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Biomedical subjects

A R Johnson

Publications and source records attributed to A R Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1992

Mechanisms of fibrin formation and lysis by human lung fibroblasts: influence of TGF-beta and TNF-alpha.

Fibrin gels form within the alveolar and interstitial compartments of the injured lung, and fibroblasts invade and facilitate organization of these transitional gels. We studied the effects of transforming growth factor-beta (TGF-beta) and tumor necrosis factor-alpha (TNF-alpha) on fibrinolytic and procoagulant activities of human lung fibroblasts (HLF) to determine their capacity to regulate pulmonary fibrin deposition. Fibrinolytic activity of cell lysates and media (n = 6 HLF cultures) were uniformly depressed by TGF-beta or TNF-alpha. In dose and time-course studies, HLF plasminogen activator inhibitor-1 (PAI-1) was increased by TGF-beta, whereas TNF-alpha induced release of PAI-1 into the media. HLF and media urokinase concentrations were depressed by TGF-beta, whereas urokinase was unchanged or increased by TNF-alpha. Tissue plasminogen activator was mainly cell associated and unchanged by TGF-beta or TNF-alpha. HLF antiplasmin activity was not detected. Plasma recalcification times of HLF media were decreased by TNF-alpha but unchanged by TGF-beta. These studies suggest that TGF-beta and TNF-alpha impair the ability of HLF to degrade fibrin by disturbing the balance of HLF plasminogen activators and PAI and that these cytokines concurrently leave unchanged or increase the capacity of HLF to initiate fibrin formation. Cytokines likely to occur in the injured lung induce abnormalities of fibrinolysis in HLF from adults; such abnormalities favor extravascular fibrin deposition, a characteristic feature of alveolitis.

Base Sequence↗
PubMed1992

Interaction of Pseudomonas aeruginosa with human lung fibroblasts: role of bacterial elastase.

Colonization of cell surfaces by Pseudomonas aeruginosa is mediated by bacterial adherence, which, in turn, is influenced by both host and microbial factors. Previous studies with this organism suggest that elastase contributes to tissue invasion and necrosis. We studied the effects of Pseudomonas elastase (PE) on the adherence of P. aeruginosa to human lung fibroblast monolayers. Treatment of fibroblasts with PE (1 microgram/ml or 0.06 U/ml) increased adherence of 35S-labeled P. aeruginosa to cells, but heat-inactivated PE did not affect bacterial adhesion. Immunocytochemistry of cultured cells showed that PE (0.06 to 0.63 U/ml) decreased fibronectin (Fn) on the cell surface and extracellular matrix of cultured human lung fibroblasts. Data obtained by cytofluorography indicated that elastase also decreased Fn receptors on fibroblasts. Additional evidence for Fn degradation was provided by SDS-PAGE analysis of soluble Fn and proteins from surface iodinated cell monolayers treated with PE. We conclude that the increased bacterial adherence to fibroblasts may be due, in part, to elastase-induced proteolysis of Fn and its receptors on cell surfaces. Degradation of Fn could thus influence the extent and course of Pseudomonas infection in the lungs.

Bacterial Adhesion↗
PubMed1992

Pathways of fibrin turnover of human pleural mesothelial cells in vitro.

The mesothelium contains both procoagulant and fibrinolytic activities. An imbalance between these activities could account for the abnormal fibrin turnover and pleural fibrin deposition that is characteristic of pleural inflammation. Procoagulant activity of human pleural mesothelial cells (HPMC) is in part due to tissue factor, and the prothrombinase complex can also assemble at the HPMC surface. HPMC express tissue plasminogen activator (tPA) but no detectable fibrinolytic activity in a fibrin plate assay. Inhibition of HPMC fibrinolytic activity is due, in part, to elaboration of plasminogen activator inhibitors-1 and -2 (PAI-1 and PAI-2) as well as antiplasmins. Synthesis of PAI-1 and PAI-2 is inhibited by actinomycin D and cyclohexamide. HPMC PAI-1 is increased by transforming growth factor-beta (TGF-beta) and tumor necrosis factor-alpha (TNF-alpha), as is tPA release, while PAI-1 mRNA is unchanged and tPA mRNA is increased. PAI-2 release is induced by TNF-alpha and TGF-beta. Because they are a rich source of PAI-1 and PAI-2, HPMC may contribute to the high levels of these inhibitors in pleural exudates. Stimulation of HPMC by TNF-alpha or TGF-beta in vitro did not alter HPMC procoagulant activity nor the balance of elevated PAI and antiplasmins relative to PA, changes that collectively favor formation and persistence of pericellular fibrin.

Base Sequence↗
PubMed1991

Differential effects of laminin and merosin on neurite outgrowth by developing retinal ganglion cells.

