MICROBIOLOGY & PATHOLOGY Nuggets (1).doc - MICROBIOLOGY AND PATHOLOGY Green is pre 2002 Yellow is post 2002 USC messed up the following questions

MICROBIOLOGY & PATHOLOGY Nuggets (1).doc - MICROBIOLOGY...

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Unformatted text preview: MICROBIOLOGY AND PATHOLOGY Green is pre 2002 Yellow is post 2002 USC messed up the following questions: 1981Q61 – wrong – should be ‘(c) fibroblasts & endothelial cells’ 1981Q68 – wrong – should be ‘basophils & mast cells’, not ‘eosinophils & mast cells’ Questions to Find Which of the following affects the widest organ range? Herpes, rubella, varicella, Moluscam m. CELLS/ORGANELLES Cell parts: Mitochondrion – double MB structure responsible for cellular metabolism – powerhouse of the cell Nucleus – controls synthetic activities and stores genetic information Ribosome – site of mRNA attachment and amino acid assembly, protein synthesis Endoplasmic reticulum – functions in intracellular transportation Gogli apparatus/complex – composed of membranous sacs – involved in production of large CHO molecules & lysosomes Lysosome – organelle contains hydrolytic enzymes necessary for intracellular digestion Membrane bag containing digestive enzymes Cellular food digestion – lysosome MB fuses w/ MB of food vacuole & squirts the enzymes inside Digested food diffuses through the vacuole MB to enter the cell to be used for energy or growth Lysosome MB keeps the cell iself from being digested Involved mostly in cells that like to phagocytose Involved in autolytic and digestive processes Formed when the Golgi complex packages up an especially large vesicle of digestive enzyme proteins Phagosome – vesicle that forms around a particle (bacterial or other) w/in the phagocyte that engulfed it Then separates from the cell MB & fuses w/ lysozome to receive contents This coupling forms phagolysosomes in which digestion of the engulfed particle occurs Microbodies: Contain catalase Bounded by a single MB Compartments specialized for specific metabolic pathways Similar in function to lysosomes, but are smaller & isolate metabolic reactions involving H 2O2 Two general families: Peroxisomes: transfer H2 to O2, producing H2O2 – generally not found in plants Glyoxysomes: common in fat-storing tissues of the germinating seeds of plants Contain enzymes that convert fats to sugar to make the energy stored in the oils of the seed available 1 Inclusions – transitory, non-living metabolic byproducts found in the cytoplasm of the cell May appear as fat droplets, CHO accumulations, or engulfed foreign matter. The cell cycle 1) Labile cells (GI tract, blood cells) Described as parenchymal cells that are normally found in the G0 phase that can be stimulated to enter the G1 Undergo continuous replication, and the interval between two consecutive mitoses is designated as the cell cycle After division, the cells enter a gap phase (G1), in which they pursue their own specialized activities If they continue in the cycle, after passing the restriction point (R), they are committed to a new round of division The G1 phase is followed by a period of nuclear DNA synthesis (S) in which all chromosomes are replicated The S phase is followed by a short gap phase (G2) and then by mitosis After each cycle, one daughter cell will become committed to differentiation, and the other will continue cycling 2) Stable cells (Hepatocytes, Kidney) After mitosis, the cells take up their specialized functions (G0). They do not re-enter the cycle unless stimulated by the loss of other cells 3) Permanent cells (neurons) Become terminally differentiated after mitosis and cannot re-enter the cell cycle Which cells do not have the ability to differentiate? Cardiac myocytes Enzymes: Serum lysozyme: Provides innate & nonspecific immunity Lysozyme is a hydrolytic enzyme capable of digesting bacterial cell walls containing peptidoglycan In the process of cell death, lysosomal NZs fxn mainly to aulolyse necrotic cells (NOT “mediate cell degradation”) Attacks bacterial cells by breaking the