bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the developmental regulation of the cyanogenic compounds in seedlings of two lines ofLinum usitatissimumL.
Authors: Krech M J , Fieldes M A
Published: November 2003

The developmental profiles and tissue distribution of the four cyanogenic compounds in seedlings of two developmentally contrasting inbred lines of flax (Linum usitatissimum L.) were examined using HPLC. During germination, the isoleucine-derived compound, neolinustatin, was hydrolysed faster in the more vigorous of the two lines. Furthermore, in this line, the neolinustatin content was higher in seeds and the accumulation of the other isoleucine-derived compound, lotaustralin, was also higher in the cotyledons of seedlings. In contrast, with one exception, the hydrolysis and accumulation of the valine-derived compounds, linustatin and linamarin, was the same in both lines. Differences in the levels of the compounds during germination, and in the hypocotyls, are interpreted as evidence for the involvement of transient levels of hydrogen cyanide in the autocatalytic regulation of ethylene production.Key words: HPLC, germination, hypocotyl, neolinustatin, lotaustralin, ethylene.
Chiral silicon-bridged 2-(N,N-dialkylamino)ethyl-substituted indenes as potential precursors for ansa-zirconocenes
Authors: Hagemeister Timo , Jutzi Peter , Stammler Anja , Stammler Hans-Georg
Published: November 2003

Chiral amino-functionalized silicon-bridged indene derivatives 4a4c were synthesized from 3-(2-(N,N-dialkylamino)ethyl)indenes 2a2c. The C-Si coupling reactions are regioselective, leading exclusively to the formation of 1,3-disubstituted isomers in a rac/meso ratio of 1:1, as indicated by NMR spectroscopy. The solid-state structure of the dimethylsilyl-bridged bisindene (R,R)-4a is described. The formation of corresponding ansa-zirconocenes via amine elimination chemistry was monitored by 1H NMR spectroscopy.Key words: amino-functionalized indenes, silicon-bridged, ansa-metallocenes, chirality, regioselectivity, amine elimination chemistry.
Hydrosilylation of alkenes and ketones catalyzed by nickel(II) indenyl complexes
Authors: Fontaine Frédéric-Georges , Nguyen René-Viet , Zargarian Davit
Published: November 2003

Abstraction of Cl from the complexes (indenyl)Ni(PPh3)Cl generates cationic species that are effective precatalysts for the hydrosilylation of some olefins and ketones. For instance, the mixture of (1-Me-indenyl)Ni(PPh3)Cl and NaBPh4 (or methylaluminoxane) reacts at room temperature with ca. 100 equiv. each of PhSiH3 and styrene to produce [1-phenyl-1-ethyl](phenyl)silane, PhCH(CH3)(SiPhH2), in 50%80% yield. The same system can also catalyze the hydrosilylation of 1-hexene and norbornene, but the products arising from these substrates consist of mixtures of regio- and stereoisomers. On the other hand, ketone hydrosilylation is regiospecific, giving the corresponding silyl ethers in high yields. A number of experimental observations have indicated that the initially generated Ni-based cation is not the catalytically active species. Indeed, the cationic initiators may be replaced by LiAlH4 or AlMe3, which generate the corresponding Ni-H or Ni-Me derivatives, respectively. Moreover, the observed regioselectivity for the addition of PhSiH3 to styrene (i.e., predominant addition of the silyl fragment to the α-C) is opposite of what would be expected if the reaction mechanism involved carbocationic intermediates. A new mechanism is proposed in which the active species is a Ni-H species originating from the transfer of H from PhSiH3 to the initially generated Ni cation. Key words: hydrosilylation, nickel indenyl complexes, cationic complexes, hydride intermediates.
Chemistry of zwitterionic penta-coordinate silicon compounds of the (ammoniomethyl)bis[glycolato(2)-O1,O2]silicate type in aqueous and nonaqueous solution
Authors: Tacke Reinhold , Bertermann Rüdiger , Biller Andreas , Burschka Christian , Penka Martin
Published: November 2003

The zwitterionic spirocyclic λ5Si-silicates bis[glycolato(2)-O1,O2][(trimethylammonio)methyl]silicate ([OCH2C(O)O]2SiCH2NMe3, 3) and bis[2-methyllactato(2)-O1,O2][(trimethylammonio)methyl]silicate ([OCMe2C(O)O]2SiCH2NMe3, 4) were synthesized by treatment of the zwitterionic λ5Si-silicate F4SiCH2NMe3 with 2 mol. equiv. of Me3SiOCR2C(O)OSiMe3 (R = H, Me) (formation of 4 mol. equiv. of Me3SiF). Compounds 3 (isolated as 32/3MeCN after drying in vacuo) and 4 were studied by solution 1H, 13C, and 29Si NMR spectroscopy and by solid-state VACP/MAS 13C, 15N, and 29Si NMR experiments, and the solvates 3MeCN and 42MeCN were structurally characterized by single-crystal X-ray diffraction. These experimental investigations were complemented by computational studies of the zwitterions 3 and 4 and the anionic model species bis[2-methyllactato(2)-O1,O2]hydridosilicate(1) ([OCMe2C(O)O]2SiH, 8). Compounds 32/3MeCN and 4 and their already known derivatives [OCH2C(O)O]2SiCH2NMe2H (1) and [OCMe2C(O)O]2SiCH2NMe2H (2) were studied for their dynamic behavior (Λ/Δ-enantiomerization) in solution by VT 1H NMR spectroscopy. In addition, compounds 1, 2, 32/3MeCN, and 4 were studied in CD3OD and D2O with 1H, 13C, and 29Si NMR experiments.Key words: penta-coordinate silicon, zwitterionic λ5Si-silicates, Λ/Δ-enantiomerism, NMR spectroscopy, computational chemistry.
Platelet-Monocyte Complexes Support Monocyte Adhesion to Endothelium by Enhancing Secondary Tethering and Cluster Formation
Authors: da Costa Martins P. , van den Berk N. , Ulfman Laurien H. , Koenderman L. , Hordijk P.L. , Zwaginga J.J.
Published: November 2003