In previous work, we showed that cultured avian embryonic retinal ganglion cells (RGC) extend neurites on EHS-laminin early in development, but lose this ability with maturation, as a result of a sharp decline in laminin receptor numbers. Here we show that EHS-laminin promotes neurite outgrowth also from embryonic mammalian RGC, in contrast to previous reports, and that these exhibit similar age-dependent growth responses on laminin. Antibody blocking studies show that this behaviour is mediated in mouse RGC by alpha 6 beta 1 integrin dimers. The laminin isoform merosin is also effective as a neurite outgrowth-promoting substrate for RGC but differs in its ability to elicit a response at advanced stages of development (up to hatching in the chick). Neurite outgrowth by RGC on merosin is inhibited, at all ages, by the function-blocking, anti-beta 1 integrin antibody, CSAT, suggesting that these neurons use alternative alpha beta 1 dimers in their interactions with EHS-laminin and merosin. Together, these findings emphasise the generality of the responsiveness of vertebrate embryonic RGC to laminin during development, and reveal interesting differences in the effects of laminin variants on CNS axon growth and regeneration.

Animals↗
PubMed1991

Chemical sensitivity in physicians.

By the nature of their work environment, physicians may be exposed to potentially toxic substances that can trigger chemical sensitivity. Nineteen physicians with chemical sensitivity were evaluated at the Environmental Health Center - Dallas regarding: type of specialty, history of chemical exposure, symptoms produced, food and water tolerance, immune parameters and double-blind chemical inhalation challenge. Food and chemical sensitivities were demonstrated in these physicians by oral, intradermal and inhalation challenges. After treatment, fifteen of the nineteen physicians were able to resume medical practice. Potential sources of chemical exposure in medical environments are evaluated.

Adult↗
PubMed1991

Confirmation of chemical sensitivity by means of double-blind inhalant challenge of toxic volatile chemicals.

Fifty chemically sensitive patients with vascular, asthmatic and arthritic signs, ranging in age from 21 to 61, were exposed to double-blind challenges of ambient doses of inhaled toxic chemicals in a specially designed booth in an Environmental Control Unit (ECU). Primary signs and symptoms were recorded before and after challenge with five chemicals and three placebos. Inhaled challenges included phenol (less than .0025 ppm), petroleum-derived ethyl alcohol (less than .5 ppm), formaldehyde (less than .2 ppm), chlorine (less than .3 ppm), and pesticide (2, 3,-D at less than .0034 ppm). Placebos were water or saline. A set on testing criteria were evaluated for maximizing the likelihood of well-defined, reproducible information from these ambient-dose double-blind challenges. For best results, these testing criteria include: Before testing, the patient must be housed in a chemically less polluted environment. The individual must have been de-adapted to food, air, and water pollutants by means of a water fat for three to four days. At the time of the challenge, the patient must be on food and water previously determined to be safe. An enclosed non-pulluted challenge booth must be used for these chemical exposures. Sign and symptom scores appropriate for that patient must be recorded, before and after challenge. Appropriate doses of the chemical in question (determined by air concentration and length of exposure) are necessary to investigate a particular problem. The conclusion of the study is that in these patients, chemical sensitivity clearly does exist (pulse rate differences between positive responses and placebo - p .001).(ABSTRACT TRUNCATED AT 250 WORDS)

2,4-Dichlorophenoxyacetic Acid↗
PubMed1991

Aliphatic hydrocarbon solvents in chemically sensitive patients.

The purpose of the present study was to see if chemically sensitive individuals had aliphatic hydrocarbon solvents as part of their total body load. This was done by measuring blood levels from 85 chemically sensitive patients. These were measured by a purging trap method with gas chromatography/mass spectrometry (GCC/MS) by the methods of Laseter. Thirteen patients had blood levels below the detection limit of less than 1 ppb and 72 were above the detection limit. An average of three solvents, out of seven measured, including n-pentane, 2,2-dimethylbutane, cyclopentane, 2-methylpentane, 3-methylpentane, n-hexane, n-heptane, was found in 85% of the patients' blood on the 1 to 299 ppb range. The means were as follows: n-pentane 14.7 ppb, 2,2-dimethylbutane 2.5 ppb, cyclopentane 9.0 ppb, 2-methylpentane 16.7 ppb, 3-methylpentane 28.0 ppb, n-heptane 5.5 ppb. The most frequently found of the above solvents was 2-methylpentane (found in 68.1% of the patients), 3-methylpentane (62.5%), n-hexane (61.1%), and pentane (40.3%).

Adolescent↗
PubMed1991

Clearing of toxic volatile hydrocarbons from humans.

