Toshiie Nakamura

Actions of benzodiazepines on the housefly. 3. In vitro binding of [3H]Ro5-4864 responding to GABA receptor ligands

1. 1. Characteristics of benzodiazepine (BZD) binding sites in the housefly are investigated using [3H]Ro5-4864, a ligand for the mammalian peripheral BZD receptor. 2. 2. [3H]Ro5-4864 specifically binds with low-nanomolar affinity to freshly prepared homogenates from the thorax plus abdomen. 3. 3. As to structural requirements for binding, housefly BZD binding sites resemble the peripheral BZD receptor of mammals. 4. 4. [3H]Ro5-4864 binding is modified by several compounds acting on the mammalian GABA receptor, suggesting that housefly BZD binding sites possess functional properties analogous to those of the GABA receptor-coupled, central BZD receptor of mammals. 5. 5. Such modifications have not been observed in [3H]diazepam binding to freeze-thawed preparations, suggesting that the insect GABAergic system is more labile than the mammalian counterpart.

Actions of benzodiazepines on the housefly: Binding to thorax/abdomen extracts and biological effects

Abstract 1. [3H]Diazepam binding studies revealed that the extracts from the housefly thoraxes and abdomens contained a single population of specific high-affinity binding sites for the benzodiazepines and related compounds. 2. Houseflies became prostrate by topical application of the benzodiazepines and related compounds that were active at the binding site. 3. The biological effects of these compounds might be explained on the basis of their interaction with the binding site.

Difference among GABA-gated chloride channel site ligands in binding to housefly head membranes

Abstract 1. 1. Displaceable (specific) binding of three ([ 3 H]α-dihydropicrotoxinin, [ 3 H] n -propylbicyclophosphate and [ 35 S] t -butylbicyclophosphorothionate) of four GABA-gated chloride channel site ligands was detected in housefly head extracts. 2. 2. Differences in their sensitivity to displacement by unlabeled compounds and in temperature dependence of binding suggest differences in the mode of interaction of the chloride channel site ligands with specific binding site(s).

Characterization of high affinity binding of [3H]propyl bicyclic phosphate to house fly head extracts

Abstract The head of the house fly, Musca domestica L., was found to contain saturable components of specific binding of 4- n -propyl[2,3- 3 H]-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane 1-oxide ([ 3 H]Pr-BP). A ratio of specific to total binding of radioreceptor assays was quite favorable, being 0.89 under the standard conditions. The apparent dissociation constant and maximal binding capacity were estimated to be about 4 n M and about 30 fmol/mg of protein, respectively, although association, dissociation, and saturation analyses suggested the presence of two or more populations of binding sites. Specific [ 3 H]Pr-BP binding showed a marked negative temperature coefficient and was little affected by pH in incubation media. Anions which pass through chloride channels attenuated specific [ 3 H]Pr-BP binding whereas impermeable anions enhanced it. Specific binding was selectively inhibited by insecticidal bicyclic phosphorus esters. Various neuroactive chemicals such as GABA agonists, GABA antagonists, cyclodiene insecticides, and benzodiazepines had little effect on specific binding. There was a correlation between GABA content and the density of specific Pr-BP binding sites in each part of the house fly body. In many respects, however, characteristics of the current binding site were different from those of GABA receptor-coupled sites already characterized with [ 3 H]Pr-BP and the [ 35 S] t -butyl thiono analog in the rat brain. Bicyclic phosphorus esters may act on site(s) apart from the GABA neurotransmission system in the house fly.

Actions of benzodiazepines on the housefly 2. Penetration and internal distribution following topical application on the dorsal thoracic surface

Abstract 1. 1. The rates of integument penetration of benzodiazepines (BZDs) and their levels inside the body were determined in houseflies treated topically at a dose of 10 μg/fly. 2. 2. Concentrations of various BZDs in hemolymph were relatively associated with their biological activities against the housefly. 3. 3. Concentrations of BZDs detected inside the body were higher than the concentrations required to inhibit specific binding of tritiated BZDs to thorax-abdomen homogenates. 4. 4. Biological effects of BZDs appear to be secondary effects even if they are caused by an action on the thorax-abdomen binding sites.

Influence of the Particle Size on the Herbicidal Efficacy of Pyrazolate

水田除草剤ピラゾレートの粒度と除草効果の関係を検討した. ピラゾレートを粒径44μm以下で5画分に分級し, 懸濁液で除草活性を評価すると, 発芽前処理では, ウリカワにはa. i. 0.5kg/haの薬量でどの画分もほぼ完全な除草効果を示したが, タイヌビエには20μmより粗い画分は活性が低下し, ミズガヤツリではa. i. 1kg/haの薬量でも10μmより粗い画分は活性が劣った. 発芽後処理では, 粗い画分の活性が低い傾向がより顕著であった. また, 粒度の異なるピラゾレートの粉砕品を用い, 押し出し造粒法によりつくられた粒剤の除草活性を評価すると, ポット試験では粒度の粗いピラゾレートを含有する粒剤 (Sw 1.36m2/g) は劣った. ほ場でも有効成分が粗い粒剤 (Sw 1.36, 1.76m2/g) は活性が劣ったが, 有効成分がきわめて微細な粒剤 (Sw5.13, 7.47m2/g) も活性が低下する傾向があり, Sw約2m2/gのピラゾレートを含有する粒剤がもっとも活性が高かった.

Influence of the Dispersion in Paddy Water on the Herbicidal Efficacy of Pyrazolate

ピラゾレートの田面水中での分散性が除草効果に及ぼす影響を田面水の流亡のないポット試験で検討した.田面水中での崩壊分散性が異なる2処方で, 押し出し粒径0.6および0.9mmの計4種の粒剤の除草効果を比較したところ, どの粒径でも崩壊分散のよい粒剤のほうが高い除草効果を示した. 崩壊分散のよい処方では粒径間の差はなかったが, 悪い処方では, 粒径が小さい粒剤のほうがミズガヤツリに対する除草効果が優れていた.同一粒度のピラゾレートを有する懸濁剤と粒剤 (施肥区と無施肥区) について除草効果を比較すると, 主剤の粒度がきわめて細かいものでは製剤型間の差はなかったが, 粒度が粗くなるにつれて粒剤の除草効果は懸濁剤より悪くなった. 粒剤の施肥区と無施肥区では崩壊分散のよい無施肥区のほうが高い除草効果を示した.同一キャリヤーより調製した崩壊分散が異なる3種類の粒剤の除草効果を施肥条件下で比較したところ, 崩壊分散のよいものが除草効果も高かった.以上のように, ピラゾレートの除草効果には, 主剤の粒度とともに, 田面水中における主剤の分散性が影響を与えた. 一方, ピラゾレート施用期の田面水は, 粒剤の崩壊分散性からみて, 10度以上の硬水に相当するものは少ないと考えられた. したがって, ピラゾレート粒剤は10度硬水中で良好な崩壊分散を示す処方とする必要がある.