bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlated effects of sperm competition and postmating female mortality
Authors: Civetta Alberto , Clark Andrew G.
Published: July 2002

Adaptations in one sex may impair fitness in the opposite sex.
Experiments with
Drosophila melanogaster
have shown that
seminal fluid from the male accessory gland triggers a series of
postmating responses in the female, including increased egg laying rate
and lower remating propensity, but that accessory gland proteins also
increase female death rate. Here, we tested the relationships among the
longevity of females mated to males from 51 chromosome-extracted
D. melanogaster
lines, male-mating ability, and
sperm-competitive ability. We found significant differences in
longevity of females mated to males of different genotypes, and all
mated females showed a higher death rate than control virgin females
shortly after mating. Both the age-independent mortality parameter (the
intercept of the female's survival function) and the slope of the
mortality rate curve were significantly correlated with the
proportion of progeny sired by the first male to mate relative to
tester males (sperm-defense ability,
P1
). No significant
correlation was found between the proportion of progeny sired by the
second-mating male relative to tester males (sperm-offense ability,
P2
) and any mortality parameter. Our results support the
hypothesis of a tradeoff between defensive sperm-competitive ability of
males and life-history parameters of mated females.
The expression of cerebellar LTD in culture is not associated with changes in AMPA-receptor kinetics, agonist affinity, or unitary conductance
Authors: Linden David J.
Published: July 2002

Cerebellar long-term synaptic depression (LTD) is a model system of neuronal information storage that is expressed postsynaptically as a functional down-regulation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. What properties of postsynaptic AMPA receptors are changed? Several lines of evidence argue against changes in AMPA-receptor kinetics. Neither LTD evoked in cultured granule-cell Purkinje cell (PC) pairs nor an LTD-like phenomenon evoked by phorbol ester application was associated with alterations in evoked AMPA receptor-mediated excitatory post-synaptic current (EPSC) or mEPSC kinetics. LTD produced by pairing glutamate pulses with depolarization was not altered by prior application of the desensitization-reducing compound cyclothiazide. Finally, rapid application of glutamate to lifted PCs revealed no significant alterations in AMPA-receptor kinetic properties after LTD induction. When this system was used to apply varying concentrations of glutamate, no alteration in AMPA-receptor glutamate affinity was seen after LTD induction. Finally, peak-scaled nonstationary fluctuation analysis was applied to estimate AMPA-receptor unitary conductance before and after LTD induction in a cultured cell pair, and this analysis too revealed no significant change. These results suggest that cerebellar LTD may be expressed solely as a reduction in the number of functional AMPA receptors in the postsynaptic density [Wang, Y.-T. & Linden, D. J. (2000)
Neuron
25, 635–664].
The ability to follow eye gaze and its emergence during development in macaque monkeys
Authors: Ferrari P. F. , Kohler E. , Fogassi L. , Gallese V.
Published: July 2002

The ability of monkeys to follow the gaze of other individuals is a matter of debate in many behavioral studies. Physiological studies have shown that in monkeys, as in humans, there are neural correlates of eye direction detection. There is little evidence at the behavioral level, however, of the presence and development of such abilities in monkeys. The aim of the present study was to assess in juveniles and adult pig-tailed macaques (Macaca nemestrina) the capacity to use eye cues only to follow the gaze of an experimenter. Biological stimuli (head, eye, and trunk movements) were presented by an experimenter to 2 adult monkeys with their heads restrained (Experiment 1) and to 11 monkeys of different ages, free to move in their home cages (Experiment 2). A nonbiological stimulus served as a control. Results showed that macaques can follow the gaze of the experimenter by using head/eye and eye cues alone. Trunk movements and nonbiological stimuli did not significantly elicit similar reactions. Juvenile monkeys were not able to orient their attention on the basis of eye cues alone. In general, gaze following was more frequent in adults than in juveniles. Like in humans, however, such abilities in macaques dramatically improve with age suggesting that the transition to adulthood is a crucial period in the development of gaze-following behavior.
Species-specific polyamines from diatoms control silica morphology
Authors: Kröger Nils , Deutzmann Rainer , Bergsdorf Christian , Sumper Manfred
Published: July 2002

Biomineralizing organisms use organic molecules to generate
species-specific mineral patterns. Here, we describe the chemical
structure of long-chain polyamines (up to 20 repeated units), which
represent the main organic constituent of diatom biosilica. These
substances are the longest polyamine chains found in nature and induce
rapid silica precipitation from a silicic acid solution. Each diatom is
equipped with a species-specific set of polyamines and
silica-precipitating proteins, which are termed silaffins. Different
morphologies of precipitating silica can be generated by polyamines of
different chain lengths as well as by a synergistic action of
long-chain polyamines and silaffins.
Hyperactivity, elevated dopaminergic transmission, and response to amphetamine in M1 muscarinic acetylcholine receptor-deficient mice
Authors: Gerber David J. , Sotnikova Tatyana D. , Gainetdinov Raul R. , Huang Shu Ying , Caron Marc G. , Tonegawa Susumu
Published: July 2002

