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Biomedical subjects

L C Wang

Publications and source records attributed to L C Wang.

At least 109 records · Page 6Linked to original sources
PubMed1994

Lumbar myelography: side effects correlated with exam findings and needle size.

STUDY DESIGN: The adverse effects of lumbar myelography in 400 patients were analyzed. OBJECTIVES: To determine whether adverse effects of lumbar myelography occur less frequently when using the fine needle technique. SUMMARY OF BACKGROUND DATA: Lumbar myelography can be performed safely on an outpatient basis. The side effects may be reduced by using the fine needle technique. METHODS: Four hundred patients were studied; 200 with a 25 gauge needle and 200 with a 22 gauge needle. Each was given a questionnaire and instructed to report details of post-myelogram adverse effects. RESULTS: Transient worsening of back or leg symptoms, headache, and nausea and vomiting, the most frequent complaints, were reduced in the 200 patients studied with a 25 gauge needle rather than a 22 gauge needle. Regardless of the needle, patients with normal myelograms reported more adverse effects. CONCLUSIONS: A lower frequency of adverse effects can be achieved when fine needle is used for lumbar myelography. More adverse effects are reported by patients with normal myelograms.

Ambulatory Care↗
PubMed1994

An active v-abl protein tyrosine kinase blocks immunoglobulin light-chain gene rearrangement.

Lymphoid cells transformed by Abelson murine leukemia virus have provided one of the classic models for study of early B-cell development and immunoglobulin rearrangement. Most of these cells have rearranged their heavy-chain locus but not their light chain genes, suggesting that an active v-abl protein interferes with this differentiation step. To test this hypothesis, light-chain gene structure was examined in pre-B cells transformed by temperature-sensitive mutants of the Abelson virus and in derivatives that survive at the nonpermissive temperature because they express a human BCL-2 gene. Our studies reveal that inactivation of the v-abl protein tyrosine kinase triggers high-frequency rearrangement of kappa and lambda light-chain genes. These events are accompanied by marked increases in the expression of RAG-1 and RAG-2 RNAs. These increases occur in the absence of protein synthesis but are dependent on inactivation of the v-abl protein tyrosine kinase. As documented in the accompanying paper (Klug et al., this issue), an active v-abl protein also suppresses the activity of NF-kappa B/rel and expression controlled by the kappa intron enhancer. Together these data demonstrate that the v-abl protein specifically interferes with light-chain gene rearrangement by suppressing at least two pathways essential for this stage of B-cell differentiation and suggest that tyrosine phosphorylation is important in regulating RAG gene expression.

Abelson murine leukemia virus↗
PubMed1994

Improved rat heart function after low Ca2+ perfused preservation at 5 degrees C for 18 hours.

To evaluate the effect of Ca2+ on recovery of heart function after hypothermic preservation, isolated working rat hearts were perfused continuously in different [Ca2+] (0.35-2.0 mM) at 37 degrees C for 30 min, during cooling to 5 degrees C, and then at 5 degrees C for 1, 6 or 18 h. After rewarming to 37 degrees C, contractile functions were assessed in working hearts perfused with Krebs-Henseleit (K-H) solution containing 2.0 mM free Ca2+. In normal K-H solution (2.0 mM Ca2+), cardiac function recovered completely after perfusion at 5 degrees C for 1 h (measured by the maximal rate of pressure development, +dP/dtmax, and heart rate x left ventricular systolic pressure, HR x LVSP). After 6 h at 5 degrees C, significant (P < 0.05) loss in function began to appear. Further, 18 h at 5 degrees C resulted in significant decreases in LVSP, +dP/dtmax, and coronary flow (CF) and a significant increase in left ventricular diastolic pressure. The deterioration of heart function consequent to hypothermic preservation could be prevented by reducing the Ca2+ in perfusion medium prior to and during cooling and rewarming from hypothermia. The optimal Ca2+ concentration was 0.5 mM. At lower Ca2+ (0.35 mM), reductions in HR, LVSP. +dP/dtmax, and CF after rewarming were evident. Our results indicate that by reducing cellular Ca2+ prior to cooling through perfusion of 0.5 mM Ca2+ K-H solution, significant benefits can be obtained both in prolonging the duration of cardiac preservation and in retaining functional integrity upon rewarming.

