Prophylaxis of local vascular graft infection with levofloxacin incorporated into albumin-sealed dacron graft (LVFX-ALB Graft).

An animal model was used to assess the efficacy of levofloxacin (LVFX) incorporated into albumin (ALB)-sealed Dacron (LVFX-ALB) graft for the prevention of vascular graft infections caused by Staphylococcus aureus. Under general anesthetic, an interposition graft was placed into dog carotid artery. On completion of the operation, 0.1 ml of normal saline containing 10(7) colony-forming units (CFU) of a slime-producing S. aureus was inoculated directly onto the graft. After 1 day, the samples were sterilely harvested. The antibacterial activity of LVFX into the LVFX-ALB graft was evaluated by colony counting in bacterial cultures and by the fluorescent antibody method staining bacteria adhesion to the grafts. LVFX-ALB grafts had a lower infection rate than the control grafts (1/4, 10(2) CFU vs 4/4, 1.50 x 10(5)+/-1.38 x 10(5)CFU (mean+/-SE)). In an immunostaining study, LVFX-ALB grafts had small fluorescent areas showing S. aureus adhesion, while fluorescence was observed over the entire surface of the control grafts. Therefore, LVFX-ALB presumably had a bactericidal action and adhesive prevention against inoculated S. aureus. LVFX-ALB may be useful in preventing graft infections during and immediately after vascular reconstruction.     

Measurement of steady-flow instability and turbulence levels in Dacron vascular grafts.

Fluid dynamic properties of Dacron vascular grafts were studied under controlled steady-flow conditions over a Reynolds number range of 800 to 4500. Knitted and woven grafts having nominal diameters of 6 mm and 10 mm were studied. Thermal anemometry was used to measure centerline velocity at the downstream end of the graft; pressure drop across the graft was also measured. Transition from laminar flow to turbulent flow was observed, and turbulence intensity and turbulent stresses (Reynolds normal stresses) were measured in the turbulent regime. Knitted grafts were found to have greater pressure drop than the woven grafts, and one sample was found to have a critical Reynolds number (Rc) of less than one-half the value of Rc for a smooth-walled tube.     

Marrow allograft success inW/W v anemic mice: Relation to skin graft survival times

Genetically anemicW/W ^v mice were cured by marrow allografts from donors of 13 out of 18 tested strains that differed at non-H-2 histocompatibility alleles defined by skin or tumor grafting. They were also cured by donors from all four tested congenic lines whose antigenic differences had been defined by induction of serum antibodies. They were not cured acrossH-2 differences. Tail skin graft survival times on uncuredW/W ^v recipients were determined for all congenic lines used as marrow donors. The longest and shortest skin graft survival times predicted correctly marrow graft success or failure. NoW/W ^v mice were cured by marrow grafts from donors of the three congenic lines whose skin grafts were rejected in fewer than three weeks. Almost everyW/W ^v mouse grafted was cured by marrow grafts from donors of the 13 congenic lines whose skin grafts survived longest, from 11 to more than 25 weeks. Intermediate skin graft survival times failed to predict whether marrow grafts would succeed.W/W ^v mice were cured by marrow from four congenic lines with mean skin graft survival times of 4.2, 4.4, 8, and 9 weeks, while marrow grafts failed from other congenic lines with mean skin graft survival times of 3.3, 3.4, 4.8, and 8.7 weeks. The simplest explanation for these results is that the antigens specified by theH-2, H-3, H-4, H-25, andH-28 loci are strongly immunogenic on both marrow precursor cells and skin,H-17 andH-24 are strongly immunogenic on skin but not on marrow, andH-12 is strongly immunogenic on marrow precursor cells but less strongly on skin.     

