Enantioselective Dearomatization of Pyridinium Salts by Copper-Catalyzed C4-Selective Addition of Silicon Nucleophiles

A copper-catalyzed C4-selective addition of silicon nucleophiles released from an Si-B reagent to prochiral pyridinium triflates is reported. The dearomatization proceeds with excellent enantioselectivity using Cu(CH3CN)4PF6 as the precatalyst and (R,R)-Ph-BPE as the chiral ligand. A carbonyl group at C3 is required, likely acting a weak group to preorganize and direct the nucleophilc attack towards C4. The resulting 4-silylated 1,4-dihydropyridines can be further converted into functionalized piperidine derivatives.

Nucleoside Phosphorylases make N7-xanthosine

Modern, highly evolved nucleoside-processing enzymes are known to exhibit perfect regioselectivity over the glycosylation of purine nucleobases at N9. We herein report an exception to this paradigm. Wild-type nucleoside phosphorylases also furnish N7-xanthosine, a "non-native" ribosylation regioisomer of xanthosine. This unusual nucleoside possesses several atypical physicochemical properties such as redshifted absorption spectra, a high equilibrium constant of phosphorolysis and low acidity. Ultimately, the biosynthesis of this previously unknown natural product illustrates how even highly evolved, essential enzymes from primary metabolism are imperfect catalysts.

Dehydrative Coupling of 1,1-Diarylalkenes and Cyclohexa-2,5-diene-1-carbaldehyde Derivatives Induced by a B(C6F5)3-Initiated [1,2]-Alkyl Migration

A four-step formal ipso allylation of benzoic acid derivatives involving a B(C₆F₅)₃-initiated and proton-catalyzed [1,2]-alkyl shift as part of a dehydrative coupling of cyclohexa-2,5-diene-1-carbaldehyde derivatives and 1,1-diarylalkenes is reported. By this, a series of allyl arenes can be regioselectively obtained from readily available benzoic acids in good yields.

Biased Borate Esterification during Nucleoside Phosphorylase-Catalyzed Reactions: Apparent Equilibrium Shifts and Kinetic Implications

Biocatalytic nucleoside (trans-)glycosylations catalyzed by nucleoside phosphorylases have evolved into a practical and convenient approach to the preparation of modified nucleosides, which are important pharmaceuticals for the treatment of various cancers and viral infections. However, the obtained yields in these reactions are generally determined exclusively by the innate thermodynamic properties of the nucleosides involved, hampering the biocatalytic access to many sought-after target nucleosides. We herein report an additional means for reaction engineering of these systems. We show how apparent equilibrium shifts in phosphorolysis and glycosylation reactions can be effected through entropically driven, biased esterification of nucleosides and ribosyl phosphates with inorganic borate. Our multifaceted analysis further describes the kinetic implications of this in situ reactant esterification for a model phosphorylase.

Public perceptions uncovered: engaging in decision-making regarding non-pharmaceutical interventions

Background

To control the COVID-19 pandemic, non-pharmaceutical interventions (NPIs) were implemented worldwide, that heavily impacted the daily lives of citizens. Occasionally, the public expressed discontent about NPIs, as NPIs did not always corresponded with their preferences. The question is if and how public engagement (PE) could aid in development and implementation of NPIs, in order to improve legitimacy, quality and compliance.

Methods

An online survey was conducted from 27 October to 9 November 2021, with a representative sample of the public in the Netherlands on gender, age, education, place of residency and migration background. In total 4981 respondents participated. Perceptions and preferences about PE in decision-making on NPIs to control COVID-19 was collected. Four NPIs were used: Nightly curfew (NC); Digital Covid Certificate (DCC); Closure of schools and daycares (CSD); and 1.5meter social distance.

Results

Around 25% of respondents expressed a desire to engage in decision-making, as it would increase understanding and quality of NPIs, and their trust in the government. Especially for the NPIs DCC and NC, respondents found it valuable to engage, by providing their perspective on certain trade-offs in values in decision-making (e.g. opening up society vs division in society by vaccination status). The public could play a role by giving feedback on bottlenecks during decision-making, however overall responsibility should stay with experts and policy-makers. Desire for engagement was lowest for CSD. Around 50% of the respondents did not want to engage, as they felt they were not knowledgeable enough to do so and did not perceive a need to engage. The other 25% had a neutral disposition.

