Biology Commons^™

Lianas Suppress Tree Regeneration And Diversity In Treefall Gaps, Stefan A. Schnitzer, Walter P. Carson

Biological Sciences Faculty Research and Publications

Treefall gaps are hypothesized to maintain diversity by creating resource‐rich, heterogeneous habitats necessary for species coexistence. This hypothesis, however, is not supported empirically for shade‐tolerant trees, the dominant plant group in tropical forests. The failure of gaps to maintain shade‐tolerant trees remains puzzling, and the hypothesis implicated to date is dispersal limitation. In central Panama, we tested an alternative ‘biotic interference’ hypothesis: that competition between growth forms (lianas vs. trees) constrains shade‐tolerant tree recruitment, survival and diversity in gaps. We experimentally removed lianas from eight gaps and monitored them for 8 years, while also monitoring nine un‐manipulated control gaps. Removing …

Regulation Of The G2/M Transition In Rodent Oocytes, Stephen M. Downs

Biological Sciences Faculty Research and Publications

Regulation of maturation in meiotically competent mammalian oocytes is a complex process involving the carefully coordinated exchange of signals between the somatic and germ cell compartments of the ovarian follicle via paracrine and cell–cell coupling pathways. This review highlights recent advances in our understanding of how such signaling controls both meiotic arrest and gonadotropin-triggered meiotic resumption in competent oocytes and relates them to the historical context. Emphasis will be on rodent systems, where many of these new findings have taken place. A regulatory scheme is then proposed that integrates this information into an overall framework for meiotic regulation that demonstrates …

Pkcα And Cpi-17 Expression And Spatial-Temporal Distribution With Activation In Pig Stomach Antrum And Fundus, Yu Zhang

Master's Theses (2009 -)

Smooth muscle contraction is a complicated process coordinated by contractile, regulatory and cytoskeletal proteins. The force generation depends on the phosphorylation of Myosin Regulatory Light Chain (MLC20). Myosin Light Chain Kinase (MLCK) and Myosin Light Chain Phosphatase (MLCP) are the two main regulators of the MLC20 phosphorylation level. MLCP is further controlled by two known pathways including the G protein coupled receptors (GPCRs)/ phospholipase C (PLC)/ diacylglycerol (DAG)/ protein kinase C (PKC)/ PKC-potentiated inhibitory protein for heterotrimeric myosin light chain phosphatase of 17 kDa (CPI-17) pathway. While messengers involved in this pathway have been proposed, studies on the details of …

The Impact Of Lianas On 10 Years Of Tree Growth And Mortality On Barro Colorado Island, Panama, Laura L. Ingwell, S. Joseph Wright, Kristen K. Becklund, Stephen P. Hubbell, Stefan A. Schnitzer

Biological Sciences Faculty Research and Publications

1. Lianas compete intensely with trees, but few studies have examined long‐term effects of liana infestation on tree growth and mortality. We quantified the effects of lianas in tree crowns (n = 2907) and rooted within 2 m of trees (n = 1086) on growth and mortality of 30 tree species from 1995 to 2005 on Barro Colorado Island (BCI), Panama, documented liana infestation in tree crowns in 1996 and 2007 to determine the dynamics of liana infestation, and quantified liana infestation in the crowns of 3231 additional canopy trees (d.b.h. ≥20 cm) in 2007 to compare with …

Negative Plant–Soil Feedback Predicts Tree-Species Relative Abundance In A Tropical Forest, Scott A. Mangan, Stefan A. Schnitzer, Edward A. Herre, Keenan M.L. Mack, Mariana C. Valencia, Evelyn I. Sanchez, James D. Bever

Biological Sciences Faculty Research and Publications

The accumulation of species-specific enemies around adults is hypothesized to maintain plant diversity by limiting the recruitment of conspecific seedlings relative to heterospecific seedlings^1,2,3,4,5,6. Although previous studies in forested ecosystems have documented patterns consistent with the process of negative feedback^{7,8,9,10,11,12,13,14,15,16}, these studies are unable to address which classes of enemies (for example, pathogens, invertebrates, mammals) exhibit species-specific effects strong enough to generate negative feedback¹⁷, and whether …

Endocannabinoid Signalling: Has It Got Rhythm?, Linda K. Vaughn, Gerene Denning, Kara L. Stuhr, Harriet De Wit, Matthew N. Hill, Cecilia J. Hillard

