Showing papers in "Handbook of experimental pharmacology in 2010"

Mechanisms of Acetaminophen-Induced Liver Necrosis

Abstract: Although considered safe at therapeutic doses, at higher doses, acetaminophen produces a centrilobular hepatic necrosis that can be fatal. Acetaminophen poisoning accounts for approximately one-half of all cases of acute liver failure in the United States and Great Britain today. The mechanism occurs by a complex sequence of events. These events include: (1) CYP metabolism to a reactive metabolite which depletes glutathione and covalently binds to proteins; (2) loss of glutathione with an increased formation of reactive oxygen and nitrogen species in hepatocytes undergoing necrotic changes; (3) increased oxidative stress, associated with alterations in calcium homeostasis and initiation of signal transduction responses, causing mitochondrial permeability transition; (4) mitochondrial permeability transition occurring with additional oxidative stress, loss of mitochondrial membrane potential, and loss of the ability of the mitochondria to synthesize ATP; and (5) loss of ATP which leads to necrosis. Associated with these essential events there appear to be a number of inflammatory mediators such as certain cytokines and chemokines that can modify the toxicity. Some have been shown to alter oxidative stress, but the relationship of these modulators to other critical mechanistic events has not been well delineated. In addition, existing data support the involvement of cytokines, chemokines, and growth factors in the initiation of regenerative processes leading to the reestablishment of hepatic structure and function.

Drug-induced liver injury.

Abstract: Many drugs and environmental chemicals are capable of evoking some degree of liver injury. The liver represents a primary target for adverse drug reactions due to its central role in biotransformation and excretion of foreign compounds, its portal location within the circulation exposing it to a wide variety of substances, and its anatomic and physiologic structure. Drug-induced liver injury (DILI) remains the single most common adverse indication leading to drug candidate failure or withdrawal from the market. However, the absolute incidence of DILI is low, and this presents a challenge to mechanistic studies. DILI remains unpredictable making prevention very difficult. In this chapter, we focus on the current understanding of DILI. We begin with an overview regarding the significance and epidemiology of DILI and then examine the clinical presentation and susceptibility factors related to DILI. This is followed by a review of the current literature regarding the proposed pathogenesis of DILI, which involves the participation of a drug, or most often a reactive metabolite of the drug, that either directly affects cellular function or elicits an immune response. It is our hope that this chapter will shed light on the major problems associated with DILI in regards to the pharmaceutical industry, drug regulatory agencies, physicians and pharmacists, and patients.

Passive and active drug targeting: drug delivery to tumors as an example.

Abstract: The paradigm of using nanoparticulate pharmaceutical carriers has been well established over the past decade, both in pharmaceutical research and in the clinical setting. Drug carriers are expected to stay in the blood for long time, accumulate in pathological sites with affected and leaky vasculature (tumors, inflammations, and infarcted areas) via the enhanced permeability and retention (EPR) effect, and facilitate targeted delivery of specific ligand-modified drugs and drug carriers into poorly accessible areas. Among various approaches to specifically target drug-loaded carrier systems to required pathological sites in the body, two seem to be most advanced – passive (EPR effect-mediated) targeting, based on the longevity of the pharmaceutical carrier in the blood and its accumulation in pathological sites with compromised vasculature, and active targeting, based on the attachment of specific ligands to the surface of pharmaceutical carriers to recognize and bind pathological cells. Here, we will consider and discuss these two targeting approaches using tumor targeting as an example.

Nanoparticle Technologies for Cancer Therapy

Abstract: Nanoparticles as drug delivery systems enable unique approaches for cancer treatment. Over the last two decades, a large number of nanoparticle delivery systems have been developed for cancer therapy, including organic and inorganic materials. Many liposomal, polymer-drug conjugates, and micellar formulations are part of the state of the art in the clinics, and an even greater number of nanoparticle platforms are currently in the preclinical stages of development. More recently developed nanoparticles are demonstrating the potential sophistication of these delivery systems by incorporating multifunctional capabilities and targeting strategies in an effort to increase the efficacy of these systems against the most difficult cancer challenges, including drug resistance and metastatic disease. In this chapter, we will review the available preclinical and clinical nanoparticle technology platforms and their impact for cancer therapy.

