Pharmacokinetic profiles of biphasic insulin aspart 30/70 and 70/30 in patients with Type 1 diabetes: a randomized double-blinded crossover study

AIMS

To compare pharmacokinetic characteristics of two biphasic insulin aspart (BIAsp) formulations: BIAsp30 and BIAsp70 (30% and 70%, respectively, of fast-acting insulin aspart) during 15 days of multiple dosing (thrice daily).

METHODS

A total of 22 patients with Type 1 diabetes (nine women, 13 men) aged 41.4 +/- 9.9 years (mean +/- sd) with a diabetes duration of 18.9 (2.3-40.3) years (median and range) completed the randomized, double-blinded, two-period crossover study. On day 1 and day 15 of each treatment period, 24-h serum insulin and glucose profiles were evaluated. Total area under the insulin aspart concentration-time curve (AUC(0-24 h)), AUC after dinner administration stratified into early (AUCdinner(0-6 h)) and intermediate-phase (AUCdinner(6-14 h)), maximum insulin concentration (Cmax), time to maximum insulin concentration (Tmax) after each meal were recorded.

RESULTS

On day 15 BIAsp70 was associated with a shorter Tmax, and more than 40% elevated Cmax. Comparing with BIAsp30, AUC(0-24 h) and AUCdinner(0-6 h) were increased by 25% and 28%, respectively, but AUCdinner (6-14 h) was markedly lower for BIAsp70 [BIAsp30/BIAsp70: 1.9; 95% CI (1.42, 2.55)]. Similar findings were also observed on day 1. The fasting or pre-meal serum insulin levels on day 15 tended to be higher with BIAsp30, but the differences were not statistically significant. CONCLUSIONS The pharmacokinetic properties of BIAsp30 and 70 remain constant during 2 weeks of daily administration in patients with Type 1 diabetes. In comparison with BIAsp30, the administration of BIAsp70 results in a shorter time to and larger maximum insulin aspart concentration. Furthermore, total and early post-dinner insulin AUC were greater, whereas late-phase insulin exposure was lower with BIAsp70.

Linker length in podophyllotoxin-acridine conjugates determines potency in vivo and in vitro as well as specificity against MDR cell lines

We have synthesized two podophyllotoxin-acridine conjugates-pACR6 and pACR8. In these compounds an 9-acridinyl moiety is beta linked to the C4 carbon of the four ring system in 4'-demethylepipodophyllotoxin (epiDPT) via eighter an N-6-aminohexanylamide linker (pACR6) or via an N-8-aminooctanylamide linker containing two more carbon atoms (pACR8). The acridine-linker moiety occupies the position where different glucoside moieties, dispensable for activity, are normally linked to epiDPT in the well known epipodophyllotoxins VP-16 and VM-26. As with VP-16 and VM-26, pACR6 and pACR8 show evidence of being topoisomerase II poisons as they stimulate topoisomerase II mediated DNA cleavage in vitro and induce DNA damage in vivo. This in vivo DNA damage, as well as pACR6/pACR8 mediated cytotoxicity, is antagonized by the catalytic topoisomerase II inhibitors ICRF-187 and aclarubicin, demonstrating that topoisomerase II is a functional biological target for these drugs. Despite their structural similarities, pACR6 was more potent than pACR8 in stimulating topoisomerase II mediated DNA cleavage in vitro as well as DNA damage in vivo and pACR6 was accordingly more cytotoxic towards various human and murine cell lines than pACR8. Further, marked cross-resistance to pACR6 was seen among a panel of multidrug-resistant (MDR) cell lines over-expressing the MDR1 (multidrug resistance protein 1) ABC drug transporter, while these cell lines remained sensitive towards pACR8. pACR8 was also capable of circumventing drug resistance among at-MDR (altered topoisomerase II MDR) cell lines not over-expressing drug transporters, while pACR6 was not. Two resistant cell lines, OC-NYH/pACR6 and OC-NYH/pACR8, were developed by exposure of small cell lung cancer (SCLC) OC-NYH cells to gradually increasing concentrations of pACR6 and pACR8, respectively. Here, OC-NYH/pACR6 cells were found to over-express MDR1 and, accordingly, displayed active transport of 3H-labeled vincristine, while OC-NYH/pACR8 cells did not, further suggesting that pACR6, but not pACR8, is a substrate for MDR1. Our results show that the spatial orientation of podophyllotoxin and acridine moieties in hybrid molecules determine target interaction as well as substrate specificity in active drug transport.

N-terminal and core-domain random mutations in human topoisomerase II alpha conferring bisdioxopiperazine resistance

Random mutagenesis of human topoisomerase II alpha cDNA followed by functional expression in yeast cells lacking endogenous topoisomerase II activity in the presence of ICRF-187, identified five functional mutations conferring cellular bisdioxopiperazine resistance. The mutations L169F, G551S, P592L, D645N, and T996L confer > 37, 37, 18, 14, and 19 fold resistance towards ICRF-187 in a 24 h clonogenic assay, respectively. Purified recombinant L169F protein is highly resistant towards catalytic inhibition by ICRF-187 in vitro while G551S, D645N, and T996L proteins are not. This demonstrates that cellular bisdioxopiperazine resistance can result from at least two classes of mutations in topoisomerase II; one class renders the protein non-responsive to bisdioxopiperazine compounds, while an other class does not appear to affect the catalytic sensitivity towards these drugs. In addition, our results indicate that different protein domains are involved in mediating the effect of bisdioxopiperazine compounds.

A novel mechanism of cell killing by anti-topoisomerase II bisdioxopiperazines

Bisdioxopiperazines are a unique class of topoisomerase II inhibitors that lock topoisomerase II at a point in the enzyme reaction cycle where the enzyme forms a closed clamp around DNA. We examined cell killing by ICRF-187 and ICRF-193 in yeast cells expressing human topoisomerase II alpha (htop-IIalpha). Expression of htop-IIalpha in yeast cells sensitizes them to both ICRF-187 and ICRF-193, compared with cells expressing yeast topoisomerase II. ICRF-193 is still able to exert growth inhibition in the presence of genes encoding both ICRF-193-resistant and ICRF-193-sensitive htop-IIalpha enzymes, indicating that sensitivity to bisdioxopiperazines is dominant. Killing by ICRF-193 occurs more rapidly, than the killing in yeast cells due to a temperature-sensitive yeast topoisomerase II incubated at the non-permissive temperature. These results are reminiscent of a top-II poison such as etoposide. However, the killing caused by ICRF-193 and ICRF-187 is not enhanced by mutations in the RAD52 pathway. The levels of drug-induced DNA cleavage observed with htop-IIalpha in vitro is insufficient to explain the sensitivity induced by this enzyme in yeast cells. Finally, arrest of cells in G(1) does not protect cells from ICRF-193 lethality, a result inconsistent with killing mechanisms due to catalytic inhibition of top-II or stabilization of a cleavable complex. We suggest that the observed pattern of cell killing is most consistent with a poisoning of htop-II by ICRF-193 by a novel mechanism. The accumulation of closed clamp conformations of htop-II induced by ICRF-193 that are trapped on DNA might interfere with transcription, or other DNA metabolic processes, resulting in cell death.

