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Biomedical subjects

W F Brown

Publications and source records attributed to W F Brown.

At least 55 records · Page 3Linked to original sources
PubMed1993

Severe axonal degeneration in acute Guillain-Barré syndrome: evidence of two different mechanisms?

Four cases of severe acute Guillain-Barré syndrome (GBS) characterized by severe axonal degeneration are presented. All had electrically inexcitable motor nerves as early as 4 days after onset. The disease was rapid in onset and the residual disability was severe. Two different types of pathology were seen. Nerve biopsies in 3 cases showed severe axonal degeneration without inflammation or demyelination. Autopsy in one of these cases showed that the dorsal and ventral roots were also significantly affected. These cases illustrate the primary axonal form of GBS. Nerve biopsy in the fourth case at day 15 showed marked inflammation and demyelination with axonal degeneration. Contralateral nerve biopsy at day 75 showed almost complete loss of axons. This case illustrates another type of axonal degeneration, that which occurs secondary to inflammation and demyelination.

Aged↗
PubMed1993

Clinicopathological features of primary lateral sclerosis are different from amyotrophic lateral sclerosis.

Primary lateral sclerosis (PLS) bears close resemblance to cases of amyotrophic lateral sclerosis (ALS) presenting with spasticity, but histopathological studies have shown significant difference between the two conditions. When the lower motor neurons in cases of ALS and PLS are compared with the equivalent cells of control subjects, morphometric studies indicate significantly decreased size and increased convexity (rounding) of the cell bodies only in ALS. In both disorders there is loss or shrinkage of the largest cortical motor neurons (Betz cells) in the primary motor cortex, though this change is not conspicuous in all cases of ALS. Morphometry reveals in both diseases a general reduction in the sizes of pyramidal cells in the precentral gyrus, indicating that smaller neurons are involved. The cortical motor neurons shrink more in PLS than in ALS. It is concluded that there is clear difference between ALS and PLS. In PLS, quantitative histopathological data show that the neuronal degeneration is confined to long descending pathways, notably the corticospinal system, with no concomitant involvement of lower motor neurons. In ALS, lower motor neuron degeneration occurs in all cases, whereas involvement of the motor cortex is variable.

Aged↗
PubMed1993

Right phrenic nerve injury in orthotopic liver transplantation.

Right hemidiaphragm paralysis has been previously documented in patients after orthotopic liver transplantation (OLT) and it may contribute to the development of postoperative pulmonary problems. It has been postulated that a crush injury to the right phrenic nerve during OLT is the cause of dysfunction of the right hemidiaphragm. To assess the incidence and effect of right phrenic nerve injury after OLT, we prospectively studied 48 adult liver recipients. Twelve patients who underwent liver resection (LR), in whom the suprahepatic vena cava was not clamped, were used as a comparison group. Diaphragm excursion by ultrasound and pulmonary function were performed preoperatively and postoperatively; transcutaneous phrenic nerve conduction studies were performed postoperatively. Right phrenic nerve injury and hemidiaphragm paralysis occurred in 79% and 38% of the liver recipients but not after LR. Conduction along the right phrenic nerve was absent in 53% and reduced in another 26%. Left phrenic nerve conduction and left hemidiaphragm excursion were normal in both liver recipients and the patients who had LR. Liver recipients with no conduction in the right phrenic nerve had a significantly greater decrease in vital capacity in the supine position (29 +/- 9.8%) compared with those with some conduction (14 +/- 6.9%, P < 0.001). However, neither the time on the ventilator nor the hospital stay was significantly different in the latter two groups. Complete recovery of phrenic nerve conduction and diaphragm function took until nine months in some patients. Right phrenic nerve injury is common after OLT and it is the cause of right hemidiaphragm dysfunction.

Adolescent↗
PubMed1993

Effects of ageing on the motor unit: a brief review.

This review briefly summarizes the current state of knowledge regarding age related changes in skeletal muscle, followed by a more in-depth review of ageing effects on animal and human motor units (MUs). Ageing in humans is generally associated with reductions in muscle mass (atrophy), leading to reduced voluntary and electrically evoked contractile strength by the 7th decade for most muscle groups studied. As well, contraction and one-half relaxation times are typically prolonged in muscles of the elderly. Evidence from animal and human studies points toward age associated MU loss as the primary mechanism for muscle atrophy, and such losses may be greatest among the largest and fastest MUs. However, based on studies in animals and humans, it appears that at least some of the surviving MUs are able to partially compensate for MU losses, as indicated by an increase in the average MU size with age. The fact that muscles in the elderly have fewer, but on average larger and slower, MUs has important implications for motor control and function in this population.

