bluuebunny/crossref_metadata_2025 huggingface dataset:
Remodeling chromatin structures for transcription: What happens to the histones?
Authors: Steger David J. , Workman Jerry L.
Published: February 2005

Activation of gene transcriptionin vivois accompanied by an alteration of chromatin structure. The specific binding of transcriptional activators disrupts nucleosomal arrays, suggesting that the primary steps leading to transcriptional initiation involve interactions between activators and chromatin. The affinity of transcription factors for nucleosomal DNA is determined by the location of recognition sequences within nucleosomes, and by the cooperative interactions of multiple proteins targeting binding sites contained within the same nucleosomes. In addition, two distinct types of enzymatic complexes facilitate binding of transcription factors to nucleosomal DNA. These include type A histone acetyltransferases (e.g. GCN5/ADA transcriptional adaptor complex) and ATP‐driven molecular machines that disrupt histone‐DNA interactions (e.g. SWI/SNF and NURF complexes). These observations raise the important question of what happens to the histones during chromatin remodeling. We discuss evidence supporting the retention of histones at transcription factorbound sequences as well as two alternative pathways of histone loss from gene control elements upon transcription factor binding: histone octamer sliding and histone dissociation.
A role for transcriptional repression during light control of plant development
Authors: von Arnim Albrecht , Deng Xing‐Wang
Published: February 2005

Light mediates plant development partly by orchestrating changes in gene expression, a process which involves a complex combination of positive and negative signaling cascades. Genetic investigations using the small crucifer Arabidopsis thaliana have demonstrated a fundamental role for the down‐regulation of light‐inducible genes in response to darkness, thus offering a suitable model system for investigating how plants repress gene expression in a developmental context. Rapid progress in eukaryotic gene repression mechanisms in general, and light control of plant gene expression in particular, sheds new light on how a class of ten pleiotropic COP/DET/FUS genes might function to down‐regulate light‐inducible genes in plants.
Reminiscences from the first curator of the whitney‐rothschild collection
Authors: Mayr Ernst
Published: February 2005

Dr Ernst Mayr has been one of the seminal figures of 20th century biology. His essential contributions were in the development of the Modern Synthesis in evolutionary biology. His landmark book Systematics and the Origin of Species, was published in 1942 and has long been acknowledged as one of the key foundations of 20th century evolutionary biology. In many subsequent articles and books on evolution and the history and philosophy of biology during the past half century, he has continued to be a key contributor of ideas and inspiration to successive generations of evolutionary biologists.

In the first of two ‘Roots’ articles, he describes the early stages of his career and the serendipitous events that furthered it. This article was first presented as a talk, on October 27, 1993, at the 50 year Jubilee celebration of the founding of the Whitney wing, the ornithological section, of the American Museum of Natural History in New York City. In next month's ‘Roots’ article, Dr Mayr will describe the events that led to the founding of the Society for the Study of Evolution in 1946, in St Louis, Missouri.
The establishment of evolutionary biology as a discrete biological discipline
Authors: Mayr Ernst
Published: February 2005

This is the second of two ‘Roots’ articles from Dr Ernst Mayr; the first appeared in the February issue. The article that follows is Dr Mayr's address on the 50th anniversary of the founding of the Society for the Study of Evolution, St Louis, USA, June 19, 1996.
Imprint switch mechanism indicated by mutations in prader‐willi and angelman syndromes
Authors: Kelsey Gavin , Reik Wolf
Published: February 2005

Genomic imprinting is an epigenetic mechanism resulting in the preferential expression of the maternal or paternal alleles of a specific subset of genes in the mammalian genome. A key but relatively unexplored question is how imprints are established in the germline. New observations(1) on two classical imprinting disorders, the Prader‐Willi (PWS) and Angleman (AS) syndromes, offer the first genetic insight into this process. Molecular analysis of imprinting mutations that interfere with the appropriate establishment of the maternal and paternal epigenotypes has led to the identification of imprinted transcripts that could be involved in switching imprints in the germlines.
Ret in human development and oncogenesis
Authors: Edery Patrick , Munnich Arnold , Lyonnet Stanislas , Eng Charis
Published: February 2005

Hirschsprung disease and the multiple endocrine neoplasia type 2 syndromes are hereditary disorders related to the abnormal migration, proliferation or survival of neural crest cells and their derivatives. Hirschsprung disease is a frequent disorder of the enteric nervous system, resulting in intestinal obstruction. The multiple endocrine neoplasia type 2 syndromes predispose to cancers of neural crest derivatives. Both diseases are associated with heterozygous mutations in the RET proto‐oncogene. RET encodes a transmembrane receptor tyrosine kinase expressed in neural crest lineages and whose ligand, glial‐cell‐line‐derived neurotrophic factor, has been very recently identified. In vitro expression studies demonstrate that while Hirschsprung disease mutations result in loss of function of the mutant RET tyrosine kinase, multiple endocrine neoplasia type 2 mutations lead to its constitutive activation. Thus, the two ‘faces’ of RET, gain of function and loss of function, each lead to a different syndrome, respectively: multiple endocrine neoplasia type 2, a cancer syndrome, or Hirschsprung disease, a developmental defect.
Encystation of entamoeba parasites
Authors: Eichinger Dan
Published: February 2005