Human small cell lung cancer NYH cells selected for resistance to the bisdioxopiperazine topoisomerase II catalytic inhibitor ICRF-187 demonstrate a functional R162Q mutation in the Walker A consensus ATP binding domain of the alpha isoform

Bisdioxopiperazine drugs such as ICRF-187 are catalytic inhibitors of DNA topoisomerase II, with at least two effects on the enzyme: namely, locking it in a closed-clamp form and inhibiting its ATPase activity. This is in contrast to topoisomerase II poisons as etoposide and amsacrine (m-AMSA), which act by stabilizing enzyme-DNA-drug complexes at a stage in which the DNA gate strand is cleaved and the protein is covalently attached to DNA. Human small cell lung cancer NYH cells selected for resistance to ICRF-187 (NYH/187) showed a 25% increase in topoisomerase IIalpha level and no change in expression of the beta isoform. Sequencing of the entire topoisomerase IIalpha cDNA from NYH/187 cells demonstrated a homozygous G-->A point mutation at nucleotide 485, leading to a R162Q conversion in the Walker A consensus ATP binding site (residues 161-165 in the alpha isoform), this being the first drug-selected mutation described at this site. Western blotting after incubation with ICRF-187 showed no depletion of the alpha isoform in NYH/187 cells in contrast to wild-type (wt) cells, whereas equal depletion of the beta isoform was observed in the two sublines. Alkaline elution assay demonstrated a lack of inhibition of etoposide-induced DNA single-stranded breaks in NYH/187 cells, whereas this inhibition was readily apparent in NYH cells. Site-directed mutagenesis in human topoisomerase IIalpha introduced into a yeast Saccharomyces cerevisiae strain with a temperature-conditional yeast TOP2 mutant demonstrated that R162Q conferred resistance to the bisdioxopiperazines ICRF-187 and -193 but not to etoposide or m-AMSA. Both etoposide and m-AMSA induced more DNA cleavage with purified R162Q enzyme than with the wt. The R162Q enzyme has a 20-25% decreased catalytic capacity compared to the wt and was almost inactive at <0.25 mM ATP compared to the wt. Kinetoplast DNA decatenation by the R162Q enzyme at 1 mM ATP was not resistant to ICRF-187 compared to wt, whereas it was clearly less sensitive than wt to ICRF-187 at low ATP concentrations. This suggests that it is a shift in the equilibrium to an open-clamp state in the enzyme's catalytic cycle caused by a decreased ATP binding by the mutated enzyme that is responsible for bisdioxopiperazine resistance.

Neuroprotection by a novel compound, NS521

NS521 (1-(1-butyl)-4-(2-oxo-1-benzimidazolinyl)piperidine) belongs to a group of novel benzimidazolones, which exhibit neurotrophic-like activities. In vitro, NS521 rescued neuronal PC12 cells from death induced by serum and nerve growth factor deprivation. The survival effect of NS521 appeared to reflect a delay of the apoptotic process, because the extent of DNA fragmentation was attenuated transiently by NS521. NS521 did not preserve the neurites of the rescued cells, which, otherwise, appeared to be healthy and were able to regenerate when serum and nerve growth factor were added back to the culture. In vivo, NS521 provided significant protection against the delayed loss of hippocampal CA1 neurons in a gerbil model of transient global ischemia. A neuroprotective effect of NS521 in the peripheral nervous system also was observed in rats after transection of the sciatic nerve, where daily treatment with NS521 was found to inhibit retrograde degeneration of the transected nerve. The neuroprotective effect of NS521 is unlikely to be mediated through neurotrophin receptors, such as TrkA, because NS521 did not induce phosphorylation of the 44- and 42-kDa isoforms of mitogen-activated protein kinases (ERK1/2) in PC12 cells.

SPD 502: a water-soluble and in vivo long-lasting AMPA antagonist with neuroprotective activity

Accumulating preclinical data suggest that compounds that block the excitatory effect of glutamate on excitatory amino acid receptors may have neuroprotective effects and utility for the treatment of neurodegeneration after brain ischemia. In the present study, the in vitro and in vivo pharmacological properties of the novel glutamate antagonist SPD 502 [8-methyl-5(4-(N,N-dimethylsulfamoyl)phenyl)-6,7, 8,9,-tetrahydro-1H-pyrrolo[3,2-h]-isoquinoline-2, 3-dione-3-O-(4-hydroxybutyric acid-2-yl)oxime] are described. In binding studies, SPD 502 was shown to display selectivity for the [3H]alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-binding site (IC50 = 0.043 microM) compared with the [3H]kainate- (IC50 = 81 microM), [3H]cis-4-phosphonomethyl-2-piperidine carboxylic acid-(CGS 19755), and [3H]glycine-binding sites (IC50 > 30 microM) in rat cortical membranes. In an in vitro functional assay, SPD 502 blocked the AMPA-induced release of [3H]gamma-aminobutyric acid from cultured mouse cortical neurons in a competitive manner with an IC50 value of 0.23 microM. Furthermore, SPD 502 potently and selectively inhibited AMPA-induced currents in cortical neurons with an IC50 value of 0.15 microM. In in vivo electrophysiology, SPD 502 blocked AMPA-evoked spike activity in rat hippocampus after i.v. administration with an ED50 value of 6.1 mg/kg and with a duration of action of more than 1 h. Furthermore, SPD 502 increased the seizure threshold for electroshock-induced tonic seizures in mice at i.v doses of 40 mg/kg and higher. In the two-vessel occlusion model of transient forebrain ischemia in gerbils, SPD 502 (10 mg/kg bolus injection followed by a 10 mg/kg/h infusion for 2 h) resulted in a highly significant protection against the ischemia-induced damage in the hippocampal CA1 pyramidal neurons.

Ligands for the benzodiazepine binding site--a survey

Gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian Central Nervous System (CNS). GABA participates in the regulation of neuronal excitability through interaction with specific membrane proteins (the GABAA receptors). The binding of GABA to these postsynaptic receptors, results in an opening of a chloride channel integrated in the receptor which allows the entry of Cl- and consequently leads to hyperpolarization of the recipient cell. The action of GABA is allosterically modulated by a wide variety of chemical entities which interact with distinct binding sites at the GABAA receptor complex. One of the most thoroughly investigated modulatory site is the benzodiazepine binding site. The benzodiazepines constitute a well-known class of therapeutics displaying hypnotic, anxiolytic and anticonvulsant effects. Their usefulness, however, is limited by a broad range of side effects comprising sedation, ataxia, amnesia, alcohol and barbiturate potentiation, tolerance development and abuse potential. Consequently, there has been an intensive search for modulatory agents with an improved profile, and a diversity of chemical entities distinct from the benzodiazepines, but with GABA modulatory effects have been identified. The existence of endogenous ligands for the GABAA receptor complex beside GABA has often been described, but their role in the regulation of GABA action is still a matter of controversy. The progress of molecular biology during the last decade has contributed enormously to the understanding of benzodiazepine receptor pharmacology. A total of 14 GABAA receptor subunits have been cloned from mammalian brain and have been expressed/co-expressed in stable cell lines. These transfected cells constitute an important tool in the characterization of subtype selective ligands. In spite of the rapidly expanding knowledge of the molecular and pharmacological mechanisms involved in GABA/benzodiazepine related CNS disorders, the identification of clinically selective acting drugs is still to come.

