In vivo interaction between alveolar macrophages and Cryptococcus neoformans

In vivo interactions of rabbit alveolar macrophages (AM) and Cryptococcus neoformans, a yeast pathogenic for humans, were studied. As a control, inert silica particles of a similar diameter (5–6 μm) were used. Of 16 rabbits, 6 were instilled intratracheally with fluorescein-labelled heat-killed C. neoformans, 6 with fluorescein-labelled silica particles and 4 with saline only. After 24 h, the AM were collected by lung lavage, and phagocytosis, oxidative metabolism, phagolysosomal pH and morphology were studied. The accumulated number of yeasts attached to the AM was almost the same for C. neoformans as for the silica particles. The ingested fraction of C. neoformans was even higher than that of the silica particles. Quantitative NBT reduction by the AM, reflecting their oxidative metabolism, was markedly increased by exposure to C. neoformans for 24 h. The phagolysosomal pH was on the average lower in phagolysosomes with C. neoformans than with the silica particles, although approximately 2% of the phagolysosomes with C. neoformans had neutral pH. Phagolysosomes with neutral pH was not observed for silica particles. Electron microscopy showed presence of C. neoformans in phagolysosomes of AM. The conclusion of this study is that the phagocytic activity, oxidative metabolism and phagolysosomal pH AM against C. neoformans are significant 24 h after the exposure. This revised version was published online in June 2006 with corrections to the Cover Date.     

Growth hormone in urine: development of an ultrasensitive assay applicable to plasma and urine

A radiometric assay for human growth hormone (HGH) was developed based on a polyclonal goat anti-HGH antiserum covalently coupled to nonsedimenting polyacrylamide particles. HGH can be specifically immunoextracted from sample volumes of up to 10 ml. Subsequently, bound HGH is identified and quantitatively measured by a 125I-labelled monoclonal anti-HGH antibody. The assay is insensitive to plasma proteins from 10 to greater than 90%, to changing NaCl and urea molarities and to pH ranges from 6 to 8. The sensitivity in the second incubation is 2 pg/tube, corresponding to a maximum sensitivity of 300 fg/ml of a sample volume of 10 ml (urine) or of 40 pg/ml, if a volume of 50 microliter (plasma) is assayed. In healthy children, a mean HGH excretion of 6.5 ng/24 h was found with a large interindividual range from undetectable to 37.4 ng. An important intraindividual night-to-night variation of HGH excretion was found in several subsequent first morning void samples in healthy children. The mean excretion in 13 HGH-deficient children was 0.9 ng/24 h off therapy and increased to a mean of 6.9 ng/24 h on therapy. In acromegalic patients, the excreted HGH amounted to 73-208 ng/24 h. Preliminary results suggest that the ultrasensitive assay applied to plasma and urine could be a considerable improvement of diagnosis and follow-up of disorders of HGH secretion.     

Surfactant protein A enhances alveolar macrophage phagocytosis of apoptotic neutrophils

Surfactant protein A (SP-A) is an innate immune molecule that binds foreign organisms that invade the lungs and targets them for phagocytic clearance by the resident pulmonary phagocyte, the alveolar macrophage (AM). We hypothesized that SP-A binds to and enhances macrophage uptake of other nonself particles, specifically apoptotic polymorphonuclear neutrophils (PMNs). PMNs are recruited into the lungs during inflammation, but as inflammation is resolved, PMNs undergo apoptosis and are phagocytosed by AMs. We determined that SP-A increases AM phagocytosis of apoptotic PMNs 280 +/- 62% above the no protein control value. The increase is dose dependent, and heat-treated SP-A still enhanced uptake, whereas deglycosylated SP-A had significantly diminished ability to enhance phagocytosis. Surfactant protein D also increased phagocytosis of apoptotic PMNs by approximately 125%. However, other proteins that are structurally homologous to SP-A, mannose-binding lectin and complement protein 1q, did not. SP-A enhances phagocytosis via an opsonization-dependent mechanism and binds apoptotic PMNs approximately 4-fold more than viable PMNs. Also, binding of SP-A to apoptotic PMNs does not appear to involve SP-A's lectin domain. These data suggest that the pulmonary collectins SP-A and SP-D facilitate the resolution of inflammation by accelerating apoptotic PMN clearance.     

