Abstract SP012: Convergent evolution of resistance pathways during early stage breast cancer treatment with combination cell cycle (CDK) and endocrine signaling inhibitors

Combining cyclin-dependent kinase (CDK) inhibitors with endocrine therapy improves outcomes for metastatic estrogen receptor positive (ER+), HER2 negative, breast cancer patients. However, the value of this combination in potentially curable earlier stage patients is not clear. Using single cell transcriptomic profiling, we examined the evolutionary trajectories of early stage breast cancer tumors using serial tumor biopsies from a clinical trial of preoperative endocrine therapy alone (letrozole) or in combination with the cell cycle inhibitor ribociclib. Applying hierarchical regression and Gaussian process mathematical modelling, we classified each tumor by whether it shrinks or persists with therapy and determined cancer phenotypes related to evolution of resistance and cell cycle transcriptional rewiring. We found that all patients’ tumors undergo subclonal evolution during therapy, irrespective of the clinical response. However, tumors subjected to endocrine therapy alone showed reduced diversity over time, those facing combination therapy exhibited increased diversity. Despite different diversity, single nuclei RNA sequencing uncovered common phenotypic changes in tumor cells that persist following treatment. In these tumors, accelerated loss of estrogen signaling is convergent with up-regulation of the JNK pathway, while persistent tumors that maintain estrogen signaling during therapy show potentiation of CDK4/6 activation consistent with ERBB4 and ERK signaling up-regulation. Cell cycle reconstruction identified that these tumors can rebound during combination therapy treatment, indicating stronger selection and promotion of a proliferative state. These results indicate that combination therapy in early stage ER+ breast cancers with ER and CDK inhibition drives rapid evolution of resistance via a shift from estrogen signaling to alternative growth factor receptor mediated proliferation and JNK signaling activation, concordant with a bypass in the G1 checkpoint.

Citation Format: JI Griffiths, J Chen, PA Cosgrove, A O'Dea, P Sharma, CX Ma, M Trivedi, K Kalinsky, KB Wisinski, R O'Reagan, I Makhoul, LM Spring, A Bardia, FR Adler, AL Cohen, JT Chang, QJ Khan, AH Bild. Convergent evolution of resistance pathways during early stage breast cancer treatment with combination cell cycle (CDK) and endocrine signaling inhibitors [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr SP012.

Correlation-Driven Charge Order in a Frustrated Two-Dimensional Atom Lattice

We thoroughly examine the ground state of the triangular lattice of Pb on Si(111) using scanning tunneling microscopy and spectroscopy. We detect electronic charge order, and disentangle this contribution from the atomic configuration which we find to be 1-down-2-up, contrary to previous predictions from density functional theory. Applying an extended variational cluster approach we map out the phase diagram as a function of local and nonlocal Coulomb interactions. Comparing the experimental data with the theoretical modeling leads us to conclude that electron correlations are the driving force of the charge-ordered state in Pb/Si(111). These results resolve the discussion about the origin of the well-known 3×3 reconstruction. By exploiting the tunability of correlation strength, hopping parameters, and band filling, this material class represents a promising platform to search for exotic states of matter, in particular, for chiral topological superconductivity.

Invited review: Examining farmers' personalities and attitudes as possible risk factors for dairy cattle health, welfare, productivity, and farm management: A systematic scoping review

We aimed to determine how research regarding farmers' personalities and attitudes as risk factors is reported (methodological approaches to assessing, extracting, and processing data and analyzing risk factors) and to explore evidence for the effect of farmers' attitudes and personalities on dairy cattle health, welfare, productivity, and management. Therefore, we conducted a systematic review of studies on personality and attitude as risk factors for dairy cattle health, welfare, productivity, and farm management. Database searches captured 1,144 records, and 38 were finally included in the review. Thirty-three manuscripts assessed farmers' attitudes, 1 assessed their personalities, and 4 assessed both as risk factors. These potential risk factors were checked for relationships with more than 50 different outcome variables regarding farm management (17 manuscripts), animal health (13 manuscripts), animal productivity (11 manuscripts), and animal welfare (4 manuscripts). The approaches to assessing risk factors and processing and interpreting data varied greatly; thus, drawing conclusions regarding the effects of attitude and personality as risk factors is impeded because manuscripts are difficult to compare. Our findings highlight the need for harmonization of attitudes and personality assessments in future research. Furthermore, researchers should carefully consider which depth of detail to apply when planning and evaluating related research. Nevertheless, results highlight the importance of the effect of personality and attitude on outcomes. Farmers' personality and attitudes are associated with dairy cattle health, welfare, productivity, and management. In general, attitudes indicating higher degrees of technical knowledge, affection with problems, perceived responsibility, perception of control of a situation, a better human-animal relationship, or a positive evaluation of the benefits of management decisions tended to affect outcomes in a beneficial way. "Agreeableness" and "conscientiousness" were shown to promote better farm performance, whereas "neuroticism" had a negative effect. Therefore, further research on attitude and personality and their consideration by professionals and decision-makers within the dairy sector and politics is strongly recommended. This might provide the chance to better understand the needs of dairy farmers and therefore develop tailored advice and support strategies to improve both satisfactory and constructive cooperation.

