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Biomedical subjects

J M Powell

Publications and source records attributed to J M Powell.

At least 19 recordsLinked to original sources
PubMed2006

Validation of feed and manure data collected on Wisconsin dairy farms.

An on-farm study of 54 representative Wisconsin dairy farms was conducted to evaluate the influence of biophysical and socioeconomic factors on overall feed, fertilizer, and manure nutrient use. This report validates 1) how well data on cow diets, feed analyses, and milk production reflected established feed-milk-manure relationships; and 2) how well farmer-recorded data on manure land application reflected literature values of manure N and P excretion, collection, and loss. Calculated feed N and P use efficiencies (18 to 33% and 18 to 35%, respectively) fell within ranges expected for dairy farms. This suggested that our on-farm methods of data collection provided reliable information on relationships among feed N and P intake, secretions in milk, and excretion in manure. On stanchion farms, there were no differences between farmer estimates (kg/farm) of manure P collected (1,140) and land-applied (1,210) and what would be calculated from the literature (1,340). On freestall farms, there were no differences in amounts (kg/farm) of manure P collected (2,889), land-applied (2,350), or literature estimates (2,675). Manure P applications (kg/ha) to tilled cropland would be similar using either farmer estimates of manure collected and land-applied, or literature estimates. The data provided a snapshot of Wisconsin industry practices, as well as information on the range of feed and manure management practices on individual dairy farms. Improvements to data collection methods would require increased skill and training of both farmers and those responsible for assisting farmers in on-farm data collection and analyses.

Agriculture↗
PubMed2005

Dietary manipulation in dairy cattle: laboratory experiments to assess the influence on ammonia emissions.

Improvements to the efficiency of dietary nitrogen use by lactating dairy cattle can be made by altering the concentration and form of protein in the diet. This study collected urine and feces from dairy cows from selected crude protein (CP) treatments of 2 lactation studies. In the first trial, collections were made from cattle fed a diet with high (19.4%) or low (13.6%) CP content (HCP and LCP, respectively). In the second trial, collections were made from cattle fed diets in which the forage legume component was alfalfa (ALF) or birdsfoot trefoil with a low (BFTL) or high (BFTH) concentration of condensed tannins (CT). A system of small laboratory chambers was used to measure NH3 emissions over 48 h from applications of equal quantities of urine and feces to cement (simulating a barn floor) and from applications of slurries, made by combining feces and urine in the proportions in which they were excreted for each treatment, to soil. Reducing dietary CP content resulted in less total N excretion and a smaller proportion of the excreted N being present in urine; urine N concentration was 90% greater for HCP than LCP. Surprisingly, NH3 emissions from the barn floor were similar in absolute terms despite the great differences in urine urea-N concentrations, presumably because urease activity was limiting. Cumulative emissions from fresh slurries applied to soil represented 18% of applied N for both HCP and LCP. Following storage at 20 degrees C for 2 wk, cumulative emissions from LCP were much lower than for HCP, representing 9 and 25% of applied N, respectively. Emissions were also lower when expressed as a proportion of slurry total ammoniacal N (TAN) content (24 and 31%, respectively) because of treatment differences in slurry pH. Increasing CT content of the dietary forage legume component resulted in a shift in N excretion from urine to feces. Cumulative NH3 emissions from the barn floor were greater for ALF than for BFTL or BFTH. Emissions from fresh and stored slurries were in proportion to slurry TAN contents, with approximately 35% of applied TAN being lost for all treatments. Emissions expressed as a proportion of total N applied were consistently lower for BFTH than for ALF.

Ammonia↗
PubMed2005

A survey of selected heavy metal concentrations in Wisconsin dairy feeds.