Acetylcholine serves an important modulatory role in the central
nervous system. Pharmacological evidence has suggested that
cholinergic activity can modulate central dopaminergic transmission;
however, the nature of this interaction and the receptors involved
remain undefined. In this study we have generated mice lacking the M1
muscarinic acetylcholine receptor and examined the effects of M1
deletion on dopaminergic transmission and locomotor behavior. We report
that M1 deficiency leads to elevated dopaminergic transmission in the
striatum and significantly increased locomotor activity. M1-deficient
mice also have an increased response to the stimulatory effects of
amphetamine. Our results provide direct evidence for regulation of
dopaminergic transmission by the M1 receptor and are consistent with
the idea that M1 dysfunction could be a contributing factor in
psychiatric disorders in which altered dopaminergic transmission has
been implicated.
Loss of high-affinity prostacyclin receptors in platelets and the lack of prostaglandin-induced inhibition of platelet-stimulated thrombin generation in subjects with spinal cord injury.
Authors: Kahn N N , Bauman W A , Sinha A K
Published: July 2002

Coronary artery disease is a leading cause of death in individuals with chronic spinal cord injury (SCI). However, platelets of those with SCI (n = 30) showed neither increased aggregation nor resistance to the antiaggregatory effects of prostacyclin when compared with normal controls (n = 30). Prostanoid-induced cAMP synthesis was similar in both groups. In contrast, prostacyclin, which completely inhibited the platelet-stimulated thrombin generation in normal controls, failed to do so in those with SCI. Scatchard analysis of the binding of [3H]prostaglandin E1, used as a prostacyclin receptor probe, showed the presence of one high-affinity (Kd1 = 8.11 +/- 2.80 nM; n1 = 172 +/- 32 sites per cell) and one low-affinity (Kd2 = 1.01 +/- 0.3 microM; n2 = 1772 +/- 226 sites per cell) prostacyclin receptor in normal platelets. In contrast, the same analysis in subjects with SCI showed significant loss (P < 0.001) of high-affinity receptor sites (Kd1 = 6.34 +/- 1.91 nM; n1 = 43 +/- 10 sites per cell) with no significant change in the low affinity-receptors (Kd2 = 1.22 +/- 0.23; n2 = 1820 +/- 421). Treatment of these platelets with insulin, which has been demonstrated to restore both of the high- and low-affinity prostaglandin receptor numbers to within normal ranges in coronary artery disease, increased high-affinity receptor numbers and restored the prostacyclin effect on thrombin generation. These results demonstrate that the loss of the inhibitory effect of prostacyclin on the stimulation of thrombin generation was due to the loss of platelet high-affinity prostanoid receptors, which may contribute to atherogenesis in individuals with chronic SCI.
DNA-protein binding assays from a single sea urchin egg: a high-sensitivity capillary electrophoresis method.
Authors: Xian J , Harrington M G , Davidson E H
Published: July 2002

A capillary electrophoresis method has been developed to study DNA-protein complexes by mobility-shift assay. This method is at least 100 times more sensitive than conventional gel mobility-shift procedures. Key features of the technique include the use of a neutral coated capillary, a small amount of linear polymer in the separation medium, and use of covalently dye-labeled DNA probes that can be detected with a commercially available laser-induced fluorescence monitor. The capillary method provides quantitative data in runs requiring < 20 min, from which dissociation constants are readily determined. As a test case we studied interactions of a developmentally important sea urchin embryo transcription factor, SpP3A2. As little as 2-10 x 10(6) molecules of specific SpP3A2-oligonucleotide complex were reproducibly detected, using recombinant SpP3A2, crude nuclear extract, egg lysates, and even a single sea urchin egg lysed within the capillary column.
Elevated interleukin 6 is induced by prostaglandin E2 in a murine model of inflammation: possible role of cyclooxygenase-2.
Authors: Hinson R M , Williams J A , Shacter E
Published: July 2002

Injection of mineral oils such as pristane into the peritoneal cavities of BALB/c mice results in a chronic peritonitis associated with high tissue levels of interleukin 6 (IL-6). Here we show that increased prostaglandin E2 (PGE2) synthesis causes induction of IL-6 and that expression of an inducible cyclooxygenase, Cox-2, may mediate this process. Levels of both PGE2 and IL-6 are elevated in inflammatory exudates from pristane-treated mice compared with lavage samples from untreated mice. The Cox-2 gene is induced in the peritoneal macrophage fraction isolated from the mice. A cause and effect relationship between increased macrophage PGE2 and IL-6 production is shown in vitro. When peritoneal macrophages are activated with an inflammatory stimulus (polymerized albumin), the Cox-2 gene is induced and secretion of PGE2 and IL-6 increases, with elevated PGE2 appearing before IL-6. Cotreatment with 1 microM indomethacin inhibits PGE2 production by the cells and reduces the induction of IL-6 mRNA but has no effect on Cox-2 mRNA, consistent with the fact that the drug inhibits catalytic activity of the cyclooxygenase but does not affect expression of the gene. Addition of exogenous PGE2 to macrophages induces IL-6 protein and mRNA synthesis, indicating that the eicosanoid stimulates IL-6 production at the level of gene expression. PGE2-stimulated IL-6 production is unaffected by addition of indomethacin. Taken together with the earlier finding that indomethacin diminishes the elevation of IL-6 in pristane-treated mice, the results show that PGE2 can induce IL-6 production in vivo and implicate expression of the Cox-2 gene in the regulation of this cytokine.
Electrical microstimulation suggests two different forms of representation of head-centered space in the intraparietal sulcus of rhesus monkeys.
Authors: Thier P , Andersen R A
Published: July 2002

