Evidence for widespread changes in the structure, composition, and fire regimes of western North American forests.

Implementation of wildfire- and climate-adaptation strategies in seasonally dry forests of western North America is impeded by numerous constraints and uncertainties. After more than a century of resource and land use change, some question the need for proactive management, particularly given novel social, ecological, and climatic conditions. To address this question, we first provide a framework for assessing changes in landscape conditions and fire regimes. Using this framework, we then evaluate evidence of change in contemporary conditions relative to those maintained by active fire regimes, i.e., those uninterrupted by a century or more of human-induced fire exclusion. The cumulative results of more than a century of research document a persistent and substantial fire deficit and widespread alterations to ecological structures and functions. These changes are not necessarily apparent at all spatial scales or in all dimensions of fire regimes and forest and nonforest conditions. Nonetheless, loss of the once abundant influence of low- and moderate-severity fires suggests that even the least fire-prone ecosystems may be affected by alteration of the surrounding landscape and, consequently, ecosystem functions. Vegetation spatial patterns in fire-excluded forested landscapes no longer reflect the heterogeneity maintained by interacting fires of active fire regimes. Live and dead vegetation (surface and canopy fuels) is generally more abundant and continuous than before European colonization. As a result, current conditions are more vulnerable to the direct and indirect effects of seasonal and episodic increases in drought and fire, especially under a rapidly warming climate. Long-term fire exclusion and contemporaneous social-ecological influences continue to extensively modify seasonally dry forested landscapes. Management that realigns or adapts fire-excluded conditions to seasonal and episodic increases in drought and fire can moderate ecosystem transitions as forests and human communities adapt to changing climatic and disturbance regimes. As adaptation strategies are developed, evaluated, and implemented, objective scientific evaluation of ongoing research and monitoring can aid differentiation of warranted and unwarranted uncertainties.

Surgical treatment of congenital scoliosis with or without Harrington instrumentation.

Of thirty-one patients who underwent posterior fusion for congenital scoliosis from 1972 through 1977 at the Children's Hospital Medical Center, Boston, Massachusetts, and were followed for two years or more, eighteen (average age, fourteen and one-half years and average curve, 62 degrees) were treated by spine fusion using Harrington instrumentation, and thirteen (average age, and one-half years and average curve, 43 degrees) were treated by fusion without instrumentation. Correction of the curve in the instrumented group was obtained at operation, while in the group without instrumentation correction was attempted using a plaster jacket applied during the postoperative period. After an average follow-up of thirty-four months in the group with Harrington instrumentation, the average curve was reduced from 62 to 40 degrees, for an average correction of 22 degrees, while in the non-instrumented group, after an average follow-up of fifty-three months the average curve was reduced from 43 to 38 degrees, for an average correction 5 degrees. A myelogram using water-soluble contrast medium should be performed in all patients who are to have instrumentation and in all patients who have any neural abnormality or are suspected of having diastematomyelia. An intraoperative wake-up test was used in all patients who had instrumentation after 1973 and averted neural complications in one. Proper treatment of congenital scoliosis requires early recognition of curves that have already progressed or will certainly do so. Fusion without instrumentation then is sufficient. If correction is necessary, staged procedures (halo-femoral traction, anterior release, and posterior fusion) may be required for severe curves. For the less severe curves, instrumentation as the primary means of obtaining correction proved to be safe and effective in this small series, but should only be attempted by experienced surgeons in institutions with all of the necessary facilities.

Intraoperative awakening to monitor spinal cord function during Harrington instrumentation and spine fusion. Description of procedure and report of three cases.

Since Vauzelle and associates first reported in 1973 on the functional monitoring of spinal cord activity during surgery on the spine, we have used intraoperative awakening routinely in patients undergoing surgery involving distraction of the spinal column. Of the 166 consecutive patients studied, three were discovered to have a neural deficiency when they were awakened during surgery. These deficits disappeared immediately on release of the distracting force. Although it is unlikely that all three patients would have proceeded to paraplegia, we believe that this is a safe and sensitive test which will identify patients in danger of neural complications.

