Including Distorted Specimens in Allometric Studies: Linear Mixed Models Account for Deformation.

Allometry-patterns of relative change in body parts-is a staple for examining how clades exhibit scaling patterns representative of evolutionary constraint on phenotype, or quantifying patterns of ontogenetic growth within a species. Reconstructing allometries from ontogenetic series is one of the few methods available to reconstruct growth in fossil specimens. However, many fossil specimens are deformed (twisted, flattened, and displaced bones) during fossilization, changing their original morphology in unpredictable and sometimes undecipherable ways. To mitigate against post burial changes, paleontologists typically remove clearly distorted measurements from analyses. However, this can potentially remove evidence of individual variation and limits the number of samples amenable to study, which can negatively impact allometric reconstructions. Ordinary least squares (OLS) regression and major axis regression are common methods for estimating allometry, but they assume constant levels of residual variation across specimens, which is unlikely to be true when including both distorted and undistorted specimens. Alternatively, a generalized linear mixed model (GLMM) can attribute additional variation in a model (e.g., fixed or random effects). We performed a simulation study based on an empirical analysis of the extinct cynodont, Exaeretodon argentinus, to test the efficacy of a GLMM on allometric data. We found that GLMMs estimate the allometry using a full dataset better than simply using only non-distorted data. We apply our approach on two empirical datasets, cranial measurements of actual specimens of E. argentinus (n = 16) and femoral measurements of the dinosaur Tawa hallae (n = 26). Taken together, our study suggests that a GLMM is better able to reconstruct patterns of allometry over an OLS in datasets comprised of extinct forms and should be standard protocol for anyone using distorted specimens.

Alometria­el estudio de patrónes midiendo los cambios de proporciónes entre diferentes partes del cuerpo­es un método popularmente usado para estudiar como clados exhiben patrónes fenotípicos que representan restricciónes evolutivas, o para cuantificar patrónes de ontogenia entre una especie. Reconstruyendo alometrias para series ontogeneticas es uno de los pocos métodos disponibles para reconstruir el crecimiento de especies fósiles. Sin embargo, fósiles sufren de deformaciónes tafonomicas que alteran la morfología original y algunas veces en maneras no deseadas. Para mitigar estas alteraciones tafonomicas, paleontólogos excluyen mediciones alteradas de sus análisis. Desafortunadamente, esto limita el numero de muestras y potencialmente elimina evidencia de variación individual, impactando reconstrucciones alometricas. Mínimos Cuadrados Ordinarios (MCO) es un método frecuentemente usado para estimar alometria, pero asume niveles constantes de varición entre especímenes; esto es improbable cuando uno incluye especímenes deformados y especímenes indeformables. Alternativamente, Modelos Lineales Generalizados Mixtos (MLGM) pueden atribuir variciónes adicionales en un modelo. Nosotros corrimos simulaciones basadas en análisis empíricos del cinodonte extinto, Exaeretodon argentinus, para determinar la eficacia de MLGM con datos alometricos. Nosotros descubrimos que MLGM estima la alometria usando un conjunto de datos completos, en lugar de solo usar datos distorsionados. Aplicamos este método en dos conjuntos de datos empíricos: medidas craneales de especímenes de E. argentinus (n = 16) y medidas femorales del dinosaurio Tawa hallae (n = 26). Nuestros estudios indican que MLGM puede reconstruir mejor los patrónes de alometria sobre MCO con conjuntos de datos que incluyen especímenes extintos, y debería ser el protocolo estándar cuándo se usan especímenes que están deformados.

Does free nicotine replacement improve smoking cessation rates in cancer patients?

