Search PubMed⌕ Search

Biomedical subjects

J C Clark

Publications and source records attributed to J C Clark.

At least 55 records · Page 3Linked to original sources
PubMed1994

A fatal overdose with 3,4-methylenedioxyamphetamine derivatives.

Methylenedioxymethylamphetamine (MDMA or 'Ecstasy') is the best known of the 3,4-methylenedioxy ring-substituted amphetamines. Reports of serious adverse reactions and fatalities associated with its use emphasise hyperpyrexia, profuse sweating and subsequent rhabdomyolysis, although cardiac deaths and fatal accidents whilst intoxicated are also prominent. Other 3,4-methylenedioxy ring-substituted amphetamines are also available in the illicit market place and may have different spectra of activity. We report here a case of fatal ingestion of a variety of drugs of this group.

3,4-Methylenedioxyamphetamine↗
PubMed1994

Immortalization of subpopulations of respiratory epithelial cells from transgenic mice bearing SV40 large T antigen.

Murine lung epithelial (MLE) cell lines were produced from lung tumors derived from transgenic mice bearing the viral oncogene, SV40 large T antigen, under transcriptional control of the promoter-enhancer region of the human surfactant protein C (SP-C) gene. Cells were selected on the basis of increased murine cystic fibrosis transmembrane conductance regulator (mCFTR) mRNA content and were dilution cloned to produce distinct immortalized epithelial cell lines. MLE-13a3 cell lines expressing high levels of mCFTR mRNA also expressed apolipoprotein J (apoJ) mRNA, a developmentally regulated glycoprotein expressed preferentially in fetal lung. SP-A, -B, and -C were not detected or were present at low levels in the MLE cells that contained abundant CFTR and apoJ mRNA. In contrast, MLE cells, cloned on the basis of abundant surfactant protein mRNAs, expressed apoJ and mCFTR mRNAs at low levels. Forskolin-stimulated short-circuit current, typical of CFTR-mediated chloride transport activity, was generated by monolayers of subclones of the MLE-13a3 cell lines. Tumor necrosis factor-alpha stimulated mCFTR mRNA, whereas dexamethasone, retinoic acid, and phorbol ester had no effect on the levels of mCFTR mRNA in MLE-13a3 cells.

Animals↗
PubMed1993

Production of immortalized distal respiratory epithelial cell lines from surfactant protein C/simian virus 40 large tumor antigen transgenic mice.

Murine lung epithelial (MLE) cell lines representing the distal bronchiolar and alveolar epithelium were produced from lung tumors generated in transgenic mice harboring the viral oncogene simian virus 40 (SV40) large tumor antigen under transcriptional control of a promoter region from the human surfactant protein C (SP-C) gene. The cell lines exhibited rapid growth, lack of contact inhibition, and an epithelial cell morphology for 30-40 passages in culture. Microvilli, cytoplasmic multivesicular bodies, and multilamellar inclusion bodies (morphologic characteristics of alveolar type II cells) were detected in some of the MLE cell lines by electron microscopic analysis. The MLE cells also maintained functional characteristics of distal respiratory epithelial cells including the expression of surfactant proteins and mRNAs and the ability to secrete phospholipids. Expression of the exogenous SV40 large tumor antigen gene was detected in all of the generated cell lines. The SP-C/SV40 large tumor antigen transgenic mice and the MLE cell lines will be useful for the study of pulmonary surfactant production and regulation as well as lung development and tumorigenesis.

Animals↗
PubMed1993

Changes in global cerebral blood flow in humans: effect on regional cerebral blood flow during a neural activation task.

