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PubMed1994

Reaction times to neon, LED, and fast incandescent brake lamps.

Standard incandescent brake lamps have a relatively slow rise time. It takes approximately a quarter of a second for them to reach 90% of asymptotic light output, causing potential delays in responses by following drivers. The present study evaluated reaction times to brake signals from standard incandescent brake lamps and from three alternative brake lamps with substantially faster rise times: neon, LED, and fast incandescent. The study, performed in a laboratory, simulated a daytime driving condition. The subject's task was to respond as quickly as possible to the onset of either of two brake lamps in the visual periphery, while engaged in a central tracking task. Brake signals were presented at two levels of luminous intensity. The results showed that reaction times to the alternative brake lamps were faster than to the standard incandescent lamp, with the advantage averaging 166 ms for the LED and neon lamps, and 135 ms for the fast incandescent lamp. A reduction of the signals' luminous intensity from 42 cd to 5 cd increased the reaction time by 84 ms.

Adult↗
PubMed2006

Formation of methanol and formate in Wistar rats after oral administration of methylated rapeseed oil: a fuel for lamps.

Low viscosity, low surface tension and low volatility are features of lamp oils contributing to chemical pneumonia that can occur after ingestion. Because lamp oils with such physico-chemical properties have been forbidden in the European Community from July 2000 onward, industry has developed different products, mostly based upon rapeseed oil. The fatty acids of these oils are methylated. The goal of this study is to demonstrate whether methanol is released in Wistar rats after oral administration of these new lamp oils. Applying a dose of 1 ml/kg body weight lamp oil, peak levels of methanol were reached at 1 h (54.6 +/- 18.6 microg/ml), methanol was not detectable at 8 h. After the instillation of 4 ml/kg of lamp oil peak levels occurred at 2 h (189.2 +/- 24.9 microg/ml). The metabolite formate increased with time, and was highest at 8 h after the administration of 1 ml/kg body weight lamp oil (32.9 +/- 2.9 microg/ml). Starvation before the administration of 1 ml/kg body weight lamp oil decreased the methanol serum concentrations, but the differences were not significant. Based upon these experimental data in rats, it can be concluded that in humans small amounts of methanol will be released after ingestion of these lamp oils. As these products are mainly ingested accidentally by toddlers in low quantities, the risk of a methanol intoxication seems to be very low.

Administration, Oral↗
PubMed1993

Increased LAMP-2 polylactosamine glycosylation is associated with its slower Golgi transit during establishment of a polarized MDCK epithelial monolayer.

An endogenous Madin-Darby canine kidney (MDCK) lysosomal membrane glycoprotein that exhibits a basolateral targeting pathway to the lysosome is shown here to exhibit significant N-terminal amino acid sequence identity to lysosomal associated membrane proteins (LAMP-2) of other species. During establishment of the MDCK monolayer after only 1 d of culture, this canine LAMP-2 has a larger molecular size (110 kDa) than following formation of a confluent monolayer after 3 d of culture (100 kDa) due to the increased presence of N-linked polylactosamine oligosaccharide chains. Neither polylactosamine glycosylation of LAMP-2 in MDCK cells nor truncation of N-linked oligosaccharide chains of LAMP-2 in a ricin-resistant MDCK-RCAR cell line influenced the basolateral polarity of its targeting. However, the rate of basolateral delivery of LAMP-2 in MDCK cells plated for 3 d was significantly faster (t1/2 = 28 min) than in 1-d cells (t1/2 = 40 min); in MDCK-RCAR cells the rate of basolateral delivery at both 1 and 3 d of plating was similar (t1/2 = 40 min). The rate differential in MDCK cells occurred after arrival of LAMP-2 to the Golgi apparatus because the rate of acquisition of endoglycosidase H resistance was the same (t1/2 = 25 min) at both days of plating. The rate of transit of LAMP-2 through the Golgi apparatus to the basolateral domain was therefore far more rapid (approximately 4-fold) in 3 d compared with 1-d MDCK cultures. The increased polylactosamine glycosylation of MDCK LAMP-2 at early times of plating during the establishment of a confluent epithelial monolayer may thus be related to its longer residence time in the Golgi apparatus.

