The application of mass spectrometric techniques to the real-time measurement and characterization of aerosols represents a significant advance in the field of atmospheric science. This review focuses on the aerosol mass spectrometer (AMS), an instrument designed and developed at Aerodyne Research, Inc. (ARI) that is the most widely used thermal vaporization AMS. The AMS uses aerodynamic lens inlet technology together with thermal vaporization and electron-impact mass spectrometry to measure the real-time non-refractory (NR) chemical speciation and mass loading as a function of particle size of fine aerosol particles with aerodynamic diameters between approximately 50 and 1,000 nm. The original AMS utilizes a quadrupole mass spectrometer (Q) with electron impact (EI) ionization and produces ensemble average data of particle properties. Later versions employ time-of-flight (ToF) mass spectrometers and can produce full mass spectral data for single particles. This manuscript presents a detailed discussion of the strengths and limitations of the AMS measurement approach and reviews how the measurements are used to characterize particle properties. Results from selected laboratory experiments and field measurement campaigns are also presented to highlight the different applications of this instrument. Recent instrumental developments, such as the incorporation of softer ionization techniques (vacuum ultraviolet (VUV) photo-ionization, Li+ ion, and electron attachment) and high-resolution ToF mass spectrometers, that yield more detailed information about the organic aerosol component are also described.

Journal Article↗

PubMedDate not supplied

Epidermal growth factor receptor not equal to nerve growth factor.

I am perplexed by the authors' complete lack of definition of neurotrophic factors. The agents Butcher and Woolf want to blame are neurite promoting factors, not neurotrophic factors. Treatment of Alzheimer's disease with NGF antagonists might instead exacerbate the death of both basal forebrain neurons and their cortical target neurons, accelerating the progress of dementia.

Alzheimer Disease↗

PubMedDate not supplied

Exogenous nerve growth factor stimulates choline acetyltransferase activity in aging Fischer 344 male rats.

The effect of age and exogenous nerve growth factor (NGF) infusion on choline acetyltransferase (ChAT) specific activity is examined in microdissections of cerebral and hippocampal cortices, and the cholinergic nuclei of the medial septum and diagonal band of Broca (MS/DB), the nucleus basalis magnocellularis (NBM), and striatum of Fischer 344 male rats. Significant, 20% losses in ChAT activity are found in the MS/DB and striatum of 24-month-old rats (n = 21) compared to 4-month-old animals, but there is no apparent loss of enzyme activity in the NBM. Loss of ChAT activity in the MS/DB is only observed in animals older than 19 months of age, while a striatal deficit is found in animals older than 7 months. Treatment for 2 weeks with NGF at 1.2 micrograms/day results in significant 70% increases of ChAT activity in the MS/DB and striatum of 24-month-old rats compared to untreated and vehicle-treated 4-month-old rats, but does not stimulate activity in the NBM. Sensitivity of ChAT activity in the MS/DB and striatum to exogenous NGF increases with age. These experiments indicate that in the MS/DB, NBM, and striatum of Fischer 344 male rat there is an age-associated, differential regulation of ChAT enzyme activity and sensitivity to exogenous NGF.

Aging↗

PubMedDate not supplied

Warts and molluscum contagiosum.

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Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

Amelioration of cholinergic neuron atrophy and spatial memory impairment in aged rats by nerve growth factor.

In aged rodents, impairments in learning and memory have been associated with an age-dependent decline in forebrain of cholinergic function, and recent evidence indicates that the cholinergic neurons in the nucleus basalis magnocellularis, the septal-diagonal band area and the striatum undergo age-dependent atrophy. Thus, as in Alzheimer-type dementia in man, degenerative changes in the forebrain cholinergic system may contribute to age-related cognitive impairments in rodents. The cause of these degenerative changes is not known. Recent studies have shown that the central cholinergic neurons in the septal-diagonal band area, nucleus basalis and striatum are sensitive to the neurotrophic protein nerve growth factor (NGF). In particular, intraventricular injections or infusions of NGF in young adult rats have been shown to prevent retrograde neuronal cell death and promote behavioural recovery after damage to the septo-hippocampal connections. It is so far not known, however, whether the atrophic cholinergic neurons in aged animals are responsive to NGF treatment. We report here that continuous intracerebral infusion of NGF over a period of four weeks can partly reverse the cholinergic cell body atrophy and improve retention of a spatial memory task in behaviourally impaired aged rats.