Objective—Adhesion of monocytes to endothelium can be supported by monocyte-monocyte interactions resulting in the formation of cell aggregates at the vessel wall (clusters). Since platelets that are bound to the injured vessel wall support monocyte adhesion and platelet activation in the circulation leads to formation of platelet-monocyte complexes (PMCs), we examined whether adhesion of PMCs to the vessel wall enhances monocyte clustering.

Methods and Results—The effect of PMC formation in monocyte adhesion and clustering on human umbilical vein endothelial cells (HUVECs) was studied in vitro with a perfusion system. In the presence of 10% to 20% PMCs, monocyte adhesion and cluster formation to stimulated HUVECs increased 2-fold above levels obtained with pure monocytes. While the observed effects increased with higher PMC levels, blocking-monoclonal antibodies directed against platelet-associated P-selectin or monocyte P-selectin glycoprotein ligand-1 (PSGL-1) reversed adhesion and clustering to control values. In the presence of PMCs, blocking L-selectin decreased adhesion by 25%. When PMCs were present, clustering was only supported by L-selectin at higher shear. These data indicate that monocyte adhesion to the vessel wall is enhanced by PMC-mediated monocyte secondary tethering. These interactions are mainly mediated by P-selectin and PSGL-1.

Conclusion—PMCs in the circulation might be proatherogenic, and prevention of their formation is a possible therapeutic goal.
Determinants of Sudden Cardiac Death in Individuals With the Electrocardiographic Pattern of Brugada Syndrome and No Previous Cardiac Arrest
Authors: Brugada Josep , Brugada Ramon , Brugada Pedro
Published: November 2003

Background—

Patients with Brugada syndrome who were resuscitated from an episode of ventricular fibrillation are at high risk for recurrent sudden death. There is general agreement about the therapeutic strategy for these patients. Conversely, the prognosis and approach in patients with a diagnostic ECG but without a previous history of sudden cardiac death is controversial. We analyzed a large cohort of patients with Brugada syndrome without previous cardiac arrest to understand the determinants of prognosis.

Methods and Results—

A total of 547 patients with an ECG diagnostic of Brugada syndrome and no previous cardiac arrest were studied. The mean age was 41±15 years, and 408 were male. The diagnostic ECG was present spontaneously in 391 patients. In the remaining 156 individuals, the abnormal ECG was noted only after the administration of an antiarrhythmic drug. One hundred twenty-four patients had suffered from at least 1 episode of syncope. During programmed ventricular stimulation, a sustained ventricular arrhythmia was induced in 163 of 408 patients. During a mean follow-up of 24±32 months, 45 patients (8%) suffered sudden death or documented ventricular fibrillation. Multivariate analysis identified the inducibility of a sustained ventricular arrhythmia (
P
<0.0001) and a history of syncope (
P
<0.01) as predictors of events. Logistic regression analysis showed that a patient with a spontaneously abnormal ECG, a previous history of syncope, and inducible sustained ventricular arrhythmias had a probability of 27.2% of suffering an event during follow-up.

Conclusions—

Individuals with Brugada syndrome and no previous cardiac arrest have a high risk of sudden death. Inducibility of ventricular arrhythmias and a previous history of syncope are markers of a poor prognosis.
Angiotensin II Signaling Pathways Mediate Expression of Cardiac T-Type Calcium Channels
Authors: Ferron Laurent , Capuano Véronique , Ruchon Yann , Deroubaix Edith , Coulombe Alain , Renaud Jean-François
Published: November 2003

Recent studies indicate that cardiac T-type Ca
2+
current (
I
CaT
) reappears in hypertrophied ventricular cells. The aim of this study was to investigate the role of angiotensin II (Ang II), a major inducer of cardiac hypertrophy, in the reexpression of T-type channel in left ventricular hypertrophied myocytes. We induced cardiac hypertrophy in rats by abdominal aorta stenosis for 12 weeks and thereafter animals were treated for 2 weeks with losartan (12 mg/kg per day), an antagonist of type 1 Ang II receptors (AT
1
). In hypertrophied myocytes, we showed that the reexpressed
I
CaT
is generated by the Ca
V
3.1 and Ca
V
3.2 subunits. After losartan treatment,
I
CaT
density decreased from 0.40±0.05 pA/pF (n=26) to 0.20±0.03 pA/pF (n=27,
P
<0.01), affecting Ca
V
3.1- and Ca
V
3.2-related currents. The amount of Ca
V
3.1 mRNA increased during hypertrophy and retrieved its nonhypertrophic level after losartan treatment, whereas the amount of Ca
V
3.2 mRNA was unaffected by stenosis. In cultured newborn ventricular cells, chronic Ang II application (0.1 μmol/L) also increased
I
CaT
density and Ca
V
3.1 mRNA amount. UO126, a mitogen-activated protein kinase kinase-1/2 (MEK1/2) inhibitor, reduced Ang II–increased
I
CaT
density and Ca
V
3.1 mRNA amount. Bosentan, an endothelin (ET) receptor antagonist, reduced Ang II–increased
I
CaT
density without affecting the amount of Ca
V
3.1 mRNA. Finally, cotreatment with bosentan and UO126 abolished the Ang II–increased
I
CaT
density. Our results show that AT
1
-activated MEK pathway and autocrine ET-activated independent MEK pathway upregulate T-type channel expression. Ang II–increased of
I
CaT
density observed in hypertrophied myocytes may play a role in the pathogenesis of Ca
2+
overload and arrhythmias seen in cardiac pathology.
Rapid Inhibition of Vasoconstriction in Renal Afferent Arterioles by Aldosterone
Authors: Uhrenholt T.R. , Schjerning J. , Hansen P.B. , Nørregaard R. , Jensen B.L. , Sorensen G.L. , Skøtt O.
Published: November 2003