Heavy metals such as zinc (Zn), copper (Cu), chromium (Cr), arsenic (As), cadmium (Cd), and lead (Pb) are potential bioaccumulative toxins of the dairy production system. The heavy metal content of dairy feeds, however, remains poorly documented, particularly in the United States. This survey determined the heavy metal content of 203 typical dairy ration components sampled from 54 dairy farms in Wisconsin. Lowest heavy metal concentrations were found in homegrown alfalfa (Medicago sativa L.) hay and haylage, and corn (Zea mays L.) grain and silage. Highest metal concentrations were found in purchased feeds, particularly mineral supplements, and to a lesser extent corn- or soybean-based concentrates. Zinc and Cu were found at the highest concentration in complete dairy (total mixed and aggregated component) rations and reflected the deliberate addition of these metals to meet animal nutrient requirements although more than half the farms fed Cu and Zn above US recommended levels. Concentrations of Cr, As, Cd, and Pb were present in much lower concentrations and decreased in the order Cr > As > Pb > Cd. No complete Wisconsin dairy ration contained heavy metal concentrations above US maximum acceptable concentrations and would be unlikely to induce any toxic effects in dairy cattle. Concentrations of Cd in complete dairy rations were closest to US maximum acceptable concentrations, suggesting the greatest potential long-term risk to exceed US maximum acceptable concentrations if whole farm levels of Cd were to increase in the future. With the exception of Pb, the main sources of Zn, Cu, Cr, As, and Cd in the complete dairy feed ration originated from imported feed. The continued importation of heavy metals in dairy feed is likely to be associated with accumulation of these metals in soils where manure is applied. Although the cycling of many heavy metals through the dairy food chain will be limited by factors such as a soil's cation exchange capacity, pH, salinity, and phytotoxicity of the metal, these may be less limiting for Cd. It is important that sources of Cd in the dairy system are identified and minimized to prevent problems associated with Cd accumulation in the dairy soil system arising over the long-term.

Animal Feed↗
PubMed2005

Influence of bedding material on ammonia emissions from cattle excreta.

Dairy cattle barns are a major source of NH3 emissions to the atmosphere. Previous studies have shown that the bedding material used in the barn can influence the magnitude of NH3 emissions, but little is known about which bedding characteristics are important in this respect. The aims of this study were to assess, at a laboratory scale, the relative importance of the chemical [pH, cation exchange capacity (CEC), C:N] and physical (urine absorbance capacity, bulk density) characteristics of 5 bedding materials (chopped wheat straw, sand, pine shavings, chopped newspaper, chopped corn stalks, and recycled manure solids) on NH3 emissions from dairy cattle urine. Recycled manure solids were the most absorbent of the bedding types (4.2 g of urine/g of bedding), and sand was the least (0.3 g of urine/g of bedding). When beddings were soaked in urine to their absorbance capacities, NH3 emissions over 48 h (expressed as a proportion of the urine N absorbed) were not significantly different among bedding types, despite differences in initial bedding pH, CEC, and C:N. When equal volumes of urine were applied to equal depths of dry bedding, NH3 emissions over 48 h were significantly less from sand and pine shavings (23 and 42% of applied urine N, respectively) than from chopped newspaper, chopped corn stalks, and recycled manure solids (62, 68, and 65% of applied urine N, respectively), whereas emissions from chopped wheat straw (55% applied urine N) only differed significantly from that from sand. Differences in the chemical characteristics of the beddings did not explain differences in emission; NH3 emissions increased linearly with CEC contrary to expectations, and there was no significant relationship with initial bedding pH. The physical characteristics of bedding materials were of more importance, as NH3 emissions increased linearly with absorbance capacity and decreased as the bulk density of the packed beddings increased.

Absorption↗
PubMed2002

An alternative to fixation of displaced fractures of the anterior intercondylar eminence in children.

Fractures of the anterior intercondylar eminence in children are relatively uncommon. There is considerable debate as to the best treatment of displaced fractures, but most methods described in the literature involve an open procedure combined with some form of fixation. Using human anatomical dissections, we have shown that the transverse meniscal ligament can become incarcerated within the fracture and act as a block to reduction. We describe an arthroscopic technique which requires no fixation device and report the results of its use in eight displaced fractures. This method gives reliable results and offers the advantage of less potential morbidity.

Adolescent↗
PubMed2001

Self-report of extent of recovery and barriers to recovery after traumatic brain injury: a longitudinal study.

OBJECTIVE: To examine the perspective of survivors of traumatic brain injury (TBI) regarding the extent and nature of their recovery over time. DESIGN: Inception cohort, longitudinal study. SETTING: Level I trauma center. PARTICIPANTS: One hundred fifty-seven consecutively hospitalized individuals with TBI (mean age, 36.1 yr; 80% men) with a broad range of injury severity. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Participants reported the extent of their recovery and barriers to full recovery at 1, 6, and 12 months. RESULTS: Participants reported a median return to normal at the 3 follow-up times of 65%, 80%, and 85%. After 1 month, self-reported extent of recovery correlated well with performance on the Glasgow Outcome Scale (p <.001 at 6 and 12 mo) and Wechsler Adult Intelligence Scale Performance IQ (p =.001 at 12 mo). The major reported barrier to recovery was physical difficulties, which constituted over half of the concerns at all time periods. Report of physical-related concerns decreased significantly (p =.002) over time whereas cognition-related concerns increased significantly (p =.02). CONCLUSION: Brain injury survivors consider themselves to have greater recovery than previously reported by clinicians or family members, consider physical problems a significant factor in their recovery, and appear to become more aware of cognitive impairments over time.

