Presence of benzodiazepine binding sites (receptors) and amplification thereof by imprinting inTetrahymena

Summary LiveTetrahymena cells bound³H-diazepam specifically, as demonstrated by autoradiographic evidence of displacement of about 25% of labeled diazepam in the presence of a 1000-fold amount of cold diazepam. The³H-diazepam bound to membrane preparations isolated from untreated (control) cells was not displaced by cold diazepam, whereas cells involved in primary interaction (imprinting) with diazepam showed amplification and specificity of diazepam binding in both in vivo (cell suspension) and in vitro (pellicle) systems, as well as displacement of bound label in the presence of 1000-fold cold diazepam. It appears that diazepam induced imprinting and, consequently, also the formation of specific receptors inTetrahymena.     

EGF receptor induction and insulin-EGF overlap inTetrahymena

Summary Offspring generations ofTetrahymena pretreated (imprinted) with insulin showed a greater binding capacity for the hormone than offspring of untreated ones. The epidermal growth factor (EGF) imprinted for insulin to a greater degree than insulin itself, and vice versa: insulin imprinted for EGF more efficiently than EGF itself. These phenomena can be explained by the overlap of insulin and EGF on one another's receptors inTetrahymena.     

Chromatosomes are not produced fromTetrahymena chromatin by micrococcal nuclease digestion

Summary The subnucleosomal organization ofTetrahymena chromatin, which has an unusual H1 histone, was investigated by NaCl extraction and micrococcal nuclease digestion of nuclei. It was found thatTetrahymena histone H1 is extracted with 0.35 M NaCl, whereas bovine thyroid H1 is not. Micrococcal nuclease digestion ofTetrahymena nuclei did not yield chromatosomes as a stable intermediate, whereas digestion of bovine thyroid nuclei did.     

Investigations of receptor-mediated phagocytosis by hormone-induced (imprinted)Tetrahymena pyriformis

Receptor-mediated endocytosis byTetrahvmena pyriformis was studied using tetramethylrhodamine isothiocyanate-labeled concanavalin A (TRITC-Con A) with fluorescence and confocal microscopy. In the presence of insulin, or 24 h after insulin pretreatment (hormonal imprinting), the binding and uptake of TRITC-Con A increased when compared to controls, owing to the binding of TRITC-Con A to sugar oligomers of insulin recptors. Mannose inhibited the binding of Con A, thus demonstrating the specificity of binding. Histamine, a phagocytosis-promoting factor in mammals andTetrahymena, and galactose, did not influence the uptake of TRITC-Con A.     

Parameters affecting the maximum cell concentration ofTetrahymena

Summary In cultures with efficient aeration a maximum cell concentration (MCC) of 6×10⁵ cells/ml (defined medium) and 5.5×10⁶ cells/ml (broth) can be reached. By culturing within Millicells with excess supply of medium and efficient removal of waste products a physical limit for MCC of about 13×10⁶ cells/ml is reached.     

Utilization of phosphate compounds for growth ofTetrahymena

Summary Taking advantage of a synthetic nutrient medium, we have studied which compounds phosphate-starvedTetrahymena thermophila can use as phosphate sources for growth and cell multiplication. Ortho-, trimeta- and -glycero-phosphate are good sources for both the wild type and a food-vacuoleless mutant; phosphorylcholine is used only by the wild type, and 2-aminoethyl phosphonic acid fails to serve as a phosphate source. Since at least two phosphatases are found in the extracellular fluid these results indicate thatTetrahymena can make use of extracellular digestion of nutrients.     

Presence of anti-Trypanosoma cruzi antibodies in the sera of mice with experimental autoimmune myocarditis

Summary The existence of antigens shared in common byT. cruzi and heart muscle cells is suggested by the presence of antibodies binding to the parasite surface in the serum of mice with autoimmune myocarditis induced by immunization with syngeneic heart antigens.     

Spasmin-like proteins in various ciliates revealed by antibody to purified spasmins ofCarchesium polypinum

Summary It was found that some ciliates,Stentor, Spirostomum andBlepharisma, which can contract rapidly like the stalks of Vorticellidae, have Ca²⁺-binding proteins that are very similar to spasmins, in the immunological sense. The presence of spasmins in other Protozoa and in some Metazoa was also investigated.     

Anthelmintic activity of a benzimidazoline compound in sheep by abomasal infusion

Summary In vitro and in vivo data on the benzimidazoline compound indicate anthelmintic potential when introduced directly into the abomasum.     

In vitro metabolism of the trichothecene 4-monoacetoxyscirpenol by fungus- and non-fungus-feeding insects

Summary The metabolism of the trichothecene 4-monoacetoxyscirpenol by intact gut tissue was determined in the fungus-feeding Nitidulid,Carpophilus hemipterus (L.) and the non-fungus-feeding caterpillars, the fall armyworm,Spodoptera frugiperda (J. E. Smith) and the corn earworm,Heliothis zea (Boddie). The primary metabolite was the hydrolysis product scirpentriol. The amount of metabolism by theC. hemipterus larvae was ca 10 times that of the caterpillars on a per mg protein basis, suggesting metabolic adaptation for feeding on fungi that may contain mycotoxins.Acknowledgment. The authors wish to thank S. Taylor for technical assistance.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

The genetics of phytotoxin production by plant pathogenic fungi

Little is known about the genetic control of phytotoxin production by plant pathogenic fungi. The production of host-selective toxins known to play a role in disease development has been genetically analyzed in three species ofCochliobolus. InC. heterostrophus, a single genetic locus with two alleles has been identified controlling the production of HMT-toxin. This locus appears to be at or near the breakpoint of a chromosome rearrangement. Single genetic loci have also been identified controlling the production of HC-toxin byC. carbonum and HV-toxin byC. victoriae. The locus inC. carbonum may be a cluster of tightly linked genes.     