Entamoeba histolytica is a protozoan parasite of humans, and the causitive agent of intestinal amebiasis. The disease‐causing stage of the parasite is an osmotically sensitive ameboid form, which differentiates into a thick‐walled cyst for transmission from person to person. The conditions within the human intestine that induce encystment of the amoeba are unknown, but studies using an amoebic parasite of reptiles are now yielding information about the molecules and host:parasite interactions involved in the process. An understanding of the amoeba's obligatory encystment pathway should provide an approach for interrupting the transmission of this parasite, for which there is currently no vaccine.
P57KIP2 targeted disruption and beckwith‐wiedemann syndrome: Is the inhibitor just a contributor?
Authors: Swanger W. Jherek , Roberts James M.
Published: February 2005

Beckwith‐Wiedemann syndrome is a human congenital disorder characterized by a wide variety of growth abnormalities, including developmental defects and predisposition to certain tumors. Genetic evidence has suggested a role for p57KIP2, a member of a family of cell cycle inhibitory genes, in Beckwith‐Wiedemann syndrome. Two independent groups(1,2) have reported the generation and characterization of mice lacking functional p57KIP2, These mice demonstrate a number of abnormal phenotypes which overlap with, although do not completely recapitulate, Beckwith‐Wiedemann syndrome. These findings advance the molecular characterization of a human disorder, and provide insight into the interplay between regulation of cell division and development.
My favourite molecule: Meiotin‐1: The meiosis readiness factor?
Authors: Riggs C. Daniel
Published: February 2005

Meiotin‐1 is a protein found in developing microsporocytes of Lilium longiflorum, and immunological assays indicate that cognates exist in both mono‐ and dicotyledonous plants. Its temporal and spatial expression pattern, coupled with its unusual distribution in chromatin and the properties it shares with histone H1, encourages speculation that it is involved in regulating meiotic chromatin structure. Molecular analyses provide support for the hypothesis that meiotin‐1 arose from histone H1 by an exon shuffling mechanism, as meiotin‐1 is an H1‐like protein that lacks the amino‐terminal domain shared by H1 molecules. We have proposed that meiotin‐1 serves to limit chromatin condensation in order to foster the unique cytological and molecular events which occur during meiotic prophase. As such, meiotin‐1 fits the role of a ‘meiosis readiness factor’, and its accumulation to a threshold level may commit mitotically dividing progenitor cells to differentiate into meiocytes.
Molecular neurogenetics of chemotaxis and thermotaxis in the nematode Caenorhabditis elegans
Authors: Mori Ikue , Ohshima Yasumi
Published: February 2005

Chemotaxis and thermotaxis in Caenorhabditis elegans are based on the chemical senses (smell and taste) and the thermal sense, respectively, which are important for the life of the animal. Laser ablation experiments have allowed identification of sensory neurons and some interneurons required for these senses. Many mutants that exhibit various abnormalies have been isolated and analyzed. These studies have predicted novel signaling pathways whose components include a putative odorant specific transmembrane receptor (ODR‐10) and a cyclic nucleotide‐gated channel (TAX‐4/TAX‐2) functioning in taste and thermosensation as well as in smell. The emerging picture of the mechanisms of sensory transduction in C. elegans seems to be basically similar to what is known of visual and olfactory sensory transduction in vertebrates. Thus, molecular and cellular analyses of chemotaxis and thermotaxis in C. elegans have proved useful and will continue to provide significant implications for the molecular basis of sensory systems in higher animals.
Building a bird brain: Sculpting neural circuits for a learned behavior
Authors: Bottjer Sarah W.
Published: February 2005

Development in animals is frequently characterized by periods of heightened capacity for both neural and behavioral change. So‐called sensitive periods of development are windows of opportunity in which brain and behavior are most susceptible to modification. Understanding what factors regulate sensitive periods constitutes one of the main goals of developmental neuroscience. Why is the ability to learn complex behavioral patterns often restricted to sensitive periods of development? Songbirds provide a model system for unraveling the mysteries of neural mechanisms of learning during development. Like many songbirds, zebra finches (Taeniopygia guttata) learn a specific vocal pattern during a restricted period early in life. Young birds must hear songs produced by members of their species; this auditory experience is thought to engender specific changes in the brain to guide the process of vocal learning. Many studies of the songbird system have focused on examining relationships between brain development and learning. One goal of this work is to elucidate mechanisms that regulate basic processes of neural development, and in so doing to shed light on factors governing the emergence of a complex learned behavior.
Proximal protection during saphenous vein graft angioplasty: The Kerberos embolic protection system
Authors: Webb John G. , Vaderah Sanjeev , Hamburger Jaap , McQueen Colleen , Whitlow Patrick
Published: February 2005

Percutaneous intervention in the setting of aortocoronary saphenous vein graft disease is associated with a significant risk of distal embolization. Devices intended to minimize the clinical impact of embolization have primarily utilized distally placed occlusive balloons or filters. Although such systems are often effective, distal protection does have limitations. We report a novel proximal embolic protection and rinsing system intended to overcome some of these limitations. Catheter Cardiovasc Interv 2005;64: 383–386. © 2005 Wiley‐Liss, Inc.
Transcatheter creation of atrial septal perforation using a radiofrequency transseptal system: Novel approach as an alternative to transseptal needle puncture
Authors: Sakata Yoshihito , Feldman Ted
Published: February 2005

