Cell adhesion and short-term patency in human endothelium preseeded 1.5-mm polytetrafluoroethylene vascular grafts: an experimental study

It has been shown that endothelialization improves short-term patency of 1.5-mm expanded polytetrafluoroethylene vascular grafts. A model for endothelialization of 1.5-mm expanded polytetrafluoroethylene vascular grafts with human endothelial cells is described. In this model, the adherence of endothelial cells was increased significantly in grafts coated with serum proteins and collagen. By means of this protocol, graft patency was tested after implantation in two animal models: the rat aorta and the rabbit common carotid artery. Anastomosis was performed with a 3M Precise Microvascular Anastomotic System. In both animal models, no significant loss of endothelial cells in the precoated grafts (rat, n = 8) were noted 1 hour after blood flow restoration. All uncoated grafts showed significant endothelial cell loss. In the rabbit model, all nonendothelialized grafts (n = 8) clotted 5 to 25 minutes after flow restoration. Seven (n = 8) endothelialized grafts showed no clotting during 1 hour's observation: one clotted immediately for a patency rate of 87.5 percent. These results indicate that endothelialization of 1.5-mm grafts is practical. Furthermore, adhesion of endothelial cells to the graft walls is not affected by short-term, pulsatile, high-pressure blood flow.     

Reconstruction of posterior mandibular defects with soft tissue using the rectus abdominis free flap

Nitric oxide (NO) plays an important regulatory role in airway function and seems to be implicated in the pathophysiology of several airway diseases. We studied the presence of NO synthase activity in human nasal mucosa and nasal polyp tissues obtained from patients undergoing septoplasty or polypectomy, respectively. NO synthase activity was quantified in tissue homogenates using citrulline release assay and was located in tissue sections using NADPH-diaphorase histochemistry. The results indicated that nasal polyps contain higher levels of total NO synthase activity than nasal mucosa tissue. In addition, nasal polyps contained mainly inducible NO synthase activity whereas all NO synthase activity detected in the nasal mucosa was in constitutive form. In both cases, NO synthase activity was localized in epithelial cells. In view of these results, we conclude that NO may be an important inflammatory mediator in the respiratory system and that the epithelium may be a source of NO production.     

Functional expression of the parathyroid cell calcium receptor in Xenopus oocytes

Various studies suggest the existence of a plasma membrane receptor on parathyroid cells that senses changes in the concentration of extracellular Ca2+. To test this hypothesis, Xenopus laevis oocytes were injected with poly(A)(+)-enriched mRNA from bovine parathyroid cells and examined for their ability to respond to increases in the concentration of extracellular Ca2+ or other polycations. Cytosolic Ca2+ concentrations were measured indirectly by recording Cl- currents through the endogenous, cytosolic Ca(2+)-activated Cl- channel. Increasing the concentration of extracellular Ca2+ (from 0.7 to 5 mM) or Mg2+ (from 0.8 to 10 mM) elicited oscillatory increases in the Cl- current. Responses to either divalent cation were not observed in oocytes injected with water or with mRNA prepared from HL-60 cells or rat liver. Responses elicited by extracellular Mg2+ persisted when extracellular Ca2+ was reduced to low micromolar levels. La3+, Gd3+, or neomycin B also evoked oscillatory increases in the Cl- current in oocytes under conditions of low extracellular Ca2+ levels. These extracellular polycations all cause the mobilization of intracellular Ca2+ in oocytes injected with parathyroid cell mRNA like they do in intact parathyroid cells. The injection of parathyroid cell mRNA thus confers on oocytes the ability to detect and respond to changes in the concentration of extracellular polycations. The data provide compelling evidence for the existence of a cell surface Ca2+ receptor protein(s) on parathyroid cells that regulates cellular function.     

Identification of a gene encoding a hyperpolarization-activated pacemaker channel of brain

The generation of pacemaker activity in heart and brain is mediated by hyperpolarization-activated cation channels that are directly regulated by cyclic nucleotides. We previously cloned a novel member of the voltage-gated K channel family from mouse brain (mBCNG-1) that contained a carboxy-terminal cyclic nucleotide-binding domain (Santoro et al., 1997) and hence proposed it to be a candidate gene for pacemaker channels. Heterologous expression of mBCNG-1 demonstrates that it does indeed code for a channel with properties indistinguishable from pacemaker channels in brain and similar to those in heart. Three additional mouse genes and two human genes closely related to mBCNG-1 display unique patterns of mRNA expression in different tissues, including brain and heart, demonstrating that these channels constitute a widely expressed gene family.     

