Partial differential equation models for invasive species spread in the presence of spatial heterogeneity

Models of invasive species spread often assume that landscapes are spatially homogeneous; thus simplifying analysis but potentially reducing accuracy. We extend a recently developed partial differential equation model for invasive conifer spread to account for spatial heterogeneity in parameter values and introduce a method to obtain key outputs (e.g. spread rates) from computational simulations. Simulations produce patterns of spatial spread which appear qualitatively similar to observed patterns in grassland ecosystems invaded by exotic conifers, validating our spatially explicit strategy. We find that incorporating spatial variation in different parameters does not significantly affect the evolution of invasions (which are characterised by a long quiescent period followed by rapid evolution towards to a constant rate of invasion) but that distributional assumptions can have a significant impact on the spread rate of invasions. Our work demonstrates that spatial variation in site-suitability or other parameters can have a significant impact on invasions and must be considered when designing models of invasive species spread.

The Association of α Angle on Disease Severity in Adolescent Femoroacetabular Impingement

BACKGROUND

Femoroacetabular Impingement (FAI) is a common cause of hip pain in adolescent patients. Clinical exam and radiographic markers, such as α angle and lateral center edge angle (LCEA), are commonly used to aid in the diagnosis of this condition. The purpose of this study was to correlate preoperative α angle and LCEA with preoperative symptoms, intraoperative findings, and preoperative and postoperative patient reported outcomes (PROs) in the adolescent patient.

METHODS

A retrospective analysis of prospectively collected data was conducted for all patients who underwent operative intervention for FAI at an academic institution over an 11-year period. Preoperative imaging was obtained and measured for LCEA and α angle. PROs (modified Harris Hip Score, Hip Disability and Osteoarthritis Outcome Score, and UCLA score) were collected preoperatively, as well as 1, 2, and 5 years postoperatively. Operative intervention was either open surgical hip dislocation or arthroscopic, and intraoperative disease was graded using the Beck Classification system. Patients with minimum 1-year follow-up were included in statistical analysis.

RESULTS

There were 86 hips (64 female hips) included with an average age of 16.3 years (range, 10.4 to 20.5 y), with an average of 37 months of follow-up. There was no correlation between severity of preoperative symptoms or difference between pre and postoperative PROs for both α angle and LCEA. Overall, significant improvement was noted in modified Harris Hip Score, Hip Disability and Osteoarthritis Outcome Score, and UCLA Score (P<0.001 for each). Independent of preoperative symptoms, increased α angle correlated with more severe intraoperative labral disease (P<0.001), and longer length of labral tear (Corr 0.295, P<0.01). Femoral head and acetabular articular cartilage damage did not correlate with α angle or LCEA, nor did overall severity of disease.

CONCLUSIONS

In adolescent patients with FAI, increased α angle was found to significantly correlate with labral pathology, including increased length of tear and severity of disease, irrespective of preoperative symptoms or postoperative patient reported outcomes.

LEVEL OF EVIDENCE

Level III-retrospective.

A mathematical model of the metabolic and perfusion effects on cortical spreading depression

Cortical spreading depression (CSD) is a slow-moving ionic and metabolic disturbance that propagates in cortical brain tissue. In addition to massive cellular depolarizations, CSD also involves significant changes in perfusion and metabolism-aspects of CSD that had not been modeled and are important to traumatic brain injury, subarachnoid hemorrhage, stroke, and migraine. In this study, we develop a mathematical model for CSD where we focus on modeling the features essential to understanding the implications of neurovascular coupling during CSD. In our model, the sodium-potassium-ATPase, mainly responsible for ionic homeostasis and active during CSD, operates at a rate that is dependent on the supply of oxygen. The supply of oxygen is determined by modeling blood flow through a lumped vascular tree with an effective local vessel radius that is controlled by the extracellular potassium concentration. We show that during CSD, the metabolic demands of the cortex exceed the physiological limits placed on oxygen delivery, regardless of vascular constriction or dilation. However, vasoconstriction and vasodilation play important roles in the propagation of CSD and its recovery. Our model replicates the qualitative and quantitative behavior of CSD--vasoconstriction, oxygen depletion, extracellular potassium elevation, prolonged depolarization--found in experimental studies. We predict faster, longer duration CSD in vivo than in vitro due to the contribution of the vasculature. Our results also help explain some of the variability of CSD between species and even within the same animal. These results have clinical and translational implications, as they allow for more precise in vitro, in vivo, and in silico exploration of a phenomenon broadly relevant to neurological disease.

