Papers by Robert Bloodgood
Cell Biology International Reports, May 1, 1978
The FASEB Journal, Apr 1, 2013
Histology laboratory instruction is moving away from the sole use of the traditional combination ... more Histology laboratory instruction is moving away from the sole use of the traditional combination of light microscopes and glass slides in favor of virtual microscopy and virtual slides. At the same time, medical curricula are changing so as to reduce scheduled time for basic science instruction as well as focusing on student-centered learning approaches such as small group active learning and peer-instruction. It is important that medical schools resist the temptation to respond to this conjunction of events by turning histology into a self-study activity. This article describes a lymphoid histology laboratory exercise, occurring in a specially equipped Learning Studio housing an entire medical class that utilizes virtual slides in the context of small group active learning and peer instruction.
Journal of Cell Science, Feb 15, 2010
A recent cluster of papers has shown that motile cilia in the respiratory and reproductive tracts... more A recent cluster of papers has shown that motile cilia in the respiratory and reproductive tracts of humans and other mammals can exhibit sensory functions, a function previously attributed primarily to non-motile primary cilia. This leads to a new paradigm that all cilia and flagella (both motile and primary) can mediate sensory functions. However, examination of the literature shows that evidence of sensory functions of motile cilia and flagella is widespread in studies of invertebrates, and extends as back as far as 1899. In this Opinion article, I review the recent and historical findings that motile cilia have a variety of sensory functions, and discuss how this concept has in fact been evolving for the past century. This article is part of a Minifocus on cilia and flagella. For further reading, please see related articles: 'The primary cilium at a glance' by Peter Satir et al.
Archives of Microbiology, Dec 1, 1974
Unusual cell surface structures found only on the symbiotic, flagellate protozoan,Pyrsonympha, ar... more Unusual cell surface structures found only on the symbiotic, flagellate protozoan,Pyrsonympha, are described for the first time.
Protoplasma, Mar 1, 1998
The biflagellate green alga Chlamydomonas can exhibit substrate-associated gliding motility in ad... more The biflagellate green alga Chlamydomonas can exhibit substrate-associated gliding motility in addition to its ability to swim through a liquid medium. The flagella are the organelles responsible for both forms of whole-cell locomotion although the mechanism in each case is very different. In this study, we demonstrate that the binding of polystyrene microspheres to the flagellar surface of Chlamydomonas initiates clustering of the major flagellar-membrane glycoprotein, which is known to be involved in motility-associated substrate adhesion. In addition, we demonstrate that microsphere binding to the flagellar surface initiates the same transmembrane signaling pathway that is initiated by antibody-or lectin-induced crosslinking of the major flagellar-membrane glycoprotein. In each case, the signaling pathway involves the activation of a calciumdependent protein phosphatase that dephosphorylates a flagellar phosphoprotein known to be associated with the major flagellarmembrane glycoprotein. Bound microspheres are translocated along the flagellar surface at approximately the same velocity as whole-cell gliding motility. Previous observations suggest that microsphere binding and translocation along the flagellar surface may be a reflection of the same force-transducing system responsible for whole-cell gliding motility. In which case, these observations suggest that the transmembrane signaling pathway initiated by crosslinking the major flagellar-membrane glycoprotein is the same one that is activated when the cell contacts a physiological substrate by its flagellar surface.
Experimental Cell Research, Feb 1, 1984
Radioactive labeling studies demonstrate a continuous incorporation of newly synthesized proteins... more Radioactive labeling studies demonstrate a continuous incorporation of newly synthesized proteins and glycoproteins into the intact flagella of Chlamydomonas. This apparent turnover is preferentially occurring for membrane components. In particular, two classes of flagellar membrane components, one a high molecular weight (HMW) group of closely migrating glycoproteins and the other a protein with a MW around 65 kD, are continuously turning over in the vegetative cell. This selective protein turnover may explain the ability of Chlamydomonas to rapidly recover from proteolytic modification of the flagellar surface and to change its flagellar surface properties during the early events in mating.