Biomedical Sciences Faculty Research and Publications

Endogenous cannabinoid signalling is widespread throughout the body, and considerable evidence supports its modulatory role in many fundamental physiological processes. The daily and seasonal cycles of the relationship of the earth and sun profoundly affect the terrestrial environment. Terrestrial species have adapted to these cycles in many ways, most well studied are circadian rhythms and hibernation. The purpose of this review was to examine literature support for three hypotheses: (i) endocannabinoid signalling exhibits brain region-specific circadian rhythms; (ii) endocannabinoid signalling modulates the rhythm of circadian processes in mammals; and (iii) changes in endocannabinoid signalling contribute to the state of hibernation. …

Bioaugmentation For Improved Recovery Of Anaerobic Digesters After Toxicant Exposure, Anne Schauer-Gimenez, Daniel Zitomer, James Maki, Craig Struble

Biological Sciences Faculty Research and Publications

Bioaugmentation was investigated as a method to decrease the recovery period of anaerobic digesters exposed to a transient toxic event. Two sets of laboratory-scale digesters (SRT = 10 days, OLR = 2 g COD/L-day), started with inoculum from a digester stabilizing synthetic municipal wastewater solids (MW) and synthetic industrial wastewater (WW), respectively, were transiently exposed to the model toxicant, oxygen. Bioaugmented digesters received 1.2 g VSS/L-day of an H₂-utilizing culture for which the archaeal community was analyzed. Soon after oxygen exposure, the bioaugmented digesters produced 25–60% more methane than non-bioaugmented controls (p < 0.05). One set of digesters produced lingering high propionate concentrations, and bioaugmentation resulted in significantly shorter recovery periods. The second set of digesters did not display lingering propionate, and bioaugmented digesters recovered at the same time as non-bioaugmented controls. The difference in the effect of bioaugmentation on recovery may be due to differences between microbial communities of the digester inocula originally employed. In conclusion, bioaugmentation with an H₂-utilizing culture is a …

Mutant Huntingtin Fragments Form Oligomers In A Polyglutamine Length-Dependent Manner In Vitro And In Vivo, Justin Legleiter, Emily M. Sontag, Gregor P. Lotz, Ellen Sapp, Cheping Ng, Marian Difiglia, Leslie M. Thompson, Paul J. Muchowski

Biological Sciences Faculty Research and Publications

Huntington disease (HD) is caused by an expansion of more than 35–40 polyglutamine (polyQ) repeats in the huntingtin (htt) protein, resulting in accumulation of inclusion bodies containing fibrillar deposits of mutant htt fragments. Intriguingly, polyQ length is directly proportional to the propensity for htt to form fibrils and the severity of HD and is inversely correlated with age of onset. Although the structural basis for htt toxicity is unclear, the formation, abundance, and/or persistence of toxic conformers mediating neuronal dysfunction and degeneration in HD must also depend on polyQ length. Here we used atomic force microscopy to demonstrate mutant htt …

Annual Rainfall And Seasonality Predict Pan‐Tropical Patterns Of Liana Density And Basal Area, Saara J. Dewalt, Stefan A. Schnitzer, Jérôme Chave, Frans Bongers, Robyn J. Burnham, Zhiquan Cai, George B. Chuyong, David B. Clark, Corneille E.N. Ewango, Jeffrey J. Gerwing, Esteban Gortaire, Terese Hart, Guillermo Ibarra-Manriquez, Kalan Ickes, David Kenfack, Manuel J. Macía, Jean-Remy Makana, Miguel Martinez-Ramos, Joseph Mascaro, Sainge Moses, Helene C. Muller-Laudau, Marc P.E. Parren, Narayanaswamy Parthasarathy, Diego R. Perez-Salicrup, Francis E. Putz, Hugo Romero-Saltos, Duncan W. Thomas

Biological Sciences Faculty Research and Publications

We test the hypotheses proposed by Gentry and Schnitzer that liana density and basal area in tropical forests vary negatively with mean annual precipitation (MAP) and positively with seasonality. Previous studies correlating liana abundance with these climatic variables have produced conflicting results, warranting a new analysis of drivers of liana abundance based on a different dataset. We compiled a pan‐tropical dataset containing 28,953 lianas (≥2.5 cm diam.) from studies conducted at 13 Neotropical and 11 Paleotropical dry to wet lowland tropical forests. The ranges in MAP and dry season length (DSL) (number of months with mean rainfall < 100 mm) represented by these datasets were 860–7250 mm/yr and 0–7 mo, respectively. Pan‐tropically, liana density and basal area decreased significantly with increasing annual rainfall and increased with increasing DSL, supporting the hypotheses of Gentry and Schnitzer. Our results suggest that much of the variation in liana density and basal area in the tropics can be accounted for by the relatively simple metrics of MAP and DSL.