Aldosterone has been suggested to elicit vessel contraction via a nongenomic mechanism. We tested this proposal in microdissected, perfused rabbit renal afferent arterioles. Aldosterone had no effect on internal diameter in concentrations from 10
−10
to 10
−5
mol/L, but aldosterone abolished the ability of 100 mmol/L KCl to induce vascular contraction. The inhibitory effect of aldosterone was observed from 1 pmol/L. The inhibitory effect was significant after 5 minutes and maximal after 20 minutes and was fully reversible. Actinomycin D (10
−6
mol/L) prolonged the effect of aldosterone. The effect was abolished by the mineralocorticoid receptor antagonist spironolactone (10
−7
mol/L) but not by the glucocorticoid receptor antagonist mifepristone (10
−6
mol/L). The K
+
-mediated increase of intracellular calcium concentration in afferent arterioles was not affected by aldosterone. Mineralocorticoid receptor was detected by reverse transcription–polymerase chain reaction and immunohistochemistry in rat renal vasculature and rabbit endothelial cells. Inhibition of phosphatidylinositol (PI)-3 kinase with LY 294002 (3×10
−6
mol/L) restored sensitivity to K
+
in the presence of aldosterone, and afferent arterioles were immunopositive for PI-3 kinase subunit p110α. Inhibition of NO formation by L-NAME (10
−4
mol/L) or inhibition of soluble guanylyl cyclase with 1H-(1,2,4)Oxadiazolo[4,3-a]quinoxaline-1-one restored K
+
-induced vasoreactivity in the presence of aldosterone. Similar to aldosterone, the NO donor sodium nitroprusside inhibited K
+
-induced vascular contraction. Geldanamycin (10
−6
mol/L), an inhibitor of heat shock protein 90, abolished aldosterone-induced vasorelaxation. We conclude that aldosterone inhibits depolarization-induced vasoconstriction in renal afferent arterioles by a rapid nongenomic mechanism that is initiated by mineralocorticoid receptor activation and involves PI-3 kinase, protein kinase B, and heat shock protein 90–mediated stimulation of NO generation.
Statewide Assessment of Hospital-Based Stroke Prevention and Treatment Services in North Carolina
Authors: Camilo Osvaldo , Goldstein Larry B.
Published: November 2003

Background and Purpose—

The first published statewide assessment of stroke prevention and treatment services in the United States was carried out in North Carolina in 1998. The purpose of the present study was to measure changes in these services that may have occurred over the last 5 years.

Methods—

A 1-page questionnaire was sent to each facility in the state in February 2003. Results were compared with the 1998 survey.

Results—

Complete responses were obtained from each of the state’s 128 facilities. The proportions of hospitals providing CT angiography (35% versus 55%,
P
≤0.01), diffusion-weighted MRI (20% versus 45%,
P
≤0.01), transesophageal echocardiography (45% versus 59%,
P
≤0.02), and inpatient rehabilitation services (25% versus 43%,
P
≤0.01) increased over the 5 years. There was a trend toward more facilities having tissue plasminogen activator protocols (43% versus 54%,
P
≤0.09) but a decrease in the proportion of hospitals with interventional radiologists (23% versus 15%,
P
<0.01). There was no change in the proportion of the state’s population living in a county with a basic stroke prevention and treatment center, with the proportion residing in a county with an advanced center increasing by 12%. Entire regions of the state lacked either type of center, and only 14% had even the essential infrastructure recommended for a Brain Attack Coalition–type primary stroke center. There was no difference in the proportions of hospitals with organized stroke teams, those having a stroke acute care unit, those using stroke care maps, or hospitals having community awareness programs.

Conclusions—

Certain technologies have become more widely available, but hospital investments in stroke-related programs have not appreciably increased.
Hoxa9 influences the phenotype but not the incidence of Mll-AF9 fusion gene leukemia
Authors: Kumar Ashish R. , Hudson Wendy A. , Chen Weili , Nishiuchi Ritsuo , Yao Qing , Kersey John H.
Published: November 2003

Identification of the targets of mixed lineage leukemia (MLL) fusion genes will assist in understanding the biology of MLL fusion gene leukemias and in development of better therapies. Numerous studies have implicated HOXA9 as one of the possible targets of MLL fusion proteins. To determine if HOXA9 was required for leukemia development by MLL fusion genes, we compared the effects of the Mll-AF9 knock-in mutation in mice in the presence or absence of Hoxa9. Both groups of mice showed myeloid expansion at 8 weeks and then developed myeloid leukemia with a similar incidence and time course. The leukemia in the mice lacking Hoxa9 generally displayed a more immature myeloid phenotype than that in the mice that were wild-type for Hoxa9. Gene expression profiling revealed that expression of Mll-AF9 led to overexpression of Hoxa5, Hoxa6, Hoxa7, Hoxa9, and Hoxa10. Thus, genes of the Hox-a cluster are important in defining the phenotype but not the incidence of Mll-AF9 leukemia. These results demonstrate that the Mll-AF9 fusion gene disrupts the expression of several Hox genes, none of which as a single gene is likely to be necessary for development of leukemia. Instead, we propose that the “Hox code” minimally defined by the Hoxa5-a9 cluster is central to MLL leukemogenesis.
Hemolytic anemia and severe rhabdomyolysis caused by compound heterozygous mutations of the gene for erythrocyte/muscle isozyme of aldolase, ALDOA(Arg303X/Cys338Tyr)
Authors: Yao David C. , Tolan Dean R. , Murray Michael F. , Harris David J. , Darras Basil T. , Geva Alon , Neufeld Ellis J.
Published: November 2003

