Clavispora,a new yeast genus of the Saccharomycetales

In Candida lusitaniae van Uden et do Carmo-Sousa (1959), strains of opposite sex have been found. Cells of the opposite mating types conjugate and form asci with one to four clavate spores. These are easily liberated from the ascus. The type strain of Candida obtusa (Dietrichson) van Uden et do Carmo-Sousa ex van Uden et Buckley (1970) also produces ascospores after mating with one of the strains of Candida lusitaniae. As clavate ascospores are unknow in yeasts, a new genus, Clavispora, is proposed with Clavispora lusitaniae spec. nov. as type species.     

Studies of the mechanisms for the induction of in vivo tumor immunity. VI. Induction of specific and nonspecific cell-mediated immunity in tumor-bearing hosts and its correlation with transplantation tumor immunity

Studies were performed to determine the development of cell-mediated cytotoxic response at tumor site in C57BL/6 mice bearing progressively growing FBL-3 ascites leukemia. The effectors isolated from tumor ascites are found to be highly cytotoxic for leukemic target cells. The levels of cytotoxicity obtained with effectors isolated from tumor site are generally higher than those obtained with immune mice. This cytotoxicity is both specific and nonspecific. The specific cytotoxicity against tumor-associated antigen is mainly mediated by T cells and the nonspecific cytotoxicity against unrelated tumor cells is mediated largely by macrophages. The T-cell-enriched preparation did not give significant natural killer activity. When testing the ability of these effectors to produce in vivo immunity against the challenge of FBL-3, it was found that only T cells could confer the transplantation-type immunity, but the immunity was transient. The macrophage-enriched preparation isolated from tumor ascites failed to give in vivo protection. These findings indicate that in FBL-3 system, mice with progressively growing tumors are able to develop immune response against tumor cells. However, this immunity is probably interfered with by a suppressor factor(s) or suppressor cells which restrict their activity to eliminate the tumor cells effectively.     

Prevalence, biotypes, plasmid profile and antimicrobial resistance of Campylobacter isolated from wild and domestic animals from northeast Portugal.

The incidence of Campylobacter jejuni and Campylobacter coli in wild and producing animals has been studied to evaluate their importance as potential reservoirs of campylobacter infection. These organisms were isolated from: 59 chicken (60.2%), 65 swine (59.1%), 31 black rats (57.4%), 61 sparrows (45.5%), 21 ducks (40.5%), 32 cows (19.5%) and 27 sheep (15.3%). Biotypes, plasmid and resistance profiles were studied in order to characterize the isolates. Biotypes I and II of C. jejuni were predominant in all reservoirs except swine, where C. coli I was more frequent. Plasmid prevalence was higher in strains isolated from swine (53.8%) and rats (45.5%). The size of the plasmids ranged from 1.3 to 82 MDa. A 2.3 MDa plasmid was the most frequent, detected in all the reservoirs except ducks. Antimicrobial susceptibility testing revealed that 5.5% of the strains were resistant to ampicillin, 5.5% to tetracycline, 12.6% to erythromycin and 23.5% to streptomycin. Resistance to erythromycin (26.2%) and to streptomycin (58.4%) was particularly high in isolates from swine. Tetracycline resistance was encoded by a 33 or a 41 MDa plasmid and transferred by conjugation.     

Amino acids are general growth inhibitors of Nicotiana silvestris in tissue culture