We examined the effects of eye position on saccades evoked by electrical stimulation of the intraparietal sulcus (IPS) of rhesus monkeys. Microstimulation evoked saccades from sites on the posterior bank, floor, and the medial bank of the IPS. The size and direction of the eye movements varied as a function of initial eye position before microstimulation. At many stimulation sites, eye position affected primarily the amplitude and not the direction of the evoked saccades. These "modified vector saccades" were characteristic of most stimulation-sensitive zones in the IPS, with the exception of a narrow strip located mainly on the floor of the sulcus. Stimulation in this "intercalated zone" evoked saccades that moved the eyes into a particular region in head-centered space, independent of the starting position of the eyes. This latter response is compatible with the stimulation site representing a goal zone in head-centered coordinates. On the other hand, the modified vector saccades observed outside the intercalated zone are indicative of a more distributed representation of head-centered space. A convergent projection from many modified vector sites onto each intercalated site may be a basis for a transition from a distributed to a more explicit representation of space in head-centered coordinates.
Minimizing a binding domain from protein A.
Authors: Braisted A C , Wells J A
Published: July 2002

We present a systematic approach to minimizing the Z-domain of protein A, a three-helix bundle (59 residues total) that binds tightly (Kd = 10 nM) to the Fc portion of an immunoglobin IgG1. Despite the fact that all the contacts seen in the x-ray structure of the complex with the IgG are derived from residues in the first two helices, when helix 3 is deleted, binding affinity is reduced > 10(5)-fold (Kd > 1 mM). By using structure-based design and phage display methods, we have iteratively improved the stability and binding affinity for a two-helix derivative, 33 residues in length, such that it binds IgG1, with a Kd of 43 nM. This was accomplished by stepwise selection of random mutations from three regions of the truncated Z-peptide: the 4 hydrophobic residues from helix 1 and helix 2 that contacted helix 3 (the exoface), followed by 5 residues between helix 1 and helix 2 (the intraface), and lastly by 19 residues at or near the interface that interacts with Fc (the interface). As selected mutations from each region were compiled (12 in total), they led to progressive increases in affinity for IgG, and concomitant increases in alpha-helical content reflecting increased stabilization of the two-helix scaffold. Thus, by sequential increases in the stability of the structure and improvements in the quality of the intermolecular contacts, one can reduce larger binding domains to smaller ones. Such mini-protein binding domains are more amenable to synthetic chemistry and thus may be useful starting points for the design of smaller organic mimics. Smaller binding motifs also provide simplified and more tractable models for understanding determinants of protein function and stability.
Magnetic resonance imaging (MRI) detection of the murine brain response to light: temporal differentiation and negative functional MRI changes.
Authors: Huang W , Plyka I , Li H , Eisenstein E M , Volkow N D , Springer C S
Published: July 2002

Using a 9.4 T MRI instrument, we have obtained images of the mouse brain response to photic stimulation during a period between deep anesthesia and the early stages of arousal. The large image enhancements we observe (often >30%) are consistent with literature results extrapolated to 9.4 T. However, there are also two unusual aspects to our findings. (i) The visual area of the brain responds only to changes in stimulus intensity, suggesting that we directly detect operations of the M visual system pathway. Such a channel has been observed in mice by invasive electrophysiology, and described in detail for primates. (ii) Along with the typical positive response in the area of the occipital portion of the brain containing the visual cortex, another area displays decreased signal intensity upon stimulation.
Complex dynamics of multilocus systems subjected to cyclical selection.
Authors: Kirzhner V M , Korol A B , Nevo E
Published: July 2002

Earlier we have shown that oscillations with a long period ("supercycles") may arise in two-locus systems experiencing cyclical selection with a short period. However, this mode of complex limiting behavior appeared to be possible for narrow ranges of parameters. Here we demonstrate that a multilocus system subjected to stabilizing selection with cyclically moving optimum can generate ubiquitous complex limiting behavior including supercycles, T-cycles, and chaotic-like phenomena. This mode of multilocus dynamics far exceeds the potential attainable under ordinary selection models resulting in simple behavior. It may represent a novel evolutionary mechanism increasing genetic diversity over long-term time periods.
Highly efficient germ-line transmission of proviral insertions in zebrafish.
Authors: Gaiano N , Allende M , Amsterdam A , Kawakami K , Hopkins N
Published: July 2002

