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Biomedical subjects

S W Peterson

Publications and source records attributed to S W Peterson.

At least 19 recordsLinked to original sources
PubMed2001

Immunohistochemical detection of myogenic cells in muscles of fetal and neonatal lambs.

Previous studies have implied that myonuclei accumulation in a muscle is more important than myofibre number in the determination of muscle size in fetal/neonatal lambs. However, due to the lack of a reliable marker, the role of myogenic precursor nuclei (satellite cells) in myofibre hypertrophy in late fetal and postnatal life is not well understood. In this study, MyoD was shown to be a useful marker for actively proliferating satellite cells in both fetal and neonatal lambs. MyoD was used to determine whether there were differences in the number of actively proliferating satellite cells between single and twin fetuses/neonates, which may explain at least some of the difference in myofibre size observed near birth. Eighteen single-bearing and 9 twin-bearing Coopworth ewes were randomly assigned to one of three slaughter groups (100, 120 and 140 days of gestation). The remaining ewes were kept on pasture until 20 days postpartum at which time 4 single and 4 twin lambs were sacrificed. Twin fetuses/neonates had lower body weights and muscle weights compared to singles. Lower muscle weights in the twins were associated with smaller myofibre cross-sectional areas and lower total nuclei numbers and myogenic precursor cell numbers per muscle in selected hind-limb muscles. These results indicate that myofibre hypertrophy in late gestation and early postnatal life is related to myogenic precursor cell number which may have important implications for growth potential of the growth-restricted fetus.

Animals↗
PubMed2000

Muscle growth, cell number, type and morphometry in single and twin fetal lambs during mid to late gestation.

Muscle growth, myofibre number, type and morphometry were studied in large hindlimb muscles of single and twin fetal lambs during mid to late gestation. Placental insufficiency, evident by lower total placentome weight and number per fetus, resulted in reduced fetal weights from 100 to 140 days gestation in twins compared with singletons (at 140 days: 5016 +/- 108 g v. 5750 +/- 246 g, respectively; P<0.05). However, competition between littermates did not consistently reduce muscle mass (15-22%) until 140 days gestation. Apparent myofibre number increased with age, indicating that the full complement of myofibres in some large hindlimb muscles may be achieved during early postnatal life. Litter size did not impact on apparent myofibre number in the semitendinosus, plantaris or gastrocnemius muscles. However, a transient effect on myofibre number in the adductor femoris muscle was observed from 80-120 days gestation. The phenotypic maturation of myofibres was unaffected by increasing litter size. Smaller muscle mass in twins was associated with smaller myofibre cross-sectional area in the semitendinosus, adductor femoris and gastrocnemius muscles at 140 days gestation. A similar trend was observed for the plantaris muscle. These results indicate that while competition between littermates for nutrients in late gestation can impact on both fetal and muscle mass, the fetus has the capacity to buffer against the effects of restricted nutrient supply on myofibre hyperplasia and phenotypic maturation, but myofibre hypertrophy is compromised.

Animals↗
PubMed2000

Morphometric analysis of myofibre development in the adductor femoris muscle of single and twin fetal lambs.

Cellular development of the adductor femoris muscle from twin and single fetuses was studied at 140 days gestation to evaluate the effect of moderate fetal growth retardation on myofibre development. Twin fetuses had lower bodyweights (13%) and disproportionately small adductor femoris muscle weights (22%) compared with single fetuses. Reduced muscle mass was associated with smaller myofibre cross-sectional areas (CSA) and lower DNA content (22%), indicative of fewer myonuclei and retarded myofibre hypertrophy. Myofibre number and the phenotypic maturation of the myofibres were similar between twins and singletons. These results indicate that even modest growth restriction during fetal life can negatively influence myofibre hypertrophy, highlighting the importance of fetal nutrition for muscle growth. Large muscles, such as the adductor femoris, have intrafascicularly terminating myofibres, which necessitates accurate sampling of the muscle when investigating possible perturbations in morphological characteristics (e.g. between singletons and twins). The second objective of the present study was to investigate the impact of the sampling site on the morphological parameters of the adductor femoris muscle. The apparent total myofibre number decreased from the proximal to the distal region of the adductor femoris muscle. The apparent number of slow-twitch fibres also decreased from the proximal to the medial region, but was not different between the medial and distal regions of the muscle. Similarly, myofibre CSA differed between the medial and distal regions. These results indicate that, particularly with large muscles, such as the adductor femoris, which has intrafascicularly terminating myofibres, single site sampling for the determination of morphological fibre characteristics may generate misleading results and that careful selection of the sampling area may be necessary.