Acetylcholinesterase↗

PubMedDate not supplied

Nurse-managed postpartum home care.

In 1989, Professional Nurse Associates, Inc., and Kaiser Permanente of Ohio collaborated to provide a home-centered postpartum recovery program to meet the postdelivery health-care needs of mothers, neonates, and families after a shortened hospital stay. This article reviews the history, process, and outcomes of that joint effort. The authors describe outcomes in terms of type and frequency of nursing diagnoses found on home visits, readmission rates, cost savings, and consumer satisfaction.

Adolescent↗

PubMedDate not supplied

A new paradigm for postpartum care.

Shortened hospital stays have decreased women's access to postpartum nursing care. Providers and payers together must address clinical and cost issues to develop a model of maternity care that covers the postpartum period. A short-stay maternity program was developed in 1989 by Professional Nurse Associates, Inc., in conjunction with Kaiser Permanente. The program includes prenatal preparation of families, a brief hospital stay, postpartum home visits, and postvisit case management. Readmission rates or mothers and newborns in the program have been less than 1%. The program has saved about $1 million a year since 1991, and consumer satisfaction has been measured at 99%.

Cost-Benefit Analysis↗

PubMedDate not supplied

Neuronotrophic and neurite-promoting factors and their clinical potentials.

Neuronal maintenance and neuritic growth during development are increasingly recognized as being under the extrinsic control of neuronotrophic- and neurite-promoting agents. Protein agents ('factors') are the most studied but not the only molecules exerting such controls. It appears increasingly likely that adult neurons in situ are equally subject to similar extrinsic regulations. Two recently studied in vivo models for peripheral and central neural regeneration have demonstrated trauma-related accumulations of neuronotrophic- and neurite-promoting factors in the adult rat, in close temporal correlation with neuronal maintenance and axonal regrowth, respectively. Deficits in the supply or utilization of similar factors may underlie neuronal or glial regressive processes in aging, and in selected neuronal diseases such as Parkinson, ALS and Alzheimer. Speculative approaches to, and potential problems of, clinical interventions addressing putative neuronotrophic deficits are discussed.

Aging↗

PubMedDate not supplied

The reliability of H-reflex recordings in standing subjects.

OBJECTIVE: Several studies have used the H-reflex to investigate the effect of upright stances and locomotion on spinal reflex excitability. The reliability of eliciting this reflex during weight-bearing has however yet to be addressed. This study was undertaken to determine the reliability of individual differences in the H-reflex recorded from healthy subjects during quiet standing. Secondary aims of the study were to evaluate individual reliability during prolonged standing, and to establish the minimum number of trials required to provide reliable measurements of the H-reflex. DESIGN AND PARTICIPANTS: Twenty neurologically healthy volunteers participated in a repeated measures design consisting of 8 blocks of 20 trials evenly distributed over two testing sessions. H-reflex recordings were elicited from the subject's dominant side soleus muscle by percutaneously stimulating the posterior tibial nerve. Stimuli were presented every 10 s, with 2 min seated rest provided between blocks of trials. Peak-to-peak amplitude of H-reflexes and m-responses determined for individual trials were used for subsequent analysis. RESULTS: It was found that the reliability of measuring the H-reflex and m-response during quiet standing was extremely robust (r = .97 for both measures). This pattern of individual differences remained consistent over 80 trials confirming the stability of the measures. High reliabilities (r = .96 and .87 for the H-reflex and m-responses respectively) were also observed when as few as four trials were analysed. When measures obtained during the first session of testing were compared with those obtained for session two, the correlation coefficients were generally of a lower order (r = .54 to .90). DISCUSSION: The results demonstrate that the H-reflex in quiet standing provides high intra-individual reliability, suggestive of a stable reflex resistant to potentially confounding postural influences, or other sources of biological variation. The between-session reliability underscores the difficulty in reproducing conditions between sessions, and emphasises the need for within-session comparisons of H-reflex amplitudes. Given the functional challenge of maintaining an upright posture, the H-reflex appears to be a well maintained and stable phenomenon.

