Showing papers by "University of Washington published in 1990"
TL;DR: In this paper, the authors have been observing for more than three decades that business performance is affected by market orientation, yet to date there has been no valid measure of market orientation.
Abstract: Marketing academicians and practitioners have been observing for more than three decades that business performance is affected by market orientation, yet to date there has been no valid measure of ...
8,812 citations
TL;DR: The total number of foveal cones is similar for eyes with widely varying peak cone density, consistent with the idea that the variability reflects differences in the lateral migration of photoreceptors during development.
Abstract: We have measured the spatial density of cones and rods in eight whole-mounted human retinas, obtained from seven individuals between 27 and 44 years of age, and constructed maps of photoreceptor density and between-individual variability. The average human retina contains 4.6 million cones (4.08-5.29 million). Peak foveal cone density averages 199,000 cones/mm2 and is highly variable between individuals (100,000-324,000 cones/mm2). The point of highest density may be found in an area as large as 0.032 deg2. Cone density falls steeply with increasing eccentricity and is an order of magnitude lower 1 mm away from the foveal center. Superimposed on this gradient is a streak of high cone density along the horizontal meridian. At equivalent eccentricities, cone density is 40-45% higher in nasal compared to temporal retina and slightly higher in midperipheral inferior compared to superior retina. Cone density also increases slightly in far nasal retina. The average human retina contains 92 million rods (77.9-107.3 million). In the fovea, the average horizontal diameter of the rod-free zone is 0.350 mm (1.25 degrees). Foveal rod density increases most rapidly superiorly and least rapidly nasally. The highest rod densities are located along an elliptical ring at the eccentricity of the optic disk and extending into nasal retina with the point of highest density typically in superior retina (5/6 eyes). Rod densities decrease by 15-25% where the ring crosses the horizontal meridian. Rod density declines slowly from the rod ring to the far periphery and is highest in nasal and superior retina. Individual variability in photoreceptor density differs with retinal region and is similar for both cones and rods. Variability is highest near the fovea, reaches a minimum in the midperiphery, and then increases with eccentricity to the ora serrata. The total number of foveal cones is similar for eyes with widely varying peak cone density, consistent with the idea that the variability reflects differences in the lateral migration of photoreceptors during development. Two fellow eyes had cone and rod numbers within 8% and similar but not identical photoreceptor topography.
2,471 citations
TL;DR: It is proposed that HLH proteins lacking a basic region may negatively regulate other HLHprotein through the formation of nonfunctional heterodimeric complexes.
2,203 citations
TL;DR: In men with coronary artery disease who were at high risk for cardiovascular events, intensive lipid-lowering therapy reduced the frequency of progression of coronary lesions, increased the frequencyof regression, and reduced the incidence of cardiovascular events.
Abstract: Background and Methods. The effect of intensive lipid-lowering therapy on coronary atherosclerosis among men at high risk for cardiovascular events was assessed by quantitative arteriography. Of 146 men no more than 62 years of age who had apolipoprotein B levels ≥125 mg per deciliter, documented coronary artery disease, and a family history of vascular disease, 120 completed the 2 1/2-year double-blind study, which included arteriography at base line and after treatment. Patients were given dietary counseling and were randomly assigned to one of three treatments: lovastatin (20 mg twice a day) and colestipol (10 g three times a day); niacin (1 g four times a day) and colestipol (10 g three times a day); or conventional therapy with placebo (or colestipol if the low-density lipoprotein [LDL] cholesterol level was elevated). Results. The levels of LDL and high-density lipoprotein (HDL) cholesterol changed only slightly in the conventional-therapy group (mean changes, −7 and +5 percent, respectivel...
2,195 citations
TL;DR: This model indicates that there may be widely different hormonal responses to male-male and male-female interactions and presumably equally plastic neural mechanisms for the transduction of these signals into endocrine secretions.
