bluuebunny/crossref_metadata_2025 huggingface dataset:
A METHOD FOR THE ESTIMATION OF NANOGRAM AMOUNTS OF COBAMIDES AND COBINAMIDES IN SHEEP RUMEN CONTENTS
Authors: Gawthorne JM
Published: December 2007

A method for the estimation of individual cobamides and cobin‐ amides in sheep rumen contents is described. After preliminary extraction and concentration, the cobamides and cobinamides were separated by high‐voltage paper ionophoresis and bioautographed with Escherichia coli 113‐3. The amount of each analogue present was determined by measuring the surface area of growth zones on the bioautogram.
EXPERIMENTAL REPRODUCTION AND HISTO‐PATHOLOGY OF SWAINSONA GALEGIFOLIA POISONING IN THE GUINEA‐PIG
Authors: Huxtable CR
Published: December 2007

A typical pattern of lesions resulting from poisoning by Swainsona galegifolia in the guinea‐pig is described. This appears to be almost identical to that seen in sheep afflicted with this disease.

The possibility that the vacuolar lesions seen may be related to an expression of lysosomal function or to disturbance of cellular water and ion transport mechanisms is discussed.
SOME PROPERTIES OF HUMAN COLOSTRAL CELLS
Authors: Lascelles AK , Gurner BW , Coombs RRA
Published: December 2007

The morphological and some functional properties of the characteristic large monanuclear cells of human colostrum have been studied in vitro. In the 25 samples examined their number varied between 2 × 104 and 6 × 106cells per ml. In Leishman‐stained smears these cells measured up to 40 μ in diameter. Their nuclei were rounded, oval or irregular in shape and were surrounded by either a thick rim of basophilic cytoplasm with a few fat‐filled vacuoles only or, more often, by an even more abundant cytoplasm packed with globular fat

The cells were shown to adhere to glass and to survive in culture for a period of 8 days or longer. The cultured cells spread out on the glass and by 4 days many cells with extremely long cytoplasmic processes (up to 100 μ) were seen. A number of multi‐nucleated cells (giant cells) which were considered to have arisen by cytoplasmic fusion rather than by amitotic division were also observed after 2 days in culture.

The cultured cells were shown to take up large amounts of colloidal carbon, carbonyl iron and colostral fat particles when these substances were added to the culture medium. Cells in fresh monolayers formed directly from colostrum and cells cultured for periods of up to 8 days strongly took up baboon macrophage‐cytophflic antibody.

We failed to detect IgA or other immunoglobulins on the surface of colostral cells in fresh monolayers formed from colostrum, or on cultured cells re‐exposed to human serum or colostrum using the highly sensitive mixed antiglobulin procedure.
TRANSFERRIN AND ALBUMIN DISTRIBUTION AND TURNOVER IN THE RABBIT
Authors: Morgan EH
Published: December 2007

The distribution and turnover of rabbit transferrin and albumin were measured simultaneously in rabbits using 131I‐ and 125I‐labelled purified transferrin and albumin. The plasma volumes determined with either protein were almost identical in 8 normal rabbits and in 4 with haemorrhagic anaemia and increased erythropoiesis. Similarly, the rates of transcapillary passage and relative distribution of the two proteins between intravascular and extravascular spaces were very similar. The fractional turnover rate of transferrin was approximately twice us great as that of albumin, but the absolute turnover of albumin was about 10 times as great as that of transferrin It is concluded that the amount of transferrin bound at cell surfaces in the rabbit is only a very small fraction of the total body transferrin, too small to be measured by the methods used.
PATHOLOGIC CHANGES IN CANINE RENAL ALLOGRAFTS WITH PROLONGED FUNCTION
Authors: Sheil AGR
Published: December 2007

The pathologic changes In 21 long functioning canine renal allografts are presented. A consistent finding was linear areas of tubular and gtomerular atrophy in the cortex in the distribution of interiobular blood vessels. Parenchyma between the radially directed scars was well preserved but there was sometimes glomerular alteration. This consisted of increased density of the glomerular tuft with increase in cellularity affecting both epithelial and endothelial cells. Blood vessel lesions were frequent and changes affecting arteries and arterioles are described. In 6 allografts renal function had deteriorated progressively before death in the manner of “chronic rejection”. Histology revealed accentuation of differing pathologic changes in these cases. In all allografts there was evidence of continuing pathological change.
IMMUNE RESPONSE OF THE TUATARA, SPHENODON PUNCTATUM
Authors: Marchalonis JJ , Ealey EHM , Diener E
Published: December 2007

The tuatara, Sphenodon punctatum, has been shown to produce antibodies to Salmonella adelaide flagellin. The serum of immunized animals contained immunoglobulins which possessed sedimentation coefficients of approx. 18S and 7S. The 18S immunoglobulins resembled the γM immunoglobulins of other vertebrates in size and polypeptide chain structure. The 7S immuneglobulins were antigenically related to the 18S proteins and possessed light chains resembling those of the latter on gel electrophoresis in urea. The heavy chains of the 7S protein differed from those of the macroglobulin, thereby indicating the presence of distinct immunoglobulin classes. Although the immunization period lasted for over eight months, antibody activity was found only in the 18S immunoglobulin.

The lymphoid system of the tuatara was found to be primitive. The only clearly recognizable lymphoid organ in the adult animal was the spleen which showed a definite demarcation into white pulp and red pulp. Injected carbon particles were taken up only by the liver. The foreign particles in this organ were associated with phagocytic cells which resembled the Kupffer‐cells of the mammalian liver.

