bluuebunny/crossref_metadata_2025 huggingface dataset:
Clomiphene‐Induced Changes in Endometrial Receptor Kinetics on the Day of Ovum Collection after Ovarian Stimulation: A Study on Cytosol and Nuclear Estrogen and Progestin Receptors and 17/β‐Hydroxysteroid Dehydrogenase
Authors: RÖNNBERG LARS , ISOTALO HANNU , KAUPPILA ANTTI , MARTIKAINEN HANNU , VIHKO REIJO
Published: December 2006

Clomiphene citrate (CC) in combination with human menopausal gonadotropin (hMG), human chorionic gonadotropin (hCG), or both (hMG‐hCG) has a central role in ovarian stimulation in present in vitro fertilization (IVF) programs. It is thought that the ovarian response to clomiphene citrate is dose‐dependent, which has led to the use of high doses of this compound.1,2 However, the success rate in embryo transfer (ET) seems to be lower after high‐dose than low‐dose stimulation.3,4 The reason for this undesirable effect is unknown. Besides having pituitary‐ovarian effects, clomiphene citrate, like other antiestrogens, also has endometrial actions. Antiestrogens bind to cytosolic estrogen receptors, and the estrogen‐receptor complex formed is transferred to the nucleus for an extended period of time, with resultant changes in female sex steroid receptor kinetics, as has been observed in animal5–7 and human studies.8,9 It is therefore possible that high doses of clomiphene citrate lead to changes in endometrial function that may be detrimental for the success of embryo transfer. We evaluated this possibility by taking endometrial specimens for determination of female sex steroid receptor and 17β‐hydroxysteroid dehydrogenase in patients receiving two different doses of clomiphene citrate for ovarian stimulation and in whom adhesions prevented oocyte collection. The results were compared with those obtained in healthy, untreated, ovulatory women.
Chromosomal Preparations from Human Oocytes
Authors: WRAMSBY H. , FREDGA K. , LIEDHOLM P.
Published: December 2006

It appears that the chance of an in vitro fertilization (IVF) embryo to produce a pregnancy carried to term is about 10%.1 Consequently, one of the most important factors in increasing the pregnancy rate after in vitro fertilization and embryo transfer is replacement of multiple embryos.2 When we consider that the estimated human fecundity rate is about 25%,3 it seems likely that the quality of the embryo is one determining factor for a successful pregnancy rate. Different types of defects of gametes and embryos might contribute to the explanation of why the vast majority of IVF embryos do not give rise to any sign of pregnancy after replacement.

It is well documented that chromosomal abnormalities among first trimester spontaneous abortions occur at a rate of about 60%, indicating that chromosomal abnormalities might be common in human gametes and early development stages.4 Abnormal karyotypes found were aneuploidy (i.e., complements with one extra or one missing chromosome) and polyploidy.

Recently, a new technique allowing direct analysis of the chromosomal constitution of human spermatozoa has been reported.5 This technique utilizes the ability of capacitated human spermatozoa to penetrate zona‐free hamster oocytes. Five to 10% of penetrating human spermatozoa have shown chromosomal abnormalities. Various degrees of hyperploidy and hypoploidy ranging from three extra to three missing chromosomes were found in a series of 1000 human spermatozoal chromosome constitutions.6 It is interesting to note that among spontaneous first trimester abortions such serious numerical abnormalities have not been found.4
The Selection of Couples for in Vitro Fertilization and Embryo Replacement
Authors: STEPTOE PATRICK
Published: December 2006

Some of the obvious factors that affect the success rates, in terms of living children, of in vitro fertilization (IVF) are the ages of the patients, the quality of ovulation and spermatogenesis, and the general and gynecologic health of the female partner in terms of the safe initiation and maintenance of a pregnancy to full term.

Discussion of the selection of patients must take into account the indications for IVF and embryo replacement (ER). The clinical applications at present are infertility due to: (1) problems of ovum pickup and transport associated with pelvic pathology or absence of the oviducts; (2) oligospermia; (3) prolonged unexplained infertility; and (4) combined male and female factors.
Psychosocial Testing and Pretreatment of Women for in Vitro Fertilization
Authors: KEMETER PETER , EDER ANSELM , SPRINGER‐KREMSER MARIANNE
Published: December 2006

Thanks to extensive media coverage, both the public, in general, and infertile patients desiring children, in particular, have been alerted to the fascinating prospects of in vitro fertilization (IVF) and embryo transfer (ET). Many infertile couples would do anything to have a child of their own. As a consequence, they have come to attach high hopes to this new method, just as they were hopeful of other methods in the past.

The patients’attitudes have thus remained the same. Therefore, we ourselves should continue to bring to bear the whole body of knowledge on the pathogenesis of sterility and infertility as well as their psychosocial background when counseling patients on any new treatment modality. For this reason it would seem appropriate to review some of the results accumulated in an ongoing study of sterility and infertility which is being carried out by the Institute of Reproductive Endocrinology and in Vitro Fertilization in cooperation with several departments of the University of Vienna since 1978.1–5
Secretory Vesicle Cytochrome b561: A Transmembrane Electron Transportera
Authors: FLEMING PATRICK J. , KENT UTE M.
Published: December 2006

The major function of cytochrome b561 is now clear. This transmembrane protein transports electrons across a secretory vesicle bilayer to supply electrons to monooxygenases inside the secretory vesicle.

