Showing papers on "In vivo published in 1988"

IL-4 is required to generate and sustain in vivo IgE responses.

Abstract: Antibodies of the IgE isotype play a predominant role in immediate hypersensitivity reactions. IL-4, a T cell-derived lymphokine that stimulates increased Ia expression by resting B cells and increased IgG1 secretion by LPS-activated B cells in vitro, has also been shown to regulate in vitro and in vivo polyclonal IgE responses. We report that large quantities of a purified anti-IL-4 mAb inhibit primary in vivo polyclonal IgE responses by 99% in mice infected with Nippostrongylus brasiliensis or injected with anti-IgD antibodies, and totally inhibit secondary Ag-specific IgE responses to TNP-keyhole limpet hemocyanin without effect on either IgG1 or IgG2a responses to these stimuli. The lack of effect of anti-IL-4 antibody on IgG1 secretion cannot be explained simply by inadequate neutralization of IL-4, inasmuch as the doses of anti-IL-4 antibody used blocked an N. brasiliensis-induced increase in B cell Ia expression by more than 85%, whereas in vitro studies indicate that enhancement of B cell Ia expression requires less IL-4 than induction of IgG1 secretion. In addition to demonstrating that IL-4 plays a necessary role in the generation of an in vivo IgE response, we show that IL-4 has an important role in sustaining established IgE responses, because anti-IL-4 antibody, when given at the peak of an N. brasiliensis- or TNP-keyhole limpet hemocyanin-induced IgE response, accelerates the declines in total serum IgE and in IgE anti-TNP antibody levels, respectively. These observations suggest that the effects of IL-4 on in vivo immune responses may be more specific than might have been predicted from in vitro observations, and that regulation of IL-4 production or action may be useful for the prevention or therapy of immediate hypersensitivity disorders.

Purification and characterization of other distinct bone-inducing factors

Abstract: We purified a factor that induces bone formation greater than 300,000-fold from guanidinium chloride extracts of demineralized bone. Fifty nanograms of highly purified protein was active in an in vivo cartilage and bone-formation assay. The activity resided in a single gel band, corresponding to a molecular mass of approximately 30 kDa, which yielded proteins of 30, 18, and 16 kDa on reduction. The partial amino acid sequence obtained from these proteins confirmed our identification of specific factors that induce new bone formation in vivo.

A versatile in vivo and in vitro eukaryotic expression vector for protein engineering

Abstract: The ability to engineer specific modifications within the coding region of a structural gene is a powerful tool with which to study the relationship between protein structure and function. The process of site-directed mutagenesis involves a) mutation of the target gene, b) verification of the mutation by sequencing and c) expression of the mutated gene. We describe here a vector, pSG5 (Fig.lA), in which each of these steps may be performed. pSG5 was constructed essentially by combining the eukaryotic expression vector, pKCR2 (1), and the high copy plasmid vector Bluescribe Ml3+ (Stratagene). The principle features of pSG5 are a) unique EcoRI and BamHI restriction enzyme sites for insertion of cDNAs, b) production of single stranded DNA containing the antisense strand of the structural gene for mutagenesis and sequencing, c) high yields of double stranded DNA, d) in vivo expression from the SV40 early promoter and e) in vitro expression from the T7 promoter situated just upstream of the cDNA insertion site. Expression from pSG5 was tested after insertion of a cDNA encoding the human oestrogen receptor (2) (ER) into the EcoRI site to produce pSG5-ER. Fig.IB shows an SDS polyacrylamide gel of the 66Kd ER protein synthesised in a rabbit reticulocyte cell-free translation cocktail programmed with mRNA transcribed from the T7 promoter of either Bluescribe-ER (BSM-ER (3)) or pSG5-ER. The ER when expressed in HeLa cells stimulates transcription from oestrogen-responsive 'reporter' genes (4) (vitellogenin-TK-globin (VTG) in Fig. 1C). Using quantitative SI nuclease analysis with an internal reference gene (RXF in Fig.lC), the ER expressed from either pSG5-ER or pKCR2-ER stimulates gene transcription equally well indicating that equivalent levels of ER are expressed in vivo using either of these two vectors.