Background: Cigarette smoking is carcinogenic and has been linked to inferior treatment outcomes and complication rates in cancer patients. Here, we report the results of an 18-month pilot smoking cessation program that provided free nicotine replacement therapy (nrt). Methods: In January 2017, the smoking cessation program at our institution began offering free nrt for actively cigarette-smoking patients with cancer. The cost of 4 weeks of nrt was covered by the program, and follow-up was provided by smoking cessation champions. Results: From January 2017 to June 2018, 8095 patients with cancer were screened for cigarette use, of whom 1135 self-identified as current or recent smokers. Of those 1135 patients, 117 enrolled in the program and accepted a prescription for nrt. The rates of patient referral and patients attending a referral appointment were significantly higher in 2018-2018 than they had been in 2015-2016 (100% vs. 80.3%, p < 0.001, and 27.6% vs. 11.3%, p < 0.001, respectively). Median follow-up was 9.0 months (25%-75% interquartile range: 5.7-11.6 months). Of the patients who accepted nrt and who also had complete data (n = 71), 25 (35.2%) reported complete smoking cessation, and 32 (45.1%) reported only decreased cigarette smoking. On univariable analysis, no factors were significantly predictive of smoking cessation, although initial cigarette use (>10 vs. ≤10 initial cigarettes) was significantly predictive of smoking reduction (odds ratio: 5.04; 95% confidence interval: 1.46 to 17.45; p = 0.011). Conclusions: This pilot study of free nrt demonstrated rates of referral and acceptance of nrt that were improved compared with historical rates, and most referred patients either decreased their use of cigarettes or quit entirely.

Trafficking of matrix collagens through bone-resorbing osteoclasts.

An intracellular pathway for proteins liberated from mineralized matrix during resorption was identified in osteoclasts. Analysis by confocal microscopy of sites of active bone resorption showed that released matrix proteins, including degraded type I collagen, were endocytosed along the ruffled border within the resorption compartment and transcytosed through the osteoclast to the basolateral membrane. Intracellular trafficking of degraded collagen, as typified by the resorbing osteoclast, may provide the cell with a regulatory mechanism for the control of tissue degradation.

The design of an observational study of hypertension management, adherence and pressure control in Blood Pressure Success Zone Program participants.

AIMS: The Blood Pressure Success Zone (BPSZ) Program, a nationwide initiative, provides education in addition to a complimentary trial of one of three antihypertensive medications. The BPSZ Longitudinal Observational Study of Success (BPSZ-BLISS) aims to evaluate blood pressure (BP) control, adherence, persistence and patient satisfaction in a representative subset of BPSZ Program participants. The BPSZ-BLISS study design is described here. METHODS: A total of 20,000 physicians were invited to participate in the study. Using a call centre supported Interactive Voice Response System (IVRS), physicians report BP and other data at enrolment and every usual care visit up to 12 +/- 2 months; subjects self-report BPs, persistence, adherence and treatment satisfaction at 3, 6 and 12 months post-BPSZ Program enrolment. In addition to BPSZ Program enrolment medications, physicians prescribe antihypertensive medications and schedule visits as per usual care. The General Electric Healthcare database will be used as an external reference. RESULTS: After 18 months, over 700 IRB approved physicians consented and enrolled 10,067 eligible subjects (48% male; mean age 56 years; 27% newly diagnosed); 97% of physicians and 78% of subjects successfully entered IVRS enrolment data. Automated IVRS validations have maintained data quality (< 5% error on key variables). Enrolment was closed 30 April 2007; study completion is scheduled for June 2008. CONCLUSIONS: The evaluation of large-scale health education programmes requires innovative methodologies and data management and quality control processes. The BPSZ-BLISS design can provide insights into the conceptualisation and planning of similar studies.

Pregnancy outcomes in women with or without placental malaria infection.