Abstract: A combination of field and laboratory investigations has revealed that the temporal patterns of testosterone (T) levels in blood can vary markedly among populations and individuals, and even within individuals from one year to the next. Although T is known to regulate reproductive behavior (both sexual and aggressive) and thus could be expected to correlate with mating systems, it is clear that the absolute levels of T in blood are not always indicative of reproductive state. Rather, the pattern and amplitude of change in T levels are far more useful in making predictions about the hormonal basis of mating systems and breeding strategies. In these contexts we present a model that compares the amplitude of change in T level with the degree of parental care shown by individual males. On the basis of data collected from male birds breeding in natural or captive conditions, polygynous males appear less responsive to social environmental cues than are monogamous males. This model indicates that there may be wi...
2,098 citations
TL;DR: The spatial distribution of presumed ganglion cells and displaced amacrine cells in unstained whole mounts of six young normal human retinas whose photoreceptor distributions had previously been characterized was quantified, suggesting meridianal differences in convergence onto individual ganglION cells.
Abstract: We quantified the spatial distribution of presumed ganglion cells and displaced amacrine cells in unstained whole mounts of six young normal human retinas whose photoreceptor distributions had previously been characterized. Cells with large somata compared to their nuclei were considered ganglion cells; cells with small somata relative to their nuclei were considered displaced amacrine cells. Within the central area, ganglion cell densities reach 32,000-38,000 cells/mm2 in a horizontally oriented elliptical ring 0.4-2.0 mm from the foveal center. In peripheral retina, densities in nasal retina exceed those at corresponding eccentricities in temporal retina by more than 300%; superior exceeds inferior by 60%. Displaced amacrine cells represented 3% of the total cells in central retina and nearly 80% in the far periphery. A twofold range in the total number of ganglion cells (0.7 to 1.5 million) was largely explained by a similar range in ganglion cell density in different eyes. Cone and ganglion cell number were not correlated, and the overall cone:ganglion cell ratio ranged from 2.9 to 7.5 in different eyes. Peripheral cones and ganglion cells have different topographies, thus suggesting meridianal differences in convergence onto individual ganglion cells. Low convergence of foveal cones onto individual ganglion cells is an important mechanism for preserving high resolution at later stages of neural processing. Our improved estimates for the density of central ganglion cells allowed us to ask whether there are enough ganglion cells for each cone at the foveal center to have a direct line to the brain. Our calculations indicate that 1) there are so many ganglion cells relative to cones that a ratio of only one ganglion cell per foveal cone would require fibers of Henle radiating toward rather than away from the foveal center; and 2) like the macaque, the human retina may have enough ganglion cells to transmit the information afforded by closely spaced foveal cones to both ON- and OFF-channels. Comparison of ganglion cell topography with the visual field representation in V1 reveals similarities consistent with the idea that cortical magnification is proportional to ganglion cell density throughout the visual field.
1,653 citations
TL;DR: Reflexions sur les relations entre l'Etat et la presse ou les presse d'España aux Etats-Unis, a partir de l'exemple du « New York Times » sur la politique au Nicaragua
Abstract: Reflexions sur les relations entre l'Etat et la presse ou la presse d'Etat aux Etats-Unis, a partir de l'exemple du « New York Times » sur la politique au Nicaragua
1,570 citations
TL;DR: In vivo administration of SCF can reverse the macrocytic anemia and locally repair the mast cell deficiency of Sl/Sld mice and provide biological and physical evidence that SCF is a ligand for the c-kit receptor.
1,485 citations
TL;DR: Defining causal pathways that predispose to diabetic limb amputation suggests practical interventions that may be effective in preventing diabetic limb loss.
