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Biomedical subjects

S David

Publications and source records attributed to S David.

At least 181 records · Page 10Linked to original sources
PubMed1984

Effects of neonatal transection on glial cell development in the rat optic nerve: evidence that the oligodendrocyte-type 2 astrocyte cell lineage depends on axons for its survival.

We have previously provided evidence that the rat optic nerve contains three types of macroglial cells that develop as two distinct lineages: one lineage comprises type 1 astrocytes, which develop before birth, while the other comprises oligodendrocytes and type 2 astrocytes, which develop after birth from a common, bipotential glial progenitor cell. In the present study we have examined the influence of axons on the development of these two glial cell lineages by cutting the optic nerve at birth so that the retinal ganglion cell axons in the nerve degenerate. Using antibodies to distinguish the different types of glial cells in suspensions and semithin frozen sections of cut and uncut optic nerves, we show that neonatal transection results in a striking decrease in the total number of oligodendrocytes, type 2 astrocytes and their progenitor cells but has much less effect on the number of type 1 astrocytes. Since the [3H]thymidine labelling indices of oligodendrocytes and their progenitor cells were not significantly decreased in cut nerves, our results suggest that the progenitor cells and/or their progeny die in large numbers following neonatal nerve transection. We conclude that axons are required for the survival of cells of the oligodendrocyte-type 2 astrocyte lineage, at least during postnatal development.

Animals↗
PubMed1984

Maternal, fetal, and neonatal effects of lidocaine with and without epinephrine for epidural anesthesia in obstetrics.

The effects of epidural lidocaine with and without 1:300,000 epinephrine on uterine activity, progress of labor, fetal heart rate, maternal blood pressure and heart rate, newborn Apgar scores, neonatal acid-base status, and the Neurologic and Adaptive Capacity Scoring System were compared in 30 parturients during labor and delivery. Patients in group I (n = 16) received 1.5% lidocaine with 1:300,000 epinephrine and those in group II (n = 14) 1.5% lidocaine alone. Addition of epinephrine to lidocaine did not have any significant effects on uterine activity, duration of first or second stages of labor, fetal heart rate variability, or the incidence of abnormal fetal heart rate patterns. Maternal heart rate and the incidence of hypotensive episodes did not differ significantly between the two groups of patients. Apgar scores, neonatal acid-base status, and the NACS were equally good in the two groups. Duration of analgesia was significantly longer in group I as compared to group II patients (106.9 +/- 6.6 vs 66.2 +/- 4.4 min, P less than 0.001). Umbilical venous concentrations of lidocaine and umbilical vein to maternal vein ratios of lidocaine were significantly higher in group II patients (P less than 0.05). It is concluded that addition of epinephrine to lidocaine during epidural anesthesia in the normal parturient has no adverse effects on mother, fetus, neonate, or the progress of labor and it significantly prolongs the duration of anesthesia and limits the placental transfer of lidocaine.

Acid-Base Equilibrium↗
PubMed1984

[The synthesis of valperinol and various 3-aminomethyl derivatives of 2,9-dioxatricyclo[4,3,1,0(3,7)]decane from didrovaltrate].

3-Aminomethyl derivatives of 2,9-dioxatricyclo [4,3,1,0(3,7)]decane, can be synthesized via an amination, starting from (1R, 3S, 4S, 6R, 7S, 8R, 10R)-3-iodomethyl-4-acetoxy-8-methoxy-10-methyl-2, 9-dioxatricyclo [4,3,1,0(3,7)]decane or (1R, 3S, 4S, 6R, 7S, 8R)-3-iodomethyl-4-acetoxy-8-methoxy-10-methylen-2,9- dioxatricyclo [4,3,1,0(3,7)]decane, which can be prepared from didrovaltrate.

Bridged-Ring Compounds↗
PubMed1983

Influence of adrenalectomy on vitamin B6 status.

Adrenalectomy results in depletion of vitamin B6 stores. This depletion is rapid and significant in liver, as compared to brain. When the adrenalectomized rats are fed with excess vitamin B6 or injected with corticosterone, the normal vitamin levels are maintained. Thus, it is possible that adrenocortical hormones help in the retention of vitamin B6 in the body.

Adrenalectomy↗
PubMed1983

Neuronal changes induced by neonatal hypothyroidism: an ultrastructural study.