Cyclosporin-A in Vivo Produces Severe Osteopenia in the Rat: Effect of Dose and Duration of Administration

Abstract: Cyclosporin-A (CsA) inhibits the in vitro boneresorbing effects of cytokines. We investigated the in vivo effects of CsA on rat bone mineral metabolism. Three groups of male Sprague-Dawley rats were administered vehicle or low dose (7.5 mg/kg) or high dose (15 mg/kg) CsA for 14 and 28 days. Ionized calcium, PTH, serum bone Gla protein, blood urea nitrogen, creatinine, magnesium, and 1,25-dihydroxyvitamin D were determined serially. No significant changes in calciotropic hormones or renal function were noted. Significant bone resorption and trabecular bone loss occurred in the high dose group by day 14 and in both groups by day 28. Bone Gla protein was significantly increased within 2 weeks in both dosage groups (P < 0.005), reflecting increased bone remodeling. CsA in vivo resulted in an unexpected and significant increase in bone remodeling, with striking bone loss. These effects are dependent on the duration and dose of CsA and appear to be mediated at a local level. (Endocrinology 123: 2571–2577,1988)

Role of adhesive proteins in platelet tumor interaction in vitro and metastasis formation in vivo.

Abstract: Platelet-adhesive protein-tumor cell interaction was studied in vitro and in vivo. Monoclonal antibody 10E5, which inhibits binding of fibronectin and von Willebrand factor to the platelet membrane glycoprotein GPIIb-GPIIIa complex, inhibited the binding of mouse CT26 and human HCT8 colon carcinoma cells to platelets by 63-65%, whereas an irrelevant monoclonal antibody, 3B2, had no effect. Monoclonal antibody 6D1, which inhibits binding of von Willebrand factor to GPIb, also had no effect. RGDS, a tetrapeptide that represents the adhesive domain of fibronectin and von Willebrand factor inhibited binding of the tumors to platelets by 64-69%. Monospecific polyclonal antifibronectin antibody inhibited binding by 60-82%; anti-von Willebrand factor antibody inhibited binding by 75-81%. In vivo, polyclonal monospecific anti-mouse von Willebrand factor antibody inhibited pulmonary metastases induced by CT26 tumor cells by 53-64%, B16a amelanotic melanoma cells by 45% and T241 Lewis bladder cells by 46% without induction of thrombocytopenia. Pulmonary metastases with CT26 cells could be inhibited by induction of thrombocytopenia, and reconstituted by infusion of either murine or human platelets. Reconstitution of pulmonary metastases with human platelets could be inhibited 77% by preincubation of human platelets with monoclonal antibody 10E5 before infusion of platelets into mice. Thus, platelets appear to contribute to metastases by their adhesive interaction with tumor cells via the adhesive proteins fibronectin and von Willebrand factor.

Oxidants, inflammation, and anti-inflammatory drugs.

Abstract: Species such as superoxide radical (O2-), hydrogen peroxide (H2O2), hydroxyl radical (.OH), and hypochlorous acid (HOCl) can be formed in vivo, e.g., by activated phagocytic cells. Generation of .OH from H2O2 in vivo usually involves iron-dependent reactions. Good evidence exists for increased generation of oxidants in vivo in patients with active rheumatoid disease, but the contribution of these oxidants to the disease process is still uncertain. The likelihood that anti-inflammatory drugs used in the treatment of arthritis could act by scavenging oxidants or preventing their formation is discussed.

In Vivo Postantibiotic Effect in a Thigh Infection in Neutropenic Mice

Abstract: The postantibiotic effect (PAE) is the suppression of bacterial growth that persists after limited exposure of organisms to antimicrobial agents. We demonstrated and standardized the in vivo PAE in a thigh infection model in neutropenic mice. Inhibitors of protein and nucleic acid synthesis induced PAEs of 1.4-7.5 h against aerobic gram-negative bacilli, whereas beta-lactam antibiotics did not induce significant PAEs. Against aerobic gram-positive cocci, cell wall-active agents and inhibitors of protein and nucleic acid synthesis induced PAEs of 1.2-7.1 h, except for penicillins, which did not induce PAEs against streptococci. With few exceptions the in vivo PAE correlated well with the PAE reported in prior in vitro studies. Residual drug in thigh tissue did not cause the PAE. Theoretically, the presence of a PAE may allow antimicrobial agents to be given more intermittently without organism regrowth after drug levels fall below the minimal inhibitory concentration.

In vivo incisional wound healing augmented by platelet-derived growth factor and recombinant c-sis gene homodimeric proteins.