An important technology in model organisms is the ability to make transgenic animals. In the past, transgenic technology in zebrafish has been limited by the relatively low efficiency with which transgenes could be generated using either DNA microinjection or retroviral infection. Previous efforts to generate transgenic zebrafish with retroviral vectors used a pseudotyped virus with a genome based on the Moloney murine leukemia virus and the envelope protein of the vesicular stomatitis virus. This virus was injected into blastula-stage zebrafish, and 16% of the injected embryos transmitted proviral insertions to their offspring, with most founders transmitting a single insertion to approximately 2% of their progeny. In an effort to improve this transgenic frequency, we have generated pseudotyped viral stocks of two new Moloney-based genomes. These viral stocks have titers up to two orders of magnitude higher than that used previously. Injection of these viruses resulted in a dramatic increase in transgenic efficiency; over three different experiments, 83% (110/133) of the injected embryos transmitted proviral insertions to 24% of their offspring. Furthermore, founders made with one of the viruses transmitted an average of 11 different insertions through their germ line. These results represent a 50- to 100-fold improvement in the efficiency of generating transgenic zebrafish, making it now feasible for a single lab to rapidly generate tens to hundreds of thousands of transgenes. Consequently, large-scale insertional mutagenesis strategies, previously limited to invertebrates, may now be possible in a vertebrate.
Activation of Jak/STAT proteins involved in signal transduction pathway mediated by receptor for interleukin 2 in malignant T lymphocytes derived from cutaneous anaplastic large T-cell lymphoma and Sezary syndrome.
Authors: Zhang Q , Nowak I , Vonderheid E C , Rook A H , Kadin M E , Nowell P C , Shaw L M , Wasik M A
Published: July 2002

Signaling through the interleukin 2 receptor (IL-2R) involves phosphorylation of several proteins including Jak3, STAT5, and, in preactivated cells, STAT3. In the present study, we examined the functional status of the IL-2R-associated Jak/STAT pathway in malignant T lymphocytes from advanced skin-based lymphomas: anaplastic large T-cell lymphoma (ALCL) and Sezary syndrome (SzS). Proliferation of three ALCL cell lines (PB-1, 2A, and 2B) was partially inhibited by rapamycin, a blocker of some of the signals mediated by IL-2R, but not by cyclosporin A, FK-506, and prednisone, which suppress signals mediated by the T-cell receptor. All the cell lines expressed on their surface the high-affinity IL-2R (alpha, beta, and gamma c chains). They showed basal, constitutive phosphorylation, and coassociation of Jak3, STAT5, and STAT3. Weak basal phosphorylation of IL-2R gamma c was also detected. In regard to SzS, peripheral blood mononuclear cells from 10 of 14 patients showed basal phosphorylation of Jak3, accompanied by phosphorylation of STAT5 in 9 patients, and STAT3 in 4 patients. However, in vitro overnight culture of SzS cells without exogenous cytokines resulted in markedly decreased Jak3 and STAT5 phosphorylation, which could be reversed by stimulation with IL-2. This indicates that the basal phosphorylation of Jak3 and STAT5 in freshly isolated SzS cells is induced rather than constitutive. The basal activation of the Jak/STAT pathway involved in IL-2R signal transduction in ALCL and SzS cells reported here suggests that this pathway may play a role in the pathogenesis of cutaneous T-cell lymphomas, although the mechanism (induced versus constitutive) may vary between different lymphoma types.
Evidence for nonrandom hydrophobicity structures in protein chains.
Authors: Irbäck A , Peterson C , Potthast F
Published: July 2002

The question of whether proteins originate from random sequences of amino acids is addressed. A statistical analysis is performed in terms of blocked and random walk values formed by binary hydrophobic assignments of the amino acids along the protein chains. Theoretical expectations of these variables from random distributions of hydrophobicities are compared with those obtained from functional proteins. The results, which are based upon proteins in the SWISS-PROT data base, convincingly show that the amino acid sequences in proteins differ from what is expected from random sequences in a statistically significant way. By performing Fourier transforms on the random walks, one obtains additional evidence for nonrandomness of the distributions. We have also analyzed results from a synthetic model containing only two amino acid types, hydrophobic and hydrophilic. With reasonable criteria on good folding properties in terms of thermodynamical and kinetic behavior, sequences that fold well are isolated. Performing the same statistical analysis on the sequences that fold well indicates similar deviations from randomness as for the functional proteins. The deviations from randomness can be interpreted as originating from anticorrelations in terms of an Ising spin model for the hydrophobicities. Our results, which differ from some previous investigations using other methods, might have impact on how permissive with respect to sequence specificity protein folding process is-only sequences with nonrandom hydrophobicity distributions fold well. Other distributions give rise to energy landscapes with poor folding properties and hence did not survive the evolution.
Different sources of reduced carbon contribute to form three classes of terpenoid emitted by Quercus ilex L. leaves.
Authors: Loreto F , Ciccioli P , Brancaleoni E , Cecinato A , Frattoni M , Sharkey T D
Published: July 2002

Quercus ilex L. leaves emit terpenes but do not have specialized structures for terpene storage. We exploited this unique feature to investigate terpene biosynthesis in intact leaves of Q. ilex. Light induction allowed us to distinguish three classes of terpenes: (i) a rapidly induced class including alpha-pinene; (ii) a more slowly induced class, including cis-beta-ocimene; and (iii) the most slowly induced class, including 3-methyl-3-buten-1-ol. Using 13C, we found that alpha-pinene and cis-beta-ocimene were labeled quickly and almost completely while there was a delay before label appeared in linalool and 3-methyl-3-buten-1-ol. The acetyl group of 3-methyl-3-buten-1-yl acetate was labeled quickly but label was limited to 20% of the moiety. It is suggested that the ocimene class of monoterpenes is made from one or more terpenes of the alpha-pinene class and that both classes are made entirely from reduced carbon pools inside the chloroplasts. Linalool and 3-methyl-3-buten-1-ol are made from a different pool of reduced carbon, possibly in nonphotosynthetic plastids. The acetyl group of the 3-methyl-3-buten-1-yl acetate is derived mostly from carbon that does not participate in photosynthetic reactions. Low humidity and prolonged exposure to light favored ocimenes emission and induced linalool emission. This may indicate conversion between terpene classes.
Dendrimer-supported combinatorial chemistry.
Authors: Kim R M , Manna M , Hutchins S M , Griffin P R , Yates N A , Bernick A M , Chapman K T
Published: July 2002