Modulation Of L-Type Calcium Current By Gaba-B Receptor Activation In The Neonatal Rat Hippocampus, Jennifer Grace Bray

Dissertations (1934 -)

During the early postnatal period, the inhibitory neurotransmitter γ-aminobutyric acid (GABA) facilitates current through voltage-dependent L-type calcium channels by activating metabotropic GABA_B receptors in the rat hippocampus. In the present study, the effects of the GABA_B receptor agonist baclofen on L-type currents were tested using whole-cell voltage clamp recording on neurons isolated from the superior region of hippocampi obtained from pups of various ages to determine the exact time course of L-type current facilitation. The facilitation of L-type current by GABA_B receptors is more prominent during the second week of development.

One developmental process that L-type current …

Candida Albicans Adhesion And Biofilm Formation On Phosphated And Non-Phosphate Containing Poly(Methylmethacrylate) Polymers, Kathryn Elizabeth Ryan

Master's Theses (2009 -)

Denture-induced stomatitis is prevalent among prosthesis users, particularly the elderly and institutionalized where it has been estimated to be present in over 60-65% of denture wearers. Treatment of this clinical condition is problematic due to incomplete disinfection of the acrylic surface and rapid microbial re-colonization. Moreover, ingestion or aspiration of pathogens in denture plaque exposes the elderly and immunocompromised to unexpected infections.

Acrylic polymers have generally been used to replace missing teeth and periodontal tissues in edentulous or partially dentate patients. Currently, edentulous adults in the US population are common, with complete edentulism greater than 41% among Americans aged 65 …

Probing The Catalytic Roles Of Arg548 And Gln552 In The Carboxyl Transferase Domain Of The Rhizobium Etli Pyruvate Carboxylase By Site-Directed Mutagenesis, Saowapa Duangpan, Sarawut Jitrapakdee, Abdussalam Adina-Zada, Lindsay Byrne, Tonya N. Zeczycki, Martin St. Maurice, W. Wallace Cleland, John C. Wallace, Paul V. Attwood

Biological Sciences Faculty Research and Publications

The roles of Arg548 and Gln552 residues in the active site of the carboxyl transferase domain of Rhizobium etli pyruvate carboxylase were investigated using site-directed mutagenesis. Mutation of Arg548 to alanine or glutamine resulted in the destabilization of the quaternary structure of the enzyme, suggesting that this residue has a structural role. Mutations R548K, Q552N, and Q552A resulted in a loss of the ability to catalyze pyruvate carboxylation, biotin-dependent decarboxylation of oxaloacetate, and the exchange of protons between pyruvate and water. These mutants retained the ability to catalyze reactions that occur at the active site of the biotin carboxylase domain, …

Most, But Not All, Yeast Strains In The Deletion Library Contain The [Pin+] Prion, Anita L. Manogaran, Viviana M. Fajardo, Robert J. D. Reid, Rodney Rothstein, Susan W. Liebman

Biological Sciences Faculty Research and Publications

The yeast deletion library is a collection of over 5100 single gene deletions that has been widely used by the yeast community. The presence of a non-Mendelian element, such as a prion, within this library could affect the outcome of many large-scale genomic studies. We previously showed that the deletion library parent strain contained the [PIN⁺] prion. [PIN⁺] is the misfolded infectious prion form of the Rnq1 protein that displays distinct fluorescent foci in the presence of RNQ1–GFP and exists in different physical conformations, called variants. Here, we show that over 97% of the …

An Exonic Splicing Enhancer Within A Bidirectional Coding Sequence Regulates Alternative Splicing Of An Antisense Mrna, Valerie K. Salato, Nathaniel W. Rediske, Chao Zhang, Michelle Laura Hastings, Stephen Munroe

Biological Sciences Faculty Research and Publications

The discovery of increasing numbers of genes with overlapping sequences highlights the problem of expression in the context of constraining regulatory elements from more than one gene. This study identifies regulatory sequences encompassed within two genes that overlap in an antisense orientation at their 3’ ends. The genes encode the α-thyroid hormone receptor gene (TRα or NR1A1) and Rev-erbα (NR1D1). In mammals TRα pre-mRNAs are alternatively spliced to yield mRNAs encoding functionally antagonistic proteins: TRα1, an authentic thyroid hormone receptor; and TRα2, a non-hormone-binding variant that acts as a repressor. TRα2-specific splicing requires two regulatory elements that overlap with Rev-erbα …