In this study, different modes of therapy for the removal of toxic chemicals from the human body have been assessed and compared. This consisted of: 1) thirteen inpatients in an environmentally controlled area in a hospital, 2) fourty-one outpatients with home environmental control and work area change, and 3) fifteen outpatients in a physical therapy/sauna program with a good environmental control. Attention to manipulation of food, food contaminants, water and air pollution as well as nutritional therapy was important in all groups. Each modality seemed efficacious in++ its own right; 100% inpatients, 80% sauna/physical therapy patients, and 70% outpatients improved their signs and symptoms. Inpatient therapy in a finally controlled environment was far superior to the other two modalities in clearing of symptoms, as well as in clearing of organic chemicals. Outpatient and sauna/physical therapy are efficacious for less ill patients.

Adolescent↗
PubMed1990

Determination of genome size of Pseudomonas aeruginosa by PFGE: analysis of restriction fragments.

Genomic DNA size was measured in three strains of Pseudomonas aeruginosa, ATCC 29260 (exotoxin A), ATCC 33467 (type I smooth) and ATCC 33468 (type 2 mucoid) by transverse alternating field electrophoresis of restriction fragments. Because of the high (67%) G + C content of Pseudomonas aeruginosa, restriction enzymes that recognize sequences with at least 4 AT base pairs were expected to be rare cutters. Eight enzymes produced fragments greater than 200 kb in size: Dral (TTT/AAA), Asnl (ATT/AAT), Hpal (GTT/AAC), AfIII (C/TTAAG), Xbal (T/CTAGA), Spel (A/CTAGT), Sspl (AAT/ATT) and Ndel (CA/TATG). All eight enzymes recognized one of three rare tetranucleotide sequences, TTAA, CTAG or ATAT. Pseudomonas aeruginosa strain 29260 has a genomic DNA size of 5573 kb. Strains 33467 and 33468 have identical restriction patterns and a possible deletion with a genomic size of 5407 kb.

DNA Restriction Enzymes↗
PubMed1990

Neutral endopeptidase from nuchal ligament of fetal calves.

The nuchal ligament of unborn calves contains a neutral endopeptidase that is biochemically and immunologically similar to the neutral endopeptidase (NEP), or enkephalinase, from human kidney. Enzymatic activity was inhibited more than 90% by phosphoramidon (1 microM). The specific activity in membrane fractions, as determined by hydrolysis of the dansylated substrate, DAPGN, was similar in tissue from fetuses of gestational ages ranging from 100 to 280 days. NEP activity in adult ligament tissue, however, was less than 10% of that in fetal tissue. Fibroblasts dissociated from ligament tissue by collagenase displayed less NEP activity than did preparations of intact ligament, and activity was even lower in cultured cells. By contrast, fibroblasts cultured from fetal calf lungs had NEP activity comparable to that in the ligament tissue. When ligament fibroblasts were cultured on subcellular matrices derived from fetal lung fibroblasts the NEP activity increased relative to those cultured on plastic alone. These studies confirm the presence of neutral endopeptidase (NEP) in the nuchal ligament of the fetal calf. The consistent activity through a range of gestational ages and the influence of the subcellular matrix suggest that this enzyme might be involved in growth of the ligament during fetal life.

Animals↗
PubMed1990

Blood constituents during the estrous cycle and early pregnancy in dairy cows.

The objective of this study was to determine if maternal platelet count, white blood cell count or other blood constituents undergo sustained alterations in concentration following fertilization. Blood samples from 17 Holstein females were collected over an 18-d period starting at estrus. Blood was analyzed for levels of platelets, white blood cells, red blood cells, hemoglobin and hematocrit. Results were analyzed for differences between nonpregnant and pregnant groups. Analysis of variance revealed a day-by-group interaction in the platelet count (P<0.01). White blood cell count showed both a day-by-group interaction and a difference between days (P<0.01). Red blood cell count, hematocrit and hemoglobin levels resulted in no significant difference between the two groups (P>0.05). While statistically significant differences were observed in platelet and white blood cell count, neither of these were sustained over a period longer than 2 d.

Journal Article↗
PubMed1990

Effects of Pseudomonas aeruginosa elastase on alveolar epithelial permeability in guinea pigs.

Elastase-deficient mutants of Pseudomonas aeruginosa are less virulent than the wild type and are easily cleared from the lungs of guinea pigs. The effect of P. aeruginosa elastase on lung epithelium, however, is not yet understood. We addressed the hypothesis that breach of the epithelial barrier by elastase from P. aeruginosa allows invading organisms and toxic substances to penetrate the interstitium. We measured the clearance of aerosolized technetium-labeled albumin (molecular weight, 69,000) from the lungs of anesthetized guinea pigs with the aid of a gamma camera and a dedicated computer. Aerosols of the elastase (0.1 to 5 micrograms) increased the rate of clearance of labeled albumin from the lungs in proportion to the elastase dose. Electron microscopic studies using horseradish peroxidase as a tracer revealed that elastase interrupts intercellular tight junctions of the epithelial lining, thereby increasing the permeability to macromolecules. The amounts of elastase used in this report did not cause interstitial or alveolar edema, as determined by both postmortem extravascular lung water volume measurement and morphological examination. The data indicate that the elastase is a potentially important virulence factor in acute lung infection.

