Showing papers by "Stony Brook University published in 1994"

Perirhinal and parahippocampal cortices of the macaque monkey: Cortical afferents

Abstract: Neuropsychological studies have recently demonstrated that the macaque monkey perirhinal (areas 35 and 36) and parahippocampal (areas TH and TF) cortices contribute importantly to normal memory function. Unfortunately, neuroanatomical information concerning the cytoarchitectonic organization and extrinsic connectivity of these cortical regions is meager. We investigated the organization of cortical inputs to the macaque monkey perirhinal and parahippocampal cortices by placing discrete injections of the retrograde tracers fast blue, diamidino yellow, and wheat germ agglutinin conjugated to horseradish peroxidase throughout these areas. We found that the macaque monkey perirhinal and parahippocampal cortices receive different complements of cortical inputs. The major cortical inputs to the perirhinal cortex arise from the unimodal visual areas TE and rostral TEO and from area TF of the parahippocampal cortex. The perirhinal cortex also receives projections from the dysgranular and granular subdivisions of the insular cortex and from area 13 of the orbitofrontal cortex. In contrast, area TF of the parahippocampal cortex receives its strongest input from more caudal visual areas V4, TEO, and caudal TE, as well as prominent inputs from polymodal association cortices, including the retrosplenial cortex and the dorsal bank of the superior temporal sulcus. Area TF also receives projections from areas 7a and LIP of the posterior parietal lobe, insular cortex, and areas 46, 13, 45, and 9 of the frontal lobe. As with area TF, area TH receives substantial projections from the retrosplenial cortex as well as moderate projections from the dorsal bank of the superior temporal sulcus; unlike area TF, area TH receives almost no innervation from areas TE and TEO. It does, however, receive relatively strong inputs from auditory association areas on the convexity of the superior temporal gyrus.

Comprehensive QA for radiation oncology: report of AAPM Radiation Therapy Committee Task Group 40.

Abstract: Published by the American Association of Physicists in Medicine DISCLAIMER: This publication is based on sources and information believed to be reliable, but the AAPM and the editors disclaim any warranty or liability based on or relating to the contents of this publication. The AAPM does not endorse any products, manufacturers, or suppliers. Nothing in this publication should be interpreted as implying such endorsement. PREFACE This document is the report of a task group of the Radiation Therapy Committee of the American Association of Physicists in Medicine and supersedes the recommendations of AAPM Report 13 (AAPM, 1984). The purpose of the report is twofold. First, the advances in radiation oncology in the decade since AAPM Report 13 (AAPM, 1984) necessitated a new document on quality assurance (QA). Second, developments in the principles of quality assurance and continuing quality improvement necessitated a report framed in this context. The title \" Comprehensive Quality Assurance for Radiation Oncology \" may need clarification. While the report emphasizes the physical aspects of QA and does not attempt to discuss issues that are essentially medical (e.g., the decision to treat, the prescription of dose), it by no means neglects issues in which the physical and medical issues intertwine, often in a complex manner. The integrated nature of QA in radiation oncology makes it impossible to consider QA as limited to, for example, checking machine output or calibrating brachytherapy sources. QA activities cover a very broad range, and the work of medical physicists in this regard extends into a number of areas in which the actions of radiation oncologists, radiation therapists, 1 dosimetrists, accelerator engineers, and medical physicists are important. Moreover, this is true for each of the disciplines-each has special knowledge and expertise which affects the quality of treatment , and each discipline overlaps the others in a broad \" gray zone. \" It is important not only to understand each discipline's role in QA, but to clarify this zone so that errors do not \" fall between the cracks. \" This report therefore attempts to cover the physical aspects of QA both in a narrow or traditional sense and in a more integrated sense. The report comprises 2 parts: Part A is for administrators, and Part B is a code of practice in six sections. The first section of Part B describes a comprehensive quality assurance program in which the importance of a written procedural …

Two functional components of the hippocampal memory system

Abstract: There is considerable evidence that the hippocampal system contributes both to (1) the temporary maintenance of memories and to (2) the processing of a particular type of memory representation. The findings on amnesia suggest that these two distinguishing features of hippocampal memory processing are orthogonal. Together with anatomical and physiological data, the neuropsychological findings support a model of cortico-hippocampal interactions in which the temporal and representational properties of hippocampal memory processing are mediated separately. We propose that neocortical association areas maintain shortterm memories for specific items and events prior to hippocampal processing as well as providing the final repositories of long-term memory. The parahippocampal region supports intermediate-term storage of individual items, and the hippocampal formation itself mediates an organization of memories according to relevant relationships among items. Hippocampal-cortical interactions produce (i) strong and persistent memories for events, including their constituent elements and the relationships among them, and (ii) a capacity to express memories flexibly across a wide range of circumstances.