Species Differences in Pharmacokinetics and Pharmacodynamics

Abstract: Veterinary medicine faces the unique challenge of having to treat many types of domestic animal species, including mammals, birds, and fishes. Moreover, these species have evolved into genetically unique breeds having certain distinguishable characteristics developed by artificial selection. The main challenge for veterinarians is not to select a drug but to determine, for the selected agent, a rational dosing regimen because the dosage regimen for a drug in a given species may depend on its anatomy, biochemistry, physiology, and behaviour as well as on the nature and causes of the condition requiring treatment. Both between- and within-species differences in drug response can be explained either by variations in drug pharmacokinetics (PK) or drug pharmacodynamics (PD), the magnitude of which varies from drug to drug. This chapter highlights selected aspects of species differences in PK and PD and considers underlying physiological and patho-physiological mechanisms in the main domestic species. Particular attention was paid to aspects of animal behaviour (food behaviour, social behavior, etc.) as a determinant of interspecies differences in PK or/and PD. Modalities of drug administration are many and result not only from anatomical, physiological and/or behavioural differences across species but also from management options. The latter is the case for collective/group treatment of food-producing animals, frequently dosed by the oral route at a herd or flock level. After drug administration, the main causes of observed inter-species differences arise from species differences in the handling of drugs (absorption, distribution, metabolism, and elimination). Such differences are most common and of greatest magnitude when functions which are phylogenetically divergent between species, such as digestive functions (ruminant vs. non-ruminant, carnivore vs. herbivore, etc.), are involved in drug absorption. Interspecies differences also exist in drug action but these are generally more limited, except when a particular targeted function has evolved, as is the case for reproductive physiology (mammals vs. birds vs. fishes; annual vs. seasonal reproductive cycle in mammals; etc.). In contrast, for antimicrobial and antiparasitic drugs, interspecies differences are more limited and rather reflect those of the pathogens than of the host. Interspecies difference in drug metabolism is a major factor accounting for species differences in PK and also in PD (production or not of active metabolites). Recent and future advances in molecular biology and pharmacogenetics will enable a more comprehensive view of interspecies differences and also between breeds with existing polymorphism. Finally, the main message of this review is that differences between species are not only numerous but also often unpredictable so that no generalisations are possible, even though for several drugs allometric approaches do allow some valuable interspecies extrapolations. Instead, each drug must be investigated on a species-by-species basis to guarantee its effective and safe use, thus ensuring the well-being of animals and safeguarding of the environment and human consumption of animal products.

Lipid nanoparticles: effect on bioavailability and pharmacokinetic changes.

Abstract: The main aim of pharmaceutical technology research is the design of successful formulations for effective therapy, taking into account several issues including therapeutic requirements and patient compliance. In this regard, several achievements have been reported with colloidal carriers, in particular with lipid nanoparticles, due to their unique physicochemical properties. For several years these carriers have been showing potential success for several administration routes, namely oral, dermal, parenteral, and, more recently, for pulmonary and brain targeting. The present chapter provides a review of the use of solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) to modify the release profile and the pharmacokinetic parameters of active pharmaceutical ingredients (APIs) incorporated in these lipid matrices, aiming to modify the API bioavailability, either upwards or downwards depending on the therapeutic requirement. Definitions of the morphological characteristics, surface properties, and polymorphic structures will also be given, emphasizing their influence on the incorporation parameters of the API, such as yield of production, loading capacity, and encapsulation efficiency.

Drug-induced liver injury in humans: the case of ximelagatran.