The fact that this ancient reptile possessed multiple classes of immunogtobulins is consistent with previous findings that distinct immunoglobulin classes, defined by the presence of different heavy chains, were present by the phylogenetic level of higher amphibians.
RESPONSE OF THE PYLORIC AND PYLORIC‐OESOPHAGEAL LIGATED RAT TO INSULIN AND 2 DEOXY‐D‐GLUCOSE
Authors: Hansky J , Soveny Claire
Published: December 2007

Acid secretion of pyloric and pyloric and oesophageal ligated rats has been assessed in response to graded doses of insulin and 2 Deoxy‐D‐glucose and tovagotomy. Neither insulin nor 2 Deoxy‐D‐glucose stimulated acid secretion in the pyloric ligated rat to a significant level above control values, but the pyloric and oesophageal ligated rat responded well to these stimulants. vagotomy markedly decreased acid secretion in the pyloric ligated rat, whereas the pyloric and oesophageal ligated rat showed a slight increase in acid output following vagotomy.

These results suggest that vagal stimulation is the probable reason for the increase in gastric acid secretion produced by ligation of the pylorus in the rat and that reflex vagal inhibition may be the reason for the decreased acid production in this preparation by concomitant oesophageal ligation. They further illustrate the usefulness of the pyloric and oesophageal ligated rat as an assay medium for gastric stimulatory substances.
TISSUE FIBRINOLYTIC ACTIVITY IN OBESITY
Authors: Grace CS , Goldrick RB
Published: December 2007

The fibrinolytic activity of adipose tissue from seven obese and seven lean subjects was studied by incubating biopsy samples on fibrin plates. The obese subjects had normal tissue fibrinolytic activity despite markedly depressed spontaneous blood fibrinolytic activity. There was no correlation between blood and tissue plasminogen activator levels. The tissue activator was associated with the blood vessels and supportive elements of the adipose samples and was not inhibited by the presence of fat cells.
IMMUNOLOGICAL STUDIES OF SHEEP AND GOAT HAEMOGLOBINS
Authors: Agar NS , Evans JV
Published: December 2007

Antisera against the sheep haemogioblins A, B, C and F and the goat haemoglobins A and C were produced in rabbits.

Hb F in sheep was found to be antigenically different from sheep Hb A and Hb B and goat Hb A. Sheep Hb A and Hb B and goat Hb A were shown to be antigenically similar. Haemoglobin C of the sheep and the goat and Hb F of the sheep were also shown to be antigenically similar.

Non‐specific reactions were observed when all the six antisera were tested with the plasma of sheep (Hb A or Hb B), goat (Hb A) and the ox. Neither the haemoglobins not the plasma of the following animal species reacted with (The antisera: horse, dog, rabbit, guinea‐pig, possum, quokka and man.
ISOLATION AND CHARACTERIZATION OF IMMUNOCLOBULIN‐LIKE PROTEINS OF THE AUSTRALIAN LUNGFISH (NEOCERATODUS FORSTERI)
Authors: Marchalonis JJ
Published: December 2007

Proteins resembling immunoglobulins of other vertebrate species in physical and chemical properties were instigated from the serum of unimmunized Australian lungfish (Neoceratodus forsteri). Two types of antigenically related proteins, characterized by sedimentation coefficients of 19.4S and 5.9S, were observed. Both proteins possessed light polypeptide chains which resembled typical immunoglobulin light chains in molecular weight (23,000) and behaviour in gel electrophoresis. The 19.4S proteins were similar to γM immunoglobulins of other vertebrates in size and chain structure. Heavy polypeptide chains from these molecules were comparable to the μ‐chain in molecular weight (70,000) and gel electrophoretic properties. The heavy chain of the 5.9S immunoglobulin‐like protein differed from those of the major classes of vertebrates in possessing a molecular weight of approximately 40,000. In both proteins the light chains and heavy chains were linked through disulfide bonds.

These data suggest that lungfish resemble higher vertebrates in possessing different immunoglobulin classes defined by the presence of distinct heavy chains. The low molecular weight type of immunoglobulin‐like proteins may represent a class of immunoglobulins which is unique to Dipnoi.
IMMUNOELECTROPHORETIC ANALYSIS OF PROTEINS IN LYMPH FROM THE LEG BEFORE AND AFTER THERMAL INJURY
Authors: Roberts JC , Courtice FC
Published: December 2007

Immunoelectrophoresis of lymph from the hind paws of rabbits before and after thermal injuries of differing intensities showed that, when an antiserum to rabbit serum was used all the proteins detected in the circulating blood serum were also present in the lymph. This suggests that all the plasma proteins take part in the increased movement of proteins through the extra‐ cellular fluid phase of an injured tissue.

However, when an antiserum to rabbit lymph collected from thermally Injured paws was employed, Immunoelectrophoresis showed an extra protein in the lymph from injured paws which was not present in normal serum or lymph, or in the serum after injury. This extra protein migrated as a β2‐ or fast γ‐globulin It was found after severe injuries at 70 and 80°, but not after the less severe injuries at 55 to 60°. Its appearance was transient, lasting for only 1 to 2 hr. after injury.

