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Jensen PD, Johnson LR, Trumble JT. Individual and joint actions of selenate and methylmercury on the development and survival of insect detritivore Megaselia scalaris (Diptera: Phoridae). ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2006; 50:523-30. [PMID: 16418899 DOI: 10.1007/s00244-005-0111-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Accepted: 08/22/2005] [Indexed: 05/06/2023]
Abstract
Despite the important roles played by insects in most ecosystems, surprisingly little is known about how anthropogenic pollutants or their mixtures interact to affect insect populations. The independent and joint actions of selenate and methylmercury on a ubiquitous insect detritivore, Megaselia scalaris (Loew), were determined in this study. Ovipositing females did not distinguish between untreated food sources and those contaminated with toxic concentrations of selenate, methylmercury, or both chemicals in combination. Even at the highest concentrations of pollutants, no negative effects were observed for the egg stage. However, larval survival was significantly decreased and development significantly prolonged by selenate and methylmercury individually at low or intermediate ecologically relevant treatment levels. Potentiation was strongly evident because mixtures containing concentrations as little as only 1% of the respective individual median lethal tolerances (LC(50)s) caused significantly more mortality and delayed larval development than would be expected from the responses selenate and methylmercury elicit individually. However, survival and pupal development was not affected at any rate tested. Female fecundity was significantly decreased by methylmercury but not by selenate or mixture treatments. The relative toxicity to M. scalaris of each of the individual and joint treatments was selenate (LC(50) = 260 microg/g) < methylmercury (LC(50) = 22 microg/g) < the mixture at approximately 5% of the LC(50) concentration of each of the components (12 microg/g selenate plus 1.0 microg/g methylmercury). The increased mortality and delayed larval development within sites contaminated by selenate, methylmercury, or combination of the two have substantial implications for the ecology, population dynamics, and sustainability of M. scalaris populations. If these results can be extrapolated to other arthropod detritivores, ecosystem food-web function may be substantially affected.
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Lamprecht R, Margulies DS, Farb CR, Hou M, Johnson LR, LeDoux JE. Myosin light chain kinase regulates synaptic plasticity and fear learning in the lateral amygdala. Neuroscience 2006; 139:821-9. [PMID: 16515842 DOI: 10.1016/j.neuroscience.2005.12.055] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Revised: 12/18/2005] [Accepted: 12/22/2005] [Indexed: 01/29/2023]
Abstract
Learning and memory depend on signaling molecules that affect synaptic efficacy. The cytoskeleton has been implicated in regulating synaptic transmission but its role in learning and memory is poorly understood. Fear learning depends on plasticity in the lateral nucleus of the amygdala. We therefore examined whether the cytoskeletal-regulatory protein, myosin light chain kinase, might contribute to fear learning in the rat lateral amygdala. Microinjection of ML-7, a specific inhibitor of myosin light chain kinase, into the lateral nucleus of the amygdala before fear conditioning, but not immediately afterward, enhanced both short-term memory and long-term memory, suggesting that myosin light chain kinase is involved specifically in memory acquisition rather than in posttraining consolidation of memory. Myosin light chain kinase inhibitor had no effect on memory retrieval. Furthermore, ML-7 had no effect on behavior when the training stimuli were presented in a non-associative manner. Anatomical studies showed that myosin light chain kinase is present in cells throughout lateral nucleus of the amygdala and is localized to dendritic shafts and spines that are postsynaptic to the projections from the auditory thalamus to lateral nucleus of the amygdala, a pathway specifically implicated in fear learning. Inhibition of myosin light chain kinase enhanced long-term potentiation, a physiological model of learning, in the auditory thalamic pathway to the lateral nucleus of the amygdala. When ML-7 was applied without associative tetanic stimulation it had no effect on synaptic responses in lateral nucleus of the amygdala. Thus, myosin light chain kinase activity in lateral nucleus of the amygdala appears to normally suppress synaptic plasticity in the circuits underlying fear learning, suggesting that myosin light chain kinase may help prevent the acquisition of irrelevant fears. Impairment of this mechanism could contribute to pathological fear learning.
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Johnson LR, Farb C, Morrison JH, McEwen BS, LeDoux JE. Localization of glucocorticoid receptors at postsynaptic membranes in the lateral amygdala. Neuroscience 2005; 136:289-99. [PMID: 16181741 DOI: 10.1016/j.neuroscience.2005.06.050] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2004] [Revised: 06/11/2005] [Accepted: 06/16/2005] [Indexed: 01/08/2023]
Abstract
Glucocorticoids, released in high concentrations from the adrenal cortex during stressful experiences, bind to glucocorticoid receptors in nuclear and peri-nuclear sites in neuronal somata. Their classically known mode of action is to induce gene promoter receptors to alter gene transcription. Nuclear glucocorticoid receptors are particularly dense in brain regions crucial for memory, including memory of stressful experiences, such as the hippocampus and amygdala. While it has been proposed that glucocorticoids may also act via membrane bound receptors, the existence of the latter remains controversial. Using electron microscopy, we found glucocorticoid receptors localized to non-genomic sites in rat lateral amygdala, glia processes, presynaptic terminals, neuronal dendrites, and dendritic spines including spine organelles and postsynaptic membrane densities. The lateral nucleus of the amygdala is a region specifically implicated in the formation of memories for stressful experiences. These newly observed glucocorticoid receptor immunoreactive sites were in addition to glucocorticoid receptor immunoreactive signals observed using electron and confocal microscopy in lateral amygdala principal neuron and GABA neuron soma and nuclei, cellular domains traditionally associated with glucocorticoid immunoreactivity. In lateral amygdala, glucocorticoid receptors are thus also localized to non-nuclear-membrane translocation sites, particularly dendritic spines, where they show an affinity for postsynaptic membrane densities, and may have a specialized role in modulating synaptic transmission plasticity related to fear and emotional memory.