Animals↗
PubMed1998

Molecular genetic variation in Emmonsia crescens and Emmonsia parva, etiologic agents of adiaspiromycosis, and their phylogenetic relationship to Blastomyces dermatitidis (Ajellomyces dermatitidis) and other systemic fungal pathogens.

Emmonsia crescens, an agent of adiaspiromycosis, Blastomyces dermatitidis, the agent of blastomycosis, and Histoplasma capsulatum, the agent of histoplasmosis, are known to form meiotic (sexual) stages in the ascomycete genus Ajellomyces (Onygenaceae, Onygenales), but no sexual stage is known for E. parva, the type species of the genus Emmonsia. To evaluate relationships among members of the putative Ajellomyces clade, large-subunit ribosomal and internal transcribed spacer region DNA sequences were determined from PCR-amplified DNA fragments. Sequences were analyzed phylogenetically to evaluate the genetic variation within the genus Emmonsia and evolutionary relationships to other taxa. E. crescens and E. parva are distinct species. E. crescens isolates are placed into two groups that correlate with their continents of origin. Considerable variation occurred among isolates previously classified as E. parva. Most isolates are placed into two closely related groups, but the remaining isolates, including some from human sources, are phylogenetically distinct and represent undescribed species. Strains of B. dermatitidis are a sister species of E. parva. Paracoccidioides brasiliensis and Histoplasma capsulatum are ancestral to most Emmonsia isolates, and P. brasiliensis, which has no known teleomorph, falls within the Ajellomyces clade.

Blastomyces↗
PubMed1998

Menadione induces changes in the membrane electrical properties associated with downregulation of insulin receptors in human erythrocytes.

We have demonstrated using dielectric relaxation measurements in the radiofrequency range that the electrical properties of human erythrocytes (membrane conductivity and permittivity as well as the conductivity of the cytosol) undergo a steady decrease over time during insulin-induced downregulation of insulin receptors (Santini et al., Experimental Hematology 22:40-44, 1994). In the present paper, we show that exposure of these erythrocytes to the strong oxidizing agent menadione before addition of insulin blocks insulin receptor internalization as well as the decrease in electrical parameters associated with this process. We hypothesize that menadione blocks internalization of these receptors by inducing oxidative damage on the erythrocytes and, consequently, disrupting the normally occurring variations in electrical parameters. This postulate was confirmed by addition of the antioxidant N-acetylcysteine to menadione-treated cells, in which a return to the original changes in electrical parameters noted in untreated cells was observed.

Down-Regulation↗
PubMed1997

Maternal constraint influences muscle fibre development in fetal lambs.

The objective was to examine myogenesis in two situations expected to be characterized by maternal constraint: (i) in fetuses due to be born in spring (n=10) or autumn (n=10); and (ii) in single (n=16) and twin (n=20) fetal lambs. Maternal constraint operating through limitation of placental size, as measured by placentome weight per fetus, was evident in each study. Although a lower placental weight did not influence body and muscle weights of fetuses due to be born in the spring or autumn, twins had lower body and muscle weights than singles. Fibre number and average fibre cross-sectional (CS) area were differentially affected by season and fetal number. The differences in muscle fibre morphology between spring- and autumn-born fetuses suggest that muscle fibre development was influenced by maternal constraint in the absence of an effect on fetal weight. The differences in muscle fibre number and CS area in particular muscles from twin and single fetuses suggest that more severe maternal constraint, reflected in a lower placental size per fetus, not only influences fetal weight but can also affect muscle development.

Animals↗
PubMed1997

An anthropomorphic hand exoskeleton to prevent astronaut hand fatigue during extravehicular activities.

This correspondence presents a prototype of a powered hand exoskeleton that is designed to fit over the gloved hand of an astronaut and offset the stiffness of the pressurized space suit. This will keep the productive time spent in extravehicular activity from being constrained by hand fatigue. The exoskeleton has a three-finger design, the third and fourth fingers being combined to lighten and simplify the assembly. The motions of the hand are monitored by an array of pressure sensors mounted between the exoskeleton and the hand. Controller commands are determined by a state-of-the-art programmable microcontroller using pressure sensor input. These commands are applied to a PWM driven dc motor array which provides the motive power to move the exoskeleton fingers. The resultant motion of the exoskeleton allows the astronaut to perform both precision grasping tasks with the thumb and forefinger, as well as a power grasp with the entire hand.

Anthropometry↗
PubMed1995

Phylogenetic relationship within Fusarium sambucinum Fuckel sensu lato, determined from ribosomal RNA sequences.