MPTP-induced Parkinsonism in minipigs: A behavioral, biochemical, and histological study

Fourteen male Göttingen minipigs were used in this study. Nine were administered N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at a dosage of 1 mg/kg/day, SC, for 6 days, the last five pigs received saline injections for 6 days. All MPTP-treated animals developed Parkinson symptoms, i.e., muscle rigidity, hypokinesia, and impaired coordination within 5 days. The brain levels of dopamine (DA), and its major metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were determined in caudatum and putamen 2, 14, and 93 days (n = 3/time point) after the last drug administration. In eight of the MPTP-treated animals, striatal DA, DOPAC, and HVA concentrations were reduced from 50 to 95% compared to control animals at all time intervals. Animals with the lowest striatal DA concentrations showed the most severe signs of Parkinsonism. The number of cells in substantia nigra (SN) showed a decline only 3 months after MPTP treatment. The minipigs represent a nonprimate model of MPTP-induced parkinsonism syndromes lasting at least months.

In vivo and in vitro evaluation of AMPA receptor antagonists in rat hippocampal neurones and cultured mouse cortical neurones

The effects of four glutamate receptor antagonists on alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)- and N-methyl-D-aspartate (NMDA)-responses were evaluated using both in vitro and in vivo electrophysiological techniques: whole cell patch-clamp recordings from cultured mouse cortical neurones and microiontophoresis in the rat hippocampus. The compounds tested were NBQX (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline), GYKI 52466 (1-(4-amino-phenyl)-4-methyl-7,8-methyl-endioxyl-5H-2,3-benzodiaze pine), PNQX (pyrido[3, 4-f]quinoxaline-2,3-dione, 1,4,7,8,9,10-hexahydro-9-methyl-6-nitro-, methanesulfonate), NS377 (7-ethyl-5-phenyl-1,6,7,8-tetrahydro-1,7-diaza-as-indacene-2 ,3-dione), and MK-801 ((+)-5-methyl-10,11-dihydro-5H-dibenz(a,d)cycloheptene-5,10-imine hydrogen maleate). In vitro, the IC50 values (in microM) for inhibition of AMPA-evoked inward currents were approximately 0.4 for NBQX, approximately 7.5 for GYKI 52466, approximately 1 for PNQX and approximately 15 for NS377. PNQX and NS377 also inhibited NMDA-induced currents with IC50 values at approximately 5 and approximately 18 microM, respectively, while NBQX at 60 microM and GYKI 52466 at 100 microM had only weak effects. The ED50 values in micromol/kg i.v. for inhibition of AMPA-evoked hippocampal neuronal spike activity in vivo were approximately 32 for NBQX, approximately 19 for GYKI 52466, approximately 17 for PNQX and approximately 11 for NS377 with efficacy values (maximal inhibition) between 71% and 81%. The ED50 values (in [Lmol/kg i.v.) and efficacy values for inhibition of NMDA-evoked hippocampal neuronal spike activity were approximately 28 with an efficacy of 61% for NBQX, approximately 16 with 35% for PNQX and approximately 6 with 61% for NS377. GYKI 52466 did not significantly affect NMDA responses, whereas MK-801 showed NMDA specificity in vivo.

Chinese hamster ovary cells resistant to the topoisomerase II catalytic inhibitor ICRF-159: a Tyr49Phe mutation confers high-level resistance to bisdioxopiperazines

Anticancer drugs targeted to the nuclear enzyme DNA topoisomerase II are classified as poisons that lead to DNA breaks or catalytic inhibitors that appear to completely block enzyme activity. To examine the effects of the bisdioxopiperazine class of catalytic inhibitors to topoisomerase II, we investigated a Chinese hamster ovary (CHO) subline selected for resistance to ICRF-159 (CHO/159-1). Topoisomerase IIalpha content in CHO/159-1 cells was reduced by 40-50%, compared to wild-type CHO cells, whereas the beta isoform was increased by 10-20% in CHO/159-1 cells. However, the catalytic activity of topoisomerase II in nuclear extracts from CHO/159-1 cells was unchanged, as was its inhibition by the topoisomerase II poison etoposide (VP-16). No inhibition of topoisomerase II catalytic activity by ICRF-187 was seen in CHO/159-1 cells up to 500 microM, whereas inhibition was evident at 50 microM in wild-type CHO cells. VP-16-mediated DNA single-strand breaks and cytotoxicity were similar in the two sublines. ICRF-187 could abrogate these VP-16 effects in the wild-type line but had no effect in CHO/159-1 cells. Western blots of topoisomerase IIalpha after incubation of CHO cells with ICRF-187 demonstrated a marked band depletion, whereas this effect was completely lacking in CHO/159-1 cells, and an equal effect of VP-16 was observed in both lines. These data imply that the CHO/159-1 topoisomerase IIalpha lacks sensitivity to bisdioxopiperazines and that the mechanism of resistance in this cell line does not confer cross-resistance to topoisomerase II poisons, suggesting that mutations conferring resistance to bisdioxopiperazines can occur at sites distinct from those responsible for resistance to complex stabilizing agents. Accordingly, CHO/159-1 cDNA showed two heterozygous mutations in the proximal NH2-terminal part of topoisomerase IIalpha (Tyr49Phe and delta 309Gln-Gln-Ile-Ser-Phe313), which is in contrast to those induced by topoisomerase II poisons, which cluster further downstream. Site-directed mutagenesis and transformation of the homologous Tyr50Phe coding mutation in human topoisomerase IIalpha in a temperature-conditional yeast system demonstrated a high-level resistance to ICRF-193, compared to cells expressing wild-type cDNA, but none toward the poisons VP-16 or amsacrine, thus confirming that the Tyr50Phe mutation confers specific resistance to bisdioxopiperazines. Thus, these results indicate that the region of the protein involved in ATP-binding also plays a critical role in sensitivity to bisdioxopiperazines, a result consistent with the known requirement for the formation of an ATP-bound closed clamp for bisdioxopiperazine activity. These results may enable a more precise understanding of the interaction of topoisomerase II-directed drugs with their target enzyme.

Cognitive theory applied to the treatment of delusions of schizophrenia

This article reviews theory regarding cognitive interventions in schizophrenia, focusing particularly on the treatment of delusions. The cognitive theory of psychopathology is first introduced and the specific goals of cognitive therapy are then presented. A range of philosophical and etiologic perspectives on the nature of delusions are explored, including the cognitive perspective. Specific stages and techniques of therapy are discussed with theoretical underpinnings and suggestions for incorporation in advanced practice psychiatric nursing.

Pharmacological profile and anti-ischemic properties of the Ca(2+)-channel blocker NS-638

Included in the sequence of events leading to neuronal death in ischemic tissue following stroke is an excessive and toxic rise in the intracellular Ca(2+)-concentration, predominantly due to an influx of Ca2+ through nonselective cation-channels as well as Ca(2+)-channels. In the present study we have characterized the pharmacological profile and anti-ischemic effects of 2-amino-1-(4-chlorobenzyl)-5-trifluoromethylbenzimidazole (NS-638), a small nonpeptide molecule with Ca(2+)-channel blocking properties. NS-638 dose dependently inhibited K(+)-stimulated [45Ca2+]-uptake in chick cortical synaptosomes and 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA)-stimulated [3H]GABA-release from cultured cortical neurons with IC50 values of 2.3 and 4.3 microM, respectively. K(+)-stimulated intracellular Ca(2+)-elevation in cultured cerebellar granule cells was equipotently blocked with an IC50 value of 3.4 microM. At this concentration no effect on Ca(2+)-induced contractions in K(+)-depolarized guinea pig taenia coli was observed. The effect of NS-638 on neuronal Ca(2+)-channels was evaluated using whole cell patch clamp techniques. The compound reversibly blocked N- and L-type Ca(2+)-channels in cultured chick dorsal root ganglion cells in the concentration range of 1-30 microM. In the mouse middle cerebral artery occlusion (MCAO) model, NS-638 administered i.p. (50 mg kg-1) at 1 h and 6 h post-ischemia, and once a day for the next two days, resulted in a 48% reduction in total infarct volume. The compound did not show protection against ischemic neuronal damage in the gerbil model of bilateral carotid artery occlusion (BCAO). This data suggests, that neuronal Ca(2+)-channel blockers may have potential in ameliorating the pathological damage after focal ischemia.