Animals↗
PubMed1990

The effects of embryonic retinal neurons on neural crest cell differentiation into Schwann cells.

Amongst the many cell types that differentiate from migratory neural crest cells are the Schwann cells of the peripheral nervous system. While it has been demonstrated that Schwann cells will not fully differentiate unless in contact with neurons, the factors that cause neural crest cells to enter the differentiative pathway that leads to Schwann cells are unknown. In a previous paper (Development 105: 251, 1989), we have demonstrated that a proportion of morphologically undifferentiated neural crest cells express the Schwann cell markers 217c and NGF receptor, and later, as they acquire the bipolar morphology typical of Schwann cells in culture, express S-100 and laminin. In the present study, we have grown axons from embryonic retina on neural crest cultures to see whether this has an effect on the differentiation of neural crest cells into Schwann cells. After 4 to 6 days of co-culture, many more cells had acquired bipolar morphology and S-100 staining than in controls with no retinal explant, and most of these cells were within 200 microns of an axon, though not necessarily in contact with axons. However, the number of cells expressing the earliest Schwann cell markers 217c and NGF receptor was not affected by the presence of axons. We conclude that axons produce a factor, which is probably diffusible, and which makes immature Schwann cells differentiate. The factor does not, however, influence the entry of neural crest cells into the earliest stages of the Schwann cell differentiative pathway.

Animals↗
PubMed1990

[A pupillographical study on the presence of organochlorine pesticides in autonomic nerve disturbance].

It is well known that the effect of organophosphate pesticides on the autonomic nervous system is a cholinergic reaction. However no study has been done assessing the effect of organochlorine pesticides on the autonomic nervous system. We evaluated the autonomic nerve function using open-loop pupillography in 20 patients who had exposure to the organochlorine pesticides. Significant differences were seen in pupil area (p less than .006), velocity of both constriction and dilatation (p less than .001), and dilatation time (p less than .02), when compared with 18 normal subjects. Autonomic nerve disturbances were detected in eighteen of 20 patients (90%) by evaluating the pupillary light reflex in each patient. Sympathetic nerve inhibition i.e. sympatholytic pattern, was recognized in ten of 18 patients (55%). Four patients with sympatholytic pattern had a disturbance not only in the sympathetic nerve, but also parasympathetic nerve involvement suggesting pandysautonomia. The residue blood level of the organochlorine pesticides was examined in each patient. A high frequency of the DDE was recognized (85%). It was concluded that the toxicity of the organochlorine pesticide on the autonomic nerve appear as an inhibitory effect on pupil light reflex.

Adult↗
PubMed1989

Detection and analysis of neutral endopeptidase from tissues with substrate gel electrophoresis.

Neutral endopeptidase from human or bovine tissues retains enzymatic activity following electrophoresis and immobilization in polyacrylamide gels. Infiltration of the gel with a fluorogenic substrate permits identification of the active enzyme by fluorescence associated with a distinct protein band. This technique both separates and identifies the enzymatically active species from a crude cell membrane fraction or from partially purified extracts that contain contaminating proteins. Enzymatic activity is quantitated by photographing the fluorescent bands and scanning the negatives with a laser densitometer. Because as little as 25 ng of enzyme can be detected by this method, it could be used where the amount of material is limited.

Animals↗
PubMed1989

The conditioning effect of optic nerve injury upon axonal regrowth from adult rat retinal ganglion cells explanted in vitro.

An in vitro assay was used to determine the effects of conditioning nerve lesions on the regeneration of adult rat retinal ganglion cell (RGC) axons from retinal explants. Following the conditioning lesion (CL) of unilateral optic nerve transection, maximal regrowth was seen from RGC explanted from ipsilateral retinae 10 days post-CL. Explants from this group initiated axonal regrowth earlier and a greater percentage regrew axons when compared with explants from normal rats. Axonal regrowth from explants of retinae contralateral to CL was also seen earlier than normal. In further experiments, the effects of both exposure of the optic nerve sheath in the orbit and the incision of the dura without injury to optic nerve axons were studied. The conditioning effect of a dural incision was found to be the same as that of optic nerve transection, whilst exposure of the optic nerve sheath had no conditioning effect on RGC axonal regrowth in vitro.

Animals↗