Monocyte kinetics: observations after pulse labeling

Because monocytes and their precursors cannot be recognized with certainty in tissues, an approach to the study of monocyte kinetics was made through examination of the peripheral blood. Injection of a single pulse of tritiated thymidine into rats resulted in the appearance of labeled monocytes identified as circulating peroxidase-positive mononuclear cells. The increase in the percent of labeled cells and in the mean grain count per cell followed a course described by a mathematical model with a generation time of 21 hours and a DNA synthesis time of 12.5 hours. The generation and synthesis times appear to be very uniform for the monocyte so that the phasing of cells represented by the uptake of label could be followed for more than two generations, a property not shared by neutrophils or lymphocytes. Monocytes appear in the circulation within eight hours of DNA synthesis.     

Neutrophil kinetics in O2-exposed rabbits

Hyperoxic injury results in an influx of polymorphonuclear leukocytes (PMN) into the lung. To better understand the role of the PMN in this injury, kinetic studies were used to assess the survival of PMNs in the circulation. The rate of deposition of PMNs in the lungs of rabbits exposed to hyperoxia was also examined. The half-lives (T1/2) of [3H]thymidine-labeled PMNs in the circulation in rabbits exposed to air or to 95% O2 for less than or equal to 48 h varied between 3.9 and 4.5 h. After 72 h of hyperoxic exposure, T1/2 fell to 2.2 h, the marginal and circulating PMN pool increased and 3H deposition in the lung increased 10-fold. Autoradiographs confirmed that [3H]thymidine was initially nuclear- and cellular-associated but, with time, [3H]thymidine dispersed throughout the lung, suggesting PMN disintegration. These PMN events seem to occur in the later phases of O2 toxicity, and because PMNs are an additional source of oxyradicals, they may further amplify oxidant injury.     

Stereoselective degradation kinetics of tebuconazole in rabbits

Tebuconazole[(RS)-1-p-chlorophenyl-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol] is a potent triazole fungicide and consists of a pair of enantiomers. The enantioselective degradation kinetics of tebuconazole was investigated in rabbits by intravenous (iv) injection. The concentrations of (-)-(R)-tebuconazole and (+)-(S)-tebuconazole in plasma and tissues were determined by HPLC with a cellulose tris(3,5-dimethylphenylcarbamate)-based chiral stationary phase. Enantioselective analysis methods for this fungicide in plasma and tissues were developed and validated. Good linearities were obtained over the concentration range of 0.25-25 mg/l for both enantiomers. The degradation followed pseudo-first-order kinetics and the degradation of the (+)-(S)-tebuconazole was much faster than that of the (-)-(R)-tebuconazole in plasma after administration of racemic tebuconazole. This study also indicated that environmental assessment of enantiomeric degradation may be needed to fully evaluate risks of tebuconazole use.     

Effect of honey on carbamazepine kinetics in rabbits

The study was undertaken to determine the effect of honey on carbamazepine kinetics in rabbits. The study was done on three occasions in each animal. Study 1 was carried out after single dose administration of carbamazepine (80 mg/kg, po), along with saline (2.34 ml/kg, po). After a wash out period of one week, the second study was carried out by co-administration of carbamazepine with honey (2.34ml/kg, po). After this, the animals continued to receive honey (2.34ml/kg, po), once daily, for 7 days. On the eighth day of honey treatment, the carbamazepine kinetics was studied again. Pharmacokinetic analysis revealed that single as well as multiple dose honey treatment showed a significant decrease in area under the plasma time concentration curve (AUC) when compared with saline treated control. A significant increase in the clearance (CL/F) rate of carbamazepine was observed only after multiple dose honey treatment. Both single and multiple dose honey treatment did not show any significant effect on other pharmacokinetic parameters like t1/2, Cmax, Tmax and Vd when compared with saline treated group. Data thus obtained suggested that honey decreases the bioavailability of carbamazepine.     

Neutrophil kinetics during active cigarette smoking in rabbits.

Polymorphonuclear leukocyte (PMN) transit through the pulmonary vasculature is slowed during inhalation of cigarette smoke in humans. This study was undertaken to determine the localization of the delayed PMN and whether they release granule-bound enzymes during smoke exposure. Anesthetized New Zealand White rabbits were exposed to cigarette smoke (n = 5) or sham (n = 5) for 10 min while they breathed spontaneously. The cardiac output, pulmonary blood volume and flow, and PMN retention were measured in each of five gravity-defined slices of lung. In three smoke-exposed and three sham animals the lungs were prepared for autoradiography, and the distribution of the radiolabeled PMN was determined. Plasma was assayed for myeloperoxidase in 10 animals. We found that smoke exposure caused increased PMN retention in the top two slices of the lungs without changing hemodynamics. The PMN were randomly distributed in the lobule, and plasma myeloperoxidase was elevated at the beginning of the exposure. We conclude that cigarette smoke may damage the lung by activating PMN in the pulmonary capillary bed.     

