Inhibitory indices

The inhibition on release of b-hexosaminidase from rat basophilic leukemia (RBL-2H3) has been employed to determine an inhibitory index of histamine release. In this test, the extract and (+)-taxifolin showed the inhibitory activity. 

The molar inhibitory index of malonic acid is 1/3 (Thron, 1953). Even more... 

In a comparative study of the in vitro antibacterial activity of cefaclor, cephradine, and cephalexin. Silver and co-workers (1977) utilized reported attainable blood levels and mean MICs of each antibiotic to express their potential efficacy as an inhibitory index. The inhibitory index was defined as a ratio between the mean peak serum levels and the mean MIC of isolates susceptible in Mueller-Hinton agar (using an inoculum of 10 organisms/ml). For organisms usually susceptible to cephalosporins (Table X), cefaclor attained the highest inhibitory indexes, demonstrating more antibacterial activity than either cephradine or cephalexin. 

TABLE X Inhibitory Indexes of Cefaclor, Cephradine, and Cephalexin... 

E I is a kinetic chimera Kj and kt are the constants characterizing the inactivation process kt is the first-order rate constant for inactivation at infinite inhibitor concentration and K, is the counterpart of the Michaelis constant. The k,/K, ratio is an index of the inhibitory potency. The parameters K, and k, are determined by analyzing the data obtained by using the incubation method or the progress curve method. In the incubation method, the pseudo-first-order constants /cobs are determined from the slopes of the semilogarithmic plots of remaining enzyme activity... 

Scheme 7.11). Here the therapeutic index was calculated as the minimal hemolytic concentration/minimal inhibitory concentration of bacteria. 

Anti-amoebic activity. Ethanol (80%) extract of the dried rhizome was inactive on Entamoeba histolytica, minimum inhibitory concentration (MIC) greater than 1 mg/ mL The extract, administered intragas-trically to male hamsters at a dose of 800 mg/kg, was active vs experimentally induced hepatic amebiasis . A dose of 250 mg/kg, administered intragastrically to rats on days 1-5, produced weak activity and a dose of 500 mg/kg was active " ". Anti-atherosclerotic activity. Ethanol (50%) extract of the dried rhizome, administered intragastrically to male rabbits at a dose of 500 mg/kg, reduced atherogenic index from 4.7 to 1.2 on the aorta . Antibacterial activity. Decoction of the dried entire plant, on agar plate, was inactive on Proteus vulgaris, Staphylococcus aureus, and Staphylococcus epidermidis MIC 125 mg/mL. Bacillus subtilis, Bordetella... 

An inhibitory effect of 8-OH-DPAT on forskolin-stimulated adenylyl cyclase activity is observed in hippocampal membranes of the guinea pig and rat, and has been used as an index of the functional activities of 5-HTIA receptors [178]. Cold stress induces a reduction of the inhibitory effect of 8-OH-DPAT in the hippocampus isolated from 18-month-old rats, although it has no influence on either the affinity or number of [3H]8-OH-DPAT binding sites. The administration of EGb (50 mg/kg p.o. for 14 days) prevents the cold stress-induced reduction in the inhibitory effect of 8-OH-DPAT on forskolin-stimulated adenylyl cyclase activity in old rats. These results indicate that EGb prevents the stress-induced desensitization of hippocampal 5-HTu receptors thus, its effects might explain anti-stress and antidepressant properties of EGb [177]. 

Two saponins from soybean seeds having soyasapogenol as aglycone were shown to have a partial inhibitory effect on HIV-induced cytopathology in infected human MT-2 lymphocytes cultures [158], The major constituent of group of B saponins from soybean seeds completely inhibited HIV-induced cytophatic effects and virus-specific antigen expression 6 days after infection at concentration > 0.25 mg/ml. Saponins isolated from soybean seeds inhibited HIV-1 replication in MT-4 cells at 0.5 [tg/ml (Nakamura et al. 1992) [159]. These saponins had a narrow therapeutic index and did not inhibit HIV-1 RT. One of them was found to inhibit HIV-induced cell fusion in MOLT-4 cells. 

Betulinic acid and platanic acid are triterpenoids isolated from Syzygium claviflorum. They exhibit inhibitory activity against HIV-1 replication in H9 lymphocyte cells at an IC50 of 1.4 and 6.5 pM, respectively (selectivity index 9.3 and 14, respectively). Hydrogenation of betulinic acid... 

Bellenamine, (R)-3,6-diamino-V-(aminomethyl)hexanamide is a (very) small-molecular-weight (MW 174) antibiotic produced by Streptomyces nashvillensis. It has only weak antibacterial activity but inhibits HIV-1 infection at an IC50 of 0.62 pg/ml (3.6 iM). With a CC50 of > 2 mg/ml (11.5 mM), the selectivity index of bellenamine can be estimated at well above 2000. Similarl to the well-established glycosylation inhibitors castanospermine and 1-deoxynojirimycin, bellenamine inhibits the secondary spread of HIV, although, unlike the glycosylation inhibitors, bellenamine had no apparent inhibitory effect on the glycosylation process. Therefore, its antiviral mechanism remains to be elucidated. 

Considering the fact that an increase in the percentage of wake parallels the decrease of REM sleep, the wake/REM (W/R) ratio might be an important index to describe the developmental levels in altricial mammals. This ratio is about 0.4 (28%/72%) in the first 10 days of life in the rat (4), dramatically increases to 1.77 at PN 21, 3.99 at PN 26 (9), and 8.1 in adulthood (calculated from Ref. 152). This ratio is 1.0 in the human newborn and is 2.6,10.3, and 11 at PN 1, PN 14-18, and adult, respectively (calculated from Ref. 12). The developmental features of sleep-wake states suggest that the strong REM sleep propensity in neonates is progressively suppressed or that a REM sleep inhibitory process is immature in neonatal rats. 

The interaction between two antimicrobial agents can be expressed by the fractional inhibitory concentration (FIC) index ... 

The excitotoxic index was developed by our group as a composite descriptor of excitatory/inhibitory amino acid neurotransmitter balance as measured by microdialysis in the brain s extracellular space (66,102). This index is defined as ... 

---