Amino Acid Sequence↗
PubMed1998

The extent of polylactosamine glycosylation of MDCK LAMP-2 is determined by its Golgi residence time.

The increased polylactosamine glycosylation of LAMP-2 in MDCK cells cultured for 1 day relative to cells cultured for 3 days has been correlated with its slower rate of Golgi transit (Nabi and Rodriguez-Boulan, 1993, Mol. Biol. Cell., 4, 627-635). To determine if the differential polylactosamine glycosylation of LAMP-2 is a consequence of glycosyltransferase expression levels, the activities of beta1-6GlcNAc-TV, beta1-3GlcNAc-T(i), beta1-2GlcNAc-TI, beta1, 4Gal-T, alpha2-6sialyl-T, and alpha2-3sialyl-T were assayed and no significant differences in the activities of these enzymes in 1 and 3 day cell extracts were detected. During MDCK epithelial polarization, the Golgi apparatus undergoes morphological changes and apiconuclear Golgi networks were more evident in 3 day cells. Treatment with nocodazole disrupted Golgi networks and generated numerous Golgi clusters in both 1 day and 3 day cells. In the presence of nocodazole the differential migration of LAMP-2 in 1 and 3 day MDCK cells was maintained and could be eliminated by treatment with endo-beta-galactosidase, indicating that gross Golgi morphology did not influence the extent of LAMP-2 polylactosamine glycosylation. Nocodazole treatment did, however, result in the faster migration of LAMP-2 which was not due to modification of core N-glycans as the precursor form of the glycoprotein migrated with an identical molecular size. Following incubation at 20 degrees C, which prevents the exit of proteins from the trans-Golgi network, the molecular size of LAMP-2 increased to a similar extent in both 1 and 3 day MDCK cells. Extending the time of incubation at 20 degrees C did not influence the size of LAMP-2, demonstrating that its glycosylation is modified not by its retention within the Golgi but rather by its equivalent slower Golgi passage at the lower temperature in both 1 and 3 day cells. An identical effect was observed in nocodazole treated cells, demonstrating that Golgi residence time determines the extent of LAMP-2 polylactosamine glycosylation, even in isolated Golgi clusters.

Amino Sugars↗
PubMed1993

Cycling of two endogenous lysosomal membrane proteins, lamp-2 and acid phosphatase, between the cell surface and lysosomes in cultured rat hepatocytes.

Our previous studies provided evidence that a 107-kDa major lysosomal membrane glycoprotein termed lamp-1 shuttles between lysosomes and the plasma membrane along the endocytic pathway in rat hepatic cells [Furuno et al. (1989) J. Biochem. 106, 708-716; Furuno et al. (1989) J. Biochem. 106, 717-722]. In the present study, we investigated the movement of a 96-kDa major lysosomal membrane glycoprotein, referred to as lamp-2, and lysosomal acid phosphatase (LAP) in the endocytic membrane transport system of cultured rat hepatocytes. Fab' fragments of anti-lamp-2 and anti-LAP antibodies conjugated with horseradish peroxidase (HRP) were used as probes to analyze quantitatively the transport of these two membrane proteins from the cell surface to lysosomes. After the addition of HRP-anti-lamp-2 and anti-LAP Fab' fragments to the culture medium, the delivery of the antibody conjugates to lysosomes was examined by cell fractionation on a Percoll density gradient. The amount of these HRP tracers in the lysosomal fraction became larger as the period of cell incubation was increased. Km values for uptake of HRP-anti-lamp-2, and LAP Fab' fragments were 0.74 and 0.62 microM, respectively, which were comparable to that of HRP-anti-lamp-1 Fab' (0.57 microM). The endocytic process of the two HRP-antibodies continued for an extended period in the cells exposed to the protein synthesis inhibitor, cycloheximide. Furthermore, we measured the transit times of HRP-anti-lamp-1, anti-lamp-2, and anti-LAP Fab' fragments from the cell surface to lysosomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Phosphatase↗
PubMed1994

Molecular control of melanogenesis in malignant melanoma: functional assessment of tyrosinase and lamp gene families by UV exposure and gene co-transfection, and cloning of a cDNA encoding calnexin, a possible melanogenesis "chaperone".