A picture book reading intervention in day care and home for children from low-income families.

Abstract: The effects of an interactive book reading program were assessed with children from low-income families who attended subsidized day-care centers in New York. The children entered the program with language development in standard English vocabulary and expression that was about 10 months behind chronological age on standardized tests. Children were pretested and assigned randomly within classrooms to 1 of 3 conditions: (a) a school plus home condition in which the children were read to by their teachers and their parents, (b) a school condition in which children were read to only by teachers, and (c) a control condition in which children engaged in play activities under the supervision of their teachers. Training of adult readers was based on a self-instructional video

Benzophenone photophores in biochemistry

Abstract: The photoactivatable aryl ketone derivatives have been rediscovered as biochemical probes in the last 5 years. The expanding use of benzophenone (BP) photoprobes can be attributed to three distinct chemical and biochemical advantages. First, BPs are chemically more stable than diazo esters, aryl azides, and diazirines. Second, BPs can be manipulated in ambient light and can be activated at 350-360 nm, avoiding protein-damaging wavelengths. Third, BPs react preferentially with unreactive C-H bonds, even in the presence of solvent water and bulk nucleophiles. These three properties combine to produce highly efficient covalent modifications of macromolecules, frequently with remarkable site specificity. This Perspectives includes a brief review of BP photochemistry and a selection of specific applications of these photoprobes, which address questions in protein, nucleic acid, and lipid biochemistry.

Interactions between saturated acyl chains confer detergent resistance on lipids and glycosylphosphatidylinositol (GPI)-anchored proteins: GPI-anchored proteins in liposomes and cells show similar behavior

Abstract: Proteins anchored by GPI are poorly solubilized from cell membranes by cold nonionic detergents because they associate with detergent-resistant membranes rich in cholesterol and sphingolipids. In this study, we demonstrated that cholesterol and sphingolipid-rich liposomes were incompletely solubilized by Triton X-100. GPI-anchored placental alkaline phosphatase incorporated in these liposomes was also not solubilized by cold Triton X-100. As sphingolipids have much higher melting temperatures (Tm) than cellular phospholipids, a property correlated with Tm might cause detergent inextractability. In support of this idea, we found that the low-Tm lipid dioleoyl phosphatidylcholine (DOPC) was efficiently extracted from detergent-resistant liposomes by Triton X-100, whereas the high-Tm lipid dipalmitoyl phosphatidylcholine (DPPC) was not. The fluorescence polarization of liposome-incorporated diphenylhexatriene was measured to determine the "fluidity" of the detergent-resistant liposomes. We found that these liposomes were about as fluid as DPPC/cholesterol liposomes, which were present in the liquid-ordered phase, and much less fluid than DOPC or DOPC/cholesterol liposomes. These findings may explain the behavior of GPI-anchored proteins, which often have saturated fatty acyl chains and should prefer a less-fluid membrane. Therefore, we propose that acyl chain interactions can influence the association of GPI-anchored proteins with detergent-resistant membrane lipids. The affinity of GPI-anchored proteins for a sphingolipid-rich membrane phase that is not in the liquid crystalline state may be important in determining their cellular localization.

On foundation of the generalized Nambu mechanics

Abstract: We outline basic principles of a canonical formalism for the Nambu mechanics—a generalization of Hamiltonian mechanics proposed by Yoichiro Nambu in 1973. It is based on the notion of a Nambu bracket, which generalizes the Poisson bracket—a “binary” operation on classical observables on the phase space—to the “multiple” operation of higher ordern≧3. Nambu dynamics is described by the phase flow given by Nambu-Hamilton equations of motion—a system of ODE's which involvesn−1 “Hamiltonians.” We introduce the fundamental identity for the Nambu bracket—a generalization of the Jacobi identity—as a consistency condition for the dynamics. We show that Nambu bracket structure defines a hierarchy of infinite families of “subordinated” structures of lower order, including Poisson bracket structure, which satisfy certain matching conditions. The notion of Nambu bracket enables us to define Nambu-Poisson manifolds—phase spaces for the Nambu mechanics, which turn out to be more “rigid” than Poisson manifolds—phase spaces for the Hamiltonian mechanics. We introduce the analog of the action form and the action principle for the Nambu mechanics. In its formulation, dynamics of loops (n−2-dimensional chains for the generaln-ary case) naturally appears. We discuss several approaches to the quantization of Nambu mechanics, based on the deformation theory, path integral formulation and on Nambu-Heisenberg “commutation” relations. In the latter formalism we present an explicit representation of the Nambu-Heisenberg relation in then=3 case. We emphasize the role ternary and higher order algebraic operations and mathematical structures related to them play in passing from Hamilton's to Nambu's dynamical picture.