OBJECTIVE: To assess delivery outcomes in women with placental malaria who presented at public hospitals in Kisumu, a holoendemic region in western Kenya. METHODS: A cross-sectional study using both histology and molecular biology was conducted with 90 consecutive pregnant women who presented at 3 hospitals during a 2-week period. Data collectors completed standardized questionnaires using each patient's hospital record and physical examination results, and registered birth indices such as weight, head circumference, and weight-head ratio. Malaria infection of the placenta was assessed using a molecular biology approach (for genomic differences among parasite species) as well as histology techniques. Of the 5 histologic classes of placental infection, class 1 corresponds to active infection and class 4 to past infection; class 2 and 3 to active chronic infection; and class 5 to uninfected individuals. Plasmodium species typing was determined by polymerase chain reaction amplification of the parasite's genome. RESULTS: In newborns at term, low birth weight was directly associated with classes 2 and 4 of placental infection (P = 0.053 and P = 0.003, respectively), and differences in birth weight remained significant between the 5 classes (P < 0.001) even after adjusting for parity and mother's age. Plasmodium falciparum was the only detected parasite. CONCLUSIONS: In Kisumu, infection with P. falciparum is an important cause of low birth weight and morbidity when it is associated with histologic classes 2 and 4 of placental infection. Moreover, polymerase chain reaction assays should be supported by ministries of health as an ancillary method of collecting data for malaria control during pregnancy and providing a baseline for future interventions.

The internal equilibrium of the hairpin ribozyme: temperature, ion and pH effects.

The hairpin ribozyme reversibly cleaves phosphodiesters of RNA substrates to generate products with 5' hydroxyl and 2',3'-cyclic phosphate termini. We previously found that the rate constant for ligation is tenfold faster than the rate constant for cleavage under standard conditions. The hammerhead ribozyme catalyzes the same reactions but is reported to favor cleavage relative to ligation by more than 100-fold under the same conditions. To explore the basis for this difference, we examined the influence of temperature, ions and pH on the hairpin ribozyme internal equilibrium. Under the same conditions, the loss of entropy associated with ligation is less for the hairpin than for the hammerhead ribozyme, consistent with the notion that a more rigid hairpin structure undergoes a smaller decrease in dynamics upon ligation than the more flexible hammerhead structure. Increased salt and reduced temperature shift the equilibrium toward ligation while pH has little effect, suggesting that conditions that stabilize RNA structure tend to promote ligation. The hairpin ribozyme appears to take up at least one tri- or divalent cation or two monovalent cations upon ligation. The efficiency with which different cations promote ligation depends strongly on valence and, less strongly, on ionic radius or electronegativity. This pattern of cation selectivity suggests that cations promote ligation through delocalized electrostatic shielding, perhaps interacting with a region of especially high charge density in the ligated ribozyme. Changes in ionic conditions produce large but compensating changes in enthalpy and entropy for cleavage and ligation. Thus, in addition to any increase in ribozyme dynamics associated with cleavage, re-organization of associated cations contributes significantly to hairpin ribozyme thermodynamics.

The kinetic mechanism of the hairpin ribozyme in vivo: influence of RNA helix stability on intracellular cleavage kinetics.

The relationship between hairpin ribozyme structure, and cleavage and ligation kinetics, and equilibria has been characterized extensively under a variety of reaction conditions in vitro. We developed a quantitative assay of hairpin ribozyme cleavage activity in yeast to learn how structure-function relationships defined for RNA enzymes in vitro relate to RNA-mediated reactions in cells. Here, we report the effects of variation in the stability of an essential secondary structure element, H1, on intracellular cleavage kinetics. H1 is the base-paired helix formed between ribozyme and 3' cleavage product RNAs. H1 sequences with fewer than three base-pairs fail to support full activity in vitro or in vivo, arguing against any significant difference in the stability of short RNA helices under in vitro and intracellular conditions. Under standard conditions in vitro that include 10 mM MgCl(2), the internal equilibrium between cleavage and ligation of ribozyme-bound products favors ligation. Consequently, ribozymes with stable H1 sequences display sharply reduced self-cleavage rates, because cleavage is reversed by rapid re-ligation of bound products. In contrast, ribozymes with as many as 26 base-pairs in H1 continue to self-cleave at maximum rates in vivo. The failure of large products to inhibit cleavage could be explained if intracellular conditions promote rapid product dissociation or shift the internal equilibrium to favor cleavage. Model experiments in vitro suggest that the internal equilibrium between cleavage and ligation of bound products is likely to favor cleavage under intracellular ionic conditions.

An unusual pH-independent and metal-ion-independent mechanism for hairpin ribozyme catalysis.

