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L H Lin

Publications and source records attributed to L H Lin.

At least 37 records · Page 2Linked to original sources
PubMed1997

Up-regulation of nitric oxide synthase and its mRNA in vagal motor nuclei following axotomy in rat.

Effects of vagotomy on nitric oxide synthase (NOS) protein and mRNA levels in the dorsal motor nucleus of vagus (DMV) and nucleus ambiguus (NA) of rats were examined by nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) staining, brain NOS (bNOS) immunostaining and in situ hybridization. NADPH-d staining and bNOS immunoreactivity increased in neurons of the ipsilateral DMV and NA 5, 10, and 20 days after vagotomy. These changes were not observed in unoperated or sham-operated rats. In situ hybridization showed that bNOS mRNA levels were also elevated in neurons of DMV and NA on the operated side. Our results suggest that transection of vagal efferents up-regulates bNOS and its mRNA expression in the DMV and NA.

Animals↗
PubMed1996

Region-specific changes in GABAA receptor delta subunit mRNA level by tolerance to and withdrawal from pentobarbital.

The aim of this study was to investigate whether the mRNA level of gamma-aminobutyric acid (GABA)A receptor delta subunit could be altered by chronic pentobarbital treatment. Male ICR mice were rendered tolerant to and dependent upon pentobarbital by repeated pentobarbital administration and by abrupt pentobarbital withdrawal, respectively. The levels of the delta subunit mRNA in the frontal cortex and cerebellum were quantified using RNase protection assay in the presence of the housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase, as an internal standard. Our results revealed that the delta subunit mRNA in the cerebellum was upregulated in pentobarbital-tolerant mice and was downregulated in pentobarbital-withdrawn mice. No significant changes were found in the frontal cortex. These results suggest that chronic pentobarbital exposure can modify the expression of GABAA receptor delta subunit in a region-specific manner.

Animals↗
PubMed1996

Differential expression of placental (P)-cadherin in sertoli cells and peritubular myoid cells during postnatal development of the mouse testis.

BACKGROUND: In previous work, RNA transcripts for placental (P)-cadherin, a calcium-dependent cell adhesion molecule, were identified in the rat testis during the first 4 weeks of postnatal development. However, the cells in the testis responsible for P-cadherin expression have not yet been identified. METHODS: We used conventional epifluorescence microscopy to examine P-cadherin immunoreactivity in cryostat sections of mouse testis and scanning laser confocal microscopy to localize P-cadherin and beta-catenin in wholemount preparations of mouse seminiferous tubules. We used fluorescent phalloidin to identify actin filaments. RESULTS: Sertoli cells expressed P-cadherin on postnatal days 1, 3, and 8, but not on any day thereafter. In contrast, peritubular cells did not express P-cadherin on postnatal day 8 and continued expression in adulthood. beta-Catenin was localized near contact areas between peritubular cells on postnatal days 12 and 15. A mature pattern of actin filament organization in peritubular cells appeared on day 15 and coincided with the uniform appearance of P-cadherin and beta-catenin near areas of contact between adjacent peritubular cells. CONCLUSIONS: During postnatal development of the testis, the earlier expression of P-cadherin by Sertoli cells is replaced by the subsequent expression of P-cadherin by peritubular cells. The expression of P-cadherin in peritubular cells is correlated temporally with the expression of beta-catenin and the development of a mature network of actin filaments and is consistent with a role in intercellular adhesion and junction formation.

Aging↗
PubMed1996

Sex-dependent expression of placental (P)-cadherin during mouse gonadogenesis.