1. The primary objective of this study was to examine in man, how induced changes in global cerebral blood flow (gCBF) affected a regional cerebral blood flow (rCBF) increase resulting from a neural activation task (opening of eyes). A secondary objective was to quantify how such induced changes in gCBF were distributed between representative regions of either predominantly grey matter or white matter. 2. Positron emission tomography with intravenous infusion of H2(15)O, was used to measure gCBF in six normal males. Concomitant measures of rCBF were obtained in three different regions of interest (ROI): a representative area of predominantly grey matter, a representative area of predominantly white matter and an area of visual cortex. 3. Cerebral blood flow was altered by establishing steady-state changes in PCO2 at a near constant ventilation of approximately 30 l min-1. The mean PET,CO2 (+/- S.D.) levels (mmHg) that resulted were: low, 21.8 +/- 1.8; normal, 39.8 +/- 1.0, and high, 54.8 +/- 1.2. The normal and high levels were obtained by adding appropriate amounts of CO2 to the inspirate. The corresponding mean gCBF levels across all six subjects with eyes closed were: low, 24.2 +/- 4.6; normal, 37.2 +/- 3.9 and high, 66.8 +/- 7.6 ml min-1 dl-1. 4. Blood flow in grey matter (insular cortex) and white matter (centrum semiovale) at normal levels of PCO2 averaged 56.8 +/- 10.1 and 20.3 +/- 3.4 ml min dl-1 respectively. As PCO2 rose, the increase in rCBF to grey matter was approximately three times greater than that to white matter. 5. An activation state of eyes open in a brightly lit room was compared to a baseline state of eyes closed in a darkened room at the three levels of PCO2 (and hence at three levels of gCBF). Over the whole gCBF range a significant (P = 0.028) effect of increasing rCBF in the visual cortex ROI was found in response to opening the eyes; the effect of this activation on rCBF was not significantly dependent (P = 0.34) on the PCO2 (and hence gCBF) level. The effect of the activation on the rCBF was apparently 'additive' to the rise of rCBF associated with PCO2-related gCBF increase. 6. The results confirm the need to normalize for changes in gCBF during studies of rCBF in response to an activation protocol. They also provide support for the use of an 'additive' model to achieve such normalization provided that other cortical areas behave in a similar manner to that of the visual cortex.

Adult↗
PubMed1992

Human Mn-superoxide dismutase in pulmonary epithelial cells of transgenic mice confers protection from oxygen injury.

To test directly whether mitochondrial Mn-superoxide dismutase (Mn-SOD) protects the lung epithelium from oxygen-induced injury, transgenic mice were produced in which the expression of human Mn-SOD mRNA was directly by transcriptional elements from the human pulmonary surfactant protein C gene. Human Mn-SOD mRNA was expressed in a lung-specific manner, and increased Mn-SOD protein was detected within mitochondria of alveolar Type II and nonciliated bronchiolar cells of the distal respiratory epithelium of the transgenic mice. The activity of Mn-SOD, but not catalase, CuZn-SOD, or glutathione peroxidase, was increased in lungs of transgenic mice. Transgenic mice were highly protected from lung injury during exposure to 95% oxygen, surviving significantly longer than nontransgenic littermates. Pulmonary pathology demonstrated decreased hemorrhage, hyaline membrane formation, and alveolar and interstitial edema in transgenic animals. The finding that increased Mn-SOD in distal respiratory epithelial cells confers protection from oxygen injury provides a basis for novel therapies to protect lung from injury during oxygen therapy of acute and chronic lung diseases.

Animals↗
PubMed1992

Simian virus 40 large T antigen directed by transcriptional elements of the human surfactant protein C gene produces pulmonary adenocarcinomas in transgenic mice.

A model of pulmonary adenocarcinomas was produced in transgenic mice harboring a chimeric gene comprising the SV40 large T antigen under the control of a transcriptional region derived from the human surfactant protein C (SP-C) gene. Transgenic mice succumbed with pulmonary tumors within 4-5 months of age. By histology, the tumors were adenocarcinomas with lepidic, papillary, and solid growth patterns that were indistinguishable from adenocarcinomas occurring in humans. Immunocytochemistry demonstrated the lack of staining for neuroendocrine markers, consistent with the identification of the tumors as non-small cell rather than small cell carcinomas. The presence of SV40 large T mRNA in the lung and tumors was detected by in situ hybridization and Northern blot analysis. Exogenous SV40 large T mRNA and endogenous CC10 (a nonciliated respiratory epithelial cell marker) and SP-C (a Type II alveolar cell marker) mRNAs were expressed at variable levels in the lung tumors. SV40 large T mRNA and CC10 mRNA were detected in the majority of tumors, while SP-C mRNA was detected less frequently. The heterogeneity of bronchiolar and alveolar cell markers in the tumors from the transgenic mice supports the concept that tumorigenesis was initiated in distinct subsets of epithelial cells that produce characteristic adenocarcinomas of the lung.