Indications for the transseptal approach to the left side of the heart have recently broadened, as it provides a therapeutic access for both left‐sided catheter ablation and also percutaneous transvenous valvular intervention. Despite rising demand for transseptal procedures, the technique and device used for this purpose have remained essentially unchanged over the past 4 decades. The possibilities of failure of puncturing distorted and thickened atrial septal tissue or risks of complications related to cardiac perforation remain limitations of the technique. A new radiofrequency catheter provides an alternative approach to create a controlled transseptal perforation. We applied this technique to a series of patients and evaluated its feasibility as an alternative to conventional transseptal needle puncture. Catheter Cardiovasc Interv 2005;64:327–332. © 2005 Wiley‐Liss, Inc.
Bilateral carotid angioplasty and stenting
Authors: Henry Michel , Gopalakrishnan Lakshmi , Rajagopal Sriram , Rath P.C. , Henry Isabelle , Hugel Michele
Published: February 2005

Bilateral carotid stenosis is generally treated by staged stenting procedure and rarely simultaneously due to concerns about hemodynamic impairment from stimulation of the carotid sinus baroreflex (severe bradycardia, hypotension) and the risk of cerebral hyperperfusion syndrome. Most of the accounts of bilateral carotid stenting are of small series. The aim of this study was to evaluate the feasibility and safety of simultaneous bilateral carotid angioplasty and stenting (CAS) in comparison with staged procedure. We retrospectively analyzed the procedural outcome and complications of bilateral CAS done between February 1995 and June 2004 in a consecutive series of 57 high‐risk patients. Mean age was 64 ± 9 years (male, 43; female 14). One hundred fifteen arteries were treated (one patient had bilateral internal carotid artery stenosis associated to an ostial common carotid artery stenosis). Thirty‐nine patients were symptomatic (70%). Thirty‐six patients had severe coronary artery disease. Seventeen patients underwent a simultaneous bilateral CAS (group 1), 40 in a staged manner (group 2). Among these 40 patients 10 were treated with a time interval of 24 hr, while the 30 other ones were treated with a time interval of 2 days to 2 months. A neuroprotection device was used in the last 42 patients. There was technical success in all patients and transient bradycardia and/or hypotension in 25 patients (44%). There was no prolonged bradycardia or hypotension. At 30 days, we observed in group 1 (simultaneous bilateral CAS) no transient ischemic attack (TIA), no minor stroke, one (5.8%) major stroke (hyperperfusion syndrome with brain hemorrhage leading to death in a patient under IIb/IIIa inhibitors), one myocardial infarction leading to death, and two (11.7%) death/stroke/myocardial infarction; in group 2 (staged procedure), two (5%) TIAs, no minor stroke, no major stroke, and one (2.5%) hyperperfusion syndrome with rapid recovery. Among the 10 patients treated with a time interval of 24 hr, we observed one TIA. Among carefully selected patients, bilateral CAS is feasible simultaneously or the day after, with a safety and complication rate comparable to that of large published series of CAS or endarterectomies in high‐risk patients. Nevertheless, careful monitoring of the patient, blood pressure, and heart rate is mandatory to avoid complications related to hyperperfusion syndrome. Routine use of neuroprotection device and meticulous technique should improve the outcomes of bilateral CAS. Catheter Cardiovasc Interv 2005;64:275–282. © 2005 Wiley‐Liss, Inc.
Superiority of endovascular grafts compared to bare metal stents with transstent coil embolization for endovascular abdominal aortic aneurysm repair in patients at high risk for surgery
Authors: Boccalandro Fernando , Cohen Alan , Raval Barat , Chen Phoebe , Muench Andreas , Achour Hela , Carter Catherine , Underwood Carol , Smalling Richard W.
Published: February 2005

We sought to determine the effectiveness of uncovered stents with aneurysm transstent coil embolization compared with endografts for percutaneous abdominal aortic aneurysm (AAA) repair. Thirty‐six patients with AAA considered inoperable underwent endovascular repair using the Ancure bifurcated endograft or overlapping uncovered stents with transstent coil embolization. Procedural success, outcomes, serial aneurysm size, aneurysm blood flow, and growth ratios were compared between groups. One patient in each group died due to the procedure and two patients in the endograft cohort required acute surgical repair. After 2.0 ± 0.8 years of follow‐up, three patients required endograft placement, four surgical repair, three had AAA rupture, with two AAA‐related deaths in the uncovered stent group. No late deaths or surgical conversion occurred in the endograft group. The primary AAA flow exclusion and aneurysm expansion rate and growth were superior in the endograft group and during follow‐up. In high‐risk patients with AAA, the use of endografts was superior compared to uncovered stents with transstent coil embolization for endovascular repair. Catheter Cardiovasc Interv 2005;64:283–290. © 2005 Wiley‐Liss, Inc.
Retrograde percutaneous aortic valve implantation for critical aortic stenosis
Authors: Hanzel George S. , Harrity Philip J. , Schreiber Theodore L. , O'Neill William W.
Published: February 2005