Conclusions

Engagement was not self-evident for most respondents, yet the ones willing to engage revealed important possibilities for future outbreaks. Next, a deliberative process for PE in decision-making could be executed, in order to implement our findings in practice.

Key messages

An Isolable 2,5‐Disila‐3,4‐Diphosphapyrrole and a Conjugated Si=P−Si=P−Si=N Chain Through Degradation of White Phosphorus with a N,N ‐Bis(Silylenyl)Aniline

White phosphorus (P₄) undergoes degradation to P₂ moieties if exposed to the new N,N‐bis(silylenyl)aniline PhNSi₂1 (Si=Si[N(tBu)]₂CPh), furnishing the first isolable 2,5‐disila‐3,4‐diphosphapyrrole 2 and the two novel functionalized Si=P doubly bonded compounds 3 and 4. The pathways for the transformation of the non‐aromatic 2,5‐disila‐3,4‐diphosphapyrrole PhNSi₂P₂2 into 3 and 4 could be uncovered. It became evident that 2 reacts readily with both reactants P₄ and 1 to afford either the polycyclic Si=P‐containing product [PhNSi₂P₂]₂P₂3 or the unprecedented conjugated Si=P−Si=P−Si=NPh chain‐containing compound 4, depending on the employed molar ratio of 1 and P₄ as well as the reaction conditions. Compounds 3 and 4 can be converted into each other by reactions with 1 and P₄, respectively. All new compounds 1–4 were unequivocally characterized including by single‐crystal X‐ray diffraction analysis. In addition, the electronic structures of 2–4 were established by Density Functional Theory (DFT) calculations.

Public engagement in the management of the COVID-19 pandemic: Views & expectations of the publics

Introduction

During an epidemic, like COVID-19, trade-offs have to be made between measures to reduce mortality and morbidity and associated social, economic and political consequences. Traditionally, epidemic management (EM) has been guided by experts and policymakers, and is executed most attentively. It can however still be controversial in the public sphere. The question arises if public engagement (PE) could be a means to improve the quality and effectiveness of EM, as it has proven to be for other domains of healthcare policy.

Methods

From June to October 2020, seven Deliberative Discussion Focus Groups were executed with 35 Dutch citizens between 19 and 84 years old, to discuss their views on PE in COVID-19 management. Timeline Interviews were conducted to elucidate meaningful experiences during the epidemic. Next, benefits, barriers, timing and possible forms of PE in EM were discussed.

Results

Almost all participants supported PE in EM, as the integration of experiences and ideas of the public would benefit the quality of EM, and PE would increase awareness and acceptance of measures. Also, participants emphasized the importance of receiving information on the process of EM, to overcome the perceived lack of transparency herein. Consultation was seen as a fitting form for PE since the public could share ideas and feedback on EM, particularly on communication campaigns and control measures, however final authority stayed with experts. PE could be executed after the first acute phase of the epidemic, but also during evaluations. Moreover, barriers for PE were identified such as time constraints and the lack of knowledge of the public.

Conclusions

A foundation of values and conditions for PE in EM from the perspective of the public was laid. Support for PE was identified and considered valuable for quality and effectiveness of EM. Next, the results should be confirmed within a broader audience and the views of experts and policymakers on PE in EM should be elucidated.

Key messages

According to participants, public engagement can increase quality and effectiveness of outbreak management, by sharing knowledge, experiences and ideas between the public, experts and policymakers.

The focus groups in this study were executed whilst the COVID-19 pandemic unfolded, which yielded very relevant outcomes of current interest.

Consecutive β,β'-Selective C(sp3 )-H Silylation of Tertiary Amines with Dihydrosilanes Catalyzed by B(C6 F5 )3

Tris(pentafluorophenyl)borane has been found to catalyze the two‐fold C(sp³)−H silylation of various trialkylamine derivatives with dihydrosilanes, furnishing the corresponding 4‐silapiperidines in decent yields. The multi‐step reaction cascade involves amine‐to‐enamine dehydrogenation at two alkyl residues and two electrophilic silylation reactions of those enamines, one inter‐ and one intramolecular.