Cytochrome b561 has been localized not only to adrenergic secretory vesicles, where it supplies electrons to dopamine β‐hydroxylase, but also to peptidergic secretory vesicles that contain peptidyl α‐amidating monooxygenase.15,21 Thus, one would expect to 6nd cytochrome b561 in the membranes of all neuroendocrine cells that contain amidated peptide secretory products. In addition, its wide Occurrence as an integral membrane protein of secretory vesicles may make it useful for investigation of vesicle biogenesis and turnover.

One of the most important potential roles of cytochrome b561 is that it can be used as a model protein to investigate long‐range biological electron transport. This cytochrome is a single polypeptide, which can be purified easily and reconstituted into a functional assembly. It also catalyzes an experimentally unambiguous transmembrane transport of electrons. A full molecular characterization of the structure and function of this cytochrome may provide insights into biological electron transfer which would otherwise be difficult or impossible to obtain.
Adsorption Kinetics of Protein Mixtures A Tentative Explanation of the Vroman Effect
Authors: CUYPERS PETER A. , WILLEMS GEORGE M. , HEMKER H. COENRAAD , HERMENS WIM TH.
Published: December 2006

A model for protein adsorption kinetics has been presented. This model includes diffusion‐limited adsorption, adsorption and desorption rate constants kon and koff, which are dependent on the surface concentration, and an interaction term for the mutual influence of the adsorbed protein molecules. It has been shown that, in first approximation, values of kon and & Koff are exponential functions of the surface concentration. Assuming an adequate interaction term, it is possible to show with this model for a mixture of proteins that the ratio of the absorbed proteins is strongly dependent on the overall surface concentration even if the ratio of the bulk concentrations of these proteins is kept constant. Differences in interaction terms for the different proteins offer a possible explanation for the peculiar behavior of plasma protein adsorption on a surface at different dilutions of the plasma, the so‐called Vroman effect.
Efficacy of Recombinant Human Granulocyte‐macrophage Colony‐stimulating Factor in Rhesus Monkeys
Authors: MAYER P. , LAM C. , OBENAUS H. , LIEHL E. , BESEMER J.
Published: December 2006

The glycosylated and the non‐glycosylated recombinant human granulocyte‐macrophage colony‐stimulating factor (rh GM‐CSF) expressed in Chinese hamster ovary cells and E. coli, respectively, were administered in rhesus monkeys either by the subcutaneous (three times daily) or intravenous route (6‐hr infusions) for seven consecutive days. Within 24 hr peripheral white blood cells (WBC) increased 2‐3‐fold over normal values. Thereafter, the WBC increased steadily in a dose‐dependent manner to reach maximum levels on the last day of or one day after the treatment period. The differential counts showed that neutrophils contributed to 50‐80%, eosinophils to 10‐20%, monocytes to 2‐7%, and lymphocytes to 15–30% of the WBC rise. No effect was found on platelets and erythrocytes. After termination of treatment, WBC counts returned to normal levels within one week. Subcutaneously administered CSF was more effective in inducing leukocytosis than that injected intravenously. In addition to the rise in WBC, the administered rh GM‐CSF also enhanced the oxidative metabolism and bactericidal activity of the circulating mature granulocytes isolated from the blood of monkeys treated with rh GM‐CSF. These results show that glycosylated or non‐glycosylated rh GM‐CSF is both an effective stimulator of leukocytosis and a potent activator of the functional activity of mature granulocytes in vivo.
Interactions of Retroviral and Cellular Transforming Genes with Hematopoietic Cells
Authors: EVA ALESSANDRA , PIERCE JACALYN H. , AARONSON STUART A.
Published: December 2006

Investigations of a small group of RNA tumor viruses, the acute transforming retroviruses, have led to important insights into the mechanisms by which their cell‐derived oncogenes confer to the virus properties essential for the induction and maintenance of the transformed state. While oncogenes were initially discovered as cellular genes captured by acute transforming retroviruses, it has become apparent in recent years that these same cellular genes or proto‐oncogenes may be frequent targets for the genetic changes that lead normal cells along the pathway to malignancy under natural conditions, independent of retrovirus involvement. The conversion of proto‐oncogenes to oncogenes can be due to DNA rearrangements resulting from chromosomal translocations, gene amplification, and other mechanisms affecting their normal regulation and expression. Even genetic changes as subtle as point mutations have been shown to lead to oncogene activation. The present review summarizes knowledge of the functions of oncogenes, their effects on hematopoietic cells, and the current stage of knowledge linking these genes to human hematopoietic malignancies.
Intracellular Ionic Calcium and the Cytoskeleton in Living Cells
Authors: SHELANSKI MICHAEL L.
Published: December 2006