Further experiments showed that this protein was not Cx‐reactive protein and that it was not produced by heating the normal extracellular fluid proteins. Preliminary experiments to test its antigen city within the species have proved negative. The levels of the enzymes lactic dehydrogenase glutamie oxalacetic transaminase and glutamic pyretic transaminase were also increased in the lymph after injury. but experiments by Immunoelectrophoresis suggest that the extra protein is probably not identical with these enzymes.
THE RETENTION OF 125I‐IMMUNOGLOBULINS, IgG SUBUNITS AND ANTIGEN‐ANTIBODY COMPLEXES IN RAT FOOTPADS AND DRAINING LYMPH NODES
Authors: Herd Zana L , Ada GL
Published: December 2007

Studies on the retention of 125I‐labelled rat and rabbit immunoglobulins and subunits thereof in rat popliteal nodes indicate that the Fc fragment of IgG is important for maintaining a relatively high concentration of this immunoglobulin in lymph nodes.

After footpad injections of the immunoglobulins and subunits, an approximate correlation was found between the initial rate of disappearance from the feet and the molecular size of the substances injected. This suggested that a major factor involved in removal of substances from rat footpads is their rate of diffusion. No correlation with molecular weight was fotind in the retention pattern of immunoglobulin subunits in the popliteal nodes which drained the footpads. Rabbit Fc fragment was retained 50 times better than rabbit Fab fragment in rat nodes 3 days after injection. Rabbit H chains were retained better than rabbit L chains.

A peptide from the Fc region of rabbit heavy chains, C3, showed high retention in rat nodes and was retained better than IgG but not as well as Fc. Rat IgG and IgM were both retained better than rat Fab in rets. Human serum albumin complexes with rabbit anti‐human serum albumin IgG was retained at least 10 times better by rat nodes than human serum albumin alone. Human serum albumin bound to rabbit anti‐human serum albumin Fab was retained only about twice as well as human serum albumin alone.
QUANTITATIVE STUDIES ON THE STIMULATION OF MOUSE BONE MARROW COLONY GROWTH IN VITRO BY NORMAL HUMAN URINE
Authors: Metcalf D , Stanley ER
Published: December 2007

Normal human urine was shown to stimulate colony formation in vitro by mouse bone marrow cells. Linear relationships were demonstrated between urine dose and the number and size of colonies stimulated to develop from a standard number of bone marrow cells. These criteria provide an assay system for quantifying levels of colony stimulating factor In human urine. A survey of factor levels in urine from normal subjects indicated that levels appeared to vary over a forty fold range and in any one subject show considerable diurnal and daily variations. Urine factor levels showed no significant variation with age, but showed a partial correlation with protein levels in the urine and were uniformly low when protein excretion was low.
PARTIAL PURIFICATION AND SOME PROPERTIES OF THE FACTOR IN NORMAL AND LEUKAEMIC HUMAN URINE STIMULATING MOUSE BONE MARROW COLONY GROWTH IN VITRO
Authors: Stanley ER , Metcalf D
Published: December 2007

The properties of the factor in human urine which stimulates mouse bone marrow colony growth in vitro were examined. The colony stimulating activity of urine was not lost on concentration of urine, exposure to RNA‐ase, DNA‐ase, ether, 8M urea, pH in the range 2–12, or on fractionation by precipitation with ethanol or ammonium sulphate. Activity was lost on heating (90°/30′), exposure to periodate and incubation with high concentrations of Pronase. There was no difference between the behaviour of the colony stimulating factor in normal and leukaemic human urine concentrates on electrophoresis and on gel‐filtration. The colony stimulating factor in urine concentrates moved in the post‐albumin‐albumin region on electrophoresis at pH 8.6 had an apparent molecular weight of approximately 190,000 on gel‐filtration and an apparent sedimentation coefficient (S20, w) of approximately 3.3S (zone sedimentation on sucrose gradients). A procedure was described for the extraction and partial purification of the colony stimulating factor from large quantities of human urine.

The data suggest that the colony stimulating factor may be a glycoprotein and that it could belong to a family of tissue‐specific humoral growth regulating macromolecules.
THE DEVELOPMENT OE CLONES OE ANTIBODY‐FORMING CELLS IN THE SPLEENS OE IRRADIATED MICE
Authors: Cunningham AJ
Published: December 2007

A markedly non‐random distribution of antibody‐plaque‐forming cells was found in the spleens of lethally irradiated mice which had been injected 5–10 days previously with sheep erythrocytes and 1−2 × 106 syngeneic spleen cells. Localised concentrations (colonies) of 19S and 7S plaque‐forming cells were identified by cutting the spleens transversely into 8 pieces, making dispersed‐cell suspensions from these segments, and testing the suspensions directly with the haemolytic plaque technique. The colonies had an average length of approximately 0.5 mm., with an upper size limit of about 1.5 mm. There was little correlation between the position of these colonies and the position of local concentrations of haemolytic antibody detected by a haemolytic focus method.
THE DEVELOPMENT OF CLONES OF ANTIBODY‐FORMING CELLS IN THE SPLEENS OF IRRADIATED MICE
Authors: Cunningham AJ
Published: December 2007

Localised concentrations of 19S antibody plaque‐forming cells developed in the spleens of lethally irradiated mice which had been injected with syngeneic spleen cells und sheep erythrocytes. Numbers of plaque‐forming cells in such colonies ranged from 28.000 down to less than 40, the largest aggregations appearing after 6–8 days of culture.

Evidence that these colonies were clones came from the finding that, in most cases, all the cells in any one colony released antibody of apparently identical specificity. In addition, the appearance of the plaques themselves was often conspicuously uniform within a colony.

Individual plaque‐forming cells were obtained from 9 colonies by micromanipulation and examined morphologically. In 4 cases all the cells examined from a single colony were closely similar in appearance.

