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Biomedical subjects

D M Lewis

Publications and source records attributed to D M Lewis.

At least 91 records · Page 5Linked to original sources
PubMed1990

Neutrophil derived interference in the fluorometric determination of histamine.

Zymogen-stimulated neutrophils release many pre- and non-preformed factors including proteolytic enzymes, oxygen free radicals and arachidonic acid metabolites. Measurement of the histamine concentration of a supernatant fluid commonly employs an organic extraction procedure followed by condensation to o-phthalaldehyde. Diamine oxidase digestion studies and high-performance liquid chromatographic analysis suggest that a factor(s) derived from zymogen-stimulated neutrophils can produce a positive interference in the fluorometric determination of histamine.

Amine Oxidase (Copper-Containing)↗
PubMed1990

Microbiological analyses and inflammatory effects of settled dusts from rice and hay.

Fourteen samples of settled dust from two factories processing rice and wheat straw near Shanghai, China, were examined by dilution plating for total bacteria, gram-negative bacteria, thermophilic actinomycetes, and fungi. They were also examined for aflatoxin, endotoxin, and potential to stimulate production of human interleukin 1 beta (IL-1 beta) and to consume complement. The concentrations of total microorganisms were consistently greater than 10(7) CFU/g and ranged from 10(7) to 10(9) CFU/g. In general, the level of microbial contamination was greater in the hay dust samples than in the rice dust samples, with bacteria being the most numerous microorganisms observed followed by molds, thermophilic actinomycetes, and yeasts. The predominant fungi were species of Aspergillus, Cladosporium, Penicillium, Trichosporon, and Cryptococcus. No significant levels of aflatoxin were observed and the isolates of A. flavus examined lack significant aflatoxigenic potential. The levels of microorganisms in these samples, the types of organisms found, and the inflammatory mediators such as endotoxin suggest that workers exposed to these dusts may be at risk for respiratory illness.

Aflatoxins↗
PubMed1989

The relationship between radionuclide bone scans and dental examinations.

Bone scans were evaluated in 57 patients referred from the nuclear medicine clinic. Areas of normal and abnormal radiopharmaceutical accumulation in the maxilla and mandible were correlated with a clinical and radiographic dental examination. There was an 80% agreement between the areas of normal and abnormal uptake with the clinical and radiographic findings. This was statistically significant (p less than 0.001). Twenty-one patients had clinical and radiographic dental examinations that were within normal limits and yet had abnormal bone scans. Five of these 21 patients were subsequently seen on an emergency basis for treatment of dental abnormalities. These positive areas on the bone scans may be indicating areas of pathosis not detectable by conventional clinical and radiographic diagnostic techniques.

Adult↗
PubMed1989

Contractile characteristics and innervation ratio of rat soleus motor units.

1. Physiological properties of motor units in the soleus muscle were studied in anaesthetized rats using ventral root splitting to isolate single units. 2. Motor unit types were classified by the same criteria used to classify cat hindlimb motor units into types FR (fast-twitch, fatigue-resistant) and type S (slow-twitch, fatigue-resistant). Type FR units were estimated to generate 10% of whole-muscle tension and type S 90%. All FR units showed sag in the unfused tetanus at frequencies with interpulse intervals greater than 175% of twitch time to peak, but not at 125% (Burke, Levine, Tsairis & Zajac, 1973). 3. The muscle fibres belonging to twelve single motor units were depleted of glycogen by prolonged stimulation, permitting analysis of their histochemical profiles. Type FR units were found to consist of type IIA muscle fibres and type S units of type I muscle fibres. 4. Direct determinations were made of fibre area, innervation ratio (number of muscle fibres supplied by one motoneurone) and hence specific tension (tetanic tension generated per unit cross-sectional area) of individually identified motor units. Motoneurons were found to innervate between 84 and 178 muscle fibres (mean 110) in type S units and between 126 and 161 fibres in type FR units (mean 142). Fibre areas were larger for type FR units and there was a significant difference in specific tension of the two unit types (type S lower). 5. Indirect estimates of innervation ratio and specific tension were obtained from counts of muscle fibre types, and relative frequencies of motor unit types in the soleus unit pool. Observations agreed well with results of direct measurements. 6. The evidence provided suggests that differences in tension generated by type FR and S units in rat soleus muscle are primarily due to differences in innervation ratio and fibre area, with a small contribution from differences in specific tension.