The influence of graft size on the induction of immunity versus tolerance to H-Y in H-2 k strains of mice

Unprimed female CBA mice do not reject large (10 mm²) syngeneic male skin grafts. However, a high proportion do reject small (4 mm²) grafts. Nevertheless, rejection does not invariably result in an anamnestic response. In some cases, the immunity induced by the rejection of a small graft was overcome, and tolerance was induced by a subsequent challenge with a large graft. This suggests that the transplantation response to minor antigens is subject to active regulation, and screening of other H-2 ^k strains indicates that the nature of the response (i. e., immunity or tolerance) is determined by a gene or genes mapping outside the major histocompatibility complex.     

A histocompatibility region (H-2IC) in theIC region of theH-2 complex of the mouse

Skin graft rejection in congenic pairs of mice differing only at theH-2 complex appears to be influenced by at least 3 genes (H-2K, H-2D, H-2I); we now describe a fourth,H- 2IC: Grafts transplanted across anIC difference are sometimes rejected. TheI-C regions of three differentH-2 haplotypes (d,k,s) were studied in different combinations, and variable patterns emerged: (a)IC ^d : B10.S(7R) show delayed or no rejection of first B10.S(9R) grafts, but grafts to immunized recipients were usually rejected in 20 days; (b)IC ^k : in two combinations (A.AL A and B10.HTT B10.S[9R]) first grafts were rejected by day 30, although grafts to immunized mice showed a different pattern. In the third combination (B10.HTTB10.S[7R]) first grafts were retained but immunized mice rejected their grafts, (c)IC ^s : B10.S(9R) regularly reject B10.S(7R) first grafts, but immunized mice retain their grafts. In two other combinations first grafts were retained but grafts to immunized recipients were rejected; while in a third combination rejection did not occur at all. The background of the recipient appeared to be important in determining the variable pattern of rejection, and there is evidence for a similarity of the H-genes inIC ^s andIC ^k , and inIC ^k andIC ^p . Graft rejection occurred independently of known differences in Ia specificities, indicating thatH-2IC and the genes determining Ia specificities are probably different, although when grafts were performed in the presence of known la differences, graft rejection usually occurred.     

<Emphasis Type="Italic">Chlamydia pneumoniae</Emphasis> aggravates vein graft intimal hyperplasia in a rat model

Background  

Along with angioplasty, autologus vein grafts are commonly used for artery bypass grafting in patients with advanced arterial stenosis and drug-resistant angina pectoris. Although initially a successful procedure, long-term functionality is limited due to proliferation and migration of smooth muscle cells. Like in atherosclerosis, common chronic infections caused by viruses and bacteria may contribute to this process of vein graft failure. Here we investigated the possible role of Chlamydia pneumoniae (Cpn) in the pathogenesis of venous graft failure in an experimental animal model. In 2 groups (n = 10 rats/group), an epigastric vein-to-common femoral artery interposition graft was placed. Immediately thereafter, rats were infected with Cpn (5*10⁸ IFU) or injected with control solutions. Rats were sacrificed three weeks after surgery and the grafts were harvested for morphometrical and immunohistochemical analysis.     

Experiments on dynamic behaviour of a Dacron aortic graft in a mock circulatory loop

Woven Dacron grafts are currently used for the surgical treatment of aortic aneurysm and acute dissection, two otherwise fatal pathologies when aortic wall rupture occurs. While Dacron is chosen for aortic grafts because of characteristics such as biocompatibility and durability, few data are available about the dynamic response of Dacron prosthetic devices and about their side effects on the cardiovascular system. In this study, a Dacron graft was subjected to physiological flow conditions in a specifically-developed mock circulatory loop. Experiments were conducted at different physiological pulsation-per-minute rates. Results show that, in comparison to an aortic segment of the same length, the prosthesis is extremely stiffer circumferentially, thus limiting the dynamical radial expansion responsible for the Windkessel effect in human arteries. The prosthesis is instead excessively compliant in the axial direction and develops preferentially bending oscillations. This very different dynamic behaviour with respect to the human aorta can alter cardiovascular pressure and flow dynamics resulting in long-term implant complications.     

