bluuebunny/crossref_metadata_2025 huggingface dataset:
Herpes simplex virus 1 activates cdc2 to recruit topoisomerase IIα for post-DNA synthesis expression of late genes
Authors: Advani Sunil J. , Weichselbaum Ralph R. , Roizman Bernard
Published: April 2003

A subset (γ
2
) of late herpes simplex virus 1 genes depends on viral DNA synthesis for its expression. For optimal expression, a small number of these genes, exemplified by U
S
11, also requires two viral proteins, the α protein infected cell protein (ICP) 22 and the protein kinase U
L
13. Earlier we showed that U
L
13 and ICP22 mediate the stabilization of cdc2 and the replacement of its cellular partner, cyclin B, with the viral DNA polymerase processivity factor U
L
42. Here we report that cdc2 and its new partner, U
L
42, bind a phosphorylated form of topoisomerase IIα. The posttranslational modification of topoisomerase IIα and its interaction with cdc2–U
L
42 proteins depend on ICP22 in infected cells. Although topoisomerase II is required for viral DNA synthesis, ICP22 is not, indicating a second function for topoisomerase IIα. The intricate manner in which the virus recruits topoisomerase IIα for post-DNA synthesis expression of viral genes suggests that topoisomerase IIα also is required for untangling concatemeric DNA progeny for optimal transcription of late genes.
A GTP-driven motor moves proteins across the outer envelope of chloroplasts
Authors: Schleiff Enrico , Jelic Marko , Soll Jürgen
Published: April 2003

The translocation of proteins across cellular membranes is a key mechanistic problem for every cell. The preprotein translocon at the chloroplast outer envelope is responsible for precursor protein recognition and translocation across the outer envelope. We have reconstituted the translocation process into proteoliposomes from single subunits or by using the purified translocon. Precursor proteins are recognized by the Toc34 receptor in an initial GTP-dependent process. Translocation across the plane of the membrane then occurs through the Toc75 channel in a GTP-dependent process. Correspondingly, GTP hydrolysis of Toc proteoliposomes is 100-fold enhanced in the presence of preprotein. Complete translocation is demonstrated by processing of the precursor form to the mature form by the stromal processing peptidase and by protease resistance of the imported protein. Molecular chaperones are not involved in this translocation event. We show that Toc159 acts as a GTP-driven motor in a sewing-machine-like mechanism.
Early light-induced proteins protect
Arabidopsis
from photooxidative stress
Authors: Hutin Claire , Nussaume Laurent , Moise Nicolae , Moya Ismaël , Kloppstech Klaus , Havaux Michel
Published: April 2003

The early light-induced proteins (ELIPs) belong to the multigenic family of light-harvesting complexes, which bind chlorophyll and absorb solar energy in green plants. ELIPs accumulate transiently in plants exposed to high light intensities. By using an
Arabidopsis thaliana
mutant (
chaos
) affected in the posttranslational targeting of light-harvesting complex-type proteins to the thylakoids, we succeeded in suppressing the rapid accumulation of ELIPs during high-light stress, resulting in leaf bleaching and extensive photooxidative damage. Constitutive expression of
ELIP
genes in
chaos
before light stress resulted in ELIP accumulation and restored the phototolerance of the plants to the wild-type level. Free chlorophyll, a generator of singlet oxygen in the light, was detected by chlorophyll fluorescence lifetime measurements in
chaos
leaves before the symptoms of oxidative stress appeared. Our findings indicate that ELIPs fulfill a photoprotective function that could involve either the binding of chlorophylls released during turnover of pigment-binding proteins or the stabilization of the proper assembly of those proteins during high-light stress.
IL-15Rα expression on CD8+T cells is dispensable for T cell memory
Authors: Burkett Patrick R. , Koka Rima , Chien Marcia , Chai Sophia , Chan Faye , Ma Averil , Boone David L.
Published: April 2003

The generation and maintenance of immunological memory requires the activation, expansion, and persistent proliferation of antigen-specific T cells. Recent work suggests that IL-15 may be important for this process. Surprisingly, we now find that expression of the high-affinity receptor for IL-15, IL-15Rα, on T cells is dispensable for the generation or maintenance of memory CD8+T cells. By contrast, IL-15Rα expression on cells other than T cells is absolutely critical for this function. These findings may be related to IL-15Rα's ability to present IL-15 in trans to low-affinity IL-15Rβ/γcreceptors on memory CD8+T cells. These unexpected results provide insights into how IL-15Rα supports memory CD8+T cells.
Induced nucleotide specificity in a GTPase
Authors: Shan Shu-ou , Walter Peter
Published: April 2003

In signal-recognition particle (SRP)-dependent protein targeting to the bacterial plasma membrane, two GTPases, Ffh (a subunit of the bacterial SRP) and FtsY (the bacterial SRP receptor), act as GTPase activating proteins for one another. The molecular mechanism of this reciprocal GTPase activation is poorly understood. In this work, we show that, unlike other GTPases, free FtsY exhibits only low preference for GTP over other nucleotides. On formation of the SRP⋅FtsY complex, however, the nucleotide specificity of FtsY is enhanced 10
3
-fold. Thus, interactions with SRP must induce conformational changes that directly affect the FtsY GTP-binding site: in response to SRP binding, FtsY switches from a nonspecific “open” state to a “closed” state that provides discrimination between cognate and noncognate nucleotides. We propose that this conformational change leads to more accurate positioning of the nucleotide and thus could contribute to activation of FtsY's GTPase activity by a novel mechanism.
Combinatorial modification of multiple lignin traits in trees through multigene cotransformation
Authors: Li Laigeng , Zhou Yihua , Cheng Xiaofei , Sun Jiayan , Marita Jane M. , Ralph John , Chiang Vincent L.
Published: April 2003

