The exceptional chelating ability of dimethylaluminum chloride and methylaluminum dichloride. The merged stereochemical impact of alpha- and beta-stereocenters in chelate-controlled carbonyl addition reactions with enolsilane and hydride nucleophiles

A systematic investigation of the stereoselectivity in Lewis acid-promoted (Mukaiyama) aldol reactions of achiral unsubstituted enolsilanes and chiral beta-hydroxy aldehydes proceeding under conditions favoring chelation control is presented. Good stereocontrol can be realized for enolsilane aldol reactions of beta-alkoxy and beta-silyloxy aldehydes bearing only an alpha- or a beta-stereogenic center. Examination of the chelated intermediates for alpha,beta-disubstituted aldehydes concludes that the syn aldehyde diastereomer possesses the arrangement of stereocenters wherein the alpha- and beta-substituents impart a reinforcing facial bias upon the aldehyde carbonyl. Aldol reactions of syn aldehydes were thus observed to proceed with uniformly excellent diastereofacial selectivity. Aldol reactions of the corresponding anti aldehydes containing opposing stereocontrol elements at the alpha- and beta-positions exhibit variable and unpredictable selectivity.

An aldol-based approach to the asymmetric synthesis of L-callipeltose, the deoxyamino sugar of L-callipeltoside A

[reaction: see text] The L-callipeltose subunit of L-callipeltoside A has been synthesized in 10 steps and 13% overall yield from D-threonine. The key steps are a highly diastereoselective Felkin anti aldol addition to a methyl ketone and a selective methylation of a secondary alcohol in the presence of a secondary carbamate.

Annual incidence of Alzheimer disease in the United States projected to the years 2000 through 2050

Alzheimer disease will affect increasing numbers of people as baby boomers (persons born between 1946 and 1964) age. This work reports projections of the incidence of Alzheimer disease(AD) that will occur among older Americans in the future. Education adjusted age-specific incidence rates of clinically diagnosed probable AD were obtained from stratified random samples of residents 65 years of age and older in a geographically defined community. These rates were applied to U.S. Census Bureau projections of the total U.S. population by age and sex to estimate the number of people newly affected each year. The annual number of incident cases is expected to more than double by the midpoint of the twenty-first century: from 377,000 (95% confidence interval = 159,000-595,000) in 1995 to 959,000 (95% confidence interval = 140,000-1,778,000) in 2050. The proportion of new onset cases who are age 85 or older will increase from 40% in 1995 to 62% in 2050 when the youngest of the baby boomers will attain that age. Without progress in preventing or delaying onset of Alzheimer disease, both the number of people with Alzheimer disease and the proportion of the total population affected will increase substantially.

Association of incident Alzheimer disease and blood pressure measured from 13 years before to 2 years after diagnosis in a large community study

BACKGROUND

It is uncertain whether high blood pressure increases the risk of developing Alzheimer disease (AD).

OBJECTIVE

To examine the association between incident AD and blood pressure measured up to 13 years before diagnosis.

DESIGN

Longitudinal cohort study conducted from 1982 to 1988, with blood pressure measured every 3 years in home interviews, and in 1973 for a portion (60%) of the sample.

SETTING

Community of East Boston, Mass.

PARTICIPANTS

Six hundred thirty-four subjects 65 years or older and without AD were selected as a stratified random sample of participants of the East Boston Established Populations for Epidemiologic Studies of the Elderly.

MAIN OUTCOME MEASURE

Alzheimer disease was diagnosed by a neurologist using a structured clinical evaluation.

RESULTS

High blood pressure was not associated with an increased risk of AD in logistic regression models adjusted for age, sex, and level of education. There was no association with systolic pressure measured 13 years before diagnosis (odds ratio = 1.03/10 mm Hg; 95% confidence interval, 0.80-1.32) and an inverse association with systolic pressure measured 4 years before diagnosis (odds ratio = 0.82/10 mm Hg; 95% confidence interval, 0.72-0.95). Associations for diastolic pressure were in the same direction as those for systolic pressure except with wider confidence intervals. The odds ratios were not materially different with further adjustment for cardiovascular risk factors and diseases.

