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Biomedical subjects

D M Schaefer

Publications and source records attributed to D M Schaefer.

34 records · Page 2Linked to original sources
PubMed1992

Prognostic significance of magnetic resonance imaging in the acute phase of cervical spine injury.

Fifty-seven patients with acute cervical spine injuries and associated major neurological deficit were examined within 2 weeks of injury by magnetic resonance (MR) imaging. All patients had abnormal scans, indicating intramedullary lesions. This study was undertaken to determine if the early MR imaging pattern had a prognostic relationship to the eventual neurological outcome. Three different MR imaging patterns were observed in these patients: 21 patients had patterns characteristic of intramedullary hematoma (Group 1); 17 had intramedullary edema over more than one spinal segment, but no hemorrhage (Group 2); and 19 had restricted zones of intramedullary edema involving one spinal segment or less (Group 3). The neurological state was determined using standard motor index scores at admission and at follow-up examination. Characteristically, the patients in Group 1 had admission motor scores significantly lower than the other two groups. At follow-up examination, the median percent motor recovery was 9% for Group 1, 41% for Group 2, and 72% for Group 3. These studies suggest that the MR imaging pattern observed in the acutely injured human spinal cord has a prognostic significance in the final outcome of the motor system. It is only when an accurate prognosis can be given at the outset that useful treatment data might be collected for homogeneous injury groups, and accurately based long-term planning made for the best patient care.

Adult↗
PubMed1990

Characterization of Egg Yolk Antibodies for Detection and Quantification of Selenomonas ruminantium by Using an Enzyme-Linked Immunosorbent Assay.

The specificity of polyclonal antibodies prepared against strains of Selenomonas ruminantium, the effect of assay conditions, and quantification of individual strains in mixed-cell suspensions of selenomonad strains were examined in this study. Whole-cell suspensions were prepared with pure cultures of S. ruminantium PC18, HD(4), GA192, and D. Each cell suspension was injected into a Leghorn laying hen, and polyclonal antibodies were harvested from eggs laid in week 3 or 7 following initial immunization. Antibodies made to the S. ruminantium strains readily discerned the homologous strain from the heterologous strains. Cross-reactivity among antibodies and the heterologous S. ruminantium strains ranged from 5 to 26%. Among non-S. ruminantium species, cross-reactivity of S. ruminantium antibodies was greatest with Selenomonas sputigena (3 to 34%) and Succinivibrio dextrinosolvens (0 to 37%). Antibodies made to strains GA192 and D were used to quantify a mixture of the two strains. Both antibodies responded to graded concentrations of the homologous antigen in the biculture mixtures in accord with the change in the direct cell counts for each strain (strain D, R = 0.92; strain GA192, R = 0.90). This enzyme-linked immunosorbent assay enabled concurrent and accurate quantification of two strains of S. ruminantium subsp. ruminantium in a mixed-cell suspension with a precision of much less than 1 order of magnitude.

Journal Article↗
PubMed1990

Acute cervical spine trauma: correlation of MR imaging findings with degree of neurologic deficit.

A retrospective analysis of magnetic resonance (MR) imaging studies of 78 patients with acute cervical spinal cord injuries was undertaken to determine which observations related directly to the neurologic injury. All MR imaging studies were performed on a 1.5-T unit and assessed with respect to 14 parameters related to the bony spine, ligaments, prevertebral soft tissues, intervertebral disks, and spinal cord. Forty-eight patients also underwent non-contrast material-enhanced thin-section computed tomography (CT) of the cervical spine. MR imaging was the definitive modality in the assessment of soft-tissue injury, especially in the evaluation of the spinal cord and intervertebral disks. All patients with a neurologic deficit had abnormal spinal cords at MR imaging. Intramedullary hemorrhage was predictive of a complete lesion. The degree of associated bone and soft-tissue injury had no bearing on the extent of spinal cord injury or neurologic deficit. Patients with residual cord compression following reduction demonstrated greater neurologic compromise than those without compression.