Localized concentrations of cells producing 7S antibody were also found, although these were relatively uncommon. Nearly half of the 7S colonies appeared in the same spleen segments as 19S colonies, statistically a highly significant association which supports the idea of a 19S to 7S antibody switch in the differentiation of some antibody‐forming cell clones.
THE LIFE CYCLE OF VIRULENT TOXOPLASMA IN CELL CULTURES
Authors: Bommer Wolfgang
Published: December 2007

The life cycle of virulent toxoplasma has been studied in slide cell cultures by means of continuous observation using phase microscopy. The active penetration of the host cell membrane by the parasite could be demonstrated by cinematography. Penetration occurs within 15 to 30 seconds. The special mode of toxoplasma division called “endodyogeny” was examined, as well as the development of the rosette‐like terminal colonies of parasites. Virulent toxoplasma destroy their host cells. The free toxoplasma show active mobility and are able to invade new cells.
DELAYED HYPERSENSITIVITY IN MURINE PULMONARY PERTUSSIS
Authors: Cheers Christina
Published: December 2007

A test for delayed hypersensitivity to pertussis antigens in mice has been developed. Unlike other infections in which cellular immunity has been implicated, murine pulmonary pertussis showed no correlation between the onset of bactericidal activity and of cutaneous delayed hypersensitivity. The implications of this finding are discussed in terms of the interdependence of cellular immunity and delayed hypersensitivity.
DISTRIBUTION OF 125I‐IMMUNOGLOBULINS, IgG SUBUNITS AND ANTIGEN‐ANTIBODY COMPLEXES IN RAT LYMPH NODES
Authors: Herd Zana L , Ada GL
Published: December 2007

The ability of rabbit IgG to localize in follicles of rat lymph nodes (heterologous system) has been shown to be due to the Fc fragment. Of the rabbit IgG subunits examined, the H chain and Fc fragment showed follicular localization in rats, while the L chain and Fab fragment did not. Two large peptides from the Fc region of the molecule, C3 and C4, also showed follicuiar localization.

Human serum albumin showed follicular localization in rats only when it was complexed with rabbit anti‐human serum albumin intact IgG. Complexes of human serum albumin with rabbit anti‐human serum albumin Fab fragment did not go to the follicles.

When major subunits of rabbit IgG were injected into rabbits (homologous system) results were qualitatively the same as those obtained in rats, with one exception. Rabbit Fab localized in follicles of rabbit nodes. It was also found the rat Fab localized in rat follicles.

Purified rat IgM has been shown to localize well in rat follicles. All substances examined have shown medullary localization.
FURTHER STUDIES ON ARTIFICIAL ANTIGENS AND IMMUNITY TO MOUSE TYPHOID
Authors: Jackson GDF , Jenkin CR
Published: December 2007

Data presented in this paper show that mice may be protected from infection by Salmonella typhimurium by previous immunisation with a gulactan containing either O‐acetyl or O‐propionyl groups.
ELECTROPHORESIS OF HUMAN SALIVA AND IDENTIFICATION OF INHERITED VARIANTS OF AMYLASE ISOZYMES
Authors: Boettcher B , de la Lande Frances A
Published: December 2007

Saliva specimens have been examined electrophoretically, using polyacrylamide gel slabs. By slicing the stabs in halves, incubating one half‐gel in starch followed by Staining with iodine and staining the other half‐gel with amido black, amylase isozymes are visualized as bands of enzymic activity, up to 8 in number, 4 of which can usually be seen on amido black staining.

Several different isozyme patterns have been observed. The results of pedigree studies suggest simple modes of inheritance of each of the variants. However, because different variants each involve only one or two of the isozymes, it appears that more than one structural gene locus is involved in the production of salivary amylase isozymes.
Quantum reaction rates and sampling of quantum equilibrium structure
Authors: Kim Hyojoon , Kapral Raymond
Published: December 2007

The time dependent quantum reaction rate may be expressed in terms of the Kubo-transformed reactive flux correlation function involving the Kubo-transformed quantum spectral density function W¯A(X,0). The rate constant, which is obtained from the long time limit of this correlation function, can also be expressed in terms of a simple quantum canonical correlation function. In this context, two useful alternative expressions, WA(X,iℏβ/2) and ReWA(X,0), to the difficult-to-compute W¯A(X,0) function are compared. The spectral density WA(X,iℏβ/2) is a real and symmetric approximation to W¯A(X,0) while ReWA(X,0) is a much simpler form obtained from the quantum canonical correlation function. Computations on a simple parabolic barrier crossing problem and a two-level system reactive system confirm that the long time reaction rate constant is the same for all spectral density expressions. Our results show that the density function WA(X,iℏβ/2) may be more suitable for simple model systems while ReWA(X,0) may be more useful for complicated systems involving many degrees of freedom.
Photoelectron spectroscopy of hydrated adenine anions
Authors: Eustis Soren , Wang Di , Lyapustina Svetlana , Bowen Kit H.
Published: December 2007

We report the observation of hydrated adenine anions, A−(H2O)n, n=1–7, and their study by anion photoelectron spectroscopy. Values for photoelectron threshold energies, ET, and vertical detachment energies are tabulated for A−(H2O)n along with those for hydrated uracil anions, U−(H2O)n, which are presented for comparison. Analysis of these and previously measured photoelectron spectra of hydrated nucleobase anions leads to the conclusion that threshold energies significantly overstate electron affinity values in these cases, and that extrapolation of hydrated nucleobase anion threshold values to n=0 leads to incorrect electron affinity values for the nucleobases themselves. Sequential shifts between spectra, however, lead to the conclusion that A−(H2O)3 is likely to be the smallest adiabatically stable, hydrated adenine anion.
Maskless writing of a flexible nanoscale transistor with Au-contacted carbon nanotube electrodes
Authors: Dockendorf Cedric P. R. , Poulikakos Dimos , Hwang Gilgueng , Nelson Bradley J. , Grigoropoulos Costas P.
Published: December 2007

