bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal structure of elongation factor P from
Thermus thermophilus
HB8
Authors: Hanawa-Suetsugu Kyoko , Sekine Shun-ichi , Sakai Hiroaki , Hori-Takemoto Chie , Terada Takaho , Unzai Satoru , Tame Jeremy R. H. , Kuramitsu Seiki , Shirouzu Mikako , Yokoyama Shigeyuki
Published: June 2004

Translation elongation factor P (EF-P) stimulates ribosomal peptidyltransferase activity. EF-P is conserved in bacteria and is essential for cell viability. Eukarya and Archaea have an EF-P homologue, eukaryotic initiation factor 5A (eIF-5A). In the present study, we determined the crystal structure of EF-P from
Thermus thermophilus
HB8 at a 1.65-Å resolution. EF-P consists of three β-barrel domains (I, II, and III), whereas eIF-5A has only two domains (N and C domains). Domain I of EF-P is topologically the same as the N domain of eIF-5A. On the other hand, EF-P domains II and III share the same topology as that of the eIF-5A C domain, indicating that domains II and III arose by duplication. Intriguingly, the N-terminal half of domain II and the C-terminal half of domain III of EF-P have sequence homologies to the N- and C-terminal halves, respectively, of the eIF-5A C domain. The three domains of EF-P are arranged in an “L” shape, with 65- and 53-Å-long arms at an angle of 95°, which is reminiscent of tRNA. Furthermore, most of the EF-P protein surface is negatively charged. Therefore, EF-P mimics the tRNA shape but uses domain topologies different from those of the known tRNA-mimicry translation factors. Domain I of EF-P has a conserved positive charge at its tip, like the eIF-5A N domain.
Relating microstructure to rheology of a bundled and cross-linked F-actin networkin vitro
Authors: Shin J. H. , Gardel M. L. , Mahadevan L. , Matsudaira P. , Weitz D. A.
Published: June 2004

The organization of individual actin filaments into higher-order structures is controlled by actin-binding proteins (ABPs). Although the biological significance of the ABPs is well documented, little is known about how bundling and cross-linking quantitatively affect the microstructure and mechanical properties of actin networks. Here we quantify the effect of the ABP scruin on actin networks by using imaging techniques, cosedimentation assays, multiparticle tracking, and bulk rheology. We show how the structure of the actin network is modified as the scruin concentration is varied, and we correlate these structural changes to variations in the resultant network elasticity.
Insulin-like growth factor I is required for vessel remodeling in the adult brain
Authors: Lopez-Lopez C. , LeRoith D. , Torres-Aleman I.
Published: June 2004

Although vascular dysfunction is a major suspect in the etiology of several important neurodegenerative diseases, the signals involved in vessel homeostasis in the brain are still poorly understood. We have determined whether insulin-like growth factor I (IGF-I), a wide-spectrum growth factor with angiogenic actions, participates in vascular remodeling in the adult brain. IGF-I induces the growth of cultured brain endothelial cells through hypoxiainducible factor 1α and vascular endothelial growth factor, a canonical angiogenic pathway. Furthermore, the systemic injection of IGF-I in adult mice increases brain vessel density. Physical exercise that stimulates widespread brain vessel growth in normal mice fails to do so in mice with low serum IGF-I. Brain injury that stimulates angiogenesis at the injury site also requires IGF-I to promote perilesion vessel growth, because blockade of IGF-I input by an anti-IGF-I abrogates vascular growth at the injury site. Thus, IGF-I participates in vessel remodeling in the adult brain. Low serum/brain IGF-I levels that are associated with old age and with several neurodegenerative diseases may be related to an increased risk of vascular dysfunction.
Crystal structure of phosphodiesterase 9 shows orientation variation of inhibitor 3-isobutyl-1-methylxanthine binding
Authors: Huai Qing , Wang Huanchen , Zhang Wei , Colman Robert W. , Robinson Howard , Ke Hengming
Published: June 2004

Cyclic nucleotide phosphodiesterases (PDEs) are enzymes controlling cellular concentrations of the second messengers cAMP and cGMP. The crystal structure of the catalytic domain of PDE9A2, a member of a PDE family specifically hydrolyzing cGMP, has been determined at 2.23-Å resolution. The PDE9A2 catalytic domain closely resembles the cAMP-specific PDE4D2 but is significantly different from the cGMP-specific PDE5A1, implying that each individual PDE family has its own characteristic substrate recognition mechanism. The different conformations of the H and M loops between PDE9A2 and PDE5A1 imply their less critical roles in nucleotide recognition. The nonselective inhibitor 3-isobutyl-1-methylxanthine (IBMX) binds to a similar subpocket in the active sites of PDE4, PDE5, and PDE9 and has a common pattern of the binding. However, significantly different orientations and interactions of IBMXs are observed among the three PDE families and also between two monomers of the PDE9A2 dimer. The kinetic properties of the PDE9A2 catalytic domain similar to those of full-length PDE9A imply that the N-terminal regulatory domain does not significantly alter the catalytic activity and the IBMX inhibition.
A family of conserved bacterial effectors inhibits salicylic acid-mediated basal immunity and promotes disease necrosis in plants
Authors: DebRoy Sruti , Thilmony Roger , Kwack Yong-Bum , Nomura Kinya , He Sheng Yang
Published: June 2004