Abstract: We defined the causal pathways responsible for 80 consecutive initial lower-extremity amputations to an extremity in diabetic patients at the Seattle Veterans Affairs Medical Center over a 30-mo interval from 1984 to 1987. Causal pathways, either unitary or composed of various combinations of seven potential causes (i.e., ischemia, infection, neuropathy, faulty wound healing, minor trauma, cutaneous ulceration, gangrene), were determined empirically after a synthesis by the investigators of various objective and subjective data. Estimates of the proportion of amputations that could be ascribed to each component cause were calculated. Twenty-three unique causal pathways to diabetic limb amputation were identified. Eight frequent constellations of component causes resulted in 73% of the amputations. Most pathways were composed of multiple causes, with only critical ischemia from acute arterial occlusions responsible for amputations as a singular cause. The causal sequence of minor trauma, cutaneous ulceration, and wound-healing failure applied to 72% of the amputations, often with the additional association of infection and gangrene. We specified precise criteria in the definition of causal pathway to permit estimation of the cumulative proportion of amputations due to various causes. Forty-six percent of the amputations were attributed to ischemia, 59% to infection, 61% to neuropathy, 81% to faulty wound healing, 84% to ulceration, 55% to gangrene, and 81% to initial minor trauma. An identifiable and potentially preventable pivotal event, in most cases an episode involving minor trauma that caused cutaneous injury, preceded 69 to 80 amputations. Defining causal pathways that predispose to diabetic limb amputation suggests practical interventions that may be effective in preventing diabetic limb loss.
1,465 citations
TL;DR: In this article, a general algorithm for constructing coherent states of dynamical groups for a given quantum physical system is presented, and the result is that the coherent states are isomorphic to a coset space of group geometrical space.
Abstract: In this review, a general algorithm for constructing coherent states of dynamical groups for a given quantum physical system is presented. The result is that, for a given dynamical group, the coherent states are isomorphic to a coset space of group geometrical space. Thus the topological and algebraic structure of the coherent states as well as the associated dynamical system can be extensively discussed. In addition, a quantum-mechanical phase-space representation is constructed via the coherent-state theory. Several useful methods for employing the coherent states to study the physical phenomena of quantum-dynamic systems, such as the path integral, variational principle, classical limit, and thermodynamic limit of quantum mechanics, are described.
1,354 citations
TL;DR: Cell adhesion by ELAM-1 is shown to be mediated by a carbohydrate ligand, sialyl-Lewis X (SLex; NeuAc alpha 2,3Gal beta 1,4(Fuc alpha 1,3)-GlcNAc-), a terminal structure found on cell-surface glycoprotein and glycolipid carbohydrate groups of neutrophils.
Abstract: Recruitment of neutrophils to sites of inflammation is mediated in part by endothelial leukocyte adhesion molecule-1 (ELAM-1), which is expressed on activated endothelial cells of the blood vessel walls. ELAM-1 is a member of the LEC-CAM or selectin family of adhesion molecules that contain a lectin motif thought to recognize carbohydrate ligands. In this report, cell adhesion by ELAM-1 is shown to be mediated by a carbohydrate ligand, sialyl-Lewis X (SLex; NeuAc alpha 2,3Gal beta 1,4(Fuc alpha 1,3)-GlcNAc-), a terminal structure found on cell-surface glycoprotein and glycolipid carbohydrate groups of neutrophils.
TL;DR: In this paper, the authors argue that the nature of the trade-offs among manufacturing capabilities is more complex than has been assumed, and they suggest a model which shows how this can be done: to build cumulative and lasting manufacturing capability, management attention and resources should go first toward enhancing quality, then, while the efforts to enhance quality are further expanded, attention should be paid to improve also the dependability of the production system, and finally, while efforts on the previous two are further enhanced, production flexibility (or reaction speed).
TL;DR: It is argued that a firm's choice of entry mode depends on the strategic relationship the firm envisages between operations in different countries, and that resolving these differences involves accepting trade-offs.
Abstract: The choice of entry mode into a foreign market has a major impact on the success of a firm's international operations. However, the existing literature on the entry mode decision has either presented a list of considerations without identifying underlying constructs, or treated each entry decision in isolation. Here, a unifying framework is developed. This framework identifies three underlying constructs that influence the entry mode decision. These constructs are linked to considerations that have been previously discussed in the literature. It is argued that a firm's choice of entry mode depends on the strategic relationship the firm envisages between operations in different countries. A particular entry decision cannot be viewed in isolation. It must be considered in relation to the overall strategic posture of the firm. Further, the paper argues that different variables often suggest different entry modes, and that resolving these differences involves accepting trade-offs.
