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At least 73 records · Page 4Linked to original sources
PubMed1990

Mormyromast electroreceptor organs and their afferent fibers in mormyrid fish. III. Physiological differences between two morphological types of fibers.

1. Mormyromast electroreceptor organs in electric fish of the family Mormyridae have two types of separately innervated sensory cells, the A and B sensory cells of Szabo and Wersall. The first paper in this series showed anatomically that afferent fibers from the two types of sensory cell terminate centrally in separate zones of the electrosensory lateral line lobe (ELL), fibers from A cells terminating in the medial zone and fibers from B cells terminating in the dorsolateral zone. The goal of the present study was to determine the physiological differences between the two morphologically distinct types of mormyromast afferent fibers. 2. The present study has two parts. In the first part, mormyromast fibers were recorded near their central terminals in the two mormyromast zones of ELL. In the second part, mormyromast fibers were recorded from a peripheral electrosensory nerve. In both parts, various electrosensory stimuli were delivered and voltage thresholds were measured at the electroreceptor. 3. In the first part of the study, mormyromast fibers terminating in the two central zones were found to be different in their thresholds and in the maximum number of spikes evoked by a single stimulus. Afferent fibers terminating in the medial zone, which arise from A sensory cells, had higher thresholds and smaller maximum spike numbers than fibers terminating in the dorsolateral zone, which arise from B sensory cells. 4. In the second part of the study, the same two groups of fibers--one group with a high threshold and a small maximum spike number, and a second group with a low threshold and a large maximum spike number--were identified in extracellular recordings from a peripheral electrosensory nerve. The thresholds of the two groups were quite distinct, allowing the fibers to be divided into high- and low-threshold groups, which most likely represent the fibers from the A and B sensory cells, respectively. 5. The high- and low-threshold groups of fibers recorded from peripheral nerve were found to be different in a number of additional properties besides threshold and maximum spike number. Additional differences were found in the following properties: strength-duration curve, correlation with a receptor potential recorded at the electroreceptor, tuning curve, and short latency facilitation by a conditioning stimulus. Thus there appear to be several physiological differences between mormyromast afferent fibers from A and B sensory cells, in addition to the differences in threshold and spike number.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

[Inhaled nonasbestos fibers; pulmonary concentrations and fiber size in autopsied urban residents].

Nonasbestos fiber concentrations and fiber size distribution in autopsied lung tissues of 53 urban residents (34 males and 19 females) were analyzed by low temperature ashing-analytical transmission electron microscopy. The following findings were obtained. 1. Pulmonary nonasbestos fibers were found in all samples. Fiber consisting mainly of aluminum and silicon represented 80.0% of the total nonasbestos fibers observed. 2. The geometric mean concentration of nonasbestos fiber was significantly higher in males (47.6 x 10(6) fibers/g dry lung) than in females (18.2 x 10(6) fibers/g dry lung) (p < 0.05). This may be caused by differences in occupational exposure to nonasbestos fibers between males and females. 3. In females, the geometric mean concentration of nonasbestos fibers of smokers (34.6 x 10(6) fibers/g dry lung) was higher than that of nonsmokers (11.4 x 10(6) fibers/g dry lung), while, in males, the geometric mean concentration of nonasbestos fibers was lower in smokers (53.9 x 10(6) fibers/g dry lung) than in nonsmokers (89.1 x 10(6) fibers/g dry lung). These differences were not statistically significant. 4. The mean value for the ratio of nonasbestos fiber to asbestos concentration which ranged from 2.3 to 268 in males, and from 1.3 to 52.0 in females, was 30.1 and 20.2 respectively. 5. The mean length, diameter and aspect ratio for nonasbestos fibers were 1.01 microns, 0.103 microns and 11.3, respectively. Although nonasbestos fibers were almost equal in length to asbestos, the mean diameter of nonasbestos fibers was almost one-half of that of asbestos. Most of nonasbestos fibers (99.0%) were too small to be visible by light microscopy.

Adult↗
PubMed1994

Single-fiber electromyography in neuromuscular disorders: correlation of muscle histochemistry, single-fiber electromyography, and clinical findings.