A flexible polymer field effect transistor with a nanoscale carbon nanotube channel is conceptualized and realized herein. Carbon nanotubes (CNTs) were dispersed on a polyimide substrate and marked in an scanning electron microscope with focused ion beam such that they could be contacted with gold nanoink. The CNTs were divided into two parts forming the source and drain of the transistor. A micropipette writing method was used to contact the carbon nanotube electrodes with gold nanoink and to deposit the poly(3-hexylthiophene) as an active layer. The mobility of the transistors is of the order of 10−5cm∕Vs. After fabrication, the flexible transistors can be peeled off the substrate.
Particular strain relaxation for La0.8Ba0.2MnO3 films on SrTiO3 (100) substrates
Authors: Chou Hsiung , Wu C. B. , Yun F. P. , Zhang Z. H. , Chu W. K.
Published: December 2007

A particular two stage strain relaxation phenomenon on La0.8Ba0.2MnO3 thick films has been observed. A fully strained bottom layer near the film/substrate interface consists of a moderate density of dislocations, while a top layer exhibits a high density of dislocations, becoming denser as it nears the surface of the film. This phenomenon can be attributed to the partial diffusion of the substrate element, Sr, into the bottom layer of the film, which reduces its lattice constant, and to the sudden change of the lattice constants at the bottom-top-layer interface due to the stoppage of Sr diffusion.
Surface hardness enhancement in sp3-bonded carbon doped SiC nanocomposite films
Authors: He Xiaodong , Yi Jian , Sun Yue , Xiao Ping , Zhao Xiaofeng
Published: December 2007

The sp3-bonded carbon/SiC composite films have been produced from electron beam-physical vapor deposition of SiC materials. The hardness of such films, measured using Hysitron indentation, reaches 50GPa, which is significantly higher than the hardness of SiC (28GPa). It appears that the superhardness of the thin films is due to the formation of nanocrystalline SiC/diamondlike carbon composites.
High-power wavelength stabilized 970nm tilted cavity laser with a 41.3dB side mode suppression ratio
Authors: Karachinsky L. Ya. , Kuntz M. , Fiol G. , Shchukin V. A. , Ledentsov N. N. , Bimberg D. , Kovsh A. R. , Mikhrin S. S. , Novikov I. I. , Shernyakov Yu. M. , Maximov M. V.
Published: December 2007

We studied wavelength stabilized all-epitaxial 970nm spectral range GaAs∕GaAlAs tilted cavity lasers (TCLs). Single transverse mode edge-emitting 4-μm-wide ridge lasers demonstrated spatial and spectral single mode continuous wave operation with a longitudinal side mode suppression ratio up to 41.3dB. Small signal modulation bandwidth of 3GHz with a resonance peak of 6dB at the relaxation oscillation frequency was measured for a 870μm long device. TCL modulation efficiency is 0.36GHz∕(mA)1∕2. S-parameter measurements indicate that much higher frequencies may be expected in case of more advanced processing and/or shorter cavity lengths.
10
6
years
extrapolated hole storage time in GaSb∕AlAs quantum dots
Authors: Marent A. , Geller M. , Schliwa A. , Feise D. , Pötschke K. , Bimberg D. , Akçay N. , Öncan N.
Published: December 2007

A thermal activation energy of 710meV for hole emission from InAs∕GaAs quantum dots (QDs) across an Al0.9Ga0.1As barrier is determined by using time-resolved capacitance spectroscopy. A hole storage time of 1.6s at room temperature is directly measured, being three orders of magnitude longer than a typical dynamic random access memory (DRAM) refresh time. The dependence of the hole storage time in different III–V QDs on their localization energy is determined and the localization energies in GaSb-based QDs are calculated using eight-band k⋅p theory. A storage time of about 106years in GaSb∕AlAs QDs is extrapolated, sufficient for a QD-based nonvolatile (flash) memory.
Microphotoluminescence evaluation of local strain for freestanding Si membranes with SiN deposition
Authors: Wang Dong , Nakashima Hiroshi , Morioka Jun , Kitamura Tokuhide
Published: December 2007

Microphotoluminescence (PL) was used to evaluate the local strain for freestanding Si membranes, which were fabricated by the mesa etching of Si on insulator followed by etching of the buried oxide. Compressive strain in the membranes was induced by SiN deposition using low-pressure chemical vapor deposition. Strain-induced band gap narrowing was directly observed by identifying the PL peak of the free exciton band-band transition in membranes, from which the strain ratio was estimated for each sample. Strain was reasonably dependent on the sample parameters, which implies that this measurement gives valid results.
Spatial heterogeneity of mesopredator release within an oceanic island system
Authors: Rayner Matt J. , Hauber Mark E. , Imber Michael J. , Stamp Rosalie K. , Clout Mick N.
Published: December 2007