University of California, San Francisco1, Harvard University2, RTI International3, National Institutes of Health4, University of Minnesota5, University of Rochester6, Duke University7, Northwestern University8, Yeshiva University9, University of Miami10, Johns Hopkins University11, Stanford University12, Tulane University13, United States Department of Veterans Affairs14, New York University15, University of Washington16
TL;DR: Zidovudine is safe and effective in persons with asymptomatic HIV infection and fewer than 500 CD4+ cells per cubic millimeter and additional study will be required to determine whether such treatment will ultimately improve survival for persons infected with HIV.
Abstract: Zidovudine (AZT) is a potent inhibitor of the replication of the human immunodeficiency virus (HIV), and it has been shown to improve survival in advanced HIV disease. We conducted a randomized, double-blind trial in adults with asymptomatic HIV infection who had CD4+ cell counts of fewer than 500 per cubic millimeter on entry into the study. The subjects (92 percent male) were randomly assigned to one of three treatment groups: placebo (428 subjects); zidovudine, 500 mg per day (453); or zidovudine, 1500 mg per day (457). After a mean follow-up of 55 weeks (range, 19 to 107), 33 of the subjects assigned to placebo had the acquired immunodeficiency syndrome (AIDS), as compared with 11 of those assigned to receive 500 mg of zidovudine (P = 0.002; relative risk, 2.8; 95 percent confidence interval, 1.4 to 5.6) and 14 of those assigned to receive 1500 mg of zidovudine (P = 0.05; relative risk, 1.9; 95 percent confidence interval, 1.0 to 3.5). In the three treatment groups, the rates of progression (per 100 person-years) to either AIDS or advanced AIDS-related complex were 7.6, 3.6, and 4.3, respectively. As compared with those assigned to placebo, the subjects in the zidovudine groups had significant increases in the number of CD4+ cells and significant declines in p24 antigen levels. In the 1500-mg zidovudine group, severe hematologic toxicity (anemia or neutropenia) was more frequent than in the other groups (P less than 0.0001). In the 500-mg zidovudine group, nausea was the only toxicity that was significantly more frequent (in 3.3 percent) than in the placebo group (P = 0.001). We conclude that zidovudine is safe and effective in persons with asymptomatic HIV infection and fewer than 500 CD4+ cells per cubic millimeter. Additional study will be required to determine whether such treatment will ultimately improve survival for persons infected with HIV.
TL;DR: A critical single-base deletion was found in the 0 gene, which results in an entirely different, inactive protein incapable of modifying the H antigen, and this work presents a molecular basis for the ABO genotypes.
Abstract: The histo-blood group ABO, the major human alloantigen system, involves three carbohydrate antigens (ABH). A, B and AB individuals express glycosyltransferase activities converting the H antigen into A or B antigens, whereas O(H) individuals lack such activity. Here we present a molecular basis for the ABO genotypes. The A and B genes differ in a few single-base substitutions, changing four amino-acid residues that may cause differences in A and B transferase specificity. A critical single-base deletion was found in the O gene, which results in an entirely different, inactive protein incapable of modifying the H antigen.
TL;DR: In this paper, a set of n independent subjects such that the counting process Ni {Ni(t), t } O} for the ith subject in the set indicates the number of observed events experienced over time t. The sample paths of the Ni are step functions with jumps of size +1 and with Ni(0) = 0.
