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Question about deep-sea ceph's

Graeme

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I was wondering if anyone knew of any membrane adaptations in deep-sea cephalopods? Examples would be temperature, pressure etc?
I think it's cell membrane adaptations as opposed to larger mebranes.

Graeme
 

Steve O'Shea

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Nope (as in not aware), but I'd be surprised if anyone had actually looked at it! Sounds interesting!
 

Graeme

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Hmmm, it's funny how Ceph's seem to generate a lot of interest, but when it actually comes down to studying them, there's not a lot of stuff compared to other animals. Mind you I s'pose it leaves a lot of niches open... Imagine doing that for a PHD though!! That would be pretty cool.

Graeme
 

Jean

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I think one of the reasons they are not studied as much as other animals, is that they are difficult to get hold of (and expensive,boats, special capture gear etc etc) and can be extremely difficult to keep alive especially the open ocean/deepwater types! But there are some intrepid souls out there who are trying.......like our own Dr SOS and TTF!

J
 

Graeme

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... I'll do it! I'm stupid enough to be thrown on a boat in the middle of an Arctic Winter all in the name of fame and fortune... I mean Science!
Seriously, I think it would be quite interesting, but I'd need a microbiologist to translate everything everything for me- I get about as far as "now the cell membrane is..." before "zzzzzzzzzzzzzzz" or "......:bugout: "

Graeme
 

Feelers

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Grab a squid research paper and read through the references. Then read the references of those. There are a quite a lot of papers out there, problem is they arent exaclty "user friendly" in the casual reading sense.

I wouldnt have a clue if there's anything about cell membranes - but there was a hell of a lot of references to see, pages and pages, so you might get lucky.

I've done a little microbio - most papers generally have a breif rundown of how things work -its when they give all the data that things get messy.
 

Steve O'Shea

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Hmmmmmmmmmmmmm

Found the following, using "squid cell membrane" as keywords:
........................
Selective open-channel block of KV1 potassium channels by S-nitrosodithiothreitol (SNDTT)
by Brock, Mathew William, Ph.D., Stanford University, 2003, 214 pages; AAT 3085165
Advisor: Gilly, William F.
School: Stanford University
School Location: United States -- California
Index terms(keywords): Open-channel block, Potassium channels, Nitrosodithiothreitol-S, Voltage-gated potassium channels
Source: DAI-B 64/03, p. 1109, Sep 2003
Source type: DISSERTATION
Subjects: Neurology, Biophysics, Organic chemistry
Publication Number: AAT 3085165
Document URL: http://proquest.umi.com.ezproxy.aut...1&sid=1&Fmt=2&clientId=7961&RQT=309&VName=PQD
ProQuest document ID: 765393901

Abstract (Document Summary)