Relation of spatial learning of rats in the Morris water maze task to the number of viable CA1 neurons following four-vessel occlusion

Male Wistar rats were tested in the Morris water maze task 1 week after 6, 9, or 12 min of transient global ischemia. The 9-min and 12-min ischemia groups were significantly impaired in the acquisition and the reversal experiment. A systematic counting of CA1 neurons in the whole hippocampal formation revealed a unilateral number of CA1 neurons of 286,000 in the sham group, of which 2/3 were located in the dorsal hippocampus. The ischemia groups showed a significant decline in the number of dorsal CA1 neurons, whereas only the 12-min ischemia group showed a significant but minor decline (10%-15%) in the number of ventral CA1 neurons. A correlation analysis showed that the escape distance declined with increasing number of viable CA1 neurons, but poor correlation coefficients were obtained. Thus, some of the ischemic rats with even very few viable CA1 neurons in the dorsal hippocampus were capable of performing this spatial learning task at sham-group level.

[Patterns of tuberculosis manifestation in the county of Roskilde]

The epidemiological and clinical features of all adult tuberculosis (tbc) cases in a Danish county over a 12 year period (82 cases) are presented. Most patients with pulmonary disease have thorax X-ray pictures showing pathological changes. Of the patients who only have extrapulmonary disease, 88% have normal X-ray examinations of the lungs. The patients can be divided into two groups: Danes and foreigners. The Danish patients are older, 81% are over the age of forty. They mostly have pulmonary disease (85%). They often have one or several concomitant diseases. The foreigners are younger, 90% are below the age of forty. They frequently have extrapulmonary disease (35%). They seldom have concomitant diseases.

Relation of spatial learning of rats in the Morris water maze task to the number of viable CA1 neurons following four-vessel occlusion

Male Wistar rats were tested in the Morris water maze task 1 week after 6, 9, or 12 min of transient global ischemia. The 9-min and 12-min ischemia groups were significantly impaired in the acquisition and the reversal experiment. A systematic counting of CA1 neurons in the whole hippocampal formation revealed a unilateral number of CA1 neurons of 286,000 in the sham group, of which 2/3 were located in the dorsal hippocampus. The ischemia groups showed a significant decline in the number of dorsal CA1 neurons, whereas only the 12-min ischemia group showed a significant but minor decline (10%-15%) in the number of ventral CA1 neurons. A correlation analysis showed that the escape distance declined with increasing number of viable CA1 neurons, but poor correlation coefficients were obtained. Thus, some of the ischemic rats with even very few viable CA1 neurons in the dorsal hippocampus were capable of performing this spatial learning task at sham-group level.

Does neuronal damage of CA1 relate to spatial memory performance of rats subjected to transient forebrain ischemia?

The effect of ischemia-induced hippocampal neuronal damage on acquisition and performance in the Morris water maze task was investigated in male Wistar rats, subjected to 8 min of transient forebrain ischemia, induced by the 4-vessel occlusion (4-VO) method. After a morphological scoring of the neuronal damage within the CA1, CA2, and CA3 subfields of the anterior-dorsal part of hippocampus we found that rats with a total neuronal cell loss of the anterior-dorsal CA1 region showed memory performance impairments in the acquisition trials, in a probe trial, and in a reversal experiment. However, rats with only partial damage to the CA1 region did not exhibit significant impairments during the acquisition trials of the water maze test or in the probe trial and the reversal experiment. In conclusion, these results suggest that it is possible to relate the histological damage score of CA1 in the anterior-dorsal hippocampus to impaired memory performance in the present water maze setup.

Microdialysis of interstitial amino acids during spreading depression and anoxic depolarization in rat neocortex

We have examined the effect of cortical spreading depression (SD) and anoxic depolarization (AD) on the interstitial concentration changes of amino acids (AA) in the neocortex of anesthetized rats using microdialysis and HPLC. Accompanying SD alanine increased to 126 +/- 11%, arginine to 116 +/- 3%, aspartate to 160 +/- 17%, glutamate to 163 +/- 9%, glycine to 158 +/- 21%, serine to 125 +/- 9%, and taurine to 172 +/- 15% (mean +/- 1 S.E.M.). The increases lasted for about 1 min. Histidine decreased to 74% +/- 4% at 1 min following SD, and returned to normal 4 min later. Cardiac arrest triggered AD after approximately 2 min, immediately followed by changes of interstitial AAs. At 5 min after AD alanine had increased to 183 +/- 13%, aspartate to 3,458 +/- 656%, GABA to 338 +/- 35%, glutamate to 1,696 +/- 546%, glycine to 297 +/- 37%, serine to 153 +/- 12%, and taurine to 1721 +/- 98% as compared to control values (mean +/- 1 S.E.M.). Histidine decreased to 78 +/- 2% at 3 min following AD while arginine exhibited insignificant variations around the baseline. The increase of glutamate during SD is consistent with activation of NMDA-receptors as an essential requirement for this reaction. The increase of AAs may also contribute to the sequence of events leading to AD, though the exact mechanism remains unknown. SD is an important pathophysiological mechanism of the ischemic penumbra associated with focal cerebral ischemia, while AD reflects the electrophysiological status of the infarct core.(ABSTRACT TRUNCATED AT 250 WORDS)

Time- and temperature-dependent forebrain ischemic damage in Mongolian gerbils

The influence of transient bilateral carotid artery occlusion time, core body temperature regulation and post-operative survival time was examined on delayed neuronal death in the hippocampal subregions of Mongolian gerbils. A simple and rapid histologically based scoring system was used. A carotid artery occlusion time of 5 min with stabile core body temperature at 37.5-38.0 degrees C and a post-operative survival time of 4 days was sufficient to induce a reproducible and almost total neuronal damage in the hippocampal subfields. Furthermore, the use of gerbils with ages varying from 50 to 100 days did not markedly influence the development of the neuronal damage although the variation in the severity of the damage seemed to decrease with age. The addition of a drop of room tempered (21-22 degrees C) isotonic water, to avoid adherence between the clips and the carotid artery, reduced neuronal damage in some animals.

Refined crystal structure of ferredoxin II from Desulfovibrio gigas at 1.7 A

The crystal structure of ferredoxin II from Desulfovibrio gigas has been determined using phasing from anomalous scattering data at a resolution of 1.7 A and refined to an R-factor of 0.157. The molecule has an overall chain fold similar to that of the other bacterial ferredoxins of known structure. The molecule contains a single 3Fe-4S cluster with geometry indistinguishable from the 4Fe-4S clusters, and a disulfide bond near the site corresponding to the position of the second cluster of two-cluster ferredoxins. The cluster is bound by cysteine residues 8, 14 and 50. The side-chain of cysteine 11 extends away from the cluster, but could rotate to become the fourth cysteine ligand in the four-iron form of the molecule given a local adjustment of the polypeptide chain. This residue is modified, however, by what appears to be a methanethiol group. There are a total of eight NH . . . S bonds to the inorganic and cysteine sulfur atoms of the Fe-S cluster. There is an additional residue found that is not reported for the chemical sequence: according to the electron density a valine residue should be inserted after residue 55.

