Diversity in nucleotide acquisition by antigenically similar Chlamydia psittaci of avian origin

Abstract Two different nucleic acid precursor utilization patterns were obtained for five avian isolates of Chlamydia psittaci . Three of the isolates bahaved in a manner similar to that previously described, showing total dependency on the host cell for ribonucleoside triphosphates and being unable to utilize medium-supplied thymidine. In contrast, the other two isolates were incapable of taking pyrimidine ribonucleotides from the host cell and they could efficiently utilize medium-supplied thymidine. These unusual isolates were resistant to 5-fluorouridine while the other three isolates were sensitive. Of the five isolates only 6BC was sensitive to sulfonamides. The five isolates were divided into two groups by comparing the Alu I restriction endonuclease patterns obtained following digestion of the major outer membrane protein (OMP1) gene, amplified by the polymerase chain reaction. The OMP1 genotyping results were confirmed by serotyping.     

Use of the polymerase chain reaction and 16S rRNA sequences for the rapid detection of Brochothrix spp. in foods

Oligonucleotide primers were designed against rRNA sequences to give a DNA-based PCR assay for the rapid identification/detection of Brochothrix spp. The PCR products could be confirmed by hybridization to an internal oligonucleotide probe. The method successfully and sensitively detected/identified these organisms in pure cultures but was of limited value as a detection method because the detection sensitivity, in relation to conventional plate counts, varied and the assay sensitivity was reduced in the presence of staphylococci. Furthermore, sensitivity was also lost when the assay was applied directly to meat samples. However, a separation step using a lectin (from Agaricus bisporus ) immobilized on magnetic beads prior to the PCR assay, allowed the direct detection of low numbers (> 10 cfu g^-1) of Brochothrix in meat samples within a working day.     

Functional cis-element sequence requirements for suppression of gene expression by the TNPA protein of the Zea mays transposon En/Spm

TNPA, one of the two transposition proteins encoded by the En/Spm transposable elements of Zea mays, suppresses the expression of genes that contain an appropriate cis element. Suppression can be monitored in tobacco protoplasts in a transient expression assay as follows. The plant promoter-driven expression of the Escherichia coli-glucuronidase (GUS)-encoding gene, uidA, is repressed in the presence of TNPA if the GUS gene contains a functional cis element in the untranslated RNA leader sequence. Earlier, we found that the minimal cis element is composed of two 12 by sequences in a tail-to-tail inverted orientation. Each 12 by sequence is sufficient to bind TNPA in vitro and can be thought of as a half-site in the cis element. Here, we investigated the sequence requirements of the minimal cis element. Our observations support our expectations that a functional cis element must provide a template to which two TNPA molecules can bind in the correct orientation. Sequences within the half-sites can be altered as long as the eight bases that make up the consensus binding sites are not changed. However, we found the following unexpected sequence specificities. Firstly, some changes to the consensus binding sequence can be tolerated in one half-site, as long as the other site matches the consensus. Secondly, although the region between the half-sites can vary in sequence and in length between two and four bases, a thymidine residue is not tolerated directly 5′ preceding the second half-site. Since many variants of the cis element sequence remain functional, the suppressor response element provides a flexible tool for artificially manipulating the expression of genes.     

Does hunting affect the demography and genetic structure of the greywing francolin Francolinus africanus?

Hunted and unhunted populations of greywing francolin Francolinus africanus have been studied in the eastern Cape Province of South Africa in order to understand the effects of hunting on the demography and genetic structure of these populations. Greywing population density cycled annually for both hunted and unhunted populations. However, there was an apparent pulse of immigration of sub-dominant birds, and earlier reproduction, in the hunted populations immediately after the winter hunting season. Average levels of allozyme heterozygosity (H) for hunted and unhunted populations were both 0.076, and although the proportion of polymorphic loci per sample and the mean number of alleles per locus for each sample were lower for the hunted populations than for the unhunted populations, these differences were not significant. However, the hunted populations displayed higher levels of outbreeding (lower F _IS and F _IT values) than those for unhunted populations. Therefore, it is concluded that although greywing francolin populations contain relatively high levels of genetic heterogeneity, it is probably the increased levels of local immigration following hunting which reduces the effects of any reduction in genetic variation due to a decrease in local population size from hunting.     