Lignin quantity and reactivity [which is associated with its syringyl/guaiacyl (S/G) constituent ratio] are two major barriers to wood-pulp production. To verify our contention that these traits are regulated by distinct monolignol biosynthesis genes, encoding 4-coumarate–CoA ligase (4CL) and coniferaldehyde 5-hydroxylase (CAld5H), we used
Agrobacterium
to cotransfer antisense
4CL
and sense
CAld5H
genes into aspen (
Populus tremuloides
). Trees expressing each one and both of the transgenes were produced with high efficiency. Lignin reduction by as much as 40% with 14% cellulose augmentation was achieved in antisense
4CL
plants; S/G-ratio increases as much as 3-fold were observed without lignin quantity change in sense
CAld5H
plants. Consistent with our contention, these effects were independent but additive, with plants expressing both transgenes having up to 52% less lignin, a 64% higher S/G ratio, and 30% more cellulose. An S/G-ratio increase also accelerated cell maturation in stem secondary xylem, pointing to a role for syringyl lignin moieties in coordinating xylem secondary wall biosynthesis. The results suggest that this multigene cotransfer system should be broadly useful for plant genetic engineering and functional genomics.
Signal sequence within FcγRIIA controls calcium wave propagation patterns: Apparent role in phagolysosome fusion
Authors: Worth Randall G. , Kim Moo-Kyung , Kindzelskii Andrei L. , Petty Howard R. , Schreiber Alan D.
Published: April 2003

Calcium oscillations and traveling calcium waves have been observed in living cells, although amino acid sequences regulating wave directionality and downstream cell functions have not been reported. In this study we identify an amino acid sequence within the cytoplasmic domain of the leukocyte IgG receptor FcγRIIA that affects the amplitude of calcium spikes and the spatiotemporal dynamics of calcium waves in the vicinity of phagosomes. By using high-speed microscopy to map calcium-signaling routes within cells, we have discovered that bound IgG-coated targets trigger two calcium waves traveling in opposite directions about the perimeter of cells expressing FcγRIIA. After phagocytosis, one calcium wave propagates around the plasma membrane to the site of phagocytosis where it splits into two calcium signals: one traveling to and encircling the phagosome once, and the second continuing around the plasma membrane to the point of origin. However, in a genetically engineered form of FcγRIIA containing a mutation in the cytoplasmic L-T-L motif, the calcium signal travels around the plasma membrane, but is not properly routed to the phagosome. Furthermore, these calcium pattern-deficient mutants were unable to support phagolysosome fusion, although recruitment of phagolysosome-associated proteins lysosome-associated protein 1, Rab5, and Rab7 were normal. Our findings suggest that: (i) calcium signaling is a late step in phagolysosome fusion, (ii) a line of communication exists between the plasma membrane and phagosome, and (iii) the L-T-L motif is a signal sequence for calcium signal routing to the phagosome.
Hyaluronidase 2 negatively regulates RON receptor tyrosine kinase and mediates transformation of epithelial cells by jaagsiekte sheep retrovirus
Authors: Danilkovitch-Miagkova Alla , Duh Fuh-Mei , Kuzmin Igor , Angeloni Debora , Liu Shan-Lu , Miller A. Dusty , Lerman Michael I.
Published: April 2003

The candidate tumor-suppressor gene hyaluronidase 2 (
HYAL2
) encodes a glycosylphosphatidylinositol-anchored cell-surface protein that serves as an entry receptor for jaagsiekte sheep retrovirus, a virus that causes contagious lung cancer in sheep that is morphologically similar to human bronchioloalveolar carcinoma. The viral envelope (Env) protein alone can transform cultured cells, and we hypothesized that Env could bind and sequester the HYAL2 receptor and thus liberate a potential oncogenic factor bound and negatively controlled by HYAL2. Here we show that the HYAL2 receptor protein is associated with the RON receptor tyrosine kinase (also called MST1R or Stk in the mouse), rendering it functionally silent. In human cells expressing a jaagsiekte sheep retrovirus Env transgene, the Env protein physically associates with HYAL2. RON liberated from the association with HYAL2 becomes functionally active and consequently activates the Akt and mitogen-activated protein kinase pathways leading to oncogenic transformation of immortalized human bronchial epithelial cells. We find activated RON in a subset of human bronchioloalveolar carcinoma tumors, suggesting RON involvement in this type of human lung cancer.
Joint effects of factors affecting exchanges between exporters and their foreign intermediaries: an exploratory study
Authors: Li Lee
Published: April 2003

How do exporting manufacturers exchange with their foreign intermediaries? This inductive study of 18 British manufacturers in China led to propositions exploring that question. The study suggests that the choice of exchange modes be determined by different factors in combination, including demand uncertainties, intermediaries’ capabilities, market‐specific knowledge, mutual trust, specialization, and competition intensity. It is the contingencies between these factors that determine the exchange modes.
Expression and Splicing of the Insulin‐Like Growth Factor Gene in Rodent Muscle is Associated with Muscle Satellite (stem) Cell Activation following Local Tissue Damage
Authors: Hill Maria , Goldspink Geoffrey
Published: April 2003

