A 4-AP-sensitive current is enhanced by chronic carbon monoxide exposure in coronary artery myocytes

A physiological role of carbon monoxide has been suggested for coronary myocytes; however, direct evidence is lacking. The objective of this study was to test the effect of chronic carbon monoxide exposure on the K(+) currents of the coronary myocytes. The effect of 3-wk chronic exposure to carbon monoxide was assessed on K(+) currents in isolated rat left coronary myocytes by the use of the patch-clamp technique in the whole cell configuration. Moreover, membrane potential studies were performed on coronary artery rings using intracellular microelectrodes, and coronary blood flow in isolated heart preparation was recorded. Carbon monoxide did not change the amplitude of global whole cell K(+) current, but it did increase the component sensitive to 1 mM 4-aminopyridine. Carbon monoxide exposure hyperpolarized coronary artery segments by approximately 10 mV and, therefore, increased their sensitivity to 4-aminopyridine. This effect was associated with an enhancement of coronary blood flow. We conclude that chronic carbon monoxide increases a 4-aminopyridine-sensitive current in isolated coronary myocytes. This mechanism could, in part, contribute to hyperpolarization and to increased coronary blood flow observed with carbon monoxide.     

A green nonsulfur bacterium,Dehalococcoides ethenogenes,with the LexA binding sequence found in gram-positive organisms

Dehalococcoides ethenogenes is a member of the physiologically diverse division of green nonsulfur bacteria. Using a TBLASTN search, the D. ethenogenes lexA gene has been identified, cloned, and expressed and its protein has been purified. Mobility shift assays revealed that the D. ethenogenes LexA protein specifically binds to both its own promoter and that of the uvrA gene, but not to the recA promoter. Our results demonstrate that the D. ethenogenes LexA binding site is GAACN(4)GTTC, which is identical to that found in gram-positive bacteria. In agreement with this fact, the Bacillus subtilis DinR protein binds specifically to the D. ethenogenes LexA operator. This constitutes the first non-gram-positive bacterium exhibiting a LexA binding site identical to that of B. subtilis.     

Porous polyethylene implants in orbital floor reconstruction

The purpose of this article is to present the authors' experience with the use of porous polyethylene ultrathin sheets for orbital floor reconstruction. Thirty-two patients with orbital floor fractures were treated with porous polyethylene ultrathin sheets. Sixteen cases corresponded to orbitozygomatic fractures, 11 cases corresponded to pure orbital floor fractures, and five corresponded to panfacial fractures. The subciliary approach was used in 15 patients and the transconjunctival approach in nine; another three patients were operated on through a preexisting eyebrow wound, two were operated on with a subtarsal approach, two were operated on through an eyebrow extension of a facial wound, and one patient was operated on through the facial wound. Intraoperatively, all patients received a prophylactic dose of intravenous antibiotics. Postoperatively, 24 patients received amoxicillin clavulanate for 5 to 7 days, two patients received clindamycin, and six patients received no antibiotics. Enophthalmos was corrected in 15 of 24 patients (62.5 percent), and hypoglobus in nine of 11 (82 percent). Diplopia was resolved in 25 of 28 patients (89.3 percent) with preoperative impairment. Extrinsic eye movement impairment was resolved in 25 of 27 patients (92.6 percent). A preoperative visual acuity deficit was present in four patients (12.5 percent) and was resolved in one (from 20/100 to 20/20). Visual acuity improved in one patient (from 20/60 to 20/30). In the other two patients, visual acuity remained altered (from 20/30 to 20/30). One patient (3.1 percent) suffered blindness induced by surgery. Nine of 26 patients (34.6 percent) had residual infraorbital nerve hypesthesia and five (19.2 percent) had residual paresthesias. Postoperatively, epiphora was present in six patients (18.8 percent) and ectropion in five (15.6 percent). Although there was no statistical significance between the surgical approach and the presence of epiphora (p = 0.211) and ectropion (p = 0.422), patients who were treated using the transconjunctival approach suffered reduced ectropion (0 percent) compared with patients treated using the subciliary approach (20 percent). However, patients treated using the transconjunctival approach suffered increased epiphora (22.2 percent) compared with those treated with the subciliary approach (13.3 percent). There were four cases (12.5 percent) of postoperative facial infections. Two of these cases were resolved with systemic antibiotics, one was resolved with bone sequestrum resection, and one patient needed removal of the implant. Orbital infections were related in all cases to titanium osteosynthesis miniplates or skull bone graft. When comparing patients who were treated with and without antibiotics, no statistical differences (p = 0.958) were found relative to the presence of infections. Correction of hypoglobus is technically easier than enophthalmos, because enophthalmic correction requires a wide, deep subperiosteal dissection and implant positioning, posterior to the equator of the globe, with the inherent risk of orbital apex injury.     

