Pollution-induced community tolerance of soil microbes in response to a zinc gradient.

The long-term accumulation of Zn in soils provides the microbial community time to adapt to this heavy metal. To assess the effects of long-term exposure to Zn on the metabolic diversity and tolerance to Zn of soil microbial community, the pollution-induced community tolerance (PICT) method, based on the Biolog microtitre plate system, was used. It especially is useful to study gradients of pollutants for detecting PICT. Such a Zn gradient was found by selecting soils at increasing distances from galvanized electricity pylons at two sites where Zn accumulation had occurred over a period of decades. Soil metabolic profiles showed a humpbacked response to increasing soil Zn concentrations, indicating that accumulation of Zn up to 2,000 mg/kg did not decrease the metabolic biodiversity in the culturable fraction of the microbial community. This fraction of the microbial community showed significant PICT, because the effective concentration that reduces the metabolic biodiversity by 50% (EC50), values for Zn added to the Biolog wells increased by up to two orders of magnitude with increasing soil-Zn concentration along the transects. Significant PICT was detectable at soil Zn concentrations above approximately 300 mg/kg. The EC50 values correlated more closely with soil total Zn than with soil pore water Zn. The results suggest that, although long-term exposure to Zn imposes stress on soil microbes, resulting in an increased tolerance, detectable PICT does not necessarily lead to a decrease in metabolic diversity.

Teletronics 330-801 atrial lead extraction via the subclavian approach.

BACKGROUND: The Telectronics 330-801 atrial J (801) lead was recalled after reports implicated lead fracture/retention wire protrusion in patient mortality and morbidity. Recent reports suggest that 801 lead extraction may be associated with substantial morbidity and, possibly, excess mortality. We hypothesized that the 801 lead could be extracted using the subclavian approach with a high success rate and acceptable morbidity. METHODS: We analyzed the clinical outcomes in 60 consecutive patients who underwent 801 lead extraction. RESULTS: Sixty patients (34 women) with a mean age of 67 +/- 14.8 years had 18 class I, 13 class II, and 29 class III fractures. The lead age was 39 +/- 17 months. The subclavian approach was successful in 58 of 60 patients (96%). Complications, three major and eight minor, occurred in 10 of 60 patients (16%). All complications were successfully treated. There were no deaths. Only concurrent ventricular lead extraction was associated with complications (p = 0.008 by Fisher's exact test). CONCLUSIONS: Telectronics 801 leads can be successfully extracted using the subclavian approach with acceptable short-term morbidity, low mortality, and excellent long-term results.

Acute pulmonary hypertension complicating the arterial switch procedure.

Two neonates undergoing arterial switch procedure developed life-threatening pulmonary hypertension intraoperatively. In one patient, bradycardia, hypotension, and electrocardiographic (ECG) evidence of myocardial ischemia suddenly occurred 20 minutes after uneventful weaning from cardiopulmonary bypass. Lifting a palpably hypertensive main pulmonary artery (MPA) resulted in reproducible hemodynamic improvement. Because the patient was already on full ventilatory support and a nitroglycerin infusion, the MPA was suspended onto the anterior chest wall. In the other patient, after removal of intraoperative drapes, severe generalized swelling and cyanosis were noted. The central venous pressure had risen to 25 mmHg, and the PO2 had dropped to 52 mmHg on 100% FIO2. The systolic arterial pressure and ECG remained normal. Immediate reexploration revealed a palpably hypertensive MPA. The coronary arteries implanted more laterally on the neoaorta were uncompromised. Amrinone loading and infusion produced immediate improvement. We believe that surgeons should be aware that pulmonary hypertension can cause coronary artery compression and right heart failure in neonates undergoing the arterial switch procedure. Lateral placement of the coronary artery and aggressive use of pulmonary vasodilators can minimize the problem.

Differential effects of 21-aminosteroids on wound healing.