Recently, a prosthetic aortic valve has been implanted percutaneously in several patients using an antegrade transseptal approach. This has been shown to be feasible and associated with dramatic hemodynamic improvement. We report a retrograde implantation of a percutaneous heart valve (PHV) in an 84‐year‐old man with critical aortic stenosis and refractory congestive heart failure after difficulties encountered with an initial antegrade approach. While attempting antegrade transseptal implantation of a PHV, the anterior leaflet of the mitral valve was tethered by the guidewire resulting in severe mitral regurgitation and pulseless electrical activity. Cardiac resuscitation was successful. Utilizing a retrograde approach, the PHV was successfully implanted in a stable position below the coronary ostia and well above the mitral valve leaflets. The aortic valve area increased from 0.55 to 1.7 cm2 with only mild paravalvular aortic regurgitation. Despite marked improvement in aortic valve function, the patient died secondary to guidewire‐induced mitral valve anterior leaflet laceration, severe mitral regurgitation, and cardiogenic shock. Retrograde implantation of a PHV can be successfully performed with substantial increase in aortic valve area and an acceptable degree of aortic regurgitation. Although the retrograde approach may be associated with greater risk of vascular access site complications, it may be considerably safer by avoiding potential guidewire injury to the mitral valve. Further refinements in technique may establish the retrograde approach as the preferred means of PHV implantation in nonsurgical patients with critical aortic stenosis. Catheter Cardiovasc Interv 2005;64:322–326. © 2005 Wiley‐Liss, Inc.
Percutaneous balloon aortic valvuloplasty: Antegrade transseptal vs. conventional retrograde transarterial approach
Authors: Sakata Yoshihito , Syed Zubair , Salinger Michael H. , Feldman Ted
Published: February 2005

Percutaneous balloon aortic valvuloplasty (BAV) has been limited predominantly to a palliative treatment for poor surgical candidates with critical aortic stenosis and multiple high‐risk or comorbid conditions. The most commonly used technique for BAV is the retrograde approach, in which the balloon is passed via the femoral artery using 12–14 Fr sheaths. We compared an antegrade transseptal approach using the Inoue balloon vs. the retrograde transarterial approach using conventional balloons. The antegrade group had an improved acute hemodynamic outcome, including 20% additional increase of aortic valve area and 20% greater reduction of transaortic valve gradient compared to the retrograde approach. Preclosure with the Perclose device was used for the 14 Fr venous access sites, resulting in immediate hemostasis, minimizing the need for transfusion, and diminishing the period of bed rest. The improved acute efficacy and relative ease of venous access for the antegrade approach facilitate BAV by eliminating the need for large‐caliber arterial access sheaths. The antegrade approach also incorporates technical elements necessary for percutaneous aortic valve replacement and may have expanded applications as an adjunct to this developing therapy. The impact of improved acute results on the long‐term clinical outcome for this patient group will require further study. Catheter Cardiovasc Interv 2005;64:314–321. © 2005 Wiley‐Liss, Inc.
Self‐Assembled Nanotapes of Oligo(p‐phenylene vinylene)s: Sol–Gel‐Controlled Optical Properties in Fluorescent π‐Electronic Gels
Authors: George Subi J. , Ajayaghosh Ayyappanpillai
Published: February 2005

A rational approach to the design of supramolecular organogels of all‐trans oligo(p‐phenylene vinylene) (OPV) derivatives, a class of well‐known organic semiconductor precursors, is reported. Self‐assembly of these molecules induced gelation of hydrocarbon solvents at low concentrations (<1 mM), resulting in high aspect ratio nanostructures. Electron microscopy and atomic force microscopy (AFM) studies revealed twisted and entangled supramolecular tapes of an average of 50–200 nm in width, 12–20 nm in thickness, and several micrometers in length. The hierarchical growth of the entangled tapes and the consequent gelation is attributed to the lamellar‐type packing of the molecules, facilitated by cooperative hydrogen bonding, π stacking, and van der Waals interactions between the OPV units. Gelation of OPVs induced remarkable changes in the absorption and emission properties, which indicated strong electronic interaction in the aggregated chromophores. Comparison of the absorption and emission spectra in the gel form and in the solid film indicated a similar chromophore organization in both phases. The presence of self‐assembled aggregates of OPVs was confirmed by solvent‐ and temperature‐dependent changes in the absorption and emission properties, and by selective excitation experiments. This is the first detailed report of the gelation‐induced formation of OPV nanotapes, assisted by weak, nondirectional hydrogen‐bonding motifs and π–π stacking. These findings may provide opportunities for the design of a new class of functional soft materials and nanoarchitectures, based on π‐conjugated organic semiconductor‐type molecules, thereby enabling the manipulation of their optical properties.
Stereochemical Investigation of Palladium(II) Complexes with Phenanthroline Ligands: A Molecular Mechanics Approach
Authors: Calligaris Mario , Zangrando Ennio , Milani,Angelica Marson Barbara
Published: February 2005