Muscle satellite cells are mononuclear cells that remain in a quiescent state until activated when they proliferate and fuse with muscle fibres to donate nuclei, a process necessary for post‐embryonic growth, hypertrophy and tissue repair in this post‐mitotic tissue. These processes have been associated with expression of the insulin‐like growth factor (IGF‐I) gene that can undergo alternative splicing to generate different gene products with varying functions. To gain insight into the cellular mechanisms involved in local tissue repair, the time courses of expression of two IGF‐I splice variants produced in muscle were determined together with marker genes for satellite cell activation following local muscle damage. Using real‐time RT‐PCR with specific primers, the mRNA transcripts in rat tibialis anterior muscles were measured at different time intervals following either mechanical damage imposed by electrical stimulation of the stretched muscle or damage caused by injection with bupivacaine. It was found that the autocrine splice variant mechano growth factor (MGF) was rapidly expressed and then declined within a few days following both types of damage. Systemic IGF‐IEa was more slowly upregulated and its increase was commensurate with the rate of decline in MGF expression. Satellite cell activation as measured by M‐cadherin and one of the muscle regulatory factors MyoD and the sequence of expression suggests that the initial pulse of MGF is responsible for satellite cell activation, as the systemic IGF‐IEa mRNA expression peaks after the expression of these markers, including M‐cadherin protein. Later splicing of the IGF‐I gene away from MGF but towards IGF‐IEa seems physiologically appropriate as IGF‐IEa is the main source of mature IGF‐I for upregulation of protein synthesis required to complete the repair.
Somatostatin Receptor type 2 Mediates Bombesin‐Induced Inhibition of Gastric Acid Secretion in Mice
Authors: Piqueras Laura , Taché Yvette , Martínez Vicente
Published: April 2003

Studies in isolated mouse stomach showed that bombesin releases somatostatin. We characterized the effects of exogenous bombesin on gastric acid secretion in mice and determined the involvement of somatostatin and somatostatin receptor type 2 (SSTR2) by using somatostatin immunoneutralization, the SSTR2 antagonist, PRL‐2903, and SSTR2 knockout mice. Gastric acid secretion was monitored under basal and pentagastrin‐, histamine‐ or bethanechol‐stimulated conditions in urethane‐anaesthetized mice. Bombesin (10–40 μg kg−1 h−1) and somatostatin‐14 (20 μg kg−1 h−1) were infused i.v. 10 and 30 min after PRL‐2903 or somatostatin antibody pretreatment, respectively. Urethane‐anaesthetized wild‐type mice had low basal acid secretion (0.12 ± 0.01 μmol (10 min)−1) compared with SSTR2 knockout mice (1.43 ± 0.10 μmol (10 min)−1). Somatostatin antibody and PRL‐2903 increased basal secretion in wild‐type mice but not in SSTR2 knockout animals. In wild‐type mice, bombesin inhibited secretagogue‐stimulated acid secretion in a dose‐dependent manner, and somatostatin‐14 inhibited pentagastrin‐stimulated secretion. In wild‐type mice pretreated with somatostatin antibody or PRL‐2903 and in SSTR2 knockout mice, bombesin and somatostatin‐14 i.v. infusion did not alter the increased gastric acid secretion. These results indicate that, in mice, bombesin inhibits gastric acid secretion through the release of somatostatin and the activation of SSTR2. These observations strengthen the important role of SSTR2 in mediating somatostatin inhibitory actions on gastric acid secretion.
What is osteoporosis?
Authors: Christodoulou C , Cooper C
Published: April 2003

Osteoporosis is a very common disorder, which results in an increase in fracture risk. The annual cost attributable to hip, vertebral, and wrist fractures in England and Wales is £1.7 billion. Significant mortality and morbidity are associated with osteoporotic fractures. The method that is most widely used for the diagnosis of osteoporosis is dual energy x-ray absorptiometry. The aim of prevention and treatment of osteoporosis is to prevent the occurrence of future fractures. Lifestyle changes should be encouraged in high risk patients. Pharmacological treatments include the bisphosphonates, hormone replacement therapy, selective oestrogen receptor modulators, calcitonin, the 1–34 fragment of parathyroid hormone, calcium and vitamin D supplements, and calcitriol.
Calbindin Immunoreactivity in Purkinje Cells of the Bullfrog Cerebellum during Thyroxine-Induced Metamorphosis
Authors: Uray Nándor , Gona Amos , Sexton Patricia
Published: April 2003

Calbindin-immunoreactive Purkinje cells were identified in the cerebella of frog tadpoles that had been treated with thyroxine to accelerate metamorphosis. The dorsal part of the cerebellar plate contained the full complement of Purkinje cells which were all CaBP-immunoreactive, while in the ventral part of the cerebellum Purkinje cells acquired CaBP-immunoreactivity only after several days of thyroxine treatment. The ventral group of Purkinje cells was separated from the dorsal group by a distinct gap, which is the site of a shallow sulcus in adult frogs. Additionally, following thyroxine treatment, the numbers of CaBP-immunoreactive Purkinje cells in the ventral group were only half the numbers seen in frogs that metamorphosed spontaneously. We suggest that the variation in the CaBP-immunoreactivity of the dorsal and ventral groups of Purkinje cells, along with the gap in the Purkinje cell layer between the two groups, may be indicative of two distinct populations of Purkinje cells, with distinct patterns of generation, maturation, and perhaps, origin and connectivity, in the cerebellum of frogs.
Comparison of Fast Startle Responses between Two Elongate Bony Fish with an Anguilliform Type of Locomotion, the African Lungfish, Protopterus annectens, and the American Eel, Anguilla rostrata, and the Implications for the Underlying Neuronal Basis of Escape Behavior
Authors: Meyers Jason R. , Copanas Elizabeth H. , Zottoli Steven J.
Published: April 2003