Animals↗
PubMed1994

Liver metabolism in cold hypoxia: a comparison of energy metabolism and glycolysis in cold-sensitive and cold-resistant mammals.

The effects of cold hypoxia were examined during a time-course at 2 degrees C on levels of glycolytic metabolites: glycogen, glucose, glucose-1-phosphate, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-bisphosphate, phosphoenolpyruvate, pyruvate, lactate and energetics (ATP, ADP, AMP) of livers from rats and columbian ground squirrels. Responses of adenylate pools reflected the energy imbalance created during cold hypoxia in both rat and ground squirrel liver within minutes of organ isolation. In rat, ATP levels and energy charge values for freshly isolated livers were 2.54 mumol.g-1 and 0.70, respectively. Within 5 min of cold hypoxia, ATP levels had dropped well below control values and by 8 h storage, ATP, AMP, and energy charge values were 0.21 mumol.g-1, 2.01 mumol.g-1, and 0.17, respectively. In columbian ground squirrels the patterns of rapid ATP depletion and AMP accumulation were similar to those found in rat. In rat liver, enzymatic regulatory control of glycolysis appeared to be extremely sensitive to the decline in cellular energy levels. After 8 h cold hypoxia levels of fructose-6-phosphate decreased and fructose-1,6-bisphosphate increased, thus reflecting an activation of glycolysis at the regulatory step catalysed by phosphofructokinase fructose-1,6-bisphosphatase. Despite an initial increase in flux through glycolysis over the first 2 min (lactate levels increased 3.7 mumol.g-1), further flux through the pathway was not permitted even though glycolysis was activated at the phosphofructokinase/fructose-1,6-bisphosphatase locus at 8 h, since supplies of phosphorylated substrate glucose-1-phosphate or glucose-6-phosphate remained low throughout the duration of the 24-h period.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1994

Etiologies of central diabetes insipidus in children.

The last major review of the etiologies of central diabetes insipidus in children was performed a quarter century ago, prior to the development of modern neuroimaging techniques. We retrospectively reviewed the records of children with central diabetes insipidus identified at Children's Hospital of Buffalo from 1979 to 1992. Of the 35 patients identified, 27 were males and 8 were females. Their ages ranged from 3 weeks to 20 years. Nineteen children had brain tumors, 7 had cerebral malformations, 3 had central nervous system infections, 1 had traumatic brain injury, and 5 were considered idiopathic. Patients with brain death were excluded from the review. Thirty-one of 35 patients developed diabetes insipidus in conjunction with other endocrinopathies. Brain tumor and its treatment account for the most common cause. Cranial magnetic resonance imaging has improved the identification of structural lesions and the understanding of the pathophysiology of central diabetes insipidus.

Adolescent↗
PubMed1994

Fibrin content of carotid thrombi alters the production of embolic stroke in the rat.

BACKGROUND AND PURPOSE: Mechanical denudation of the endothelium of the carotid artery in animals produces a nonocclusive thrombus, but the brains of these animals have not been examined for the presence of embolic stroke. METHODS: The endothelium of the right carotid artery of 16 Wistar rats was denuded using a balloon catheter. Phosphotungstic acid hematoxylin (PTAH) staining and scanning electron micrographs of the nonocclusive thrombi in the carotid arteries were compared with those produced by photochemical methods, and brains were examined for infarcts. RESULTS: Although nonocclusive thrombi were present in the carotid arteries of 4 of 4 rats killed at 4 hours and in 8 of 12 killed at 24 hours, neither cerebral infarcts nor emboli were seen in the 14 brains evaluated by light microscopy. PTAH demonstrated a high fibrin content in the thrombus produced by the endothelial denudation, with almost no fibrin seen in photochemically induced thrombi. Scanning electron microscopy confirmed dense networks of fibrin in the thrombi produced by balloon denudation. CONCLUSIONS: The composition of a nonocclusive thrombus may determine the embolic potential of this thrombus. A low fibrin content in a nonocclusive platelet thrombus may enhance the embolic potential. This suggests that platelet inhibition may also be indicated in patients with carotid artery disease who are being treated with anticoagulant.