Characterization of [3H]-valinomycin binding to red blood cell membrane.

Valinomycin was tritiated by exchange and its biological activity found to be similar to that of non-labeled drug. [3H]-valinomycin binds to red blood cell membranes following a biphasic pattern. High concentrations of the drug lead to an irreversible binding while low concentrations lead to a completely reversible binding. Maximum binding was obtained at acidic pH (pH 4.2) and physiological temperature (37 degrees C). We demonstrate that valinomycin binds strongly to the lipidic phase of the membrane. When binding to erythrocytes and reticulocytes was compared, it was found that the mature red blood cells had less binding capacity than the reticulocytes.

Recombinant human superoxide dismutase enhances the effect of inhaled nitric oxide in persistent pulmonary hypertension.

We investigated the pulmonary vascular effects of superoxide dismutase (SOD) alone and in combination with inhaled nitric oxide (iNO) in newborn lambs with persistent pulmonary hypertension (PPHN) following prenatal ligation of the ductus arteriosus. In in vitro experiments, pretreatment with SOD significantly enhanced vascular relaxation in response to the NO donor S-nitrosyl-acetylpenicillamine (SNAP) in fifth-generation pulmonary arteries isolated from lambs with PPHN. In vivo treatment of fully instrumented newborn lambs with a single intratracheal dose of recombinant human CuZn SOD (rhSOD; 5 mg/kg) produced selective dilation of the pulmonary circulation. Further studies, of the combination of rhSOD and iNO, showed enhancement of the pulmonary vascular effects of iNO after brief periods of inhalation of 5 ppm and 80 ppm NO. We conclude that rhSOD reduces pulmonary vascular resistance and facilitates the action of iNO in a lamb model of PPHN. This suggests that rhSOD may prove to be an effective adjunctive treatment for newborns with PPHN.

Effects of granulocyte colony-stimulating factor on hyperoxia-induced lung injury in newborn piglets.

Granulocyte colony-stimulating factor (G-CSF) increases the concentration and activation of neutrophils in the peripheral blood and has been used to prevent late-onset infection in premature infants. However, if G-CSF also augmented the inflammatory response in the lung, the incidence and severity of acute and chronic lung injury might be expected to increase. Using a newborn piglet model of acute lung injury, we examined the effects of rhG-CSF (recombinant-metHuG-CSF) on lung injury. Thirty-three newborn piglets were studied as follows: 1). Unventilated controls; 2). normally ventilated (PaCO2 = 35-45 torr) with room air(RA) for 48 h; 3). normally ventilated with RA for 48 h and received rhG-CSF (10 mg/kg/dose IV) at 0, 12, 24, and 36 h; 4). hyperventilated (PaCO2 = 15-25 torr) with 100% O2 for 48 h; 5) hyperventilated with 100% O2 for 48 h and received rhG-CSF (10 mg/kg/dose IV) at 0, 12, 24 and 36 h. Complete blood counts and and differentials were performed at 0, 24, and 48 h. Animals were sacrificed at 48 h, lungs were removed en bloc, and bronchoalveolar lavage (BAL) was performed. Total blood white blood cells and neutrophil counts increased significantly over 48 h in animals who received rhG-CSF either with normoventilation (p <0.0001) or hyperventilation with 100% O2 (p <0.003), and did not change significantly in the other experimental groups. However, there were no significant differences in BAL total cell counts, neutrophil chemotaxis activity, total protein, or albumin concentrations among the groups. Despite significantly increasing peripheral neutrophil counts, rhG-CSF did not potentiate acute lung injury or inflammation. This suggests that prophylactic administration strategies using rhG-CSF to prevent sepsis in premature infants should not increase the risk for developing acute and chronic lung disease.