Abstract: Ximelagatran was the first orally available direct thrombin inhibitor under clinical development that also reached the market. Ximelagatran was tested in an extensive clinical programme. Short-term use ( 35 days) use of ximelagatran (incidence of >3x upper limit of normal (ULN) plasma ALT was 7.9%). The frequency of elevated total bilirubin levels was similar in the ximelagatran and the comparator groups. However, the combination of ALT > 3x ULN and total bilirubin > 2xULN was 0.5% among patients treated with ximelagatran and 0.1% among patients in the comparator group. Symptoms such as fever and rash potentially indicating hypersensitivity (immunologic type of reaction) were low and did not differ between ximelagatran and the comparators. The withdrawal of ximelagatran from the market and termination of the ximelagatran development program was triggered by safety data from a 35-day study, indicating that severe hepatic injury in a patient could develop after exposure to the drug has been completed and that regular liver function monitoring may not mitigate the possible risk of severe hepatic injury. As for many drugs causing liver injury, the standard preclinical toxicological studies provided no indication that ximelagatran affected hepatic functions. In addition, extensive investigations using human-based in vitro models have not been able to define mechanisms explaining the pattern of hepatic injury observed in long-term clinical trials. A pharmacogenomic study provided evidence that the ALT increases were associated with major histocompatibility complex (MHC) alleles DRB1'07 and DQA1*02 suggesting a possible immunogenic pathogenesis. This example provides important clues to the mechanism of idiosyncratic drug-induced liver toxicity.

Role of reactive metabolites in drug-induced hepatotoxicity.

Abstract: Drugs are generally converted to biologically inactive forms and eliminated from the body, principally by hepatic metabolism. However, certain drugs undergo biotransformation to metabolites that can interfere with cellular functions through their intrinsic chemical reactivity towards glutathione, leading to thiol depletion, and functionally critical macromolecules, resulting in reversible modification, irreversible adduct formation, and irreversible loss of activity. There is now a great deal of evidence which shows that reactive metabolites are formed from drugs known to cause hepatotoxicity, such as acetaminophen, tamoxifen, isoniazid, and amodiaquine. The main theme of this article is to review the evidence for chemically reactive metabolites being initiating factors for the multiple downstream biological events culminating in toxicity. The major objectives are to understand those idiosyncratic hepatotoxicities thought to be caused by chemically reactive metabolites and to define the role of toxic metabolites.

The Athlete’s Biological Passport and Indirect Markers of Blood Doping

Abstract: In the fight against doping, disciplinary sanctions have up to now been primarily based on the discovery of an exogenous substance in a biological fluid of the athlete. However, indirect markers of altered erythropoiesis can provide enough evidence to differentiate between natural variations and blood doping. Forensic techniques for the evaluation of the evidence, and more particularly Bayesian networks, allow antidoping authorities to take into account firstly the natural variations of indirect markers – through a mathematical formalism based on probabilities – and secondly the complexity due to the multiplicity of causes and confounding effects – through a distributed and flexible graphical representation. The information stored in an athlete’s biological passport may be then sufficient to launch a disciplinary procedure against the athlete. The strength of the passport is that it relies on a statistical approach based on sound empirical testing on large populations and justifiable protocols. Interestingly, its introduction coincides with the paradigm shift that is materializing today in forensic identification science, from archaic assumptions of absolute certainty and perfection to a more defensible empirical and probabilistic foundation.

Androgenic anabolic steroid abuse and the cardiovascular system.

Abstract: Abuse of anabolic androgenic steroids (AAS) has been linked to a variety of different cardiovascular side effects. In case reports, acute myocardial infarction is the most common event presented, but other adverse cardiovascular effects such as left ventricular hypertrophy, reduced left ventricular function, arterial thrombosis, pulmonary embolism and several cases of sudden cardiac death have also been reported. However, to date there are no prospective, randomized, interventional studies on the long-term cardiovascular effects of abuse of AAS. In this review we have studied the relevant literature regarding several risk factors for cardiovascular disease where the effects of AAS have been scrutinized:

Mitochondrial involvement in drug-induced liver injury.

