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Biomedical subjects

C J Lees

Publications and source records attributed to C J Lees.

29 records · Page 2Linked to original sources
PubMed1994

Bone mass in female cynomolgus macaques: a cross-sectional and longitudinal study by age.

A cross-sectional study by age was designed to evaluate and describe the bone mineral content (BMC, g) and density (BMD, g/cm2) in a population of female cynomolgus macaques (Macaca fascicularis). Dual-energy X-ray absorptiometry was used to measure, in segments L2-L4 of the lumbar spine, the BMC (BMCs), BMD (BMDs), length, and total-body BMC(BMCTB) in 171 female monkeys ranging in age between 3.7 and 22.0 years. The animals were divided into three age groups: (1) young (< 6.5 years, n = 51); (2) adult (> 6.5 years and < 10.5 years, n = 63); and (3) mature (> 10.5 years, n = 57). Young animals had a significantly lower (P < 0.05) body weight and shorter trunk length than adult or mature animals. Young animals also had significantly less (P < 0.05) BMCS, BMDS, and BMCTB than adult or mature animals, and had significantly shorter (P < 0.01) lumbar spine vertebral segments than the other two groups. Longitudinally, 63 animals had repeated lumbar spine scans to examine changes over time. Young animals showed a positive and significant change (P < 0.05) in BMCs and BMDs through time, whereas these parameters did not change in adult animals, and mature animals had a trend towards bone loss through time. Densitometric results suggested that peak bone mass in the lumbar spine was achieved by 9 years of age. Radiographic and dental criteria were developed to identify animals that had reached peak bone mass, and the combined radiographic and dental scoring system reliably identified animals 9 years and older. Female cynomolgus macaques 9 years old or older are recommended for investigations of bone remodeling and associated conditions, such as osteoporosis.

Aging↗
PubMed1994

Determining otitis media severity from middle ear fluid analysis.

Otitis media has a complex multifactorial pathogenesis, and the middle ear inflammatory response is typified by the accumulation of cellular and chemical mediators in middle ear effusion. However, specific biochemical and immunochemical factors that may be responsible for the severity or chronicity of otitis media have not been identified. Identification of factors involved in chronicity appears to be an essential step in the treatment and ultimate prevention of chronic otitis media. We analyzed 70 effusion samples from patients 1 to 10 years of age who had chronic otitis media with effusion for two cytokines (interleukin-1 beta and tumor necrosis factor alpha) and total collagenase. The highest concentrations of all three inflammatory mediators were found in purulent otitis media, and concentrations were higher in younger than in older patients. Mediator concentrations were similar in samples obtained from patients having their first myringotomy for otitis media with effusion and in those who had had multiple previous myringotomies. The multiresponse star, which incorporates several biochemical parameters in one graphic illustration, may best characterize the complex nature of middle ear inflammation.

Child↗
PubMed1984

Co-localization of superoxide generation and NADP formation in plasma membrane fractions from human neutrophils.

In order to resolve discrepancies in the literature concerning the subcellular localization of NADPH oxidase, we disrupted human neutrophils by nitrogen cavitation and fractionated the subcellular organelles on a discontinuous sucrose density gradient. The lightest fraction was 20- to 40-fold enriched for plasma membranes as determined by the marker enzymes alkaline phosphatase and phosphodiesterase I as well as by the ratio of lipid phosphorus to protein. There was a significant decrease in the specific activities of the granule markers myeloperoxidase, lysozyme, and beta-glucuronidase. An intermediate fraction was enriched in membrane markers but not to the extent the lightest fraction was enriched. This fraction contained more granular contamination, as shown by the marker enzymes. In contrast, the densest bands of the gradient were enriched for granule markers with little contamination by plasma membrane. Superoxide generation and NADP formation were primarily associated with the two membrane-enriched fractions from polymorphonuclear leukocytes stimulated with phorbol myristate acetate. The NADP formation associated with a dense granule fraction observed previously in our laboratory was probably due to a cyanide-stimulated oxidation of NADPH by myeloperoxidase.

Alkaline Phosphatase↗
PubMed1982

Identification and quantitation of electron-transport components in human polymorphonuclear neutrophils.

Using dithionite difference spectra we have detected cytochrome b in highly purified human neutrophils at a concentration of 0.08 nmol/mg protein. The presence of quinone was identified in lipid extracts at a concentration of approx. 0.06 nmol/mg protein. It was identified as ubiquinone-10 by mass spectrographic analysis. Simultaneous measurements of cytochrome oxidase indicated that these compounds could not be attributed to mitochondrial contamination. These results are compatible with the hypothesis that initiation of the respiratory burst in human neutrophils involves a multicomponent electron-transport system.

Cytochrome b Group↗
PubMed1982

Comparison of the calcium ionophore and phorbol myristate acetate on the initiation of the respiratory burst in human neutrophils.

We investigated the ability of the calcium ionophore A23187 and phorbol myristate acetate to elicit a respiratory burst in human neutrophils. In general, the ionophore was considerably more potent than phorbol myristate acetate in generating a chemiluminescent response and slightly less active in generating superoxide anion. In contrast, the ionophore caused a much smaller stimulation of glucose oxidation via the hexose monophosphate shunt. This relative inability of the ionophore to stimulate the shunt could not be ascribed to an effect on glucose transport or to a direct inhibition of any of the enzymes involved in glucose metabolism. These data suggest that different stimuli may have markedly different effects on various activities associated with the respiratory burst and emphasize the necessity for measurement of more than one parameter to assess the oxidative metabolism of the neutrophil.

Anti-Bacterial Agents↗
PubMed1981

Role of extracellular calcium and neutrophil degranulation responses to 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine.