GaInN/GaN-Heterostructures and Quantum Wells Grown by Metalorganic Vapor-Phase Epitaxy

The dependence of the In-incorporation efficiency and the optical properties of MOVPE-grown GaInN/GaN-heterostructures on various growth parameters has been investigated. A significant improvement of the In-incorporation rate could be obtained by increasing the growth rate and reducing the H2-partial pressure in the MOVPE reactor. However, GaInN layers with a high In-content typically show an additional low energy photoluminescence peak, whose distance to the band-edge increases with increasing In-content. For GaInN/GaN quantum wells with an In-content of approximately 12%, an increase of the well thickness is accompanied by a significant line broadening and a large increase of the Stokes shift between the emission peak and the band edge determined by photothermal deflection spectroscopy. With a further increase of the thickness of the GaInN layer, a second GaInN-correlated emission peak emerges. To elucidate the nature of these optical transitions, power-dependent as well as time-resolved photoluminescence measurements have been performed and compared to the results of scanning transmission electron microscopy.

[Kyphoplasty in combination with intraoperative radiotherapy. Technical and regulatory characteristics of a concept for treatment of vertebral metastases]

BACKGROUND

Operative and radiotherapeutic procedures are available for the treatment of symptomatic vertebral metastases. The method for treatment of vertebral metastases presented in this article involves a combination of intraoperative radiotherapy (IORT) and kyphoplasty.

METHODS AND RESULTS

Kyphoplasty-IORT allows treatment of symptomatic vertebral metastases between vertebrae T3 and L5. With the patient under intubation narcosis an extrapedicular or bipedicular access to the vertebra is selected as for conventional kyphoplasty. This is followed by insertion of special sheaths of the radiation applicator and radiation therapy is intraoperatively administered via a radiation generator (Intrabeam®, Carl Zeiss Surgical, Oberkochen, Germany). The radiation dose is 8 Gy at a depth of 5-10 mm depending on the study protocol (50 kV X-radiation). Following radiation a conventional kyphoplasty procedure (Medtronic, USA) is carried out and the vertebra stabilized with cement.

CONCLUSIONS

The procedure presented demonstrates a new approach to treatment of vertebral metastases and represents a valuable alternative to previously established methods.

Intraosseous CSF fistula in a patient with Gorham disease resulting in intracranial hypotension

A 7-year-old girl with a history of headaches and Gorham disease was surgically treated in infancy for Chiari I malformation. Subsequent investigation revealed that her cerebellar tonsillar ectopia was due to a long-standing spinal CSF-lymphatic fistula causing intracranial hypotension. Percutaneous fistula closure was performed several times, resulting in transient symptomatic improvement.

Optical frequency comb spectroscopy

Optical frequency combs offer enormous potential in the detection and control of atoms and molecules by combining their vast spectral coverage with the extremely high spectral resolution of each individual comb component. Sensitive and multiplexed trace gas detection via cavity-enhanced direct frequency comb spectroscopy has been demonstrated for various molecules and applications; however, previous demonstrations have been confined to the visible and near-infrared wavelength range. Future spectroscopic capabilities are created by developing comb sources and spectrometers for the deep ultraviolet and mid-infrared spectral regions. Here we present a broadband high resolution mid-infrared frequency comb-based Fourier transform spectrometer operating in the important molecular fingerprint spectral region of 2100-3600 cm(-1) (2.8-4.8 microm). The spectrometer, employing a multipass cell, allows simultaneous acquisition of broadband, high resolution spectra (down to 0.0035 cm(-1) of many molecular species at concentrations in the part-per-billion range in less than 1 min acquisition time. The system enables precise measurements of concentration even in gas mixtures that exhibit continuous absorption bands. The current sensitivity, 2 x 10(-8) cm(-1) Hz-1/2 per spectral element, is expected to improve by two orders of magnitude with an external enhancement cavity. We have demonstrated this sensitivity increase by combining cavity-enhanced frequency comb spectroscopy with a scanning Fourier transform spectrometer in the near-infrared region and achieving a sensitivity of 4.7 x 10(-10) cm(-1) Hz(-1/2). A cavity-enhanced mid-infrared comb spectrometer will provide a near real-time, high sensitivity, high resolution, precisely frequency calibrated, broad bandwidth system for many applications.