Partial ribosomal RNA nucleotide sequences were determined for 11 strains of Fusarium sambucinum Fuckel sensu lato to assess by molecular genetic means, Nirenberg's recent morphotaxonomic interpretation which split the species into three distinct taxa: F. sambucinum sensu stricto, F. torulosum, and one other species, as yet unnamed (Fusarium species nova). Four sequence patterns were identified among the 11 strains. Two sequences that varied at one site were found among strains of F. sambucinum, strains of F. torulosum and Fusarium sp. nov. showed no intraspecific variation. Interspecific comparisons revealed nucleotide sequence differences of 3-9 substitutions in the ca. 240 nucleotide rRNA segment examined. Although interspecific differences are not large in terms of percent nucleotide substitution, they are much larger than the observed intraspecific variation and support the morphological interpretation distinguishing three taxa. When the data were analysed using parsimony and bootstrapping, the three taxon tree was well supported. The phylogenetic arrangement of these strains is congruent with secondary metabolite profile similarities.

Base Sequence↗
PubMed1995

Highly mobile space suit material optimization.

This paper discusses the factors that control the flexibility of fabric space suit elements by examining a bending model of a pressurized fabric tube. Results from the model are used to evaluate the current direction in highly mobile EVA glove research and suggest that changes are necessary in the suit and glove fabric selection methodology.

Computer Simulation↗
PubMed1994

Osteomyelitis caused by Neosartorya pseudofischeri.

The first case of osteomyelitis caused by Neosartorya pseudofischeri is reported. The patient, a 77-year-old male with a history of silicosis and tuberculosis, on X-ray examination revealed lytic lesions of L2 and L3 vertebrae suspicious for metastatic lesions. Histologic examination of biopsy specimens from vertebral bodies showed short, distorted, extra- and intracellular, hyaline hyphal fragments. The culture from the biopsy tissue produced numerous, evanescent asci containing eight ellipsoidal ascospores with two distinctive equatorial bands ca. 1 micron wide. When examined by a scanning electron microscope, ascospores exhibited a convex surface ornamented with raised flaps of tissue, in shape resembling triangular projections or long ridge lines. The conidial state (anamorph) was identified as Aspergillus thermomutatus on the basis of conidial columns which were smaller and less tightly packed as well as of a lighter shade of green than those observed in Aspergillus fumigatus. On the basis of the morphologic features of the ascospores, the teleomorph was identified as N. pseudofischeri.

Aged↗
PubMed1994

Membrane electrical properties associated with insulin receptor downregulation in human erythrocytes.

This study investigated the alterations in the electrical properties of human erythrocytes that occur during the insulin-induced internalization of insulin receptors (downregulation). Using a dielectric relaxation technique based on the Maxwell-Wagner effect, the data indicate a steady decrease over time in membrane conductivity, membrane permittivity, and conductivity of the cytosol in erythrocytes that have been stimulated to undergo downregulation by the addition of insulin. We hypothesize that variations in active transport properties as well as changes in membrane lipids and/or proteins occur during the process of insulin-induced downregulation of insulin receptors.

Cell Membrane↗
PubMed1994

Cytoskeletal oxidative changes lead to alterations of specific cell surface receptors.

Electron acceptors in biological systems, termed "oxidants", have been associated with numerous cytopathic conditions. In particular, oxygen-derived free radicals have been shown to induce various subcellular oxidative injuries which can lead to different types of pathologies. It has also been suggested that oxidative stress induced by xenobiotics can determine specific subcellular alterations in in vitro models. An oxidative imbalance in cells seems in fact to affect intracellular functions including the expression of some growth factor surface receptors. In this work, we observed a specific early alteration of the microfilament system and the microtubular network induced in K562 cells by oxidative stress. In particular, we hypothesize that oxidative imbalance could lead to an impairment of the expression of these receptors, such as transferrin receptors, via a modification of the cytoskeleton. This could represent a general mechanism by which a modification of receptor regulation can lead to cell aging, injury or death.

Cell Membrane↗
PubMed1993

Human erythrocyte insulin receptor processing is affected by the oxidizing agent menadione.

Insulin-induced down-regulation of erythrocyte insulin receptors is a simplified model that can provide useful information on the cell surface regulative phenomena and on role of the plasma membrane and cytoskeleton in such physiological processes. Oxidative imbalance was examined since it was shown to play an important role in numerous cellular pathologies as well as in cell aging. Specifically, the free radical inducer menadione was used in order to evaluate if this compound is able to modify (and in which manner) the down-regulation process. Biochemical, biophysical, and ultrastructural approaches were used. The results obtained seem to indicate that menadione-induced oxidative damage was able to decrease the insulin-induced down-regulation process, as measured by binding assays. This effect was accompanied by slight alterations in plasma membrane ultrastructure and insignificant variations in plasma membrane lipid composition. In addition, the decrease in membrane order, measured by electron paramagnetic resonance, which was shown to usually occur during the process of down-regulation, was not observed. In contrast, cytoskeletal protein assembly, as previously shown in other in vitro systems, appeared to be remarkably altered. Such changes in specific cytoskeletal elements could lead to the decrease of down-regulation phenomenon induced by menadione. Changes in electrophoretic pattern of some cytoskeletal proteins (e.g., spectrin) reinforce this hypothesis. Considering the importance of free radicals in cell injury, data reported here could represent a specific example of a general mechanism by which cell surface receptor expression and recycling can be modified by changes in some intracellular molecule redox status and cell ionic homeostasis.