Outcomes of an Emergent Literacy Intervention in Head Start.

Abstract: Classrooms of 4-year-olds attending Head Start were randomly assigned to an intervention condition, involving an add-on emergent literacy curriculum, or a control condition, involving the regular Head Start curriculum. Children in the intervention condition experienced interactive book reading at home and in the classroom as well as a classroom-based sound and letter awareness program. Children were pretested and posttested on standardized tests of language, writing, linguistic awareness, and print concepts

VO2: Peierls or Mott-Hubbard? A view from band theory.

Abstract: The electronic and structural properties of ${\mathrm{VO}}_{2}$ across its metal-insulator transition are studied using the local-density approximation. Band theory finds a monoclinic distorted ground state in good agreement with experiment, and an almost open gap to charge excitations. Although rigid criteria for distinguishing correlated from band insulators are not available, these findings suggest that ${\mathrm{VO}}_{2}$ may be more bandlike than correlated.

Laboratory measurement of compaction-induced permeability change in porous rocks: Implications for the generation and maintenance of pore pressure excess in the crust

Abstract: Permeability exerts significant control over the development of pore pressure excess in the crust, and it is a physical quantity sensitively dependent on the pore structure and stress state. In many applications, the relation between permeability and effective mean stress is assumed to be exponential and that between permeability and porosity is assumed to be a power law, so that the pressure sensitivity of permeability is characterized by the coefficient γ and the porosity sensitivity by the exponent α. In this study, we investigate experimentally the dependence of permeability on pressure and porosity in five sandstones with porosities ranging from 14% to 35% and we review published experimental data on intact rocks, unconsolidated materials and rock fractures. The laboratory data show that the pressure and porosity sensitivities differ significantly for different compaction mechanisms, but for a given compaction mechanism, the data can often be approximated by the empirical relations. The permeabilities of tight rocks and rock joints show relatively high pressure sensitivity and low porosity sensitivity. A wide range of values for α and γ have been observed in relation to the mechanical compaction of porous rocks, sand and fault gouge, whereas the porosity sensitivity for chemical compaction processes is often observed to be given by α≈3. We show that since the ratio γ/α corresponds to the pore compressibility, the different dependences of permeability on porosity and pressure are related to the pore structure and its compressibility. Guided by the laboratory data, we conduct numerical simulations on the development of pore pressure in crustal tectonic settings according to the models ofWalder andNur (1984) andRice (1992). Laboratory data suggest that the pressure sensitivity of fault gouge is relatively low, and to maintain pore pressure at close to the lithostatic value in the Rice model, a relatively high influx of fluid from below the seismogenic layer is necessary. The fluid may be injected as vertically propagating pressure pulses into the seismogenic system, andRice's (1992) critical condition for the existence of solitary wave is shown to be equivalent to α>1, which is satisfied by most geologic materials in the laboratory. Laboratory data suggest that the porosity sensitivity is relatively high when the permeability is reduced by a coupled mechanical and chemical compaction process. This implies that in a crustal layer, pore pressure may be generated more efficiently than cases studied byWalder andNur (1984) who assumed a relatively low porosity sensitivity of α=2.

Topographic organization of the reciprocal connections between the monkey entorhinal cortex and the perirhinal and parahippocampal cortices.

Abstract: The perirhinal and parahippocampal cortices constitute the major sources of cortical input to the monkey entorhinal cortex. Neuropsychological studies have shown that these three cortical regions contribute in an important way to normal memory function. We have investigated the topographic and laminar organization of the reciprocal projections between the entorhinal cortex and these two adjacent cortical areas by placing anterograde and retrograde tracers in all three regions. There were three major findings. First, the perirhinal and parahippocampal cortices have distinct but partially overlapping interconnections with the entorhinal cortex. The perirhinal cortex tends to be interconnected with the rostral two-thirds of the entorhinal cortex while the parahippocampal cortex tends to be interconnected with approximately the caudal two-thirds of the entorhinal cortex. Second, the degree of reciprocity of the interconnections of the entorhinal cortex with the perirhinal and parahippocampal cortices differs. The parahippocampal/entorhinal connections have a high degree of reciprocity. In contrast, the degree of reciprocity of the perirhinal/entorhinal interconnections varies depending on the mediolateral position within the perirhinal cortex; medial portions of the perirhinal cortex exhibit a higher degree of reciprocity with the entorhinal cortex than lateral portions. Third, the projections from the perirhinal and parahippocampal cortices to the entorhinal cortex resemble a feedforward projection, while the projections from the entorhinal cortex to the perirhinal and parahippocampal cortices resemble a feedback projection pattern.