Structure of rubredoxin from Desulfovibrio vulgaris at 1.5 A resolution

The X-ray model of rubredoxin from Desulfovibrio vulgaris has been refined against 1.5 A X-ray diffraction data collected on a diffractometer. The final model comprises 395 non-hydrogen protein atoms, and 180 solvent O atoms. The final R-value for the model with calculated H atom positions included as fixed contributions is 0.098 over all reflections greater than 2 sigma I from infinity to 1.5 A. The error in co-ordinates is estimated to be 0.08 A. The solvent model was twice redetermined during the later stages of refinement and was instrumental in its success. One sequence error has been detected and corrected (Thr21----Asp). The iron-sulfur site bond angles are distorted from true tetrahedral symmetry, as found in other rubredoxin structures. A significant deviation from tetrahedral angles is seen at C alpha atoms 9, 10, 42 and 43, interior angles of the loops binding the iron atom. The planes of two aromatic groups, Tyr4 and Trp37, are nearly parallel to, and lie under, an extended system of atoms that includes the peptide bonds preceding the first cysteine residue of each cysteine loop as well as the cysteine side-chain, the iron, and the cysteine side-chain of the opposite loop, forming a previously unrecognized extended system that may function in electron transfer.

Dopamine release in the nucleus caudatus and in the nucleus accumbens is under glutamatergic control through non-NMDA receptors: a study in freely-moving rats

Perfusion with quisqualate (5 x 10(-6) M) and kainate (5 x 10(-7) M), selective agonists of glutamate receptors, enhanced the release of dopamine in both caudate and accumbens nuclei of freely-moving rats, measured by the transcerebral microdialysis technique. In contrast, N-methyl-D-aspartate (NMDA) did not affect dopamine release, except at very high concentrations (10(-2) M). The quisqualate-kainate antagonist, FG 9041 (DNQX), antagonized the elevation of dopamine release induced by quisqualate and, furthermore, reduced that of kainate. CPP, a selective NMDA antagonist, did not counteract the quisqualate- or kainate-induced stimulation of dopamine release. The enhancement of dopamine release after quisqualate and kainate was accompanied by behavioural stimulation characterized by grooming, rearing, hypermotility with sniffing and confined sniffing. This behavioural syndrome could be blocked by haloperidol. Conversely, perfusion with NMDA did not activate behaviour even at high concentrations. These results indicate that the dopaminergic system, within the caudate and the accumbens nuclei, is under glutamatergic control through kainate and quisqualate receptors, while the NMDA receptors do not appear to be involved.

Solvent model for protein crystals: on occupancy parameters for discrete solvent sites and the solvent continuum

On the basis of test calculations, Kundrot & Richards [Acta Cryst. (1987), B43, 544-547] suggest that for models of protein crystal structures based on limited-resolution X-ray data, it is not appropriate to vary both the occupany (Q) and thermal (B) parameters for the solvent molecules during refinement. There are compelling reasons, however, to adjust both parameters. If the data are sufficiently extensive to include a B parameter for each solvent site, then an adjustable Q parameter should also be included if the model is to represent physical reality. To fix Q at some arbitrary value as suggested, means that differences in occupancy will be absorbed in the 'thermal' parameters, leading to the errors corresponding to the electron density plots of Kundrot & Richards. Although the errors appear to be relatively small, they will be accentuated in Fourier maps of complex structures based on real data, causing error peaks, both positive and negative, that may greatly exceed the random errors. The current practice of using the scattering factor of the O atom, fO, for the water molecule neglects the scattering from the H atoms. A modified scattering factor based on fO- would approximate the scattering from water molecules better. Finally, the solvent continuum should be included in the model, and the low-order data included in calculating the Fourier maps from which the Q parameters are estimated.

Anticonvulsant action of the beta-carboline abecarnil: studies in rodents and baboon, Papio papio

Abecarnil (ZK 112119; isopropyl-6-benzyloxy-4-methoxymethyl-beta-carboxylate) is a metabolically stable beta-carboline derivative with potent anxiolytic and few sedative and ataxic effects in rodents. The anticonvulsant and muscle relaxant actions of abecarnil have been evaluated in mice, rats, gerbils and baboons. Abecarnil raised the threshold for tonic electroconvulsions in mice after corneal but not after auricular application, had no effect on maximal electroshock-induced tonic convulsions triggered by either method, protected mice against the tonic hindlimb extension in PTZ-, picrotoxin- and 3-mercaptopropionate-induced seizures and blocked clonus after PTZ, DMCM (methyl-4-ethyl-6,7-dimethoxy-9H-pyrido-(3,4-b)-indol-3-carboxylate) and 3-mercaptopropionate. Abecarnil had no effect on convulsions induced by bicuculline and strychnine. Furthermore, abecarnil blocked kindled seizures after chronic administration of PTZ and FG 7142 (beta-carboline-3-carboxylic acid methylamide) and protected mice and rats against limbic convulsions induced by pilocarpine. Severity and afterdischarge duration of amygdala-kindled seizures were reduced in rats treated with abecarnil. Abecarnil also antagonized selectively convulsions induced by i.c.v. administration of kainate, but not those triggered by N-methyl-D-aspartate or quisqualate. In genetic models of reflex epilepsy, abecarnil was effective against sound-induced convulsions in DBA/2 mice, against air blast-induced generalized seizures in gerbils and against myoclonus in baboons Papio papio. The anticonvulsant effect of abecornil in a PTZ seizure model in mice was potentiated by ethosuximide, whereas no significant potentiation was found with diazepam, clonazepam, diphenylhydantoin, carbamazepine and phenobarbital. Electromyographic monitoring in a etorphine model of muscle rigidity in rats showed no or little muscle relaxant effect of abecarnil.(ABSTRACT TRUNCATED AT 250 WORDS)

Abecarnil, a metabolically stable, anxioselective beta-carboline acting at benzodiazepine receptors

Abecarnil (isopropyl 6-benzyloxy-4-methoxymethyl-beta-carboline-3-carboxylate) is a novel ligand for central benzodiazepine (BZ) receptors, possessing anxiolytic and anticonvulsant properties, but with considerably reduced muscle relaxant effects in comparison to diazepam (DZP). In vitro, abecarnil inhibited the binding of the BZ [3H]lormetazepam to rat cerebral cortex membranes with an IC50 value of 0.82 nM in comparison to 56 nM for DZP. The ability of abecarnil to displace [3H]lormetazepam was enhanced 1.24-fold in the presence of 30 microM gamma-aminobutyric acid; the corresponding value for DZP was 2.8-fold. DZP and abecarnil were equally effective in enhancing the binding of t-[35S]butylbicyclophosphorothionate to rat cortical membranes. In vivo, abecarnil exhibited a 3- to 6-fold higher affinity to forebrain BZ receptors than DZP. Abecarnil was from 2 to 10 times more potent than DZP in most rodent tests of anxiolytic activity, and in reducing locomotor activity in mice and rats thoroughly habituated to the test chamber. However, in rats newly exposed to a novel cage, abecarnil was less potent than DZP in reducing locomotor activity. In tests of motor coordination, abecarnil, in contrast to DZP, showed no or only weak activity, and in potentiating the effects of ethanol and hexobarbital on motor performance abecarnil was 4 to 25 times less potent than DZP. Abecarnil antagonized the effects of BZs in the chimney and loss of righting reflex tests, but not in the rotarod test.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of photosensitive seizures in man by the beta-carboline, ZK 95962, a selective benzodiazepine receptor agonist