Melanogenesis is a cascade of events significantly controlled by regulatory genes which are associated with the melanosomal membrane. This report introduces our current research efforts dealing with (a) the gene and protein expressions of tyrosinase and Lamp (lysosome-associated membrane protein) families by human melanoma cells after repeated exposures to UV light, (b) the coordinated alterations in the expression of the Lamp family gene and its encoding product after transfection of two genes of the tyrosinase family in human melanoma cells and (c) cloning and sequencing of a Ca(2+)-binding phosphoprotein, calnexin, which could be a candidate as a chaperone for sorting and maturation of tyrosinase and Lamp family glycoproteins in melanogenesis cascade. Our UV exposure study, as well as gene transfection and antisense hybridization experiments, has clearly indicated a marked and coordinated interaction of the Lamp-1 gene with the tyrosinase and TRP-1 genes in this process. We propose that melanogenesis is controlled at least by two major gene family products, i.e., (a) the tyrosinase family of tyrosinase, TRP-1 and TRP-2, and the Lamp family of Lamp-1, Lamp-2 and Lamp-3. These two gene families probably derived from primordial melanogenesis-associated genes which are common or closely related to each other.

Antigens, CD↗
PubMed2006

Lysosome-associated membrane protein 1 (LAMP-1) in Alzheimer's disease.

Lysosome-associated membrane protein 1 (LAMP-1) is a glycoprotein highly expressed in lysosomal membranes. The present study was initiated to test LAMP-1 mRNA and protein levels in post mortem frontal cortex (area 8) of Alzheimer's disease (AD) stages I-IIA/B and stages V-VIC of Braak and Braak, compared with age-matched controls. TaqMan PCR assays and Western blots demonstrated upregulation of LAMP-1 mRNA and protein in the cerebral cortex in ADVC. In addition, immunohistochemical studies have shown increased LAMP-1 immunoreactivity in neurones, and in glial cells surrounding senile plaques, in AD cases. Interestingly, LAMP-1 immunoreactivity has little correlation with phosphorylated tau deposition and neurofibrillary tangles (NFTs), as neurones with NFTs were rarely LAMP-1 immunoreactive. In contrast, LAMP-1 expression was enhanced in neurones with granulovacuolar degeneration. Finally, LAMP-1 occurred in microglia and multinucleated giant cells in one AD case in whom amyloid burden was cleared following betaA-peptide immunization. These findings support the participation of lysosomes in betaA-amyloid and, probably, in hyperphosphorylated tau turnover in AD.

Aged↗
PubMed1988

Pre-lysosomal divergence of alpha 2-macroglobulin and transferrin: a kinetic study using a monoclonal antibody against a lysosomal membrane glycoprotein (LAMP-1).