The growth of Nicotiana silvestris in suspension culture is inhibited by all of the common protein amino acids at the millimolar level, except for L-glutamine. A defined experimental system for growth/inhibition studies has been established, and growth studies were carried out with cells that had been maintained in the exponential growth phase for at least 10 generations (EE cells). The following results were obtained after particularly detailed studies with aromatic amino acids. The onset of inhibition was preceded by a duration of normal growth rate which varied within a range of 12 to 48 h. The degree of inhibition was directly proportional to amino acid concentration and inversely related to the initial cell density of the inoculum. A slowed, but still exponential rate of growth persisted during an early phase of inhibition. Under sufficiently severe conditions, this was followed by progressive diminution of growth rate and eventual lysis. The most drastic inhibitory effects caused by aromatic amino acids were in the order: phenylalanine, tryptophan and tyrosine. When EE cells cultivated under conditions of growth inhibition were diluted into fresh medium, immediate resumption of growth at the uninhibited rate occurred and persisted. On the other hand, when growth-inhibited EE cells were diluted into medium containing the same concentration of amino acid used in the first round of growth, an initial burst of uninhibited growth lasting about 24 h was followed by a drastic, progressively declining growth rate which deteriorated to cell death and lysis. When cells in stationary phase were used as an inoculum, as is done in typical growth characterizations with suspension cultures, the sensitivity to inhibition during the subsequent exponential growth phase was several-fold greater than was the case with EE cells. Hypotheses that growth inhibition might be caused by ammonia toxicity, keto-acid toxicity, or by inhibition of nitrate utilization were ruled out. Observations that provide new insight are: (i)growth-inhibited cells undergo drastic plasmolysis, (ii) L-glutamine is an effective antagonist of amino-acid inhibitors, and (iii) growth-inhibited cells exhibit a transient restoration of normal growth rate upon dilution into fresh growth medium. These results implicate a linkage of amino acids with osmotic regulation and nitrogen metabolism.     

Strains of Colletotrichum coffeanum Noack Causing Coffee Berry Disease in Angola and Malawi with Characteristics Different to the Kenya Strain

Strains of Colletotrichum isolated from berries of Coffea arabica from Angola and Malawi were identified as C. coffeanum causing coffee berry disease (CBD). The isolates were highly aggressive to berries of the cultivar ‘Catimor’ and produced high numbers of acervuli and extremely large masses of pink conidia when cultivated in the dark. These strains are apparently different in aggressiveness and morphology to those described in the past from Kenya.     

A gustatory mutant of Drosophila defective in pyranose receptors

Summary Mutations in an X-linked gene, gust-A, block the responses of Drosophila melanogaster to a group of pyranose sugars. It is shown that the behavioural effects of this mutation are correlated with a loss of electrical responses in taste receptors. The mutation affects the chemoacceptors for pyranose sugars leaving the furanose acceptors intact.     

Studies of the mechanisms for the induction of in vivo tumor immunity. V. A comparison of the generation of the primary cell-mediated cytotoxic response using in vitro mixed-lymphocyte--tumor cell culture and an in vivo technique

In vivo immunization of C57BL/6 mice with FBL-3, a syngeneic Friend-virus-induced leukemia, can induce a specific, T-cell-mediated cytotoxic response, as measured by the ¹²⁵IUdR release assay. In vitro it was difficult to generate an analogous, primary cytotoxic response, using a normal spleen responder population. After modification of the splenic responders by adding normal peritoneal cells, this modified population then had the capacity to mount a primary cytotoxic response in the mixed-lymphocyte-tumor cell culture reaction to FBL-3. We have characterized the effector population as well as the helper (peritoneal) cells which were responsible for elevating the cytolytic response to FBL-3. The results indicate that there are at least two populations of cells which are essential for inducing a primary cell-mediated cytotoxic response. First, the effectors which are directly responsible for mediating the cytotoxic reactions and are derived from radiosensitive T cells and second, a helper cell population which is radioresistant and has the characteristics of macrophages.     

Effects of flask sealing and growth regulators on in vitro propagation of neem (Azadirachta indica A. Juss.)

In vitro propagation of neem (Azadirachta indica A. Juss.) may offer an efficient alternative to seed propagation of this species. For optimization of in vitro propagation, different basal salt formulations, growth regulators, and culture container sealants (polytetrafluoroethylene hydrophobic membranes [PTFE]) were evaluated. Nodal segments cultured on Murashige and Skoog (MS) medium showed the highest shoot formation per explant (1.67). Explants cultured in flasks containing MS medium with 0.5 mg L⁻¹ benzyladenine, 0.5 mg L⁻¹ kinetin, and 0.05 mg L⁻¹ naphthaleneacetic acid, and sealed with two PTFE membranes, produced the highest number of shoots (4.04). In contrast, explants cultured in flasks without membranes showed leaf chlorosis and senescence. For plant recovery, regenerants were acclimatized in a substrate of coconut fiber and eucalyptus bark (1:1) and showed 80% survival. Our results indicated that the use of flasks with vents was beneficial for in vitro propagation of this important plant.