Fluid-body interactions: clashing, skimming, bouncing

Solid-solid and solid-fluid impacts and bouncing are the concern here. A theoretical study is presented on fluid-body interaction in which the motion of the body and the fluid influence each other nonlinearly. There could also be many bodies involved. The clashing refers to solid-solid impacts arising from fluid-body interaction in a channel, while the skimming refers to another area where a thin body impacts obliquely upon a fluid surface. Bouncing usually then follows in both areas. The main new contribution concerns the influences of thickness and camber which lead to a different and more general form of clashing and hence bouncing.

Paroxysmal intracranial hypertension

We present the case of a man who presented with headache and severe papilloedema which was caused not by chronic intracranial hypertension but by paroxysms of raised intracranial pressure, and we speculate what relationship this disorder has to idiopathic intracranial hypertension.

The Human Genome Project: an update

The mapping, sequencing, and analysis of the human genome that has occurred during the last decade through the Human Genome Project are providing fundamental advances for basic science and medicine. Genomic information is providing insights into causes of, susceptibility to, and protection from cancer and a host of other diseases. Already, information generated by the Human Genome Project has been incorporated into the care of cancer patients. Perhaps more so than other types of medical information, genetic knowledge can have profound implications for individuals, families, and society. As a result, nursing professionals in clinical and academic settings are being called upon to identify and deliberate medical, social, ethical, and legal issues stemming from Human Genome Project advancements. The purpose of this article is to review the goals and implications of the Human Genome Project to further prepare cancer nurses to actively participate in the deliberations, research, and clinical activities evolving from the Human Genome Project.

Maintenance of bone density: outcomes over five years of attendance at an osteoporosis center

BACKGROUND

This is a longitudinal analysis of the data from women who visited the Osteoporosis Prevention Center for at least five years. The study is part of an ongoing evaluation of the results of the Center visits.

METHODS

A random sample of 100 women who had attended the clinic for more than five years and were not referred for a definite medical diagnosis was pulled from the records. Descriptive statistics were compiled on this sample. Seventy-five women were postmenopausal and over 49 years of age. This subgroup was studied for change in bone mineral density (BMD) over the five years.

RESULTS

The BMD change was 0.03 gm/cm2 in the spine, -0.01 gm/cm2 in the femoral-neck. and -0.008 gm/cm2 at the radius over the five years.

CONCLUSION

Attendance at the Osteoporosis Prevention Center was associated with maintenance of bone density in the spine over a five-year period.

Cerumen management: professional issues and techniques

Cerumen management is now within the scope of practice for audiologists. This paper describes the knowledge and skills required to perform cerumen management safely and effectively. Procedures for mechanical removal, suction, and irrigation are provided.

Osteoporosis. It steals more than bone

Research shows that osteoporotic fractures all too often cause an irreversible decline in the quality of life. To help these patients, here's what you need to know about primary and secondary prevention.

Callier Center for Communication Disorders, University of Texas at Dallas

The Callier Center offers a wide variety of services for those with communication disorders, as well as programs for research and academic training. Bringing together clinical and research specialists from a variety of related disciplines, Callier affords an unusual opportunity for interdisciplinary clinical programs, research, and enriched student training.

