Condet

John P. Lichtenberger III, MD

• Department of Diagnostic Imaging
• David Grant USAF Medical Center
• Travis AFB, California

The appearance of powered avian flight Symmetrical pennaceous wing feathers are adequate for balancing medications ranitidine cheap 40mg atomoxetine fast delivery, gliding medicine express discount atomoxetine 18 mg line, and even leaping into the air in pursuit of insects symptoms of a stranger discount 25mg atomoxetine visa, but powered flight requires asymmetrical primaries to provide thrust medications known to cause seizures order 10 mg atomoxetine fast delivery. Symmetrical feathers were widespread among coelurosaurs, but so far asymmetrical feathers have been described only from Archaeopteryx and more derived forms. Thus, there are two conflicting lines of evidence about the time at which powered flight evolved. But the shoulder joint From the ground up the strongly cursorial (specialized for running) morphology of proavian ancestors suggests that the origin of flight should be sought in terrestrial locomotion. Chukars (Alectoris chukar) walk or run on flat ground (A) and up slopes as steep as 45 degrees (B) without flapping their wings. On steeper slopes, they use their wings in addition to their legs (C), and can even ascend vertical objects such as tree trunks (D). They had a long body, with the center of gravity near the hindlegs, a shallow trunk (because they lacked the sternal keel of extant birds), a long bony tail, forelegs that retained claws, and a full set of teeth. This fossil is thought to be that of a male bethe Early Cretaceous, however, sevcause of the forked tail; other fossils of Confuciusornis lack a forked tail, suggesting that it was a sexually dimorphic character. Longirostravis probed for buried invertebrates the center of gravity had shifted forward toward the wings such as worms and larvae, and Archaeorhynchus ate plant as in extant birds, the bony tail was greatly shortened, and leaves and buds. Sapeornis, Jeholornis, and Hongshanornis apfused vertebrae at the end of the tail formed a pygostyle pear to have been seed eaters, and the role of birds in seed as they do in extant birds. Except for Bohaiornis, the strutlike coracoids (bones that help the shoulder girdle which may have been the first avian raptor, hawklike birds resist the pressures exerted on the chest by the wing musappear to have been rare or absent during the Cretaceous, cles), a reduction in the size of the claws on the feet (makpossibly because that feeding niche was filled by pterosaurs ing them better suited to perching in trees), and a larger in the air and by proavians on the ground. During the Late Jurassic and throughout the Cretaceous, several lineages of proavians lived side by side with the 21. Amber from the Cretaceous of France and Canada contains feathers from both proavians and birds. The the Mesozoic saw two independent radiations of birds proavians were carnivores, and we have occasional direct (Figure 21. The birds in the earlier radiation are known as Enantiornithes (Greek enantios, "opposite"; ornis "bird") evidence of predation; for example, a fossil of Microraptor because the articulation between the scapula and coracoid gui from China contains the remains of a enantiornithine is the reverse of the arrangement in extant birds. Probably both proavians and the earliest birds were nithines were the dominant birds of the Cretaceous, and generalized predators, eating anything smaller than themthey ranged from small to large; Sinornis was the size of a selves that they could catch. Although we cannot step back in time to directly observe Most enantiornithines were small to medium-size and feeding behavior, morphological evidence such as beak probably lived in trees, but some had long legs and appear shape and the presence of a crop (an enlarged portion of to have been wading birds, and others had powerful claws the esophagus specialized for temporary food storage), and like those of extant hawks. By the Cretaceous, some birds (Longipteryx, Jiana wide variety of ecological types. Early ornithurines were changornis, Ichthyornis, Confuciusornis, and Hesperornis) were small, finchlike arboreal species, but by the Late Cretaceous eating fish. Clearly, there was some radiation of modern forms during the lineage had expanded to include waders, perchers, and the Mesozoic, because in addition to V. So far the fossil record during the Late Cretaceous, and the last common ancestor is too sparse to say whether the big bang of neornithine Note of Neornithes may have been a seed eater. Enantiornithes was the first lineage to radiate and was the dominant group of birds during the Cretaceous. Neither of these lineages survived the end of the Mesozoic, and extant birds (Neornithes) are modern ornithurines. The shaded areas indicate the changes in diversity of the lineages; the areas representing passerines and nonpasserines overlap. The derived skeletal characters of birds evolved independently of flight among coelurosaurs, a lineage of bipedal theropod dinosaurs. A furcula is present in nearly all theropod lineages, as is pneumatization of the postcranial skeleton. A wrist joint that allows the hands to be folded against the ulna and radius appeared in basal coelurosaurs, while uncinate processes on the ribs appeared with oviraptors. Filamentous protofeathers appeared with tyrannosaurs, and symmetrical pennaceous feathers with ornithomimosaurs.