Abstract: Human platelet-derived growth factor (hPDGF) is likely to be important in stimulating tissue repair, based upon its in vivo chemotactic and stimulatory activities for inflammatory cells and fibroblasts and upon the presence of PDGF and related proteins in platelets, macrophages, and activated fibroblasts, cell types that make up the milieu of the healing wound. Recombinant human c-sis (rPDGF-B), homodimers of the B chain of PDGF, were compared with hPDGF in vitro. rPDGF-B was immunologically similar to hPDGF and, at identical concentrations, similar to hPDGF in stimulating fibroblast mitogenesis and chemotaxis of polymorphonuclear leukocytes, monocytes, and fibroblasts. Purified hPDGF and rPDGF-B were also tested in vivo for potency in a model of tissue repair using a linear incision wound through rat dermis. A single application of hPDGF or rPDGF-B (2-20 micrograms/wound) in a slow release vehicle at the time of wounding resulted in a dose-dependent, statistically highly significant increase of breaking strength of treated wounds. Wound healing in animals treated with rPDGF-B was 170% stronger and accelerated by 2 d during the first week over control wounds and by 4-6 d over the next 2 wk. Histologic evaluation of growth factor-treated wounds correlated the in vitro chemotactic activity and the accelerated healing of wounds with a striking inflammatory cell infiltrate early after wounding, markedly increased formation of granulation tissue by 4-d, and increased fibrosis by 14 d in comparison to control wounds. The results thus demonstrate that rPDGF-B is fully active in in vitro tests of mitogenesis and chemotaxis and, for the first time, demonstrate directly that PDGF significantly advances wound healing in incisional wounds of experimental animals.

In vivo administration of recombinant IFN-gamma induces macrophage activation, and prevents acute disease, immune suppression, and death in experimental Trypanosoma cruzi infections.

Abstract: Recombinant murine IFN-gamma (rMu-IFN-gamma) was demonstrated to be a potent in vivo activator of mouse peritoneal macrophages to kill Trypanosoma cruzi in vitro and to be capable of conferring protection against death from acute T cruzi infection Following ip injections of rMu-IFN-gamma, resident peritoneal macrophages were cultured and infected with T cruzi in vitro Numbers of intracellular parasites were determined at different times thereafter Ten or 100 micrograms (1 microgram = 65 X 10(5) U) of Mu-IFN-gamma, injected both 24 and 4 h before macrophage harvest, induced up to 99% inhibition of T cruzi One microgram of rMu-IFN-gamma was not effective under these conditions In vitro inhibition of T cruzi by peritoneal macrophages occurred by 24 h after infection and continued until at least 120 h after infection There were no significant differences in initial parasite uptake by macrophages from IFN-gamma-treated or control mice, indicating that the rMu-IFN-gamma induced parasite killing One ip dose of 10 micrograms was as effective as two doses if the single injection was given 24 h before macrophage harvest In subsequent experiments, mice were given multiple injections of 10 micrograms rMu-IFN-gamma beginning 24 h before or 2 h after infection with virulent T cruzi Mice treated with rMu-IFN-gamma had significantly lower parasitemias and decreased morbidity compared with control mice Proliferative responses to Con A and antibody responses to SRBC were not significantly lowered in IFN-gamma-treated mice, in contrast to untreated infected controls All of the IFN-gamma-treated mice survived acute T cruzi infection, whereas 100% of saline-treated infected mice died It was demonstrated in this study that rMu-IFN-gamma activated mouse macrophages in vivo to kill T cruzi and that rMu-IFN-gamma significantly reduced morbidity and immune suppression, and eliminated mortality resulting from acute infection with this parasite

Efficacy of Antibodies to Epidermal Growth Factor Receptor Against KB Carcinoma In Vitro and in Nude Mice