Influence of honey on orally and intravenously administered diltiazem kinetics in rabbits

Effect of honey on plasma concentration of diltiazem after oral and intravenous administration in rabbits, has been studied. For oral study, single dose of diltiazem (5 mg/kg, p.o.) along with saline was administered to New Zealand white rabbits (n=8). Blood samples were collected at 0, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6 and 8 hr after drug administration from marginal ear vein. After a washout period of one week, diltiazem was administered with honey (2.34 ml/kg; p.o.) and the blood samples were collected as above. To the same animals honey (2.34 ml/kg; p.o.) was continued once daily for 7 days. On 8th day, honey and diltiazem were administered simultaneously and blood samples were collected at similar time intervals as mentioned above. For intravenous study the pharmacokinetic was done in each animal on two occasions. The first study was done after single dose administration of diltiazem (5 mg/kg; i.v.) along with saline (2.34 ml/kg; p.o.). Blood samples were collected at 0, 0.083, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4 and 6 hr after i.v. diltiazem administration. The same animals were treated with honey (2.34 ml/kg; p.o.) for seven days. On day 8, the second study was carried out with single dose i.v. administration of diltiazem along with honey (2.34 ml/kg; p.o.) and blood samples were collected. In the oral study, single dose administration of honey decreased the AUC and Cmax of diltiazem associated with significant increase in clearance and volume of distribution when compared to saline treated group. After one week administration of honey, diltiazem kinetic data showed further reduction in AUC and Cmax and increase in clearance and volume of distribution. In the i.v. study also, multiple dose administration of honey significantly reduced the AUC and increased the clearance value of diltiazem. The results suggest that honey may decrease the plasma concentration of diltiazem after its oral or i.v. administration in rabbits.     

Trichostrongylus colubriformis: epithelial cell kinetics in the small intestine of infected rabbits

Epithelial cell kinetic parameters were compared in intestines of control and Trichostrongylus colubriformis infected rabbits using a microdissection and metaphase accumulation technique in regions of gut with heavy (proximal site) and small (distal site) burdens of worms. In control animals, the cell production rates were respectively 4.3 cells/crypt/hr in the proximal region and 3.7 cells/crypt/hr in the distal one; and the influx of cells onto villi were respectively 67.5 cells/hr and 37.4 cells/hr. In the parasitized rabbits, in the main site of infection, a fourfold increase was recorded in the cell proliferation rate and in the influx of cells onto villi. In the region distal to the main site of infection, the same parameters were twice the control values, although only a low number of T. colubriformis were recovered from this part of gut. These large modifications in the epithelial renewal probably underlies the morphological and enzymological changes previously described in both parts of the T. colubriformis infected gut.     

Monocyte Scintigraphy in Rheumatoid Arthritis: The Dynamics of Monocyte Migration in Immune-Mediated Inflammatory Disease

Background

Macrophages are principal drivers of synovial inflammation in rheumatoid arthritis (RA), a prototype immune-mediated inflammatory disease. Conceivably, synovial macrophages are continuously replaced by circulating monocytes in RA. Animal studies from the 1960s suggested that macrophage replacement by monocytes is a slow process in chronic inflammatory lesions. Translation of these data into the human condition has been hampered by the lack of available techniques to analyze monocyte migration in man.

Methods/Principal Findings

We developed a technique that enabled us to analyze the migration of labelled autologous monocytes in RA patients using single photon emission computer tomography (SPECT). We isolated CD14+ monocytes by CliniMACS in 8 patients and labeled these with technetium-99m (^99mTc-HMPAO). Monocytes were re-infused into the same patient. Using SPECT we calculated that a very small but specific fraction of 3.4×10⁻³ (0.95−5.1×10⁻³) % of re-infused monocytes migrated to the inflamed joints, being detectable within one hour after re-infusion.

Conclusions/Significance

The results indicate monocytes migrate continuously into the inflamed synovial tissue of RA patients, but at a slow macrophage-replacement rate. This suggests that the rapid decrease in synovial macrophages that occurs after antirheumatic treatment might rather be explained by an alteration in macrophage retention than in monocyte influx and that RA might be particularly sensitive to treatments targeting inflammatory cell retention.     

Monocyte function in mixed lymphocyte reactions

Subpopulations of human peripheral blood lymphocytes were isolated by sequential separation techniques. The stimulating and responding capacity of these cells together with the T-cell population remaining after the removal of other populations was studied in one-way allogeneic mixed lymphocyte culture. Incorporation of [³H]thymidine was used as a measure of response. Monocytes, present in the stimulating or responding cell population, were necessary for lymphocyte response. T cells stimulated responding T-cell populations containing monocytes but not B cells. Stimulation by T cells could be inhibited with DRW antisera. Response was also inhibited by sera detecting DRw antigens on the monocytes of the responding cell population. It is concluded that monocytes play an important functional role in mixed lymphocyte reactions. In addition, it appears that the combination of anti-DRw sera and monocytes influences mixed lymphocyte reactions by an active process in that inhibition of response cannot be explained entirely by blocking DRw determinants.     