Aldolase (E.C. 4.1.2.13), a homotetrameric protein encoded by the ALDOA gene, converts fructose-1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. Three isozymes are encoded by distinct genes. The sole aldolase present in red blood cells and skeletal muscle is the A isozyme. We report here the case of a girl of Sicilian descent with aldolase A deficiency. Clinical manifestations included transfusion-dependent anemia until splenectomy at age 3 and increasing muscle weakness, with death at age 4 associated with rhabdomyolysis and hyperkalemia. Sequence analysis of the ALDOA coding regions revealed 2 novel heterozygous ALDOA mutations in conserved regions of the protein. The paternal allele encoded a nonsense mutation, Arg303X, in the enzyme-active site. The maternal allele encoded a missense mutation, Cys338Tyr, predicted to cause enzyme instability. This is the most severely affected patient reported to date and only the second with both rhabdomyolysis and hemolysis.
The immunoglobulin superfamily inDrosophila melanogasterandCaenorhabditis elegansand the evolution of complexity
Authors: Vogel Christine , Teichmann Sarah A. , Chothia Cyrus
Published: November 2003

Drosophila melanogaster is an arthropod with a much more complex anatomy and physiology than the nematode Caenorhabditis elegans. We investigated one of the protein superfamilies in the two organisms that plays a major role in development and function of cell-cell communication: the immunoglobulin superfamily (IgSF). Using hidden Markov models, we identified 142 IgSF proteins in Drosophila and 80 in C. elegans. Of these, 58 and 22, respectively, have been previously identified by experiments. On the basis of homology and the structural characterisation of the proteins, we can suggest probable types of function for most of the novel proteins. Though overall Drosophila has fewer genes than C. elegans, it has many more IgSF cell-surface and secreted proteins. Half the IgSF proteins in C. elegans and three quarters of those in Drosophila have evolved subsequent to the divergence of the two organisms. These results suggest that the expansion of this protein superfamily is one of the factors that have contributed to the formation of the more complex physiological features that are found in Drosophila.
Chromatin remodeling and neuronal response: multiple signaling pathways induce specific histone H3 modifications and early gene expression in hippocampal neurons
Authors: Crosio Claudia , Heitz Estelle , Allis C. David , Borrelli Emiliana , Sassone-Corsi Paolo
Published: November 2003

Plasticity in gene expression is achieved by a complex array of molecular mechanisms by which intracellular signaling pathways directly govern transcriptional regulation. In addition to the remarkable variety of transcription factors and co-regulators, and their combinatorial interaction at specific promoter loci, the role of chromatin remodeling has been increasingly appreciated. The N-terminal tails of histones, the building blocks of nucleosomes, contain conserved residues that can be post-translationally modified by phosphorylation, acetylation, methylation and other modifications. Depending on their nature, these modifications have been linked to activation or silencing of gene expression. We wanted to investigate whether neuronal stimulation by various signaling pathways elicits chromatin modifications that would allow transcriptional activation of immediate early response genes. We have analysed the capacity of three drugs – SKF82958 (a dopaminergic receptor agonist), pilocarpine (a muscarinic acetylcholine receptor agonist) and kainic acid (a kainate glutamate receptor agonist) – to induce chromatin remodeling in hippocampal neurons. We show that all stimulations induce rapid, transient phosphorylation of histone H3 at serine 10. Importantly, the same agonists induce rapid activation of the mitogen-activated protein kinase pathway with similar kinetics to extracellular-regulated-kinase phosphorylation. In the same neurons where this dynamic signaling cascade is activated, there is induction of c-fos transcription. Histone H3 Ser10 phosphorylation is coupled to acetylation at the nearby Lys14 residue, an event that has been linked to local opening of chromatin structure. Our results underscore the importance of dynamic chromatin remodeling in the transcriptional response to various stimuli in neuronal cells.
Active surface transport of metabotropic glutamate receptors through binding to microtubules and actin flow
Authors: Sergé Arnauld , Fourgeaud Lawrence , Hémar Agnès , Choquet Daniel
Published: November 2003

Receptors for neurotransmitters are concentrated and stabilized at given sites such as synapses through interactions with scaffolding proteins and cytoskeletal elements. The transport of receptors first involves directed vesicular trafficking of intracellularly stored receptors followed by their targeting to the plasma membrane. Once expressed at the cell surface, receptors are thought to reach their final location by random Brownian diffusion in the plasma membrane plane. Here, we investigate whether the metabotropic glutamate receptor mGluR5 can also be transported actively on the cell surface. We used single particle tracking to follow mGluR5 movement in real time at the surface of neuronal growth cones or fibroblast lamellipodia, both of which bear a particularly active cytoskeleton. We found that after a certain lag time mGluR5 undergoes directed rearward transport, which depends on actin flow. On actin depolymerization, directed movement was suppressed, but receptors still bound to a rigid structure. By contrast, receptor transport and immobilization was fully suppressed by microtubule depolymerization but favored by microtubule stabilization. Furthermore, mGluR5 could be immunoprecipitated with tubulin from rat brains, confirming the ability of mGluR5 to bind to microtubules. We propose that mGluR5 can be transported on the cell surface through actin-mediated retrograde transport of microtubules. This process may play a role in receptor targeting and organization during synapse formation or during glutamate-mediated growth cone chemotaxis.
Malignancy in patients with sickle cell disease
Authors: Schultz William H. , Ware Russell E.
Published: November 2003