Blockade of voltage-gated K + (Kv) channels is a feature of many large quaternary and tertiary amines. These compounds bind with a 1:1 stoichiometry in an aqueous cavity along the channel pore that is exposed to the cytoplasm only when channels are open. This thesis addresses the action of S-nitrosodithiothreitol (SNDTT; ONSCH 2 CH(OH)CH(OH)CH 2 SNO), which produces qualitatively similar "open-channel block" in Kv channels despite its unconventional (small, electrically neutral, and polar) structure. In whole-cell voltage-clamped squid giant fiber lobe neurons, bath-applied SNDTT causes reversible time-dependent block of delayed-rectifier K + channels, but not Na + or Ca 2+ channels. The inactivation-removed Shaker B (ShBΔ) Kv1 channel expressed in HEK 293 cells is blocked in a similar manner and was used to further characterize the action of SNDTT. Dose-response data for ShBΔ indicate that two molecules of SNDTT can bind to each open channel, but binding of a single molecule is sufficient for block. The dissociation constant for the second molecule bound (0.14 mM) is lower than for the first (0.67 mM), indicating cooperativity. Surprisingly, the steady-state level of block by this electrically neutral compound has a voltage-dependence (∼-0.25 e 0 ) similar in magnitude but opposite in directionality to that reported for amines. Both nitrosyl (-NO) groups on SNDTT (one on each sulfur atom) are required for block, but transfer of these reactive groups to channel cysteine residues is not involved. Competition with internal tetraethylammonium indicates that bath-applied SNDTT crosses the cell membrane to act at an internal site. Through targeted mutagenesis, we have identified two contiguous residues (Thr469 and Ile470) in the channel cavity that are strong determinants of SNDTT sensitivity. At position 469, a side chain -OH group is required for high affinity block, and may form a hydrogen bond with an -NO group on SNDTT. Finally, SNDTT is remarkably selective for Kv1 subfamily channels. When individually expressed in HEK 293 cells, rat Kv1.1-1.6 display profound time-dependent block by SNDTT, an effect not seen for rat Kv2.1, 3.1, or 4.2. SNDTT may therefore be useful as a pharmacological probe of Kv subtype, and may represent the prototype for a new class of pharmaceuticals selectively targeting Kv1 channels.
...................................
Nanoparticles: Engineering, assembly, and biomedical applications
by Kim, Do-Kyung, Ph.D., Kungliga Tekniska Hogskolan (Sweden), 2002, 216 pages; AAT C809956
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School: Kungliga Tekniska Hogskolan (Sweden)
School Location: Sweden
Index terms(keywords): Nanoparticles, Biomedical, Ferrofluids, Superparamagnetism
Source: DAI-C 63/04, p. 854, Winter 2002
Source type: DISSERTATION
Subjects: Materials science
Publication Number: AAT C809956
ISBN: 9172832657
Document URL: http://proquest.umi.com.ezproxy.aut...1&sid=1&Fmt=2&clientId=7961&RQT=309&VName=PQD
ProQuest document ID: 725953091

Abstract (Document Summary)

This thesis deals with novel aspects of Nanotechnology through " bottom-up " and " top-down " strategies, applied to biotechnology as an interdisciplinary study.

The main objectives of this thesis are to design SPION (superparamagnetic iron oxide nanoparticles) surface modified with other biocompatible agents, varying from organic to polymer and biocompatible materials, such as proteins. The particles have been introduced to intact organs of living animals (rat brain) to examine how they interact in the brain tissue and to confirm the feasibility of using SPION for biomedical applications such as MR imaging.

Several different types of materials including SPION (first generation), immobilized biocompatible materials on SPION (second generation), for in-vivo biomedical applications, nanowires, nanotubes have been prepared by using different aspects of Nanotechnology. Various processes and techniques for the preparation of functional nanomaterials such as coprecipitaion, microemulsion (μE), and template-assisted electrodeposition are developed.

Core-shell structure nanocomposites are fabricated by template-directed self-assembly ( bottom-up ). Controlled electroless deposition of Au is followed by a subsequent removal of the template core without destroying the formed Au shells. The work also includes the development of microcontact printing (μCP) techniques, where the ink used on the surface of the stamp is made of aminopropyl trimethoxy silane (APTMS). The approach is demonstrated with the formation of 2D and 3D structures.

Several different types of magnetic measurements of SPION are investigated. Authentication of superparamagnetism has been carried out by SQUID measurements, up to 7 Tesla, and evaluating the basic physical properties by the Langevien theory. Electron spin resonance (ESR) measurements have been performed as a function of temperature with different particle sizes. The line width of the ESR spectra can be correlated to the distribution of the SPION exchange interactions. Microwave energy absorption rates of SPION have been calculated using a non-linear fitting to experimental data.

The in-vivo experiments showed that, after injection of starch coated SPION into rat brain parenchyma in striatum, a strong phagocytic uptake of the particles is observed due to their strong affinity to the body cell. Diffusion barriers between blood and neural tissue, in the endothelium of the parenchymal vessels (BBB), in the epithelia of the chroid plexuses, and arachnoid membrane (blood-CSF barriers), severely restrict penetration of several diagnostic agents.