Specific force field parameters have been derived through an optimisation procedure based on crystal structure data to describe the geometry of PdII‐phenanthroline complexes. The X‐ray structure of [Pd(CH3)(3‐sBu‐phen)2][OTf] is also reported. Molecular mechanics calculations show that intramolecular steric interactions yield severe distortions from a square‐planar geometry of the metal atom, both in bischelated [Pd(3‐R‐phen)2]2+ and monochelated [Pd(CH3)(3‐R‐phen)2]+ complexes. A complete stereochemical analysis of the possible diastereoisomers of this last complex (R = sBu) allows the rationalisation of its fluxional behaviour observed in solution. Complexes like [Pd(H)(3‐tmp‐phen)2]+ and [Pd{CH(C6H5)CH2C(O)OCH3}(3‐tmp‐phen)(CH3OH)]+ (tmp = 1,2,2‐trimethylpropyl) have also been investigated as species reasonably involved in the copolymerisation reactions. It is suggested that the remarkable increase of the copolymer molecular weight obtained with the 3‐tmp‐phen ligand derives from the steric destabilisation of an intermediate species postulated for the termination reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
New Complexes of Divalent Thulium with Substituted Phospholyl and Cyclopentadienyl Ligands (Eur. J. Inorg. Chem. 4/2005)
Authors: Nief François , Tayart de Borms Brice , Ricard Louis , Carmichael Duncan
Published: February 2005

The cover picture shows the X‐ray crystal structure of bis(1,3‐di‐tert‐butylcyclopentadienyl)thulium(tetrahydrofuran), a new organothulium(II) complex and the first one with all‐carbon κ‐ligands. Two new and particularly stable phospholylthulium(II) complexes are also described. The very existence and relative ease of formation of the so far described thulium(II) molecular compounds strongly suggest that many more such compounds can be prepared, provided that adequate steric and/or electronic protection of the thulium(II) ion can be archieved, thus paving the way to new and hopefully exciting studies in the field of thulium(II) chemistry. Details are discussed in the article by F. Nief et al. on p. 637 ff. The cover picture was rendered in POVRAY 3.5, and the initial input file was obtained with Louis J. Farrugia′s ORTEP‐III for Windows programme.
Case teaching and evaluation
Authors: Patton Michael Quinn , Patrizi Patricia
Published: February 2005

This chapter reviews the benefits of case teaching, examines evaluation issues that cases can be used to surface, and provides guidance for using the case method in evaluation teaching and training.
Evaluation of the Fighting Back initiative
Authors: Sherwood Kay E.
Published: February 2005

The Robert Wood Johnson Foundation Fighting Back initiative is a community‐based drug abuse prevention effort. The case illustrates the importance of taking context into account in evaluation, raises questions about how community interventions are conceptualized and evaluated, and provides a cautionary tale about the manageability of large‐scale, comprehensive evaluations.
Evaluation of the Central Valley Partnership of the James Irvine Foundation
Authors: Campbell Martha S. , Patton Michael Quinn , Patrizi Patricia
Published: February 2005

The focus of this teaching case is the Central Valley Partnership initiative of the James Irvine Foundation. This case traces the varying roles of the external evaluator as the program changed and developed.
Evaluation case teaching from a participant perspective
Authors: Bare John
Published: February 2005

Evaluation professionals can benefit from practice in the same way that lawyers, doctors, and other professionals improve their performance through practice. The case method enables practice through role plays and situational analyses.
Aromatic plants of tropical Central Africa. XLVIII. Comparative study of the essential oils of four Hyptis species from Cameroon: H. lanceolata Poit., H. pectinata (L.) Poit., H. spicigera Lam. and H. suaveolens Poit.
Authors: Tchoumbougnang F. , Zollo P. H. Amvam , Boyom F. Fekam , Nyegue M. A. , Bessière J. M. , Menut C.
Published: February 2005

The chemical composition of the essential oils obtained by hydrodistillation of fresh leaves from Hyptis lanceolata, H. pectinata, H. spicigera and H. suaveolens growing in Cameroon were analysed by GC and GC–MS. The oil of H. suaveolens was rich in sabinene (20.6%), β‐caryophyllene (17.5%) and bergamotol (10.9%), while the oil of H. pectinata contained germacrene D (28.0%) and β‐caryophyllene (22.1%) as the major constituents. H. spicigera oil contained α‐pinene (28.3%), β‐caryophyllene (19.1%), limonene (13.4%) and ß‐pinene (10.3%) as the main components. The most abundant constituents identified in the oil of H. lanceolata were β‐pinene (40.7%) and germacrene D (19.9%). These chemical profiles were compared with literature results; relative similarities were found in chemical compositions of each species, but some quantitative and qualitative variations were noted. Copyright © 2005 John Wiley & Sons, Ltd.
Calcium uptake in glycerol‐extracted rabbit psoas muscle fibers II. Electron microscopic localization of uptake sites
Authors: Pease D. C. , Jenden D. J. , Howell J. N.
Published: February 2005