Differential PDGF secretion by graft and aortic SMC in response to oxidized LDL

Smooth muscle cells (SMC) from prosthetic vascular grafts constitutively secrete higher levels of platelet-derived growth factor-AA (PDGF-AA) than aortic SMC. Lipid oxidation products accumulate in grafts and may stimulate PDGF production. The effect of oxidized low-density lipoprotein (oxLDL) on PDGF-AA secretion by aortic and graft SMC was compared. SMC isolated from canine thoracic aorta or Dacron thoracoabdominal grafts (n = 10) were incubated with native LDL or oxLDL (0-400 microg/ml) for 72 h. PDGF-AA in the conditioned medium was measured with enzyme-linked immunosorbent assay. OxLDL increased PDGF-AA production by graft SMC from 78 +/- 2 to 256 +/- 16 pg PDGF/microg DNA and aortic SMC from 21 +/- 1 to 40 +/- 2 pg PDGF/microg DNA. Native LDL had no effect. N-acetylcysteine inhibited oxLDL-induced PDGF increase. Both superoxide and H(2)O(2) stimulated PDGF secretion by graft SMC had little effect on aortic SMC. Our results suggest that PDGF production by graft (synthetic) SMC is more sensitive to stimulation by oxidative stress than aortic (contractile) SMC. Lipid oxidation products that accumulate in prosthetic vascular grafts can cause an oxidative stress, which stimulates PDGF production by graft SMC. PDGF can induce migration of aortic SMC onto the graft, contributing to the development of intimal hyperplasia.     

树鼩细菌感染模型的建立及抗菌药物的治疗效果评价(英文)

在抗微生物感染药物开发过程中, 动物模型是必不可少的。虽然目前已经用啮齿类动物建立了一些细菌感染动物模型, 但在小型灵长类动物中还很少见。这里首次报道两个树鼩细菌感染动物模型。第一种是在三度烫伤后的皮肤表面接种 5×106 CFU 的金黄色葡萄球菌构建的皮肤烫伤感染模型。这个数量的金黄色葡萄球菌可以造成 7 d 持续性感染, 并且在第 4天可以看到明显的炎症反应。第二种是用绿脓杆菌构建的涤纶补片感染模型, 接种 2×106 CFU 的绿脓杆菌同样可以引起持续 6 d 感染, 并在第三天在伤口处观察到大量的脓液。进一步用这两种模型评价头孢哌酮钠和左氧氟沙星的治疗效果。左氧氟沙星和头孢哌酮钠在皮肤烫伤感染模型中能分别将 100 mg 皮肤组织中的细菌降低到 4log10 和 5log10 CFU, 并且在涤纶补片植入感染模型中这两种抗生素都能显著地将感染的细菌降低了 4log10 CFU (P<0.05)。结果表明用金黄色葡萄球菌和绿脓杆菌成功构建了两个细菌感染的树鼩模型。此外, 树鼩对金黄色葡萄球菌和绿脓杆菌很敏感, 适合用于构建细菌感染动物模型和评价新的抗细菌感染药物的效果。     

Surgical and Antimicrobial Treatment of Prosthetic Vascular Graft Infections at Different Surgical Sites: A Retrospective Study of Treatment Outcomes

Objective

Little is known about optimal management of prosthetic vascular graft infections, which are a rare but serious complication associated with graft implants. The goal of this study was to compare and characterize these infections with respect to the location of the graft and to identify factors associated with outcome.

Methods

This was a retrospective study over more than a decade at a tertiary care university hospital that has an established multidisciplinary approach to treating graft infections. Cases of possible prosthetic vascular graft infection were identified from the hospital''s infectious diseases database and evaluated against strict diagnostic criteria. Patients were divided into groups according to the locations of their grafts: thoracic-aortic, abdominal-aortic, or peripheral-arterial. Statistical analyses included evaluation of patient and infection characteristics, time to treatment failure, and factors associated specifically with cure rates in aortic graft infections. The primary endpoint was cure at one year after diagnosis of the infection.