Abstract: Mitochondrial dysfunction is a major mechanism of liver injury. A parent drug or its reactive metabolite can trigger outer mitochondrial membrane permeabilization or rupture due to mitochondrial permeability transition. The latter can severely deplete ATP and cause liver cell necrosis, or it can instead lead to apoptosis by releasing cytochrome c, which activates caspases in the cytosol. Necrosis and apoptosis can trigger cytolytic hepatitis resulting in lethal fulminant hepatitis in some patients. Other drugs severely inhibit mitochondrial function and trigger extensive microvesicular steatosis, hypoglycaemia, coma, and death. Milder and more prolonged forms of drug-induced mitochondrial dysfunction can also cause macrovacuolar steatosis. Although this is a benign liver lesion in the short-term, it can progress to steatohepatitis and then to cirrhosis. Patient susceptibility to drug-induced mitochondrial dysfunction and liver injury can sometimes be explained by genetic or acquired variations in drug metabolism and/or elimination that increase the concentration of the toxic species (parent drug or metabolite). Susceptibility may also be increased by the presence of another condition, which also impairs mitochondrial function, such as an inborn mitochondrial cytopathy, beta-oxidation defect, certain viral infections, pregnancy, or the obesity-associated metabolic syndrome. Liver injury due to mitochondrial dysfunction can have important consequences for pharmaceutical companies. It has led to the interruption of clinical trials, the recall of several drugs after marketing, or the introduction of severe black box warnings by drug agencies. Pharmaceutical companies should systematically investigate mitochondrial effects during lead selection or preclinical safety studies.

Viral vectors for gene transfer: current status of gene therapeutics.

Abstract: Gene therapy for the correction of inherited or acquired disease has gained increasing importance in recent years. Successful treatment of children suffering from severe combined immunodeficiency (SCID) was achieved using retrovirus vectors for gene transfer. Encouraging improvements of vision were reported in a genetic eye disorder (LCA) leading to early childhood blindness. Adeno-associated virus (AAV) vectors were used for gene transfer in these trials. This chapter gives an overview of the design and delivery of viral vectors for the transport of a therapeutic gene into a target cell or tissue. The construction and production of retrovirus, lentivirus, and AAV vectors are covered. The focus is on production methods suitable for biopharmaceutical upscaling and for downstream processing. Quality control measures and biological safety considerations for the use of vectors in clinical trials are discussed.

Signal transduction pathways involved in drug-induced liver injury.

Abstract: Hepatocyte death following drug intake is the critical event in the clinical manifestation of drug-induced liver injury (DILI). Traditionally, hepatocyte death caused by drugs had been attributed to overwhelming oxidative stress and mitochondria dysfunction caused by reactive metabolites formed during drug metabolism. However, recent studies have also shown that signal transduction pathways activated/inhibited during oxidative stress play a key role in DILI. In acetaminophen (APAP)-induced liver injury, hepatocyte death requires the sustained activation of c-Jun kinase (JNK), a kinase important in mediating apoptotic and necrotic death. Inhibition of JNK using chemical inhibitors or knocking down JNK can prevent hepatocyte death even in the presence of extensive glutathione (GSH) depletion, covalent binding, and oxidative stress. Once activated, JNK translocates to mitochondria, to induce mitochondria permeability transition and trigger hepatocyte death. Mitochondria are central targets where prodeath kinases such as JNK, prosurvival death proteins such as bcl-xl, and oxidative damage converge to determine hepatocyte survival. The importance of mitochondria in DILI is also observed in the Mn-SOD heterozygous (+/−) model, where mice with less mitochondrial Mn-SOD are sensitized to liver injury caused by certain drugs. An extensive body of research is accumulating suggesting a central role of mitochondria in DILI. Drugs can also cause redox changes that inhibit important prosurvival pathways such as NF-κB. The inhibition of NF-κB by subtoxic doses of APAP sensitizes hepatocyte to the cytotoxic actions of tumor necrosis factor (TNF). Many drugs will induce liver injury if simultaneously treated with LPS, which promotes inflammation and cytokine release. Drugs may be sensitizing hepatocytes to the cytotoxic effects of cytokines such as TNF, or vice versa. Overall many signaling pathways are important in regulating DILI, and represent potential therapeutic targets to reduce liver injury caused by drugs.