A new methodology for the construction of combinatorial libraries is described. The approach, termed dendrimer-supported combinatorial chemistry (DCC), centers on the use of dendrimers as soluble supports. Salient features of DCC include solution phase chemistry, homogeneous purification, routine characterization of intermediates, and high support loadings. To demonstrate the feasibility of DCC, single compounds and a small combinatorial library were prepared via the Fischer indole synthesis. Excellent product yields and purities were obtained, and dendrimer-protected intermediates could be routinely analyzed by 1H and 13C NMR and by mass spectrometry. The results indicate that DCC is a general and efficient strategy for the generation of combinatorial libraries.
Disruption of RB/E2F-1 interaction by single point mutations in E2F-1 enhances S-phase entry and apoptosis.
Authors: Shan B , Durfee T , Lee W H
Published: July 2002

The retinoblastoma protein (RB) has been proposed to function as a negative regulator of cell proliferation by complexing with cellular proteins such as the transcription factor E2F. To study the biological consequences of the RB/E2F-1 interaction, point mutants of E2F-1 which fail to bind to RB were isolated by using the yeast two-hybrid system. Sequence analysis revealed that within the minimal 18-amino acid peptide of E2F-1 required for RB binding, five residues, Tyr (position 411), Glu (419), and Asp-Leu-Phe (423-425), are critical. These amino acids are conserved among the known E2F family members. While mutation of any of these five amino acids abolished binding to RB, all mutants retained their full transactivation potential. Expression of mutated E2F-1, when compared with that of wild-type, significantly accelerated entry into S phase and subsequent apoptosis. These results provide direct genetic evidence for the biological significance of the RB/E2F interaction and strongly suggest that the interplay between RB and E2F is critical for proper cell cycle progression.
Conformational influences of glycosylation of a peptide: A possible model for the effect of glycosylation on the rate of protein folding
Authors: Live David H. , Kumar R. Ajay , Beebe Xenia , Danishefsky Samuel J.
Published: July 2002

Improved strategies for synthesis make it possible to expand the
range of glycopeptides available for detailed conformational studies.
The glycopeptide 1 was synthesized using a new solid phase synthesis of
carbohydrates and a convergent coupling to peptide followed by
deprotection. Its conformational properties were subjected to NMR
analysis and compared with a control peptide 2 prepared by conventional
solid phase methods. Whereas peptide 2 fails to manifest any
appreciable secondary structure, the glycopeptide 1 does show
considerable conformational bias suggestive of an equilibrium between
an ordered and a random state. The implications of this ordering effect
for the larger issue of protein folding are considered.
Fipronil insecticide: Novel photochemical desulfinylation with retention of neurotoxicity
Authors: Hainzl Dominik , Casida John E.
Published: July 2002

Fipronil is an outstanding new insecticide for crop protection with
good selectivity between insects and mammals. The insecticidal action
involves blocking the γ-aminobutyric acid-gated chloride channel with
much greater sensitivity of this target in insects than in mammals.
Fipronil contains a trifluoromethylsulfinyl moiety that is unique among
the agrochemicals and therefore presumably important in its outstanding
performance. We find that this substituent unexpectedly undergoes a
novel and facile photoextrusion reaction on plants upon exposure to
sunlight, yielding the corresponding trifluoromethylpyrazole, i.e., the
desulfinyl derivative. The persistence of this photoproduct and its
high neuroactivity, resulting from blocking the γ-aminobutyric
acid-gated chloride channel, suggest that it may be a significant
contributor to the effectiveness of fipronil. In addition,
desulfinylfipronil is not a metabolite in mammals, so the safety
evaluations must take into account not only the parent compound but
also this completely new environmental product.
Redistribution of phosphatidylethanolamine at the cleavage furrow of dividing cells during cytokinesis
Authors: Emoto Kazuo , Kobayashi Toshihide , Yamaji Akiko , Aizawa Hiroyuki , Yahara Ichiro , Inoue Keizo , Umeda Masato
Published: July 2002

Ro09-0198 is a tetracyclic polypeptide of 19 amino acids that
recognizes strictly the structure of phosphatidylethanolamine (PE) and
forms a tight equimolar complex with PE on biological membranes. Using
the cyclic peptide coupled with fluorescence-labeled streptavidin, we
have analyzed the cell surface localization of PE in dividing Chinese
hamster ovary cells. We found that PE was exposed on the cell surface
specifically at the cleavage furrow during the late telophase of
cytokinesis. PE was exposed on the cell surface only during the late
telophase and no alteration in the distribution of the plasma
membrane-bound cyclic peptide was observed during the cytokinesis,
suggesting that the surface exposure of PE reflects the enhanced
scrambling of PE at the cleavage furrow. Furthermore, cell surface
immobilization of PE induced by adding the cyclic peptide coupled with
streptavidin to prometaphase cells effectively blocked the cytokinesis
at late telophase. The peptide-streptavidin complex treatment had no
effect on furrowing, rearrangement of microtubules, and nuclear
reconstitution, but specifically inhibited both actin filament
disassembly at the cleavage furrow and subsequent membrane fusion.
These results suggest that the redistribution of the plasma membrane
phospholipids is a crucial step for cytokinesis and the cell surface PE
may play a pivotal role in mediating a coordinate movement between the
contractile ring and plasma membrane to achieve successful cell
division.
Neuronal type information encoded in the basic-helix–loop–helix domain of proneural genes
Authors: Chien Cheng-ting , Hsiao Chwan-Deng , Jan Lily Y. , Jan Yuh Nung
Published: July 2002