We performed single-fiber electromyography (SFEMG) and correlated the results with muscle-biopsy histochemistry in 56 patients with various neuromuscular diseases. Increased muscle-fiber density, delineated by SFEMG, was most prominent in diseases of ordinary denervation, namely motor neuron disorders and peripheral neuropathies, and it correlated with histochemical fiber type grouping. Both phenomena reflect denervation followed by reinnervation. In patients with central core disease and rod disease, fiber density was not increased despite massive type I fiber predominance. The normal distribution of type I fiber subtypes in those patients indicated tht their fiber predominance was not due to sprouting and reinnervation, but probably to paucity of the type II fibers. In type I fiber hypotrophy with central nuclei, fiber density was increased, perhaps attributable to the small diameter and consequent denser packing of the type I fibers. Fiber density was slightly increased in the majority of patients with acid-maltase deficiency, limb-girdle dystrophy, and polymyositis, in nearly half with mitochondrial myopathy, and in 1 older Duchenne dystrophy patient. In these myopathic disorders, myogenous deinnervation (followed by reinnervation) is one possible explanation. Normal fiber density was present in all patients with muscle phosphorylase deficiency, myotonia congenita, and in the hypokalemic periodic paralysis patients under age 40.

Adult↗
PubMed1987

Response dynamics of goldfish saccular fibers: effects of stimulus frequency and intensity on fibers with different tuning, sensitivity, and spontaneous activity.

The effects of stimulus frequency and intensity on response patterns (PST histograms) to tone burst stimulation were examined in differently tuned saccular fibers of the goldfish. In addition, the sensitivity of these fibers to amplitude-modulated (AM) signals of different carrier frequencies was measured. The response patterns evoked by unmodulated signals were a complex function of tuning, spontaneous activity and sensitivity of the fiber, and the frequency and intensity of the signal. Frequency-dependent response patterns were found in low-frequency fibers with best frequencies (BF) below 200 Hz. Responses in these fibers ranged from tonic to phasic in nonspontaneous fibers and included more complex patterns in spontaneously active fibers, such as suppression of evoked activity below spontaneous levels. Midfrequency fibers (BF = 500-600 Hz) showed responses similar to those in low-frequency fibers, but with less dependence on frequency. In contrast, both high-frequency (BF = 800-1000 Hz) and wideband, untuned fibers showed frequency-invariant patterns of adaptation. High-frequency fibers were equally sensitive to AM signals at all frequencies tested. The sensitivity of low-frequency fibers to AM, however, increased as a function of carrier frequency and corresponded to the degree of adaptation in response to unmodulated tones. In general, the AM sensitivity of a fiber could be predicted more by its pattern of response to unmodulated signals than by its tuning characteristics.

Acoustic Stimulation↗
PubMed2005

Greater capillary-fiber interface per fiber mitochondrial volume in skeletal muscles of old rats.

The objective was to examine whether muscle structural capacity for O2 flux (i.e., capillary-to-fiber surface ratio) relative to fiber mitochondrial volume deteriorates with the muscle atrophy of aging in predominantly slow- (soleus, S) and fast-twitch (extensor digitorum longus, EDL) muscles of old (24 mo) and very old (35 mo) F344BN rats compared with adult (12 mo old). Wet muscle mass decreased 29% (196 +/- 4 to 139 +/- 5 mg) in S and 22% (192 +/- 3 to 150 +/- 3 mg) in EDL between 12 and 35 mo of age, without decline in body mass. Capillary density increased 65% (1,387 +/- 54 to 2,291 +/- 238 mm(-2)) in S and 130% (964 +/- 95 to 2,216 +/- 311 mm(-2)) in EDL, because of the muscle fiber atrophy, whereas capillary per fiber number remained unchanged. Altered capillary geometry, i.e., lesser contribution of tortuosity and branching to capillary length, was found in S at 35 compared with 12 and 24 mo, and not in EDL. Accounting for capillary geometry revealed 55% (1,776 +/- 78 to 2,750 +/- 271 mm(-2)) and 113% (1,194 +/- 112 to 2,540 +/- 343 mm(-2)) increases in capillary length-to-fiber volume ratio between 12 and 35 mo of age in S and EDL, respectively. Fiber mitochondrial volume density was unchanged over the same period, causing mitochondrial volume per micrometer fiber length to decrease in proportion to the fiber atrophy in both muscles. As a result of the smaller fiber mitochondrial volume in the face of the unchanged capillary-to-fiber number ratio, capillary-to-fiber surface ratio relative to fiber mitochondrial volume not only did not deteriorate, but in fact increased twofold in both muscles between 12 and 35 mo of age, independent of their different fiber type.