The rabbit polymorphonuclear neutrophil degranulation response to 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine depends on extracellular calcium. In the absence of this bivalent cation, neutrophil suspensions pretreated with cytochalasin B responded to the lipid by releasing minimal amounts of lysozyme and beta-glucuronidase. Incremental increases in extracellular calcium over a range of 20-200 microM led to increasing amounts of lipid-stimulated enzyme release. In contrast, extracellular magnesium neither supported nor enhanced the degranulation responses. Verapamil (25-200 microgram/ml), a calcium channel blocker, inhibited degranulation. Neutrophil suspensions exposed to the phosphocholine stimulus rapidly took up radiolabeled extracellular calcium. The kinetics of this calcium uptake were similar to the kinetics of enzyme release, and the amount of calcium taken up correlated closely with the amount of released lysozyme and beta-glucuronidase. Finally, in a dosage which blocked degranulation, verapamil inhibited calcium uptake. Thus, the rapid association of extracellular calcium with the neutrophil may mediate, at least in part, the degranulating actions of the phosphocholine stimulus.

Animals↗
PubMed1981

Neutrophil-degranulating action of 5,12-dihydroxy-6,8,10,14-eicosatetraenoic acid and 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine. Comparison with other degranulating agents.

5,12-Dihydroxy-6,8,10,14-eicosatetraenoic acid was prepared from rabbit neutrophils challenged with ionophore A23187 plus arachidonic acid. It was purified by reverse-phase high-performance liquid chromatography with the use of a two-step procedure that effectively resolved the lipid from closely eluting contaminants. The phospholipid 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine was prepared from beef heart plasmalogen. Confirming earlier reports, both lipids stimulated human polymorphonuclear neutrophils to release granule-bound enzymes. Their respective degranulating actions took less than 5 minutes to become maximal, were dependent upon the presence of cytochalasin B, and required intact pathways of arachidonic acid metabolism, as judged by the inhibitory actions of arachidonate antimetabolites. Neither lipid required more than trace concentrations of extracellular calcium to effect optimal amounts of enzyme release. In one or more of these regards the two lipids differed strikingly from other neutrophil-degranulating agents such as A23187, N-formyl-methionyl-leucyl-phenylalanine, and phorbol myristate acetate. The mechanism of action of the two lipid stimuli, therefore, appear to differ somewhat from the mechanisms of the other three stimuli.

Animals↗
PubMed1981

Selective desensitization of neutrophils: further studies with 1-O-alkyl-sn-glycero-3-phosphocholine analogues.

Human polymorphonuclear neutrophils aggregate and degranulate in response to 2 recently described platelet-activating phospholipids: 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine and 1-O-alkyl-2-O-ethyl-sn-glycero-3-phosphocholine. Here, we find that the 2 phospholipids can also desensitize neutrophils. Thus, cells incubated with either phosphocholine for 1 to 5 min in the absence of calcium and magnesium (which are required for aggregation) did not aggregate when exposed to the bivalent cations and fresh lipid stimulus. Also, cells incubated with either lipid for 5 min in the absence of cytochalasin B (which is required for degranulation) did not degranulate when exposed to cytochalasin B and fresh lipid stimulus. However, these desensitized neutrophils aggregated and degranulated fully in response to the chemotactic oligopeptide N-formyl-methionyl-leucylphenylalanine and C5a. In relation to the aggregation response, this selective desensitization was not due to lipid inactivation; it persisted after thorough cell washing; and it was not induced by a nonaggregating analogue, 1-O-alkyl-sn-glycerol-3-phosphocholine. Furthermore, cells desensitized to the formylated oligopeptide or C5a (by preincubation with either stimulus in the absence of bivalent cations) did not aggregate when challenged with the oligopeptide or C5a, respectively, but exhibited a normal or enhanced aggregation response to the 2 active phospholipids. These data support the concept that C5a, formylated oligopeptides, and phosphocholines represent 3 distinct classes of stimulants that activate and densensitize neutrophils by at least partially independent pathways. This activation and desensitization may be mediated by 3 types of cellular receptors, each of which interacts with only 1 class of stimuli.

Animals↗
PubMed1981

Neutrophil-aggregating activity of monohydroxyeicosatetraenoic acids.

The following oxidative derivatives of arachidonic acid were prepared and assayed for their ability to aggregate cytochalasin-B-pretreated human neutrophils: 5-, 8-, 9-, 11-, 12-, and 15-hydroxyeicosatetraenoic acids. The compounds were prepared by oxidation of arachidonic acid and purified by direct and reverse phase high performance liquid chromatography. Each lipid was racemic at the hydroxy residue and had a cistrans conjugated double bond adjacent to the hydroxy residue. Except for racemization, therefore, they were identical to hydroxyeicosatetraenoic acids generated by neutrophils exposed to diverse aggregating stimuli. In addition, 15-L-hydroxyeicosatetraenoic acid was prepared from soybean lipoxygenase. Of these 7 fatty acid preparations, only 5- and 12-hydroxyeicosatetraenoic acid aggregated the cells. Thus, the bioactions of these lipids are crucially dependent upon the position of the hydroxy residue. The 5- and 12-hydroxy derivatives were potent aggregating agents, inducing half-maximal responses at 200 and 40 nM, respectively. Their bioactions required extracellular calcium and magnesium. And the response to both fatty acids was effectively blocked by three inhibitors of cellular arachidonic acid metabolism: nordihydroguaiaretic acid, 5,8,11,14-eicosatetraynoic acid, and indomethacin. The 5- and 12- hydroxyeicosatetraenoic acids, therefore, may induce neutrophils to metabolize their endogenous arachidonate. Alternatively, the two hydroxy acids themselves may be further metabolized through pathways inhibited by arachidonate antimetabolites into a final mediator(s) of aggregate formation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