Malignancy in patients with sickle cell disease (SCD) has been previously reported, but the types of cancer and its incidence remain undefined. With the advent of hydroxyurea therapy, there is concern about increasing the cancer risk for patients with SCD. The International Association of Sickle Cell Nurses and Physician Assistants identified 52 cases of cancer (49 patients) among 16,613 patients with SCD followed at 52 institutions. The median age at malignancy diagnosis was 34 years (range, 14 months–62 years). Twenty‐one cases (40%) occurred in pediatric patients, primarily leukemia (n = 7) or Wilms' tumor (n = 5), with 15 children surviving. Most adults had solid tumors, especially carcinomas, and only nine were known to be alive. Three patients received hydroxyurea before the diagnosis of malignancy. These data provide essential baseline information for the accurate interpretation of future reports of malignancy in patients with SCD, especially those receiving hydroxyurea therapy. Am. J. Hematol. 74:249–253, 2003. © 2003 Wiley‐Liss, Inc.
Acute renal failure after intravenous anti‐D immune globulin in an adult with immune thrombocytopenic purpura
Authors: Chun Nancy S. , Savani Bipin , Seder Richard H. , Taplin Mary Ellen
Published: November 2003

Intravenous anti‐D immune globulin (anti‐D IGIV) is indicated for the treatment of immune thrombocytopenic purpura (ITP) in nonsplenectomized patients who are Rh(D)‐positive. Recent reports have described episodes of intravascular hemolysis (IVH) and acute renal failure (ARF) after anti‐D IGIV. We report the first adult patient with ITP who required and received dialysis after IVH and ARF complicating treatment with anti‐D IGIV. Whether the transfusion of 2 units of Rh(D)‐positive red cells, indicated for the resulting anemia, exacerbated the IVH and renal failure is unclear. Three weeks after the administration of anti‐D IGIV (13 days after two hemodialysis treatments), the patient's renal function had returned to normal. This case highlights the infrequent but potentially serious side effects of anti‐D IGIV and the need to monitor a patient's renal function closely if there is evidence of IVH after infusion of anti‐D IGIV. If red cell transfusion is indicated, we recommend the use of Rh(D)‐negative red cell products. Am. J. Hematol. 74:276–279, 2003. © 2003 Wiley‐Liss, Inc.
Teaching medical histology at the University of South Carolina School of Medicine: Transition to virtual slides and virtual microscopes
Authors: Blake Charles A. , Lavoie Holly A. , Millette Clarke F.
Published: November 2003

We describe how the histology course we teach to first‐year medical students changed successfully from using glass slides and microscopes to using virtual slides and virtual microscopes. In 1988, we taught a classic medical histology course. Subsequently, students were loaned static labeled images on projection slides to introduce them to their microscope glass slides, and we made laser disks of histological images available in the teaching lab. In 2000, we placed the static labeled images and laboratory manual on the Web. We abandoned the Web‐based approach in 2001. Faculty selected specific areas on microscope glass slides in student collections for scanning at a total magnification of 40, 100, 200, or 400. Christopher M. Prince of Petro Image, LLC, scanned the glass slides; digitized, encoded, and compressed (95%) the images; and placed them on CD‐ROMs. The scanned images were viewed up to a magnification of 400 using the MrSID viewer (LizardTech software) and the computer as a virtual microscope. This viewer has many useful features, including effective microscope and telescope functions that provide greater versatility for sample study and speed in localizing structures than was possible with the actual microscope. Image detail is indistinguishable from that viewed under the light microscope at equivalent magnifications. Static labeled images were also placed on CD‐ROMs to introduce students to the virtual slides. Students could view all the images on their CD‐ROMs at any time and in any place with their laptop computers without going online. Students no longer rented light microscopes in 2002. Both students and faculty have shown strong support for using this approach to teaching histology during the past 2 years. Anat Rec (Part B: New Anat) 275B:196–206, 2003. © 2003 Wiley‐Liss, Inc.
Chromatin remodeling by ATP‐dependent molecular machines
Authors: Lusser Alexandra , Kadonaga James T.
Published: November 2003

The eukaryotic genome is packaged into a periodic nucleoprotein structure termed chromatin. The repeating unit of chromatin, the nucleosome, consists of DNA that is wound nearly two times around an octamer of histone proteins. To facilitate DNA‐directed processes in chromatin, it is often necessary to rearrange or to mobilize the nucleosomes. This remodeling of the nucleosomes is achieved by the action of chromatin‐remodeling complexes, which are a family of ATP‐dependent molecular machines. Chromatin‐remodeling factors share a related ATPase subunit and participate in transcriptional regulation, DNA repair, homologous recombination and chromatin assembly. In this review, we provide an overview of chromatin‐remodeling enzymes and discuss two possible mechanisms by which these factors might act to reorganize nucleosome structure. BioEssays 25:1192–1200, 2003. © 2003 Wiley Periodicals, Inc.
The blood coagulation system as a molecular machine
Authors: Spronk Henri M.H. , Govers‐Riemslag José W.P. , ten Cate Hugo
Published: November 2003