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Sullivan GM, Apergis J, Bush DEA, Johnson LR, Hou M, Ledoux JE. Lesions in the bed nucleus of the stria terminalis disrupt corticosterone and freezing responses elicited by a contextual but not by a specific cue-conditioned fear stimulus. Neuroscience 2004; 128:7-14. [PMID: 15450349 DOI: 10.1016/j.neuroscience.2004.06.015] [Citation(s) in RCA: 248] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/18/2004] [Indexed: 11/26/2022]
Abstract
The bed nucleus of the stria terminalis (BNST) is believed to be a critical relay between the central nucleus of the amygdala (CE) and the paraventricular nucleus of the hypothalamus in the control of hypothalamic-pituitary-adrenal (HPA) responses elicited by conditioned fear stimuli. If correct, lesions of CE or BNST should block expression of HPA responses elicited by either a specific conditioned fear cue or a conditioned context. To test this, rats were subjected to cued (tone) or contextual classical fear conditioning. Two days later, electrolytic or sham lesions were placed in CE or BNST. After 5 days, the rats were tested for both behavioral (freezing) and neuroendocrine (corticosterone) responses to tone or contextual cues. CE lesions attenuated conditioned freezing and corticosterone responses to both tone and context. In contrast, BNST lesions attenuated these responses to contextual but not tone stimuli. These results suggest CE is indeed an essential output of the amygdala for the expression of conditioned fear responses, including HPA responses, regardless of the nature of the conditioned stimulus. However, because lesions of BNST only affected behavioral and endocrine responses to contextual stimuli, the results do not support the notion that BNST is critical for HPA responses elicited by conditioned fear stimuli in general. Instead, the BNST may be essential specifically for contextual conditioned fear responses, including both behavioral and HPA responses, by virtue of its connections with the hippocampus, a structure essential to contextual conditioning. The results are also not consistent with the hypothesis that BNST is only involved in unconditioned aspects of fear and anxiety.
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Nelson DA, Walters TJ, Ryan KL, Emerton KB, Hurt WD, Ziriax JM, Johnson LR, Mason PA. Inter-species extrapolation of skin heating resulting from millimeter wave irradiation: modeling and experimental results. HEALTH PHYSICS 2003; 84:608-615. [PMID: 12747480 DOI: 10.1097/00004032-200305000-00006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This study reports measurements of the skin surface temperature elevations during localized irradiation (94 GHz) of three species: rat (irradiated on lower abdomen), rhesus monkey (posterior forelimb), and human (posterior forearm). Two exposure conditions were examined: prolonged, low power density microwaves (LPM) and short-term, high power density microwaves (HPM). Temperature histories were compared with calculations from a bio-heat transfer model. The mean peak surface temperature increase was approximately 7.0 degrees C for the short-term HPM exposures for all three species/locations, and 8.5 degrees C (monkey, human) to 10.5 degrees C (rat) for the longer-duration LPM exposures. The HPM temperature histories are in close agreement with a one-dimensional conduction heat transfer model with negligible blood flow. The LPM temperature histories were compared with calculations from the bio-heat model, evaluated for various (constant) blood flow rates. Results suggest a variable blood flow model, reflecting a dynamic thermoregulatory response, may be more suited to describing skin surface temperature response under long-duration MMW irradiation.
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Vollmer WM, Tsai R, Wu Y, Li YH, Johnson LR, Williams OD, Li Y, Rao X, Buist AS. Patterns of lung function in asymptomatic nonsmoking men and women in the People's Republic of China. Ann Epidemiol 2002; 12:295-302. [PMID: 12062915 DOI: 10.1016/s1047-2797(01)00288-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
PURPOSE To evaluate patterns of lung function in healthy, working Chinese men and women in different geographic areas of the People's Republic of China (PRC). METHODS We conducted lung function tests on 2926 asymptomatic, never smoking Chinese men and women aged 35-56 years residing in or around Beijing and Guangzhou. Within each of these locations, separate urban and rural samples were recruited. RESULTS Age and height adjusted lung function was greater in Beijing than in Guangzhou, and within each city for residents of rural vs. urban areas. Among women, estimated rates of lung aging were greater in Beijing than in Guangzhou, and in urban vs. rural areas. Both FEV(1) and FVC exhibited a curvilinear association with body mass index. CONCLUSIONS Lung function data from this largely working cohort exhibited marked geographic and urban-rural differences in this never smoking, adult Chinese cohort. Such variation is not uncommon and may reflect differences in body size, diet, and environmental and occupational exposures across these different settings. Caution should be used in applying published reference equations to populations from different parts of the PRC.