Animals↗
PubMed1994

Retinal axon divergence in the optic chiasm: dynamics of growth cone behavior at the midline.

To study how retinal ganglion cell axons diverge in the optic chiasm, the behavior of dye-labeled fibers was monitored in real time with video microscopy in an isolated preparation of embryonic mouse brain, with a focus on embryonic day 15-16. These real-time studies have revealed the dynamics of the growth of individual retinal axons, especially the tempo of extension and growth cone behaviors during divergence in the chiasm, a model for "decision" regions in developing pathways. Within the chiasm, retinal growth cones extend by saltatory growth, consisting of bursts of rapid advance alternating with pauses in extension. During pauses, growth cone appendages remain motile, and develop asymmetries prior to a change in the axis of growth. In a zone straddling the midline, retinal fibers, irrespective of destination, display long pauses for up to several hours, making small advances and retractions with no net extension. While crossed fibers ultimately progress through the midline, uncrossed fibers from inferior temporal retina develop wide-ranging branched growth cones, and then turn back to the ipsilateral side. Turns are effected by the selective retraction or micropruning of asymmetric foci of motile activity, and by the transformation of a backward-directed filopodium into a new growth cone. The behavior of retinal axons at the midline supports the hypothesis that this locus contains cues important for retinal axon divergence. Moreover, the observations of growth cone kinetics in the chiasm elucidate which growth cone forms seen in static preparations mediate growth cone turning, and suggest a model of axon navigation in decision regions in the intact nervous system.

Animals↗
PubMed1994

Astroglial differentiation is required for support of neurite outgrowth.

Models of astrocyte differentiation stress a lineage program that involves a progressive loss of astroglial support of neuronal differentiation. These models predict that astroglial promotion of neurite extension declines with the "age" of the astrocyte. An alternative view is that astroglial support of neurite growth is regulated by epigenetic factors that induce the cells either to differentiate and support neuronal functions or to undergo cell proliferation and fail to support neurons. To compare the contribution of astroglial cell "age" to astroglial support of neurite extension, mouse cerebellar astroglia were maintained in vitro for 3-90 d, and assayed for their ability to support neurite formation. When cultured in isolation, astroglial support of neurite extension declined with time in vitro, as assayed by quantifying outgrowth from explants of pontine nuclei, falling from a robust level just after the astroglia were harvested to negligible levels 21-90 d later. Since previous studies have shown that neurons can change the state of astroglial cells (Hatten, 1985), we tested the neurite promoting activity of astroglia that were cultured for 21-90 d in vitro and subsequently induced to differentiate by the addition of neurons. When granule neurons were added to aged astroglia and pontine explants plated 2 d later, neurite growth from the explants was exuberant, regardless of the time astroglia spent in vitro prior to the addition of neurons. The state of astroglia that were growth promoting or growth inhibiting was examined by bromodeoxyuridine staining and with antisera to glial filament protein. Aged astroglia cultured alone and thus inhibitory to axon growth, proliferated at high rates and had polygonal shapes. In contrast, aged astroglia to which neurons had been added, proliferated at low rates and developed process-bearing stellate shapes. To test further whether proliferation levels related to the growth-supporting properties of astroglia, astroglia were plated alone in medium without serum, or with the addition of transforming growth factor-beta 1, each treatment known to arrest proliferation. In both cases, promotion of neurite growth was restored in aged astroglia, but the morphology of astroglia did not correlate with the ability to support neurite growth. Finally, the growth-inhibiting properties of aged astroglia do not appear to be mediated by diffusible factors, and require close apposition with living astroglial cells. We conclude that astroglial support of neurite extension depends on the state of differentiation of astroglial cells, and that these properties can be modified by coculture with neurons or conditions that arrest of astroglial proliferation, irrespective of astroglial "age".

