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Biomedical subjects

W F Brown

Publications and source records attributed to W F Brown.

At least 37 records · Page 2Linked to original sources
PubMed1997

Cottonseed meal or feather meal supplementation of ammoniated tropical grass hay for yearling cattle.

Despite high N intake by cattle consuming ammoniated forages, improvements in ADG might be expected be feeding proteins that supply ruminally available and(or) undegraded intake protein. Growth studies with 220-kg steers were conducted to evaluate ammoniated hay plus a liquid cane molasses-based supplement containing urea or a combination of urea and .07, .14, or .21 kg of CP daily from cottonseed meal (CSM) or feather meal (FM). Steers grazed dormant pasture and were fed hay plus 1.36 kg of DM daily per steer of the supplement. In each of 3 yr, total DM intake was similar (P > .60) among treatments, averaging 3.0% of BW. Daily gain by steers supplemented with urea and maximum ADG were similar across years, ranging from .21 to .23 kg and .50 to .60 kg, respectively. In all years for CSM supplementation, and in two of the three years for FM supplementation, increasing level of CP supplementation resulted in linear (P < .01) increases in ADG and gain:feed ratio (GF), with no differences (P > .10) between the protein sources. In one year, ADG and GF by steers supplemented with FM were maximized at the .07 kg of CP level, suggesting greater efficiency of protein utilization in FM. Improved performance by cattle fed ammoniated tropical grass hay may be obtained by feeding a protein supplement that provides preformed protein that is either moderately or highly resistant to ruminal degradation. Ruminal degradation characteristics of protein sources may influence efficiency of protein utilization in cattle fed ammoniated tropical grass hay plus molasses-based supplements.

Aging↗
PubMed1995

Pyridoxine dependent epilepsy with iatrogenic sensory neuronopathy.

An 18-year-old man was treated from birth with chronic high dose pyridoxine (vitamin B6) up to 2000 mg per day for pyridoxine-dependent seizures. Within two years of onset of treatment, he developed a sensory neuropathy which did not progress over the following 16 years. Electrophysiological studies were consistent with a pure sensory neuronopathy expressed as centripetal degeneration of processes of the dorsal root ganglion cells.

Action Potentials↗
PubMed1995

Methods for estimating the numbers of motor units in human muscles.

After the introduction by A. J. McComas of the original method for estimating the number of motor units based on manual incremental stimulation of a motor nerve, several new techniques have been developed, designed to correct for some of the errors inherent in the original technique. These methods incorporate algorithms to adjust for alternation and, to a greater or lesser extent, automate the methods, rendering the techniques less subject to operator bias and various physiological and technical errors. This review explores the advantages and drawbacks in the multiple-point stimulation (MPS), spike-triggered averaging (STA), and decomposition-enhanced STA techniques, illustrates some of the current applications of the techniques, and explores some tantalizing prospects for new studies of motor-unit physiology in the future.

Algorithms↗
PubMed1995

Value of feather meal in a molasses-based liquid supplement fed to yearling cattle consuming a forage diet.

Hydrolyzed feather meal (FM) was compared to other sources of CP to determine its value as a protein source in a molasses-based liquid supplement. Ruminal N escape values (measured in situ) for FM, ring-dried blood meal, cottonseed meal, and soybean meal approximated reported values. Ruminal N escape value for catfish meal was lower than values reported for other fish meals. In two trials (194 d), 84 yearling heifers were allotted to 12 pastures (3 pastures/treatment) and fed one of four supplements (1.7 kg of DM.heifer-1.d-1) containing either molasses and urea; molasses, urea,and FM; molasses, urea, FM, and catfish meal; or molasses, urea, FM, and catfish oil. Heifers were exposed to bulls for 60 d. In two trials, 112 steers were allotted to 16 pastures (4 Pastures/treatment) and fed one of four supplements (1.7 kg of DM.steer-1.d-1) containing molasses and urea; molasses, urea and FM; molasses, urea, FM and ring-dried poultry blood meal; or molasses, urea, and poultry feathers and blood hydrolyzed together. In all trials, cattle fed molasses containing FM had faster gains (P < .05) and heifers had heavier live weights at breeding (P < .05) and higher pregnancy rates (P < .05) than cattle fed molasses and urea. Combining poultry blood with molasses, urea, and FM improved (P < .05) steer gains in one of two trials. Combining catfish meal with molasses, urea, and FM did not improve (P > .05) ADG of pregnancy rate of heifers. Combining catfish oil with molasses, urea, and FM increased (P < .05) ADG in one trial and blood cholesterol and live weight of heifers at breeding in both trials. It is concluded that protein feeds, such as FM, that contain a large portion of ruminally undegradable protein may provide much of the CP in liquid supplements fed to growing cattle consuming moderate-quality forage. Adding catfish oil to a liquid supplement may improve ADG and live weight of yearling heifers at breeding.

