Persistently infected cultures as a source of hepatitis A virus.

Primary African green monkey kidney, continuous African green monkey kidney cell line BS-C-1, and buffalo green monkey kidney cultures were infected with a uniform inoculum of hepatitis A virus (HAV). Although both the cell line BS-C-1 and primary African green monkey kidney cultures produced useful amounts of virus, HAV was detected earlier and in greater quantities in primary African green monkey kidney cultures. A persistently infected primary African green monkey kidney culture was developed. The influence of incubation time (4 to 40 days) and concentration (2 to 15%) of fetal calf serum in the maintenance medium on production of HAV by this culture was examined. An incubation period of 24 to 28 days was found to be optimal; reducing this period led to decreased yields of HAV. No significant difference in the amount of HAV produced was observed with differing concentrations of fetal calf serum. Three different methods of extraction and the effect of multiple extractions on the recovery of HAV from cell lysates were examined. Sonication was a critical factor. Two extractions yielded more than 90% recoverable virus. Yields in excess of 10(11) physical particles of HAV per 850-cm2 roller bottle were routine. The total yield could be increased by concentrating the HAV present in spent maintenance medium by using bentonite or organic flocculation.     

In vitro photoinduction of leaf tissue ofStreptocarpus nobilis

Leaf expiants from vegetative plants of the short-day plantStreptocarpus nobilis (C. B. Clarke) developed flower budsin vitro when cultured in 8 h photoperiods. Tn non-inductive photoperiods only vegetative buds were formed.In vitro photoinduction was demonstrated by giving the expiants short-day (SD) cycles and then transferring them to non-inductive photoperiods for expression of flowering. On medium containing 6-benzylaminopurine (BAP) organogenesis was initiated during the photoinductive treatments. Photoinduction of leaf tissue without adventitious bud development was obtained on medium without BAP. The photoinductive state of the leaf tissue was fairly stable, being expressed after 2–3 weeks in non-inductive photoperiods when adventitious buds were formed. The quantitativein vitro flowering response to the endogenous floral stimuli, resulting from photoinduction, could provide the basis of a bioassay for presumptive flower inducing chemicals.     

Food selection by locusts: The rôle of learning in rejection behaviour

The food selection behaviour of male fifth instar nymphs of Locusta migratoria was monitored on the host plant wheat and on the non-host plants Senecio vulgaris, S. jacobaea and Brassica oleracea. The non-hosts were rejected, but the mode of rejection altered with time in a way which suggested associative learning. This hypothesis was tested and the results discussed in relation to classical theories of learning.

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La sélection des aliments chez les criquets: Le rôle de l'apprentissage dans le comportement de rejet

Résumé Des larves mâles de cinquième stade de Locusta migratoria ont été placées dans des cages avec des végétaux qui pouvaient être changées sans troubler les insectes. Le contact avec des pieds de blé entraînait généralement une palpation suivie de morsures et alors d'alimentation continue. Les plantes non-hôtes Senecio vulgaris, S. jacobaea et Brassica oleracea étaient rejetées, d'abord après morsures suivant la palpation, mais ultérieurement par palpation seule. Nous avons vérifié l'hypothèse que la sensation obtenue par palpation était initialement inadéquate pour provoquer le rejet, ce qui était assuré par les morsures ultérieures mais qu'avec l'expérience l'insecte apprenait à lier la sensation de palpation avec celle de morsures et progressivement rejetait après palpation seule. Ainsi les 8 premiers contacts avec des aliments désagréables ont été observés, soit quant S. vulgaris était présenté continuellement, soit quand S. vulgaris était remplacé par une autre plante désagréable après 4 contacts. Une analyse mathématique des résultats révèle une tendance au rejet par palpation seule à travers les contacts successifs, et que cette tendance est interrompue et se restaure quand l'espace végétal est changé. Ces résultats sond discutés dans le contexte des théories de l'apprentissage et on en a conclu que le phénomène observé est le résultat d'un apprentissage associatif.

     

EHNA is a poor inhibitor of deoxyadenosine catabolism in cultured human lymphocytes

Erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA) has been used by many workers as enzyme inhibitor in vitro to simulate the in vivo situation in inherited adenosine deaminase (ADA) deficiency. In this study the metabolism of 8-14C deoxyadenosine (dAR) has been followed in cultured lymphocytes from patients deficient in enzymes associated with the catabolism and salvage of dAR, in the absence and presence of 10 microM EHNA. The results show that EHNA, at these concentrations, does not prevent the catabolism of dAR and thus does not provide a valid model for investigating the toxicity to the immune system in inherited ADA deficiency.     