The calcium ion is present in the cytoplasm of living cells at resting concentrations of between 50 and 150 nanomolar while total cellular calcium concentrations, primarily bound non‐ionic calcium, are in the millimolar range. Over the past several decades this ion has been suggested to play a critical role in the control of a wide range of cellular functions including excitability, endocytosis, exocytosis, motility, and cell division. Attention has focused on calcium activation of various enzymes and on an expanding class of calcium‐binding proteins. Except for the case of electrophysiological responses, most of our insight into calcium control mechanisms has been derived from studies on cell fractions rather than intact cells. The exceptions to this have been those which have used cells large enough to penetrate with calcium‐sensitive ion selective electrodes or cells which have been injected with the calcium‐sensitive photoprotein aequorin. Both of these approaches have serious limitations to their application. In the past five years the development and exploitation of calcium‐sensitive fluorescent reporter dyes1 has enabled the measurement of nanomolar concentrations of the cytoplasmic ionic calcium ([Ca2+]i) in living cells. In the studies reviewed here, I shall move away from the nervous system, which has been the focus of this symposium, to non‐neural cells in culture in order to discuss the possible role of the calcium ion in the local control of cytoskeletal function in interphase cells, in mitosis, and finally in Alzheimer's disease.
Ethics and Nuclear Weapons Researcha
Authors: BROWN PAUL S.
Published: December 2006

Nuclear weapons are the ultimate weapons. Hence, for many who would debate military research and development, research on nuclear weapons represents the ultimate point of contention. Those of us involved in nuclear weapons research are frequently asked why we do what we do, rather than participating in the supposedly more peaceful endeavors open to scientists and engineers. There are a variety of answers to this question.
Ethics and Biological Warfare Research
Authors: COLE LEONARD A.
Published: December 2006

Biological weapons, unlike any other weapons, have been entirely renounced, and their possession by nations has been prohibited by international treaty. Nevertheless, many ethical questions that apply to biological warfare research have bearing on other forms of military research. This is especially true where specific categories of arms have been or are expected to be restricted by law. In this regard, the relationship of scientists to the U.S. Biological Defense Program can be instructive.
Health Research in Africa: Priorities, Promise, and Performance
Authors: LUCAS ADETOKUNBO O.
Published: December 2006

I am delighted to participate at this conference because it gives me the opportunity of acknowledging the contributions of individuals, institutions and agencies who have dedicated their skills and resources to the fight against death, disease, and disability in developing countries. I am particularly pleased to join in congratulating Dr. Ken Warren, not only for his direct contributions as a research scientist on tropical diseases, but more importantly for his inspiration and support, which has encouraged and enabled many others to work on these problems.

I have been asked specifically to provide an African perspective and I would like to examine the subject of health research in Africa by reviewing the subject in three historical periods: (a) the colonial era, (b) the post‐independence period, and (c) the future.
FCNC b’Decays May Be Prime
Authors: HOU GEORGE WEI‐SHU , STUART ROBIN G.
Published: December 2006

Calling the fourth family quarks “b” and “t'” shows a lack of imagination on the part of particle physicists, and to some it shows that the authors using such names do not really believe in them (or, maybe it indicates that the fourth family is rather special; e.g. it may be the end of the notion of “family repetition’as we know it). However, I hope I have made good use of it in the title. Personally, I would like to call the fourth u‐type quark “Glory” and the fourth d‐type quark “Humor,” for obvious reasons. Maybe we should start a naming contest in this natural setting of the second reunion of fourth family workers….
Why There Should Not be a Fourth Family
Authors: PECCEI R. D.
Published: December 2006

To my knowledge there are no really good arguments that fix the number of generations of quarks and leptons. Nevertheless, to be provocative, in this symposium on the fourth family, I have tried to muster some arguments against the existence of more than three families of fundamental fermions. I begin by giving a purely prejudicial tirade against a fourth family.
Fermion Families: Conference Summary
Authors: OKUN L. B.
Published: December 2006

My task of summing up our symposium is difficult, in particular, because of its (the symposium's) high density (more than fifty talks in three days) and high diversity.
Bd0—Bd0 Mixing, Flavor‐Changing Rare Processes, and the Electric Dipole Moment of the Neutrona
Authors: SHIN MICHAEL , BANDER MYRON , SILVERMAN DENNIS
Published: December 2006

In our present understanding of the weak interaction sector, there is one potentially important piece of experimental data whose explanation may require new physics beyond the standard model (SM). It is the surprisingly large Bd0—Bd0 mixing, first reported here at this conference two years ago by the ARGUS1 collaboration, which has been further confirmed by the CLEO2 collaboration.
Rare Decays and the Fourth Generationa
Authors: HEWETT JOANNE L.
Published: December 2006

Rare decays are quite sensitive1 to physics beyond the Standard Model (SM), due to the effects of virtual, new, heavy particles (i.e., a fourth generation, SUSY, charged Higgs, E6 exotic fermions,…). These new contributions can either enhance or suppress (sometimes quite substantially) the rates for rare processes compared to the corresponding SM predictions. Current experiments are already closing in on the SM rates for some processes and are starting to be able to probe the possible contributions from new physics. With the advent of K and B factories, as well as with detector improvements, future experiments expect to actually observe the predicted SM rate for several decays and may be able to rule out some extended models. In this case, rare processes may hold a rare advantage over collider physics, as they will be able to explore new higher energy regimes in the near future.
Dark Matter and the Solar Neutrino Problem: Can Particle Physics Provide a Single Solution?
Authors: WEST GEOFFREY B.
Published: December 2006