Results

Characterization of graft infections according to the graft location did show that these infections differ in terms of their characteristics and that the prognosis for treatment seems to be influenced by the location of the infection. Cure rate and all-cause mortality at one year were 87.5% and 12.5% in 24 patients with thoracic-aortic graft infections, 37.0% and 55.6% in 27 patients with abdominal-aortic graft infections, and 70.0% and 30.0% in 10 patients with peripheral-arterial graft infections. In uni- and multivariate analysis, the type of surgical intervention used in managing infections (graft retention versus graft replacement) did not affect primary outcome, whereas a rifampicin-based antimicrobial regimen was associated with a higher cure rate.

Conclusions

We recommend that future prospective studies differentiate prosthetic vascular graft infections according to the location of the grafts and that rifampicin-based antimicrobial regimens be evaluated in clinical trials involving vascular graft infections caused by staphylococci.     

Axons of Xenopus neural tube respond to reversals of neural tube orientation

Axonal trajectories of the Kolmer-Agduhr (KA) neurons of Xenopus embryos, were observed after anterior-posterior (A-P) inversions of neural tube grafts to determine whether KA axons follow cell-inherent directional cues, cues from their immediate environment, or rostrocaudal signals from the embryo. KA axons form one of the earliest ascending spinal pathways in Xenopus and are visible in the lateral marginal zone of whole mounts processed for GABA immunoreactivity. Grafts were made at trunk levels at stages 22–24, 3–5 h before the first KA neurons were detectable and prior to axonal outgrowth. Embryos were fixed and immunostained 6–36 h later. KA trajectories within and adjacent to reversed grafts were compared to those of nonrotated control grafts and to neural tube lengths comparable in position and in length in unoperated embryos. Most KA axons within rotated grafts followed the graft's orientation. However, others changed direction, taking novel routes including turning to conform to the orientation of the host embryo. Reorientations were most common near the posterior host/graft interface. Some host KA cells also reoriented, always within a few hundred microns of the graft interface. Taken together, these growth patterns show that most KA axons within the grafts grow normally with respect to the original polarity of the graft neural tube and maintain that direction even into tissue of opposite polarity, suggesting that their routes are mainly determined by cell-intrinsic and/or local tissue factors. However, the reorientation of many other axons, particularly near graft seams, implies that KA axons can respond to local fluctuations in directional or segment identity signals generated in both host and graft after this perturbation. © 1996 John Wiley & Sons, Inc.     

Survival of xenogeneic grafts of embryonic pigment and carapace rudiments in embryos of Chelydra serpentina

In a study of survival of embryonic grafts in turtles, Chelydra was used as host and Chrysemys and Amyda as donors. Somites and overlying ectoderm with or without adjacent neural tube were transplanted. The operations were unilateral and orthotopic. The involved the anterior portion of the carapace. In other experiments, bilateral neural crest and dorsal neural tube were transplanted orthotopically. In experiments with Chrysemys as donor, pigment cells formed conspicuous red areas ventrally when neural crest was included in the graft. This pigment faded gradually but persisted for three or four years. When somites and adjacent ectoderm of Chrysemys carapace were transplanted, the graft area was lightly pigmented at hatching. This pigmentation increased subsequently. The Chrysemys grafts were either accepted or partially rejected. In cases of apparent complete acceptance, the graft region took on characteristics of the host. When Amyda served as donor of carapace rudiments, the graft area retained characteristics of the donor. At hatching, dark spots on a yellow background were present and scutes were absent. A few months after hatching, the graft area became necrotic. Subsequently, scutes with host characteristics or skin covered the graft area.     