OBJECTIVE: The aim of this study was to examine the effects of the 21-aminosteroid U74389F on wound healing, compared with corticosteroids using a murine incisional wound model. BACKGROUND DATA: The 21-aminosteroids are extremely potent inhibitors of iron-dependent lipid peroxidation and peroxyl radical formation, and have proven significantly beneficial in reducing neurologic sequelae following head and spinal cord trauma in experimental models. The detrimental effects of currently administered corticosteroids on wound healing are well-documented; however, the effects of the 21-aminosteroids on wound healing are poorly defined to date. METHODS: Male BDF1 mice (n = 28/group) given a left paraspinous wound received daily intraperitoneal injection of vehicle or U74389F (1 to 100 mg/kg/day) for 10 days. Wound disruption strengths (WDSs) in grams were determined on freshly harvested (F) and 36-hour formalin-fixed (FF) wounds. In addition, U74389F (3 mg/kg/day) was compared with equipotent doses of methylprednisolone, dexamethasone, and hydrocortisone (n = 12/group) for alterations in wound healing. RESULTS: The WDSs of the U74389F animals F or following FF were not significantly different from controls. In the comparison study, no significant difference in F or FF WDS was found for U74389F (3 mg/kg/day) or methylprednisolone animals when compared with controls. Dexamethasone-treated and hydrocortisone-treated animals had F and FF WDSs that were 50% of control and U74389F values (p < 0.001; ANOVA). Wounds harvested from both the control and U74389F-treated animals demonstrated the greatest extent of wound cleft contraction, collagen deposition, and neovascularity, with no obvious internal differences detectable under light microscopy. CONCLUSIONS: These results show that the 21-aminosteroid U74389F did not impair wound healing, as determined by WDS and light microscopy. Furthermore, given their greater efficacy in cell membrane stabilization and potent ability to scavenge peroxyl radicals, the 21-aminosteroids may prove beneficial in treating a variety of clinical conditions, wherein ischemia-reperfusion injury plays a major component.

Use of the native aortic valve as the pulmonary valve in the Ross procedure.

The placement of a foreign valve in the pulmonary position using the Ross procedure requires reoperation. To circumvent this problem, we devised a method of reimplanting the native aortic valve in the pulmonary position, and successfully performed this procedure in a 12-year-old diabetic boy operated on for the treatment of aortic insufficiency. Although diseased, the reimplanted aortic valve functioned well, with trivial stenosis and insufficiency. This modification offers patients with aortic valve disease a potentially curative operation.

Safety of patent ductus arteriosus closure in premature infants without tube thoracostomy.

During a 30-month period, 34 premature infants underwent surgical closure of a patent ductus arteriosus. The mean gestational age at birth was 25 +/- 0.3 weeks and the mean age at the time of operation was 3 +/- 0.3 weeks (mean weight, 829 +/- 54 g). Indomethacin therapy had failed in 32 patients, and 2 had contraindications to its use. The initial 8 patients had parascapular incision and ligation of the patent ductus arteriosus; the last 26 patients had a short transaxillary incision and clipping. The average duration of the operation from the time of incision to skin closure was 36 +/- 2 minutes (range, 15 to 65 minutes). One patient (3%) needed chest tube insertion intraoperatively because of visceral pleura disruption. Two patients (5.8%) had a "small pneumothorax" (< 10% of the lung field) that resolved within 24 hours. There was no morbidity or mortality directly related to the operative procedure, although 3 patients (8.8%) ultimately died from problems related to their severe prematurity. We conclude that surgical closure of patent ductus arteriosus without chest tube drainage can be accomplished safely in premature infants. Postoperative nursing care is simplified and the cost is reduced because the need for the chest tube and drainage system is eliminated and the number of chest radiograms needed postoperatively is reduced.

Interferon-gamma increases mortality following cecal ligation and puncture.

Interferon-gamma (IFN-gamma) has been demonstrated to improve outcome following localized infection and hemorrhagic shock in experimental studies. We sought to determine the effects of IFN-gamma in a clinically relevant murine model of intra-abdominal polymicrobial sepsis. Fifty male BDF1 mice, each weighing 23-28 g, underwent cecal ligation and puncture (CLP) followed by administration of subcutaneous injections of IFN-gamma 100-22,500 U or vehicle control immediately post-CLP and then daily. In a second set of experiments, 60 mice underwent daily injections of vehicle control or 100 U IFN-gamma 24, 48, or 72 hours prior to CLP. Interferon-gamma administered following CLP led to increased mortality and earlier deaths in a dose-dependent fashion (p < 0.05). Interferon-gamma given 24, 48, or 72 hours prior to CLP resulted in no demonstrable benefit when compared with animals that did not receive IFN-gamma (p = 0.14, p = 0.94, and p = 0.97, respectively). While IFN-gamma has been reported to be of value in selected clinical situations by improving resistance to infection, it may not be capable of conferring protection following surgery or trauma with intra-abdominal sepsis, and in fact may be detrimental.

Systemic administration of interferon-gamma impairs wound healing.