单核细胞的血管壁募集

在机体的许多病理生理过程中,均可见外周血单核细胞粘附于内皮表面,并向内皮下游走,这一现象称为单核细胞的血管壁募集。粘附分子和粘受体在这一过程中起重要作用,多种细胞因子和趋化因子参与了单核细胞募集的调节。本文将对单核细胞募集的过程及特点、单核细胞募集的机制、调节及生物学效应和意义进行概述。     

Monocyte and macrophage heterogeneity

Heterogeneity of the macrophage lineage has long been recognized and, in part, is a result of the specialization of tissue macrophages in particular microenvironments. Circulating monocytes give rise to mature macrophages and are also heterogeneous themselves, although the physiological relevance of this is not completely understood. However, as we discuss here, recent studies have shown that monocyte heterogeneity is conserved in humans and mice, allowing dissection of its functional relevance: the different monocyte subsets seem to reflect developmental stages with distinct physiological roles, such as recruitment to inflammatory lesions or entry to normal tissues. These advances in our understanding have implications for the development of therapeutic strategies that are targeted to modify particular subpopulations of monocytes.     

Monocyte antibody-dependent cellular cytotoxicity in cancer patients

Summary Antibody-dependent cellular cytotoxicity (ADCC) mediated by peripheral blood monocytes was determined in 120 patients who had gastrointestinal tract (GIT), lung and breast cancer, melanoma, or Hodgkin's and non-Hodgkin's lymphoma. Results were expressed in terms of maximum cytotoxicity and cytotoxicity at E : T=1 : 10 and were compared with the results obtained in 63 normal subjects. There was a significant decrease in maximal cytotoxicity for both the GIT cancer and the melanoma patient groups, but not for any of the other groups. These differences were not confirmed when results were expressed at low effector: target cell ratios, e.g., cytotoxicity at E : T=1 : 10. The relationship between monocyte ADCC and disease extent was examined in those groups with sufficient numbers. Monocyte ADCC was higher in patients with GIT cancer of limited extent than in patients with extensive GIT cancer and in the control group.     

Monocyte antibody-dependent cellular cytotoxicity in splenectomized subjects

Monocyte antibody-dependent cellular cytotoxicity (ADCC) was determined in normal subjects by using human A1 erythrocytes and immune human anti-A1 antiserum. The experimental data were fitted to a mathematical model and the values for maximal cytotoxicity and monocyte numbers required to produce 15% specific cytotoxicity (MD15) were subsequently computed and compared with the values for these two parameters estimated from the dose response curves. The values for both were significantly associated, and the mathematical model permitted precise quantitation of cytotoxicity in instances where this was impossible by standard methods. Maximal monocyte ADCC was significantly reduced in a group of splenectomized subjects, whereas the MD15 was increased. These findings emphasize the possible influences of the method of quantitation of ADCC and provide one explanation for the apparent conflict of published data.     

Monocyte attachment to laminin in diabetes mellitus

Monocyte-extracellular matrix interactions have been implicated in atherosclerosis pathophysiology. Laminin, the main basement membrane protein contains cell binding domains that can be cryptic, presented only after protein modification. In the present study we evaluated monocyte attachment to laminin-1 in the presence of ATP. Monocytes were derived from either healthy volunteers or patients with diabetes mellitus type II. For the estimation of monocyte attachment to laminin the myeloperoxidase assay was used. Monocytes derived from diabetic patients, showed an increased ability to attach to laminin (p=0.0055). The presence of ATP increased the attachment of control monocytes to laminin (p = 0.0022). On the contrary, the presence of ATP did not affect the attachment of monocytes derived from diabetic patients to laminin. Our results indicate a modified interaction between monocytes and laminin-1 in diabetes mellitus.     

Monocyte chemotactic protein-3.

Monocyte chemotactic protein-3 (MCP-3) belongs to the MCP subgroup of CC chemokines that are structurally closely related but, which differ in receptor usage and hence in biological activities. MCP-3 is one of the most pluripotent chemokines since it activates all types of leukocytes, by binding to at least four different chemokine receptors. The natural protein is heterogeneous due to glycosylation and NH2-terminal processing. Only small amounts of MCP-3 are induced in various cell types by endogeneous (cytokines) or exogeneous (bacteria, viruses) agents. Nevertheless, this omnipotent chemokine, inducible in most body compartments, might play an important role in normal homeostasis as well as in various pathologies including cancer, auto-immune diseases and chronic inflammation.