Cephalosporin-probenecid drug interactions

The effect of concurrent probenecid administration on the pharmacokinetics of cephalosporin antibiotics varies with the available cephalosporins. Most cephalosporins are affected to some degree by concurrent probenecid administration, although ceforanide, ceftazidime, ceftriaxone and latamoxef (moxalactam) have no significant changes in pharmacokinetics. For those cephalosporins affected by probenecid, the predominant findings are impairment in renal clearance resulting in increased peak serum concentrations, an increased area under the concentration-time curve (AUC), and both delayed and prolonged recovery of the cephalosporin in the urine. The distribution of the cephalosporins is affected to varying degrees, with reports of increased penetration into ocular, central nervous system and blister fluids noted with some agents. The clinical relevance of the changes in cephalosporin distribution associated with probenecid administration has not been investigated. The dose and timing of probenecid administration appear to be major determinants in any possible interaction. Studies with ceftizoxime and cefoxitin suggest that larger probenecid doses result in greater changes in the pharmacokinetics of cephalosporins. Prolonged probenecid therapy before administration of a cephalosporin did not seem to be as relevant as the probenecid dosage in determining the magnitude of the interaction. Probenecid administration with or immediately before cephalosporin administration appears able to produce these documented changes in cephalosporin pharmacokinetics. The route of administration (oral versus parenteral) of either prolosporin pharmacokinetics. The route of administration (oral versus parenteral) of either probenecid or the cephalosporin does not appear to influence the characteristics of the interactions. The therapeutic efficacy of a combination of a cephalosporin with probenecid has been most thoroughly studied for single-dose treatment of gonorrhoea. The addition of probenecid to cephalosporin therapy results in sustained systemic concentrations adequate for eradication of Neisseria gonorrhoeae. Regimens involving either second or third generation cephalosporins demonstrate good success rates with single-dose therapy. However, the success of ceftriaxone administered alone for treatment of both penicillase-producing and non-penicillase-producing strains of N. gonorrhoeae suggests that the addition of probenecid is unnecessary. The use of probenecid, in combination with cephalosporins, to enhance the treatment of other venereal and systemic infections has preliminary, inconclusive support.     

Temperature effect on the sensitivity of ELISA, PA and WB to detect anti-HIV-1 antibody and infectivity of HIV-1

BACKGROUND: This study is designed to resolve the problem of whether temperature or freeze/thaw cycle will have any impact on the sensitivity for detection of anti-HIV-1 antibody by particle agglutination (PA), enzyme-linked immunosorbent assay (ELISA) and western blotting (WB). To reduce potential risk for laboratory personnel exposed to HIV-infection, it will be useful to determine the temperature effect on HIV infectivity. METHODS: Testing sera were incubated at different temperatures or treated with several cycles of freeze and thaw. PA, ELISA and WB were used to detect anti-HIV-antibodies, whereas syncytia formation assay and polymerase chain reaction (PCR) were applied to detect HIV-infection. RESULTS: The data showed that certain temperature points (no treatment, 25 degrees C for 1 hr, 2 hrs and 4 hrs, 37 degrees C for 30 minutes and 60 minutes, 56 degrees C for 30 minutes and 60 minutes, 65 degrees C for 15 minutes and 30 minutes) had no impact on the testing results of ELISA, PA and WB in detection of anti-HIV-1 antibody. In addition, testing results of 50 normal human serum samples which had been heated to 56 degrees C for 30 minutes were still negative by ELISA and PA. Only the samples incubated at 65 degrees C for 60 minutes had slight differences in results. Freeze and thaw treatments of the serum did not alter anti-HIV testing results, either. Treatments of supernatant of HTLV-IIIB culture at 56 degrees C for 30 minutes and 60 minutes, 65 degrees C for 15 minutes and 30 minutes could eliminate the syncytia formation caused by HIV-infection. Further analysis of the samples by PCR was able to detect HIV-specific sequences in all the treatments. CONCLUSIONS: Anti-HIV antibody is quite stable in serum, even when it is pre-heated to 56 degrees C for 30 minutes. Freeze and thaw treatment of serum samples up to seven cycles did not change the results, either. In addition, to minimize the potential risk of laboratory personnel exposed to HIV infection, pre-treatment of serum samples with heat at 56 degrees C for 30 minutes or 60 minutes can reduce HIV infectivity. However, laboratories still must emphasize the importance of universal precautions rather than heat-inactivation of serum to prevent occupational transmission of HIV.     

Asteroid hyalosis and vision loss after posterior capsulotomy

We describe the case of a 77-year-old man with asteroid hyalosis who had phacoemulsification and implantation of a plate-haptic intraocular lens (IOL). Intraoperatively, a tear occurred in the anterior capsule, and vision loss occurred 3 months after a neodymium:YAG posterior capsulotomy. Because of the asteroid hyalosis, a posteriorly dislocated IOL, which occurred after the capsulotomy, was difficult to diagnose. Careful retinoscopy established the aphakic condition of the eye, and the B-scan ultrasonography indicated the IOL's location.     

Molecular dynamics study of water and Na+ ions in models of the pore region of the nicotinic acetylcholine receptor

The nicotinic acetylcholine receptor (nAChR) is an integral membrane protein that forms ligand-gated and cation-selective channels. The central pore is lined by a bundle of five approximately parallel M2 helices, one from each subunit. Candidate model structures of the solvated pore region of a homopentameric (alpha7)5 nAChR channel in the open state, and in two possible forms of the closed state, have been studied using molecular dynamics simulations with restraining potentials. It is found that the mobility of the water is substantially lower within the pore than in bulk, and the water molecules become aligned with the M2 helix dipoles. Hydrogen-bonding patterns in the pore, especially around pore-lining charged and hydrophilic residues, and around exposed regions of the helix backbone, have been determined. Initial studies of systems containing both water and sodium ions together within the pore region have also been conducted. A sodium ion has been introduced into the solvated models at various points along the pore axis and its energy profile evaluated. It is found that the ion causes only a local perturbation of the water structure. The results of these calculations have been used to examine the effectiveness of the central ring of leucines as a component of a gate in the closed-channel model.