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Biomedical subjects

B Yoder

Publications and source records attributed to B Yoder.

10 recordsLinked to original sources
PubMed2006

Trafficking of donor-derived bone marrow correlates with chimerism and extension of composite allograft survival across MHC barrier.

We proposed to evaluate differences between recipient's immune response to vascularized skin and combined vascularized skin/bone allografts, under a 7-day alphabeta-TCR plus cyclosporine (CsA) treatment protocol. Thirty-six transplantations were performed in six groups: group I (isograft control-vascularized skin graft; n=6); group II (isograft control-combined vascularized skin/bone graft; n=6); group III (allograft rejection control group-vascularized skin graft; n=6); group IV (allograft rejection control-combined vascularized skin/bone graft; n=6); group V (allograft treatment-vascularized skin graft; n=6); and group VI (allograft treatment-combined vascularized skin/bone graft; n=6). Isograft transplantations were performed between Lewis rats and allografts were transplanted across the MHC barrier from Brown Norway to Lewis rats. In the allograft treatment group, a combined alphabeta-TCR+CsA protocol was applied for 7 days. All groups were compared clinically, immunologically and histologically. Statistical significance was determined with two-tailed Student's t test. Indefinite graft survival was achieved in the isograft control group (>300 days). Allograft rejection controls rejected within 5 to 9 days posttransplant; chimerism levels were undetectable (<.5%). Allografts under the alphabeta-TCR+CsA protocol had significantly extended survival when skin was combined with bone (61-125 days) compared to vascularized skin allografts (43-61 days). Lymphoid macrochimerism was significantly higher in group VI than group V. Histology confirmed skin and bone viability. Combined vascularized skin/bone allografts had higher and sustained levels of donor-specific chimerism and extended allograft survival.

Animals↗
PubMed2005

Lung function in immature baboons with respiratory distress syndrome receiving early caffeine therapy: a pilot study.

AIM: The cardiopulmonary effects of early caffeine therapy in surfactant-treated immature baboons were measured. METHODS: Nine 125-d (term = 185 d) baboons receiving caffeine citrate at 1 and 12 h age as part of a pilot study on the use of nasal CPAP at 24 h were compared to six untreated animals destined for prolonged ventilator support. All received surfactant prior to their first breath and again at 6 h age. Serial physiologic and ventilatory parameters were recorded. Lung mechanics were measured by body plethysmography. Data were compared from 1 through 24 h age. RESULTS: There were no between-group differences in any study variables prior to caffeine therapy at 1 h age. Airway resistance (RA) was significantly lower in caffeine-treated compared to non-caffeine-treated animals at 12 and 24 h age [median (range)12 h: 47 (35-107) cm H2O/l/s to 135 (120-259) cm H2O/l/s; and 24 h: 93(60-137) cm H2O/l/s to 211 (86-235) cm H2O/l/s; p < 0.05]. Respiratory system compliance (CRS) was higher in caffeine-treated compared to non-caffeine-treated animals at 18 and 24 h age [median (range) 18 h: 0.60 (0.29-1.58) ml/cm H2O/kg to 0.39 (0.33-0.46) ml/cm H2O/kg; and 24 h: 0.68 (0.36-1.20) ml/cm H2O/kg to 0.36 (0.33-0.55) ml/cm H2O/kg; p < 0.05]. Ventilatory efficiency index and arterial/alveolar ratio significantly improved in caffeine-treated animals over the 24-h study period (p < 0.05, repeated measures ANOVA). CONCLUSIONS: In this pilot study, early caffeine treatment, combined with prophylactic surfactant therapy, was associated with better lung function during the initial 24 h of life. This combined approach may facilitate earlier extubation or prophylactic efforts to support infants on nasal CPAP. Randomized, controlled investigation is warranted.

Animals↗
PubMed1994

Seasonal biochemical changes in coniferous forest canopies and their response to fertilization.

Seasonal changes in concentrations of total nitrogen, free amino acids, chlorophyll, starch and sugar were measured in foliage from fertilized and unfertilized conifer forests in New Mexico and Oregon. In the New Mexico Douglas-fir (Pseudotsuga menziesii var glauca (Beissn.) Franco) forest, fertilization resulted in elevated foliar nitrogen concentrations on all dates, from an average of 9 mg g(-1) in unfertilized trees to 14 mg g(-1) in fertilized trees. In the Oregon western hemlock (Tsuga heterophylla (Raf.) Sarg.) forest, fertilization increased total N by only 15%, from 13 mg g(-1) in unfertilized trees to 15 mg g(-1) in fertilized trees. Foliar nitrogen concentrations on a weight basis were lowest in winter and spring, but did not vary seasonally when expressed on a leaf area basis. Chlorophyll concentrations increased with fertilization and had greater seasonal variation than did total nitrogen concentrations. Chlorophyll concentrations were significantly higher during the growing season than in the winter and spring months. Fertilization did not result in major changes in the proportion of total nitrogen in chlorophyll at either the Oregon or the New Mexico site. Concentrations of free amino acids varied with date and fertilization treatment; in New Mexico, amino acids were highest in the winter sample, whereas in Oregon, they were lowest in winter and spring. At both sites, amino acid concentrations were significantly higher in fertilized trees than in control trees on most dates and the ratios of amino acid-N to total N were also significantly higher in fertilized trees. For both sites, starch concentrations were nearly zero for most of the year, but increased sharply just before bud break and initiation of new growth in the spring. Although fertilization resulted in increased nitrogen concentrations in foliage at both sites, the response in New Mexico was much greater than in Oregon. These results are in agreement with forest productivity data that suggest that growth in the New Mexico site is limited by nitrogen, whereas in the Oregon site it is not.