J-Holomorphic Curves and Quantum Cohomology

Abstract: Introduction Local behaviour Moduli spaces and transversality Compactness Compactification of moduli spaces Evaluation maps and transversality Gromov-Witten invariants Quantum cohomology Novikov rings and Calabi-Yau manifolds Floer homology Gluing Elliptic regularity Bibliography Indexes.

Peripheral and Central Mechanisms of NGF‐induced Hyperalgesia

Abstract: Mechanisms underlying the hyperalgesia induced by a single systemic injection of nerve growth factor (NGF) in adult rats were studied in vivo. A single dose of NGF initiated a prolonged thermal hyperalgesia to a radiant heat source within minutes that lasted for days. Animals which had been pretreated with the mast cell degranulating compound 48/80 or either one of two specific 5-hydroxytryptamine receptor antagonists (ICS 205-930 and methiothepin) also developed an NGF-induced thermal hyperalgesia, but onset was delayed by more than 3 h. In the presence of ICS 205-930 or methiothepin the early component NGF-induced hyperalgesia was reversed and the animals responded with an initial hypoalgesia to the thermal stimuli. Whereas these results indicate a peripheral mechanism for the initial thermal hyperalgesia, the later phase (7 h-4 days after NGF) appeared to be centrally maintained, since it could be selectively blocked by the non-competitive NMDA receptor antagonist MK-801. In contrast to the almost immediate thermal hyperalgesia following a single injection of NGF, a significant mechanical hyperalgesia began only after a 7 h latency. This NGF-induced mechanical hyperalgesia was not blocked by any of the treatments that attenuated the thermal hyperalgesia, indicating that a separate mechanism may be involved. Additional electrophysiological experiments showed that NGF-induced hyperalgesia was not maintained by an increased amount of spontaneous activity in C-fibres. A final result showed that endogenous release of NGF in a model of acute inflammation (complete Freund's adjuvant-induced inflammation) may be involved in the development of thermal hyperalgesia, since it could be blocked by concomitant treatment with anti-NGF antisera. These data indicate that NGF-induced thermal and mechanical hyperalgesia are mediated by different mechanisms. The rapid onset component of thermal hyperalgesia is due to a peripheral mechanism involving the degranulation of mast cells, whereas the late component involves central NMDA receptors. In contrast, the NGF-induced mechanical hyperalgesia seems to be independent of mast cell degranulation or central NMDA receptor sites.

Comparing self-reported and physician-reported medical history.

Abstract: The authors compared self-reported medical history and medication use in a cataract case-control study of 1,380 persons (1985-1989) in Boston, Massachusetts, with information from the participants' physicians. Under- and overreporting varied by condition and type of medication. A self-reported history of hypertension had the highest sensitivity (91%), and diabetes history had the highest specificity (97%). Among different medications investigated, self-reported antihypertensive medication use was the most sensitive (88%), while self-reported use of insulin was the most specific (99%). Differences between patient- and physician-reported frequencies were very small, except for arthritis (15%) and regular aspirin use (21%). Results suggest an accurate recall of medical and drug usage history in well-defined chronic conditions.

Transthyretin sequesters amyloid beta protein and prevents amyloid formation

Abstract: The cardinal pathological features of Alzheimer disease are depositions of aggregated amyloid beta protein (A beta) in the brain and cerebrovasculature. However, the A beta is found in a soluble form in cerebrospinal fluid in healthy individuals and patients with Alzheimer disease. We postulate that sequestration of A beta precludes amyloid formation. Failure to sequester A beta in Alzheimer disease may result in amyloidosis. When we added A beta to cerebrospinal fluid of patients and controls it was rapidly sequestered into stable complexes with transthyretin. Complexes with apolipoprotein E, which has been shown to bind A beta in vitro, were not observed in cerebrospinal fluid. Additional in vitro studies showed that both purified transthyretin and apolipoprotein E prevent amyloid formation.