Aging↗
PubMed1995

Urea ammoniation effects on the feeding value of guineagrass (Panicum maximum) hay.

Laboratory, digestion, and growth studies evaluated urea as a source of ammoniation for quality improvement in guineagrass (Panicum maximum) hay. In a laboratory trial, 5.0-kg portions of hay were reconstituted with water to yield final forage moisture concentrations or 25 of 40% and treated with urea at 0, 4, 6, or 8% of the forage DM, with or without urease addition. Main effects of forage moisture or urease addition did not influence (P > .10) CP or NDF concentration or in vitro OM disappearance (IVOMD) of the guineagrass hay. Hay CP concentration and IVOMD increased linearly (P < .01), whereas concentrations of hemicellulose and ADL decreased linearly (P < .05) with increasing urea level. In other experiments, round bales of hay (320 kg) were reconstituted with water to yield final forage moisture concentrations of 25 or 40% and treated with urea at 0, 4, or 6% of the forage DM. The urea solution was applied as a spray onto the cut edges of the bales, or by low pressure (10 psi) injection. Two- and three-way interactions (P < .05) existed among forage moisture concentration, urea application method, and urea level for CP and NDF concentration and IVOMD of the guineagrass hay. Greatest enhancements in these forage quality characteristics were obtained when the urea solution was sprayed onto the hay at the 25% forage moisture concentration. In two digestion and two growth trials, round bales of hay were treated with 0, 4, and 6% urea sprayed onto the hay at the 25% forage moisture level. In each growth trial, 30 St. Croix white hair castrated male sheep (Trial 1:34 +/- 5.5 kg, Trial 2: 17 +/- 3.5 kg) were allotted to six pens of five head each, resulting in two pens per treatment. In the digestion trials, six similar sheep were used in a replicated 3 x 3 Latin square design. In the digestion and growth trials, hay intake increased in a quadratic (P < .05) manner with increasing urea level. Apparent NDF and ADF digestibilities increased linearly (P < .05) with increasing urea level. Linear improvements in ADG (P < .05) and gain/feed (P < .07) were observed with increasing urea level. Urea ammoniation offers potential for improving the feeding value of tropical forages and provides an option for quality forage during the dry season.

Ammonia↗
PubMed1995

Effect of molasses-based liquid supplements on digestibility of creeping bluestem and performance of mature cows on winter range.

Poor quality of tropical range forage leads to excessive weight loss and poor reproductive performance of beef cows. This research measured 1) the digestibility by steers fed creeping bluestem (Schizachyrium scoparium var. stoloniferum) diets supplemented with cane molasses (0 or 20% of diet DM) and(or) added CP (no added CP, urea, or soybean meal) and 2) the performance of mature cows grazing creeping bluestem range and supplemented with 1.6 kg/(cow.d) (DM basis) of either molasses-urea or molasses-cottonseed meal-urea, each containing 30% CP (DM basis). Bluestem averaged 4.7% CP and 37.0% in vitro OM digestion. In the digestion trial, diets supplemented with molasses had greater (P < .01) apparent OM digestibility but lower (P < .01) apparent NDF, ADF, and hemicellulose digestibilities than diets not supplemented with molasses. Apparent OM digestibility of diets supplemented with soybean meal was greater (P < .05) than that of diets supplemented with urea but not different (P > .05) from the control. While grazing range, mature cows supplemented with molasses-urea lost less (P < .05) body condition (-1.7 vs -1.3) than cows supplemented with molasses-cottonseed meal-urea. Treatment did not affect cow weight loss on range (P = .85) or pregnancy rate (P = .51). Cows supplemented with molasses-urea tended to wean a heavier calf (P = .09). When fed at 1.6 kg/(cow.d) to mature cows grazing range, a molasses-based supplement containing urea was of equal value to one containing a natural protein.