A comparison of oxidized LDL-induced collagen secretion by graft and aortic SMCs: role of PDGF

Smooth muscle cells (SMCs) from prosthetic vascular grafts constitutively secrete higher levels of collagen than aortic SMCs. Lipid oxidation products accumulate in grafts, and we postulated that they stimulate SMC production of collagen. The effect of oxidized low-density lipoprotein (oxLDL) on type I collagen secretion by aortic and graft SMCs was compared. SMCs isolated from the canine thoracic aorta or Dacron thoracoabdominal grafts (n = 10) were incubated with native LDL or oxLDL (0-400 microg cholesterol/ml) for 72 h. Type I collagen in the conditioned medium was measured by ELISA. OxLDL increased collagen production by graft SMCs from 4.1 +/- 0.3 to 11.0 +/- 0.4 ng/microg DNA and by aortic SMCs from 2.3 +/- 0.1 to 3.5 +/- 0.2 ng/microg DNA. Native LDL had little effect. LY-83583, a superoxide generator, stimulated a dramatic increase in collagen secretion by graft SMCs and a smaller but significant elevation by aortic SMCs. OxLDL has been shown to increase PDGF production by graft SMCs, and PDGF can stimulate collagen production. Anti-PDGF antibody inhibited the increase in collagen production by graft SMCs that was stimulated by oxLDL, implicating PDGF as one mechanism of oxLDL-induced collagen production. Lipid oxidation products that accumulate in prosthetic vascular grafts can cause an oxidative stress that stimulates PDGF production by graft SMCs that in turn stimulates collagen production, contributing to the progression of intimal hyperplasia.     

Quorum sensing inhibitor FS3-coated vascular graft enhances daptomycin efficacy in a rat model of staphylococcal infection

The aim of the study was to investigate the efficacy of the quorum sensing inhibitor FS3 and daptomycin in preventing prosthesis biofilm in a rat model of staphylococcal vascular graft infection. Graft infections were established in the back subcutaneous tissue of adult male Wistar rats by implantation of Dacron prostheses followed by topical inoculation with 2 × 10⁷ colony-forming units of Staphylococcus aureus, strain Smith diffuse. The study included a control group, a contaminated group that did not receive any antibiotic prophylaxis and three contaminated groups that received: (i) intraperitoneal daptomycin, (ii) FS3-soacked graft, and (iii) daptomycin plus FS3-soaked graft, respectively. Each group included 15 animals. The infection burden was evaluated by using sonication and quantitative agar culture. Moreover, an in vitro binding-study was performed to quantify the how much FS3 was coated to the surface of the prosthesis. The in vitro studies showed, that minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values for daptomycin were lower in presence of FS3. In in vivo studies, when tested alone, daptomycin and FS3 showed good efficacies. Their combination showed efficacies significantly higher than that of each single compound. Daptomycin is an important candidate for prevention of staphylococcal biofilm related infection and FS3 could serve as an interesting anti-staphylococcal antibiotic enhancer.     

The impact of transportation time on apoptosis in allogeneic stem cell grafts and the clinical outcome in malignant patients with unrelated donors

BackgroundThe quality of cells in peripheral blood stem cell (PBSC) grafts is important for allogeneic stem cell transplantation outcome. The viability of PBSC grafts may decrease during transportation time between donor and transplant center. We hypothesize that the graft viability based on apoptosis and necrosis in the graft may better reflect graft quality and clinical outcome.MethodsPBSC graft viability from unrelated donors was analyzed in 91 patients. Viable cells were defined as 7-aminoactinomycin D– and Annexin V–negative. The clinical outcome, including survival, transplant-related mortality and graft-versus-host disease (GvHD), was correlated to graft viability.ResultsGrafts transported for 1 day had a median viability of 86.4% (range 63.8 to 98.9%), and grafts transported for 2 days had median viability of 83.2% (range 52.8% to 96.2%) (P = .003). Grafts were divided into two groups based on the median graft viability of 85.1%. Patients who received low viability grafts had lower 1-year survival of 63.7% compared with 88.9% for those who received high viability grafts (P = .007). In the multivariate analysis, transplant-related mortality (TRM) was higher in the low viability group (P = .03), whereas overall survival was not significantly associated with graft viability. The incidence of acute GvHD grade II to IV, chronic GvHD and relapse risk remained comparable between the groups.ConclusionLow graft viability was an independent predictor of 1-year survival and TRM after adjusting for multiple confounders. Better graft quality markers are important for the detection of clinically important variations in the stem cell graft.     