Actin Cytoskeleton↗
PubMed1992

Changes in erythrocyte membrane lipid composition affect the transient decrease in membrane order which accompanies insulin receptor down-regulation.

We have recently demonstrated, using electron paramagnetic resonance (EPR) spectroscopy, that insulin receptor internalization in response to insulin incubation (down-regulation) in human erythrocytes is accompanied by a transient decrease in membrane order, as measured by the 2T' parallel order parameter. Since membrane lipids play such an important role in receptor internalization, we investigated the possible effects that an alteration of the normally-occurring lipid profile might have on down-regulation and the concomitant transient decrease in membrane order. Consequently, human erythrocytes enriched with cholesterol and erythrocytes from cirrhotic patients were examined, because both of these groups of cells have a higher cholesterol/phospholipid molar ratio (CH/PL) than controls. The 5-nitroxystearate spin label, which inserts into the lipid bilayer of cell membranes, was used to monitor changes in 2T' parallel for a 3-h period at 37 degrees C. We report here that both cholesterol-enriched and cirrhotic erythrocytes do not down-regulate, as demonstrated by binding assays, and that they do not show the typical transient decrease in membrane order observed in controls. The results seem to indicate that a more ordered membrane inhibits internalization of the insulin receptor in erythrocytes, and that an increase in membrane disorder is necessary for insulin receptor down-regulation.

Cholesterol↗
PubMed1992

Effect of intravenous polyunsaturated phosphatidylcholine infusion on insulin receptor processing and lipid composition of erythrocytes in patients with liver cirrhosis.

The aim of this study was to determine whether insulin receptor processing capabilities of human erythrocytes could be improved by changing the cell membrane lipid composition using an intravenous infusion of polyunsaturated phosphatidylcholine. Thirteen cirrhotics were submitted to the i.v. infusion of phosphatidylcholine (2 g day-1 for 3 days). Both erythrocyte lipid composition and insulin receptor processing ability were examined at the beginning of the study and at 0, 3 and 11 days after the end of the treatment. This treatment decreased the erythrocyte cholesterol to phospholipid molar ratio and increased the proportion of polyunsaturated fatty acids (mainly linoleic acid) immediately after the end of the treatment. The proportion of arachidonic acid increased immediately in the phosphatidylserine class and, a few days later, also in phosphatidylethanolamine. The phospholipid class distribution did not show any relevant modification in the course of the study. Surface insulin receptors, which generally were up-regulated in the untreated subject (-7.1 +/- 20.4%), showed an improvement in down regulation capabilities that appeared to be well correlated with the changes in lipid composition of cell membranes induced by i.v. infusion of polyunsaturated phosphatidylcholine. The confirmation of these findings also in target cells for insulin may open new perspectives in the treatment of diabetes mellitus.

Adult↗
PubMed1992

Altered insulin receptor processing and membrane lipid composition in erythrocytes of cirrhotic patients.

Insulin binding and insulin receptor down-regulation characteristics were evaluated, as well as cholesterol and phospholipid levels in erythrocytes from 22 patients with liver cirrhosis. These parameters were correlated with clinical characteristics and with scores related to severity of the liver injury. Nine healthy subjects were studied as a control group. It was observed that insulin binding was generally greater in patients than in controls because of an increase in surface insulin receptor numbers, rather than from a change in receptor affinities. In cirrhotic patients, the erythrocyte insulin receptors did not undergo the normal down-regulation process but, in most cases, increased in response to insulin incubation. The alterations in insulin processing characteristics were more frequent in patients with alcoholic cirrhosis and more severe liver impairment and correlated with the changes in the lipid composition of erythrocyte membranes. In particular, an increase in the cholesterol to phospholipid molar ratio and a decrease in polyunsaturated fatty acid content of phospholipids in erythrocyte membranes of cirrhotic patients was associated with impairments in insulin receptor processing. Similar changes in insulin receptor processing were observed when the molar ratio of cholesterol to phospholipid in normal erythrocytes was modified in vitro by incubation with cholesterol-rich liposomes.

Adult↗