Abstract: SUMMARY Graphical methods based on the analysis of residuals are considered for the setting of the highly-used Cox (1972) regression model and for the Andersen-Gill (1982) generalization of that model. We start with a class of martingale-based residuals as proposed by Barlow & Prentice (1988). These residuals and/or their transforms are useful for investigating the functional form of a covariate, the proportional hazards assumption, the leverage of each subject upon the estimates of 13, and the lack of model fit to a given subject. 1 1. Model Consider a set of n independent subjects such that the counting process Ni {Ni(t), t } O} for the ith subject in the set indicates the number of observed events experienced over time t. The sample paths of the Ni are step functions with jumps of size +1 and with Ni(0) =0. We assume that the intensity function for Ni(t) is given by Yi(t)dA{t, Zi(t)} = Yi(t) eP'Z(t) dAO(t), (1) where Yi(t) is a 0-1 process indicating whether the ith subject is a risk at time t, 13 is a vector of regression coefficients, Zi(t) is a p dimensional vector of covariate processes, and Ao is the baseline cumulative hazard function. Several familar survival models fit into this framework. The Andersen & Gill (1982) generalization of the Cox (1972) model arises when AO(t) is completely unspecified. The further restriction that Yi(t) = 1 until the first event or censoring, and is 0 thereafter yields the Cox model. The parametric form AO(t) = t yields a Poisson model, or an exponential if restricted to a single event per subject, and AO(t) = tP a Weibull model. Our attention will focus primarily on the Andersen-Gill and Cox models; however, the
TL;DR: The results are discussed in relation to the potential for minor parenting stresses to influence microsocial processes within parent-child relationships and contribute to dysfunction in children and families.
Abstract: The importance of major life stress and minor daily hassles associated with parenting was studied in 74 mothers and their 5-year-old children. Of interest were the relative and absolute contributions of the stress factors to indices of parental, child, and family functioning. Mothers completed questionnaires regarding stressors, aspects of parenting and individual psychological status, social support, family functioning, and child behavioral status. Mother-child pairs were also observed in interactions in a laboratory setting. Analyses indicated that life stress and parenting daily hassles significantly predicted aspects of child, parent, and family status. Hassles, however, proved to be a more powerful stress construct. Further analyses indicated that mothers' social support moderated the influence of hassles on indices of maternal behavior. The results are discussed in relation to the potential for minor parenting stresses to influence microsocial processes within parent-child relationships and contribute to dysfunction in children and families.
TL;DR: It is demonstrated that MAP kinase is only active when both tyrosyl and threonyl residues are phosphorylated and suggested therefore that the enzyme functions in vivo to integrate signals from two distinct transduction pathways.
Abstract: MAP kinase (relative molecular mass, 42,000), a low abundance serine--threonine protein kinase, is transiently activated in many cell types by a variety of mitogens, including insulin, epidermal growth factor, and phorbol esters. In vitro, MAP kinase will phosphorylate and reactivate S6 kinase II previously inactivated by phosphatase treatment. Because many of the stimuli that activate MAP kinase are also stimulators of cell proliferation, and regulation of the cell cycle seems to involve a network of protein kinases, MAP kinase could be important in the transmission of stimuli eventually leading to the progression from G0 to G1 in the cell cycle. Activated MAP kinase contains both phosphotyrosine and phosphothreonine. We report here that MAP kinase can be deactivated completely by treatment with either phosphatase 2A, a protein phosphatase specific for phosphoserine and phosphothreonine, or CD45, a phosphotyrosine-specific protein phosphatase. We demonstrate that MAP kinase is only active when both tyrosyl and threonyl residues are phosphorylated and suggest therefore that the enzyme functions in vivo to integrate signals from two distinct transduction pathways.
TL;DR: Inadequate ventilation was used to describe claims in which it was evident that insufficient gas exchange had produced the adverse outcome, but it was not possible to identify the exact cause.
Abstract: Adverse outcomes associated with respiratory events constitute the single largest class of injury in the American Society of Anesthesiology Closed Claims Study (522 of 1541 cases; 34%). Death or brain damage occurred in 85% of cases. The median cost of settlement or jury award was +200,000. Most outcomes (72%) were considered preventable with better monitoring. Three mechanisms of injury accounted for three-fourths of the adverse respiratory events: inadequate ventilation (196; 38%), esophageal intubation (94; 18%), and difficult tracheal intubation (87; 17%). Inadequate ventilation was used to describe claims in which it was evident that insufficient gas exchange had produced the adverse outcome, but it was not possible to identify the exact cause. This group was characterized by the highest proportion of cases in which care was considered substandard (90%). The esophageal intubation group was notable for a recurring diagnostic failure: in 48% of cases where auscultation of breath sounds was performed and documented, this test led to the erroneous conclusion that the endotracheal tube was correctly located in the trachea. Claims for difficult tracheal intubation were distinguished by a comparatively small proportion of cases (36%) in which the outcome was considered preventable with better monitoring. A better understanding of respiratory risks may require investigative protocols that initiate data collection immediately upon the recognition of a critical incident or adverse outcome.