An effort has been made to ascertain the site of calcium uptake in rabbit psoas muscle by electron microscopy. Following a brief glycerol extraction, small groups of fibers were exposed in a suitable electrolyte environment to calcium and ATP. Conditions were such that calcium was accumulated as an insoluble oxalate salt. Conventional preparatory procedures for electron microscopy were modified so that the calcium oxalate deposits were retained in situ in ultrathin sections. These were found localized in the longitudinal component of the sarcoplasmic reticulum including the terminal dilatations which form the outer elements of the triads. The possible participation of the intermediate element of the triad in the uptake of calcium could not be determined. The results are regarded as direct evidence that the sarcoplasmic reticulum is intimately concerned with the uptake and release of calcium associated with the contraction‐relaxation cycle.
The involvement of pH, Adenosine triphosphate, calcium, and magnesium in the contraction of the glycerinated stalks of Vorticella
Authors: Townes Mary M. , Brown Dugald E. S.
Published: February 2005

A glycerinated Vorticella stalk is prepared which remains relaxed at pH 6.8 or lower but contracts maximally when the pH is raised from 6.8 to 7.0. At pH 6.8, a maximum contraction is also produced when the Ca++ concentration is increased to 3 μ M.

The degree of relaxation below pH 6.8 is fostered by ATP and Mg++ which, along with Ca++, determine the degree of contraction at pH 7.0. A major role of calcium on the pH‐induced contraction is to lower the pH‐threshold from pH 7.5, obtaining in its absence to a stable value of pH 6.8. The only condition in which ATP is shown to cause a maximum contraction is at pH 7.0 in a medium containing 6 × 10−3 M Mg++ and 3 × 10−9 Ca++.

It is considered that Ca++, Mg++, and ATP react with the contractile proteins to form a contractile complex which is in the relaxed form at pH 6.8. At this pH an increase of 0.2 pH units or the addition of 3 μ M Ca++ converts the complex to the shortened form, a contraction ensuing.
Possible carriers in erythrocytes
Authors: Hunter F. R. , George Jaime , Ospina Bertha
Published: February 2005

Using a densimeter technique, the effect of tannic acid and n‐butanol on the permeability to non‐electrolytes of erythrocytes of various species was studied. If both tannic acid and butanol decrease the permeability it is suggested that a carrier mechanism is involved. If tannic acid has little or no effect and butanol increases the permeability it is suggested that the penetration of such a molecule depends only on diffusion. According to this theory carriers are involved in the following systems: Urea — mouse, sheep, pig, ox and man; Ethylene glycol — man and possibly mouse; Glycerol — man, mouse, rabbit; Erythritol — mouse and possibly man; Ribose — mouse, man; Mannose, glucose, sorbose — man. No carriors are involved in the following systems: Urea — chicken; Ethylene glycol — pig, chicken, ox, sheep; Thiourea — rabbit, chicken, sheep, man, pig, ox; Glycerol — chicken, pig, sheep, ox; Erythritol — rabbit; Ribose — rabbit.
The effect of potassium concentration on Ca45 uptake in frog sartorius muscle
Authors: Weiss George B. , Bianchi C. P.
Published: February 2005

Radiocalcium uptake by frog sartorius muscle is increased as the potassium concentration of the bathing Ringer is increased from 1.6 mM to 32.0 mM; at higher concentrations of K+ no further increase in radiocalcium uptake occurs. Substitution of the chloride of Ringer solution by nitrate increases the amount of radiocalcium uptake at potassium concentrations between 1.6 and 32.0 mM but not at higher concentrations. The nitrate anion enhances both the maximum tension and the area of the contracture curves that occur between 16 and 80 mM K+. Comparison of paired muscle preparations in nitrate Ringer at 32 mM K+ and 80 mM K+ shows no difference in total radiocalcium uptake and no difference in the area under the contracture curves. When a three minute prequilibration period in Ca45 is omitted, the radiocalcium uptake by the sartorius muscle in 80 mM K+, Ca45 Ringer nitrate is reduced by 50% as compared to its mated muscle soaked in 32 mM K+, Ca45 Ringer nitrate. Within the limitations of the experimental techniques employed, it appears that calcium uptake is more prolonged at lower levels of potassium (32.0 mM) but the total amount taken up is the same as at higher levels of potassium (80 mM).
Growth, survival and biochemical alteration of Euglena gracilis in medium limited in sulfur
Authors: Buetow D. E.
Published: February 2005

The sulfur requirement for growth and survival of Euglena gracilis is satisfied by sulfate or by certain organic sources, especially methionine. When deprived of sulfur, cultures remain fully viable for about 1.5 days. By 15 days of sulfur deprivation, viability is reduced to 25%. Sulfur is found in significant quantity in all the major cellular fractions of Euglena including the hot‐TCA‐soluble fraction. During external sulfur deprivation, sulfur is redistributed within the cell in order to maintain “structural protein.” Cells which survive apparently are able to regulate the utilization and redistribution of their depleted sulfur reserves.
Modification of receptors for acetylcholine in the early embryonic heart
Authors: Roberts Carmel Montgomery , Gimeno Martha A. , Leyden Webb J.
Published: February 2005