The postnatal development of the neurons of the cuneate nucleus was examined ultrastructurally in euthyroid and hypothyroid rats from birth to the sixth postnatal week. In the euthyroid animals, the neurons at birth displayed mild nuclear invaginations and a scanty cytoplasm with few organelles. By 2 weeks, there was a considerable increase in Nissl bodies. At 3 weeks, the neurons contained short lamellar arrays of endoplasmic reticulum. Between 3 and 6 weeks there was a reduction in the Nissl substance. In the hypothyroid animals, although the sequence of maturational changes generally resembled that of the controls, a number of differences were noted. The neurons at 1 week displayed dilations of perinuclear space, rough endoplasmic reticulum, Golgi complexes, and mitochondria. At 4 weeks both perikaryon and myelinated axons contained glycogen. Several neurons with cytoplasmic inclusions considered to be nonfunctional RNA were seen. The 6-week hypothyroid neuron exhibited large, clear, cytoplasmic vacuoles associated with a drastic reduction in cytoplasmic organelles. Presynaptic terminals showed a 50% reduction in mitochondrial numbers associated with the presence of glycogen granules. Three changes observed in neurites in all the age groups included: (1) large accumulation of glycogen in presynaptic terminals; (2) clear vacuoles; and (3) the presence of numerous lamellar bodies within reactive axons. Aberrant myelination, such as a single myelin sheath enclosing multiple processes, and instances of collapsed and redundant myelin were encountered.

Animals↗
PubMed1983

Effects of crush injury on the abnormalities in the spinal roots and peripheral nerves of dystrophic mice.

Lumbosacral spinal roots and peroneal nerves in dystrophic and control mice were crushed and allowed to regenerate. Six weeks after crush injury, the dystrophic roots no longer showed the typical groups of unensheathed axons that characterize the uncrushed roots. Thus, the location of this ensheathment defect in the spinal roots cannot be the exclusive mechanism responsible for its development. Crush injury and regeneration also tended to correct a second abnormality in the peripheral nervous system of dystrophic mice: the discontinuities in the Schwann cell basal laminas. Because the regenerated nerves contained increased amounts of collagen, the results of this study support the evidence from tissue culture experiments that the extracellular matrix may be involved in the pathogenesis of these disorders. However, the outcome of the present in vivo experiments indicates that genetically normal fibroblasts are not required for this change to occur.

Animals↗
PubMed1983

Acquired B antigen: further studies using synthetic oligosaccharides.

The reactivity of acquired-B red cells with various antisera has been investigated by agglutination inhibition assays using four trisaccharides obtained by chemical synthesis. Two of these had the structure GalNAc alpha 1-3 (LFuc alpha 1-2). Gal and Gal alpha 1-3 (LFuc alpha 1-2) Gal which are characteristic of the A and B determinants respectively and were indeed strong inhibitors of human anti-A and -B antibodies. The other two sugars denoted B-OAc and B-NH2 are derivatives of the B-trisaccharide by substitution of the hydroxyl group on carbon-2 of the alpha-galactose residue with the O-acetyl group (B-OAc) or the amino group (B-NH2) respectively. We have shown that both B and B-NH2 trisaccharides inhibited strongly the agglutination of acquired B red cells by the anti-B reagents (crude or affinity purified) whereas sera containing "anti-acquired B" agglutinins were specifically inhibited by B-NH2 but not by the A, B or B-OAc structures. We have also shown that the agglutination of Tk-activated erythrocytes by the BS-II lectin is specifically inhibited by N-acetylglucosamine but not by B, B-OAc or B-NH2 structures. These results and the observation that anti-acquired B agglutinins cannot be adsorbed on Tk red cells suggest that (i) the "B-like" and the "acquired-B" determinants share a common structure best represented by B-NH2 and (ii) Tk and "acquired-B" antigens are not identical.

ABO Blood-Group System↗
PubMed1983

Familial spinocerebellar ataxia with skin hyperpigmentation.

Previous reports have shown the association between familial spastic paraplegia and hypopigmentation of the skin. A family is reported in which three siblings presented with progressive spastic paraparesis and cerebellar ataxia. All the siblings had large hyperpigmented naevi of the lower extremities while none of the unaffected members had a skin lesion. A definite association appears to exist between heredo-familial ataxias and disordered skin pigmentation, but the exact mechanism remains unclear.

Adult↗
PubMed1983

Short dialysis.