Acute Disease↗
PubMed1989

Magnetic resonance imaging of acute cervical spine trauma. Correlation with severity of neurologic injury.

Prior to the advent of computer-assisted imaging techniques, conventional radiographic studies did not accurately depict the severity of soft tissue injury (spinal cord and paravertebral tissue) attending severe spinal trauma. Computed tomography scanning is clearly superior to plain radiography in the demonstration of osseous fractures and impactions, but this modality does not clearly depict ligamentous or disc injuries and does not image the spinal cord directly. The authors' preliminary experience indicates that magnetic resonance imaging (MRI) more accurately defines the extent of soft tissue damage in the zone of injury. In this study, the authors correlate these objective imaging techniques with findings on neurologic exam. Seventy-eight patients with cervical spine injuries admitted to the Regional Spinal Cord Injury Center of the Delaware Valley between August 1987 and January 1989 were evaluated with surface-coil MRI on a 1.5-Tesla unit. Fifty-nine patients were studied within 7 days of injury. Image sequences consisting of T1-, proton density, and T2-weighted images were obtained in saggital views. Axial gradient recalled acquisitions in the steady state (GRASS) images were obtained from most patients. We learned that certain patterns of MRI signal were associated with severe neurologic deficit. These include: 1) intramedullary hematoma and 2) spinal cord contusion associated with edema encompassing more than one spinal segment. Magnetic resonance imaging findings also correlated with less severe injury and include 1) normal spinal cord signal and 2) small focal contusions associated with edema encompassing one spinal segment or less.

Adult↗
PubMed1989

Effects of prechilling and sequential washing on enumeration of microorganisms from refuse.

Techniques were evaluated for formation of a liquid inoculum from shredded municipal refuse, including chilling the refuse at 4 degrees C prior to blending and multiple washing and blending cycles. The average count of cellulolytic bacteria from six different detachment treatments was 5.1 x 10 cells per g (dry weight) of refuse with a range of 0.7 x 10 to 12.7 x 10 cells per g (dry weight). The liquid obtained from blending the refuse in phosphate buffer followed by hand squeezing was the selected detachment procedure. The inoculum formation procedure was validated by the addition of ruminal cellulolytic bacteria to refuse and recovery of the cellulolytic bacteria by most-probable-number enumerations. The ratio of measured to expected cell counts among tests in which different volumes of ruminal fluid were added to refuse ranged from 2.7 to 14.4. There was no evidence of anaerobic cellulolytic fungi in a refuse sample.

Journal Article↗
PubMed1989

Bacterial population development and chemical characteristics of refuse decomposition in a simulated sanitary landfill.

Population development of key groups of bacteria involved in municipal refuse conversion to methane was measured from the time of initial incubation through the onset of methane production. Hemicellulolytic bacteria, cellulolytic bacteria, hydrogen-producing acetogens, and acetate- and H(2)-plus-CO(2)-utilizing methanogens were enumerated by the most-probable-number technique with media containing oat spelt xylan, ball-milled cellulose, butyrate, acetate, and H(2) plus CO(2), respectively. Refuse decomposition was monitored in multiple replicate laboratory-scale sanitary landfills. A laboratory-scale landfill was dismantled weekly for microbial and chemical analysis. Leachate was neutralized and recycled to ensure methanogenesis. The methane concentration of the sampled containers increased to 64% by day 69, at which time the maximum methane production rate, 929 liters of CH(4) per dry kg-year, was measured. Population increases of 2, 4, 5, 5, and 6 orders of magnitude were measured between fresh refuse and the methane production phase for the hemicellulolytic bacteria, cellulolytic bacteria, butyrate-catabolizing acetogens, and acetate- and H(2)-CO(2)-utilizing methanogens, respectively. The cellulolytic bacteria and acetogens increased more slowly than the methanogens and only after the onset of methane production. The initial decrease in the pH of the refuse ecosystem from 7.5 to 5.7 was attributed to the accumulation of acidic end products of sugar fermentation, to the low acid-consuming activity of the acetogenic and methanogenic bacteria, and to levels of oxygen and nitrate in the fresh refuse sufficient for oxidation of only 8% of the sugars to carbon dioxide and water. Cellulose and hemicellulose decomposition was most rapid after establishment of the methanogenic and acetogenic populations and a reduction in the initial accumulation of carboxylic acids. A total of 72% of these carbohydrates were degraded in the container sampled after 111 days. Initially acetate utilization, but ultimately polymer hydrolysis, limited the rate of refuse conversion to methane. Microbial and chemical composition data were combined to formulate an updated description of refuse decomposition in four phases: an aerobic phase, an anaerobic acid phase, an accelerated methane production phase, and a decelerated methane production phase.