A comparative anatomical and behavioral approach was used to elucidate the role of medullary networks associated with Mauthner cells (M-cells) in determining the type of fast startle responses of elongate bony fish with an anguilliform type of locomotion. The M-cell initiates fast startle responses in goldfish and is thought to initiate such responses in other fish as well [Wilson, 1959; Eaton et al., 1977; Currie and Carlsen, 1987; Currie, 1991]. Goldfish M-cells have a specialized structure, termed an axon cap, that surrounds their axon hillock-initial segment region and is critical for the control of M-cell excitability. The M-cell axon cap is present in some elongate fish such as the African lungfish (Protopterus, Lepidosireniformes) and absent in others such as the American eel (Anguilla, Anguilliformes). The lungfish startle response is characterized by a rotation of the head and upper trunk, similar to the initial phase of the goldfish (Carassius, Cypriniformes) startle response. The American eel, on the other hand, displays a withdrawal-type startle response. We hypothesize that the withdrawal-type startle response of the American eel results from the absence of inhibitory networks associated with the M-cell axon cap. The correlation of the absence of an axon cap and a withdrawal-type startle response may be a general feature of all Anguilliformes and elongate ray-finned fish with an anguilliform type of locomotion.
Of Mice and Genes: Evolution of Vertebrate Brain Development
Authors: Fritzsch Bernd
Published: April 2003

In this review the current understanding of genetic and molecular evolution of development, in particular the formation of the major axis of bilateral animals, is critically evaluated, and the early pattern formation in the hindbrain is related as much as possible to these processes. On the genetic level it is proposed that the exuberant multiplication of regulatory genes compared to that of structural genes relates to the increased flexibility of early vertebrate development. In comparisons to fruit flies, many conserved genes are found to be expressed very differently, while many others seem to reflect a comparable pattern and thus suggest a conservation of function. Even genes with a largely conserved pattern of expression may change the level at which they are expressed and the mechanisms by which they are regulated in their expression. Evolution and development of hindbrain motoneurons is reviewed, and it is concluded that both comparative data as well as more recent experimental data suggest a limited importance for the rhombomeres. Clearly, many cell fate-specifying processes work below the level of rhombomeres or in the absence of rhombomeres. It is suggested that more comparative developmental data are needed to establish firmly the relationship between homeobox genes and rhombomere specification in vertebrates other than a few model species.
Parvalbumin Immunoreactive Neurons in the Main Olfactory Bulb of the House Musk Shrew, Suncus murinus
Authors: Kakuta Sachiko , Oda Satoko , Takayanagi Masaaki , Kishi Kiyoshi
Published: April 2003

The distribution, morphological features, and postnatal development of parvalbumin (PV) immunoreactive neurons in the main olfactory bulb (MOB) of the house musk shrew, Suncus murinus, were studied to report for the first time on PV positive bulbar interneurons in the order Insectivora. In adult animals, PV neurons are distributed in the glomerular layer (GL), the external plexiform layer (EPL), the internal plexiform layer (IPL) and the granule cell layer (GCL) of the MOB. These neurons were identified as a subpopulation of periglomerular cells and perinidal cells [Alonso et al., 1995] in the GL and at the GL-EPL border, respectively, and as bipolar and multipolar neurons in the EPL and four types of the interneurons (horizontal cells, Cajal cells, Golgi cells, and bitufted cells) in the layers deeper than the mitral cell layer. During development of PV neurons, neurons exhibiting extremely faint PV immunoreactivity first appeared in the GCL at postnatal day 14 and increased markedly in number and intensity of their PV immunoreactivity from postnatal days 14 to 28. At postnatal day 21, PV neurons were identified as periglomerular cells in the GL, perinidal cells at the GL-EPL border, and morphologically unidentifiable neurons in the EPL, IPL and GCL. At postnatal day 28, PV neurons exhibited a nearly adult pattern with respect to distribution and structural features. The present results strongly suggest that a wide variety of PV positive neurons in the MOB of the house musk shrew may develop postnatally.
Morphology and Dye-Coupling of Cells in the Pigeon Isthmo-Optic Nucleus
Authors: Li Wen-Chang , Wang Shu-Rong
Published: April 2003