Bacterial and Viral Genetic Systems 235 Genes his2 and aro3+ his2+ and try2+ his2+ and aro1+ his2+ and tyr1+ his2+ and aro2+ + Rate of cotransfer 0 medicine evolution cheap atomoxetine 40 mg free shipping. Where more than one cross was completed for a pair of genes treatment mrsa order atomoxetine 10 mg free shipping, average the recombination rates from the different crosses symptoms thyroid problems buy discount atomoxetine 18mg on line. Two mutations that affect plaque morphology in phages (a- and b-) have been isolated treatment 20 10 mg atomoxetine overnight delivery. Phages carrying both mutations (a- b-) are mixed with wild-type phages (a+ b+) and added to a culture of bacterial cells. Subsequent to infection and lysis, samples of the phage lysate are collected and cultured on bacterial cells. The following numbers of plaques are observed: Plaque phenotype a b a+ b- a- b+ a- b- + + On the basis of these data, which gene is farthest from his2+ Seven of the strains that they used in their study are listed here, along with the mutation found in that strain. On the basis of complementation studies, they found four proline auxotrophs: proA, proB, proC, and proD. To determine whether proA, proB, proC, and proD loci were located close together on the bacterial chromosome, they conducted a transduction experiment. Bacterial strains that were proC + and had mutations at proA, proB, or proD, were used as donors. The bacteria were then plated on a selective medium that allowed only proC + bacteria to grow. The following results were obtained: Donor genotype Transductant genotype Number 2765 3 1838 2 1166 0 To map the genes for tryptophan synthesis, they carried out a series of transformation experiments on strains having different mutations and determined the percentage of recombinants among the transformed bacteria. Which genotypes represent single transductants and which represent cotransductants Previous mapping experiments have established that the genes responsible for these two mutations are 8 m. The geneticist mixes phages with genotype c+ m+ and genotype c- m- and uses the mixture to infect bacterial cells. What numbers of the different types of plaques (c+ m+, c- m-, c+ m-, c- m+) should she expect to see The geneticist carries out the same experiment described in Problem 30, but this time she mixes phages with genotypes c+ m- and c- m+. A geneticist isolates two bacteriophage r mutants (r13 and r2) that cause rapid lysis. He carries out the following crosses and counts the number of plaques listed here: Genotype of parental phage h + Progeny phage genotype h c h c h+ c h c+ h+ c h c+ h+ c+ h c + + Number of plaques 321 338 26 30 106 110 5 6 st st st st+ st+ st st st+ + a. A donor strain of bacteria with genes a+ b+ c+ is infected with phages to map the donor chromosome with generalized transduction. The phage lysate from the bacterial cells is collected and used to infect a second strain of bacteria that are a- b- c-. Bacteria with the a+ gene are selected, and the percentage of cells with cotransduced b+ and c+ genes are recorded. The phage lysate from the bacterial cells is collected and used to infect a second strain of bacteria that are leu- gal+ pro-. One strain has a mutant host range, is temperature sensitive, and produces clear plaques (genotype is h st c); another strain carries the wild-type alleles (genotype is h+ st+ c+). The genotypes of the progeny phages are given here: Donor leu gal pro + - + Recipient leu- gal+ pro- Which genes are closest, leu and gal or leu and pro To determine whether these mutations occur at the same functional gene, he simultaneously infects E. As a summer project, a microbiology student independently isolates two mutations in E. The student wants to know whether these two mutants are at the same functional unit. Outline a procedure that the student could use to determine whether these two gly- mutations occur within the same functional unit. A group of genetics students mix two auxotrophic strains of bacteria: one is leu+ trp+ his- met- and the other is leu- trp- his+ met+.