Intramolecular Friedel-Crafts alkylation with a silylium-ion-activated cyclopropyl group: formation of tricyclic ring systems from benzyl-substituted vinylcyclopropanes and hydrosilanes

A trityl-cation-initiated annulation of benzyl-substituted vinylcyclopropanes (VCPs) with hydrosilanes is reported. Two Si–C(sp³) bonds and one C(sp²)–C(sp³) bond are formed in this process where an intramolecular 6-endo-tet Friedel–Crafts alkylation of a silylium-ion-activated cyclopropane ring is the rate-determining key step. The reaction mechanism is proposed based on computations and is in agreement with experimental observations. The new reaction leads to an unprecedented silicon-containing 6/6/5-fused ring system. A phenethyl-substituted VCP derivative yields another unknown tricycle having 6/6/6 ring fusion by reacting in a related but different way involving a 6-exo-tet ring closure.

Downstream to alkene hydrosilylation, the opening of the cyclopropane ring in benzyl-substituted VCPs is interlinked with an S_EAr of the aryl group.

Nurses' needs when collaborating with other healthcare professionals in palliative dementia care

Adequate interprofessional collaboration is essential to provide high quality palliative dementia care across different settings. Within interprofessional collaboration, nurses are the frontline healthcare professionals (HCPs), who interact closely with people with dementia, their loved ones, and other HCPs. A survey was conducted to explore the needs of nurses regarding interprofessional collaboration in home care (HC) organisations, nursing homes (NHs) and during NH admissions. The survey identified the perceived quality of and preferred needs regarding interprofessional collaboration. In total, 384 participants (53.9% home care nurses) completed the survey. The most frequently reported collaboration needs in HC organisations and NH were optimal communication content e.g. information transfer and short communication lines (being able to easily contact other disciplines), and coordination e.g. one contact person, and clear task division and responsibilities). During NH admissions, it was important to create transparency about agreements concerning end-of-life wishes, optimize nurse-to-nurse handover during NH admissions (through performing visits prior to admissions, and receiving practical information on how to guide relatives), and improve coordination (e.g. one contact person). In conclusion, the key collaboration needs were organising central coordination, establishing optimal communication, and creating transparency on end-of-life care agreements.

Boron Lewis Acid-Catalyzed Hydroboration of Alkenes with Pinacolborane: BArF3 Does What B(C6 F5 )3 Cannot Do!

The transition-metal-free hydroboration of various alkenes with pinacolborane (HBpin) initiated by tris[3,5-bis(trifluoromethyl)phenyl]borane (BAr^F₃ ) is reported. The choice of the boron Lewis acid is crucial as the more prominent boron Lewis acid tris(pentafluorophenyl)borane (B(C₆ F₅ )₃ ) is reluctant to react. Unlike B(C₆ F₅ )₃ , BAr^F₃ is found to engage in substituent redistribution with HBpin, resulting in the formation of Ar^F Bpin and the electron-deficient diboranes [H₂ BAr^F ]₂ and [(Ar^F )(H)B(μ-H)₂ BAr^F₂ ]. These in situ-generated hydroboranes undergo regioselective hydroboration of styrene derivatives as well as aliphatic alkenes with cis diastereoselectivity. Another ligand metathesis of these adducts with HBpin subsequently affords the corresponding HBpin-derived anti-Markovnikov adducts. The reactive hydroboranes are regenerated in this step, thereby closing the catalytic cycle.

Mechanism of the cooperative Si-H bond activation at Ru-S bonds

The heterolytic splitting of hydrosilanes by ruthenium(ii) thiolates is illuminated by a combined spectroscopic, crystallographic, and computational analysis.

The nature of the hydrosilane activation mediated by ruthenium(ii) thiolate complexes of type [(R₃P)Ru(SDmp)]⁺[BAr^F₄]^– is elucidated by an in-depth experimental and theoretical study. The combination of various ruthenium(ii) thiolate complexes and tertiary hydrosilanes under variation of the phosphine ligand and the substitution pattern at the silicon atom is investigated, providing detailed insight into the activation mode. The mechanism of action involves reversible heterolytic splitting of the Si–H bond across the polar Ru–S bond without changing the oxidation state of the metal, generating a ruthenium(ii) hydride and sulfur-stabilized silicon cations, i.e. metallasilylsulfonium ions. These stable yet highly reactive adducts, which serve as potent silicon electrophiles in various catalytic transformations, are fully characterized by systematic multinuclear NMR spectroscopy. The structural assignment is further verified by successful isolation and crystallographic characterization of these key intermediates. Quantum-chemical analyses of diverse bonding scenarios are in excellent agreement with the experimental findings. Moreover, the calculations reveal that formation of the hydrosilane adducts proceeds via barrierless electrophilic activation of the hydrosilane by sterically controlled η¹ (end-on) or η² (side-on) coordination of the Si–H bond to the Lewis acidic metal center, followed by heterolytic cleavage of the Si–H bond through a concerted four-membered transition state. The Ru–S bond remains virtually intact during the Si–H bond activation event and also preserves appreciable bonding character in the hydrosilane adducts. The overall Si–H bond activation process is exergonic with ΔG0r ranging from –20 to –40 kJ mol^–1, proceeding instantly already at low temperatures.