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Johnson LR, Stoller NH. Rationale for the use of Atridox therapy for managing periodontal patients. COMPENDIUM OF CONTINUING EDUCATION IN DENTISTRY (JAMESBURG, N.J. : 1995) 2002; 20:19-25; quiz 35. [PMID: 11908360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
This article reviews the studies that provided the safety and efficacy data essential for the Food and Drug Administration approval of Atridox. These studies detail the clinical effectiveness of Atridox and provide the foundation for an understanding of the use of Atridox in the clinical management of patients with periodontitis. Atridox is a locally delivered, controlled-release system for the administration of high concentrations of doxycycline to the periodontal pocket. Nine-month clinical studies involving more than 800 patients have shown Atridox and scaling and root planing to be superior to placebo and oral hygiene for the efficacy parameters of attachment level, probing depth, and bleeding on probing. The positive clinical effects are consistent throughout a wide range of patients with varied histories of periodontal therapy. The implications of these findings as they relate to clinical practice are briefly addressed.
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Pfeffer LM, Yang CH, Murti A, McCormack SA, Viar MJ, Ray RM, Johnson LR. Polyamine depletion induces rapid NF-kappa B activation in IEC-6 cells. J Biol Chem 2001; 276:45909-13. [PMID: 11590175 DOI: 10.1074/jbc.m108097200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The proliferation of the rat intestinal mucosal IEC-6 cell line requires polyamines, whose synthesis is catalyzed by the enzyme ornithine decarboxylase (ODC). ODC inhibition leads to polyamine depletion, as well as inhibition of both cell proliferation and apoptosis by regulating gene expression. The NF-kappa B transcription factor regulates genes involved in apoptotic, immune, and inflammatory responses. In the present study we tested the hypothesis that NF-kappa B is activated following ODC inhibition. We found that the inhibition of ODC by alpha-difluoromethylornithine (DFMO) resulted in a approximately 50% decrease in intracellular putrescine levels within 1 h. NF-kappa B is activated by DFMO through the degradation of the inhibitory protein I kappa B alpha that sequesters NF-kappa B in the cytoplasm. The DFMO-induced NF-kappa B complexes contain the p65 and p50 members of the Rel protein family. DFMO-induced NF-kappa B activation was accompanied by the translocation of p65 from the cytoplasm into the nucleus. DFMO selectively inhibited a gene reporter construct dependent on the kappa B site present in the HLA-B7 gene. In contrast, DFMO had no effect on a gene reporter construct dependent on the kappa B site present in the interleukin-8 gene. Thus, we report that ODC inhibition activates the NF-kappa B transcription factor, which may mediate the altered physiological state of intestinal cells that occurs following polyamine depletion.
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Johnson LR, Fales WH. Clinical and microbiologic findings in dogs with bronchoscopically diagnosed tracheal collapse: 37 cases (1990-1995). J Am Vet Med Assoc 2001; 219:1247-50. [PMID: 11697368 DOI: 10.2460/javma.2001.219.1247] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To investigate the role of bacteria in bronchoscopically diagnosed tracheal collapse in dogs by evaluating qualitative results of bacteriologic cultures. DESIGN Retrospective study. ANIMALS 37 dogs with tracheal collapse. PROCEDURE Clinical records for dogs with tracheal collapse confirmed with bronchoscopy were reviewed. A protected catheter brush was used to obtain samples for bacteriologic culture from the large airways. RESULTS Results of bacterial culture were negative for 5 of 29 dogs. For 24 dogs, 1 (n = 10), 2 (6), or > or = 3 (8) species of bacteria were isolated. Pseudomonas spp were isolated most frequently (17/29), and a single Pseudomonas sp grew in 7 samples. Other bacteria included Enterobacter spp (4/29), Citrobacter spp (3/29), and Moraxella spp, Klebsiella spp, Bordetella spp, or Acinetobacter spp (2/29 dogs each). Anaerobic and aerobic cultures yielded positive results in samples from 2 dogs. Cytologic results were available for 13 dogs with positive results of bacteriologic culture; epithelial cells were reported most commonly. Five samples had a small number of neutrophils; bacteria were identified cytologically in 2 of 5 samples that contained neutrophils. Bacteria were also seen in 2 samples that lacked inflammatory cells. CONCLUSIONS AND CLINICAL RELEVANCE Bacteria are commonly isolated from samples obtained via airway brushing in dogs with tracheal collapse; however, in the absence of cytologic confirmation of inflammation or infection, an association between bacteria and clinical signs of tracheal collapse cannot be established.