Inhibition of neurite growth by the NG2 chondroitin sulfate proteoglycan

Abstract: The chondroitin sulfate proteoglycans (CSPGs) have been implicated as both positive and negative modulators of axonal growth; however, the functional properties of only a few specific CSPGs have been investigated. Here we demonstrate that NG2, an integral membrane CSPG expressed on the surfaces of glial progenitor cells, inhibits neurite growth from neonatal rat cerebellar granule neurons when presented to the cells as a component of the substrate. Growth inhibition occurred when NG2 was mixed with either laminin or L1, two potent promoters of axonal extension. Moreover, when given a choice between surfaces coated with NG2 and laminin or L1, the axons of the cerebellar neurons extended preferentially on laminin or L1 and avoided areas of the substrate containing NG2. The NG2 proteoglycan inhibited neurite growth after digestion with chondroitinase ABC, demonstrating that the inhibitory activity is a property of the core protein and not the covalently attached chondroitin sulfate glycosaminoglycan chains. NG2 also inhibited neurite growth from embryonic rat dorsal root ganglia neurons on substrates containing laminin. However, when the sensory neurons were plated onto surfaces containing the L1 glycoprotein and NG2, neurite growth was not inhibited. These results demonstrate that the NG2 proteoglycan provides an unfavorable substrate for axonal growth. Cells that express this proteoglycan in vivo may participate in axonal guidance by defining areas of the developing CNS that are nonpermissive for axonal extension from specific classes of developing neurons.

Increased expression of the NG2 chondroitin-sulfate proteoglycan after brain injury.

Abstract: Injury to the adult mammalian CNS results in reactive changes among the glial cells surrounding the site of damage. Recently, an unusual class of glial cells has been identified within the intact adult rat cerebellum on the basis of the expression of the NG2 chondroitin- sulfate proteoglycan (Levine and Card, 1987). To determine whether the cells that express the NG2 proteoglycan show reactive changes after injury, small puncture lesions were made into the cerebelli of adult rats, and changes among astrocytes, microglia and NG2-positive cells were examined using immunohistochemical staining with cell type- specific marker antibodies. Beginning at 24 hr after lesion, NG2- positive cells immediately adjacent to the lesion site bound the anti- NG2 antibodies more heavily than cells within the undamaged areas of the cerebellum. This increase in anti-NG2 immunoreactivity was transient, reaching a maximum at 7 d postlesion and declining slowly thereafter. The increase in anti-NG2 immunoreactivity was accompanied by an increase in the levels of mRNA encoding the NG2 core protein as demonstrated by in situ hybridization. NG2-positive cells adjacent to the lesion site incorporated 3H-thymidine into their nuclei beginning at 24 hr postlesion and increased in number. Concurrent with these changes, microglia became activated and increased in number, monocytes invaded the damaged tissue, and an astrocytic scar formed. These observations demonstrate that the cells that express the NG2 proteoglycan are a reactive cell type that responds to brain injury. The increased expression of the NG2 chondroitin-sulfate proteoglycan may contribute to the failure of damaged CNS axons to regenerate successfully.

Spectrum of the QCD Dirac operator and chiral random matrix theory.

Abstract: We argue that the spectrum of the QCD Dirac operator near zero virtuality can be described by random matrix theory. As in the case of the classical random matrix ensembles of Dyson we have three different cases: the chiral orthogonal ensemble, the chiral unitary ensemble, and the chiral symplectic ensemble. They correspond to gauge groups SU(2) in the fundamental representation, SU(${\mathit{N}}_{\mathit{c}}$), ${\mathit{N}}_{\mathit{c}}$\ensuremath{\ge}3 in the fundamental representation, and non-Abelian gauge groups SU(${\mathit{N}}_{\mathit{c}}$) for all ${\mathit{N}}_{\mathit{c}}$ with fermions in the adjoint representation, respectively. The joint probability density reproduces Leutwyler-Smilga sum rules.

XSB as an efficient deductive database engine

Abstract: This paper describes the XSB system, and its use as an in-memory deductive database engine. XSB began from a Prolog foundation, and traditional Prolog systems are known to have serious deficiencies when used as database systems. Accordingly, XSB has a fundamental bottom-up extension, introduced through tabling (or memoing)[4], which makes it appropriate as an underlying query engine for deductive database systems. Because it eliminates redundant computation, the tabling extension makes XSB able to compute all modularly stratified datalog programs finitely and with polynomial data complexity. For non-stratified programs, a meta-interpreter with the same properties is provided. In addition XSB significantly extends and improves the indexing capabilities over those of standard Prolog. Finally, its syntactic basis in HiLog [2], lends it flexibility for data modelling.The implementation of XSB derives from the WAM [25], the most common Prolog engine. XSB inherits the WAM's efficiency and can take advantage of extensive compiler technology developed for Prolog. As a result, performance comparisons indicate that XSB is significantly faster than other deductive database systems for a wide range of queries and stratified rule sets. XSB is under continuous development, and version 1.3 is available through anonymous ftp.