The human blood coagulation system comprises a series of linked glycoproteins that upon activation induce the generation of downstream enzymes ultimately forming fibrin. This process is primarily important to arrest bleeding (hemostasis). Hemostasis is a typical example of a molecular machine, where the assembly of substrates, enzymes, protein cofactors and calcium ions on a phospholipid surface markedly accelerates the rate of coagulation. Excess, pathological, coagulation activity occurs in “thrombosis”, the formation of an intravascular clot, which in the most dramatic form precipitates in the microvasculature as disseminated intravascular coagulation. Thrombosis occurs according to a biochemical machine model in the case of atherothrombosis on a ruptured atherosclerotic plaque, but may develop at a slower rate in venous thrombosis, illustrating that the coagulation machinery can act at different velocities. The separate coagulation enzymes are also important in other biological processes, including inflammation for which the rapid conversion of one coagulation factor by the other is not a prerequisite. The latter role of coagulation enzymes may be related to the old and probably maintained function of the coagulation machine in innate immunity. BioEssays 25:1220–1228, 2003. © 2003 Wiley Perioicals, Inc.
Macromolecular complexes that unwind nucleic acids
Authors: von Hippel Peter H. , Delagoutte Emmanuelle
Published: November 2003

In this essay, we consider helicases, defined as enzymes that use the free energies of binding and hydrolysis of ATP to drive the unwinding of double‐stranded nucleic acids, and ask how they function within, and are “coupled” to, the macromolecular machines of gene expression. To illustrate the principles of the integration of helicases into such machines, we consider the macromolecular complexes that direct and control DNA replication and DNA‐dependent RNA transcription, and use these systems to illustrate how machines centered around coupled polymerase–helicase systems can be regulated by small changes in the interactions of their functional components. BioEssays 25:1168–1177, 2003. © 2003 Wiley Periodicals, Inc.
The spliceosome: the most complex macromolecular machine in the cell?
Authors: Nilsen Timothy W.
Published: November 2003

The primary transcripts, pre‐mRNAs, of almost all protein‐coding genes in higher eukaryotes contain multiple non‐coding intervening sequences, introns, which must be precisely removed to yield translatable mRNAs. The process of intron excision, splicing, takes place in a massive ribonucleoprotein complex known as the spliceosome. Extensive studies, both genetic and biochemical, in a variety of systems have revealed that essential components of the spliceosome include five small RNAs–U1, U2, U4, U5 and U6, each of which functions as a RNA, protein complex called an snRNP (small nuclear ribonucleoprotein). In addition to snRNPs, splicing requires many non‐snRNP protein factors, the exact nature and number of which has been unclear. Technical advances, including new affinity purification methods and improved mass spectrometry techniques, coupled with the completion of many genome sequences, have now permitted a number of proteomic analyses of purified spliceosomes. These studies, recently reviewed by Jurica and Moore,1 reveal that the spliceosome is composed of as many as 300 distinct proteins and five RNAs, making it among the most complex macromolecular machines known. BioEssays 25:1147–1149, 2003. © 2003 Wiley Periodicals, Inc.
New tight frames of curvelets and optimal representations of objects with piecewise C2 singularities
Authors: Candès Emmanuel J. , Donoho David L.
Published: November 2003

This paper introduces new tight frames of curvelets to address the problem of finding optimally sparse representations of objects with discontinuities along piecewise C2 edges. Conceptually, the curvelet transform is a multiscale pyramid with many directions and positions at each length scale, and needle‐shaped elements at fine scales. These elements have many useful geometric multiscale features that set them apart from classical multiscale representations such as wavelets. For instance, curvelets obey a parabolic scaling relation which says that at scale 2−j, each element has an envelope that is aligned along a “ridge” of length 2−j/2 and width 2−j.

We prove that curvelets provide an essentially optimal representation of typical objects f that are C2 except for discontinuities along piecewise C2 curves. Such representations are nearly as sparse as if f were not singular and turn out to be far more sparse than the wavelet decomposition of the object. For instance, the n‐term partial reconstruction f obtained by selecting the n largest terms in the curvelet series obeys

This rate of convergence holds uniformly over a class of functions that are C2 except for discontinuities along piecewise C2 curves and is essentially optimal. In comparison, the squared error of n‐term wavelet approximations only converges as n−1 as n → ∞, which is considerably worse than the optimal behavior. © 2003 Wiley Periodicals, Inc.
Statistical sensitivity analysis of packed column reactors for contaminated wastewater
Authors: Fassò A. , Esposito A. , Porcu E. , Reverberi A. P. , Vegliò F.
Published: November 2003

In this article we consider the statistical sensitivity analysis of heavy metal biosorption in contaminated wastewater packed column reactors. In particular, the model describes the biosorption phenomenon using the Advection Dispersion Reaction equation under rapid local equilibrium. This allows computer simulation with random input parameters chosen from appropriate probability distributions. In order to have a statistical framework for analyzing the simulated data and assessing input importance, we introduce heteroskedastic and multivariate sensitivity analysis, which extends standard sensitivity analysis. Copyright © 2003 John Wiley & Sons, Ltd.
Membrane actions of vitamin D metabolites 1α,25(OH)2D3 and 24R,25(OH)2D3 are retained in growth plate cartilage cells from vitamin D receptor knockout mice
Authors: Boyan Barbara D. , Sylvia V.L. , McKinney N. , Schwartz Z.
Published: November 2003