BACKGROUND: Hairpin ribozymes (RNA enzymes) catalyze the same chemical reaction as ribonuclease A and yet RNAs do not usually have functional groups analogous to the catalytically essential histidine and lysine sidechains of protein ribonucleases. Some RNA enzymes appear to recruit metal ions to act as Lewis acids in charge stabilization and metal-bound hydroxide for general base catalysis, but it has been reported that the hairpin ribozyme functions in the presence of metal ion chelators. This led us to investigate whether the hairpin ribozyme exploits a metal-ion-independent catalytic strategy. RESULTS: Substitution of sulfur for nonbridging oxygens of the reactive phosphate of the hairpin ribozyme has small, stereospecific and metal-ion-independent effects on cleavage and ligation mediated by this ribozyme. Cobalt hexammine, an exchange-inert metal complex, supports full hairpin ribozyme activity, and the ribozyme's catalytic rate constants display only a shallow dependence on pH. CONCLUSIONS: Direct metal ion coordination to phosphate oxygens is not essential for hairpin ribozyme catalysis and metal-bound hydroxide does not serve as the general base in this catalysis. Several models might account for the unusual pH and metal ion independence: hairpin cleavage and ligation might be limited by a slow conformational change; a pH-independent or metal-cation-independent chemical step, such as breaking the 5' oxygen-phosphorus bond, might be rate determining; or finally, functional groups within the ribozyme might participate directly in catalytic chemistry. Whichever the case, the hairpin ribozyme appears to employ a unique strategy for RNA catalysis.

Screening for microalbuminuria by use of microproteinuria.

We aimed to develop a reliable, low cost method to assess the early stages of renal impairment in diabetes, for use in high-risk populations in countries with limited resources. We evaluated a trichloroacetic acid (TCA) turbidimetric method for microproteinuria screening in patients with diabetes. The method was compared with an immunoturbidimetric procedure for the detection of microalbumuniuria. Both methods performed within limits of allowable uncertainty based on inter- and intra-individual variation. A urinary albumin/creatinine ratio of 3.0 g/mol, assumed as diagnostic of microalbuminuria, was found to correlate with a cut-off value of 24 mg/L for microproteinuria. The clinical sensitivity and specificity of the TCA method determined against this ratio were 86% and 90% respectively. The reliability and practicability of the TCA method renders it suitable for the detection of early stage renal damage, with emphasis on screening high-risk populations in countries with limited resources.

Integrins on rat osteoclasts: characterization of two monoclonal antibodies (F4 and F11) to rat beta 3.

Two monoclonal antibodies, F4 and F11, were raised to newborn rat bone cell suspensions. These antibodies are shown by immunocytochemistry on tissue sections to recognize an antigen shared between osteoclasts, megakaryocytes, and platelets. Immunoprecipitation analysis of the antigen from C6 rat glial cells followed by SDS-PAGE showed a heterodimeric molecule with a characteristic integrin-like shift in apparent molecular mass upon reduction (137/78 kD nonreduced; 118/100 kD reduced); the low-molecular-mass band comigrates with the beta 3 subunit precipitated with polyclonal antihuman vitronectin receptor antiserum, and the high-molecular-mass band comigrates with the alpha v subunit precipitated with a polyclonal antiserum to a C-terminal amino acid sequence of human alpha v. Antibody F4 strongly cross-reacts with human cells and is shown in cross-blocking experiments and immunoprecipitation analysis with a human melanoma cell line DX3 to recognize a seemingly identical molecule as identified by anti-alpha v beta 3 monoclonal antibody 23C6. Expression of F4 and F11 is reduced in platelets from a patient heterozygous for Glanzmann's thrombasthenia. Taken together, these results indicate that F4 and F11 recognize rat CD61, the integrin beta 3 chain, which, as was confirmed with polyclonal anti CD61 antisera, is highly expressed in rat osteoclasts. These antibodies may be useful tools in investigating the biochemical nature and biologic function of beta 3 integrins in rat osteoclasts. Additionally, because high expression of beta 3 in vivo is restricted to osteoclasts, megakaryocytes, and platelets, these antibodies may be used to help identify osteoclasts in tissue sections and bone cell suspensions.(ABSTRACT TRUNCATED AT 250 WORDS)

Rat osteoclasts adhere to a wide range of RGD (Arg-Gly-Asp) peptide-containing proteins, including the bone sialoproteins and fibronectin, via a beta 3 integrin.