Animals↗
PubMed1993

The modulatory effects of mu and kappa opioid agonists on 5-HT release from hippocampal and hypothalamic slices of euthermic and hibernating ground squirrels.

To elucidate the role of opioids in regulating hibernation, the modulatory effects of different opioids on 35 mM K(+)-stimulated [3H]-5-HT release from brain slices were examined in the Richardson's ground squirrels. DAGO ([D-Ala2,N-Me-Phe4,Gly-ol5]-enkephalin), a specific mu agonist, evoked a significant dose-dependent (10(-7)-10(-5) M) inhibition of K(+)-stimulated 5-HT release from hippocampal slices of the non-hibernating squirrels. The inhibitory effect of DAGO was attenuated by either the opioid antagonist naloxone (10(-6) M) or the voltage dependent sodium channel blocker tetrodotoxin (TTX, 10(-6) M). The inhibitory effect of DAGO persisted in the hibernating squirrels; however, a ten fold higher concentration of DAGO (10(-6)-10(-5) M) was required to elicit a significant inhibition. In contrast, kappa agonist U50488 (10(-5) M) exerted a significant enhancement of K(+)-stimulated 5-HT release from hippocampal slices of the non-hibernating squirrels. This enhancement was blocked by either the specific kappa antagonist nor-binaltorphimine (10(-6) M) or TTX (10(-6) M). However, in the hibernating squirrels, the stimulatory effect of U50488 (10(-5) M) on 5-HT release was absent. DAGO and U50488 had no modulatory effects on K(+)-stimulated 5-HT release from the hypothalamic slices of either the non-hibernating or hibernating squirrels. These results demonstrate that the modulatory effects of opioids on 5-HT release are receptor-specific and state-dependent, indicating the complex nature of the roles of different opioids in regulating hibernation.

Amino Acid Sequence↗
PubMed1993

Thermoregulatory responses following injection of 5-hydroxytryptamine into the septohippocampal complex in rats.

The present study investigated the change in thermoregulatory responses following microinjection of 5-hydroxytryptamine (5-HT) into the lateral septum and the hippocampus of unanesthetized, unrestrained rats. Intraseptal injection of 5-HT (5 to 20 micrograms) caused a dose-related fall in core temperature (Tb), which was associated with a decrease in heat production (HP). As the decrease in HP can not completely account for the magnitude of the decrease in Tb, increase in heat loss may also be involved in the 5-HT-induced hypothermia. In contrast to observed changes following intraseptal injection, no significant change in either Tb or HP was observed after microinjection of the same doses of 5-HT into the hippocampal areas, indicating that the hypothermic response to intraseptal injection of 5-HT is site specific. Further, the hypothermic response to intraseptal injection of 5-HT was only attenuated by systemic pretreatment with cyproheptadine, but not by naloxone or scopolamine, indicating that the hypothermic response is mediated by 5-HT receptor, but not by endogenous opioid and cholinergic systems.

Animals↗
PubMed1993

Age-dependent change in the inhibitory effect of an adenosine agonist on hippocampal acetylcholine release in rats.