Ground-feeding birds such as pigeons possess the most developed isthmo-optic nucleus in all classes of vertebrates. A previous study showed that this centrifugal or retinopetal nucleus modulates visual activity in tectal cells of pigeons; the present study aimed at revealing the morphology and possible dye-coupling of neurons in the isthmo-optic nucleus and in the ectopic cell region by intracellular injections of Lucifer yellow into neurons in slices. One hundred and twelve successfully labeled cells of the isthmo-optic nucleus were classified into bipolar (83%) and multipolar (17%) types, each of which was further divided into two subtypes, B and P and M and N, respectively. Neurons of B- and P-types are similar in that they have apical dendrites and axons usually arising from the opposite pole of piriform perikarya, but they differ in the length (20–120 vs. 10–20 μm) of their dendritic stems; M- and N-types possess polygonal perikarya giving rise to two to five primary dendrites either in the same orientation (M) or in a radiation fashion (N), and their axons originate from perikarya or occasionally from dendritic stems. Twelve single-injections resulted in the labeling of 26 cells, including 11 pairs and 1 quadruple labeling. About half of these are closely apposed ‘twin-cells’. Dye-coupling was found only between neighboring cells in the cell lamina. Thirteen cells in the ECR rostroventral to the ION were labeled and could be grouped into large or L- (46%) and small or S- (54%) types, mainly depending on the dendritic field size and the number of primary dendrites. No dye-coupling was observed between the presumptive ECR cells. The functional role of the ION and the significance of dye-coupling between neurons are discussed.
Tectal Fiber Connections in a Non-Teleost Actinopterygian Fish, the Sturgeon Acipenser
Authors: Yamamoto Naoyuki , Yoshimoto Masami , Albert James S. , Sawai Nobuhiko , Ito Hironobu
Published: April 2003

Tectal fiber connections were studied in members of an early branch of the actinopterygian lineage, the sturgeons Acipenser transmontanus and A. schrenkii, by means of biocytin, HRP, biotinylated dextran amine, and DiI tract tracing methods. The aim of this study is to elucidate the visual pathway via the optic tectum to the thalamus as a part of a series of studies on the visual pathways in sturgeons. After biocytin or biotinylated dextran amine injections to the optic tectum terminals are found bilaterally in the medial and lateral portions of both the dorsal thalamus and ventral thalamus. Ipsilateral projections are much more abundant. Tectal recipient areas in the thalamus overlap in part with the retinal recipient areas. After HRP or DiI injections to the dorsal or ventral thalamus, tectal neurons projecting to the thalamus were labeled in the ipsilateral or bilateral stratum periventriculare. Dendritic morphology of tectothalamic neurons suggests that they receive direct retinal input. These results suggest that visual information passes through the tectum to the thalamic areas which also receive direct retinal projections. In this regard, the visual system of Acipenser resembles that of chondrichthyans (sharks). Other fiber connections of the tectum are also described, which have not previously been studied by tracer methods in a sturgeon.
Posthatching Development of Spinal Motoneurons in the Angelfish Pterophyllum scalare
Authors: Yoshida Masayuki , Fudoji Masaomi , Sakamoto Hirotaka , Uematsu Kazumasa
Published: April 2003

We investigated the posthatching developmental sequence of spinal motoneurons innervating the axial muscles in the teleost angelfish, Pterophyllum scalare, by means of retrograde labeling with horseradish peroxidase. Two discrete types of spinal motoneurons, primary-type motoneurons and secondary motoneurons were labeled in a temporally different sequence during the course of larval development. These two types of motoneurons were morphologically distinguishable from one other. Primary-type motoneurons are generated by day 1 posthatching and do not increase in number over the observed period (to day 12 posthatching). In contrast, the secondary motoneurons increase in number through posthatching day 3. Differentiation of the spinal motoneurons appears to be nearly complete a few days before the onset of free swimming. In addition, the data suggest that the differentiation of secondary motoneurons precedes the development of the red muscle that is to be innervated by the motoneurons.
Hippocampal Volume Is Related to Complexity of Nesting Habitat in Leach’s Storm-Petrel, a Nocturnal Procellariiform Seabird
Authors: Abbott Marsha L. , Walsh Carolyn J. , Storey Anne E. , Stenhouse Ian J. , Harley Carolyn W.
Published: April 2003

The hippocampal and telencephalon volumes of the nocturnal Leach’s storm-petrel (Oceanodroma leucorhoa, n = 15) were compared with published data for food-storing and non-storing Passerines. The hippocampus to telencephalon ratio of Leach’s storm-petrels is intermediate between food-storing and non-storing birds. Leach’s storm-petrels taken from nesting burrows in wooded habitat had a larger relative hippocampal volume than those taken from burrows in an open meadow. Relative olfactory volume did not differ between woods and open-nesting storm-petrels. The larger relative hippocampal volume of storm-petrels may be associated with increased spatial demands of returning to their nests at night in the darker, more navigationally complex woods. It is not known whether the larger hippocampus in storm-petrels from the woods is due to selection on different subpopulations or whether experience in a more complex environment results in greater hippocampal volume. Hippocampal volume from the brain of one diurnal Procellariiforme, the northern fulmar (Fulmaris glacialis), fell within the range of non-storing species, which supports the view that hippocampal enlargement in the storm-petrel is related to the spatial demand of returning to the nest at night.
Steroid Hormones, Dendritic Remodeling and Neuronal Death: Insights from Insect Metamorphosis
Authors: Weeks Janis C.
Published: April 2003