Salicylic acid (SA)-mediated host immunity plays a central role in combating microbial pathogens in plants. Inactivation of SA-mediated immunity, therefore, would be a critical step in the evolution of a successful plant pathogen. It is known that mutations in conserved effector loci (CEL) in the plant pathogens
Pseudomonas syringae
(the ΔCEL mutation),
Erwinia amylovora
(the
dspA
/
E
mutation), and
Pantoea stewartii
subsp.
stewartii
(the
wtsE
mutation) exert particularly strong negative effects on bacterial virulence in their host plants by unknown mechanisms. We found that the loss of virulence in ΔCEL and
dspA
/
E
mutants was linked to their inability to suppress cell wall-based defenses and to cause normal disease necrosis in
Arabidopsis
and apple host plants. The ΔCEL mutant activated SA-dependent callose deposition in wild-type
Arabidopsis
but failed to elicit high levels of callose-associated defense in
Arabidopsis
plants blocked in SA accumulation or synthesis. This mutant also multiplied more aggressively in SA-deficient plants than in wild-type plants. The
hopPtoM
and
avrE
genes in the CEL of
P. syringae
were found to encode suppressors of this SA-dependent basal defense. The widespread conservation of the HopPtoM and AvrE families of effectors in various bacteria suggests that suppression of SA-dependent basal immunity and promotion of host cell death are important virulence strategies for bacterial infection of plants.
Total synthesis of the cytotoxic cyclodepsipeptide (-)-doliculide: The “ester” effect in acyclic 1,3-induction of deoxypropionates
Authors: Hanessian Stephen , Mascitti Vincent , Giroux Simon
Published: June 2004

The total synthesis of the marine cyclodepsipeptide (-)-doliculide is described. An acyclic (2
S
,4
S
,6
R
)-trimethyl alkanoic acid precursor to the “hydrocarbon” portion of doliculide was synthesized starting with
l
-ascorbic acid based on a stereocontrolled iterative conjugate addition of lithium dimethylcuprate to acyclic δ-
C
methyl α,β-unsaturated ester derivatives.
syn/syn
selectivity was achieved by relying on 1,3-induction in preferred folded conformations that avoid 1,5-
syn
–pentane interactions in the transition states. The nature of the ester moiety seems to play an important role in determining the
syn/anti
ratios of
C
-methyl adducts. The 1-methyl-1-cyclopentyl ester group was found to confer the best
syn
selectivity to the cuprate addition products, especially in seven-carbon enoates.
Unified synthesis of caged
Garcinia
natural products based on a site-selective Claisen/Diels–Alder/Claisen rearrangement
Authors: Tisdale Eric J. , Slobodov Irina , Theodorakis Emmanuel A.
Published: June 2004

A unified synthetic strategy toward caged
Garcinia
natural products has been designed and implemented. Central to the strategy is a tandem Claisen/Diels–Alder/Claisen rearrangement of a suitably substituted xanthone precursor to form forbesione (1a). Serving as a template, forbesione is then used to deliver representative members of this family, including desoxygaudichaudione A (4), desoxymorellin (5), and gambogin (10). Studies on the timing of this reaction cascade suggest that the C-ring Claisen/Diels–Alder rearrangement proceeds initially and is followed by the A-ring Claisen reaction. The electronic and steric effects that govern the outcome of this cascade are presented.
Gravitational vacuum condensate stars
Authors: Mazur Pawel O. , Mottola Emil
Published: June 2004

A new final state of gravitational collapse is proposed. By extending the concept of Bose–Einstein condensation to gravitational systems, a cold, dark, compact object with an interior de Sitter condensate

p
v

= -ρ

v

and an exterior Schwarzschild geometry of arbitrary total mass
M
is constructed. These regions are separated by a shell with a small but finite proper thickness ℓ of fluid with equation of state
p
= +ρ
,
replacing both the Schwarzschild and de Sitter classical horizons. The new solution has no singularities, no event horizons, and a global time. Its entropy is maximized under small fluctuations and is given by the standard hydrodynamic entropy of the thin shell, which is of the order
k
B
ℓ
Mc
/

, instead of the Bekenstein–Hawking entropy formula,
S
BH
=
4
π
k
B

GM
2

/

c
. Hence, unlike black holes, the new solution is thermodynamically stable and has no information paradox.
Prolonged hyperpolarizing potentials precede spindle oscillations in the thalamic reticular nucleus
Authors: Fuentealba Pablo , Timofeev Igor , Steriade Mircea
Published: June 2004

The thalamic reticular (RE) nucleus is a key structure in the generation of spindles, a hallmark bioelectrical oscillation during early stages of sleep. Intracellular recordings of RE neurons
in vivo
revealed the presence of prolonged hyperpolarizing potentials preceding spindles in a subgroup (30%) of neurons. These hyperpolarizations (6-10 mV) lasted for 200-300 ms and were present just before the onset of spontaneously occurring spindle waves. Corticothalamic volleys also were effective in generating such hyperpolarizations followed by spindles in RE neurons. A drop of up to 40% in the apparent input resistance (
R
in
) was associated with these hyperpolarizing potentials, suggesting an active process rather than disfacilitation. Accordingly, the reversal potential was approximately -100 mV for both spontaneous and cortically elicited hyperpolarizations, consistent with the activation of slow K
+
conductances. QX-314 in the recording pipettes decreased both the amplitude and incidence of prolonged hyperpolarizations, suggesting the participation of G protein-dependent K
+
currents in the generation of hyperpolarizations. Simultaneous extracellular and intracellular recordings in the RE nucleus demonstrated that some RE neurons discharged during the hyperpolarizations and, thus, may be implicated in their generation. The prolonged hyperpolarizations preceding spindles may play a role in the transition from tonic to bursting firing of RE neurons within a range of membrane potential (-60 to -65 mV) at which they set favorable conditions for the generation of low-threshold spike bursts that initiate spindle sequences. These data are further arguments for the generation of spindles within the thalamic RE nucleus.
Targeting expression of expanded polyglutamine proteins to the endoplasmic reticulum or mitochondria prevents their aggregation
Authors: Rousseau Erwann , Dehay Benjamin , Ben-Haïem Léa , Trottier Yvon , Morange Michel , Bertolotti Anne
Published: June 2004