We have used electron microscopic immunocytochemistry to compare the distribution of LAMP-1, a marker for lysosomal membranes, with the intracellular localization of alpha 2-macroglobulin (alpha 2-M) and transferrin at various time points after their endocytosis into cultured NIH 3T3 cells. The purposes of this study were (a) to determine how soon endocytic ligands reach lysosomal organelles, (b) to examine whether the intermediate endocytic vesicles gained lysosomal markers gradually or in a precipitous, discrete event, and (c) to examine the relationship, if any, between the pathway of recycling ligands and lysosomes. At early time points (0-5 min) after initiation of endocytosis, most structures containing alpha 2-M labeled with colloidal gold (receptosomes) were not labeled by anti-LAMP-1 detected using ferritin bridge or peroxidase immunocytochemistry. At late time points (greater than or equal to 15 min), the structures containing alpha 2-M (lysosomes) were strongly labeled by anti-LAMP-1. In contrast, transferrin that was directly labeled with ferritin was mostly located in LAMP-1-negative structures at all time points studied. The proportion of alpha 2-M-gold containing vesicles strongly labeled for LAMP-1 roughly paralleled the proportion of alpha 2-M-gold-containing structures positive for cytochemically detectable acid phosphatase. Our data indicate that ligands such as transferrin that are internalized through coated pits and receptosomes, but not delivered to lysosomes, do not traverse a lysosomal organelle compartment as marked by LAMP-1 content. Ligands such as alpha 2-M that are destined for lysosomal delivery reach a LAMP-1-positive organelle compartment only after they traverse LAMP-1-negative, non-lysosomal vesicles previously described as receptosomes.

Acid Phosphatase↗
PubMed2004

Extremely elevated relative risk of paraffin lamp oil exposures in Orthodox Jewish children.

BACKGROUND: In observance of the Sabbath and other religious holidays, many Orthodox Jews maintain a burning lamp that uses paraffin lamp oil as fuel. Unintentional pediatric exposure to paraffin lamp oil, a hydrocarbon, is typically by ingestion and carries a risk of aspiration with subsequent pneumonitis. This investigation was prompted by an apparent increase in paraffin lamp oil exposures during the Jewish Sabbath, from sunset Friday until sunset Saturday, noted by the staff of our regional poison control center. OBJECTIVE: In this investigation, we retrospectively reviewed all exposures to paraffin lamp oil occurring in our large city in children <18 years old reported to our regional poison control center between January 1, 2000, and February 1, 2003. Reports were investigated to ascertain the frequency of occurrence of paraffin lamp oil exposures on the Jewish Sabbath and Jewish religious holidays. Caregivers of involved children were surveyed by telephone to determine the exposed child's religion and circumstances of exposure. RESULTS: During these 25 months, 45 cases met inclusion criteria, and all were ingestions. Orthodox Jews accounted for 32 cases (71%), 4 cases (9%) occurred in children who were not Orthodox Jews, and demographic data were unavailable in 9 cases (20%). Twenty-four cases (53%) occurred within 10 hours before or during the Jewish Sabbath or Jewish religious holidays. The relative risk of Orthodox Jewish children to ingest paraffin lamp oil, calculated by using census data, is 374 times that of other children. CONCLUSIONS: Public health authorities and caregivers of Orthodox Jewish children should be cognizant of this phenomenon. Educational efforts directed toward both Orthodox Jews and the general public aimed at preventing paraffin lamp oil exposures are warranted.

Child↗
PubMed1998

The effect of farrowing crate heat lamp location on sow and pig patterns of lying and pig survival.

Three experiments were conducted to study sow and pig behavior during the 1st 3 d after birth and pig survival during the 1st 2 wk after farrowing. In Exp. 1, 23 sows were housed in conventional farrowing crates that were divided into five sections: a .5- x 1.5-m front creep section and the remaining area divided into four sections, .75 x 1.05 m each. Air temperature was maintained at 19 degrees C, and a 250-W heat lamp was placed at the right side of the front creep in Treatment 1 (T1), or in the creep at the right side of the sow for Treatment 2 (T2). The percentage of pigs within 8 cm of the sow's trunk was not affected by treatment, but it decreased (P < .001) from 61.8 +/- 3.4% on d 1 to 28.1 +/- 3.5% on d 3. As the percentage of pigs near the sow decreased, the percentage of pigs within the section containing the heat lamp increased (T1, P < .05; T2, P < .10). Experiment 2 involved 15 sows and litters housed as in Exp. 1, except that heat lamps were not provided, and average air temperature was 27.3 +/- .2 degrees C during behavioral observations. Even though the portion of the litter near the sow decreased (P < .001) from d 1 to d 3 (d 1, 57.0 +/- 3.4%; d 2, 42.9 +/- 3.3%; d 3, 31.7 +/- 3.3%), pigs did not concentrate in any specific section as they moved away from the sow. The average number of pigs within the front creep section (Section 1) for the 3-d period was less than (P < .01) the number in any other crate section. Experiment 3 involved 147 sows and tested the effect of solid creep floor covering on pig survival for each of the heat lamp locations used in Exp. 1. Neither heat lamp location nor floor covering affected pig survival. During the 1st 3 d of life, pigs tend to lie near the sow regardless of heat lamp location or air temperature. Heat lamp position and floor covering under the lamp do not affect pig survival.

