Grazing management contributions to net global warming potential: a long-term evaluation in the Northern Great Plains.

The role of grassland ecosystems as net sinks or sources of greenhouse gases (GHGs) is limited by a paucity of information regarding management impacts on the flux of nitrous oxide (N(2)O) and methane (CH(4)). Furthermore, no long-term evaluation of net global warming potential (GWP) for grassland ecosystems in the northern Great Plains (NGP) of North America has been reported. Given this need, we sought to determine net GWP for three grazing management systems located within the NGP. Grazing management systems included two native vegetation pastures (moderately grazed pasture [MGP], heavily grazed pasture [HGP]) and a heavily grazed crested wheatgrass [Agropyron desertorum (Fisch. ex. Link) Schult.] pasture (CWP) near Mandan, ND. Factors evaluated for their contribution to GWP included (i) CO(2) emissions associated with N fertilizer production and application, (ii) literature-derived estimates of CH(4) production for enteric fermentation, (iii) change in soil organic carbon (SOC) over 44 yr using archived soil samples, and (iv) soil-atmosphere N(2)O and CH(4) fluxes over 3 yr using static chamber methodology. Analysis of SOC indicated all pastures to be significant sinks for SOC, with sequestration rates ranging from 0.39 to 0.46 Mg C ha(-1) yr(-1). All pastures were minor sinks for CH(4) (<2.0 kg CH(4)-C ha(-1) yr(-1)). Greater N inputs within CWP contributed to annual N(2)O emission nearly threefold greater than HGP and MGP. Due to differences in stocking rate, CH(4) production from enteric fermentation was nearly threefold less in MGP than CWP and HGP. When factors contributing to net GWP were summed, HGP and MGP were found to serve as net CO(2equiv.) sinks, while CWP was a net CO(2equiv.) source. Values for GWP and GHG intensity, however, indicated net reductions in GHG emissions can be most effectively achieved through moderate stocking rates on native vegetation in the NGP.

Lipoinjection as a treatment of pacemaker pocket neuralgia.

Chronic severe pacemaker pocket neuralgia secondary to inadequate subcutaneous tissue between the pacemaker and overlying skin typically is treated by surgical pocket revision or relocation of the system. A case of this complication successfully treated by lipoinjection is reported. Additional experience is needed to confirm the usefulness of the technique as a means of providing symptomatic relief without the risks associated with more invasive procedures.

Congenital cytomegalovirus infection after recurrent infection in a mother with a renal transplant.

A woman with a renal transplant developed a systemic cytomegalovirus infection. She recovered and 3 years later she became pregnant. She had 3 days of fever in the first trimester. She delivered an infant severely affected with congenital cytomegalovirus infection. The incidence of symptomatic congenital cytomegalovirus infection in infants born to immunosuppressed mothers who develop reactivated cytomegalovirus during their pregnancy seems high.

Bayesian forecasting of serum vancomycin concentrations in neonates and infants.

A dynamic pharmacokinetic model for i.v. vancomycin administration was developed and tested in 47 neonates and infants. Twenty-nine patients (Group 1), having two or more concentrations, were used to estimate population parameters by nonlinear least-squares analysis. Multiple stepwise linear regression techniques showed that estimated creatinine clearance, Clcr, and postnatal age were significant demographic factors related to vancomycin clearance (CL). No strong associations were found for the apparent volume of distribution. A one-compartment model was constructed using the associations of CLcr and postnatal age with vancomycin CL. Eighteen patients (Group 2), receiving 35 courses of vancomycin therapy, with both initial and subsequent sets of peak and trough concentrations, were used to test the predictive performance of the model with and without the use of Bayesian forecasting. Using only population-based parameters, the respective mean error (ME) (bias) and mean absolute error (MAE) (precision) for predicting subsequent peak concentrations were -1.20 and 3.89 mg/L and for trough concentrations, 0.83 and 2.23 mg/L, respectively. For the Bayesian method, these values were, respectively, 0.45 and 4.13 mg/L for peak concentrations and 1.55 and 2.40 mg/L for trough concentrations. When predicted concentrations occurred within 30 days of feedback concentrations, the Bayesian method tended to be slightly less biased and more precise than the population-based parameters. The opposite was true > 30 days of the initial set of feedback concentrations. The use of population-specific pharmacokinetic parameters and Bayesian forecasting should allow accurate dosage regimen design as well as minimize the need for monitoring serum vancomycin concentrations in neonates and young infants.

Prediction of gentamicin concentrations in neonates and infants using a Bayesian pharmacokinetic model.