Journal Article↗
PubMed1988

Differentiation of ruminal bacterial species by enzyme-linked immunosorbent assay using egg yolk antibodies from immunized chicken hens.

Cross-reactivity among four species of ruminal bacteria was examined by using egg yolk antibodies from immunized Leghorn laying hens and an enzyme-linked-immunosorbent assay. The effects of the four species on the hens were compared on various days postimmunization. Hens injected with the same bacterial species had similar apparent antibody levels over the entire postimmunization period, but only Bacteroides ruminicola B1(4) and Selenomonas ruminantium D antigens elicited early increases in apparent antibody levels during weeks 2 and 3. Antibody cross-reactivity was greatly reduced by week 2, except for antibodies against Streptococcus bovis JB1.

Animals↗
PubMed1987

Influence of rumen ammonia concentration on the rumen degradation rates of barley and maize.

Four rumen-cannulated steers were given barley and maize diets supplemented with graded levels of an ammonium acetate solution. Animals were fed hourly from automatic feeders and water consumption was controlled to achieve steady-state conditions in the rumen. Dacron bags containing rolled barley or ground barley were incubated in the rumen of barley-fed steers, while ground maize and autoclaved maize were incubated in the rumen of maize-fed steers. Fractional degradation rates of dry matter were estimated for each cereal substrate incubated using a single-pol exponential decay model. No differences in degradation rate due to the method of feed processing were detected; however, barley was degraded at a faster rate than maize. Furthermore, the minimum rumen ammonia-nitrogen concentration required to maximize the degradation rate of barley (125 mg/l) was greater than that required to maximize the degradation rate of maize (61 mg/l). These results indicate that the optimal NH3-N concentration required to maximize the rate of grain digestion in the rumen is influenced by the chemical or structural characteristics of the grain.

Acetates↗
PubMed1987

Alteration of fermentation in continuous culture of mixed rumen bacteria by isolated alfalfa saponins.

Saponins isolated from alfalfa by ethanol extraction and acid hydrolysis were incorporated into protein-free purified diets at 0, .5, 1, 2, and 4% of dietary dry matter to investigate the effect of saponins on fermentation by mixed rumen bacteria maintained in continuous culture. Inoculum was obtained from a lactating dairy cow fed alfalfa hay and a 13% crude protein grain mixture with forage to grain ratios of 33:67, 67:33, or 100:0. Outflow of microbial protein was lower in fermenters fed purified diet containing 1% saponins. Accumulation of ammonia was observed in fermenters fed purified diets containing alfalfa saponins. Total volatile fatty acid production was reduced by addition of isolated alfalfa saponin fraction at .5, 1, 2, and 4% concentrations. Acetate to propionate ratios were reduced from 1.93 in control to 1.37 in fermenters with 1% saponins. Extent of change in fermentation was not proportional to the concentration of added saponins.

Animals↗
PubMed1987

Evaluation of some commercial media for the cultivation and enumeration of Clostridium perfringens from the chick intestine.