Journal of Cell Biology, Aug 1, 1983
Mating in Chlamydomonas is a complex process initiated by contact of gametic flagellar surfaces, ... more Mating in Chlamydomonas is a complex process initiated by contact of gametic flagellar surfaces, resulting in transmission of a signal from the flagella to the cell bodies. This signal triggers later events of cell wall loss, mating structure activation, and cell-cell fusion. Little is known about the nature of the signal or the role of Ca in these events. It was found that extracellular Ca is not necessary for successful mating in Chlamydomonas. However, cells will take up Ca from the medium in a linear manner for many hours and will accumulate micromolar concentrations, presumably by sequestering Ca within intracellular storage sites. If gametic cells of one mating type (preloaded with 45Ca) are mated with gametes of the opposite mating type (preloaded with unlabeled calcium), there is a rapid, transient increase in calcium efflux rate (20 times that of the control) that lasts ,-6 min. This effect is not associated with cell-cell fusion, since the same observation is made if (+) gametes preloaded with 45-Ca are agglutinated by isolated flagella from (-) gametes preloaded with unlabeled Ca. Other experiments have shown that the increased efflux rate is not a simple consequence of cell wall release. Ca efflux in unmated gametes is greatly reduced in deflagellated cells, suggesting that much of the Ca movement is associated with the flagellar membrane. Although signaling itself may involve Ca fluxes across the flagellar membrane, it is also possible that a consequence of signaling is release of Ca from intracellular storage sites (perhaps functional equivalents of the sarcoplasmic reticulum). The observed transient increase in Ca efflux rate may reflect a transient increase in the cytoplasmic free-Ca concentration. This increase in cytoplasmic Ca may regulate the later events in mating (such as cell wall release and mating structure activation). Ca has been frequently implicated in the early events of fertilization, particularly in marine eggs (see references 13, 25, 58, 68 for reviews). In these systems, external Ca is generally necessary for sperm activation, but is not necessary for fertilization of eggs by previously acrosome-reacted sperm (55, 56). Fertilization results in a transient increase in free cytoplasmic Ca, presumably released from some intracellular membrane-bounded compartment. The increase in cytoplasmic free-Ca concentration induces the cortical granule reaction, which results in formation of the fertilization membrane from the vitelline envelope. Mating events in Chlamydomonas have been the subject of intense study (17, 19, 22). Chlamydomonas is an isogamous green alga in which the gametes of the two different mating types are of equal size and of almost identical structure. Gametes of opposite mating types interact by their flagellar surfaces by means of species-, gamete-, and mating type (mr)specific agglutinin molecules (1, 39); this reaction has been intensively studied as a model system for specific cell-cell interactions. Flagellar membrane contact is followed by reorientation of the flagella (6, 32, 36), flagellar tip activation (38), transmission of a signal from the flagella to the cell bodies (14, 64), loss of cell walls due to release of a specific lysin (53, 60, 65), activation of a specific mating structure on each partner (20, 21), cell-cell fusion (67), and de-adhesion of the flagellar surfaces (61, 62). This carefully programmed sequence of events can be completed in under 5 min, resulting in a heterokaryon that will later become a zygote after flagellar resorption and nuclear fusion. Little is known about the role of Ca during fertilization in Chlamydomonas. Flagellar surface motility is known to be Ca-dependent (7). FlageUar surface motility, cell-wall release, and cell fusion in Chlarnydomonas are all inhibited by similar concentrations of lidocaine (xylocaine) (63) and trifluoperazine (11). Since lidocaine is known to affect the interaction of calcium with membranes (33, 57) and to affect capping in
Tissue & Cell, 1977
The structure of the accessory nidamental gland of the female squid, Lo&o pealei, has been invest... more The structure of the accessory nidamental gland of the female squid, Lo&o pealei, has been investigated using transmission and scanning electron microscopy. The accessory gland has many of the structural features of a secretory organ. The basic structural unit is a tubule composed of a single layer of epithelial cells containing ordered arrays of rough endoplasmic reticulum and a lumenal surface covered with microvilli, cilia, and structural specializations presumed to be involved in secretion. The lumen of each tubule is filled with a dense population of bacteria. During sexual maturation of the squid, the accessory gland changes in color from white to mottled red. The accessory gland of the sexually mature squid has a mixture of red, white, and yellow tubules; in each case, the color of the tubule is due to the bacterial population occupying the tubule. Since the red color of the gland is due to the pigmentation of the bacteria, the bacteria must be responsive to the sexual state of the host, possibly through a change in the nature of the material secreted into the tubule lumen. The bacteria can be cultured easily, but in culture they fail to synthesize the red pigment.
Cytoskeleton, 1989
... Address reprint requests to Robert A. Bloodgood, Department of Anatomy and Cell Biology, Univ... more ... Address reprint requests to Robert A. Bloodgood, Department of Anatomy and Cell Biology, University of Virginia School of Medi-cine, Charlottesville ... In Rembaum, A., and Tokes, Z. (eds.): Micro-spheres: Medical and Biological Applications. Boca Raton, FL: CRC Press, pp. ...