Aging↗
PubMed1993

Effects of motor unit losses on strength in older men and women.

The influence of age-associated motor unit loss on contractile strength was investigated in a representative sample of healthy, active young and older men and women. In 24 younger subjects (22-38 yr) and 20 older subjects (60-81 yr) spike-triggered averaging was employed to extract a sample of surface-recorded single motor unit action potentials (S-MUAPs) from the biceps brachii and brachialis muscles. The amplitude of the maximum compound muscle action potential of the biceps brachii and brachialis muscles was divided by the mean S-MUAP amplitude to estimate the numbers of motor units present. The maximum isometric twitch contraction (MTC) and maximum voluntary contraction (MVC) of the elbow flexors were also recorded in 18 of the younger subjects and in all older subjects. The estimated numbers of motor units were significantly reduced (47%, P < 0.001) in older subjects with a mean value of 189 +/- 77 compared with a mean of 357 +/- 97 in younger subjects. The sizes of the S-MUAPs, however, were significantly larger in older subjects (23%, P < 0.01). Significant but less marked age-associated reductions in the MTC (33%, P < 0.05) and MVC (33%, P < 0.001) were also found and were similar for both men and women. These results suggest that motor unit losses, even in healthy active individuals, are a primary factor in the age-associated reductions in contractile strength.

Action Potentials↗
PubMed1993

Cane molasses and cottonseed meal supplementation of ammoniated tropical grass hay for yearling cattle.

Laboratory, digestion, and growth studies were used to evaluate liquid cane molasses (MOL) and(or) cottonseed meal (CSM) supplementation of ammoniated (4% of the forage DM) stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) hay. Ammoniation increased (P < .01) total N concentration (1.0 to 1.4% vs 1.7 to 2.8%) and in vitro digestion of OM, NDF, and ADF and decreased (P < .01) NDF concentration of stargrass hay. Two digestion (4 x 4 Latin square, 250-kg steers) and two growth (230-kg Brahman crossbred steers, seven to eight steers per pasture, three to four pastures per treatment, October through February) trials evaluated MOL and(or) CSM supplementation of ammoniated hay. Supplementation with CSM alone did not influence (P > .05) apparent digestibilities of OM or NDF, whereas supplementation with MOL either alone or with CSM increased (P < .05) apparent OM digestibility, but decreased (P < .05) apparent NDF digestibility. In the growth trials, hay intake was not affected (P > .05) by supplementation with CSM alone and was decreased (P < .05) by supplementation with MOL either alone or with CSM; however, total feed intake was increased (P < .05) by MOL supplementation. Cattle fed only ammoniated hay gained approximately .20 kg/d. In both trials, daily gain and gain/feed were improved (P < .05) by CSM (.39 to .47 kg; .062 to .071) or MOL (.34 to .35 kg; .047 to .048) supplementation. Improvements (P < .05) in daily gain (.54 to .76 kg) and gain/feed (.077 to .083) by supplementation with MOL plus CSM were additive to responses from supplementation with MOL or CSM individually.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗
PubMed1992

Influence of peripheral afferents on cortical and spinal motoneuron excitability.

The objective of this study was to establish to what extent muscle, cutaneous, and joint afferents alter the excitability of spinal and cortical motor neurons. This question was examined by studying the impact of electrical stimulation of the second and third digits, the median nerve at the wrist, and the recurrent thenar motor branch on the F/H and magneto-electrical cortical motor responses (MEPs) of the thenar muscles. The firing frequencies of single F/H motor unit action potentials were unaltered by the foregoing conditioning peripheral stimuli. MEPs conditioned by motor threshold stimulation of the median nerve at the wrist or the recurrent motor branch were significantly increased in size at conditioning to test intervals of 50 to 80 milliseconds. No significant change in MEP size resulted from conditioning stimulation of the digital nerves. We conclude that muscle afferents were primarily responsible for the increase in MEP size. Conditioning stimuli may allow examiners to assess central motor conduction where it would otherwise be impossible.

Action Potentials↗
PubMed1992

Motor-evoked responses in primary lateral sclerosis.