Genetic Basis For Rhizobium Etli Ce3 O-Antigen O-Methylated Residues That Vary According To Growth Conditions, Kristylea J. Ojeda, Jodie M. Box, K. Dale Noel

Biological Sciences Faculty Research and Publications

The Rhizobium etli CE3 O antigen is a fixed-length heteropolymer with O methylation being the predominant type of sugar modification. There are two O-methylated residues that occur, on average, once per complete O antigen: a multiply O-methylated terminal fucose and 2-O methylation of a fucose residue within a repeating unit. The amount of the methylated terminal fucose decreases and the amount of 2-O-methylfucose increases when bacteria are grown in the presence of the host plant, Phaseolus vulgaris, or its seed exudates. Insertion mutagenesis was used to identify open reading frames required for the presence of these O-methylated …

Chlamydomonas Mutants Display Reversible Deficiencies In Flagellar Beating And Axonemal Assembly, Mei Wei, Priyanka Sivadas, Heather A. Owen, David R. Mitchell, Pinfen Yang

Biological Sciences Faculty Research and Publications

Axonemal complexes in flagella are largely prepackaged in the cell body. As such, one mutation often results in the absence of the co-assembled components and permanent motility deficiencies. For example, a Chlamydomonas mutant defective in RSP4 in the radial spoke (RS), which is critical for bend propagation, has paralyzed flagella that also lack the paralogue RSP6 and three additional RS proteins. Intriguingly, recent studies showed that several mutant strains contain a mixed population of swimmers and paralyzed cells despite their identical genetic background. Here we report a cause underlying these variations. Two new mutants lacking RSP6 swim processively and other …

A New Species Of Gekko (Squamata: Gekkonidae) From Tà Kóu Nature Reserve, Binh Thuan Province, Southern Vietnam, Van Tri Ngo, Tony Gamble

Biological Sciences Faculty Research and Publications

A new species of Gekko Laurenti is described from Ta Kou Mountain, an isolated granitic peak in Ta Kou Nature Reserve, Ham Thuan Nam district, Binh Thuan province, southern Vietnam. The species is distinguished from its congeners by its moderate size, with snout to vent length (SVL) reaching a maximum 107.0 mm; dorsal pattern of 5–8 white vertebral blotches between the nape and sacrum and 6–8 pairs of short white bars on the flanks; 11–14 precloacal pores in males; 14–17 longitudinal rows of smooth dorsal tubercles; and 18–20 broad lamellae beneath the fourth toe. Gekko takouensis sp. nov. is the …

Interaction Between The Biotin Carboxyl Carrier Domain And The Biotin Carboxylase Domain In Pyruvate Carboxylase From Rhizobium Etli, Adam D. Lietzan, Ann L. Menefee, Tonya N. Zeczycki, Sudhanshu Kumar, Paul V. Attwood, John C. Wallace, W. Wallace Cleland, Martin St. Maurice

Biological Sciences Faculty Research and Publications

Pyruvate carboxylase (PC) catalyzes the ATP-dependent carboxylation of pyruvate to oxaloacetate, an important anaplerotic reaction in mammalian tissues. To effect catalysis, the tethered biotin of PC must gain access to active sites in both the biotin carboxylase domain and the carboxyl transferase domain. Previous studies have demonstrated that a mutation of threonine 882 to alanine in PC from Rhizobium etli renders the carboxyl transferase domain inactive and favors the positioning of biotin in the biotin carboxylase domain. We report the 2.4 Å resolution X-ray crystal structure of the Rhizobium etli PC T882A mutant which reveals the first high-resolution description of …

A Review Of Sex Determining Mechanisms In Geckos (Gekkota: Squamata), Tony Gamble

Biological Sciences Faculty Research and Publications

Geckos are a species-rich clade of reptiles possessing diverse sex determining mechanisms. Some species possess genetic sex determination, with both male and female heterogamety, while other species have temperature-dependent sex determination. I compiled information from the literature on the taxonomic distribution of these sex determining mechanisms in geckos. Using phylogenetic data from the literature, I reconstructed the minimum number of transitions among these sex determining mechanisms with parsimony-based ancestral state reconstruction. While only a small number of gecko species have been characterized, numerous changes among sex determining mechanisms were inferred. This diversity, coupled with the high frequency of transitions, makes …