Aggregation of misfolded proteins is a characteristic of several neurodegenerative diseases. The huntingtin amino-terminal fragment with extended polyglutamine repeat forms aggregates closely associated with chaperones both in the cytoplasm and the nucleus. Because each cellular compartment contains distinct chaperones and because the molecular mechanisms controlling polyglutamine aggregation are largely unknown, we decided to investigate the influence of different cellular environments on the aggregation of this pathological protein. Here, we show that aggregation of a protein containing a polyglutamine stretch of pathological length is abolished when its expression is targeted to the endoplasmic reticulum. Once retrogradely transported outside the endoplasmic reticulum, the aggregation-prone polyglutamine-containing protein recovers its ability to aggregate. When expressed in the mitochondria, a protein containing 73 glutamines is entirely soluble, whereas the nucleocytosolic equivalent has an extremely high tendency to aggregate. Our data imply that polyglutamine aggregation is a property restricted to the nucleocytosolic compartment and suggest the existence of compartment-specific cofactors promoting or preventing aggregation of pathological proteins.
Acute neuroprotective synergy of erythropoietin and insulin-like growth factor I
Authors: Digicaylioglu Murat , Garden Gwenn , Timberlake Sonia , Fletcher Lauren , Lipton Stuart A.
Published: June 2004

Erythropoietin (EPO) and insulin-like growth factor I (IGF-I) are cytokines that inhibit neuronal apoptosis. However, their maximal antiapoptotic effect, even at high concentrations, is observed only when neurons are pretreated for several hours before insult. Here we show that simultaneous administration of EPO and IGF-I (EPO+IGF-I) eliminates the preincubation period required to prevent
N
-methyl-
d
-aspartate (NMDA)-induced apoptosis in cultured rat cerebrocortical neurons. The synergistic effect of EPO+IGF-I was mediated, at least in part, by activation of phosphatidylinositol 3-kinase (PI3-K). EPO+IGF-I synergistically activated Akt (protein kinase B), a downstream target of PI3-K, and prevented dephosphorylation of Akt. Overexpression of a dominant interfering form of Akt (dnAkt) abrogated EPO+IGF-I-mediated neuroprotection. EPO+IGF-I treatment did not prevent initial NMDA-induced caspase-3 activation, which was observed within 6 h of insult; however, EPO+IGF-I-treated neurons survived at least 2 days after NMDA insult. These cytokines prevented neuronal apoptosis downstream of caspase activation by facilitating association between X-linked inhibitor of apoptosis protein, an inhibitor of caspase proteolytic activity, and activated caspase-3. These results imply that EPO+IGF-I exert cooperative actions that afford acute neuroprotection via activation of the PI3-K-Akt pathway.
Nicotinic receptors regulate the survival of newborn neurons in the adult olfactory bulb
Authors: Mechawar Naguib , Saghatelyan Armen , Grailhe Régis , Scoriels Linda , Gheusi Gilles , Gabellec Marie-Madeleine , Lledo Pierre-Marie , Changeux Jean-Pierre
Published: June 2004

Cholinergic axons and nicotinic receptors are abundant in all layers of the olfactory bulb (OB), the main region of newborn neuron integration in the adult brain. Here, we report that the OB granule cell layer in mice lacking the predominant form of brain high-affinity nicotinic acetylcholine receptors (β
2
-/-
mice) displayed nearly 50% more newborn neurons and significantly fewer apoptotic cells than did β
2
+/+
mice. Conversely,
in vivo
chronic nicotine exposure significantly decreased the number of newborn granule cells in β
2
+/+
but not β
2
-/-
adult mice, confirming that the survival of newborn neurons can be controlled by the activation of β
2
-containing nicotinic acetylcholine receptors. Unexpectedly, investigating the behavioral consequence of an increased number of granule cells in β
2
-/-
mice revealed that these animals have a less robust short-term olfactory memory than their wild-type counterparts. Taken together, these results provide evidence that high-affinity nicotinic receptors are involved in the maturation of adult OB local circuits. They also indicate that an increase in the number of granule cells does not necessarily correlate with better olfactory performance and further highlight the importance of cholinergic afferents for olfactory processing.
Identification of tandem duplicate regulatory small RNAs in
Pseudomonas aeruginosa
involved in iron homeostasis
Authors: Wilderman Paula J. , Sowa Nathaniel A. , FitzGerald David J. , FitzGerald Peter C. , Gottesman Susan , Ochsner Urs A. , Vasil Michael L.
Published: June 2004