A single-dose study of the beta-carboline, ZK 95962, on photosensitive generalized paroxysmal activity in the EEG was conducted in 6 patients with primary generalized epilepsy. Four of the patients were newly diagnosed and did not receive any antiepileptic drug or other medication during the study. Two were receiving current therapy with carbamazepine. A double-blind cross-over study with 2 injections of ZK 95962 (20 micrograms/kg body weight repeated 10 min after 1st injection) and 2 placebo injections were carried out in a randomized order, with 4 h intervals between the injections with active drug and placebo. On the day before the trial, the sensitivity range (standardized photosensitivity range, SPR) was determined hourly using flash frequencies of 2, 6, 8, 10, 15, 20, 30 and 40 Hz for 4 sec in ascending and descending order until generalized spikes or spike waves occurred. A significant reduction in photosensitivity was observed 2-12 min after injection of ZK 95962 in all patients, lasting 2-3 h. No change in the SPR was observed after placebo injections. The feelings of uneasiness and myoclonic jerks, provoked by photostimulation, were also abolished by ZK 95962, but not by placebo injections. Side effects, including sedation were not observed. The results suggest that benzodiazepine receptor ligands such as ZK 95962 may be potent antiepileptic drugs.

Refinement of triclinic lysozyme: II. The method of stereochemically restrained least squares

Refinement of triclinic lysozyme by restrained least squares against the 2 A resolution X-ray data is described, beginning with the model from cycle 17 of the preceding paper [Hodsdon, Brown, Sieker & Jensen (1990). Acta Cryst. B46, 54-62]. After 20 refinement cycles, R stood at 0.172. Nevertheless, serious errors involving both main-chain and side-chain atoms still remained, requiring numerous model rebuilding sessions interleaved with refinement cycles. After 63 cycles R = 0.124 for the model which includes all protein atoms, 249 water oxygen sites and five nitrate ions. Although the overall B is relatively low, 10.5 A2, B's for atoms in the region of residues 101-103, toward the termini of some of the longer side chains, and in the region of the C terminus of the main chain exceed 20 A2, indicating relatively high atomic mobilities, disorder, or remaining errors in the model.

Refinement of triclinic lysozyme: I. Fourier and least-squares methods

X-ray diffraction data to 1.5 A resolution have been collected for triclinic crystals of hen egg white lysozyme. The triclinic model was derived from the tetragonal one by the rotation function and refined initially by Fo-Fc and differential difference syntheses against 2 A resolution data. Refinement was continued by differential difference cycles against the 1.5 A data until R was reduced to 0.220. Although the initial refinement was rapid, it was subsequently a matter of attrition, leading to a complete recheck of the data and the discovery of systematic error which affected primarily the high-resolution data. Refinement was continued against the corrected 2 A data by block-diagonal least squares. After five cycles the refinement was terminated at R = 0.254 because of the imminent availability of a preferred refinement program. Problems with the protein model, the solvent, and the interaction of the scale and thermal parameters are discussed. The experiences gained in this study are summarized.

The structure of rubredoxin from Desulfovibrio desulfuricans strain 27774 at 1.5 A resolution

The structure of a small rubredoxin from the bacterium Desulfovibrio desulfuricans has been determined and refined at 1.5 A resolution. The hairpin loop containing seven residues in other rubredoxins is missing in this 45 residue molecule, and once that fact was determined by amino acid sequencing studies, refinement progressed smoothly to an R value of 0.093 for all reflections from 5 to 1.5 A resolution. Nearly all of the water molecules in the well-ordered triclinic unit cell have been added to the crystallographic model. As in the other refined rubredoxin models, the Fe-S4 complex is slightly distorted from ideal tetrahedral coordination.

A potent antagonist of the strychnine insensitive glycine receptor has anticonvulsant properties

5.7-Dinitro-quinoxaline-2.3-dione (MNQX) displaced [3H]glycine binding to cortical membranes but had no effect n [3H]3-((+/-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid ([3H]CPP) binding. MNQX potently antagonized N-methyl-D-aspartate (NMDA)-evoked release of [3H]GABA from cultured cortical neurones, NMDA evoked spreading depression and NMDA depolarizations in the rat neo-cortex. All of these responses were reversed by addition of glycine to the perfusion media. These results suggested that MNQX is an antagonist at the strychnine-insensitive glycine receptor associated with the NMDA receptor/ionophore complex. Furthermore the compound was found to antagonise audiogenic seizures in DBA-2 mice indicating the potential of glycine antagonists of this type in anticonvulsant therapy.

The crystal structure of the three-iron ferredoxin II from Desulfovibrio gigas

The crystal structure of oxidized ferredoxin II from the sulfate-reducing bacterium Desulfovibrio gigas has been determined and refined at 1.7 A resolution. The folding of the polypeptide chain is similar to that of the 2[4Fe-4S] ferredoxin in Peptococcus aerogenes, except for an extended helical segment near the C-terminus. The single [3Fe-4S] cluster in D. gigas is similar to a [4Fe-4S] cluster, but lacks one Fe atom and is coordinated to Cys-8, -14 and -50. The side chain of Cys-11 is not bound to the cluster, but is rotated toward the solvent and modified by some, as yet undetermined, chemical group. Cys-18 and Cys-42 form a disulfide bridge. A previously undetected extra amino acid is found after residue 55.

Structure of ferredoxin I from Azotobacter vinelandii

The structure of Azotobacter vinelandii ferredoxin I (Av FdI, 106 amino acids) has been redetermined, based on x-ray diffraction data from tetragonal crystals of the native protein and two heavy atom derivatives. The current model differs greatly from the one previously reported and is in agreement with arguments based on various spectroscopic and other methods. The unit cell parameters are a = b = 55.62 A and c = 95.51 A, whereas the space group was found to be P4(1)2(1)2 instead of P4(3)2(1)2. The sequence of the first half of Av FdI is closely homologous with ferredoxin from Peptococcus aerogenes (Pa Fd, 54 amino acids) and the fold of the corresponding chain is almost identical. The ligands of the 3Fe complex are Cys-8, -16, and -49, corresponding to three of the four ligands in complex I of Pa Fd; the ligands of the 4Fe complex are Cys-20, -39, -42, and -45, corresponding to the four ligands in complex II of Pa Fd.

Lorazepam and FG 7142 induce tolerance to the DMCM antagonistic effect of benzodiazepine receptor ligands

Mice were given chronic treatment with lorazepam 10 mg/kg PO or FG 7142 40 mg/kg IP once a day for 14 days. The pretreatments with lorazepam and FG 7142 did not change the sensitivity of the mice to the convulsant effect of DMCM. Lorazepam pretreated mice showed a significantly lower sensitivity to the anticonvulsant effects of the benzodiazepine (BZ) receptor ligands lorazepam, ZK 93423, ZK 91296, Ro 15-1788 and ZK 93426 administered acutely by the IP route when challenged with DMCM 24 hr after the last dose of lorazepam. FG 7142 pretreated mice showed a significantly lower sensitivity to the anticonvulsant effect of the two agonists lorazepam and ZK 93423 and to the antagonist Ro 15-1788, whereas the effects of ZK 91296 and ZK 93426 were left unchanged. The reduced DMCM antagonistic effects of the BZ receptor ligands may indicate that these ligands may either have lost some of their affinity to those BZ receptors being responsible for the DMCM-induced seizures or they may have lost some efficacy in allosterically inhibiting DMCM binding or as a third possibility may have lost efficacy at a BZ receptor site downstream to the seizure-inducing center in the brain.

