Transient suppression of macrophage functions by liposome-encapsulated drugs

Macrophages play an important role in host defense reactions, for example, by phagocytosis of particulate materials. This process also results in the rapid removal of targeting devices such as liposomes and adenovirus vectors and of non-autologous grafted cells and materials. Another aspect of macrophage function is their production and secretion of proinflammatory cytokines. Transient and organ-specific suppression of macrophage function by liposome-mediated manipulation has been shown to improve the efficacy of drug and gene targeting and to reduce the symptoms of inflammatory reactions.

Monitoring fibrinogen adsorption kinetics by interfacial TIRF rheometry

The adsorption kinetics of purified fibrinogen to unmodified and aminopropylsilane-modified quartz glass surfaces were studied under pseudo-first order (binding-unit excess) conditions by the total internal reflection fluorescence (TIRF) method. Fluorescence in the adsorbed protein layer (350 nm) was excited by the evanescent wave at 285-290 nm. In order to reduce and possibly eliminate the influence of mass transfer on the kinetics of fibrinogen adsorption, a novel protein adsorption chamber containing a cone-and-plate rheometer with total internal reflection technology was employed. The aim of the study was to obtain critical shear rates, at which the adsorption rate of fibrinogen became independent of diffusion. Therefore, shear rates were varied between 0 and 7200 s-1 at initial fibrinogen concentrations of c9 = 4.7 and 17.7 micrograms mL-1. The adsorption rate of fibrinogen increased 5-17-fold, depending on the surface, as the critical shear rate was approached. Above the critical shear rates the kinetic data of fibrinogen adsorption could be fitted at c9 = 4.7 micrograms mL-1 to a single exponential function, indicating the predominance of a single binding step with a half-life of ca 20 s. At the higher initial concentration of c9 = 17.7 micrograms/mL-, however, a significant deviation from the single exponential behavior was observed in the first 10 s of the adsorption reaction, indicating a very fast initial event with a half-life of ca 5 s in addition to a slower binding reaction with a half-life of ca 35 s. Thus the novel TIRF rheometer can resolve kinetics down to half-lives of 5 s and possibly even lower.

Developing and revising the American Heart Association guidelines for advanced cardiac life support

Cardiovascular nurses are active participants in implementing emergency cardiac care (ECC) guidelines as advanced cardiac life support (ACLS) providers and instructors. Cardiovascular nurses should play a key role in the ECC guidelines revision process. The article discusses the process of the most recent ECC guideline developments and revisions and describes subsequent changes to ACLs protocols.

Apoptosis of macrophages induced by liposome-mediated intracellular delivery of clodronate and propamidine

Liposomes can be used as vehicles for intracellular delivery of drugs into phagocytic cells. Clodronate and propamidine, delivered into macrophages in this way, will kill these cells as a result of intracellular accumulation and irreversible metabolic damage. The so-called liposome-mediated macrophage 'suicide' approach, which is based on this principle, is now frequently applied in studies aimed at unravelling macrophage function. In the present study, the mechanism of phagocytic cell death induced by liposome encapsulated drugs was investigated 'in vitro'. Peritoneal macrophages and macrophages of the RAW 264 cell line were cultured in the presence of the liposome encapsulated drugs clodronate, propamidine and several forms of ethylenediaminetetraacetic acid (EDTA). The results obtained suggest that apoptotic death is induced in phagocytic cells both by liposomally delivered clodronate and by liposomally delivered propamidine. Although intracellular EDTA did induce apoptosis in a minority of the experiments, the results support earlier findings that EDTA does not deplete macrophages as effectively as clodronate and propamidine.

Kupffer cell depletion by liposome-delivered drugs: comparative activity of intracellular clodronate, propamidine, and ethylenediaminetetraacetic acid

Macrophages such as Kupffer cells in the liver are multifunctional cells. They are involved in host defense mechanisms and have a regulatory role in many biomedical processes. Their selective depletion, using liposome-encapsulated drugs, forms a widely accepted approach to studying their functional aspects in vivo. We have compared the Kupffer cell-depleting activities of liposome-encapsulated clodronate, propamidine, and ethylenediaminetetraacetic acid (EDTA) for this purpose. These molecules represent the drug families of bisphosphonates, diamidines (or aromatic polyamidines), and polyaminopolycarboxylic acid-chelating agents, respectively. The Kupffer cell-depleting activity of the liposome-encapsulated antimicrobial drug propamidine exceeded that of clodronate by about a factor of 10. EDTA appeared to be inefficacious for depletion of Kupffer cells in the rat.

Kupffer cell depletion by liposome-delivered drugs: comparative activity of intracellular clodronate, propamidine, and ethylenediaminetetraacetic acid

Macrophages such as Kupffer cells in the liver are multifunctional cells. They are involved in host defense mechanisms and have a regulatory role in many biomedical processes. Their selective depletion, using liposome-encapsulated drugs, forms a widely accepted approach to studying their functional aspects in vivo. We have compared the Kupffer cell-depleting activities of liposome-encapsulated clodronate, propamidine, and ethylenediaminetetraacetic acid (EDTA) for this purpose. These molecules represent the drug families of bisphosphonates, diamidines (or aromatic polyamidines), and polyaminopolycarboxylic acid-chelating agents, respectively. The Kupffer cell-depleting activity of the liposome-encapsulated antimicrobial drug propamidine exceeded that of clodronate by about a factor of 10. EDTA appeared to be inefficacious for depletion of Kupffer cells in the rat.