Animal Feed↗
PubMed1994

AAEM minimonograph #42: intraoperative monitoring of peripheral and cranial nerves.

Intraoperative studies of focal neuropathies have become increasingly common both as an aid to the localization of the neuropathy and a means of monitoring the integrity of the nerve in the course of surgery. Success very often depends on careful attention to the technical problems presented by working in the operating theater. Despite these difficulties, assessment of conduction directly from the exposed nerve offers opportunities for better understanding the pathophysiology of these neuropathies and correlating these findings with conventional electrodiagnostic studies.

Action Potentials↗
PubMed1994

Physiological properties of single thenar motor units in the F-response of younger and older adults.

The purpose of this study was to characterize the properties of single thenar motor units in the F-response of healthy younger (n = 15; age 33 +/- 11 years) and older subjects (n = 15; age 68 +/- 3 years). Trains of 300 stimuli at intensities evoking M-potentials 10%, 20%, and 30% of the peak-to-peak amplitude of the maximum M-potential, were delivered to the median nerve. In the young, observed firing probabilities of surface-detected motor unit action potentials (S-MUAPs) extracted from the F-response ranged from less than 1-10%, the S-MUAPs varied in size from 0.015% to 5.3% of the maximum M-potential negative peak area, and they were similar in size to the population of S-MUAPs collected by multiple point stimulation of the median nerve. The percentage difference between the slowest and fastest conducting fibers for individual subjects ranged from 8% to 20%, which translated to conduction velocities (CVs) of 48-68 m.s-1 (mean 59 +/- 4). The preceding were all independent of stimulus intensity. The S-MUAP sizes were significantly larger in older subjects (39%), and the range and distribution of motor unit CVs (38-61 m.s-1; mean 52 +/- 3) were markedly shifted to reflect a slower population of motor fibers. These findings suggest that age-related axonal slowing may uniformly affect all median motor fibers.

Action Potentials↗
PubMed1994

Motor unit number estimates based on the automated analysis of F-responses.

An automated technique for estimating the number of motor units based on single motor unit action potentials in the F-response is described. The average surface detected motor unit action potential (S-MUAP) was calculated from the datapoint-by-datapoint average of a sample of S-MUAPs automatically selected from a population of F-responses. The technique was applied to the thenar muscles of young (n = 18, aged 31 +/- 11 years) and older (n = 15, aged 68 +/- 3) subjects. Motor unit number estimates based on the automated selection of S-MUAPs from the F-responses compared well with those derived using a computer-assisted manual method for selecting S-MUAPs from the F-response (automated 245 +/- 105 vs. manual 241 +/- 100, r = 0.93) and were similar to estimates obtained using multiple point stimulation (219 +/- 77). The advantages of the automated technique for collecting S-MUAPs from the F-response include the ready tolerance of the technique by subjects, the minimal amount of operator interaction required, and the additional information relating to the conduction velocities and latencies of single motor axons.

Action Potentials↗
PubMed1994

A method for the longitudinal study of human thenar motor units.

Methods currently available to study the electrophysiological and contractile properties of single human motor units (MUs) preclude the same MU from being studied on repeated occasions. We have developed a method which allows single thenar MUs to be studied longitudinally. Sites were located along the median nerve where, using percutaneous stimulation, it was possible to selectively activate a single thenar motor axon as determined by: (a) the presence of an "all-or-nothing" surface-detected motor unit action potential (S-MUAP); (b) the occasional presence of F-responses identical in size and shape to the direct S-MUAP; (c) excitation thresholds widely separated from the next highest threshold motor axon so as to allow high frequency stimulation. To ensure that the same motor axon had been located and stimulated in successive studies, additional criteria included: (a) the motor axon was found at approximately the same site along the nerve; (b) the threshold for excitation remained widely separated from the next highest threshold motor axon; (c) the shape of the S-MUAP was almost identical on repeated studies; (d) S-MUAP and F-response latencies were similar. This method provides, for the first time, the ability to track longitudinally the electrical and contractile properties of single MUs in health and during the course and treatment of disease.

Axons↗
PubMed1994

Electrodiagnosis in the management of focal neuropathies: the "WOG" syndrome.