1α,25(OH)2D3 regulates rat growth plate chondrocytes via nuclear vitamin D receptor (1,25‐nVDR) and membrane VDR (1,25‐mVDR) mechanisms. To assess the relationship between the receptors, we examined the membrane response to 1α,25(OH)2D3 in costochondral cartilage cells from wild type VDR(+/+) and VDR(−/−) mice, the latter lacking the 1,25‐nVDR and exhibiting type II rickets and alopecia. Methods were developed for isolation and culture of cells from the resting zone (RC) and growth zone (GC, prehypertrophic and upper hypertrophic zones) of the costochondral cartilages from wild type and homozygous knockout mice. 1α,25(OH)2D3 had no effect on [3H]‐thymidine incorporation in VDR(−/−) GC cells, but it increased [3H]‐thymidine incorporation in VDR(+/+) cells. Proteoglycan production was increased in cultures of both VDR(−/−) and VDR(+/+) cells, based on [35S]‐sulfate incorporation. These effects were partially blocked by chelerythrine, which is a specific inhibitor of protein kinase C (PKC), indicating that PKC‐signaling was involved. 1α,25(OH)2D3 caused a 10‐fold increase in PKC specific activity in VDR(−/−), and VDR(+/+) GC cells as early as 1 min, supporting this hypothesis. In contrast, 1α,25(OH)2D3 had no effect on PKC activity in RC cells isolated from VDR(−/−) or VDR(+/+) mice and neither 1β,25(OH)2D3 nor 24R,25(OH)2D3 affected PKC in GC cells from these mice. Phospholipase C (PLC) activity was also increased within 1 min in GC chondrocyte cultures treated with 1α,25(OH)2D3. As noted previously for rat growth plate chondrocytes, 1α,25(OH)2D3 mediated its increases in PKC and PLC activities in the VDR(−/−) GC cells through activation of phospholipase A2 (PLA2). These responses to 1α,25(OH)2D3 were blocked by antibodies to 1,25‐MARRS, which is a [3H]‐1,25(OH)2D3 binding protein identified in chick enterocytes. 24R,25(OH)2D3 regulated PKC in VDR(−/−) and VDR(+/+) RC cells. Wild type RC cells responded to 24R,25(OH)2D3 with an increase in PKC, whereas treatment of RC cells from mice lacking a functional 1,25‐nVDR caused a time‐dependent decrease in PKC between 6 and 9 min. 24R,25(OH)2D3 dependent PKC was mediated by phospholipase D, but not by PLC, as noted previously for rat RC cells treated with 24R,25(OH)2D3. These results provide definitive evidence that there are two distinct receptors to 1α,25(OH)2D3. 1α,25(OH)2D3‐dependent regulation of DNA synthesis in GC cells requires the 1,25‐nVDR, although other physiological responses to the vitamin D metabolite, such as proteoglycan sulfation, involve regulation via the 1,25‐mVDR. © 2003 Wiley‐Liss, Inc.
Biochemical and functional changes of rat liver spheroids during spheroid formation and maintenance in culture: I. morphological maturation and kinetic changes of energy metabolism, albumin synthesis, and activities of some enzymes
Authors: Ma Mingwen , Xu Jinsheng , Purcell Wendy M.
Published: November 2003

In the process of isolated single liver cells coming together to form three‐dimensional spheroids, cells undergo dramatic environmental changes. How liver cells respond to these changes has not been well studied before. This study characterized the functional and biochemical changes during liver spheroid formation and maintenance. Spheroids were prepared in 6‐well plates from freshly isolated liver cells from male Sprague rats by a gyrotatory‐mediated method. Morphological formation, and functional and biochemical parameters of liver spheroids were evaluated over a period of 21 days in culture. Liver spheroid formation was divided into two stages, immature (1–5 days) and mature (>5 days), according to their size and shape, and changes in their functionality. Galactose and pyruvate consumption was maintained at a relatively stable level throughout the period of observation. However, glucose secretion and cellular GPT and GOT activities were higher in immature spheroids, decreased upto day 5 and remained stable thereafter. Cellular γ‐glutamyltransferase (γ‐GT) and lactate dehydrogenase (LDH) activities were initially undetectable or low and increased as spheroids matured. Albumin secretion decreased rapidly within the first 2 days and increased as spheroids matured. It is concluded that cells undergo functional and biochemical changes during spheroid formation following isolation of liver cells from intact tissue. Functionality and biochemical properties recovered and were maintained in mature spheroids. A relatively stable period (6–15 days) of functionality in mature spheroids was identified and is recommended for applications of the model. © 2003 Wiley‐Liss, Inc.
Transcriptional characterization of bone morphogenetic proteins (BMPs)‐mediated osteogenic signaling
Authors: Peng Ying , Kang Quan , Cheng Hongwei , Li Xinmin , Sun Michael H. , Jiang Wei , Luu Hue H. , Park Jae Yoon , Haydon Rex C. , He Tong‐Chuan
Published: November 2003

Bone formation is presumably a complex and well‐orchestrated process of osteoblast lineage‐specific differentiation. As members of the TGFβ superfamily, bone morphogenetic proteins (BMPs) play an important role in regulating osteoblast differentiation and subsequent bone formation. Several BMPs are able to induce de novo bone formation. Although significant progress has recently been made about the transcriptional control of osteoblast differentiation, detailed molecular events underlying the osteogenic process remain to be elucidated. In order to identify potentially important signaling mediators activated by osteogenic BMPs but not by non‐osteogenic BMPs, we sought to determine the transcriptional differences between three osteogenic BMPs (i.e., BMP‐2, BMP‐6, and BMP‐9) and two inhibitory/non‐osteogenic BMPs (i.e., BMP‐3 and BMP‐12). Through the microarray analysis of approximately 12,000 genes in pre‐osteoblast progenitor cells, we found that expression level of 203 genes (105 up‐regulated and 98 down‐regulated) was altered >2‐fold upon osteogenic BMP stimulation. Gene ontology analysis revealed that osteogenic BMPs, but not inhibitory/non‐osteogenic BMPs, activate genes involved in the proliferation of pre‐osteoblast progenitor cells towards osteoblastic differentiation, and simultaneously inhibit myoblast‐specific gene expression. BMP‐regulated expression of the selected target genes was confirmed by RT‐PCR, as well as by the CodeLink Bioarray analysis. Our findings are consistent with the notion that osteogenesis and myogenesis are two divergent processes. Further functional characterization of these downstream target genes should provide important insights into the molecular mechanisms behind BMP‐mediated bone formation. © 2003 Wiley‐Liss, Inc.
Evolution of the thymus size in response to physiological and random events throughout life
Authors: Domínguez‐Gerpe Lourdes , Rey‐Méndez Manuel
Published: November 2003