Adenocarcinoma↗
PubMed1992

Transforming growth factor-beta inhibits surfactant protein A expression in vitro.

Effects of members of the transforming growth factor-beta (TGF-beta) family on expression of surfactant protein A (SP-A) were determined in human pulmonary adenocarcinoma cells. TGF-beta decreased SP-A content in two distinct pulmonary adenocarcinoma cell lines with bronchiolar (NCI-H441-4) and alveolar (NCI-H820) cell characteristics. TGF-beta 1, beta 2 and beta 3 were equally effective in decreasing SP-A. Effects of the TGF-beta's on SP-A content were dose dependent, EC50 approximately 20-30 pg/ml for each form of TGF-beta. TGF-beta decreased cellular SP-A content in association with decreased levels of SP-A mRNA. Inhibitory effects of TGF-beta 1 on SP-A mRNA was time dependent, reaching maximal effects within 12-24 h, after which SP-A mRNA was approximately 10% of that present in untreated cells. Maximal inhibition of SP-A mRNA was observed at 250 pg/ml TGF-beta 1. TGF-beta-dependent inhibition of SP-A expression was not associated with altered cell morphology, growth, or viability. TGF-beta family members act directly on pulmonary adenocarcinoma cells to inhibit SP-A expression by mechanisms which are mediated, at least in part, at a pretranslational level.

Adenocarcinoma↗
PubMed1992

Pulmonary reactivity to vanadium pentoxide following subchronic inhalation exposure in a non-human primate animal model.

An experimental study was conducted to evaluate changes in pulmonary reactivity resulting from repeated vanadium pentoxide (V2O5) dust inhalation. The study assessed pulmonary reactivity to V2O5 through the use of provocation challenges, and compared V2O5 reactivity before and after subchronic V2O5 exposure. A total of 24 adult, male cynomolgus monkeys (Macaca fascicularis) were exposed by inhalation for 6 h per day, 5 days per week, for 26 weeks. Two V2O5-exposed groups (n = 8 each) received equal weekly V2O5 exposures (concentration x time) with different exposure profiles. One V2O5-exposed group received 0.1 mg V2O5 m-3 on Mondays, Wednesday and Fridays, with a twice-weekly peak exposure of 1.1 mg V2O5 m-3 on Tuesdays and Thursdays, and was included to investigate the influence of an exposure regimen with peaks on the development of pulmonary hyper-reactivity. The other V2O5-exposed group received a constant daily concentration of 0.5 mg V2O5 m-3. A control group (n = 8) received filtered, conditioned air. Pre-exposure challenges with V2O5 produced a concentration-dependent impairment in pulmonary function, characterized by airway obstructive changes (increased resistance and decreased flow). Analysis of respiratory cells recovered from the lung by bronchoalveolar lavage demonstrated that airway obstruction was accompanied by a significant influx of inflammatory cells into the lung. Subchronic V2O5 inhalation did not produce an increase in V2O5 reactivity in comparison to the control group, and cytological, immunological and skin test results indicate the absence of allergic sensitization. Instead, a trend toward decreased pulmonary reactivity was found following subchronic V2O5 inhalation.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1992

Human cystic fibrosis transmembrane conductance regulator directed to respiratory epithelial cells of transgenic mice.

Human cystic fibrosis transmembrane conductance regulator (CFTR) was expressed in transgenic mice under the control of transcriptional elements derived from the human surfactant protein C (SP-C) gene. The hCFTR mRNA was expressed in lungs and testes: in the lung, we found hCFTR mRNA in bronchiolar and alveolar epithelial cells, and CFTR protein in respiratory epithelial cells. While the level of expression of hCFTR mRNA varied, hCFTR mRNA and protein were detected in pulmonary epithelial cells of several lines. Lung weight, morphology, somatic growth and reproductive capacity were not altered by expression hCFTR in lung and testes of the transgenics. Our findings suggest that hCFTR can be safely transferred to lung epithelial cells for CF therapy.