Animals↗
PubMed2004

Leadership, administration, management, and professionalism (LAMP) in physical therapy: a Delphi study.

BACKGROUND AND PURPOSE: The knowledge and skills needed by physical therapists entering practice in the areas of leadership, administration, management, and professionalism (LAMP) are not known. Using the LAMP components identified by American Physical Therapy Association's Section on Administration, this study sought to define the range of LAMP content pertinent to physical therapy clinical management and to explore LAMP knowledge and skills required of physical therapists upon entry into the profession. SUBJECTS AND METHODS: Thirty-four physical therapist managers participated in a Delphi study to (1) create a comprehensive list of defined LAMP components, (2) determine the perceived importance of each component in the management of clinical practices, and (3) identify the level of knowledge and skill for each component believed to be necessary for a new physical therapist graduate. RESULTS: Respondents agreed that 178 items should be on the LAMP component list. They perceived that almost all LAMP components are important in the management of a clinical practice, and they indicated that new graduates needed moderate to extensive knowledge in 44% of them. They believed that new graduates needed no skill in 29% of the components, whereas they needed at least intermediate skill for 22% of them. Top-ranked component categories across the 3 scales (importance, knowledge, and skill) were communication, professional involvement and ethical practice, delegation and supervision, stress management, reimbursement sources, time management, and health care industry scanning. DISCUSSION AND CONCLUSION: This study provides a basis for further exploration of which LAMP components should be included in professional (entry-level) physical therapist curricula and which components should be learned after graduation.

Delphi Technique↗
PubMedDate not supplied

Polymerization efficiency of curing lamps: a universal energy conversion relationship predictive of conversion of resin-based composite.

A universal energy-conversion relationship (ECRu) predictive of conversion of a resin-based composite (RBC) polymerized with any light source has been described. This relationship was derived from an energy conversion relationship for RBC polymerized with a tungsten-halogen lamp and the lamp's efficiency relative to a hypothetical standard lamp. The ECRu was then used to predict conversion throughout RBC polymerized with an LED lamp using the lamp's relative efficiency compared to the standard lamp. The universal energy scale has also been described as predictive of scrape-back lengths for this RBC family when polymerized with any light source. Despite a 31% greater relative efficiency, scrape-back lengths from RBC polymerized using the LED lamp were predicted to be only 6% greater than those polymerized with the tungsten-halogen lamp when RBC is polymerized on an equal energy basis. This result was experimentally verified.

Algorithms↗
PubMed2004

[Differences in plant hormone level of cucumber seedlings grown under sulfur or xenon lamp].

The primary mechanism of growth difference of cucumber (Cucumis sativus L.) seedlings cultured under sulfur lamp and xenon lamp in a phytotron was investigated. Compared with cucumber seedlings grown under xenon lamp, those under sulfur lamp were shorter, and the cell number in the middle hypocotyls epidermis and cortex of them were more (Fig. 1, Table 1). Endogenous hormone analysis indicates that the content of IAA and GA(3) of seedlings under sulfur lamp were 17% and 24% lower, while ABA content was 31% higher than that under xenon lamp (Fig. 2). Based on these results, it is suggested that the growth difference between cucumber seedlings grown under sulfur lamp and under xenon lamp might be related to the control of endogenous hormones.

