Following 1 hr incubation with ACTH, cytochalasin D or ACTH/cytochalasin, detergent-solubilized mouse adrenal tumor cells cytoskeletal changes were examined using scanning and transmission electron microscopy. Steroid production was also examined.

No description available.

Thesis (MSc (Biochemistry))--Stellenbosch University, 2008. / Gonadotropin-releasing hormone (GnRH) acting through the cognate GnRH receptor (GnRH-R) plays an important role in the regulation of mammalian reproductive function by regulating the synthesis and release of follicle stimulating hormone (FSH) and luteinizing hormone (LH). The sensitivity of pituitary gonadotropes to GnRH depends on the number of GnRH receptors present on the gonadotrope cell surface. GnRH-R is regulated at a transcriptional, post-transcriptional and post-translational level. Hormones such as GnRH and glucocorticoids (GCs) regulate GnRH-Rs in a time- and dose-dependent manner. Previous studies have shown that the GnRH-R promoter confers glucocorticoid-dependent activation via the activating protein 1 (AP-1) site in the nongonadotrope GGH3 cell line. The mechanism by which GCs regulate the GnRH-R promoter is not precisely known as the literature is contradictory. Therefore this study investigates the mechanism of transcriptional regulation of the mouse GnRH-R promoter in the mouse gonadotrope cell line LβT2, treated with the synthetic GC dexamethasone (dex). Assays used include promoter-reporter studies, Western blotting, endogenous mRNA expression studies, electrophoretic mobility shift assay (EMSA) as well as the in vivo chromatin immunoprecipitation (ChIP) assay. A transfected promoter-reporter plasmid containing 600 bp of the mouse GnRH-R promoter was used to investigate the effect of dex on transcriptional regulation. Previously it was determined in our laboratory that the GnRH-R promoter is activated via an AP-1 binding site in the LβT2 cell line, and is regulated in a time- and dose-dependent manner by dex. In the present study in the LβT2 cell line a small induction was indeed seen upon dex treatment. Cotransfecting a expression vector for rat GR succeeded in inducing a 2 fold positive dex response. Western blot analysis revealed that GR levels remain consistent even after 8 hours dex induction. The effect of dex on the endogenous GnRH-R gene was investigated by means of real-time RT-PCR. Dex did indeed upregulate the gene in a time-dependant manner. Maximal induction (7.4 fold) was obtained after at least 12 hours of dex treatment. Untreated LβT2 nuclear extracts were investigated using EMSA, for protein binding to the mouse GnRH-R promoter AP-1 binding site, and these proteins were identified as c- Fos and GR. This suggests that the GR interacts with the AP-1 transcription factor via a tethering mechanism to mediate the positive dex response. The results of an in vivo ChIP assay were consistent with this hypothesis, showing that the GR interacted with a genomic fragment containingthe AP-1 site, in response to dex. The transactivation of the GnRH-R promoter by means of the GR tethering to AP-1 has not been shown before in the LβT2 cell line.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This study describes: - the characterization and comparison of the enzymatic activity of both Angora and ovine 3βHSD expressed in non-steroidogenic COS-1 cells. The apparent Km and Vmax values for the metabolism of PREG, 17-OHPREG and DHEA were determined; - the characterization of steroid metabolites produced by COS-1 cells coexpressing either Angora or ovine 3βHSD together with Angora CYP17, in the presence and absence of overexpressed Cyt-b5, following the metabolism of PREG and 17-OHPREG. 