The proneural genes encode basic-helix–loop–helix (bHLH) proteins
and promote the formation of distinct types of sensory organs. In
Drosophila
, two sets of proneural genes,
atonal
(
ato
) and members of the
achaete–scute
complex (
ASC
), are required
for the formation of chordotonal (ch) organs and external sensory (es)
organs, respectively. We assayed the production of sensory organs in
transgenic flies expressing chimeric genes of
ato
and
scute (
sc
), a member of
ASC
, and found
that the information that specifies ch organs resides in the bHLH
domain of ato; chimeras containing the b domain of ato and the HLH
domain of sc also induced ch organ formation, but to a lesser extent
than those containing the bHLH domain of ato. The b domains of ato and
sc differ in seven residues. Mutations of these seven residues in the b
domain of ato suggest that most or perhaps all of these residues are
required for induction of ch organs. None of these seven residues is
predicted to contact DNA directly by computer simulation using the
structure of the myogenic factor MyoD as a model, implying that
interaction of ato with other cofactors is likely to be involved in
neuronal type specification.
Memory systems analyses of mnemonic disorders in aging and age-related diseases
Authors: Gabrieli John D. E.
Published: July 2002

The effects upon memory of normal aging and two age-related neurodegenerative diseases, Alzheimer disease (AD) and Parkinson disease, are analyzed in terms of memory systems, specific neural networks that mediate specific mnemonic processes. An occipital memory system mediating implicit visual-perceptual memory appears to be unaffected by aging or AD. A frontal system that may mediate implicit conceptual memory is affected by AD but not by normal aging. Another frontal system that mediates aspects of working and strategic memory is affected by Parkinson disease and, to a lesser extent, by aging. The aging effect appears to occur during all ages of the adult life-span. Finally, a medial-temporal system that mediates declarative memory is affected by the late onset of AD. Studies of intact and impaired memory in age-related diseases suggest that normal aging has markedly different effects upon different memory systems.
Symmetry in chemistry from the hydrogen atom to proteins
Authors: Kellman Michael E.
Published: July 2002

The last 2 decades have seen discoveries in highly excited states
of atoms and molecules of phenomena that are qualitatively different
from the “planetary” model of the atom, and the near-rigid model
of molecules, characteristic of these systems in their low-energy
states. A unified view is emerging in terms of approximate dynamical
symmetry principles. Highly excited states of two-electron atoms
display “molecular” behavior of a nonrigid linear structure
undergoing collective rotation and vibration. Highly excited states of
molecules described in the “standard molecular model” display
normal mode couplings, which induce bifurcations on the route to
molecular chaos. New approaches such as rigid–nonrigid correlation,
vibrons, and quantum groups suggest a unified view of collective
electronic motion in atoms and nuclear motion in molecules.
Linking genome and proteome by mass spectrometry: Large-scale identification of yeast proteins from two dimensional gels
Authors: Shevchenko Andrej , Jensen Ole N. , Podtelejnikov Alexandre V. , Sagliocco Francis , Wilm Matthias , Vorm Ole , Mortensen Peter , Shevchenko Anna , Boucherie Helian , Mann Matthias
Published: July 2002

The function of many of the uncharacterized open reading frames
discovered by genomic sequencing can be determined at the level of
expressed gene products, the proteome. However, identifying the cognate
gene from minute amounts of protein has been one of the major problems
in molecular biology. Using yeast as an example, we demonstrate here
that mass spectrometric protein identification is a general solution to
this problem given a completely sequenced genome. As a first screen,
our strategy uses automated laser desorption ionization mass
spectrometry of the peptide mixtures produced by in-gel tryptic
digestion of a protein. Up to 90% of proteins are identified by
searching sequence data bases by lists of peptide masses obtained with
high accuracy. The remaining proteins are identified by partially
sequencing several peptides of the unseparated mixture by
nanoelectrospray tandem mass spectrometry followed by data base
searching with multiple peptide sequence tags. In blind trials,
the method led to unambiguous identification in all cases. In the
largest individual protein identification project to date, a total of
150 gel spots—many of them at subpicomole amounts—were successfully
analyzed, greatly enlarging a yeast two-dimensional gel data base. More
than 32 proteins were novel and matched to previously uncharacterized
open reading frames in the yeast genome. This study establishes that
mass spectrometry provides the required throughput, the certainty of
identification, and the general applicability to serve as the method of
choice to connect genome and proteome.
Fas-dependent CD4+cytotoxic T-cell-mediated pathogenesis during virus infection
Authors: Zajac Allan J. , Quinn Daniel G. , Cohen Philip L. , Frelinger Jeffrey A.
Published: July 2002