Persistently infected cultures as a source of hepatitis A virus

Primary African green monkey kidney, continuous African green monkey kidney cell line BS-C-1, and buffalo green monkey kidney cultures were infected with a uniform inoculum of hepatitis A virus (HAV). Although both the cell line BS-C-1 and primary African green monkey kidney cultures produced useful amounts of virus, HAV was detected earlier and in greater quantities in primary African green monkey kidney cultures. A persistently infected primary African green monkey kidney culture was developed. The influence of incubation time (4 to 40 days) and concentration (2 to 15%) of fetal calf serum in the maintenance medium on production of HAV by this culture was examined. An incubation period of 24 to 28 days was found to be optimal; reducing this period led to decreased yields of HAV. No significant difference in the amount of HAV produced was observed with differing concentrations of fetal calf serum. Three different methods of extraction and the effect of multiple extractions on the recovery of HAV from cell lysates were examined. Sonication was a critical factor. Two extractions yielded more than 90% recoverable virus. Yields in excess of 10(11) physical particles of HAV per 850-cm2 roller bottle were routine. The total yield could be increased by concentrating the HAV present in spent maintenance medium by using bentonite or organic flocculation.     

Antitumor properties of vindesine-monoclonal antibody conjugates

Summary The anticancer alkaloid vindesine (VDS) was conjugated to four mouse monoclonal antibodies recognizing human tumor-associated antigens. The antibodies were 96.5 (antimelanoma, IgG2a); 791T/36 (antiosteogenic sarcoma, IgG2b); 11.285.14, and 14.95.55 (anticarcinoembryonic antigen, IgG1 and IgG2a respectively). Conjugates VDS-96.5 and VDS-791T/36 were tested in vitro and shown to be specifically cytotoxic for target cells expressing the appropriate antigen. The in vivo effects of the antibodies and conjugates were tested against human tumor xenografts in athymic or immunodeprived mice using multiple treatments. Conjugate VDS-96.5 retarded the initial growth of a melanoma xenograft, whereas free antibody was without effect. Similarly, VDS-791T/36 but not free antibody retarded the growth of osteogenic sarcoma 791T. The most marked antitumor effects observed were those obtained with VDS conjugates of the anti-CEA antibodies against a colorectal tumor xenograft. Antibody 14.95.55 suppressed tumor growth both alone and as a VDS conjugate, whereas 11.285.14 produced only a slight effect alone but an almost complete and lasting suppression of tumor growth as a VDS conjugate. Free VDS had little effect at nontoxic levels. Acute studies showed that VDS-11.285.14 conjugate was considerably less toxic than free VDS in Balb/c mice.     

Insect-antifeedant and antibacterial activity of diterpenoids from species of Plectranthus

Bio-assay guided fractionation of an acetone extract of leaf material from Plectranthus saccatus Benth. resulted in the isolation of a beyerane diterpenoid. This compound, characterised by spectroscopic methods as ent-3beta-(3-methyl-2-butenoyl)oxy-15-beyeren-19-oic acid, showed insect antifeedant activity against Spodoptera littoralis. Known quinonoid abietane diterpenoids obtained from new sources included a mixture of the (4R,19R) and (4R,19S) diastereoisomers of coleon A from P. aff. puberulentus J.K. Morton, coleon A lactone from P. puberulentus J.K. Morton, and coleon U and coleon U quinone from P. forsteri 'Marginatus' Benth. These compounds, and the crude acetone extracts from the leaf surfaces of 11 species of Plectranthus, were tested for antifeedant activity against S. littoralis, antibacterial activity against Bacillus subtilis and Pseudomonas syringae and antifungal activity against Cladosporium herbarum. The coleon A mixture showed potent antifeedant activity against S. littoralis, whereas coleon U showed the greatest antimicrobial activity.     

The novel nucleotide 4KNTP, in high concentrations in erythrocytes of renal failure children: a comparison with accumulation of other putative precursors in the plasma

We have measured the concentrations of metabolites related to the turnover of NAD, which accumulate in the blood of children with renal failure. One is a novel nucleotide, identified as the N1-riboside triphosphate of 4-pyridone-3-carboxamide (4PYTP), also described as 4KNTP, which accumulates in the erythrocytes in parallel with renal failure.     

A comparative method for finding and folding RNA secondary structures within protein-coding regions

Existing computational methods for RNA secondary-structure prediction tacitly assume RNA to only encode functional RNA structures. However, experimental studies have revealed that some RNA sequences, e.g. compact viral genomes, can simultaneously encode functional RNA structures as well as proteins, and evidence is accumulating that this phenomenon may also be found in Eukaryotes. We here present the first comparative method, called RNA-DECODER, which explicitly takes the known protein-coding context of an RNA-sequence alignment into account in order to predict evolutionarily conserved secondary-structure elements, which may span both coding and non-coding regions. RNA-DECODER employs a stochastic context-free grammar together with a set of carefully devised phylogenetic substitution-models, which can disentangle and evaluate the different kinds of overlapping evolutionary constraints which arise. We show that RNA-DECODER's parameters can be automatically trained to successfully fold known secondary structures within the HCV genome. We scan the genomes of HCV and polio virus for conserved secondary-structure elements, and analyze performance as a function of available evolutionary information. On known secondary structures, RNA-DECODER shows a sensitivity similar to the programs MFOLD, PFOLD and RNAALIFOLD. When scanning the entire genomes of HCV and polio virus for structure elements, RNA-DECODER's results indicate a markedly higher specificity than MFOLD, PFOLD and RNAALIFOLD.