BACKGROUND: Placental (P)-cadherin is one of a family of cell adhesion molecules that participate in embryonic sorting and organogenesis. In previous work, P-cadherin was localized to Sertoli cells in the mouse testis as early as postnatal day 1. This early postnatal localization raised questions about when P-cadherin first appeared in the embryonic testis and whether P-cadherin was expressed differentially in the embryonic testis and ovary. METHODS: The localization of P-cadherin, epithelial (E)-cadherin, and Müllerian inhibiting substance was determined in frozen sections of mouse gonads between embryonic days 10.5 and 18 using indirect immunohistochemistry. Alkaline phosphatase reactivity was used to identify germ cells. RESULTS: The expression of P-cadherin was traced back to the indifferent stage of gonadogenesis where uniform distribution was observed in the indifferent gonad of both sexes. However, after sexual differentiation, the expression of P-cadherin in the testis was localized to Sertoli cells in the testicular cords, while its expression in the ovary fell below detectable levels. CONCLUSIONS: The localization of P-cadherin in the male and female indifferent gonad is similar and cannot be used to distinguish the future testis and ovary. The localization of P-cadherin in the testis after sexual differentiation suggests a role for P-cadherin in testicular cord formation. The common temporal pattern of P-cadherin and Müllerian inhibiting substance expression in Sertoli cells is consistent with a shared regulatory mechanism.

Aging↗
PubMed1996

Applicability of short-lived radiometallic nuclide for high sensitivity two-site "sandwich" immunoradiometric assay: human growth hormone assay.

The sensitivity of the IRMA method is limited by the specific activity (SA) of the conventionally employed radioisotropic label and high sensitivity radioimmunoassay should theoretically be attained by the use of short-lived radiometallic nuclides. Our group have achieved radiolabeling of high SA IgG by using the radiometal, gallium-67 (67Ga) with a short half-life (T1/2 = 78 h) and deferoxamine (DF), a bifunctional chelating agent bound through a multispacer (dialdehyde starch, DAS) as the linker (J Nucl Med 32:825, 1991). In the present work, the application of the approach is attempted by employing a two-site IRMA for human growth hormone (hGH); the monoclonal antibody to hGH (MAB2) is bound to DF via DAS and the coupled DF-DAS-MAB2 is radiolabeled with 67Ga. The 67Ga-DF-DAS-MAB2 of high SA (4,884 MBq/mg versus 370-518 MBq/mg calculated for radioiodinated MAB2) was thus used for the two site 'sandwich' 67Ga-IRMA. Excellent correlation with the 125I-IRMA was registered, and higher detection capability obtained by using 67Ga over the 125I in the hGH IRMA offered a good basis for the exploitation of short-lived radio-nuclides in the IRMA system.

Antibodies, Monoclonal↗
PubMed1995

A monoclonal antibody identifies vimentin filaments in Sertoli cells and in a subset of epithelial cells in the rat epididymis, urinary bladder, and prostate.

PURPOSE: We describe a monoclonal antibody (Mab B2) against vimentin filaments in rat Sertoli cells and in a subset of epithelial cells in the rat epididymis, prostate and urinary bladder. MATERIALS AND METHODS: The immunoreactivity of Mab B2 was examined on cryostat sections and immunoblots and compared with the reactivity of a previously characterized monoclonal antibody against vimentin. RESULTS: While both antibodies recognized vimentin in Sertoli cells, only Mab B2 recognized vimentin in urogenital tract epithelia. CONCLUSIONS: Vimentin is expressed in the urogenital tract, and differential reactivities of antibodies may be responsible for conflicting results reported elsewhere for vimentin expression.

Animals↗
PubMed1994

Head-direction cells in the rat posterior cortex. I. Anatomical distribution and behavioral modulation.