The Keap1-Nrf2 Cellular Defense Pathway: Mechanisms of Regulation and Role in Protection Against Drug-Induced Toxicity

Abstract: Adverse drug reactions pose a significant public health problem. In some cases, the process of drug metabolism can contribute to the onset of toxicity through the bioactivation of a parent molecule to a chemically reactive intermediate. In order to maintain a favorable balance between bioactivation and detoxification, mammalian cells have evolved an inducible cell defense system known as the antioxidant response pathway. The activity of this cytoprotective pathway is largely regulated by the transcription factor Nrf2, which governs the expression of many phase II detoxification and antioxidant enzymes. In turn, the activity of Nrf2 is regulated by the cysteine-rich cytosolic inhibitor Keap1, which acts as a “sensor” for chemical/oxidative stress. This article summarizes our current understanding of the molecular mechanisms that regulate the function of the Keap1-Nrf2 pathway and highlights the importance of Nrf2 in the protection against drug-induced toxicity.

Carriers in the topical treatment of skin disease.

Abstract: Topical drug application is less prone to severe systemic side-effects than systemic application. Starting with the liposomes, various types of nanosized and microsized drug carriers have been developed to increase the notoriously low penetration of active agents into the skin, which limits not only the topical therapy of skin disease but also transdermal therapy. Today, liposome- and microsponge-based preparations are approved for dermatomycosis, acne and actinic keratosis. Under investigation are drug carriers such as lipid nanoparticles, polymeric particles, dendrimers, and dendritic-core multi-shell nanotransporters. According to the rapidly increasing research in this field, both in academia and industry, a breakthrough appears likely, once stability problems (nanoparticles) and safety concerns (dendrimers) are overcome. Technical approaches and results of in vitro, ex vivo and in vivo testing are described, taking into account pharmacokinetic, efficacy and safety aspects.

Hormonal Growth Promoting Agents in Food Producing Animals

Abstract: In contrast to the use of hormonal doping agents in sports to enhance the performance of athletes, in the livestock industry hormonal growth promoters (“anabolics”) are used to increase the production of muscle meat. This leads to international disputes about the safety of meat originating from animals treated with such anabolics.

New insights into sperm physiology and pathology.

Abstract: Infertility is a relatively common condition affecting approximately one in ten of the population In half of these cases, a male factor is involved, making defective sperm function the largest single, defined cause of human infertility Among other factors, recent data suggest that oxidative stress plays a major role in the etiology of this condition Spermatozoa spontaneously produce a variety of reactive oxygen species (ROS) including the superoxide anion, hydrogen peroxide and nitric oxide Produced in small amounts, ROS are functionally important in driving the tyrosine phosphorylation cascades associated with sperm capacitation However, when ROS production exceeds the spermatozoa’s limited antioxidant defenses, a state of oxidative stress is induced characterized by peroxidative damage to the sperm plasma membrane and DNA strand breakage in the sperm nucleus Such oxidative stress not only disrupts the fertilizing potential of human spermatozoa but also the ability of these cells to create a normal healthy embryo As a result, DNA damage in human spermatozoa is correlated with an increased incidence of miscarriage and various kinds of morbidity in the offspring These insights into the pathophysiology of defective sperm function have clear implications for the diagnosis and treatment of male infertility, particularly with respect to the potential importance of antioxidant therapy These concepts may also be relevant to the design of novel approaches to male contraception that attempt to replicate the pathological situation

Mechanisms of Drug-Induced Nephrotoxicity

Abstract: Drug-induced nephrotoxicity is a common complication of several medications and diagnostic agents. It is seen in both inpatient and outpatient settings with variable presentations ranging from mild, reversible injury to advanced kidney disease. Manifestations of drug-induced nephrotoxicity include acid-base abnormalities, electrolyte imbalances, urine sediment abnormalities, proteinuria, pyuria, hematuria, and, most commonly, a decline in the glomerular filtration rate. The mechanisms of drug-induced nephrotoxicity may differ between various drugs or drug classes, and they are generally categorized based on the histological component of the kidney that is affected. Aminoglycoside antibiotics, radiocontrast media, conventional nonselective nonsteroidal anti-inflammatory drugs, and selective cyclooxygenase-2 inhibitors, amphotericin B, and angiotensin-converting enzyme inhibitors have been frequently implicated. This chapter reviews the clinical presentation and basic mechanisms of drug-induced nephrotoxicity.