Abstract: Iodine-125-labeled monoclonal antibody 108.4 (108.4 mAb), raised against the extracellular domain of the epidermal growth factor (EGF) receptor, was shown to visualize sc xenografts of human oral epidermoid carcinoma (KB) cells in nude mice. In vitro, although EGF caused an increase in the number of KB cell colonies (150% at a concentration of 160 mM), the anti-EGF receptor antibodies reduced clone formation. At a concentration at which EGF caused a 50% increase in colony number, the addition of a 100-fold molar excess of 108.4 mAb resulted in a decrease in the number of cell colonies to 20% of the original value. Therefore, the effect of antibody on the KB tumor was studied in vivo in three different modes of tumor transplantation. Antitumor activity was demonstrated first by retardation (versus controls) of the growth of tumor cells as sc xenografts (P greater than .017), then by prolongation of the life span of animals with the ip form of the tumor (P less than .001), and finally on an experimental lung metastasis by a reduction in the number and size of tumors (P less than .05). When the anti-EGF receptor antibodies were added together with cisplatin, the antitumor effect was greatly enhanced, suggesting that the toxic activity of these agents is synergistic (P less than .007). The antitumor effect persisted when animals were treated with the F(ab)'2 fragment of the antibody, although it was less efficient. The Fab fragment of the antibody, whose ability to bind to the cell-associated receptor was completely conserved, did not affect the growth of the tumor. The activity manifested by the F(ab)'2 fragment of the anti-EGF receptor antibodies suggested that the antitumor effect was not due to immune mechanisms requiring the Fc portion of the antibody.

Gamma-interferon regulates vascular smooth muscle proliferation and Ia antigen expression in vivo and in vitro.

Abstract: A significant fraction of the arterial smooth muscle cells in atherosclerotic plaques and injury-induced intimal thickenings express class II major histocompatibility complex (Ia) antigens. This might be the consequence of gamma-interferon secretion by T lymphocytes also present in these lesions. We have therefore analyzed the effects of gamma-interferon on cultured rat aortic smooth muscle cells. Recombinant gamma-interferon inhibited smooth muscle proliferation in vitro in a dose-response relation; inhibition was detectable down to a concentration of 1 unit/ml. In similar concentrations, gamma-interferon also induced Ia expression by the cells. This suggested that Ia antigens might be selectively expressed by nonproliferating smooth muscle cells. In vivo, there was a strong negative correlation between Ia expression and 3H-thymidine labeling of smooth muscle cells in intimal thickenings induced by balloon catheter injury. In rats receiving continuous infusions of 3H-thymidine for two weeks after injury, Ia-positive 3H-positive cells had undergone fewer rounds of replication than Ia-negative ones. This indicates that Ia-expression both in vivo and in vitro is associated with a reduced proliferative capacity. These results suggest that gamma-interferon, a secretory product of activated T lymphocytes, acts as a natural regulator of smooth muscle cell growth and Ia expression in injury-induced intimal thickenings and atherosclerotic plaques.

Synthesis, in vitro and in vivo activity of novel 9-deoxo-9a-AZA-9a-homoerythromycin A derivatives; a new class of macrolide antibiotics, the azalides.

Abstract: A series of erythromycin A-derived semisynthetic antibiotics, featuring incorporation of a basic nitrogen atom into a ring expanded (15-membered) macrocyclic lactone, have been prepared and biologically evaluated. Semisynthetic modifications focused upon (1) varied substitution at the macrocyclic ring nitrogen and (2) epimerization or amine substitution at the C-4" hydroxyl site within the cladinose sugar. In general, the new azalides exhibit improved Gram-negative potency, expanding the spectrum of erythromycin A to fully include Haemophilus influenzae and Neisseria gonorrhoeae. When compared to erythromycin A, the azalides exhibit substantially increased half-life and area-under-the-curve values in all species studied. The overall in vitro/in vitro performance of N-methyl, C-4" epimers 3a and 9; and C-4" amine 11 identify these compounds as the most interesting erythromycin A-superior agents. Compound 3a has been advanced to clinical study.

A newly defined property of somatotropin: priming of macrophages for production of superoxide anion.

Abstract: Macrophages can be activated to produce reactive oxygen intermediates, such as superoxide anion (O2-), which are responsible for intracellular killing of pathogenic microbes. Treatment with either native or recombinant somatotropin augmented the production of O2- by both peripheral blood-derived and alveolar macrophages stimulated with opsonized zymosan in vitro. This effect was abolished by prior treatment with an antibody specific for somatotropin. When either native or recombinant porcine somatotropin or native rat somatotropin was administered to hypophysectomized rats in vivo, activation of peritoneal macrophages, as measured by release of O2- in response to opsonized zymosan, was equivalent to that of macrophages from rats primed with the macrophage-activating factor interferon-gamma. Priming of macrophages in vivo was observed at physiologically relevant doses of somatotropin that caused a 10 to 40 percent increase in growth rate. Priming of mononuclear phagocytes for augmented production of reactive oxygen metabolites is a newly defined property of somatotropin.