We examined the behavioral modulation of head-directional information processing in neurons of the rat posterior cortices, including the medial prestriate (area Oc2M) and retrosplenial cortex (areas RSA and RSG). Single neurons were recorded in freely moving rats which were trained to perform a spatial working memory task on a radial-arm maze in a cue-controlled room. A dual-light-emitting diode (dual-LED) recording headstage, mounted on the animals' heads, was used to track head position and orientation. Planar modes of motion, such as turns, straight motion, and nonlocomotive states, were categorized using an objective scheme based upon the differential contributions of movement parameters, including linear and angular velocity of the head. Of 662 neurons recorded from the posterior cortices, 41 head-direction (HD) cells were identified based on the criterion of maintained directional bias in the absence of visual cues or in the dark. HD cells constituted 7 of 257 (2.7%) cells recorded in Oc2M, 26 of 311 (8.4%) cells in RSA, and 8 of 94 (8.5%) cells in RSG. Spatial tuning of HD cell firing was modulated by the animal's behaviors in some neurons. The behavioral modulation occurred either at the preferred direction or at all directions. Moreover, the behavioral selectivity was more robust for turns than straight motions, suggesting that the angular movements may significantly contribute to the head-directional processing. These behaviorally selective HD cells were observed most frequently in Oc2M (4/7, 57%), as only 5 of 26 (19%) of RSA cells and none of the RSG cells showed behavioral modulation. These data, taken together with the anatomical evidence for a cascade of projections from Oc2M to RSA and thence to RSG, suggest that there may be a simple association between movement and head-directionality that serves to transform the egocentric movement representation in the neocortex into an allocentric directional representation in the periallocortex.

Animals↗
PubMed1994

Head-direction cells in the rat posterior cortex. II. Contributions of visual and ideothetic information to the directional firing.

This study investigated the effects of visual and ideothetic cues on the spatial tuning of head-direction (HD) cells recorded in the rat posterior cortices. Extracellular, single unit responses were recorded from animals performing each of two different tasks, a spatial working memory task on a radial-arm maze and a passive rotation task on a modified "lazy Susan" platform. The influence of visual cues was assessed by manipulating the position of one white and three black cue-cards placed around the maze. We found three major categories of HD cells based on their response to cue manipulations in the maze tasks. Type A cells (10/41) rotated their preferred directions along with the rotation of the cues. The majority (type B, 25/41) of the HD cells were unaffected by the rotation of visual cues, maintaining their established preferred direction. Type C cells (6/41) showed complex responses to cue rotation, with the preferred direction reflecting either a combination of both type A and type B responses or an unpredictable response. The results indicate that the internal representation of directionality can be calibrated by visual cues and that some mnemonic processes may have been involved in the registration of the previous cue locations. Eleven cells were tested in both the maze task and the passive rotation task. Most (9/11) showed a significant directionality in the former task, but showed either no or weak directionality in the latter task, suggesting that movement-related ideothetic cues may be used in supporting the directional firing of these cells. Only two cells showed significant directionality in both tasks. Their established preferred directions did not rotate along with the cues in the maze task, but did rotate with the cues in the passive rotation task. We conclude that the dynamic aspect of the directional tuning in these cortical HD cells may represent on-line calibration of an angular coordinate representation.

Animals↗
PubMed1994

Modification of cysteine residues within G(o) and other neuronal proteins by exposure to nitric oxide.

Nitric oxide (NO), a free-radical gas produced endogenously by some neurons, functions as a diffusible intercellular messenger and appears to play a role in activity-dependent modification of synaptic efficacy in the mammalian CNS. The molecular targets and mechanisms of action of NO in neurons remain largely uncharacterized. Employing in vitro brain slices and isolated synaptosomes, we show here that exposure to exogenous or endogenously generated NO results in the modification of cysteine residues within neuronal proteins, as revealed by reduced binding of agents which react with cysteine sulfhydryls. In particular, exposure of synaptosomes to NO inhibits subsequent thiol-linked ADP-ribosylation of the heterotrimeric G-protein, G(o), by pertussis toxin. Our results demonstrate directly that NO may exert its neuronal effects through modification of protein cysteine thiols, and identify G(o) as a potential synaptic target of NO.

Animals↗
PubMed1994

Inhibition of protein kinase C- and casein kinase II-mediated phosphorylation of GAP-43 by S100 beta.

