Further investigation of the primary mechanism of benzimidazole resistance in Haemonchus contortus

The binding of the [³H] benzimidazole carbamates (BZCs)—albendazole (ABZ), oxibendazole (OBZ), parbendazole (PBZ), mebendazole (MBZ), fenbendazole (FBZ) and oxfendazole (OFZ)—to tubulin from three ecologically-related isolates of adult Haemonchus contortus has been examined. The extent of binding of each BZC was inversely proportional to the known resistance status of the isolate. Biochemically, the change in the formation of the BZC-tubulin complex was due to a reduction in the amount of drug bound to resistant tubulin, with no significant change in the association constant of the complex. The resistance factors derived from the binding data support the hypothesis that the complex is ligand-dependent, with the aryl-substituted BZCs—MBZ, OFZ and FBZ—demonstrating lower resistance factors than those of the alkyl-substituted BZCs—ABZ, OBZ and PBZ. Examination of the slope derived from plots of binding against protein concentration demonstrated that the failure of resistant or partially resistant isolates to bind was due to either a decrease in the number of binding sites or, more likely, to reduced stability of the BZC-tubulin complex rendering it unstable to charcoal extraction.     

Interactions between hosts and non-hosts of Pinus spp. and Matsucoccus josephi: anatomical responses of stem to infestation

Artificial infestation of seven pine species revealed that Matsucoccus josephi (Homoptera: Margarodidae) completes its development on Pinus brutia , P. eldarica and P. halepersis , whereas only a small number of the scale larvae infesting P. cunariensis and P. pined reached the second instar and none developed to the adult stage. M. josephi crawlers died while trying to feed on P. radiata and P. pinaster. Histological examination of the infested plant sections indicated that necrosis in shoot and stem barks of P. eldarica and P. halepensis occurs just before or after the scale completes its development. Injury reached the cambium, and traumatic resin ducts; parenchyma cells instead of tracheids and curved tracheids were formed. In P. brutia wound periderm was observed in the stem section but not in the shoot cortex following scale development. Wound periderm was also formed in the stem cortex of P. canariensis and P. pinena whereas no pathological changes were detected in the infested cortex of P. pinaster and P. radiata.
Mechanical lesions caused by needle punctures resulted in the production of parenchyma cells instead of tracheids in all four pine species investigated. The response of the pine cortex was non-specific; however several similarities in the response to scale infestation, such as the formation of resin ducts, were observed. We hypothesize that the response of the pine tissue to the scale saliva is a hypersensitive reaction. It is suggested that the development of Matsucoccus species on particular pine species is related to the scale's inability to trigger the defence system of the host while the larvae are feeding.     

The purine path to chemotherapy

Antimetabolites of purine metabolism have found a use as anti-leukaemic, antiprotozoal and antiviral drugs, in immunosuppression and transplantation, and in gout and hyperuricemia. Their mechanisms of action are reviewed.Nobel Lecture given on December 8, 1988; by Dr Gertrude B. Elion and published inLes Prix Nobel 1988, printed in Sweden by Norstedts Tryckeri, Stockholm, Sweden, 1989, republished here with the permission of the Nobel Foundation, the copyright holder.     

Immunotoxins up to the present day

Immunotoxins consist of monoclonal or polyclonal antibodies conjugated to bacterial or plant toxins. The toxins used are typically of the A-B type in which a toxic A chain is coupled to a B chain responsible for cell binding and facilitation of A chain entry into the cytosol. Two broad strategies have been followed: coupling intact toxins, or A chains alone, to antibodies. This review examines current progress inin vitro andin vivo research, including recent clinical studies, concentrating principally on ricin or ricin A chain conjugates. The future role of conjugates using membrane-acting toxins, immunolysins, is also discussed.     

Rhizobium leguminosarum genes required for expression and transfer of host specific nodulation

The contributions of various nod genes from Rhizobium leguminosarum biovar viceae to host-specific nodulation have been assessed by transferring specific genes and groups of genes to R. leguminosarum bv. trifolii and testing the levels of nodulation on Pisum sativum (peas) and Vicia hirsuta. Many of the nod genes are important in determination of host-specificity; the nodE gene plays a key (but not essential) role and the efficiency of transfer of host specific nodulation increased with additional genes such that nodFE < nodFEL < nodFELMN. In addition the nodD gene was shown to play an important role in host-specific nodulation of peas and Vicia whilst other genes in the nodABCIJ gene region also appeared to be important. In a reciprocal series of experiments involving nod genes cloned from R. leguminosarum bv. trifolii it was found that the nodD gene enabled bv. viciae to nodulate Trifolium pratense (red clover) but the nodFEL gene region did not. The bv. trifolii nodD or nodFEL genes did significantly increase nodulation of Trifolium subterraneum (sub-clover) by R. leguminosarum bv. viciae. It is concluded that host specificity determinants are encoded by several different nod genes.     