Mechanisms of adverse drug reactions to biologics.

Abstract: Biologics encompass a broad range of therapeutics that include proteins and other products derived from living systems. Although the multiplicity of target organs often seen with new chemical entities is generally not seen with biologics, they can produce significant adverse reactions. Examples include IL-12 and an anti-CD28 antibody that resulted in patient deaths and/or long stays in intensive care units. Mechanisms of toxicities can be categorized as pharmacological or nonpharmacological, with most, excepting hypersensitivity reactions, associated with the interaction of the agent with its planned target. Unexpected toxicities generally arise as a result of previously unknown biology. Manufacturing quality is a significant issue relative to the toxicity of biologics. The development of recombinant technology represented the single biggest advance leading to humanized products with minimal or no contaminants in comparison to products purified from animal tissues. Nevertheless, the type of manufacturing process including choice of cell type, culture medium, and purification method can result in changes to the protein. For example, a change to the closure system for erythropoietin led to an increase in aplastic anemia as a result of changing the immunogenicity characteristics of the protein. Monoclonal antibodies represent a major class of successful biologics. Toxicities associated with these agents include those associated with the binding of the complementary determining region (CDR) with the target. First dose reactions or infusion reactions are generally thought to be mediated via the Fc region of the antibody activating cytokine release, and have been observed with several antibodies. Usually, these effects (flu-like symptoms, etc.) are transient with subsequent dosing. Although biologics can have nonpharmacologic toxicities, these are less common than with small molecule drugs.

Veterinary medicines and the environment.

Abstract: Veterinary medicines may be emitted either directly or indirectly into the environment, following its use. As veterinary medicines are biologically active compounds, there is a concern that their occurrence in the environment may have an adverse impact on aquatic and terrestrial organisms. This chapter reviews the major sources by which veterinary medicines enter the environment, the fate, behaviour and occurrence of veterinary medicines in the environment and the potential effects on environmental and human health. Finally, gaps in the current knowledge are identified and recommendations provided on priorities for future research.

Receptor- and reactive intermediate-mediated mechanisms of teratogenesis.

Abstract: Drugs and environmental chemicals can adversely alter the development of the fetus at critical periods during pregnancy, resulting in death, or in structural and functional birth defects in the surviving offspring. This process of teratogenesis may not be evident until a decade or more after birth. Postnatal functional abnormalities include deficits in brain function, a variety of metabolic diseases, and cancer. Due to the high degree of fetal cellular division and differentiation, and to differences from the adult in many biochemical pathways, the fetus is highly susceptible to teratogens, typically at low exposure levels that do not harm the mother. Insights into the mechanisms of teratogenesis come primarily from animal models and in vitro systems, and involve either receptor-mediated or reactive intermediate-mediated processes. Receptor-mediated mechanisms involving the reversible binding of xenobiotic substrates to a specific receptor are exemplified herein by the interaction of the environmental chemical 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or "dioxin") with the cytosolic aryl hydrocarbon receptor (AHR), which translocates to the nucleus and, in association with other proteins, binds to AH-responsive elements (AHREs) in numerous genes, initiating changes in gene transcription that can perturb development. Alternatively, many xenobiotics are bioactivated by fetal enzymes like the cytochromes P450 (CYPs) and prostaglandin H synthases (PHSs) to highly unstable electrophilic or free radical reactive intermediates. Electrophilic reactive intermediates can covalently (irreversibly) bind to and alter the function of essential cellular macromolecules (proteins, DNA), causing developmental anomalies. Free radical reactive intermediates can enhance the formation of reactive oxygen species (ROS), resulting in oxidative damage to cellular macromolecules and/or altered signal transduction. The teratogenicity of reactive intermediates is determined to a large extent by the balance among embryonic and fetal pathways of xenobiotic bioactivation, detoxification of the xenobiotic reactive intermediate, detoxification of ROS, and repair of oxidative macromolecular damage.

Side effects of anabolic androgenic steroids: pathological findings and structure-activity relationships.

