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James W Hicks

Publications and source records attributed to James W Hicks.

18 recordsLinked to original sources
PubMed2005

Postprandial increase of oleoylethanolamide mobilization in small intestine of the Burmese python (Python molurus).

Oleoylethanolamide (OEA) is an endogenous lipid mediator that inhibits feeding in rats and mice by activating the nuclear receptor peroxisome proliferator-activated receptor-alpha (PPAR-alpha). In rodents, intestinal OEA levels increase about threefold upon refeeding, a response that may contribute to the induction of between-meal satiety. Here, we examined whether feeding-induced OEA mobilization also occurs in Burmese pythons (Python molurus), a species of ambush-hunting snakes that consume huge meals after months of fasting and undergo massive feeding-dependent changes in gastrointestinal hormonal release and gut morphology. Using liquid chromatography/mass spectrometry (LC/MS), we measured OEA levels in the gastrointestinal tract of fasted (28 days) and fed (48 h after feeding) pythons. We observed a nearly 300-fold increase in OEA levels in the small intestine of fed compared with fasted animals (322 +/- 121 vs. 1 +/- 1 pmol/mg protein, n = 3-4). In situ OEA biosynthesis was suggested by the concomitant increase of N-acyl phosphatidylethanolamine species that serve as potential biosynthetic precursors for OEA. Furthermore, we observed a concomitant increase in saturated, mono- and diunsaturated, but not polyunsaturated fatty-acid ethanolamides (FAE) in the small intestine of fed pythons. The identification of OEA and other FAEs in the gastrointestinal tract of Python molurus suggests that this class of lipid messengers may be widespread among vertebrate groups and may represent an evolutionarily ancient means of regulating energy intake.

Animals↗
PubMed2005

Physiology: postprandial cardiac hypertrophy in pythons.

Oxygen consumption by carnivorous reptiles increases enormously after they have eaten a large meal in order to meet metabolic demands, and this places an extra load on the cardiovascular system. Here we show that there is an extraordinarily rapid 40% increase in ventricular muscle mass in Burmese pythons (Python molurus) a mere 48 hours after feeding, which results from increased gene expression of muscle-contractile proteins. As this fully reversible hypertrophy occurs naturally, it could provide a useful model for investigating the mechanisms that lead to cardiac growth in other animals.

Adaptation, Physiological↗
PubMed2005

Genetic and molecular in vivo analysis of herpes simplex virus assembly in murine visual system neurons.

Herpes simplex virus (HSV) infects both epithelial cells and neuronal cells of the human host. Although HSV assembly has been studied extensively for cultured epithelial and neuronal cells, cultured neurons are biochemically, physiologically, and anatomically significantly different than mature neurons in vivo. Therefore, it is imperative that viral maturation and assembly be studied in vivo. To study viral assembly in vivo, we inoculated wild-type and replication-defective viruses into the posterior chamber of mouse eyes and followed infection in retinal ganglion cell bodies and axons. We used PCR techniques to detect viral DNA and RNA and electron microscopy immunohistochemistry and Western blotting to detect viral proteins in specific portions of the optic tract. This approach has shown that viral DNA replication is necessary for viral DNA movement into axons. Movement of viral DNA along ganglion cell axons occurs within capsid-like structures at the speed of fast axonal transport. These studies show that the combined use of intravitreal injections of replication-defective viruses and molecular probes allows the genetic analysis of essential viral replication and maturation processes in neurons in vivo. The studies also provide novel direct evidence for the axonal transport of viral DNA and support for the subassembly hypothesis of viral maturation in situ.

Animals↗
PubMed2005

Terrestrial locomotion does not constrain venous return in the American alligator, Alligator mississippiensis.