Steroid hormones influence neuronal structure and function throughout the animal kingdom, via highly conserved receptor proteins. Insights into steroid effects on neurons and behavior have come from a range of vertebrate species including reptiles, amphibians, fish, birds, rodents and primates. In many instances, steroid hormones regulate the volume of particular regions of the nervous system by affecting both the number of constituent neurons and their size. A major determinant of neuronal number is the process of programmed cell death (PCD), which involves molecular machinery that is conserved across species. This article reviews steroid-mediated PCD and dendritic remodeling during metamorphosis of the hawkmoth, Manduca sexta. Metamorphosis is driven by a class of steroid hormones, the ecdysteroids. During the transformation from larva to pupa to adult moth, accessory planta retractor (APR) motoneurons of Manduca undergo dendritic regression and regrowth, and segment-specific PCD, in response to specific ecdysteroid cues. Experiments utilizing APRs in primary cell culture show that PCD is a direct response to ecdysteroids, regulated by the intrinsic segmental identity of individual APRs. As in other systems, activation of caspases (cysteine proteases) is involved in the execution phase of PCD. Other experiments demonstrate that the ecdysteroid-mediated regression of APRs’ dendrites at pupation causes weakening of monosynaptic excitatory inputs from sensory neurons that trigger a larval withdrawal reflex. Thus, the steroid-mediated reduction in dendritic extent is linked to a specific electrophysiological and behavioral change during metamorphosis. The comparative approach, taking advantage of a variety of vertebrate and invertebrate species, holds the most promise for elucidating the full spectrum of steroid effects on neurons and behavior.
Sex Steroids and Communication Signals in Electric Fish: A Tale of Two Species
Authors: Zakon Harold H. , Dunlap Kent D.
Published: April 2003

Weakly electric fish are good model animals to study the evolution of interspecific and sexual differences in communication signals. This is because the neural circuits producing these signals are simple and conserved among related species while the signals are highly species-specific, sexually-dimorphic, and under hormonal control. Here we focus on two related species of weakly electric gymnotiform fish that emit a wave-type discharge. These species differ in the direction of the sexual dimorphism of their electric organ discharge (EOD) frequencies and their propensity to produce aggressive communication signals called ‘chirps’. Brown ghost (Apteronotus leptorhynchus) males produce high frequency EODs while females produce low frequency EODs. When presented with an EOD mimic, males chirp frequently, while females seldom chirp. By contrast, black ghost (A. albifrons) males discharge at lower EOD frequencies than females, and there is no sex difference in chirping in this species. Accordingly, non-aromatizable androgens raise EOD frequency in brown ghosts, but lower it in black ghosts. Androgens induce chirping in female brown ghosts, but do not increase the propensity to chirp in female black ghosts. Thus, the difference in sexually-dimorphic communication signals between these two species can be explained by differences in their responses to sex steroids. Future studies will elucidate how the neural circuits generating these signals are differentially sensitive to steroids in these species.
Brain Size Is Not Correlated with Forelimb Dexterity in Fissiped Carnivores (Carnivora): A Comparative Test of the Principle of Proper Mass
Authors: Iwaniuk Andrew N. , Pellis Sergio M. , Whishaw Ian Q.
Published: April 2003

To test the hypothesis that brain size and forelimb dexterity are positively correlated, the relative brain size of 41 species of fissiped (terrestrial) carnivores (Order: Carnivora) was examined with respect to their forelimb use during feeding. With the use of a newly derived dexterity index, the forelimb dexterity executed by each of the species was calculated as a single, continuous variable which was then regressed against the residuals of brain size. To account for confounding effects of phylogenetic inertia, the analysis was performed with independent contrasts analysis using a speciational model of evolutionary change (i.e. equal branch lengths). The results suggest that relative brain size and isocortex size are not correlated with the dexterity of the proximal or distal segments or a combination of the two (total forelimb dexterity). The presence of species with widely different brain sizes and similar dexterities, and vice versa, suggests that an increase in the amount of neural substrate might not be necessary for the production of finely coordinated forelimb movements. It is suggested that this outcome is representative of the plasticity of both mammalian brain size and behavior and that variations in brain size and forelimb dexterity could be linked to disparate ecological and phylogenetic factors which act in concert to promote or constrain neural development and behavior in different species.
Relative Medial and Dorsal Cortex Volume in Relation to Foraging Ecology in Congeneric Lizards
Authors: Baird Day Lainy , Crews David , Wilczynski Walter
Published: April 2003

The need to locate distributed resources such as mates, food, and nests is correlated with an enlarged hippocampus in many mammalian and avian species. This correlation is believed to be a consequence of selection for spatial ability. Little is known about how such ecological needs affect non-mammalian, non-avian species. In lizards, the putative hippocampal homologues are the dorsal cortex (DC) and medial cortex (MC). We examined the relationship between foraging ecology and the size of the DC and MC in congeneric male lizards. We predicted based on the mammalian and avian literature that Acanthodactylus boskianus, an active forager that captures clumped, immobile prey would have a larger MC and DC than A. scutellatus, a sit-and-wait predator, that captures mobile prey. Our previous behavioral studies showed that A. boskianus did not differ from A. scutellatus on a spatial task but that A. boskianus was significantly better at the reversal of a visual discrimination, another task that is hippocampally dependent in mammals. In the current study, we found that, relative to telencephalon volume, the MC and DC were larger in the active forager whereas a control region, the lateral, olfactory, cortex, was similar in size between species. The current anatomical results suggest that MC and DC size is related to active foraging in lizards and, along with our previous behavioral studies, show that it is possible for this relationship to occur in the absence of evidence for species differences in spatial memory.
Neurochemical and Cellular Specializations in the Mammalian Neocortex Reflect Phylogenetic Relationships: Evidence from Primates, Cetaceans, and Artiodactyls
Authors: Hof Patrick R. , Glezer Ilya I. , Nimchinsky Esther A. , Erwin Joseph M.
Published: April 2003