Unlike ambulocetids treatment for uti buy atomoxetine 40 mg fast delivery, remingtonocetids had delicate skulls with long medications while breastfeeding purchase atomoxetine 25 mg online, narrow snouts and very small eyes medicine 93 5298 atomoxetine 10 mg free shipping, indicating that they fed underwater on fish treatment vertigo generic atomoxetine 10 mg visa. Features of the ear anatomy of both remingtonocetids and the later protocetids indicate improved underwater hearing; these include an enlarged canal in the lower jaw that in modern cetaceans houses a sound-conducting fat pad. There was also a reduction in the size of the semicircular canals, which in modern cetaceans is associated with underwater navigation. The tooth isotopes of remingtonocetids (and of all later cetaceans) show that they did not drink fresh water, but must have obtained all of their water from their food, as modern cetaceans do. Modern cetaceans differ from archaeocetes in having a "telescoped" skull, whereby, over the course of embryonic development, the nostrils move to the top of the head and form the blowhole, and the upper and lower jaws are elongated. The mode of skull telescoping is somewhat different in mysticetes and odontocetes, indicating that this feature evolved in parallel in the two groups. Evidence suggests that they may have lost the teeth in association with suction feeding before acquiring the baleen that modern members of the group use for suspension feeding. Evidence of echolocation is present in the earliest toothed whales, which became adapted for catching large prey underwater. The modern cetacean radiation was probably related to changes in oceanic circulation that increased the productivity of the oceans, resulting in the novel feeding strategies of echolocation-assisted predation (toothed whales) and suspension feeding (baleen whales). Another pulse of cetacean radiation occurred in the late Miocene, again concurrent with a lowering of higher-latitude temperatures and changes in oceanic circulation. At this time, many existing families became extinct, and some modern forms (such as dolphins and porpoises) made their first appearance. The gigantic baleen whales seen today did not appear until the Pliocene, along with increases in seasonal ocean upwelling providing more nutrients for their prey. Sadly, recent molecular analyses suggest that North Atlantic baleen whales were up to 20 times more abundant before the start of human commercial exploitation than they are today. Protocetidae, a paraphyletic grouping, had progressed to a condition more like that of modern cetaceans. Most retained a connection of the hindlimb to the vertebral column, although they would probably have been clumsy on land. More derived protocetids retained the pelvic girdle but lost the connection between the ilium in the pelvis and the sacrum in the vertebral column. However, evidence that at least some protocetids came on land to give birth, as pinnipeds do today, can be inferred from a fossil Maiacetus that was preserved with a late-stage embryo in its body. The embryo was positioned so as to be born headfirst, like terrestrial mammals, rather than in the tail-first mode of modern cetaceans. The earlier protocetids probably still relied on their hindlimbs for paddling, but later ones may have had an axial swimming locomotion, with oscillations of the lumbar spine. Protocetids were the first cetaceans to be found in offshore marine habitats and beyond the Indo-Pakistan region, as far afield as the coasts of North America and Africa. They may have had a lifestyle like that of modern seals: fully aquatic, but not obligatorily so, and still able to come onto land at least for reproductive purposes. Their inner ears show that they were somewhat intermediate in hearing function between terrestrial mammals and modern cetaceans, and were able to hear both in air and underwater. Specialized underwater hearing appears to have evolved independently in the two groups of modern cetaceans (ultrasonic in toothed whales and infrasonic in baleen whales). These cetaceans had lost the hindlimb connection to the vertebral column and had greatly reduced hindlimbs, although all of the skeletal elements were still present and the reduced hindlimbs might have been used as copulatory guides. The ears of basilosaurids were essentially like those of modern cetaceans, with the entire bony ear region isolated from the rest of the skull by air-filled sinuses, although they still retained an external auditory meatus (earhole). The basilosaurines, known from the Northern Hemisphere, had long bodies (up to 16 m), with greatly elongated trunk vertebrae and small heads. When first discovered, they were mistaken for sea serpents-hence the root word "saurus" in their name. The dorudontines, known from both the Northern and Southern hemispheres, were more dolphinlike in appearance and contained the ancestors of the modern cetaceans. This was the time Antarctic Circumpolar Genomic evidence Many features that evolved as cetaceans adapted to their marine realm are not documented in their fossils. These include adaptations for diving, massive fat reserves for both metabolic and thermoregulatory functions, and changes in their senses. Land-based senses of smell and taste do not work underwater, and both vision and hearing must adapt.