Tumor proliferative fraction in solid malignant neoplasms. A comparative study of Ki-67 immunostaining and flow cytometric determinations

Tumor proliferative fraction (TPF) has been shown to correlate with prognosis in some malignancies. A method for its determination that is practical, accurate, and reproducible is still being sought. In this comparative study of techniques, TPF values were determined in mirror-image samples of 126 consecutive solid malignant neoplasms using flow cytometry and immunostaining with Ki-67, a monoclonal antibody that recognizes an unknown nuclear antigen expressed during the entire cell proliferation cycle but not in resting cells. The mean TPF values for all cases were 19.5 +/- 15.6% (percentage of tumor cells stained) by Ki-67 (range, 1-86%) and 15.7 +/- 9.6% (S + G2M) by flow cytometry (range, 3-60%), which correlated significantly at r = 0.53 and P = 0.005. The correlation was less strong in tumors with low S-phase values (less than or equal to 10%, r = 0.28) than in tumors with intermediate and high S-phase values (r = 0.66). Ki-67 staining percentages did not correlate with patient age, sex, or tissue origin of the tumor. Ki-67 staining appears comparable to flow cytometry determination of TPF in solid malignancies with intermediate and high S-phase values. In tumors with low S-phase values, Ki-67 immunostaining shows higher TPF values, which perhaps reflect an increase in the proportion of G1-phase cells or dilutional effect of nonneoplastic cells in the tumors with low proliferative fraction.

Determinants of susceptibility and resistance to feline leukemia virus infection. I. Role of macrophages

The role of autochthonous peritoneal feline macrophages (Mθ) in the age-related resistance of cats to feline leukemia virus (FeLV) was investigated by a study of the functional properties and FeLV susceptibility of Mθ from kittens and adult cats and the effect of hydrocortisone (HC) and silica on Mθ-FeLV interactions. Although the phagocytic functions of isolated Mθ from kittens and adults were equivalent, the mean FeLV susceptibility of Mθ from kittens was five times that of Mθ from adult cats, thus establishing a direct correlation between the age-related susceptibility of cats and Mθ from cats to FeLV. Mθ of viremic cats were found to be infected with FeLV in vivo; virus titers were slightly higher than those obtained after in vitro infection of Mθ. Mθ from cats that had experienced regressive FeLV infection were not significantly more resistant to FeLV infection in vitro than were Mθ from naive adult specific-pathogen-free cats. HC, which has been shown to enhance the in vivo FeLV susceptibility of cats, also enhanced the permissiveness of Mθ from cats to FeLV in vitro (600-fold for Mθ from adult cats and 200-fold for Mθ) from kittens. Mθ permissiveness to FeLV was highly sensitive to HC and occurred in Mθ infected in vivo or in vitro. In parallel with the effect of HC on the natural resistance of cats to FeLV, administration of silica before virus inoculation also markedly enhanced the FeLV susceptibility of adult cats. Silica was toxic for isolated Mθ but not for lymphocytes in vitro, and silica produced monocytopenia and neutrophilia, delayed skin allograft rejection, and augmented feline oncovirus-associated cell membrane antigen antibody responses in vivo. These experiments indicate that Mθ were linked to the natural resistance of cats to FeLV and that the temporary elimination of Mθ functions (e.g., by silica) and/or the conversion of the Mθ-FeLV relationship from a nonpermissive to a permissive state (e.g., by corticosteroids) resulted in failure of early virus containment, in persistent virus amplification in hemolymphatic tissues, and in subsequent FeLV-related proliferative or antiproliferative disease.

Obstetric use of continuous epidural block in a private community hospital: review of 500 cases

Five hundred consecutive births in which continuous lumbar epidural block was used for analgesia were reviewed retrospectively. We wished to evaluate the safety and practicality of this anesthetic technic as done by practicing obstetricians in a predominantly private practice. Although many of the results confirmed those of previous studies, the most important findings were than the cesarean section rate was no higher than in the total obstetric population during the study period and that there was a high incidence of forceps usage in patients who had epidural analgesia. There was no maternal mortality, low maternal morbidity, and complications were not serious. Perinatal morbidity was not increased despite the high incidence of forceps deliveries. Continuous lumbar epidural analgesia was shown to be an effective and safe anesthetic technic for use by practicing obstetricians.