The effect of the glial-derived protein, S100 beta, on the in vitro phosphorylation of the growth-associated protein GAP-43 was investigated. S100 beta inhibited in a dose dependent manner the phosphorylation of GAP-43 by protein kinase C (PKC) or by casein kinase II (CKII). S100 beta appeared to slow down the rate and the degree to which GAP-43 can be phosphorylated by either kinase. The specificity of the inhibition was demonstrated by the observation that the phosphorylation of two other CKII substrates, casein and a selective peptide substrate, was not inhibited by S100 beta. The marked inhibitory effect of S100 beta required the presence of calcium in the phosphorylation reactions. In addition, S100 beta inhibition of GAP-43 phosphorylation was seen with GAP-43 purified under a variety of conditions that alter acylation, suggesting that the acylation state of GAP-43 does not affect the ability of S100 beta to modulate CKII- or PKC-mediated phosphorylation of GAP-43.

Amino Acid Sequence↗
PubMed1994

Experimental transfer of Paragonimus westermani from rodents to rodents following subcutaneous and intraperitoneal routes.

In order to investigate the experimental transfer of Paragonimus westermani from rodents to rodents following subcutaneous and intraperitoneal routes, 13 rats and 23 mice were inoculated with a total of 115 (1 mature and 114 immature) worms of P. westermani subcutaneously and intraperitoneally. The age of worms before transfer was 25-193 days. The transfer was performed immediately after worm collection from rodents which were killed at various intervals from 4 to 144 days after infection. The location, development and size of worms were recorded. An infection rate of 58% (or 21/36) was demonstrated in rodents after experimental transfer of P. westermani by intraperitoneal and subcutaneous routes. Twenty-seven worms were recovered, giving a worm recovery rate of 23.5%. The rate was significantly higher by the subcutaneous route (34.8%) than by the intraperitoneal route (20.7%) but no difference was found between mice (23.9%) and rats (23.0%). The sizes of worms in the abdominal cavity, pleural cavity and thoracic muscles of mice, and in the leg muscles of rats were much less than in the pleural cavity and lung cysts of rats. A mature worm (7 x 5 mm) and numerous eggs were found in the uterus and pleural cavity of one rat. It is evidence that these rodents are unfavourable definitive hosts of P. westermani, because the worm size, infectivity, maturation and egg production are usually very low. However, the worms are usually widely distributed in their rodent hosts and remain small in size for a long period. Therefore, these rodents are good paratenic hosts for P. westermani and can play an important role in infecting cats and dogs with P. westermani in the laboratory.

Animals↗
PubMed1993

Laparoscopic Meckel's diverticulectomy in infants: report of three cases.

Three infants younger than 2 years presented with episodic bloody-to-tarry stool of moderate amount. Two of them were diagnosed to have Meckel's diverticulum because of a positive 99mTc pertechnetate scan. Although the third infant had two negative radionuclide scans within 3 months, Meckel's diverticulum was still suspected by exclusion studies. All three infants underwent laparoscopic surgery. At laparoscopy, a Meckel's diverticulum was identified in all. Besides, an ileoileo intussusception just proximal to the diverticulum was also found in one patient. Reduction of the intussusception and diverticulectomy were performed successfully by laparoscopic procedure. Compared with conventional laparotomy, this procedure has the advantages of direct preoperative visual confirmation of the diagnosis, less traumatic access, much shorter recovery period and perhaps fewer intraoperative and postoperative complications. And thus, laparoscopic surgery has the potential of becoming regular treatment for symptomatic Meckel's diverticulum of infants.

Female↗
PubMed1993

Enflurane inhibits NMDA, AMPA, and kainate-induced currents in Xenopus oocytes expressing mouse and human brain mRNA.