Four commercial media marketed for the detection and enumeration of Clostridium perfringens were found to adequately support the growth of a pure culture (ATCC 13124) of this species but enumeration of colony-forming units was difficult on Clostrisel and lecithin-lactose-agar base (LLA) media. Colonies of C. perfringens on LLA had typical opalescent zones, a distinctive feature that can aid in presumptive identification. Colonies on sulfite-polymyxin-sulfadiazone and tryptose-sulfite-neomycin (TSN) agar media were morphologically similar but black colonies were observed on TSN incubated at 46 C. Extreme difficulty was encountered in enumerating enteric bacteria from the chick intestine on Clostrisel medium because of the pinpoint size of the colonies and on LLA because of the opacity of the medium. Morphological characteristics of bacteria picked from colonies which formed after these media had been inoculated with chick intestinal contents were in sharp contrast to those of the pure culture of C. perfringens. Numbers of colony-forming units were higher than documented levels of C. perfringens in the intestine of chicks. These observations led to the conclusion that these formulations are inadequate for the selective cultivation and enumeration of this bacterial species from the intestine of healthy chicks, unless used in combination with further tests for specific identification.

Animals↗
PubMed1985

Characterization of limestones and their effects in vitro and in vivo in dairy cattle.

Capacities of limestones of differing particle size to neutralize acid in vitro and to modify pH and utilization of feedstuffs in vivo were compared. Acid neutralization during pH-stat titrations was faster for fine than for coarse limestone, and mixed microbial cultures were more resistant to pH change when they contained fine calcium carbonate. Diets containing 25:75 corn silage to concentrates and .95% calcium from either coarse or fine limestone were fed to rumen-fistulated heifers. Total ruminal volatile fatty acid concentrations were higher for the fine limestone treatment. Ruminal volumes, dry matter disappearance, and ruminal fluid pH and dilution rate did not differ between fine and coarse limestone treatments. Ruminal fluid volume, osmolality, ratios of acetate to propionate, and concentrations of total volatile fatty acids were unaffected in rumen-fistulated Holstein cows fed 60:40 corn silage to concentrates and either .5% calcium (control) or 1.0% calcium from either coarse or fine limestone. Ruminal pH increased .07 to .10 units with limestone supplementation. Ruminal fluid dilution and particulate turnover rates were slower for the coarse limestone than the control treatment. Differences between coarse and fine limestones in vitro were observed under some conditions in vivo, but they were not consistent.

Animal Feed↗
PubMed1982

Neutralization of acid in the rumen by magnesium oxide and magnesium carbonate.

Two reagent and two feed grade magnesium oxides and reagent grade magnesium carbonate, sodium bicarbonate, and calcium carbonate were evaluated to ascertain their ability to neutralize acid in the rumen. Rumen fluid pH was increased in vitro, compared to the control, by antacid compounds, and their increased ranked: calcium carbonate less than feed grade magnesium oxide A less than light magnesium oxide and feed grade magnesium oxide B less than heavy magnesium oxide less than magnesium carbonate less than sodium bicarbonate. Titrations at constant pH's ranging from 3.0 to 7.5 indicated that these magnesium compounds were reactive at pH's normally in the rumen although reactivity decreased with increasing pH. Intraruminal doses of feed grade magnesium oxide A and calcium carbonate did not change rumen fluid pH for other compounds ranked: feed grade magnesium oxide B less than magnesium carbonate less than heavy magnesium oxide. Feeding of heavy magnesium oxide or magnesium carbonate increased rumen fluid pH as compared to the control diet. Feeding feed grade magnesium oxide B in three quantities to cattle resulted in proportional increased in fecal pH and fluidity of feces. Two feed grade magnesium oxides differed in their ability to neutralize acid in the rumen.

Animals↗
PubMed1980

Ammonia saturation constants for predominant species of rumen bacteria.