It has been known for some time that weakly interacting massive particles (WIMPS or cosmions) can simultaneously solve both the dark matter and solar neutrino problem.1 The idea is quite simple and elegant: such particles being the constituents of dark matter2 would, if sufficiently massive, acrete in the core region of the sun. As they orbit in the sun's interior, they transfer heat from the inner to the outer regions thereby cooling the core. Lowering the core temperature (T) by only 10% is sufficient to reduce the predicted output of observable neutrinos by a factor of 3 to 4 leading to a resolution of the solar neutrino problem.3 The crucial point is that almost 80% of the observable neutrinos (which represent only 10−6 of the total neutrino output of the sun!) result from the decay 8B±8Be*+e+ve and the rate for this is very sensitive to T). On the other hand, solar models that accurately describe bulk properties of the sun such as its total luminosity, radius, mass, and surface abundance of elements are not very sensitive to T). Indeed, changing T) by 10% has only a negligible effect on these gross properties, including the total neutrino output of the sun.3 Roughly speaking the necessary properties of the cosmion, such as its mass (Mc) and cross‐section off of protons (σ) can be deduced by requiring that it lowers T± by ±10% without appreciably affecting the temperature beyond a radius ±0.1 R, where most of the solar luminosity (L) originates.
Toward the Constructive Theory of Human Social Behavior. V. Labor Behavior under Piecework Pay
Authors: CHERNYAK YURI B. , LEONOV ARKADII I. , LERNER ALEXANDR Y.
Published: December 2006

This paper is the fifth in our series (see references 1–4) aimed at describing the functioning of a human community (for example, a firm, a region, or a state) on the basis of a “microscopic” picture that represents individual deeds (behavior, in fact). General principles are outlined in reference 1, where we formulate an extremal principle that governs the behavior of individs and, thereby, the life of whole community. The description is, generally, closed, by which it is implied that the goods and services consumed by each individ result mainly from the labor of other members of the society (see also references 5 and 6).
Proper Functions with the Baire Property
Authors: SZYMANSKI ANDRZEJ
Published: December 2006

The problem of determining which functions with the Baire property have proper preimages of some open sets is dealt with.
Second Messengers in Neuronal Signalinga
Authors: AGRANOFF BERNARD W.
Published: December 2006

The past decade has witnessed an enormous increase in our knowledge of the variety and complexity of intracellular signaling events that follow receptor binding on the cell surface. This overview emphasizes the phosphoinositidase C‐mediated dual messenger pathway in brain and in brain‐derived cells, with special reference to possible significance for research on the dementias.
Changes in G Protein‐mediated Signal Transduction in Aging and Alzheimer's Disease
Authors: JOSEPH J. A. , CUTLER R. , ROTH G. S.
Published: December 2006

Previous reports have shown that there are age‐related reductions in muscarinic receptor (mAChR) sensitivity to agonist stimulation. Our research has elucidated the mechanisms involved in this loss. These studies have shown that this decline is the result of decreases in mAChR concentration, reductions in the number of neuronal cells, and altered phosphoinositide (PI)‐mediated signal transduction (ST). The decrements in PI‐mediated ST are observed as a reduced ability of muscarinic (m) agonists to enhance K+‐evoked release of DA (K+ERDA) from striatal slices from old rats. Additional experiments indicated that the locus of the ST deficits appears to be at the mAChR‐G protein interface, since attempts to bypass this interface reduced m‐enhanced K+ERDA deficits in the striata from old rats. Moreover, it appears that the ability of mAChR to decouple from their respective G proteins is reduced as a function of age, since carbachol‐stimulated low KM GTPase activity was found to be reduced in hippocampal and striatal tissue obtained from old rats. Similar findings were observed in this parameter in AD hippocampus and basal ganglia. Further reductions were seen in carbachol‐stimulated low KM GTPase as a function of the duration of the disease. Results are discussed in terms of structural membrane alterations in aging and disease that may lead to reductions in the efficacy of receptor‐G protein coupling/uncoupling.
X‐Ray Diffraction Analysis of Brain Lipid Membrane Structure in Alzheimer's Disease and β‐Amyloid Peptide Interactionsa
Authors: MASON R. PRESTON , SHAJENKO LYDIA , HERBETTE LEO G.
Published: December 2006

Small angle x‐ray diffraction analysis of Alzheimer's disease (AD) lipid membranes reconstituted from cortical gray matter showed significant, reproducible structure changes relative to age‐matched control samples.1 Specifically, there was an average 4 Å reduction in the lipid bilayer width and marked changes in membrane electron density profiles of AD cortical samples. There were no significant structure differences in the membrane bilayers isolated from an unaffected region (cerebellum) of the AD brain. Lipid and protein analysis of six AD and six age‐matched controls showed that the phospholipid : protein mass ratio was unchanged, but that the unesterified chlolesterol : phospholipid (C : PL) mole ratio decreased by 30% in the AD temporal gyrus relative to age‐matched controls. The C : PL mole ratio was not significantly different for samples prepared from cerebellum of AD versus control patients. X‐ray diffraction analysis of a cholesterol‐enriched AD sample demonstrated a virtual restoration of the normal membrane bilayer width and electron density profile, suggesting that the cholesterol deficit played a major role in the AD lipid membrane structure perturbation. Addition of β‐amyloid peptide to bovine brain phospholipid membranes signficantly changed the electron density associated with the hydrocarbon core. Alterations in the composition and structure of the membrane bilayer may play an important role in the pathophysiology of AD by altering the activity and catabolism of membrane‐bound proteins, including the β‐amyloid precursor protein.
Protease Inhibitors and Indolamines Selectively Inhibit Cholinesterases in the Histopathologic Structures of Alzheimer's Diseasea
Authors: WRIGHT CHRISTOPHER I. , GEULA CHANGIZ , MESULAM M.‐MARSEL
Published: December 2006