The gyrase inhibitor albicidin consists of p-aminobenzoic acids and cyanoalanine

Albicidin is a potent DNA gyrase inhibitor produced by the sugarcane pathogenic bacterium Xanthomonas albilineans. Here we report the elucidation of the hitherto unknown structure of albicidin, revealing a unique polyaromatic oligopeptide mainly composed of p-aminobenzoic acids. In vitro studies provide further insights into the biosynthetic machinery of albicidin. These findings will enable structural investigations on the inhibition mechanism of albicidin and its assessment as a highly effective antibacterial drug.

Isolation and structure elucidation of the nucleoside antibiotic strepturidin from Streptomyces albus DSM 40763

The antibiotic strepturidin (1) was isolated from the microorganism Streptomyces albus DSM 40763, and its structure elucidated by spectroscopic methods and chemical degradation studies. The determination of the relative and absolute stereocenters was partially achieved using chiral GC/EI-MS analysis and microderivatization by acetal ring formation and subsequent 2D-NMR analysis of key (1)H,(1)H-NOESY NMR correlations and extraction of (1)H,(13)C coupling constants from (1)H,(13)C-HMBC NMR spectra. Based on these results, a biosynthesis model was proposed.

Chronic pain has a negative impact on sexuality in testis cancer survivors

Testis cancer is a disease that directly affects a man's sense of masculinity and involves treatments compromising sexual function. The aim of this study was to investigate the prevalence of sexual dysfunction and the influence of chronic pain on sexuality in long-term testis cancer survivors. Thus, we examined 539 patients after they had one testis removed because of a testicular germ cell tumor. Having completed oncologic therapy, all patients received a detailed questionnaire asking about the occurrence and clinical presentation of testis pain before and after orchiectomy. In addition, items from the abridged International Index of Erectile Function and Brief Sexual Function Inventory were used to gain precise information on individual sexual function. Overall, 34.5% of our testicular cancer survivors complained of reduced sexual desire, and sexual activity was reduced in 41.6%. Erectile dysfunction was present in up to 31.5% of patients. In 24.4%, the ability to maintain an erection during intercourse was impaired. Ejaculatory disorders (premature, delayed, retrograde, or anejaculation) occurred in 84.9% of our testis cancer survivors. A total of 32.4% of our participants experienced a reduced intensity of orgasm, and 95.4% experienced reduced overall sexual satisfaction. There was a significant correlation between the occurrence of chronic pain symptoms and the relative frequency and intensity of erectile dysfunction, inability to maintain an erection, ejaculation disorders, and reduced intensity of orgasm. In conclusion, chronic pain has a negative impact on sexuality in testis cancer survivors.

Group epitope mapping considering relaxation of the ligand (GEM-CRL): including longitudinal relaxation rates in the analysis of saturation transfer difference (STD) experiments

In the application of saturation transfer difference (STD) experiments to the study of protein-ligand interactions, the relaxation of the ligand is one of the major influences on the experimentally observed STD factors, making interpretation of these difficult when attempting to define a group epitope map (GEM). In this paper, we describe a simplification of the relaxation matrix that may be applied under specified experimental conditions, which results in a simplified equation reflecting the directly transferred magnetisation rate from the protein onto the ligand, defined as the summation over the whole protein of the protein-ligand cross-relaxation multiplied by with the fractional saturation of the protein protons. In this, the relaxation of the ligand is accounted for implicitly by inclusion of the experimentally determined longitudinal relaxation rates. The conditions under which this "group epitope mapping considering relaxation of the ligand" (GEM-CRL) can be applied were tested on a theoretical model system, which demonstrated only minor deviations from that predicted by the full relaxation matrix calculations (CORCEMA-ST) [7]. Furthermore, CORCEMA-ST calculations of two protein-saccharide complexes (Jacalin and TreR) with known crystal structures were performed and compared with experimental GEM-CRL data. It could be shown that the GEM-CRL methodology is superior to the classical group epitope mapping approach currently used for defining ligand-protein proximities. GEM-CRL is also useful for the interpretation of CORCEMA-ST results, because the transferred magnetisation rate provides an additional parameter for the comparison between measured and calculated values. The independence of this parameter from the above mentioned factors can thereby enhance the value of CORCEMA-ST calculations.