To investigate the possibility that age-dependent deficits in acetylcholine (ACh) release are precipitated by the alteration of endogenous purinergic activities, the effects of (-)N6-phenylisopropyladenosine (PIA), an adenosine agonist, in modulating K+ (25 mM)-induced [3H]ACh release from the hippocampal slices of young (3-6 months old) and old rats (26-30 months old) were examined. In young rats, PIA (0.1-10 microM) caused a dose-related inhibition of [3H]ACh release from the hippocampal slices and a significant reduction in [3H]ACh release was observed in the presence of 1 microM PIA. In old rats, a similar pattern of PIA suppression of K(+)-induced [3H]ACh release was observed; however, a 10-fold higher concentration of PIA (10 microM) was required to elicit a significant inhibition. This age-dependent reduction in responsiveness to PIA may be due to an enhanced endogenous adenosine activity in aged rats leading to downregulation of the adenosine receptors. This notion is supported by the finding that both the adenosine concentration and activity of 5'-nucleotidase, an enzyme partially governing adenosine synthesis, were increased in the hippocampus of old rats as compared to their younger counterparts.

Acetylcholine↗
PubMed1993

Studies on cryopreservation of third-stage larvae of Parastrongylus cantonensis.

Attempts have been made to increase the survival rate of third-stage larvae of Parastrongylus cantonensis during cryopreservation. Parasites were obtained from experimentally infected snails, Biomphalaria glabrata. The maximum non-toxic concentrations of cryoprotectants dimethyl sulphoxide (DMSO) and glycerol were determined as 10% v/v in NCTC 109 medium. Different pre-cooling times and serum additives were assayed to determine their effects on the viability of larvae. Larvae pre-cooled at -20 degrees C for 15-20 minutes before transfer to -70 degrees C had the optimum survival rate. The presence of serum was essential for further cooling to -196 degrees C. There were no differences between native and heat-inactivated sera on the larval viability. The survival of larvae recovered after storage at -196 degrees C was higher in sera collected from the rat, man, or fetal calf than in sera collected from the mouse, dog, or horse. Viability assessed by mouse-infections showed that thawed larvae retained infectivity for susceptible hosts, but it was significantly lower than that of unfrozen control worms.

Angiostrongylus cantonensis↗
PubMed1993

Prevalence of larval helminths in freshwater snails of the Kinmen Islands.

A survey of larval helminths in freshwater snails of Kinmen was conducted from 1986 to 1987. Parasitological examinations of a total of 726 live snails collected from 25 loci revealed that 20 of 80 Bithynia fuchsiana were infected with metacercariae of Echinostoma gotoi and 36 with metacercariae of other echinostomes. Among 57 Radix auricularia swinhoei snails, 27 were infected with echinostomes and eight with metacercariae of other flukes. Of 20 Cipangopaludina chinensis, 18 were found with larvae of echinostomes. Larval trematodes were also found in three of 37 Austropeplea ollula and two of 87 Gyraulus spirillus. Third-stage larvae of Parastrongylus cantonensis were found in Ampullarius canaliculatus (5/103), Sinotaia quadrata (20/141), Hippeutis umbilicalis cantori (1/70) and Gyraulus spirillus (2/87). Segmentina hemisphaerula were not infected. Cercariae of Centrocestus formosanus, Haplorchis pumilio and a xiphidiocercaria were found in three, two and two specimens, respectively, of 37 Thiara tuberculata.

Animals↗
PubMed1993

Sleep and mammalian hibernation: homologous adaptations and homologous processes?

Evidence from electroencephalographic, thermoregulatory and cellular neurophysiological studies suggests that sleep and hibernation may be homologous adaptations for energy conservation. However, despite the similarities between non-rapid eye movement (NREM) sleep and hibernation, the restorative function normally associated with slow wave sleep appears not to occur during hibernation, perhaps because of the low body temperature (Tb). Cellular neurophysiological studies also suggest that a bout of hibernation is not exclusively NREM sleep but is punctuated by periods of wakefulness. The entrance to hibernation involves both an inhibition of cortical activity and activation of hypothalamic regions, whereas the arousal from hibernation is primarily a hypothalamic function. Multiple neurochemical systems are affected by the arousal state change that occurs in hibernation, and a serotonergic-opiatergic interaction, in particular, may be important in regulating these events. Among regulated physiological systems affected by arousal state changes, the episodic respiration evident in hibernation shows striking similarities to the apneas observed during sleep in both humans and other mammals. Although the slight down-regulation of Tb and metabolism that accompanies the transition from wakefulness to NREM sleep may have served as a preadaptation for the evolution of hibernation among the mammals, increasing consideration must be given to the possibility that hibernation represents an arousal state distinct from any known normothermic arousal state.

