pRJ5: a naturally occurring Staphylococcus aureus plasmid expressing constitutive macrolide-lincosamide-streptogramin B resistance contains a tandem duplication in the leader region of the ermC gene

The 2.55 kb Staphylococcus aureus plasmid, pRJ5, confers constitutive resistance to macrolide-lincosamide-streptogramin B (MLS) antibiotics. pRJ5 is nearly identical to the inducible MLS resistance plasmid pT48, and has homology with the S. aureus plasmids pE194 and pSN2. The HindIII-C and/or Hind-B fragments were required for stable maintenance of the plasmid and probably carry palA. Plasmids pRJ5 and pT48 were shown to belong to the same incompatibility group, Inc12 (L). DNA sequencing showed that pRJ5 contains a 28 bp direct tandem duplication in the leader/attenuator region of ermC. This is likely to change the secondary structure of the methylase mRNA, allowing constitutive expression of ermC. The type of mutation found on plasmid pRJ5 is different from those observed in similar 2.5 kb constitutive MLS-resistance plasmids isolated from other Gram-positive bacteria, including staphylococci.     

Relationships between dental hygienists' career attitudes and their retention of practice. Part II. From the results of the Ohio Dentist and Dental Hygiene Surveys

This article utilizes findings from the Ohio Dental Hygiene Survey and Ohio Dentist Survey to uncover what specific dental hygiene attitudes exist relative to employment and what factors have led to job termination and to re-entry. Ohio dental hygiene employees are most satisfied with patient relationships, co-worker relationships, and flexible working hours. The dental hygienists are least satisfied with fringe benefits, financial growth, and career creativity. Salary, benefits, nor career longevity were significant factors in determining satisfaction. Dental hygienists who were not working when surveyed, said they would consider returning to practice if a better salary were available, if they could find part-time work, if there were a good wage scale with benefits, or if their own financial need changed. Thirty-six percent of the non-practitioners said they would not ever consider returning to practice due to working conditions, establishment of a new career, or inadequate compensation. Dentist employers stated that they were satisfied or very satisfied with their dental hygienists' patient care and contribution to the practice.     

Effects of L-malate, an inhibitor of glutamate decarboxylase, on learning and memory in mice

Oral administration of L-malate 600 mg.kg-1 for 5 days before training can significantly promote memory acquisition, consolidation and retrieval, respectively, on anisodine-, chloramphenicol-, and ethanol-induced memory impairment in mice. Ketamine (8.5 mg.kg-1, i.p.), a selective NMDA receptor antagonist, was found to inhibit the anti-amnesic activity of L-malate. The glutamate (Glu) and GABA content in mice brain was measured by high-performance liquid chromatography with fluorescence detection. The content of GABA was shown to be decreased from 2.3 +/- 0.5 mumol.g-1 to 1.3 +/- 0.5 mumol.g-1 (P < 0.01), so the Glu/GABA ratio was increased significantly. These results suggest that the decrease of cerebral GABA level and the increase of Glu/GABA ratio is favorable to learning and memory.     

Prevalence of pyruvate kinase deficiency among the Chinese: determination by the quantitative assay

The prevalence of pyruvate kinase (PK) deficiency among the Chinese population has not been established. Fung et al. (Arch Dis Child 44:373-376, 1969) and Wu et al. (Am J Hematol 20:139-144, 1985) indicate 3.4% and 2.1% PK deficiency prevalence rates, respectively, the higher figure based on Beutler's screening test [3] without confirmatory testing. Neither figure is consistent with the occurrence of hemolytic anemia from this cause in the experiences of hematologists in Hong Kong. Using the standard quantitative assay, we measured PK activity in blood samples from 1,100 local Chinese people. The assay was automated on a centrifugal analyser, and the results were expressed in IU per gram of hemoglobin (IU/g Hb). Blood samples from 497 healthy male adults were measured, and PK activity was found to have a range of 15.2 +/- 5.2 (mean +/- 2 SD). A total of 100 cord blood samples were also measured, and the reference interval for this subgroup was 17.7 +/- 4.8. Additionally, samples from 503 anaemic patients were measured, and all were found to have values above the lower limit of the reference interval. The prevalence of PK deficiency among the Hong Kong Chinese population determined by this study was < 0.1%.     