Animals↗
PubMed1989

A comparison of the effects of denervation on the mechanical properties of rat and guinea-pig skeletal muscle.

1. A fast (extensor digitorum longus) and slow (soleus) twitch muscle were denervated in rats and guinea-pigs and isometric and isotonic contractions were followed for periods of up to 6 months after. 2. The decay of tetanic tension with time could be described as exponential. The rate of decay of tension was greatest in rat soleus and least in guinea-pig soleus by a factor of more than three. The fast muscles atrophied at intermediate rates. 3. The contraction and relaxation times of soleus and extensor digitorum longus of rat, initially prolonged by denervation, became shorter after 3 weeks. There was no such reversal in either guinea-pig muscle, indeed extensor digitorum longus twitch became even more prolonged. Guinea-pig muscles often showed signs of repetitive response to a single stimulus, resulting in distortion of relaxation of the twitch. 4. There was a slowing of isotonic shortening velocity in the late stage of denervation of guinea-pig extensor digitorum longus, accompanied by a fall in the rate of development of isometric tetanic tension. There was a just-significant (P less than 0.1) increase in the shortening velocity of rat soleus. None of the other muscles showed any change in either rate characteristic. 5. In guinea-pig extensor digitorum longus the type I fibres atrophied less than type II fibres; in all other muscles the atrophy was more uniform, possibly faster in type II. Guinea-pig soleus remained pure type I contrasting with an increase in the numbers of type II fibres in rat soleus. There was a possible increase in the number of type I fibres in guinea-pig fast muscle and no change in the rat.

Animals↗
PubMed1989

Effects of different extraction protocols on endotoxin analyses of airborne grain dusts.

The detection of gram-negative bacterial endotoxins in occupational dusts, specifically those from agricultural environments, is of increasing importance in research on occupational lung disease. In this study, the quantitative chromogenic Limulus amebocyte lysate test for the detection of endotoxins in airborne dusts from spring wheat and oats was examined. Different extraction fluids were tested, as were the effects of time on extraction and of repeated freeze-thaw cycles on the extracts. The data suggest that the chromogenic method can be used effectively in the analysis of environmental dusts or their frozen extracts for endotoxin quantitation. Water appears to be the preferable extraction medium, and the length of extraction time may affect the results.

Dust↗
PubMed1988

Production and properties of histamine-releasing factor of guinea pigs.

The production of histamine-releasing factor (HRF) by human mononuclear cells has previously been reported. In this paper we describe the production of HRF by guinea pig spleen cells, thymocytes, and PBMC. Guinea pig lymphoid cells were cultured either alone or in the presence of mitogens (PHA and Con A) or specific Ag(OVA and keyhole limpet hemocyanin) and the dialyzed cell-free supernatant was tested for histamine-releasing activity on guinea pig lung mast cells and blood basophils. Lung mast cells were isolated by enzymatic digestion and partially purified by countercurrent elutriation and discontinuous Percoll gradient centrifugation. Guinea pig spleen cells, thymocytes, and PBMC spontaneously produced significant amounts of HRF. The production was enhanced upon stimulation with PHA or specific Ag in animals immunized with Ag in CFA. Two distinct species of HRF were identified with m.w. of 50,000 to 70,000 and 5000 to 8000 by gel chromatography. HRF is a trypsin- and chymotrypsin-sensitive heat-stable protein. It does not bind to Con A-Sepharose and its production is not inhibited by tunicamycin. HRF-induced histamine release from lung mast cells is a temperature-dependent process and is complete in 10 min at 37 degrees C. Intradermal injection of HRF caused an immediate ear-swelling reaction in guinea pigs. The most severe ear-swelling reactions did not resolve within 1 h, but instead evolved over a period of 12 to 24 h.