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McCormack SA, Johnson LR. Polyamines and cell migration. JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY : AN OFFICIAL JOURNAL OF THE POLISH PHYSIOLOGICAL SOCIETY 2001; 52:327-49. [PMID: 11596855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
Leeuwenhoek first described polyamines in 1677, but active investigation did not begin until the 1970's. When intracellular polyamine levels are reduced by inhibitors, mutation, or transfection, severe reductions occur in cell division, cell differentiation, and cell migration. These effects are not difficult to demonstrate and measure, and all can be prevented if supplemental exogenous polyamines are supplied. However, linking the overall effects to molecular events remains to be accomplished. In this review, we discuss work (mostly from the last 10 years) that relates to cell migration. Specifically, we have discussed the biology and biochemistry of the polyamines, their transport and regulation, the structure of the cytoskeleton and the mechanics of cell movement. We have also considered four specific processes that polyamines participate in that may affect cell migration significantly. These are: 1) the regulation of intracellular Ca++ concentration by voltage-gated K+ channels, 2) the maintenance of normal RhoA levels that, with Rac, regulate the assembly of actin stress fibers, focal adhesions, and contractility, 3) the formation of ATP-Mg++-polyamine trimers that enhance the phosphorylation activity of ATP toward enzymes in specific signaling pathways and, 4) alterations in the structure of RNA that change translation initiation sites and affect the expression of proteins.
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Ray RM, Viar MJ, McCormack SA, Johnson LR. Focal adhesion kinase signaling is decreased in polyamine-depleted IEC-6 cells. Am J Physiol Cell Physiol 2001; 281:C475-85. [PMID: 11443046 DOI: 10.1152/ajpcell.2001.281.2.c475] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Polyamines are essential to the migration of epithelial cells in the intestinal mucosa. Cells depleted of polyamines do not attach as rapidly to the extracellular matrix and do not form the actin stress fibers essential for migration. Because both attachment and stress fiber formation depend on integrin signaling and the formation of focal adhesions, we examined these and related processes in polyamine-depleted IEC-6 cells. There was general decreased tyrosine phosphorylation of focal adhesion kinase (FAK), and, specifically, decreased phosphorylation of Tyr-925, the paxillin binding site. In control cells, FAK phosphorylation was rapid after attachment to the extracellular matrix, while attached cells depleted of polyamines had significantly delayed phosphorylation. FAK activity was also significantly inhibited in polyamine-depleted cells as was the phosphorylation of paxillin. Polyamine-depleted cells failed to spread normally after attachment, and immunocytochemistry showed little colocalization of FAK and actin compared with controls. Focal adhesion complex formation was greatly reduced in the absence of polyamines. These data suggest that defective integrin signaling may, at least in part, account for the decreased rates of attachment, actin stress fiber formation, spreading, and migration observed in polyamine-depleted cells.
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Ray RM, McCormack SA, Johnson LR. Polyamine depletion arrests growth of IEC-6 and Caco-2 cells by different mechanisms. Am J Physiol Gastrointest Liver Physiol 2001; 281:G37-43. [PMID: 11408253 DOI: 10.1152/ajpgi.2001.281.1.g37] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The polyamines spermidine and spermine and their precursor, putrescine, are required for the growth and proliferation of eukaryotic cells. This study compares and contrasts growth arrest caused by polyamine depletion in the untransformed IEC-6 cell line with that in the p53-mutated colon cancer Caco-2 cell line. Cells were grown in the presence or absence of alpha-difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase, the first rate-limiting enzyme in the synthesis of polyamines. Depletion of polyamines inhibited the growth of both cell lines equally and over the same time frame. However, whereas IEC-6 cells were arrested in the G(1) phase of the cell cycle, there was no accumulation of Caco-2 cells in any particular phase. In IEC-6 cells, growth arrest was accompanied by elevated levels of p53 and p21(Waf1/Cip1) (p21). There were no changes in p53 levels in Caco-2 cells. Levels of p21 increased in Caco-2 cells on day 2 without any effect on cell cycle progression. The amount of cyclin-dependent kinase (Cdk)2 protein was unchanged by polyamine depletion in both cell lines. However, the activity of Cdk2 was significantly inhibited by DFMO in IEC-6 cells. These data suggest that in the untransformed IEC-6 cells the regulation of Cdk2 activity and progression through the cell cycle are p53- and p21 dependent. Growth arrest in the p53-mutated Caco-2 line after polyamine depletion occurs by a different, yet unknown, mechanism.