This explains the very large losses of muscle mass medicine q10 buy 25mg atomoxetine with visa, particularly in adults medications 247 buy cheap atomoxetine 25 mg line, resulting from prolonged caloric undernutrition symptoms 0f low sodium atomoxetine 18 mg with mastercard. The study of tissue protein breakdown in vivo is difficult medicine nobel prize 2015 generic atomoxetine 10 mg without a prescription, because amino acids released during intracellular breakdown of proteins can be extensively reutilized for protein synthesis within the cell, or the amino acids may be transported to other organs where they enter anabolic pathways. However, actin and myosin are methylated by a posttranslational reaction, forming 3-methylhistidine. During intracellular breakdown of actin and myosin, 3methylhistidine is released and excreted into the urine. The urinary output of the methylated amino acid provides a reliable index of the rate of myofibrillar protein breakdown in the musculature of human subjects. Summary of Major Features of the Biochemistry of Skeletal Muscle Related to Its Metabolis1 Skeletal muscle functions under both aerobic (resting) and anaerobic (eg, sprinting) conditions, so both aerobic and anaerobic glycolysis operate, depending on conditions. Skeletal muscle contains different types of fibers primarily suited to anaerobic (fast twitch fibers) or aerobic (slow twitch fibers) conditions. In the fed state, most glucose is used to synthesize glycogen, which acts as a store of glucose for use in exercise; "preloading" with glucose is used by some long-distance athletes to build up stores of glycogen. Epinephrine stimulates glycogenolysis in skeletal muscle, whereas glucagon does not because of absence of its receptors. Skeletal muscle cannot contribute directly to blood glucose because it does not contain glucose-6-phosphatase. Lactate produced by anaerobic metabolism in skeletal muscle passes to liver, which uses it to synthesize glucose, which can then return to muscle (the Cori cycle). Skeletal muscle contains phosphocreatine, which acts as an energy store for short-term (seconds) demands. Free fatty acids in plasma are a major source of energy, particularly under marathon conditions and in prolonged starvation. Skeletal muscle is the principal site of metabolism of branched chain amino acids, which are used as an energy source. Major amino acids emanating from muscle are alanine (destined mainly for gluconeogenesis in liver and forming part of the glucose-alanine cycle) and glutamine (destined mainly for the gut and kidneys). These cellular functions are carried out by an extensive intracellular network of filamentous structures constituting the cytoskeleton. Essentially all eukaryotic cells contain three types of filamentous structures: actin filaments (also known as microfilaments), microtubules, and intermediate filaments. Each type of filament can be distinguished biochemically and by the electron microscope. For example, keratins are distributed widely in epithelial cells and adhere via adapter proteins to desmosomes and hemidesmosomes. Non-Muscle Cells Contain Actin that Forms Microfilaments G-actin is present in most if not all cells of the body. With appropriate concentrations of magnesium and potassium chloride, it spontaneously polymerizes to form double helical F-actin filaments like those seen in muscle. Both types can coexist in the same cell and probably even copolymerize in the same filament. These bundles are prominent just underlying the plasma membrane of many cells and are there referred to as stress fibers. The stress fibers disappear as cell motility increases or upon malignant transformation of cells by chemicals or oncogenic viruses. Although not organized as in muscle, actin filaments in nonmuscle cells interact with myosin to cause cellular movements. Microtubules are necessary for the formation and function of the mitotic spindle and thus are present in all eukaryotic cells.