CONCLUSION

In this large community study, high blood pressure was not associated with an increased risk of AD.

Synthesis of (-)-epibatidine

The synthesis of (-)-epibatidine has been accomplished utilizing a highly exo-selective asymmetric hetero Diels-Alder reaction. The key steps employed to transform the resulting bicycle into the natural product include a fluoride-promoted fragmentation and a Hofmann rearrangement. Reaction: see text.

C(2)-symmetric Cu(II) complexes as chiral lewis acids. Catalytic, enantioselective cycloadditions of silyl ketenes

[reaction: see text] C(2)-Symmetric bis(oxazoline)-Cu(II) complexes (4a-g) catalyze the enantioselective [2 + 2] cycloaddition between (silyl)ketenes and chelating carbonyl substrates. A range of substituted beta-lactones can be produced in excellent yields and selectivities. It was also found that (trimethylsilyl)ketene (1) may also undergo a highly selective hetero Diels-Alder reaction with beta,gamma-unsaturated alpha-keto esters.

Enantioselective and diastereoselective Mukaiyama-Michael reactions catalyzed by bis(oxazoline) copper(II) complexes

The scope of highly enantioselective and diastereoselective Michael additions of enolsilanes to unsaturated imide derivatives has been developed with use of [Cu((S,S)-t-Bu-box)](SbF6)2 (1a) as a Lewis acid catalyst. The products of these additions are useful synthons that contain termini capable of differentiation under mild conditions. Michael acceptor pi-facial selectivity is consistent with two-point binding of the imide substrate and can be viewed as an extension of substrate enantioselection in the corresponding Diels-Alder reactions. A model analogous to the one employed to describe the hetero Diels-Alder reaction is proposed to account for the observed relation between enolsilane geometry and product absolute diastereocontrol. Insights into modes of catalyst inactivation are given, including spectroscopic evidence for inhibition of the catalyst by a dihydropyran intermediate that evolves during the course of the reaction. A procedure is disclosed in which an alcohol additive is used to hydrolyze the inhibiting dihydropyran and afford the desilylated Michael adduct in significantly shortened reaction time.

Intramolecular O-arylation of phenols with phenylboronic acids: application to the synthesis of macrocyclic metalloproteinase inhibitors

[reaction: see text]. The copper acetate mediated intramolecular O-arylation of phenols with phenylboronic acid pseudopeptides is the key step in the preparation of macrocyclic biphenyl ether hydroxamic acid inhibitors of collagenase 1 and gelatinases A and B. The intramolecular macrocyclization was found to be mild and tolerant of common chemical functionality. This methodology should provide a general route to macrocyclic biphenyl ethers.

Experience with a one-stop colorectal clinic

BACKGROUND AND OBJECTIVE

Colorectal services have traditionally been arranged for the convenience of hospitals rather than patients. This model is not ideal, particularly for minor interventions and diagnostic procedures. In order to address this a one-stop colorectal clinic was set up.

PATIENTS AND METHODS

Weekly clinics ran from 6.00 to 9.30 p.m. on Wednesdays for a period of 6 months. Patients with rectal bleeding, altered bowel habit, anorectal symptoms and those requesting screening advice were seen by a consultant or specialist registrar. Patients were asked to fill in a questionnaire at the end of their clinic attendance.

RESULTS

197 patients were seen in 17 clinics; 134 underwent proctoscopy, 72 had a rigid sigmoidoscopy and 85 had a flexible sigmoidoscopy carried out. Twenty-four patients subsequently had a barium enema and 3 were listed for colonoscopy. The main diagnosis was haemorrhoids (n = 104); 14 colorectal neoplasms were discovered (5 cancers and 9 polyps). During the study period the number of patients waiting for lower gastrointestinal endoscopy fell from 119 to 63; 2 months after ending the pilot scheme, the number had risen to 108.

CONCLUSION

The clinic was found to have significantly improved patient care. The majority of patients were satisfied with an evening clinic. Flexible sigmoidoscopy without sedation was well tolerated and the ability to perform this at initial assessment had a marked effect on the number of patients awaiting lower gastrointestinal endoscopy.