Inhibitors Of Pyruvate Carboxylase, Tonya N. Zeczycki, Martin St. Maurice, Paul V. Attwood

Biological Sciences Faculty Research and Publications

This review aims to discuss the varied types of inhibitors of biotin-dependent carboxylases, with an emphasis on the inhibitors of pyruvate carboxylase. Some of these inhibitors are physiologically relevant, in that they provide ways of regulating the cellular activities of the enzymes e.g. aspartate and prohibitin inhibition of pyruvate carboxylase. Most of the inhibitors that will be discussed have been used to probe various aspects of the structure and function of these enzymes. They target particular parts of the structure e.g. avidin – biotin, FTP – ATP binding site, oxamate – pyruvate binding site, phosphonoacetate – binding site of the …

Isoform- And Cell-Specific Function Of Tyrosine Decarboxylase In The Drosophila Malpighian Tubule, Edward M. Blumenthal

Biological Sciences Faculty Research and Publications

The biogenic amine tyramine (TA) is a potent diuretic factor when applied to the Malpighian tubule (MT) of Drosophila melanogaster, stimulating both urine production and transepithelial chloride conductance. Isolated MTs can respond not only to TA but also to its precursor, tyrosine; this observation led to the proposal that MTs are able to synthesize TA from applied tyrosine through the action of the enzyme tyrosine decarboxylase (TDC). In the current study it is shown that the non-neuronal isoform of TDC, Tdc1, is expressed in the principal cells of the MT. A mutant allele of Tdc1, Tdc1^{f03311 …}

Novel Lc8 Mutations Have Disparate Effects On The Assembly And Stability Of Flagellar Complexes, Pinfen Yang, Chun Yang, Maureen Wirschell, Stephanie Davis

Biological Sciences Faculty Research and Publications

LC8 functions as a dimer crucial for a variety of molecular motors and non-motor complexes. Emerging models, founded on structural studies, suggest that the LC8 dimer promotes the stability and refolding of dimeric target proteins in molecular complexes, and its interactions with selective target proteins, including dynein subunits, is regulated by LC8 phosphorylation, which is proposed to prevent LC8 dimerization. To test these hypotheses in vivo, we determine the impacts of two new LC8 mutations on the assembly and stability of defined LC8-containing complexes in Chlamydomonas flagella. The three types of dyneins and the radial spoke are disparately affected …

Mapping Of The Saccharomyces Cerevisiae Oxa1-Mitochondrial Ribosome Interface And Identification Of Mrpl40, A Ribosomal Protein In Close Proximity To Oxa1 And Critical For Oxidative Phosphorylation Complex Assembly, Lixia Jia, Jasvinder Kaur, Rosemary A. Stuart

Biological Sciences Faculty Research and Publications

The Oxa1 protein plays a central role in facilitating the cotranslational insertion of the nascent polypeptide chains into the mitochondrial inner membrane. Mitochondrially encoded proteins are synthesized on matrix-localized ribosomes which are tethered to the inner membrane and in physical association with the Oxa1 protein. In the present study we used a chemical cross-linking approach to map the Saccharomyces cerevisiae Oxa1-ribosome interface, and we demonstrate here a close association of Oxa1 and the large ribosomal subunit protein, MrpL40. Evidence to indicate that a close physical and functional relationship exists between MrpL40 and another large ribosomal protein, the Mrp20/L23 protein, is …

Influx Of Calcium Through L-Type Calcium Channels In Early Postnatal Regulation Of Chloride Transporters In The Rat Hippocampus, Jennifer Grace Bray, Michelle Mynlieff

Biological Sciences Faculty Research and Publications

During the early postnatal period, GABA_B receptor activation facilitates L-type calcium current in rat hippocampus. One developmental process that L-type current may regulate is the change in expression of the K⁺Cl⁻ co-transporter (KCC2) and N⁺K⁺2Cl⁻ co-transporter (NKCC1), which are involved in the maturation of the GABAergic system. The present study investigated the connection between L-type current, GABA_B receptors, and expression of chloride transporters during development. The facilitation of L-type current by GABA_B receptors is more prominent in the second week of development, with the highest percentage of cells exhibiting …

Camp Pulsing Of Denuded Mouse Oocytes Increases Meiotic Resumption Via Activation Of Amp-Activated Protein Kinase, Jing Chen, Maggie M. Chi, Kelle H. Moley, Stephen M. Downs