Phantom testis syndrome: prevalence, phenomenology and putative mechanisms

Chronic phantom pain has been found in up to 78% of limb amputees and is a major complication of limb amputation. Less is known about phantom phenomena after the amputation of other, i.e. visceral, parts of the body. In a retrospective design, we identified 539 patients in whom one testis was removed between 1995 and 2005. The operative technique was a unilateral standard radical inguinal orchiectomy. The underlying pathology in all cases was a testicular germ cell tumour. All patients received a detailed questionnaire asking about the occurrence of phantom testis pain (pain felt in the removed testis), phantom testis sensations (non-painful sensations as if the removed testis was still intact) and hallucinations (illusionary perceptions on the removed testis). Furthermore, we asked about the occurrence and clinical presentation of pain before and after surgery and about pre-operative testicular pain. Out of 238 respondents, 125 patients (53%) reported any kind of phantom experience. The prevalence of phantom testis pain was 25% (60/238), non-painful phantom sensations 16% (37/238) and male gonad hallucinations 12% (28/238). Patients with phantom symptoms reported pre-operative pain in the removed testis more often than patients without phantom symptoms. This study presents first data on the clinical characteristics and possible mechanisms of the phantom testis syndrome after surgical removal of one testis.

Jacobsen's catalyst for hydrolytic kinetic resolution: structure elucidation of paramagnetic Co(III) salen complexes in solution via combined NMR and quantum chemical studies

NMR investigation of chiral Co(III) salen catalysts, important for enantioselective hydrolytic kinetic resolution (HKR), revealed the presence of a paramagnetic high-spin Co(III) species, which is in solvent- and temperature-dependent equilibrium with the known diamagnetic low-spin Co(III) complex. Combined with quantum chemical DFT calculations, the para- and diamagnetic chemical shifts were used to study the salen ligand conformation of the para- and diamagnetic complexes, resulting in a mechanistic proposal for the enantioselective step in catalysis.

Highly diverse variable number tandem repeat loci in the E. coli O157:H7 and O55:H7 genomes for high-resolution molecular typing

AIM

Evaluation of the Escherichia coli genome for variable number tandem repeat (VNTR) loci in order to provide a subtyping tool with greater discrimination and more efficient capacity.

METHODS AND RESULTS

Twenty-nine putative VNTR loci were identified from the E. coli genomic sequence. Their variability was validated by characterizing the number of repeats at each locus in a set of 56 E. coli O157:H7/HN and O55:H7 isolates. An optimized multiplex assay system was developed to facility high capacity analysis. Locus diversity values ranged from 0.23 to 0.95 while the number of alleles ranged from two to 29. This multiple-locus VNTR analysis (MLVA) data was used to describe genetic relationships among these isolates and was compared with PFGE (pulse field gel electrophoresis) data from a subset of the same strains. Genetic similarity values were highly correlated between the two approaches, through MLVA was capable of discrimination amongst closely related isolates when PFGE similar values were equal to 1.0.

CONCLUSIONS

Highly variable VNTR loci exist in the E. coli O157:H7 genome and are excellent estimators of genetic relationships, in particular for closely related isolates.

SIGNIFICANCE AND IMPACT OF THE STUDY

Escherichia coli O157:H7 MLVA offers a complimentary analysis to the more traditional PFGE approach. Application of MLVA to an outbreak cluster could generate superior molecular epidemiology and result in a more effective public health response.

Factors Associated With Residual Breast Cancer After Re-excision for Close or Positive Margins

BACKGROUND

Successful breast conservation surgery (BCS) requires complete tumor excision. Margin status of the initial specimen determines the need for additional surgery. We explored factors associated with residual cancer (RC) upon follow-up surgery in patients with close, positive, or undetermined margins following BCS.