The ligand binding ability of rat osteoclast adhesion receptors was investigated in an attachment assay using osteoclasts disaggregated from bone. Osteoclasts adhered well to the Arg-Gly-Asp (RGD)-containing proteins osteopontin (bone sialoprotein I) and BSP (bone sialoprotein II), vitronectin, fibrinogen, von Willebrand factor, and fibronectin. Osteoclasts also adhered, but less strongly, to type I collagen. No attachment of osteoclasts was observed to thrombospondin, tenascin, laminin, or a range of non-RGD-containing bone proteins and proteins from other sources. The attachment of osteoclasts to all ligands was abolished in the presence of GRGDSP peptide, indicating the involvement of the RGD cell binding sequence in ligand binding. Attachment of osteoclasts to all substrates, with the exception of type I collagen, was also strongly inhibited by the addition of monoclonal antibody F11 to the beta 3 integrin subunit, indicating that a beta 3 integrin, probably the vitronectin receptor, was involved. Attachment to type I collagen was blocked by EDTA chelation of divalent cations and was not significantly affected by anti-beta 3 or anti-beta 1 antibodies; when taken with the inhibition by RGD peptide, this suggests the involvement of various receptors, possibly including nonintegrin collagen receptors, in the binding of osteoclasts to this protein. These results define the wide range of ligands for extracellular matrix receptors in osteoclasts in vitro. It remains to be established which of these proteins are important in osteoclast adhesion and osteoclastic bone resorption in vivo.

Modulation of vitronectin receptor-mediated osteoclast adhesion by Arg-Gly-Asp peptide analogs: a structure-function analysis.

This study details the investigation of induction of retractile shape change in the osteoclast through inhibition of adhesion between osteoclasts and matrix with (1) peptide analogs bearing an Arg-Gly-Asp (RGD) sequence, (2) antibodies to the integrin alpha V beta 3 vitronectin receptor, and (3) the RGD-containing snake venom peptide echistatin. Osteoclast retraction on dentin has been demonstrated for GRGDSP peptide, in contrast to the inactivity of the analog containing the conservative RGE sequence modification. An osteoclast adhesion assay employing rat or chick bone cells and serum-coated glass coverslips as substrate was developed for routine evaluation of inhibition of adhesion. Antibodies F4 and F11 to the beta 3 chain of rat vitronectin receptor were effective at submicromolar concentrations in rat osteoclasts (IC50 0.29 and 0.05 microM, respectively), whereas MAb 23C6 to human/chick vitronectin receptor was somewhat less effective against chick osteoclasts (IC50 1.6 microM). A rank order of RGD analog activity (mean IC50, microM) in the serum-coated glass adhesion assay was derived for the linear peptides GRGDSP (201 microM), GRGDTP (180 microM), Ac-RGDS-NH2 (84 microM), Ac-RGDV-NH2 (68 microM), RGDV (43 microM), GRGDS (38 microM), and RGDS (26 microM). The two most potent short peptides were the cyclic analog SK&F 106760 Ac-S,S-cyclo-(Cys-(N alpha Me)Arg-Gly-Asp-Pen)-NH2 (IC50 7.0 microM), and the Telios peptide H-Gly-S,S-cyclo-(Pen-Gly-Arg-Gly-Asp-Ser-Pro-Cys)-Ala-OH (IC50 6.6 microM). The snake venom peptide echistatin was the most potent substance evaluated in the serum-coated glass assay (IC50 0.78 nM) employing either rat or chick osteoclasts.(ABSTRACT TRUNCATED AT 250 WORDS)

Parental hyperdynamic circulation predicts insulin resistance in offspring: The Tecumseh Offspring Study.