During embryogenesis and in the early stages of life, the thymus is a crucial organ for the generation of the T cell repertoire. T cells are generated from hematopoietic stem cells already differentiated to precursor T cells in the bone marrow. These cells enter the thymus guided by chemotactic factors secreted by this organ. The complex maturation process takes place that ensures self‐tolerance and homeostasis. Thymocytes that show autoreactivity do not leave the thymus, but rather die by apoptosis. The final percentage of mature T cells that survive to migrate from the thymus to the periphery is very low: at most 5%, under optimal conditions. The highest migration occurs in childhood and adulthood, at least in mice and humans; however, it declines throughout life and is minimal in the elderly. Under normal circumstances, the thymus commences involution soon after birth, and this involution correlates with the capacity to export mature T cells to the periphery. Hormones, cytokines, and neurotransmitters all play a role in this age‐associated process, but the reasons for and mechanisms of this involution remain unknown. Apart from physiological conditions that change throughout life and govern age‐related thymus evolution, random states and events provoked by intrinsic or extrinsic factors can induce either thymus involution, as in reversible transient thymic hypoplasias, or thymic hyperplasias. The age‐associated involution, unlike transient involutions, follows a regular pattern for all individuals, though there are clear differences between the sexes. Nevertheless, even the age‐associated involution seems to be reversible, raising the possibility of therapeutic strategies aimed at enhancing thymus function in the elderly. Microsc. Res. Tech. 62:464–476, 2003. © 2003 Wiley‐Liss, Inc.
Aging of the vertebrate immune system
Authors: Torroba Marta , Zapata Agustín G.
Published: November 2003

We have summarized current knowledge on the aging of the immune system in three vertebrate groups: fish, amphibians and birds. Available data are few due to difficulties in studying ageing in natural populations and in accurately determining age. In all vertebrates, the most obvious evidence of the senescence of lymphoid tissue is the involution of thymus, which courses with decreased numbers of thymocytes, and loss of the histological organization of gland. On the other hand, there is little information on aged secondary lymphoid organs. Possible influence of the endocrine system in the changes observed in aged lymphoid organs is also discussed. Microsc. Res. Tech. 62:477–481, 2003. © 2003 Wiley‐Liss, Inc.
Age‐related changes in the avian primary lymphoid organs (thymus and bursa of Fabricius)
Authors: Ciriaco Emilia , Píñera Pablo P. , Díaz‐Esnal Belén , Laurà Rosaria
Published: November 2003

The avian primary lymphoid organs, the thymus and the bursa of Fabricius, undergo age‐dependent changes leading in some cases to the complete atrophy of the organ. Nevertheless, the timetable of the involutive process as well as the consequences in the structure and functionality of the organs vary largely in the time frame and structural changes among species. On the other hand, and in contrast with the large body of literature reporting the structural and functional changes in mammalian primary lymphoid organs, the age‐dependent changes in avian thymus and bursa of Fabricius are scarce, fragmentary, and heterogeneous. This article reviews the current literature on this topic, and focuses primarily on the involution of the bursa of Fabricius. Microsc. Res. Tech. 62:482–487, 2003. © 2003 Wiley‐Liss, Inc.
Hepatitis C virus core protein upregulates transforming growth factor‐β1 transcription
Authors: Taniguchi Hiroyoshi , Kato Naoya , Otsuka Motoyuki , Goto Tadashi , Yoshida Hideo , Shiratori Yasushi , Omata Masao
Published: November 2003

The majority of persons with chronic hepatitis C virus (HCV) infection develop liver fibrosis. Transforming growth factor (TGF)‐β1 plays a pivotal role in the pathogenesis of post‐inflammatory liver scarring. To clarify the influence of HCV infection on liver fibrosis, a reporter assay was used to investigate the effect of viral proteins on TGF‐β1 expression in human hepatoma cells. Of all HCV proteins investigated (core, E1/E2/p7, NS2, NS3, NS4A, NS4B, NS5A, and NS5B), only the core protein activated the TGF‐β1 promoter and upregulated TGF‐β1 expression measured by an RNase protection assay. Bases −376 to −331 bp in the promoter region of TGF‐β1 are responsible for upregulation by HCV core protein, and the nuclear protein that binds to this region increased with the stimulation of HCV core protein. Blocking the mitogen‐activated protein kinase pathway prevented upregulation of TGF‐β1 by HCV core protein. The immunological response is supposed to be a major factor to cause the secretion of TGF‐β1 from non‐parenchymal cells, but the results suggest that the HCV core protein expression may upregulate directly TGF‐β1 transcription in parenchymal cells and suggest a new paradigm for exacerbation of liver fibrosis by HCV infection. J. Med. Virol. 72:52–59, 2004. © 2004 Wiley‐Liss, Inc.