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Biomedical subjects

J Toop

Publications and source records attributed to J Toop.

17 recordsLinked to original sources
PubMed1994

Extreme population structuring in the threatened ghost bat, Macroderma gigas: evidence from mitochondrial DNA.

The ghost bat, Macroderma gigas, has undergone a major range contraction and is currently restricted around a few, highly disjunct maternity sites. The amount and distribution of mitochondrial DNA (mtDNA) variation within extant populations has been used to assess levels of current and historical maternal gene flow between these populations. An approximately 330 base pair fragment spanning a hypervariable area of the mtDNA control region was amplified and sequenced by using 22 individuals from four current ghost bat populations. The mean sequence diversity of 4.5% between populations was six times higher than that within populations (0.68%), and alleles within populations were monophyletic. Restriction enzyme analysis of amplified products from an additional 100 individuals revealed fixed allelic differences in the distribution of control region genotypes between the four populations. It is suggested that this extreme genetic subdivision is a consequence of long-term female philopatry. For the purposes of management each population should be treated as an independent entity. The depth of the genetic structuring suggests that the isolation of extant populations preceded the historical range contraction.

Alleles↗
PubMed1993

Recommended coordinate systems for thin spherocylindrical lenses.

Because the set of thin spherocylindrical lenses forms a vector space, any such lens can be expressed in terms of its cartesian coordinates with respect to whatever set of basis lenses we may choose. Two types of cartesian coordinate systems have become prominent, those having coordinates associated with the lens power matrix and those having coordinates associated with the Humphrey Vision Analyzer. This paper emphasizes the value of a particular cartesian coordinate system of the latter type, and the cylindrical coordinate system related to it, by showing how it can simplify the trigonometry of adding lenses and how it preserves symmetry in depicting the sets of all spherical lenses, all Jackson crossed-cylinders, and all cylindrical lenses. It also discusses appropriate coordinates for keeping statistics on lenses and shows that an easy extension of the lens vector space to include general optical systems is not possible.

Eyeglasses↗
PubMed1985

Cross-reinnervated motor units in cat muscle. I. Flexor digitorum longus muscle units reinnervated by soleus motoneurons.

The properties of flexor digitorum longus (FDL) muscles and of individual motor units were studied in cats 30-50 wk after self-reinnervation by FDL motoneurons (FDL----FDL) or cross-reinnervation by soleus (SOL) motoneurons (SOL----FDL). Individual motor units were functionally isolated by intracellular recording and stimulation of identified SOL alpha-motoneurons. Glycogen-depletion methods permitted histochemical study of muscle fibers belonging to physiologically characterized muscle units. The observations were compared with data from normal cat FDL muscles and motor units (27). Intentionally self-reinnervated FDL muscles (FDL----FDL; n = 5) were normal in size and wet weight. FDL----FDL motor units could be classified into the same physiological categories found in normal FDL [types: fast contracting, fatigable (FF), fast contracting, fatigue resistant (FR), and slow (S); n = 24], with approximately the same proportions as normal. The histochemical muscle fiber types associated with these categories were also qualitatively normal although there was evidence of marked distortion of the normal histochemical mosaic. These data confirm other studies of self-reinnervation and suggest that self-reinnervation can produce complete interconversion of muscle fiber types. Cross-reinnervation of FDL muscle by SOL motoneurons (SOL----FDL; n = 12) produced muscles that were smaller (about half the normal wet weight) and more red than normal. SOL----FDL muscle contracted more slowly than normal or FDL----FDL muscles and had much higher proportions of histochemical type I muscle fibers. In those SOL----FDL muscles, in which little or no unwanted self-reinnervation could be demonstrated, greater than 95% of the muscle fibers were type I. Forty-one individual motor units in SOL----FDL muscles were isolated by intracellular penetration in functionally identified SOL alpha-motoneurons. Their muscle units were all type S by physiological criteria (absence of "sag" in unfused tetani and marked resistance to fatigue). SOL----FDL muscle units had contraction times and fatigue properties that were essentially identical to those of type S units in the normal FDL. All of the seven units, successfully studied by glycogen depletion, exhibited histochemical type I fibers. SOL motoneurons that innervated FDL muscle units had slightly shorter afterhyperpolarization durations than normal SOL cells, but axonal conduction velocities were normal.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Cross-reinnervated motor units in cat muscle. II. Soleus muscle reinnervated by flexor digitorum longus motoneurons.