Cold Spring Harbor Symposia on Quantitative Biology, 1982
Methods in Cell Biology, 1995
Publisher Summary Flagella are generally thought to promote whole-cell locomotion through the ini... more Publisher Summary Flagella are generally thought to promote whole-cell locomotion through the initiation and propagation of bends along the organelle. Chlamydomonas and certain other flagellated protists provide a striking exception to this rule. While Chlamydomonas species can clearly swim through liquid medium by the coordinated initiation and propagation of bends along their two flagella, this is probably not the physiologically most relevant form of whole-cell locomotion for these cells. Chlamydomonas exhibit whole-cell locomotion along a solid substrate, be it soil, glass or agar. This is referred to as gliding motility. Gliding motility is exhibited by all flagellated stages of Chlamydomonas. During the course of gliding motility, the flagella can appear to be absolutely straight and immotile, exhibiting no obvious bends or undulations. On occasion, however, the distal 1 μm of the leading flagellum can be seen to wiggle; this observation, coupled with the fact that cells can glide in curved trajectories, suggests the possibility that Chlamydomonas can regulate the direction of gliding motility. A wide variety of paralyzed flagellar strains, exhibit normal gliding behavior, suggesting that gliding motility is not coupled to axonemal motility and is not dependent on the motor responsible for axonemal motility and flagellar beating, also involvement of a minus end-directed micro-tubule-associated motor. This chapter discusses procedures for observing gliding motility and polystyrene microsphere movements. Nongliding cell strains of Chlamydomonas were unable to exhibit microsphere movement along the flagellar surface, suggesting that microsphere movements are a manifestation of the same force transduction system responsible for whole-cell gliding motility. Attachment to and movement along the flagellar surface of polystyrene microspheres provides an easy, quantitative assay for the force transduction system responsible for gliding motility. Availability of nongliding mutants, especially that have been insertionally tagged, provides the opportunity to identify genes whose products are involved in this form of whole-cell locomotion.
Cell Biology International, Dec 1, 2000
Much exciting research has been done on the co-translational and post-translational targeting ofs... more Much exciting research has been done on the co-translational and post-translational targeting ofspecific classes of proteins to membrane-boundedorganelles using targeting sequences or motifslocated within the proteins themselves. In contrast,cilia and flagella have not always been consideredas organelles in the same sense as rough endoplas-mic reticulum, mitochondria or the nucleus; theyhave been seen partly as cell surface specializationsand partly as an extension of the cytoskeleton, bothof which are true. However, despite the fact thatthese organelles are not totally enclosed by a mem-brane, there is good reason to view them as rela-tively ‘closed’ compartments. If this view is correct,one would expect cilia and flagella to utilize specifictargeting and import mechanisms for both mem-brane proteins being delivered via a vesicular trans-port pathway from the Golgi and cytoskeletalproteins that are synthesized on free polyribo-somes. Cilia and flagella can be viewed as tubularextensions of the plasma membrane, ‘plugged’ attheir proximal end by a very complex cytoarchitec-ture (including the basal body and transition zone)tightly associated with the adjacent plasma mem-brane by structures referred to as ciliary necklaces.These basal structures clearly serve as selective bar-riers; for instance, the soluble compartment of ciliaand flagella does not have the same composition asthe general cytoplasm. In terms of comparisonswith other cellular compartments with known tar-geting systems, cilia and flagella can best be com-pared with the nucleus. Entry into and exit from thenucleus does not require passage across a mem-brane but rather occurs through a complex cytoar-chitecture (the nuclear pore) that allows proteinsbelow a certain size to diffuse through an aqueousspace while utilizing a complex mechanism for im-port and export of larger proteins. Cilia and flagellamay need to utilize similar targeting and uptakemechanisms involving targeting sequences ormotifs in the proteins destined for cilia and flagella,along with an active translocation apparatus. Forthe first time, a recent group of papers have re-ported the presence of specific targeting sequencesor motifs in both membrane and cytoskeletal pro-teins destined for flagella of trypanosomatids, afamily of flagellated, parasitic protozoa.Cilia and flagella can be viewed as organellescontaining three ‘domains’: a membrane domain, ahighly structured cytoskeleton (the axoneme) and asoluble compartment. This latter compartment hasbeen variously referred to as the ‘matrix’ compart-ment or ‘flagelloplasm’ or ‘cilioplasm’. The ciliaryor flagellar membrane is a specialized domain ofthe plasma membrane with a protein and lipidcomposition distinct from that of the rest of theplasma membrane (Bloodgood, 1990). A numberof membrane proteins are known to be specificallylocalized to various ciliary or flagellar membranes;among the trypanosomatids, these include specificisoforms of glucose transporters (Snapp andLandfear, 1997), adenylate cyclases (Paindavoine