The role of heterogeneity in the persistence and prevalence of Sin Nombre virus in deer mice

Many diseases persist at a relatively low prevalence, seemingly close to extinction. For a chronic disease in a homogeneous population, reducing the transmission rate by a fraction proportional to the prevalence would be sufficient to eradicate the disease. This study examines how higher prevalence of the Sin Nombre virus in male deer mice (Peromyscus maniculatus) might contribute to disease persistence. Analyzing data from over 2,000 individual mice captured in 19 sites over 4 years, we found prevalences of 18.5% in males and 8.8% in females. By examining recaptures, we determined that males are more likely to contract the infection because of higher susceptibility or higher encounter rates. Comparing across 86 sampling periods, we found a higher proportion of males when population densities were low. A capture-recapture analysis indicates that males live longer than females. A mathematical model based on the measured parameters and population size trajectories suggests that the combined heterogeneity in encounters, susceptibility, and mortality may buffer the disease from extinction by concentrating disease in the subgroup most likely to transmit the disease. This buffering effect is not significantly stronger in a fluctuating population, indicating that these forms of heterogeneity might not be the key for disease persistence through host population bottlenecks.

Highly versatile confocal microscopy system based on a tunable femtosecond Er:fiber source

The performance of a confocal microscopy setup based on a single femtosecond fiber system is explored over a broad range of pump wavelengths for both linear and nonlinear imaging techniques. First, the benefits of a laser source in linear fluorescence excitation that is continuously tunable over most of the visible spectrum are demonstrated. The influences of subpicosecond pulse durations on the bleaching behavior of typical fluorophores are discussed. We then utilize the tunable near-infrared output of the femtosecond system in connection with a specially designed prism compressor for dispersion control. Pulses as short as 33 fs are measured in the confocal region. As a consequence, 2 mW of average power are sufficient for two-photon microscopy in an organotypic sample from the mouse brain. This result shows great prospect for deep-tissue imaging in the optimum transparency window around 1100 nm. In a third experiment, we prove that our compact setup is powerful enough to exploit even higher-order nonlinearities such as three-photon absorption that we use to induce spatially localized photodamage in DNA.

Mid-infrared difference-frequency generation of ultrashort pulses tunable between 3.2 and 4.8 microm from a compact fiber source

We report single-pass difference-frequency generation of mid-infrared femtosecond pulses tunable in the 3.2-4.8 microm range from a two-branch mode-locked erbium-doped fiber source. Average power levels of up to 1.1 mW at a repetition rate of 82 MHz are obtained in the mid infrared. This is achieved via nonlinear mixing of 170 mW, 65 fs pump pulses at a fixed wavelength of 1.58 microm, with 11.5 mW, 40 fs pulses tunable in the near-infrared range between 1.05 and 1.18 microm. These values indicate that the tunable near-infrared input component is downconverted with a quantum efficiency that exceeds 30%.

Maintaining Diversity in an Ant Community: Modeling, Extending, and Testing the Dominance‐Discovery Trade‐Off

Ant communities often consist of many species with apparently similar niches. We present a mathematical model of the dominance-discovery trade-off, the trade-off between the abilities to find and to control resources, showing that it can in principle facilitate the coexistence of large numbers of species. Baiting studies of dominance and discovery abilities in an ant community from the Chiricahua Mountains of Arizona indicate that real communities fail to fit the assumptions of the simple model in several ways: (1) dominance depends on the size of the food resource; (2) for some ants, dominance depends on the presence or absence of specialist parasitoids; (3) pairwise dominance is not an all-or-nothing trait; and (4) a consistent negative relationship between pairwise differences in per capita discovery rates and dominance can be detected for only one bait type. Extended models incorporating these factors successfully predict the coexistence of five of the six most abundant members of this community but fail to accurately predict their relative abundances. Sensitivity analysis indicates that each complicating factor enhances the extent of coexistence.