Animals↗
PubMed1992

In vitro activities of penciclovir and acyclovir against herpes simplex virus types 1 and 2.

Penciclovir (PCV) and acyclovir are acyclic guanine analogs which inhibit herpes simplex virus (HSV) DNA polymerase. Their 50% infective doses were 0.5 to 0.8 microgram/ml for clinical isolates of HSV-1 and 1.3 to 2.2 micrograms/ml for HSV-2. Furthermore, HSV-infected cultures receiving 2-h pulses of PCV had 2- to 50-fold less HSV than acyclovir-treated cultures, consistent with the prolonged intracellular half-life of PCV triphosphate.

Acyclovir↗
PubMed1992

Diffuse axonal injury caused by assault.

The case reports of 50 fatal head injuries caused by assault and managed at the Institute of Neurological Sciences, Glasgow, were reviewed. Fifteen cases had diffuse axonal injury. Diffuse axonal injury is a well recognised type of brain damage brought about by a head injury, usually as a result of a road traffic accident or fall from a height. It does not seem to be widely appreciated that it may also occur as a result of an assault. This has important medicolegal implications.

Adolescent↗
PubMed1992

Sequence, ontogeny, and cellular localization of murine surfactant protein B mRNA.

We have isolated and characterized murine surfactant protein (SP-B) cDNAs and determined both the cellular distribution and developmental expression of SP-B mRNA. The nucleotide sequence of the composite SP-B cDNAs and cloned genomic SP-B DNA predicted a primary translation product of 377 amino acids (molecular mass = 41.7 kDa) that contained a single asparagine linked glycosylation site. The 410 base 3' untranslated region contained a novel sequence consisting of a (CCA)21 repeat. Tissue specificity and developmental expression of SP-B mRNA was assessed by Northern blot analysis. A single 1.6-kb mRNA species was detected specifically in lung tissue. In fetal mouse lung SP-B mRNA was detected at low levels on day 15 of gestation and increased markedly between days 16 and 17, reaching adult levels by birth. In situ hybridization analysis of SP-B mRNA demonstrated SP-B expression primarily in bronchiolar and alveolar epithelium, although discrete bronchial cells also contained the SP-B mRNA. The murine SP-B mRNA was expressed in proximal and distal epithelial cells within the respiratory tract and shares a close structural relationship to SP-B from other species.

Animals↗
PubMed1992

Effects of TNF-alpha and phorbol ester on human surfactant protein and MnSOD gene transcription in vitro.

Tumor necrosis factor-alpha (TNF-alpha) and the phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) decrease the synthesis of surfactant proteins association with decreased SP-A and SP-B mRNA. Nuclear run-on assays were utilized to test whether the inhibitory effects of TNF-alpha and TPA were associated with changes in surfactant protein gene transcription. SP-A gene transcription was inhibited by both TNF-alpha and TPA as assessed by nuclear run-on assays. Inhibitory effects of both agents on SP-A gene transcription were readily detected within 6 h after exposure and persisted for 24 h. While TNF-alpha and TPA decreased cellular SP-B mRNA content, transcription of the SP-B gene was not influenced by these agents. In contrast to the inhibitory effects of TPA and TNF-alpha on SP-A and SP-B mRNAs, steady-state mRNA and rate of transcription of human manganese superoxide dismutase (MnSOD) were increased by both agents. The time course and extent of increased MnSOD gene transcription by TNF-alpha and TPA were distinct. Transcription of the human beta-actin gene was not altered by either agent. The inhibitory effects of TPA and TNF-alpha on SP-A expression in pulmonary adenocarcinoma cells are associated with the inhibition of SP-A gene transcription. Loss of SP-B mRNA was not accompanied by decreased SP-B gene transcription. Actinomycin D blocked the inhibitory effects of TNF-alpha and TPA on SP-A and SP-B mRNA, supporting a role for posttranscriptional events in the modulation of the expression of the surfactant proteins SP-A and SP-B.

Adenocarcinoma↗
PubMed1992

Murine pulmonary surfactant SP-A gene: cloning, sequence, and transcriptional activity.