Investigations on cellular defense reactions with Galleria mellonella against Bacillus thuringiensis

In contrast to a great number of foreign particles (bacteria and inorganic materials), cells of some strains of Bacillus thuringiensis are not phagocytosed in the first hours after injection into the hemocoel of Galleria mellonella. This phenomenon is not caused by the production of β-exotoxin or exoenzymes, because heat-killed cells are not phagocytosed and the phagocytosis of latex particles is not prevented by the presence of living B. thuringiensis. The phagocytosis of heat-killed B. thuringiensis subtoxicus can be encouraged by treatment of the cells and by simultaneous injection of latex particles. A factor stimulating the phagocytosis is discussed. It is induced by the injection of phagocytosable latex particles into the hemocoel but not by injection of living or killed B. thuringiensis subtoxicus.     

Differential gene expression of adrenomedullin receptors in pressure- and volume-overloaded heart--role of angiotensin II

Left ventricular (LV) adrenomedullin (AM) gene expression differs between pressure overload (POL) and volume overload (VOL) and angiotensin II could be a critical stimulator of AM gene expression in POL and VOL models. Calcitonin receptor-like receptor (CRLR) co-expressed with receptor activity modifying protein 2 (RAMP2) or RAMP3 functions as an AM receptor. Levels of CRLR, RAMP2 and RAMP3 mRNA that were significantly increased within 24 h returned to the basal level at 5 days after the imposition of POL in the present study. In contrast, mRNA levels of CRLR and RAMP2 gradually increased over 6 weeks after the imposition of VOL. Continuous infusion of angiotensin II stimulated LV AM gene and AM receptor gene expression independently of LV peak-systolic and LV end-diastolic pressure. The gene expression of LV AM receptors increased in different types of cardiac overload. The present study revealed an intimate association between the AM signaling system and angiotensin II.     

PLATELET PHAGOCYTOSIS AND AGGREGATION

The addition of latex particles to native (no anticoagulant) or citrated human platelet-rich plasma (PRP), or to a once-washed platelet suspension causes platelet aggregation. This aggregation is associated with phagocytosis of the latex particles by the platelets and appears to be due to release of adenosine diphosphate (ADP) from the platelets. Adenosine and adenosine monophosphate, which are known to inhibit platelet aggregation induced by ADP, also block that induced by latex. These compounds do not prevent the phagocytosis of latex particles by the platelet. The addition of iodoacetate and 2,4-dinitrophenol in appropriate concentrations to the PRP, prior to the addition of the latex, blocks platelet aggregation and phagocytosis. This is also true for the chelating agent ethylenediaminetetraacetate (EDTA). Platelets left in contact with latex for a sufficient period of time show loss of their granules. Leucocytes phagocytose both latex and platelets that had themselves phagocytosed latex. It is concluded that phagocytosis of latex particles by platelets resembles that by white cells, and that in both processes metabolic changes appear to be involved.     

Rapid phagocytosis and melanization of bacteria and Plasmodium sporozoites by hemocytes of the mosquito Aedes aegypti

Mosquitoes are vectors of many deadly and debilitating pathogens. In the current study, we used light and electron microscopies to study the immune response of Aedes aegypti hemocytes to bacterial inoculations, Plasmodium gallinaceum natural infections, and latex bead injections. After challenge, mosquitoes mounted strong phagocytic and melanization responses. Granulocytes phagocytosed bacteria singly or pooled them inside large membrane-delimited vesicles. Phagocytosis of bacteria, Plasmodium sporozoites, and latex beads was extensive; we estimated that individual granulocytes have the capacity to phagocytose hundreds of bacteria and thousands of latex particles. Oenocytoids were also seen to internalize bacteria and latex particles, although infrequently and with low capacity. Besides phagocytosis, mosquitoes cleared bacteria and sporozoites by melanization. Interestingly, the immune response toward 2 species of bacteria was different; most Escherichia coli were phagocytosed, but most Micrococcus luteus were melanized. Similar to E. coli, most Plasmodium sporozoites were phagocytosed. The immune response was rapid; phagocytosis and melanization of bacteria began as early as 5 min after inoculation. The magnitude and speed of the cellular response suggest that hemocytes, acting in concert with the humoral immune response, are the main force driving the battle against foreign invaders.     