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Johnson LR, Doherty G, Lairmore T, Moley JF, Brunt LM, Koenig J, Scott MG. Evaluation of the performance and clinical impact of a rapid intraoperative parathyroid hormone assay in conjunction with preoperative imaging and concise parathyroidectomy. Clin Chem 2001; 47:919-25. [PMID: 11325897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
BACKGROUND (99m)Tc-sestamibi scans and rapid, intraoperative intact parathyroid hormone (PTH) assays allow preoperative identification of diseased glands and intraoperative confirmation of diseased gland removal, respectively. Use of these two new technologies may facilitate simpler, more concise surgery, shorter hospital stays, and decreased costs for frozen-section analysis. One major drawback to this new strategy has been the high cost of rapid point-of-care PTH assays. METHODS We performed rapid PTH assays with the DPC Turbo PTH assay on the DPC IMMULITE automated analyzer. The number of intraoperative frozen sections, type of anesthesia, surgical approach, length of hospital stay, and pre- and postoperative calcium values were compared between a group of 49 patients undergoing parathyroidectomy where the intraoperative PTH assay was used in conjunction with preoperative imaging, and a historical control group of 55 patients before the use of these two technologies in our institution. RESULTS Comparison of the Turbo PTH assay to the standard IMMULITE PTH assay gave the following: y = 1.08 x - 4.36 (r = 0.97; n = 48). For the 49 patients, the median turnaround time for each intraoperative PTH determination was 19 min (range, 14-40 min). The median decrease in PTH values from baseline was 88% (range, 33-99%). Thirty-seven patients required two PTH determinations, 7 required three, 4 had four, and 1 required five determinations. The average laboratory cost for the rapid intraoperative PTH assays was < $100 per patient (range, $55 to $113). Compared with the control group, the experimental group had significantly fewer frozen sections (1.4 vs 2.5; P < 0.0001), shorter hospital stays (17 discharged on the day of surgery vs none discharged on the day of surgery; P < 0.0001), greater use of local anesthesia (33% vs 0%; P < 0.001), and more unilateral, rather than bilateral neck explorations (65% vs 0%; P < 0.001). CONCLUSIONS The combination of intraoperative Turbo PTH assay and preoperative (99m)Tc-sestamibi scans can lead to significant decreases in laboratory and surgical pathology costs, hospital stays, and exposure to general anesthesia by facilitating concise parathyroidectomy surgery.
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Abstract
The addiction potential of anabolic steroids remains largely unexplored. Here, we demonstrate voluntary oral testosterone intake in hamsters. Using a 2-bottle choice test, males preferred an aqueous solution of 200 microg/ml testosterone over vehicle. However, the taste of testosterone is not highly preferred. Addition of testosterone at 400 microg/ml increased fluid consumption from the nonpreferred bottle in a 2-bottle choice test, but cholesterol at the same concentration reduced drinking, suggesting that testosterone reward is not common to all sterols. With food-induced drinking, testosterone maintained fluid intake when food was withdrawn. These data demonstrate that oral self-administration of testosterone is reinforcing in hamsters, suggesting the potential for dependence in human users.
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Johnson LR, Rush JW, Turk JR, Price EM, Laughlin MH. Short-term exercise training increases ACh-induced relaxation and eNOS protein in porcine pulmonary arteries. J Appl Physiol (1985) 2001; 90:1102-10. [PMID: 11181626 DOI: 10.1152/jappl.2001.90.3.1102] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We tested the hypothesis that short-term exercise (STEx) training and the associated increase in pulmonary blood flow during bouts of exercise cause enhanced endothelium-dependent vasorelaxation in porcine pulmonary arteries and increased expression of endothelial cell nitric oxide synthase (eNOS) and superoxide dismutase-1 (SOD-1) protein. Mature, female Yucatan miniature swine exercised 1 h twice daily on a motorized treadmill for 1 wk (STEx group, n = 7); control pigs (Sed, n = 6) were kept in pens. Pulmonary arteries were isolated from the left caudal lung lobe, and vasomotor responses were determined in vitro. Arterial tissue from the distal portion of this pulmonary artery was processed for immunoblot analysis. Maximal endothelium-dependent (ACh-stimulated) relaxation was greater in STEx (71 +/- 5%) than in Sed (44 +/- 6%) arteries (P < 0.05), and endothelium-independent (sodium nitroprusside-mediated) responses did not differ. Sensitivity to ACh was not altered by STEx training. Immunoblot analysis indicated a 3.9-fold increase in eNOS protein in pulmonary artery tissue from STEx pigs (P < 0.05) with no change in SOD-1 or glyceraldehyde-3-phosphate dehydrogenase protein levels. We conclude that STEx training enhances ACh-stimulated vasorelaxation in pulmonary arterial tissue and that this adaptation is associated with increased expression of eNOS protein.
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Stoller NH, Johnson LR, Garrett S. Periodontal regeneration of a class II furcation defect utilizing a bioabsorbable barrier in a human. A case study with histology. J Periodontol 2001; 72:238-42. [PMID: 11288798 DOI: 10.1902/jop.2001.72.2.238] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This case report describes human histologic data of periodontal regeneration following guided tissue regeneration therapy (GTR) with a bioabsorbable barrier composed of polylactic acid. The tooth that was examined was part of a previously published study of the clinical effects of GTR therapy without the use of bone or bone substitutes on Class II furcation defects. Twenty-five months following the surgical procedure, the tooth was extracted for non-periodontal reasons. During this extraction, the bone within the furcation that was treated in the study was luxated with the tooth. At the completion of the study (month 12), the furcation's vertical probing depth had decreased by 2 mm with a 2 mm gain in clinical attachment. The horizontal furcation measurement decreased by 3 mm. Following extraction, the tooth was prepared for light microscopy and sectioned in the mesial-distal plane. Reference notches were not placed in the tooth at the time of surgery as there were no plans to perform histologic analysis in the study. However, using the buccal root prominences and what we interpreted to be root planing marks on the cementum, we were able to demonstrate that complete periodontal regeneration occurred on the root surface that was exposed to the pocket environment prior to surgery. New alveolar bone, cementum, and periodontal ligament were consistently observed throughout the furcation in the areas that demonstrated clinical attachment gain and a decrease in horizontal probing depth. This case report adds to the accumulating evidence of histologic periodontal regeneration following guided tissue regeneration with bioabsorbable polylactic acid barriers.