Aging↗
PubMedDate not supplied

Apparent fiber digestibility and fecal short-chain fatty acid concentrations with ingestion of two types of dietary fiber.

Short-chain fatty acids (SCFAs) are products of dietary fiber fermentation. As such, fiber digestibility is thought to be related to SCFA production. The effects of two concentrations of cereal fiber as wheat bran (WB) and vegetable fiber (VF) on fiber digestibility were examined in 34 free-living volunteers. Five diets consisting of a fiber-free liquid nutrition supplement and quick breads containing either (1) 0 g of fiber, (2) 10 g of WB, (3) 30 g of WB, (4) 10 g of VF, or (5) 30 g of VF were consumed in random order. Apparent digestibility of neutral detergent fiber (NDF) was determined. Colonic fluid, collected by in vivo dialysis in 9 subjects, was analyzed for SCFAs by gas chromatography. Digestibility of NDF was greater with WB than with VF ingestion in those 9 subjects, but digestibility was not different with ingestion of both fibers when all 34 subjects were considered. No effect of intake level was seen with either WB or VF. Fiber ingestion increased acetate, propionate, and butyrate concentrations above those on the 0 g of fiber diet (43%, 31%, and 90%, respectively; p < .0001). Propionate and butyrate concentrations were greater on WB than VF (p < .01); acetate concentrations were similar with both fibers. No correlation between NDF digestibility and SCFA concentrations was observed. Despite differences in origin, chemistry, particle size, and subject transit time, the WB and VF were similar in NDF fermentability. Molar ratios of specific SCFAs were influenced by type of fiber ingested.

Adult↗
PubMed1990

Risks associated with source of fiber and fiber components in cancer of the colon and rectum.

In this case-control study, we examined the food sources of fiber and fiber solubility to determine whether particular components of dietary fiber were differentially associated with risk of colon and rectal cancer. In Western New York, cases with pathologically confirmed, single, primary cancers of the colon and rectum as well as age-, sex- and neighborhood-matched controls were interviewed from 1975-1986. The sample included 428 colon case-control pairs (223 females, 205 males) and 422 rectal case-control pairs (145 females, 277 males). Subjects were interviewed regarding usual quantity and frequency of consumption of foods. For the colon, risk decreased with intake of grain fiber for both females and males and with intake of fruit/vegetable fiber for males only. Insoluble grain fiber was more strongly associated with risk than soluble grain fiber. For the rectum, fruit/vegetable fiber was associated with decreased risk, whereas grain fiber was not. There was no difference in risk for soluble and insoluble fiber components for the rectum. Analysis of risk associated with fiber by food source and by components of the fiber may provide insight into possible mechanisms of a fiber effect on cancer of the colon and rectum.

Colonic Neoplasms↗
PubMed2003

Generation of fiber-modified adenovirus vectors containing heterologous peptides in both the HI loop and C terminus of the fiber knob.