Adolescent↗
PubMed2001

The distress and risk assessment method (DRAM).

Our aim was to judge the influence of preoperative psychological disturbance on the outcome of lumbar discectomy. We evaluated 66 patients, before and after operation, using a self-administered questionnaire. Disability was assessed using the Oswestry disability index and psychological disturbance the Distress and Risk Assessment Method (DRAM) score. Patients were classified as normal, at risk or distressed, and the outcome of surgery in the three groups was compared at a follow-up of six months. The mean self-reported preoperative disability was significantly higher in those with psychological disturbance. A total of 54 patients (82%) returned completed postoperative questionnaires. Postoperative disability scores at six months were not significantly different in the three risk groups. Psychological disturbance improved after surgery. Our study suggests that the early outcome of lumbar discectomy is not affected by preoperative psychological disturbance. We conclude that a patient with a symptomatic prolapsed intervertebral disc should not be denied surgery on the basis of preoperative psychological assessment.

Adult↗
PubMed2000

Enhanced peroxynitrite formation is associated with vascular aging.

Vascular aging is mainly characterized by endothelial dysfunction. We found decreased free nitric oxide (NO) levels in aged rat aortas, in conjunction with a sevenfold higher expression and activity of endothelial NO synthase (eNOS). This is shown to be a consequence of age-associated enhanced superoxide (.O(2)(-)) production with concomitant quenching of NO by the formation of peroxynitrite leading to nitrotyrosilation of mitochondrial manganese superoxide dismutase (MnSOD), a molecular footprint of increased peroxynitrite levels, which also increased with age. Thus, vascular aging appears to be initiated by augmented.O(2)(-) release, trapping of vasorelaxant NO, and subsequent peroxynitrite formation, followed by the nitration and inhibition of MnSOD. Increased eNOS expression and activity is a compensatory, but eventually futile, mechanism to counter regulate the loss of NO. The ultrastructural distribution of 3-nitrotyrosyl suggests that mitochondrial dysfunction plays a major role in the vascular aging process.

Acetylcholine↗
PubMed1999

Immunolocalization and expression of prohibitin, a mitochondrial associated protein within the rat ovaries.

This study was designed to determine the cellular distribution and pattern of expression for the mitochondria-associated protein, prohibitin, during the transitional stages of follicular differentiation within the rat ovary. Immunohistochemical staining techniques were used on frozen sections to examine the localization of prohibitin to preantral, antral, preovulatory, and atretic follicles. Prohibitin localization was also determined in corpus luteum from adult rats, in addition to those from infant and juvenile ovaries, before and after gonadotropin stimulation. Western and Northern blotting techniques were used for qualitative and quantitative assessment of prohibitin expression levels within the ovary. Prohibitin was localized within granulosa cells of infant and juvenile ovaries in a relatively heterogeneous staining pattern. The oocyte also exhibited robust prohibitin expression at all stages of follicular development. In addition, strong prohibitin expression was evident in the corpus luteum as well as in follicles undergoing atresia. Additional data derived from studies involving a GnRH-agonist indicate that increases in prohibitin protein expression correlate with the initial events of apoptosis. Collectively, these results support a growth regulatory role for prohibitin within the rat ovary. Therefore, we propose that prohibitin may serve as an important regulator of granulosa cell fate during follicular development.

Animals↗
PubMed1998

Cytochemical demonstration of sites of hydrogen peroxide generation and increased vascular permeability in isolated pig hearts after ischaemia and reperfusion.

Isolated pig hearts, subsequently perfused with pig or human blood, were prepared for the cytochemical demonstration of sites of hydrogen peroxide generation and increased vascular permeability. Oxidant stress was associated with ultrastructural changes commonly seen following myocardial reperfusion. In addition, the precipitation of cerium perhydroxide following perfusion with physiological saline containing cerium chloride suggested the vascular endothelium and leukocytes as sources of oxidants. This was associated with rapid penetration of horseradish peroxidase through the intercellular clefts of the vascular endothelium into the interstitial space, suggesting increased vascular leakiness at these sites. The rapid penetration of horseradish peroxidase was observed at all monitored periods of reperfusion with pig or human blood. This indicates that the increased permeability occurred during the ischaemic period and continued during reperfusion. Morphological damage was greatest in pig hearts reperfused with whole human blood and this was attenuated if the blood was preabsorbed to remove antibodies prior to reperfusion. We conclude that oxidant stress was initiated during ischaemia and continued during reperfusion in this model.