In many bacteria, iron homeostasis is controlled primarily by the ferric uptake regulator (Fur), a transcriptional repressor. However, some genes, including those involved in iron storage, are positively regulated by Fur. A Fur-repressed regulatory small RNA (sRNA), RyhB, has been identified in
Escherichia coli
, and it has been demonstrated that negative regulation of genes by this sRNA is responsible for the positive regulation of some genes by Fur. No RyhB sequence homologs were found in
Pseudomonas aeruginosa
, despite the identification of genes positively regulated by its Fur homolog. A bioinformatics approach identified two tandem sRNAs in
P. aeruginosa
that were candidates for functional homologs of RyhB. These sRNAs (PrrF1 and PrrF2) are >95% identical to each other, and a functional Fur box precedes each. Their expression is induced under iron limitation. Deletion of both sRNAs is required to affect the iron-dependent regulation of an array of genes, including those involved in resistance to oxidative stress, iron storage, and intermediary metabolism. As in
E. coli
, induction of the PrrF sRNAs leads to the rapid loss of mRNAs for
sodB
(superoxide dismutase),
sdh
(succinate dehydrogenase), and a gene encoding a bacterioferritin. Thus, the PrrF sRNAs are the functional homologs of RyhB sRNA. At least one gene,
bfrB
, is positively regulated by Fur and Fe
2+
, even in the absence of the PrrF sRNAs. This work suggests that the role of sRNAs in bacterial iron homeostasis may be broad, and approaches similar to those described here may identify these sRNAs in other organisms.
Functional variants within the secreted frizzled-related protein 3 gene are associated with hip osteoarthritis in females
Authors: Loughlin John , Dowling Barbara , Chapman Kay , Marcelline Lucy , Mustafa Zehra , Southam Lorraine , Ferreira Athena , Ciesielski Cathleen , Carson Dennis A. , Corr Maripat
Published: June 2004

Osteoarthritis (OA) is a leading cause of disability in Western society with multiple risk factors, including a complex genetic pattern. Identifying loci involved in the heredity of OA might lead to insights into the molecular pathogenesis of this common disorder. A previous genome scan mapped a primary hip OA susceptibility locus to chromosome 2q with a maximum multipoint logarithm of odds score of 1.6 in 378 affected sibling pair families. Here, microsatellite targeting of eight candidate genes in this region from 2q23-2q32 demonstrated significant associations with thetumor necrosis factorα-induced protein 6gene in all probands and theintegrinα6andfrizzled motif associated with bone development(FRZB) genes in female probands. However, genotyping showed lack of association for a nonsynonymous single-nucleotide polymorphism intumor necrosis factorα-induced protein 6, whereas a single-nucleotide polymorphism inFRZBresulting in an Arg324Gly substitution at the carboxyl terminus was associated with hip OA in the female probands (P= 0.04). This association was confirmed in an independent cohort of female hip cases (n= 338;P= 0.04). In addition, a haplotype coding for substitutions of two highly conserved arginine residues (Arg200Trp and Arg324Gly) inFRZBwas a strong risk factor for primary hip OA, with an odds ratio of 4.1 (P= 0.004). FRZB encodes secreted frizzled-related protein 3, which is a soluble antagonist of wingless (wnt) signaling. Variant secreted frizzled-related protein 3 with the Arg324Gly substitution had diminished ability to antagonize wnt signalingin vitro. Hence, functional polymorphisms withinFRZBconfer susceptibility for hip OA in females and implicate the wnt signaling pathway in the pathogenesis of this disease.
The role of iron and copper molecules in the neuronal vulnerability of locus coeruleus and substantia nigra during aging
Authors: Zecca Luigi , Stroppolo Antonella , Gatti Alberto , Tampellini Davide , Toscani Marco , Gallorini Mario , Giaveri Giuseppe , Arosio Paolo , Santambrogio Paolo , Fariello Ruggero G. , Karatekin Erdem , Kleinman Mark H. , Turro Nicholas , Hornykiewicz Oleh , Zucca Fabio A.
Published: June 2004

In this study, a comparative analysis of metal-related neuronal vulnerability was performed in two brainstem nuclei, the locus coeruleus (LC) and substantia nigra (SN), known targets of the etiological noxae in Parkinson's disease and related disorders. LC and SN pars compacta neurons both degenerate in Parkinson's disease and other Parkinsonisms; however, LC neurons are comparatively less affected and with a variable degree of involvement. In this study, iron, copper, and their major molecular forms like ferritins, ceruloplasmin, neuromelanin (NM), manganese-superoxide dismutase (SOD), and copper/zinc-SOD were measured in LC and SN of normal subjects at different ages. Iron content in LC was much lower than that in SN, and the ratio heavy-chain ferritin/iron in LC was higher than in the SN. The NM concentration was similar in LC and SN, but the iron content in NM of LC was much lower than SN. In both regions, heavy- and light-chain ferritins were present only in glia and were not detectable in neurons. These data suggest that in LC neurons, the iron mobilization and toxicity is lower than that in SN and is efficiently buffered by NM. The bigger damage occurring in SN could be related to the higher content of iron. Ferritins accomplish the same function of buffering iron in glial cells. Ceruloplasmin levels were similar in LC and SN, but copper was higher in LC. However, the copper content in NM of LC was higher than that of SN, indicating a higher copper mobilization in LC neurons. Manganese-SOD and copper/zinc-SOD had similar age trend in LC and SN. These results may explain at least one of the reasons underlying lower vulnerability of LC compared to SN in Parkinsonian syndromes.
ATP-binding cassette transporters G1 and G4 mediate cellular cholesterol efflux to high-density lipoproteins
Authors: Wang Nan , Lan Debin , Chen Wengen , Matsuura Fumihiko , Tall Alan R.
Published: June 2004