Quantification and stability of everolimus (SDZ RAD) in human blood by high-performance liquid chromatography-electrospray tandem mass spectrometry

We report here a validated method for the quantification of a new immunosuppressant drug, everolimus (SDZ RAD), using HPLC-tandem mass spectrometry. Whole blood samples (500 microl) were prepared by protein precipitation, followed by C(18) solid-phase extraction. Mass spectrometric detection was by selected reaction monitoring with an electrospray interface operating in positive ionization mode. The assay was linear from 0.5 to 100 microg/l (r(2) > 0.996, n = 9). The analytical recovery and inter-day imprecision, determined using whole blood quality control samples (n = 5) at 0.5, 1.2, 20.0, and 75.0 microg/l, was 100.3 - 105.4% and < or = 7.6%, respectively. The assay had a mean relative recovery of 94.8 +/- 3.8%. Extracted samples were stable for up to 24 h. Fortified everolimus blood samples were stable at -80 degrees C for at least 8 months and everolimus was found to be stable in blood when taken through at least three freeze-thaw cycles. The reported method provides accurate, precise and specific measurement of everolimus in blood over a wide analytical range and is currently supporting phase II and III clinical trials.     

Effect of the arbuscular mycorrhizal symbiosis upon uptake of cesium and other cations by plants

Pot experiments were set up to determine the species-specific uptake of cesium (Cs) by mycorrhizal (AM) and non-mycorrhizal (non-AM) plants. Using stable Cs and K application, side-effects of mineral fertilization (K) on AM development and uptake of Cs and the other cations Na, Ca and Mg were investigated. AM colonization by the fungus Glomus mosseae led to a significant decrease in shoot Cs content of Agrostis tenuis from the first (4 weeks) to the third harvest (8 weeks). With regard to the root system, statistically significant differences were observed from the first (4 weeks) to the second harvest (6 weeks). Supply of additional K produced a significant decrease in Cs uptake by both AM and non-AM plants over a 10-week period. In the case of AM plant shoots, K fertilization did not very effectively reduce Cs uptake by A. tenuis. Cs contents of fertilized AM roots were similar to non-AM controls. Potassium application resulted in an increase in K content and a slight reduction in Na and Mg contents of shoots and roots. Without K fertilization, the Na content of non-AM controls was significantly enhanced over AM shoots. Shoot and root Ca contents were generally higher without than with K addition. Negative side-effects of K fertilization as a countermeasure to Cs uptake were not observed in relation to AM development. The intensity of colonization by G. mosseae was not significantly depressed by K treatment. AM development in plants appeared to decrease Cs uptake, at least at moderate nutrient levels. It is possible that Cs is sequestered by AM extraradical fungal hyphae and consequently not transferred to the plant to the extent found in non-AM roots. Accepted: 6 November 2000     

Microfluorometric Evaluation of Calcein Acetoxymethyl Ester as a Probe for P-Glycoprotein-Mediated Resistance: Effects of Cyclosporin A and Its Nonimmunosuppressive Analogue SDZ PSC 833

A microtiter plate-based fluorometric assay for functional measurement of 170-kDa P-glycoprotein (Pgp)-mediated transport using fluorescent calcein as a probe is described. The myeloma RPMI 8226 cell line and two of its doxorubicin-resistant Pgp-expressing sublines, dox40 (high expression) and dox6 (low expression), were used as models. Nonfluorescent calcein acetoxymethyl ester (calcein/AM) was added to the cells and subsequent accumulation of calcein was measured in a 96-well scanning fluorometer after 30 min. There was an inverse relationship between Pgp expression and calcein/AM accumulation, which increased dose-dependently in the presence of cyclosporin A (CsA) and the nonimmunosuppressive analogue SDZ PSC 833 (PSC) in the Pgp-expressing cell lines. PSC appeared to restore uptake more effectively than CsA at low concentrations. Calcein accumulation was also increased in Pgp-expressing cells by the addition of the Pgp substrate vincristine and the metabolic inhibitor potassium cyanide, KCN. No effect was observed in parental cell lines. When parental and dox40 cells were mixed, 10% of dox40 cells could reproducibly be detected. The results indicate that microtiter-plate determination of calcein accumulation is a simple and sensitive method for functional determination of Pgp-mediated drug transport. The method may become useful, not only for preclinical screening for novel and improved resistance modifiers, but also for determination of Pgp activity in individual clinical tumor samples.     