Interethnic variability in human drug responses

The scientific study of interethnic differences in responses to drugs has been extant for 80 years. Many of these differences have been described at the phenotypic level, and some have been explained by genetic factors. However, it is frequently difficult to disentangle accurately the hereditary and environmental influences in phenotypic comparisons. This is where the recent developments in knowledge of the genes responsible for drug receptors are starting to make a big impact. The beta 2 adrenoceptor is described; it has three genetic polymorphisms. The different genotypes influence responses to agonists such as albuterol (Salbutamol). New gene frequency data including those for Saudi Arabians, Indians, and Africans are shown. The expanding body of knowledge about genetic (and interethnic) variability in drug receptors is likely to be important in clinical medicine.

Asymmetric synthesis of the chlorocyclopropane-containing callipeltoside A side chain

[reaction: see text] The callipeltoside A chlorocyclopropyl-containing dienyne side chain has been synthesized in nine steps and 33% overall yield from commercially available 1,2,5,6-O-dicyclohexylidene-D-mannitol. The key steps in the synthesis are a highly diastereoselective cyclopropanation of a vinyl chloride allylic ether and a Suzuki cross-coupling to complete the carbon framework.

Is the risk of developing Alzheimer's disease greater for women than for men?

A large proportion of people with Alzheimer's disease (AD) are women; however, it is not clear whether this is due to higher risk of disease or solely to the larger number of women alive at ages when AD is common. Beginning in 1982, two stratified random samples of people aged > or =65 years in East Boston, Massachusetts underwent detailed, structured clinical evaluation for prevalent (467 people) and incident (642 people from a cohort previously ascertained to be disease-free) probable AD. The prevalence sample was followed for mortality for up to 11 years (through December 1992). The age-specific incidence of AD did not differ significantly by sex (for men vs. women, odds ratio = 0.92; 95% confidence interval (CI): 0.51, 1.67). Controlled for age, prevalence also did not differ significantly by sex (for men vs. women, odds ratio = 1.29; 95% CI: 0.67, 2.48). The increase in risk of mortality due to AD did not vary by sex. The odds ratio for women with AD compared with women without AD was 2.07 (95% CI: 1.21, 3.56). For men, the odds ratio was 2.22 (95% CI: 1.02, 4.81). These findings suggest that the excess number of women with AD is due to the longer life expectancy of women rather than sex-specific risk factors for the disease.

Comparison of informal caregiving by black and white older adults in a community population

OBJECTIVES

To examine the prevalence of informal caregiving and demographic factors associated with caregiving time in older community residents and compare caregiving prevalence and time spent providing care by black and white residents.

DESIGN

A cross-sectional, population-based study.

SETTING

The study was conducted as part of the Chicago Health and Aging Project (CHAP) in a geographically defined community of black and white residents aged 65 and older.

PARTICIPANTS

Participants were 5,924 community residents (61.4% black; 38.6% white) who answered questions about informal caregiving responsibilities during a structured interview about a broad range of health and social factors.

METHODS

Data were collected during an in-home interview. Multiple logistic and linear regression models were used to examine the association between caregiving and race, gender, age, marital status, and education.

RESULTS

More than 16% of residents had provided care to others during the previous 12 months, and 10.3% were currently providing care. Compared with whites, blacks were 30% more likely to be caregivers, spent almost 13 more hours each week in caregiving activities, and were more likely to assist friends. The probability of caregiving increased significantly with age for married persons, decreased with age for unmarried persons, and was lower for men compared with women. The time spent providing care each week increased significantly with age for married persons and did not differ between men and women.

CONCLUSIONS

Although physicians and other healthcare providers typically view older people as the recipients of informal care, individuals older than age 65 provide a substantial amount of care to others with health problems and disability. Most research has focused on the needs of young and middle-aged caregivers, and little is known about the needs of these older caregivers. Future research should use sampling strategies that provide adequate numbers of white and non-white participants for meaningful comparisons. This will permit identification of racial and cultural differences in caregiving so that interventions can be tailored to specific groups.

Premorbid reading activity and patterns of cognitive decline in Alzheimer disease

BACKGROUND

Educational and occupational attainment have been associated with progression of Alzheimer disease in some studies. One hypothesis about this association is that education and occupation are markers for lifelong participation in cognitively stimulating activities like reading.