3βHSD was identified as an additional factor in causing hypocortisolism in the South African Angora goat; - the influence of Cyt-b5 on the enzymatic activity of both Angora and ovine 3βHSD coexpressed in non-steroidogenic COS-1 cells; - the influence of purified ovine live Cyt-b5 and anti-Cyt-b5 IgG on adrenal microsomal 3βHSD activity. Cyt-b5 was shown to specifically augment 3βHSD activity which represents the first documentation of such augmentation in any species; - the overexpression and purification of Angora 3βHSD using a baculovirus expression system coupled with a detergent based enzyme purification method; - the characterization of both substrate and co-factor kinetics for the individual dehydrogenase and isomerase activities of purified 3βHSD, in the presence and absence of purified ovine liver Cyt-b5. Cyt-b5 was shown to increase the affinity of 3βHSD towards NAD+ during the dehydrogenase reaction whilst having no significant influence on the isomerase reaction. This represents the first documentation of Cyt-b5 influencing co-factor binding in any member of the -ydroxysteroid dehydrogenases; - the FRET analysis of COS-1 cells coexpressing 3βHSD-eCFP and Cyt-b5-eYFP fusion proteins, suggesting an allosteric interaction between 3βHSD and Cyt-b5. / AFRIKAANSE OPSOMMING: Hierdie studie beskryf: - die karakterisering en vergelyking van die ensiematiese aktiwiteit van beide Angora en skaap 3βHSD, wat uitgedruk was in nie-steroïed genererende COS-1 selle. Die Km en Vmax waardes tydens die metabolisme van PREG, 17-OHPREG en DHEA was bepaal; - die karakterisering van steroïed metaboliete gegenereer deur COS-1 selle wat Angora of skaap 3βHSD uitdruk saam met Angora CYP17, in die aanwesigheid of afwesigheid van sitochroom b5, na die metaboliseering van PREG en 17-OHPREG. 3βHSD was geïdentifiseer as ‘n bydraende faktor in die oorsaak van hipokortisolisme in die Suid-Afrikaanse Angorabok; - die invloed van sitochroom b5 op die ensiematiese aktiwiteit van beide Angora en skaap 3βHSD wat saam uitgedruk was in nie-steroïed genererende COS-1 selle; - die invloed van gesuiwerde skaap lewer sitochroom b5 en sitochroom b5 teenstof op mikrosomale 3βHSD aktiwiteit. Dit is getoon dat sitochroom b5 die aktiwiteit van 3βHSD spesifiek verhoog. Hierdie studie verteenwoordig die eerste dokumentasie van so ‘n verhoging in enige spesie; - die uitdrukking en suiwering van Angora 3βHSD deur middel van ‘n bakulo-virus sisteem gekoppel aan ‘n detergent gebaseerde ensiem suiwerings metode; - die karakterisering van beide substraat en ko-faktor kinetika vir die afsonderlike dehidrogenase en isomerase aktiwiteite van gesuiwerde 3βHSD, in die aanwesigheid of afwesigheid van gesuiwerde sitochroom b5. Dit is getoon dat sitochroom b5 die affiniteit van 3βHSD teenoor NAD+ tydens die dehidrogenase reaksie verhoog sonder om ‘n beduidende invloed op die isomerase reaksie te hê. Hierdie studie verteenwoordig die eerste dokumentasie van sitochroom b5 wat ko-faktor binding beïnvloed in enige lid van die hidroksisteroïed dehidrogenase familie van ensieme; - die analise van FRET sein in COS-1 selle wat beide 3βHSD-eCFP en Cyt-b5- eYFP fusie proteïene uitdruk. Die resultate stel voor dat sitochroom b5 3βHSD aktiwiteit beïnvloed deur middel van ‘n allosteriese meganisme.