The prediction of SPION transport has been made by the modeling of the movement of a single SPION in a biological capillary system. The model considered the four most important factors, i.e. particle size, capillary diameter, distance between the magnets, and capillary length.
.....................................
 

Steve O'Shea

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Mechanisms of synaptic vesicle endocytosis: The functions of clathrin in the nerve terminal
by Morgan, Jennifer R., Ph.D., Duke University, 2001, 263 pages; AAT 3057435
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Advisor: Augustine, George J.
School: Duke University
School Location: United States -- North Carolina
Index terms(keywords): Synaptic vesicle, Endocytosis, Clathrin, Nerve terminal
Source: DAI-B 63/06, p. 2738, Dec 2002
Source type: DISSERTATION
Subjects: Neurology, Cellular biology
Publication Number: AAT 3057435
ISBN: 0493727124
Document URL: http://proquest.umi.com.ezproxy.aut...1&sid=1&Fmt=2&clientId=7961&RQT=309&VName=PQD
ProQuest document ID: 727313791

Abstract (Document Summary)

Clathrin-coated vesicles (CCVs) mediate membrane budding and recycling in all cell types. CCVs are formed when clathrin and other accessory proteins are recruited to the donor membrane and assemble together into a proteinaceous coat, thereby inducing the invagination and pinching off of a small vesicle coated with these proteins. Following CCV formation, clathrin must be uncoated from the vesicle before the vesicle can be re-used. Although some of the proteins involved in CCV formation and uncoating have been identified, the precise molecular mechanisms underlying clathrin-mediated endocytosis are not well understood.

In neurons, CCVs are involved in synaptic vesicle recycling under conditions of heavy stimulation. However, whether CCVs participate in synaptic vesicle recycling under more physiological levels of synaptic activity is not known. Therefore, I examined the role of CCVs in synaptic vesicle recycling under low levels of synaptic activity, and I examined molecular mechanisms of CCV formation and uncoating in nerve terminals. To do so, I first identified peptides or protein fragments that inhibited clathrin assembly or uncoating in vitro . Then, I injected these inhibitory reagents into squid giant presynaptic terminals and tested for their effects on synaptic transmission and CCV formation and uncoating in vivo at 0.03 Hz stimulation.

My results indicate that the clathrin assembly activity of the synapse-specific clathrin assembly protein (AP), AP180, is essential for synaptic vesicle endocytosis. In addition, my results show that the structurally-diverse monomeric AP180 and the tetrameric AP-2 assemble clathrin by virtue of possessing multiple copies of a DLL tripeptide motif. These results allowed me to propose a novel model for CCV formation in which APs assemble clathrin by cross-linking several clathrin molecules together. Finally, my results provide the first evidence that Hsc70 and auxilin, as well as their interaction at auxilin's well-conserved HPD tripeptide motif, are essential for CCV uncoating in vivo and synaptic vesicle endocytosis. Together, my results indicate that clathrin functions are essential for synaptic vesicle endocytosis under physiological levels of nerve activity. In addition, my results provide novel details to the mechanisms of CCV formation and uncoating that can be extrapolated to clathrin-mediated endocytosis in all cell types.
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The cellular and biochemical environment of the symbiotic light organ of the Hawaiian squid Euprymna scolopes
by Nyholm, Spencer Victor, Ph.D., University of Hawai'i, 2001, 130 pages; AAT 3030190
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Advisor: McFall-Ngai, Margaret
School: University of Hawai'i
School Location: United States -- Hawaii
Index terms(keywords): Symbiotic, Light organ, Euprymna scolopes, Vibrio fischeri
Source: DAI-B 62/10, p. 4415, Apr 2002
Source type: DISSERTATION
Subjects: Zoology, Microbiology
Publication Number: AAT 3030190
ISBN: 0493427996
Document URL: http://proquest.umi.com.ezproxy.aut...1&sid=1&Fmt=2&clientId=7961&RQT=309&VName=PQD
ProQuest document ID: 726046171