The effects of treadmill exercise on components of the cardiovascular (heart rate, mean arterial blood pressure, central venous pressure, venous return) and respiratory (minute ventilation, tidal volume, breathing frequency, rate of oxygen consumption, rate of carbon dioxide production) systems and on intra-abdominal pressure were measured in the American alligator, Alligator mississippiensis, at 30 degrees C. Alligators show speed-dependent increases in tidal volume and minute ventilation, demonstrating that the inhibition of ventilation during locomotion that is present in some varanid and iguanid lizards was not present in alligators. Exercise significantly increases intra-abdominal pressure; however, concomitant elevations in central venous pressure acted to increase the transmural pressure of the post caval vein and thus increased venous return. Therefore, despite elevated intra-abdominal pressure, venous return was not limited during exercise in alligators, as was the case in Varanus exanthematicus and Iguana iguana. Respiratory cycle variations in intra-abdominal pressure, central venous pressure and venous return indicate that, at high tidal volumes, inspiration causes a net reduction in venous return during active ventilation and thus may act to limit venous return during exercise. These results suggest that, while tonically elevated intra-abdominal pressure induced by exercise does not inhibit venous return, phasic fluctuations during each breath cycle may contribute to venous flow limitation during exercise.

Alligators and Crocodiles↗
PubMed2004

Eat and run: prioritization of oxygen delivery during elevated metabolic states.

The principal function of the cardiopulmonary system is the matching of oxygen and carbon dioxide transport to the metabolic requirements of different tissues. Increased oxygen demands (VO2), for example during physical activity, result in a rapid compensatory increase in cardiac output and redistribution of blood flow to the appropriate skeletal muscles. These cardiovascular changes are matched by suitable ventilatory increments. This matching of cardiopulmonary performance and metabolism during activity has been demonstrated in a number of different taxa, and is universal among vertebrates. In some animals, large increments in aerobic metabolism may also be associated with physiological states other than activity. In particular, VO2 may increase following feeding due to the energy requiring processes associated with prey handling, digestion and ensuing protein synthesis. This large increase in VO2 is termed "specific dynamic action" (SDA). In reptiles, the increase in VO2 during SDA may be 3-40-fold above resting values, peaking 24-36 h following ingestion, and remaining elevated for up to 7 days. In addition to the increased metabolic demands, digestion is associated with secretion of H+ into the stomach, resulting in a large metabolic alkalosis (alkaline tide) and a near doubling in plasma [HCO3-]. During digestion then, the cardiopulmonary system must meet the simultaneous challenges of an elevated oxygen demand and a pronounced metabolic alkalosis. This paper will compare and contrast the patterns of cardiopulmonary response to similar metabolic increments in these different physiological states (exercise and/or digestion) in a variety of reptiles, including the Burmese python, Python morulus, savannah monitor lizard, Varanus exanthematicus, and American alligator Alligator mississipiensis.

Animals↗
PubMed2004

Why savannah monitor lizards hyperventilate during activity: a comparison of model predictions and experimental data.

The functional and structural factors that limit maximal oxygen uptake (VO2 max) in lizards are not completely understood. Using an integrative model describing the interactive nature of the individual oxygen transport conductances, we performed an analysis of the oxygen transport system in the highly aerobic lizard Varanus exanthematicus with specific reference to the sensitivity of VO2 max to potential limitations in the ventilatory system. Our analysis predicts that DLO2 must increase more than three-fold at VO2 max and even with this increase in DLO2 , the VO2 max may be sensitive to factors that alter lung ventilation and/or lower lung PO2. To test the predictions of the model analysis, we experimentally determined the effects of reducing inspired O2 on VO2 max during treadmill exercise. We conclude from both our theoretical and experimental analyses that V. exanthematicus operates near the functional limits of its lung.

Animals↗
PubMed2004

Hypometabolism in reptiles: behavioural and physiological mechanisms that reduce aerobic demands.

During exposure to hypoxia all vertebrates utilize a suite of cardiovascular and ventilatory responses that, in combination, strive to maintain adequate delivery of oxygen to the metabolizing tissues. In addition to maintaining oxygen delivery through cardio-respiratory responses, oxygen demands in the tissues can also be reduced. Reptiles use this alternative strategy during periods of moderate to severe hypoxia by behavioural reductions in preferred body temperature and by active down-regulation of aerobic metabolism. Below we review these two different strategies and discuss their possible mechanisms and physiological significance.