Degradation of the insecticide Hydramethylnon byPhanerochaete chrysosporium

The decomposition of the amidinohydrazone-type insecticide Hydramethylnon (HMN) by soil fungi has been investigated. A simple spectrophotometric method was developed for the estimation of HMN in soil and fungal culture media. HMN was found to be degraded in soil with a half life of 14 to 25 days.Degradation of HMN by the lignolytic fungus,Phanerochaete chrysosporium yielded two major breakdown products;p-(trifluoromethyl)-cinnamic acid (TFCA) andp-(trifluoromethyl)-benzoic acid (TFBA). TFCA was converted to TFBA which was subsequently metabolised via themeta-fission pathway. Fluoride release from HMN could not be detected.Abbreviations BzDAc benzene, dioxane, acetic acid (60: 36: 4) - DCM dichloroethane - DNPH 2,4-dinitro-phenylhydrazine - HMN Hydramethylnon - TDAc toluene, dioxane, acetic acid (90: 30: 1) - TFCA p-(trifluoromethyl)-cinnamic acid - TFBA p-(trifluoromethyl)-benzoic acid - TFP 1,5-bis(trifluoro-p-tolyl)-1,4-pentadien-3-one - VA veratryl alcohol     

INBREEDING IN DARWIN'S MEDIUM GROUND FINCHES (GEOSPIZA FORTIS)

We studied the frequency and causes of inbreeding and its effect on reproductive success in a population of Darwin's Medium Ground Finches (Geospiza fortis) on Isla Daphne Major, Galápagos, during four breeding seasons (1981, 1983, 1984, and 1987). Pedigree analysis showed that levels of inbreeding were low but comparable with those observed in other passerine birds. For pairs with at least half of their grandparents known, approximately 20% of all pairings were between detectably related birds. The frequency of pairings between closely related birds (coefficient of kinship [φ] ≥ 0.250) among all pairs was 0.6%. We detected no effect of inbreeding on reproductive success, although sample sizes were small. The observed reproductive output of related pairs was not significantly different from the output of unrelated pairs, and there was no correlation between a pair's kinship coefficient and an estimate of the potential magnitude of inbreeding depression. Comparisons with a study of Great Tits (Parus major) by van Noordwijk and Scharloo (1981) suggest that, even if present, the fitness costs of inbreeding in this population of G. fortis would be low. Observed levels of inbreeding in each breeding episode were accurately predicted by simulations of random mating in which relatedness had no influence on pairing between individuals. This result suggests that levels of inbreeding in this population are determined more by demographic factors than by behavioral avoidance of mating with kin.     

The effect of birthweight on tooth-size variability in twins.

Studies indicate that low birthweight (LBW) children display reduced deciduous tooth size but there is little information about permanent tooth size. It has also been shown that dental fluctuating asymmetry (FA) increases in response to various environmental influences, but the relationship between birthweight and FA remains unclear. The aim of this study was to compare tooth size and asymmetry, according to birthweight, in the deciduous and permanent dentitions of a sample of Australian twins. The study sample comprised 436 twins, classified into 2 groups: normal birthweight (NBW > 2500 g) and low birthweight (LBW < or = 2500 g). For each individual it was generally possible to measure maximum mesiodistal crown diameters of both deciduous and permanent central incisors from serial dental models. Correlations were calculated between tooth-size variables and birthweight; subsequently comparisons of tooth size and FA were made between the LBW and NBW samples using Student's t tests. Small positive correlations (around .1) were noted between birthweight and tooth-size variables. There was no evidence of tooth-size reduction in the LBW male sample, but the LBW females displayed tooth-size reduction of approximately 2-3% for both deciduous and permanent incisors, compared to the NBW females. There was no evidence of increased FA in the LBW individuals of either sex. These findings indicate that developing teeth are generally well-protected from developmental disturbances during prenatal and perinatal periods. Further research is needed to clarify the biological basis of an apparently true but weak association between tooth size and birthweight.