Most of the available data on the cytoarchitecture of the cerebral cortex in mammals rely on Nissl, Golgi, and myelin stains and few studies have explored the differential morphologic and neurochemical phenotypes of neuronal populations. In addition, the majority of studies addressing the distribution and morphology of identified neuronal subtypes have been performed in common laboratory animals such as the rat, mouse, cat, and macaque monkey, as well as in postmortem analyses in humans. Several neuronal markers, such as neurotransmitters or structural proteins, display a restricted cellular distribution in the mammalian brain, and recently, certain cytoskeletal proteins and calcium-binding proteins have emerged as reliable markers for morphologically distinct subpopulations of neurons in a large number of mammalian species. In this article, we review the morphologic characteristics and distribution of three calcium-binding proteins, parvalbumin, calbindin, and calretinin, and of the neurofilament protein triplet, a component of the neuronal cytoskeleton, to provide an overview of the presence and cellular typology of these proteins in the neocortex of various mammalian taxa. Considering the remarkable diversity in gross morphological patterns and neuronal organization that occurred during the evolution of mammalian neocortex, the distribution of these neurochemical markers may help define taxon-specific patterns. In turn, such patterns can be used as reliable phylogenetic traits to assess the degree to which neurochemical specialization of neurons, as well as their regional and laminar distribution in the neocortex, represent derived or ancestral features, and differ in certain taxa from the laboratory species that are most commonly studied.
Arealization of the Neocortex in Mammals: Genetic and Epigenetic Contributions to the Phenotype
Authors: Krubitzer Leah , Huffman Kelly J.
Published: April 2003

The neocortex is composed of areas that are functionally, anatomically and histochemically distinct. In comparison to most other mammals, humans have an expanded neocortex, with a pronounced increase in the number of cortical areas. This expansion underlies many complex behaviors associated with human capabilities including perception, cognition, language and volitional motor responses. In the following review we consider data from comparative studies as well as from developmental studies to gain insight into the mechanisms involved in arealization, and discuss how these mechanisms may have been modified in different lineages over time to produce the remarkable degree of organizational variability observed in the neocortex of mammals. Because any phenotype is a result of the complex interactions between genotypic influences and environmental factors, we also consider environmental, or epigenetic, contributions to the organization of the neocortex.
Signal Decoding and Receiver Evolution
Authors: Ryan Michael J. , Getz Wayne
Published: April 2003

We use a connectionist model, a recurrent artificial neural network, to investigate the evolution of species recognition in sympatric taxa. We addressed three questions: (1) Does the accuracy of artificial neural networks in discriminating between conspecifics and other sympatric heterospecifics depend on whether the networks were trained only to recognize conspecifics, as opposed to being trained to discriminate between conspecifics and sympatric heterospecifics? (2) Do artificial neural networks weight most heavily those signal features that differ most between conspecifics and sympatric heterospecifics, or those features that vary less within conspecifics? (3) Does selection for species recognition generate sexual selection? We find that: (1) Neural networks trained only on self recognition do not classify species as accurately as networks trained to discriminate between conspecifics and heterospecifics. (2) Neural networks weight signal features in a manner suggesting that the total sound environment as opposed to the relative variation of signals within the species is more important in the evolution of recognition mechanisms. (3) Selection for species recognition generates substantial variation in the relative attractiveness of signals within the species and thus can result in sexual selection.
Relationship of Some Risk Factors with Typical and Atypical Manifestations of Coronary Heart Disease
Authors: Menotti Alessandro , Blackburn Henry , Seccareccia Fulvia , Kromhout Daan , Nissinen Aulikki , Karvonen Martti , Fidanza Flaminio , Giampaoli Simona , Buzina Ratko , Mohacek Ivan , Nedeljkovic Srecko , Aravanis Christ , Dontas Anastasios
Published: April 2003

Background: This analysis explores whether ‘typical’ clinical manifestations of coronary heart disease (CHD) such as myocardial infarction and sudden death, relate to major cardiovascular risk factors in the same way as the ‘atypical’ manifestations, e.g. heart failure and chronic arrhythmias. Patients and Methods: Sixteen cohorts of men aged 40–59 in seven countries were examined, risk factors measured (age, systolic blood pressure, serum cholesterol and smoking habits) and 25-year mortality data collected in a systematic way. Cohorts were located in the US (n = 1), Finland (n = 2), the Netherlands (n = 1), Italy (n = 3), former Yugoslavia (n = 5), Greece (n = 2) and Japan (n = 2), with a total of 12,763 individuals. Ecological analysis based on regression equations and correlation among cohorts, and individual analyses based on proportional hazard models in pools of cohorts were conducted with typical and atypical CHD deaths as dependent variables. Results: The ecological analysis suggests a significant relationship of populational mean levels of serum cholesterol and of systolic blood pressure to age-adjusted death rates from typical CHD manifestations. The relationships for atypical CHD deaths were not statistically significant. In the ecological approach with multivariate analysis, none of the risk factors showed relevant associations with event rates, except serum cholesterol and typical CHD deaths. The ecological relationship of serum cholesterol to atypical CHD death rates was negative but not significant. On average, mean age at death was statistically higher among atypical CHD than typical CHD patients (70.2 vs. 65.8 years). In the individual multivariate analysis conducted on pools of countries, the relationship of risk factors with typical CHD deaths was direct and significant for age, systolic blood pressure, and smoking habits in Northern Europe and America and Southern Europe, but only for systolic blood pressure and smoking habits in Japan, whereas for atypical CHD, the predictive factors were age, systolic blood pressure and cigarette smoking in Northern Europe and America and Southern Europe, but only age in Japan. Conclusions: The usual relationship of blood pressure and smoking habits and the differential relationship of serum cholesterol with atypical CHD (negative or absent) versus typical CHD (direct and significant) could be explained by ‘two different diseases’ or by a mix of poorly classified conditions among the atypical cases.
Aortic Intramural Hematoma: An Increasingly Recognized Aortic Disease
Authors: Bolognesi Roberto , Manca Carlo , Tsialtas Dimitri , Vasini Paolo , Zeppellini Roberto , De Domenico Renato , Cucchini Francesco , Visioli Odoardo
Published: April 2003