BACKGROUND: Fiber-modified adenovirus (Ad) vectors can be effective in overcoming the limitations of conventional Ad vectors, specifically their inefficient gene transfer into cells lacking the primary receptor, the coxsackievirus and adenovirus receptor (CAR). Several types of fiber-modified Ad vectors have been developed. In this study, we evaluated the functionality of several fiber-modified Ad vectors. METHODS: We developed a simple method based on in vitro ligation to construct Ad vectors containing heterologous foreign peptides in both the HI loop and C terminus of the fiber knob. A functional comparison of Ad vectors containing RGD and/or K7 (KKKKKKK) peptide in the HI loop or C terminus of the fiber knob was performed in several types of human, mouse, and rat cells, including CAR-positive and -negative cells, and tumor cells in mice in vivo. RESULTS: In the case of the in vitro experiment, Ad vectors containing RGD peptide in the HI loop of the fiber knob showed a higher level of gene transfer than vectors containing RGD peptide at the C terminus of the fiber knob. Ad vectors containing K7 peptide at the C terminus of the fiber knob showed levels of gene transfer similar to those of Ad vectors containing RGD peptide in the HI loop of the fiber knob, depending on the cell type. Ad vectors containing both peptides in the HI loop or C terminus of the fiber knob showed the highest levels of gene transfer and a broader tropism. For gene transfer into tumor cells in vivo, the Ad vectors containing RGD peptide were the most efficient. CONCLUSIONS: In the experiment using cultured cells, Ad vectors containing both RGD and K7 peptides were the most efficient with a broader tropism. In contrast, in the experiment in vivo, Ad vectors containing RGD peptide in the HI loop of the fiber knob were more efficient than the vectors containing K7 peptide (including double-modified vectors containing both the RGD and K7 peptides). These comparative analyses could provide a systemic reference for the use of fiber-modified Ad vectors. Our simple method, in which the peptide of interest can be expressed in Ad vectors in either the HI loop or the C terminus of the fiber knob, or both, could be a powerful tool for gene transfer into mammalian cells in studies of gene function as well as in gene therapy.

Adenoviridae↗
PubMed1991

Fatigue in type I fiber predominance: a muscle force and surface EMG study on the relative role of type I and type II muscle fibers.

The relative proportions of fiber types within muscle and the characteristics of these fiber types are important determinants of the surface electromyogram (SEMG) during fatigue. In this study, patients suffering from congenital myopathy characterized by a strong type I fiber predominance were studied. Six patients with 95-100% type I fibers, 2 patients with 80% type I fibers, and 12 healthy volunteers participated in an ischemic, isomeric, intermittent exercise test of m. quadriceps femoris at 80% MVC. Considering the results of the morphometric analysis of muscle biopsy specimen and of the anthropometric estimated muscle-bone volume, it was found that type I muscle fibers had a lower force generating capacity than type II fibers. The initial conduction velocity along the muscle fiber membrane (MFCV) was low in patients with 95-100% type I fibers. During the ischemic exercise test, the 95-100% type I fibers showed less fatigability than type II fibers, which was reflected by a nearby absent decrease of the muscle membrane excitability as measured by the MFCV, and only a slight increase of the SEMG amplitude compared with patients having 80% type I fibers and controls. The absence of a definite MFCV decrease was related to the nearby lacking lactate formation in 95-100% type I fibers.

Adolescent↗
PubMed1986

Muscle fiber type transformation in nemaline myopathy and congenital fiber type disproportion.

In a morphometric study on biopsied muscles from 5 patients with nemaline myopathy (NM) and 5 with congenital fiber type disproportion (CFTD), the common findings were relative type 1 fiber smallness, type 1 fiber predominance and occasional hypertrophic type 2 fibers. In NM, the relatively larger type 1 fibers increased in number with age in parallel with a decrease in the number of normal to hypertrophic type 2 fibers, reflecting active fiber type transformation from type 2 to type 1, which resulted in striking type 1 fiber predominance. The presence of scattered non-atrophic type 2C fibers also reflected active fiber type transformation because the fibers during the maturational or degenerating process are known to show the type 2C reaction on ATPase staining. On the other hand, the type 1 fibers in CFTD were small in caliber and showed minimal variation in size, suggesting practically no fiber type transformation from hypertrophic type 2 to type 1.

Child↗
PubMed2003

Pulmonary deposition modeling with airborne fiber exposure data: a study of workers manufacturing refractory ceramic fibers.