Biological Sciences Faculty Research and Publications

cAMP plays a critical role in the control of oocyte maturation, as a high level of cAMP maintains oocyte arrest at the first meiotic prophase. Yet this study shows that pulsing meiotically arrested denuded oocytes (DO) with cAMP induces oocyte maturation through the activation of AMP-activated protein kinase (PRKA). Short-term (3 h) pulsing of meiotically arrested oocytes with forskolin, an adenyl cyclase (AC) activator, increased oocyte cAMP, led to elevated AMP, and induced oocyte meiotic resumption compared to oocytes continuously cultured in the control medium with or without forskolin. Western analysis showed that germinal vesicle (GV)-stage oocytes after forskolin pulsing …

Circadian Timing Of Food Intake Contributes To Weight Gain, Deanna M. Arble, Joseph Bass, Aaron D. Laposky, Martha H. Vitaterna, Fred W. Turek

Biological Sciences Faculty Research and Publications

Studies of body weight regulation have focused almost entirely on caloric intake and energy expenditure. However, a number of recent studies in animals linking energy regulation and the circadian clock at the molecular, physiological, and behavioral levels raise the possibility that the timing of food intake itself may play a significant role in weight gain. The present study focused on the role of the circadian phase of food consumption in weight gain. We provide evidence that nocturnal mice fed a high‐fat diet only during the 12‐h light phase gain significantly more weight than mice fed only during the 12‐h dark …

Genome 10k: A Proposal To Obtain Whole-Genome Sequence For 10 000 Vertebrate Species, Tony Gamble, Genome 10k Community Of Scientists

Biological Sciences Faculty Research and Publications

The human genome project has been recently complemented by whole-genome assessment sequence of 32 mammals and 24 nonmammalian vertebrate species suitable for comparative genomic analyses. Here we anticipate a precipitous drop in costs and increase in sequencing efficiency, with concomitant development of improved annotation technology and, therefore, propose to create a collection of tissue and DNA specimens for 10 000 vertebrate species specifically designated for whole-genome sequencing in the very near future. For this purpose, we, the Genome 10K Community of Scientists (G₁₀KCOS), will assemble and allocate a biospecimen collection of some 16 203 representative vertebrate species spanning …

Differences In Leaf Traits, Leaf Internal Structure, And Spectral Reflectance Between Two Communities Of Lianas And Trees: Implications For Remote Sensing In Tropical Environments, G. Arturo Sanchez-Azofeifa, Karen Castro, S. Joseph Wright, John Gamon, Margaret Kalacska, Benoit Rivard, Stefan A. Schnitzer, Ji Lu Feng

Biological Sciences Faculty Research and Publications

Increasing dominance of lianas in many tropical forests is considered a fingerprint of global environmental change. Despite the key role they play in ecosystem functioning, lianas remain one of the least studied life forms in tropical environments. This paper contrasts leaf traits and spectral properties (400–1100 nm) of liana and tree communities from a tropical dry forest and a tropical rainforest in Panama, Central America. Differences between lianas and tree leaf traits were analyzed using spectroscopy, leaf histology and pigment extractions. Results from this study indicate that many of the biochemical, structural, and optical properties of lianas …

Tropical Dry Forest Succession And The Contribution Of Lianas To Wood Area Index (Wai), Arturo Sanchez-Azofeifa, Margaret Kalacska, Mario Marcos Do Espirito-Santo, G. Wilson Fernandes, Stefan A. Schnitzer

Biological Sciences Faculty Research and Publications

The transmission and interception of light through the canopy is an important indicator of forest productivity in tropical forest ecosystems, and the amount of light that eventually reaches the forest floor is influenced by its interactions with leaves, branches, fruits, and flowers among many different canopy elements. While most studies of forest canopy light interception focus on leaf area index (LAI), very few studies have examined wood area index (WAI), which may account for a substantial component of light interception in tropical forests. The influence of lianas on the interception of light and their overall contribution to WAI is a …

Defective Gut Function In Drop-Dead Mutant Drosophila, Cassandra R. Peller, Elizabeth M. Bacon, Julie A. Bucheger, Edward M. Blumenthal

Biological Sciences Faculty Research and Publications

Mutation of the gene drop-dead (drd ) causes adult Drosophila to die within 2 weeks of eclosion and is associated with reduced rates of defecation and increased volumes of crop contents. In the current study, we demonstrate that flies carrying the strong allele drd^lwf display a reduction in the transfer of ingested food from the crop to the midgut, as measured both as a change in the steady-state distribution of food within the gut and also in the rates of crop emptying and midgut filling following a single meal. Mutant flies have abnormal triglyceride (TG) and glycogen stores …