METHODS

A retrospective analysis of 276 patients with initial close, positive, or undetermined margins who underwent re-excision (RE) or mastectomy was conducted. All initial excisions were intended as definitive procedures. Chi-square analysis was used to identify factors that may predict RC.

RESULTS

Of 276 patients, 87 had close, 168 had positive, and 21 had undetermined margins on initial excision. Of this group, 63% (175/276) had RC upon RE or mastectomy. Of positive-margin patients, 68% had RC, compared with 53% of close-margin and 67% of undetermined-margin patients (P = .006). Tumors >/=2 cm were more often associated with RC than smaller tumors (70.8% vs. 56.5%; P = .07). This association was strongest in positive-margin patients (P = .04). High tumor grade was associated with RC in all groups. RC linearly increased with the number of involved margins (P = .02). Specimen inking with multiple colors was associated with decreased risk of RC (P = .004).

CONCLUSIONS

Over half of patients with involved or undetermined margins had RC upon RE or mastectomy. Positive and undetermined margins were more often associated with RC than close margins. Larger tumor size was associated with RC in patients with positive. Increasing tumor grade suggests a greater chance of detecting RC in all groups. Multiple involved margins led to a greater risk of RC.

Longitudinal change in language production: effects of aging and dementia on grammatical complexity and propositional content

Mixed modeling was used to examine longitudinal changes in linguistic ability in healthy older adults and older adults with dementia. Language samples, vocabulary scores, and digit span scores were collected annually from healthy older adults and semiannually from older adults with dementia. The language samples were scored for grammatical complexity and propositional content. For the healthy group, age-related declines in grammatical complexity and propositional content were observed. The declines were most rapid in the mid 70s. For the group with dementia, grammatical complexity and propositional content also declined over time, regardless of age. Rates of decline were uniform across individuals. These analyses reveal how both grammatical complexity and propositional content are related to late-life changes in cognition in healthy older adults aswell as those with dementia. Alzheimer's disease accelerates this decline, regardless of age.

Pharmacokinetics of a new transdermal testosterone gel in gonadotrophin-suppressed normal men

OBJECTIVE

In a phase I single-centre, open, randomized study, the pharmacokinetics of two doses of a transdermal testosterone gel containing 2.5% testosterone were evaluated in 26 healthy male volunteers.

DESIGN

To eliminate the influence of endogenous serum testosterone, gonadotrophins and endogenous testosterone secretion were suppressed by a single intramuscular injection of 400 mg norethisterone enanthate. Fourteen men applied 5.0 g and 12 men applied 2.5 g testosterone gel daily for 10 days. Half the men in each group washed the gel off 10 min after it had been applied.

RESULTS

In all the men, a marked suppression of LH, FSH, testosterone, dihydrotestosterone (DHT) and oestradiol was observed after norethisterone treatment. Physiological serum concentrations of testosterone were restored during the 10-day treatment period in the group of men applying 5.0 g testosterone gel. Increasing serum concentrations of testosterone from day 1 to day 10 were observed. Oestradiol and DHT concentrations did not exceed normal values. Washing 10 min after gel application did not influence the resorption of testosterone. A dose of 2.5 g testosterone gel was insufficient to achieve physiological serum concentrations of testosterone.

CONCLUSION

Testosterone replacement treatment with 5.0 g of this 2.5% testosterone gel is able to achieve constant physiological testosterone concentrations in gonadotrophin-suppressed men. Washing the skin after 10 min does not influence the pharmacokinetic profile and thus significantly reduces the risk of contamination of female partners or infants.

Longitudinal change in language production: effects of aging and dementia on grammatical complexity and propositional content

Mixed modeling was used to examine longitudinal changes in linguistic ability in healthy older adults and older adults with dementia. Language samples, vocabulary scores, and digit span scores were collected annually from healthy older adults and semiannually from older adults with dementia. The language samples were scored for grammatical complexity and propositional content. For the healthy group, age-related declines in grammatical complexity and propositional content were observed. The declines were most rapid in the mid 70s. For the group with dementia, grammatical complexity and propositional content also declined over time, regardless of age. Rates of decline were uniform across individuals. These analyses reveal how both grammatical complexity and propositional content are related to late-life changes in cognition in healthy older adults aswell as those with dementia. Alzheimer's disease accelerates this decline, regardless of age.