Increasing production of refractory ceramic fiber (RCF), a synthetic vitreous material with industrial applications (e.g., kiln insulation), has created interest in potential respiratory effects of exposure to airborne fibers during manufacturing. An ongoing study of RCF manufacturing workers in the United States has indicated an association between cumulative fiber exposure and pleural plaques. Fiber sizing data, obtained from electron microscopy analyses of 118 air samples collected in three independent studies over a 20-year period (1976-1995), were used with a computer deposition model to estimate pulmonary dose of fibers of specified dimensions for 652 former and current RCF production workers. Separate dose correction factors reflecting differences in fiber dimensions in six uniform job title groups were used with data on airborne fiber concentration and employment duration to calculate cumulative dose estimates for each worker. From review of the literature, critical dimensions (diameter <0.4 microm, length <10 microm) were defined for fibers that may translocate to the parietal pleura. Each of three continuous exposure/dose metrics analyzed in separate logistic regression models was significantly related to plaques, even after adjusting for possible past asbestos exposure: cumulative fiber exposure, chi(2) = 15.2 (p < 0.01); cumulative pulmonary dose (all fibers), chi(2) = 14.6 (p < 0.01); cumulative pulmonary dose (critical dimension fibers), chi(2) = 12.4 (p < 0.01). Odds ratios (ORs) were calculated for levels of each metric. Increasing ORs were statistically significant for the two highest dose levels of critical dimension fibers (level three, OR = 11, 95%CI = [1.4, 98]; level four, OR = 25, 95%CI = [3.2, 190]). Similar associations existed for all metrics after adjustment for possible asbestos exposure. It was concluded that development of pleural plaques follows exposure- and dose-response patterns, and that airborne fibers in RCF manufacturing facilities include those with critical dimensions associated with pleural plaque formation. Analysis of additional air samples may improve estimates of the dose-response relationship.

Air Pollutants, Occupational↗
PubMed1994

In vitro cytotoxicity of asbestos and man-made vitreous fibers: roles of fiber length, diameter and composition.

The present study investigated (i) the impact of various fiber parameters on in vitro toxicity to cells and (ii) the validity of an in vitro test system as a toxic screen for fibrous materials. Chinese hamster ovary cells were exposed in vitro to a series of size-selected inorganic test fibers that represented a range of different diameters, lengths and compositions (glass, refractory ceramic, mineral wool, asbestos). Toxic end-points included inhibition of proliferation, induction of micronuclei and polynuclei and viability. For all compositions tested, toxic effects were similar: a concentration-dependent decrease in proliferation and increase in incidence of morphologically abnormal nuclei with minor decreases in viability. Diameter-dependent differences in toxicity were slight or absent for fiber diameters ranging from 0.3-7 microns when concentration was expressed as number of fibers/cm2. Length-dependent differences in toxicity were, however, striking. EC50 values (concentration in fibers/cm2 that reduced cell proliferation to 50% of unexposed control cultures) plotted against fiber length produced a hyperbolic curve, demonstrating that toxicity increases with fiber length up to 20 microns. All fibers tested fell on this hyperbola. These data suggest that: (a) the primary toxic effect of fibers on CHO cells is the induction of nuclear morphologic alterations resulting in cytostasis; (b) fiber diameter has little or no impact on in vitro toxicity when concentration is calculated as fibers/cm2; (c) fiber length is directly proportional to in vitro toxicity; and (d) toxicity of asbestos and vitreous fibers to CHO cells is not affected by composition. The lack of compositional effect in CHO cells does not correlate with findings from recent rodent inhalation studies using the same test fibers. Thus CHO cells may not be an appropriate in vitro model of fiber pathogenesis and would not constitute a valid toxicologic screening system for fibers.

Animals↗
PubMedDate not supplied

Optimization of cardiac fiber orientation for homogeneous fiber strain during ejection.

The strain of muscle fibers in the heart is likely to be distributed uniformly over the cardiac walls during the ejection period of the cardiac cycle. Mathematical models of left ventricular (LV) wall mechanics have shown that the distribution of fiber strain during ejection is sensitive to the orientation of muscle fibers in the wall. In the present study, we tested the hypothesis that fiber orientation in the LV wall is such that fiber strain during ejection is as homogeneous as possible. A finite-element model of LV wall mechanics was set up to compute the distribution of fiber strain at the beginning (BE) and end (EE) of the ejection period of the cardiac cycle, with respect to a middiastolic reference state. The distribution of fiber orientation over the LV wall, quantified by three parameters, was systematically varied to minimize regional differences in fiber shortening during ejection and in the average of fiber strain at BE and EE. A well-defined optimum in the distribution of fiber orientation was found which was not significantly different from anatomical measurements. After optimization, the average of fiber strain at BE and EE was 0.025 +/-0.011 (mean+/-standard deviation) and the difference in fiber strain during ejection was 0.214+/-0.018. The results indicate that the LV structure is designed for maximum homogeneity of fiber strain during ejection.