Neurofibrillary tangles and amyloid plaques express acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activity in Alzheimer's disease. We had found that traditional AChE inhibitors such as BW284C51, tacrine and physostigmine were more potent inhibitors of the AChE in normal axons and cell bodies than of the AChE in plaques and tangles (1). We now report that the reverse pattern is seen with indolamines, carboxypeptidase inhibitor, and the nonspecific protease inhibitor bacitracin. These substances are more potent inhibitors of the cholinesterases in plaques and tangles than of those in normal axons and cell bodies. These results show that the enzymatic properties of plaque and tangle‐associated cholinesterases diverge from those of normal axons and cell bodies. The selective susceptibility to bacitracin and carboxypeptidase inhibitor indicates that the catalytic sites of plaque and tangle‐bound cholinesterases are more closely associated with peptidase or protease‐like properties than the catalytic sites of cholinesterases in normal neurons and axons. This shift in enzymatic affinity may lead to the abnormal protein processing which is thought to play a major role in the pathogenesis of AD. The availability of pharmacological and dietary means for altering brain indolamines raises novel therapeutic possibilities for inhibiting the abnormal cholinesterase activity associated with Alzheimer's disease.
Free Radicals in the Genesis of Alzheimer's Diseasea
Authors: RICHARDSON J. STEVEN
Published: December 2006

As part of an ongoing investigation of the role of oxygen free radicals in Alzheimer's disease (AD), the formation of peroxidation products, the activities of free radical defense enzymes, and the level of total iron were determined in autopsy brain tissue from donors with AD and from age‐matched non‐demented donors. Calcium uptake was also investigated in mitochondria harvested from fibroblasts grown in tissue culture from skin samples taken from brain donors.

Compared to controls, homogenates of AD frontal cortex produced elevated levels of peroxidation products and this difference was amplified in a dose‐dependent manner by iron (1 to 200 μM). Peroxidation produced by 200 μM iron was reduced dose dependently by the lazaroid U‐74500A. The IC50 was 10 μM in AD cortex and 2.5 μM in controls.

Superoxide dismutase (SOD), one of the free radical defensive enzymes, was reduced by 25 to 35% in AD frontal cortex, hippocampus and cerebellum. In other brain areas, SOD did not differ between AD and control. The activities of catalase and glutathione peroxidase were the same in AD and control samples. Endogenous iron levels were higher in AD frontal cortex (2.5 nmol/mg protein) than in controls (1.5 nmol/mg protein).

Calcium uptake by AD fibroblast mitochondria is 50% lower than in controls under basal conditions. Following exposure to 200 μM iron, mitochondrial calcium uptake is increased by 58% in AD and by 38% in controls. Pretreatment with 200 μM U‐74500A or 1 mM deferoxamine, prior to exposure to 200 μM iron, gave complete protection to control mitochondria but gave only partial protection to AD mitochondria.

These studies indicate that in AD, both CNS and peripheral cells show increased sensitivity to oxygen free radicals. The source of this increased sensitivity has not yet been identified but could reflect either reduced free radical defenses or increased free radical formation or both. Work is underway using electron paramagnetic resonance spectrometry to determine in vivo, premortem free radical activity in AD patients.
Comparative Effects of Aging Process on Phosphatidylcholine Biosynthesis Pathway: A Key Role for CTP‐Phosphocholine Cytidylyltransferase?
Authors: LEPAGNOL J. M. , HEIDET V.
Published: December 2006

The effects of aging on phosphatidylcholine (PtdCho) biosynthesis were investigated in liver and brain subcellular fractions of the rat, by studying the activity and regulation of CTP phosphocholine cytidylyltransferase (CT), the rate limiting enzyme in PtdCho biosyntheses. With both tissues, CT activity was present in cytosolic and microsomal fractions, but in brain, CT activity seemed to escape to an inhibiting feed back mechanism. In brain, CT activity was greater in the microsomal fraction, whilst in liver, a higher CT activity was seen in the cytosolic fraction.

In liver fractions of aged animals, there was no significant change in CT activity or its sensitivity to negative feedback regulation, as compared to young animals. In contrast, a progressive age related decline in CT activity was observed in the brain microsomal fraction. Furthermore, the incorporation of newly formed CDPCho into PtdCho was also reduced in aged animals, and paralleled the decreased incorporation of choline in PtdCho. The age‐related decrease in CT activity cannot be explained by product feed back inhibition or decreased diacylglycerol levels.