Controversy surrounds the pathogenetic mechanisms of the relationship between hyperdynamic circulation and insulin resistance. Two hundred eight children and young adults (mean age, 17.2+/-3.0 years; range, 11 to 26 years) from the Tecumseh Offspring Study whose parents had been assessed with Doppler echocardiography at the age of 34 years during the previous Tecumseh Blood Pressure Study were considered for this analysis. Offspring data were stratified according to tertiles of parental cardiac index. Parents in the top cardiac index tertile had increased heart rate (P=0.001), stroke volume (P=0.0001), left ventricular fractional shortening (P=0.02), and plasma epinephrine (P=0.02) compared with parents in the other tertiles. Body mass index (BMI) and blood pressure were similar in all groups. Offspring of parents with a high cardiac index had greater BMI (P=0.001), skinfold thickness (P=0.008), and waist/hip ratio (P=0.02), higher diastolic blood pressure (P=0.02) and plasma insulin level (P=0.001), and higher heart rate during Stroop's color test (P=0.02) than offspring of parents with a lower cardiac index. In a multivariate regression analysis, offspring BMI was predicted by parental BMI and cardiac index (P=0.0001 and 0.003, respectively). The mother-child relationship explained most of the cardiac index-BMI association. In summary, parental hyperdynamic circulation was an important predictor of overweight, abnormal fat distribution, increased blood pressure, and hyperinsulinemia in offspring. Our results illustrate the complexity of interaction between a genetic tendency and its phenotypic expression. We speculate that the degree of beta-adrenergic responsiveness may be a major determinant of the phenotypic differences between the parents and offspring found in this study.

Angiotensin mediates forearm glucose uptake by hemodynamic rather than direct effects.

Insulin sensitivity may be improved with the angiotensin-converting enzyme inhibitor captopril, suggesting that inhibition of angiotensin II (Ang II) improves insulin resistance. However, the administration of systemic Ang II has also been associated with an improvement in rather than worsening of glucose utilization. Since both stimulating and antagonizing the renin-angiotensin system improve glucose uptake and both angiotensin-converting enzyme inhibitors and intravenous Ang II elicit skeletal muscle vasodilation, it is conceivable that hemodynamic factors rather than a direct effect of either Ang II or angiotensin-converting enzyme inhibitors on skeletal muscle metabolism modulate the increase in glucose utilization. The direct effects of Ang II on glucose extraction in intact human skeletal muscle have not been previously described. We investigated the effects of local infusion of Ang II on glucose uptake in the forearm of 20 healthy subjects. With the use of the isolated insulin-perfused forearm model, local plasma insulin values were raised to 100 mU/mL over fasting values and maintained there for a 90-minute infusion period. After the first 60 minutes of insulin alone, Ang II was infused into the brachial artery for the last 30 minutes. Intra-arterial Ang II infusion caused a 38% decrease in forearm blood flow (P <.05) and 59% increase in the arteriovenous glucose gradients (P <.05) to maintain a steady glucose utilization (a decrease of 4%, P=NS). Thus, local Ang II infusion does not impair insulin-stimulated glucose utilization. Furthermore, glucose extraction increases to compensate for the decrease in forearm blood flow (as the Fick principle would predict for freely diffusible substances). We conclude that the described increase in glucose utilization from systemic infusion of Ang II and during angiotensin-converting enzyme inhibitor treatment is mediated by hemodynamic factors rather than a direct effect of Ang II on skeletal muscle metabolism.

Beta 1 integrins and osteoclast function: involvement in collagen recognition and bone resorption.