Animals↗
PubMed2006

Altered fiber distribution and fiber-specific glycolytic and oxidative enzyme activity in skeletal muscle of patients with type 2 diabetes.

OBJECTIVE: We investigated whether alterations of glycolytic and oxidative enzyme capacity in skeletal muscle of patients with type 2 diabetes pertain to specific muscle fibers and are associated with changes in muscle fiber composition. RESEARCH DESIGN AND METHODS: Vastus lateralis muscle was obtained by percutaneous biopsy from 10 patients with type 2 diabetes and 15 age- and BMI-matched healthy volunteers. Using cytophotometry, muscle fiber composition and fiber type-specific glycolytic and oxidative enzyme activities were measured in slow oxidative, fast oxidative glycolytic, and fast glycolytic fibers. RESULTS: In the whole muscle, oxidative activity was decreased in patients with type 2 diabetes. The slow oxidative fiber fraction was reduced by 16%, whereas the fast glycolytic fiber fraction was increased by 49% in skeletal muscle from the diabetic patients. Both oxidative and glycolytic enzyme activities were significantly increased in fast glycolytic and fast oxidative glycolytic fibers of type 2 diabetic patients. However, the fiber-specific ratio of glycolytic enzyme activity relative to oxidative activity was not different between type 2 diabetic patients and the control subjects. The myofibrillic ATP activity was significantly lower in all fiber types of patients with type 2 diabetes and correlates with glucose infusion rate during the steady state of a euglycemic-hyperinsulinemic clamp and maximal aerobic capacity and negatively with HbA(1c) values. CONCLUSIONS: Reduced oxidative enzyme activity in muscle of type 2 diabetic patients is most likely due to a reduction in slow oxidative fibers. Increased glycolytic and oxidative enzyme activities in individual muscle fibers are closely related to measures of long-term glycemic control and whole-body insulin sensitivity and could therefore represent a compensatory mechanism of the muscle in function of the altered glucose metabolism.

Adenosine Triphosphatases↗
PubMed2002

Degeneration of myelinated efferent fibers induces spontaneous activity in uninjured C-fiber afferents.

We demonstrated recently that uninjured C-fiber nociceptors in the L4 spinal nerve develop spontaneous activity after transection of the L5 spinal nerve. We postulated that Wallerian degeneration leads to an alteration in the properties of the neighboring, uninjured afferents from adjacent spinal nerves. To explore the role of degeneration of myelinated versus unmyelinated fibers, we investigated the effects of an L5 ventral rhizotomy in rat. This lesion leads to degeneration predominantly in myelinated fibers. Mechanical paw-withdrawal thresholds were assessed with von Frey hairs, and teased-fiber techniques were used to record from single C-fiber afferents in the L4 spinal nerve. Behavioral and electrophysiological data were collected in a blinded manner. Seven days after surgery, a marked decrease in withdrawal thresholds was observed after the ventral rhizotomy but not after the sham operation. Single fiber recordings revealed low-frequency spontaneous activity in 25% of the C-fiber afferents 8-10 d after the lesion compared with only 11% after sham operation. Paw-withdrawal thresholds were inversely correlated with the incidence of spontaneous activity in high-threshold C-fiber afferents. In normal animals, low-frequency electrocutaneous stimulation at C-fiber, but not A-fiber, strength produced behavioral signs of secondary mechanical hyperalgesia on the paw. These results suggest that degeneration in myelinated efferent fibers is sufficient to induce spontaneous activity in C-fiber afferents and behavioral signs of mechanical hyperalgesia. Ectopic spontaneous activity from injured afferents was not required for the development of the neuropathic pain behavior. These results provide additional evidence for a role of Wallerian degeneration in neuropathic pain.

Action Potentials↗
PubMed1997

Optimization of cardiac fiber orientation for homogeneous fiber strain at beginning of ejection.