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Yuan Q, Ray RM, Viar MJ, Johnson LR. Polyamine regulation of ornithine decarboxylase and its antizyme in intestinal epithelial cells. Am J Physiol Gastrointest Liver Physiol 2001; 280:G130-8. [PMID: 11123206 DOI: 10.1152/ajpgi.2001.280.1.g130] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Ornithine decarboxylase (ODC) is feedback regulated by polyamines. ODC antizyme mediates this process by forming a complex with ODC and enhancing its degradation. It has been reported that polyamines induce ODC antizyme and inhibit ODC activity. Since exogenous polyamines can be converted to each other after they are taken up into cells, we used an inhibitor of S-adenosylmethionine decarboxylase, diethylglyoxal bis(guanylhydrazone) (DEGBG), to block the synthesis of spermidine and spermine from putrescine and investigated the specific roles of individual polyamines in the regulation of ODC in intestinal epithelial crypt (IEC-6) cells. We found that putrescine, spermidine, and spermine inhibited ODC activity stimulated by serum to 85, 46, and 0% of control, respectively, in the presence of DEGBG. ODC activity increased in DEGBG-treated cells, despite high intracellular putrescine levels. Although exogenous spermidine and spermine reduced ODC activity of DEGBG-treated cells close to control levels, spermine was more effective than spermidine. Exogenous putrescine was much less effective in inducing antizyme than spermidine or spermine. High putrescine levels in DEGBG-treated cells did not induce ODC antizyme when intracellular spermidine and spermine levels were low. The decay of ODC activity and reduction of ODC protein levels were not accompanied by induction of antizyme in the presence of DEGBG. Our results indicate that spermine is the most, and putrescine the least, effective polyamine in regulating ODC activity, and upregulation of antizyme is not required for the degradation of ODC protein.
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Luster TA, Johnson LR, Nowling TK, Lamb KA, Philipsen S, Rizzino A. Effects of three Sp1 motifs on the transcription of the FGF-4 gene. Mol Reprod Dev 2000. [PMID: 10954851 DOI: 10.1002/1098-2795(200009)57:1<4::aid-mrd3>3.0.co;2-i] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Previous studies have shown that the transcription of the fibroblast growth factor-4 (FGF-4) gene is regulated by a powerful enhancer located approximately three kilobases downstream of the transcription start site. Several conserved cis-regulatory elements in the promoter and the enhancer have been identified, including two Sp1 motifs located in the promoter and one Sp1 motif located in the enhancer. Each of these Sp1 motifs has been shown previously to bind the transcription factors Sp1 and Sp3 in vitro. The main objective of this study was to examine the potential interaction of the FGF-4 promoter and enhancer Sp1 motifs. Using site-directed mutagenesis, we demonstrate that disruption of these sites, individually or in combination, reduce the expression of FGF-4 promoter/reporter gene constructs in embryonal carcinoma cells. Importantly, we demonstrate that disruption of the enhancer Sp1 motif exerts a more pronounced effect on the expression of these constructs than disruption of the promoter Sp1 motifs. We also demonstrate that changing the spacing and the stereo-alignment of the enhancer Sp1 motif, relative to the other cis-regulatory elements of the enhancer, has little effect on the ability of the enhancer to stimulate transcription. Furthermore, embryonic stem cells that contain two disrupted Sp1 alleles were used to demonstrate that the transcription factor Sp1 is not necessary for expression of the endogenous FGF-4 gene. Finally, the significance of these findings relative to a looping model for the transcriptional activation of the FGF-4 gene is discussed.