Animals↗
PubMed1988

Identification of a histamine release inhibitory factor (HRIF) and an inhibitor of histamine releasing factor synthesis (IHS) produced by guinea pig lymphoid cells.

Guinea pig spleen cells, thymocytes, and blood mononuclear cells have been shown to produce a histamine releasing factor (HRF) spontaneously or after stimulation with PHA or specific antigens. In this study we have shown that antigenic stimulation of spleen cells obtained from animals immunized with high doses of antigen suppresses the spontaneous HRF production. Likewise, stimulation with Con A of spleen cells also inhibits the spontaneous HRF production. When the supernatants from Con A- and antigen-stimulated cultures were added to fresh thymocyte cultures, a significant inhibition of HRF production was observed. These supernatants also inhibited HRF-induced histamine release from mast cells. We have identified an inhibitor of HRF synthesis (IHS) and also a histamine release inhibitory factor (HRIF) by gel chromatography. Virtually all mitogen- and antigen-stimulated culture supernatants elaborated the activities of HRF, IHS, and HRIF in various quantities depending on the dose of antigen and the kind of adjuvant used for immunization. IHS has a MW of 22K-35K and 10K. This cytokine also inhibits DNA synthesis by thymocytes. HRIF has a MW of 15K-20K and 10K. It inhibits both HRF- and antigen-induced histamine release from lung mast cells. These results suggest that lymphocytes produce a variety of factors which function to regulate histamine release from mast cells.

Animals↗
PubMed1988

Activation of guinea pig lymphocytes and mast cells by grain-dust extract.

Previous studies have demonstrated that grain dust can stimulate lymphocyte proliferation and the production of interleukin-1 by macrophages. This study was undertaken to investigate whether grain dust could stimulate the production of histamine-releasing factor (HRF) by guinea pig spleen cells. We also studied the direct action of grain dust on guinea pig lung mast cells and basophils. Plastic nonadherent cells from immunized animals were cultured for 24 hours in the presence of grain dust or lipopolysaccharide, and the cell-free supernatants were assayed for HRF activity in the mast cell and basophil histamine release test. Lung mast cells were isolated by enzymatic digestion and discontinuous Percoll gradient centrifugation. It has been demonstrated that grain dust stimulated the production of HRF by spleen cells from the immunized animals but not from the control animals. Stimulation of spleen cells with lipopolysaccharide did not enhance the HRF production. Gel chromatography of grain dust-stimulated supernatant revealed that HRF has a molecular weight in the range of 50 to 70 kd and 5 to 8 kd. We also found that grain dust directly released significant amount of histamine from both mast cells and basophils. The results of this study suggest that grain dust contains some potent active substances that can activate lymphocytes, mast cells, and basophils.

Animals↗
PubMed1988

Inflammatory potential of grain dust.

A comparative analysis of toxicity and inflammatory potential of spring wheat, oat, corn, and flax seed was performed. The extracts were examined by quantification of gram-negative bacterial endotoxin and protein contents, chemotaxis for purified human polymorphonuclear leukocytes, and several alveolar macrophage functions including phagocytosis, release of lactate dehydrogenase, macromolecular synthesis (protein and RNA), and interleukin-1 production. The results suggested that the extracts of all four grain dusts inhibited protein synthesis and decreased phagocytosis of alveolar macrophages at 7.5-25 mg/ml. Protein synthesis was inhibited to 40.2% of control and phagocytosis to 47.9% of control. Interleukin-1 production was stimulated, as indicated by a stimulation index range from 3.8-fold to 14.3-fold over controls. The activity of these grain dust extracts did not correlate with the endotoxin content of the samples. The data demonstrate that the extracts of all four dusts produced ill effects in rat alveolar macrophages in vitro and suggested a potential hazard to agricultural workers exposed to grain dust.