Predator–prey communities are ubiquitous in ecology, but introduced predators can drive native species to extinction within island systems, prompting the eradication of such exotics. Ecological theory predicts that elimination of top-introduced predators from islands can lead to the counterintuitive decline of native prey populations through the ecological release of smaller introduced species in a process termed “mesopredator release.” We show, in accordance with mesopredator release theory and counter to conservation goals for a New Zealand island reserve, that initial eradication of cats on Little Barrier Island led to reduced breeding success of Cook's petrels, which also are vulnerable to predation by a mesopredator, the Pacific rat. The rat's impact on prey productivity varied with elevation within the island. Rat eradication was followed by a rise in petrel productivity, in support of both ecological theory and practical conservation management goals. It appears that interactions among introduced predators, native prey, and environmental gradients can drive counterintuitive and spatially heterogeneous responses to predator eradications from islands. Location-specific, ecosystem-level understanding is essential for predicting the outcomes of such restoration management techniques.
The product of
uncI
gene in F
1
F
o
-ATP synthase operon plays a chaperone-like role to assist
c
-ring assembly
Authors: Suzuki Toshiharu , Ozaki Yoko , Sone Nobuhito , Feniouk Boris A. , Yoshida Masasuke
Published: December 2007

Bacterial operons for F
1
F
o
-ATP synthase typically include an
uncI
gene that encodes a function-unknown small hydrophobic protein. When we expressed a hybrid F
1
F
o
(F
1
from thermophilic
Bacillus
PS3 and Na
+
-translocating F
o
from
Propionigenium modestum
) in
Escherchia coli
cells, we found that
uncI
derived from
P. modestum
was indispensable to produce active enzyme; without
uncI
,
c
-subunits in F
1
F
o
existed as monomers but not as functional
c
11
-ring. When
uncI
was expressed from another plasmid at the same time, active F
1
F
o
with
c
11
-ring was produced. A plasmid containing only
uncI
and
c
-subunit gene produced
c
11
-ring, but a plasmid containing only
c
-subunit gene did not. Direct interaction of UncI protein with
c
-subunits was suggested from copurification of His-tagged UncI protein and
c
-subunits, both in the state of
c
11
-ring and
c
-monomers. Na
+
induced dissociation of His-tagged UncI protein from
c
11
-ring but not from
c
-monomers. These results show that UncI is a chaperone-like protein that assists
c
11
-ring assembly from
c
-monomers in the membrane.
BMP signaling mediates stem/progenitor cell-induced retina regeneration
Authors: Haynes Tracy , Gutierrez Christian , Aycinena Juan-Carlos , Tsonis Panagiotis A. , Del Rio-Tsonis Katia
Published: December 2007

We identified a mechanism whereby retina regeneration in the embryonic chick can be induced by the contribution of stem/progenitor cells. We show that bone morphogenetic protein (BMP) signaling is sufficient and necessary to induce retina regeneration and that its action can be divided into two phases. By 3 days after postretinectomy (d PR), the BMP pathway directs proliferation and regeneration through the activation of Smad (canonical BMP pathway) and the up-regulation of FGF signaling by the MAPK pathway. By 7d PR, it induces apoptosis by activating p38 (a noncanonical BMP pathway) and down-regulating FGF signaling (by both MAPK and AKT pathways). Apoptosis at this later stage can be prevented, and BMP-induced regeneration can be further induced by inhibition of p38. These results unravel a mechanism for stem/progenitor cell-mediated retina regeneration, where BMP activation establishes a cross-talk with the FGF pathway and selectively activates the canonical and noncanonical BMP pathways. Retina stem/progenitor cells exist in other species, including humans. Thus, our findings provide insights on how retinal stem cells can be activated for possible regenerative therapies.
Chemokines and the pathophysiology of neuropathic pain
Authors: White Fletcher A. , Jung Hosung , Miller Richard J.
Published: December 2007

Chemokines and chemokine receptors are widely expressed by cells of the immune and nervous systems. This review focuses on our current knowledge concerning the role of chemokines in the pathophysiology of chronic pain syndromes. Injury- or disease-induced changes in the expression of diverse chemokines and their receptors have been demonstrated in the neural and nonneural elements of pain pathways. Under these circumstances, chemokines have been shown to modulate the electrical activity of neurons by multiple regulatory pathways including increases in neurotransmitter release through Ca-dependent mechanisms and transactivation of transient receptor channels. Either of these mechanisms alone, or in combination, may contribute to sustained excitability of primary afferent and secondary neurons within spinal pain pathways. Another manner in which chemokines may influence sustained neuronal excitability may be their ability to function as excitatory neurotransmitters within the peripheral and central nervous system. As is the case for traditional neurotransmitters, injury-induced up-regulated chemokines are found within synaptic vesicles. Chemokines released after depolarization of the cell membrane can then act on other chemokine receptor-bearing neurons, glia, or immune cells. Because up-regulation of chemokines and their receptors may be one of the mechanisms that directly or indirectly contribute to the development and maintenance of chronic pain, these molecules may then represent novel targets for therapeutic intervention in chronic pain states.
Autophosphorylation-dependent activation of human Mps1 is required for the spindle checkpoint
Authors: Kang Jungseog , Chen Yue , Zhao Yingming , Yu Hongtao
Published: December 2007

The spindle checkpoint ensures the accuracy of chromosome segregation during mitosis. The protein serine/threonine kinase, Mps1, is a critical component of the spindle checkpoint in human cells and regulates the kinetochore localization of key checkpoint proteins. The kinase activity of Mps1 is required for the spindle checkpoint, but how Mps1 is activated during mitosis is unclear. Here, we show that the endogenous Mps1 in mitotic HeLa cells is phosphorylated on T676, a residue in the activation loop. This phosphorylation event on Mps1 is required for its kinase activity
in vitro
and for spindle checkpoint signaling
in vivo
. T676 phosphorylation of Mps1 increases during mitosis and can occur through intermolecular/
trans
autophosphorylation. Induced dimerization of Mps1 is sufficient to activate its kinase activity in cells. We speculate that the kinetochore localization of Mps1 raises its local concentration, leading to its activation during mitosis through more efficient
trans
autophosphorylation.
GABA
A
-current rundown of temporal lobe epilepsy is associated with repetitive activation of GABA
A
“phasic” receptors
Authors: Palma Eleonora , Roseti Cristina , Maiolino Francesca , Fucile Sergio , Martinello Katiuscia , Mazzuferi Manuela , Aronica Eleonora , Manfredi Mario , Esposito Vincenzo , Cantore Gianpaolo , Miledi Ricardo , Simonato Michele , Eusebi Fabrizio
Published: December 2007