The extracellular matrix of bone is composed mainly of type I collagen. In this report we studied the role and collagen-binding properties of osteoclast integrins (alpha v, alpha 2, beta 1, and beta 3). Cell adhesion assays with rat osteoclasts and affinity chromatography/SDS-PAGE analysis with purified human osteoclast membranes demonstrated adhesion of osteoclasts to native type I collagen in a divalent cation and Arg-Gly-Asp (RGD)-dependent way via alpha 2 beta 1 integrin, whereas osteoclast adhesion to denatured collagen predominantly involved alpha v beta 3. In receptor-binding assays, the involvement of human recombinant alpha v beta 3 in adhesion to denatured collagen was confirmed. Additionally, osteoclasts adhered to type I collagen fibers and to monomeric types II-V collagen with characteristics similar to those on native monomeric type I collagen. Osteoclastic bone resorption in vitro was inhibited (> 40%) in the presence of alpha 2 and beta 1 antibodies. Using scanning laser confocal microscopy, alpha v beta 3, alpha 2, and beta 1 integrin were detected within podosomes in nonresorbing osteoclasts and in the ruffled border area and basolateral membrane in resorbing osteoclasts, but not in the sealing zone of resorbing osteoclasts. These results demonstrate that alpha 2 beta 1, in addition to alpha v beta 3, has an important role in osteoclast function and acts as a receptor for native, but not denatured, collagen.

New technologies in scanning probe microscopy for studying molecular interactions in cells.

Atomic force microscopy (AFM) is a specialised form of scanning probe microscopy, which was invented by Binnig and colleagues in 1986. Since then, AFM has been increasingly used to study biomedical problems. Because of its high resolution, AFM has been used to examine the topography or shape of surfaces, such as during the molecular imaging of proteins. This, combined with the ability to operate under known force regimes, makes AFM technology particularly useful for measuring intermolecular bond forces and assessing the mechanical properties of biological materials. Many of the constraints (e.g. complex instrumentation, slow acquisition speeds and poor vertical range) that previously limited the use of AFM in cell biology are now beginning to be resolved. Technological advances will enable AFM to challenge both confocal laser scanning microscopy and scanning electron microscopy as a method for carrying out three-dimensional imaging. Its use as both a precise micro-manipulator and a measurement tool will probably result in many novel and exciting applications in the future. In this article, we have reviewed some of the current biological applications of AFM, and illustrated these applications using studies of the cell biology of bone and integrin-mediated adhesion.

Cost-effectiveness of outpatient parenteral antibiotics: a review of the literature.

The results of studies completed on parenteral antibiotic therapy administered in an outpatient setting are reviewed. Although they varied in both size and sophistication, the studies all found that when patients and their families were carefully screened, outpatient therapy was a cost-effective, safe method of administering intravenous antibiotics. The methods used to compare the costs of inpatient and outpatient intravenous antibiotic therapy varied widely. Only direct costs were included in the early comparisons of inpatient and outpatient therapy, whereas the more recent studies included both direct and indirect costs and benefits. All studies found cost savings in the outpatient setting. Unfortunately, very few elderly patients were included because of a Medicare requirement that intravenous antibiotic therapy be administered or supervised by a physician. However, beginning in 1990, the Medicare Catastrophic Coverage Act of 1988 will cover intravenous drugs administered at home. Thus, it will be possible to study applicability of this therapy for the elderly population.

Genetic contribution to the variance in left ventricular mass: the Tecumseh Offspring Study.

OBJECTIVE: To estimate the contribution of heredity to the variance in left ventricular mass (LVM), and to ascertain whether genetic factors may interact with non-genetic factors in promoting LVM growth. SUBJECTS AND SETTING: The study population consisted of 290 healthy parents and 251 healthy children living in Tecumseh, Michigan, USA. MAIN OUTCOME MEASURE: Correlation of parents' LVM with offspring's LVM adjusting for a number of clinical variables. METHODS: LVM in parents and offspring was measured with M-mode echocardiography by the same investigators. RESULTS: Parents unadjusted LVM was unrelated to offspring unadjusted LVM, but after removing the confounding effect of age, sex, anthropometric measurements, systolic blood pressure, plasma insulin and urinary sodium excretion, parent-child correlation for LVM was 0.28 (P = 0.006). The relative contribution of parental-adjusted LVM and of several offspring phenotypic and environmental variables on offspring LVM was evaluated by multivariable regression analysis. When age, gender, anthropometric measurements and systolic blood pressure were accounted for, adjusted LVM of parents explained only 1.6% of the total variance in offspring LVM. However, after inclusion of insulin and urinary sodium in the model heredity explained 7.6% of the total variance in offspring LVM, and its predictive power was second only to that of child's height. Furthermore, an interactive effect of parental LVM with offspring systolic blood pressure was found on child's left ventricular mass. CONCLUSION: Heredity can explain a small, but definite proportion of the variance in LVM. Higher blood pressure favors the phenotypic expression of the genes that regulate LVM growth.

