Biomedical subjects

V Subramani

Publications and source records attributed to V Subramani.

16 recordsLinked to original sources

PubMed1999

Variation in the isocentre of a Philips linear accelerator (SL-20) used for stereotactic radiosurgery/stereotactic radiotherapy.

Stereotactic irradiation, either in the form of stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) of brain lesions requires high precision and submillimetre accuracy in the isocentre, the main determinants being gantry and couch rotations. It is thus necessary to evaluate the isocentre variation due to gantry and couch rotations in the particular setup for SRS/SRT. This paper describes variation in the isocentre of a Philips (now Elekta) SL-20 linear accelerator modified for adapting a couch-mounted radiosurgery system. By considering the isocentre as defined by a mechanical index as the standard, the variations in the isocentre of the linear accelerator were independently measured for the gantry and for couch rotations. The variation in the isocentre for gantry rotation was found to be between 0.1 mm and 0.9 mm, conforming to the submillimetre accuracy required for SRS/SRT. However, the isocentre variation due to couch rotation varied considerably, possibly because the couch is of the RAM type. The isocentre variation due to couch rotation is rectified by microadjusting the couch mount at the time of treatment using a laser target localizing frame. It is our conclusion that a modified linear accelerator can be used for performing SRS/SRT after careful and separate evaluation of the isocentre stability due to gantry and couch rotations.

Brain Neoplasms↗

PubMed1990

Morphology and morphometry of motor endings on macaque intrafusal fibers.

The ultrastructural studies have shown three types of motor endings in the macaque intrafusal fibers: 1) unindented axon terminals with smooth or shallowly folded postsynaptic membrane; 2) indented terminals with few postsynaptic folds; and 3) indented terminals with heavily folded postsynaptic membrane. The terminals on bag 1 and chain fibers were generally more indented than those on the bag 2 fibers. Deeply indented terminals with highly folded postsynaptic membranes were noticed on the bag 1 and chain endings in spindles from lumbrical but not the biceps muscle. In the individual intrafusal fibers from the biceps and lumbrical spindles, the degree of indentation did not correlate with the extent of postsynaptic folding (P greater than .01). Endings on bag 1 and chain fibers in the lumbrical spindles showed a positive correlation between indentation of terminals and their distance from the primary sensory endings (P less than .01), whereas the lumbrical bag 2 endings and the biceps intrafusal endings did not (P greater than .01). The shape of the intrafusal motor endings thus is independent of their location but dependent on the type of intrafusal fibers.

Animals↗

PubMed1989

Membrane abnormality in malignant hyperthermia.

In this study we report on the effect of halothane exposure on the skeletal muscle membrane and calcium localization in 9 patients with confirmed susceptibility to malignant hyperthermia and compare them with 11 non-susceptible cases of malignant hyperthermia. Two normal muscle specimens with physiologically induced muscle contractures were also included for comparison. Halothane exposure in malignant hyperthermia-susceptible cases showed severe muscle contractures, definite breaks in the plasma membrane with peroxidase penetration, and large number of calcium granules within the mitochondria and sarcoplasmic reticulum. Malignant hyperthermia-non-susceptible cases and muscle with physiological contractures did not show discontinuity of the plasma membrane or excessive calcium deposits. Based on these findings we conclude that the halothane exposure in malignant hyperthermia-susceptible patients causes breaks in the muscle plasma membrane.

Adolescent↗

PubMed1988

Effect of fiber types, fascicle size and halothane on caffeine contractures in rat muscles.

Caffeine contractures were recorded from thin bundles and whole extensor digitorum longus (EDL) and soleus muscles of rat, and correlated with preparation size and fiber types. Thin bundles were more sensitive to caffeine and halothane than whole muscles, and bundles of 100% type I fibers were more sensitive than bundles of 100% type II fibers. Magnitude of contracture had significant correlation with maximal tetanic tension, total number of fibers, thickness of the preparation, and proportion of type I fibers. These results suggest that fascicle size and fiber types significantly affect results of in vitro contracture test for susceptibility to malignant hyperthermia.

Animals↗

PubMed1988

Variability of mitochondrial cytochemistry in human neuromuscular diseases.

This study describes mitochondrial cytochemistry with reference to cytochrome c oxidase and NADH oxidase activities as well as calcium localization at subcellular level in a variety of human mitochondrial disorders. The enzyme activities, calcium homeostasis, and myofibrillary architecture were retained in the lipid storage myopathies with carnitine and carnitine palmityl transferase deficiency. The loss of enzyme reaction, excessive Ca++ deposit, and myonecrosis were the features of the group comprised of a variety of disorders with mitochondrial pathology (Kearns-Sayre's syndrome, chronic progressive ophthalmoplegia, polymyositis, neurogenic atrophy, and fascioscapulo humeral dystrophy). Based on these and our previous experimental study (Shah et al., 1985), we suggest that the human mitochondrial disorders may be grouped into two types: one in which the morphologically altered mitochondria retain the enzyme activities and Ca++ homeostasis and the other in which the altered mitochondria associated with muscle necrosis represent the loss/reduction of the enzyme activities as well as Ca++ homeostasis.