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Rubin LJ, Johnson LR, Dodam JR, Dhalla AK, Magliola L, Laughlin MH, Jones AW. Selective transport of adenosine into porcine coronary smooth muscle. Am J Physiol Heart Circ Physiol 2000; 279:H1397-410. [PMID: 10993808 DOI: 10.1152/ajpheart.2000.279.3.h1397] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adenosine (ADO), an endogenous regulator of coronary vascular tone, enhances vasorelaxation in the presence of nucleoside transport inhibitors such as dipyridamole. We tested the hypothesis that coronary smooth muscle (CSM) contains a high-affinity transporter for ADO. ADO-mediated relaxation of isolated large and small porcine coronary artery rings was enhanced 12-fold and 3.4-fold, respectively, by the transport inhibitor, S-(4-nitrobenzyl)-6-thioinosine (NBTI). Enhanced relaxation was independent of endothelium and was selective for ADO over synthetic analogs. Uptake of [(3)H]ADO into freshly dissociated CSM cells or endothelium-denuded rings was linear and concentration dependent. Kinetic analysis yielded a maximum uptake (V(max)) of 67 +/- 7.0 pmol. mg protein(-1). min(-1) and a Michaelis constant (K(m)) of 10. 5 +/- 5.8 microM in isolated cells and a V(max) of 5.1 +/- 0.5 pmol. min(-1). mg wet wt(-1) and a K(m) of 17.6 +/- 2.6 microM in intact rings. NBTI inhibited transport into small arteries (IC(50) = 42 nM) and cells. Analyses of extracellular space and diffusion kinetics using [(3)H]sucrose indicate the V(max) and K(m) for ADO transport are sufficient to clear a significant amount of extracellular adenosine. These data indicate CSM possess a high-affinity nucleoside transporter and that the activity of this transporter is sufficient to modulate ADO sensitivity of large and small coronary arteries.
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Luster TA, Johnson LR, Nowling TK, Lamb KA, Philipsen S, Rizzino A. Effects of three Sp1 motifs on the transcription of the FGF-4 gene. Mol Reprod Dev 2000; 57:4-15. [PMID: 10954851 DOI: 10.1002/1098-2795(200009)57:1<4::aid-mrd3>3.0.co;2-i] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Previous studies have shown that the transcription of the fibroblast growth factor-4 (FGF-4) gene is regulated by a powerful enhancer located approximately three kilobases downstream of the transcription start site. Several conserved cis-regulatory elements in the promoter and the enhancer have been identified, including two Sp1 motifs located in the promoter and one Sp1 motif located in the enhancer. Each of these Sp1 motifs has been shown previously to bind the transcription factors Sp1 and Sp3 in vitro. The main objective of this study was to examine the potential interaction of the FGF-4 promoter and enhancer Sp1 motifs. Using site-directed mutagenesis, we demonstrate that disruption of these sites, individually or in combination, reduce the expression of FGF-4 promoter/reporter gene constructs in embryonal carcinoma cells. Importantly, we demonstrate that disruption of the enhancer Sp1 motif exerts a more pronounced effect on the expression of these constructs than disruption of the promoter Sp1 motifs. We also demonstrate that changing the spacing and the stereo-alignment of the enhancer Sp1 motif, relative to the other cis-regulatory elements of the enhancer, has little effect on the ability of the enhancer to stimulate transcription. Furthermore, embryonic stem cells that contain two disrupted Sp1 alleles were used to demonstrate that the transcription factor Sp1 is not necessary for expression of the endogenous FGF-4 gene. Finally, the significance of these findings relative to a looping model for the transcriptional activation of the FGF-4 gene is discussed.
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Johnson LR, Laughlin MH. Chronic exercise training does not alter pulmonary vasorelaxation in normal pigs. J Appl Physiol (1985) 2000; 88:2008-14. [PMID: 10846012 DOI: 10.1152/jappl.2000.88.6.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exercise training increases acetylcholine-induced pulmonary vasorelaxation in pigs with coronary occlusion. The present study tested the hypothesis that chronic exercise training enhances endothelium-mediated vasorelaxation in pulmonary arteries from normal pigs. Yucatan miniswine exercised for 16 wk on a treadmill (Ex); control pigs (Sed) remained in pens. Pulmonary artery rings (2- to 3-mm OD) were studied using standard isometric techniques. Contractile responses to 80 mM KCl and norepinephrine (NE) were determined. Vessels were constricted with levels of NE that resulted in half-maximal contraction to examine endothelium-dependent relaxation to ACh and endothelium-independent relaxation to sodium nitroprusside in the presence and absence of nitric oxide synthase inhibition, cyclooxygenase inhibition, and endothelial denudation. Arteries from Ex pigs developed increased contraction to 80 mM KCl, but the response to NE did not differ between groups. Endothelium-dependent and endothelium-independent responses did not differ between Sed and Ex in the presence or absence of pharmacological inhibitors or denudation. We conclude that chronic exercise training does not alter endothelium-dependent or endothelium-independent vasorelaxation responses of pulmonary arteries from normal pigs.