The properties of whole soleus (SOL) muscles and of individual motor units were studied in cats 30-50 wk after self-reinnervation by soleus (SOL) motoneurons (SOL----SOL) or cross-reinnervation by flexor digitorum longus (FDL) motoneurons (FDL----SOL). As in the preceding paper (22), intracellular and glycogen-depletion methods were used to examine the physiological and histochemical properties of individual motor units. The results were compared with data from normal SOL motor units (8, 12). Intentionally self-reinnervated SOL muscles (SOL----SOL; n = 6) were normal in size and wet weight, and all of the five SOL----SOL motor units studied had physiological and histochemical characteristics that matched those of normal SOL units. Cross-reinnervation of SOL by FDL alpha-motoneurons (FDL----SOL; n = 7) produced muscles with wet weights and appearance essentially identical to normal SOL. However, whole-muscle twitch contraction times were much shorter (mean 60.4 ms) than those of normal (mean 136.9 ms, n = 18) or SOL----SOL muscles (mean 115.3 ms; n = 6). Despite this difference, none of the FDL----SOL muscles contained more than 7% histochemical type II muscle fibers, all of which were type IIA. Normal cat SOL muscles can contain up to 5% type IIA fibers, but none of our SOL----SOL muscles showed any type II fibers. Two FDL----SOL muscles had significant amounts of unintended self-reinnervation, permitting side-by-side comparison of FDL----SOL and SOL----SOL muscle fibers. The twitch contraction times of the two populations differed markedly, but they were histochemically indistinguishable except for the fact that SOL----SOL fibers had high neutral fat content (as do normal SOL fibers), whereas FDL----SOL showed much lower fat content. The 23 FDL----SOL muscle units studied were classified as physiological type S by criteria ("sag" test and fatigue resistance) used to identify motor-unit types in normal cat muscles. All five of the FDL----SOL units studied histochemically after glycogen depletion showed the type I histochemical profile, which is characteristic of the normal cat SOL. In marked contrast to the preceding study, cross-reinnervation of cat SOL by FDL motoneurons produced no conversion of muscle-unit properties into those associated with fast-twitch unit types, despite significant decreases in isometric twitch contraction time. The altered twitch speed was not associated with evident changes in conventional myofibrillar adenosine triphosphatase (ATPase) histochemistry.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

The effect of spinal cord transection on motor units in cat medial gastrocnemius muscles.

We studied the properties of whole medial gastrocnemius (MG) and soleus muscles, and of 74 individual MG motor units in three cats with long-term complete low thoracic spinal transection (TS). All animals remained paraplegic and there was considerable atrophy of MG and soleus muscles. Motor units in the MG pool were readily classified into the same groups, types FF, F(int), FR, and S, found in normal MG, but tetanic force outputs and mean fiber areas for the corresponding muscle fiber types were decreased in all unit types as were isometric twitch contraction times. The proportion of type F(int) motor units was greater (19.0%) than expected from normal samples (5.8%) and this was also true of the corresponding type 2AB muscle fibers (6.9% in TS vs 3.3% in controls). In addition, FR and S units were less numerous (17.5% each) than in control muscles (23.0% and 25.2%, respectively), and histochemical examination revealed a similar decrease in the percentage of type 2A (11.6%) and 1 (16.4%) fibers compared with controls (20.0% and 30.5%, respectively). The changes found in chronic paraplegic atrophy were different in some details from those found after chronic simple limb immobilization.

Animals↗
PubMed1983

Androgens enhance in vivo 2-deoxyglucose uptake by rat striated muscle.