Cucumis sativus↗
PubMed1996

The lysosomal granule membrane protein, LAMP-2, is also present in platelet dense granule membranes.

Lysosomal Associated Membrane Protein-2 (LAMP-2) is an inherent component of lysosomal granule membranes in diverse cell types, including platelets. We examined platelets for evidence of LAMP-2 in dense granule membranes as CD63 has previously been shown to be present in both lysosomal and dense granule membranes. Immunological techniques were used to examine the localization of LAMP-2 in control platelets and those from an individual with Hermansky-Pudlak syndrome (HPS), a condition characterised by platelet dense granule deficiency. Immunoblotting studies demonstrated that LAMP-2 was enriched in a dense granule preparation. Flow cytometry of thrombin-stimulated control platelets was consistent with biphasic surface expression of LAMP-2. The early expression was accompanied by dense granule, but minimal lysosomal granule, release. The late expression was accompanied by additional lysosomal granule release only. Thrombin stimulation of HPS platelets showed only late, lysosome-associated LAMP-2 expression. Immunoelectron microscopy indicated the presence of LAMP-2 in the membranes of serotonin-containing granules as identified by an anti-serotonin polyclonal antibody. These data indicate that LAMP-2 is present in the membranes of platelet dense granules in addition to lysosomal granules, and has a similar distribution to CD63.

Albinism, Oculocutaneous↗
PubMed2002

Complementary expression and heterophilic interactions between IgLON family members neurotrimin and LAMP.

Neurotrimin (Ntm) and the limbic system-associated membrane protein (LAMP) are members of the IgLON (LAMP, OBCAM, Ntm) family of glycorylphosphatidylinositol anchored neural cell adhesion molecules. We previously reported that LAMP and Ntm promote adhesion and neurite outgrowth via a homophilic mechanism, suggesting that these proteins promote the formation of specific neuronal circuits by homophilic interactions. In this report, we have further characterized the expression and binding specificity of Ntm. Using a newly generated monoclonal antibody to Ntm, we demonstrated that this protein is largely expressed in a complementary pattern to that of LAMP in the nervous system, with co-expression at a few sites. Ntm is expressed at high levels in sensory-motor cortex and, of particular note, is transiently expressed in neurons of cortical barrel fields and corresponding thalamic "barreloids." Binding of a recombinant, soluble form of Ntm to CHO cells expressing either Ntm or LAMP demonstrates that Ntm and LAMP interact both homophilically and heterophilically. In contrast to conventional growth-promoting activity of Ig superfamily members, LAMP strongly inhibits the outgrowth of Ntm-expressing dorsal root ganglion (DRG) neurons in a heterophilic manner. These anatomical and functional data support the concept that homophilic and heterophilic interactions between IgLON family members are likely to play a role in the specification of neuronal projections via growth promoting and inhibiting effects, respectively.

Animals↗
PubMed1996

Identification of the lysosomal membrane glycoprotein Lamp-1 as a receptor for type-1-fimbriated (mannose-specific) Escherichia coli.

The presence of several glycosylated sites with high-mannose oligosaccharides on the lysosome-associated membrane glycoproteins (Lamps)_ combined with the fact that neutrophil Lamps are present in mobilizable organelles inspired us to investigate their ability to bind type-1 fimbriated (mannose-binding) Escherichia coli and subsequently define a potential function for the Lamps in human neutrophils. Bacterial binding to Lamps purified from chronic myeloic leukemia cells was investigated by separation of the proteins by sodium dodecyl sulfate polyacrylamide gel electrophoresis, transfer to a blotting membrane and overlay with type-1-fimbriated bacteria. The overlays were developed by growth. The bacteria bound readily to Lamp-1 while there was almost no binding to Lamp-2. Hence, we state that a possible function for neutrophil Lamp-1 is bacterial binding.