Whole chick embryo blastoderms at zero‐ to 7‐somites have been explanted onto a nutrient medium and incubated at 37°C for 20 hours, in order to develop to 18‐ to 19‐somites, when the heart rate is depressed by acetylcholine and even more strongly by a number of parasympathomimetic drugs and cholinesterase inhibitors. Hence we have concluded that receptors for acetylcholine are present in the early chick embryo heart before innervation by the vagus nerve is initiated, but that the receptors do not possess the specificity of adult acetylcholine cardiac receptors. Incubation of the zero‐ to 7‐somite blastoderms on media containing certain of the parasympathomimetic drugs and cholinesterase inhibitors greatly increased the sensitivity of the hearts to depression of rate by acetylcholine at 18‐ to 19‐somites, and we have concluded that development of acetylcholine receptors has been stimulated by the drugs. A possible stereochemical relationship between acetylcholine receptors and drugs that are able to stimulate the development of the receptors is postulated.
Factorizations and characterizations of induced‐hereditary and compositive properties
Authors: Farrugia Alastair , Mihók Peter , Richter R. Bruce , Semanivšin Gabriel
Published: February 2005

An Erratum has been published for this article in Journal of Graph Theory 50:261, 2005.

A graph property (i.e., a set of graphs) is hereditary (respectively, induced‐hereditary) if it is closed under taking subgraphs (resp., induced‐subgraphs), while the property is additive if it is closed under disjoint unions. If ${\cal P}$ and ${\cal Q}$ are properties, the product ${\cal P}\circ {\cal Q}$ consists of all graphs G for which there is a partition of the vertex set of G into (possibly empty) subsets A and B with G[A] $\in {\cal P}$ and G[B] $\in {\cal Q}$. A property is reducible if it is the product of two other properties, and irreducible otherwise.

We show that very few reducible induced‐hereditary properties have a unique factorization into irreducibles, and we describe them completely. On the other hand, we give a new and simpler proof that additive hereditary properties have a unique factorization into irreducible additive hereditary properties [J. Graph Theory 33 (2000), 44–53]. We also introduce analogs of additive induced‐hereditary properties, and characterize them in the style of Scheinerman [Discrete Math. 55 (1985), 185–193]. © 2005 Wiley Periodicals, Inc. J Graph Theory 49: 11–27, 2005
The integumentary, pulmonary, and cardiac modifications correlated with increased cutaneous respiration in the amphibia: A solution of the ‘hairy frog’ problem
Authors: Noble G. K.
Published: February 2005

Astylosternus robustus has greatly reduced lungs. All Amphibia exhibiting such a reduction have their epidermis either penetrated by capillaries or thinned to facilitate greater cutaneous respiration. The epidermis of both sexes of A. robustus is penetrated by capillaries. The «hairs» of the adult male are merely extensions of this vasculated epidermis to compensate for the greater muscularity, size, and activity of this sex.

The digits of terrestrial urodeles do not serve as special centers of cutaneous respiration. Digital sinuses are present in all urodeles. The abdominal and femoral tubercles of arboreal and some terrestrial frogs may function greatly in respiration, for their epidermis is penetrated by capillaries.

All urodeles and frogs having well‐developed and frequently emptied lungs possess a functionally complete auricular septum and a spiral valve. Injection experiments demonstrate a complete separation of arterial and venous blood in living specimens. A reduction of the lungs conditions a reduction of the left auricle, but disuse causes no change in size. A great decrease of the lungs, or even a disuse of them, conditions a fenestration of the auricular septum and a loss of the spiral valve. The spiral valve is formed by a backward growth of one of the synangial valves and is not homologous with the accessory valves of dipnoans. Lungless salamanders have no left auricle and no spiral valve.
External reproductive organs of the common grass spider, agelena naevia walckenaer
Authors: Petrunkevitch Alexander
Published: February 2005

One of the most perfect “lock and key” adaptations known, the external reproductive organs in spiders are subject to considerable variations. Two extreme types of female reproductive organs are described in detail, and these in turn compared with the European species of the same genus. Thus it is shown that the reproductive system in the same genus of spiders may exhibit great differences in structure while all other characters remain more or less the same, the natural conclusion being that caution should be exercised in creating new or splitting up old genera on the basis of characters of the external reproductive system. The same applies to the male.

Two extreme types of palpi are described and then compared with the palpi of the European species. In the case of the male, however, the differences seem to be of a less profound nature.
The primordial germ cells of Hemidactylium and other amphibia
Authors: Humphrey R. R.
Published: February 2005

The primordial germ cells of urodeles and anurans can occupy comparable positions in the embryo only in very early stages of development, if at all. When first recognizable as reproductive elements, their situation in the two amphibian orders is quite strikingly different.

The germ cells first become recognizable in urodeles in the medial edge of the lateral mesoderm; there is no evidence that their position previous to this time is other than mesodermal. In the anura they are entodermal in association during early development; they are finally separated from the dorsal portion of the roof of the archenteron to form a single axial germ‐cell cord. No amphibian species studied showed a mode of origin different from that characteristic of its order.

The so‐called migration of the amphibian germ cells to their definitive situation is interpreted as the result of growth shiftings of related parts. Germ cells do not migrate independently through the tissues. Aberrant or ectopic cells for the most part result from failures or faulty correlations of growth processes. Certain aberrant cells of the caudal portion of the body in urodeles indicate the inclusion of sex elements in the ventral as well as in the lateral mesoderm.
Modification of development on the basis of differential susceptibility to radiation I. Fundulus heteroclitus and ultraviolet radiation
Authors: Hinrichs Marie A.
Published: February 2005

This paper reports experiments with Fundulus heteroclitus to modify larval development by means of ultraviolet radiation. Eggs were exposed to radiation at various intervals after fertilization for varying periods of time. The results accord with previous work on fish teratology, and the developmental types obtained are essentially similar to those produced by chemicals, cold, and hybridization. The deviations from normal development occur in the same body regions as do those in other vertebrates whose early development has been modified by the action of radiation (x‐rays, radium, etc.).