Analysis of the expression of the <Emphasis Type="Italic">Rhodobacter sphaeroides lexA</Emphasis> gene

The regulation of the Rhodobacter sphaeroides lexA gene has been analyzed using both gel-mobility experiments and lacZ gene fusions. PCR-mediated mutagenesis demonstrated that the second GAAC motif in the sequence GAACN₇GAACN₇GAAC located upstream of the R. sphaeroides lexA gene is absolutely necessary for its DNA damage-mediated induction. Moreover, mutagenesis of either the first or the third GAAC motif in this sequence reduced, but did not abolish, the inducibility of the R. sphaeroides lexA gene. A R. sphaeroides lexA-defective (Def) mutant has also been constructed by replacing the active lexA gene with an inactivated gene copy constructed in vitro. Crude extracts of the R. sphaeroides lexA(Def) strain are unable to form any protein-DNA complex when added to the wild-type lexA promoter of R. sphaeroides. Likewise, the R. sphaeroides lexA(Def) cells constitutively express the recA and lexA genes. All these data clearly indicate that the lexA gene product is the negative regulator of the R. sphaeroides SOS response. Furthermore, the morphology, growth and viability of R. sphaeroides lexA(Def) cultures do not show any significant change relative to those of the wild-type strain. Hence, R. sphaeroides is so far the only bacterial species whose viability is known not to be affected by the presence of a lexA(Def) mutation.     

Effect of testosterone on n-methyl-d, l-aspartate-induced growth hormone secretion in male swine

Previous research from our laboratory demonstrated that n-methyl-d, l-aspartate (NMA), a potent agonist of glutamate, increased growth hormone (GH) secretion in barrows and boars. To determine if testosterone modulates NMA-induced GH secretion, Poland China x Yorkshire swine were challenged with NMA in a model that compared GH responses in boars with those of barrows or barrows treated with testosterone propionate (TP). Boars and barrows weighing 112.6+/-1.4 kg (mean +/- SE) were fitted with indwelling jugular vein catheters. Barrows (n = 16) were given i.m. injections of TP (25 mg in corn oil) twice daily from d 0 to d 6. Boars (n = 16) and control barrows (n = 15) received twice daily injections of corn oil. On d 6, blood was sampled every 15 min for 4 h. Two h after sampling began, all animals received an i.v. injection of NMA at a dose of 2.5 mg/kg body weight. Mean testosterone concentrations (ng/ml serum) were similar (P > .1) for boars (8.1+/-0.8) and barrows receiving TP (7.3+/-0.3), but were greater in both cases (P < .05) than for barrows receiving corn oil (.2+/-.01). Prior to NMA injections, mean GH concentrations were similar (P > .1) among groups and averaged 2.7+/-.2 ng/ml serum across treatments. Serum concentrations of GH after NMA increased (P < .05) similarly among groups and averaged 6.3+/-0.3 ng/ml across treatments during the 2-h period after injection. These results were not supportive of a role for testosterone as a modulator of NMA-induced GH secretion in male swine.     

Long-term response of the biotic community to fluctuating water levels and changes in water quality in Cootes Paradise Marsh,a degraded coastal wetland of Lake Ontario

During the early 1900s, more than 90% of the surface area of Cootes Paradise Marsh was covered with emergent vegetation; currently, less than 15% of the surface is covered with aquatic vegetation and the remainder is wind-swept, turbid, open water. The loss of emergent cover is significantly correlated with mean annual water levels that increased more than 1.5 m over the past 60 years. Species diversity and the percent cover of the submerged macrophtye community also declined dramatically after the 1940s, coincident with decreased water clarity and increased nutrients from pollution by sewage and stormwater effluent. Phosphorus levels in the marsh dropped ten-fold after the sewage plant was upgraded to a tertiary-treatment facility in 1978; however, there was no measurable improvement in water clarity, in spite of a decrease in chlorophyll concentrations. Long-term changes in the composition of the planktonic, benthic and fish communities accompanied changes in water clarity, nutrient status and macrophyte cover. Phytoplankton changed from a community dominated by diverse taxa of green algae and diatoms during the 1940s, to a less diverse community dominated by a few taxa of green and blue-green algae in the 1970s, then to a much more diverse community recently, including many taxa of green algae, diatoms and chrysophytes; however, because water turbidity continues to be high, and algae tolerant of low light levels are now very abundant. Daphnia, which were prominent during the 1940s (especially in the vegetated sites) were replaced in the 1970s by smaller zooplankton such as the cladoceran, Bosmina, and several rotifer species including Brachionus, Asplanchna and Keratella. In the recent survey conducted in 1993 and 1994, small-bodied forms still dominate the turbid open-water areas, while medium-sized cladocerans such as Moina were common near macrophyte beds. Generally, total herbivorous zooplankton biomass tended to be highest next to Typha beds and declined with increasing distance from the plants. Conversely, biomass of edible algae at these sites increased with distance from the macrophytes. Species diversity of aquatic insects declined dramatically over the past 40 years, from 57 genera (23 families and 6 orders) in 1948, to 9 genera (6 families and 3 orders) in 1978, to only 5 genera (3 families and 2 orders) in 1995. The diverse benthic community present 5 decades ago has now been replaced by a community consisting primarily of chironomid larvae, oligochaetes and other worms associated with low-oxygen environments. These successional changes illustrate the impact of natural (fluctuating water levels) and anthropogenic (deterioration in water quality) stressors on the character of the biotic communities, and reveal the complex interactions among the various trophic levels and the abiotic environment as degradation and remediation proceeded.