Adaptation, Physiological↗
PubMed2004

Elevated intra-abdominal pressure limits venous return during exercise in Varanus exanthematicus.

The effects of treadmill exercise on components of the cardiovascular (venous return, heart rate, arterial blood pressure) and respiratory systems (minute ventilation, tidal volume, breathing frequency, oxygen consumption, carbon dioxide production) and intra-abdominal pressure were investigated in the Savannah monitor lizard, Varanus exanthematicus B., at 35 degrees C. Compared with resting conditions, treadmill exercise significantly increased lung ventilation, gular pumping, intra-abdominal pressure, mean arterial blood pressure and venous return (blood flow in the post caval vein). However, venous return declines at high levels of activity, and mean arterial pressure and venous return did not attain peak values until the recovery period, immediately following activity. Elevating intra-abdominal pressure in resting lizards (via saline infusion) resulted in significant reductions in venous return when the transmural pressure of the post caval vein became negative (i.e. when intra-abdominal pressure exceeded central venous pressure). Together these results suggest that increments in intra-abdominal pressure compress the large abdominal veins and inhibit venous return. During locomotion, the physical compression of the large abdominal veins may represent a significant limitation to cardiac output and maximal oxygen consumption in lizards.

Abdomen↗
PubMed2004

Mice expressing SV40 T antigen directed by the intestinal trefoil factor promoter develop tumors resembling human small cell carcinoma of the colon.

The colonic epithelium contains three major types of mature cells, namely, absorptive, goblet, and enteroendocrine cells. These cells are maintained by a complex process of cell renewal involving progenitor and stem cells, and colon cancers develop when this process goes awry. Much is known about the genetic and epigenetic changes that occur in cancer; however, little is known as to the specific cell types involved in carcinogenesis. In this study, we expressed the SV40 Tag oncogene in the intestinal epithelium under the control of an intestinal trefoil factor (ITF) promoter. This caused tumor formation in the proximal colon with remarkable efficiency. ITFTag tumors were rapidly growing, multifocal, and invasive. ITFTag tumor cells express synaptophysin and contain dense core secretory granules, markers of neuroendocrine differentiation. The cell type involved in the early steps of ITFTag tumorigenesis was studied by examining partially transformed crypts that contained populations of both normal and dysplastic cells. The dysplastic cell population always expressed both Tag and synaptophysin. Cells expressing Tag alone were never observed; however, normal enteroendocrine cells expressing synaptophysin but not Tag were readily visualized. This suggests that ITFTag tumor cells originate from the enteroendocrine cell lineage following a transforming event that results in Tag expression. ITFTag tumors closely resemble human small cell carcinomas of the colon, suggesting the possibility that these tumors might be derived from the enteroendocrine cell lineage as well.

Animals↗
PubMed2004

Ethnicity, race, and forensic psychiatry: are we color-blind?

Race, ethnicity, and culture have an effect on all aspects of mental illness. Forensic psychiatrists and psychologists should consider these issues when performing evaluations for legal purposes and when providing treatment to the special populations with whom they work. This article defines race and ethnicity and reviews the available literature on the impact of race and ethnicity on diagnosis, dangerousness assessment, involuntary commitment, competency, criminal matters, evaluation of children and matters related to them, and tort issues. Also discussed is the effect of ethnicity on the role of the forensic evaluator in his or her interactions with the subject and the justice system. Forensic evaluators are encouraged to develop specific skills related to competency in dealing with cultural matters.

Child↗
PubMed2003

Initiation of transcription of the MUC3A human intestinal mucin from a TATA-less promoter and comparison with the MUC3B amino terminus.