Mechanism of phagocytosis in dictyostelium discoideum: phagocytosis is mediated by different recognition sites as disclosed by mutants with altered phagocytotic properties

The recognition step in the phagocytotic process of the unicellular amoeba dictyostelium discoideum was examined by analysis of mutants defective in phagocytosis, Reliable and simple assays were developed to measure endocytotic uptake. For pinocytosis, FITC-dextran was found to be a suitable fluid-phase marker; FITC-bacteria, latex beads, and erythrocytes were used as phagocytotic substrates. Ingested material was isolated in one step by centrifuging through highly viscous poly(ethyleneglycol) solutions and was analyzed optically. A selection procedure for isolating mutants defective in phagocytosis was devised using tungsten beads as particulate prey. Nonphagocytosing cells were isolated on the basis of their lower density. Three mutant strains were found exhibiting a clear-cut phenotype directly related to the phagocytotic event. In contrast to the situation in wild-type cells, uptake of E. coli B/r by mutant cells is specifically and competitively inhibited by glucose. Mutant amoeba phagocytose latex beads normally but not protein-coated latex, nonglucosylated bacteria, or erythrocytes. Cohesive properties of mutant cells are altered: they do not form EDTA-sensitive aggregates, and adhesiveness to glass or plastic surfaces is greatly reduced. Based upon these findings, a model for recognition in phagocytosis is proposed: (a) A lectin-type receptor specifically mediates binding of particles containing terminal glucose (E. coli B/r). (b) A second class of "nonspecific" receptors mediate binding of a variety of particles by hydrophobic interaction. Nonspecific binding is affected by mutation in such a way that only strongly hydrophobic (latex) but not more hydrophilic particles (e.g., protein-coated latex, bacteria, erythrocytes) can be phagocytosed by mutant amoebae.     

Effect of orexin-A on phagocytic activity of peritoneal macrophage in starved rats

The aim of this study was to investigate the effect of fasting-induced orexin-A (OXA) on inflammation and macrophage phagocytic activity. Fifty six male wistar rats were fasted for 36 h to stimulate OXA synthesis. In 24 rats, air pouches were induced subcutaneously in the intrascapular area. After (6 h) carrageenan injection into the pouches, the contents of the air pouches were removed. The exudate volume, protein content and cell count were measured. After the determination of fasting on inflammation, the peritoneal macrophages were collected from 32 rats to investigate the effect of fasting-induced OXA on macrophage phagocytic activity. Plasma OXA levels were markedly higher in fasted rats compared with control rats. The phagocytic capability of peritoneal macrophages was obtained as a percentage of phagocytosing macrophages and number of phagocytosed particles per cell. In spite of increased blood OXA level SB-334867, selective orexin type 1 receptor antagonist (10 mg/kg) did not change phagocytic activity of peritoneal macrophages. These findings indicate that 36 h fasting-induced OXA has no significant effect to phagocytosis of peritoneal macrophages.     

Mode of action of SDZ NIM 811, a nonimmunosuppressive cyclosporin A analog with activity against human immunodeficiency virus (HIV) type 1: interference with HIV protein-cyclophilin A interactions.

Cyclosporins, in particular the nonimmunosuppressive derivative SDZ NIM 811, exhibit potent anti-human immunodeficiency virus type 1 (HIV-1) activity in vitro. SDZ NIM 811 interferes at two stages of the viral replication cycle: (i) translocation of the preintegration complex to the nucleus and (ii) production of infectious virus particles. Immunosuppressive activity is not correlated with anti-HIV-1 activity of cyclosporins. However, binding to cyclophilin A, the major cellular receptor protein of cyclosporins, is a prerequisite for HIV inhibition: all structural changes of the cyclosporin A molecule leading to loss of affinity to cyclophilin abolished the antiviral effect. Cyclosporin derivatives did not interact directly with HIV-1 proteins; cyclophilin was the only detectable receptor protein for antivirally active cyclosporins. There is no evidence that inhibition of HIV occurs via a gain of function of cyclophilin in the presence of cyclosporins: the complex of cyclophilin A with SDZ NIM 811 does not bind to calcineurin or to any other viral or cellular proteins under conditions in which calcineurin binding to the cyclophilin A-cyclosporin A complex is easily detectable. Thus, the loss of function caused by binding of cyclosporins to cyclophilin seems to be sufficient for the anti-HIV effect. Cyclophilin A was demonstrated to bind to HIV-1 p24gag, and the formation of complexes was blocked by cyclosporins with 50% inhibitory concentrations of about 0.7 microM. HIV-2 and simian immunodeficiency virus are only weakly or not at all inhibited by cyclosporins. For gag-encoded proteins derived from HIV-1, HIV-2, or simian immunodeficiency virus particles, cyclophilin-binding capacity correlated with sensitivity of the viruses to inhibition by cyclosporins. Cyclophilin A also binds to HIV-1 proteins other than gag-encoded proteins, namely, p17gag, Nef, Vif, and gp120env; the biological significance of these interactions is questionable. We conclude that HIV-1 Gag-cyclophilin A interaction may be essential in HIV-1 replication, and interference with this interaction may be the molecular basis for the antiviral activity of cyclosporins.     