12-fs pulses from a continuous-wave-pumped 200-nJ Ti:sapphire amplifier at a variable repetition rate as high as 4 MHz

We demonstrate a novel compact femtosecond Ti:sapphire laser system operating at repetition rates from 10 kHz to 4 MHz. The scheme is based on the combination of a broadband cavity-dumped oscillator and a double-pass Ti:sapphire amplifier pumped by a low-noise cw solid-state laser. Amplified pulses with an extremely smooth spectrum, a duration of only 12 fs, and less than 0.25% rms fluctuation are generated in a beam with M2 < 1.2. A maximum pulse energy of 210 nJ and an average output power of as much as 720 mW are achieved. This output energy is sufficient to generate a stable continuum in a sapphire disk.

Survival effect of lung transplantation among patients with cystic fibrosis

CONTEXT

Patients with cystic fibrosis (CF) are the second largest group of lung transplant recipients in the United States. The survival effect of transplantation on a general CF population has not previously been measured.

OBJECTIVE

To determine the impact of bilateral lung transplantation on survival in patients with CF.

DESIGN, SETTING, AND PATIENTS

Retrospective observational cohort study of 11 630 CF patients who did not undergo lung transplantation (controls) and 468 transplant recipients with CF from 115 CF centers in the United States, 1992-1998. Patients were stratified into 5 groups based on a 5-year survival prediction model (survival group 1: <30%; survival group 2: 30 to <50%; survival groups 3-5: 50 to <100%.)

MAIN OUTCOME MEASURE

Five-year survival from date of transplantation in 1992-1997 in the transplant group and from January 1, 1993, in the control group.

RESULTS

Lung transplantation increased 5-year survival of CF patients in survival group 1. Survival group 2 had equivocal survival effects, and groups 3-5 had negative survival effects from transplantation. From 1994-1997, there was a mean annual prevalence of 238 patients in survival group 1 and mean annual incidence of 154 patients entering the group, approximately 1.5 times the number of lung transplantations performed each year in CF patients (mean, 104). Use of the criterion of forced expiratory volume in 1 second of less than 30% resulted in an equivocal survival benefit and identified 1458 potential candidates for transplantation in 1993.

CONCLUSIONS

Cystic fibrosis patients in group 1 have improved 5-year survival after lung transplantation. The majority of patients with CF have equivocal or negative survival effects from the procedure. Selection of patients with CF for transplantation based on group 1 survival predictions maximizes survival benefits to individuals and may reduce the demand for scarce donor organs.

A comparison between bipedal and quadrupedal rats: do bipedal rats actually assume an upright posture?

STUDY DESIGN

A basic science animal investigation.

OBJECTIVES

To determine if bipedal rats differ in upright posture compared with quadrupedal rats.

SUMMARY OF BACKGROUND DATA

It has been reported that surgically induced bipedalism in the rat leads to habitual upright posture. Based on this finding, bipedal rats have been used to study the changes erect posture induces in bone, ligament, muscle, and intervertebral discs. Previous studies have used direct observation as a means to describe posture. This study is the first to quantify postural differences between bipedal and quadrupedal rats.

METHODS

Eleven bipedal rats were created by forelimb and tail amputation within 24 hours of birth. Eleven quadrupedal rats served as controls. Specialized cages were used with infrared sensors, and a computer program measured the total amount of time in the upright stance, the number of stands, and the amount of horizontal movement in the upright stance. Statistical comparisons were made between bipedal and quadrupedal rats hourly and over a 24-hour period of time.

RESULTS

Quadrupedal rats assumed an upright posture for a significantly greater amount of time than bipedal rats when monitored over 24 hours (P = 0.016). Quadrupedal and bipedal rats did not differ in the number of stands (P = 0.63) or in the amount of horizontal movement in the upright stance (P = 0.34) over 24 hours. Similar results were obtained when comparing hourly intervals.

CONCLUSION

This study quantifiably indicates that bipedal rats do not assume a more erect posture and spend no more time in an upright position compared with quadrupedal rats. The upright posture may not be the cause of some previously reported anatomic changes observed in the bipedal rat.

Predictive 5-year survivorship model of cystic fibrosis

The objective of this study was to create a 5-year survivorship model to identify key clinical features of cystic fibrosis. Such a model could help researchers and clinicians to evaluate therapies, improve the design of prospective studies, monitor practice patterns, counsel individual patients, and determine the best candidates for lung transplantation. The authors used information from the Cystic Fibrosis Foundation Patient Registry (CFFPR), which has collected longitudinal data on approximately 90% of cystic fibrosis patients diagnosed in the United States since 1986. They developed multivariate logistic regression models by using data on 5,820 patients randomly selected from 11,630 in the CFFPR in 1993. Models were tested for goodness of fit and were validated for the remaining 5,810 patients for 1993. The validated 5-year survivorship model included age, forced expiratory volume in 1 second as a percentage of predicted normal, gender, weight-for-age z score, pancreatic sufficiency, diabetes mellitus, Staphylococcus aureus infection, Burkerholderia cepacia infection, and annual number of acute pulmonary exacerbations. The model provides insights into the complex nature of cystic fibrosis and supplies a rigorous tool for clinical practice and research.