TL;DR: Much of the evidence that has led to the current understanding of multiple isozymes of phosphodiesterase is summarized, with emphasis on aspects that may be relevant to drug design.
TL;DR: It is speculated that early CPR permits definitive procedures, including defibrillation, medications, and intubation, to be more effective and hence survival appears to be highest in double-response systems because CPR is started early.
TL;DR: Clinical cases had more pain during all jaw excursions as well as during muscle and joint palpation, and joint clicking sounds were also observed more frequently in clinic cases.
Abstract: An epidemiologic study of clinical signs and symptoms of temporomandibular disorders (TMD) was conducted with a probability sample of adults enrolled in a major health maintenance organization (HMO). This report presents data from a first wave field examination and interview conducted by trained, calibrated dental hygienist field examiners. Significant gender differences for vertical jaw opening measures were observed but no significant age differences were found for the distribution of clinically relevant findings. Clinic cases showed smaller amounts of vertical range of jaw motion but did not differ from community cases or controls on extent of lateral, protrusive, or retrusive mandibular movements; on classification of occlusion; or on dentally related variables. Clinic cases had more pain during all jaw excursions as well as during muscle and joint palpation. Joint clicking sounds were also observed more frequently in clinic cases.
TL;DR: It is suggested that some of the biological functions of Myc family proteins are accomplished by sequence-specific DNA binding that is mediated by the carboxyl-terminal region of the protein.
Abstract: While it has been known for some time that the c-Myc protein binds to random DNA sequences, no sequence-specific binding activity has been detected. At its carboxyl terminus, c-Myc contains a basic--helix-loop-helix (bHLH) motif, which is important for dimerization and specific DNA binding, as demonstrated for other bHLH protein family members. Of those studied, most bHLH proteins bind to sites that contain a CA- -TG consensus. In this study, the technique of selected and amplified binding-sequence (SAAB) imprinting was used to identify a DNA sequence that was recognized by c-Myc. A purified carboxyl-terminal fragment of human c-Myc that contained the bHLH domain bound in vitro in a sequence-specific manner to the sequence, CACGTG. These results suggest that some of the biological functions of Myc family proteins are accomplished by sequence-specific DNA binding that is mediated by the carboxyl-terminal region of the protein.
TL;DR: Penytoin exerts a beneficial effect by reducing seizures only during the first week after severe head injury, and could not be attributed to differential mortality, low phenytoin levels, or treatment of some early seizures in patients assigned to the placebo group.
Abstract: Background. Antiepileptic drugs are commonly used to prevent seizures that may follow head trauma. However, previous controlled studies of this practice have been inconclusive. Methods. To study further the effectiveness of phenytoin (Dilantin) in preventing post-traumatic seizures, we randomly assigned 404 eligible patients with serious head trauma to treatment with phenytoin (n = 208) or placebo (n = 196) for one year in a double-blind fashion. An intravenous loading dose was given within 24 hours of injury. Serum levels of phenytoin were maintained in the high therapeutic range (3 to 6 μmol of free phenytoin per liter). Follow-up was continued for two years. The primary data analysis was performed according to the intention to treat. Results. Between drug loading and day 7, 3.6 percent of the patients assigned to phenytoin had seizures, as compared with 14.2 percent of patients assigned to placebo (P<0.001; risk ratio, 0.27; 95 percent confidence interval, 0.12 to 0.62). Between day 8 and the ...