Journal Article↗
PubMed1993

False-negative urine latex particle agglutination testing in neonates with group B streptococcal bacteremia. A function of improper test implementation?

Although blood cultures remain the most specific indicator of Group B streptococcus (GBS) sepsis, a potentially life-threatening infection in neonates, test results may not be available for 24 to 48 hours. Detection of GBS antigen in the urine by latex particle agglutination (LPA) may speed diagnosis. This study analyzed the sensitivity of the GBS urine LPA assay under clinical conditions. The urine of neonates with early-onset GBS bacteremia was analyzed for GBS antigen over a three-year period at six military medical centers. Overall, 53.5% (38/71) of infants with positive blood cultures had a positive urine LPA test. Only one medical center routinely followed manufacturer's recommendations to concentrate urine specimens before testing. These data suggest that the sensitivity for the urine LPA assay, when performed on unconcentrated urine, is lower than previously reported. Clinicians should insist that the laboratory maximize sensitivity by concentrating urine prior to GBS LPA testing.

Antigens, Bacterial↗
PubMed1991

Fall lifting and long-term freezer storage of ponderosa pine seedlings: effects on post-storage leaf water potential, stomatal conductance, and root growth potential.

Post-storage water relations, stomatal conductance, and root growth potential were examined in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) seedlings from high- and low-elevation seed sources that had been lifted either in October or November and freezer stored, or in March, and then grown hydroponically in a greenhouse for 31 days. Seedlings lifted in October had poor root initiation (< 17 new roots per seedling), low predawn leaf water potentials (< -1.5 MPa), and low stomatal conductance (7.10 mmol m(-2) s(-1)) compared with seedlings lifted in November or March. There was little difference in post-storage water relations and stomatal conductance between seedlings lifted in November and those lifted in March. Throughout the 31-day test, seedlings from the high-elevation seed source produced 3-9 times more new roots, had higher predawn leaf water potentials (-0.6 to -0.7 MPa versus -1.1 to -1.6 MPa), and 1.3-5 times greater stomatal conductance than seedlings from the low-elevation seed source. For all seedlings on Day 31, the number of new roots was significantly related to predawn leaf water potential (r(2) = 0.65) and stomatal conductance (r(2) = 0.82). Similarly, the dry weight of new roots per seedling on Day 31 accounted for a significant amount of the variation in predawn leaf water potential (r(2) = 0.81) and stomatal conductance (r(2) = 0.49).

Journal Article↗
PubMed1990

Extracorporeal membrane oxygenation in the newborn.

Extracorporeal membrane oxygenation (ECMO) is used in the treatment of reversible pulmonary disease in the newborn. The ECMO program at Wilford Hall USAF Medical Center began in 1985 and to date, 57 patients have been placed on bypass for a mean of 125 hours. The indications for ECMO are severe, prolonged hypoxemia in patients with an estimated mortality of greater than 90% using conventional ventilator support. The major diagnoses in the patients placed on ECMO were meconium aspiration, congenital diaphragmatic hernia, and neonatal sepsis or pneumonia. Overall survival was 79%, or 45 out of 57. The most frequent complications were intracranial hemorrhage as well as hemorrhage from the surgical site. We have found ECMO to be an extremely valuable adjunct in the care of the critically ill newborn and believe it can significantly improve survival in infants with reversible pulmonary disease.

Extracorporeal Membrane Oxygenation↗
PubMed1978

Cell lineages of the embryo of the nematode Caenorhabditis elegans.

Embryogenesis of the free-living soil nematode Caenorhabditis elegans produces a juvenile having about 550 cells at hatching. We have determined the lineages of 182 cells by tracing the divisions of individual cells in living embryos. An invariant pattern of cleavage divisions of the egg generates a set of stem cells. These stem cells are the founders of six stem cell lineages. Each lineage has its own clock--i.e., an autonomous rhythm of synchronous cell divisions. The rhythms are maintained in spite of extensive cellular rearrangement. The rate and the orientation of the cell divisions of the cell lineages are essentially invariant among individuals. Thus, the destiny of cells seems to depend primarily on their lineage history. The anterior position of the site of origin of the stem cells in the egg relates to the rate of the cell cycle clock, suggesting intracellular preprogramming of the uncleaved egg. We used a technique that allows normal embryogenesis, from the fertilized egg to hatching, outside the parent under a cover glass. Embryogenesis was followed microscopically with Nomarski interference optics and high-resolution video recording.

Animals↗
PubMedDate not supplied

The use of high-frequency oscillatory ventilation (HFOV) and extracorporeal membrane oxygenation (ECMO) in the management of the term/near term infant with respiratory failure.

The use of high-frequency oscillatory ventilation (HFOV) was evaluated as a rescue intervention in 122 consecutive infants meeting criteria for extracorporeal membrane oxygenation (ECMO). Fifty-three percent responded to HFOV and never required ECMO, 3/65 died. Infants who ultimately required ECMO had lower aortic and pulmonary peak flow velocities, and lower pulmonary acceleration, circumferential fiber shortening and shortening fraction than those who were successfully managed with HFOV. The use of HFOV with an appropriate strategy decreased the need for ECMO in this patient population.

Extracorporeal Membrane Oxygenation↗