β2-Microglobulin-deficient (β2m−) mice generate a CD4+major histocompatibility complex class II-restricted cytotoxic T-lymphocyte (CTL) response following infection with lymphocytic choriomeningitis (LCM) virus (LCMV). We have determined the cytotoxic mechanism used by these CD4+CTLs and have examined the role of this cytotoxic activity in pathogenesis of LCM disease in β2m−mice. Lysis of LCMV-infected target cells by CTLs from β2m−mice is inhibited by addition of soluble Fas-Ig fusion proteins or by pretreatment of the CTLs with the protein synthesis inhibitor emetine. In addition, LCMV-infected cell lines that are resistant to anti-Fas-induced apoptosis are refractory to lysis by these virus-specific CD4+CTLs. These data indicate that LCMV-specific CD4+CTLs from β2m−mice use a Fas-dependent lytic mechanism. Intracranial (i.c.) infection of β2m−mice with LCMV results in loss of body weight. Fas-deficient β2m−.lprmice develop a similar wasting disease following i.c. infection. This suggests that Fas-dependent cytotoxicity is not required for LCMV-induced weight loss. A potential mediator of this chronic wasting disease is tumor necrosis factor (TNF)-α, which is produced by LCMV-specific CD4+CTLs. In contrast to LCMV-induced weight loss, lethal LCM disease in β2m−mice is dependent on Fas-mediated cytotoxicity. Transfer of immune splenocytes from LCMV-infected β2m−mice into irradiated infected β2m−mice results in death of recipient animals. In contrast, transfer of these splenocytes into irradiated infected β2m−.lprmice does not cause death. Thus a role for CD4+T-cell-mediated cytotoxicity in virus-induced immunopathology has now been demonstrated.
Fine mapping of colon tumor susceptibility (Scc) genes in the mouse, different from the genes known to be somatically mutated in colon cancer.
Authors: Moen C J , Groot P C , Hart A A , Snoek M , Demant P
Published: July 2002

The predisposition to colon cancer is multigenetically controlled in animals and probably also in humans. We have analyzed the multigenic control of susceptibility to 1,2-dimethylhydrazine-induced colon tumors in mice by using a set of 20 homozygous CcS/Dem recombinant congenic strains, each of which contains a different random subset of approximately 12.5% of genes from the susceptible strain STS/A and 87.5% of genes from the relatively resistant strain BALB/cHeA. Some CcS/Dem strains received the alleles from the susceptible strain STS/A at one or more of the multiple colon tumor susceptibility loci and are susceptible, whereas others are resistant. Linkage analysis shows that these susceptibility genes are different from the mouse homologs of the genes known to be somatically mutated in human colon cancer (KRAS2, TP53, DCC, MCC, APC, MSH2, and probably also MLH1). Different subsets of genes control tumor numbers and size. Two colon cancer susceptibility genes, Scc1 and Scc2, map to mouse chromosome 2. The Scc1 locus has been mapped to a narrow region of 2.4 centimorgans (90% confidence interval).
Transcriptional activation by protein-induced DNA bending: evidence for a DNA structural transmission model.
Authors: Parekh B S , Hatfield G W
Published: July 2002

Integration host factor (IHF) is a DNA-bending protein that binds to an upstream activating sequence (UAS1) and, on a negatively supercoiled DNA template, activates transcription from the ilvPG promoter of the ilvG-MEDA operon of Escherichia coli. The transcriptional initiation site of the ilvGMEDA operon is located 92 bp downstream of UAS1. Activation is still observed when the orientation of the upstream IHF binding site is reversed. This manipulation places the IHF binding site on the opposite face of the DNA helix, directs the IHF-induced DNA bend in the opposite direction, and presents the opposite face of the nonsymmetrical, heterodimeric, IHF molecule to the downstream RNA polymerase. Lymphoid enhancer-binding factor, LEF-1, is a DNA-bending, lymphoid-specific, mammalian transcription factor that shares no amino acid sequence similarity with IHF. When the IHF site in UAS1 is replaced with a LEF-1 site, LEF-1 activates transcription from the downstream ilvPG promoter in E. coli as well as it is activated by its natural activator, IHF. These results suggest that specific interactions between IHF and RNA polymerase are not required for activation. The results of DNA structural studies show that IHF forms a protein-DNA complex in the UAS1 region that, in the absence of RNA polymerase, alters the structure of the DNA helix in the -10 hexanucleotide region of the downstream ilvPG promoter. The results of in vitro abortive transcription assays show that IIIF also increases the apparent rate of RNA polymerase isomerization from a closed to an open complex. We suggest, therefore, that IHF activates transcription by forming a higher-order protein-DNA complex in the UAS1 region that structurally alters the DNA helix in a way that facilitates open complex formation at the downstream ilvPG promoter site.
G protein subunits and the stimulation of phospholipase C by Gs-and Gi-coupled receptors: Lack of receptor selectivity of Galpha(16) and evidence for a synergic interaction between Gbeta gamma and the alpha subunit of a receptor activated G protein.
Authors: Zhu X , Birnbaumer L
Published: July 2002