Animals↗
PubMed1993

RAG-1 and RAG-2 are not sufficient to direct all phases of immunoglobulin gene rearrangement in pre-B-cell lines.

To probe the factors controlling immunoglobulin heavy-chain gene rearrangement, we analyzed Abelson virus-transformed pre-B-cell lines that fail to undergo VH-to-DJH joining at an appreciable frequency. Despite this feature, some of these cell lines (rechi) rearrange an extrachromosomal recombination substrate at levels normal for transformed pre-B cells. Others (reclo) rearrange these substrates at levels characteristic of nonlymphoid hematopoietic cells. The DJH rearrangements from a representative rechi cell line were aberrant, suggesting that these cells probably fail to complete heavy-chain gene assembly because some of the necessary cis-acting signals are missing. In contrast, both DJH rearrangements from a reclo cell line appeared normal in structure, indicating that trans-acting factors necessary for recombination might be missing. Introduction of the RAG-1 and RAG-2 genes, genes encoding two such factors, failed to confer a rechi phenotype to these cells. However, fusion of the reclo cells to a rechi cell line generated a high frequency of rechi hybrids. In addition, most of the hybrids rearranged the endogenous kappa light-chain locus. Neither the rechi phenotype nor kappa-chain rearrangement correlated with levels of RAG-1 and RAG-2 expression in all of the hybrids. Thus, both gene transfer and cell fusion experiments indicate that RAG-1 and RAG-2 are not sufficient to activate immunoglobulin gene recombination in at least some pre-B-cell lines. In addition, the fusion experiments suggest that two gene products in addition to RAG-1 and RAG-2 may be required for kappa-gene rearrangement.

3T3 Cells↗
PubMed1993

Effects of temperature and pH on cardiac myofilament Ca2+ sensitivity in rat and ground squirrel.

Chemically skinned papillary muscles from active and hibernating ground squirrels were used to determine whether the enhanced cardiac contractility observed in hibernation is due to a change in myofilament Ca2+ sensitivity. A similar preparation from rats was used to reflect the changes in a nonhibernator. When examined at pH 7.00 in all three groups and under physiological pH with varying temperatures in the ground squirrels, the calcium concentration at which muscle tension is at 50% maximum (pCa2+50) decreased significantly (P < 0.05) with decreasing temperature (25, 15, and 5 degrees C). When hibernating and active ground squirrels were compared, no significant difference in pCa2+50 was observed at 25 degrees C; however, the values at 15 and 5 degrees C were significantly higher (P < 0.05) in the hibernating squirrels. The results indicate that cardiac myofilament Ca2+ sensitivity decreases significantly at low temperature in both active and hibernating ground squirrels; however, the higher Ca2+ sensitivity in the hibernating squirrels at 15 and 5 degrees C could partially contribute to the enhanced cardiac contractility typically seen during hibernation.

Actin Cytoskeleton↗
PubMed1992

Central role for differential gene expression in mammalian hibernation.

Mammalian hibernators experience dramatic reductions in body temperature, metabolic rate, respiratory rate, and heart rate during hibernation. These changes are precisely controlled and reversible with only internally driven mechanisms, suggesting specific biochemical regulation. We present a model that integrates our observations of differential liver gene expression during preparation for, and maintenance of, the hibernating state, with the known phylogenetic interspersion of hibernating species in several major mammalian lineages. This model predicts a major role for the differential expression of existing mammalian genes in the biochemical regulation of hibernation.

Animals↗