OBJECTIVE

To assess the relation of premorbid reading activity with patterns of cognitive decline in Alzheimer disease.

METHODS

During a 4-year period, 410 persons with Alzheimer disease had annual clinical evaluations, which included administration of 17 cognitive function tests from which global, verbal, and nonverbal summary measures were derived. At baseline, a knowledgeable informant was questioned about the affected person's reading frequency and access to reading materials before dementia onset.

RESULTS

A composite measure of premorbid reading activity was developed. It had moderately high internal consistency and was positively correlated with education and baseline level of cognitive function. In analyses that controlled for baseline cognitive function, education, and other demographic variables, higher level of premorbid reading activity was associated with more rapid decline on the global cognitive and verbal measures but not on the nonverbal measure.

CONCLUSIONS

These results suggest that both the extent and nature of premorbid cognitive experiences may affect how Alzheimer disease pathology is clinically expressed.

Decline of language among women and men with Alzheimer's disease

Previous research raises the possibility that gender differences occur in language function in Alzheimer's disease, but this hypothesis has not been evaluated systematically in longitudinal studies. The authors examined the association of gender with rate of decline in language and other cognitive functions among 410 persons with Alzheimer's disease. Participants were recruited from a dementia clinic and followed for up to 5 annual evaluations. Follow-up participation among survivors exceeded 90%. Decline in a composite score based on 8 language tests was evaluated in random effects models with age, education, and race controlled. Annual decline was 0.71 standard units (95% confidence interval [CI] = 0.62-0.79) for women and 0.74 units (95% CI = 0.61-0.86) for men, not a significant difference. Decline on the individual language tests and on composite measures of memory, perception, and global cognition also indicated no significant association with gender. These results suggest that Alzheimer's disease affects language and other cognitive functions similarly in women and men.

Six-year effect of depressive symptoms on the course of physical disability in community-living older adults

BACKGROUND

Late-life depression affects physical health and impedes recovery from physical disability. But whether milder symptoms that occur frequently in the general population increase the risk of developing a disability or decrease the likelihood of recovery remains unclear.

OBJECTIVE

To examine the effect of mild symptoms of depression, assessed by a reduced version (10 items, ranging from 0-10) of the Center for Epidemiological Studies-Depression Scale, on the course of physical disability, assessed by items from the Katz Activities of Daily Living Scale, the Rosow-Breslau Functional Health Scale, and the Nagi Index.

METHODS

A population-based longitudinal study was conducted, with 6 follow-up interviews of 3434 community-dwelling persons aged 65 years and older in East Boston, Mass.

RESULTS

The likelihood of becoming disabled increased with each additional symptom of depression (for the Katz measure: odds ratio, 1.16 per symptom; 95% confidence interval, 1.13-1.19; for the Rosow-Breslau measure: odds ratio, 1.14; 95% confidence interval, 1.11-1.16; and for the Nagi measure: odds ratio, 1.17; 95% confidence interval, 1.14-1.19). As the number of depressive symptoms increased, the likelihood of recovering from a physical disability decreased (for the Katz measure: odds ratio, 0.96; 95% confidence interval, 0.93-0.99; for the Rosow-Breslau measure: odds ratio, 0.86; 95% confidence interval, 0.84-0.89; and for the Nagi measure: odds ratio, 0.89; 95% confidence interval, 0.87-0.91). This effect was not accounted for by age, sex, level of educational attainment, body mass index, or chronic health conditions.

CONCLUSION

Mild depressive symptoms in older persons (those aged > or =65 years) are associated with an increased likelihood of becoming disabled and a decreased chance of recovery, regardless of age, sex, and other factors that contribute to physical disability.