Hydrodynamic hot-electron transport simulation based on the Monte Carlo method

A hydrodynamic hot electron model is used to study electron transport through a submicron N⁺ --- N --- N⁺ GaAs structure. This study is used to investigate improvements which the unique features of this model offer to analysis of devices operating under nonstationary transport conditions. The model is based upon semiclassical “hydrodynamic” conservation equations for the average carrier density, momentum and energy. The general model includes particle relaxation times, momentum relaxation times, energy relaxation times, electron temperature tensors and heat flow vectors as a function of average carrier energy for the Γ, X and L valleys of GaAs. For this study, we utilized a simplified single electron gas version of our model to clearly reveal the impact of the nonstationary terms in the model. Results from both a drift-diffusion model approach and a Monte Carlo analysis are used to show the relative accuracy and facility this new model offers for investigating practical submicron device structures operating under realistic conditions.     

An investigation of the filtration capacity and the fate of large filtered sterically-stabilized microspheres in rat spleen

The results from a recent study by Bruce and Schurg (1990) indicate that the gluteus medius (Gm) of the horse is a complex muscle subdivided by an internal tendinous sheet into two regions (dorsal and ventral) which may subserve different functions. In the present study, both regions were found to contain a similar proportion of histochemically-determined muscle fibre types. Fibre type composition did not generally vary over the length of the muscle at the same relative depth. In contrast, there was a significant tendency for the percentage of type I fibres to increase gradually in accordance with depth. These histochemical results do not suggest that the two regions of the Gm assume distinct functional roles; they do, however, indicate that at a given relative depth the muscle fibre type distribution is relatively uniform over the length of the muscle. Nevertheless, care should be exercised in sampling and interpreting data obtained from limited biopsy of equine Gm, due to the substantial histochemical variation of fibre type composition as a function of sampling depth.     

Effect of capacitation on bull sperm binding to homologous oviductal epithelium

Sperm binding to oviductal epithelium is thought to be an important mechanism regulating sperm reservoir formation in the oviduct. On the basis of evidence in the hamster, we hypothesized that capacitation affects release of bovine sperm, allowing them to fertilize. Oviducts were obtained from the ovulatory side of estrous Holstein heifers. The isthmic and ampullar epithelia were milked out and reduced to fragments, which formed everted vesicles (explants). Explants were placed in tissue culture wells in TALP medium and incubated at 39 degrees C in 5% CO2. Frozen-thawed sperm were prepared by swim-up in TALP and capacitated by incubation for 4 h in TALP with 20 micrograms/ml heparin (without glucose). Uncapacitated sperm were used immediately after dilution into capacitation medium. Within 2 h of surgery, sperm were added to the explants and incubated with them for 15 min. Sperm and explants were videotaped, and the tapes were analyzed to determine the numbers of sperm bound per surface area. ANOVA did not show a difference between the number of sperm bound/0.1 mm2 in the isthmus and ampulla (p > 0.05); however, an effect of capacitation was detected (p = 0.0015). Also, the percentage of capacitated sperm, determined by chlortetracycline labeling, was greater in sperm that remained free-swimming in the presence of explants than in the absence of explants (p = 0.001). In conclusion, capacitation appears to be involved in the release of bovine sperm from oviductal epithelium and therefore could enable sperm to leave the reservoir and fertilize oocytes.     

Potent CD14-mediated signalling of human leukocytes by Escherichia coli can be mediated by interaction of whole bacteria and host cells without extensive prior release of endotoxin

How invading microorganisms are detected by the host has not been well defined. We have compared the abilities of Escherichia coli and lipopolysaccharides (LPS) purified from these bacteria to prime isolated neutrophils for phorbol myristate acetate-stimulated arachidonate release, to trigger respiratory burst in 1% blood, and to increase steady-state levels of tumor necrosis factor alpha mRNA in whole blood. In all three assays, bacteria were > or = 10-fold more potent than equivalent amounts of LPS and could trigger maximal cellular responses at ratios as low as one bacterium per 20 to 200 leukocytes. Both E. coli and LPS-triggered responses were enhanced by LPS-binding protein and inhibited by an anti-CD14 monoclonal antibody and the bactericidal/permeability-increasing protein (BPI). However, whereas O polysaccharide did not affect the potency of isolated LPS, intact E. coli carrying long-chain LPS (O111:B4) was less potent than rough E. coli (J5). Furthermore, material collected by filtration or centrifugation of bacteria incubated under conditions used to trigger arachidonate release or chemiluminescence was 5- or 30-fold less active, respectively, than whole bacterial suspensions. Extracellular BPI (not bound to bacteria) inhibited bacterial signalling, but BPI bound to bacteria was much more potent. Taken together, these findings indicate that E. coli cells can strongly signal their presence to human leukocytes not only by shedding LPS into surrounding fluids but also by exposing endotoxin at or near their surface during direct interaction with host cells.