Animals↗
PubMed1995

Capillary surface area is reduced and tissue thickness from capillaries to myocytes is increased in the left ventricle of streptozotocin-diabetic rats.

The left ventricles of normal and diabetic rats, fixed by vascular perfusion were examined using modern stereological techniques to quantify changes in the morphology accompanying streptozotocin-induced diabetes. The heart weight to body weight ratio increased in diabetic rats whilst left ventricular volume remained unchanged. Papillary muscles from the diabetic animals showed prolonged time to peak tension and relaxation, and altered sensitivity to adrenalin and calcium. The apparent cardiomyopathy observed when body weight loss exceeds heart weight loss in experimental diabetes was accompanied by specific pathological changes in the composition of the left ventricle. In the diabetic animals the volume of extracellular components increased threefold and the volume of capillaries fell. The surface density and total surface area of capillaries was reduced, and oxygen diffusion distance to myocyte mitochondria increased. The volume fraction of myocyte mitochondria was reduced during streptozotocin-induced diabetes.

Animals↗
PubMed1991

Bony transfixion of the median nerve following Colles' fracture. A case report.

Reported herein is the case of a 45-year-old man with a Colles' fracture complicated by median nerve transfixion by a bony spike. This seems not to have been reported previously and reinforces the belief that early median nerve exploration should be performed if there is nerve dysfunction associated with a volar bony spike on the postreduction roentgenograms.

Colles' Fracture↗
PubMed1990

Factors influencing the result of posterior spinal fusion in the treatment of adolescent idiopathic scoliosis.

Sixty-six consecutive patients with adolescent idiopathic scoliosis treated by posterior spinal fusion using Harrington distraction compression instrumentation were followed for a minimum of 3 years. Initial surgical correction was satisfactory, but during the follow-up period, mean 4.4 years (3-5 years), there was a loss of correction. Several factors (age, sex, the number of vertebrae in the fusions, and the use of cross wires) were important influences on correction. A method of assessing the balance of a posterior spinal fusion is described that is useful when assessing radiographs.

Adolescent↗
PubMed1988

Intra-articular knee injuries in racquet sports. A review of 128 arthroscopies.

Within the last decade, there has been a significant increase in racquet sport participation. The authors report that in a 5-year period, 17% of the injuries seen in a busy sports injuries clinic were associated with racquet sports, and over half of these were injuries to the knee. The findings are reported of those patients requiring knee arthroscopy, and the patterns of injury sustained are identified. Injuries to the knee in racquet sports are largely unavoidable and are inherent to the nature of the game.

Adult↗
PubMed1988

Metastatic carcinoid of bone. Report of two cases and review of the literature.

The skeletal manifestations of malignant carcinoid seem not to have been reported in the orthopedic literature. Bronchial and hindgut carcinoid tumors are less numerous than midgut tumors but metastasize to bone much more frequently. Carcinoid skeletal deposits are usually osteoblastic and most commonly affect the axial skeleton. The radiologic appearance is frequently indistinguishable from prostatic skeletal metastases or chronic sclerosing osteomyelitis. Two cases of skeletal metastases from midgut carcinoid are reported to demonstrate that metastases from carcinoid should be considered in the differential diagnosis of either bone malignancy or chronic sclerosing osteomyelitis.

Aged↗
PubMed1988

New clinical test for fracture of the scaphoid.

The authors noted that in patients with scaphoid fractures pronation of the affected wrist followed by ulnar deviation produces pain in the anatomic snuff box that is not present in those without a scaphoid fracture. They therefore evaluated this test prospectively in 73 patients. The test gave a 52% positive predictive value and a 100% negative predictive value. They recommend that the test may be used with confidence in the emergency department to exclude a scaphoid fracture in patients with clinical features suggesting scaphoid injury but a normal x-ray film. Use of this test would reduce the number of patients whose wrists are needlessly immobilized in a scaphoid cast.

Carpal Bones↗
PubMed1987

Recurrent ureteric obstruction in association with Henoch-Schönlein purpura.

The most common urological manifestation of Henoch-Schönlein purpura is focal proliferative glomerulonephritis. Ureteric obstruction as a consequence of the disease has been reported in children but is rare. We report an adult male patient with Henoch-Schönlein purpura causing unilateral, bi-focal, recurrent ureteric obstruction. We speculate that ureteric involvement in Henoch-Schönlein purpura may be more common than hitherto suspected and that even with a demonstrable obstructive episode, consideration must be given for an initial conservative approach.

Adult↗