TL;DR: In this paper, a new approach to automated analysis is designed to fill a gap in present flow-injection methodology, which is based on the random walk model and sequential injection analysis.
TL;DR: Chlamydia pneumoniae strain TWAR, the new third species of Chlamydia, is a common cause of pneumonia and other acute respiratory tract infections as mentioned in this paper, and about 10% of hospitalized and outpatient pneumonia cases have been associated with TWAR infection.
Abstract: Chlamydia pneumoniae strain TWAR, the new third species of Chlamydia, is a common cause of pneumonia and other acute respiratory tract infections. About 10% of hospitalized and outpatient pneumonia cases have been associated with TWAR infection. TWAR is among the four or five most commonly identified causes of all pneumonia. Most TWAR infections are mild or asymptomatic, but occasionally severe pneumonia with death has been observed. Laboratory diagnosis is not generally available. Vigorous treatment with tetracycline or erythromycin is recommended. Both epidemic and endemic infections have been described in North America and the Nordic Countries. Population prevalence antibody studies suggest that TWAR infection is wide-spread throughout the world, that nearly everyone is infected and reinfected during their life-time, and that infection is common in all ages except those less than 5 years in temperate zone countries. The infection is transmitted from person to person, apparently with a long incubation period.
TL;DR: There are several different ways of representing dispersal in spatially structured environments, as well as several possibilities for allowing environmental variation to come into play as mentioned in this paper, and the theoretical possibilities are thus contingent on spatial scale and dispersal rates.
Abstract: Population dynamics and species interactions are spread out in space. This might seem like a trivial observation, but it has potentially important consequences. In particular, mathematical models show that the dynamics of populations can be altered fundamentally simply because organisms interact and disperse rather than being confined to one position for their entire lives. Models that deal with dispersal and spatially distributed populations are extraordinarily varied, partly because they employ three distinct characterizations of space: as \`islands' (or \`metapopulations'), as `stepping-stones', or as a continuum. Moreover, there are several different ways of representing dispersal in spatially structured environments, as well as several possibilities for allowing environmental variation to come into play. In spite of this variety, a few common themes emerge from spatial models. First, island and stepping-stone models emphasize that little can be concluded from simply recording patterns of occupancy, instead a metapopulation's fate will be determined by the balance between local extinction and recolonization and how that balance interacts with random catastrophes. Island and stepping-stone models also make it clear that the spatial dimension, in particular spatial subdivision, can alter the stability of species interactions and opportunities for coexistence in both predator-prey and competitive systems. Continuum models, which usually take the form of reaction-diffusion equations, address slightly different questions. Reaction-diffusion theory suggests that in uniform environments, certain combinations of local dynamics and dispersal can produce persistent irregularities in the dispersion of species. These striking spatial patterns, which are called diffusive instabilities, can arise from predator-prey interactions, Lotka-Volterra competitive interactions, and from density-dependent population growth in an age-structured population. Moreover, although they differ fundamentally in their structure, the three major classes of spatial models share the common generalization that spatial effects should be expected only for: (i) selected spatial scales; (ii) specific dispersal rates, and (iii) particular patterns of environmental variation relative to the frequency and range of dispersal. The theoretical possibilities are thus contingent on spatial scale and dispersal rates. Although explicit experimental tests of spatial models are non-existent, a handful of studies report general changes in species interactions associated with manipulations of habitat subdivision. Observational studies with adequate data concerning dispersal and scale are also scarce; but those few observational studies with the appropriate supporting information consistently show profound spatial effects, especially effects due to habitat subdivision. The challenge for empiricists is to investigate more rigorously the roles of spatial subdivision and dispersal in natural communities. The challenge for theoreticians is to make the empiricist's job easier; this can best be done by delineating when spatial effects are most likely to be influential, and by offering guidance on how to design appropriate experiments. Simply saying that the spatial environment is important is to mouth a platitude: what we need to know is whether this presumed importance amounts to much in natural systems.