Bidirectional effects of beta-carbolines in rats with spontaneous petit mal-like seizures

Seven benzodiazepine-receptor ligands of the beta-carbolines' group were administered IP in Wistar rats from (1) a strain displaying spontaneous petit mal-like seizures (PMLS) characterized by spike and wave discharges (SWD) and, (2) a strain where no seizure is ever observed (NS). Five different types of effects were observed. (1) Injection of a full agonist (ZK 93 423) suppressed SWD in PMLS rats, in a dose-dependent manner, and induced marked sedation with alteration of EEG background activity; (2) Injection of partial agonists (ZK 95 962, ZK 91 296) suppressed SWD in PMLS rats without sedation; (3) Injection of low doses of a full inverse agonist (DMCM) significantly increased the total duration of SWD in PMLS rats and induced SWD in NS rats. Higher doses of DMCM induced convulsions in both strains; (4) Injection of partial inverse agonists (FG 7142, ZK 90 886) aggravated SWD in PMLS and induced SWD in NS rats. FG 7142 induced convulsions only in PMLS animals, whereas no convulsions were ever observed with ZK 90 886; (5) Injection of an antagonist (ZK 93 426) did not significantly modify SWD in PMLS rats. However, this compound was able to reverse both antiepileptic effects of agonists and epileptogenic effects of inverse agonists. These results suggest the involvement of the benzodiazepine-GABA receptor complex in the control of petit mal-like seizures in rats.

Modulation of anxiety by beta-carbolines and other benzodiazepine receptor ligands: relationship of pharmacological to biochemical measures of efficacy

Several beta-carbolines and other benzodiazepines (BZ) receptor ligands have been investigated for anxiolytic or anxiogenic action in 4 unrelated animal models of anxiety using rats. The substances could be grouped into essentially 2 groups. The first, anxiolytics, exhibited antipunishment activity in a lick-suppression test, antagonised the discriminative stimulus provided by pentylenetetrazol, resembled chlordiazepoxide (CDP) in a drug discrimination test, and reduced the rise in plasma corticosterone levels following swim stress. Such substances included several benzodiazepines, the beta-carboline ZK 93 423, and the triazolapyridazine CL 218 872. A subgroup of anxiolytics were active in only some of these tests. They included two beta-carbolines, ZK 91 296 and ZK 95 962, and the pyrazoloquinoline CGS 9896, and these 3 substances were also distinguishable in not producing rate-decreasing effects in any of the 3 operant tests. The second group were anxiogenic in that they produced a discriminative stimulus resembling that of PTZ, they antagonised the CDP cue, exhibited propunishment effects in the lick-suppression test, and themselves caused increases in plasma corticosterone in otherwise unstressed animals. Such substances included the beta-carbolines DMCM, FG 7142 and ZK 90 886, and the pyrazoloquinoline CGS 8216. Two substances, Ro 15-1788 and ZK 93 426 had little or only weak activity in any test. The classification of these substances into anxiolytics or anxiogenics could be predicted qualitatively both by their ability to enhance (anxiolytics) or decrease the binding of 35S-TBPS to rat brain membranes and by whether their own binding was increased (anxiolytics) by adding the GABA agonist muscimol to the in vitro incubation medium. For the limited number of substances for which full data was available, there was also a quantitative relationship between the degree of enhancement of 35S-TBPS binding by a substance and its potency in the CDP cue test when such potency was expressed as numbers of BZ receptors occupied at the ED50 value in the pharmacological test. Furthermore, for the anxiolytics, activity in the CDP cue correlated significantly with potency in 2 other tests. Otherwise, surprisingly weak correlations existed between potencies in the different tests. In particular, the beta-carboline ZK 95 962 was highly potent in antagonising the PTZ cue but inactive in both a conflict test and in protecting against stress. These results are discussed in terms of differences in the neuropharmacologies of the 4 tests and in selectivity of the BZ receptor ligands for subtypes of BZ receptor.

Bidirectional effects of beta-carbolines and benzodiazepines on cognitive processes

Experiments with benzodiazepine receptor ligands in two paradigms involving cognitive processing were performed in order to test whether the concept of bidirectional effects of benzodiazepine receptor ligands could also be applied to cognitive functions. Benzodiazepine receptor agonists like chlordiazepoxide, lorazepam, ZK 93423 and ZK 91296 induced amnesia in a passive avoidance paradigm. Mice treated with the benzodiazepine receptor antagonist, ZK 93426, reached a learning criterion after fewer foot-shocks than saline treated mice both in naive animals and in scopolamine pre-treated animals. Furthermore, ZK 93246, attenuated the amnesic effect of corneal electroshock. The inverse agonists FG 7142 and DMCM decreased the detrimental effect of scopolamine on retrieval. In a signal detection paradigm, chlordiazepoxide impaired signal detection. In aged rats ZK 93426, ZK 90886 and FG 7142 had no effect on signal detection but ZK 93426 and FG 7142 attenuated the impairment of signal detection induced by scopolamine. These effects of benzodiazepine receptor ligands may reflect changes in arousal/vigilance, suggesting that BZ inverse agonists may have useful properties in enhancing vigilance.

Chronic treatment with lorazepam and FG 7142 may change the effects of benzodiazepine receptor agonists, antagonists and inverse agonists by different mechanisms

Treatment of mice with lorazepam 10 mg/kg p.o. or FG 7142 40 mg/kg i.p. once a day for 14 days changed the effects of benzodiazepine (BZ) receptor ligands injected acutely on the threshold of pentylenetetrazol (PTZ)-induced seizures. The effects of the two pretreatments differed qualitatively as well as quantitatively. Lorazepam elicited a shift in the effects of all BZ receptor ligands tested, whereby the agonists lorazepam and ZK 93423 now acted like partial agonists given acutely, the partial agonist ZK 91296 acted like an antagonist and the antagonists Ro 15-1788 and ZK 93426 like partial inverse agonists. The proconvulsant effects of the partial inverse agonist FG 7142 and the full inverse agonist DMCM on the PTZ-induced seizures did not change. However, FG 7142 became a full inverse agonist i.e. became convulsant, and DMCM may have increased in potency as a convulsant. After FG 7142 pretreatment lorazepam and ZK 93423 behaved like partial agonists given acutely whereas there was no change in effect for ZK 91296, Ro 15-1788 and ZK 93426. FG 7142 became convulsant (i.e. kindling occurred) and the potency of DMCM as a convulsant was non-significantly increased, while their proconvulsant effects with respect to PTZ-induced seizures were not altered. The fact that the effects of the two very different pretreatments on the BZ receptor ligand continuum were in the same direction may be explainable by assuming two different mechanisms, both of which may involve the GABA receptors.

Preliminary X-ray studies of the tetra-heme cytochrome c3 and the octa-heme cytochrome c3 from Desulfovibrio gigas

A tetra-heme and an octa-heme cytochrome c3 from the sulfate bacterium Desulfovibrio gigas have been crystallized. Diffraction quality crystals of the tetra-heme cytochrome are obtained from solution by the addition of polyethylene glycol at pH 6.5. The crystals are orthorhombic, space group P2(1)2(1)2 with unit cell parameters a = 42.27 A, b = 52.54 A and c = 52.83 A. The octa-heme cytochrome crystals develop from low ionic strength solutions of phosphate or Tris-Cl in the pH range 6.2-7.6. The crystals belong to the trigonal system, space group P3(1) or the enantiomorph P3(2), with unit cell parameters a = b = 57.4 A, c = 97.3 A, gamma = 120 degrees. Single crystal diffraction studies of the structures of these two low-potential cytochromes are in progress.