Thesis (PhD (Biochemistry))--Stellenbosch University, 2008. / This study describes: • the cloning and sequencing of cytochrome P450 17 -hydroxylase/17,20 lyase (CYP17), 3 -hydroxysteroid dehydrogenase (3 HSD) and cytochrome b5 from the South African Angora goat; • the identification of two CYP17 genes encoding two unique CYP17 isoforms in the Angora goat; • the development of a UPLC-APCI-LC method for the separation and quantification of seven adrenal steroids; • the characterisation of the enzymatic activity of the two Angora CYP17 isoforms expressed in non-steroidogenic COS-1 cells. The Km and Vvalues for the metabolism of pregnenolone and progesterone were determined; • the development of a rapid and accurate real-time PCR genotyping test for CYP17 in Angora goats. Three unique genotypes were identified; • the determination of blood cortisol levels upon the stimulation of the HPAaxis by intravenous insulin injection in the three Angora goat genotypes.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This study describes: • the comparison of the enzymatic activities of the two ovine cytochrome P450 17 - hydroxylase/17,20-lyase (CYP17) isoforms expressed in non-steroidogenic COS-1 cells. The Km and Vmax values for the metabolism of pregnenolone and progesterone were determined, while time-dependent metabolism of pregnenolone, 17-hydroxypregenolone, progesterone and 17-hydroxyprogesterone was also reported. The cloning and sequencing of ovine cytochrome b5 is reported and was co-expressed with CYP17. The results showed that the wild type 1 (WT1) isoform of ovine CYP17 produce more cortisol precursors than the wild type 2 (WT2) isoform; • the analysis of the frequency distribution of the CYP17 genotypes within a South African Merino population, which were divergently selected for (H-line) or against (L-line) the ability of a ewe to rear multiple offspring per birthing opportunity. It was observed that the CYP17 frequency distribution was the same within the H- and L-line, with 78.3 % heterozygous WT1/WT2 and 21.7 % homozygous WT1/WT1. No homozygous WT2/WT2 individuals were identified; • the development of a UPLC-MS/MS method for the separation and quantification of all thirteen adrenal steroids that are produced in the adrenal gland; • the relative contribution of the CYP17 genotypes in the total steroidogenic output in adult adrenocortical cells from the adrenal glands of H- and L-line sheep, with particular emphasis on cortisol production. The adrenocortical cells from the H-line sheep showed a marked higher cortisol production than the L-line, while adrenocortical cells from homozygous WT1/WT1 sheep also produced more cortisol than heterozygous WT1/WT2 sheep; • the blood cortisol responses upon the stimulation of the HPA axis by insulin induced hypoglycaemia of the H- and L-line sheep with known CYP17 genotypes. It was observed that the CYP17 genotype and selection line are important factors affecting the cortisol responses of sheep, where L-line heterozygous WT1/WT2 sheep showed the lowest cortisol response and glucose recovery; • the association of the CYP17 genotype with behavioural responses of H- and L-line sheep to flock isolation stress, as well as the association of the CYP17 genotype with ewe reproduction and lamb output. While reproduction seemed to be unaffected by the CYP17 genotype, the behavioural stress responses of sheep to flock isolation correlated with the CYP17 genotype, where the heterozygous WT1/WT2 genotype was associated with a wilder nature. / AFRIKAANSE OPSOMMING: Hierdie studie ondersoek: • die vergelyking van die ensiemaktiwiteite vir twee isoforme van skaap sitochroom P450 17 -hidroksilase/17,20-liase (CYP17), wat uitgedruk was in nie-steroïed genererende