Somatic embryogenesis in cell suspension culture of carnation (Dianthus caryophyllus L.)

Somatic embryogenesis and plantlet formation were obtained from 60–75 day old cell cultures of carnation. Callus was generated on MS basal medium supplemented with 2,4-dichchlorophenoxy acetic acid (2,4-D). Removal of 2,4-D during subsequent subculturing of cell suspensions resulted in formation of embroids. These somatic embryos originated from single cells and their early development proceeded normally with clearly defined apical and root meristems. Some embryos developed into plants and were acclimatized to ex vitro conditions.     

A rapid bactometer method for screening of biocides against sulfate-reducing bacteria

A rapid and efficient bactometer method was developed for screening biocides against sulfate-reducing bacteria. The method is based on impedance microbiology principles and uses double-layer API (American Petroleum Institute) agar medium supplemented with 0.1% sodium thioglycolate as a reducing agent. Compared to the conventional API procedure, which requires 28 days, the present technique takes only 1 day to obtain test results. Excellent linear correlation (r=–0.98) was found between the impedance detection time and log initial cell concentration. The results of the bactometer test were comparable to that of the API bottle test.     

Models of comorbidity for multifactorial disorders.

We develop several formal models for comorbidity between multifactorial disorders. Based on the work of D. N. Klein and L. P. Riso, the models include (i) alternate forms, where the two disorders have the same underlying continuum of liability; (ii) random multiformity, in which affection status on one disorder abruptly increases risk for the second; (iii) extreme multiformity, where only extreme cases have an abruptly increased risk for the second disorder; (iv) three independent disorders, in which excess comorbid cases are due to a separate, third disorder; (v) correlated liabilities, where the risk factors for the two disorders correlate; and (vi) direct causal models, where the liability for one disorder is a cause of the other disorder. These models are used to make quantitative predictions about the relative proportions of pairs of relatives who are classified according to whether each relative has neither disorder, disorder A but not B, disorder B but not A, or both A and B. For illustration, we analyze data on major depression (MD) and generalized anxiety disorder (GAD) assessed in adult female MZ and DZ twins, which enable estimation of the relative impact of genetic and environmental factors. Several models are rejected--that comorbid cases are due to chance; multiformity of GAD; a third independent disorder; and GAD being a cause of MD. Of the models that fit the data, correlated liabilities, MD causes GAD, and reciprocal causation seem best. MD appears to be a source of liability for GAD. Possible extensions to the models are discussed.     

Polystomatidae (Monogenea) of southern African Anura: Polystoma claudecombesi n. sp. parasitic in Rana angolensis Bocage

Polystoma claudecombesi is described as a new species of the Polystomatidae (Monogenea) parasitic in the urinary bladder of the anuran host Rana angolensis. This parasite was collected at three localities in South Africa, namely Vernon Crookes Nature Reserve in Natal province, Witsieshoek Mountain Resort in the north-eastern Orange Free State and Bovenste Oog in the province of Transvaal. It is the largest African polystome described to date. Prevalence at Vernon Crookes Nature Reserve was 4.0% and 2.7% in two successive years, with a mean intensity of 1.0 (n=25 and 36, respectively). One of the two R. angolensis from Witsieshoek was infected with 5 parasites. The diversity and distribution of southern African polystomes is also discussed.     

Bactericidal effect of bovine normal and immune serum, colostrum and milk against Helicobacter pylori

Serum and colostrum but not post-colostral milk from non-immunized Friesian cows was found highly bactericidal for Helicobacter pylori NCTC 11637. This bactericidal activity was destroyed by heating at 56°C for 30 min and restroed by the addition of fetal calf serum as a source of complement, indicating that the bactericidal effect was probably dependent on an antibody-complement system. Systemic, serial immunization of non-lactating, pregnant cows with H. pylori resulted in high specific antibody titres in serum and colostrum. No titres were found in post-colostral milk, even after booster-immunization during lactation. Immunization did not enhance the bactericidal activity of serum and colostrum, but increased it in post-colostral milk. The bactericidal activity was not correlated with titres of specific antibody or with IgG concentrations.     

The potential of and limitations to marine population prognosis

Following the 19th century recognition and definition of basic ecological entities, functional analysis has been the highlight of this century. The synthesis of these findings enables ecological prognosis. The population as the basic functional unit has been repeatedly treated; in the marine field, fisheries management approaches developed into multi-species population analysis. As in planktology, theoretical ecology, and classic biocoenotic research, the population interactions are of increasing scientific interest. A mathematical model is suggested that combines these extrinsic and intrinsic functional relationships in order to define the fit of the ecological niche to the environment, the decisive measure of the expected population success, and thus of the probable population development needed for prognostic purposes. It is discussed in how far the orientation towards the predictive power or — with respect to the “skill” of meteorological prognoses — the “ecological prognostic skill” improvement may serve as a means to choose the best investigative strategy.     

Heterologous Radioimmunoassay for Llama and Alpaca Luteinizing Hormone with a Monoclonal Antibody,an Equine Standard and a Human Tracer

A radioimmunoassay for llama and alpaca LH was developed using a human I125LH tracer from a commercial kit, equine LH diluted in human LH free serum as standard, and a monoclonal antibody (518B7) specific for LH but with low species specificity. A 60-min delay in the addition of the tracer and overnight incubation gave a sensitivity of 0.8 μg L−1. The intra-assay coefficient of variation was 37% at 1 μg L−1, declined to 15% at 4 pg L−1 and was below 6% for concentrations up to 32 μg L−1. The inter-assay coefficients of variation for 3 control samples were 20% (2.8 μg L−1), 16% (7.1 μg L−1) and 9.8% (19 μg L−1). In an attempt to increase sensitivity, all tubes were preincubated for 4 h at room temperature before adding the tracer, and the sample volume was increased from 50 μL to 100 μL· (in the standard curve the increased volume was compensated for by human LH free serum). With this protocol, the assay sensitivity was 0.5 μg L−1. The assay was validated clinically and demonstrated increased concentrations of LH after mating in llamas and alpacas. Furthermore, the assay was used to monitor LH responses to a single dose of GnRH in llamas (adult males and females at different ages).     

Isolation and characterization of four polycyclic aromatic hydrocarbon degrading bacteria from soil near an oil refinery

Four bacterial strains (I-IV) capable of optimum growth on 0·1% naphthalene, anthracene or a mixture of naphthalene and phenanthrene were isolated from soil near an oil refinery. Two isolates (I and II) were identified as belonging to the genus Micrococcus , while strains III and IV were identified as Pseudomonas and Atcaligenes respectively. All the isolates were found to bear high molecular weight plasmid DNA (isolate I and IV 89%, II 67·5% and III 92·1% of Λ DNA), which is presumed to aid in the metabolism of polycyclic aromatic hydrocarbons. The strains also showed appreciable growth at high concentrations of NaCl (up to 7·5%).