bond between NAG and NAM. Peptidoglycan – the rigid component of cell walls in most bacteria – not found in archaebacteria or eukaryotic cells Lysozyme is found in serum, tears, saliva, egg whites & phagocytic cells protecting the host nonspecifically from microorganisms Superoxide dismutase: catalyzes the destruction of O2 free radicals protecting O2-metabolizing cells against harmful effects Catalase: catalyzes the decomposition of H2O2 into H2O & O2 Aerobic bacteria and facultative anaerobic w/ catalase are able to resist the effects of H 2O2 Anaerobic bacteria w/o catalase are sensitive to H2O2 (Peroxide), like Strep Anaerobic bacteria (obligate anaerobes) lack superoxide dismutase &/or catalase Staph makes catalase, where Strep does not have enough staff to make it!! Coagulase NOT an NZ, its an adhesin Converts Fibronogen to fibrin 2 Coagulase test is the prime criterion for classifying a bug as Staph aureus – from other Staph species Coagulase is important to the pathogenicity of S. aureus because it helps to establish the typical abscess lesion Coagulase also coats the surface w/ fibrin upon contact w/ blood, making it harder to phagocytize NOTE: this is NOT a polysaccharide capsule that forms Cell Functions: Autolysis: degradative reactions in cells caused by indigenous intracellular enzymes – usually occurs after cell death Irreversible (along with Coagulative necrosis or infarcts) – reversible: fatty degeneration, & hydropic degeneration Autolysin: Ab causing cellular lysis in the presence of complement Autolytic enzymes produced by the organism degrade the cell’s own cell wall structures In the presence of cephalosporins & penicillins, growing bacterial cells lyse W/o functional cell wall structures, the bacterial cell bursts Heterolysis: cellular degradation by enzymes derived from sources extrinsic to the cell (e.g., bacteria) Necrosis: sum of intracellular degradative reactions occurring after individual cell death w/in a living organism Lymph nodes If a foreign antigen enters through the skin, it will first hit the lymphoid system in the lymph nodes NOT the MALT, liver, spleen, or thymus Lymphocytes Motile Immunoglobulin production Produce MIF (Macrophage inhibiting factor) If a T-lymphocyte from a pt with chronic periodontitis were cultered in vitro with dental plaque antigen, production of MIF would occur DO NOT PHAGOCYTIZE When T cells from people with chronic PD are reacted with certain plaque bacterial antigens, they produce: MIF, OAF, & lymphotoxin (NOT Ab, collagenase, or C3) B-lymphocytes: Are WBCs that complete maturation in bone marrow then migrate to lymphoid organs Search out, identify, & bind w/ specific Ag/s Recognize specific antigens by virtue of membrane-bound immunoglobulin Committed to differentiate into Ab-producing plasma cells involved in Ab-mediated immunity When an immature B cell is exposed to a specific Ag (they recognize Ag by MB-bound Ig), the cell is activated It then travels to spleen or lymph nodes, differentiates, and rapidly produces plasma & memory cells Mature B cells have surface IgM & IgD that bind Ag & cause release of immunoglobulins B-cell immunodeficiency can be treated with injections of gamma-globulin 3 Plasma cells: The predominant cell in synthesis of Abs More common in chronic inflammation than acute inflammation Cells of Chronic inflammation are Lymphocytes, Plasma cells, and Macrophages T-lymphocytes: Affected by IL-4??? WBC that complete maturation in thymus & become thymocytes Responsible for initially recognition of antigen In pts with chronic PD, when the T cells react with certain plaque bacterial antigens, they produce: IL-2, TNF-alpha, IFN-gamma NOT Immunoglobulin – That would be B-cells. Responses to viral infections: Production of lymphokines Direct cell-mediated cytotoxicity Helper activity to B cells to make Abs Major classes include helper T-cells, suppressor T-cells, & cytotoxic (killer) T-cells T helper cells: CD4+ NOT antigen-specific (Antigen-specific cells are): B cells, Macrophages, Dendritic, and Langerhans (So, reticuloendothelial cells + B-cells). Two classes of helper T cells→Th1 & Th2 cells Distinguished by the types of cytokines they secrete Th1: release IL-2 & IFN-gamma Stimulate proliferation & cytotoxic responses Th2: release Il-4, IL-5, IL-6, Il-10 Stimulate B cell maturation, differentiation & class-switching Cytotoxic T-cells CD8+ First activated w/ IL-2, which is secreted by active helper T-cells Act by recognizing foreign Ag & MHC I molecules w/ their TCR Natural Killer (NK) cells Also activated w/ IL-2 Recognize foreign Ag w/o need for Ag presentation on MHC molecules NON specific immunity Activated by cytokines, such as IFN-gamma Deficiency in T-cells can predispose a person to candidiasis (NOT a deficiency in basophils/eosinophils/plasma cells/MФs) Eosinophils Release histaminase & aryl sulfatase to help control allergic reactions Basophils Have receptors for the Fc portion of IgE IgE binding promotes degranulation = release of histamine, etc, which lead to symptoms seen in atopic allergies Mast Cells IgE has an affinity for the Fc portion of Mast cells 4 Type I Hypersensitivity Secrete Histamine Heparin ECF-A (Eosinophil Chemotactic Factor of Anaphylaxis) SRS-A (Slow-Reacting Substances of anaphylaxis (SRS-As) Leukotrienes Lymphocytes T helper cells (Th) Cytotoxic T cells (Tc) T suppressor cells (Ts) T memory cells B lymphocytes B memory cells Natural killer cells (NK) Plasma cells Function Help or assist other T cells and B cells to express their immune function Kill target cells expressing foreign Ag/s (cells containing obligate intracellular parasistes & tumor cells) Suppress or inhibit the immune function of other lymphocytes Long-lived cells that recognize previously encountered T dependent antigens Differentiate into antibody-producing plasma cells and B memory cells in response to an antigen Long lived cells that recognize a previously encounter antigen Kill and lyse target cells that express foreign antigens Actively secrete antibody Cells that maintain latent capacity for mitotic division: Blood (RBCs live for 120 days, WBCs only 2-5 hours), bone marrow, liver, and salivary glands Liver undergoes regeneration: occurs as adaptive mechanism for restoring a tissue or organ After removal of 70% of liver, numerous mitoses of hepatocytes occur reaching a peak at 33 hours By day 12 the mass of liver is totally restored Liver is the least common site for infarcts (than brain, heart, kidney, adrenals) NOTE: Bone cartilage & intestinal mucosa are also able to regenerate Cells that do not have ability to undergo mitosis: Nerve cells (least ability to regenerate) in the CNS, skeletal, cardiac, & smooth muscle cells, lungs Striated muscle is harder to regenerate than smooth muscle Heart, brain, & lungs are very vulnerable to hypoxia & anoxia They die & are unable to regenerate The heart can undergo hypertrophy in response to injury BACTERIA A quick note on organisms in general: Commensalism: Interaction between two populations of different species living together in which one population benefits from the association, while the other is not affected Symbiosis: An obligatory interactive association between members of two populations 5 Produces a stable condition in which the two organisms live together in close physical proximity It may, but does not necessarily, benefit each member Mutualism: Form of symbiosis – both members live together w/ mutual benefit Cell types: Eukaryote Has a true nucleus – surrounded by a nuclear MB & uses a mitotic apparatus in allocating chromosomes Contains organelles & larger (80S) ribosomes Mitotic replication EXs: plants, animals, protozoa, fungi Prokaryote No nucleus, organelles, or cytoskeleton Nuclear material NOT contained w/in a nucleus Naked, single circular molecule of losely organized dsDNA Single chromosome Located in nucleoid (membraneless structure/region containing DNA – little resemblance to eukaryotic nucleus) Contains no MB-bound organelles & smaller (70S) ribosomes Has a rigid external cell wall containing peptidoglycan (mycoplasmas lack a cell