A study was made of the “rundown” of GABA
A
receptors, microtransplanted to
Xenopus
oocytes from surgically resected brain tissues of patients afflicted with drug-resistant human mesial temporal lobe epilepsy (mTLE). Cell membranes, isolated from mTLE neocortex specimens, were injected into frog oocytes that rapidly incorporated functional GABA
A
receptors. Upon repetitive activation with GABA (1 mM), “epileptic” GABA
A
receptors exhibited a GABA
A
-current (
I
GABA
) rundown that was significantly enhanced by Zn
2+
(≤250 μM), and practically abolished by the high-affinity GABA
A
receptor inverse agonist SR95531 (gabazine; 2.5–25 μM). Conversely,
I
GABA
generated by “control” GABA
A
receptors microtransplanted from nonepileptic temporal lobe, lesional TLE, or authoptic disease-free tissues remained stable during repetitive stimulation, even in oocytes treated with Zn
2+
. We conclude that rundown of mTLE epileptic receptors depends on the presence of “phasic GABA
A
receptors” that have low sensitivity to antagonism by Zn
2+
. Additionally, we found that GABA
A
receptors, microtransplanted from the cerebral cortex of adult rats exhibiting recurrent seizures, caused by pilocarpine-induced status epilepticus, showed greater rundown than control tissue, an event also occurring in patch-clamped rat pyramidal neurons. Rundown of epileptic rat receptors resembled that of human mTLE receptors, being enhanced by Zn
2+
(40 μM) and sensitive to the antiepileptic agent levetiracetam, the neurotrophin brain-derived neurotrophic factor, and the phosphatase blocker okadaic acid. Our findings point to the rundown of GABA
A
receptors as a hallmark of TLE and suggest that modulating tonic and phasic mTLE GABA
A
receptor activity may represent a useful therapeutic approach to the disease.
Charge Scan Reveals an Extended Region at the Intracellular End of the GABA Receptor Pore that Can Influence Ion Selectivity
Authors: Wotring Virginia E. , Weiss David S.
Published: December 2007

Selective permeability is a fundamental property of ion channels. The Cys-loop receptor superfamily is composed of both excitatory (ACh, 5-HT) and inhibitory (GABA, glycine) neurotransmitter-operated ion channels. In the GABA receptor, it has been previously shown that the charge selectivity of the integral pore can be altered by a single mutation near the intracellular end of the second transmembrane-spanning domain (TM2). We have extended these findings and now show that charge selectivity of the anionic ρ1 GABA receptor can be influenced by the introduction of glutamates, one at a time, over an 8–amino acid stretch (−2′ to 5′) in the proposed intracellular end of TM2 and the TM1–TM2 intracellular linker. Depending on the position, glutamate substitutions in this region produced sodium to chloride permeability ratios (PNa+/Cl−) varying from 0.64 to 3.4 (wild type PNa+/Cl− = 0). In addition to providing insight into the mechanism of ion selectivity, this functional evidence supports a model proposed for the homologous nicotinic acetylcholine receptor in which regions of the protein, in addition to TM2, form the ion pathway.
Incorporating gene networks into statistical tests for genomic data via a spatially correlated mixture model
Authors: Wei Peng , Pan Wei
Published: December 2007

Motivation: It is a common task in genomic studies to identify a subset of the genes satisfying certain conditions, such as differentially expressed genes or regulatory target genes of a transcription factor (TF). This can be formulated as a statistical hypothesis testing problem. Most existing approaches treat the genes as having an identical and independent distribution a priori, testing each gene independently or testing some subsets of the genes one by one. On the other hand, it is known that the genes work coordinately as dictated by gene networks. Treating genes equally and independently ignores the important information contained in gene networks, leading to inefficient analysis and reduced power.

Results: We propose incorporating gene network information into statistical analysis of genomic data. Specifically, rather than treating the genes equally and independently a priori in a standard mixture model, we assume that gene-specific prior probabilities are correlated as induced by a gene network: while the genes are allowed to have different prior probabilities, those neighboring ones in the network have similar prior probabilities, reflecting their shared biological functions. We applied the two approaches to a real ChIP-chip dataset (and simulated data) to identify the transcriptional target genes of TF GCN4. The new method was found to be more powerful in discovering the target genes.

