Heat stress in the presence of low RNA polymerase activity increases chromosome copy number of Escherichia coli

Summary A temperature shift-up accompanied by a reduction in RNA polymerase activity in Escherichia coli causes an increased rate of initiation leading to a 1.7- to 2.2-fold increase in chromosome copy number. A temperature shift-up without a reduction in polymerase activity induces only a transient non-scheduled initiation of chromosome replication caused by heat shock with no detectable effect on chromosome copy number.     

Two new species of gorgonian octocorals from the Tropical Eastern Pacific Biogeographic Region (Cnidaria,Anthozoa, Gorgoniidae)

The gorgoniid Eugorgia is exclusively an eastern Pacific genus. It has a wide geographic and bathymetric range of distribution, found from California to Perú and extends down to 65 m deep. Two new species are herein described. The morphological characters were analyzed and illustrated by light and scanning electron microscopy. Eugorgia beebei sp. n. can be distinguished by its white, ascending, sparse colony growth. Eugorgia mutabilis sp. n. can be distinguished by its white colony that changes color after collection, and the conspicuous sharp-crested disc sclerites. From a morphological point of view the new species are related to the daniana-group, the rubens-group and the siedenburgae-group of Eugorgia; their affiliations, and the proposal of a new group are discussed. These new species increases the number of species in the genus to 15, and contribute to the knowledge of the eastern Pacific octocoral biodiversity.     

Heterotopic microvascular growth plate transplantation of the proximal fibula: an experimental canine model

The reconstructive potential of microvascular transplantation of skeletal growth plates was investigated through heterotopic transfers. The distal radius was resected in two series of puppies of a known large breed and substituted with a microsurgically revascularized transplant from the proximal fibula. Evaluation was conducted through serial roentgenograms, goniometric registration of joint mobility, volume measurements, histology, and fluorescent bone labeling. In the first series, development of neuropathic-like destruction of the weight-bearing graft ensued in the majority of the animals. In the second series, prolonged protection from weight bearing inhibited this destruction and resulted in hypertrophy of the revascularized epiphyseal end of the transplant but clearly reduced longitudinal growth, with only one transplant exhibiting longitudinal growth that exceeded 50 percent of the value for the control. This experiment demonstrates that skeletal growth plates possess a capacity for hypertrophy under the influence of increased loads. Whether this adaptability is sufficient to allow microvascular transplantation of growth plates to become a clinically useful procedure in children remains unclear. Further laboratory investigations are mandatory prior to clinical application of microvascular transfers of epiphyseal growth plates.     

The impact of ticks on pheasant territoriality

Pheasants are competent reservoir hosts for the Lyme disease spirochaete, Borrelia burgdorferi s.l., and carry large, but highly over-dispersed, infestations of the vector ticks, Ixodes ricinus . The effects of experimental reduction of tick infestation levels on the survival and territorial behaviour of male pheasants were studied. Over three years in two woodlands in southern England, birds were marked individually and half were fitted with a slow-release acaricide, which substantially reduced their tick burdens from March to August. Acaricide treatment affected reproductive success but had no discernible impact on the survival rates of male pheasants. The degree of wattle inflation by males, an indicator of territorial status and a correlate of harem acquisition, was significantly greater among treated males. In each year, a significantly higher proportion of treated (overall 44%) than control (22%) males acquired harems. Males that acquired females ranged over small areas on field edges. By contrast, those with no females ranged more widely in woods and the adjoining fields, increasing their exposure to questing ticks. The relative contribution of such roving males to tick-borne pathogen transmission may thus increase.     

Identification of highly reactive cysteinyl and methionyl residues of rabbit muscle phosphofructokinase

The reactivity of the 16 thiol groups of rabbit skeletal muscle phosphofructokinase has been studied extensively over the past 20 years. Several of these thiols show high reactivity with a variety of reagents, display differential reactivity in the presence of allosteric ligands and substrates, and appear to be important to function because their modification changes activity and regulatory properties. In the present study, the location in the primary structure of several highly reactive thiol groups has been established by reaction with [14C]iodoacetate. In the course of these studies, 2 methionyl residues that are located at or near proposed ligand-binding sites are readily carboxymethylated by iodoacetate. In addition to confirming the presence of the most reactive thiol group at sequence position 88, a thiol protected from reaction by the presence of fructose-6-P and cyclic AMP has been found at position 169. Cysteine 169 is close to a residue important to the binding of fructose-6-P in the homologous structure from Bacillus stearothermophilis phosphofructokinase. The modification of Cys-169 brings about extensive, but not total, loss of activity. Another cysteine, at position 232, was found to be highly reactive also. Substrate provided partial protection against carboxymethylation at this position. Carboxymethylation of enzyme restricted to methionines 74 and 173 brought about no changes in the total activity or in the ATP inhibition profile of the enzyme. This is significant since position 74 was projected on the basis of the homologous procaryotic structure to be important in the binding of nucleotide to the allosteric site.     

Transforming c-Ki-ras mutation is a preneoplastic event in mouse mammary carcinogenesis induced in vitro by N-methyl-N-nitrosourea.

Mouse mammary epithelial cells can be transformed in primary cultures to preneoplastic and neoplastic states when treated with N-methyl-N-nitrosourea (MNU). Mammary carcinomas arising from MNU-induced hyperplastic alveolar nodules (a type of mouse mammary preneoplastic lesion) contained transforming c-Ki-ras genes when examined by the NIH 3T3 focus assay. Hybridization of allele-specific oligonucleotides to c-Ki-ras sequences amplified by the polymerase chain reaction demonstrated the presence of a specific G-35----A-35 point mutation in codon 12 in each of the NIH 3T3 foci as well as the mammary carcinomas. This mutation resulted in the substitution of the normal glycine with an aspartic acid. Furthermore, this mutation in the c-Ki-ras proto-oncogenes was also detected in 9 of 10 hyperplastic alveolar nodules. These results demonstrate that the specific c-Ki-ras mutation is a preneoplastic event in MNU-induced mouse mammary carcinogenesis.