Since PtdCho is a major membrane lipid, the reduction in CT activity may lead to a decreased membrane integrity and fluidity during the aging process, and these effects may be greater in neuronal cells.
Regulation and Expression of the Alzheimer's β/A4 Amyloid Protein Precursor in Health, Disease, and Down's Syndromea
Authors: BEYREUTHER KONRAD , POLLWEIN PETER , MULTHAUP GERD , MÖNNING URSULA , KÖNIG GERHARD , DYRKS THOMAS , SCHUBERT WALTER , MASTERS COLIN L.
Published: December 2006

A four‐ to fivefold overexpression of the gene for the Alzheimer β/A4 amyloid precursor protein (APP) in individuals with Down's Syndrome (DS) appears to be responsible for the fifty year earlier onset of Alzheimer's disease (AD) pathology in DS compared to the normal population. It is therefore likely that a deregulated overexpression of the APP gene is a risk factor for the β/A4 amyloid formation. To test this hypothesis and to get a better understanding of how APP expression is regulated, we studied the 5′ control region of the human APP gene, alternative splicing of the 19 APP exons, and APP biogenesis, metabolism and function. The analysis of the APP promoter revealed its similarity with those of housekeeping genes by the presence of a GC‐rich region around the transcription start site and the lack of a TATA box. Gene transfer experiments showed this GC‐rich region to contain overlapping binding sites for different transcription factors whose binding is mutually excluded. An imbalance between these factors may cause APP overexpression and predispose to AD pathology. Another putative risk factor for AD is regulation of splicing of exon 7 in APP mRNA's which changes in brain during aging. This is relevant for APP processing since exon 7 codes for a Kunitz protease inhibitory domain. Investigation of further splicing adjacent to the β/A4 exons 16 and 17 which might also interfere with APP processing led to the identification of the leukocyte‐derived (L‐APP) splice forms which lack exon 15. In brain this splicing occurs in activated astrocytes and microglia. The localization of APP at synaptic sites in brain suggests that APP regulation and expression are critical determinants of a potential and early impairment of central synapses. This may be the case during pathological evolution of AD and DS when β/A4 derived from synaptic APP is converted to β/A4 amyloid by radical generation.
Production of Amyloid β Protein from Normal Amyloid β‐Protein Precursor (βAPP) and the Mutated βAPPS Linked to Familial Alzheimer's Diseasea
Authors: GOLDE TODD E. , CAI XIAO‐DAN , SHOJI MIKIO , YOUNKIN STEVEN G.
Published: December 2006

The ∼4 kD (39–43 amino acid) polypepride (amyloid β protein, Aβ) deposited as amyloid in Alzheimer's disease (AD) is derived from a set of 695–770 residue precursor proteins collectively referred to as the amyloid β‐protein precursor (βAPP). Using immunoblotting techniques, metabolic labeling, and sequencing we have analyzed βAPP derivatives in medium conditioned by (1) human mononuclear leukemic (K562) cells expressing a model βAP‐bearing carboxyl‐terminal βAPP derivative (2) human neuroblastoma (Ml7) cells transfected with constructs expressing full length βAPP and (3) M17 cells expressing only endogenous βAPP. In each case, we observed the release of a ∼4 kD βAPP derivative essentially identical to the Aβ found in AD amyloid. A similar, if not identical, βAPP fragment was readily detected in CSF from both Alzheimer's disease patients and controls. These observations indicate that the Aβ is produced and released by normal processing of the βAPP. To determine if the production of Aβ or Aβ‐tearing COOH‐terminal βAPP derivatives is altered in cells expressing the mutant βAPPs linked to familial AD, we have compared M17 cells expressing wild type βAPP with those expressing mutant βAPPs (βAPPΔI or βAPPΔNL). After continuous metabolic labeling for 8 hours, cells expressing the βAPPΔNL mutant showed a 5‐fold increase in the relative amount of an ∼ 11.4 kD Aβ‐bearing carboxyl‐terminal βAPP derivative, and they released 6‐fold more 4 kD Aβ into the medium. These observations provide strong evidence that (1) the pathway producing Aβ in cultured cells is highly relevant to AD and (2) the βAPPΔNL mutant causes AD because its processing is altered in a way that releases increased amounts of Aβ.
Normal Cellular Processing of the β‐Amyloid Precursor Protein Results in the Secretion of the Amyloid β Peptide and Related Moleculesa
Authors: HAASS CHRISTIAN , HUNG ALBERT Y. , SCHLOSSMACHER MICHAEL G. , OLTERSDORF TILMAN , TEPLOW DAVID B. , SELKOE DENNIS J.
Published: December 2006

Alzheimer's disease is characterized by the extracellular deposition in the brain and its blood vessels of insoluble aggregates of the amyloid β peptide (Aβ). This peptide is derived from a large integral membrane protein, the β‐amyloid precursor protein (βAPP), by proteolytic processing. The Aβ has previously been found only in the brains of patients with Alzheimer's disease or advanced aging. We describe here the finding that Aβ is produced continuously by normal processing in tissue culture cells. Aβ and closely related peptides were identified in the media of cells transfected with cDNAs coding for βAPP in a variety of cell lines and primary tissue cultured cells. The identity of these peptides was confirmed by epitope mapping and radiosequencing. Peptides of a molecular weight of ∼3 and ∼4 kDa are described. The 4 kDa range contains mostly the Aβ and two related peptides starting N‐terminal to the beginning of Aβ. In the 3 kDa range, the majority of peptides start at the secretase site; in addition, two longer peptides were found starting at amino acid F(4) and E(11) of the Aβ sequence. To identify the processing pathways which lead to the secretion of these peptides, we used a variety of drugs known to interfere with certain cell biological pathways. We conclude that lysosomes may not play a predominant role in the formation of 3 and 4 kDa peptides. We show that an acidic environment is necessary to create the N‐terminus of the Aβ and postulate that alternative secretory cleavage might result in the formation of the N‐terminus of Aβ and related peptides. This cleavage takes place either in late Golgi, at the cell‐surface or in early endosomes, but not in lysosomes. The N‐terminus of most of the 3 kDa peptides is created by secretory cleavage on the cell surface or within late Golgi.
Protein Phosphorylation Regulates Relative Utilization of Processing Pathways for Alzheimer β/A4 Amyloid Precursor Proteina
Authors: GANDY SAMUEL E. , CAPORASO GREGG L. , BUXBAUM JOSEPH D. , SILVA ODETE DA CRUZ E , IVERFELDT KERSTIN , NORDSTEDT CHRISTER , SUZUKI TOSHI , CZERNIK ANDREW J. , NAIRN ANGUS C. , GREENGARD PAUL
Published: December 2006