The mechanisms responsible for the inverse relationship between plasma high-density lipoprotein (HDL) levels and atherosclerotic cardiovascular disease are poorly understood. The ATP-binding cassette transporter A1 (ABCA1) mediates efflux of cellular cholesterol to lipid-poor apolipoproteins but not to HDL particles that constitute the bulk of plasma HDL. We show that two ABC transporters of unknown function, ABCG1 and ABCG4, mediate isotopic and net mass efflux of cellular cholesterol to HDL. In transfected 293 cells, ABCG1 and ABCG4 stimulate cholesterol efflux to both smaller (HDL-3) and larger (HDL-2) subclasses but not to lipid-poor apoA-I. Treatment of macrophages with an liver X receptor activator results in up-regulation of ABCG1 and increases cholesterol efflux to HDL. RNA interference reduced the expression of ABCG1 in liver X receptor-activated macrophages and caused a parallel decrease in cholesterol efflux to HDL. These studies indicate that ABCG1 and ABCG4 promote cholesterol efflux from cells to HDL. ABCG1 is highly expressed in macrophages and probably mediates cholesterol efflux from macrophage foam cells to the major HDL fractions, providing a mechanism to explain the relationship between HDL levels and atherosclerosis risk.
A molecular link between SR protein dephosphorylation and mRNA export
Authors: Huang Yingqun , Yario Therese A. , Steitz Joan A.
Published: June 2004

In metazoans, multiple RNA-binding proteins, including the shuttling serine/arginine-rich (SR)-splicing factors, function as adapters for mRNA nuclear export by interacting with the export receptor TAP/nuclear export factor 1 (NXF1). Yet, it is unclear how interactions between adapters and TAP are regulated. Here, we demonstrate that the SR proteins 9G8 and ASF/SF2 exhibit higher affinity for TAP/NXF1 when hypophosphorylated. 9G8 is recruited to the pre-mRNA in a hyperphosphorylated form but becomes hypophosphorylated during splicing both
in vivo
and
in vitro
. TAP preferentially binds spliced mRNA–protein complexes compared with pre-mRNA–protein complexes. Thus, the phosphorylation state of the SR protein adapters may underlie the selectivity of TAP-mediated export of spliced mRNA.
Ecogeographic and genetic determinants of kernel weight and colour of wild barley (Hordeum spontaneum) populations in Israel
Authors: Chen Guoxiong , Suprunova Tatiana , Krugman Tamar , Fahima Tzion , Nevo Eviatar
Published: June 2004

The aim of this study was to establish associations of kernel weight and colour with ecogeographic factors and molecular markers, based on ten wild barley [Hordeum spontaneum(C. Koch) Thell.] populations sampled in Israel across a southward transect of increasing aridity. Kernel weight and colour category were scored using barley kernels (naked caryopsis). Small kernel sizes (0.011 g kernel–1) and dark kernels were found in xeric populations. A higher variation of kernel weight was observed in xeric populations. A higher proportion of variation occurred within, rather than among, populations. Water, temperature and soil factors were associated with kernel size variation. Among 18 simple sequence repeats (SSRs) investigated, HVM14, HVM36, HVM43, BMS64 and BMS90 were associated with kernel weight, and HVM68 with kernel colour. The results indicated that high phenotypic variation and genetic diversity are related to ecological stress, and that the association of phenotypic traits with molecular markers, based on natural plant populations, should be interpreted cautiously due to the high chance of spurious associations between traits and molecular markers.
The influence of rehydration technique on the response of recalcitrant seed embryos to desiccation
Authors: Perán Rosa , Pammenter N.W. , Naicker Janine , Berjak Patricia
Published: June 2004

The concept of ‘imbibitional damage’ arose when it was observed that considerable leakage of cell contents could occur when dry seed or pollen tissues are plunged directly into water. It is now common practice to imbibe dehydrated tissue slowly, to permit the re-establishment of functional membranes, prior to placing the tissue into liquid water. However, this argument may not hold if the tissue of interest is inherently desiccation-sensitive. Slow drying of desiccation-sensitive (recalcitrant) seeds or excised embryonic axes results in damage at high water contents, because it permits time for aqueous-based deleterious processes to occur. The same argument may apply if partially dried material is re-imbibed slowly, as this technique will also expose the tissue to intermediate water contents for protracted periods. This hypothesis was tested using embryos or axes from seeds of three recalcitrant species (Artocarpus heterophyllus, Podocarpus henkelii and Ekebergia capensis). Excised material was rapidly dried to water contents within the range over which viability is lost during drying, and re-imbibed either rapidly, by plunging directly into water, or slowly, by placing the material on damp filter paper or exposing it to a saturated atmosphere for several hours. Although details of the response differed among species and developmental stage, in all cases direct re-imbibition in water resulted in higher (or similar, but never lower) survival than either of the slow rehydration techniques.
Seed behaviour in Phoenix reclinata Jacquin, the wild date palm
Authors: von Fintel Gundula T. , Berjak Patricia , Pammenter N.W.
Published: June 2004

Despite the importance of the palm family,Arecaceae, little has been systematically documented about the seed behaviour of the many species. The post-harvest seed behaviour ofPhoenix reclinata, the highly utilized wild date palm species distributed along the eastern seaboard of Africa, is investigated in the present study. While both embryo and endosperm water concentration declined as the seeds ofPhoenix reclinatamatured, they remained relatively high: this is a characteristic of (but not confined to) non-orthodox seeds. The ultrastructure of embryo cells, and the finding that negligible water uptake was required for the initiation of germination, were in keeping with the possible non-orthodox nature of the seeds. A developmental study revealed that between the acquisition of full germinability and complete pre-shedding maturity, germination performance appeared to be constrained, suggesting the presence of an inhibitor. Pre-treatment by soaking, mechanical or acid scarification had no significant promotory effect on either rate or totality of germination of matureP. reclinataseeds, while use of water transiently at 100°C was highly deleterious. However, germination of partially dehydrated seeds was initiated sooner if they had been soaked or scarified. MatureP. reclinataseeds tolerated dehydration to a mean embryo water concentration of 0.40 g g–1(dry mass basis; dmb), but at 0.14 g g–1, both rate and totality of germination were adversely affected. However, viability of seeds dehydrated to the mean embryo water concentration 0.40 g g–1declined during storage for 16 weeks. It is concluded thatP. reclinataseeds are non-orthodox, and are best categorized as showing intermediate post-harvest behaviour.
Ageing increases the sensitivity of neem (Azadirachta indica) seeds to imbibitional stress
Authors: Neya Oblé , Golovina Elena A. , Nijsse Jaap , Hoekstra Folkert A.
Published: June 2004