The results of these experiments indicate that there is a non‐specificity in susceptibility relations with the production of similar types of monsters for widely different reagents. That these eggs are differentially susceptible to the action of ultraviolet radiation is indicated by the fact that those regions which have the highest metabolic activity when an inhibiting influence is active are the ones most generally affected. Thus modifications of the nervous system, sense organs, circulatory system, tail region, and body axis result, respectively, in the production of varying degrees of cyclopia, inadequate circulation, short, stubby or bent, non‐motile tails (some bifid), and anterior twinning.

As these modifications may be produced by applying inhibiting influences during the first few minutes after fertilization, it is evident that there is in the egg at this stage some constitutional or physiological basis which determines early differences in susceptibility of its various parts.
Egg formation in a leech
Authors: Heath Harold
Published: February 2005

In a leech infesting the Alaskan codfish germinal masses in the ovary proliferate secondary groups, comprising about forty cells in which a follicle and central supporting cell early differentiate. Active division results in approximately 500 cells which apparently develop ductules extending to a point on the surface of the egg. Granules of unknown origin then appear in each nurse cell, and are drawn down the ductules into the egg which can now be distinguished. Reasons are given for the belief that the nutritive material is drained from the nurse cells by amoeboid activity of the egg. In early stages the nutritive mateiral forms a loose reticulum which gradually becomes transformed into a more extensive network, persisting until the maturation divisions. In this latest period the follicle and nurse cells, which become shrunken as the ovum enlarges, usually are stripped off and soon disintegrate.
The germ cells of anurans. II. An embryological study of sex differentiation in Rana catesbeiana
Authors: Swingle W. W.
Published: February 2005

Embryological study of bullfrog tadpoles collected from various parts of the United States has shown the existence of local races which differ markedly in regard to the time of occurrence and character of the developmental processes involved in the formation of the definitive testis of the male individuals. Those races in which the gonads of the two sexes are easily distinguished in early larval stages are called differentiated. Other local races show a peculiar gonadic development chiefly affecting the males, the definitive testis sometimes not appearing until near the end of the second year of larval life. Such races are called undifferentiated, because the morphological features of the definitive testes are not established until late. The larvae first develop a peculiar gonad (progonad) which later degenerates and is replaced by the definitive testis. All male animals of the undifferentiated strains exhibit the gonad cycle.

The progonad varies among the local frog races in regard to the length of persistence and degree of differentiation attained before undergoing degeneration. Its germ cells may exhibit a typical male maturation cycle ending in degeneration, or the cells may differentiate along both male and female lines or remain sexually neutral.

The development and differentiation of the progonad in the various races are described and a detailed account given of the origin of the definitive testis. The problems of sex differentiation and continuity of the Keimbahn in anurans are discussed.
Branchiomerism and the theory of head segmentation
Authors: Kingsbury B. F.
Published: February 2005

The summary of this paper is as follows:

A critical review of the developmental evidence shows that the branchial pouches are formed in cephalocaudal sequence subsequently to the segmentation of the dorsal mesoderm.

The pouches interrupt a continuous sheet of mesoderm to form the branchial arches.

The arches when formed do not correspond topographically to the dorsal somites.

Branchiomerism does not therefore coincide with somitic metamerism.

The branchial structures do not support the theory of head segmentation.

The nervi trigeminus, facialis, glossopharyngeus, and vagus cannot be regarded as segmental nerves.

There is no evidence that branchial pouches or arches have been elided from the series.

The problem of meristic homology is briefly discussed.
The metabolic gradients of vertebrate embryos. II. The brook lamprey
Authors: Hyman L. H.
Published: February 2005

Disintegration in killing agents was studied throughout development. In the unfertilized egg and cleavage stages the death gradient runs from animal to vegetal pole. In the late blastula stage the future dorsal surface and future point of gastrulation show heightened susceptibility. The gastrula has a gradient from anterior to posterior end along its dorsal surface, with a slight reverse gradient around the blastopore; lateral and ventral regions are least susceptible.

Before and after the appearance of the neural groove, the dorsal surface shows increased susceptibility with gradient in it from anterior to posterior end. The neural tube is highly susceptible, with a death gradient from anterior to posterior end and a slight reverse gradient at its posterior end.

During late stages and in the larva the double gradient is present; death begins at the two ends and progresses backward from head, forward from anus; from the former most rapidly. The least susceptible place is near the posterior end. The posterior reverse gradient is less developed in the lamprey than in other vertebrate embryos, due, probably, to its lack of a tail bud.

Assuming that death differences indicate differences in rate of activity, it appears that such differences in activity may be causes and not results of developmental processes, for the development of certain parts (dorsal surface, blastopore, central nervous system) is indicated by heightened activity before it is evident morphologically.