Human intestinal mucin genes MUC3A and MUC3B are members of a membrane mucin gene family residing at chromosome 7q22. In this paper, we utilized genomic and cDNA cloning to elucidate the sequence of the 5'-region of the MUC3A gene including the gene promoter and the amino terminus coding sequence. Following its 21-residue signal peptide, the amino terminus of the mucin consists of a 233-residue Thr-, Ser-, and Pro-rich nonrepetitive sequence that is contiguous with its hypervariable domain of 375-residue repeats. RNase protection analysis and 5'-GeneRacer PCR indicated that MUC3A gene transcripts initiate from multiple start sites along a region spanning approximately 180 bases. The 5'-flanking region of the gene had promoter activity when fused to a luciferase reporter gene in all of the tested cell lines. This region contained binding sites for several transcription factors, including those implicated in the regulation of intestinal genes, but lacked a cognate TATA box. These features of the gene promoter may enable the gene to be expressed at variable levels in several cell types with different repertoires of transcription factors. We also utilized 5'-GeneRacer PCR to determine the sequence of the 5'-terminus of the MUC3B message. The amino termini of the MUC3A and MUC3B mucins are 91% conserved at the amino acid level. Thus, MUC3A and MUC3B have highly conserved amino and carboxyl termini, suggesting a recent duplication of the entire ancestral gene. It remains to be determined whether other members of the 7q22 membrane mucin gene family have amino-terminal domains similar to MUC3A and MUC3B.

Amino Acid Sequence↗
PubMed2003

Ontogeny of baroreflex control in the American alligator Alligator mississippiensis.

Baroreflex regulation appears in different species at different points in embryonic development. This study was designed to understand the development of the baroreflex in embryos of the American alligator at four different points of embryonic development (60%, 70%, 80% and 90% of a total incubation period of 72 days) and in 1-week-old hatchlings. Data from a separate study on 1-year-old alligators were included for comparison. The gain of the cardiac limb of the baroreflex was calculated from heart rate changes triggered by pharmacological manipulation of arterial pressure with sodium nitroprusside and phenylephrine. The results demonstrated that a vagally mediated hypertensive baroreflex was present during the final 30% of alligator development. A hypotensive baroreflex was not present in embryos but appeared in hatchlings, mediated by a combined effect of vagal and sympathetic efferents. Absolute baroreflex gain was maximal at 80% of incubation (41.22 beats kPa(-1) min(-1)) and dropped thereafter, reaching a minimum in 1-year-old alligators (9.69 beats kPa(-1) min(-1)). When the baroreflex gain was normalized to resting arterial pressure and heart rate, the maximum gain was observed in 1-year-old alligators (normalized index of 2.12 versus 0.75 in hatchlings and 0.69 as the highest gain in embryos). In conclusion, baroreflex regulation appeared during embryonic development with a substantial gain. These findings indicate that embryonic development is a period of preparation for cardiovascular regulatory mechanisms that will be necessary in adult life and that the baroreflex control mechanism is required for cardiovascular control during ontogeny.

Alligators and Crocodiles↗
PubMed2002

MUC17, a novel membrane-tethered mucin.

Membrane mucins have several functions in epithelial cells including cytoprotection, extravasation during metastases, maintenance of luminal structure, and signal transduction. In this paper we describe a large membrane mucin expressed in the normal intestine. This novel mucin, designated MUC17, contains an extended, repetitive extracellular glycosylation domain and a carboxyl terminus with two EGF-like domains, a SEA module domain, a transmembrane domain, and a cytoplasmic domain with potential serine and tyrosine phosphorylation sites. RNA blot analysis and in situ hybridization indicates that MUC17 is expressed in select pancreatic and colon cancer cell lines and in intestinal absorptive cells. Radiation hybrid mapping localized MUC17 to chromosome 7q22 where it resides in close proximity with three other membrane mucin genes, MUC3A, MUC3B, and MUC12. Thus, these membrane mucins reside together in a gene cluster, but are expressed in different tissues and are likely to have different functions as well.

Amino Acid Sequence↗
PubMed2002

An integrative model to predict maximum O2 uptake in animals with central vascular shunts.

Gas exchange in the tissues and lungs is accurately described by simple equations, and mathematical models of O(2) transport play a paramount role in the conceptual understanding of respiratory physiology. In the present paper, we review an integrative approach to describe maximum oxygen uptake in animals with tidally ventilated lungs. Further, we expand the analysis by including a central vascular shunt compartment to mimic the cardiovascular anatomy of embryonic birds and mammals as well as many ectothermic vertebrates. Finally, we predict the effects of right-to-left and left-to-right cardiac shunts on maximal oxygen uptake and present a new hypothesis that relates the interaction of metabolic rates and central shunts in air breathing ectothermic vertebrates.