Nonrecurrent laryngeal nerve during carotid artery surgery: case report and literature review

The anomalous position of a nonrecurrent inferior laryngeal nerve predisposes it to injury during surgery in the neck. We present the case of a patient who underwent a carotid endarterectomy in which a rare left nonrecurrent laryngeal nerve was found intraoperatively. This abnormality, which occurs much less often on the left than the right side of the neck, should be familiar to vascular surgeons. Historical, embryologic, and surgical significance of this anomaly is addressed.

Genetic and phylogenetic consequences of island biogeography

Island biogeography theory predicts that the number of species on an island should increase with island size and decrease with island distance to the mainland. These predictions are generally well supported in comparative and experimental studies. These ecological, equilibrium predictions arise as a result of colonization and extinction processes. Because colonization and extinction are also important processes in evolution, we develop methods to test evolutionary predictions of island biogeography. We derive a population genetic model of island biogeography that incorporates island colonization, migration of individuals from the mainland, and extinction of island populations. The model provides a means of estimating the rates of migration and extinction from population genetic data. This model predicts that within an island population the distribution of genetic divergences with respect to the mainland source population should be bimodal, with much of the divergence dating to the colonization event. Across islands, this model predicts that populations on large islands should be on average more genetically divergent from mainland source populations than those on small islands. Likewise, populations on distant islands should be more divergent than those on close islands. Published observations of a larger proportion of endemic species on large and distant islands support these predictions.

How to make a biological switch

Some biological regulatory systems must "remember" a state for long periods of time. A simple type of system that can accomplish this task is one in which two regulatory elements negatively regulate one another. For example, two repressor proteins might control one another's synthesis. Qualitative reasoning suggests that such a system will have two stable states, one in which the first element is "on" and the second "off", and another in which these states are reversed. Quantitative analysis shows that the existence of two stable steady states depends on the details of the system. Among other things, the shapes of functions describing the effect of one regulatory element on the other must meet certain criteria in order for two steady states to exist. Many biologically reasonable functions do not meet these criteria. In particular, repression that is well described by a Michaelis-Menten-type equation cannot lead to a working switch. However, functions describing positive cooperativity of binding, non-additive effects of multiple operator sites, or depletion of free repressor can lead to working switches.

Teaching a new dog old tricks: identifying quantitative trait loci using lessons from plants

Locating quantitative trait loci (QTL) in mammalian systems has proven difficult due to the lack of genetic control and reproducibility, as well as the expense of maintaining sufficiently large populations for genotyping and phenotyping. In plants, populations of recombinant inbred lines (progeny bred to homozygosity from a single cross) do not have these problems. Methods developed to identify QTL in a recombinant inbred soybean population provide a basis for analysis of a suitable mammalian population, such as Portuguese water dogs in the United States. The more than 6,000 dogs have accurate pedigrees, available phenotypic data and samples for genotyping, as well as interesting quantitative trait variation. The computer program Georgie allows us to choose large subpopulations with desirable characteristics such as high degrees of consanguinity that capture some of the benefits of recombinant inbred lines in plants. Computer simulations extending methods developed for simpler plant populations indicate that QTL with realistic effects can be identified from such subpopulations. Currently we are developing markers and collecting phenotypic and genotypic data from this population to begin the process of unraveling the genetic basis of quantitative traits in dogs.