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Ray RM, Viar MJ, Yuan Q, Johnson LR. Polyamine depletion delays apoptosis of rat intestinal epithelial cells. Am J Physiol Cell Physiol 2000; 278:C480-9. [PMID: 10712236 DOI: 10.1152/ajpcell.2000.278.3.c480] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The polyamines spermidine, spermine, and their precursor putrescine are essential for cell growth and the regulation of the cell cycle. Recent studies suggest that excessive accumulation of polyamines favors either malignant transformation or apoptosis, depending on the cell type and the stimulus. This study examines the involvement of polyamines in the induction of apoptosis by the DNA topoisomerase I inhibitor, camptothecin. In IEC-6 cells, camptothecin induced apoptosis within 6 h, accompanied by detachment of cells. Detached cells showed DNA laddering and caspase 3 induction, characteristic features of apoptosis. Depletion of putrescine, spermidine, and spermine by DL-alpha-difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase (ODC) that is the first rate-limiting enzyme for polyamine biosynthesis, decreased the apoptotic index. Delayed apoptosis was accompanied by a decrease in caspase 3 activity in polyamine-depleted cells. Addition of putrescine restored the induction of apoptosis as indicated by an increase in the number of detached cells and caspase 3 activity. Polyamine depletion did not change the level of caspase 3 protein. Inhibition of S-adenosylmethionine decarboxylase by a specific inhibitor [diethylglyoxal bis-(guanylhydrazone); DEGBG] led to depletion of spermidine and spermine with a significant accumulation of putrescine and induction of ODC. The DEGBG-treated cells showed an increase in apoptosis, suggesting the importance of putrescine in the apoptotic process. Addition of putrescine to DFMO-treated cell extracts did not increase caspase 3 activity. The above results indicate that polyamine depletion delays the onset of apoptosis in IEC-6 cells and confers protection against DNA damaging agents, suggesting that polyamines might be involved in the caspase activating signal cascade.
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Johnson LR, Dodam JR, Laughlin MH. Endothelium-dependent relaxation differs in porcine pulmonary arteries from the left and right caudal lobes. J Appl Physiol (1985) 2000; 88:827-34. [PMID: 10710375 DOI: 10.1152/jappl.2000.88.3.827] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that pulmonary arteries (PA) from identical branch orders within left and right caudal lung lobes would exhibit similar vasomotor responses. Arterial rings from caudal lung lobes of female swine were examined in vitro. Vascular smooth muscle contraction to KCl and norepinephrine did not differ. Vascular relaxation to endothelium-dependent (bradykinin, acetylcholine, A-23187) and -independent (sodium nitroprusside, zero-calcium Krebs solution) vasodilators was assessed. Right PA exhibited less maximal relaxation to acetylcholine (50%) than did left PA (69%; P < 0.001). Maximal relaxation to sodium nitroprusside did not differ, although right PA had a lower drug concentration resulting in half-maximal relaxation (6.26 x 10(-8) M) than did left PA (9.57 x 10(-8) M; P < 0.05). Nitric oxide synthase inhibition with an arginine analog (N(omega)-nitro-L-arginine methyl ester) depressed acetylcholine-induced relaxation but the left vs. right difference persisted. Indomethacin enhanced relaxation to acetylcholine and abolished the difference between left and right. We conclude that endothelium-dependent vasorelaxation is less in porcine right than in left PA because of greater release of one or more constricting prostanoids in arteries from the right caudal lobe.
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Walters TJ, Blick DW, Johnson LR, Adair ER, Foster KR. Heating and pain sensation produced in human skin by millimeter waves: comparison to a simple thermal model. HEALTH PHYSICS 2000; 78:259-267. [PMID: 10688448 DOI: 10.1097/00004032-200003000-00003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Cutaneous thresholds for thermal pain were measured in 10 human subjects during 3-s exposures at 94 GHz continuous wave microwave energy at intensities up to approximately 1.8 W cm(-2). During each exposure, the temperature increase at the skin's surface was measured by infrared thermography. The mean (+/- s.e.m.) baseline temperature of the skin was 34.0+/-0.2 degrees C. The threshold for pricking pain was 43.9+/-0.7 degrees C, which corresponded to an increase in surface temperature of approximately 9.9 degrees C (from 34.0 degrees C to 43.9 degrees C). The measured increases in surface temperature were in good agreement with a simple thermal model that accounted for heat conduction and for the penetration depth of the microwave energy into tissue. Taken together, these results support the use of the model for predicting thresholds of thermal pain at other millimeter wave (length) frequencies.
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Nowling TK, Johnson LR, Wiebe MS, Rizzino A. Identification of the transactivation domain of the transcription factor Sox-2 and an associated co-activator. J Biol Chem 2000; 275:3810-8. [PMID: 10660531 DOI: 10.1074/jbc.275.6.3810] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The importance of interactions between Sox and POU transcription factors in the regulation of gene expression is becoming increasingly apparent. Recently, many examples of the involvement of Sox-POU partnerships in transcription have been discovered, including a partnership between Sox-2 and Oct-3. Little is known about the mechanisms by which these factors modulate transcription. To better understand the molecular interactions involved, we mapped the location of the transactivation domain of Sox-2. This was done in the context of its interaction with Oct-3, as well as its ability to transactivate as a fusion protein linked to the DNA-binding domain of Gal4. Both approaches demonstrated that Sox-2 contains a transactivation domain in its C-terminal half, containing a serine-rich region and the C terminus. We also determined that the viral oncoprotein E1a inhibits the ability of the Gal4/Sox-2 fusion protein to transactivate, as well as the transcriptional activation mediated by the combined action of Sox-2 and Oct-3. In contrast, a mutant form of E1a, unable to bind p300, lacks both of these effects. Importantly, we determined that p300 overcomes the inhibitory effects of E1a in both assays. Together, these findings suggest that Sox-2 mediates its effects, at least in part, through the co-activator p300.
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