Aortic intramural hematoma (IMH) is a rarely diagnosed pathological condition that is not well characterized to date. We diagnosed IMH in 4 of 31 patients with suspected aortic dissection admitted to our coronary care unit from 1992 to 1995. In all 4 cases, IMH was located in the ascending aorta. At the time of hospitalization, all patients showed tachycardia, hypotension and pericardial effusion. Diagnosis of IMH was made by transesophageal echocardiography and computed tomography. We performed aortography in 2 patients, but it was non-diagnostic in both of them. One patient died before surgery. Autopsy confirmed the diagnosis of IMH and showed severe pericardial effusion. In another patient, the diagnosis was confirmed during successful surgery, while the remaining 2 patients recovered after medical therapy. The 3 surviving patients are still under follow-up control 12, 16 and 20 months after the initial acute event. We briefly discuss the epidemiological, clinical, diagnostic, therapeutic and prognostic aspects of IMH.
One-Year Mortality after Acute Myocardial Infarction prior to and after the Implementation of a Widespread Use of Thrombolysis and Aspirin
Authors: Herlitz Johan , Hartford Marianne , Karlson Björn W. , Dellborg Mikael , Källström Gerd , Karlsson Thomas
Published: April 2003

During 1 year of follow-up, we compared the mortality after acute myocardial infarction (AMI) prior to and after the introduction of a more widespread use of thrombolytic agents and aspirin. Study period: Two periods (I = 1986–1987 and II = 1989–1990) were compared. Patients: All patients admitted to the coronary care units at the two city hospitals in the community of Göteborg who fulfilled the criteria for development of AMI participated in the evaluation. Results: The overall 1-year mortality rate was 24% during period I and 23% during period II (NS). However, among patients up to 70 years of age, the mortality was reduced from 15 to 11% (p < 0.05), whereas among patients aged over 70 years the mortality remained almost unchanged (34 vs. 35%; NS). Conclusion: The introduction of a more widespread use of thrombolytic agents and aspirin has not substantially changed the overall mortality in AMI. However, among younger patients, the mortality appears to have been reduced but not among the elderly.
Antihypertensive Treatment in Postmenopausal Women: Results from a Prospective, Randomized, Double-Blind, Controlled Study Comparing an ACE Inhibitor (Moexipril) with a Diuretic (Hydrochlorothiazide)
Authors: Stimpel Michael , Koch Brigitte , Oparil Suzanne
Published: April 2003

The present study was designed to compare the safety and efficacy of the new angiotensin-converting enzyme inhibitor moexipril with that of hydrochlorothiazide (HCTZ) in postmenopausal women with mild-to-moderate hypertension. After a 4-week single-blind placebo period, 97 postmenopausal hypertensive women (42–74 years of age) with a sitting diastolic blood pressure (SDBP) of 95–114 mm Hg were randomized to receive either once daily moexipril 15 mg or HCTZ 25 mg for a 12-week double-blind treatment period. At study endpoint, HCTZ caused significantly greater increases from baseline in serum uric acid levels than did moexipril (0.8 ± 0.1 vs. 0.1 ± 0.1 mg/dl, p < 0.01). Furthermore, 12-week treatment with HCTZ resulted in significant increases in glucose (+11.0 ± 4.1 mg/dl) and total cholesterol/HDL ratio (+0.3±0.1 mg/dl) and a significant decrease in HDL (–3.2±0.7 mg/dl). In contrast, moexipril treatment was not associated with significant changes in any metabolic parameter. Both drugs efficiently lowered SDBP with reductions of –10.0 ± 1.3 and –11.8 ± 1.1 mm Hg in the moexipril and HCTZ group, respectively. Clinical adverse events were reported by a greater percentage of HCTZ patients (53%) than moexipril patients (40%), with headache and rhinitis as the most frequent events. The results indicate that moexipril was better tolerated than HCTZ in postmenopausal women and did not adversely affect metabolic parameters. Both drugs were effective in lowering blood pressure.
Diastolic and Systolic Function as Predictors of Exercise Capacity after Myocardial Infarction in Young Men
Authors: Eriksson S.V. , Caidahl K. , de Faire U. , Lindvall K. , Rehnqvist N. , Hamsten A.
Published: April 2003

We evaluated the power of measurements of left ventricular (LV) systolic and diastolic function for predicting exercise capacity in 97 young male survivors of a myocardial infarction. The patients were evaluated with M-mode echocardiography, a symptom-limited exercise test and coronary and LV angiography. In univariate analyses, maximum exercise workload was most closely related to the atrial emptying index, an index of diastolic function (r = 0.37, p < 0.005), but not to LV ejection fraction (r = 0.001, NS). This relationship was stronger in the 42 patients without signs of ischemia during exercise (r = 0.51, p < 0.005). Multivariate analyses indicated that the atrial emptying index (p < 0.005) provided independent contribution to the prediction of maximum exercise capacity. LV diastolic function but not LV systolic function was related to exercise capacity in young survivors of myocardial infarction.