Abstract (Document Summary)

The light organ symbiosis between the Hawaiian bobtail squid Euprymna scolopes and the bioluminescent bacterium Vibrio fischeri provides the opportunity to study the influence of beneficial bacteria on animal tissues. The extracellular bacterial symbionts are housed in epithelia-lined crypt spaces in the host's light organ. The host provides the symbionts with nutrients while the bacteria provide light for the host that is likely used in the squid's nocturnal foraging behavior. The association is very specific and begins within hours after hatching, when V. fischeri from the environment colonize the squid host. The goal of this dissertation was to characterize the microenvironment surrounding the symbiont population from the earliest onset of colonization of the juvenile squid to the adult animal. Within 1 h after hatching, ciliated host cells on the surface of the light organ secreted mucus and created currents that entrained Gram-negative bacteria in dense aggregates outside the light organ and near pores that lead to sites of colonization. The bacterial membrane component peptidoglycan was shown to induce mucus secretion. Bacterial aggregation, and subsequent migration and colonization of the light organ, proceeded with an increased specificity for the symbiont V. fischeri . Experimental manipulation of the host provided evidence that once colonized, the host undergoes a diel behavior in which 95% of the symbionts are vented each morning. The ventate emerged as a thick exudate that contained a mixture of V. fischeri and host cells, a subpopulation of which were squid hemocytes, all embedded in a thick protein-rich matrix. The soluble proteins in the light organ environment changed on a diel rhythm, as did the host epithelium, which exhibited cell shedding during the day. Finally, hemocytes of adult hosts were capable of binding to a variety of bacteria with different affinities. Adhesion of these cells to V. fischeri changed when the light organs were cured with antibiotics, suggesting that the symbiosis alters the behavior of host hemocytes. Together these studies add to the knowledge of how symbiotic environments are created and maintained.
 

Steve O'Shea

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Characterization of squid KV1 voltage-gated potassium channels by expression in Xenopus oocytes
by Liu, Taylor I-Tso, Ph.D., Stanford University, 2000, 191 pages; AAT 9961919
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Advisor: Gilly, William F.
School: Stanford University
School Location: United States -- California
Index terms(keywords): Squid, KV1, Voltage-gated, Potassium channels, Oocytes, Xenopus
Source: DAI-B 61/02, p. 716, Aug 2000
Source type: DISSERTATION
Subjects: Neurology, Cellular biology
Publication Number: AAT 9961919
ISBN: 0599659203
Document URL: http://proquest.umi.com.ezproxy.aut...1&sid=1&Fmt=2&clientId=7961&RQT=309&VName=PQD
ProQuest document ID: 731864011

Abstract (Document Summary)

Studies of voltage-gated sodium and potassium channels in squid giant axons have founded our understanding of action potential propagation. Cloning α-subunits of voltage-gated potassium channels (SqKv1) and the putative sodium channel (GFLN1) from the squid stellate ganglion (SG) has allowed us to study these ion channels at the molecular and cellular level. We first determined cell-type specificity of expression for GFLN1 and four SqKv1 cDNA clones (SqKv1 A-D) within the squid SG. SqKv1 A-D differ in N-terminal length and in isolated amino acid residues in the tetramerization domain (T1) and C-terminus. We characterized differences in properties among SqKv1 channels by expression in Xenopus oocytes, and explored the relationship between primary structure and functional variation.

In situ hybridization was used to localize GFLN1 mRNA to neurons with large or long axons. GFLN1-specific cRNA probes labeled both giant fiber lobe (GFL) neurons and large neurons in the cellular layer of the main stellate ganglion. In contrast, SqKv1A is prominently expressed in the GFL and not in the main SG. SqKv1B exhibits the opposite pattern, localizing to the main SG. SqKv1D was only expressed in SG at low levels, and SqKv1C expression was not detectable.