Evolution of virulence: a unified framework for coinfection and superinfection

Models of the evolution of parasite virulence have focused on computing the evolutionarily stable level of virulence favored by tradeoffs within a host and by competition for hosts, and deriving conditions under which strains with different virulence levels can coexist. The results depend on the type of interaction between disease strains, such as single infection (immunity of infected individuals to other strains), coinfection (simultaneous infection by two strains), and superinfection (instantaneous takeover of host by the more virulent strain). We present a coinfection model with two strains and derive the superinfection model as the limit where individuals are rapidly removed from the doubly-infectious class. When derived in this way, the superinfection model includes not only the takeover of hosts infected by the less virulent strain, but new terms which take into account the possibility of increased mortality of doubly-infected individuals. Coinfection tends to favor higher virulence and support more coexistence than the single infection model, but the detailed results depend sensitively on two factors: (1) whether and how the model is near the superinfection limit, and (2) the shape of the coinfection function (the function describing the rate at which a more virulent strain can infect a host). If the superinfection limit arises due to rapid mortality of doubly-infected hosts, there is a region of uninvadable virulence levels rather than coexistence. When the coinfection function is discontinuous, as in many previous models, neither the coinfection model nor the superinfection limit can support an evolutionarily stable virulence level. Piecewise differentiable and differentiable coinfection functions produce qualitatively different results, and we propose that these more general cases should be used to study evolution of virulence when other mechanisms like space, population dynamics, and stochasticity interact.

Relevance of muscular sensitivity, muscular activity, and cognitive variables for pain reduction associated with EMG biofeedback in fibromyalgia

18 patients suffering from primary fibromyalgia received nine training sessions using EMG biofeedback over a period of four weeks. Pre- and posttreatment measurement of the baseline EMG activity of the trapezius, muscular sensitivity, and cognitive variables (helplessness and belief of control) were taken. Analysis indicated a significant reduction occurred in general intensity of pain and in EMG activity as well as a significant increase in muscular sensitivity. Multiple regression analyses indicated that the increase in muscular sensitivity correlated with the decrease of EMG activity in the trapezius baseline. Self-reported pain reduction was predicted by a change in cognitive variables.

A meta-analysis of the efficacy of non-operative treatments for idiopathic scoliosis

With use of data culled from twenty studies, members of the Prevalence and Natural History Committee of the Scoliosis Research Society conducted a meta-analysis of 1910 patients who had been managed with bracing (1459 patients), lateral electrical surface stimulation (322 patients), or observation (129 patients) because of idiopathic scoliosis. Three variables - the type of treatment, the level of maturity, and the criterion for failure - were analyzed to determine which had the greatest impact on the outcome. We also examined the effect of the type of brace that was used and the duration of bracing on the success of treatment. The number of failures of treatment in each study was determined by calculating the total number of patients who had unacceptable progression of the curve (as defined in the study), who could not comply with or tolerate treatment, or who had an operation. The percentage of patients who completed a given course of treatment without failure, adjusted for the sample sizes of the studies in which that treatment was used, yielded the weighted mean proportion of success for that treatment. The weighted mean proportion of success was 0.39 for lateral electrical surface stimulation, 0.49 for observation only, 0.60 for bracing for eight hours per day, 0.62 for bracing for sixteen hours per day, and 0.93 for bracing for twenty-three hours per day. The twenty-three-hour regimens were significantly more successful than any other treatment (p < 0.0001). The difference between the eight and sixteen-hour regimens was not significant, with the numbers available. Although lateral electrical surface stimulation was associated with a lower weighted mean proportion of success than observation only, the difference was not significant, with the numbers available. This meta-analysis demonstrates the effectiveness of bracing for the treatment of idiopathic scoliosis. The weighted mean proportion of success for the six types of braces included in this review was 0.92, with the highest proportion (0.99) achieved with the Milwaukee brace. We found that use of the Milwaukee brace or another thoracolumbosacral orthosis for twenty-three hours per day effectively halted progression of the curve. Bracing for eight or sixteen hours per day was found to be significantly less effective than bracing for twenty-three hours per day (p < 0.0001).

Biochemical characterization of a novel KRAS insertion mutation from a human leukemia

A novel alteration in exon 1 of KRAS was detected by single strand conformational polymorphism analysis of DNA amplified from the bone marrow of a 4-year-old child with myeloid leukemia. Sequencing of this mutant allele revealed an insertion of three nucleotides between codons 10 and 11 resulting in an in-frame insertion of glycine. Expression of the mutant protein in NIH 3T3 cells caused cellular transformation, and expression in COS cells activated the Ras-mitogen-activated protein kinase signaling pathway. Surprisingly, Ras.GTP levels measured in COS cells established that this novel mutant accumulates to 90% in the GTP state, considerably higher than a residue 12 mutant. Biochemical analysis confirmed that the higher Ras.GTP levels correspond to a dramatic decrease in intrinsic GTP hydrolysis as well as resistance to GTPase-activating proteins. This mutation is the first dominant Ras mutation found in human cancer that does not involve residues 12, 13, or 61, and its biochemical properties should help elucidate the mechanism of oncogenic activation.