This study retrospectively characterized population-based pharmacokinetic parameters for gentamicin in neonates and young infants, and evaluated the predictive performance of these parameters in a Bayesian forecasting program. Population parameter estimates were determined from the serum concentration-time data of 19 neonates and infants using a one-compartment open infusion model and nonlinear least-squares regression analysis. Univariate and multiple stepwise linear regression analyses were used to determine significant relationships between demographic characteristics and gentamicin pharmacokinetic parameters. Creatinine clearance and postnatal age were the most significant predictors of weight-standardized gentamicin clearance (model r2 = 0.86). The relationships between patient characteristics and population-based parameters were incorporated into the one-compartment Bayesian forecasting model. A second group of 17 neonates and infants receiving 35 courses of gentamicin therapy were used to evaluate the predictive performance of the population-based parameters and a Bayesian forecasting model. The population parameters provided accurate prediction of steady state gentamicin concentrations throughout multiple courses of therapy within the same patient. Bayesian forecasting further minimized the mean prediction error (bias) once a set of steady state peak and trough serum gentamicin concentrations became available (peak concentrations: -0.062 vs. -0.273 mg/l; trough concentrations: -0.006 vs. -0.161 mg/l). The mean absolute error (accuracy) was similar for the two sets of parameters. The observed accuracy of both the population parameters and Bayesian forecasting suggests that monitoring of serum gentamicin concentrations can be kept to minimum in neonates and infants.

Laryngeal tuberculosis as manifested in the decades 1963-1983.

Laryngeal tuberculosis is usually a complication of pulmonary tuberculosis and the clinical patterns have changed in recent decades. To evaluate the changing patterns, we reviewed 15 patients seen at the Massachusetts Eye and Ear Infirmary over a 20-year period and diagnosed as having laryngeal tuberculosis. The results showed a mean age of 56 years; a male predominance by a 2:1 ratio; minimal pulmonary lesions on radiographic studies in nine patients and one normal radiograph; clinical simulation by the tuberculous lesion of laryngeal cancer; excellent response to antituberculosis therapy; and low infectivity. Laryngeal lesions and concurrent pulmonary lesions should alert the otolaryngologist to consider systemic disease processes and the most frequent granulomatous lesion of the larynx, tuberculosis.

Assessment of neonatal platelet function using a viscoelastic technique.

The Sonoclot, a simple viscoelastometer, measures changes in the viscoelastic properties of plasma as it is recalcified. Platelet rich plasma (PRP) and platelet poor plasma (PPP) each have characteristic Sonoclot tracings. This technique was applied to evaluate the coagulability and platelet function, specifically, in PRP prepared from 53 normal term newborn cord bloods and whole blood from 17 very low birth weight premature infants. These values were compared to each other and to those previously reported adult control values obtained by one of the authors (C.B.). The cord PRP samples had shorter time related parameters than adult controls. The values from premature infants were suggestive of diminished platelet function when compared to cord values but were similar to adult values. This technique allows the use of small sample volumes, the minimization of the introduction of infection risks, and avoids manipulation of fragile, very premature infants.

Vancomycin pharmacokinetics in premature infants.

Vancomycin pharmacokinetics were studied in nine premature infants. Infants weighing less than 1,000 gm had significantly larger volumes of drug distribution and consequently longer drug half-lives than larger premature infants, regardless of postconceptual or actual age. These differences alter the vancomycin dosing recommendations in these two groups of premature infants. We recommend initial dosage regimens consisting of a loading dose of vancomycin of 25 mg/kg followed by doses of 15 mg/kg every 12 hours for infants with weights less than 1,000 gm. Infants weighing over 1,000 gm should receive 10 mg/kg every 12 hours, with a loading dose of 12.5 mg/kg. Serum vancomycin concentration should be monitored, however, for final optimization of therapy.

The effect of manganese deficiency upon the ultrastructure of the eggshell.

Manganese deficiency in the laying hen results in decreased egg production and eggshell thickness. Eggshells from deficient hens show specific changes in appearance characterized by translucent areas. Examination of these translucent areas with the scanning electron microscope revealed changes in the ultrastructure of the shell. The most prominent feature was large irregular mammillary knobs probably due to the fusion of several mammillary cores during the early phases of eggshell formation. Chemical analysis of the organic matrix of the eggshell showed a decrease in hexosamine and hexuronic acid content consistent with the known role of manganese in polysaccharide synthesis. Studies on the characteristics of the polysaccharide chains isolated from normal eggshells suggested that these polysaccharides were considerably different from those isolated from cartilage proteoglycans.