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Biomedical subjects

Simon R Johnson

Publications and source records attributed to Simon R Johnson.

7 recordsLinked to original sources
PubMed2006

Air travel in women with lymphangioleiomyomatosis.

BACKGROUND AND OBJECTIVE: The safety of air travel in patients with pneumothorax-prone pulmonary diseases, such as lymphangioleiomyomatosis (LAM), has not been studied to any great extent. A questionnaire-based evaluation of air travel in patients with LAM was conducted to determine experiences aboard commercial aircraft. METHODS: A survey was sent to women listed in the US LAM Foundation registry (n = 389) and the UK LAM Action registry (n = 59) to assess air travel, including problems occurring during flight. Women reporting a pneumothorax in flight were followed up to ascertain further details about the incident. RESULTS: 327 (73%) women completed the survey. 308 women answered the travel section, of whom 276 (90%) had "ever" travelled by aeroplane for a total of 454 flights. 95 (35%) women had been advised by their doctor to avoid air travel. Adverse events reported included shortness of breath (14%), pneumothorax (2%, 8/10 confirmed by chest radiograph), nausea or dizziness (8%), chest pain (12%), unusual fatigue (11%), oxygen desaturation (8%), headache (9%), blue hands (2%), haemoptysis (0.4%) and anxiety (22%). 5 of 10 patients with pneumothorax had symptoms that began before the flight: 2 occurred during cruising altitude, 2 soon after landing and 1 not known. The main symptoms were severe chest pain and shortness of breath. DISCUSSION AND CONCLUSION: Adverse effects occurred during air travel in patients with LAM, particularly dyspnoea and chest pain. Hypoxaemia and pneumothorax were reported. The decision to travel should be individualised; patients with unexplained shortness of breath or chest pain before scheduled flights should not board. Patients with borderline oxygen saturations on the ground should be evaluated for supplemental oxygen therapy during flight. Although many women had been advised not to travel by air, most travelled without the occurrence of serious adverse effects.

Adult↗
PubMed2006

Subcellular distribution of the TSC2 gene product tuberin in human airway smooth muscle cells is driven by multiple localization sequences and is cell-cycle dependent.

The products of the tuberous sclerosis complex (TSC) genes, hamartin and tuberin (TSC1 and 2), form a heteromer, which represses the kinase mammalian target of rapamycin. Loss of TSC1 or 2 results in diseases characterized by loss of cell-cycle control, including TSC and lymphangioleiomyomatosis. As tuberin has multiple signaling inputs, including phosphatidylinositide-3-OH kinase, mitogen-activated protein kinase, and adenosine monophosphate kinase, we postulated tuberin would have multiple protein interactions governed by subcellular localization and cellular status and examined this in primary human airway smooth muscle cells. Using immunofluorescence and confocal microscopy, tuberin was detected in cytoplasm, nucleus, nucleoli, and mitochondria. Fractionation of synchronized airway smooth cells showed that tuberin enters the nucleus in late G(1), and passage through the cell cycle is necessary for nuclear entry. Deletion constructs showed localization sequences for the nucleus between amino acids 1351 and 1807, for mitochondria between 901 and 1350, and for cytoplasmic speckles between 1 and 450. Using fluorophore-tagged proteins, we observed fluorescence resonance energy transfer between tuberin and hamartin within these speckles, indicating a direct interaction between the proteins at this site. The observations that tuberin is localized to mitochondria and translocated to the nucleus in G(1) are novel and consistent with interactions with proteins within multiple signaling pathways. Dynamic relocalization of tuberin may control these interactions to integrate these pathways. As tuberin has potential roles in proliferation, migration, and cell phenotype, it therefore warrants further investigation in diseases categorized by abnormalities in airway smooth muscle.

Active Transport, Cell Nucleus↗
PubMed2006

Synthesis and crystal structure of Li4BH4(NH2)3.

The solid solution, (LiNH2)x(LiBH4)(1-x), formed through the reaction of the two potential hydrogen storage materials, LiNH2 and LiBH4, is dominated by a compound that has an ideal stoichiometry of Li4BN3H10 and forms a body-centred cubic structure with a lattice constant of ca. 10.66 A.

Journal Article↗
PubMed2004

Matrix metalloproteinase expression and activity in human airway smooth muscle cells.

Airway remodelling is a feature of chronic asthma comprising smooth muscle hypertrophy and deposition of extracellular matrix (ECM) proteins. Matrix metalloproteinases (MMPs) breakdown ECM, are involved in tissue remodelling and have been implicated in airway remodelling. Although mesenchymal cells are an important source of MMPs, little data are available on airway smooth muscle (ASM) derived MMPs. We therefore investigated MMP and tissue inhibitor of metalloproteinase (TIMP) production and activity in human ASM cells. MMPs and TIMPs were examined using quantitative real-time RT-PCR, Western blotting, zymography and a quench fluorescence (QF) assay of total MMP activity. The most abundant MMPs were pro-MMP-2, pro- MMP-3, active MMP-3 and MT1-MMP. TIMP-1 and TIMP-2 expression was low in cell lysates but high in conditioned medium. High TIMP secretion was confirmed by the ability of ASM-conditioned medium to inhibit recombinant MMP-2 in a QF assay. Thrombin increased MMP activity by activation of pro-MMP-2 independent of the conventional smooth muscle thrombin receptors PAR 1 and 4. In conclusion, ASM cells express pro-MMP-2, pro and active MMP-3, MMP-9 and MT1-MMP. Unstimulated cells secrete excess TIMP 1 and 2, preventing proteolytic activity. MMP-2 can be activated by thrombin which may contribute to airway remodelling.

Cell Line, Tumor↗
PubMed2002

Lymphangioleiomyomatosis.

Lymphangioleiomyomatosis (LAM) is a rare disease categorized by an overgrowth of atypical smooth muscle cells (LAM cells) in the lungs and axial lymphatics, which is associated with the mesenchymal tumor angiomyolipoma. The disease occurs in women generally in their mid thirties with a prevalence approximately 1 per million in the general population but is much more frequent in women with tuberous sclerosis complex (TSC). LAM is categorized by airflow obstruction, lung cysts, recurrent pneumothorax, and pleural and abdominal chylous collections. The disease is progressive, generally resulting in respiratory failure and death. The TSC-2 gene is abnormal in LAM cells and may be responsible for their disordered growth. These cells are of an unusual phenotype, expressing smooth muscle proteins, melanoma proteins, estrogen and progesterone receptors. Although at present of unknown significance these are useful in diagnosis. Treatment is largely supportive, being directed at airflow obstruction, pneumothorax, chylous complications, and bleeding from angiomyolipomas. In patients with rapidly progressive disease, hormone manipulation is frequently tried in the form of progesterone or antiestrogen therapies although no firm evidence of their efficacy exists.

Journal Article↗