Calcium↗

PubMed1987

Attachments of human intrafusal fibers.

The human intrafusal fibers have two major types of attachments: (1) extracapsular, involving the bag and long chain fibers which tapered into the extrafusal endomysium; and (2) intracapsular, involving only the short chain fibers which attached to the outer or inner capsule as well as to the bag, and other chain fibers. At all the attachment sites except the interfiber attachments, the intrafusal fibers showed alterations in the basement and plasma membrane, streaming of the Z band, and rod bodies. This profile was similar to the myotendinous junctions. The terminal sarcomere segment consisted of the actin filaments, thickening of the plasma membrane, and folded basal lamina. The interfiber attachments were of two types--the gap and tight junctions. There were thus two major functional types of attachment, the myotendinous type contacts which were mechanical and the interfiber attachments which represent electrical continuity between the two chain fibers.

Adolescent↗

PubMed1986

Morphology and morphometry of motor endings in primate intrafusal fibers.

The pre- and postsynaptic structure of 243 axon terminals of bag 1, bag 2, and chain fibers were studied in cynomolgus monkey skeletal muscle spindles. The motor endings of the biceps and gastrocnemius spindles (long limb muscle) were compared to the motor endings of lumbricals and opponens pollicis (intrinsic hand muscle) spindles. In both muscle groups the only significant difference observed in the presynaptic features was in the presynaptic membrane length. The postsynaptic features of bag 1, bag 2 and chain endings were similar in the long limb muscle spindles. In the intrinsic hand muscle, however, the bag 1 and chain endings showed complex postsynaptic structure which resembled the extra fusal endings while the postsynaptic structure of bag 2 endings was much simpler. From these studies we conclude that the postsynaptic structure of various intrafusal fiber types is dissimilar in different muscles.

Animals↗

PubMed1985

Mitochondrial cytochemistry in experimental myopathies.

In this paper, we have described mitochondrial cytochemistry (NADH oxidase, cytochrome c oxidase), in the light and electron microscopic studies of the experimental mitochondrial myopathies. DNP, oleate and crotoxin were employed to produce mitochondrial changes in the rat skeletal muscle. The DNP and oleic acid lesions showed strong NADH oxidase and cytochrome c oxidase activities in mitochondria--both at the light microscopic as well as at ultrastructural level. However, the crotoxin lesions showed marked reduction of both the enzyme activities in histochemistry and electron microscopy. Muscle necrosis was seen only in the crotoxin lesion. On the basis of these data, we propose that DNP and oleic acid treatment produced mitochondrial myopathies in which the mitochondrial structure was altered but they were enzymatically active, while the crotoxin treatment produced the structural and enzymatic alterations of the mitochondria.

2,4-Dinitrophenol↗

PubMed1983

Ultrastructure of muscle spindle in congenital myotonic dystrophy. A study of preterm infant muscle spindles.

The muscle spindle in the preterm infants with congenital myotonic dystrophy consisted of numerous, unfused intrafusal fibers. These fibers showed immature myofilament arrangement at 27 weeks but had the nuclear arrangement of bag and chain type. The motor endings were very sparse while prominent sensory endings were seen. At 34-37 weeks, even though the muscle fibers were unfused, the nuclear bag and chain fibers could be differentiated by the presence and absence of M line. Immature motor endings were seen at this stage. In conclusion, the muscle spindle in the preterm infants is immature.

Cytoskeleton↗

PubMed1983

Skeletal muscle in preterm infants with congenital myotonic dystrophy. Morphologic and histochemical study.

The skeletal muscle in 3 preterm infants (27, 34, 37 weeks gestation age) born to mothers with myotonic dystrophy showed a syncytial pattern at 27 weeks and a decreasing percentage of satellite cells and central nuclei at 34 and 37 weeks gestation. The fiber type differentiation was observed only at 37 weeks of gestational age. In all 3 cases muscle fibers with multiple acid phosphatase positive were seen. The muscle spindles also had thick capsules and showed lack of morphologic and histochemical differentiation into fiber types. These findings suggest immaturity of skeletal muscle in comparison to the normal. The immaturity of the skeletal muscle correlated well with the prognosis of the patients.

Acid Phosphatase↗

PubMed1983

Morphologic and morphometric studies of muscle in idiopathic scoliosis.