Mathematical models of left ventricular (LV) wall mechanics show that fiber stress depends heavily on the choice of muscle fiber orientation in the wall. This finding brought us to the hypothesis that fiber orientation may be such that mechanical load in the wall is homogeneous. Aim of this study was to use the hypothesis to compute a distribution of fiber orientation within the wall. In a finite element model of LV wall mechanics, fiber stresses and strains were calculated at beginning of ejection (BE). Local fiber orientation was quantified by helix (HA) and transverse (TA) fiber angles using a coordinate system with local r-, c-, and l-directions perpendicular to the wall, along the circumference and along the meridian, respectively. The angle between the c-direction and the projection of the fiber direction on the cl-plane (HA) varied linearly with transmural position in the wall. The angle between the c-direction and the projection of the fiber direction on the cr-plane (TA) was zero at the epicardial and endocardial surfaces. Midwall TA increased with distance from the equator. Fiber orientation was optimized so that fiber strains at BE were as homogeneous as possible. By optimization with TA = 0 degree, HA was found to vary from 81.0 degrees at the endocardium to -35.8 degrees at the epicardium. Inclusion of TA in the optimization changed these angles to respectively 90.1 degrees and -48.2 degrees while maximum TA was 15.3 degrees. Then the standard deviation of fiber strain (epsilon f) at BE decreased from +/- 12.5% of mean epsilon f to +/- 9.5%. The root mean square (RMS) difference between computed HA and experimental data reported in literature was 15.0 degrees compared to an RMS difference of 11.6 degrees for a linear regression line through the latter data.

Heart↗
PubMed1994

Excretion and degradation of dietary fiber constituents in ileostomy subjects consuming a low fiber diet with and without brewer's spent grain.

Excretion of total dietary fiber and dietary fiber components was studied in 10 human subjects with ileostomies, consuming in a crossover design a low fiber diet (15 g total dietary fiber/d) or this diet supplemented with 62 g/d of brewer's spent grain. Food and excreta were collected and analyzed on d 2, 3 and 7 of each dietary period. No significant differences in excretion of total dietary fiber or dietary fiber components were found on the three days. Excreta from subjects consuming the low fiber diet contained significantly more total dietary fiber than was ingested (20%, P < 0.01), indicating the importance of endogenous and microbial material, contributing to the total dietary fiber value, in ileostomy effluents. Analysis of specific dietary fiber components showed that this increased excretion was mainly due to fucose, mannose, galactose and uronic acid residues. When the high-fiber diet was consumed, there was a significantly greater excretion of the same non-starch polysaccharide residues as for consumption of the low fiber diet, but with a simultaneous decrease in excretion of arabinose, xylose and glucose residues (12%, P < 0.01), which were the major fiber components in the diet.

Adult↗
PubMed1998

The function of sensory nerve fibers in lumbar radiculopathy. Use of quantitative sensory testing in the exploration of different populations of nerve fibers and dermatomes.

STUDY DESIGN: The function of sensory nerve fibers in patients with lumbar radiculopathy and in control individuals was evaluated using quantitative sensory testing. OBJECTIVES: To investigate the effect of lumbar nerve root compression on different populations of nerve fibers and to explore the function of sensory nerve fibers in neighboring nerve roots not involved in the mechanical compression. BACKGROUND DATA: Results from experimental and clinical studies indicate that chronic compression of lumbar nerve roots affects the large myelinated nerve fibers. The majority of nerve fibers involved in the sensation of pain, however, are small afferent nerve fibers. It is therefore of interest to study the effect of compression on large and small sensory afferent channels. Several authors have elucidated the biochemical interaction between disc tissue and nerve roots. Chemical substances in the epidural space can reach the nerve fibers in nerve roots at the same or neighboring lumbar segments. In this way, fibers not involved in the mechanical compression may be affected. METHODS: The small nerve fibers were studied using tests for thermal thresholds (thermotest), and the large myelinated fibers were studied by vibrametry. Forty-two patients were investigated in the symptomatic and the asymptomatic leg, and the results were compared with those of 21 healthy individuals. RESULTS: The thresholds of cold, warmth, and vibration were significantly increased in the dermatome of the compressed nerve root, indicating that large and small sensory nerve fibers were affected. Further, the thresholds were significantly increased in the neighboring dermatomes in the symptomatic and the asymptomatic leg. CONCLUSION: Large and small sensory afferent nerve fibers are affected in lumbar radiculopathy. The increase in sensation thresholds in the ipsilateral neighboring dermatome and in the dermatomes in the asymptomatic leg indicates that adjacent nerve roots are involved in the pathophysiology of sciatica in patients with lumbar disc herniation.

Adult↗