The Alzheimer amyloid precursor protein (APP) is a phosphoprotein, and the phosphorylation state of APP at Ser655 can be regulated by protein kinase C, calcium/calmodulin‐dependent protein kinase II, and okadaic acid‐sensitive protein phosphatases. Other enzymes may also play a role at Ser655 of APP and, perhaps, at other residues.

Signal transduction via protein phosphorylation regulates APP metabolism. In particular, APP processing via the nonamyloidogenic secretory cleavage pathway is increased following the activation of protein kinase C or the inactivation of okadaic acid‐sensitive protein phosphatases.

The mechanism(s) by which protein phosphorylation regulates APP secretory cleavage include (among others): substrate activation, substrate redistribution, protease activation and/or protease redistribution. Current experimental evidence will be discussed, addressing the relative importance of each of these possibilities and the implications for these events in the modulation of β/A4‐amyloidogenesis.
Sequestration of Amyloid β‐Peptidea
Authors: GOLDGABER D. , SCHWARZMAN A. I. , BHASIN R. , GREGORI L. , SCHMECHEL D. , SAUNDERS A. M. , ROSES A. D. , STRITTMATTER W. J.
Published: December 2006

Amyloid β‐protein, or β/A4, is a 4‐kilodalton peptide that forms poorly soluble extracellular depositions of amyloid in brains and leptomeninges of patients with Alzheimer's disease (AD), Down's syndrome (DS), and hereditary cerebral hemorrhage with amyloidosis‐Dutch type (HCHWA‐D). β/A4 peptide is a derivative of a large transmembrane glycoprotein (APP) and is found in the extracellular space, i.e., in the cerebrospinal fluid and serum of individuals with and without AD and in the conditioned media of many different cells grown in culture.1 The mechanism by which normally produced amyloid β peptide forms extracellular aggregates in patients is unknown. One possible explanation is a failure of a mechanism for removal of the β/A4 peptide that prevents this highly aggregating peptide from forming extracellular amyloid depositions.
The Role of Extracellular Matrix in the Processing of the Amyloid Protein Precursor of Alzheimer's Diseasea
Authors: SMALL DAVID H. , NURCOMBE VICTOR , CLARRIS HEIDI , BEYREUTHER KONRAD , MASTERS COLIN L.
Published: December 2006

Alzheimer's disease (AD) is characterized by the presence of extracellular amyloid plaques, which contain a protein referred to as the amyloid or βA4 protein. The βA4 protein is derived from a larger precursor protein (APP). Studies of autosomal‐dominant forms of AD have established the central role of APP in the pathogenesis of the disease. Despite considerable research, the function of APP is unknown. APP can be processed by at least two separate routes. The first route involves a protease known as “APP secretase,” which cleaves within the amyloid sequence, thereby mitigating amyloid formation. The second route may result in the production of potentially amyloidogenic fragments. Our studies suggest that following release from the cell membrane, APP interacts with components of the extracellular matrix (ECM) such as the heparan sulfate proteoglycans (HSPG's). The interaction of APP with HSPG's may be important for the function of APP. Substratum‐bound APP was found to dramatically increase neurite outgrowth and survival of chick sympathetic neurons in vitro. This effect was dependent upon the presence of substratum‐bound HSPG. The results suggest that normally, when bound to the ECM, APP functions to promote neurite outgrowth and/or cell survival. Loss of this normal trophic function might occur in AD, when APP is proteolytically processed via the amyloidogenic pathway.
Expression of L‐APP mRNA in Brain Cellsa
Authors: SANDBRINK RUPERT , BANATI RICHARD , MASTERS COLIN L. , BEYREUTHER KONRAD , KÖNIG GERHARD
Published: December 2006

Several reports addressed the issue of how the alternative splicing of exon 7 and 8 in the APP pre‐mRNA is regulated in different tissues. Of special interest here was the potential involvement of exon 7 containing APP splice isoforms, since this exon codes for a serine protease inhibitor and is therefore of putative relevance for amyloidogenic catabolism of the precursor protein. The recent identification of a third alternative splice site in close proximity to the βA4‐amyloid portion in the APP gene which may also increase APP amyloidogenicity, allowed us to investigate its regulation in cells of the central nervous system. With our assay, we were able to resolve six different APP isoforms of the eight potential isoforms which can be generated from the three alternatively spliced exons 7, 8, and 15. We demonstrate here that, in addition to rat brain microglia cells, astrocyte‐enriched cultures also skip the novel alternative 3′‐splice site in front of exon 15, generating L‐APP mRNA. Neurons are the only cells in the central nervous system which seem to use the 3′‐splice site of intron 14 nearly 100%. Interestingly, this very 3′‐splice site is the only one present in the APP gene that completely matches the consensus sequence for the branchpoint sequence proposed for introns. We would therefore suggest that neurons lack a specific splicing factor which inhibits the use of the rather strong 3′‐splice site in front of exon 15. It remains to be shown whether this is also the case for neurons in Alzheimer's disease.
Alzheimer's Disease Families with Amyloid Precursor Protein Mutationsa
Authors: ROSSOR M. N. , NEWMAN S. , FRACKOWIAK R. S. J. , LANTOS P. , KENNEDY A. M.
Published: December 2006