The role of electrodiagnosis in managing patients with focal neuropathies is discussed from the differing perspectives of a peripheral nerve surgeon and a practitioner of electrodiagnostic medicine. Both clinical evaluation and electrodiagnosis are useful methodologies, each having limitations. Dr. Dellon labels the overreliance on electrodiagnosis and the "WOG" (Word of God) syndrome, and describes its signs, symptoms, and treatment. Dr. Brown contends Dr. Dellon's crusade is misdirected. The exchange is an eloquent polemic on the virtues and foibles of these different approaches to evaluating peripheral nerve function and the imperative to practice them in a complementary rather than a contentious manner.

Diagnostic Errors↗
PubMed1993

Electrophysiological changes in the acute "axonal" form of Guillain-Barre syndrome.

The acute "axonal" form of Guillain-Barre syndrome is characterized by rapid progression to severe widespread paralysis and respiratory dependence within 2-5 days of the onset of weakness with very poor and delayed recovery. In 3 cases studied within the first 7 days, the maximum thenar, hypothenar, tibialis anterior, and extensor digitorum brevis "M" potentials were either very reduced in size or absent in response to stimulation at the usual most distal sites of stimulation at the wrist, fibular head, and/or ankle. In the latter instances, advancing the site of stimulation closer to the motor point often evoked an M response. Furthermore, continued distal advance of the site of stimulation evoked progressively larger sized M potentials. Over succeeding days even these very distally evoked M potentials disappeared. Maximum conduction velocities in motor nerve fibers just prior to total loss of excitability were often very reduced. The pattern in these cases is most consistent with progressive loss of excitability and conduction in nerve fibers undergoing axonal degeneration, although coexisting primary demyelination in the terminal segment could not be excluded as the basis for the sometimes very slowed conduction velocities.

Acute Disease↗
PubMed1993

The estimated numbers and relative sizes of thenar motor units as selected by multiple point stimulation in young and older adults.

Multiple point stimulation (MPS) is described as a method of estimating the numbers of motor units in the median innervated thenar muscles of young and older control subjects. Stimulation at multiple sites along the course of the median nerve was employed to collect a sample of the lowest threshold, all-or-nothing surface-recorded motor unit action potentials (S-MUAPs). The average, negative peak area, and peak-to-peak amplitude of the sample of S-MUAPs was determined and divided into the corresponding value for the maximal compound muscle action potential to derive the motor unit estimate (MUE). In 37 trials from 17 younger subjects (20-40 years), the mean MUE was 288 +/- 95 SD based on negative peak area and, in 33 trials from 20 older subjects, mean values were 139 +/- 68. In 23 young and older subjects, MPS was performed on at least two occasions and the MUEs were found to be highly correlated (r = 0.88).

Action Potentials↗
PubMed1993

AAEM case report #27: acute retrohumeral radial neuropathies.

Acute radial neuropathies localized to the retrohumeral course of the radial nerve are common. Most individuals fully recover within a matter of days or, at the most, a few weeks. In a few, recovery may take longer and occasionally remains incomplete. In almost all instances the site of injury to the radial nerve can be accurately localized to the region of the spiral groove and the relative contributions of conduction block and axonal degeneration assessed using electrophysiologic techniques.

Action Potentials↗
PubMed1993

Determinants of mean motor unit size: impact on estimates of motor unit number.

The purpose of this study was to compare two fundamentally different methods of deriving the average surface-detected motor unit action potential (S-MUAP) size from which to calculate a motor unit number estimate (MUNE), namely: (1) the simple arithmetic average of S-MUAP parameter values; and (2) a computer-derived datapoint by datapoint average waveform which takes account of differences in S-MUAP shapes and durations. Multiple point stimulation was used to collect representative samples of between 11 and 20 S-MUAPs (mean 15 +/- 2 SD) from the median-innervated thenar muscles of 20 healthy control subjects between 20 and 76 years of age (mean 48 +/- 19 SD). The average S-MUAP size based on peak-to-peak amplitude, negative peak amplitude, and negative peak area measurements was calculated using the two different methods. The mean S-MUAP sizes based on the average waveform were significantly lower in all cases than those based on the simple average of S-MUAP parameter values. Differences tended to be greatest for MUNEs based on peak-to-peak amplitude (35%), less for negative peak amplitude (20%), and least for negative peak area (16%).

Action Potentials↗