Antigens, CD↗
PubMed1994

Cotransfection of genes encoding human tyrosinase and tyrosinase-related protein-1 prevents melanocyte death and enhances melanin pigmentation and gene expression of Lamp-1.

We constructed two genes specific to melanogenesis, human tyrosinase (HT) and tyrosinase-related protein-1 (TRP-1) genes, into two separate expression vectors so that the cloned genes were under the control of a human cytomegalovirus promoter and enhancer. Monkey kidney COS-7 cells and human amelanotic and melanotic melanoma cells were then cotransfected by both HT and TRP-1 or transfected individually with each gene. The transfectants were examined for mRNA expression by reverse transcription-mediated RNA-PCR amplification. HT or TRP-1 mRNA was strongly expressed in HT or TRP-1 transfectants and cotransfectants of the two genes. Both light and electron microscopic observations indicated that degeneration and premature death of melanocytes occurred in HT transfectants, but not in TRP-1 transfectants or in HT and TRP-1 cotransfectants. Cotransfected cells from five cell lines revealed numerous granular reaction products with an anti-TRP-1 antibody and lysosomal granules with electron-dense material. Our melanin assay confirmed the new production of melanin pigments in these cells, indicating that the lysosomal granules would contain melanin pigments. The gene expression studies of lysosomal protein (beta-galactosidase, CD63, Lamp-1, and Lamp-2) revealed a dramatically elevated gene expression of Lamp-1, which is associated with the membrane receptor of lysosomal granules, in HT- and TRP-1-cotransfected cells. Conversely, the treatment of melanoma cells with antisense oligodeoxynucleotides against Lamp-1 resulted in a decreased expression of TRP-1 protein by immunoprecipitation, supporting the observations of the HT and TRP-1 cotransfection study regarding the up-regulation of Lamp-1 expression. We conclude that HT, TRP-1, and Lamp-1 gene products may function together, being expressed as a multiprotein complex within the melanosomal compartment. Specifically, HT and TRP-1 may function together via Lamp-1 by stabilizing the enzyme-protein complex within the melanosome and prevent the premature death of melanocytes due to tyrosinase-mediated cytotoxicity.

Animals↗
PubMed1997

Limbic system-associated membrane protein (LAMP) induces neurite outgrowth and intracellular Ca2+ increase in primary fetal neurons.

The ability of cell adhesion molecules (CAMs) to transduce cell surface signals into intracellular responses is critical for developing neurons, particularly during axonal pathfinding and targeting. It has been suggested that different CAMs can promote neuronal outgrowth via activation of common neuronal CAM-specific second-messenger pathways, although the elements involved in this cascade could differ. Limbic system-associated membrane protein (LAMP), a member of the Ig superfamily, is a molecule that promotes cell adhesion and neurite outgrowth from specific populations of fetal neurons. In the present study, we show that LAMP can induce several types of calcium (Ca2+) signals. Neurite outgrowth is promoted if fetal hippocampal neurons are grown on lamp-transfected CHO cells. This LAMP-induced outgrowth of neurons is mediated in part through activation of L-type Ca channels. Application of soluble LAMP to cultures of fetal hippocampal neurons caused a sustained (up to 60 min) elevation of intracellular Ca2+ as measured by fluo-3 fluorescence on a confocal microscope. The number of responding hippocampal neurons was initially low, but increased with age in culture and the [Ca2+]i elevation was only partially decreased by an L-type Ca(2+)-channel blocker. In contrast, at all times in culture, only a small fraction of neurons from visual cortex responded to LAMP application and only with transient elevation of cytosolic Ca2+ (< 15 min). Based on these observations, LAMP appears to function primarily through homophilic interactions and acts in part by modulating intracellular Ca2+ levels during neurite outgrowth by increasing the Ca2+ influx through L-type calcium channels, but has additional effects on intracellular Ca2+ signaling at later developmental stages.

Animals↗