Smoking is associated with higher cardiovascular risk in young women than in men: the Tecumseh Blood Pressure Study.

BACKGROUND: Tobacco smoking is associated with a higher prevalence of atherosclerosis and respiratory disease. OBJECTIVE: To investigate differences between hemodynamic and biochemical findings in smokers and nonsmokers in the two sexes separately in the Tecumseh population. METHODS: We studied 851 subjects. They were divided according to smoking habits into group 1, nonsmokers (258 men and 234 women); and group 2, smokers (185 men and 174 women). RESULTS: Unpaired Student's t-tests and nonparametric tests were performed to determine the between-group P-values. Only hematocrit differed significantly between smokers and nonsmokers in both sexes (43.9 +/- 0.2 and 44.6 +/- 9.3%, P < 0.05 in men; 39.2 +/- 0.3 and 40.3 +/- 0.3%, P = 0.007 in women, respectively in nonsmokers and smokers). Triglycerides (80.6 +/- 3.8 and 99.6 +/- 4.3 mg/dl, P < 0.001), left ventricular mass index (95.4 +/- 1.9 and 100.0 +/- 1.2 g/m2, P = 0.008), and posterior wall thickness (9.5 +/- 0.1 and 9.71 +/- 0.01 mm, P = 0.044) were elevated and high-density lipoproteins were decreased (48.7 +/- 0.8 and 44.5 +/- 0.9 mg/dl, P < 0.01) only in women smokers. After adjustment for home systolic blood pressure and body mass index the differences in women remained significant except for posterior wall thickness. CONCLUSION: Tobacco smoking is deleterious to both sexes but it appears to be particularly harmful to women. Our data can, in part, explain why the relative risk of myocardial infarction is higher in women than it is in men.

Determinants of left ventricular structure and mass in young subjects with sympathetic over-activity. The Tecumseh Offspring Study.

OBJECTIVE: In this study, we tested the hypothesis that sympathetic over-activity may cause metabolic abnormalities and affect left ventricular (LV) structure and mass early in life. SUBJECTS AND SETTING: The study population consisted of 111 healthy adolescents and young adults living in Tecumseh, Michigan (USA). MAIN OUTCOME MEASURES: Correlations of LV mass and structure with several clinical variables in relation to the activity of the sympathetic nervous system. METHODS: Power spectrum density estimates of heart rate variability were calculated with an auto-regressive method, and subjects were divided by cluster analysis into two groups according to low-frequency and high-frequency components. LV data were obtained by echocardiographic assessment RESULTS: Subjects with signs of sympathetic over-activity (n = 38, group 1) had higher heart rate, blood pressure (BP), waist/hip ratio and cholesterol levels than the rest of the group (n = 73, group 2). In group 1 subjects, insulin emerged as the strongest univariate correlate of interventricular septum and posterior wall thicknesses (P< 0.001 for both) and of LV mass (P= 0.009). These relationships remained significant when body mass index was accounted for. By contrast, the marginal univariate relationship with diastolic BP did not remain significant in multivariate analysis. In group 2 subjects, BP was strongly correlated with LV wall thickness and mass both in univariate (P values from 0.03 to < 0.001) and multivariate analyses, while insulin was not. The interactive effect of sympathetic activity and insulin on echocardiographic data was confirmed by multivariate analyses performed in the subjects grouped together (P values from 0.02 to 0.001 for the sympathetic activity x insulin interaction term). CONCLUSIONS: In young subjects with heightened sympathetic activity and initial metabolic abnormalities, insulin is a strong determinant of LV wall thickness and geometry, while in subjects with normal autonomic nervous system activity, the main determinant of left ventricular size is the haemodynamic load.