Role of virus-specific CD4+ cytotoxic T cells in recovery from mouse hepatitis virus infection

Macrophages and T lymphocytes play an important role in recovery from viral infections. During mouse hepatitis virus (MHV-A59) infection, a clear virus-specific class II-restricted cytotoxic T-cell response is generated. Transfer of these CD4+ cytotoxic T cells (CTL) into naive mice protects against a lethal challenge with MHV. However, their in vivo antiviral effector mechanism is not yet clear. To further investigate a possible effector mechanism, we studied the effect of adoptive transfer of CD4+ CTL on virus localization in spleen and liver. We showed that adoptive transfer of virus-specific T cells does not affect localization of MHV-A59 in different macrophage subsets. Interestingly, a rapid and large infiltrate of CD4+ T cells in and around MHV-A59-infected foci in the liver was observed early in infection, whereas no CD8+ T cells were detectable. Moreover, transfer of virus-specific T cells resulted in significantly decreased viral titres in the liver and spleen and a marginally increased anti-MHV-A59 IgM production. These results imply an important role for virus-specific CD4+ CTL in elimination of infectious MHV-A59 and induction of an effective immune response in the absence of CD8+ CTL.

Killing of Entamoeba invadens using liposome-encapsulated drugs

Liposomes are used as carriers of drugs intended to manipulate macrophage functions. The normal in vivo fate of liposomes is phagocytosis, followed by phospholipase-mediated disruption of their phospholipid bilayers and intracellular release of their contents. Using this method for intracellular delivery of drugs, we have developed an approach for in vivo depletion of macrophages. Phagocytosis also forms a major feature of parasitic amoebae. In the present experiments, we investigated whether amoebae could be killed using the same approach (liposome-mediated "suicide" of amoebae). The results confirm that liposomes are ingested by Ent-amoeba invadens cultured under routine laboratory conditions. From various chelator molecules and their metalion complexes that were active in the liposome-mediated elimination of macrophages, Cu-ethylenediaminetetraacetic acid (EDTA) complexes appeared to be the most efficacious compounds in the elimination of E. invadens.

Acute postobstructive pulmonary edema

Acute postobstructive pulmonary edema may occur after airway obstruction. A decrease in intrathoracic and intraalveolar pressures causes an increased blood flow into the pulmonary vasculature and favors the development of pulmonary edema. Two mechanisms for the development of acute postobstructive pulmonary edema are proposed: type 1 follows acute airway obstruction, and type 2 follows relief of chronic airway obstruction.

Acute Postobstructive Pulmonary Edema

Acute postobstructive pulmonary edema may occur after airway obstruction. A decrease in intrathoracic and intraalveolar pressures causes an increased blood flow into the pulmonary vasculature and favors the development of pulmonary edema. Two mechanisms for the development of acute postobstructive pulmonary edema are proposed: type 1 follows acute airway obstruction, and type 2 follows relief of chronic airway obstruction.

The emergency physician and patient confidentiality: a review

Confidentiality is a promise rooted in tradition, law, and medical ethics. Emergency physicians treat a variety of patients to whom confidentiality is of vital importance: employees, celebrities, victims of violence or disaster, minors, students, criminals, drug abusers, and patients with STDs. EDs should develop methods of ensuring confidentiality for all patients. Although confidentiality is an important principle that should be respected and guarded, it is not absolute. Various laws mandate disclosure of certain patient information; in addition, an overriding moral duty may occasionally require a breach of confidentiality. As Beauchamp and Childress noted, "the therapeutic role may sometimes have to yield to one's role as citizen and as protector of the interests of others." In general, however, circumstances requiring a breach of confidentiality are rare.

Liposome mediated depletion of macrophages: mechanism of action, preparation of liposomes and applications

Selective depletion of macrophages from tissues in vivo can be used to investigate whether these cells are playing a role in defined biological processes. This question is particularly relevant to various host defense mechanisms. We have developed a macrophage 'suicide' technique, using the liposome mediated intracellular delivery of dichloromethylene-bisphosphonate (Cl2MBP or clodronate). The method is specific with respect to phagocytic cells of the mononuclear phagocyte system (MPS) for the following reasons: (1) The natural fate of liposomes is phagocytosis. (2) Once ingested by macrophages, the phospholipid bilayers of the liposomes are disrupted under the influence of lysosomal phospholipases. (3) Cl2MBP intracellularly released in this way does not easily escape from the cell by crossing the cell membranes. (4) Cl2MBP released in the circulation from dead macrophages or by leakage from liposomes, will not easily enter non-phagocytic cells and has an extremely short half life in the circulation and body fluids. In the present review, the preparation of Cl2MBP-liposomes has been described in detail. Furthermore, the mechanism of action of the new approach and its applicabilities are discussed.