COS- 1 selle. Die Km and Vmax waardes was bepaal vir die metabolisme van pregnenoloon en progesteroon, terwyl die tyd-afhanklike metabolisme van pregnenoloon, 17- hidroksiepregnenoloon, progesteroon en 17-hidroksieprogesteroon ook gerapporteer word. Die klonering en volgorde bepaling van skaap sitochroom b5 was gedoen en gevolglik was sitochroom b5 saam met CYP17 uitgedruk in COS-1 selle. Die resultate het gewys dat wilde tipe 1 (WT1) meer voorlopers van kortisol produseer as wilde tipe 2 (WT2); • die frekwensie distrubusie van die CYP17 genotipes in ‘n Suid-Afrikaanse Merino populasie, waar skape in teenoorgestelde rigtings geselekteer was vir (H-lyn) of teen (L-lyn) die vermoë van ‘n ooi om geboorte te gee aan veelvoudige lammers per lamgeleentheid. Die frekwensie distrubusie van CYP17 was dieselfde in beide die H- en L-lyn, waar 78.3 % van die populasie heterosigoties WT1/WT2 en 21.7 % homosigoties WT1/WT1 was. Geen homosigote WT2/WT2 individue was geïdentifiseer nie; • die ontwikkeling van ‘n UPLC-MS/MS metode vir die skeiding en kwantifisering van al dertien steroïede wat natuurlik geproduseer word in die bynier van die skaap; • die relatiewe bydrae van die CYP17 isoforme tot die totale steroïedale uitsette vanuit die bynier kortex selle, vanaf die byniere van H- en L-lyn skape, waar klem geplaas word op die produksie van kortisol. Die bynierselle van die H-lyn skape het aansienlik meer kortisol produseer as die L-lyn, terwyl die bynierselle van die homosigotiese WT1/WT1 skape ook meer kortisol produseer het as heterosigotiese WT1/WT2 skape; • die bloed kortisol in reaksie tot die stimulering van die hipotalamus-hipofise-adrenale aksis, deur insulien geïnduseerde hipoglisemiese stress, in skape van die H- en L-lyne met bekende CYP17 genotipes. Dit was gevind dat die kortisol reaksie geaffekteer word deur beide die CYP17 genotipe en seleksie lyn, waar L-lyn heterosigotiese WT1/WT2 skape die minste kortisol geproduseer het en die stadigste herstel van glukose vlakke getoon het; • die assosiasie tussen die CYP17 genotipe en die gedrags reaksies op trop-isolasie, sowel as ooi-reproduksie en lamuitset, van die H- en L-lyn skape. Die reproduksie parameters was onafhanklik van die CYP17 genotipe, terwyl ‘n sterk assosiasie gevind was tussen die CYP17 genotipe en gedrags reaksies op trop-isolasie. Die heterosigotiese WT1/WT2 skape het ‘n wilder natuur getoon gedurende trop-isolasie in vergelyking met homosigotiese WT1/WT1 skape.

by Martin Li. / Year shown on spine: 1997. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 150-157). / DECLARATION --- p.II / ABSTRACT --- p.III / ACKNOWLEDGEMENTS --- p.VII / CONTENTS --- p.VIII / LIST OF ABBREVIATIONS --- p.XIV / LIST OF TABLES --- p.XVI / LIST OF CHART --- p.XXIII / LIST OF FIGURES --- p.XXIV / Chapter CHAPTER 1 --- OBSTRUCTIVE AIRWAY DISEASE: PUBLIC HEALTH AND CLINICAL ASPECTS --- p.1 / Chapter 1.1. --- Background --- p.1 / Chapter 1.2. --- Magnitude of the problem --- p.2 / Chapter 1.2.1. --- Asthma --- p.2 / Chapter 1.2.2. --- Chronic obstructive pulmonary disease --- p.3 / Chapter 1.2.3. --- Prevalence of osteoporosis in Hong Kong --- p.4 / Chapter 1.2.4. --- History of asthma care --- p.5 / Chapter 1.2.5. --- Treatment of OAD --- p.5 / Chapter 1.3. --- Side effects of Glucocorticoid in OAD patients --- p.6 / Chapter 1.4. --- Side effccts of inhaled corticosteroids in OAD patients --- p.7 / Chapter 1.5. --- Trend of asthma therapy in Hong Kong --- p.8 / Chapter CHAPTER 2: --- OSTEOPOROSIS: PUBLIC HEALTH AND CLINICAL ASPECTS --- p.11 / Chapter 2.1. --- Bone Biology --- p.11 / Chapter 2.2. --- Skeletal Organisation --- p.11 / Chapter 2.3. --- Bone remodelling --- p.12 / Chapter 2.4. --- Effect of corticosteroids on bone remodelling --- p.13 / Chapter 2.5. --- Corticosteroids induccs osteoporosis --- p.13 / Chapter 2.6. --- Factors affecting BMD --- p.14 / Chapter 2.6.1. --- Peak bone mass --- p.14 / Chapter 2.6.2. --- Ethnic factors --- p.14 / Chapter 2.6.3. --- Aging --- p.15 / Chapter 2.6.4. --- Calcium intake --- p.15 / Chapter 2.6.5. --- Oestrogen --- p.16 / Chapter 2.6.6. --- Alcohol consumption --- p.17 / Chapter 2.6.7. --- Cigarette smoking --- p.17 / Chapter 2.7. --- Physical activity and BMD --- p.17 / Chapter 2.8. --- Body composition in Chinese subjects --- p.18 / Chapter CHAPTER 3 --- "PHASE I: BODY COMPOSITION AND BONE MINERAL DENSITY IN OBSTRUCTIVE AIRWAY DISEASE PATIENT AND NORMAL CONTROL SUBJECTS: OBJECTIVES, SUBJECTS AND METHODS" --- p.20 / Chapter 3.1. --- Objectives --- p.20 / Chapter 3.2. --- Subjects and methods --- p.21 / Chapter 3.2.1 --- OAD patients --- p.21 / Chapter 3.2.1.1 --- Disease definition and selection criteria --- p.21 / Chapter 3.2.1.2. --- Normal Control subjects --- p.21 / Chapter 3.3. --- Power of estimation --- p.22 / Chapter 3.4. --- Survey methods --- p.22 / Chapter 3.5. --- Questionnaire --- p.23 / Chapter 3.6. --- Body composition and bone mineral density measurement --- p.23 / Chapter 3.6.1. --- Body composition analysis --- p.24 / Chapter 3.6.2. --- Lumbar spine and proximal hip bone mineral density analysis --- p.24 / Chapter 3.6.3. --- Routine quality control of measurements --- p.24 / Chapter 3.6.4. --- Precision on patient repositioning --- p.25 / Chapter 3.7. --- Statistical methods --- p.25 / Chapter 3.8. --- Bone mineral density of normal control subjects --- p.25 / Chapter CHAPTER 4 --- PHASE II: FLUORIDE IN THE TREATMENT OF OSTEOPOROSIS --- p.27 / Chapter 4.1. --- Introduction --- p.27 / Chapter 4.2. --- Mechanisms of action --- p.28 / Chapter 4.2.1. --- Antiresorptive effect of fluoride --- p.28 / Chapter 4.2.2. --- Force-oriented osteogenic effect of fluoride --- p.28 / Chapter 4.2.3. --- Biochemical osteogenic effect --- p.29 / Chapter 4.3. --- Effect of fluoride salts on BMD: results of clinical trials --- p.29 / Chapter 4.4. --- Effcct of fluoride on bone histomorphology --- p.30 / Chapter 4.5. --- Compliance with sodium fluoride therapy --- p.31 / Chapter 4.6. --- Contradiction of fluoride treatment --- p.31 / Chapter 4.7. --- Sodium monofluorophosphate preparation --- p.32 / Chapter CHAPTER 5 --- PHASE II: THE EFFECTS OF FLUORIDE ON BONE MINERAL DENSITY OF OAD PATIENTS ON STEROID TREATMENT --- p.37 / Chapter 5.1. --- Objectives --- p.37 / Chapter 5.2. --- Subjects and methods --- p.37 / Chapter 5.2.1. --- Power of the study --- p.37 / Chapter 5.2.2. --- Subjects --- p.37 / Chapter 5.2.3. --- Method of randomisation --- p.38 / Chapter 5.2.4. --- Treatment modalities --- p.39 / Chapter 5.2.4.1. --- Treatment group --- p.39 / Chapter 5.2.4.2. --- Control group --- p.39 / Chapter 5.2.5. --- Bone mineral density measurements --- p.39 / Chapter 5.2.6. --- Routine quality control of measurement and precision on patient repositioning --- p.40 / Chapter 5.2.7. --- Methods of monitoring drug compliance --- p.40 / Chapter 5.2.8 --- Statistical methods --- p.40 / Chapter CHAPTER 6 --- RESULTS FOR PHASE I --- p.42 / Chapter 6.1. --- Statistical power of this phase of the study --- p.42 / Chapter 6.2. --- Clinical features of OAD subjects on inhaled steroid --- p.42 / Chapter 6.3. --- Anthropometric measurements and bone mineral density --- p.45 / Chapter 6.4. --- Analysis of covariance for BMDs differences --- p.48 / Chapter 6.5. --- Multiple regression --- p.50 / Chapter 6.6 --- Correlation --- p.51 / Chapter CHAPTER 7 --- RESULTS FOR PHASE II: FLUORIDE AND CALCIUM TRIAL --- p.81 / Chapter 7.1. --- Factors affects the power of studies --- p.81 / Chapter 7.2. --- Clinical findings --- p.82 / Chapter 7.3. --- Body measurements and bone mineral densitometry --- p.85 / Chapter CHAPTER 8: --- DISCUSSION FOR PHASE I --- p.117 / Chapter CHAPTER 9: --- DISCUSSION FOR PHASE II: TRIDIN AND CALCIUM TRIAL --- p.124 / APPENDIX 1: QUESTIONNAIRE FOR OAD BONE MINERAL DENSITY STUDY --- p.132 / APPENDIX 2: BONE SCANS FROM HOLOGIC QDR2000 --- p.137 / APPENDIX 3. TABLES AND REFERENCE CURVES FOR NORMAL HONG KONG CHINESE FEMALE OR MALE BMD --- p.142 / REFERENCE --- p.150