A model of self-thinning through local competition

Explanations of self-thinning in plant populations have focused on plant shape and packing. A dynamic model based on the structure of local interactions successfully reproduces the pattern and can be approximated to identify key parameters and relationships. The approach generates testable new explanations for differences between species and populations, unifies self-thinning with other patterns in plant population dynamics, and indicates why organisms other than plants can follow the law.

Loss of NF1 results in activation of the Ras signaling pathway and leads to aberrant growth in haematopoietic cells

Individuals with neurofibromatosis type 1 (NF1) are predisposed to certain cancers including juvenile chronic myelogenous leukaemia (JCML). The NF1 tumour-suppressor gene encodes a protein (neurofibromin) that accelerates GTP hydrolysis on Ras proteins. Here we show that primary leukaemic cells from children with NF1 show a selective decrease in NF1-like GTPase activating protein (GAP) activity for Ras but retain normal cellular GAP activity. Leukaemic cells also show an elevated percentage of Ras in the GTP-bound conformation. JCML cells are hypersensitive to granulocyte-macrophage colony stimulating factor (GM-CSF), and we observed a similar pattern of aberrant growth in haematopoietic cells from Nf1-/- mouse embryos. These data define a specific role for neurofibromin in negatively regulating GM-CSF signaling through Ras in haematopoietic cells and they suggest that hypersensitivity to GM-CSF may be a primary event in the development of JCML.

Interactions between quantitative trait loci in soybean in which trait variation at one locus is conditional upon a specific allele at another

A large recombinant inbred population of soybean has been characterized for 220 restriction fragment-length polymorphism (RFLP) markers. Values for agronomic traits also have been measured. Quantitative trait loci (QTL) for height, yield, and maturity were located by their linkage to RFLP markers. QTL controlling large amounts of trait variation were analyzed for the dependence of trait variation on particular alleles at a second locus by comparing cumulative distributions of the trait for each genotype (four genotypes per pair of loci). Interesting pairs of loci were analyzed statistically with maximum likelihood and Monte Carlo comparison of additive and epistatic models. For each locus affecting height, variation was conditional upon the presence of a particular allele at a second unlinked locus that itself explained little or no trait variation. The results show that interactions between QTL are frequent and control large effects. Interactions distinguished between different QTL in a single linkage group and between QTL that affect different traits closely linked to one RFLP marker--i.e., distinguished between pleiotropy and closely linked genes. The implications for the evolution of inbreeding plants and for the construction of agronomic breeding strategies are discussed.

Aggregated distributions in models for patchy populations

We investigate a model describing immigration, birth, and death of parasites on a dynamic host population. The model can also be interpreted as describing a herbivore population distributed on discrete patches of vegetation. We derive differential equations for the total number of hosts/patches and the mean number of parasites/herbivores per host/patch. The equations explicitly involve the variance-to-mean ratio of the distribution. It is shown that the positive equilibrium is stable if and only if the variance-to-mean ratio as a function of the mean increases with increasing mean. Thus aggregation of the parasites alone is not sufficient to stabilize the system; it is rather the density-dependent increase in parasite mortality due to a higher aggregation at higher mean parasite loads that causes stability. From this it follows that introducing a distribution with a constant clumping parameter into the model artificially stabilizes the steady state. We derive a three-dimensional model based on an assumption about the form of the distribution of the parasites on the hosts, but without introducing additional parameters into the model. We compare stability results for this model for different types of aggregated distributions and show that the underlying distribution determines the qualitative results about the stability of the equilibrium.

The effects of averaging on the basic reproduction ratio

This paper formalizes the process of averaging the mixing patterns of behaviorally distinct individuals or groups. This averaging process is shown to decrease or leave unaltered the basic reproduction ratio R0 in epidemiological models with symmetric transmission between groups.

Aggregation and stability in parasite-host models

This paper generalizes the two-dimensional approximation of models of macroparasites on homogeneous populations developed by Anderson & May (1978), focusing on how the dispersion (the variance to mean ratio) of the equilibrium distribution of parasites on hosts is related to the stability of the equilibrium. We show in the approximate system that the equilibrium is stabilized not by aggregation, but by dispersion which increases as a function of the mean. Computer simulations indicate, however, that this analysis fails to capture properly the dynamics of the full system, raising the question of whether any two-dimensional system could produce an adequate approximation. We discuss the relevance of our results to several empirical studies which have examined teh relation of dispersion to the mean.