Imbibitional stress was imposed on neem (Azadirachta indica) seeds by letting them soak for 1 h in water at unfavourable, low temperatures before further incubation at 30°C. Sensitivity to low imbibition temperatures increased with a decrease in seed moisture content (MC). To investigate a possible involvement of seed age in the extent of imbibitional damage, initially high-quality seed lots that differed in storage history (10 weeks versus 10 months) were examined at 4 and 7% MC (fresh weight basis). After 10 months of storage, the 7% MC seeds had become sensitive to imbibitional stress. Further drying (1 week) to 4% MC affected aged seeds more than non-aged seeds. Barrier properties of cellular membranes in axes excised after 1 d of rehydration were estimated using a spin-probe technique. The proportion of cells with intact membranes increased with increasing imbibition temperature. For each temperature tested, there were more cells with leaky membranes after 10 months than after 10 weeks of dry storage. Localization of embryo cells displaying loss of turgor and abnormal cellular structure was accomplished using cryo-planing, followed by cryo-scanning electron microscopy. Inspection of the cryo-planed surfaces confirmed that imbibitional damage was temperature dependent, occurring at the periphery. Ageing increased the number of imbibitionally damaged, peripheral cell layers. Germination was estimated to fail when less than 70% of axis cells were alive. We conclude that ageing increases the sensitivity to imbibitional stress. Both the fast ageing and the sensitivity to imbibitional stress might explain the apparent controversies about neem seed desiccation tolerance and storage behaviour.
Seedling desiccation tolerance of Leymus racemosus (Poaceae) (wild rye), a perennial sand-dune grass inhabiting the Junggar Basin of Xinjiang, China
Authors: Huang Zhenying , Gutterman Yitzchak
Published: June 2004

Leymus Racemosus, The Mammoth Wild Rye, Is A Rhizomatous Perennial Grass, Mainly Distributed In The Moving Or Semi-Stabilized Sand Dunes In Deserts Of The Junggar Basin In Xinjiang, China. The Revival Ability Of The Young Seedling After Periods Of Desiccation Can Be Influenced By Several Factors: (1) The Stage Of Seedling Development – The Later The Stage At Dehydration, The Longer The Root Length And The Lower Is The Percentage Of Seedlings That Survive; (2) The Length Of The Period Of Desiccation – The Longer The Period That The Seedlings Are Under Desiccation, The Lower Is The Percentage Of Seedlings That Survive; (3) Endosperm Size – The Smaller The Proportion Of Endosperm That Remains In The Caryopses, The Lower Is The Percentage Of Seedlings That Revive, Determined By (A) The Stage Of Seedling Development, And (B) The Proportion Of The Endosperm That Is Removed By Cutting; And (4) Caryopsis Size – The Larger The Polymorphic Caryopses, The Higher Is The Percentage Of Young Seedlings That Revive From Periods Of Desiccation. The Physiological And Ecological Implications Of L. Racemosus Seedling Desiccation Tolerance Are That Under Extreme Desert And Unpredictable Environmental Conditions, The Chances Of Seedling Establishment Are Increased.
THE BINDING OF PENICILLIN IN RELATION TO ITS CYTOTOXIC ACTION
Authors: Eagle Harry
Published: June 2004

1. (a) Mammalian cells in tissue culture (mouse fibroblasts and malignant human uterine epithelium) did not concentrate penicillin from the culture medium. Even at low concentrations, the cellular accumulation was usually less than that in the surrounding fluid, and most of it was removed by washing. The radioactive material in such eluates was actively bactericidal, and was presumably in large part unchanged penicillin.

(b) Penicilloic acid, produced by the action of penicillinase, was bound to the same (limited) extent as the active antibiotic. In both these respects mammalian cells behaved like naturally penicillin-resistant bacteria, and unlike such penicillin-sensitive bacteria as Streptococcus pyogenes or Diplococcus pneumoniae.

2. Cell-free sonic extracts of the L strain had the same limited reactivity with penicillin as the intact cells. The relatively minute amounts bound by the cells are therefore not due to their impermeability, but instead reflect the inherently low reactivity of the cellular constituents with penicillin.

3. It is suggested that the relative non-toxicity of penicillin for the mammalian host, and for mammalian cells in tissue culture, may be related to this low order of reactivity with the antibiotic.
CATALASE ACTIVITY OF LIVER AND KIDNEY IN FROGS WITH SPONTANEOUS RENAL CARCINOMA
Authors: Lucké Balduin , Berwick Mary
Published: June 2004

The kidney carcinoma of the leopard frog has served for various studies on catalase activity, as a first step in gaining information on enzymatic properties of neoplasms in cold blooded animals.

It was found that the activity level of this tumor is reduced to approximately 13 per cent of that of the normal frog's kidney.

Systemic effects of the tumor on catalase activity of liver and kidney are evident. Liver catalase in tumor-bearing frogs is diminished to about 50 per cent of the normal, and kidney catalase to an even greater degree; i.e., to about 34 per cent. A positive correlation exists between levels of catalase in tumor and in liver.