The bile salts pass on to the ileum medicine you can take while pregnant buy atomoxetine 10 mg amex, where most are absorbed into the enterohepatic circulation (Chapter 26) treatment 4 burns buy 10mg atomoxetine overnight delivery. Within the intestinal epithelium symptoms acid reflux cheap atomoxetine 10mg free shipping, 1-monoacyglycerols are hydrolyzed to fatty acids and glycerol and 2-monoacylglycerols are reacylated to triacylglycerols via the monoacylglycerol pathway symptoms 22 weeks pregnant discount atomoxetine 10 mg fast delivery. Glycerol released in the intestinal lumen is not reutilized but passes into the portal vein; glycerol released within the epithelium is reutilized for triacylglycerol synthesis via the normal phosphatidic acid pathway (Chapter 24). Long-chain fatty acids are esterified to yield to triacylglycerol in the mucosal cells and together with the other products of lipid digestion, secreted as chylomicrons into the lymphatics, entering the bloodstream via the thoracic duct (Chapter 25). Short- and medium-chain fatty acids are mainly absorbed into the hepatic portal vein as free fatty acids. The values given for percentage uptake may vary widely but indicate the relative importance of the three routes shown. Cholesterol is absorbed dissolved in lipid micelles, and is mainly esterified in the intestinal mucosa before being incorporated into chylomicrons. Unesterified cholesterol and other sterols are actively transported out of the mucosal cells into the intestinal lumen. Plant sterols and stanols (in which the B ring is saturated) compete with cholesterol for esterification, but are poor substrates. They therefore reduce the absorption of cholesterol, and act to lower serum cholesterol. Several Groups of Enzymes Catalyze the Digestion of Proteins There are two main classes of proteolytic digestive enzymes (proteases), with different specificities for the amino acids forming the peptide bond to be hydrolyzed. Endopeptidases hydrolyze peptide bonds between specific amino acids throughout the molecule. Pepsin in the gastric juice catalyzes hydrolysis of peptide bonds adjacent to aromatic and branchedchain amino acids and methionine. Trypsin, chymotrypsin, and elastase are secreted into the small intestine by the pancreas. Trypsin catalyzes hydrolysis of lysine and arginine esters, chymotrypsin esters of aromatic amino acids, and elastase esters of small neutral aliphatic amino acids. Exopeptidases catalyze the hydrolysis of peptide bonds, one at a time, from the ends of peptides. Carboxypeptidases, secreted in the pancreatic juice, release amino acids from the free carboxyl terminal; aminopeptidases, secreted by the intestinal mucosal cells, release amino acids from the amino terminal. Dipeptidases and tripeptidases in the brush border of intestinal mucosal cells catalyze the hydrolysis of di- and tripeptides, which are not substrates for amino- and carboxypeptidases. The proteases are secreted as inactive zymogens; the active site of the enzyme is masked by a small region of the peptide chain that is removed by hydrolysis of a specific peptide bond. Pepsinogen is activated to pepsin by gastric acid and by activated pepsin (autocatalysis). In the small intestine, trypsinogen, the precursor of trypsin, is activated by enteropeptidase, which is secreted by the duodenal epithelial cells; trypsin can then activate chymotrypsinogen to chymotrypsin, proelastase to elastase, procarboxypeptidase to carboxypeptidase, and proaminopeptidase to aminopeptidase. Free Amino Acids & Small Peptides Are Absorbed by Different Mechanisms the end product of the action of endopeptidases and exopeptidases is a mixture of free amino acids, di- and tripeptides, and oligopeptides, all of which are absorbed. Free amino acids are absorbed across the intestinal mucosa by sodium-dependent active transport. There are several different amino acid transporters, with specificity for the nature of the amino acid side-chain (large or small, neutral, acidic or basic). The various amino acids carried by any one transporter compete with each other for absorption and tissue uptake. Dipeptides and tripeptides enter the brush border of the intestinal mucosal cells, where they are hydrolyzed to free amino acids, which are then transported into the hepatic portal vein. Relatively large peptides may be absorbed intact, either by uptake into mucosal epithelial cells (transcellular) or by passing between epithelial cells (paracellular). Many such peptides are large enough to stimulate antibody formation-this is the basis of allergic reactions to foods. The fat-soluble vitamins are absorbed in the lipid micelles that are the result of fat digestion; watersoluble vitamins and most mineral salts are absorbed from the small intestine either by active transport or by carrier-mediated diffusion followed by binding to intracellular proteins to achieve concentrative uptake. Vitamin B12 absorption requires a specific transport protein, intrinsic factor (Chapter 44); calcium absorption is dependent on vitamin D; zinc absorption probably requires a zinc-binding ligand secreted by the exocrine pancreas, and the absorption of iron is limited (see below). Calcium Absorption Is Dependent on Vitamin D In addition to its role in regulating calcium homeostasis, vitamin D is required for the intestinal absorption of calcium. Synthesis of the intracellular calcium-binding protein, calbindin, required for calcium absorption, is induced by vitamin D, which also affects the permeability of the mucosal cells to calcium, an effect that is rapid and independent of protein synthesis.

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