The preimplantation pig embryo: cell number and allocation to trophectoderm and inner cell mass of the blastocyst in vivo and in vitro.

Abstract: Total cell number as well as differential cell numbers representing the inner cell mass (ICM) and trophectoderm were determined by a differential staining technique for preimplantation pig embryos recovered between 5 and 8 days after the onset of oestrus. Total cell number increased rapidly over this time span and significant effects were found between embryos of the same chronological age from different females. Inner cells could be detected in some but not all embryos of 12–16 cells. The proportion of inner cells was low in morulae but increased during differentiation of ICM and trophectoderm in early blastocysts. The proportion of ICM cells then decreased as blastocysts expanded and hatched. Some embryos were cultured in vitro and others were transferred to the oviducts of immature mice as a surrogate in vivo environment and assessed for morphology and cell number after several days. Although total cell number did not reach in vivo levels, morphological development and cell number increase was sustained better in the immature mice than in vitro. The proportion of ICM cells in blastocysts formed in vitro was in the normal range.

Inhibition of the tumor-promoting action of 12-O-tetradecanoylphorbol-13-acetate by some oleanane-type triterpenoid compounds.

Abstract: Since glycyrrhetinic acid was proved to suppress tumor promoter effects, several oleanane-type triterpenes which were chemically derived from oleanolic acid and hederagenin were tested in vitro and in vivo against the action of tumor promoter, 12-O-tetradecanoylphorbol 13-acetate. By in vitro experiment monitoring with 12-O-tetradecanoylphorbol-13-acetate-induced stimulation of 32Pi incorporation into phospholipids and an in vivo test on skin tumor formation in mice initiated with 7,12-dimethylbenz[a]anthracene and promoted with 12-O-tetradecanoylphorbol-13-acetate, 18 beta-olean-12-ene-3 beta,28-diol (= erythrodiol), 18 beta-olean-12-ene-3 beta,23,28-triol, 18 alpha-olean-12-ene-3 beta,28-diol, and 18 alpha-olean-12-ene-3 beta,23,28-triol showed remarkable suppressive effects. Especially 18 alpha-oleanane derivatives having a CH2OH grouping converted from the COOH group initially allocated at C-17 were 100 times more effective than glycyrrhetinic acid both in vitro and in vivo.

Preclinical studies and clinical correlation of the effect of alkylating dose.

Abstract: Dose-response studies were performed with the alkylating agents [nitrogen mustard, N,N'-bis(2-chloroethyl)-N-nitrosourea, melphalan, cisplatin (CDDP), 4-hydroperoxycyclophosphamide (4-HC), and trimethyleneiminethiophosphoramide] in both the MCF-7 human breast carcinoma cell line and the EMT6 and FSaIIC murine tumor lines Increasing selection pressure with the alkylating agents CDDP, melphalan, and 4-HC in vitro produced low levels (65- to 9-fold) of drug resistance, despite an intensive and prolonged treatment program The MCF-7 sublines made resistant to CDDP and 4-HC did not exhibit cross-resistance to other alkylating agents; however, the MCF-7 subline resistant to melphalan was partially cross-resistant to nitrogen mustard, 4-HC, and CDDP A log-linear relationship was maintained between surviving fraction of MCF-7 cells in culture and drug concentration with alkylating agents, whereas for nonalkylating agents the survival curves tended to plateau at high drug concentrations Log-linear tumor cell kill was also obtained over a wide dosage range with several alkylating agents in murine tumors treated in vivo Tumor cell survival assay by colony formation indicated the continuing importance of dose in the action of the drugs even at high levels of tumor cell kill With some agents, there was a difference between the slopes of the tumor cell killing curves in vivo as compared to in vitro Cyclophosphamide was far more potent in vitro (4-HC) than in vivo (cyclophosphamide) Trimethyleneiminethiophosphoramide and N,N'-bis(2-chloroethyl)-N-nitrosourea were both more potent in vivo than in vitro These differences may be explained by the various metabolic patterns of these drugs Dose of alkylating agents is clearly a crucial variable particularly where multilog tumor cell kill is the goal, and in this regard, the effect of drug dose on the tumoricidal action of the alkylating agents is substantially greater than for nonalkylating agents

T-lymphocyte clone specific for pancreatic islet antigen.