Peroxidases do not move in phloem

Phloem exudates from grafts between Queensland Blue pumpkin (Cucurbita maxima Duch.) and Candy Red Hawkesbury watermelon (Citrullus vulgaris Schrad.) were analysed by iso-electric focusing to detect iso-enzymes of peroxidase. These enzymes did not move in intact phloem but, when stems were cut, they surged rapidly through graft unions.     

Liver tissue graft rejection in murine major histocompatibility complex mutants

Liver tissue grafts between seven H-2 mutants and their parental strains have been studied. Each of these mutants was originally identified by reciprocal mutant—parental strain skin graft rejection. However, liver grafts among mutants and parental standard strains are not uniformly rejected. Liver graft rejection also fails to correlate with mutant—parental stimulation in CML and MLC. In addition, the immune reaction pattern of female mutant animals against grafts of male liver differs from the reaction pattern found in parental standard strains. Several explanations for the differences between immune response to liver and skin grafts are proposed, including different T cell subsets involved in recognition, availability of antigenic sites to immunocompetent cells, and structural differences between mutant and parental H-2 antigens. Abbreviations used in this paper: bml, 2, 3, 4,14; dml; fm2=mutants of strains C57BL/6, B10.D2 and B10.M respectively; B6=C57BL/6     

Nerve cells of Drosophila Notch mutant are differentiated inside amphibian brain: a new approach for the analysis of genetic control of nerve cell differentiation

Fragments of the neural primordium of a new Notch mutant of Drosophila melanogaster produced in our laboratory were transplanted into the neural tube of embryos of 4 amphibian species (caudate and ecaudate) immediately after completion of neurulation. The grafts were identified by using a light microscope, scanning electron miscroscope, and in situ hybridization with mobile genetic elements of Drosophila and fluorescent dyes as markers. As has been shown, Drosophila nerve cells survive and differentiate inside the neural tube of amphibian embryos. The grafts increase in size by twentyfold and the cell proliferation zones are retained during the period of six months. Differentiated cells of the graft formed axon-dendritic contacts with recipient cells and penetrated into the organisms' brain structures. The effect of Drosophila transplants proved to be different for caudate and ecaudate amphibians. The presence of the graft accelerated the development of Xenopus laevis and it also affected their behavior. This approach can be very useful for the study of genetic basis of development and behavior.     

Overexpression of thioredoxin in islets transduced by a lentiviral vector prolongs graft survival in autoimmune diabetic NOD mice

   

Pancreatic islet transplantation is considered an appropriate treatment to achieve insulin independence in type I diabetic patients. However, islet isolation and transplantation-induced oxidative stress and autoimmune-mediated destruction are still the major obstacles to the long-term survival of graft islets in this potential therapy. To protect islet grafts from inflammatory damage and prolong their survival, we transduced islets with an antioxidative gene thioredoxin (TRX) using a lentiviral vector before transplantation. We hypothesized that the overexpression of TRX in islets would prolong islet graft survival when transplanted into diabetic non-obese diabetic (NOD) mice.     

Some factors affecting the spread of mycoplasma in plants

Studying the spread of mycoplasma, the causal agent of potato witches' broom disease, in tomato plants after grafting with infectious grafts ofNicotiana glauca Grah., we found that after 9 days of graft symbiosis a hundred per cent infection occurred, whereas with infectious grafts ofSolanum lycopersicum this took place after 16 days. The first symptoms of the disease were manifested on tomato plants 21 days after grafting with infectiousNicotiana glauca grafts and 28 days after grafting with infectious tomato grafts. The results obtained present evidence for the possible preference of tomato plants for mycoplasma.