Abstract: Side effects of anabolic steroids with relevance in forensic medicine are mainly due to life-threatening health risks with potential fatal outcome and cases of uncertain limitations of criminal liability after steroid administration. Both problems are typically associated with long-term abuse and excessive overdose of anabolic steroids. Side effects may be due to direct genomic or nongenomic activities (myotrophic, hepatotoxic), can result from down-regulation of endogenous biosynthesis (antiandrogenic) or be indirect consequence of steroid biotransformation (estrogenic).

Mucoadhesive Drug Delivery Systems

Abstract: The uptake of drugs is often limited by the short contact time between the formulation and the absorption membrane and by a fast washout. Using mucoadhesive polymers, however, the residence time of the dosage form on the mucosa can be significantly increased. In this chapter the composition of the mucus, the different mucoadhesion theories and binding types between mucus and mucoadhesives, mucoadhesion tests and factors influencing mucoadhesion are introduced. Various mucoadhesive polymers are also described and an overview of various mucoadhesive delivery systems is provided.

Estrogen Signaling in the Regulation of Female Reproductive Functions

Abstract: Estrogens influence fertility and infertility in animals. This chapter reviews the use of estrogen as a contraceptive through the regulation of its production and action. It is concluded that the use of specific agonists and antagonists of estrogen action that avoid the global and unwanted side effects of estrogen offers new potential methods of contraception.

Detecting the administration of endogenous anabolic androgenic steroids.

Abstract: The detection of the administration of an androgen such as testosterone that could be present normally in human bodily fluids is based upon the methodical evaluation of key parameters of the urinary profile of steroids, precisely measured by GC/MS. Over the years, the markers of utilization were identified, the reference ranges of diagnostic metabolites and ratios were established in volunteers and in populations of athletes, and their stability in individual subjects was studied. The direct confirmation comes from the measurement of delta (13)C values reflecting their synthetic origin, ruling out a potential physiological anomaly. Several factors may alter the individual GC/MS steroid profile besides the administration of a testosterone-related steroid, the nonexhaustive list ranging from the microbial degradation of the specimen, the utilization of inhibitors of 5alpha-reductase or other anabolic steroids, masking agents such as probenecid, to inebriating alcohol drinking. The limitation of the testing strategy comes from the potentially elevated rate of false negatives, since only the values exceeding those of the reference populations are picked up by the GC/MS screening analyses performed by the laboratories on blind samples, excluding individual particularities and subtle doping. Since the ranges of normal values are often described from samples collected in Western countries, extrapolating data to all athletes appears inefficient. Furthermore, with short half-life and topical formulations, the alterations of the steroid profile are less pronounced and disappear rapidly. GC/C/IRMS analyses are too delicate and fastidious to be considered for screening routine samples. An approach based upon the individual athlete's steroid profiling is necessary to pick up variations that would trigger further IRMS analysis and investigations.

Erythropoietin and analogs.

Abstract: Erythropoietin (EPO), a glycoprotein hormone, stimulates the growth of red blood cells and as a consequence it increases tissue oxygenation. This performance enhancing effect is responsible for the ban of erythropioetin in sports since 1990. Especially its recombinant synthesis led to the abuse of this hormone, predominatly in endurance sports. The analytical differentiation of endogenously produced erythropoietin from its recombinant counterpart by using isoelectric focusing and double blotting is a milestone in the detection of doping with recombinant erythropoietin. However, various analogous of the initial recombinant products, not always easily detectable by the standard IEF-method, necessitate the development of analytical alternatives for the detection of EPO doping. The following chapter summarizes its mode of action, the various forms of recombinant erythropoietin, the main analytical procedures and strategies for the detection of EPO doping as well as a typical case report.

Drug-eluting medical implants.