Abstract: A cloned T-lymphocyte line, BDC-2.5, was derived from a nonobese diabetic (NOD) mouse and has been found to exhibit specificity for islet cell antigen in vitro and in vivo. This clone is a CD4+ T-lymphocyte that proliferates and makes lymphokine in response to islet cell antigen- and NOD antigen-presenting cells. In an in vivo transplantation system in which islet grafts were made in the presence or absence of the BDC-2.5 T-lymphocytes, it was found that incorporation of the islet-specific T-lymphocytes into the graft site resulted in complete destruction of the transplanted tissue. Similar grafts made with pituitary tissue were not affected by the T-lymphocyte clone. These results suggest that the islet-specific T-lymphocytes mediate islet destruction in a tissue-specific manner.

The genetic toxicity of human carcinogens and its implications

Abstract: 23 chemicals and chemical combinations have been designated by the International Agency for Research on Cancer (IARC) as causally associated with cancer in humans. The literature was searched for reports of their activity in the Salmonella mutagenicity assay and for evidence of their ability to induce chromosome aberrations or micronuclei in the bone marrow of mice or rats. In addition, the chemical structures of these carcinogens were assessed for the presence of electrophilic substituents that might be associated with their mutagenicity and carcinogenicity. The purpose of this study was to determine which human carcinogens exhibit genetic toxicity in vitro and in vivo and to what extent they can be detected using these two widely employed short-term tests for genetic toxicity. The results of this study revealed 20 of the 23 carcinogens to be active in one or both short-term tests. Treosulphan, for which short-term test results are not available, is predicted to be active based on its structure. The remaining two agents, asbestos and conjugated estrogens, are not mutagenic to Salmonella; asbestos is not likely to induce cytogenetic effects in the bone marrow and the potential activity of conjugated estrogens in the bone marrow is difficult to anticipate. These findings show that genetic toxicity is characteristic of the majority of IARC Group 1 human carcinogens. If these chemicals are considered representative of human carcinogens, then two short-term tests may serve as an effective primary screen for chemicals that present a carcinogenic hazard to humans.

New features of microtubule behaviour observed in vivo.

Abstract: The microtubule cytoskeleton is thought to be intimately involved in generating and maintaining cell polarity1,2 and can generate many different morphological structures from a few structural elements3. The mechanism by which these structures are generated has been partially elucidated from studies of microtubule polymerization both in vitro4–6 and in vivo7,8. Microtubules in vitro exist in growing (polymerizing) and shrinking (depolymerizing) populations that interconvert infrequently. This behaviour, termed dynamic instability4, permits microtubules in the cell rapidly to explore different arrangements and allows selective stabilization of specific morphologies9,10. To investigate the regulation of these processes, we have implemented techniques for direct observation of fluorescently labelled microtubules11 and developed them to observe the dynamic behaviour of individual microtubules in single living cells. Sammak and Borisy12 recently used this technique to show that the dynamics of microtubules in fibroblasts is explained by dynamic instability. Although we also conclude here that dynamic instability explains much of microtubule behaviour in vivo, we find significant deviations from the properties of tubulin in vitro. These results suggest that local cytoplasmic factors strongly influence microtubule dynamics; such control has important implications for cellular morphogenesis.

In vitro and in vivo analysis of the effects of recombinant human granulocyte colony-stimulating factor in patients.

Abstract: Twelve patients with small cell lung cancer were treated with recombinant human granulocyte colony-stimulating factor, rhG-CSF, given by continuous infusion at doses ranging from 1 to 40 micrograms kg-1 day-1. Patients received the rhG-CSF before the start of intensive chemotherapy and after alternate cycles of chemotherapy. Several in vitro assays were performed using peripheral blood neutrophils and marrow progenitor cells collected from patients prior to and after infusion of the growth factor. Peripheral blood neutrophils were tested for mobility and phagocytic activity. In addition, in vitro clonogenic assays of marrow haemopoietic progenitor cells and analysis of bone marrow trephines and aspirates were carried out. We found that rhG-CSF in vivo has at least two main effects: (a) an early fall in peripheral neutrophils, within the first hour, followed by a rapid influx of mature neutrophils into the circulatory pool; (b) stimulation of proliferation and differentiation of neutrophil precursors in the bone marrow. Neutrophils released into the circulation were normal in tests of their mobility and phagocytic activity.