 100 mu. Myelographically, the spinal cord was most severely compressed by the C5-6 nodule. C. Because of the absence of family histories and predisposing factors, the case was considered one of primary or idiopathic CPPD crystal deposition disease. The origin of the deposition of mixed crystals was discussed and it appeared likely that the central part of CPPD crystal deposition had transformed to hydroxyapatite at the C5-6 level. In the literature a considerable number of cases have been reported under the title, "Calcification of the Ligamentum Flavum", and some of them have been shown to have hydroxyapatite deposition. Considering the great similarities in clinical, radiological and histological findings between the so-called "calcification of the lig. fl." and CPPD crystal deposition disease, the present case was the first to clearly indicate that these two conditions belong to a single category, i.e. CPPD crystal deposition disease.(ABSTRACT TRUNCATED AT 400 WORDS)