The pharmacology of SDZ EAA 494, a competitive NMDA antagonist

SDZ EAA 494 ( -CPPene) was characterized as a competitive NMDA antagonist, having a pA₂ value against NMDA depolarizations in frog spinal cord and rat neocortex of 6.7–6.8 and a pK_i of 7.5 in a [³H]CGP39653 binding assay, with no action on other receptors or amine reuptake. The compound was orally active in rodent maximal electroshock models with an ED₅₀ of around 16 mg/kg, was protective in rats even 24 hours after oral application and had an oral therapeutic index of around 8. Muscle relaxation, ataxia, flattened body posture and reduced acquisition of a passive avoidance task, suggesting potential effects on memory formation, occurred at supra-anticonvulsant doses in rodents, with PCP-like stimulatory effects produced only by high i.p. doses or constant i.v. infusions. This favourable profile is discussed in relation to the negative outcome of a recent trial of the compound in patients with intractable epilepsy. The conclusion is drawn that standard models for screening new anticonvulsants are inappropriate to seeking drugs active in patients with a protracted convulsive history. The anti-ischaemic action of SDZ EAA 494 encourages further testing in brain trauma, in which the anticonvulsant action of the compound may be an added benefit.     

Measurement of lung fluid volumes and albumin exclusion in sheep

A radioactive tracer technique was used to determine interstitial diethylenetriaminepentaacetic acid (DTPA) and albumin distribution volume in sheep lungs. 125I- and/or 131I-labeled albumin were injected intravenously and allowed to equilibrate for 24 h. 99mTc-labeled DTPA and 51Cr-labeled erythrocytes were injected and allowed to equilibrate (2 h and 15 min, respectively) before a lethal dose of thiamylal sodium. Two biopsies (1-3 g) were taken from each lung and the remaining tissue was homogenized for wet-to-dry lung weight and volume calculations. Estimates of distribution volumes from whole lung homogenized samples were statistically smaller than biopsy samples for extravascular water, interstitial 99mTc-DTPA, and interstitial albumin. The mean fraction of the interstitium (Fe), which excludes albumin, was 0.68 +/- 0.04 for whole lung samples compared with 0.62 +/- 0.03 for biopsy samples. Hematocrit may explain the consistent difference. To make the Fe for biopsy samples match that for homogenized samples, a mean hematocrit, which was 82% of large vessel hematocrit, was required. Excluded volume fraction for exogenous sheep albumin was compared with that of exogenous human albumin in two sheep, and no difference was found at 24 h.     

Determination of SDZ ICM 567 in blood and muscle microdialysis samples by microbore liquid chromatography with ultraviolet and fluorescence detection

Fast, simple and accurate method for the determination of SDZ ICM 567, the 7-methoxy derivative of tropisetron, in microdialysates have been developed. Sampling by microdialysis from freely moving rats in the portal and jugular vein offers a new technology for pharmacokinetic studies by direct and continuous measurement of unbound drug concentrations with time. SDZ ICM 567 can be identified in small sample volumes of dialysates on a microbore high-performance liquid chromatography column-switching system with ultraviolet detection. In addition, determination of SDZ ICM 567 by fluorimetric detection has been developed for muscle microdialysates from rats. [¹⁴C]SDZ ICM 567 was used as reference substance for the estimation of the amount of substance transferred through the dialysis membrane. The radioactive measurement (RA) gave the recovery information, whereas the liquid chromatographic method detected the sum of [¹⁴C]SDZ ICM 567 and dialyzed SDZ ICM 567.     

The human immunodeficiency virus type 1 capsid p2 domain confers sensitivity to the cyclophilin-binding drug SDZ NIM 811.

