Effect of ciprofloxacin on experimental osteomyelitis in the rabbit tibia, induced with a mixed infection of Staphylococcus epidermidis and Bacteroides thetaiotaomicron

After induction of experimental polymicrobic osteomyelitis with Staphylococcus epidermidis and Bacteroides thetaiotaomicron (ciprofloxacin MIC, 0.5 micrograms/ml and 4.0 micrograms/ml, respectively), in the presence of a foreign body implant, in a rabbit tibia model, ciprofloxacin was administered to infected animals for 2- and 4-week periods. At necropsy, rabbits in the 2-weeks-treated group had mean ciprofloxacin levels of 5.94 micrograms/ml in serum, 3.63 micrograms/g in marrow, and 1.88 micrograms/g in bone. Rabbits in the 4-weeks-treated group had mean ciprofloxacin levels of 7.77 micrograms/ml in serum, 5.84 micrograms/g in marrow, and 2.01 micrograms/g in bone. Quantitative bacterial plate counts were conducted on weighed samples of infected bone, marrow, and the catheter implant, taken at necropsy from treated and control rabbits. Variable reduction of bacterial numbers was observed in samples from treated animals, as compared to untreated controls. Samples of infected bone, marrow and catheter, showed comparable evidence of osteomyelitis and bacterial colonization in both treated and control animals. Although relatively high tissue levels of ciprofloxacin were attained, little therapeutic effect was observed.     

Effect of starvation and sampling time on plasma alkaline phosphatase activity and calcium homeostasis in the rat

The effect of starvation and sampling time on plasma alkaline phosphatase activity, total plasma calcium concentration and whole blood ionized calcium concentration was determined in the rat. Starvation caused a significant fall in total and ionized calcium concentrations as well as in alkaline phosphatase activity. These changes were accompanied by a fall in whole blood pH and an increase in the anion gap and a decrease in urinary excretion of calcium. These indices were restored to normal following refeeding. There was no change in serum 25-OH vitamin D concentrations following starvation for 3 days. Alkaline phosphatase activity showed a pattern compatible with the presence of a circadian rhythm when sampling took place between 0800 and 1800 h. Total and ionized calcium concentrations did not show such a rhythm when animals were fed the present diet.     

C-banding variation in the Moroccan oat species Avena agadiriana (2n=4x=28)

The C-banding technique was used to describe the chromosomes of a relatively recently-discovered Moroccan oat species, Avena agadiriana (2n=4x=28). A substantial amount of polymorphism for arm ratios and C-banding patterns was observed among five accessions of this species. However a common set of ten putatively homologous chromosomes was identifiable among the five accessions. The chromosomes of A. Agadiriana do not closely match those of any of the previously described diploid or tetraploid oat species in terms of their arm ratios and C-banding patterns. However, their overall C-banded appearance generally resembles the A/B/D groups of chromosomes of Avena species, rather than the more hetrochromatic C genomes. Implications of these findings in terms of chromosome evolution in the genus Avena are discussed.Contribution no. 95-490-J of the Kansas Agricultural Experiment Station, Kansas State University, Manhattan, KS, USA     

Hydrogen Peroxide and the Proliferation of Bhk-21 Cells

Intracellular levels of H2O2 in BHK-21 cells are not static but decline progressively with cell growth. Exposure of cells to inhibitors of catalase, or glutathione peroxidase, not only diminishes this decline but also depresses rates of cell proliferation, suggesting important growth regulatory roles for those antioxidant enzymes. Other agents which also diminish the growth-associated decline in intracellular levels of H₂O₂, such as the superoxide dismutase mimic, copper II—(3,5-diisopropylsalicylate)₂, or docosahexaenoic acid, also reduced cell proliferation. In contrast, proliferation can be stimulated by the addition of 1 μM exogenous H₂O₂ to the culture medium. Under these conditions, however, intracellular levels of H₂O₂ are unaffected, whereas there is a reduction in intracellular levels of glutathione. It is argued that critical balances between intracellular levels of both H₂O₂ and glutathione are of significance in relation both to growth stimulation and inhibition. In addition growth stimulatory concentrations of H₂O₂, whilst initially leading to increased intracellular levels of lipid peroxidation breakdown products, appear to “trigger” their metabolism, possibly through aldehyde dehydrogenase, whose activity is also stimulated by H₂O₂     