TL;DR: It is demonstrated that certain passive motions of theglenohumeral joint are reproducibly accompanied by translation of the head of the humerus on the glenoid, andative tightening of the posterior portion of the capsule increased the anterior translation on flexion and cross-body movement and caused it to occur earlier in the arc of motion compared with the intact glenohueral joint.
Abstract: We have demonstrated that certain passive motions of the glenohumeral joint are reproducibly accompanied by translation of the head of the humerus on the glenoid. We investigated the relationship of these translations to the position of the glenohumeral joint and to applied torques and forces in seven isolated glenohumeral joints from fresh cadavera, using a six-degrees-of-freedom position sensor and a six-axis force and torque transducer. Reproducible and significant translation occurred in an anterior direction with glenohumeral flexion and in a posterior direction with extension. We also observed translation with cross-body movement. The translation occurring with flexion was obligate in that it could not be prevented by the application of an oppositely directed force of thirty to forty newtons. Operative tightening of the posterior portion of the capsule increased the anterior translation on flexion and cross-body movement and caused it to occur earlier in the arc of motion compared with the intact glenohumeral joint. Operative tightening of the posterior part of the capsule also resulted in significant superior translation with flexion of the glenohumeral joint.
TL;DR: Rheological studies on the elastic behavior of two types of boehmite alumina gels, Catapal and Dispal powders, showed the strong-link behavior and the results are in good agreement with the theoretical predictions.
Abstract: The scaling behavior of the elastic properties of colloidal gels that are well above the gelation threshold is studied both theoretically and experimentally. A scaling theory was developed by considering the structure of the gel network as a collection of flocs, which are fractal objects closely packed throughout the sample. Two regimes are found based on the relative value of the elastic constant of the interfloc links to that of the flocs. In the strong-link (interfloc) regime, the elastic constant of the gels increases but the limit of linearity decreases with increasing particle concentration, whereas in the weak-link regime both the elastic constant and the limit of linearity increase with increasing particle concentration. Rheological studies on the elastic behavior of two types of boehmite alumina gels, Catapal and Dispal powders, were performed. Both types of gels in the concentration range studied showed the strong-link behavior and the results are in good agreement with the theoretical predictions. The value of the fractal dimension of the flocs D\ensuremath{\simeq}1.95, deduced from the rheological measurements, is in agreement with the value D\ensuremath{\simeq}2.04 deduced from the static light-scattering measurements on dilute suspensions. Therefore the scaling theory we developed also enables us to extract structural information from the rheological measurements.
TL;DR: It is shown that the CD28 antigen, expressed in Chinese hamster ovary cells, mediated specific intercellular adhesion with human lymphoblastoid and leukemic B-cell lines and with activated primary murine B cells, and represents a heterophilic interaction between members of the immunoglobulin superfamily that may serve to regulate T-cell cytokine levels at sites of B- cell activation.
Abstract: Studies using monoclonal antibodies (mAbs) have implicated the homodimeric glycoprotein CD28 as an important regulator of human T-cell activation, in part by posttranscriptional control of cytokine mRNA levels. Although the CD28 antigen has functional and structural characteristics of a receptor, a natural ligand for this molecule has not been identified. Here we show that the CD28 antigen, expressed in Chinese hamster ovary (CHO) cells, mediated specific intercellular adhesion with human lymphoblastoid and leukemic B-cell lines and with activated primary murine B cells. CD28-mediated adhesion was not dependent upon divalent cations. Several mAbs were identified that inhibited CD28-mediated adhesion, including mAb BB-1 against the B-cell activation antigen B7/BB-1 and some mAbs against major histocompatibility complex class I antigens. B7/BB-1 expression correlated closely with CD28-mediated adhesion, but class I expression did not. Transfected COS cells expressing the B7/BB-1 antigen adhered to CD28+ CHO cells; this adhesion was blocked by mAbs to CD28 and B7/BB-1. The specific recognition by CD28 of the B-cell activation antigen B7/BB-1 represents a heterophilic interaction between members of the immunoglobulin superfamily that may serve to regulate T-cell cytokine levels at sites of B-cell activation.