Interferon-gamma (IFN-gamma), a cytokine that has been shown to upregulate macrophage function, has recently been demonstrated to improve outcome when exogenously administered in several animal models of injury. Because the macrophage is also important in the events that govern wound healing, we evaluated the effects of IFN-gamma upon wound healing in a murine model. IFN-gamma was administered in doses of 937.5-22,500 u synchronous with the creation of a left paraspinous wound and then daily. At Day 10, wounds were harvested, evaluated for wound disruption strength (WDS), and subjected to morphometric analysis. Wounds were also subjected to 36-hr formalin fixation to maximally cross-link collagen fibrils and retested for WDS. We found that IFN-gamma impaired wound healing at all doses relative to control, and WDS was impaired in a dose-dependent fashion. Our highest dose of IFN-gamma (22,500 u) produced a WDS only 65% of the control. Morphometric studies demonstrated less collagen deposition and a lower degree of neovascularity in IFN-gamma-treated animals. In addition, formalin fixation studies suggested that IFN-gamma may impair collagen cross-linking. The potential benefits of IFN-gamma in the multiply injured patient must be weighed against the possibility that IFN-gamma might deleteriously effect events fundamental to wound healing.

Laparoscopy: the preferred method of cholecystectomy in the morbidly obese.

BACKGROUND: Morbid obesity has been considered a contraindication to laparoscopic cholecystectomy (LC). METHODS: To evaluate this we reviewed our first 201 patients undergoing LC and compared the operative procedure and outcome in morbidly obese (greater than or equal to 100 pounds over ideal body weight [IBW]) and nonobese patients. We also compared a group of morbidly obese patients who underwent standard open cholecystectomy (n = 11) with the obese group undergoing LC (n = 21). All groups were comparable in terms of age, sex, and symptoms (acute vs chronic). The obese groups undergoing LC and open cholecystectomy had similar weights (134.0 +/- 9.4 pounds over IBW [range, 100 to 286 pounds] and 133.8 +/- 6.0 pounds over IBW [range, 108 to 170 pounds], respectively) and were significantly different from the nonobese group undergoing LC (28.3 +/- 2.0 pounds over IBW [range, 23 to 98 pounds]). Parameters evaluated included operative time, resumption of normal diet, length of postoperative hospitalization, complications, conversion to open procedure, and ability to perform cholangiography. RESULTS: There were no statistically significant differences between the obese and nonobese groups undergoing LC in any parameters studied (operative time, 151.7 +/- 4.0 minutes vs 160.7 +/- 9.9 minutes; tolerance of diet, 1.2 +/- 0.1 days vs 1.1 +/- 0.1 days; time to discharge, 2.0 +/- 0.1 days vs 1.8 +/- 0.2 days; complications, 7.0% vs 0.0%). Operative time (117.6 +/- 11.6 minutes) was shorter (p = 0.45) in obese patients undergoing open cholecystectomy. However, time to normal diet and length of postoperative hospitalization were significantly longer (3.1 and 4.6 days, respectively; p less than 0.01), and there were more complications (18.2%). CONCLUSIONS: Rather than being contraindicated in the morbidly obese, LC appears to be the preferred method of cholecystectomy.

Local skin burn causes systemic (lung and kidney) endothelial cell injury reflected by increased circulating and decreased tissue factor VIII-related antigen.

Inasmuch as xanthine oxidase (XO)-derived O2* metabolites may contribute to vascular endothelial injury and Factor VIII antigen (F8Ag) is a component of endothelial cells, we hypothesized that XO-derived O2* might damage and cause distant organ endothelial cells to release F8Ag in rats subjected to skin burn. We found that serum F8Ag (ELISA) increased in the blood of rats subjected to skin burn (70 degrees C water to shaved dorsal skin for 30 seconds) but not in sham control rats (30 degrees C water). Coincidentally, F8Ag levels also decreased in lung and kidney tissue sections (immunofluorescent staining) of burned rats but not sham rats. Increases in circulating F8Ag levels and decreases in tissue F8Ag levels appeared to result from XO-derived O2* metabolites: F8Ag levels did not increase in the blood and did not decrease in the tissues of rats pretreated with allopurinol (a specific XO inhibitor, 50 mg/kg) or dimethylthiourea (DMTU) (a permeable O2* metabolite scavenger, 250 mg/kg). Lung injury as assessed by permeability studies (I125-albumin leak) paralleled changes in blood F8Ag levels in sham, burn, allopurinol-, and DMTU-treated groups. We conclude that skin burn causes a systemic vascular injury that can be inhibited by allopurinol or DMTU and is reflected by increased circulating and tissue decreased Factor VIII antigen levels. Release of Factor VIII antigen may serve as a valuable marker of distant organ injury in patients with skin burn.