Alterations in calcium homeostasis on lead exposure in rat synaptosomes

The effects of lead on Ca²⁺ homeostasis in nerve terminals was studied. Incubation with leadin vitro stimulated the activity of calmodulin and the maximum effect was observed at 30 M lead, higher concentrations had an inhibitory effect.In vivo exposure to lead increased the activity of calmodulin by 45%. Lead had an inhibitory effect on Ca²⁺ ATPase activity in both calmodulin-rich and calmodulin-depleted synaptic plasma membranes, the IC₅₀ values for inhibition being 13.34 and 16.69 M respectively. Exogenous addition of calmodulin (5 g) and glutathione (1 mM) to calmodulin rich synaptic plasma membranes reversed the inhibition by IC₅₀ concentration of lead.In vivo exposure of lead also significantly reduced the Ca²⁺ ATPase activity, resulting in an increase in intrasynaptosomal calcium. Concomitant with the increase in intrasynaptosomal calcium, lipid peroxidation values also increased significantly in lead-treated animals. In addition lead also had an inhibitory effect on depolarization induced Ca²⁺ uptake and the inhibition was found to be a competitive one. The results sugest that lead exerts its toxic effects by modifications of the intracellular calcium messenger system which would have serious consequences on neuronal functioning.     

A model and lexicon for pollen fate

As pollination biology undergoes unprecedented growth as a discipline, confusion in the use of terms has become increasingly common. The need for a flexible yet unambiguous terminology has become urgent. As an example we discuss how the term “pollination efficiency” is used differently by 18 studies, and “pollinator effectiveness” by seven others. Here we present flowcharts of two general models of pollination systems (biotic and abiotic) that trace all the events from pollen production to development of seed or fruit, and we develop a lexicon for the quantities of pollen, processes of transfers (to a vector, to a stigma), and ratios of quantities that are of interest in studies of pollination and mating systems. An appendix includes a glossary of the definitions we suggest.     

Genetic mapping of 14 short tandem repeat polymorphisms on human chromosome 22

We have constructed a linkage map of 14 short tandem repeat polymorphisms (11 with heterozygosity > 70%) on the long arm of human chromosome 22 using 23 non-CEPH pedigrees. Twelve of the markers could be positioned uniquely with a likelihood of at least 1,000:1, and distributed at an average distance of 6.62 cM (range 1.5–16.1 cM). The sex-combined map covers a total of 79.6 cM, the female map 93.2 cM and the male map 64.6 cM. Based on comparisons between physical maps and other genetic maps, we estimate that our map covers 70%–80% of the chromosome. The map integrates markers from previous genetic maps and uniquely positions one marker (D22S307). Data from physical mapping on the location of four genetic markers correlates well with our linkage map, and provides information on an additional marker (D22S315). This map will facilitate high resolution mapping of additional polymorphic loci and disease genes on chromosome 22, and act as a reference for building and verifying physical maps.     

Conservation of motifs within the unusually variable polypeptide sequences of type I restriction and modification enzymes

Type I restriction enzymes comprise three subunits encoded by genes designated hsdR, hsdM, and hsdS; S confers sequence specificity. Three families of enzymes are known and within families, but not between, hsdM and hsdR are conserved. Consequently, interfamily comparisons of M and R sequences focus on regions of putative functional significance, while both inter- and intrafamily comparisons address the origin, nature and role of diversity of type I restriction systems. We have determined the sequence of the hsdR gene for EcoA, thus making available sequences of all three hsd genes of one representative from each family. The predicted R polypeptide sequences share conserved regions with one superfamily of putative helicases, so-called ‘DEAD box’ proteins; these conserved sequences may be associated with the ATP-dependent translocation of DNA that precedes restriction. We also present hsdM and hsdR sequences for EcoE, a member of the same family as EcoA. The sequences of the M and R genes of EcoA and EcoE are at least as divergent as typical genes from Escherichia coli and Salmonella, perhaps as the result of selection favouring diversity of restriction specificities combined with lateral transfer among different species.