Stimulatory guanine nucleotide binding protein (Gs)-coupled receptors activated by luteinizing hormone, vasopressin, and the catecholamine isoproterenol (luteinizing hormone receptor, type 2 vasopressin receptor, and types 1 and 2 beta-adrenergic receptors) and the Gi-coupled M2 muscarinic receptor (M2R) were expressed transiently in COS cells, alone and in combination with Gbeta gamma dimers, their corresponding Galphas (Galpha(s), or Galpha(i3)) and either Galpha(q) or Galpha(16). Phospholipase C (PLC) activity, assessed by inositol phosphate production from preincorporated myo[3H]inositol, was then determined to gain insight into differential coupling preferences among receptors and G proteins. The following were observed: (i) All receptors tested were able to stimulate PLC activity in response to agonist occupation. The effect of the M2R was pertussis toxin sensitive. (ii) While, as expected, expression of Galpha(q) facilitated an agonist-induced activation of PLC that varied widely from receptor to receptor (400% with type 2 vasopressin receptor and only 30% with M2R), expression of Galpha(16) facilitated about equally well the activation of PLC by any of the tested receptors and thus showed little if any discrimination for one receptor over another. (iii) Gbeta gamma elevated basal (agonist independent) PLC activity between 2- and 4-fold, confirming the proven ability of Gbeta gamma to stimulate PLCbeta. (iv) Activation of expressed receptors by their respective ligands in cells coexpressing excess Gbeta gamma elicited agonist stimulated PLC activities, which, in the case of the M2R, was not blocked by pertussis toxin (PTX), suggesting mediation by a PTX-insensitive PLC-stimulating Galpha subunit, presumably, but not necessarily, of the Gq family. (v) The effects of Gbeta gamma and the PTX-insensitive Galpha elicited by M2R were synergistic, suggesting the possibility that one or more forms of PLC are under conditional or dual regulation of G protein subunits such that stimulation by one sensitizes to the stimulation by the other.
Twilight-zone and canopy shade induction of the Athb-2 homeobox gene in green plants.
Authors: Carabelli M , Morelli G , Whitelam G , Ruberti I
Published: July 2002

We present evidence that a novel phytochrome (other than phytochromes A and B, PHYA and PHYB) operative in green plants regulates the "twilight-inducible" expression of a plant homeobox gene (Athb-2). Light regulation of the Athb-2 gene is unique in that it is not induced by red (R)-rich daylight or by the light-dark transition but is instead induced by changes in the ratio of R to far-red (FR) light. These changes, which normally occur at dawn and dusk (end-of-day FR), also occur during the daytime under the canopy (shade avoidance). By using pure light sources and phyA/phyB null mutants, we demonstrated that the induction of Athb-2 by changes in the R/FR ratio is mediated for the most part by a novel phytochrome operative in green plants. Furthermore, PHYB plays a negative role in repressing the accumulation of Athb-2 mRNA in the dark and a minor role in the FR response. The strict correlation of Athb-2 expression with FR-induced growth phenomena suggests a role for the Athb-2 gene in mediating cell elongation. This interpretation is supported by the finding that the Athb-2 gene is expressed at high levels in rapidly elongating etiolated seedlings. Furthermore, as either R or FR light inhibits cell elongation in etiolated tissues, they also down-regulate the expression of Athb-2 mRNA. Thus, these data support the notion that changes in light quality perceived by a novel phytochrome regulate plant development through the action of the Athb-2 homeobox gene.
The neck region of the myosin motor domain acts as a lever arm to generate movement.
Authors: Uyeda T Q , Abramson P D , Spudich J A
Published: July 2002

The myosin head consists of a globular catalytic domain that binds actin and hydrolyzes ATP and a neck domain that consists of essential and regulatory light chains bound to a long alpha-helical portion of the heavy chain. The swinging neck-level model assumes that a swinging motion of the neck relative to the catalytic domain is the origin of movement. This model predicts that the step size, and consequently the sliding velocity, are linearly related to the length of the neck. We have tested this point by characterizing a series of mutant Dictyostelium myosins that have different neck lengths. The 2xELCBS mutant has an extra binding site for essential light chain. The delta RLCBS mutant myosin has an internal deletion that removes the regulatory light chain binding site. The delta BLCBS mutant lacks both light chain binding sites. Wild-type myosin and these mutant myosins were subjected to the sliding filament in vitro motility assay. As expected, mutants with shorter necks move slower than wild-type myosin in vitro. Most significantly, a mutant with a longer neck moves faster than the wild type, and the sliding velocities of these myosins are linearly related to the neck length, as predicted by the swinging neck-lever model. A simple extrapolation to zero speed predicts that the fulcrum point is in the vicinity of the SH1-SH2 region in the catalytic domain.
Effects of population and affluence on CO2 emissions
Authors: Dietz Thomas , Rosa Eugene A.
Published: July 2002

We developed a stochastic version of the Impact = Population·Affluence·Technology (IPAT) model to estimate the effects of population, affluence, and technology on national CO2emissions. Our results suggest that, for population, there are diseconomies of scale for the largest nations that are not consistent with the assumption of direct proportionality (log–linear effects) common to most previous research. In contrast, the effects of affluence on CO2emissions appear to reach a maximum at about $10,000 in per- capita gross domestic product and to decline at higher levels of affluence. These results confirm the general value of the IPAT model as a starting point for understanding the anthropogenic driving forces of global change and suggest that population and economic growth anticipated over the next decade will exacerbate greenhouse gas emissions.