Abstract: Drug-eluting medical implants are actually active implants that induce healing effects, in addition to their regular task of support. This effect is achieved by controlled release of active pharmaceutical ingredients (API) into the surrounding tissue. In this chapter we focus on three types of drug-eluting devices: drug-eluting vascular stents, drug-eluting wound dressings and protein-eluting scaffolds for tissue regeneration, thus describing both internal and external implants. Each of these drug-eluting devices also presents an approach for solving the drug release issue. Most drug-eluting vascular stents are loaded with water-insoluble antiproliferative agents, and their diffusion from the device to the surrounding tissue is relatively slow. In contrast, most drug-eluting wound dressings are loaded with highly water-soluble antibacterial agents and the issue of fast release must therefore be addressed. Growth factor release from scaffolds for tissue regeneration offers a new approach of incorporating high-molecular-weight bioactive agents which are very sensitive to process conditions and preserve their activity during the preparation stage. The drug-eluting medical implants are described here in terms of matrix formats and polymers, incorporated drugs and their release profiles from the implants, and implant functioning. Basic elements, such as new composite core/shell fibers and structured films, can be used to build new antibiotic-eluting devices. As presented in this chapter, the effect of the processing parameters on the microstructure and the resulting drug release profiles, mechanical and physical properties, and other relevant properties, must be elucidated in order to achieve the desired properties. Newly developed implants and novel modifications of previously developed approaches have enhanced the tools available for creating clinically important biomedical applications.

Drug hypersensitivity reactions involving skin.

Abstract: Immune reactions to drugs can cause a variety of diseases involving the skin, liver, kidney, lungs, and other organs. Beside immediate, IgE-mediated reactions of varying degrees (urticaria to anaphylactic shock), many drug hypersensitivity reactions appear delayed, namely hours to days after starting drug treatment, showing a variety of clinical manifestations from solely skin involvement to fulminant systemic diseases which may be fatal. Immunohistochemical and functional studies of drug-specific T cells in patients with delayed reactions confirmed a predominant role for T cells in the onset and maintenance of immune-mediated delayed drug hypersensitivity reactions (type IV reactions). In these reactions, drug-specific CD4+ and CD8+ T cells are stimulated by drugs through their T cell receptors (TCR). Drugs can stimulate T cells in two ways: they can act as haptens and bind covalently to larger protein structures (hapten-carrier model), inducing a specific immune response. In addition, they may accidentally bind in a labile, noncovalent way to a particular TCR of the whole TCR repertoire and possibly also major histocompatibility complex (MHC)-molecules - similar to their pharmacologic action. This seems to be sufficient to reactivate certain, probably in vivo preactivated T cells, if an additional interaction of the drug-stimulated TCR with MHC molecules occurs. The mechanism was named pharmacological interaction of a drug with (immune) receptor and thus termed the p-i concept. This new concept may explain the frequent skin symptoms in drug hypersensitivity to oral or parenteral drugs. Furthermore, the various clinical manifestations of T cell-mediated drug hypersensitivity may be explained by distinct T cell functions leading to different clinical phenotypes. These data allowed a subclassification of the delayed hypersensitivity reactions (type IV) into T cell reactions which, by releasing certain cytokines and chemokines, preferentially activate and recruit monocytes (type IVa), eosinophils (type IVb), or neutrophils (type IVd).

History of doping and doping control.

Abstract: Although attempts to enhance athletic performance are probably much older, the word “doping” was first mentioned in 1889 in an English dictionary. It described originally a mixed remedy containing opium, which was used to “dope” horses. “Dope” was a spirit prepared from the residues of grapes, which Zulu warriors used as a “stimulant” at fights and religious procedures and which also reportedly was called “doop” in Afrikaans or Dutch. Later, the meaning of “dope” was extended in a broader sense to other beverages with stimulating properties. The expression was introduced into English Turf Sport about 1900 for illegal drugging of racehorses.

New insights into ovarian function.

Abstract: Infertility adversely affects many couples worldwide. Conversely, the exponential increase in world population threatens our planet and its resources. Therefore, a greater understanding of the fundamental cellular and molecular events that control the size of the primordial follicle pool and follicular development is of utmost importance to develop improved in vitro fertilization as well as to design novel approaches to regulate fertility. In this review we attempt to highlight some new advances in basic research of the mammalian ovary that have occurred in recent years focusing primarily on mouse models that have contributed to our understanding of ovarian follicle formation, development, and ovulation. We hope that these new insights into ovarian function will trigger more research and translation to clinically relevant problems.