Effects of enflurane, an inhalational anesthetic, on NMDA, AMPA, and kainate-gated currents were examined in Xenopus laevis oocytes expressing mouse or human brain mRNA. In oocytes expressing mouse mRNA, enflurane at an anesthetic concentration (1.8 mM) inhibited the NMDA-, AMPA-, and kainate-induced currents by 29-40%, 30-33%, and 20-27%, respectively, suggesting that all three glutamate ionotropic receptors are susceptible to suppression by inhalational anesthetics. Furthermore, inhibition by enflurane was independent of the concentrations of the agonists (NMDA, AMPA, and kainate) or the NMDA-coagonist (glycine). This suggests that enflurane inhibition does not result from a competitive interaction at glutamate or glycine binding sites. Enflurane also suppressed the oscillation and apparent desensitization of NMDA currents, suggesting an inhibition of Ca2+ influx through the NMDA channel. In oocytes expressing human brain mRNA, only kainate produced observable currents. Kainate currents of human channels were smaller in size than those of the mouse; however, the kainate concentration-response curve and percent inhibition (27-29%) by enflurane were similar for mice and humans. The results suggest that human and mouse kainate receptors have similar pharmacological characteristics.

Aged↗
PubMed1993

Molecular determinants of general anesthetic action: role of GABAA receptor structure.

Using receptors expressed from mouse brain mRNA in Xenopus oocytes, we found that enhancement of type A gamma-aminobutyric acid (GABAA) receptor-gated Cl- channel response is a common action of structurally diverse anesthetics, suggesting that the GABAA receptor plays an important role in anesthesia. To determine if GABAA receptor subunit composition influences actions of anesthetics, we expressed subunit cRNAs in Xenopus oocytes and measured effects of enflurane on GABA-activated Cl- currents. Potentiation of GABA-activated currents by enflurane was dependent on the composition of GABAA receptor protein subunits; the order of sensitivity was alpha 1 beta 1 > alpha 1 beta 1 gamma 2S = alpha 1 beta 1 gamma 2L > total mRNA. The results suggest that anesthetics with simple structures may act on the GABAA receptor protein complex to modulate the Cl- channel activity and provide a molecular explanation for the synergistic clinical interactions between benzodiazepines and general anesthetics.

Anesthesia↗
PubMed1993

Experimental infection of Paragonimus westermani in mice and rats.

To determine the infectivity and maturity of metacercariae of Paragonimus westermani after keeping at low temperature for a long period, 45 mice and 45 rats were each infected with 20 metacercariae which were kept at 4 degrees C for 8 to 234 days. The worm recovery in mice increased with age of worm and reached a peak of 32% at 41-50 days and then decreased with age. The rate in rats first decreased to a lowest point of 6% at 71-100 days and then increased with age. In 42 infected mice and 41 infected rats, 187 immature worms (183 tiny and 4 juvenile ones) and 190 worms (164 tiny, 19 juvenile and 7 mature ones) were recovered respectively. Two worm cysts with eggs only and 8 empty worm cysts were also found in the rats. In addition, the frozen metacercariae can still develop to mature worms in SD rats.

Animals↗
PubMed1993

Enflurane inhibits the function of mouse and human brain phosphatidylinositol-linked acetylcholine and serotonin receptors expressed in Xenopus oocytes.

Modulation of the inositol 1,4,5-trisphosphate (IP3)-mediated signal transduction pathway by the inhalational anesthetic enflurane was studied in Xenopus oocytes expressing mouse and human cortical mRNA. We found that enflurane significantly inhibited ion currents activated by m1 muscarinic and 5-hydroxytryptamine (5-HT)1c receptors. This inhibition was dependent upon the concentration of acetylcholine or 5-HT, with large inhibition (80-89%) of low concentrations and small inhibition (8-44%) of high concentrations of acetylcholine and 5-HT. Similar effects were found with either mouse or human receptors. To investigate the mechanism of enflurane action, ion currents induced by intracellular injection of guanosine 5'-(3-O-thio)triphosphate and IP3 were examined. Enflurane strongly suppressed the guanosine 5'-(3-O-thio)triphosphate-activated current but not the IP3-activated current. These results suggest that an inhalational anesthetic can disrupt the function of mouse and human brain phosphatidylinositol-linked receptors by selectively inhibiting the guanine nucleotide-binding protein activity.

Acetylcholine↗