Explore the source record for details and available documents.

Adolescent↗
PubMed1983

An integrated programme of haemodialysis and peritoneal dialysis: a single two-litre exchange per night plus haemodialysis every four to six days.

Critical problems of CAPD: (a) protein loss; (b) peritonitis; (c) glucose overload; (d) intra-abdominal pressure, can be rationally managed by an integrated intracorporeal and extracorporeal approach. A single two-litre peritoneal exchange performed during the night in addition to haemodialysis every four to six days (HD-PD) reduces a, b, c and eliminates d. This HD-PD technique has been evaluated in eight uraemic patients over a total period of 20.5 patient months. Preliminary results show that this procedure can provide adequate biochemical control, with low protein losses and limited interdialysis weight gain.

Aged↗
PubMed1982

Effects of estradiol benzoate on the pattern of eating and ethanol consumption.

The effects of daily injections of 5 microgram estradiol benzoate (EB) on the patterns of food and ethanol consumption were studied in ovarectomized rats given free access to food, a 10% ethanol solution, and water. EB led to an immediate, but transient, suppression of both food and ethanol intake. The time course and magnitude of these effects were virtually identical. While the decrease in total food intake was achieved by a permanent decrease in the duration of eating bouts, the decline in total ethanol consumption apparently resulted from decreased rates of licking within bouts. Gradual increases in the frequency of eating and ethanol-drinking bouts allowed total food and ethanol intake to return to baseline within three weeks of the first injection. Total water intake rose three-fold during EB administration and this was due to increases in both the duration and frequency of drinking bouts. The similarity in effects induced by EB on the patterns of food and ethanol intake were discussed in terms of ethanol's caloric property.

Alcohol Drinking↗
PubMed1981

Axonal elongation into peripheral nervous system "bridges" after central nervous system injury in adult rats.

The origin, termination, and length of axonal growth after focal central nervous system injury was examined in adult rats by means of a new experimental model. When peripheral nerve segments were used as "bridges" between the medulla and spinal cord, axons from neurons at both these levels grew approximately 30 millimeters. The regenerative potential of these central neurons seems to be expressed when the central nervous system glial environment is changed to that of the peripheral nervous system.

Animals↗
PubMed1981

Influences of the glial environment on the elongation of axons after injury: transplantation studies in adult rodents.

Tissue transplantation methods, previously used to study neural development, myelination and inherited disorders of myelin can be applied also to the investigation of repair and regeneration in the mammalian CNS. The elongation of axons from injured peripheral nerve of CNS has been studied in adult mice and rats by observing the growth of axons into PNS or CNS tissue grafts. Following spinal cord injury and also after transplantation of optic nerves into the PNS there is axonal sprouting but these neuronal processes fail to elongate more than a few mm into the surrounding glia. On the other hand if segments of a peripheral nerve are grafted into the transected spinal cord, axons arising from spinal neurons and dorsal root ganglia become associated with the transplanted Schwann cells and elongate along the graft, approximately 1 cm. Recently the elongation of axons from spinal and medullary neurones was studied using a new experimental model which employed PNS grafts as 'bridges' to connect the spinal cord and the brain stem. In a series of adult C57BL/6J mice and Sprague Dawley rats, autologous segments of sciatic nerve were used to create 'bridges' between the lower cervical or upper thoracic spinal cord and the medulla oblongata. The spinal cord between these two levels was left intact. Grafted segments examined by light and electron microscope 1-7 months after surgery were well innervated by Schwann cell ensheathed axons that had grown the entire length of the graft (2 cm in mice and 3.5 cm in rats). The origin and termination of these axons were determined by transecting the regenerated grafts and applying horseradish peroxidase to the cut ends. Retrogradely labelled neurones were found to be distributed widely in the gray matter of the spinal cord and medulla near the sites of insertion of the graft. Anterogradely labelled fibres coursing within the graft penetrated the CNS for short distances, approximately 2 mm. These new results indicate that following CNS injury a conducive glial environment does allow spinal and brain stem neurones to elongate axons for distances that can be greater than those they usually extend for in the intact animal. This evidence that the regenerative response of similar axons differs in CNS and PNS neuroglia supports the hypothesis that influences arising from the environment play an important role in the success or failure of regeneration. The regenerative potentiality of central neurones may be expressed only when the CNS neuroglial environment is changed to resemble that in the PNS.

Animals↗