wall) that’s why they don’t stain. EXs: BACTERIA, mycoplasmas, rickettsia, chlamydia Gram-staining Based on interaction w/ cell wall Limitations: Treponema (too thin to be visualized) Use Darkfield for Syphilis Rickettsia (intracellular parasite) Mycobacteria (high-lipid content cell wall) Use acid-fast Mycoplasma (NO cell wall) – M. pneumoniae (walking pneumonia) Legionella Pneumophila (Primarily Intracellular) Use Silver stain Chlamydia (intracellular parasite) Acid-fast organisms appear red against blue background (due to lipids/waxes [mycolic acids] in the cell wall) Staining in tubercle bacilli is due to lipid/waxes mycolic acid Mycobacteria & Nocardia are acid-fast True bacteria multiply by binary fission NOTE: viruses are not cells – they are “obligate intracellular parasites” Either RNA or DNA; no organelles; protein capsid & lipoprotein envelope Classification: Neutrophiles (pH = 7.0) P. aeruginosaqo Clostridium sporogenes Proteus species Acidophiles (pH < 7.0) Thiobacillus thiooxidans Sulfollobus acidocaldaarius 6 Bacillus acidocaldarius Alkaliphiles (pH > 7.0) Nitrobacter species Streptococcus pneumoniae Bacterial growth 1) Lag phase (Think lagging behind) Metabolically active, non-dividing 2) Log phase = logarithmic phase (Log Growth) Exponential growth Most of the cidal Abx work best in this phase i.e. Ampicillin Best phase for staining bacterial cultures For uniform staining rxn, morphology, and biochemical activity 3) Stationary phase # of cells are dying = # of cells being produced 4) Death phase/phase of decline More death than new cell production Logarithmic decrease in cell # Glucose metabolism (respiration) Oxidative phosphorylation involves the Cell MB in bacterial cells BUT, ETC in Eukaryotes happens on the inner mitochondrial MB Aerobic respiration Results in greatest release of energy The primary result of bacterial carbohydrate metabolism is production of energy (NOT heat, alcohol, or acetone) Involves a cell MB respiratory chain (electron transport chain = ETC) O2 is the terminal hydrogen acceptor, with final end products of H2O and CO2 Fermentation Substrate phosphorylation Formation of ATP not coupled to electron transfer Occurs when final electron acceptor is an organic compound An intermediate glucose product (i.e., pyruvate) is the final hydrogen acceptor Takes place in cytoplasm How Anaerobic bugs get their energy Aerobic metabolism (obligate aerobes & facultative anaerobes) – They have the Faculty to be Aerobes too Toxic byproducts: H2O2 & free superoxide radicals Final endproducts are H2O and CO2 Cells possess a defense system to destroy these endproducts: Enzymes include superoxide dismutase & catalase 1) Superoxide dismutase catalyzes the decomposition of free superoxide radicals into H2O2 & H2O 2) Catalase then catalyzes H2O2 → H2O + O2 Cytochromes: Respiratory enzymes capable of undergoing alternate reduction & oxidation Contain central iron atom which can be cycled between oxidized ferric state (Fe 3+) & reduced ferrous state (Fe2+) 7 Chemically related to hemoglobin Aerobic organotropic (heterotrophic) bacteria which oxidize a substance to CO2 and H2O in the final electron transport, use NZs containing cytochromes EXs: Cytochrome oxidase – terminal enzyme in chain of events constituting cellular O2 consumption – found in mitochondria Cytochrome P450 – important in metabolism of many drugs – found in liver microsomes (small particles typically consisting of fragmented endoplasmic reticulum to which ribosomes are attached) Cytochrome b – cytochrome of respiratory chain Cytochrome b5 – cytochrome of endoplasmic reticulum Transcription Synthesis of mRNA from DNA by DNA-dependent RNA polymerase Occurs in cytoplasm of prokaryotes (nucleus of eukaryotes) Two strands of DNA are temporarily pulled apart to allow RNA polymerase to access DNA as a template Translation Process wherein nitrogenous bases are used to determine the aa sequence of a protein Reverse transcription Formation of DNA from RNA template Retroviruses (HIV, RNA tumor viruses) use this process