The dynamics of simultaneous infections with altered susceptibilities

We describe a model in which individuals can be infected simultaneously by multiple diseases or parasites, taking into account the fact that individuals already infected by a subset of n co-circulating diseases may see their susceptibility to concurrent infection by another disease from the pool either enhanced or reduced. We propose an n-dimensional approximation to the 2n dimensional model required to describe the dynamics of each possible subset of the pool of n co-circulating diseases, using as state variables the overall prevalence of each infection. Analysis of the two disease case shows that the reduced model provides a very good approximation throughout the full dynamics for small alterations of susceptibility, and, after a transient error, a good approximation to the complete model when susceptibilities are highly enhanced. As the number of diseases becomes large, the approximation remains close for small alterations of susceptibility.

Population variation in tooth, jaw, and root size: a radiographic study of two populations in a high-attrition environment

Radiographs were taken of the jaws of skeletal remains of two populations of different-phenotype Prehistoric Australians from Roonka and Early New Zealanders (Maoris). On these radiographs crown, root, and corpus size were measured. Corpus height was subdivided into alveolar bone height, defined as the bone superior to the mandibular canal, and basal bone height, defined as that inferior to the mandibular canal. Both between and within the two populations there was a significant and negative correlation between crown size and corpus height. The differences between the two populations in corpus height were associated with differences in alveolar bone height rather than basal bone height and support hypotheses associating continued eruption of adult teeth with growth of the alveolar bone. The findings also support previous studies that have shown only a low correlation between crown size, root size, and corpus height.

[Therapeutic transfemoral testicular vein occlusion of varicocele]

It is reported on the percutaneous transfemoral obliteration of the testicular vein with ethoxysclerol. This method was used in 75 patients for the treatment of the varicocele. 81.3% could successfully be treated by this means. The applicability of the method is restricted by anatomical particularities in the course of the testicular vein. Advantages and disadvantages of the method are discussed.

Post-pleistocene changes in tooth root and jaw relationships

Mandibles of 126 sexed skeletal specimens, from Near Eastern sites dating over the past 12,000 years were radiographed. From the radiographs obtained, digitised tracings were made of crown length (mesiodistal), root height and width, and corpus height mesial to the premolars and first and second molars. The data obtained were analysed using rank transformation procedures. The significance of unidirectional trends in relation to periods sampled was examined graphically and analytically through linear regression analysis of the ranks on the chronological scale, and Spearman's rank correlation was used to compare relationships between different parameters of individual teeth in different periods. Significant reduction was found in crown length between 12,000 B.P. and 6,000 B.P., but no further reduction was found between 6,000 B.P. and 1,000 B.P. Little change was observed in root size, but corpus height showed significant reduction over the past 6,000 years. The differences observed in the timing and extent of reduction in crown, root, and corpus height are associated with a low intrapopulation correlation between them.

[Varicocele and fertility--spermiographic and histologic findings]

The results of the treatment of 251 patients with varicocele are demonstrated. By means of spermiographic and histologic investigations the fertility-disturbing influence of this vascular disease of the testis shall be proved and the effect of the operative sanation shall be estimated. For many years the high ligature of the testicular vein has been favoured method of operation; since 1984 exclusively the percutaneous transfemoral occlusion of the testicular vein has been performed, when a left-sided varicocele is present. In 61% of the patients examined an improvement of the spermiogram is to be proved, in which case the most conspicuous rate of increase lies at the motility of spermatozoa with 58%. After removal if the varicocele the investigations of the testicular tissue reveal in 42% of the cases an improvement of the findings by decrease of the tubular atrophy and increase of the tubular cell number. Among the number of our patients the rate of conception is 49%. The treatment of varicocele is a fertility-protective measure and therefore should be performed in all adolescents and males at fertile age.

Hemangiomas of the cecum. Colonoscopic diagnosis and therapy

Five cases of hemangiomas of the cecum and gastrointestinal bleeding are presented. All were demonstrated by colonscopy after more conventional diagnostic methods failed. The hemangiomas were bright red, flat lesions clearly seen through the colonscope. They were successfully treated by electrocoagulation. All patients in this series had some type of associated cardiac or vascular disease. These patients may represent a syndrome of gastrointestinal blood loss of obscure cause, hemangiomas of the cecum, and cardiovascular disease.

New technics in the operative treatment of scoliosis

Preoperative correction of scoliotic curves by traction and casting improves the results achieved by operation. Use of the halo-hoop apparatus allows controlled correction when combined with spinal osteotomies. The anterior approach to the spine allows better correction and fusion of the more difficult curves of congenital scoliosis and those associated with neurofibromatosis and myelomeningocele.