Primary lateral sclerosis (PLS) may be distinguished on the basis of clinical and pathological features from amyotrophic lateral sclerosis (ALS). The former is featured by a much longer clinical course, exclusively upper motor neuron findings, losses of precentral pyramidal neurons, and preservation of anterior horn cells. Electrophysiological studies of 7 PLS cases have shown normal peripheral motor conduction, absent or very delayed motor-evoked potentials, the occasional late development of denervation activity in distal muscles, and normal somatosensory-evoked potentials.

Aged↗
PubMed1992

Early postoperative ulnar neuropathies following coronary artery bypass surgery.

Ulnar neuropathies following surgery are common. However, they often go undetected during the early postoperative period, because the patient may be unaware of symptoms related to the neuropathy. Nerve conduction studies are useful in localizing the lesion, but are usually employed only in cases developing signs and symptoms. We undertook this study to determine the incidence, time of onset, and outcome of clinical and subclinical ulnar neuropathies. Electrophysiological studies were carried out preoperatively, immediately following surgery, and 4 to 6 weeks postoperatively in 20 coronary artery bypass patients. Conduction velocity across the elbow was reduced in 3 limbs (8%) postoperatively, all of which were detected immediately following surgery. One patient developed conduction block and weakness in ulnar supplied intrinsic hand muscles. Denervation was seen in 2 cases and, in 1 case (5%), a right brachial plexus injury was clinically evident 5 days following surgery. All newly developing ulnar neuropathies were asymptomatic, with most recovering to their preoperative electrophysiological status at follow-up.

Brachial Plexus↗
PubMed1992

Quantitation of axon loss and conduction block in acute radial nerve palsies.

Eleven acute radial nerve palsies were examined between 3 days and 14 weeks following the onset of the neuropathy. Our objective was to quantify the relative extent of axon loss and conduction block in radial motor fibers supplying the extensor and abductor pollicis longus (EPL/APL) muscles. In 10 of 11 cases, conduction block exceeded axon loss. Maximum motor and sensory conduction velocities were normal distal to the spiral groove, suggesting that the larger myelinated fibers were not selectively involved in this acute neuropathy. The localization of the conduction block and slowing was, in every case, across the spiral groove. This method provides a relatively simple way of assessing the approximate contributions of axon loss and conduction block, and fits well with the early and usually complete clinical recovery in these cases.

Adult↗
PubMed1992

Primary lateral sclerosis. Clinical features, neuropathology and diagnostic criteria.

Eight patients with a homogeneous syndrome of progressive symmetric spinobulbar spasticity were studied. Clinical features were limited to those associated with dysfunction of the descending motor tracts and included spastic quadriparesis, pseudobulbar affect, spastic dysarthria, hyper-reflexia and bilateral Babinski signs. Lower motor neuron findings were absent and higher cognitive function preserved. Median age of onset was 50.5 yrs and median disease duration was 19 yrs. Neuropathologic features (including morphometric analysis) in the single autopsied case confirmed the selective involvement of the motor cortex. There was complete absence of Betz cells from layer 5 of the precentral cortex and the remaining pyramidal cells were significantly smaller than those seen in normal controls. Magnetic resonance imaging (MRI) revealed atrophy of the precentral gyrus and positron emission tomography (PET) scans showed diminished glucose [18F]fluorodeoxyglucose uptake in the pericentral cortex. Magnetic motor cortex stimulation revealed markedly prolonged central motor conduction times. The literature is reviewed and diagnostic criteria for primary lateral sclerosis based on clinical, laboratory and imaging features are proposed.

Aged↗
PubMed1992

Detection of hereditary motor sensory neuropathy type I in childhood.

Clinical signs and slowed motor nerve conduction velocities were found in 17 of 36 children under 10 years of age who had one parent with hereditary motor sensory neuropathy type I (HMSN I). Four children had slowed conduction velocities at one year or less. Clinical signs were subtle and included pes planus, distal foot wasting, weakness of ankle eversion and dorsiflexion and areflexia. HMSN I can be detected reliably in children, even before one year of age.

Child↗
PubMed1991

Paramyotonia congenita and hyperkalemic periodic paralysis are linked to the adult muscle sodium channel gene.