Contact:  weip@biostat.umn.edu
Real-Time PCR-Based Monitoring of DNA Pools in the Tri-Trophic Interaction Between Norway Spruce, the Rust Thekopsora areolata, and an Opportunistic Ascomycetous Phomopsis sp.
Authors: Hietala Ari M. , Solheim Halvor , Fossdal Carl Gunnar
Published: December 2007

The difficulty in subculturing biotrophic fungi complicates etiological studies related to the associated plant diseases. By employing internal transcribed spacer rDNA-targeted quantitative real-time polymerase chain reaction, we now show that the heteroecious rust Thekopsora areolata, commonly associated in natural conditions to sapling shoots and cones of Norway spruce and leaves of wild bird cherry, frequently infects nursery-grown seedlings of the conifer. A spatial sampling scheme was used to investigate seedlings and saplings of Norway spruce showing phloem necrosis: the highest concentration of DNA of T. areolata was recorded in the area with necrotic phloem. The separate analysis of bark and wood tissues suggested that the initial spread of the rust to healthy tissues neighboring the infection site takes place in the bark. A Phomopsis species found to coexist with T. areolata in several seedlings showed very high DNA levels in the upper part of the lesion, and even in the visually healthy proximal tissues above the lesions, which indicates that the ascomycete, most probably a secondary invader following primary infection by T. areolata, has a latent stage during early host colonization. We hypothesize that this hemibiotrophic mode of infection contributes to the successful coexistence of Phomopsis with a biotrophic rust.
Rainfall and Temperature Distinguish Between Karnal Bunt Positive and Negative Years in Wheat Fields in Texas
Authors: Workneh F. , Allen T. W. , Nash G. H. , Narasimhan B. , Srinivasan R. , Rush C. M.
Published: December 2007

Karnal bunt of wheat, caused by the fungus Tilletia indica, is an internationally regulated disease. Since its first detection in central Texas in 1997, regions in which the disease was detected have been under strict federal quarantine regulations resulting in significant economic losses. A study was conducted to determine the effect of weather factors on incidence of the disease since its first detection in Texas. Weather variables (temperature and rainfall amount and frequency) were collected and used as predictors in discriminant analysis for classifying bunt-positive and -negative fields using incidence data for 1997 and 2000 to 2003 in San Saba County. Rainfall amount and frequency were obtained from radar (Doppler radar) measurements. The three weather variables correctly classified 100% of the cases into bunt-positive or -negative fields during the specific period overlapping the stage of wheat susceptibility (boot to soft dough) in the region. A linear discriminant-function model then was developed for use in classification of new weather variables into the bunt occurrence groups (+ or –). The model was evaluated using weather data for 2004 to 2006 for San Saba area (central Texas), and data for 2001 and 2002 for Olney area (north-central Texas). The model correctly predicted bunt occurrence in all cases except for the year 2004. The model was also evaluated for site-specific prediction of the disease using radar rainfall data and in most cases provided similar results as the regional level evaluation. The humid thermal index (HTI) model (widely used for assessing risk of Karnal bunt) agreed with our model in all cases in the regional level evaluation, including the year 2004 for the San Saba area, except for the Olney area where it incorrectly predicted weather conditions in 2001 as unfavorable. The current model has a potential to be used in a spray advisory program in regulated wheat fields.
Quantitative systems-level determinants of human genes targeted by successful drugs
Authors: Yao Lixia , Rzhetsky Andrey
Published: December 2007

What makes a successful drug target? A target molecule with an appropriate (druggable) tertiary structure is a necessary but not the sufficient condition for success. Here we analyzed specific properties of human genes and proteins targeted by 919 FDA-approved drugs and identified several quantitative measures that distinguish them from other genes and proteins at a highly significant level. Compared to an average gene and its encoded protein(s), successful drug targets are more highly connected (but far from being the most highly connected), have higher betweenness values, lower entropies of tissue expression, and lower ratios of nonsynonymous to synonymous single-nucleotide polymorphisms. Furthermore, we have identified human tissues that are significantly over- or undertargeted relative to the full spectrum of genes that are active in each tissue. Our study provides quantitative guidelines that could aid in the computational screening of new drug targets in human cells.
Gene number expansion and contraction in vertebrate genomes with respect to invertebrate genomes
Authors: Prachumwat Anuphap , Li Wen-Hsiung
Published: December 2007

Where did vertebrate genes come from? Here we address this question by analyzing eight completely sequenced land vertebrate genomes and six completely sequenced invertebrate genomes. Approximately 70% of the vertebrate genes can be found in the six invertebrate genomes with the standard homology search criteria (denoted as V.MCL), another ∼6% can be found with relaxed search criteria, and an additional ∼2% can be found in sequenced fungal and bacterial genomes. Thus, a substantial proportion of vertebrate genes (∼22%) cannot be found in the nonvertebrate genomes studied (denoted as Vonly). Interestingly, genes in Vonly are predominantly singletons, while the majority of genes in the other three groups belong to gene families. The proteins of Vonly tend to evolve faster than those of V.MCL. Surprisingly, in many cases the family sizes in V.MCL are only as large as or even smaller than their counterparts in the invertebrates, contrary to the general perception of a larger family size in vertebrates. Interestingly, in comparison with the family size in invertebrates, vertebrate gene families involved in regulation, signal transduction, transcription, protein transport, and protein modification tend to be expanded, whereas those involved in metabolic processes tend to be contracted. Furthermore, for almost all of the functional categories with family size expansion in vertebrates, the number of gene types (i.e., the number of singletons plus the number of gene families) tends to be over-represented in Vonly, but under-represented in V.MCL. Our study suggests that gene function is a major determinant of gene family size.
Short read fragment assembly of bacterial genomes
Authors: Chaisson Mark J. , Pevzner Pavel A.
Published: December 2007

In the last year, high-throughput sequencing technologies have progressed from proof-of-concept to production quality. While these methods produce high-quality reads, they have yet to produce reads comparable in length to Sanger-based sequencing. Current fragment assembly algorithms have been implemented and optimized for mate-paired Sanger-based reads, and thus do not perform well on short reads produced by short read technologies. We present a new Eulerian assembler that generates nearly optimal short read assemblies of bacterial genomes and describe an approach to assemble reads in the case of the popular hybrid protocol when short and long Sanger-based reads are combined.