RNA genome is used as a template for RNA-dependent DNA polymerase The virion-associated reverse transcriptase makes DNA copies from RNA This DNA is then integrated into the host genome **Retrovirus is an oncogenic RNA virus (papillomavirus is NOT – because it is a DNA virus – don’t get clowned) 3 types of RNA: 1) rRNA – combines w/ proteins to form ribosomes 2) mRNA – dictates sequence of aa assembly 3) tRNA – transports aa’s to ribosomes for protein assembly Genetic Transfer in Bacteria – 3 processes: 1) DNA TRANSFORMATION Process in which DNA is released by lysis of one bacterium & taken up by a second, leading to a change in phenotype Another Q: Transformation is best described as acquisition of an inheritable trait by bacteria mediated by DNA Transfer of inheritable characteristics among bacteria is dependent upon DNA Rough pneumoncocci grown in the presence of DNA from smooth pneumococci developed capsules The most primitive mechanism for gene transfer among bacteria Used in lab to create recombinant DNA & to map gene locations No cell-to-cell contact required Involves the uptake of naked DNA molecules (the other processe of genetic transfer do NOT involve…) The DNA picked up by the recipient cell must be dsDNA Intracellular DNAase (endonuclease) degrades one strand, providing energy for uptake of the other ssDNA 8 Uptake depends on presence of protein called competence factor The ssDNA inserts into homologous regions of recipient chromosome 2) TRANSDUCTION Transfer of genetic material from one bacterial cell to another by viral infection No cell-to-cell contact required Least susceptible to DNAase Transfer of DNA via a bacteriorphage = phage-mediated 3) CONJUGATION (THINK Conjugal Visit) A form of sexual reproduction in which ssDNA is transferred from one live bacterium to another through direct contact Pili establish the physical contact Does NOT require flagella for pair formation NOTE about pili: The most important function of bacterial pili in causing human infectious disease is by allowing bacteria to adhere to human cells, and NOT in the transfer of DNA between bacteria – although pili do both This process transfers the greatest amount of genetic information (compared to transformation & transduction) Ability to grow in the presence of ABX is passed in vivo from one bacterium to another The pattern of resistance is transferred to other bacteria via conjugation F factors Plasmids transferred from a donor cell (F+ cell) to a recipient cell (F– cell) during conjugation Integration of the F factor plasmid into the chromosome is essential in order for the F factor to be transferred during conjugation An Hfr (high freq of recombination) is a cell w/ an F plasmid incorporated into the chromosome During conjugation, portions of the Hfr chromosome are transferred from the Hfr bacterium to the F– bacterium NOTE: all 3 processes contribute to increase in genetic variation w/in a population Cell Parts (inside→out): Nuclear material Single, double stranded DNA molecule not confined within a nuclear membrane Plasmid Contains a variety of genes for ABX resistance, enzymes, and toxins DNAs Ribosome Protein Synthesis RNA and protein in 50S and 30S subunits Cell MB = Cytoplasmic Membrane = Plasma MB Dynamic, selectively permeable MB involved in energy transformations (i.e., oxidative phosphorylation) Regulates movement of substances, including water, into/out of the cell Most active cellular structure of bacteria that controls the intake of solutions Encloses the cytoplasm Bordered externally by the cell wall In gram + bacteria, the teichoic acid induces TNF and IL-1 (acute phase) Periplasm 9 Space between the cytoplasmic membrane and outer membrane in gram – bacteria Contains many hydrolytic NZs, including Beta-lactamases Cell Wall – see notes below on G+ & G- cell wall contents The basic difference between G+ & G- bacteria is the cell wall structure Surrounds plamsa MB Protects cell from changes in osmotic pressure Anchors flagella Maintains c...
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