The hyperkalemic periodic paralyses are a clinically heterogeneous group of autosomal dominant syndromes characterized by episodic paralysis associated with an elevated serum potassium level. Affected individuals in the same family tend to have homogeneous symptom complexes, although phenotypic variation is present among different families. For example, myotonia is absent in some pedigrees, present in others, and, in a third variant, paramyotonia congenita, myotonia coexists with cold-induced paralysis. Electrophysiological studies have demonstrated variant-specific abnormalities in skeletal muscle membrane sodium conductance. We tested the hypothesis that hyperkalemic periodic paralysis (without myotonia) and paramyotonia congenita are tightly linked to the tetrodotoxin-sensitive adult skeletal muscle sodium channel gene on chromosome 17q23-25 in two large pedigrees. The DNA polymorphisms detected in the growth hormone skeletal muscle sodium channel complex (GH1-SCN4A) and by flanking polymorphic markers (D17S74 and D17S40) demonstrated no recombinants between the disease phenotypes and this complex. Phenotypic variation in the hereditary hyperkalemic periodic paralyses may result from allelic heterogeneity at the tetrodotoxin-sensitive adult skeletal muscle sodium channel locus.

Adult↗
PubMed1991

Quantitation of axon loss and conduction block in peroneal nerve palsies.

We compared conduction in motor fibers supplying the extensor digitorum brevis (EDB) and anterior lateral compartment (AL) muscles. The object was to determine whether there were any differences in the relative proportions of degenerated and blocked nerve fibers between the longer EDB and shorter AL fibers. In almost every case the percentage of motor fibers undergoing axonal degeneration was greatest in EDB fibers. Conversely, the percentage of conduction block was greatest in the AL motor fibers. As clinical recovery is dependent on AL muscles rather than EDB, electrophysiological study of the relative proportions of degenerated and blocked fibers in the former should provide a more reliable measure of outcome than similar studies of EDB. Conduction velocity distal to the fibular head was not slowed despite the large loss of EDB motor fibers. Evidence for selective involvement of the larger myelinated fibers is, therefore, lacking. The location of the major conduction abnormalities was in almost every case between the mid-fibular head and popliteal fossa.

Adult↗
PubMed1991

Patterns and severity of conduction abnormalities in Guillain-Barré syndrome.

Whether the conduction abnormalities and lesions underlying them are randomly distributed throughout the peripheral nervous system (PNS) or certain regions are selectively more vulnerable to attack is an unresolved question in Guillain-Barré syndrome (GBS). To examine this question, 15 cases of GBS were comprehensively examined using electrophysiological techniques which allowed close examination, quantitation and comparison of conduction abnormalities in motor and sensory fibres of the upper limb between the spinal cord and the distal extremities of the nerve fibres. Comparison of these studies with results expected in a model where the chances of conduction failure were uniformly distributed led to the conclusion that conduction slowing and block were not uniformly distributed in most cases. Conduction block was maximal in the terminal segment distal to the wrist and to a lesser extent both conduction block and conduction slowing were disproportionately greater across the elbow and in the axillary to spinal root segments in over one half of the cases. These findings support the hypothesis that certain regions, perhaps because of relative deficiencies of the blood-nerve barrier, may be more vulnerable in GBS than other regions.

Electric Stimulation↗
PubMed1991

Effects of energy and protein supplementation of ammoniated tropical grass hay on the growth and carcass characteristics of cull cows.

Laboratory, digestion and growth studies were used to evaluate energy and protein supplements for ammoniated (4% of the forage DM) stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) hay. Ammoniation increased (P less than .05) total N concentration (.7 to .9% vs 1.7 to 2.0%) and in vitro digestion of OM, NDF and ADF and reduced (P less than .05) NDF concentration of stargrass hay. Two digestion (3 x 3 Latin square, 250-kg steers) and two growth (400-kg Brahman crossbred cull cows, eight head per pasture, two pastures per treatment, November through February) trials evaluated citrus pulp or liquid cane molasses (Trial 1) and molasses or molasses plus cottonseed meal (Trial 2) supplementation of ammoniated hay. Supplementation with byproduct energy sources, citrus pulp or molasses (either alone or with cottonseed meal), improved (P less than .05) OM digestibility but reduced (P less than .05) NDF and ADF digestibilities. Apparent nutrient digestibilities were similar (P greater than .05) between diets supplemented with citrus pulp and molasses and between diets supplemented with molasses and molasses plus cottonseed meal. In Trial 1, ADG by cull cows was greater (P less than .05) for citrus pulp- (.71 kg) or molasses-(.68 kg) supplemented diets than for hay fed alone (.49 kg). In Trial ADG was greater (P less than .05) for cull cows fed ammoniated hay supplemented with molasses plus cottonseed meal (.85 kg) than for those supplemented with molasses only (.69 kg). Feeding cows over the winter increased their (P less than .05) carcass weight, marbling score, USDA quality grade and lipid percentage of the 9-10-11 rib section compared with cows slaughtered at the beginning of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