Heterologous expression of SqKv1 A-D in Xenopus oocytes and biophysical analysis by cell-attached patch clamp and two-microelectrode voltage clamp revealed differences in functional expression levels among SqKv1 variants. SqKv1D expressed ∼10-fold more current than SqKv1B and ∼80-fold more current than SqKv1A. Using site-directed mutagenesis we determined that low expression level of SqKv1A is attributable to the distal N-terminus (first 11 residues) and one residue in the T1 domain. In contrast, a single amino acid difference in the T1 domain accounts for the expression level difference between SqKv1B and SqKv1D.

Differences in functional expression level were also accompanied by differential glycosylation states among SqKv1 variants. High functional expression levels appeared to correlate with presence of channels containing complex-processed oligosaccharides. However, glycosylation was determined to be unnecessary for expression of functional channels on the cell surface. Nonetheless, analysis of glycosylation status may indicate the maturation state of SqKv1 channels within the membrane protein processing pathway and provide a biochemical correlate to the functional analyses.
.............................
Induction of ouabain-sensitive channel activity by acid pH
by Khater, Kevin, Ph.D., The Herman M. Finch University of Health Sciences - The Chicago Medical School, 1999, 90 pages; AAT 9945848
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Advisor: Rakowski, Robert F.
School: The Herman M. Finch University of Health Sciences - The Chicago Medical School
School Location: United States -- Illinois
Index terms(keywords): Transient currents, Sodium,potassium-ATPase, Ouabain-sensitive, Channel activity, Acid pH
Source: DAI-B 60/09, p. 4465, Mar 2000
Source type: DISSERTATION
Subjects: Biophysics
Publication Number: AAT 9945848
ISBN: 0599476257
Document URL: http://proquest.umi.com.ezproxy.aut...1&sid=1&Fmt=2&clientId=7961&RQT=309&VName=PQD
ProQuest document ID: 730183181

Abstract (Document Summary)

The effect of varying external pH on pre-steady state charge movement and steady state current mediated by the Na + /K + -ATPase was investigated in South African clawed toad ( Xenopus laevis ) oocytes. The experiments focused on determining the characteristics of a ouabain-sensitive inward current induced by acid pH and seen in external K + -free solutions [1] [2-4]. Five experimental techniques were used to study this inward current in Xenopus oocytes. (1) The two-microelectrode voltage clamp technique was used to determine the effect of changes in external [Na + ] on the ouabain-sensitive, current under K + -free external conditions at pH 5.6. High external [Na + ] increased the inward current at moderate membrane potentials (V m more positive than about -60 mV) and inhibited the current at membrane potentials more negative than about -80 mV. (2) The cut-open oocyte vaseline seal technique was used to determine the effects of external acidification on presteady-state transient currents under 3Na + /3Na + exchange conditions. At pH 5.6, an inward current is observed that increased in magnitude when pH was lowered to 4.6 and then 3.6. (3) Simultaneous current and flux measurements in squid ( Loligo peali ) giant axons were performed to determine the characteristics of H 2 DTG-sensitive 22 Na efflux and current at acidic external pH in external Na + - and K + -free solutions. The results showed that at pH 7.7, there is a Na + /K + -ATPase mediated (H 2 DTG-sensitive) 22 Na + efflux (3.8 pmol cm -2 s -1 ) present that increases in magnitude when external pH is lowered to 6.6 (6.8 pmol cm -2 s -1 ). (4) The cell-attached patch clamp technique with a pipette perfusion system was used to observe ouabain-sensitive single channel activity induced by acidic pH. The channel activity had a single channel conductance of 10.5 pS ± 0.0004, a mean open time of 8.05 msec ± 0.99, a mean short closed time constant of 1.93 msec ± 0.14, and a mean long closed time constant of 1220 msec ± 860 (at -100 mV and 100 mM external [Na + ]). A single binding site noncompetitive Na + inhibition model of permeation described the data. We, therefore, conclude that low pH induces a channel-like conformation of the Na + /K + pump.
 

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