Ammonia saturation constants were determined for representative pure cultures of predominant, anaerobic, fermentative rumen bacteria. Based on growth experiments with ammonia limited continuous cultures, average estimates for ammonia saturation constants of Bacteroides amylophillus and Bacteroides ruminicola were 10.5 and 23.5 microM ammonia-nitrogen, respectively. With ammonia-limited linear-growth cultures, the estimates for the ammonia saturation constants of B. amylophilus, B. ruminicola, and Selenomonas ruminantium were, respectively, 6, 33.5, and 18 microM ammonia nitrogen. By a third method, which involved estimation of ammonia concentration in the medium when the growth rate of ammonia-limited batch cultures reached half maximal, the ammonia saturation constant was determined for the species mentioned as well as Megaspaera elsdenii and Ruminococcus flavefaciens. Except for M. elsdenii, saturation constants of the other bacteria were less than 50 microM ammonia nitrogen. An organism with a saturation constant for ammonia of 50 microM growing in a medium containing 1 mM ammonia should achieve 95% of its maximum specific growth rate. Many of the predominant species of rumen bacteria are efficient scavengers of ammonia.

Ammonia↗
PubMedDate not supplied

The effect of the prone position on venous pressure and blood loss during lumbar laminectomy.

STUDY OBJECTIVE: To determine the effects of three different prone support systems (Andrews spinal surgery frame, Cloward surgical saddle, and longitudinal bolsters) on inferior vena cava (IVC) and superior vena cava (SVC) pressures; the validity of measuring central venous pressure (CVP) for the determination of ideal positioning of the patient; and the relationship among frame type, blood loss, and hemodynamic measurements. DESIGN: Prospective, randomized study of the hemodynamic effects of the prone position. SETTING: Inpatient surgery at a university hospital (regional spinal cord injury treatment center). PATIENTS: Eighteen patients free of significant coexisting disease (ASA physical status I and II) undergoing elective lumbar laminectomy. INTERVENTIONS: Patients were assigned to one of three support frames and measurement of SVC pressure, IVC pressure, and mean arterial pressures (MAP) were obtained supine, prone, and after repositioning. These pressures and measured blood loss were obtained every 15 minutes during the surgical laminectomy portion of the procedure. MEASUREMENTS AND MAIN RESULTS: Patients positioned on the Andrews frame had decreased mean SVC and IVC pressures from 8.7 mmHg and 8.4 mmHg in the supine position to 3.3 mmHg and 1.8 mmHg in the prone position, respectively (p less than 0.001). Prone position CVP also was significantly lower in the Andrews group compared with that in the other two groups (p less than 0.001). Repositioning efforts did not significantly decrease CVP. Blood loss was higher in the Cloward group (1,150 +/- 989 ml) than in the Andrews (245 +/- 283 ml) and bolsters (262 +/- 188 ml) groups (p less than 0.02). CONCLUSIONS: Increased blood loss was not associated with increased SVC or IVC pressure, nor was there any significant correlation between any demographic or hemodynamic variable and blood loss. There was no evidence that CVP is useful in determining the ideal prone position in patients undergoing lumbar laminectomy.

Blood Loss, Surgical↗
PubMedDate not supplied

Hatching eggs sanitized with chlorine dioxide foam: egg hatchability and bactericidal properties.

The efficacy of chlorine dioxide (ClO2) as an alternative sanitizing agent for hatching eggs was investigated because of the health concerns about formaldehyde fumigation. Hatchability of chicken eggs was reduced when the eggs were dipped in the ClO2 solutions for more than 5 minutes or in concentrations greater than 100 ppm Cl. However, treating hatching eggs with a ClO2 foam or fumigating with formaldehyde had no adverse effect on hatchability compared with untreated control eggs. Sanitizing soiled duck eggs with ClO2 foam improved hatchability by more than 10% and hatch by more than 6% compared with untreated eggs (P less than 0.05). A novel method for assessing bactericidal potential of egg-sanitizing agents was developed. Using this technique, both chlorine dioxide foam and formaldehyde fumigation reduced the number of egg-contaminant bacteria inoculated on sterile chicken eggs compared with the number of bacteria on untreated eggs (P less than 0.05). These findings suggest that sanitizing hatching eggs with ClO2 foam may be a viable alternative to fumigating with formaldehyde.

Animals↗