Imaging endogenous dopamine competition with [11C]raclopride in the human brain

Abstract: This study images dopamine release in response to a neurochemically specific challenge with the psychostimulant drug methylphenidate. Changes in synaptic dopamine induced by methylphenidate were evaluated with positron emission tomography and [11C]raclopride, a D2 receptor radioligand that is sensitive to endogenous dopamine. Methylphenidate significantly decreased striatal [11C]raclopride binding. The decrease was variable and was negatively correlated with age. Mood and anxiety at baseline, were also correlated with methylphenidate-induced DA changes. This strategy provides a tool to investigate the responsiveness of the dopamine system in the normal and diseased human brain and to investigate the neurochemical correlates of behavior.

Predicting mild and severe husband-to-wife physical aggression

Abstract: Nonordered multinomial logistic models were used to estimate the odds of mild and severe husband-to-wife physical aggression in 11,870 White men. Being younger, having a lower income, and having an alcohol problem significantly increased the odds of either mild or severe physical aggression. A drug problem uniquely increased the risk of severe physical aggression. Marital discord and depressive symptomatology, but not work stress, further increased the odds of both mild and severe physical aggression, with martial discord being the most influential psychological variable. Compared with mildly physically aggressive men, those who were severely physically aggressive earned lower income, were more likely to report an alcohol or a drug problem, and had more marital discord and depressive symptomatology.

Physical aggression in early marriage: Prerelationship and relationship effects.

Abstract: Spousal physical aggression at 30 months after marriage was predicted for 393 young couples who were interviewed for a longitudinal study. The prerelationship predictor variables were history of violence in the family of origin, aggression against others during childhood and adolescence, and personality characteristics. Relationship predictor variables were marital discord and spouse-specific psychological aggression, both measured at 18 months after marriage. The findings suggest that predictive models are different for husbands and wives. For both sexes, there were direct paths to marital violence that were not mediated by characteristics of the relationship, as well as paths that originated in or flowed through indicators of the marital relationship. Implications for intervention through marital therapy, individual therapy, or both are discussed.

Global marital satisfaction versus marital adjustment: An empirical comparison of three measures.

Abstract: Two measures of marital satisfaction, the Quality of Marriage Index (R. Norton, 1983) and the Relationship Satisfaction Questionnaire (D. D. Burns & S. L. Sayers, 1992) were compared to a measure of marital adjustment, the Dyadic Adjustment Scale (G. B. Spanier, 1976). The measures showed excellent convergent validity (high correlations among each other and with other measures of marital functioning) and discriminant validity (low or nonsignificant correlations with psychopathology subscales). However, spouses' ratings of frequency of disagreements differed significantly from their ratings of satisfaction in the same areas. Formulas for converting scores among the measures are given, and the measures were found to have modest classification powers. The relative advantages and disadvantages of adjustment and satisfaction measures are discussed, and recommendations are made for when to use each type of measure

The Salmonella typhimurium invasion genes invF and invG encode homologues of the AraC and PulD family of proteins

Abstract: Summary We have identified two novel Salmonella typhimurium genes, invF and invG, which are required for the efficient entry of these organisms into cultured epithelial cells. invF and invG are located immediately upstream of invE, a previously identified gene also required for Salmonella entry. Non-polar mutations in these genes rendered S. typhimurium severely deficient for entry into cultured epithelial cells. The nucleotide sequences of invF and invG indicated that these genes encode polypeptides with predicted molecular weights of 24373 and 62275, respectively. Proteins of similar sizes were observed when invF and invG were expressed in a bacteriophage T7 RNA polymerase-based expression system. Comparison of the predicted sequence of InvF with translated sequences in the existing databases indicated that this protein is homologous to members of the AraC family of prokaryotic transcription regulators. However, mutations in invF did not significantly affect the expression of other members of the inv locus. InvG was found to be homologous to members of the PuID family of specialized translocases. This homology suggests that InvG may be necessary for the export of invasion-related determinants or involved in the assembly of a supramolecular structure that promotes entry.