Frogs kept at 3 different temperatures, 8, 18, and 26.5°C., for upward of 29 days exhibited no significant change in activity levels either of tumor or of livers from normal or from tumor-bearing animals. It is suggested that a seasonal variation may occur in catalase activity of the frog. During the winter months catalase activity of the tumors was found to be higher than during the summer, whereas liver catalase was below the level of normal frogs examined during the summer.

Intracoelomic injections of homogenates of tumors promptly lead to diminution of liver catalase lasting for several days. Injection of normal kidney has no such effect.

These results with a spontaneous tumor of a cold blooded animal are in essential agreement with the many observations made with transplanted tumors of warm blooded animals. They lend support to the view that neoplasia is a ubiquitous biological process with similar characteristics in all species or classes of vertebrates.
A STUDY OF THE ANTIGENICITY OF T3 AND T4 COLI-DYSENTERY BACTERIOPHAGES DURING THE VEGETATIVE STAGE OF DEVELOPMENT
Authors: Barry Guy T.
Published: June 2004

The development of viral neutralizing antibodies in animals injected with T3 or T4 phage is considerably inhibited by the presence of bacterial antigens.

A new procedure has been described to liberate phage from infected E. coli B bacteria by inducing lysis with penicillin.

By immunological means it has been shown that T4-infected cultures of E. coli B, in which phage development has been inhibited with proflavine, contain the viral neutralizing antigen after lysis.

In contrast, it has not been possible to demonstrate by immunological means the appearance of viral neutralizing antigen in E. coli B infected with T3 prior to the appearance of intracellular phage.
STRUCTURE AND DEVELOPMENT OF VIRUSES AS OBSERVED IN THE ELECTRON MICROSCOPE
Authors: Morgan Councilman , Ellison Solon A. , Rose Harry M. , Moore Dan H.
Published: June 2004

Herpes simplex virus was visualized by the electron microscope in sections of infected chorioallantoic membrane of chicken embryos. Removal of the embedding methacrylate from relatively thick sections permitted large numbers of viral particles to be seen but caused extensive alteration of cellular components as well as variable distortion of viral structure. This distortion was characterized by disruption of particles and loss of central bodies, resulting in ring or empty shell forms. An inner structure of the virus was revealed in ultrathin sections from which the embedding plastic was not removed. The nuclei of infected cells contained small, dense, primary bodies (30 to 40 mµ in diameter) as well as slightly larger and less dense particles (40 to 50 mµ in diameter) surrounded by a single membrane (70 to 100 mµ in diameter). In the cytoplasm most of the particles possessed a double outer membrane (120 to 130 mµ in diameter). It is suggested that the initial site of viral development is restricted to the nucleus where primary bodies form and become enclosed by a single outer membrane. Upon release into the cytoplasm these particles appear to acquire a second outer membrane and presumably represent the mature virus.
MORPHOLOGICAL AND QUANTITATIVE COMPARISON BETWEEN INFECTIOUS AND NON-INFECTIOUS FORMS OF INFLUENZA VIRUS
Authors: Werner Georges H. , Schlesinger R. Walter
Published: June 2004

Electron microscopic study has revealed the morphological entity responsible for the rise in viral hemagglutinin observed in brains of mice after intracerebral inoculation of non-neurotropic strains of influenza virus. This rise in hemagglutinin, although dependent on inoculation of fully infectious virus, is not associated with an increase in infectious titer. The hemagglutinating principle is functionally similar to the "incomplete" influenza virus which can be obtained from chick embryos by serial egg-to-egg transfer of undiluted, infected allantoic fluid according to the method of von Magnus.

A method has been described which facilitates selective adsorption of viral particles recovered from organ extracts on saponine-lysed ghosts of fowl erythrocytes. This procedure has been utilized in studying the morphology of non-infectious, hemagglutinating virus from chorio-allantoic membranes or mouse brains and in comparing these two forms with each other and with ordinary, infectious (standard) influenza virus.

Standard virus isolated from allantoic fluids or membranes of infected eggs was found to contain uniform particles of predominantly spherical shape with smooth surface and even density, resembling those described by others. The appearance of such particles was not affected by the procedure of extraction and concentration used.

In contrast, non-infectious, hemagglutinating virus obtained either from allantoic sacs ("undiluted passages") or from mouse brain was pleomorphic and seemed to consist of disintegrating particles. The majority appeared flattened and bag-like and had a rough, granular surface and reduced, uneven density. 37 per cent of the non-infectious particles isolated from mouse brain infected with the non-neurotropic strain WS had diameters in excess of 170 mµ, as compared with only 2 per cent of the particles of the parent strain itself.

Regardless of whether or not the contrast in appearance of standard and of non-infectious particles was due to differing resistance to the preparatory treatment, it indicated the existence of basic structural differences between the two types of virus.

Correlation of particle counts with hemagglutinin titers has shown that the non-infectious virus obtained from mouse brain is, unit for unit, an equivalent counterpart of standard virus derived from infected eggs. The end-point of hemagglutination in a pattern test corresponds for both forms to that dilution at which the ratio virus particles/red cells approaches one. The quantitative data based on particle counts support the assumption that non-infectious virus arises in mouse brain as a product of viral multiplication.
CYTOLOGICAL AND PHARMACOLOGICAL OBSERVATIONS ON THE RELEASE OF HISTAMINE BY MAST CELLS
Authors: Fawcett Don W.
Published: June 2004

Experimental solutions known to affect mast cells or to cause liberation of histamine from the tissue were introduced into the peritoneal cavity of rats. Samples of the peritoneal fluid were withdrawn at intervals afterward and assayed for histamine and the condition of the mast cells was subsequently ascertained by microscopic examination of stained spreads of the mesenteries.