Air Pollutants↗
PubMed1987

Demonstration of inflammatory cell population changes in rat lungs in response to intratracheal instillation of spring wheat dust using lung enzymatic digestion and centrifugal elutriation.

The inhalation of grain dust by grain workers is responsible for a large number of pulmonary pathophysiologies. These problems may be acute or chronic and may be mediated by the chronic activation of the immune system. Constant inflammatory states in the lung may eventually lead to tissue damage and respiratory deficit. This study was designed to measure the changes in the relative number of inflammatory cells in peripheral blood, bronchoalveolar spaces, and lung interstitium that occur in response to intratracheally instilled airborne spring wheat dust in rats. It was found that 6 h after instillation with dust, neutrophils were present in greater numbers in the blood and bronchoalveolar spaces than in lung interstitium. After 24 h, there appeared to be a larger number of neutrophils in the lung interstitium in dust-instilled animals than in saline-instilled controls. These results indicate that intratracheal instillation of grain dust initiates an acute inflammatory reaction, and that there is an initial influx of neutrophils into the air spaces of the lung followed by transit of these cells into the lung interstitium.

Animals↗
PubMed1987

The role of frequency in the effects of long-term intermittent stimulation of denervated slow-twitch muscle in the rat.

1. Rat soleus muscle was denervated by sciatic transection and electrically stimulated for periods of between 3 and 9 weeks with intermittent 1 s bursts of pulses. Most of the bursts were either repeated every 90 s and pulses within them had frequencies between 10 and 100 Hz, or had a frequency of 50 Hz and were repeated at intervals between 60 and 600 s. Comparisons were made with continuous stimulation at 10 Hz. 2. At the end of the period of stimulation, isometric twitches and tetani were measured and, in a proportion, also isotonic shortening velocity. 3. Isometric twitch duration (contraction and relaxation) decreased with time of stimulation. Very similar effects were seen in all animals in which intermittent stimulation had been used. There was a significant relationship between the change in twitch duration and the frequency used within the bursts of chronic stimulation, with slightly larger effects at frequencies of 40 and 60 Hz. The lowest burst repetition rate produced the largest effects. 4. It was confirmed that similar changes were found in denervated muscles that were not stimulated, although these changes were smaller and developed more slowly. 5. The extreme loss of tetanic tension induced in the muscle by denervation was reduced by chronic stimulation, with no significant difference between different regimes, although there were small differences which showed the same patterns of effectiveness described for twitch durations. 6. Continuous stimulation at 10 Hz maintained the twitch contraction and relaxation phases at the values found 3 weeks after denervation, that is it prevented secondary shortening of the twitch. Continuous stimulation reduced tension loss but was, perhaps, less effective than intermittent stimulation. 7. Twitch-tetanus ratio increased with denervation with little spontaneous reversal later. Stimulation at all frequencies reduced the ratio, but it did not reach normal values. 8. Isotonic shortening velocity was measured in many of the muscles. Maximum velocity was estimated and normalized by muscle length.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Multiple osteosclerotic masses of the jaw.

Florid osseous dysplasia is a peculiar reactive or developmental bone disease that is known to appear only in the jaws. It has an inexplicable decided predilection for occurrence in middle-aged, black women. Extent of the disease may vary from a few isolated periapical lesions to diffuse involvement of the mandibular and maxillary alveolar processes. Radiographically, it is characterized by multiquadrant, globular, radiolucent-radiopaque lesions. Histopathologically, it is a benign fibro-osseous lesion that must be differentiated from other benign fibro-osseous lesions such as fibrous dysplasia, ossifying fibroma, Paget's disease, and sclerosing osteomyelitis on the basis of combined clinical, radiographic, and histological features. Correctly identifying this disease is important because it requires no treatment unless a secondary osteomyelitis develops. Sequestrae and osteomyelitis are complications arising when teeth are removed and removable dental prostheses are supported by diseased bone.

Diagnosis, Differential↗