Induction of hepatic drug metabolizing enzymes by DL-methionine in rats

A single intraperitoneal injection of DL-methionine (500 mg/kg body wt.) to adult male Wistar rats was shown to significantly induce all the components of the hepatic microsomal mixed function oxidase system such as NADPH cytochrome C reductase activity, cytochromes P-450 and b₅, as well as activities of drug metabolizing enzymes such as aminopyrine demethylase and uridine 5′ -diphosphate-glucuronosyltransferase. Combined administration of nicotinamide (250 mg/kg body wt.) and DL-methionine (500 mg/kg body wt.) was shown to bring about an additional increase (25-30%) in the activities of these enzymes as compared to their induction on independent administration of the two endobiotics. In rats bearing Yoshida sarcoma (ascites) tumour as well as in normal rats injected with serum from tumour bearing animals, the decreased activities of hepatic mixed function oxidases could be restored to their normal levels by administration of DL-methionine (500 mg/kg body wt.) to these rats. Whereas actinomycin D (1 mg/kg body wt.) had no effect on the increased incorporation of [¹⁴C] labelled leucine into microsomal proteins following administration of nicotinamide, the enhanced incorporation of the label following DL-methionine administration was completely inhibited by the same dose of actinomycin D. Administration of cycloheximide (0·5 mg/kg body wt.) to rats could completely inhibit the increased incorporation of [¹⁴C] leucine into hepatic microsomal proteins following independent administration of nicotinamide and DL-methionine. Similar inhibitory pattern with actinomycin D and cycloheximide was also demonstrated in case of induction of NADPH cytochromeC reductase activity by both these endobiotics.     

Temporal changes in the egglaying behaviour of the Hessian fly

Responses of mated female Hessian flies were investigated by analysing the behaviour of individual flies in wheat and oats. The behavioural repertoire of such females included: flying, alighting on leaves, arching of the body so that the tip of the abdomen touched the leaf surface, antennation, movements of the tip of the abdomen across the leaf at right angles to leaf veins, sitting with the ovipositor straight but still extended, and sitting with the ovipositor telescoped into the body. After alighting, females on wheat showed a higher frequency of transitions from arching to antennation and a lower frequency of transitions from arching to abdomen straight than females on oats. During the first 5 min of observations, individuals released into arenas with wheat arched and antennated 2–3 times more frequently than females released into oats. Time allotted to behaviours also differed; during the first 5 min, females in wheat spent 50 percent more time arching, whereas females in oats spent 50 percent more time sitting. Females in wheat also stayed longer and laid 4 times more eggs than females in oats. Temporal changes in egglaying were monitored by quantifying hourly rates of egglaying in no-choice assays for several hours following mating at 9:00 am. During the first and second hours post-mating, egglaying occurred infrequently. However, during the third hour post-mating (11:00 am to noon) females on wheat laid 5 times more eggs than females on oats. Rates of egglaying decreased on wheat but increased on oats during the fourth hour, and then during the fifth hour, decreased on both wheat and oats. Changes in egglaying responses were also evident when behaviours of individual females were measured 1–3 h vs. 3–7 h post-mating. Females deprived of host plants and released into wheat or oats later in the day showed higher frequencies of arching and antennation and laid more eggs before leaving the arena.

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Résumé Les réactions de femelles préalablement accouplées de Mouches de Hesse ont été examinées en analysant le comportement de femelles isolées sur blé et sur avoine. Le répertoire comportemental de ces femelles comprenait: le vol, l'atterrissage sur feuille, la flexion du corps de sorte que l'extrémité de l'abdomen touchât la surface de la feuille, l'antennation, les mouvements de l'extrémité de l'abdomen sur la feuille à angle droit des nervures, le repos avec la tarière droite et encore dévaginée, le repos avec la tarière télescopée à l'intérieur du corps. Sur blé plus que sur avoine, les femelles après atterrissage ont présenté une fréquence plus élevée de passage de la flexion à l'antennation que de la flexion à l'abdomen droit. Durant les 5 premières minutes d'observation, les individus libérés dans des enceintes avec blé fléchirent et antennèrent 2 à 3 fois plus que ceux libérés sur avoine. Les durées des différentes séquences différaient aussi: sur blé, pendant les 5 premières minutes, les femelles passèrent plus de 50% du temps à fléchir, tandis que sur avoine elles passèrent plus de 50% du temps en repos. Les femelles restèrent aussi plus longtemps sur les feuilles de blé et y pondirent 4 fois plus d'oeufs que sur avoine.Les femelles de M. destructor ont montré une plasticité du seuil d'acceptation. Pendant les premières heures de ponte, elles ont été très sélectives et refusèrent, ou ne pondirent que quelques oeufs sur avoine, mais acceptèrent volontiers le blé. La discrimination s'est poursuivie tant que les femelles ont eu accès au blé en même temps qu'à l'avoine. Cependant, quand les femelles ont été privées de blé pendant plusieures heures, l'acceptation de l'avoine a augmenté. Cet accroissement de l'acceptation a eu lieu à peu près au moment où les femelles sur blé pondaient leurs derniers oeufs.