Structure of rubredoxin from the bacterium Desulfovibrio desulfuricans

The X-ray crystallographic structure of rubredoxin from Desulfovibrio desulfuricans strain 27774 is described. This molecule is 15% smaller than previously studied rubredoxins, lacking a seven-residue loop of chain but containing a histidine and a free-sulfhydryl cysteine. Except for solvent exposure of the single invariant tryptophan, no other major difference occurs in the molecule.

Actions of the beta-carboline ZK 93426 in an animal test of anxiety and the holeboard: interactions with Ro 15-1788

The effects of the beta-carboline ZK 93426, a putative benzodiazepine receptor antagonist, were investigated in the social interaction test of anxiety and in the holeboard. Like the receptor antagonist Ro 15-1788, ZK 93426 (2.5-10 mg/kg) caused a specific reduction in social interaction (interpreted as an anxiogenic effect) and caused a significant elevation in exploratory head-dipping (5 mg/kg). When low (ineffective) doses of both compounds (1 mg/kg ZK 93426; 4 mg/kg Ro 15-1788) were administered together they significantly reduced social interaction. No further reductions in social interaction were observed when effective doses of both compounds (5 mg/kg ZK 93426; 10 mg/kg Ro 15-1788) were tested in combination; it is likely that this is due to almost total benzodiazepine receptor occupancy at effective doses of either compound. When doses of each compound (5 mg/kg ZK 93426; 10 mg/kg Ro 15-1788) that resulted in stimulation of head-dipping were examined in combination, the elevation in exploration was no longer observed. Since at higher doses of both compounds there is an attenuation of the elevation in head-dipping, it is again likely that the effects of the two compounds are additive.

Influence of solvent accessibility and intermolecular contacts on atomic mobilities in hemerythrins

Thermal factor parameters (B values) have been compared from the refined crystal structures of the myohemerythrin from Themiste zostericola and of the octameric hemerythrin from Themiste dyscrita. These B values, which are directly related to atomic mobilities, were found to correlate rather closely with the solvent accessible areas within the respective crystals. Although protomeric units of the two molecules have exceptionally similar three-dimensional structures, there are marked differences between the patterns of relative atomic mobilities along the polypeptide chains. The differences correspond to lattice and oligomer contacts. An adjustment of the B values based on the fraction of accessible area occluded by contacts yields values that correlate well between the independent subunits and that should pertain more closely to those for the protomer free in solution.

Active site structures of deoxyhemerythrin and oxyhemerythrin

The physiologically active forms of the nonheme-iron, oxygen-transport protein hemerythrin have been studied by x-ray crystallographic techniques. At 3.9-A resolution, a difference electron-density map between the deoxy form and met form (methemerythrin) of the protein suggests only small differences in the binuclear iron complexes. The coordination of the iron atoms appears to be the same in both the deoxy and met forms, one iron of the complexes being pentacoordinate, the other iron being hexacoordinate. The iron atoms appear to be somewhat farther apart in the deoxy form. A 2.2-A resolution study of oxyhemerythrin shows that dioxygen binds to one iron atom--the pentacoordinate one in the met form of the protein, the same binding site found for azide in azidomethemerythrin.

Crystallization and preliminary x-ray diffraction study of the 3-Fe ferredoxin II from the bacterium Desulfovibrio gigas

The 3-Fe ferredoxin (FdII) from the bacterium Desulfovibrio gigas has been crystallized at pH 5.0 and 23 degrees C in two different crystal forms. One form is monoclinic, space group C2, with unit cell parameters a = 40.78 A, b = 44.98 A, c = 26.47 A, beta = 104.6 degrees, and one monomer of the FdII tetramer per asymmetric unit. The molecule can be either the monomer of molecular weight 6400 or a dimer of twice this molecular weight with 2-fold symmetry coincident with the 2-fold axis of the crystal. The other crystal form is orthorhombic, space group P2(1)2(1)2 and unit cell parameters a = 109.5 A, b = 37.0 A, c = 30.5 A. The asymmetric unit of this crystal contains two monomers of FdII. The orthorhombic crystal has not been reproduced since the initial crystallization.

Proconflict effect of benzodiazepine receptor inverse agonists and other inhibitors of GABA function

GABA seems to be a neurotransmitter with great impact on conflict behaviour in rats. We studied the effects of different types of GABA function inhibitors on conflict behaviour in rats. Among these inhibitors, the benzodiazepine (BZ) receptor inverse agonists are a new type of compound downregulating GABA-mediated functions allosterically. The most effective proconflict inducing compounds were pentylenetetrazol and the three BZ inverse agonists beta-CCM, beta-CCE and ZK 90886. The BZ receptor inverse agonists, FG 7142, DMCM and CGS 8216, the GABA antagonist bicuculline and the GABA synthesis inhibitor isoniazid were moderately active. Only a weak effect was seen with just subconvulsive doses of picrotoxin, a chloride channel inhibitor. These results show that the mode of GABA function inhibition determines the degree to which proconflict action is elicited and that proconflict effects and proconvulsant or convulsant effects may be separated. Evidence is presented that proconflict action in rats is predictive of an anxiogenic action in man.

Antiepileptic action of the beta-carboline ZK 91296 in a genetic petit mal model in rats

The anticonvulsant action of the benzodiazepine (BZ) receptor partial agonist, ethyl 5-benzyloxy-4-methoxymethyl-beta-carboline-3-carboxylate (ZK 91296) was studied in rats of Wistar origin exhibiting spontaneous bilateral cortical synchronous spike and wave discharges with a symptomatology paralleling that of human petit mal seizures. ZK 91296 1-16 mg/kg i.p.) attenuated the absence seizures without inducing signs of sedation or disorganized EEG patterns at any dose. Diazepam (1-8 mg/kg i.p.) suppressed seizures but also induced sedation and modified EEG background activity in a dose-related manner.

Evaluation of the beta-carboline ZK 93 426 as a benzodiazepine receptor antagonist

We describe here biochemical and pharmacological effects of the beta-carboline ZK 93426 was compared with Ro 15-1788 and CGS 8216, two compounds previously described as BZ receptor antagonists. Certain effects of ZK 93426, Ro 15-1788 and CGS 8216 were quite similar (e.g., 3H-FNM displacement, "GABA ratio", "photo-shift"). In most pharmacological tests ZK 93426 and Ro 15-1788 lacked overt effects; Ro 15-1788 was a weak agonist in some paradigms, while ZK 93426 exhibited a potent proconflict effect but also a weak anticonvulsant effect. This interesting finding with ZK 93426 suggests that BZ receptor ligands may possess differential efficacy at BZ receptor subtypes. In contrast, CGS 8216 exhibited potent proconvulsant effects in several paradigms in addition to proconflict and pentylenetetrazol generalizing effects. ZK 93426, Ro 15-1788 and CGS 8216 were almost equally potent as antagonists of the effects of BZ receptor agonists, such as diazepam and lorazepam. However, ZK 93426 was the most potent inhibitor of the convulsions produced by the BZ receptor inverse agonist DMCM.