Decline of language among women and men with Alzheimer's disease

Previous research raises the possibility that gender differences occur in language function in Alzheimer's disease, but this hypothesis has not been evaluated systematically in longitudinal studies. The authors examined the association of gender with rate of decline in language and other cognitive functions among 410 persons with Alzheimer's disease. Participants were recruited from a dementia clinic and followed for up to 5 annual evaluations. Follow-up participation among survivors exceeded 90%. Decline in a composite score based on 8 language tests was evaluated in random effects models with age, education, and race controlled. Annual decline was 0.71 standard units (95% confidence interval [CI] = 0.62-0.79) for women and 0.74 units (95% CI = 0.61-0.86) for men, not a significant difference. Decline on the individual language tests and on composite measures of memory, perception, and global cognition also indicated no significant association with gender. These results suggest that Alzheimer's disease affects language and other cognitive functions similarly in women and men.

Multiple roles of the Dcdc42 GTPase during wing development in Drosophila melanogaster

The Rho sub-family of GTPases, comprising Rho, Rac and Cdc42. regulates many biological processes, including morphogenesis, cell polarity, migration, the cell cycle and gene expression. It is important to develop genetic approaches to allow the dissection, in vivo, of the mechanisms of GTPase regulation and signal transmission, and their biological consequences. In this regard, wing development in Drosophila melanogaster is an excellent model system. To investigate the functions of the Drosophila Cdc42 GTPase (Dcdc42), we generated phenotypes during wing development, by expression of the dominant-negative N17 and L89 mutants of Dcdc42. We have identified roles for Dcdc42 in wing growth, and in cell fate choice during the development of the wing veins and the peripheral nervous system. Reduction of Dcdc42 signalling following over-expression of Dcdc42N17 resulted in a broader but more diffuse domain characterised by wing-margin sensory bristles. This was correlated with a broadened stripe of wingless expression along the dorsal-ventral boundary of third-instar wing imaginal discs. Together with genetic interactions with loss- and gain-of-function Notch alleles, these data support a role for wild-type Dcdc42 as a negative regulator of Notch signalling.

Hallucinations, delusions, and cognitive decline in Alzheimer's disease

OBJECTIVES

To examine the occurrence of hallucinations and delusions in Alzheimer's disease over a 4 year period and their association with rate of cognitive decline.

METHODS

A cohort of 410 persons with clinically diagnosed Alzheimer's disease underwent annual clinical evaluations over a 4 year period. Participation in follow up exceeded 90% in survivors. Evaluations included structured informant interview, from which the presence or absence of hallucinations and delusions was ascertained, and detailed testing of cognitive function. The primary cognitive outcome measure was a composite cognitive score based on 17 individual performance tests. The mini mental state examination (MMSE) and summary measures of memory, visuoconstruction, repetition, and naming were used in secondary analyses.

RESULTS

At baseline, hallucinations (present in 41%) and delusions (present in 55%) were common and associated with lower cognitive function. In analyses that controlled for baseline level of cognitive function, demographic variables, parkinsonism, and use of antipsychotic medications, hallucinations, but not delusions, were associated with more rapid cognitive decline on each cognitive measure. In the primary model, there was a 47% increase in the average annual rate of decline on a composite cognitive measure in those with baseline hallucinations compared with those without them. This effect was mainly due to a subgroup with both auditory and visual hallucinations.

CONCLUSION

These findings suggest that the presence of hallucinations is selectively associated with more rapid cognitive decline in Alzheimer's disease.

Molecular misreading in non-neuronal cells

+1 Frame-shifted proteins such as amyloid precursor protein(+1) and ubiquitin-B(+1) have been identified in the neuropathological hallmarks of Alzheimer's disease. These frameshifts are caused by dinucleotide deletions in GAGAG motifs of messenger RNA encoded by genes that have maintained the unchanged wild-type DNA sequence. This process is termed 'molecular misreading'. A key question is whether this process is confined to neurons or whether it could also occur in non-neuronal cells. A transgenic mouse line (MV-B) carrying multiple copies of a rat vasopressin minigene as a reporter driven by the MMTV-LTR promotor was used to screen non-neuronal tissues for molecular misreading by means of detection of the rat vasopressin(+1) protein and mutated mRNA. Molecular misreading was demonstrated to occur in several organs (e.g., epididymis and the parotid gland) where transgenic vasopressin expression is abundant, but its penetrance is variable both between and within tissues. This implies that non-neural tissues too, could be affected by cellular derangements caused by molecular misreading.