     

Increase in hepatic microsomal lipid peroxidation mediated by α-adrenergic system under cold stress and noradrenaline treatment

A membrane protein recognized by monoclonal antibody SQM1 was identified in human squamous carcinomas, including those originating in the head and neck (SqCHN), lung and cervix. Cell lines derived from SqCHN of previously untreated patients expressed high amounts of this protein. In contrast, many cell lines established from SqCHN of patients previously treated with chemotherapy and/or radiation showed diminished amounts of this SQM1 protein. The expression of SQM1 antigen was determined in several SgCHN cell lines made resistant by exposure to methotrexate (MTX) in vitro. The parent cell lines all exhibited strong binding to SQM1 antibody. The MTX-resistant sublines showed much lower membrane binding of SQM1. The lowest SQM1 reactivity was found in cell lines with high resistance to MTX and with diminished rate of MTX transport. Some highly MTX-resistant cell lines which had high levels of dihydrofolate reductase, but which retained a high rate of MTX transport, also retained high levels of SQM1 binding. Reduced SQM1 protein was also found in SgCHN cells which developed resistance to the alkylating drug cis-platinum (CDDP) and which showed reduced membrane transport of CDDP. Cell growth kinetics and non-specific antigenic shifts were not responsible for the differences in SQM1 binding between the parent cell lines and their drug-resistant sublines. The finding of a novel protein which is reduced in cells resistant to MTX and CDDP could contribute to our understanding of the basic mechanisms of drug resistance. By detecting SQM1 protein in clinical specimens, it may be possible to monitor the development of drug resistance in tumors.Abbreviations SqCHN Squamous Carcinoma of the Head and Neck - MTX Methotrexate - CDDP Cis-Platinum - DHFR Dihydrofolate Reductase     

New ecological information onScytalina cerdale (Pisces: Scytalinidae) from a central California rocky intertidal zone

Synopsis New information regarding the ecology ofScytalina cerdale was obtained over a four year period as a consequence of a long-term marine ecological study at the Diablo Canyon Power Plant (DCPP), San Luis Obispo County, California. Twenty intertidal fish surveys were conducted at approximately quarterly intervals, between March 1979 and June 1983, at three separate rocky shore locations (stations). During each survey, a total of 108 square meters (36 m² per station) was searched for fish during periods of low tide. A total of 280S. cerdale were collected, identified, measured, and released back into the same 4 m² area, from the same intertidal station (Diablo Cove), throughout the study period. This limited intertidal occurrence most likely reflectsS. cerdale microhabitat requirements; a combination of intertidal elevation (mean = +0.3 MLLW), substratum specificity (loose gravel, 5–10mm size range, overlying a base of sand and shell fragments), and degree of wave exposure (semi-protected). Throughout the study,S. cerdale was seasonally more abundant during summer months (June through August) and less abundant during winter months (November through February). The only exception to this abundance trend followed the 1982 winter storms, which coincided with an El Niño event, whenS. cerdale abundance uncharacteristically dropped during the subsequent 1983 spring and summer surveys. Mean total lengths did not vary greatly, reflecting the absence of early juvenile fishes, and relatively high mean fish densities (3.5 fish per m² for 20 surveys) were recorded. Qualitative comparisons betweenS. cerdale abundance and seasonal changes in water temperature indicated an inverse relationship. Gravid females, demersal egg masses, and early juvenile individuals were never observed during the four years of the study. This suggests that unlike most other intertidal fishes, particularly other blennioids,S. cerdale may not utilize the intertidal zone for reproductive and recruitment purposes; Diablo Canyon is the most southerly reported distribution for this intertidal species, and therefore, may not entirely represent the species' biology as a whole.