Adolescent↗

PubMedDate not supplied

Reliability of individual differences for H-reflex recordings.

Complementary data from two closely-related experiments were analyzed to investigate the reliability of individual differences of H-reflex amplitude. Some concomitant analysis of M-reflex was also included. The purpose was to do this in a manner that was more direct and more detailed than found hitherto in the literature. Fundamental techniques espoused particularly by F.M. Henry (1969) formed the basis of this approach. The aims included a clearer quantification of reliability with a distinction between inter- and intra-individual sources of variation, an analysis of the effects different numbers of trials had on reliability, and an investigation of the progression of reliability over a 20-trial sequence of observations. The control conditions of both experiments were designed to be essentially identical with respect to subject position, stimulus and recording configurations. Experiment 1 had 20 subjects, four control conditions of 10-trials in each while experiment 2 had 18 subjects, five control conditions and 20 trials. The posterior tibial nerve was percutaneously stimulated every 10 sec. and surface electromyographic recordings were made from the soleus muscle. H-reflex and M-reflex amplitudes were measured on every trial. It was found that the reliability of individual differences of both H-reflex and M-reflex was extremely robust with the majority of coefficients being above .950. In addition, the reliabilities remained high when as few as four trials were examined. The pattern of individual differences over the longer series of trials confirmed the stability of interindividual differences and showed that subjects became more consistent in their responses as trials progressed.(ABSTRACT TRUNCATED AT 250 WORDS)

H-Reflex↗

PubMedDate not supplied

Use of solid phase Florisil cartridges to separate fat from semivolatile organic compounds in adipose tissue.

A quick method for separation of semivolatile organic compounds from fat in adipose tissue has been developed. This method uses commercially available solid phase cartridges for sample cleanup. The results indicate that the recoveries, from hexane-extracted fat, of 4 representative classes of organic compounds range from 86.2 to 116%. The solid phase cartridges provide excellent separations of the fat from the analytes; no extraneous interference peaks were detected in the gas chromatograms. The method requires only 0.1 g sample and is quick and simple to use. Although results are reported for samples containing 1-14 ppm, the final extract can be concentrated to a volume allowing detection between 10 and 100 ppb.

Adipose Tissue↗

PubMedDate not supplied

Rapid, low-cost cleanup procedure for determination of semivolatile organic compounds in human and bovine adipose tissues.

A gas chromatographic/mass spectrometric (GC/MS) method is described for determination of organic environmental pollutants in human and bovine adipose tissues. Compounds such as organochlorine pesticides, polychlorinated biphenyls, polynuclear aromatic hydrocarbons, polychlorinated aromatics, and brominated aromatics are extracted with organic solvents and separated from coextracted lipids on a Florisil column. The eluate is concentrated and compounds are identified and quantitated by GC/MS analysis. The method was evaluated in a single laboratory for ability to recover compounds of environmental and regulatory importance. Except for a few more polar compounds, such as phthalates and phosphates, recoveries averaged about 85%. The elution system maximized recovery and allowed minimal coelution of lipid materials. Detection limits for most compounds studied were in the range of 5-50 ng/g (ppb).

Adipose Tissue↗

PubMedDate not supplied

Preoperative hemodynamic evaluation of aortoiliac occlusive disease: correlation with intraoperative measurements.

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Aortic Diseases↗