Is ATP synthesized by a vacuolar-ATPase in the extremely halophilic bacteria?

The proton-dependent synthesis of ATP was demonstrated in representative members of the generaHalobacterium, Haloarcula, andHaloferax. In all cases, synthesis was not inhibited by nitrate or N-ethylmaleimide, inhibitors of the vacuolar-like ATPase found in Archaea, but was affected by azide, an inhibitor of F₀F₁-ATP syntheses. These observations extend the earlier observations withHalobacterium saccharovorum and suggest that ATP synthesis in these organisms is brought about by an F₀F₁-APT synthase.     

Localization of concanavalin-A binding sites inTetrahymena by scanning electron microscopy

Summary Binding sites of concanavalin-A were detected inTetrahymena on the body ciliature, while the cell membrane itself and the oral ciliature failed to bind the lectine.Supported by the Scientific Research Council, Ministry of Health, Hungary 1-01-0302-02-1/Cs.     

Selection of biting sites on man by two malaria mosquito species

While searching for blood, female mosquitoes pass through a behavioural process involving responses to visual, physical and chemical properties of the host. Temperature and humidity are thought to dominate mosquito orientation near the host. We observed that biting of two malaria mosquito species, i.e.Anopheles atroparvus (van Thiel) andAnopheles gambiae s.s. (Giles) preferentially occurs on different body regions of a naked motionless human host. Their preference for the head and foot regions respectively correlated with particular combinations of skin temperature and eccrine sweat gland density. Subsequent modification of the host's odour profile by removing exhaled breath and washing feet results in significant changes of these preferences.     

Infection of frog tadpoles (Amphibia) by insect parasitic nematodes (Rhabditida)

Summary Infective stage juveniles ofNeoaplectana carpocapsae (Steinernematidae) andHeterohabditis heliothidis (Heterorhabditidae) were able to penetrate through the alimentary tract of young tadpoles ofHyla regilla (Hylidae) andXenopus laevis (Pipidae) and enter the body cavity. Some infectives ofN. carpocapsae were able to release their symbiotic bacterium,Xenorhabdus nematophilus inside the host and in two cases, the nematodes developed into adult females before they perished. Tadpole mortality was associated with foreign bacteria entering the penetration holes made by the invading nematodes. The infective stage juveniles of both nematodes frequently encountered a host defense reaction upon reaching the tadpole's infective stage juveniles of both nematodes frequently encountered a host defense reaction upon reaching the tadpole's coelom.     

Studies on the fungal phytotoxin victorin: Structures of three novel amino acids from the acid hydrolyzate

Summary The host-selective phytotoxin victorin, produced by the fungusCochliobolus victoriae, was found to be at least partially peptidic in nature, and did not contain victoxinine. The exact mass of the M-H ion was measured by FABMS as 795.1877. Derivatives of three major acid hydrolysis products were isolated. The structures of the corresponding amino acids were assigned as 2S,3R-3-hydroxyleucine, 5,5-dichloroleucine, and 3-hydroxylysine. A into victorin by the fungus in vivo.     

On the mechanism of killing ofTrypanosoma cruzi by human polymorphonuclear leukocytes

Summary The temperature-dependence of some processes involved in the killing of sensitizedT. cruzi epimastigotes by human polymorphonuclear leukocytes (PMN) was determined. The rate of the reactions was related to the temperature of incubation according to the Arrhenius equation and the apparent energies of activation (Ea) were calculated. The Ea values separated these complex reactions into two groups: one with Ea of about 10 kcal/mol for the phagocytosis of the parasites and the release of lysosomal enzymes by PMN, and the other with Ea of about 22 kcal/mol for the cytotoxicity against sensitizedT. cruzi, the rate of oxygen consumption by PMN, and the lysis of the parasites with added hydrogen peroxide.This work was supported by research grants from CONICET and SUBCYT, Argentina, and UNDP/Word Bank/WHO Special Programme for Research and Training in Tropical Diseases. The author wish to thank Dr I. Reisin, Dr. A. Boveris and Dr M.M.E. de Bracco for their helpful discussion.     

β-Lactam resistance in Staphylococcus aureus: the adaptive resistance of a plastic genome

Staphylococci have two mechanisms for resistance to β-lactam antibiotics. One is the production of β-lactamases, enzymes that hydrolytically destroy β-lactams. The other is the expression of penicillin-binding protein 2a (PBP 2a), which is not susceptible to inhibition by β-lactam antibiotics. Strains of S. aureus exhibiting either β-lactamase or PBP 2a-directed resistance (or both) have established a considerable ecological niche among human pathogens. The emergence and subsequent spread of bacterial strains designated as methicillin-resistant S. aureus (MRSA), from the 1960s to the present, has created clinical difficulties for nosocomial treatment on a global scale. The recent variants of MRSA that are resistant to glycopeptide antibiotics (such as vancomycin) have ushered in a new and disconcerting chapter in the evolution of this organism. Received 2 April 2005; received after revision 15 July 2005; accepted 25 July 2005     

Transfer of secondary metabolites from the spongesDysidea fragilis andPleraplysilla spinifera to the mantle dermal formations (MDFs) of the mudibranchHypserlodoris webbi

The opisthobranch molluscHypselodoris webbi is able to select, among its potential preys, sponges chemically rich in furanosesquiterpenoids. The sequestered secondary metabolites act as defensive allomones against predators and are accumulated in some dorsal glands (MDFs). This transfer from sponges to MDFs has been proven by maintainingH. webbi together with some selected sponges in an aquarium for a prolonged period.