Testosterone propionate causes a striking increase in in vivo uptake of 2-deoxyglucose by the levator ani muscle of immature male rats. Autoradiography showed the labeled 2-deoxyglucose to be uniformly distributed over the entire muscle. Liquid scintillation counting of whole muscles allowed quantification of 2-deoxyglucose uptake. After a single sc injection of testosterone propionate, no enhancement of 2-deoxyglucose uptake could be seen before 3.5 h, at which time uptake was increased 2-fold; maximum enhancement (4-fold) was attained at 12 h. 2-Deoxyglucose uptake remained elevated at twice the control value at 72 h. Muscle weight did not increase until sometime after 24 h; by 39 h, it was 50% greater than the control value; by 72 h, wet weight was double the control value. The effect of testosterone propionate probably is mediated by specific androgen receptors, since the administration of either 5 alpha-dihydrotestosterone or fluoxymesterone, potent androgens, caused severalfold increases in 2-deoxyglucose uptake in the levator ani muscle, while administration of 17 beta-estradiol, corticosterone, and etiocholanolone, an inactive metabolite of testosterone, did not. Furthermore, the effect of testosterone propionate was blocked by simultaneous administration of an androgen antagonist, cyproterone acetate. Testosterone propionate also enhanced uptake of 2-deoxyglucose in the bulbocavernosus (253% over control) and extensor digitorum longus muscles (150% over control), but not in the biceps brachii or soleus. Increased glucose uptake may be an important early step in the anabolic response of muscle to androgens.

Androgens↗
PubMed1982

2-deoxyglucose autoradiography of single motor units: labeling of individual acutely active muscle fibers.

2-Deoxy-D-[l-14C]glucose (2DG) was given intravenously during repetitive stimulation of single motor units in adult cats and autoradiographs were made of frozen sections of the target muscles in order to evaluate methods designed to improve the spatial resolution of [14C]2DG autoradiography. With the modifications used, acutely active muscle fibers, independently identified by depletion of intrafiber glycogen, were associated with highly localized accumulations of silver grains over the depleted fibers. The results indicate that [14C]2DG autoradiography can successfully identify individual active muscle fibers and might in principle be used to obtain quantitative data about rates of glucose metabolism in single muscle fibers of defined histochemical type. The modifications may be applicable also to other tissues to give improved spatial resolution with [14C]-labeled metabolic markers.

Animals↗
PubMed1978

Scleromyxedema myopathy. Histochemical and electron microscopic observations.

A biopsy-proven case of scleromyxedema (papular mucinosis) with IgG lambda light chain paraproteinemia, eosinophilia and severe proximal myopathy is presented. Muscle biopsy revealed an atypical necrotizing vacuolar myopathy. Histochemical studies of cryostat sections revealed fiber necrosis, severe type II fiber atrophy, and fiber vacuolization with NADH tetrazolium reductase hyperactivity. Electron microscopy showed myocytolysis, reduplication of the basement membrane, and unit membrane-lined vacuoles negative for acid mucopolysaccharide.

Biopsy↗
PubMed1976

A rapid method for demonstrating skeletal muscle motor innervation in frozen sections.

Longitudinal 50-100 mum-thick frozen sections of muscle are picked up on slides coated with 3% EDTA and after drying are incubated to demonstrate acetylcholinesterase. Subsequent incubation in 0.5% K3Fe(CN)6 is followed by fixation for 30 minutes in formol-calcium or formol-saline. After washing, the slides are incubated in 20% aqueous AgNO3 containing 0.1% CuSO4 for 2-30 minutes at 37 C. Following development in a 1% solution of quinol (w/v) 5% with respect to NaSO3 (w/v), axons and subneural apparatus stain dark brown to black in contrast to the less well stained muscle fibers and nuclei. This procedure permits study of the pattern of neuromuscular innervation in skeletal muscle 3 1/2-4 hours after receipt of a sample, and makes possible determination of the terminal innervation ratio.

Frozen Sections↗