Age differences in implicit and explicit associative memory: exploring elaborative processing effects

Research in memory processes suggests implicit memory is more resistant to the effects of aging than explicit memory. Two experiments examined how variations in level of processing affect memory for novel word-pair associations across age groups. The results indicate that new learning may rely on some degree of elàborate and even explicit processing and that older adults show deficits in any form of new learning. Explicit associative memory benefited from elaborative processing for both age groups and age differences appeared to relate to overall working-memory capacity rather than effective use of elaborative processes. These results support a model of associative memory that distinguishes automatic unconscious processes versus conscious controlled processes in which older adults exhibit deficits in associative memory tasks that actually rely on consciously controlled processes.

The structure of verbal abilities in young and older adults

Four language sample measures as well as measures of vocabulary, verbal fluency, and memory span were obtained from a sample of young adults and a sample of older adults. Factor analysis was used to analyze the structure of the vocabulary, fluency, and span measures for each age group. Then an "extension" analysis was performed by using structural modeling techniques to determine how the language sample measures were related to the other measures. The measure of grammatical complexity was associated with measures of working memory including reading span and digit span. Two measures, sentence length in words and a measure of lexical diversity, were associated with the vocabulary measures. The fourth measure, propositional density, was associated with the fluency measures as a measure of processing efficiency. The structure of verbal abilities in young and older adults is somewhat different, suggesting age differences in processing efficiency.

Language decline across the life span: findings from the Nun Study

The present study examines language samples from the Nun Study. Measures of grammatical complexity and idea density were obtained from autobiographies written over a 60-year span. Participants who had met criteria for dementia were contrasted with those who did not. Grammatical complexity initially averaged 4.78 (on a 0-to-7-point scale) for participants who did not meet criteria for dementia and declined .04 units per year; grammatical complexity for participants who met criteria for dementia initially averaged 3.86 and declined .03 units per year. Idea density averaged 5.35 propositions per 10 words initially for participants who did not meet criteria for dementia and declined an average of .03 units per year, whereas idea density averaged 4.34 propositions per 10 words initially for participants who met criteria for dementia and declined .02 units per year. Adult experiences, in general, did not moderate these declines.

Cognitive construct measurement in small samples of younger and older adults: an example of verbal working memory

An important issue in experimental aging research is the accurate measurement of cognitive constructs, particularly in small-sample studies. Latent variable modeling approaches to assessing age-based construct similarity are difficult to implement in smaller-scale studies, which tend to have small samples and measurement of a single construct. We discuss factor score comparison methods for assessing age-based construct similarity that may be more appropriate for small-scale studies. We then examine these methods for a series of single-factor models of verbal working memory (VWM) based on data from three separate studies in which small samples of younger and older adults' completed VWM-based tasks. Our single-factor models accounted well for the associations among the sets of VWM tasks. This construct was also measured well across age groups and different samples. Our analyses suggest that factor score comparison methods may be useful for small-scale studies that require assessment of age-based measurement similarity in cognitive constructs.

Selective insulin signaling through A and B insulin receptors regulates transcription of insulin and glucokinase genes in pancreatic beta cells

Insulin signaling is mediated by a complex network of diverging and converging pathways, with alternative proteins and isoforms at almost every step in the process. We show here that insulin activates the transcription of its own gene and that of the beta cell glucokinase gene (betaGK) by different mechanisms. Whereas insulin gene transcription is promoted by signaling through insulin receptor A type (Ex11-), PI3K class Ia, and p70s6k, insulin stimulates the betaGK gene by signaling via insulin receptor B type (Ex11+), PI3K class II-like activity, and PKB (c-Akt). Our data provide evidence for selectivity in insulin action via the two isoforms of the insulin receptor, the molecular basis being preferential signaling through different PI3K and protein kinases.

Sentence repetition and processing resources in Alzheimer's disease

Sentence processing in Alzheimer's disease (AD) has been found to be influenced by several grammatical and extragrammatical factors, including phrase structure and verb-argument relations, number of propositions/verbs, and processing resource capacity. This study examines the effects of these variables on sentence production in AD. Normal control and AD subjects were asked to repeat six types of sentences varying along the above dimensions of complexity. Subjects' processing resource capacity was measured using several verbal working memory tests. AD subjects' sentence-repetition performance was impaired compared to the normal control group. Significant effects were observed for branching direction of phrase structure, canonicity of verb-argument relations, and serial position of errors. Sentence-repetition performance significantly correlated with working memory scores. The findings are interpreted within a resource capacity theory of sentence processing.