The gluteus maximus and paraspinal muscles in 15 cases of idiopathic scoliosis at the apex of the curve showed myopathic changes and a significant decrease in the type II fibers. Fiber type II atrophy was observed only on the concave side. Ultrastructure of paraspinal and gluteus muscle biopsies showed disruption of myofilaments, Z band streaming and subsarcolemmal accumulation of glycogen, lipid and mitochondria. Quantitative estimation of these subcellular organelles pointed out that a higher glycogen content was significant in both paraspinal as well as the gluteus muscles while a higher mitochondrial content was significant only on the convex side and the gluteus muscle but not the concave side of the apex when compared to normal quadriceps muscle. These findings suggest that idiopathic scoliosis is a diffuse disease process and may be considered a primary muscle disease.

Adolescent↗

PubMed1983

Muscle in chronic uremia--a histochemical and morphometric study of human quadriceps muscle biopsies.

This report describes qualitative and quantitative studies performed on ten muscle biopsies from chronic uremic patients on renal dialysis at light and electron microscopic (EM) levels. The muscle biopsies showed myopathic changes (variation in fiber size, central nuclei, and fiber splitting). Histochemical studies showed type II fiber atrophy and lipid deposits. The ultrastructural study showed disruption of myofibrillary architecture and subsarcolemmal deposits of glycogen, mitochondria, and lipids. Quantitative estimations of the subcellular organelles revealed a statistically significant increase in lipid and glycogen contents of the muscle. The myopathic changes, type II atrophy, and lipid and glycogen deposits in chronic uremic patients raise the question of the effects of uremia and/or chronic dialysis on muscle metabolism.

Adult↗

PubMed1982

Morphogenesis of the mitochondrial alterations in muscle diseases.

In this paper we present sequential morphologic changes produced in rat muscle mitochondria. Respiratory toxins such as crotoxin (rattle-snake venom) and 2,4-dinitrophenol (DNP-an uncoupler of oxidative phosphorylation) were injected in rat quadriceps muscle and the mitochondrial alterations were studied at various time intervals. The series of mitochondrial changes consisted of rounding and swelling of mitochondria, unfolding of the cristae as straight lines, formation of the concentric rings, appearance of paracrystalline inclusions, formation of multiple vesicles and finally vacuole formation. These changes were comparable to the range of mitochondrial alterations seen in the human material examined. Similarity of the time-related mitochondrial changes in the rat to the spectrum of changes observed in human muscle biopsies suggests that the mitochondrial alteration in the human muscle disorders is a stepwise process in which respiratory alterations and calcium ion may play a role.

2,4-Dinitrophenol↗

PubMed1981

Morphological and histochemical correlation of recovery after spinal transection in rat.

Previous studies from our laboratory have shown disappearance of aminergic terminals with relative preservation of cholinergic activity below the level of the lesion (Rodriques & Sahgal, 1978). Since then we have extended our study to look at the behaviour of aminergic fibres and neurons at various time intervals following the lesion and attempted to correlate with the functional recovery. Three to 4 weeks after spinal transection (thoracic), the rats started to show spinal-stepping which became stronger and dexterous with the passage of time. Up to 6 months after thoracic transection, maximum recovery was observed. Studies of catecholamine fluorescence revealed proliferation of new aminergic terminals which were observed four or five segments below the transection. These observations demonstrate regeneration of aminergic fibres in rat. The significance of the data in the light of neurophysiologic studies will be discussed.

Acetylcholinesterase↗

PubMed1979

On the pathogenesis of mitochondrial myopathies. An experimental study.

The intra-arterial injection of 2-4 dinitrophenol, an uncoupler of oxidative phosphorylation, resulted in the production of ragged red fibers. The ultrastructure of these fibers showed intramitochondrial paracrystalline inclusions, laminar and fingerprint bodies. Antimycin A and oligomycin injection (which inhibit mitochondrial respiration) only caused swelling and disruption of the mitochondria. An increase in muscle lactic acid, decrease in ATP, glycogen and phosphocreatine was observed after the injection of all these agents. This indicates that lactic acidosis has no significant role in the pathogenesis of mitochondrial pathology. It is concluded that mitochondrial changes are a morphological expression of uncoupled but intact mitochondrial respiration.

Animals↗

PubMed1977

Neurotransmitters in spinal cord injury.

The authors report the distribution of acetylcholinesterase activity and catecholamine fluorescence in the intact and completely transected rat spinal cord. The catecholamine terminals were scarce in the posterior horn and abundant in the intermediale and anterior horn regions. In the thoracic region, intense amine fluorescence was seen in the intermediolateral cell column. Spinal transection resulted in the enhancement of fluorescence above the lesion and disappearance below the lesion within seven days. The cholinesterase activity in the controls was found mostly in the anterior horn region and the tip of the posterior horn. Following transection, there was no significant change in the distribution of this enzyme. These changes correlated with the appearance of spasticity.

Acetylcholinesterase↗