Intraperitoneal injection of distilled water caused osmotic disruption of the mast cells and the appearance of an appreciable amount of histamine in the peritoneal fluid.

Injection of Tyrode solution alone was not particularly damaging to the mast cells and little or no histamine was released.

Injection of Tyrode solution containing compound 48/80 resulted in extensive release of granules from mast cells and the appearance of large amounts of histamine in the fluid. Solution of 48/80 failed however to cause histamine release when injected into rats whose subserosal mast cells had previously been destroyed.

A series of increasing doses of compound 48/80 had a graded morphological effect upon mast cells and resulted in a graded increase in the amount of histamine that appeared in the peritoneal fluid. It is unlikely therefore that this compound acts by simply lysing the plasma membrane.

It is concluded that mast cells in the rat are extraordinarily rich in histamine which is liberated under conditions which cause mast cells to release their granules. The histamine set free by the potent histamine liberator, compound 48/80, appears to come principally from the tissue mast cells.
STUDIES ON THE TRANSFER OF LYMPH NODE CELLS
Authors: Harris T. N. , Harris Susanna , Beale Henry D. , Smith J. J.
Published: June 2004

Cells of the popliteal lymph node were teased 3 days after the injection of Shigella paradysenteriae into the hind foot pads of rabbits. These cells were transferred to normal and x-irradiated recipients. It was noted that the serum titers of dysentery agglutinins in irradiated recipients were higher than in normal recipients. This was represented both in a higher peak: titer and a tendency to remain higher for a longer period than in normal animals.

Recipients were x-irradiated within 1 hour after receiving cells of the lymph node prepared as indicated above. The serum titers of these recipients were markedly reduced in comparison with those of non-irradiated control animals. If the irradiation of the recipients followed the transfer of cells by a day, however, this difference was much smaller and in the case of a 2 day interval after the transfer of the lymph node cells the irradiation appeared to have no effect on the resulting serum titer.
THE PERSISTENCE OF BOVINE γ-GLOBULIN INJECTED AS AN ANTIGEN INTO RABBITS
Authors: McMaster Philip D. , Kruse Heinz , Sturm Ernest , Edwards Joshua L.
Published: June 2004

A sensitive biological test has been used to detect the persistence of minute traces of a foreign protein, bovine γ-globulin, in the blood and livers of rabbits intravenously injected with it, as an antigen. At various intervals after injecting these rabbits (donors) serum or liver tissue was transferred from them to the peritoneal cavities of normal or unilaterally adrenalectomized mice (recipients) with the aim of rendering the latter hypersensitive to the antigen that might be persisting in the transferred materials; a state of affairs detectable, 2 days later, by the appearance of signs of reversed passive anaphylaxis when the recipient mice were intravenously challenged with a strong anti-bovine γ-globulin rabbit serum.

The protein persisted in the blood of the donor rabbits, in readily demonstrable amounts for 1 month, and in the blood of one animal, in minute traces, or as long as 6 weeks. It was detectable in the livers for 8 weeks.

The persistence of bovine γ-globulin in rabbits, which form circulating antibodies to it well, is not as long as that in mice, which form antibodies to it poorly, since in previous work with the mouse the antigen was found (1) in the blood after 8 weeks and in the liver for 14 weeks. Nevertheless the antigen persists in the rabbit much longer than is generally supposed. Indeed it can be found in the liver all through the period in which circulating antibody is demonstrable in the blood. Explanations for the phenomenon have been suggested. Its significance in relation to the mechanisms of antibody formation is obvious.
THE PURIFICATION OF HYPERTENSIN I
Authors: Skeggs Leonard T. , Marsh Walton H. , Kahn Joseph R. , Shumway Norman P.
Published: June 2004

The purification of hypertensin I has been described. The final product which is four times as powerful a pressor agent as l-arterenol, is obtained with an over-all recovery of 40 per cent. The product consists of a single component in countercurrent distribution, having a nitrogen content of 15.97 per cent and a specific activity of 7050 Goldblatt units per mg. of N or 1125 units per mg. of solid. Acid hydrolysis and paper chromatography indicate in a preliminary fashion that there are about nine amino acids present in the intact polypeptide.
THE EFFECT OF ALLOXAN DIABETES ON EXPERIMENTAL CHOLESTEROL ATHEROSCLEROSIS IN THE RABBIT
Authors: Duff G. Lyman , Brechin Doris J. H. , Finkelstein W. E.
Published: June 2004

Experiments were undertaken to ascertain whether the previously demonstrated inhibition of the development of experimental aortic atherosclerosis in alloxan-diabetic rabbits fed cholesterol was due to the injection of alloxan per se or to the existence of the diabetic state produced by alloxan.

It was established that, by treating the diabetic state with insulin, the diabetic state could be ameliorated and the inhibitory effect obviated. It was therefore concluded that the inhibitory phenomenon was not due to the injection of alloxan per se but that it was associated with one or more factors that characterize the alloxan diabetic state in the rabbit and that are reversible by insulin therapy.

In the course of the experiment it was demonstrated that the inhibitory effect was apparent in cholesterol-fed diabetic rabbits whether or not their diet was supplemented with vegetable oil. The previously reported metabolic abnormalities of the diabetic animals were confirmed. It was established that suitable treatment of the cholesterol-fed diabetic animals with insulin would bring all the metabolic aberrations, including those of the serum lipids, into reasonably close correspondence with those observed in non-diabetic rabbits fed cholesterol.