Early onset Familial Alzheimer's Disease (FAD) is an autosomal dominant disease with apparent complete penetrance. It is genetically heterogeneous with some families carrying mutations in the amyloid precursor protein (APP) gene which segregate with the disease. In addition, there is allelic heterogeneity with four mutations associated with FAD. Three mutations have been reported at APP 717, just distal to the C‐terminus of the β‐amyloid domain, APP 717 val‐ile, APP 717 val‐phe, and APP 717 val‐gly, which are associated with autopsy‐proven Alzheimer's disease (AD). APP 670/671 lies at the N terminus of the β‐amyloid domain and is associated with clinically diagnosed FAD in two Swedish families. FAD tends to have prominent myoclonus and this is shared by the cases with APP mutations. In two unrelated UK families with APP 717 val‐ile mutations there was early prominent memory impairment with dyscalculia proceeding to generalized cognitive impairment with a lack of insight. There was a late development of a gait disturbance with extrapyramidal features in some members. Positron emission tomography (PET) with fluorodeoxyglucose demonstrated posterior bitemporal biparietal hypometabolism in one case. Magnetic resonance imaging (MRI) showed generalized cerebral atrophy particularly affecting the temporal lobes and hippocampus. At autopsy, a single case showed extensive β‐amyloid deposition with congophilic angiopathy and widespread senile plaques and neurofibrillary tangles. The cytoskeletal pathology associated with abnormally phosphorylated tau was similar to cases of sporadic AD. In addition, there were widespread cortical and subcortical Lewy bodies. A single family with the APP 717 val‐gly mutation also showed prominent myoclonus, lack of insight, and seizures, PET, in a single case, showed classical biparietal bitemporal hypometabolism. Autopsy, in a single case, showed diffuse deposits of β‐amyloid throughout the cortex with frequent neuritic plaques and neurofibrillary tangles. No other inclusion bodies were seen. There was severe congophilic angiopathy. The age at onset of APP mutations is around 50 years of age by contrast to other early onset FAD pedigrees.
Search for the Genes Responsible for Familial Alzheimer's Disease
Authors: WASCO WILMA , PEPPERCORN JEFFREY , TANZI RUDOLPH E.
Published: December 2006

Inherited or Familial Alzheimer's Disease (FAD) has clearly been shown to be a genetically heterogeneous disorder. Mutations in the gene on chromosome 21 encoding the β—amyloid protein precursor (APP) have been shown to be linked to 2–3% of FAD kindreds examined around the world. A late onset FAD locus has been mapped to a region of chromosome 19 in which a recently isolated APP‐like gene, APLP1 has also been localized, making this gene a strong candidate to harbor a late‐onset FAD defect. More recently, a major FAD locus has been mapped to the long arm of chromosome 14. The chromosome 14 locus appears to be mainly linked to the gene defect in early onset FAD pedigrees. Besides the FAD loci on chromosome 21, 19, and 14, at least two other loci must exist since the gene defect in some early‐ and late‐onset FAD pedigrees do not appear to segregate with markers from any of these autosomes. As different gene defects responsible for various forms of FAD are discovered, perhaps, a common basis for the etiology of this devastating disorder can be discerned.
Decreased Density of Forebrain Cholinergic Neurons and Disintegration of the Spatial Organization of Behavior in Experimental Autoimmune Dementia (EAD)a
Authors: MICHAELSON DANIEL M. , DUBOVIK VLADIMIR , FAIGON MARIA , EILAM DAVID , FELDON JORAM
Published: December 2006

Experimental autoimmune dementia (EAD) is a rat model designed to examine the potential role of anti‐cholinergic neurons antibodies (Abs) in the neuropathology of Alzheimer's disease (AD) and dementia. We have previously shown that sera of AD and Down's syndrome patients contain Abs which bind specifically to the high molecular weight neurofilament protein (NF‐H) of the purely cholinergic electromotor neurons of Torpedo. Production of such Abs in EAD rats by prolonged immunization with Torpedo cholinergic NF‐H results in the accumulation of IgG in the septum and hippocampus of the immunized rats and in memory deficits.

In the present study, we examined immunohistochemically whether the anti‐cholinergic NF‐H immune response of the FAD rats affects their brain cholinergic neurons. In addition, since dementia is associated with severe deterioration in the spatio‐temporal organization of behavior, we examined whether EAD rats also mimic this important feature of dementia. The results obtained show that production in EAD rats of anti‐cholinergic NF‐H Abs similar to those found in AD patients results in a marked decrease in the density of forebrain cholinergic neurons and in derangements in the spatio‐temporal organization of their behavior. These findings may replicate pathogenic processes in AD and support a role for anti‐cholinergic NF‐H Abs in the degeneration of cholinergic neurons in the disease.