Journal Article↗
PubMed2002

Characterization and cardiovascular actions of endothelin-1 and endothelin-3 from the American alligator.

The structures and biological activities of the isoforms of endothelin (ET) in a reptile are unknown. ET-3, whose primary structure is identical to human ET-3 except for the substitution Phe4 --> Tyr, and a peptide identical to human ET-1 were isolated from an extract of the lung of the alligator, Alligator mississipiensis. Bolus intravenous injections of alligator ET-3 (10, 30, and 100 pmol/kg) into anesthetized alligators produced dose-dependent decreases in systemic blood pressure (P(sys)) and systemic vascular resistance (R(sys)) without change in heart rate (HR), systemic blood flow (Q(sys)), pulmonary pressure (P(pul)), pulmonary vascular resistance (R(pul)), or pulmonary blood flow (Q(pul)). At a dose of 300 pmol/kg, the initial vasodilatation was followed by an increase in R(sys) and decreases in Q(sys) and P(pul). The response to intravenous human/alligator ET-1 (10, 30, 100, and 300 pmol/kg) was biphasic at all doses with initial decreases in P(sys) and R(sys) being followed by sustained increases in these parameters. In the pulmonary circulation, ET-1 produced a dose-dependent decrease in Q(pul) and an increase in R(pul) during the first phase of the response but no significant change during the second phase. There was no change in HR in response to ET-1. The vasodilatator action of arginine, but not ET-1, was attenuated by N(omega)-nitro-L-arginine methyl ester, indicating that the effect of the peptide is probably not mediated through increased synthesis of nitric oxide. The data demonstrate that the structure of the ET isoforms has been strongly conserved during the evolution of vertebrates but that cardiovascular actions differ significantly between the alligator and mammals, especially in the magnitude and duration of the hypotensive response.

Alligators and Crocodiles↗
PubMed2002

The physiological and evolutionary significance of cardiovascular shunting patterns in reptiles.

The morphology of the reptilian heart results in the mixing of oxygenated and deoxygenated blood (cardiac shunts). In birds and mammals cardiac shunts are detrimental, but in reptiles this condition is often considered a derived trait, conveying important physiological functions and favored by natural selection. Alternative views are advanced suggesting that, in reptiles, cardiac shunts represent either an ancestral condition or an embryonic trait.

Animals↗
PubMedDate not supplied

Cardiac output and shunt during voluntary activity at different temperatures in the turtle, Trachemys scripta.

Red-eared slider turtles (Trachemys scripta) were chronically instrumented with blood flow probes for a long-term study of voluntary behavior in an enriched laboratory setting. Cardiovascular measures consisting of total cardiac output (Q(tot)), pulmonary blood flow (Q(pul)), systemic blood flow (Q(sys)), net cardiac shunt (Q(shunt)), heart rate (HR), and stroke volume (SV) were obtained during spontaneous activity at a constant body temperature (Tb=2 degrees C) and at unstable (variable) T(b)'s ranging from 19 degrees to 37 degrees C. The effects of temperature and activity differed between the pulmonary and systemic circuits, with increases in Q(sys) due to HR alone, while both HR and SV contributed to gains in Q(pul). At stable 20 degrees C, cardiovascular responses during diving, submerged swimming, and walking were qualitatively similar, and increases in Q(tot) during activity ( approximately 2 x resting levels) were due to greater gains in Q(pul) than Q(sys). At unstable T(b)'s and in general, net Q(shunt) while active depended on the integration of individual physiological influences such as heating, cooling, and initial behavioral state acting on the cardiovascular system. During activity, net left-to-right (L-R) shunts predominated at constant T(b) of 20 degrees C (mean shunt fraction approximately 30%-40%), while both net L-R and right-to-left (R-L) shunts of varying size were found at unstable T(b)'s (19 degrees - 37 degrees C).

Analysis of Variance↗