Experimentally disentangling what's beneficial about elderspeak from what's not

Three studies evaluated different varieties of elderspeak using a referential communication task. Experiment 1 compared the effects of syntactic simplifications and semantic elaborations. Experiment 2 contrasted syntactic simplifications and prosodic exaggerations. Experiment 3 contrasted 2 different syntactic simplification strategies and 2 different prosodic exaggerations. Providing semantic elaborations and reducing the use of subordinate and embedded clauses benefit older adults and improve their performance on the referential communication task, whereas reducing sentence length, slowing speaking rate, and using high pitch do not. The use of short sentences, a slow rate of speaking, and high pitch resulted in older adults' reporting more communication problems. These experiments validate a version of elderspeak that benefits older adults without sounding patronizing and insulting.

Experimentally disentangling what's beneficial about elderspeak from what's not

Three studies evaluated different varieties of elderspeak using a referential communication task. Experiment 1 compared the effects of syntactic simplifications and semantic elaborations. Experiment 2 contrasted syntactic simplifications and prosodic exaggerations. Experiment 3 contrasted 2 different syntactic simplification strategies and 2 different prosodic exaggerations. Providing semantic elaborations and reducing the use of subordinate and embedded clauses benefit older adults and improve their performance on the referential communication task, whereas reducing sentence length, slowing speaking rate, and using high pitch do not. The use of short sentences, a slow rate of speaking, and high pitch resulted in older adults' reporting more communication problems. These experiments validate a version of elderspeak that benefits older adults without sounding patronizing and insulting.

Aging and resolution of quantifier scope effects

Two experiments were conducted to compare young and older adults' processing of complex sentences involving quantifier scope ambiguities. Young adults were hypothesized to use a mix of syntactic processing strategies to interpret sentences such as Every actor used a prop or An actor used every prop. Older adults, particularly those with limited working memories, were hypothesized to rely on a simple pragmatic principle. Participants read the quantifier sentences and judged whether a continuation sentence "made sense." Reading times for the quantifier sentences and decision times and continuation sentence acceptability judgements were analyzed. Whereas young and older adults exhibited similar patterns of reading times for the quantifier sentences, they preferred different continuations for the Every ... a quantifier sentences. As predicted, both young adults and older adults interpreted a quantifier sentence such as An actor used every prop as referring to a single entity resulting in a preference for continuations such as The actor was on the stage. In contrast, young and older adults made different interpretations of a quantifier sentence such as Every actor used a prop; young adults preferred continuations postulating multiple entities such as The props were on the stage whereas older adults, particularly those with working memory limitations, preferred continuations with a single entity such as The prop was on the stage. These results support models of the effects of aging on language processing in which immediate syntactic analysis is not affected by aging or working memory limitations whereas postcomprehension processes are affected by aging and/or working memory limitations.

Grammatical abilities in Parkinson's disease: evidence from written sentences

This study examined the grammatical content of written sentences elicited from 96 Parkinson's patients, 30 Parkinson's with dementia patients and 167 control subjects. Parkinson's patients without dementia or with mild dementia presented no impairments in sentence length, syntactic complexity or amount of information content. Moderately demented Parkinson's patients showed reduced sentence length and information content but normal syntactic complexity. This pattern of results provides evidence that lexical-semantic content is more susceptible to decline than syntactic structure with the progression of dementia in Parkinson's disease.

Younger and older adults' on-line processing of syntactically ambiguous sentences

Off-line studies of younger and older adults' processing of syntactically complex sentences have shown that there is a consistent negative relationship between task performance and working memory for older adults. However, it is not evident from these studies whether working memory affects the immediate syntactic analysis of a sentence, off-line processes, or both. In the current study an online reading paradigm was used to examine the working memory capacity-constrained sentence processing model from M.C. MacDonald, M.A. Just, and P.A. Carpenter (1992). Working memory span, type of syntactic ambiguity (ambiguous vs. unambiguous), and type of syntactic ambiguity resolution (main verb vs. relative clause) interacted to influence younger and older adults' on-line reading times and off-line sentence comprehension.