Xu Li. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 204-242). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Graduation date: 1993

La neumonía adquirida en la comunidad (NAC) continúa siendo en la actualidad una enfermedad potencialmente grave, que con frecuencia presenta una evolución desfavorable, a pesar del tratamiento antibiótico adecuado. La hipótesis de la tesis plantea que es posible monitorizar la respuesta inflamatoria que tiene lugar durante la NAC y, que dicha respuesta, puede ser influenciada por los antibióticos utilizados en su tratamiento, así como modulada mediante una terapia adyuvante con corticoides. Con la intención de demostrar esta hipótesis, se desarrollaron dos estudios prospectivos y un ensayo randomizado. En el primer estudio, se incluyeron consecutivamente 38 pacientes que ingresaron con NAC con extensa afectación radiológica e insuficiencia respiratoria. En todos ellos, se realizó una determinación seriada de citocinas (TNF-alfa, IL-1beta, IL-6, IL-8 e IL-10) en el momento del ingreso y en los días 1, 2, 3, 5 y 7 de tratamiento. En el segundo estudio, se incluyeron consecutivamente 52 pacientes con neumonía neumocócica. En este estudio, se comparó la respuesta inflamatoria en los pacientes tratados con beta-lactámicos con aquellos que recibieron terapia combinada: beta-lactámicos más fluoroquinolona. En todos los pacientes, se realizó una determinación seriada de citocinas en sangre. Finalmente, se llevó a cabo un ensayo randomizado, doble ciego, metilprenisolona vs placebo, en el que se incluyeron 56 pacientes con NAC con extensa afectación radiológica e insuficiencia respiratoria. Todos los pacientes recibieron tratamiento con ceftriaxona y levofloxacino, y de manera randomizada y doble ciego, se administró un bolus de metilprednisolona o placebo, 30 minutos antes del inicio del antibiótico seguido de una pauta descendente de nueve días de duración. Los resultados de la tesis sugieren que es posible detectar la presencia de las citocinas estudiadas en sangre venosa. Sin embargo, sólo las citocinas IL-6, IL-8 e IL-10 fueron detectadas en todos los pacientes con neumonía en el momento del ingreso, con un rápido descenso a las 48 horas que coincidió con la defervescencia clínica. Respecto a la relación entre respuesta inflamatoria y pronóstico de la neumonía, las concentraciones iniciales de citocinas fueron superiores y se mantuvieron más tiempo elevadas en los pacientes que evolucionaron desfavorablemente. Entre los objetivos de la tesis se incluía estudiar el impacto del tratamiento antibiótico sobre la respuesta inflamatoria en la neumonía neumocócica. Los resultados de la tesis muestran que la terapia combinada (beta-lactámico y fluoroquinolona) produjo un descenso más rápido de las concentraciones de IL-6 a las 48 horas de tratamiento. Finalmente, el objetivo principal de la tesis fue demostrar que la asociación de corticoides como terapia adyuvante anti-inflamatoria en el tratamiento de la NAC podría ser beneficiosa. Los resultados de la tesis muestran que en pacientes con NAC que ingresaron con insuficiencia respiratoria y una extensa afectación radiológica, la administración de metilprednisolona en combinación con el tratamiento antibiótico se asoció a mejor