SP-A is an abundant pulmonary surfactant-associated protein whose expression is controlled in a cell- and developmental-specific manner. To analyze regulation of SP-A gene expression, the murine SP-A gene was cloned and sequenced. The murine DBA/2J gene was approximately 4.6 kb in length comprised of six exons and five introns. Three mRNAs of 3.0, 1.7, and 0.9 kb were detected by Northern blot analysis of murine lung mRNA. Expression of the SP-A mRNAs was first detected at day 15 of gestation and increased dramatically before birth. A single SP-A gene was detected in the DBA/2J mouse genome. SP-A mRNA was detected in lung but not in the gastrointestinal tract, kidney, brain, liver, or heart and was detected by in situ hybridization in bronchial and alveolar cells of the murine lung. Primer extension analysis with a primer to exon three revealed two extension products differing by 9 bp in length, suggesting two closely juxtaposed transcription initiation sites. Chimeric gene(s) containing 1.8 kb of 5' SP-A sequences and the bacterial chloramphenicol acetyltransferase gene were expressed in pulmonary adenocarcinoma cells and in HeLa cells. Expression of the murine SP-A gene is partially controlled by non-cell-selective transcriptionally active sequences.

Amino Acid Sequence↗
PubMed1991

Rapid analysis for metabolites of 11C-labelled drugs: fate of [11C]-S-4-(tert.-butylamino-2-hydroxypropoxy)-benzimidazol-2-one in the dog.

Positron emission tomography (PET) requires the use of compounds labelled with short-lived, positron-emitting isotopes (e.g., t1/2 of 11C approximately 120 min). As the concentration of unbound, non-metabolised drug is required as the input function for modeling, this presents particular problems for the study of the kinetics and metabolism of such compounds. We have now developed a rapid extraction procedure, followed by high-performance liquid chromatography using a short analytical column coupled to an on-line gamma-detector to determine the metabolism and kinetics of a non-selective beta-adrenergic antagonist of high affinity, S-4-(tert.-butylamino-2-hydroxypropoxy)benzimidazol-2-one. This antagonist is potentially well suited to the non-invasive localisation of beta-receptors in vivo. The ligand was rapidly taken up into the beta-receptor pool or excreted in urine, with less than 5% of the drug converted to metabolites. Plasma protein binding was only 16%. No significant metabolism of the ligand was observed in the anaesthetised dog, and, therefore, no correction for blood metabolite concentration is required for kinetic analysis of the 11C-labelled ligand during PET studies in this species. The analytical method reported here should be widely applicable: quantification of metabolites enables accurate estimation of the input function and is critical to the interpretation of PET data.

Adrenergic beta-Antagonists↗
PubMed1991

Evaluation of the onset and duration of response to cold air inhalation challenge in cynomolgus monkeys (Macaca fascicularis).

Cold air inhalation challenge (CAIC) for the evaluation of bronchial reactivity has been proposed as a physical agent alternative to chemical agent challenges (methacholine or histamine), especially suitable for the occupational environment. The present investigation describes and evaluates a method for performing cold air inhalation challenge in Cynomolgus monkeys (Macaca fascicularis), a species shown to be useful in animal modeling studies of occupational asthma. Six adult male anesthetized monkeys were ventilated by changes in external pressure while breathing cold air (-25 degrees C to -30 degrees C). Pulmonary function testing was performed at 10, 25, 40 and 55 min post-challenge. Significant increases (P less than 0.05) in average pulmonary flow resistance (RL) and decreases in dynamic compliance (CL dyn) were observed, with maximum impairment occurring at 25 min post-challenge, with a trend towards a return to baseline values at 55 min post-challenge. Peak expiratory flow rate (PEFR), forced expiratory volume in 0.5 s/forced vital capacity (FEV0.5/FVC) and forced expiratory flow at 50% forced vital capacity (FEF50) showed the same general pattern of reduction as seen with RL; however, these results were not statistically significant, most probably owing to individual monkey variability and the small number of monkeys (N = 6) used. A repeat challenge at 25 min after a primary challenge yielded increased RL in one monkey, suggesting that no absolute refractory period is present from CAIC. Results of these studies demonstrate that CAIC causes bronchoconstriction in monkeys and may be useful in further animal modeling studies designed to determine the asthmogenic/airway irritant potential of occupational toxicants.

Air↗