Human immunodeficiency virus type 1 (HIV-1) specifically incorporates the host cell peptidyl-prolyl isomerase cyclophilin A into virions via contacts with the capsid (CA) domain of the Gag polyprotein Pr55gag. The immunosuppressant drug cyclosporin A and the nonimmunosuppressive cyclosporin A analog SDZ NIM 811 bind to cyclophilin A and inhibit its incorporation into HIV-1 virions. Both drugs inhibit the virion association of cyclophilin A and the replication of HIV-1 with a similar dose dependence. In contrast, these compounds are inactive against other primate lentiviruses which do not incorporate cyclophilin A, such as simian immunodeficiency virus (SIV). To locate determinants which confer sensitivity to SDZ NIM 811, we generated chimeric proviruses between HIV-1 and SIVmac. A hybrid SIVmac which has the CA-p2 domain of the Gag polyprotein replaced by the corresponding domain from HIV-1 replicated in an established CD4+ cell line and in human but not macaque peripheral blood mononuclear cells. The transfer of the HIV-1 CA-p2 domain to SIVmac led to the efficient incorporation of cyclophilin A, and SDZ NIM 811 effectively inhibited both the virion association of cyclophilin A and the spread of the hybrid virus in infected cultures. We conclude that the HIV-1 CA-p2 domain contains determinants which confer the necessity to interact with cyclophilin A for efficient virus replication. Furthermore, our data show that the CA-p2 domain can play a crucial role in species tropism.     

Effects of dose and route of administration of cloprostenol on luteolysis,estrus and ovulation in beef heifers

Four experiments were conducted (with crossbred beef heifers) to determine the effects of dose and route of administration of cloprostenol on luteolysis, estrus and ovulation. In Experiment 1, 19 heifers with a CL > or = 17 mm in diameter were randomly allocated to receive cloprostenol as follows: 100 microg s.c., 250 microg s.c., or 500 microg i.m. Heifers given 100 microg s.c. had a longer (P<0.03) interval (120.0 h+/-10.7 h; mean+/-S.E.M.) from treatment to ovulation than those given either 250 microg s.c. or 500 microg i.m. (92.0 h+/-7.4 h and 84.0 h+/-8.2 h, respectively). In Experiment 2, 28 heifers were given porcine LH (pLH), followed in 7 days by cloprostenol (same doses and routes as in Experiment 1), and a second dose of pLH 48 h after cloprostenol. Luteolysis occurred in all heifers, and no difference was detected among treatment groups in the interval from cloprostenol treatment to ovulation (mean, 101 h; P<0.9). In Experiment 3, 38 heifers at random stages of the estrous cycle (but with plasma progesterone concentrations > or =1.0 ng/ml) received 500 or 125 microg cloprostenol by either i.m. or s.c. injection (2/2 factorial design). There was no difference (P<0.4) among groups in the proportions of heifers that were detected in estrus or that ovulated. However, the interval from cloprostenol treatment to estrus was shorter (P<0.02) in the group that received 500 microg i.m. (58.5h) than in the other three groups (500 microg s.c., 75.0 h; 125 microg i.m., 78.0 h; and 125 microg s.c., 82.3h). In Experiment 4, 36 heifers were treated (as in Experiment 3) on Day 7 after ovulation. The proportions of heifers detected in estrus and ovulating after 125 microg s.c. (33 and 44%, respectively) or 125 microg i.m. (55 and 55%) were lower (P<0.05) than in those that received 500 microg s.c. (100 and 100%), but not different from those receiving 500 microg i.m. (78 and 89%, respectively). Overall, ovulation was detected in 9/18 heifers given 125 microg and 17/18 heifers given 500 microg of cloprostenol, on Day 7 (P<0.01) and was detected in 17/20 heifers given 125 microg and 18/18 heifers given 500 microg of cloprostenol, at random stages of the estrous cycle (P>0.05). Although there was no significant difference in luteolytic efficacy between i.m. and s.c. injections of the recommended dose (500 microg) of cloprostenol, variability in responsiveness to a reduced dose depended upon CL sensitivity, therefore, reduced doses cannot be recommended for routine use.     

The phagocytic capacity of macrophages in the S phase of the cell cycle

An inflammatory reaction was induced in the peritoneal cavity of mice. Two days later, the peritoneal macrophages, containing a proportion of S-phase (DNA-synthesizing) cells, were harvested and adhered to glass. Then the S-phase macrophages were labeled with [³H]thymidine (radioautography) and the macrophage monolayers were tested with regard to their ability to phagocytose immunoglobulincoated sheep red blood cells (SRBC). The percentages of S-phase macrophages which had phagocytosed SRBC were a little lower than those found for G-phase (G₁ + G₂) cells. Otherwise, the number of phagocytosed SRBC per macrophage was about equal for macrophages in both phases, and they both responded well by increasing the phagocytosis when the SRBC: macrophage ratio was increased. The S-phase macrophages also phagocytosed latex beads and zymosan particles efficiently.