Advances in Molecular and Cell Biology, 1987
Publisher Summary The Chlamydomonas flagellum is one system where considerable attention has been... more Publisher Summary The Chlamydomonas flagellum is one system where considerable attention has been given to the study of the flagellar membrane in terms of adhesive, motile, and signaling events during the mating of gametes and in relation to the dynamics of vegetative Chlamydomonas flagellar membrane glycoproteins. Cilia and flagella possess a number of distinct advantages for the study of plasma-membrane dynamics. Ciliated and flagellated cells provide the opportunity to gain ready access to a defined subset of the cell's general plasma membrane and to the cytoskeletal machinery, which underlies plasma-membrane domain. Ciliary and flagellar membranes exhibit a number of interesting dynamic phenomena. In Chlamydomonas , the flagella of gametic cells are of critical importance for reproduction, and mating in this organism involves highly specific membrane–membrane adhesion and membrane-signaling phenomena associated with the flagellar membrane. The current state of knowledge about the Chlamydomonas reinhardtii flagellar membrane suggests that the 350-kd class of glycoproteins exhibits a surface-exposed substrate-binding domain, which also possesses binding sites for the lectin concanavalin A and certain anticarbohydrate monoclonal antibodies.
The Anatomical Record Part B: The New Anatomist, 2006
Owing to competition for faculty time among the three major missions of today&amp... more Owing to competition for faculty time among the three major missions of today's academic medical centers, as well as the rapid development of computer-based instructional technologies, laboratory instruction in medical schools in the United States has been undergoing dramatic change. In order to determine recent trends in histology laboratory instruction at U.S. medical schools, a detailed Web survey was administered to histology course directors, with about two-thirds of schools responding. The survey was designed to identify trends in the number of hours of histology laboratory instruction that each medical student receives, the amount of faculty effort devoted to histology laboratory instruction, and the use of various computer-based technologies (including virtual microscopy and virtual slides) in histology laboratory instruction. Consistent with the long-term trend of declining total laboratory teaching hours in U.S. medical schools, there is an ongoing reduction in the number of hours of faculty-directed histology laboratory instruction that each medical student receives, with a concomitant reduction in hours of faculty time devoted to histology laboratory instruction. In terms of the tools used in the histology laboratory, there has been a dramatic increase in the use of various forms of computer-aided instruction (including virtual slides). The large increase in the number of schools using computer-aided instruction has not been accompanied by an equivalent decrease in the number of schools that utilize microscopes and glass slides. Rather, the clear trend has been toward a blending of the new computer-based instructional technologies with the long-standing use of microscopes and glass slides.
Journal of Bacteriology, Jun 1, 1990
Surface proteins of the gliding bacterium Cytophaga sp. strain U67 that make contact with glass s... more Surface proteins of the gliding bacterium Cytophaga sp. strain U67 that make contact with glass substrata were radioiodinated, using a substratum-immobilized catalyst (Iodo-Gen). At least 15 polypeptides were iodinated, fewer than the number labeled by surface biotinylation of whole cells; these polypeptides define the set of possible candidates for the surface protein(s) that mediates gliding-associated substratum adhesion. The labeling of three adhesion-defective mutants exhibited two characteristic patterns of surface iodination which involved addition, loss, or alteration of several polypeptides of high molecular weight. An adhesion-competent revertant of mutant Adh3 and one of Adh2 exhibited the wild-type labeling pattern. Two other Adh2 revertants resembled their adhesion-defective parent. The labeling pattern of surface polypeptides of a nongliding but adhesive cell strain was similar to that of the wild type.
Cytoskeleton, Nov 1, 2020
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as ,Bloodgood, (2020), Prey capture in protists utilizing microtubule filled processes and surface motility.
Cell Biology International Reports, Mar 1, 1978
A system of rapid, unidirectional motility associated with the surface of Echinosphaerium axopodi... more A system of rapid, unidirectional motility associated with the surface of Echinosphaerium axopodia is demonstrated using polystyrene microspheres as exc,genous markers.
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Papers by Robert Bloodgood