evolución de varias variables clínicas como el cociente pO2/FiO2, la resolución radiológica y la escala del “time to resolution of morbidity” (TRM), así como a una reducción de la necesidad de ventilación mecánica. El efecto beneficioso de los corticoides sobre el curso clínico se reflejó asimismo en el comportamiento de los marcadores inflamatorios. Las concentraciones en sangre de IL-6 y proteína C reactiva fueron inferiores y disminuyeron más rápidamente en los pacientes tratados con metilprednisolona. / The community-acquired pneumonia (CAP) remains an important cause of disease worldwide. Despite advances in diagnostic methods and antibiotic treatment, the morbidity and mortality of NAC remain high. The hypothesis of the thesis suggests that it is possible to monitor the inflammatory response that occurs during the NAC and that this response may be influenced by antibiotics used to treat it, and modulated by adjuvant therapy with corticosteroids. In order to demonstrate this hypothesis, we developed two prospective studies and a randomized trial. In the first study, a total of 38 consecutive patients with CAP and with extensive radiographic involvement and respiratory failure were prospectively included. For all cases, serial determination of cytokines (TNF- alpha, IL-1beta, IL-6, IL-8 and IL-10) were obtained at the time of admission and on days 1, 2, 3, 5 and 7 of treatment. In the second study, 52 consecutive patients with pneumococcal pneumonia were prospectively included. Concentrations of circulating were determined for all patients. To asses the effects of treatment on the systemic expression of cytokine production, patients were divided into two groups: those initially treated only with beta-lactam (beta-lactam group) and those initially treated with combination therapy including beta-lactams plus fluoroquinolone (combination therapy group). Finally, we conducted a randomized, double-blind, placebo-controlled trial, which included 56 patients admitted with CAP and with extensive radiographic involvement and respiratory failure. All patients were treated with ceftriaxone and levofloxacin, and were randomly assigned to treatment with corticosteroid therapy, administered in the form of a methyl-prednisolone bolus given prior to antibiotic treatment followed by a tapering of nine days. The results of the thesis suggest that all studied cytokine, except for IL-1beta, could be detected in venous blood. However, only the cytokines IL-6, IL-8 and IL-10 were detected in all patients with pneumonia on admission, with a significant decrease at 48 hours that correlate with the clinical defervescence. Regarding the relationship between inflammatory response and prognosis of pneumonia, the initial concentrations of cytokines were higher and remained elevated longer in patients who poor outcome. Finally, the main objective of the thesis was to demonstrate that the use of corticosteroids as an adjunct therapy for pneumonia could prevent an excessive inflammatory response, improving the prognosis of more severe episodes of CAP. The results of the tesis show that in patients with CAP admitted with respiratory failure and extensive radiographic involment, the administration of methyl-prednisolone in combination with antibiotic treatment was associated with better outcomes of several clinical variables as the ratio pO2/FiO2, radiological resolution and scale “time to resolution of morbidity” (TRM), and a reduced need for mechanical ventilation. The beneficial effect of corticosteroids on the clinical course was also reflected in the behavior of inflammatory markers. Blood concentrations of IL-6 and C- reactive protein were lower and quickly reduced in patients treated with methyl-prednisolone.